Vehicle drive device

Abstract

A drive device (3) is mounted on a vehicle (1) that regeneratively brakes at least the left and right rear wheels (13, 14) out of the left and right front wheels (11, 12) and the left and right rear wheels (13, 14) when decelerating, and drives the left and right rear wheels (13, 14). The drive device (3) has a motor (31) and a differential device (33) that distributes driving force output from the motor (31) to the left and right rear wheels (13, 14). The differential device (33) limits differential rotation of the left and right rear wheels (13, 14) with a differential limiting force corresponding to a regenerative braking force generated by the motor (31).

Description

Technical Field

[0001] This invention relates to a drive system for vehicles. Background Technology

[0002] Previously, vehicles were known to use separate electric motors to drive the left and right front wheels and the left and right rear wheels. Patent Document 1 describes a front-wheel drive electric vehicle with: a front-wheel drive unit having a front-side MG (electric generator) as a front-side drive source and a front-side transmission mechanism; and a rear-wheel drive unit having a rear-side MG as a rear-side drive source and a rear-side transmission mechanism. The output of the front-side transmission mechanism is distributed to the left and right front wheels by a front-side differential, and the output of the rear-side transmission mechanism is distributed to the left and right rear wheels by a rear-side differential.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2023-102684 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In vehicles powered by electric motors, regenerative control is applied to the motor during deceleration, enabling it to function as a generator. This regenerative power charges the battery and provides regenerative braking. However, in vehicles like the electric car described in Patent Document 1, where a differential mechanism distributes the driving / regenerative force from the electric motor to the left and right wheels, if either wheel slips relative to the road surface during regenerative deceleration, even if the other wheel rotates, the regenerative braking force from the electric motor cannot be adequately utilized for regenerative braking. This is particularly problematic on the rear wheel side, where the vehicle's load shifts towards the front wheels during deceleration, reducing the load on the rear wheels and making wheel slippage more likely.

[0008] The present invention was made in view of the above circumstances, and its object is to provide a drive device for a vehicle that, in a vehicle in which the left and right rear wheels are driven by an electric motor, can easily transmit the regenerative braking force of the electric motor to the wheels during deceleration.

[0009] Methods for solving problems

[0010] To achieve the above-mentioned objective, the present invention provides a vehicle drive device mounted on a vehicle, wherein the vehicle performs regenerative braking on at least one of the left and right front wheels and the left and right rear wheels during deceleration, the vehicle drive device drives the left and right rear wheels, wherein the vehicle drive device includes an electric motor and a differential device, the differential device distributing the driving force output from the electric motor to the left and right rear wheels, and the differential device restricting the differential rotation of the left and right rear wheels by using a differential limiting force corresponding to the regenerative braking force generated by the electric motor.

[0011] Invention Effects

[0012] According to the present invention, the differential rotation of the left and right rear wheels is suppressed by the differential limiting force of the differential device, thereby easily generating the regenerative braking force of the electric motor that drives the left and right rear wheels. Attached Figure Description

[0013] Figure 1 This is a schematic diagram illustrating a structural example of a vehicle equipped with a drive device according to an embodiment of the present invention.

[0014] Figure 2 It is a cross-sectional view showing the differential device and its surrounding parts.

[0015] Figure 3 It is a perspective view showing the differential mechanism housed in the differential housing, with a portion of the main body of the housing cut away.

[0016] Figure 4 yes Figure 2 A cross-sectional view of the shell body and differential mechanism at line AA.

[0017] Figure 5 This is an explanatory diagram showing the vehicle behavior during a driving test on a test track, illustrating the vehicle behavior of the embodiment and the comparative example vehicle.

[0018] Figure 6 This is a graph showing the steering angles of the vehicle and the comparative vehicle used in the driving test.

[0019] Figure 7 This is a graph showing the converted wheel speeds of the left and right rear wheels of the vehicle and the comparative example vehicle during the driving test.

[0020] Figure 8 This is a graph showing the wheel torque of the left and right rear wheels of the vehicle and the comparative example vehicle during the driving test.

[0021] Figure 9 This is a graph showing the yaw rate of the vehicle and the comparative vehicle used in the driving test. Detailed Implementation

[0022] [Implementation Method]

[0023] Reference Figures 1 to 9 Embodiments of the present invention will be described below. Furthermore, the embodiments described below are shown as preferred examples for carrying out the present invention. Although some details specifically illustrate various technically preferred aspects, the scope of the present invention is not limited to these specific embodiments.

