In-wheel electric motor

Abstract

An in-wheel electric motor for a vehicle, comprising a stator, a first rotor arranged to be accommodated within a wheel of the vehicle, and coupling means for selectively coupling the first rotor to the wheel of the vehicle and for disconnecting the first rotor from the wheel, wherein when the first rotor is coupled to the wheel, the first rotor is arranged to rotate with the wheel, and when the first rotor is disconnected from the wheel, the first rotor is arranged to be stationary relative to the stator when the wheel rotates relative to the stator, and the coupling means.

Description

Technical Field

[0001] The present invention relates to an in-wheel electric motor, particularly an in-wheel electric motor for a vehicle.

Background Art

[0002] As the interest in environmentally friendly vehicles increases, naturally, the interest in the use of electric vehicles is also increasing accordingly.

[0003] An electric vehicle typically uses an electric motor to provide both driving the vehicle and regenerative braking for stopping the vehicle. To perform regenerative braking, the rotational motion of the drive wheels connected to the electric motor is converted into electrical energy, consuming the kinetic energy to apply a braking force to the drive wheels. The regenerated electrical energy is stored in a device such as a battery and then used to supply power to the electric motor.

[0004] However, currently, it is not practical for an electric vehicle to supply complete braking torque to all wheels only with regenerative braking. Therefore, an additional braking system such as a friction brake attached to the rotor of an in-wheel electric motor attached to the vehicle's wheel is required.

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in order to reduce the loss of the electric motor, there may be situations where it is desirable to stop the rotation of the rotor of the electric motor under certain conditions. However, if the main vehicle friction braking system is attached to the rotor of the electric motor, when the rotor is disengaged from the wheel, the vehicle will not meet the legal braking requirements.

[0006] It is desirable to improve this situation.

Means for Solving the Problems

[0007] According to one aspect of the present invention, an in-wheel electric motor, a vehicle, and a method as claimed in the claims are provided.

[0008] The present invention provides the advantage that the loss of the electric motor can be reduced when the electric motor for driving the vehicle does not need to provide driving force. For example, by disconnecting the rotor of the electric motor from the wheel of the vehicle, the rotor can be kept substantially stationary relative to the stator of the electric motor while the wheel of the vehicle is rotating, and the rotation of the rotor can be entangled with the rotation of the wheel during braking operation. Further, the present invention also provides the advantages of reducing noise and vibration while the rotor of the electric motor is disconnected from the wheel, and providing a failure mode when a problem occurs in the electric motor.

Brief Description of the Drawings

[0009] Hereinafter, the present invention will be described by way of example with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

[0010] Figure 1 shows a first embodiment of an in-wheel electric motor according to an embodiment of the present invention. The electric motor includes a stator 101 and a rotor 102. The stator 101 is arranged to be coupled to a vehicle (not shown). The stator 101 includes electric coils 103. The coils 103 are formed on a stator tooth laminate and form coil windings.

[0011] The rotor 102 includes a front portion 104 and a cylindrical portion 105 that forms a cover substantially surrounding the stator 101. The rotor 102 includes a plurality of permanent magnets 106 arranged around the inside of the cylindrical portion 105.

[0012] The magnets 106 are close to the coil windings 103 on the stator 101, and the magnetic field generated by the coils interacts with the magnets 106 arranged inside the cylindrical portion 105 of the rotor 102, so that when an alternating current is applied to the coil windings 102, the rotor 102 rotates. Since the permanent magnets 106 are used to generate a driving torque for driving the electric motor, the permanent magnets are generally called driving magnets.

[0013] The rotor 102 is attached to the stator 101 by a first bearing 107, and the vehicle wheel 109 is attached to the vehicle directly or indirectly via the stator 101 by a second bearing 108. The first bearing 107 can include a plurality of bearings, and similarly, the second bearing 108 can also include a plurality of bearings. As is well known to those skilled in the art, the wheel 109 includes a front portion 110 and a cylindrical portion 111 that forms a cover. The cover substantially surrounds the rotor 102, and a tire (not shown) is attached to the outer surface of the cylindrical portion 111.

[0014] The first bearing 107 consists of two parts. The first part is fixed to the axial inner surface of the stator 101, and the second part is fixed to the axial outer surface of the rotor 102. Therefore, the rotor 102 is rotatably fixed to the stator 101 used together via the first bearing 107, enabling the rotor 102 to rotate relative to the stator 101.

