WO2025196676A1 - A drive system with a reduction gear box and an electric motor therefor - Google Patents

Abstract

The application relates to an electric motor and a drive system designed for electric bike applications, integrating a stator and a rotor within the electric motor. The rotor is equipped with a transmitter driving section and a magnet holding section that holds at least one magnet on its radially outer surface. This configuration improves magnetic interaction and power generation. The electric motor is preferably incorporated into a drive system that further includes a bottom bracket axle, a reduction gear box, a force measurement device, a control module, and a drive housing. This system features a specially configured reduction gear box, facilitating efficient power transmission and enhancing the electric bike's performance. Additionally, the inclusion of a force measurement device and a control module allows for dynamic adjustment of the motor's output, providing cyclists with optimal support and improving the overall riding experience.

Description

A DRIVE SYSTEM WITH A REDUCTION GEAR BOX AND AN ELECTRIC MOTOR THEREFOR

The present application relates generally to a drive system with a reduction gear box, and more specifically to the design and functionality of the drive system.

US 20160245386 A1 discloses a harmonic pin ring gear system comprising an input shaft, an output shaft, two outer gears each with internal toothing and a single inner gear with external toothing. The inner gear is arranged concentrically to a first outer gear and in axial direction within the first outer gear. A drive means extends between the two outer gears and the inner gear and comprises a pin-retaining ring formed as one part in circumferential direction and a multiplicity of pins that protrude laterally in axial direction from the pin-retaining ring. A rotary transmitter lifts the drive means off the external toothing of the inner gear and presses the drive means into the internal toothing of the outer gears.

The object of the application is to provide a drive system with a reduction gear box or an electric motor therefore which improves the efficiency and performance.

The object of the application is solved by the features of the independent claims. Advantageous embodiments of the application are described in the dependent claims.

In particular, the application provides solutions for improving the design and functionality of an electric motor and/or a respective drive system with a reduction gear box in order to enhance the overall performance and power transmission.

In this context, the disclosed electric motor may include a unique rotor design with a magnet holding section comprising at least one magnet which is located on a radially outer surface of the rotor shaft, which allows for improved interaction between the magnet and the coils included in the stator. This results in improved power generation. Additionally, the electric motor incorporates preferably a transmitter driving section positioned outside the stator, enabling efficient conversion of rotational movement into radial movement or force. The drive system may further include a reduction gear box with a specially designed pin-ring, inner gear and outer gear arrangement, ensuring smooth and reliable power and/or torque transmission from the electric motor to an output shaft.

The drive system can be suitable for an electric bike and may also incorporate a force measurement device and a control module, allowing for real-time monitoring and adjustment of the motor's output to provide optimal support for a cyclist. Overall, these innovations address the need for a more efficient and effective electric bike drive system, enhancing the riding experience and performance for cyclists.

In a first aspect the application refers to elements of an electric motor with magnets on a radially outer rotor surface, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described below.

The electric motor is suitable for an electric bike drive system with a reduction gear box having a gear unit with a rotationally symmetrical structure. The electric motor comprises a stator and a rotor, wherein the rotor comprises a rotor shaft with a transmitter driving section and a magnet holding section. At least one magnet is located on a radially outer surface of the rotor shaft.

The electric motor for an electric bike drive system with a reduction gear box having a gear unit with a rotationally symmetrical structure enables efficient power transmission due to the positioning of the at least one magnet on the radially outer surface of the rotor shaft at the holding section inside the stator. In particular, the embodiment brings the magnets closer to the stator coils, resulting in higher efficiency.

In order to counteract the resulting higher centrifugal force, the magnets are preferably attached to the rotor in a form-fitting manner. To realize the form-fitting manner constructively, the magnets can be designed with complementary shapes that match the contours of designated slots on the rotor shaft's surface. For example, a dovetail joint design could be provided for the magnets and the slots on the rotor shaft. The dovetail joint is characterized by its trapezoidal shape, where the wider part of the trapezoid is facing outward. This design prevents the magnet from moving radially outward due to centrifugal force when the motor is spinning at high speeds. The magnets are shaped to fit precisely into corresponding dovetail-shaped slots on the rotor shaft. This interlocking mechanism ensures a robust mechanical connection.

A reduction gear box is preferably a mechanical component that reduces the rotational speed while increasing the torque output of an electric motor. It efficiently transmits power from the electric motor to the output shaft, ensuring that the machinery or vehicle, such as an electric bike, operates smoothly and effectively. This component improves performance, allowing for precise control and adaptation to various riding conditions, thereby enhancing the overall efficiency and functionality of the drive system.

The rotor of the electric motor may have a rotor shaft with two sections extending along the longitudinal axis. A first section provides a magnet holding section and a second section provides a transmitter driving section. In particular, a transmitter driving section is used to transmit the kinetic energy of the rotor to a component of a gearbox. The type of motion, such as rotary motion of the rotor, can be converted to another type of motion, such as linear motion.

Furthermore, the rotor shaft can be designed as a hollow shaft. This hollow construction comprises both a radially inner surface and a radially outer surface. The radially inner surface is located closer to the center or core of the shaft, facing towards the axis around which the rotor rotates. Conversely, the radially outer surface of the rotor shaft is the external surface that extends away from the shaft's central axis. This outer surface is in particular equipped with magnets. The placement of the magnets on this radially outer surface improves the magnetic interactions with the coils of the stator, leading to an improvement in the efficiency of the motor and its ability to generate electricity more effectively. The design choice of a hollow shaft further can contribute to a reduction in the overall weight of the rotor, which also improves the motor's performance and efficiency. The electric motor can be configured with the magnet holding section being positioned inside the stator, and the transmitter driving section being positioned outside the stator. The rotor shaft is preferably made of steel and magnets are attached to the magnet holding section on a radially outer surface. This arrangement allows a particularly compact and integrated design in which the rotor motion can be efficiently transmitted to a gearbox, reducing the overall size and weight of the electric motor.

The magnet holding section can be a part of the rotor shaft which has a uniform surface to which magnets can be securely attached. The magnet holding section extends preferably along the longitudinal axis and the diameter of the rotor shaft does not substantially change in this section.

Moreover, the electric motor can comprise a transmitter driving section being designed as an eccentric section or an elliptic section. The primary function of an eccentric or elliptical section is preferably to convert the rotational movement of the rotor into radial movement or force. This feature is particularly suitable for integrating the electric motor with a harmonic drive gearbox, where the radial movement from the eccentric or elliptical section is transferred to a component of the harmonic drive gearbox, for example to an inner gear or a pin ring. Also, the eccentric or elliptical sections can be integrated as discs on the rotor shaft, enhancing the compactness and efficiency of the design. The harmonic drive gearbox can be also considered as strain wave gear box.

The elliptical section can form part of the rotor shaft and has an elliptical cross section. On the other hand, the eccentric section maintains a circular cross section but is characterized by its non-centre axis of rotation. Both the shape of the elliptical section and the non-centre axis of rotation of the eccentric section contribute to the smooth conversion of rotary motion into radial force or motion.

The electric motor can comprise a plurality of magnets being concentrically mounted on the outer surface of the rotor shaft, in particular in the magnet holding section. The concentric mounting of a plurality of magnets on the outer surface of the rotor shaft in the electric motor ensures a more uniform magnetic field distribution, resulting in smoother and more efficient motor operation.

Preferably, the magnets are attached to the magnet holding section of the rotor shaft by a form-fit connection, but other connections, such as adhesive and/or force-fit connections, as well as combinations of the above, are also conceivable.

Additionally, the stator of the electric motor preferably comprises three coils and a three phase inverter. This specific configuration has proven to be exceptionally effective and durable. The use of three coils and a three-phase inverter in the stator of the motor allows for precise control of the motor's speed and torque, enabling optimal performance and responsiveness.

Furthermore, the application relates to a drive system for an electric bike comprising: an electric motor described above, a bottom bracket axle, a reduction gear box having a gear unit with a rotationally symmetrical structure, a force measurement device, a control module and a drive housing.

The drive system for an electric bike, incorporating the electric motor described above, offers improved power delivery and efficiency. The drive system further provides the advantage of improved operability by incorporating a force measuring device that can accurately detect radial forces applied by a cyclist to a pedal shaft included in the bottom bracket axle. The control module can analyze the signals received from the force measurement device and effectively control the electric motor to generate a force that supports the cyclist. The system ensures additionally the reliability by employing a reduction gear box with a gear unit that has a gear unit with a rotationally symmetrical structure, allowing for smooth and efficient transmission of power to the output shaft.

Additionally, the drive system can comprise an outer double-row ball bearing being located radially outwards on the transmitter driving section of the electric motor and an inner double-row ball bearing is located radially inwards. The use of an outer double-row ball bearing and an inner double-row ball bearing in the drive system provides enhanced stability and support to the transmitter driving section of the electric motor, resulting in improved overall performance. The inclusion of the outer and inner double-row ball bearings helps to distribute the load evenly, increasing the lifespan of the drive system. Further, the arrangement of the outer and inner double-row ball bearings allows for efficient power transmission and smooth operation of the electric motor, resulting in reduced energy consumption and improved energy efficiency.

The rotor of the electric motor may be supported by a rotor support ring and a rotor bearing in the drive housing. The inclusion of a rotor support ring and a rotor bearing provides enhanced stability and support to the rotor of the electric motor, resulting in improved overall performance. The use of a rotor support ring and a rotor bearing helps to reduce vibrations and noise generated during operation, resulting in a quieter and more efficient drive system. The presence of a rotor support ring and a rotor bearing ensures proper alignment and positioning of the rotor, minimizing the risk of damage or malfunction, and increasing the reliability of the drive system. In addition, the rotor support ring allows the diameter of the rotor or rotor shaft to be large, as it acts as a connecting element or bridge element between the rotor bearing and the rotor. It is desirable for the diameter of the rotor to be large, as this in turn provides the magnets close to the stator.

Preferably, the rotor support ring is made of plastic. The use of a plastic rotor support ring provides several advantages, including reduced weight, improved corrosion resistance, and enhanced durability, resulting in a more efficient and long-lasting drive system. The plastic rotor support ring offers excellent insulation properties. The plastic rotor support ring can be manufactured using cost-effective methods, resulting in a more affordable drive system without compromising on performance or quality.

Also, the drive system can comprise a reduction gear box with a pin-ring, an outer gear with internal toothing and an inner gear with external toothing. The inclusion of a reduction gear box comprising a pin-ring, an outer gear with internal toothing, and an inner gear with external toothing allows for precise and efficient power transmission, resulting in improved overall performance of the drive system. The use of a reduction gear box helps to increase torque and reduce rotational speed. The arrangement of the pin-ring, outer gear, and inner gear provides a very compact and space-saving design, allowing for easy integration into various devices and systems.

Preferably, an outer gear is located on the periphery or outside of a gear assembly or the gear unit. It may be fixed or attached to a drive housing or directly formed as part of the drive housing, for example, by milling. The outer gear further comprises internal toothing that is configured to mesh with the external teeth of an inner gear and/or a pin ring.

Preferably, an inner gear refers to a gear located towards the center or inside of a gear assembly or the gear unit. It may engage with or mesh with an outer gear or a pin ring. The inner gear comprises external teeth that can mesh with the teeth of an outer gear, a pin ring or other components.

Generally, a pin ring may comprise a series of pins arranged evenly in a ring or circular plate. These pins can be regarded as teeth and engage with corresponding recesses or teeth on another component, such as a gear or other transmission component.

Accordingly, the pin ring is also referred to as a toothed ring, featuring teeth on both its radially inner and outer surfaces. The pins within the pin ring are radially offset from one another, effectively forming a double-toothed ring. The function of a pin ring is generally to transmit torque and/or convert motion between different parts of a gearbox. Through the precise arrangement of the pins, the pin ring can ensure even and efficient power transmission. By using a pin ring instead of traditional gear connections, a compact design and a better transmission ratio can be achieved.

Further, the pin ring can be C-shaped in cross section, wherein a radially outer leg of the C is toothed on both sides/surfaces, while a radially inner leg of the C is preferably smooth or not toothed or unprofiled. The C-shaped cross section of the pin ring, with a toothed radially outer leg and a non-toothed radially inner leg, allows for efficient power transmission, precise control of rotational movement in the drive system and still enables for a particularly compact design. By both sides of the radially outer leg, it is meant in particular that both the radially outer surface of the radially outer leg of the C-shaped pin ring has teeth and the radially inner surface of the radially outer leg has teeth.

A radially inner surface of the inner gear can be disposed on the radially inner leg of the pin ring. During operation, always a different part of the inner gear may be disposed on the inner leg of the pin ring. This depends on the position of the driving transmitter section of the electric motor. At the locations where the outer leg of the pin ring engages with the outer gear, the inner gear is in contact with the inner leg of the pin ring. The disposition of the radially inner surface of the inner gear on the radially inner leg of the pin ring ensures precise alignment and engagement between the gears, resulting in smooth and efficient power transmission. The use of the radially inner leg of the pin ring as a support surface for the inner gear provides enhanced stability and reduces the risk of misalignment or disengagement during operation, increasing the reliability of the drive system.

The outer double-row ball bearing may be in contact with the transmitter driving section and the radially inner leg of the pin ring. The radial motion or force of the outer doublerow ball bearing, caused by contacting the transmitter drive section, allows for effective meshing of the teeth between the inner gear and the radially outer leg of the pin ring, as well as between the outer leg of the pin ring and the outer gear with internal toothing, resulting in smooth and efficient transmission of rotation. In other words, due to the radial motion or force of the outer double-row ball bearing, the radially outer leg of the pin ring mesh with the outer gear with internal toothing, and/or with inner gear with external toothing. For this purpose, the outer double-row ball bearing may be designed flexible.

The drive system can further incorporate a reduction gear box with a roller bearing which is operatively coupled with the inner gear, so that a rotation of the inner gear can be transmitted to an inner ring of the roller bearing.

In addition, the drive system may comprise a first freewheel that is operatively coupled to the roller bearing, wherein the inner ring of the roller bearing is in contact with the first freewheel. Plus, the first freewheel can be further operatively coupled with the output shaft. The integration of the first freewheel within the drive system allows for more precise control over the bike's power output and speed. Since the freewheel is directly connected to the roller bearing and the output shaft and thus acts as a force transmitter between the motor and the output shaft, it can quickly disengage when a support force of the motor is no longer required, for example because the driver is already driving too fast, or the driver stops abruptly. In this respect, the first freewheel is designed to decouple the inner ring of the roller bearing from the output shaft, resulting in decoupling the support force from the output shaft.

Further, the drive system may incorporate an output bearing that supports the output shaft in the drive housing, enhancing the overall stability and load-bearing capacity of the system. This allows for smooth and efficient rotation of the output shaft and increases the overall lifespan and reliability of the system. The output bearing could for example be a ball bearing.

The drive system can also comprise a second freewheel being operatively coupled with the output shaft. The second freewheel can in addition be operatively coupled to a pedal shaft and is able to transmit the rotational movement of the pedal shaft which is generated by the cyclist to the output shaft. The second freewheel is configured to decouple the pedal shaft from the output shaft. The inclusion of a second freewheel that is operatively coupled with the output shaft ensures that the pedal shaft does not automatically and unintentionally rotate in the direction of rotation of the output shaft. This feature enhances the cycling experience, particularly during scenarios like downhill riding, where the cyclist doesn't need to pedal, ensuring the pedals remain stationary and the ride is more comfortable.

Moreover, the drive system may comprise a chainring adapter being connected to the output shaft. The presence of a chainring adapter connected to the output shaft allows a chain to be driven, which in turn is operatively coupled to the rear tire of the electric bike. The chainring adapter also allows for easy customization and interchangeability of chainrings so that the user can adapt the system to their specific needs and preferences. The drive system can comprise an outer shaft seal ring being placed between the output shaft and the drive housing. The inclusion of an outer shaft seal ring between the output shaft and the drive housing provides effective sealing, preventing the ingress of dirt, dust, and moisture into the system. This ensures the longevity and reliability of the system.

The inner double-row ball bearing can be located between a section of the inner gear and the transmitter driving section. The use of an inner double-row ball bearing between a section of the inner gear and the transmitter driving section enhances the load-bearing capacity and stability of the system, while allowing the design of the drive system to be extremely compact. The inner double-row ball bearing is preferably flexible.

Additionally, the drive system may comprise a bottom bracket axle comprising pedal shaft with a first crank bearing and a second crank bearing. A left crank arm with a left pedal can be supported in the second crank bearing and a right crank arm with a right pedal can be supported in the first crank bearing. These features make it possible for the cyclist to apply his movement effort to the drive system. This is intended to be the main force that sets the bike in motion and is supported in certain situations by the electric motor and its applied motor power.

The drive system may comprise a pedal shaft being supported in the drive housing with a left bottom bracket bearing and supported against the output shaft with a right bottom bracket bearing. This design ensures compact construction and smooth rotation of the pedals or pedal shaft.

Further, the drive system may comprise a left bottom bracket bearing and/or the right bottom bracket bearing being a ball bearing. The use of ball bearings in the bottom bracket enhances durability, resulting in improved overall performance and longevity of the drive system.

The drive system can comprise an inner shaft seal ring being located on the pedal shaft.

This seal ring prevents dust, dirt, and moisture from entering the system, thereby protecting the internal components and ensuring the longevity and reliability of the system. The inner shaft seal may also be located at the radial inner surface of a threaded sleeve which has a radial outer thread. The threaded sleeve is preferably screwed into the hollow output shaft and serves to hold the chain ring adapter firmly in place.

It is also possible that the drive system comprises a force measurement device comprising at least one strain gauge and/or a communication interface. This allows for accurate measurement of the force applied by the cyclist during cycling. The force measurement device is preferably configured to acquire the radial force applied on the pedal shaft and transmit a corresponding signal to the control module, providing accurate and real-time feedback on the cyclist's effort.

The drive system can furthermore comprise a control module comprising a printed circuit board, a microprocessor, a memory, an input interface, an output interface, analogue-to- digital converter and/or a digital-to-analogue converter. This control module enables precise control and adjustment of various parameters of the drive system. The control module analyzes the signal received from the force measurement device and controls the electric motor, allowing for precise and adaptive support to the cyclist based on their needs.

The drive system may comprise a drive housing comprising a gearbox housing half, electric motor housing half, housing cover, and screw connections.

In this context, the drive system can comprise an electric motor being located in the electric motor housing half and/or the force measurement device can be located in the electric motor housing half and/or the reduction gear box can be located in the gearbox housing half. This allows for efficient use of space and easy access for maintenance and repairs. Furthermore, the force measurement device could act as a housing cover for the drive system.

In summary, the electric motor is able to be configured to generate an electromagnetic force that causes the rotor shaft to rotate, wherein the transmitter driving section can convert the rotational movement of the rotor shaft into a radial movement or radial force. The reduction gear box is accordingly configured to convert a radial movement or force, which is applied to the reduction gear box via the transmitter driving section, into a rotational movement, the rotational movement being directed to an output shaft. The bottom bracket axle may comprise, on the other hand, a pedal shaft which is configured to be set into a rotational movement by the cyclist via a right pedal and right crank arm and a left pedal and left crank arm, and wherein the pedal shaft preferably comprises means for transmitting the rotational movement to an output shaft. In this respect, the drive system has two power sources, the electric motor and the cyclist's power, both of which can be transferred to the output shaft via a power or force flow through the gearbox arrangement and/or the pedal shaft.

In particular, the force measurement device is further configured to acquire a radial force applied on the pedal shaft and to transmit a corresponding signal to the control module. The control module is, on the other hand, configured to analyze the signal received from the force measurement device and to control the electric motor, the electric motor being used to generate a force to support a cyclist.

In further aspects that refer to elements of a rotor support ring, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described above and below.

In this respect, the drive system may comprise an electric motor with a stator and a rotor, a reduction gear box with a gear unit, and a drive housing, wherein the gear unit has a rotationally symmetric structure, and wherein the stator, the rotor and the gear unit are arranged coaxially. The rotor may be supported at a first side by the drive housing through a rotor support ring and via a rotor bearing which is provided as a rolling contact bearing. Further, the rotor support ring may be elastically deformed in an axial direction, thereby generating a preload, such that an axial movement of the rotor results in a deformation of the rotor support ring. This design provides improved support for the rotor in the drive system, resulting in improved stability and efficiency of the drive system. The rotor support ring may have two main functions. Firstly, it bridges the diameter of the rotor bearing and therefore the drive housing to the rotor or rotor shaft. This design allows for a larger rotor diameter, bringing the magnets of the electric motor closer to the stator and improving the efficiency of the motor. Secondly, the elastic deformation of the rotor support ring to create a preload ensures that the axial movement of the rotor is controlled, which can lead to reduced vibration and noise during operation, improving the performance and longevity of the drive system. The term “elastic deformation” here implies that the rotor support ring is flexible, springy, and/or resilient.

