CN119790581A

CN119790581A - Brushless DC motor

Info

Publication number: CN119790581A
Application number: CN202380061005.2A
Authority: CN
Inventors: 徐勇辉; 韦开明; 方相钰; 张国安
Original assignee: Techtronic Cordless GP
Current assignee: Techtronic Cordless GP
Priority date: 2023-05-26
Filing date: 2023-05-26
Publication date: 2025-04-08
Also published as: AU2023450042A1; WO2024243728A1

Abstract

A brushless DC motor is disclosed that includes a shaft, a rotor, and a stator assembly disposed about the rotor. A plurality of windings are supported on the stator. The circuit board is attached to an end of the stator and includes a plurality of slots that receive the winding portions therein. One or more strain relief tabs extend from the stator proximate to at least one slot of the plurality of slots to abut at least a portion of a winding wound thereon.

Description

Brushless DC motor

Technical Field

The present disclosure relates to electric motors, and more particularly to a brushless direct current (BLDC) motor, a stator suitable for use in the motor, a tool using such a motor, and a method of manufacturing such a motor.

Background

A battery operated motor in a power tool is typically arranged for rotating a shaft to which the tool is attached in dependence of electromagnetic interactions occurring between the windings and permanent magnets in the motor. In a permanent magnet brushed DC motor, the windings are wound on a magnetizable core (rotor) that rotates within a stationary permanent magnet (stator). The windings receive current via brushes and commutators, and are therefore referred to as brushed DC motors.

In an alternative arrangement (i.e., brushless DC motor), the stator windings surround the inner permanent magnet rotor. Brushless DC motors are typically more durable than brushed motors, with higher speed and torque capabilities. In addition, brushless DC motors typically produce less noise and have a longer life.

In a brushless DC motor, switching of the current in the surrounding stator windings drives rotation of the rotor and attached shaft. Injecting current into successive stator coils creates varying electromagnetic poles on the stator perimeter. These varying poles of the stator coil are in turn energized to attract opposite poles on the rotor to produce torque and rotation of the motor shaft, which in turn is used to drive the driven member of the power tool.

As is known in the art, in the operation of brushless DC motors, it is critical to ensure synchronization of the rotating magnetic poles produced by energizing the stator coils with the rotating magnetic poles of the rotor. Typically, a sensor (e.g., a hall effect sensor) mounted on a sensor board attached to the stator is arranged to detect the position of the rotor poles relative to the coil windings. The detected position is then provided to a motor controller circuit for controlling the current to the stator coils. Typically, the wires of the stator coils pass through slots in the sensor board to the power supply, with a mass of solder securing the wires in the slots.

Unfortunately, in many cases, the wires of the stator coils may fatigue at the slots from long runs in view of the different vibration frequencies inherent to the stator body and the sensor plate during operation, resulting in eventual failure of the motor.

It is an object of the present disclosure to provide an alternative arrangement which solves or at least partially ameliorates the above-mentioned disadvantages or at least provides the public with a further choice.

Disclosure of Invention

Features and advantages of the disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the principles disclosed herein. The features and advantages of the disclosure may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.

According to a first aspect of the present disclosure, there is provided a brushless DC motor comprising an elongate motor shaft, a rotor comprising a plurality of magnets fixed about the elongate motor shaft, a stator assembly arranged about the rotor, the stator assembly comprising a plurality of windings supported on the stator, a circuit board attached to an end of the stator, the circuit board comprising a plurality of slots in which winding portions are received, wherein one or more strain relief protrusions may extend from the stator adjacent to at least one of the plurality of slots to bear against at least a portion of a winding wound thereon.

A portion of one or more strain relief protrusions may extend radially outward relative to the elongate motor shaft and be positioned to be offset in a path between a slot and a corresponding winding of a stator assembly received therein.

A portion of the one or more strain relief protrusions may extend downward and toward an end of the stator.

One or more strain relief protrusions may extend in an L-shape from an end of the stator.

Alternatively, one or more strain relief protrusions may extend from the end of the stator in an at least partially U-shape.