[0024] Figure 1 This is a schematic diagram showing a structural example of a vehicle 1 equipped with the drive device 3 according to an embodiment of the present invention. The vehicle 1 is a four-wheel drive vehicle capable of driving the left and right front wheels 11, 12 and the left and right rear wheels 13, 14.

[0025] Vehicle 1 has a front-wheel drive unit 2 that drives the left and right front wheels 11 and 12; a rear-wheel drive unit 3 that drives the left and right rear wheels 13 and 14; and a control unit 40 that controls the front-wheel drive unit 2 and the rear-wheel drive unit 3. The left and right front wheels 11 and 12 are steering wheels steered by a steering operation device 15. The control unit 40 controls the front-wheel drive unit 2 and the rear-wheel drive unit 3 based on the vehicle status. The vehicle status includes: the detection value of the steering wheel 151 operated by the driver; the detection values ​​of the accelerator pedal sensor and the brake pedal sensor that detect the amount of pressure applied to the accelerator pedal 16 and the brake pedal 17; the detection values ​​of the wheel speed sensor that detects the rotational speed of the front wheels 11 and 12 and the rear wheels 13 and 14; and the detection values ​​of various sensors such as the yaw rate sensor.

[0026] The front-wheel drive unit 2 includes: an electric motor 21, which is the drive source for the left and right front wheels 11 and 12; a transmission 22, which changes the speed of the rotation of the output shaft 210 of the electric motor 21; and a differential device 23, which distributes the driving force of the electric motor 21 transmitted from the transmission 22 to the left and right front wheels 11 and 12. The left and right front wheels 11 and 12 are connected to the differential device 23 via left and right drive shafts 181 and 182.

[0027] The rear-wheel drive unit 3 also includes: an electric motor 31, which is the drive source for the left and right rear wheels 13 and 14; a transmission 32, which changes the speed of the rotation of the output shaft 310 of the electric motor 31; and a differential device 33, which distributes the driving force of the electric motor 31 transmitted from the transmission 32 to the left and right rear wheels 13 and 14. The left and right rear wheels 13 and 14 are connected to the differential device 33 via the left and right drive shafts 191 and 192.

[0028] In this embodiment, the gearboxes 22 and 32 are speed reducers that reduce the rotation of the output shafts 210 and 310 of the motors 21 and 31 by a fixed reduction ratio. However, the gearboxes 22 and 32 may also be gearboxes capable of changing the gear ratio in a multi-stage or continuously variable manner.

[0029] Additionally, vehicle 1 is equipped with a front-wheel-side inverter 41 that supplies current to the motor 21 of the drive unit 2 on the front wheels, a rear-wheel-side inverter 42 that supplies current to the motor 31 of the drive unit 3 on the rear wheels, and a rechargeable secondary battery, i.e., a high-voltage storage battery 43. Inverters 41 and 42 have multiple switching elements that switch the DC current supplied from the high-voltage storage battery 43 and then supply it to the motors 21 and 31 respectively. Control unit 40 controls motors 21 and 31 by outputting PWM (Pulse Width Modulation) signals to inverters 41 and 42. Motors 21 and 31 are, for example, three-phase AC motors.

[0030] When vehicle 1 accelerates, the motor 21 of the front-wheel drive unit 2 and the motor 31 of the rear-wheel drive unit 3 generate positive torque corresponding to the current supplied from inverters 41 and 42. When vehicle 1 decelerates, the motor 21 of the front-wheel drive unit 2 and the motor 31 of the rear-wheel drive unit 3 function as generators and generate negative torque. The positive torque is the driving force that increases the rotation of the left and right front wheels 11 and 12 and the left and right rear wheels 13 and 14, while the negative torque is the regenerative braking force that decreases the rotation of the left and right front wheels 11 and 12 and the left and right rear wheels 13 and 14.

[0031] When the control device 40 decelerates the vehicle 1, it causes the electric motor 31 of the drive unit 3 on the rear wheel side to generate a greater regenerative braking force than the electric motor 21 of the drive unit 2 on the front wheel side. This mitigates the so-called front-end drop that occurs when the front of the vehicle body becomes lower than the rear, thereby improving the ride comfort of the driver and other passengers.

[0032] The differential 23 of the front-wheel drive unit 2 includes: a ring gear 230, driven and connected to the output shaft 210 of the electric motor 21 via the transmission 22; a differential housing 231, rotating integrally with the ring gear 230; a pinion shaft 232, fixed to the differential housing 231; a pair of pinions 233, supported on the pinion shaft 232; and a first half-shaft gear 234 and a second half-shaft gear 235, meshing with the pair of pinions 233. The pair of pinions 233, the first half-shaft gear 234, and the second half-shaft gear 235 are bevel gears. The left drive shaft 181 is connected to the first half-shaft gear 234 in a non-rotatable manner. The right drive shaft 182 is connected to the second half-shaft gear 235 in a non-rotatable manner.