A coaxial arrangement of the stator, rotor, and gear unit may contribute to a compact and efficient design, reducing the overall size and weight of the drive system. In this context, the drive system provides also the advantage of having gear unit with a rotationally symmetric structure, which in addition to compactness, ensures balanced and efficient operation. The gear unit is preferably part of the reduction gear box and can comprise for example an inner gear, a pin ring and/or an outer gear.

Preferably, a gear unit with rotationally symmetric structure is a mechanical transmission system in which the arrangement of gears or other transmission elements exhibits rotational symmetry. This means that when the gear unit or any of its components are rotated around its main axis, they will return to their original position after completing a full circle. In this context, a gear unit with a rotationally symmetric structure may be understood as a rotationally cyclic gearbox, in which, after each cycle, the gears and/or transmission elements — or any of their components — return to their initial position following a complete rotation around the main axis of the gearbox. Essentially, this ensures that the gear setup remains consistent, displaying the same configuration as before the rotation. A gear unit with a rotationally symmetric structure can, for example, be designed as planetary gear systems, harmonic drive gear systems, harmonic pin drive gear system and/or cycloidal drive systems. The use of a rolling contact bearing as the rotor bearing ensures smooth and reliable support for the rotor.

The first side of the rotor is preferably referred to as the area in which a magnet holding section is located. This side is inside the stator. A second side of the rotor is preferably on the opposite side and has a transmitter drive section. This side is preferably outside the stator.

Furthermore, the drive system may comprise a bottom bracket axle. The bottom bracket axle can be supported by the drive housing and is preferably axially secured therein, wherein the rotor can be supported at a second side by the bottom bracket axle. The support of the rotor at the second side by the bottom bracket axle provides additional stability and alignment for the rotor. This preferably provides a fixed-fixed mounting for the rotor, i.e. the rotor can only move axially against further deformation of the support ring. In particular, this embodiment is designed as an indirect bearing/support, wherein the rotor is supported in the bottom bracket axle by other elements of the drive system. These other elements can be, for example, an inner ring, an inner double-row ball bearing and a plain bearing. Accordingly, the gear unit, the rotor and the bottom bracket axle share preferably the same bearing.

The bottom bracket axle may also be supported by a left bottom bracket bearing in the drive housing and by a right bottom bracket bearing in an output shaft, which may be supported by an output bearing in the drive housing. The support of the bottom bracket axle by bearings on both sides (left and right) allows for good load distribution and stability. The inclusion of an output bearing in the drive housing for supporting the output shaft provides a point of stability, which reduce stress on the system and improve the smoothness of operation.

The gear unit may comprise an inner gear which supports the rotor on the second side, wherein the bottom bracket axle supports the inner gear. The support of the rotor on the second side by the inner gear, which is in turn supported by the bottom bracket axle, creates a direct and robust connection between the motor and the gear unit. The configuration where the bottom bracket axle supports the inner gear can simplify the assembly process and reduce the number of required components.

Also, the gear unit may comprise a pin ring, and wherein the rotor can be supported in two bearings on the second side. An outer double-row ball bearing can be positioned on the radially outer surface of the rotor and contacts the pin ring and an inner double-row ball bearing can be positioned on the radially inner surface of the rotor and contacts the inner gear. The positioning of the outer double-row ball bearing in contact with the pin ring and the inner double-row ball bearing in contact with the inner gear ensures that the rotor is precisely centered. The configuration of the bearings on the radially outer and inner surfaces of the rotor provides a balanced support system that can absorb the forces generated during operation more effectively.

The rotor support ring can be made of plastic. Preferably, the support ring is made of polyamide, polyphenylene sulfide or polyetheretherketone. Utilizing a plastic material for the rotor support ring reduces the overall weight of the system. The incorporation of plastic in the rotor support ring offers corrosion resistance, thereby enhancing the durability and longevity of the system when exposed to harsh environments. The use of plastic allows for effective manufacturing processes such as injection molding.

The selection of high-performance polymers such as polyamide, polyphenylene sulfide, or polyetheretherketone for the rotor support ring provides thermal stability and mechanical strength, ensuring reliable operation under high-temperature and high-stress conditions. These materials exhibit low friction coefficients, which can minimize wear and tear on the rotor support ring.

The rotor bearing may be designed as a ball bearing, a roller bearing or split bearing. The use of these types of bearings can lead to smooth and quiet operation.

Further, the rotor support ring can comprise a radially inner surface and a radially outer surface, the rotor being positioned on the radially outer surface of the rotor support ring and the rotor bearing seating against the radially inner surface of the rotor support ring. Positioning the rotor on the radially outer surface and the bearing on the radially inner surface provides a stable and balanced support structure, which can improve the precision and reliability of the rotor's operation. In particular, the rotor support ring serves as a link or bridge between the rotor bearing and the rotor.

The rotor support ring can comprise a first step on the radially outer surface, which acts as an axial limit stop for the rotor. The inclusion of a first step on the radially outer surface acting as an axial limit stop for the rotor ensures precise axial positioning of the rotor, which can prevent misalignment and reduce vibration during operation. By acting as a physical barrier, the first step is used to create a preload that provides axial fixation. The rotor support ring is effectively clamped between the rotor and the rotor bearing, with the first step acting as a kind of anchorage.

Furthermore, the rotor support ring can comprise a second step on the radially inner surface, which acts as an axial limit stop for the rotor bearing, in particular for a radially outer ring of the rotor bearing. The inclusion of a second step on the radially inner surface of the rotor support ring provides a reliable axial limit stop for the rotor bearing, which enhances the stability and alignment of the rotor within the system. By acting as an axial limit stop specifically for the radially outer ring of the rotor bearing, the second step ensures that the bearing is securely positioned. The second step also acts as an anchor or retention point to create a preload when the rotor support ring is clamped between the rotor and the rotor bearing.

Alternatively, the rotor support ring may comprise a radially inner surface and a radially outer surface, the rotor bearing being positioned on the radially outer surface of the rotor support ring and the drive housing seating against the radially inner surface of the rotor support ring. In this context, the rotor comprises preferably a third step on the radially inner surface, which acts as an axial limit stop for the rotor bearing, in particular for a radially outer ring of the rotor bearing. The rotor support ring comprises on the other hand a first step on the radially outer surface, which acts as an axial limit stop for the rotor bearing, in particular for a radially inner ring of the rotor bearing. This variant is a different arrangement compared to the aforementioned variant. Instead of the rotor support ring being clamped between the rotor and the rotor bearing, the rotor bearing is now clamped between the rotor support ring and the rotor.

The rotor support ring may be designed as a double-walled cylinder comprising a radially outer wall and a radially inner wall connected with a disc, the radially outer surface being formed on the radially outer wall and the radially inner surface being formed on the radially inner wall of the double-walled ring. The double-walled ring structure with a radially outer wall and a radially inner wall, which are connected by a disc, offers increased properties in terms of elasticity.

In further aspects that refer to elements of a gear unit with a C-shaped pin ring, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described above and below.

In this context, a drive system can comprise an electric motor with a stator and a rotor, a reduction gear box with a gear unit, and a drive housing. The gear unit features a rotationally symmetric structure and preferably includes a pin ring, an inner gear with external toothing, and an outer gear with internal toothing, which may be attached to the drive housing. The pin ring is preferably C-shaped in cross section, a radially outer leg of the C-shaped pin ring being toothed on both sides. In contrast, a radially inner leg of the C-shapes pin ring may remain not toothed or smooth or untoothed. The inner gear is preferably positioned between the radially inner leg and the radially outer leg.

The C-shaped cross-section of the pin ring offers the advantage of holding the inner gear between its radially inner and outer legs, which on the one side allows for a compact design, reducing the overall size of the drive system, and on the other side ensures that meshing between the inner gear and outer gear are in a single plane. Compared to prior art solutions, this avoids tilting moments of the pins of the pin ring and ensures precise meshing. Accordingly, this aspect results in improved meshing efficiency and stability of the drive system. In sense of the application a C-shaped pin ring can also be understood as a double-walled cylinder with a connecting disc. The connecting disc is located at one end face of the double-walled cylinder and connects the two walls of the cylinder. A first wall is to be understood as a radially outer leg of the C-shaped pin ring, while a second wall of the cylinder is to be understood as a radially inner leg of the of the C-shaped pin ring. The disc, on the other hand, is related to a central part of the C-shaped pin ring.

The two legs of the C-shaped pin ring each have two surfaces. One radially outer and one radially inner surface. These surfaces are also to be understood as sides. The two sides of the radially outer leg of the C-shaped pin ring are toothed, while the two sides of the radially inner leg of the C-shaped pin ring are preferably not toothed.

The inner gear or a part of the inner gear can be located or positioned between the radially inner and outer legs of the C-shaped pin ring. In other words, the inner gear can be located between the two walls of the double-walled cylinder. This can also to be understood as meaning that the pin ring holds, supports, surrounds, houses, encases, encloses, embraces, accommodates the inner gear.

Preferably, the pin ring is rigid. This rigidity ensures that the pin ring maintains its C- shaped cross-section without bending or distorting, in particular also during operation of the drive system. The pin ring may be made from a single piece and can for example be composed of metal or fibre reinforced materials.

In addition, the radially outer leg in lateral view of the C-shaped pin ring may comprise a meandering profile which is formed over the entire circumference. The meandering profile accordingly forms teeth on both sides of the radially outer leg which can simplify the production of the pin ring, especially the simultaneous application of the teeth/pins on the outside and inside.

The teeth on the radially outer leg of the pin ring can mesh with the teeth of the outer gear and of the inner gear, ensuring meshing in a single plane and extending across the entire width of the outer gear and/or the inner gear. The meshing of the teeth on the radially outer leg of the pin ring with the teeth of the outer and inner gears in a single plane prevents the generation of tilting moments, which can reduce stress on the components and extend the lifespan of the system. The extension of the teeth across the entire width of the outer and inner gears provides a large contact area, enhancing the load-bearing capacity and enabling the system to handle higher torque demands.

Moreover, a radially inner surface of the inner gear can be disposed on the radially inner leg of the pin ring, and wherein the contacting surfaces of the inner gear and the radially inner leg of the pin ring are not toothed. During operation, the contact points between these surfaces shift dynamically. The location of contact depends on the position of the transmitter driving section of the rotor coupled to the pin ring. At certain positions, the inner leg of the pin ring and the inner surface of the inner gear touch, particularly when the outer leg of the pin ring engages with the outer gear. At other positions, the inner leg of the pin ring loses contact with the inner gear because the outer leg of the pin ring is actively engaged with the external teeth of the inner gear, which are located on its radially outer surface.

The rotor may further comprise a rotor shaft with a transmitter driving section, the pin ring being coupled to the transmitter driving section via a transmitter bearing, wherein the transmitter driving section can be designed as an eccentric section, thereby causing a conversion of a rotational motion of the rotor into a radial motion or force. The coupling of the pin ring to the transmitter driving section via a transmitter bearing allows for smooth transmission of motion. The transmitter bearing is therefore flexible to allow a good conversion and transmission of the force applied from the eccentric section.

Due to radial motion or force applied to the inner leg of the pin ring, the radially outer leg of the pin ring can mesh with the outer gear with internal toothing, and/or with inner gear with external toothing. When the pin ring is meshed with the outer gear and/or the inner gear, an output is generated on the inner gear. This can be forwarded or transmitted to other components of the reduction gearbox. Preferably, the transmitter bearing is flexible. The transmitter bearing can be an outer double-row ball bearing and can be located radially outwards on the transmitter driving section of the electric motor. Further, an inner double-row ball bearing can be located radially inwards on the transmitter driving section of the electric motor, wherein the inner double-row ball bearing is flexible. The inherent flexibility in the bearing designs may allow radial movement.

The use of double-row ball bearings, both inner and outer, provides the advantage of flexibility and adjustability, allowing the pin ring to engage with the gears at the desired height and ensuring proper alignment. The use of double-row ball bearing further provides a robust support for the transmitter driving section of the electric motor. The double-row configuration of the ball bearing increases the contact surface area with the raceways, which can lead to improved stability and smoother operation under varying load conditions, contributing to the efficiency of the electric motor.

In further aspects that refer to elements of an outer double-row rolling bearing, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described above and below.

In this respect, a drive system may comprise an electric motor with a stator and a rotor, and a reduction gear box with a gear unit, wherein the gear unit has a rotationally symmetric structure. The stator, the rotor and the gear unit are preferably arranged coaxially. Further, the rotor may comprise a rotor shaft with a transmitter driving section. An outer double-row rolling bearing is provided radially outwards on the transmitter driving section and radially inwards to the gear unit.

A double-row rolling bearing is preferably a bearing with two parallel rows of rolling elements, such as balls or rollers. An outer double-row rolling bearing with balls as rolling elements is preferably referred to as an outer double-row ball bearing.

The outer double-row rolling bearing or the outer double-row ball bearing serves especially as a force transmitting means between the transmitter driving section and the gear unit. The inclusion of an outer double-row ball bearing radially outside the transmitter driving section further enhances radial support and stability to the transmitter driving section and gear unit which leads also to the advantage of reliable and efficient power transfer.

The double ball bearing is preferably designed to be flexible in order to efficiently transmit radial force or motion to the gearbox. This force or motion originates from a transmitter drive section, which can be configured as either an eccentric or elliptical section. This configuration converts rotary motion into radial force or motion. In particular, the outer double ball bearing must adapt to changes in the circumference of the elliptical or eccentric section during rotation to ensure smooth and efficient transmission of force or motion.

Furthermore, the drive system may comprise a drive housing, and the gear unit may comprise a pin ring, an inner gear with external toothing, and an outer gear with internal toothing which is attached to the drive housing. Additionally, the pin ring is mounted on a radially outer ring of the outer double-row ball bearing. As already mentioned in the other embodiments of the application this design lead to improved performance characteristics, such as increased torque transmission or higher efficiency.

Preferably, the double-row ball bearing is configured to transmit radial force or motion from the transmitter drive section to the pin ring. As a result, the pin ring is able to mesh with the teeth of the outer gear and/or inner gear, generating an output rotation for the inner gear.

Also, the pin ring can be C-shaped in cross section, a radially outer leg of the C-shaped pin ring being toothed on both sides, while a radially inner leg of the C-shapes pin ring being not toothed. The inner gear can be located between the radially inner leg and the radially outer leg, and the radially inner leg is provided on the radially outer ring of the outer double-row ball bearing. The provision of the radially inner leg on the radially outer ring of the outer double row ball bearing ensures that the bearing is connected to the structural design of the pin ring. The double-toothed design of the radially outer leg of the C-shaped pin ring can allow the pin ring to engage simultaneously in the internal toothing of the outer gear at a first location and in the external toothing the inner gear at a second location.

The rotor can be designed as a hollow shaft, and an inner double-row rolling bearing can be provided radially inwards on the transmitter driving section. This bearing is preferably an inner double-row ball bearing.

The inner double-row ball bearing primarily supports the rotor in relation to a concentrically arranged component, such as a bottom bracket axle, around which the rotor rotates. Placing the inner double-row ball bearing radially inwards on the transmitter driving section enhances load-bearing capacity and stability. When precisely aligned with an outer rolling bearing, this configuration prevents tilting moments, ensuring even force distribution and contributing to the longevity, reliability, and smooth operation of the drive system.

The inner gear may be also C-shaped in cross-section and, insofar, may comprise a radially inner leg and a radially outer leg, between which the radially inner leg of the C- shape pin ring, the outer double-row ball bearing, the transmitter driving section of the rotor and the inner double-ball bearing can be positioned. The C-shaped cross-section of the inner gear provides a compact and efficient design that can accommodate the necessary components within a limited space, reducing the size of the drive system. The arrangement of the radially inner leg of the C-shaped pin ring, the outer double-row ball bearing, the transmitter driving section of the rotor, and the inner double-row ball bearing creates a robust and well-supported assembly. This specific configuration of the inner gear and associated bearings allows for an even distribution of forces throughout the drive system.

Moreover, the transmitter driving section can comprise a first axial limit stop which abuts a radially inner ring of the outer double-row ball bearing. Preferably, the transmitter driving section also comprises a second axial limit stop which abuts a radially outer ring of the inner double-row ball bearing. This ensures that the double-row ball bearings are axially fixed, since a central part of the inner gear is provided on the opposite side where the axial limit stops are not provided. In this context, the central part connects the two legs of the C-shaped inner gear.

In further aspects that refer to elements of an inner double-row rolling bearing, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described above and below.

In this context, a drive system may comprise an electric motor with a stator and a rotor, and a reduction gear box with a gear unit. The gear unit has preferably a rotationally symmetric structure. Furthermore, the stator, the rotor and the gear unit are preferably arranged coaxially. The rotor is preferably designed as a hollow shaft and may comprise a transmitter driving section. An inner double-row rolling bearing is preferably provided radially inwards on the transmitter driving section. A double-row rolling bearing can be designed as a double-row ball bearing.

This aspect improves particularly the drive system by providing a more efficient and reliable structure for transmitting force and motion between the transmitter driving section or the electric motor and the gear unit. The bearing support and guide means are improved by using double-row ball bearings or more general double-row rolling bearings. The inclusion of an inner double row ball bearing radially inwards of the transmitter drive section ensures robust support and smooth rotation on a concentrically arranged component, as for example the bottom bracket axle or the inner gear.

The transmitter driving section can comprise a second axial limit stop which abuts a radially outer ring of the inner double-row ball bearing. The second axial limit stop on the transmitter driving section provides a precise positioning of the radially outer ring of the inner double-row ball bearing, which helps to maintain alignment and reduce wear. The axial limit stop enhances the structural integrity of the drive system by preventing axial movement of the bearing. Further, an outer double-row rolling bearing can be provided radially outwards on the transmitter driving section and radially inwards to the gear unit so as to serve as a force transmitting means between the transmitter driving section and the gear unit. By also acting as a support or guiding means, the outer double-row rolling bearing ensures precise alignment of the rotating components, which results in smoother operation and reduced vibration. The outer double-row rolling bearing may be designed as a doublerow ball bearing.

The drive system may comprise a drive housing. Additionally, the gear unit can comprise a pin ring, an inner gear with external toothing, and an outer gear with internal toothing which is attached to the drive housing. The pin ring may be mounted on a radially outer ring of the outer double-row ball bearing.

The inner double-row ball bearing can also be supported by an inner gear. The support of the inner double-row ball bearing by an inner gear provides a secure and stable bearing arrangement. The inner gear's support for the bearing allows fora more integrated design.

In further aspects that refer to elements of an inner gear with axial teeth, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described above and below.

In this respect, an inner gear may be provided for a reduction gear box with a gear unit having a rotationally symmetric structure. The inner gear can comprise a ring with external toothing and a support section connected thereto. The support section comprises preferably axial teeth which can engage with corresponding toothed components such as a gear or a ring. For example, the axial teeth of the inner gear can engage with the inner ring of a roller bearing. In this respect, the inner ring of the roller bearing comprises axial recesses or grooves and/or teeth which can engage with the axial teeth of the inner gear.

This aspect improves in general the design and functionality of inner gear in a reduction gear box, particularly enhancing the support and engagement of the inner gear with other components, such as gears or rings. The axial toothing of the inner gear enables efficient power transmission while maintaining a compact design. The support section has two functions in particular. Firstly, the support section is intended to support the inner gear on another component, such as a shaft or a ring or, for example, the bottom bracket axle, and secondly to transmit the output generated in the gear unit to another component of the reduction gear box. The ability of the support part to support the inner gear on a shaft or ring contributes to the stability and alignment of the gear unit or reduction gear box by maintaining a very compact design.

In general, axial teeth refer to a configuration of teeth or projections arranged along the axial direction, designed for interlocking engagement with corresponding features on another part, such as a gear, ring, or bearing. The axial teeth are preferably integral to the support section of an inner gear. For optimum transmission of rotary motion, the axial teeth are positioned evenly, circumferentially on the inner gear or the support section of the inner gear. However, the term axial teeth also mean, for example, radial teeth positioned on a ring or disc, wherein the ring or disc is laterally displaced in the axial direction in relation to the inner gear or rests laterally against the inner gear, is attached to it or is integrated into the inner ring.