The circuit board may be attached to the ends of the stator by fasteners disposed proximate to and between a pair of adjacent ones of the plurality of slots.

The fasteners may be positioned equidistantly around the circuit board to attach the circuit board to the stator.

Optionally, the fastener is a screw.

The circuit board may be attached to the end of the stator by three equidistant screws disposed between adjacent slots located at the periphery of the circuit board.

Optionally, the circuit board is a sensor board.

According to a second aspect of the present disclosure, a brushless DC motor is provided that includes an elongated motor shaft, a rotor including a plurality of magnets fixed about the elongated motor shaft, a stator assembly disposed about the rotor, the stator assembly including a plurality of windings supported on a stator, wherein the stator may include a mounting portion for receiving fasteners engaged with a circuit board, the mounting portion may be disposed between a pair of adjacent windings extending from the stator. Optionally, a circuit board is attached to an end of the stator, the circuit board including a plurality of slots in which the winding portions are received.

Each of the mounting portions may receive a screw therein.

The brushless DC motor may further include one or more strain relief tabs extending from the stator proximate at least one of the plurality of slots to abut at least a portion of the winding wound thereon.

Optionally, the circuit board is a sensor board.

According to a third aspect of the present disclosure, there is provided a stator for a brushless DC motor, the stator comprising one or more strain relief tabs arranged to extend from an end of the stator adjacent to one or more corresponding slots of a stator-engagable circuit board, the one or more strain relief tabs abutting at least a portion of one of a plurality of windings wound thereon.

One or more strain relief tabs may extend radially outward from the stator and deviate from a path between one or more corresponding slots and corresponding windings wound around the stator when assembled.

Optionally, the stator includes mounting portions for receiving fasteners engaged with the circuit board, each of the mounting portions being positionable between a pair of adjacent windings extending from the stator.

The mounting portion may receive a screw therein.

Optionally, the circuit board is a sensor board.

According to a fourth aspect of the present disclosure there is provided a stator for a brushless DC motor, the stator comprising a mounting portion for receiving a corresponding fastener for engagement with a circuit board, the mounting portion being disposed between a pair of adjacent windings extending from the stator.

The mounting portion may receive a screw therein.

Optionally, the circuit board is a sensor board.

According to a fifth aspect of the present disclosure there is provided an appliance or tool comprising a stator as described above or a motor as described above.

According to a sixth aspect of the present disclosure, there is provided a method of manufacturing a brushless DC motor as described above, wherein one or more windings of the plurality of windings are at least partially wound around the strain relief protrusion.

Optionally, the circuit board is attached to the stator by a plurality of fasteners, wherein each fastener is disposed on the circuit board adjacent to and between a pair of slots to receive windings therethrough.

According to a seventh aspect of the present disclosure, there is provided a method of manufacturing a stator as described above, wherein one or more of the plurality of windings is at least partially wound around the strain relief protrusion.

It is an object of the present disclosure to solve or at least partially ameliorate some of the above problems with current methods.

Drawings

In order to describe the manner in which the above-recited and other advantages and features of the disclosure can be obtained, a more particular description of the principles of the disclosure briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is to be understood that the drawings depict only exemplary embodiments of the disclosure and are therefore not to be considered limiting of its scope, the principles herein will be described and explained with additional specificity and detail through the use of the accompanying drawings.

Preferred embodiments of the present disclosure will be explained in further detail below by way of example and with reference to the accompanying drawings, in which

In the figure:

fig. 1A depicts an exploded perspective view of various components of a brushless DC motor according to a conventional design.

Fig. 1B depicts a perspective view of a hall sensor plate and stator of a conventional brushless DC motor assembly.

Fig. 1C depicts an enlarged perspective view of a disconnection between stator wires and a circuit board.

Fig. 2A depicts an exploded perspective view of various components of a brushless DC motor of improved design in accordance with an embodiment of the present invention.

Fig. 2B depicts an exploded perspective view of the various components of a brushless DC motor of improved design in accordance with another embodiment of the invention.

