In-wheel motor

Abstract

An in-wheel motor for a vehicle comprises 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 and disengaging the first rotor from the wheel of the vehicle such that 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 not coupled to the wheel, the first rotor is arranged to rotate with the wheel. And when the first rotor is disengaged from the wheel and when the wheel rotates relative to the stator, the first rotor is arranged stationary relative to the stator.

Description

Technical Field

[0001] The invention relates to an in-wheel motor, in particular to an in-wheel motor for a vehicle. Background Art

[0002] As interest in environmentally friendly vehicles increases, the use of electric vehicles has also received more attention.

[0003] Electric vehicles typically use electric motors to provide driving force for the vehicle and regenerative braking for stopping the vehicle. To achieve regenerative braking, the rotational motion of the drive wheels connected to the electric motor is converted into electrical energy, which involves the consumption of kinetic energy and provides braking force to the drive wheels. The regenerated electrical energy can be stored in a device such as a battery and subsequently used to power the electric motor.

[0004] However, it is currently impractical for electric vehicles to provide full braking torque on all wheels through regenerative braking alone. This leads to the need for additional braking systems, such as friction brakes that need to be connected to the rotor of the in-wheel electric motor, which in turn is connected to the vehicle's wheels.

[0005] However, in order to reduce motor losses, situations may arise where it is desirable to stop the motor rotor from rotating under certain conditions. However, if the primary vehicle friction brake system is connected to the motor rotor, the rotor being disconnected from the wheel will result in the vehicle being unable to meet legal braking requirements.

[0006] Hopefully this situation will improve. Summary of the invention

[0007] According to one aspect of the invention, there is provided an in-wheel electric motor, a vehicle and a method according to the accompanying claims.

[0008] The invention provides the advantage of reducing motor losses when the vehicle's drive motor is not required to provide drive force, for example by disengaging the motor's rotor from the wheel so that the rotor remains substantially stationary relative to the motor's stator as the wheel rotates, while locking the rotor's rotation to the wheel's rotation during braking operations. The invention also provides the advantages of reduced noise and reduced vibration when the motor's rotor is disengaged from the wheel, and provides a failure mode in the event of a problem with the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0010] Figure 1 A first embodiment of a motor according to an embodiment of the present invention is shown;

[0011] Figure 2 A second embodiment of a motor according to an embodiment of the present invention is shown;

[0012] Figure 3 A third embodiment of a motor according to an embodiment of the present invention is shown;

[0013] Figure 4 A fourth embodiment of a motor according to an embodiment of the present invention is shown;

[0014] Figure 5 A fifth embodiment of a motor according to an embodiment of the present invention is shown;

[0015] Figure 6 A sixth embodiment of a motor according to an embodiment of the present invention is shown;

[0016] Figure 7 A seventh embodiment of a motor according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0017] Figure 1 A first example of an in-wheel electric motor according to an embodiment of the invention is shown. The electric motor comprises a stator 101 and a rotor 102. The stator 101 is arranged to be coupled to a vehicle (not shown). The stator 101 comprises an electric coil 103. The coil 103 is formed on a stator tooth lamination to form a coil winding.

[0018] The rotor 102 includes a front portion 104 and a cylindrical portion 105 forming a cover, the cylindrical portion 105 substantially surrounding the stator 101. The rotor 102 includes a plurality of permanent magnets 106 arranged around the interior of the cylindrical portion 105.

[0019] The magnets 106 are in close proximity to the coil windings 103 on the stator 101, so that the magnetic field generated by the coils interacts with the magnets 106 arranged inside the cylindrical portion 105 around the rotor 102, thereby rotating the rotor 102 when alternating current is applied to the coil windings 102. Since the permanent magnets 106 are used to generate the drive torque that drives the motor, the permanent magnets are often referred to as drive magnets.

[0020] The rotor 102 is attached to the stator 101 via a first bearing 107, and a wheel 109 of the vehicle is attached to the vehicle via the stator 101 directly or indirectly via a second bearing 108. The first bearing 107 may include a plurality of bearings, and similarly, the second bearing 108 may 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 forming a cover, the cylindrical portion 111 substantially surrounding the rotor 102, and a tire (not shown) mounted on an outer surface of the cylindrical portion 111.