The support section in the context of an inner gear for a reduction gearbox may refer to a structural component that is integral to the gear's design, providing a means for physical connection and alignment within the gear unit assembly. It may facilitate the support of the inner gear to other components, such as shafts or rings, ensuring the proper placement and function of the gear within the system by maintaining a compact design.

The support section may comprise a radial part and an axial part, wherein the axial part is aligned parallel to the ring with external teeth and connected to the ring through the radial part, so that the inner gear forms a C-shape in cross section.

The axial part can be mounted on a shaft or a ring to support the inner gear. In particular, the radially outer surface of the axial part is parallel to the radially inner surface of the ring with external teeth. The radial part is also to be understood as a disc. Further, the support section can comprise a tooth ring which is placed lateral to the radial part of the support section. The tooth ring provides the axial teeth via concentrically arranged bulges and extensions on the circumference. The tooth ring placed lateral to the radial part of the support section provides additional surface area for axial teeth, which can improve the engagement with corresponding toothed components and result in better torque transmission.

Furthermore, a reduction gear box may be provided. The reduction gear box can comprise a gear unit and an output shaft. The gear unit can have a rotationally symmetric structure and may comprise an above mentioned inner gear and an outer gear with internal toothing. The gear unit is preferably coupled to the output shaft. In a further variant, the gear unit further comprises a pin ring. These embodiments are specifically related to a strain wave gear, a harmonic drive gear or a harmonic pin ring drive gear. The benefits of this gear configuration have been outlined in previous descriptions, highlighting enhanced power transmission within a compact design. In particular, the proposed C-shaped inner gear contributes to this.

Also, a drive system may be provided. The drive system can comprise an electric motor, a reduction gear box described above, a drive housing, a bottom bracket axle with a pedal shaft, a force measurement device and a control module. The outer gear can be attached to the drive housing, and the inner gear can be supported on the pedal shaft. The support of the inner gear on the pedal shaft is another feature that allows the drive system to be very compact without compromising power transmission.

In further aspects that refer to elements of providing two plain bearings, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described above and below.

In this context, a drive system for an electric bike may comprise an electric motor, a reduction gearbox with a gear unit and an output shaft, a bottom bracket axle with a pedal shaft, and a drive housing that at least partially accommodates these components. The reduction gearbox, in particular the gear unit, is preferably coupled to the electric motor, and the pedal shaft is coupled to the output shaft. Further, the inner gear may be supported on the bottom bracket axle, wherein a first and second plain bearing are located between the inner gear and the pedal shaft.

Supporting the inner gear on the bottom bracket axle with the inclusion of first and second plain bearings minimizes friction between the moving parts, enhancing the durability and longevity of the drive system. The presence of these bearings ensures smooth and reliable rotation, improving overall efficiency. Furthermore, this bearing arrangement allows the bottom bracket axle and pedal shaft to function as passive cooling surfaces, dissipating heat generated during operation. This effect is further enhanced by the fact that the pedal shaft is designed as a hollow shaft, promoting efficient heat dissipation.

According to the application, the inner gear can be supported or mounted on the bottom bracket axle, wherein other components can also be arranged between the inner gear and the bottom bracket axle. For example, the inner gear can be mounted in a first plain bearing on a hollow shaft, while the hollow shaft is mounted in a second plain bearing on the pedal shaft of the bottom bracket axle. A plain bearing can also be understood as a slide bearing, a journal bearing, a friction bearing or a sliding contact bearing in the sense of the application.

Further, the first plain bearing and the second plain bearing can intersect a same radial plane. The arrangement of the first and second plain bearings, which intersect in the same radial plane, ensures an even load distribution on the bearings, which can improve the stability and reliability of the drive system. The plain bearings are preferably arranged in parallel.

The inner gear may be supported on the output shaft by guiding the output shaft through the inner gear. In this respect, the inner gear may comprise a ring with external toothing and a support section connected thereto, with which the inner gear is supported on the output shaft. In particular, the support section preferably comprises both a radial part and an axial part, the axial part extending parallel to the ring and connecting to it via the radial part, wherein the axial part is supported on the output shaft. The support section connected to the inner gear ensures stability and alignment within the system. By supporting the inner gear on the output shaft, the system can handle higher loads and transmit greater forces, which is beneficial for applications requiring robust performance under demanding conditions.

Moreover, the output shaft may be coupled to the inner gear by a first freewheel. The inner gear may be coupled to the first freewheel via a coupling shaft. The inner gear and the first freewheel are positioned on the output shaft at the same radial level.

The output shaft may be designed as a hollow shaft and may be supported on the pedal shaft, wherein the first plain bearing is located between the inner gear and the output shaft. The pedal shaft may be guided through the output shaft, and the second plain bearing is preferably located between the output shaft and the pedal shaft.

Additionally, a second freewheel is provided between the pedal shaft and the output shaft for decoupling the pedal shaft from the output shaft.

In addition, the gear unit may comprise a pin ring which is coupled to a transmitter driving section of the electric motor.

In a preferred variant, the drive system may further comprise a measurement device arranged on the bottom bracket axle or a component connected thereto, configured to detect forces acting on the bottom bracket axle, and a control unit operatively connected to both the electric motor and the force measurement device to regulate motor output based on the detected forces.

In further aspects that refer to elements of a force measurement device having a meander shaped measuring region, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described above and below. In this context, a force measurement device may be provided for determining a radial force on a shaft in a drive system. The force measurement device may comprise a receiving sleeve for receiving a ring of a bearing, a fastening ring for attaching the force measurement device in a drive housing and a measuring region for receiving radial forces of the receiving sleeve which are transmitted from the ring of the bearing. The measuring region can connect the receiving sleeve to the fastening ring. Further the measuring region may be meander shaped, having radial aligned walls and axial aligned walls, wherein at least one strain sensor can be attached to a radial aligned wall.

This aspect leads to improved accurately measuring radial forces on a shaft in a drive system. The preferred force measurement device can receive and transmit radial forces from a bearing ring, incorporating strain sensors to accurately measure these forces. The measurement device is further designed to be attached to the drive housing and can be used in electric bike drive systems, providing precise measurements for monitoring and control purposes.

The meander-shaped measuring region with radially and axially aligned walls or surfaces allows radial forces to be decoupled from axial forces which leads to more accurate measurement results. In addition, the meander-shaped measuring region provides enhanced structural integrity, allowing for precise force transmission and measurement without compromising the device's durability. The integration of at least one strain sensor on a radially aligned wall enables the force measurement device to accurately detect and quantify radial forces exerted by the bearing ring, ensuring reliable monitoring of shaft load conditions.

Furthermore, the at least one strain sensor may comprise a strain gauge. The use of a strain gauge as the strain sensor ensures high sensitivity to minute deformations. Strain gauges are not only simple to implement, but also facilitate seamless integration of the measurement device with electronic data processing systems, ensuring efficient and accurate data collection. The receiving sleeve can be formed by an axial and radial aligned wall of the measuring region. This integrated design approach minimizes the mechanical complexity of the device. The structural unity of the receiving sleeve and measuring region enhances the direct transmission of forces to the strain sensor.

Moreover, the at least one strain sensor can be attached to the radial aligned wall forming the receiving sleeve. Attaching the strain sensor directly to the radial aligned wall forming the receiving sleeve ensures that force measurements are taken at the point of force application, leading to highly accurate and localized sensing capabilities. This arrangement minimizes the influence of extraneous forces and vibrations on the sensor readings, increasing the precision of the force measurements.

The measuring device can comprise four strain sensors which are arranged concentrically at an angle of 90° to each other at the radial aligned wall. The arrangement of four strain sensors at 90° intervals allows for the balanced detection of forces from all directions, providing a comprehensive assessment of the shaft's radial load. This concentric sensor configuration can detect any asymmetrical loading or misalignment of the shaft. The use of multiple sensors enhances the redundancy and reliability of the measurement device, ensuring that even if one sensor fails, the remaining sensors can continue to provide accurate force measurements.

It is clear to the skilled person that the reference angle is “essentially” 90° (or “essentially” a quarter turn of a circle), encompassing angles within a similar range. For instance, two strain sensors may be positioned on a circular circumference at angles ranging from 70 to 90° relative to each other. Moreover, it is acknowledged that the arrangement can include more than four strain sensors, such as 5, 6, 7, 8, and so on.

The fastening ring may comprise fastening areas in which fastening holes are provided. The inclusion of fastening areas with fastening holes in the fastening ring provides a secure and reliable means of attaching the measurement device to the drive housing, ensuring stability and precision in the measurement. The fastening ring's design facilitates easy assembly and disassembly, allowing for convenient maintenance and replacement of components without compromising the structural integrity of the electric bike's drive system.

Further, a drive system for an electric bike can be provided. The drive system may comprise an above-mentioned force measurement device, an electric motor, a reduction gear box, a bottom bracket axle, a drive housing and a control module. The bottom bracket axle comprises pedal shaft which can be supported in the drive housing with a left bottom bracket bearing and with a right bottom bracket bearing. Further, the left bottom bracket bearing can be supported in the drive housing via the force measurement device, wherein the force measurement device can be attached to the drive housing through the fastening ring. The receiving sleeve can receive an outer ring of the left bottom bracket bearing.

The support of the pedal shaft by both left and right bottom bracket bearings in the drive housing ensures a balanced distribution of forces. The integration of the measurement device into the support structure of the left bottom bracket bearing allows for accurate monitoring of radial force applied to the pedal shaft. The attachment of the measurement device through the fastening ring and the receiving sleeve's accommodation of the outer ring of the left bottom bracket bearing contribute to a compact and efficient design. The force measurement device can furthermore serve as a reference for the drive housing.

Additionally, the left bottom bracket bearing may be a ball bearing or a needle bearing. The use of a ball bearing or a needle bearing can enhance the durability and longevity.

A cover seal ring can be located between the force measurement device and the bottom bracket axle. The presence of a cover seal ring between the measurement device and the bottom bracket axle serves to protect the measurement electronics from contaminants such as dirt and moisture, thereby ensuring consistent and accurate data collection over time. The cover seal ring is preferably located between an axial aligned wall of the measurement device and the pedal shaft. Further, the right bottom bracket bearing may be a ball bearing. The use of a ball bearing for the right bottom bracket bearing ensures smooth and efficient rotation of the pedal shaft, contributing to a more comfortable and less strenuous cycling experience for the rider.

Preferably, the electric motor is operatively coupled to the reduction gear box, which has an output shaft. The pedal shaft can be guided through the hollow output shaft. Additionally, a second freewheel may be provided between the pedal shaft and the hollow output shaft for decoupling the pedal shaft from the output shaft. The integration of a second freewheel between the pedal shaft and the hollow output shaft allows for seamless transition between manual pedaling and electric motor assistance, enhancing the user experience by providing smooth operation without mechanical interference. The configuration wherein the pedal shaft is guided through the hollow output shaft optimizes the spatial arrangement of the components, leading to a compact and efficient design. The decoupling feature provided by the second freewheel ensures that the user can pedal without resistance when the electric motor is not engaged.

The control module may comprise a printed circuit board, a microprocessor, a memory, an input interface, an output interface, analogue-to-digital converter and/or a digital-to- analogue converter. The inclusion of a control module with a microprocessor and memory enables intelligent control of the system, allowing for programmable operation modes and adaptability to different riding conditions or user preferences. The presence of both Analogue-to-digital and Digital-to-analogue converters in the control module facilitates the integration of various sensors and actuators. The control module's input and output interfaces provide the means for connectivity and expandability, offering the potential for future upgrades or the incorporation of additional features such as remote diagnostics or user interface enhancements.

In a variant, the printed circuit board may be attached to the drive housing and covered by the force measurement device. Attaching the printed circuit board to the drive housing ensures that the electronic components are securely housed and protected from external environmental factors, which can improve the durability and reliability of the system. The force measurement device may be configured to acquire a radial force applied on the pedal shaft and to transmit a corresponding signal to the control module, and the control module may be configured to analyze the signal received from the force measurement device and to control the electric motor, the electric motor being used to generate a force to support a cyclist using a bike comprising the drive system.

In further aspects that refer to elements of a force measurement device supported on the bottom bracket axle by a needle ring, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described above and below.

In this context, a drive system for an electric bike may comprise a force measurement device, an electric motor, a reduction gear box, a bottom bracket axle, a drive housing, and a control module. The force measurement device can comprise a receiving sleeve for receiving a ring of a bearing. The bottom bracket axle can comprise a pedal shaft which is supported in the drive housing with a left bottom bracket bearing and with a right bottom bracket bearing. In this regard, the left bottom bracket bearing can be supported in the drive housing via the force measurement device. The receiving sleeve may receive an outer ring of the left bottom bracket bearing, wherein the left bottom bracket bearing is a needle bearing.

Integrating the force measurement device directly with the left bottom bracket bearing allows for precise measurement of the rider's exerted force, leading to more accurate motor assistance control. This setup utilizes a needle bearing and receiving sleeve to support the bottom bracket axle, alongside a fastening ring and measuring area for exact force measurement. Consequently, the drive system offers precise force measurement, leading to accurate control and performance of the electric bike. This approach also minimizes hysteresis at the force measurement device compared to other bearings, which is for example useful for systems using a single freewheel. Further, the needle bearing may be press-fitted onto the pedal shaft, ensuring a play-free engagement. Utilizing a press-fitted needle bearing in the pedal shaft enhances stability and precision in force transmission. This configuration allows for more accurate force measurement, improving motor assistance control and system performance. Moreover, it reduces also hysteresis effects in the force measurement device and contributes to the drive system's reliability.

The force measuring device may comprise a fastening ring for attaching the force measurement device in the drive housing, and a measuring region for receiving radial forces of the receiving sleeve which are transmitted from the ring of the bearing. The measuring region connects the receiving sleeve to the fastening ring, The fastening ring provides a robust attachment of the force measurement device within the drive housing, which contributes to the durability and maintenance of calibration over time. The measuring region's design to receive radial forces allows for accurate force readings. The direct connection between the receiving sleeve and the fastening ring via the measuring region ensures that the force measurement device is less susceptible to external influences, such as vibrations or misalignments, which could otherwise affect measurement accuracy.

In further aspects that refer to elements of a circular flange in the drive housing, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described above and below.

In this respect, a drive system for an electric bike may comprise an electric motor, a reduction gearbox with a gear unit and an output shaft, a bottom bracket axle with a pedal shaft, and a drive housing that at least partially accommodates these components. The reduction gearbox, in particular the gear unit, is preferably coupled to the electric motor, and the pedal shaft is coupled to the output shaft.

The drive housing may comprise a circular flange extending radially outward from the drive housing, wherein the circular flange is preferably configured to engage with a complementary circular holding section of a drive system mounting bracket on the electric bike in such a way that the drive housing is secured in the axial direction.

The primary function of the circular flange is to define the axial position of the drive system within the bike frame (acting as an axial stop). Maintaining an accurate axial position is important for ensuring the correct chainline by setting the appropriate distance between the chainring and the bike frame. Additionally, compared to a drive housing without a flange, the inclusion of the flange reduces maximum stress by approximately 30%, significantly improving durability and reliability.

The term "flange" in this context may refer to a radial extension or collar-like structure on the drive housing, designed to provide a defined axial stop within the bike frame. It can take the form of a circular flange, collar, or protruding ring. In mechanical terms, a flange (or collar) serves as a mechanical interface that helps secure the housing, distribute loads, and optimize the structural integrity of the assembly

Preferably, the circular flange is positioned near an axial end section of the housing.

The term "near" in this context means preferably that the circular flange does not have to be positioned exactly at the axial end of the housing but should be within a specific range of it. This could imply a distance of less than 10 mm from the axial end section, preferably between 0 and 5 mm. The term allows for some design flexibility, ensuring that the flange is functionally close to the end section without being strictly limited to the very edge of the housing. On the other hand, the term "end section" may refer to the final portion of the housing along its longitudinal axis, typically extending over a defined length of about 5% to 20% of the total housing length.

Moreover, the drive system may further comprise a force measurement device coupled to the pedal shaft for determining a radial force on the pedal shaft. In this respect, the force measurement device may be arranged within a housing cover of the drive housing, and the flange may be located on the housing cover and/or on the opposite side of the drive housing, where the housing cover is absent. In a preferred embodiment, the flange is located exclusively on the housing cover, which simplifies installation. Additionally, having the flange on only one side provides the advantage of optimized axial fixation while allowing for easier assembly and disassembly of the drive system.

The circular flange may have a diameter in the range of 55 to 60 mm, preferably 58 mm. These values ensure a balanced combination of structural stability, compatibility with standard mounting interfaces, and efficient load distribution within the drive system.

The electric bike preferably comprises a bike frame, and wherein a clamping device and a support interface on the bike frame together form the holding section, wherein the clamping device is detachably mountable to the bike frame. The detachable clamping device allows for easy installation and maintenance.

Further, the clamping device and the bike frame may comprise means for a screw connection to form the holding section and secure the drive system to the electric bike. The clamping device may include through-holes, threaded inserts, or integrated mounting flanges designed to accommodate bolts or screws for a secure attachment to the bike frame. Correspondingly, the bike frame may feature threaded bores, welded nuts, or reinforced mounting plates to receive the screws, ensuring a stable, detachable, and reliable connection that effectively secures the drive system in place.

The flange and a shoulder in the outer contour of the drive housing may form a circumferential groove in the drive housing, wherein both the clamping device and the support interface may include a projection that can engage with the groove, thereby establishing a form-fit connection in the axial direction. By engaging their respective projections within the groove, axial displacement of the drive system is effectively prevented, while ensuring precise positioning and stable fixation within the bike frame.

The shoulder in the outer contour of the drive housing preferably acts as a radial step that defines part of the circumferential groove and provides a supporting surface for engagement elements. The circumferential groove preferably serves as a guiding and locking feature, allowing projections from the clamping device and support interface to interlock securely and prevent axial displacement.

The projections on the clamping device and support interface are preferably engagement elements that fit into the circumferential groove, ensuring a form-fit connection and stabilizing the drive system within the bike frame.

The groove may vary in width along its circumference, wherein the groove can have a greater width in the circumferential segment where the clamping device engages than in the segment where the support interface engages when the drive system is mounted on the drive system mounting bracket of the electric bike. This variation in groove width may allow for differentiated engagement of the clamping device and support interface, optimizing fixation while enabling controlled assembly tolerances.

A circumferential segment in this context refers to a specific angular section of the groove along the perimeter of the drive housing where either the clamping device or the support interface engages.

The circular flange may include a flattened section at a specific location, allowing for the formation of a borehole in the housing behind it. This design can facilitate mounting options, cable routing, or ventilation openings without compromising the structural integrity of the flange. lin a preferred embodiment, an electric bike may comprise a bike frame with a drive system mounting bracket, and a drive system according to any of the preceding embodiments. The drive housing of the drive system can be secured to the drive system mounting bracket via a holding section, which may include a clamping device and a support interface, ensuring a stable and detachable connection. In further aspects that refer to elements of a hybrid gear construction, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described above and below.

In this context, a reduction gear box may comprise a gear unit and an output shaft. The gear unit may have a rotationally symmetric structure, including gears and/or transmission elements that return to their original position after a full rotation around a main axis of the gearbox. Additionally, the gear unit is coupled to the output shaft, and at least one gear of the gear unit is made from a composite material comprising steel and plastic. This composite material combines steel for stiffness and durability with plastic for lightweight flexibility and thermal resilience. The combination achieves high torque density while minimizing thermal expansion, ensuring consistent performance. The integration of steel and plastic in critical gear components provides a balance between rigidity and weight, with steel offering the necessary stiffness to handle high torque loads, while plastic reduces weight and compensates for thermal expansion.

The at least one gear may comprise an interaction surface that is operatively coupled with another gear in the gear unit, the interaction surface being made of plastic. The interaction surface can be considered an interaction layer or an overlay layer. For example, the at least one gear comprises a steel core and a plastic overlay layer. This plastic layer may reduce friction, dampens noise, and enhances wear resistance.

The plastic overlay layer may have a thickness of 0.1 - 1.5 mm, preferably of 0.2 - 1.2 mm. These values provide an optimal balance between mechanical strength, weight reduction, and thermal stability.

