DE102023202486A1 - Electric work machine - Google Patents

Abstract

The invention relates to an electric work machine (10), comprising a first electric drive (20) with a first electric motor (21), a first energy store (22) and a first control unit (24) and a second electric drive (30) with a second electric motor (31), a second energy store (32) and a second control unit (34), further comprising an internal interface (11) via which the first electric drive (20) is electrically connected to the second electric drive (30). The work machine (10) according to the invention is characterized in that the internal interface (11) is designed to allow an energy flow from the first electric drive (20) to the second electric drive (30) and to prevent an energy flow from the second electric drive (30) to the first electric drive (20).

Description

The invention relates to an electric working machine according to the preamble of claim 1 and a corresponding truck mixer.

The state of the art includes truck mixers that use a mixing drum to transport concrete from a cement plant to a place where the concrete is used, usually a construction site. In order to keep the concrete liquid both during loading of the mixing drum in the cement plant and during transport to the construction site, the mixing drum must remain in constant rotation. The mixing drum must also be rotated when unloading at the construction site, but now in the opposite direction in order to convey the concrete out of the mixing drum.

It is also known that the mixing drum can be driven by a hydraulic motor, for example, which in turn is driven by hydraulic pumps. The pumps in turn can be driven by a combustion engine of the truck mixer, which is also used to drive the truck mixer.

It is also known to drive the mixing drum using an electric motor. The electric motor can be supplied with electrical power during a transport journey, for example from a generator, whereby the generator is driven by the combustion engine of the truck mixer. The use of an electric motor makes it possible to switch off the combustion engine, particularly during loading with concrete, while waiting for the concrete to be unloaded and during the actual unloading. The electric motor for driving the mixing drum can meanwhile be supplied with the required electrical power, for example from a battery in the truck mixer or from an external power source. This means that the consumption of fuel in the truck mixer can be reduced. At the same time, CO ₂ and NO _x emissions are also reduced and noise generation is greatly reduced, which is an advantage, especially near residential areas.

Such electric drum drives are known, for example, from JP 2003 226 192 A , JP 2003 301 802 A and the DE 20 2009 001 416 U known.

The EP3 680 080 B1 describes a cement truck comprising a motor vehicle with a first drive system for driving the vehicle and a drum device with a second drive system for rotating a drum. The first and second drive systems are each battery-electric drive systems with a first and a second battery set, respectively. Energy flows from the first to the second drive system can be enabled via an electrical connection means in order to charge the second battery set by means of the first battery set and vice versa.

However, the known electric drives for truck mixers have the disadvantage that they either have completely separate drive systems for the traction drive and the drum drive, so that no energy exchange is possible between the two systems. Or energy can flow from both the traction drive and the drum drive and vice versa. The former leads to the disadvantage that two complete drive trains have to be provided, in particular two comparatively expensive battery storage units. The latter requires complex adaptation and coordination of the mixer structure to the vehicle, which in practice often fails because both components come from different suppliers who do not want to disclose their system specifications in detail to the other supplier.

It is an object of the present invention to propose an improved electrical working machine.

This object is achieved according to the invention by the electrical work machine according to claim 1. Advantageous embodiments emerge from the subclaims.

The invention relates to an electric work machine, comprising a first electric drive with a first electric motor, a first energy storage device and a first control unit and a second electric drive with a second electric motor, a second energy storage device and a second control unit, further comprising an internal interface via which the first electric drive is electrically connected to the second electric drive.

The invention therefore relates to an electrically driven work machine which comprises two electrical drives which can be operated independently of one another, namely the first electrical drive and the second electrical drive. Each electrical drive comprises an electric motor, an energy storage device and a control unit.

The first control unit controls the first electric motor, for example via a first inverter assigned to the first electric motor, and advantageously monitors a state of the first Energy storage device in order to prevent damage or destruction of the first energy storage device by removing or supplying excessive electrical currents. The first control unit preferably also monitors a charge level of the first energy storage device.

In an analogous manner, the second control unit controls the second electric motor, for example via a second inverter assigned to the second electric motor, and advantageously monitors a state of the second energy storage device in order to prevent damage to or destruction of the second energy storage device by removing or supplying excessive electrical currents. The second control unit preferably also monitors a charge level of the second energy storage device.

It is preferably provided that the first and second drives are designed to be capable of recuperation, i.e. that the first energy storage device can be charged in a recuperation mode of the first electric motor and the second energy storage device can be charged in a recuperation mode of the second electric motor. The recuperation mode of the first electric motor is also advantageously controlled by the first control unit, so that no higher currents are supplied to the first energy storage device than can be absorbed by it and damage to or destruction of the first energy storage device can be ruled out.