[0021] The first bearing 107 includes two parts, a first part fixed to the inner axial surface of the stator 101, and a second part fixed to the outer axial surface of the rotor 102. Therefore, the rotor 102 is rotatably fixed to the stator 101 through the first bearing 107 so that the rotor 102 rotates relative to the stator 101.

[0022] The second bearing 108 is typically a standard bearing housing, such as a wheel hub. The second bearing 108 comprises two parts, a first part fixed to the stator 101 in this embodiment, and a second part 113 fixed to the wheel 109. In this way, the first part of the second bearing 108 is fixed to the vehicle directly or via the stator 101, while the second part of the second bearing 108 is fixed to the wheel. Therefore, the second part 113 of the second bearing 108 and the wheel form a single entity, so any reference to the wheel includes the second part 113 of the second bearing 108. Therefore, the wheel 109 is rotatably fixed to the vehicle via the second bearing 108.

[0023] The rotor 102 comprises an engagement device comprising a selector sleeve having a sliding pin 114, wherein the sliding pin 114 is arranged to slide from a first position within the rotor 102 to a second position extending axially away from the stator and engaging with a hole (not shown) formed on the wheel 109, thereby coupling the rotor 102 and the wheel 109. In this way, 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 be stationary relative to the stator 101.

[0024] When the pin 114 is in the second position, the rotor 102 is coupled to the wheel 109 and the movement of the rotor 102 and the wheel 109 are synchronized so that there is a one-to-one correspondence between the rotation angles of the rotor and the wheel.

[0025] Thus, 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 decoupled from the wheel 109 , the first bearing 107 is stationary while the second bearing 108 is rotating.

[0026] To enable the rotor 102 to be connected to the wheel 109 when the rotor 102 is disengaged from the wheel 109, and to avoid damaging the rotor or the wheel, the rotor is preferably arranged to rotate synchronously with the wheel, for example using motor torque generated by current flowing through the coil windings 102, as described above. Once the rotation of the rotor and the wheel is synchronized, the pin 114 is arranged to move from the first position to the second position.

[0027] Preferably, the movement of the pin 114 between the first position and the second position is performed by an activation circuit (not shown) in response to an electrical signal received from a control unit (not shown). For example, the activation circuit may include an electromagnet that controls the position of the pin 114 in response to the electrical signal. When the rotor 102 and the wheel 109 are to be disengaged, in order to help the pin 114 move back into the selector sleeve, the selector sleeve includes one or more return springs so that the pin 114 is compressed by the spring within the selector sleeve.

[0028] Preferably, the stator 101 also includes a mechanism for keeping the rotor 102 stationary relative to the stator 101 when the rotor 102 is disengaged from the wheel 109. For example, the mechanism may include an activation circuit (not shown) for applying current to the coil windings 103 mounted on the stator 101 to generate a magnetic field that interacts with the magnets 106 mounted on the rotor 102, thereby inhibiting the movement of the rotor 102 relative to the stator 101. Preferably, the activation of the mechanism is in response to an electrical signal received from a control unit (not shown). However, the mechanism for keeping the rotor 102 stationary can be implemented by any mechanical or electrical means.

[0029] although Figure 1 An engagement device comprising a selector sleeve having a sliding pin 114 for connecting and disconnecting the rotor 102 from the wheel 109 is shown, but any form of engagement device may be used, for example, a face dog, radial dog, clutch, cone clutch, synchronizer.

[0030] As an example, Figures 2 to 6 An alternative embodiment of an electric motor according to an aspect of the invention is shown, wherein an alternative engagement means is indicated in each of the figures. The same reference numerals are used in the different figures to indicate the same features.

[0031] Figure 2 A second example of an electric motor according to an embodiment of the present invention is shown, wherein the engagement means comprises a wet clutch. The wet clutch comprises a wet clutch assembly 201 mounted between the inner axial surface of the rotor 102 and the opposite axial surface on the wheel 109, and a hydraulically actuated piston 202 is mounted on the stator 101 for engaging and disengaging the wet clutch assembly 201, thereby coupling and disengaging the rotor 102 from the wheel 109. The activation of the piston 202 is performed in response to an electrical signal received from a control unit.

[0032] Figure 3A third example of an electric motor according to an embodiment of the invention is shown, wherein the meshing means comprises a dry clutch. The dry clutch comprises a dry clutch plate 301 mounted between the inner axial surface of the rotor 102 and the radial wall of the wheel 109, wherein activation of the dry clutch plate 301 is performed by a clutch application plate 302, a diaphragm spring 305, an actuator rod 303 and an axial thrust bearing 304, thereby coupling and decoupling the rotor 102 from the wheel 109. Activation of the actuator rod 303 is preferably performed in response to an electrical signal received from a control unit.