The plastic may be a high-performance polymer, preferably PEEK (Polyetheretherketone). PEEK offers high wear resistance, low friction, and excellent thermal and chemical stability, making it ideal for high-load and high-temperature applications. Its exceptional mechanical strength and dimensional stability ensure longterm durability, even under continuous stress and harsh environmental conditions. Preferably, the gear unit may comprise an inner gear with external toothing and an outer gear with internal toothing. The gear unit may further comprise a pin ring located between the inner gear and the outer gear. In this respect, the pin ring may have a surface facing the inner gear, the surface being provided with a plastic layer, and wherein the inner gear is made of steel. Conversely, the pin ring may have a surface facing the outer gear, the surface being made of steel, and wherein the outer gear is provided with a plastic layer. This strategic material distribution optimizes load distribution, wear resistance, and noise reduction, ensuring efficient power transmission while minimizing weight and thermal expansion effects.

In some embodiments, the outer gear may be machined into the housing, and a plastic layer is applied to its surface. Machining the outer gear directly into the housing eliminates the need for a separate gear component, reduces assembly complexity, improves alignment precision, enhances structural rigidity, and enables a more compact and lightweight design while ensuring efficient power transmission. In particular, the teeth of the gear are directly milled into the housing.

Furthermore, a drive system can be provided, comprising an electric motor, a reduction gearbox according to the embodiments described above, a drive housing, a bottom bracket axle with a pedal shaft, a force measurement device, and a control module. The gear unit is coupled to the motor, while the output shaft is connected to the pedal shaft to ensure efficient power transmission. The control module is operatively linked to both the force measurement device and the motor, enabling precise regulation of motor assistance. The force measurement device is coupled to the pedal shaft, allowing it to detect applied forces and transmit the corresponding data to the control module. Based on these measurements, the control module dynamically adjusts the motor output, optimizing performance and support for the cyclist.

In further aspects that refer to elements of a modular gearbox system, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described above and below. In this context, a modular reduction gearbox may comprise a gear unit and an output shaft. The gear unit may have a rotationally symmetric structure, including gears and/or transmission elements that return to their original position after a full rotation around a main axis of the gearbox. The gear unit may be designed to allow modular exchange of specific components to achieve different gear ratios by replacing only two components.

For example, the gearbox can be configured with a reduction ratio of 1 :17.5 in a first configuration and 1 :36 in a second configuration by replacing just two components. This modular approach enhances scalability and cost-efficiency, enabling a single design platform to accommodate multiple applications. Additionally, the gearbox is optimized for quick adaptation to torque and precision requirements, making it particularly suitable for use in robotics and e-mobility.

In some embodiments, the gear unit may comprise an inner gear with external toothing, an outer gear with internal toothing, and a pin ring positioned between them. The pin ring can have a surface facing the inner gear, which is preferably provided with a plastic layer forming a toothed surface. The inner gear is made of steel, while the plastic layer can be an exchangeable component, allowing for easy replacement. Additionally, the inner gear with external toothing may also be an exchangeable component, enabling modular adjustments to optimize performance and extend the gearbox’s service life.

Furthermore, a drive system can be provided, comprising an electric motor, a reduction gearbox according to the embodiments described above, a drive housing, a bottom bracket axle with a pedal shaft, a force measurement device, and a control module. The gear unit is coupled to the motor, while the output shaft is connected to the pedal shaft to ensure efficient power transmission. The control module is operatively linked to both the force measurement device and the motor, enabling precise regulation of motor assistance. The force measurement device is coupled to the pedal shaft, allowing it to detect applied forces and transmit the corresponding data to the control module. Based on these measurements, the control module dynamically adjusts the motor output, optimizing performance and support for the cyclist. In further aspects that refer to elements of backlash-free gears, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described above and below.

In this regard, a reduction gear box may comprise a gear unit and an output shaft. The gear unit may have a rotationally symmetric structure, including gears and/or transmission elements that return to their original position after a full rotation around a main axis of the gearbox. The gear unit is preferably coupled to the output shaft, and manufactured using advanced manufacturing techniques to achieve minimal backlash. Designed for precision applications, particularly in robotics and automation, the gear tolerances are optimized to maintain consistent performance under varying temperature conditions, enhancing operational stability and durability.

At least one gear of the gear unit may be designed as a hybrid component, comprising a steel core with a plastic layer. In other words, the gear is made of a composite material. In this respect, the plastic layer may be precision-milled to an exact thickness between 0.5 mm and 1.2 mm, ensuring minimal manufacturing tolerances. This precise layering enhances gear meshing accuracy, reduces backlash, and improves overall efficiency and durability in high-performance applications. Further, the combination of steel and plastic provides thermal stability, ensuring consistent performance under varying temperature conditions. The differing thermal expansion coefficients of the steel core and plastic layer maintain constant backlash clearance, preventing fluctuations due to temperature changes.

The precisely fitted plastic layer in a gear profile may improve torque transmission while maintaining minimal play. A gear profile may refer to the geometric shape of the tooth flanks of a gear, defining how the teeth engage with one another to ensure efficient power transmission. It includes parameters such as module, tooth height, tooth shape, pressure angle, and involute contour, all of which influence the mechanical performance, efficiency, and noise generation of the gearbox. Precisely manufactured gear profiles minimize friction, wear, and energy losses, enabling smooth, backlash-free power transmission and improved durability in high-performance applications. The gear tolerances are preferably configured to ensure consistent performance under varying temperature conditions.

It is understood that a drive system may also be provided, incorporating the manufactured reduction gearbox.

In further aspects that refer to elements of an enhanced hollow shaft, various advantageous effects can be seen. These elements can be combined with the other elements in the present application as described above and below.

In this context, a drive system may comprise an electric motor with a stator and a rotor, and a reduction gearbox with a gear unit. The gear unit may have a rotationally symmetric structure, including gears and/or transmission elements that return to their original position after a full rotation around the main axis of the gearbox. The stator, the rotor, and the gear unit may be arranged coaxially. The rotor may be designed as a hollow shaft and may comprise a transmitter driving section. The transmitter driving section may include a circumferential groove defined by two shoulders, each shoulder being supported on a rolling bearing on a shaft. The rolling bearings, on which each shoulder is supported, are preferably ball bearings.

The strategic placement of the bearings allows the shaft of the drive system to have a larger diameter while maintaining structural integrity without compromising compactness. The shaft can be either a pedal shaft of a bottom bracket axle for an electric bike drive system or an output shaft for a robotic drive system. If the shaft is a hollow shaft, its enlarged diameter facilitates internal cable routing, reducing clutter and improving motor integration, for example, in robotic arms.

An outer double-row rolling bearing may be positioned in the groove, on which the gear unit is supported. The outer double-row rolling bearing can be a double-row ball bearing. A further embodiment combines one or more elements of the aspect relating to the electric motor with magnets on a radially outer rotor surface described above with one or more elements of the aspect relating to the rotor support ring described above.

A further embodiment combines one or more elements of the aspect relating to the electric motor with magnets on a radially outer rotor surface described above with one or more elements of the aspect relating to the gear unit with a C-shaped pin ring described above.

A further embodiment combines one or more elements of the aspect relating to the electric motor with magnets on a radially outer rotor surface described above with one or more elements of the aspect relating to the outer double-row rolling bearing described above.

A further embodiment combines one or more elements of the aspect relating to the electric motor with magnets on a radially outer rotor surface described above with one or more elements of the aspect relating to the inner double-row rolling bearing described above.

A further embodiment combines one or more elements of the aspect relating to the electric motor with magnets on a radially outer rotor surface described above with one or more elements of the aspect relating to the inner gear with axial teeth described above.

A further embodiment combines one or more elements of the aspect relating to the electric motor with magnets on a radially outer rotor surface described above with one or more elements of the aspect relating to two plain bearings described above.

A further embodiment combines one or more elements of the aspect relating to the electric motor with magnets on a radially outer rotor surface described above with one or more elements of the aspect relating to the force measurement device having a meander shaped measuring region described above. A further embodiment combines one or more elements of the aspect relating to the electric motor with magnets on a radially outer rotor surface described above with one or more elements of the aspect relating to the force measurement device supported on the bottom bracket axle by a needle ring described above.

A further embodiment combines one or more elements of the aspect relating to the electric motor with magnets on a radially outer rotor surface described above with one or more elements of the aspect relating to the circular flange in the drive housing described above.

A further embodiment combines one or more elements of the aspect relating to the electric motor with magnets on a radially outer rotor surface described above with one or more elements of the aspect relating to the hybrid gear construction described above.

A further embodiment combines one or more elements of the aspect relating to the electric motor with magnets on a radially outer rotor surface described above with one or more elements of the aspect relating to the modular gearbox system described above.

A further embodiment combines one or more elements of the aspect relating to the electric motor with magnets on a radially outer rotor surface described above with one or more elements of the aspect relating to the backlash-free gears described above.

A further embodiment combines one or more elements of the aspect relating to the electric motor with magnets on a radially outer rotor surface described above with one or more elements of the aspect relating to the enhanced hollow shaft described above.

A further embodiment combines one or more elements of the aspect relating to the rotor support ring described above with one or more elements of the aspect relating to the gear unit with a C-shaped pin ring described above. A further embodiment combines one or more elements of the aspect relating to the rotor support ring described above with one or more elements of the aspect relating to the outer double-row rolling bearing described above.

A further embodiment combines one or more elements of the aspect relating to the rotor support ring described above with one or more elements of the aspect relating to the inner double-row rolling bearing described above.

A further embodiment combines one or more elements of the aspect relating to the rotor support ring described above with one or more elements of the aspect relating to the inner gear with axial teeth described above.

A further embodiment combines one or more elements of the aspect relating to the rotor support ring described above with one or more elements of the aspect relating to two plain bearings described above.

A further embodiment combines one or more elements of the aspect relating to the rotor support ring described above with one or more elements of the aspect relating to the force measurement device having a meander shaped measuring region described above.

A further embodiment combines one or more elements of the aspect relating to the rotor support ring described above with one or more elements of the aspect relating to the force measurement device supported on the bottom bracket axle by a needle ring described above.

A further embodiment combines one or more elements of the aspect relating to the rotor support ring described above with one or more elements of the aspect relating to the circular flange in the drive housing described above.

A further embodiment combines one or more elements of the aspect relating to the rotor support ring described above with one or more elements of the aspect relating to the hybrid gear construction described above. A further embodiment combines one or more elements of the aspect relating to the rotor support ring described above with one or more elements of the aspect relating to the modular gearbox system described above.

A further embodiment combines one or more elements of the aspect relating to the rotor support ring described above with one or more elements of the aspect relating to the backlash-free gears described above.

A further embodiment combines one or more elements of the aspect relating to the rotor support ring described above with one or more elements of the aspect relating to the enhanced hollow shaft described above.

A further embodiment combines one or more elements of the aspect relating to the gear unit with a C-shaped pin ring described above with one or more elements of the aspect relating to the outer double-row rolling bearing described above.

A further embodiment combines one or more elements of the aspect relating to the gear unit with a C-shaped pin ring described above with one or more elements of the aspect relating to the inner double-row rolling bearing described above.

A further embodiment combines one or more elements of the aspect relating to the gear unit with a C-shaped pin ring described above with one or more elements of the aspect relating to the inner gear with axial teeth described above.

A further embodiment combines one or more elements of the aspect relating to the gear unit with a C-shaped pin ring described above with one or more elements of the aspect relating to two plain bearings described above.

A further embodiment combines one or more elements of the aspect relating to the gear unit with a C-shaped pin ring described above with one or more elements of the aspect relating to the force measurement device having a meander shaped measuring region described above.

A further embodiment combines one or more elements of the aspect relating to the gear unit with a C-shaped pin ring described above with one or more elements of the aspect relating to the force measurement device supported on the bottom bracket axle by a needle ring described above.

A further embodiment combines one or more elements of the aspect relating to the gear unit with a C-shaped pin ring described above with one or more elements of the aspect relating to the circular flange in the drive housing described above.

A further embodiment combines one or more elements of the aspect relating to the gear unit with a C-shaped pin ring described above with one or more elements of the aspect relating to the hybrid gear construction described above.

A further embodiment combines one or more elements of the aspect relating to the gear unit with a C-shaped pin ring described above with one or more elements of the aspect relating to the modular gearbox system described above.

A further embodiment combines one or more elements of the aspect relating to the gear unit with a C-shaped pin ring described above with one or more elements of the aspect relating to the backlash-free gears described above.

A further embodiment combines one or more elements of the aspect relating to the gear unit with a C-shaped pin ring described above with one or more elements of the aspect relating to the enhanced hollow shaft described above.

A further embodiment combines one or more elements of the aspect relating to the outer double-row rolling bearing described above with one or more elements of the aspect relating to the inner double-row rolling bearing described above. A further embodiment combines one or more elements of the aspect relating to the outer double-row rolling bearing described above with one or more elements of the aspect relating to the inner gear with axial teeth described above.

A further embodiment combines one or more elements of the aspect relating to the outer double-row rolling bearing described above with one or more elements of the aspect relating to two plain bearings described above.

A further embodiment combines one or more elements of the aspect relating to the outer double-row rolling bearing described above with one or more elements of the aspect relating to the force measurement device having a meander shaped measuring region described above.

A further embodiment combines one or more elements of the aspect relating to the outer double-row rolling bearing described above with one or more elements of the aspect relating to the force measurement device supported on the bottom bracket axle by a needle ring described above.

A further embodiment combines one or more elements of the aspect relating to the outer double-row rolling bearing described above with one or more elements of the aspect relating to the circular flange in the drive housing described above.

A further embodiment combines one or more elements of the aspect relating to the outer double-row rolling bearing described above with one or more elements of the aspect relating to the hybrid gear construction described above.

A further embodiment combines one or more elements of the aspect relating to the outer double-row rolling bearing described above with one or more elements of the aspect relating to the modular gearbox system described above. A further embodiment combines one or more elements of the aspect relating to the outer double-row rolling bearing described above with one or more elements of the aspect relating to the backlash-free gears described above.

A further embodiment combines one or more elements of the aspect relating to the outer double-row rolling bearing described above with one or more elements of the aspect relating to the enhanced hollow shaft described above.

A further embodiment combines one or more elements of the aspect relating to the inner double-row rolling bearing described above with one or more elements of the aspect relating to the inner gear with axial teeth described above.

A further embodiment combines one or more elements of the aspect relating to the inner double-row rolling bearing described above with one or more elements of the aspect relating to two plain bearings described above.

A further embodiment combines one or more elements of the aspect relating to the inner double-row rolling bearing described above with one or more elements of the aspect relating to the force measurement device having a meander shaped measuring region described above.

A further embodiment combines one or more elements of the aspect relating to the inner double-row rolling bearing described above with one or more elements of the aspect relating to the force measurement device supported on the bottom bracket axle by a needle ring described above.

A further embodiment combines one or more elements of the aspect relating to the inner double-row rolling bearing described above with one or more elements of the aspect relating to the circular flange in the drive housing described above. A further embodiment combines one or more elements of the aspect relating to the inner double-row rolling bearing described above with one or more elements of the aspect relating to the hybrid gear construction described above.

A further embodiment combines one or more elements of the aspect relating to the inner double-row rolling bearing described above with one or more elements of the aspect relating to the modular gearbox system described above.

A further embodiment combines one or more elements of the aspect relating to the inner double-row rolling bearing described above with one or more elements of the aspect relating to the backlash-free gears described above.

A further embodiment combines one or more elements of the aspect relating to the inner double-row rolling bearing described above with one or more elements of the aspect relating to the enhanced hollow shaft described above.

A further embodiment combines one or more elements of the aspect relating to the inner gear with axial teeth described above with one or more elements of the aspect relating to two plain bearings described above.

A further embodiment combines one or more elements of the aspect relating to the inner gear with axial teeth described above with one or more elements of the aspect relating to the force measurement device having a meander shaped measuring region described above.

A further embodiment combines one or more elements of the aspect relating to the inner gear with axial teeth described above with one or more elements of the aspect relating to the force measurement device supported on the bottom bracket axle by a needle ring described above. A further embodiment combines one or more elements of the aspect relating to the inner gear with axial teeth described above with one or more elements of the aspect relating to the circular flange in the drive housing described above.

A further embodiment combines one or more elements of the aspect relating to the inner gear with axial teeth described above with one or more elements of the aspect relating to the hybrid gear construction described above.

A further embodiment combines one or more elements of the aspect relating to the inner gear with axial teeth described above with one or more elements of the aspect relating to the modular gearbox system described above.

A further embodiment combines one or more elements of the aspect relating to the inner gear with axial teeth described above with one or more elements of the aspect relating to the backlash-free gears described above.

A further embodiment combines one or more elements of the aspect relating to the inner gear with axial teeth described above with one or more elements of the aspect relating to the enhanced hollow shaft described above.

A further embodiment combines one or more elements of the aspect relating to two plain bearings described above with one or more elements of the aspect relating to the force measurement device having a meander shaped measuring region described above.

A further embodiment combines one or more elements of the aspect relating to two plain bearings described above with one or more elements of the aspect relating to the force measurement device supported on the bottom bracket axle by a needle ring described above.

A further embodiment combines one or more elements of the aspect relating to two plain bearings described above with one or more elements of the aspect relating to the circular flange in the drive housing described above. A further embodiment combines one or more elements of the aspect relating to two plain bearings described above with one or more elements of the aspect relating to the hybrid gear construction described above.

A further embodiment combines one or more elements of the aspect relating to two plain bearings described above with one or more elements of the aspect relating to the modular gearbox system described above.

A further embodiment combines one or more elements of the aspect relating to two plain bearings described above with one or more elements of the aspect relating to the backlash-free gears described above.

A further embodiment combines one or more elements of the aspect relating to two plain bearings described above with one or more elements of the aspect relating to the enhanced hollow shaft described above.

A further embodiment combines one or more elements of the aspect relating to the force measurement device having a meander shaped measuring region described above with one or more elements of the aspect relating to the force measurement device supported on the bottom bracket axle by a needle ring described above.

A further embodiment combines one or more elements of the aspect relating to the force measurement device having a meander shaped measuring region described above with one or more elements of the aspect relating to the circular flange in the drive housing described above.

A further embodiment combines one or more elements of the aspect relating to the force measurement device having a meander shaped measuring region described above with one or more elements of the aspect relating to the hybrid gear construction described above. A further embodiment combines one or more elements of the aspect relating to the force measurement device having a meander shaped measuring region described above with one or more elements of the aspect relating to the modular gearbox system described above.

A further embodiment combines one or more elements of the aspect relating to the force measurement device having a meander shaped measuring region described above with one or more elements of the aspect relating to the backlash-free gears described above.

A further embodiment combines one or more elements of the aspect relating to the force measurement device having a meander shaped measuring region described above with one or more elements of the aspect relating to the enhanced hollow shaft described above.

A further embodiment combines one or more elements of the aspect relating to the circular flange in the drive housing described above with one or more elements of the aspect relating to the hybrid gear construction described above.

A further embodiment combines one or more elements of the aspect relating to the circular flange in the drive housing described above with one or more elements of the aspect relating to the modular gearbox system described above.

A further embodiment combines one or more elements of the aspect relating to the circular flange in the drive housing described above with one or more elements of the aspect relating to the backlash-free gears described above.

A further embodiment combines one or more elements of the aspect relating to the circular flange in the drive housing described above with one or more elements of the aspect relating to the enhanced hollow shaft described above. A further embodiment combines one or more elements of the aspect relating to the hybrid gear construction described above with one or more elements of the aspect relating to the modular gearbox system described above.

A further embodiment combines one or more elements of the aspect relating to the hybrid gear construction described above with one or more elements of the aspect relating to the backlash-free gears described above.

A further embodiment combines one or more elements of the aspect relating to the hybrid gear construction described above with one or more elements of the aspect relating to the enhanced hollow shaft described above.

A further embodiment combines one or more elements of the aspect relating to the modular gearbox system described above with one or more elements of the aspect relating to the backlash-free gears described above.

A further embodiment combines one or more elements of the aspect relating to the modular gearbox system described above with one or more elements of the aspect relating to the enhanced hollow shaft described above.

A further embodiment combines one or more elements of the aspect relating to the backlash-free gears described above with one or more elements of the aspect relating to the enhanced hollow shaft described above.