Fig. 2C depicts a perspective view of the hall sensor plate and stator of fig. 2A or 2B.

Fig. 2D depicts an enlarged perspective view of an exemplary strain relief tab and end retention member of the stator of fig. 2A.

Fig. 2E depicts an enlarged perspective view of an exemplary strain relief tab and end retention member of the stator of fig. 2B.

Fig. 2F depicts an enlarged perspective view of the example fastener, sensor plate, a portion of a winding, and a stator of fig. 2A.

Fig. 3A depicts a schematic side view of an exemplary strain relief tab.

Fig. 3B depicts a schematic side view of an alternative exemplary strain relief tab.

Fig. 4A depicts a schematic diagram of an exemplary tool in which a brushless DC motor is disposed.

Fig. 4B depicts an enlarged schematic view of the brushless DC motor of fig. 4A.

Detailed Description

A number of different embodiments of the present disclosure are discussed in detail below. While specific embodiments are discussed, it should be understood that this is done for illustrative purposes only. One skilled in the relevant art will recognize that other components and configurations may be used without departing from the scope of the disclosure.

The disclosed technology addresses the need in the art for an improved brushless DC motor that addresses or at least ameliorates some of the disadvantages of the prior art.

As depicted in the embodiment of the present disclosure shown in fig. 1A, the front cover 102 receives a front coil retainer 104 in which a stator stack 106 and insulation paper 108 are also received. Stator assembly 110 includes front coil retainers 104, rear coil retainers 105, and stator stack assemblies 106 and windings 112. The stator 111 includes a front coil retainer 104, a rear coil retainer 105, and a stator stack 106.

A Printed Circuit Board (PCB) 114 (typically with hall effect sensors) may be attached to the back coil retainer 105 of the stator 111 via fasteners 116. Typically, but not exclusively, such fasteners may be screws or the like which engage into corresponding threaded portions comprised in the rear coil retainer 105. Typically, these screws extend through holes 117 (not shown) in the circuit board 114, the specific location may be based on the design of the circuit.

The rotor assembly 130 (including the magnets 128 arranged around the elongate shaft 134 and rotor lamination stack 131) is supported by various components on the front side of the motor. Typically, these components include wave washers 118, ball bearings 120, 126, front balance washers 122, and rubber rings 124, although other arrangements may be used. The rotor assembly 130 is also supported at the rear of the motor by a rear balance washer 132.

In the conventional motor 100 depicted in fig. 1A, the rotor assembly 130, the elongated shaft 134, and the stator assembly 110 are thus received and supported between the front cover 102 and the rear cover 136, secured together by screws or other fasteners 138. It should be appreciated that although not depicted, other arrangements of prior art brushless motors that do not include the front cover 102 and the rear cover 136 are also used.

Fig. 1B depicts an enlarged perspective view of the hall sensor plate and stator of the conventional brushless DC motor assembly of fig. 1A. For ease of reference, this enlarged view depicts a conventional arrangement of a brushless DC motor in which the windings 112 are received in slots 115 of a printed circuit board 114.

It will be appreciated that the ends 113 of the windings 112 have been truncated in the figures, and ultimately these ends are connected to a motor controller (not shown) for connection to a power source.

As depicted, the ends 113 of the windings 112 are supported on the stator 111 and extend directly above through corresponding slots 115 defined in the circuit board 114. Typically, the windings are secured in the slots with a mass of solder (not shown).

Referring now to fig. 1C, an enlarged perspective view of a disconnection between stator wires and a circuit board is depicted. The winding heads 113 have sheared from another portion of the winding (not shown for clarity) that is retained in slots 115 of PCB114 by a small amount of solder.

Fig. 2A depicts an exploded perspective view of various components of a brushless DC motor of improved design in accordance with an embodiment of the present invention. It should be noted that this arrangement includes a pair of end caps for securing the components of the motor.

Similar to the arrangement depicted in fig. 1A, a front cover 202 is shown that receives a front coil retainer 204 in which a stator stack 206 and insulating paper 208 are also received. The stator assembly 210 includes a front coil retainer 204, a rear coil retainer 205, and a stator stack 206 of a stator 211, and windings 212. The stator 211 includes a front coil retainer 204, a rear coil retainer 205, and a stator stack 206.