[0033] Figure 4 A fourth example of an electric motor according to an embodiment of the invention is shown, wherein the engagement means comprises a central actuation pin arrangement. The central actuation pin arrangement comprises a selector sleeve 401 with a sliding pin, wherein the sliding pin is arranged to slide from a first position within the rotor 102 to a second position, the second position extending axially away from the stator and engaging with a hole formed on the wheel 109, wherein activation of the pin is performed via a diaphragm spring 402, an actuator rod 403 and an axial thrust bearing 404, thereby coupling and decoupling the rotor 102 to and from the wheel 109. Activation of the actuator rod 403 is preferably performed in response to an electrical signal received from a control unit.

[0034] Figure 5 A fifth example of an electric motor according to an embodiment of the invention is shown, wherein the engagement means comprises a face-pawl device. The face-pawl device comprises a selector sleeve 501 having face-pawls, wherein the face-pawls are arranged to slide from a first position within the rotor 102 to a second position, the second position extending axially away from the stator and engaging with corresponding face-pawls 502 formed on the wheel 109 or the second portion 113 of the second bearing 108. Actuation of the selector sleeve between the first position and the second position is performed by an actuator rod 503, a thrust bearing 504 and a diaphragm spring 505, thereby coupling and decoupling the rotor 102 from the wheel 109. Activation of the actuator rod 503 is preferably performed in response to an electrical signal received from a control unit.

[0035] Figure 6 A sixth example of an electric motor according to an embodiment of the invention is shown, wherein the engagement means comprises a sliding sleeve means. The sliding sleeve means comprises a sliding selector sleeve 601 having radial claws formed on an inner axial surface of the sliding selector sleeve 601. The sliding 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, such as Figure 6As shown, when the sliding selector sleeve 601 is in the first position, the radial claws formed on the sliding selector sleeve 601 are arranged to engage with corresponding radial claws formed on the wheel 109 or the second part 113 of the second bearing 108, and when the sliding selector sleeve 601 is in the second position, the radial claws formed on the sliding selector sleeve 601 are arranged to disengage from corresponding radial claws formed on the wheel 109 or the second part 113 of the second bearing 108, thereby coupling and decoupling the rotor 102 from the wheel 109. Activation of the sliding selector sleeve 601 between the first position and the second position is preferably performed in response to an electrical signal received from a control unit.

[0036] Preferably, for each of the above embodiments, a disc brake (not shown) is mounted on the cylindrical portion 105 of the rotor 102 for providing braking torque to the vehicle, so that when the rotor 102 is connected to the wheel 109 by the meshing device, any braking torque applied to the rotor 102 is correspondingly applied to the wheel 109. Alternatively, the disc brake (not shown) may be mounted on the cylindrical portion of the wheel 109.

[0037] like Figure 7 As shown, in another embodiment of the present invention, the rotor may include an inner rotor 701 and an outer rotor 702. The inner rotor 701 is attached to the stator 101 through the first bearing 107, and the outer rotor 702 is attached to the vehicle directly or indirectly via the stator 101 through the second bearing 108. Figure 7 The same reference numerals are used to denote Figure 1 The same features are shown.

[0038] The inner rotor 701 comprises a front portion and a cylindrical portion forming a cover, which substantially surrounds the stator 101. The inner rotor 701 comprises a plurality of permanent magnets 106 arranged around the interior of the cylindrical portion.

[0039] The magnets 106 are very close to the coil windings 103 mounted on the stator 101, so that the magnetic field generated by the coils interacts with the magnets 106 arranged around the inside of the cylindrical portion of the inner rotor 701, so that when alternating current is applied to the coil windings 102, the inner rotor 701 rotates. Since the permanent magnets 106 are used to generate the driving torque that drives the motor, the permanent magnets are generally referred to as driving magnets.

[0040] The outer rotor 702 is arranged to be coupled directly or indirectly to a wheel (not shown) of the vehicle, for example by one or more bolts or other coupling means, and to the second portion 113 of the second bearing 108 .