[0033] The differential device 33 of the rear-wheel drive unit 3 has a differential limiting function, which uses a differential limiting force corresponding to the driving force and regenerative braking force generated by the electric motor 31 to limit the differential rotation of the left and right rear wheels 13 and 14. The differential device 33 is a mechanical differential device without electronic control components such as an electromagnetic clutch. Next, referring to... Figures 2 to 4 The structure of the differential device 33 of the rear wheel-side drive unit 3 is described in detail.

[0034] Figure 2 This is a cross-sectional view showing the differential device 33 and its surrounding parts. The differential device 33 includes: a gear ring 330, which is driven and connected to the output shaft 310 of the electric motor 31 via the transmission 32; a differential housing 5, which rotates integrally with the gear ring 330; and a differential mechanism 6, which is housed in the differential housing 5.

[0035] The differential housing 5 is housed within the differential housing 70 mounted on the body of the vehicle 1, and is supported by bearings 71 and 72 in a manner that allows it to rotate relative to the differential housing 70 about the rotation axis O. The differential housing 5 has a bottomed cylindrical housing body 51 and a housing cover 52 configured to block the opening of the housing body 51. The housing body 51 and the housing cover 52 are fastened together by a plurality of bolts 53. The gear ring 330 is fastened to the differential housing 5 by a plurality of bolts 54. Hereinafter, the direction parallel to the rotation axis O of the differential housing 5 will be referred to as the axial direction.

[0036] The differential housing 70 is sealed with lubricating oil (differential oil) for lubricating the differential mechanism 6. In addition, the differential housing 70 is provided with insertion holes 701 and 702 for the left and right drive shafts 191 and 192 to be inserted, and sealing members 73 and 74 for preventing lubricating oil leakage are arranged inside the insertion holes 701 and 702.

[0037] Figure 3 This is a perspective view showing the differential mechanism 6 housed in the differential housing 5, with a portion of the housing body 51 cut away. Figure 4 yes Figure 2 A cross-sectional view of the shell body 51 and the differential mechanism 6 at line AA.

[0038] The differential mechanism 6 includes: a first half-shaft gear 61 and a second half-shaft gear 62, arranged side-by-side along the axial direction; a plurality of pinion gear sets 63; a central washer 64 disposed between the first half-shaft gear 61 and the second half-shaft gear 62; a first side washer 65 disposed between the first half-shaft gear 61 and the housing body 51; and a second side washer 66 disposed between the second half-shaft gear 62 and the housing cover 52. The first half-shaft gear 61 and the second half-shaft gear 62 are helical gears with spiral tooth lines. The first half-shaft gear 61 outputs driving force to the left rear wheel 13, and the second half-shaft gear 62 outputs driving force to the right rear wheel 14.

[0039] A splined fitting hole 610 is formed at the center of the first half-shaft gear 61, allowing the end of the drive shaft 191 to be connected in a non-rotatable manner. A splined fitting hole 620 is formed at the center of the second half-shaft gear 62, allowing the end of the drive shaft 192 to be connected in a non-rotatable manner. A pinion set 63 is disposed on the outer periphery of the first half-shaft gear 61 and the second half-shaft gear 62. In this embodiment, the differential mechanism 6 includes three pinion sets 63.

[0040] Each pinion set 63 is formed by multiple pinions meshing with each other. In this embodiment, a pinion set 63 is formed by meshing two second pinions 632 with one first pinion 631. The first pinion 631 and the second pinion 632 are supported on the differential housing 5 in a manner that allows them to rotate about a rotation axis parallel to the rotation axis O.

[0041] The first pinion 631 and the second pinion 632 are helical gears with spiral tooth lines. The axial length of the first pinion 631 is equivalent to the length obtained by adding the axial length of the first half-shaft gear 61 and the axial length of the second half-shaft gear 62. The axial length of the second pinion 632 is equivalent to the axial length of the second half-shaft gear 62.

[0042] The first pinion 631 meshes with the first half-shaft gear 61. Two second pinions 632 mesh with the second half-shaft gears 62 on both sides of the first pinion 631 in the circumferential direction of the differential housing 5. The first pinion 631 and the two second pinions 632 mesh at the outer circumference of the second half-shaft gear 62. The portion of the first pinion 631 that meshes with the first half-shaft gear 61 is formed to have a larger diameter than the portion that meshes with the two second pinions 632.