A printed circuit board 214 (typically with hall effect sensors) may be attached to the back coil retainer 205 of the stator 211 via fasteners 216. Such fasteners may be screws or the like that engage into corresponding threaded portions included in the rear coil retainer 205. These screws extend through holes 217 (not shown) in the circuit board 214.

Rotor assembly 230 (including magnets 228 and rotor lamination stack 231 disposed about shaft 234) is supported by various components on the front side of the motor. Typically, these components include wave washers 218 (not shown), ball bearings 220, 226 (not shown), front balance washers 222, and rubber rings 224, although other arrangements may be used. The rotor assembly 230 is also supported at the rear of the motor by a rear balance washer 232.

In the motor 200 depicted in fig. 2A, the rotor assembly 230, shaft 234, and stator 211 are thus received and supported between the front cover 202 and rear cover 236, secured together by screws or other fasteners 238.

Basically, the embodiment depicted in FIG. 2B is identical to the embodiment shown in FIG. 2A, except that there is no change in shape of the end cap members 202, 236 and the strain relief tab 250, which will be described in further detail below.

Fig. 2C depicts an enlarged perspective view of the hall sensor plate and stator of the brushless DC motor assembly of fig. 2A and/or 2B.

As can be seen from the enlarged view, the windings 212 are received in slots 215 of the printed circuit board 214. (some of the reference numerals for some slots/windings have been omitted for clarity). It should be appreciated that the ends of windings 212 have been truncated in the figures, and ultimately these ends are connected to a motor controller (not shown) for connection to a power source.

As depicted, the windings 212 are supported on the stator 211 and pass from the stator around strain relief tabs 250 formed on the rear coil retainers 205. As shown, the strain relief tab 250 extends or protrudes outwardly away from the elongate shaft 234 (not shown), as shown in more detail in fig. 2D-2F.

The strain relief tab 250 is provided such that the path of the windings 212 as they exit the stator assembly 210 when assembled does not pass directly through the slot 215 of the circuit board 214 as in conventional prior art arrangements. Rather, in an arrangement according to the present disclosure, the windings exit from the stator, bend and rest against the strain relief tabs to bear around the tabs, and then extend upwardly through slots 215 of circuit board 214.

Thus, in manufacturing the motor, the windings are at least partially wound around the strain relief member 250.

During operation, the positioning of the strain relief member 250 relative to the slots and windings on the stator means that the forces caused by the vibration frequency differences of the stator and the circuit board no longer act on the solder joints, but on the strain relief protrusions. The windings have the ability to deform and move slightly around the strain relief member 250. This increases the lifetime of the motor, as fatigue in the windings is avoided.

Fig. 2D depicts an enlarged perspective view of an exemplary strain relief member and end retention member of the stator.

As depicted, the strain relief protrusion may be a generally L-shaped arrangement with the first body portion 252 extending in a direction parallel to the longitudinal axis of the elongate shaft and the arm portion 254 extending radially outward from the elongate shaft. This arrangement is particularly suitable for smaller motors or shorter motors, wherein the stator winding coils have a smaller diameter.

Fig. 2E depicts an enlarged perspective view of an exemplary strain relief tab (which is U-shaped in this arrangement) of the stator.

Fig. 2F depicts a perspective view of an exemplary sensor plate 214 and an end of the stator 211, particularly the back coil retainer 205.

In the depicted embodiment, three equidistant apertures 217 are provided between each pair of adjacent slots 215 located at the periphery of the sensor plate 214, which slots receive windings of the stator. As shown, there are three fasteners (in this case screws) 216 configured to engage the sensor plate 214 with the stator 211. Slots 215 in circuit board 214 are located on either side of apertures 217 of screws 216.

It should be noted that the apertures for the fasteners of the circuit board 214 may be defined proximate to and between the slots of the circuit board in conjunction with the strain relief tabs extending from the stators described herein.