[0015] The second bearing 108 is typically a standard bearing block, such as a wheel hub for example. The second bearing 108 consists of two parts. The first part is fixed to the stator 101 in this embodiment, and the second part 113 is fixed to the wheel 109. Thus, the first part of the second bearing 108 is fixed to the vehicle directly or via the stator 101, and the second part of the second bearing 108 is fixed to the wheel. As a result, the second part 113 of the second bearing 108 and the wheel form a single entity. Therefore, a reference to the wheel includes the second part 113 of the second bearing 108. Thus, the wheel 109 is rotatably fixed to the vehicle in use via the second bearing 108.

[0016] The rotor 102 includes engagement means including a selector sleeve with a slide pin 114. The slide pin 114 extends axially away from the stator from a first position within the rotor 102 and is arranged to slide to a second position where it engages an opening (not shown) formed in the wheel 109, thereby coupling the rotor 102 and the wheel 109. Thus, when the pin 114 is in the first position, the rotor 102 is disengaged from the wheel 109, and when the wheel 109 rotates relative to the stator, the rotor 102 is arranged to remain stationary relative to the stator 101.

[0017] When the pin 114 is in the second position, the rotor 102 is coupled to the wheel 109, and since the movements of the rotor 102 and the wheel 109 are synchronized, there is a one-to-one correspondence between the rotation angle of the rotor and the rotation angle of the wheel.

[0018] As a result, when the rotor 102 is coupled to the wheel 109, the movements of the first bearing 107 and the second bearing 108 are synchronized, and when the rotor 102 is disengaged from the wheel 109, the first bearing 107 remains stationary while the second bearing 108 is rotating.

[0019] When the rotor 102 is disengaged from the wheel 109, in order to avoid damage to either the rotor or the wheel, the rotor 102 can be coupled to the wheel 109. Preferably, the rotor is arranged to rotate in synchronization with the wheel using, for example, the motor torque generated by the current flowing through the coil winding 102 as described above. When the rotations of the rotor and the wheel are synchronized, the pin 114 is arranged to move from the first position to the second position.

[0020] Preferably, the movement of the pin 114 between the first position and the second position is carried out via a starting circuit (not shown) in response to an electrical signal received from a control unit (not shown). For example, the starting circuit can include an electromagnet that controls the position of the pin 114 in response to the electrical signal. When separating the rotor 102 from the wheel 109, one or more return springs are included in the selector sleeve to assist the movement of the pin 114 back into the selector sleeve so that the pin 114 is spring-loaded within the selector sleeve.

[0021] Preferably, the stator 101 also includes a mechanism for maintaining the rotor 102 in a stationary state relative to the stator 101 when the rotor 102 is disengaged from the wheel 109. For example, this mechanism includes a starting circuit (not shown) that passes a current through a coil winding 103 attached to the stator 101 to generate a magnetic field that interacts with a magnet 106 attached to the rotor 102 and suppresses the movement of the rotor 102 relative to the stator 101. Preferably, the activation of this mechanism responds to an electrical signal received from a control unit (not shown). However, the mechanism for maintaining the rotor 102 in a stationary state can be implemented by any mechanical or electrical means.

[0022] FIG. 1 shows an engaging means including a selector sleeve with a slide pin 114 for coupling and separating the rotor 102 from the wheel 109, but any form of engaging means can be used. For example, face dogs, radial dogs, clutches, cone clutches, synchronizers, etc.

[0023] As an example, FIGS. 2-6 show alternative embodiments of an electric motor according to an aspect of the present invention, and alternative engagement means are represented in each figure. The same reference numerals are used within different figures to represent the same components.

[0024] FIG. 2 shows a second example of an electric motor according to an embodiment of the present invention, and the engagement means includes a wet clutch. The wet clutch includes a wet clutch pack 201 attached between the axial inner surface of the rotor 102 and the opposing axial surface of the wheel 109, and the wet clutch pack 201 is engaged and disengaged by a hydraulic piston 202 attached to the stator 101, so that the rotor 102 is coupled and separated from the wheel 109. The operation of the piston 202 is performed in response to an electrical signal received from the control unit.

[0025] FIG. 3 shows a third example of an electric motor according to an embodiment of the present invention, and the engagement means includes a dry clutch. The dry clutch includes a dry clutch plate 301 attached between the axial inner surface of the rotor 102 and the radial wall of the wheel 109, and the operation of the dry clutch plate 301 is performed via a clutch application plate 302, a diaphragm spring 305, an actuator rod 303, and an axial thrust bearing 304, whereby the rotor 102 can be coupled and separated from the wheel 109. The operation of the actuator rod 303 is preferably performed in response to an electrical signal received from the control unit.