The present disclosure is illustrated by way of example and not limited in the accompanying figures in which like reference numerals indicate similar elements. Embodiments of the application will now be described with reference to the attached drawings:

Fig. 1 shows an embodiment of the drive system, illustrating a section that represents in particular the electric motor. Fig. 2 shows an embodiment of the drive system, wherein the entire drive system is shown in cross-section.

Fig. 3 shows an embodiment of the drive system, illustrating a section that represents in particular the reduction gear box.

Fig. 4 shows an embodiment of the drive system, illustrating a section that represents in particular the bottom bracket axle.

Fig. 5 shows an embodiment of the drive system, illustrating a section that represents in particular the rotor support.

Fig. 6 shows an embodiment of the pin ring.

Fig. 7 shows an embodiment of the drive system, illustrating a section that represents in particular the gear unit and the rotor.

Fig. 8 shows a detailed lateral view of the interaction between the pin ring, the inner gear, and the outer gear.

Fig. 9 shows an embodiment of the drive system, wherein the entire drive system is shown in cross-section.

Fig. 10 shows an embodiment of the drive system, wherein the entire drive system is shown in cross-section.

Fig. 11 shows an embodiment of the drive system, illustrating a section that represents in particular the force measurement device.

Fig. 12 shows an embodiment of the drive system, illustrating a section that represents in particular the force measurement device. Fig. 13 shows an embodiment of the force measurement device.

Fig. 14 shows an embodiment of the force measurement device.

Fig. 15 shows schematically the directions and pathways in which forces are transmitted within an embodiment of the drive system to generate an output that drives a bike.

Fig. 16 shows an embodiment of the drive system, illustrating how it is mounted within the bike frame.

Fig. 17 shows a section of a bike frame with a drive system mounting bracket.

Fig. 18 shows a sectional view of an embodiment of the drive system, highlighting a flattened section in relation to a flange on the housing.

Fig. 19 shows an embodiment of the drive system, illustrating a section that represents in particular the gear unit.

Fig. 20 shows an embodiment of the drive system, wherein the entire drive system is shown in cross-section.

Fig. 1 shows a part of an embodiment of the electric bike drive system 1 , the part representing in particular an embodiment of the electric motor 2 housed in the motor housing half 19. The drive system 1 comprises a reduction gear box 54 wherein partial elements of the reduction gear box 54 are also shown in Fig. 1 , especially a gear unit 67 which comprises a pin ring 102, outer gear 8 and an inner gear 7.

The electric motor 2 comprises a stator 3 and a rotor 5. During operation, torque is generated on the rotor 5 by electromagnetic force wherein the electric motor is powered by a battery. The rotor 5 includes a rotor shaft 26 having a transmitter driving section 55 and a magnet holding section 28. The magnet holding section 28 comprises at least one magnet 25 disposed on a radially outer surface of the rotor shaft 26. The rotor shaft 26 is formed as a hollow shaft, so that the rotor shaft 26 can be mounted around a pedal shaft 35 or a bottom bracket axle 6 (not shown in Fig. 1).

The magnet holding section 28 is positioned inside the stator 3, while the transmitter driving section 55 is positioned outside the stator 3. The transmitter driving section 55 is preferably formed as an eccentric section. The eccentric section, i.e. the transmitter driving section 55, preferably has a smaller diameter than the magnet holding section 28 and also does not extend as long as the magnet holding section 28 in the axial direction. The larger the surface area of the magnet holding section 28 covered by magnets 25 in the stator 3, the more efficient the motor is and the better an electromagnetic force can be converted into rotary motion. Furthermore, the eccentric section, i.e. the transmitter driving section 55, and the magnetic holding section 28 are preferably connected by a tapered section of the rotor shaft 26 due to the different diameters.

In addition, a plurality of magnets 25 may be concentrically mounted on the outer surface of the rotor shaft 26. The stator 3 is preferably equipped with three coils 21 and connected to a three-phase inverter.

The eccentric section, i.e. the transmitter driving section 55, is supported radially outwardly in an outer double-row ball bearing 33 and radially inwardly in an inner double-row ball bearing 34. The eccentric section, i.e. the transmitter driving section 55, makes it possible to convert the rotary motion of the rotor shaft 26 into a radial force/radial motion and to press the outer double-row ball bearing 33 radially outwards, which in turn transmits the radial force/motion to a pin ring 102.

The pin ring 102 is formed in cross-section like a letter "C". Accordingly, the pin ring 102 comprises a radially inner leg 101 of the "C" and a radially outer leg 103 of the "C". The radially outer leg 103 has teeth on both surface/sides, while the radially inner leg 101 has no teeth at all. The pin ring 102 accommodates or holds an inner gear 7 between the two legs 101 , 102. The inner gear 7 can rest on the radially inner leg 101 , which has no teeth on its contact surface with the inner gear 7. On the side/surface of the inner gear 7 which does not contact the inner leg 101 , the inner gear 7 also comprises teeth.

During operation, the radially inner leg 101 of the pin ring 102, due to their rigid connection, presses the double-toothed radially outer leg 103 of the pin ring 102 against the outer gear 8, which includes internal toothing, causing the teeth to mesh at one location or position. At another position of the pin ring 102, the inner leg 101 of the pin ring 102 is pulled or pressed inward, as the transmitter driving section is designed eccentrically. To enable this, the bearings - the outer double-row ball bearing 33 and the radially inward inner double-row ball bearing 34 - are designed to be flexible, allowing the radially outer leg 103 to press against the inner gear 7, so that the teeth of the inner gear 7 and the outer leg 103 mesh.

Furthermore, the rotor shaft 26 is supported by a rotor support ring 27 which axially secures the outer ring of a rotor bearing 29. The rotor bearing 29 is preferably designed as a ball bearing.

The described components and their arrangements provide the structural basis for the functioning of the electric motor 2 within the electric bike's drive system 1. Features such as the positioning of the magnet holding section 28 and the design of the transmitter driving section 55 are important for the operational aspects of the preferred drive system 1.

Fig. 2 illustrates an embodiment of the drive system 1 for an electric bike, wherein the entire drive system 1 is shown in cross-section. The preferred drive system 1 comprises an electric motor 2, a bottom bracket axle 6, a reduction gear box 54, and a force measurement device 13 housed within a drive housing 17. The electric motor 2 corresponds to the features mentioned in Fig. 1 , including a stator 3 that surrounds the rotor 5, and the rotor 5 is supported within the drive housing 17 by a rotor support ring 27 and a rotor bearing 29. Accordingly, reference is made to the description of Fig. 1 . The electric motor 2 is configured to generate an electromagnetic force that causes the rotor shaft 26 to rotate, wherein the transmitter driving section 55, as an eccentric section, can convert the rotational movement of the rotor shaft 26 into a radial movement or radial force.

An outer double-row ball bearing 33 is in contact with the transmitter driving section 55 of the electric motor 2 and, in operation, the radial force/ motion is applied from transmitter driving section 55 to the outer double-row ball bearing 33.

The pin-ring 102 with a C-shaped cross section already mentioned in Fig.1 is part of the reduction gear box 54 and, in particular of the gear unit 67, engaging with an inner gear 7 and an outer gear 8. The radially outer leg 103 of the pin-ring 102 has teeth on both sides, while the radially inner leg 101 is not toothed. The radially inner surface of the inner gear 7 is disposed on the radially inner leg 101 of the pin-ring 102.

The outer double-row ball bearing 33 is furthermore in contact with the radially inner leg 101 of the pin-ring 102. In operation, due to the radial motion/force, the outer doublerow ball bearing 33 presses the radially inner leg 101 of the pin-ring 102. Since the radially inner leg 101 of the pin ring 102 is connected via a stiff disc to the radially outer leg 103, the radially outer leg 103 is pressed against the outer gear 8 with internal teeth. As a result, the teeth interlock. Simultaneously, at another position of the pin ring 102, both the radially inner leg 101 and the radially outer leg 103 are pulled inward, as the rotor 5 features a driving eccentric section. This causes the teeth of the radially outer leg 103 to mesh with the teeth of the inner gear at the other location. The outer doublerow ball bearing 33 and/or the inner double-row ball bearing 34 are designed to be flexible for this purpose. This creates an output, which leads in rotating the inner gear 7.

The reduction gear box 54 further comprises a roller bearing 31 that is operatively coupled with the inner gear 7. Additionally, a first freewheel 40 is coupled to this roller bearing 31 and is in contact with an output shaft 39 which is supported by an output bearing 41 , illustrated as a ball bearing. A second freewheel 49 is operatively coupled with the output shaft 39, which also connects to a chainring adapter 43. An outer shaft seal ring 51 is placed between the output shaft 39 and the drive housing 17.

The rotation of the inner gear 7 is transmitted to the inner ring of the roller bearing 31 , in operation. This in turn is operatively connected to the first freewheel and transmits the rotation to the output shaft 39.

Furthermore, the bottom bracket axle 6 comprises a pedal shaft 35 with a first crank bearing 37 and a second crank bearing 38. A left crank arm 9 with a left pedal 11 and a right crank arm 10 with a right pedal 12 are supported by these bearings. The pedal shaft 35 is disposed partially in the interior of the rotor shaft 26 and partially in the interior of the output shaft 39 and concentric with the rotor shaft 26 and the output shaft 39. The pedal shaft 35 is further supported by a left bottom bracket bearing 45 against the drive housing and a right bottom bracket bearing 46 against the output shaft 39. Both bearings are ball bearings.

The pedal shaft 35 is set into rotary motion by the cyclist and includes means, in particular a second freewheel 49, for transmitting this motion to the output shaft 39.

The force measurement device 13 is able to acquire the radial force on the pedal shaft 35, with a corresponding signal transmitted to the control module which, in turn, controls the electric motor 2 to support the cyclist. The force measurement device 13 preferably comprises at least one strain gauge 14. The control module comprises preferably components such as a printed circuit board, a microprocessor, a memory and various interfaces and/or converters.

An inner shaft seal ring 50 is located on the pedal shaft 35 and secured with a nut, a threaded sleeve or cap/cover to ensure a tight seal, effectively preventing dirt from entering. The electric motor 2 is located within the electric motor housing half 19, and the force measurement device 13 may also be located within this housing half 19. The reduction gear box 54 is housed within the gearbox housing half 20.

The assembly of the electric bike drive system 1 is preferably executed by initially preparing the two halves 19, 20 of the drive housing 17 separately, with each half being equipped with its designated components.

The process can for example begin with the insertion of the stator 3 into the electric motor housing half 19. This can preferably be followed by the installation of the rotor shaft 26, which is equipped with magnets 25. The assembly can proceed with the placement of the rotor support ring 27, utilizing the rotor bearing 29 to secure these components within the electric motor housing half 19.

The gearbox half 20 can then be assembled, for example, in a prescribed sequence. The assembly begins with the installation of the outer shaft seal ring 51 in the gearbox half 20, followed by the installation of the output bearing 41 . The procedure can continue with the installation of the output shaft 39 together with the first freewheel 40, followed by the roller bearing 31 , and the right bottom bracket bearing 46. The process can continue with the assembly of the second freewheel 49 and the pedal shaft 35, and ends with the assembly of the outer gear 8 featuring internal toothing, the inner gear 7 with external toothing, and the pin ring 102.

Once the gearbox half 20 has been assembled, it is combined with the other electric motor housing half 19. A critical aspect of this stage could be ensuring the accurate placement of the outer double-row ball bearing 33 and the inner double-row ball bearing 34 on the rotor 5, as well as the left bottom bracket bearing 45.

The assembly can be completed by installing the force measurement device 13 and its cover. The final step is to carefully secure all components through screwing via screw connections 24, thus completing the assembly of the electric bike drive system 1. This systematic approach leads to the correct alignment and fixation of each component, yielding a durable and efficient drive system 1 ready for operation.

The electric bike drive system 1 is further designed to adapt to a wide range of riding conditions, providing dynamic support and smooth operation to enhance the riding experience. Exemplary riding conditions a) - f) are described below. a) Cyclist pedaling with electric motor 2 support

When the cyclist pedals, the pedal shaft 35 rotates via the pedal crank arms 9,10. The rotation is transmitted to the output shaft 39 via the second freewheel 49, causing the chainring adapter 43 mounted on the output shaft 39 to rotate.

The force measurement device 13 detects a radial force and transmits it to the control module. Based on the measured force, the control module can determine that the cyclist needs assistance and controls the electric motor 2 by applying a voltage to the coils 21 of the stator 3.

The voltage causes the rotor shaft 26 to start moving and transmit a rotation to the inner gear 7 via the gear unit 67. A further torque can then be applied to the output shaft 39 via the inner gear 7 and the first freewheel 40 which is operatively connected to it. This supports the torque applied by the cyclists. b) No pedaling and no electric motor 2 support

In situations where the cyclist is not pedaling and the electric motor 2 provides no support, the pedal shaft 35 remains static, with no force exerted. The second freewheel 49 prevents any abrupt stop of the output shaft 39, which can continue rotating independently.

With no radial force detected, the force measurement device 13 instructs the control module to interrupt the power supply to the electric motor 2, leading to its stoppage. However, this has no immediate effect on the output shaft's 39 rotation due to the first freewheel 40, which prevents a sudden stop. c) Manual pedaling without electric motor 2 support

During manual pedaling without electric motor 2 support, the motion from the pedal shaft 35 is transferred to the output shaft 39 through the second freewheel 49, causing the chainring adapter 43 to rotate. Without the electric motor's input, no extra force is applied from the reduction gear box 54, requiring the cyclist to pedal without assistance. d) Cyclist pedals faster than electric motor 2 support

If the cyclist pedals faster than the electric motor's 2 support speed, for example due to regulatory speed limits. The drive system's 1 design ensures that the electric motor 2 does not provide additional support. The output shaft 39 rotating faster than the inner gear 7 results in no extra force being transmitted through the first freewheel 40, allowing the cyclist to pedal beyond the electric motor's capacity without interference. e) Complete inactivity

In the event of complete inactivity, i.e. when both pedaling and electric motor 2 support are absent, the pedal shaft 35, the electric motor 2 and insofar the inner gear 7 remain standstill. f) Reverse pedalling

Pedaling in reverse does not alter the output shaft’s 39 condition because of the second freewheel 49 mechanisms. This design ensures that reverse pedaling does not impact the drive system's 1 forward efficiency.

Fig. 3 illustrates a focused view of the reduction gear box 54 of the drive system 1 , detailing the interplay between the various gears and bearings. All components have already been described in Fig. 1 and/or Fig. 2. In this respect, reference is also made to these Figures.

The reduction gear box 54 includes a pin-ring 102, which is C-shaped in cross section. The radially outer leg 103 of the pin-ring is toothed on both sides, while the radially inner leg 101 is not toothed. The inner gear 7, which features external toothing, is disposed on this radially inner leg 101.

The inner gear 7 comprises a ring 80 with external toothing and a support section connected thereto. Further the support section comprises a radial part and an axial part 78, wherein the axial part 78 is aligned parallel to the ring 80 with external teeth and connected to the ring 80 through the radial part, so that the inner gear 7 forms also a C- shape in cross section. Insofar, the axial part 78 of the support section is to be understood as a radially inner leg 78 of the C-shaped inner gear 7 and the ring 80 with external toothing is to be understood as radially outer leg 80 of the C-shaped inner gear 7.

The arrangement allows the outer double-row ball bearing 33 to contact both the transmitter driving section 55 and the radially inner leg 101 of the pin-ring 102. Furthermore, this configuration enables the radial force or motion of the outer doublerow ball bearing 33 caused by the transmitter driving section 55 of the electric motor 2 to press on the radially inner leg 101. The radially inner leg 101 in turn causes the radially outer leg 103 of the pin ring 102 to mesh with the outer gear 8 with internal teeth and/or with the inner gear 7 with external teeth, due to the rigid connection.

Additionally, the reduction gear box 54 comprises a roller bearing 31 operatively coupled to the inner gear 7, allowing the rotation of the inner gear 7 to be transmitted to the roller bearing's inner ring. A first freewheel 40 is also part of this gear box 54, operatively coupled to the roller bearing 31 , wherein the inner ring of the roller bearing 31 is located on the freewheel 40. This freewheel 40 is in contact with an output shaft 39, which is supported by an output bearing 41. Moreover, a second freewheel 49 is operatively coupled with the output shaft 39, which further connects to a chainring adapter 43. An outer shaft seal ring 51 is situated between the output shaft 39 and the drive housing 17, ensuring a seal and smooth operation. The inner double-row ball bearing 34 is placed between a section of the inner gear 7 and the transmitter driving section 55, contributing to the stability and efficiency of the gear system.

Fig. 4 provides a longitudinal section view of the bottom bracket axle 6 of the drive system 1 , highlighting the components responsible for the interface between the cyclist's input and the mechanical output that drives the electric bike.

The bottom bracket axle 6 includes a pedal shaft 35 that is equipped with a first crank bearing 37 and a second crank bearing 38. Attached to this assembly are the left crank arm 9 with the left pedal 11 and the right crank arm 10 with the right pedal 12, which are supported by the second and first crank bearings 37, 38, respectively.

The pedal shaft 35 is further supported by a left bottom bracket bearing 45 against the drive housing 17 and a right bottom bracket bearing 46 against the output shaft 39. Both bearings 45, 46 are preferably ball bearings.

In addition, an inner shaft seal ring 50 is provided on the pedal shaft 35 to prevent the ingress of contaminants and to maintain lubrication.

Fig. 5 shows a part of an embodiment of the drive system 1 , which comprises a drive housing 17, a reduction gear box 54 with a gear unit 67, and an electric motor 2 comprising a stator 3 and a rotor 5. The gear unit 67 has a rotationally symmetric structure and is coaxially arranged with the stator 3 and the rotor 5.

The rotor 5 is supported on a first side by the drive housing 17 through a rotor support ring 27 and a rotor bearing 29, which is a ball bearing. The rotor support ring 27 is elastically deformed in the axial direction, thereby generating a preload, such that an axial movement of the rotor 5 results in a further deformation of the rotor support ring 27. In other words, the rotor support ring 27 provides axial fixation of a radially outer ring 66 of the rotor bearing 29 and generates a preload so that a fixed-fixed mounting is formed for the rotor 5.

The rotor support ring 27 is a cylinder-shaped element. It has a radially inner surface 56 that contacts the rotor bearing 29 and a radially outer surface 58 upon which the rotor 5 is mounted. Furthermore, the rotor support ring 27 is designed with a first step 60 on the radially outer surface 58 to provide an axial limit stop for the rotor 5, and a second step 62 on the radially inner surface 56, which serves as an axial limit stop for the radially outer ring 66 of the rotor bearing 29.

The rotor support ring 27 is designed as a double-walled cylinder, which includes a connecting disc 64. The double-walled construction forms two separate surfaces: the radially outer wall forms the radially outer surface 58, designed to support the rotor 5, while the radially inner wall forms the radially inner surface 56, against which the rotor bearing 29 is positioned.

An inner gear 7 of the gear unit 67, which provides support to the rotor 5 on a second side, is itself supported by the bottom bracket axle 6. Further, the rotor 5 is supported on this side by two bearings: an outer double-row ball bearing 33, situated on the rotor's 5 radially outer surface in contact with a pin ring 102 of the gear unit, and an inner double-row ball bearing 34, positioned on the rotor's 5 radially inner surface, contacting the inner gear 7.

The inner gear 7 is C-shaped in cross-section and includes a radially inner leg 78 and a radially outer leg 80. Between these legs are positioned the radially inner leg 101 of a C-shaped pin ring 102, the outer double-row ball bearing 33, the transmitter driving section 55 of the rotor 5, and the inner double-row ball bearing 34.

The rotor, in particular the transmitter driving section 55, is equipped with first and second axial limit stops 74 and 76, respectively. The first axial limit stop 74 abuts a radially inner ring of the outer double-row ball bearing 33, and the second axial limit stop 76 abuts a radially outer ring of the inner double-row ball bearing 34.

Fig. 6 illustrates an embodiment of a pin ring 102. The pin ring 102 has a C-shaped cross section. It features a radially outer leg 103 that is toothed on both its sides, contributing to the mechanical engagement within the inner gear 7 and outer gear 8 (not shown in Fig. 8). The toothing is continuous around the entire circumference, comprising a meandering profile when viewed laterally, which forms teeth on both sides of the radially outer leg 103.

In contrast, the radially inner leg 101 of the C-shaped pin ring 102 is untoothed. The pin ring 102 is not flexible, the inner leg and the outer leg being connected by a rigid disc.