Alternatively, apertures 217 for fasteners of the circuit board 214 may be defined proximate to and between each pair of slots of the circuit board as an alternative to strain relief protrusions extending from the stator described herein. In either arrangement, the location of the apertures near the slots 215 reduces the force and displacement on the windings by minimizing the moment created by the difference in relative vibrations of the stator assembly 210 and the circuit board 214.

Fig. 3A depicts a schematic side view of an exemplary strain relief tab.

As depicted, the winding includes an end portion 213 that is in contact with a strain relief tab 250. In particular, as depicted, the strain relief protrusion may be a generally L-shaped arrangement with the first body portion 252 extending in a direction parallel to the longitudinal axis of the elongate shaft and the arm portion 254 extending radially outward from the elongate shaft. This arrangement is particularly suitable for smaller motors where the stator winding coils have a small diameter and where no end caps are applied. Typically, although not exclusively, such smaller motors may have a diameter of the stator laminations 206 of less than 38 mm.

As depicted, the winding includes an end portion 213 that is in contact with a strain relief tab 250. In particular, as depicted, the strain relief protrusion may be a generally U-shaped arrangement with the first body portion 252 extending in a direction parallel to the longitudinal axis of the elongate shaft and the arm portion 254 extending radially outward from the elongate shaft. The second body portion 256 extends generally downwardly from the arm portion 254 in a direction arranged generally parallel to the elongate axis. This arrangement is particularly suitable for larger diameter motors or longer motors where the stator winding coils have a larger diameter, and where the end caps may not be suitable because the additional body portion 256 provides additional securement of the windings over-wound therethrough.

It should be understood by those skilled in the art that while fig. 3A and 3B both depict windings disposed at or near the junction of the body portions of the arms and strain relief protrusions, other arrangements are possible in which the windings are against the body portions and spaced farther from the junction of the arms and body portions without departing from the scope of the present disclosure.

Fig. 4A depicts an exemplary tool in which a brushless DC motor is provided, while fig. 4B depicts an enlarged portion thereof.

As depicted, tool 310 is an exemplary drill bit that includes motor 320 that includes stator assembly 330 and rotor assembly 340, and circuit board 350 (not shown) configured as described above. It should be understood that other tools provided with similar motors, such as power saws, blowers, etc., may also be used without departing from the scope of the present disclosure.

The arrangement of the aperture of the circuit board and the strain relief member together or separately can demonstrate an increase in lifetime of the brushless DC micro motor (e.g., from 30mm to 60mm in diameter). However, it should be understood that the teachings of the present disclosure are not limited to the present application and are applicable for use with larger motors.

The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the present disclosure as defined in the appended claims.

While various examples and other information are used to explain aspects within the scope of the appended claims, in such examples no limitation to the claims should be implied based on the particular features or arrangements because such examples would be used by a person of ordinary skill to derive a variety of implementations. Further, although some subject matter may have been described in language specific to structural features and/or methodological steps, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the described features or acts. For example, such functionality may be distributed differently or performed in components other than those identified herein. Rather, the described features and steps are disclosed as examples of components of systems and methods that are within the scope of the following claims.

Claims

1. A brushless DC motor, comprising:

An elongated motor shaft;

a rotor including a plurality of magnets secured about the elongated motor shaft;

a stator assembly disposed about the rotor, the stator assembly comprising a plurality of windings supported on a stator;

a circuit board attached to an end of the stator, the circuit board including a plurality of slots for receiving winding portions therein,

wherein one or more strain relief protrusions extend from the stator proximate at least one slot of the plurality of slots to abut against at least a portion of a winding wound thereon.

2. The brushless DC motor of claim 1 , wherein a portion of the one or more strain relief protrusions extend radially outward relative to the elongated motor shaft and are positioned to be offset in a path between a slot and a corresponding winding of the stator assembly received therein.

3. A brushless DC motor according to claim 1 or claim 2, wherein a portion of the one or more strain relief projections extends downwardly and towards an end of the stator.