Likewise, the recuperation operation of the second electric motor is advantageously also controlled by the second control unit, so that no higher currents are supplied to the second energy storage device than it can absorb.

The first energy storage device stores electrical energy that can be used to operate the first electric motor by supplying it to the motor in accordance with the first control unit.

Likewise, the second energy storage device stores electrical energy that can be used to operate the second electric motor by supplying it to the motor in accordance with the second control unit.

Finally, the electric work machine also includes an internal interface. The internal interface is an electrical interface via which the first electric drive is electrically connected to the second electric drive, so that in principle an electric current can be transmitted through the internal interface.

According to the invention, it is now provided that the internal electrical interface is designed to allow a flow of energy from the first electrical drive to the second electrical drive and to prevent a flow of energy from the second electrical drive to the first electrical drive.

This results in the technical effect that the first drive remains completely unaffected by the second drive, since there is no energy flow from the second drive to the first drive, for example not when the second drive is recuperating. Instead, the internal interface - similar to a socket - only enables one-sided energy supply to the second drive by the first drive, without the first drive, in particular without an output voltage, charging capacity or similar of the first energy storage device, having to be adapted to the properties of the second drive.

Likewise, the first control unit does not have to be adapted to the properties of the second drive, since the second drive can only access the internal interface as an energy source, but not any element of the first drive.

In other words, the first drive supplies the internal interface with electrical energy and the second drive can access the internal interface to obtain energy.

This results in the advantage that the first drive and the second drive do not have to be coordinated with each other, but can be combined almost freely and arbitrarily in a working machine.

In conventional combustion-powered machines, the first drive usually provides a power take-off shaft, which can then be used by the second drive. Since no complex coordination of the different drives is required, the first drive can be combined with almost any second drive.

Thanks to the invention, this almost unrestricted combinability of a first drive with a second drive can now also be transferred to purely electrically powered work machines.

According to a preferred embodiment of the invention, it is provided that the first energy storage device is designed as a battery storage device, which is capacitively designed to permanently supply the first drive and the second drive with This means that the first energy storage device can store enough energy to permanently supply both the first and the second drive with the electrical energy required to operate the working machine. Depending on the specific type of working machine, this can bring with it different requirements to which the first energy storage device is then adapted in accordance with the invention.

For example, the work machine can be a municipal sweeper, in which the first drive is the travel drive and the second drive is the sweeping drive. In order to enable continuous operation within the meaning of the invention, i.e. a sensible and typical operating time for such a work machine, the first energy storage device, i.e. the battery storage device, can preferably store an energy of 20 kWh to 80 kWh.

Alternatively, the work machine can also be a tractor, the first drive of which is the traction drive, for example, and the second drive of which is assigned to an attachment, e.g. a hay tedder. In this case, the first energy storage unit must be larger to enable continuous operation, as the tractor usually has to travel longer distances between two charging processes and both the first drive and the second drive require more energy than in a sweeper. For example, the first energy storage unit, i.e. the battery storage unit, can store at least 80 kWh of energy in this case.

Continuous operation within the meaning of the invention is understood to mean, in particular, an operating period which lies between two refueling operations in the case of a work machine of the same type but powered by combustion power.

The battery storage is preferably designed as a so-called high-voltage battery, for example as a 400 V battery or an 800 V battery. Higher battery voltages are also conceivable. Such high-voltage batteries generally enable more efficient operation than is possible with lower voltages.

According to a further preferred embodiment of the invention, the second energy storage device is designed as a capacitor. The second energy storage device can thus be designed to be comparatively compact and cost-effective. Since the second drive can be supplied with the required energy mainly by the first energy storage device, the second energy storage device does not have to be as large and powerful as is currently usual in the prior art. Instead, it can be functionally limited to enabling short-term power peaks of the second drive, for example as part of a boost function, or to at least partially absorbing recuperated energy from the second drive.

According to an alternative preferred embodiment of the invention, the second energy storage device is designed as a battery storage device, which is capacitively designed exclusively to supply the second drive with the electrical energy required to cover requested power peaks for a short time. In this case too, the second energy storage device can be designed to be comparatively compact and cost-effective, since it does not have to supply the second drive with energy permanently - as is usual in the prior art. In this case too, the second energy storage device is preferably functionally limited to enabling short-term power peaks of the second drive as part of a boost function or to at least partially absorbing recuperated energy from the second drive.

According to a further preferred embodiment of the invention, the internal interface is designed to convert a voltage of the first energy storage device into a voltage required to operate the second drive. This results in the advantage that any second drive can actually be selected to combine any first drive in the work machine, since the operating voltage of the first drive or the voltage of the first energy storage device can be adapted to the requirements of the second drive using the internal interface.