Fig. 7 provides a cross-sectional view of a part of the drive system 1 , showing in particular the relationship between the pin ring 102, the inner gear 7 and the outer gear 8 which are part of a rotationally symmetric gear.

The pin ring 102 has C-shaped cross-sectional form, wherein the inner gear 7 is located between a radially inner leg 101 and a radially outer leg 103 of the C-shaped pin ring 102. The radially outer leg 103 of the pin ring 102 has a meandering profile formed over its entire circumference, which allows it to engage both the outer gear 8 and the inner gear 7. The depicted engagement also ensures that the teeth mesh in a single plane and cover the full width of both gears 7 and 8.

Moreover, the radially inner surface of the inner gear 7 is positioned on the radially inner leg 101 of the pin ring 102. Radial motion or force applied to the inner leg 101 , by rotor 5 and the transmitter bearing 68 which is designed as an outer double-row ball bearing 33. Additionally, an inner double-row ball bearing 34 is provided which support the rotor 5 on the inner gear 7. Both the inner double-row ball bearing 34 and the outer doublerow ball bearing 33 are flexible. In operation, the radial movement/force applied to the inner leg 101 of the pin ring 102 causes the pin ring 102 to move radially outwards. Since the two legs 101 ,103 are connected to each other via a rigid disc, the teeth of the outer leg 103 mesh with the teeth of the outer gear 8 at a first location 104. In contrast, due to the eccentric section of the rotor the pin ring 102 is also pushed radially inwards on the opposite side. As the inner gear 7 is supported on the bottom bracket axle 6 and therefore remains in position, the pin ring 102 is meshed with the inner gear 7 at a second location 105. This is possible because the double-row ball bearings 33, 34 are flexible. This causes the inner gear 7 to rotate, resulting in an output torque which can be transmitted to other parts of the reduction gear 54.

The inner gear 7 comprises of a ring 80 equipped with external toothing and is connected to a support section 81 that includes axial teeth 70. These teeth are capable of meshing with corresponding toothed elements such as another gear or a ring.

The support section 81 of the inner gear 7 is designed to allow for support on a shaft or a ring, as for example on the pedal shaft 35 of the bottom bracket axle 6. Additionally, the support section 81 has both a radial part and an axial part 78, with the axial part 78 running parallel to the ring 80 and connecting to it via the radial part, thus giving the inner gear 7 a C-shaped cross-section. The axial part 78 is capable of being mounted onto a shaft or a ring support the inner gear 7.

Furthermore, the inner gear comprises a tooth ring 72 within the support section 81 , positioned adjacent to its radial part. The tooth ring 72 features axial teeth 70 formed by concentrically arranged protrusions and extensions around its perimeter.

Fig. 8 shows a detailed lateral view of the interaction between the pin ring 102, the inner gear 7 and the outer gear 8. The pin ring 102, with its C-shaped cross-section, has a radially outer leg 103 that includes a meandering profile forming teeth on both sides. These teeth are configured to engage with the teeth of the outer gear 8. Similarly, the teeth on the radially outer leg 103 are designed to mesh with the teeth of the inner gear 7. Fig. 9 shows a cross-sectional view of a part of the drive system 1. In particular, a part of an electric motor 2, a reduction gear box 54 with a gear unit 67, and a part of a bottom bracket axle 6 that includes a pedal shaft 35 are depicted as well as a drive housing 17. Reference is made to the descriptions in the other figures, which already describe a large number of features. The reference signs correspond to each other and are kept consistent in the figures.

The gear unit 67 within this assembly has a rotationally symmetric structure and is composed of an inner gear 7 featuring external toothing, and an outer gear 8 that has internal toothing. The outer gear is attached to the drive housing 17.

The inner gear 7 is positioned on the bottom bracket axle 6 and is supported by a first plain bearing 106 and a second plain bearing 108, both situated between the inner gear 7 and the pedal shaft 35. The first plain bearing 106 and the second plain bearing 108 intersect a same radial plane 83. It is understood that the plain bearings 106, 108 may also be referred to as slide bearings or friction bearings.

The output shaft 39 is guided through the inner gear 7, and the first plain bearing 106 is located between the inner gear 7 and the output shaft 39.

The inner gear 7 comprises a ring 80 with external toothing and a support section 81. The support section 81 consists of a radial part and an axial part 78. The axial part 78 extends parallel to the ring 80 and connects to it via the radial part. The axial part 78 is supported on the output shaft 39.

The output shaft 39 is coupled to the inner gear 7 by the first freewheel 40. The inner gear 7 is connected to the first freewheel 40 via a coupling shaft 128. The inner gear 7, in particular the axial part 78 of the support section 81 , and the first freewheel 40 are arranged at the same radial level on the output shaft 39. Further, the pedal shaft 35 is guided through the hollow-designed output shaft 39. A second freewheel 49 is situated between the pedal shaft 35 and the output shaft 39 to disengage the pedal shaft 35 from the output shaft 39, while the first plain bearing 108 is located between the output shaft 39 and the pedal shaft 35.

The gear unit 67 further includes a pin ring 102 that is connected to the transmitter driving section 55 of the electric motor 2.

Fig. 10 shows a drive system 1 for an electric bike, wherein the entire drive system 1 is shown in cross-section. The drive system 1 comprises an electric motor 2, a bottom bracket axle 6, a reduction gear box 54, and a force measurement device 13 housed within a drive housing 17.

The electric motor 2 is operatively coupled to the reduction gear box 54, which has an hollow output shaft 39. The bottom bracket axle 6, on the other hand, comprises a pedal shaft 35 which is guided through the hollow output shaft 39. Further a second freewheel 49 is provided between the pedal shaft 39 and the hollow output shaft 39 for decoupling the pedal shaft 35 from the output shaft 39.

The bottom bracket axle 6, in particular the pedal shaft 35, is supported in the drive housing 17 via a left 45 and a right 46 bottom bracket bearing. The left bottom bracket bearing 45 is mounted in the drive housing 17 through the measurement device 13. Specifically, the receiving sleeve 82 of the measurement device 13 receives an outer ring of the left bottom bracket bearing 45.

The force measurement device 13 is capable of capturing radial force applied to the pedal shaft 35 and communicating a corresponding signal to the control module for the operation of the electric motor 2.

The force measurement device 13 comprises a receiving sleeve 82 configured to hold a ring of a bearing and a fastening ring 84 which secures the force measurement device 13 within the drive housing 17. Furthermore, the force measurement device 13 comprises a measuring region 86 which is meander-shaped with radially aligned/orientated walls 88 and axially aligned/orientated walls 90 and which connects the receiving sleeve 82 to the fastening ring 84.

At least one strain gauge 14 is attached to a radially aligned/orientated wall 88 within the measuring region 86. This configuration allows axial and radial forces applied to be decoupled. The force measuring device can also serve as a cover for the drive system 1. The fastening ring 84 features fastening areas 92 with provided fastening holes 94 for assembly. Moreover, a cover seal ring 99 is located between the force measurement device 13 and the bottom bracket axle 6.

The control module is designed to process signals from the force measurement device 13 and to regulate the electric motor 2 accordingly. A printed circuit board 96, which is part of the control module, is mounted to the drive housing 17.

Fig. 11 shows a cross-section of a force measurement device 13 integrated into a drive system 1 for an electric bike. The measurement device 13 comprises a receiving sleeve 82 designed to receive a ring of a bearing, and a fastening ring 84 for securing the force measurement device 13 within a drive housing 17.

A measuring region 86 bridges the receiving sleeve 82 to the fastening ring 84 and is structured in a meander shape, featuring radial aligned walls 88 and axial aligned walls 90. The fastening ring 84 is equipped with fastening areas 92 that include fastening holes 94 for the attachment to the drive housing 17. A printed circuit board 96, which is part of a control module, is attached to the drive housing 17 and is covered by the force measurement device 13.

Fig. 12 shows a force measuring device 13 attached to a drive housing 17 of a drive system 1. The force measuring device 13 comprises a receiving sleeve 82, a fastening ring 84 and a meander-shaped measuring region 86. Compared to the embodiment shown in Figure 11 , the shape of the measuring region 86 is different, although it is still meander-shaped with radially aligned walls 88 and axially aligned walls 90. A printed circuit board 96 is located adjacent to these features and is attached to the drive housing 17.

Fig. 13 shows a top perspective of the force measurement device 13. The force measuring device 13 comprises a receiving sleeve 82, a fastening ring 84 and a meandershaped measuring region 86.

The receiving sleeve 82 is designed to hold a ring of a bearing, allowing for the transmission of radial forces to the measuring region 86. The fastening ring 84 serves to secure the force measurement device 13 within a drive housing 17. The meander-shaped measuring region 86, which links the receiving sleeve 82 with the fastening ring 84, features radially aligned walls 88 and axially aligned walls 90.

Four strain gauges 14 are attached to a radially aligned wall 88. This configuration enables the decoupling of axial and radial forces at the measurement device. The receiving sleeve 82 is formed by the junction of the axial and radial aligned walls 88, 90 of the measuring region 86. The strain gauges 14 are arranged concentrically and spaced at 90-degree intervals on the radially aligned wall 88. Lastly, the fastening ring 84 is equipped with fastening areas 92, within which fastening holes 94 are provided to facilitate mounting.

Fig. 14 illustrates a force measurement device 13. Reference is made to the description of Fig. 13. In contrast to the force measuring device 13 shown in Fi3. 14, the embodiment of Fig. 14 also has four concentrically arranged recesses 98. In particular, these are arranged on a circular line like the strain gauges 14 and are always positioned in the intermediate spaces.

Fig. 15 shows an embodiment of the drive system 1 for an electric bike, wherein the entire drive system 1 is shown in cross-section. In particular, Fig. 15 shows schematically the directions and pathways in which forces are transmitted within the structure in order to generate an output that drives the bike. The arrows shown are referred to as force flows. The present drive system 1 comprises two sources of force or power. Force is applied to the drive system 1 by the cyclist by operating a left crank arm 9 with a left pedal 11 and a right crank arm 10 with a right pedal 12. The force is transmitted to a pedal shaft 35 via a first crank bearing 37 and a second crank bearing 38. The pedal shaft 35 is in turn connected to an output shaft 39 using a second freewheel 49 which can transmit the force or rotational movement of the pedal shaft 35 to the output shaft 39. The output shaft 39, on the other hand, transmits the force to a chainring adapter 43 and drives it, setting in motion the chainring connected to the rear wheel/ tire of the bike.

Furthermore, an electric motor 2 generates an electromagnetic force which sets a rotor 5 or a rotor shaft 26 in motion. The rotational movement or force of the rotor shaft 26 is converted into a radial force via a transmitter driving section 55. Since the transmitter driving section 55 is coupled to a radially inner leg 101 of a C-shaped pin ring 102 through an outer double-row ball bearing 33 the radial force is transmitted to the pin ring 102.

An inner gear 7 or a part of the inner gear 7 is located within the C-shaped form of the pin ring 102, wherein the inner gear 7 is also supported on the pedal shaft 35. The pin ring 102 is not flexible. Accordingly, the radial force presses the radial outer leg 103 of the pin ring 102 against an outer gear 8 at a first position. Simultaneously, the radial outer leg 103 is pulled at a second position radially inward against the inner gear 7 because of the eccentric or elliptical designed transmitter driving section 55. The teeth of the inner gear 7, pin ring 102 and outer gear 8 engage with each other and an output is generated that causes the inner gear 7 to rotate.

Accordingly, the force is transferred to the inner gear 7. The inner gear 7 transmits the rotation/ force to an inner ring of a roller bearing 31 . For this purpose, the inner gear 7 can comprise axial teeth 70. The roller bearing 31 transmits the force to a first freewheel 40, which transmits the force to the output shaft 39 and can therefore be regarded as a support for the rider's applied force. Fig. 16 shows an embodiment of the drive system 1 , illustrating how it is mounted within the bike frame 124. The figure includes two views: a cross-sectional view (a) of the drive system 1 and an enlarged sectional detail (b) of the mounting interface.

In view (a), the bottom bracket axle 6, including the pedal shaft 35, extends through the drive housing 17. The housing cover 23 is attached to the drive housing 17. A circular flange 110 extends radially outward from the drive housing 17 near an axial end section.

View (b) provides a detailed representation of the connection between the drive system 1 and the bike frame 124. The drive system 1 is secured to the bike frame 124 via a drive system mounting bracket 120. The drive system mounting bracket 120 comprises a holding section 112, which consists of a clamping device 114 and a support interface 116. The clamping device 114 is detachably mountable to the bike frame 124.

The outer contour of the drive housing 17 features a shoulder 117. The shoulder 117 and the circular flange 110 together form a circumferential groove 118. A projection 126, which extends from the support interface 116, engages with the groove 118, creating a form-fit connection in the axial direction.

The groove 118 varies in width along its circumference. The groove 118 has a greater width in the circumferential segment where the clamping device 114 engages than in the circumferential segment where the support interface 116 engages when the drive system 1 is mounted on the drive system mounting bracket 120 of the bike frame 124.

Fig. 17 shows a section of a bike frame 124 with a drive system mounting bracket 120. The drive system is attachable to the bike frame 124 or the drive system mounting bracket 120 via a holding section 112, which comprises a support interface 116 and a clamping device 114.

The clamping device 114 is detachably mountable to the bike frame 124 and can secure the drive system 1 to the bike frame 124 or the drive system mounting bracket 120. The clamping device 114 and the bike frame 124 comprise means 122 for a screw connection to fasten the clamping device 114 to the drive system mounting bracket 120, thereby clamping the drive system 1 to the electric bike.

The clamping device 114 and the support interface 116 each include a projection 126. The projections 126 can engage with the groove 118, which is formed by the flange 110 and the shoulder 117 in the housing 17, to establish a form-fit connection in the axial direction.

Fig. 18 shows a sectional view of an embodiment of the drive system 1 , highlighting a flattened section 125 in relation to a flange 110 on the housing 17. Reference is made to Figs 16 and 17.

Fig. 19 provides a cross-sectional view of a part of the drive system 1 , showing in particular the relationship between the pin ring 102, the inner gear 7 and the outer gear 8 which are part of a rotationally symmetric gear. The inner gear 7 features external toothing, while the outer gear 8 has internal toothing. Positioned between them, the pin ring 102 ensures proper engagement and force transmission.

The pin ring 102 has a C-shaped cross-section, with the inner gear 7 located between its radially inner leg 101 and radially outer leg 103. The outer leg 103 exhibits a meandering profile along its entire circumference, enabling precise engagement with both the outer gear 8 and the inner gear 7. This configuration ensures that the teeth mesh within a single plane while covering the full width of both gears.

To enhance performance and wear resistance, the teeth of the pin ring 102 on the radially outer leg 103, which face the inner gear 7, are coated with a plastic overlay layer 129. This layer 129 may have a thickness ranging from 0.1 to 1.5 mm, preferably between 0.2 and 1.2 mm, and may be composed of a high-performance polymer, preferably PEEK (Polyetheretherketone).

The inner gear 7 itself is preferably made of steel 130, providing durability and stability. The surface 130 of the pin ring 102, particularly the part of the outer leg 103 facing the outer gear 8, is made of steel, while the outer gear 8 is coated with a plastic layer 129. The outer gear 8 can be machined directly into the housing, with the plastic layer 129 applied to its surface.

Fig. 20 shows an embodiment of the drive system 1 , wherein the entire drive system 1 is shown in cross-section. The drive system comprises an electric motor with a stator 3 and a rotor 5. The drive system includes a reduction gearbox with a gear unit 67. The gear unit 67 has a rotationally symmetric structure. The stator 3, the rotor 5, and the gear unit 67 are arranged coaxially. The rotor 5 is designed as a hollow shaft and comprises a transmitter driving section 55.

The transmitter driving section 55 includes a circumferential groove 132, which is defined by two shoulders 134. Each shoulder 134 is supported on a rolling bearing. A double-row rolling bearing is positioned in the groove 132, on which the gear unit 67 is supported. The double-row rolling bearing is designed as a double-row ball bearing 136. The shoulders 134 are each supported by a ball bearing 136 on a shaft 137.

The shaft 137 can be configured as a pedal shaft 35 of a bottom bracket axle 6 for an electric bike drive system or as an output shaft for a robotic drive system. In contrast to the previous embodiments, such as the one shown in Fig. 2, the shaft 137 can have a larger diameter because the transmitter driving section 55 of the rotor 5 is no longer supported by a double-row ball bearing 136 on the shaft 137, which occupies significant space. Instead, due to the shoulders 134 and the strategic arrangement of two rolling bearings 136 at the shoulders 134, the design can be more compact in the radial direction. As a result, more space is now available for the shaft 137.

The first itemized list refers to the aspect relating to the rotor support ring. The items of the first itemized list can be combined with one or more items of all other itemized lists in this document as well as with one or more features of the claims.

First itemized list: 1.A drive system comprising an electric motor with a stator and a rotor, a reduction gear box with gear unit, and a drive housing,

- wherein the gear unit has a rotationally symmetric structure, and

- wherein the stator, the rotor and the gear unit are arranged coaxially, and

- wherein the rotor is supported on a first side by the drive housing through a rotor support ring and via a rotor bearing which is provided as a rolling contact bearing, and

- wherein the rotor support ring is elastically deformed in an axial direction, thereby generating a preload, such that an axial movement of the rotor results in a deformation of the rotor support ring.

2. The drive system according to item 1 comprising a bottom bracket axle which is supported by the drive housing and is axially secured therein, wherein the rotor is supported on a second side by the bottom bracket axle.

3. The drive system according to item 2, wherein the bottom bracket axle is supported by a left bottom bracket bearing in the drive housing and by a right bottom bracket bearing in an output shaft, which is supported by an output bearing in the drive housing.

4. The drive system according to item 2 or 3, wherein the gear unit comprises an inner gear which supports the rotor on the second side, wherein the bottom bracket axle supports the inner gear.

5. The drive system according to item 4, wherein the gear unit comprises a pin ring, and

- wherein the rotor is supported in two bearings on the second side, and

- wherein an outer double-row ball bearing is positioned on the radially outer surface of the rotor and contacts the pin ring, and

- wherein an inner double-row ball bearing is positioned on the radially inner surface of the rotor and contacts the inner gear. 6. The drive system according to any of the preceding items, wherein the rotor support ring is made of plastic.

7. The drive system according to item 6, wherein the rotor support ring is made of polyamide, polyphenylene sulfide or polyetheretherketone.

8. The drive system according to any of the preceding items, wherein the rotor bearing is designed as a ball bearing, a roller bearing or split bearing.

9. The drive system according to any of the preceding items, wherein the rotor support ring comprises a radially inner surface and a radially outer surface, the rotor being positioned on the radially outer surface of the rotor support ring and the rotor bearing seating against the radially inner surface of the rotor support ring.

10. The drive system according to item 9, wherein the rotor support ring comprises a first step on the radially outer surface, which acts as an axial limit stop for the rotor.

11. The drive system according to item 9 - 10, wherein the rotor support ring comprises a second step on the radially inner surface, which acts as an axial limit stop for the rotor bearing, in particular for a radially outer ring of the rotor bearing.

12. The drive system according to any of the preceding items 1 - 8, wherein the rotor support ring comprises a radially inner surface and a radially outer surface, the rotor bearing being positioned on the radially outer surface of the rotor support ring and the drive housing seating against the radially inner surface of the rotor support ring.

13. The drive system according to item 12, wherein the rotor comprises a third step on the radially inner surface, which acts as an axial limit stop for the rotor bearing, in particular for a radially outer ring of the rotor bearing. 14. The drive system according to any of the preceding items 12 - 13, wherein the rotor support ring comprises a first step on the radially outer surface, which acts as an axial limit stop for the rotor bearing, in particular for an radially inner ring of the rotor bearing.

15. The drive system according to any of the preceding items 9 - 14, wherein the rotor support ring is designed as a double-walled cylinder comprising a radially outer wall and a radially inner wall connected with a disc, the radially outer surface being formed on the radially outer wall and the radially inner surface being formed on the radially inner wall of the double-walled ring.

The second itemized list refers to the aspect relating to the gear unit with a C-shaped pin ring. The items of the second itemized list can be combined with one or more items of all other itemized lists in this document as well as with one or more features of the claims.