4 . The brushless DC motor of claim 1 , wherein the one or more strain relief protrusions extend from an end of the stator in an L-shape.

5. The brushless DC motor of claim 1, wherein the one or more strain relief protrusions extend from an end of the stator in at least a partial U-shape.

6. The brushless DC motor of claim 1, wherein the circuit board is attached to the end of the stator by fasteners disposed proximate to and between a pair of adjacent slots of the plurality of slots.

7. The brushless DC motor of claim 6, wherein the fasteners are positioned equidistantly around the circuit board to attach the circuit board to the stator.

8. A brushless DC motor according to claim 6 or claim 7, wherein the fastener is a screw.

9. A brushless DC motor according to claim 6 or claim 7, wherein the circuit board is attached to the end of the stator by three equidistant screws arranged between adjacent slots at the periphery of the circuit board.

10. The brushless DC motor of claim 1, wherein the circuit board is a sensor board.

11. A brushless DC motor comprising:

An elongated motor shaft;

a stator assembly disposed about the rotor, the stator assembly including a plurality of windings supported on a stator, wherein the stator includes a mounting portion for receiving a fastener engaged with a circuit board, the mounting portion being disposed between a pair of adjacent windings extending from the stator;

A circuit board is attached to an end of the stator, the circuit board including a plurality of slots receiving winding portions therein.

12. The brushless DC motor of claim 11, wherein each of the mounting portions is configured to receive a screw therein.

13. A brushless DC motor according to claim 11 or claim 12, further comprising: one or more strain relief protrusions extending from the stator proximate at least one slot of the plurality of slots to abut against at least a portion of a winding wound thereon.

14. The brushless DC motor of claim 11, wherein the circuit board is a sensor board.

15. A stator for a brushless DC motor, the stator comprising

One or more strain relief tabs are arranged to extend from an end of the stator proximate one or more corresponding slots of a circuit board to which the stator can be engaged, and the one or more strain relief tabs abut at least a portion of one of the plurality of windings wound thereon.

16. The stator of claim 15, wherein the one or more strain relief protrusions are configured to extend radially outward from the stator and offset from a path between the one or more corresponding slots and corresponding windings wound around the stator when assembled.

17. A stator according to claim 15 or claim 16, wherein a portion of the one or more strain relief projections extends downwardly and towards an end of the stator.

18. The stator of claim 15, wherein the one or more strain relief tabs extend from an end of the stator in an L-shape.

19. The stator of claim 15, wherein the one or more strain relief tabs extend from an end of the stator in at least a partial U-shape.

20. The stator of claim 15, comprising mounting portions for receiving fasteners that engage a circuit board, each of the mounting portions being disposed between a pair of adjacent windings extending from the stator.

21. The stator of claim 20, wherein the mounting portion is configured to receive a screw therein.

22. The stator of claim 15, wherein the circuit board is a sensor board.

23. A stator for a brushless DC motor, the stator comprising:

A mounting portion for receiving a corresponding fastener that engages a circuit board is disposed between a pair of adjacent windings extending from the stator.

24. The stator for a brushless DC motor according to claim 23, wherein the mounting portion is configured to receive a screw therein.

25. The stator for a brushless DC motor according to claim 23, wherein the circuit board is a sensor board.

26. An electrical appliance or tool comprising a stator according to claims 15 to 24 or a motor according to claims 1 to 14.

27. A method for manufacturing the brushless DC motor of claim 1, wherein one or more of the plurality of windings are wound at least partially around the strain relief tab.

28. A method for manufacturing a brushless DC motor according to claim 1, wherein the circuit board is attached to the stator by a plurality of fasteners, wherein each fastener is disposed on the circuit board adjacent to and between a pair of slots to receive a winding therethrough.

29. The method for manufacturing a stator of claim 15, wherein one or more of the plurality of windings are wound at least partially around the strain relief protrusion.

30. The method for manufacturing a stator according to claim 15, wherein the circuit board is attached to the stator by a plurality of fasteners, wherein each fastener is disposed on the circuit board adjacent to and between a pair of slots to receive a winding therethrough.