[0041] The inner rotor 701 includes a meshing device for selectively connecting the inner rotor 701 to the outer rotor 702 and disconnecting the inner rotor 701 from the outer rotor 702, so that when the inner rotor 701 is connected to the outer rotor 702, the wheel is arranged to rotate with the inner rotor 701, and when the inner rotor is disconnected from the outer rotor 702, the inner rotor 701 is arranged to be stationary relative to the stator 101, while the wheel rotates relative to the inner rotor 701. As with the embodiment of the present invention having a single rotor 102, as Figures 1 to 6 As shown, any type of meshing device can be used, for example, face claws, radial claws, clutches, cone clutches, synchronizers.

[0042] For the purposes of this embodiment, the engagement means comprises a face claw device. The face claw device comprises a selector sleeve 703 having face claws, wherein the face claws are arranged to slide from a first position within the inner rotor 701 to a second position extending axially away from the stator 101 and to engage with corresponding face claws 707 formed on the outer rotor 702 or the second portion 113 of the second bearing 108. Actuation of the selector sleeve 703 between the first position and the second position is performed by an actuator rod 704, a thrust bearing 705 and a diaphragm spring 706, thereby coupling and decoupling the inner rotor 701 from the outer rotor 702. Activation of the actuator rod 704 is preferably performed in response to an electrical signal received from a control unit.

[0043] Preferably, a disc brake (not shown) is mounted on the cylindrical portion of the outer rotor 702 for providing braking torque to the vehicle, so that when the inner rotor 701 is coupled to the outer rotor 702 by a meshing device, any braking torque applied to the inner rotor 701 is correspondingly applied to the outer rotor 702 and thereby to the wheels of the vehicle.

Claims

1. An in-wheel electric motor for a vehicle, comprising a stator, a first rotor arranged to be housed in a wheel of the vehicle, and a coupling device for selectively coupling the first rotor to and decoupling the first rotor from the wheel of the vehicle, such that 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 decoupled from the wheel, the first rotor is arranged to be stationary relative to the stator when the wheel rotates relative to the stator.

2. The in-wheel motor according to claim 1, wherein: The coupling device is configured to selectively couple the first rotor to and decouple the first rotor from a wheel of the vehicle in response to an electrical signal.

3. The in-wheel motor according to claim 1 or 2, wherein: The coupling device comprises a facial claw interface or a radial claw interface for coupling the first rotor to the wheel.

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

5. The in-wheel motor according to claim 4, wherein: When the rotor is coupled to the wheel, the pins are arranged to be located in holes in the wheel.

6. The in-wheel motor according to claim 1 or 2, wherein: The coupling device comprises a clutch for coupling the first rotor to the wheel.

7. The in-wheel electric motor of claim 1, further comprising a means for holding the first rotor stationary relative to the stator when the first rotor is disengaged from the wheel.

8. The in-wheel motor according to claim 2, wherein: The means for retaining includes an activation circuit for applying current to coil windings mounted on the stator to generate a magnetic field that interacts with the first rotor to inhibit movement of the first rotor relative to the stator.

9. An in-wheel electric motor according to any preceding claim, further comprising a first bearing and a second bearing, the first bearing allowing the wheel to rotate relative to the stator, the second bearing allowing the first rotor to rotate relative to the stator.

10. The in-wheel motor according to claim 4, wherein: When the first rotor is coupled to the wheel, the movements of the first bearing and the second bearing are synchronized.

11. The in-wheel motor according to claim 4 or 5, wherein: When the first rotor is disengaged from the wheel, the second bearing is stationary while the first bearing rotates.

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

13. The in-wheel motor according to claim 12, wherein: The outer rotor is arranged to be coupled to the wheel, and the coupling device is arranged to selectively couple the inner rotor to the outer rotor and decouple the inner rotor from the outer rotor, so that 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 decoupled from the outer rotor, the inner rotor is arranged to be stationary relative to the stator and the wheel rotates relative to the inner rotor.

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

15. A vehicle having a wheel and an in-wheel electric motor according to any one of the preceding claims.

16. A method for an in-wheel electric motor for a vehicle, wherein the in-wheel electric motor includes a stator, a first rotor, the first rotor is arranged to be accommodated in a vehicle wheel, and a coupling device, the coupling device is used to selectively couple the first rotor to the wheel of the vehicle and decouple the first rotor from the wheel, so that 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 including coupling the first rotor to the wheel and decoupling the first rotor from the wheel in response to receipt of an actuation signal.

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