Second itemized list:

1. A drive system comprising an electric motor with a stator and a rotor, a reduction gear box with a gear unit, and a drive housing,

- wherein the gear unit has a rotationally symmetric structure, and

- wherein the gear unit comprises a pin ring, an inner gear with external toothing, and an outer gear with internal toothing which is attached to the drive housing, and

- wherein the pin ring is C-shaped in cross section, a radially outer leg of the C- shaped pin ring being toothed on both sides, while a radially inner leg of the C- shapes pin ring being preferably not toothed, and

- wherein the inner gear is positioned between the radially inner leg and the radially outer leg.

2. The drive system according to item 1 , wherein the radially outer leg in lateral view of the C-shaped pin ring comprises a meandering profile which is formed over the entire circumference and accordingly forms teeth on both sides of the radially outer leg. 3. The drive system according to any of the preceding items, wherein the teeth on the radially outer leg of the pin ring can mesh with the teeth of the outer gear and of the inner gear, ensuring meshing in a single plane and extending across the entire width of the outer gear and/or the inner gear.

4. The drive system according to any of the preceding items, wherein a radially inner surface of the inner gear is disposed on the radially inner leg of the pin ring, and wherein the contacting surfaces of the inner gear and the radially inner leg of the pin ring are not toothed.

5. The drive system according to any of the preceding items, wherein the rotor comprises a rotor shaft with a transmitter driving section, the pin ring being coupled to the transmitter driving section via a transmitter bearing, wherein the transmitter driving section is designed as an eccentric section, thereby causing a conversion of a rotational motion of the rotor into a radial motion or force.

6. The drive system according to any of the preceding items, wherein due to radial motion or force applied to the inner leg of the pin ring, the radially outer leg of the pin ring mesh with the outer gear with internal toothing, and/or with inner gear with external toothing.

7. The drive system according to item 5 wherein the transmitter bearing is flexible.

8. The drive system according to item 5 or 7, wherein the transmitter bearing is an outer double-row ball bearing and is located radially outwards on the transmitter driving section of the electric motor.

9. The drive system according to any of the preceding items, wherein an inner doublerow ball bearing is located radially inwards on the transmitter driving section of the electric motor, wherein the inner double-row ball bearing is flexible. The third itemized list refers to the aspect relating to the outer double-row rolling bearing. The items of the third itemized list can be combined with one or more items of all other itemized lists in this document as well as with one or more features of the claims.

Third itemized list:

1. A drive system comprising an electric motor with a stator and a rotor, and a reduction gear box with a gear unit,

- wherein the gear unit has a rotationally symmetric structure,

- wherein the stator, the rotor and the gear unit are arranged coaxially, and

- wherein the rotor comprises a rotor shaft with a transmitter driving section, and

- wherein an outer double-row rolling bearing is provided radially outwards on the transmitter driving section and radially inwards to the gear unit.

2. The drive system according to item 1 , wherein the outer double-row rolling bearing is designed as an outer double-row ball bearing.

3. The drive system according to item 1 or item 2, wherein the drive system further comprises a drive housing, and

- wherein the gear unit comprises a pin ring, an inner gear with external toothing, and an outer gear with internal toothing which is attached to the drive housing, and

- wherein the pin ring is mounted on a radially outer ring of the outer double-row ball bearing.

4. The drive system according to item 3, wherein the double row ball bearing is configured to transmit radial force or motion from the transmitter driving section to the pin ring.

5. The drive system according to items 3 or 4, wherein the pin ring is C-shaped in cross section, a radially outer leg of the C-shaped pin ring being toothed on both sides, while a radially inner leg of the C-shapes pin ring being not toothed, and - wherein at least a part of the inner gear is located between the radially inner leg and the radially outer leg, and

- wherein the radially inner leg is provided on the radially outer ring of the outer double-row ball bearing.

6. The drive system according to any of the preceding items, wherein the rotor is designed as a hollow shaft, and an inner double-row rolling bearing is provided radially inwards on the transmitter driving section.

7. The drive system according to claim 6, wherein the inner double-row rolling bearing is designed as an inner double-row ball bearing.

8. The drive system according to item 7, wherein the inner gear is C-shaped in crosssection and comprises a radially inner leg and a radially outer leg, between which the radially inner leg of the C-shape pin ring, the outer double-row ball bearing, the transmitter driving section of the rotor and the inner double-ball bearing are positioned.

9. The drive system according to any of the preceding items, wherein the transmitter driving section comprise a first axial limit stop which abuts a radially inner ring of the outer double-row ball bearing.

10. The drive system according to item 7, wherein the transmitter driving section comprise a second axial limit stop which abuts a radially outer ring of the inner doublerow ball bearing.

The fourth itemized list refers to the aspect relating to the inner double-row rolling bearing. The items of the fourth itemized list can be combined with one or more items of all other itemized lists in this document as well as with one or more features of the claims.

Fourth itemized list: 1. A drive system comprising an electric motor with a stator and a rotor, and a reduction gear box with a gear unit,

- wherein the gear unit has a rotationally symmetric structure,

- wherein the stator, the rotor and the gear unit are arranged coaxially, and

- wherein the rotor is designed as a hollow shaft and comprises a transmitter driving section, and

- wherein an inner double-row rolling bearing is provided radially inwards on the transmitter driving section.

2. The drive system according to item 1 , wherein the inner double-row rolling bearing is designed as an inner double-row ball bearing.

3. The drive system according to item 2, wherein the transmitter driving section comprise a second axial limit stop which abuts a radially outer ring of the inner double-row ball bearing.

4. The drive system according to any of the preceding items, wherein an outer doublerow rolling bearing is provided radially outwards on the transmitter driving section and radially inwards to the gear unit so as to serve as a force transmitting means between the transmitter driving section and the gear unit.

5. The drive system according to item 4, wherein the outer double-row rolling bearing is designed as an outer double-row ball bearing.

6. The drive system according to any of the preceding items, wherein the drive system further comprises a drive housing, and

- wherein the gear unit comprises a pin ring, an inner gear with external toothing, and an outer gear with internal toothing which is fixed to the drive housing, and

- wherein the pin ring is mounted on a radially outer ring of the outer double-row ball bearing. 7. The drive system according to item 6, wherein the outer double row ball bearing is configured to transmit radial force or motion from transmitter driving section to the pin ring.

8. The drive system according to any of the preceding items, wherein the inner doublerow ball bearing is supported by an inner gear.

9. The drive system according to item 8, wherein the pin ring is C-shaped in cross section, a radially outer leg of the C-shaped pin ring being toothed on both sides, while a radially inner leg of the C-shapes pin ring being not toothed, and

- wherein at least a part of the inner gear is located between the radially inner leg and the radially outer leg, and

- wherein the radially inner leg of the C-shaped pin ring is provided on the radially outer ring of the outer double-row ball bearing.

10. The drive system according to any of the preceding items, wherein the inner gear is C-shaped in cross-section and comprises a radially inner leg and a radially outer leg, between which the radially inner leg of the C-shape pin ring, the outer double-row ball bearing, the transmitter driving section of the rotor and the inner double-ball bearing are positioned.

11. The drive system according to item 5, wherein the transmitter driving section comprises a first axial limit stop which abuts a radially inner ring of the outer double-row ball bearing.

The fifth itemized list refers to the aspect relating to the inner gear with axial teeth. The items of the fifth itemized list can be combined with one or more items of all other itemized lists in this document as well as with one or more features of the claims.

Fifth itemized list: 1. An inner gear for a reduction gear box with a gear unit having a rotationally symmetric structure, wherein the inner gear comprises a ring with external toothing and a support section connected thereto, and

- wherein support section comprises axial teeth which can engage with corresponding toothed components such as a gear or a ring.

2. The Inner gear according to item 1 , wherein the support section can support the inner gear on a shaft or a ring,

3. The inner gear according to item 1 or 2, wherein the support section comprises a radial part and an axial part, wherein the axial part is aligned parallel to the ring with external teeth and connected to the ring through the radial part, so that the inner gear forms a C- shape in cross section, wherein the axial part can be mounted on a shaft or a ring to support the inner gear.

4. The inner gear according to item 3, wherein the support section comprises a tooth ring which is placed lateral to the radial part of the support section, and wherein the tooth ring provides the axial teeth via concentrically arranged bulges and extensions on the circumference.

5. A reduction gear box comprising a gear unit and an output shaft, and

- wherein the gear unit has a rotationally symmetric structure, and

- wherein the gear unit comprises an inner gear according to any of the preceding items 1 - 4, and an outer gear with internal toothing, and

- wherein the gear unit is coupled to the output gear.

6. A reduction gear box according to item 5, wherein the gear unit further comprises a pin ring.

7. A drive system comprising an electric motor, a reduction gear box according to item 5 or 6, a drive housing, a bottom bracket axle with a pedal shaft, a force measurement device and a control module, wherein in the outer gear is attached to the drive housing, and the inner gear is supported on the pedal shaft.

The sixth itemized list refers to the aspect relating to two plain bearings. The items of the sixth itemized list can be combined with one or more items of all other itemized lists in this document as well as with one or more features of the claims.

Sixth itemized list:

1. A drive system for an electric bike comprising,

- an electric motor,

- a reduction gear box with a gear unit and an output shaft coupled to the electric motor,

- a bottom bracket axle with a pedal shaft coupled to the output shaft;

- a drive housing that at least partially accommodates the electric motor, the reduction gearbox, the bottom bracket axle, and wherein:

- the gear unit has a rotationally symmetric structure, and comprises an inner gear with external toothing, and an outer gear with internal toothing which is attached to the drive housing, and

- the inner gear is supported on the bottom bracket axle, wherein a first plain bearing and second plain bearing are located between the inner gear and the pedal shaft.

2. The Drive system according to item 1 ,

- wherein the inner gear is supported on the output shaft by guiding the output shaft through the inner gear, and

- wherein the output shaft is designed as a hollow shaft and supported on the pedal shaft, and

- wherein the first plain bearing is located between the inner gear and the output shaft. 3. The drive system according to item 1 or 2, wherein the inner gear comprises a ring with external toothing and a support section connected thereto, with which the inner gear is supported on the output shaft.

4. The drive system according to item 3, wherein the support section comprises both a radial part and an axial part, the axial part extending parallel to the ring and connecting to it via the radial part, wherein the axial part is supported on the output shaft.

5. The drive system according to any of the preceding items, wherein the output shaft is coupled to the inner gear by a first freewheel.

6. The drive system according to item 5,

- wherein the inner gear is coupled to the first freewheel via a coupling shaft, and

- wherein the inner gear and the first freewheel are positioned on the output shaft at the same radial level.

7. The drive system according to any of the preceding items,

- wherein the pedal shaft is guided through the output shaft, and

- wherein the second plain bearing is located between the output shaft and the pedal shaft.

8. The drive system according to item 7, wherein a second freewheel is provided between the pedal shaft and the output shaft for decoupling the pedal shaft from the output shaft.

9. The drive system according to any of the preceding items, wherein the gear unit further comprises a pin ring which is coupled to a transmitter driving section of the electric motor.

10. The drive system according to any of the preceding items, wherein the first plain bearing and the second plain bearing intersect a same radial plane and are arranged in parallel. 11. The drive system according to any of the preceding items, wherein the drive system comprises a measurement device arranged on the bottom bracket axle or a component connected thereto, configured to detect forces acting on the bottom bracket axle, and a control unit operatively connected to both the electric motor and the force measurement device to regulate motor output based on the detected forces.

The seventh itemized list refers to the aspect relating to the force measurement device having a meander shaped measuring region. The items of the seventh itemized list can be combined with one or more items of all other itemized lists in this document as well as with one or more features of the claims.

Seventh itemized list:

1. A force measurement device for determining a radial force on a shaft in a drive system, wherein the force measurement device comprises:

- a receiving sleeve for receiving a ring of a bearing, and

- a fastening ring for attaching the force measurement device in a drive housing, and

- a measuring region for receiving radial forces of the receiving sleeve which are transmitted from the ring of the bearing, and

- wherein the measuring region connect the receiving sleeve to the fastening ring, and

- wherein in the measuring region is meander shaped, having radial aligned walls and axial aligned walls, wherein at least one strain sensor is attached to a radial aligned wall.

2. The force measurement device according to item 1 , wherein the at least one strain sensor comprises a strain gauge. 3. The force measurement device according to item 1 or 2, wherein the receiving sleeve is formed by an axial and radial aligned wall of the measuring region.

4. The force measurement device according to item 3, wherein the at least one strain sensor is attached to the radial aligned wall forming the receiving sleeve.

5. The measuring device according to any of the preceding items, wherein the measuring device comprises four strain sensors which are arranged concentrically at an angle of 90° to each other at the radial aligned wall.

6. The force measurement device according to any of the preceding items, wherein the fastening ring comprises fastening areas in which fastening holes are provided.

7. A drive system for an electric bike comprising: a force measurement device according to any of the preceding items, an electric motor, a reduction gear box, a bottom bracket axle, a drive housing, and a control module, and

- wherein the bottom bracket axle comprises pedal shaft which is supported in the drive housing with a left bottom bracket bearing and with a right bottom bracket bearing, and

- wherein the left bottom bracket bearing is supported in the drive housing via the force measurement device, wherein the force measurement device is attached to the drive housing through the fastening ring, the receiving sleeve receiving an outer ring of the left bottom bracket bearing.

8. The drive system according to item 7, wherein the left bottom bracket bearing is a ball bearing or a needle bearing.

9. The drive system according to item 7 or 8, wherein a cover seal ring is located between the force measurement device and the bottom bracket axle.

10. The drive system according to any of the preceding items 7 - 9, wherein the right bottom bracket bearing is a ball bearing. 11 . The drive system according to any of the preceding items 7 - 10, wherein the electric motor is operatively coupled to the reduction gear box, which has a hollow output shaft, and

- wherein the pedal shaft is guided through the hollow output shaft, and wherein a second freewheel is provided between the pedal shaft and the hollow output shaft for decoupling the pedal shaft from the output shaft.

12. The drive system according to any of the preceding items 7 - 11 , wherein the control module comprises a printed circuit board, a microprocessor, a memory, an input interface, an output interface, analogue-to-digital converter and/or a digital-to-analogue converter.

13. The drive system according to item 12, wherein the printed circuit board is attached to the drive housing and covered by the force measurement device.

14. The drive system according to any of the preceding claims 7 - 13, wherein the force measurement device is configured to acquire a radial force applied on the pedal shaft and to transmit a corresponding signal to the control module, and the control module is configured to analyze the signal received from the force measurement device and to control the electric motor, the electric motor being used to generate a force to support a cyclist using a bike comprising the drive system.

The eighth itemized list refers to the aspect relating to the force measurement supported on the bottom bracket axle by a needle ring. The items of the eighth itemized list can be combined with one or more items of all other itemized lists in this document as well as with one or more features of the claims.

Eighth itemized list: 1. A drive system for an electric bike comprising a force measurement device, an electric motor, a reduction gear box, a bottom bracket axle, a drive housing, and a control module, and

- wherein the force measurement device comprises a receiving sleeve for receiving a ring of a bearing, and

- wherein the bottom bracket axle comprises pedal shaft which is supported in the drive housing with a left bottom bracket bearing and with a right bottom bracket bearing, and

- wherein the left bottom bracket bearing is supported in the drive housing via the force measurement device, and

- wherein the receiving sleeve receives an outer ring of the left bottom bracket bearing, and

- wherein the left bottom bracket bearing is a needle bearing.

2. The drive system according to item 1 , wherein the needle bearing is press-fitted onto the pedal shaft, ensuring a play-free engagement.

3. The drive system according to item 1 or 2, wherein the force measuring device comprises:

- a fastening ring for attaching the force measurement device in the drive housing, and

- a measuring region for receiving radial forces of the receiving sleeve which are transmitted from the ring of the bearing, and

- wherein the measuring region connect the receiving sleeve to the fastening ring,

4. The drive system according to item 3, wherein the measuring device is attached to the drive housing through the fastening ring.

5. The drive system according to item 3 or 4, wherein the measuring region is meander shaped, having radial aligned walls and axial aligned walls, wherein at least one strain sensor is attached to a radial aligned wall. 6. The drive system according to item 5, wherein the at least one strain sensor comprises a strain gauge.

7. The drive system according to any of the preceding items 3 - 6, wherein the fastening ring comprises fastening areas in which fastening holes are provided.

8. The drive system according to any of the preceding items, wherein the right bottom bracket bearing is a ball bearing.

9. The drive system according to any of the preceding items, wherein the electric motor is operatively coupled to the reduction gear box, which has an output shaft which is a hollow shaft, wherein the pedal shaft is guided through the hollow output shaft, and wherein a first freewheel is provided between the pedal shaft and the hollow output shaft for decoupling the pedal shaft from the output shaft.

10. The drive system according to any of the preceding items, wherein the control module comprises a printed circuit board, a microprocessor, a memory, an input interface, an output interface, analogue-to-digital converter and/or a digital-to-analogue converter.

11. The drive system according to any of the preceding items, wherein the force measurement device is configured to acquire a radial force applied on the pedal shaft and to transmit a corresponding signal to the control module, and the control module is configured to analyze the signal received from the force measurement device and to control the electric motor, the electric motor being used to generate a force to support a cyclist using a bike comprising the drive system.

The nineth itemized list refers to the aspect relating to the circular flange in the drive housing. The items of the nineth itemized list can be combined with one or more items of all other itemized lists in this document as well as with one or more features of the claims.

Nineth itemized list:

1. A drive system for an electric bike comprising,

- an electric motor,

- a reduction gear box with a gear unit and an output shaft coupled to the electric motor,

- a bottom bracket axle with a pedal shaft coupled to the output shaft;

- a drive housing that at least partially accommodates the electric motor, the reduction gearbox, the bottom bracket axle, and wherein:

- the drive housing comprises a circular flange extending radially outward from the drive housing,

- the circular flange is configured to engage with a complementary circular holding section of a drive system mounting bracket at the electric bike in such a way that the drive housing is secured in the axial direction

2. The drive system according to item 1 , wherein the circular flange is positioned near an axial end section of the housing.

3. The drive system according to item 1 or item 2, further comprising a force measurement device coupled to the pedal shaft for determining a radial force on the pedal shaft, wherein:

- the force measurement device is arranged within a housing cover of the drive housing, and

- the flange located at the housing cover and/or on the opposite side of the drive housing, where the housing cover is absent.

4. The drive system according to item 3, wherein the flange is located in only the housing cover. 5. The drive system according to any of the preceding items, wherein the circular flange has a diameter in the range of 55 to 60 mm, preferably 58 mm.

6. The drive system according to any of the preceding items, wherein the electric bike comprises a bike frame, and wherein a clamping device and a support interface on the bike frame together form the holding section, wherein the clamping device is detachably mountable to the bike frame.

7. The drive system according to item 6, wherein the clamping device and the bike frame comprise means for a screw connection to form the holding section and secure the drive system to the electric bike.

8. The drive system according to item 6 or item 7, wherein the flange and a shoulder in the outer contour of the drive housing form a circumferential groove in the drive housing, wherein both the clamping device and the support interface include a projection that can engage with the groove, thereby establishing a form-fit connection in the axial direction.

9. The drive system according to item 8, wherein the groove varies in width along its circumference.

10. The drive system according to item 9, wherein the groove has a greater width in the circumferential segment where the clamping device engages than in the circumferential segment where the support interface engages, when the drive system is mounted on the drive system mounting bracket of the electric bike.

11 . The drive system according to any of the preceding items, wherein the circular flange includes a flattened section at a specific location to allow for the formation of a borehole in the housing behind it.

12. An electric bike, comprising:

- a bike frame with a drive system mounting bracket,

- a drive system according to any of the preceding items 1 to 11 , - wherein the drive housing of the drive system is secured to the drive system mounting bracket via a holding section, which includes a clamping device and a support interface.

The tenth itemized list refers to the aspect relating to the hybrid gear construction. The items of the tenth itemized list can be combined with one or more items of all other itemized lists in this document as well as with one or more features of the claims.

Tenth itemized list:

1. A reduction gear box comprising a gear unit and an output shaft,

- wherein the gear unit has a rotationally symmetric structure, including gears and/or transmission elements that return to their original position after a full rotation around a main axis of the gearbox,

- wherein the gear unit is coupled to the output shaft, and

- wherein at least one gear of the gear unit is made from a composite material comprising steel and plastic.