For example, an operating voltage of 800 V of the first drive can be reduced to a voltage of 400 V via the interface, which enables the combination of a first drive with an operating voltage of 800 V with a second drive with an operating voltage of 400 V.

According to a further preferred embodiment of the invention, it is provided that the first energy storage device and the second energy storage device have different voltages. Due to the design of the internal interface already described, a first drive or energy storage device can also be combined with a second drive in a working machine that has different operating voltages.

According to a further preferred embodiment of the invention, it is provided that only the first electric drive has an external interface for supplying external electrical energy. This advantageously makes it possible to supply the first energy store with external electrical energy via the external interface.

According to a further preferred embodiment of the invention, it is provided that only the first electric drive has an internal combustion engine and a generator for generating electrical energy. In this case, the first drive is therefore not purely electric, but is designed as a so-called hybrid drive. The internal combustion engine and the generator can supply electrical energy to the first energy storage device or the first electric motor in addition to or as an alternative to the external interface.

According to a further preferred embodiment of the invention, the work machine is designed to regeneratively charge the first energy storage device and the second energy storage device via the first electric motor. This results in the advantage that energy recuperated by the first electric motor can be fed not only to the first energy storage device, but also to the second energy storage device via the internal interface. In particular, power peaks during recuperation can thus be distributed between two energy storage devices, so that as large a proportion of the recuperated energy as possible can later be used again to operate the first and second drives.

According to a further preferred embodiment of the invention, it is provided that the work machine is designed to exclusively charge the second energy storage device recuperatively via the second electric motor. This ensures that no energy flows from the second drive to the first drive. Therefore, the first drive and the second drive do not have to be adapted to one another.

According to a further preferred embodiment of the invention, it is provided that the working machine is designed as an electric truck mixer. It is thus advantageously possible to apply the advantages according to the invention to a truck mixer which has two different drives.

Alternatively, the working machine can be designed as a garbage collection vehicle, drilling vehicle, wheel loader or tractor.

According to a further preferred embodiment of the invention, it is provided that the first electric drive is designed as a traction drive and the second electric drive is designed as a drum drive. This advantageously makes it possible to fit almost any electric drum drive to almost any truck with an electric traction drive.

The invention is explained below by way of example with reference to embodiments shown in the figures.

• 1 beispielhaft und schematisch eine mögliche Ausbildungsform einer erfindungsgemäßen Arbeitsmaschine mit einem ersten elektrischen Antrieb und mit einem zweiten elektrischen Antrieb.

It shows:

• 1 by way of example and schematically, a possible embodiment of a work machine according to the invention with a first electric drive and with a second electric drive.

Identical objects, functional units and comparable components are designated with the same reference symbols across all figures. These objects, functional units and comparable components are identical in terms of their technical features, unless the description explicitly or implicitly indicates otherwise.

1 shows, by way of example and schematically, a possible embodiment of a working machine 10 according to the invention with a first electric drive 20 and with a second electric drive 30.

The working machine 10 is, for example, an electrically driven truck mixer 10. The first drive 20 represents, for example, the travel drive 20 of the truck mixer 10 and the second electrical drive 30 represents the working drive 30, i.e. the drum drive 30.

The first drive 20 comprises a first electric motor 21, a first energy storage device 22, a first inverter 23, a first control unit 24 and an external interface 25.

The first energy storage device 22 is designed, for example, as a Li-ion battery 22 with an output voltage of 800 V, i.e. as a so-called high-voltage battery. The maximum energy content of the first energy storage device is, for example, 300 kWh. The first energy storage device 22 is therefore suitable for permanently supplying both the drive 20 and the drum drive 30 with electrical energy.

The first control unit 24 is connected at the data level to the first inverter 23 in order to control it in accordance with a driving request. The first inverter 23 in turn controls the first electric motor 21 accordingly in order to provide the mechanical power required for the driving request. The first control unit 24 is also connected to the first energy storage device 22 at the data level in order to record the charge level, the temperature, the voltage and a current flow of the first energy storage device.

The external interface 25 is intended for supplying external electrical energy and makes it possible to connect the first energy storage device 22 to an external energy source for charging with the electrical energy. The external energy source can be, for example, a high-voltage socket in the form of a so-called charging station.

Likewise, the second drive 30 comprises a second electric motor 31, a second energy storage device 32, a second inverter 33 and a second control unit 34.

The second energy storage device 32 is also designed as a Li-ion battery 32, for example, but only with an output voltage of 400 V. The maximum energy content of the second energy storage device is, for example, 5 kWh. This is sufficient to enable short-term power peaks of the drum drive 30 to be requested by supplying the second electric motor 32 not only with electrical energy from the first energy storage device 22, but also from the second energy storage device 32.