[0026] Figure 4 shows a fourth example of an electric motor according to an embodiment of the present invention, and the engaging means includes a central actuating pin arrangement. The central actuating pin arrangement includes a selector sleeve 401 having a slide pin, the slide pin being arranged to slide from a first position within the rotor 102 to a second position extending axially away from the stator and engaging an opening formed in the wheel 109, the actuation of the pin being effected via a diaphragm spring 402, an actuator rod 403 and an axial thrust bearing 404, whereby the rotor 102 can be coupled to and separated from the wheel 109. The actuation of the actuator rod 403 is preferably effected in response to an electrical signal received from a control unit.

[0027] Figure 5 shows a fifth example of an electric motor according to an embodiment of the present invention, and the engaging means includes a face dog arrangement. The face dog arrangement includes a selector sleeve 501 having a face dog, the face dog being arranged to slide from a first position within the rotor 102 to a second position extending axially away from the stator and engaging a corresponding face dog 502 formed in the wheel 109 or a second part 113 of the second bearing 108. The actuation of the selector sleeve between the first and second positions is effected via an actuator rod 503, a thrust bearing 504 and a diaphragm spring 505, whereby the rotor 102 can be coupled to and separated from the wheel 109. The actuation of the actuator rod 503 is preferably effected in response to an electrical signal received from a control unit.

[0028] Figure 6 shows a sixth example of an electric motor according to an embodiment of the present invention, and the engaging means includes a slide sleeve arrangement. The slide sleeve arrangement includes a slide selector sleeve 601 having a radial dog formed on an axially inner surface of the slide selector sleeve 601. The slide selector sleeve 601 is arranged to slide from a first position within the rotor 102 to a second position extending axially away from the stator. As shown in Figure 6, when the slide selector sleeve 601 is in the first position, the radial dog formed on the slide selector sleeve 601 is arranged to engage with a corresponding radial dog formed on the wheel 109 or a second portion 113 of the second bearing 108. When the slide selector sleeve 601 is in the second position, the radial dog formed on the slide selector sleeve 601 is arranged to disengage from the corresponding radial dog formed on the wheel 109 or the second portion 113 of the second bearing 108, whereby the rotor 102 can be coupled to and separated from the wheel 109. The operation of moving the actuating sleeve 601 of the slide selector between the first position and the second position is preferably carried out in response to an electrical signal received from the control unit.

[0029] Preferably, in each of the above embodiments, a disc brake (not shown) is attached to the cylindrical portion 105 of the rotor 102, and when a braking torque is applied to the vehicle and the rotor 102 is coupled to the wheel 109 via the engaging means, the braking torque applied to the rotor 102 is also applied to the wheel 109. Alternatively, a disc brake (not shown) may be attached to the cylindrical portion of the wheel 109.

[0030] In a further embodiment of the present invention, as shown in FIG. 7, the rotor can include an inner rotor 701 and an outer rotor 702. The inner rotor 701 is attached to the stator 101 by a first bearing 107, and the outer rotor 702 is attached to the vehicle directly or indirectly via the stator 101 by a second bearing 108. In FIG. 7, the same reference numerals are used to represent the same shapes as those shown in FIG. 1.

[0031] The inner rotor 701 includes a front portion and a cylindrical portion that forms a cover substantially surrounding the stator 101. The inner rotor 701 includes a plurality of permanent magnets 106 disposed around the inside of the cylindrical portion.

[0032] The magnet 106 is close to the coil winding 103 attached to the stator 101, and when a magnetic field generated by the coil interacts with the magnet 106 disposed inside the cylindrical portion of the inner rotor 701 and an alternating current is applied to the coil winding 102, the inner rotor 701 is rotated. Since the permanent magnet 106 is used to generate a driving torque for driving the electric motor, the permanent magnet is usually called a driving magnet.

[0033] The outer rotor 702 is arranged to be directly or indirectly coupled to a wheel (not shown) of the vehicle via, for example, one or more bolts or other coupling means and coupled to the second portion 113 of the second bearing 108.

[0034] The inner rotor 701 includes engagement means for selectively coupling the inner rotor 701 to the outer rotor 702 and separating the inner rotor 701 from the outer rotor 702. When the inner rotor 701 is coupled to the outer rotor 702, the wheel is configured to rotate with the inner rotor 701. Also, when the inner rotor is separated from the outer rotor 702, the wheel rotates relative to the inner rotor 701 while the inner rotor 701 is configured to be stationary relative to the stator 101. As shown in FIGS. 1 to 6, similar to the embodiments of the present invention having a single rotor 102, any form of engagement means can be used. For example, face dogs, radial dogs, clutches, cone clutches, synchronizers, etc.