2. The reduction gear box according to item 1 , wherein the at least one gear comprises an interaction surface that is operatively coupled with another gear in the gear unit, the interaction surface being made of plastic.

3. The reduction gear box according to item 1 or item 2, wherein the at least one gear comprises a steel core and a plastic overlay layer.

4. The reduction gear box according to item 3, wherein the plastic overlay layer has a thickness of 0.1 - 1.5 mm, preferably of 0.2 - 1.2 mm.

5. The reduction gear box according to any of the preceding items, wherein the plastic is a high-performance polymer, preferably PEEK (Polyetheretherketone). 6. The reduction gear box according to any of the preceding claims, wherein the gear unit comprises an inner gear with external toothing and an outer gear with internal toothing.

7. The reduction gear box according to item 6, wherein the gear unit further comprises a pin ring located between the inner gear and the outer gear.

8. The reduction gear box according to item 7, wherein the pin ring has a surface facing the inner gear, the surface being provided with a plastic layer, and wherein the inner gear is made of steel.

9. The reduction gear box according to item 7 or item 8, wherein the pin ring has a surface facing the outer gear, the surface being made of steel, and wherein the outer gear is provided with a plastic layer.

10. The reduction gearbox according to any of the preceding items, wherein the outer gear is machined into the housing, and a plastic layer is applied to its surface.

11. A drive system comprising an electric motor, a reduction gear box according to item 1 - 10, a drive housing, a bottom bracket axle with a pedal shaft, a force measurement device and a control module,

- wherein the gear unit is coupled to the motor,

- wherein the output shaft is coupled to the pedal shaft,

- wherein the control module is coupled to the force measurement device and the motor,

- wherein the force measurement device is coupled to the pedal shaft for measuring force and transmitting it to the control module, and

- wherein the control module controls the motor based on the measured force.

The eleventh itemized list refers to the aspect relating to the modular gearbox system.

The items of the eleventh itemized list can be combined with one or more items of all other itemized lists in this document as well as with one or more features of the claims. Eleventh itemized list:

1. A modular reduction gearbox comprising:

- a gear unit with an output shaft,

- wherein the gear unit has a rotationally symmetric structure with gears and/or transmission elements that return to their original position after a full rotation around a main axis of the gearbox,

- wherein the gear unit is designed to allow modular exchange of specific components to achieve different gear ratios, including a first configuration with a first reduction ratio and a second configuration with second reduction ratio by replacing only two components.

2. The reduction gearbox according to item 1 , wherein the first reduction ratio is 1 :17.5, and the second reduction ratio is 1 :36.

3. The reduction gearbox according to item 1 or item 2, wherein the gear unit comprises an inner gear with external toothing, an outer gear with internal toothing, and a pin ring located between the inner gear and the outer gear.

3. The reduction gear box according to any of the preceding items, wherein the pin ring has a surface facing the inner gear, the surface being provided with a plastic layer forming a toothed surface, wherein the inner gear is made of steel, wherein the plastic layer is an exchangeable component, and wherein the inner gear with external toothing is also an exchangeable component.

4. A drive system comprising an electric motor, a reduction gear box according to item 1 - 3, a drive housing, a bottom bracket axle with a pedal shaft, a force measurement device and a control module,

- wherein the gear unit is coupled to the motor,

- wherein the output shaft is coupled to the pedal shaft, - wherein the control module is coupled to the force measurement device and the motor,

- wherein the force measurement device is coupled to the pedal shaft for measuring force and transmitting it to the control module, and

- wherein the control module controls the motor based on the measured force.

The twelfth itemized list refers to the aspect relating to the backlash-free gears. The items of the twelfth itemized list can be combined with one or more items of all other itemized lists in this document as well as with one or more features of the claims.

Twelfth itemized list:

1. A reduction gear box comprising a gear unit and an output shaft,

- wherein the gear unit has a rotationally symmetric structure, including gears and/or transmission elements that return to their original position after a full rotation around a main axis of the gearbox,

- wherein the gear unit is coupled to the output shaft, and

- wherein the gear unit is manufactured using advanced manufacturing techniques to achieve minimal backlash.

2. The reduction gear box according to item 1 , wherein at least one gear of the gear unit is a hybrid component, comprising a steel core with a plastic layer.

3. The reduction gear box according to item 2, wherein the plastic layer is precision- milled to an exact thickness between 0.5 mm and 1.2 mm, ensuring minimal manufacturing tolerances.

4. The reduction gear box according to item 3, wherein the precisely fitted plastic layer in the gear profile improves torque transmission while maintaining minimal play. 5. The reduction gear box according to any of the preceding items, wherein the gear tolerances are configured to ensure consistent performance under varying temperature conditions.

The thirteenth itemized list refers to the aspect relating to the enhanced hollow shaft. The items of the thirteenth itemized list can be combined with one or more items of all other itemized lists in this document as well as with one or more features of the claims.

Thirteenth itemized list:

1. A drive system comprising an electric motor with a stator and a rotor, and a reduction gearbox with a gear unit,

- wherein the gear unit has a rotationally symmetric structure, including gears and/or transmission elements that return to their original position after a full rotation around a main axis of the gearbox,

- wherein the stator, the rotor, and the gear unit are arranged coaxially,

- wherein the rotor is designed as a hollow shaft and comprises a transmitter driving section, and

- wherein the transmitter driving section includes a circumferential groove defined by two shoulders, the shoulders each being supported on a rolling bearing on a shaft.

2. The drive system according to item 1 , wherein the shaft can be a pedal shaft of a bottom bracket axle for an electric bike drive system or an output shaft for a robotic drive system.

3. The drive system according to item 1 or item 2, wherein an outer double-row rolling bearing is positioned in the groove, on which the gear unit is supported.

4. The drive system according to item 3, wherein the outer double-row rolling bearing is a double-row ball bearing. 5. The drive system according to any of the preceding items, wherein the rolling bearings, on which each shoulder is supported, are ball bearings.

All of the above items can also be combined with one or more the following items.

1. The drive system is suitable for an electric bike or a robotic application.

2. The drive system comprising a drive housing, an electric motor, a bottom bracket axle, a force measurement device and/or a control module.

4. The drive system, wherein the rotor comprises a rotor shaft with a transmitter driving section and a magnet holding section comprising at least one magnet, and wherein the at least one magnet is located on a radially outer surface of the rotor shaft.

5. The drive system, wherein the magnet holding section is positioned inside the stator, and the transmitter driving section is positioned outside the stator.

6. The drive system, wherein the transmitter driving section is designed as an eccentric section or an elliptic section.

7. The drive system, wherein a plurality of magnets are concentrically mounted on the outer surface of the rotor shaft.

8. The drive system, wherein the stator comprises three coils and a three phase inverter.

9. The drive system, wherein an outer double-row ball bearing is located radially outwards on the transmitter driving section of the electric motor and an inner double-row ball bearing is located radially inwards. 10. The drive system, wherein the gear unit comprises a pin-ring, an outer gear with internal toothing and an inner gear with external toothing.

11. The drive system, wherein the pin ring is C-shaped in cross section, wherein a radially outer leg of the C is toothed on both sides, while a radially inner leg of the C is not toothed.

12. The drive system, wherein a radially inner surface of the inner gear is disposed on the radially inner leg of the pin ring.

13. The drive system, wherein the outer double-row ball bearing is in contact with the transmitter driving section and the radially inner leg of the pin ring.

14. The drive system, wherein due to radial motion or force of the outer double-row ball bearing, the radially outer leg of the pin ring mesh with the outer gear with internal toothing, and/or with inner gear with external toothing.

15. The drive system, wherein the reduction gear box comprises a roller bearing which is operatively coupled with the inner gear, so that a rotation of the inner gear can be transmitted to an inner ring of the roller bearing.

16. The drive system, wherein the reduction gear box comprises a first freewheel and the first freewheel is operatively coupled to the roller bearing, wherein the inner ring of the roller bearing is in contact with the first freewheel.

17. The drive system, wherein the reduction gear box comprises an output shaft and wherein the first freewheel is operatively coupled with the output shaft.

18. The drive system, wherein the output bearing is a ball bearing.

19. The drive system, wherein a second freewheel is operatively coupled with the output shaft. 20. The drive system, wherein a chainring adapter is connected to the output shaft.

21 .The drive system, wherein an outer shaft seal ring is placed between the output shaft and the drive housing.

22. The drive system, wherein the inner double-row ball bearing is located between a section of the inner gear and the transmitter driving section.

23. The drive system, wherein the bottom bracket axle comprises pedal shaft with a first crank bearing and a second crank bearing.

24. The drive system, wherein a left crank arm with a left pedal is supported in the second crank bearing and a right crank arm with a right pedal is supported in the first crank bearing.

25. The drive system, wherein the pedal shaft is supported in the drive housing with a left bottom bracket bearing and supported against the output shaft with a right bottom bracket bearing.

26. The drive system, wherein the left bottom bracket bearing and/or the right bottom bracket bearing is a ball bearing.

27. The drive system, wherein an inner shaft seal ring is located on the pedal shaft.

28. The drive system comprising a force measurement device, wherein the force measurement device comprises at least one strain gauge and/or a communication interface.

29. The drive system comprising a control module, wherein the control module comprises a printed circuit board, a microprocessor, a memory, an input interface, an output interface, analogue-to-digital converter and/or a digital-to-analogue converter. 30. The drive system, wherein the drive housing comprises a gearbox housing half, electric motor housing half, housing cover, and screw connections.

31 .The drive system, wherein the electric motor is located in the electric motor housing half and/or the force measurement device is located in the electric motor housing half and/or the reduction gear box is located in the gearbox housing half.

32. The drive system, wherein the electric motor is configured to generate an electromagnetic force that causes the rotor shaft of the rotor to rotate, wherein a transmitter driving section can convert the rotational movement of the rotor shaft into a radial movement or radial force.

33. The drive system, wherein the reduction gear box is configured to convert a radial movement or force, which is applied to the reduction gear box via a transmitter driving section, into a rotational movement, the rotational movement being directed to an output shaft.

34. The drive system, wherein the bottom bracket axle comprises a pedal shaft which is configured to be set into a rotary motion by the cyclist via a right pedal and right crank arm and a left pedal and left crank arm, and wherein the pedal shaft comprises means for transmitting the rotary motion to an output shaft.

35. The drive system, wherein the force measurement device is configured to acquire a radial force applied on the pedal shaft and to transmit a corresponding signal to the control module, and the control module is configured to analyze the signal received from the force measurement device and to control the electric motor, the electric motor being used to generate a force to support a cyclist using a bike comprising the drive system.

Reference is made to the earlier patent applications DE 10 2024 107 872.3 of 20 March 2024, EP2416873.9 of 20 March 2024, EP25162468.0 of 08 March 2025, and EP25164600.6 of 19 March 2025 the contents of which are herein incorporated by reference. Protection may be sought for combinations of features which are disclosed in these reference documents. It is disclosed there how these features combinations contribute to achieving the technical aim of the present application and they are thus comprised in the solution of the technical problem underlying the subject matter of the present application. The features combinations which are disclosed in the reference documents implicitly belong to the description of the subject matter in the present application and thus to the content of the present application as filed.

REFERENCE NUMERAL LIST

1 drive system

2 electric motor

3 stator

5 rotor

6 bottom bracket axle

7 inner gear

8 outer gear

9 left crank arm

10 right crank arm

11 left pedal

12 right pedal

13 force measurement device

14 strain gauge

17 drive housing

19 electric motor housing half

20 gearbox housing half

21 coils

23 housing cover

24 screw connections

25 magnets

26 rotor shaft

27 rotor support ring

28 magnet holding section

29 rotor bearing

31 roller bearing

33 outer double-row ball bearing

34 inner double-row ball bearing

35 pedal shaft

37 first crank bearing

38 second crank bearing

39 output shaft 40 first freewheel

41 output bearing

43 chainring adapter

45 left bottom bracket bearing

46 right bottom bracket bearing

49 second freewheel

50 inner shaft seal ring

51 outer shaft seal ring

54 reduction gear box

55 transmitter driving section

56 radially inner surface

58 radially outer surface

60 first step

62 second step

64 disc

66 radially outer ring of the rotor bearing

67 gear unit

68 transmitter bearing

70 axial teeth

72 tooth ring

74 first axial limit stop at the transmitter driving section

76 second axial limit stop at the transmitter driving section

78 radially inner leg of the C-shaped inner gear I axial part of support section of the inner gear

80 radially outer leg of the C-shaped inner gear I ring with external toothing

81 support section of the inner gear

82 receiving sleeve

83 radial plane

84 fastening ring

86 measuring region

88 radial aligned wall of the measuring region

90 axial aligned wall of the measuring region 92 fastening areas at fastening ring

94 fastening holes

96 printed circuit board

98 recess in measurement measuring region

99 cover seal ring

101 radially inner leg of C-shaped pin ring

102 pin-ring

103 radially outer leg of C-shaped pin ring

104 first location of meshing

105 second location of meshing

106 first plain bearing

108 second plain bearing

110 circular flange

112 circular holding section

114 clamping device

116 support interface

117 shoulder

118 groove in the drive housing

120 drive system mounting bracket

122 means for screw connection

124 bike frame

125 flattened section

126 projection

128 coupling shaft

129 plastic layer

130 steel layer

132 groove of transmitter driving section

134 shoulder defining groove of transmitter driving section

136 ball bearing supporting the shoulder

137 shaft of the drive system

Claims

1.An electric motor (2) for an electric bike drive system (1) with a reduction gear box (54) having a gear unit (67) with a rotationally symmetrical structure, comprising: a stator (3) and a rotor (5), wherein the rotor (5) comprises a rotor shaft (26) with a transmitter driving section (55) and a magnet holding section (28) comprising at least one magnet, and wherein the at least one magnet is located on a radially outer surface of the rotor shaft (26).

2. The electric motor (2) according to claim 1 , wherein the magnet holding section (28) is positioned inside the stator (3), and the transmitter driving section (55) is positioned outside the stator (3).

3. The electric motor (2) according to any of the preceding claims, wherein the transmitter driving section (55) is designed as an eccentric section or an elliptic section.

4. The electric motor (2) according to any of the preceding claims, wherein a plurality of magnets (25) are concentrically mounted on the outer surface of the rotor shaft (26).

5. The electric motor (2) according to any of the preceding claims wherein the stator (3) comprises three coils (21) and a three phase inverter.

6. A drive system (1) for an electric bike comprising an electric motor (2) according to any of the preceding claims, a bottom bracket axle (6), a reduction gear box (54) having a gear unit (67) with a rotationally symmetrical structure, a force measurement device (13), a control module and a drive housing (17).

7. The drive system (1) according to claim 6, wherein an outer double-row ball bearing (33) is located radially outwards on the transmitter driving section (55) of the electric motor (2) and an inner double-row ball bearing (34) is located radially inwards.

8. The drive system (1) according to any of the preceding claims 6 - 7, wherein the rotor (5) of the electric motor (2) is supported by a rotor support ring (27) and a rotor bearing (29) in the drive housing (17).

9. The drive system (1) according to claim 8, wherein rotor support ring (27) is made of plastic.

10. The drive system (1) according to any of the preceding claims 6 - 9, wherein the reduction gear box (54) comprises a pin-ring (102), an outer gear (8) with internal toothing and an inner gear (7) with external toothing.

11. The drive system (1) according to claim 10, wherein the pin ring (102) is C-shaped in cross section, wherein a radially outer leg (103) of the C is toothed on both sides, while a radially inner leg (101) of the C is not toothed.

12. The drive system (1) according to claim 11 , wherein a radially inner surface of the inner gear (7) is disposed on the radially inner leg (101) of the pin ring (102).

13. The drive system (1) according to claim 12, wherein the outer double-row ball bearing (33) is in contact with the transmitter driving section (55) and the radially inner leg (101) of the pin ring (102).

14. The drive system (1) according to claim 13, wherein due to the radial motion or force of the outer double-row ball bearing (33), the radially outer leg (103) of the pin ring (102) mesh with the outer gear (8) with internal toothing, and/or with inner gear (7) with external toothing.

15. The drive system (1) according to any of the preceding claims 10 - 14, wherein the reduction gear box (54) comprises a roller bearing (31) which is operatively coupled with the inner gear (7), so that a rotation of the inner gear (7) can be transmitted to an inner ring of the roller bearing (31).

16. The drive system (1) according to claim 15 wherein the reduction gear box (54) comprises a first freewheel (40) and the first freewheel (40) is operatively coupled to the roller bearing (31), wherein the inner ring of the roller bearing (31) is in contact with the first freewheel (40).

17. The drive system (1) according to claim 16, wherein the reduction gear box (54) comprises an output shaft (39) and wherein the first freewheel (40) is operatively coupled with the output shaft (39).

18. The drive system (1) according to claim 17, wherein the output shaft (39) is supported in an output bearing (41).

19. The drive system (1) according to claim 18, wherein the output bearing (41) is a ball bearing.

20. The drive system (1) according to any of the preceding claims 17 - 19, wherein a second freewheel (49) is operatively coupled with the output shaft (39).

21. The drive system (1) according to any of the preceding claims 17 - 20, wherein a chainring adapter (43) is connected to the output shaft (39).

22. The drive system (1) according to any of the preceding claims 17 - 21 , wherein an outer shaft seal ring (51) is placed between the output shaft (39) and the drive housing (17).

23. The drive system (1) according to claim 10, wherein the inner double-row ball bearing (34) is located between a section of the inner gear (7) and the transmitter driving section (55).

24. The drive system (1) according to any of the preceding claims 6 - 23, wherein the bottom bracket axle (6) comprises pedal shaft (35) with a first crank bearing (37) and a second crank bearing (38).

25. The drive system (1) according to claim 24, wherein a left crank arm (9) with a left pedal (11) is supported in the second crank bearing (38) and a right crank arm (10) with a right pedal (12) is supported in the first crank bearing (37).

26. The drive system (1) according to any of the preceding claims 24 - 25, wherein the pedal shaft (35) is supported in the drive housing (17) with a left bottom bracket bearing (45) and supported against the output shaft (39) with a right bottom bracket bearing (46).

27. The drive system (1) according to claim 26 wherein the left bottom bracket bearing (45) and/or the right bottom bracket bearing (46) is a ball bearing.

28. The drive system (1) according to any of the preceding claims 24 - 27 wherein an inner shaft seal ring (50) is located on the pedal shaft (35).

29. The drive system (1) according to any of the preceding claims 6 - 28, wherein the force measurement device (13) comprises at least one strain gauge (14) and/or a communication interface.

30. The drive system (1) according to any of the preceding claims 6 - 29, wherein the control module comprises a printed circuit board, a microprocessor, a memory, an input interface, an output interface, analogue-to-digital converter and/or a digital-to-analogue converter.

31 .The drive system (1) according to any of the preceding claims 6 - 30, wherein the drive housing (17) comprises a gearbox housing half (20), electric motor housing half (19), housing cover (23), and screw connections (24).

32. The drive system (1) according to claim 31 , wherein the electric motor (2) is located in the electric motor housing Half (19) and/or the force measurement device (13) is located in the electric motor housing Half (19) and/or the reduction gear box (54) is located in the Gearbox Housing Half (20).

33. The drive system (1) according to any of the preceding claims 6 - 32, wherein the electric motor (2) is configured to generate an electromagnetic force that causes the rotor shaft (26) to rotate, wherein the transmitter driving section (55) can convert the rotational movement of the rotor shaft (26) into a radial movement or radial force.

34. The drive system (1) according to any of the preceding claims 6 - 33, wherein the reduction gear box (54) is configured to convert a radial movement or force, which is applied to the reduction gear box (54) via the transmitter driving section (55), into a rotational movement, the rotational movement being directed to an output shaft (39).

35. The drive system (1) according to any of the preceding claims 6 - 35, wherein the bottom bracket axle (6) comprises a pedal shaft (35) which is configured to be set into a rotary motion by the cyclist via a right pedal (12) and right crank arm (10) and a left pedal (11) and left crank arm (9), and wherein the pedal shaft (35) comprises means for transmitting the rotary motion to an output shaft (39).

36. The drive system (1) according to any of the preceding claims 6 - 35, wherein -the force measurement device (13) is configured to acquire a radial force applied on the pedal shaft (35) and to transmit a corresponding signal to the control module, and -the control module is configured to analyze the signal received from the force measurement device (13) and to control the electric motor (2), the electric motor (2) being used to generate a force to support a cyclist using a bike comprising the drive system (1).