The second control unit 34 is connected at the data level to the second inverter 33 in order to control it in accordance with a rotation request from the drum drive 30. The second inverter 33 in turn controls the second electric motor 31 accordingly in order to provide the mechanical power required for the rotation request. The second control unit 34 is also connected at the data level to the second energy storage device 32 in order to record the charge level, the temperature, the voltage and a current flow of the second energy storage device 32.

The work machine 10 further comprises an internal interface 11, via which the first electric drive 20 is electrically connected to the second electric drive 30. However, the internal interface 11 is only designed to allow a flow of energy from the first electric drive 20 to the second electric drive 30. However, the internal interface 10 prevents a flow of energy from the second electric drive 30 to the first electric drive 20.

At the same time, the internal interface 11 is designed to convert the voltage of the first energy storage device 22 into the voltage of the second energy storage device 32, i.e. to reduce the voltage from 800 V to the voltage of 400.

The first electric motor 21 is designed to drive the drive 20 of the truck mixer. The first electric motor 21 is also designed to recuperate electrical energy, for example during a braking process. The recuperated electrical energy can then be fed to the first energy storage device 22 in order to charge it, and also fed to the second energy storage device 32 via the internal interface 11 in order to charge it as well.

The second electric motor 31 is designed to drive the drum drive 30 of the truck mixer. The second electric motor 31 is also designed to recuperate electrical energy, for example during a braking process of the mixer drum. The recuperated electrical energy can then be fed exclusively to the second energy storage device 32. Since only small amounts of energy can usually be recuperated when the mixer drum is braked, the entire energy recuperated by the second electric motor 31 can usually be absorbed by the second energy storage device 32.

Independently of the recuperation by the second electric motor 31, the second energy storage device 32 can also be charged by an energy flow from the first energy storage device 22 to the second energy storage device 32. Since the second drive 30 does not have an external interface, the second energy storage device 32 cannot be charged with external energy.

Reference symbol

10

Working machine, truck mixer

11

internal interface

20

first electric drive, traction drive

21

first electric motor

22

first energy storage, Li-ion battery

23

first inverter

24

first control unit

25

external interface

30

second electric drive, drum drive

31

second electric motor

32

second energy storage, Li-ion battery

33

second inverter

34

second control unit

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• JP 2003226192 A [0005]
• JP 2003301802 A [0005]
• DE 202009001416 U [0005]
• EP 3680080 B1 [0006]

Claims (12)

Electric work machine (10), comprising a first electric drive (20) with a first electric motor (21), a first energy store (22) and a first control unit (24) and a second electric drive (30) with a second electric motor (31), a second energy store (32) and a second control unit (34), further comprising an internal interface (11) via which the first electric drive (20) is electrically connected to the second electric drive (30), characterized in that the internal interface (11) is designed to allow an energy flow from the first electric drive (20) to the second electric drive (30) and to prevent an energy flow from the second electric drive (30) to the first electric drive (20). Working machine (10) after Claim 1 , characterized in that the first energy store (22) is designed as a battery store (22) which is capacitively designed to permanently supply the first drive (20) and the second drive (30) with electrical energy required for operation. Working machine (10) according to at least one of the Claims 1 and 2 , characterized in that the second energy store (32) is designed as a capacitor. Working machine (10) according to at least one of the Claims 1 and 2 , characterized in that the second energy store (32) is designed as a battery store (32) which is capacitively designed exclusively to supply the second drive (30) with electrical energy required for covering requested power peaks in the short term. Working machine (10) according to at least one of the Claims 1 until 4 , characterized in that the internal interface (11) is designed to convert a voltage of the first energy store (22) into a voltage required to operate the second drive (30). Working machine (10) according to at least one of the Claims 1 until 5 , characterized in that the first energy storage device (22) and the second energy storage device (32) have different voltages. Working machine (10) according to at least one of the Claims 1 until 6 , characterized in that only the first electric drive (20) has an external interface (25) for supplying external electrical energy. Working machine (10) according to at least one of the Claims 1 until 7 , characterized in that exclusively the first electric drive (20) has an internal combustion engine and a generator for generating electrical energy. Working machine (10) according to at least one of the Claims 1 until 8 , characterized in that the working machine (10) is designed to recuperatively charge the first energy storage device (22) and the second energy storage device (32) via the first electric motor (21). Working machine (10) according to at least one of the Claims 1 until 9 , characterized in that the working machine (10) is designed to exclusively regeneratively charge the second energy storage device (22) via the second electric motor (21). Working machine (10) according to at least one of the Claims 1 until 10 , characterized in that the working machine (10) is designed as an electric truck mixer (10). Working machine (10) after Claim 11 , characterized in that the first electric drive (20) is designed as a travel drive (20) and the second electric drive (30) is designed as a drum drive (30).

Images