[0035] For the purposes of this embodiment, the engagement means includes a face dog arrangement. The face dog arrangement includes a selector sleeve 703 having face dogs. The face dogs are arranged to slide from a first position within the inner rotor 701 to a second position axially away from the stator 101 and engaging corresponding face dogs 707 formed in the outer rotor 702 or a second portion 113 of the second bearing 108. The operation between the first position and the second position of the selector sleeve 703 is performed via an actuator rod 704, a thrust bearing 705, and a diaphragm spring 706, thereby enabling the inner rotor 701 to be coupled to and separated from the outer rotor 702. The operation of the actuator rod 704 is preferably performed in response to an electrical signal received from a control unit.

[0036] Preferably, a disk brake (not shown) is attached to the cylindrical portion of the outer rotor 702 to supply braking torque to the vehicle. When the inner rotor 701 is coupled to the outer rotor 702 via the engagement means, the braking torque applied to the inner rotor 701 is applied to the outer rotor 702 and thus to the vehicle wheel.

Claims

1. An in-wheel electric motor for a vehicle, comprising a stator, a first rotor arranged to be housed within a wheel of the vehicle, and coupling means for selectively coupling the first rotor to the wheel of the vehicle and for disconnecting the first rotor from the wheel, wherein when the first rotor is coupled to the wheel, the first rotor is arranged to rotate with the wheel, and when the first rotor is disconnected from the wheel, the first rotor is arranged to remain stationary relative to the stator when the wheel rotates relative to the stator; and the coupling means.

2. The in-wheel electric motor according to claim 1, wherein the coupling means selectively couples the first rotor to the wheel of the vehicle and disconnects the first rotor from the wheel in response to an electrical signal.

3. The in-wheel electric motor according to claim 1 or 2, wherein the coupling means includes a face dog tooth interface or a radial dog tooth interface for coupling the first rotor to the wheel.

4. The in-wheel electric motor according to claim 1 or 2, wherein the coupling means includes a pin for coupling the first rotor to the wheel.

5. The in-wheel electric motor according to claim 4, wherein the pin is arranged to be disposed in an opening of the wheel when the rotor is coupled to the wheel.

6. The in-wheel electric motor according to claim 1 or 2, wherein the coupling means includes a clutch for coupling the first rotor to the wheel.

7. The in-wheel electric motor according to claim 1, further comprising maintaining means for maintaining the first rotor in a stationary state relative to the stator when the first rotor is disconnected from the wheel.

8. In the in-wheel electric motor according to claim 2, the maintaining means includes a starting circuit that passes an electric current through a coil winding attached to the stator to generate a magnetic field that interacts with the first rotor to suppress movement of the first rotor with respect to the stator. An in-wheel electric motor.

9. The in-wheel electric motor according to any one of the preceding claims, further comprising a first bearing that enables the wheel to rotate with respect to the stator, and a second bearing that enables the first rotor to rotate with respect to the stator. An in-wheel electric motor.

10. In the in-wheel electric motor according to claim 4, when the first rotor is coupled to the wheel, the movements of the first bearing and the second bearing are synchronized. An in-wheel electric motor.

11. In the in-wheel electric motor according to claim 4 or 5, when the first rotor is separated from the wheel, the second bearing is stationary when the first bearing is rotating. An in-wheel electric motor.

12. The in-wheel electric motor according to any one of the preceding claims, wherein the first rotor includes an inner rotor and an outer rotor. An in-wheel electric motor.

13. In the in-wheel electric motor according to claim 12, the outer rotor is arranged to be coupled to the wheel, the coupling means is arranged to selectively couple the inner rotor to the outer rotor and to separate the inner rotor from the outer rotor, and when the inner rotor is coupled to the outer rotor, the wheel is arranged to rotate with the inner rotor, and when the inner rotor is separated from the outer rotor, the inner rotor is stationary with respect to the stator and the wheel is arranged to rotate with respect to the inner rotor. An in-wheel electric motor.

14. The in-wheel electric motor according to claim 13, further comprising a brake disk attached to the outer rotor. An in-wheel electric motor.

15. A vehicle comprising a wheel and an in-wheel electric motor according to any one of claims 1 to 4.

16. A method for an in-wheel electric motor for a vehicle, the in-wheel electric motor comprising a stator, a first rotor arranged to be accommodated within a wheel of the vehicle, and coupling means for selectively coupling the first rotor to the wheel of the vehicle and for decoupling the first rotor from the wheel, wherein when the first rotor is coupled to the wheel, the wheel is arranged to rotate with the first rotor, and when the first rotor is decoupled from the wheel, the first rotor is arranged to be stationary relative to the stator while the wheel rotates relative to the first rotor, the method comprising, in response to receiving an actuation signal, coupling the first rotor to the wheel and decoupling the first rotor from the wheel.

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