[0043] When the driving force of the motor 31 is transmitted from the differential housing 5 to the drive shafts 191 and 192 via the differential mechanism 6, an axial thrust corresponding to the helix angle of the tooth line is generated on the first half-shaft gear 61, the second half-shaft gear 62, the first pinion 631, and the second pinion 632. Additionally, when the motor 31 generates regenerative braking force, a thrust in the opposite direction to the driving force generated by the motor 31 is generated on the first half-shaft gear 61, the second half-shaft gear 62, the first pinion 631, and the second pinion 632.

[0044] The first pinion 631 and the second pinion 632 are held in pinion holding portions 510 formed on the housing body 51. In this embodiment, since the differential mechanism 6 has three sets of pinion sets 63, three pinion holding portions 510 are formed on the housing body 51. Each pinion holding portion 510 has a first holding hole 511 for holding the first pinion 631 and a second holding hole 512 for holding the second pinion 632. When the rotational speeds of the left and right rear wheels 13 and 14 differ, and the first half-shaft gear 61 and the second half-shaft gear 62 rotate differentially, the first pinion 631 rotates in the first holding hole 511, and the second pinion 632 rotates in the second holding hole 512.

[0045] When the first pinion 631 and the second pinion 632 rotate within the first retaining hole 511 and the second retaining hole 512, the tooth tip surface 631a of the first pinion 631 slides on the inner surface 511a of the first retaining hole 511, and the tooth tip surface 632a of the second pinion 632 slides on the inner surface 512a of the second retaining hole 512. The friction generated by this sliding becomes a differential limiting force that inhibits the differential rotation of the first half-shaft gear 61 and the second half-shaft gear 62.

[0046] Furthermore, the frictional force generated by the axial end faces 631b and 631c of the first pinion 631 and the axial end faces 632b and 632c of the second pinion 632 relative to the housing body 51 or the housing cover 52 also serves as a differential limiting force to suppress the differential rotation of the first half-shaft gear 61 and the second half-shaft gear 62. Moreover, the frictional forces between the first half-shaft gear 61 and the second half-shaft gear 62 and the central washer 64, the frictional forces between the first half-shaft gear 61 and the housing body 51 and the first side washer 65, and the frictional forces between the second half-shaft gear 62 and the housing cover 52 and the second side washer 66 also serve as differential limiting forces to suppress the differential rotation of the first half-shaft gear 61 and the second half-shaft gear 62.

[0047] Vehicle 1, controlled by control device 40, performs regenerative braking on at least the left and right rear wheels 13 and 14 during deceleration. The differential rotation of the left and right rear wheels 13 and 14 is limited by the differential limiting force of differential device 33, so that even if the friction (traction) between one of the left and right rear wheels 13 and 14 and the road surface decreases significantly, as long as the friction between the other wheel and the road surface is ensured, driving force or braking force can be transmitted to that other wheel.

[0048] The force exerted by the tooth tip surfaces 631a and 632a of the first pinion 631 and the second pinion 632 on the inner surfaces 511a and 512a of the first retaining hole 511 and the second retaining hole 512 increases accordingly with the torque generated by the motor 31. Furthermore, the axial pressing force on the first pinion 631, the second pinion 632, the first half-shaft gear 61, and the second half-shaft gear 62 also increases accordingly with the torque generated by the motor 31. That is, the differential device 33 is an LSD (Limited Slip Differential) with torque proportional differential limiting function, which uses a differential limiting force corresponding to the torque (driving force and regenerative braking force) generated by the motor 31 to limit the differential rotation of the left and right rear wheels 13 and 14.

[0049] On the other hand, in a conventional differential device (hereinafter referred to as an "open differential"), such as the differential device 23 on the front wheel side, where a pair of pinions and a pair of half-shaft gears made of bevel gears mesh within the differential housing, if one of the left or right wheels slips relative to the road surface during acceleration, the pinion and half-shaft gears spin freely, preventing the transmission of driving force to the other wheel. Similarly, during deceleration, if one of the left or right wheels slips relative to the road surface, the pinion and half-shaft gears spin freely, preventing the electric motor that rotates the differential housing from generating regenerative braking force.

[0050] In this embodiment, the torque bias ratio (TBR) of the differential device 33 is 1.4 or higher and 2.8 or lower. Here, the torque bias ratio refers to the torque distribution ratio expressed as the ratio of the torque transmitted to the wheel on the low torque side (e.g., the left rear wheel 13) to the torque transmitted to the wheel on the high torque side (e.g., the right rear wheel 14) when a torque difference is generated between the left rear wheel 13 and the right rear wheel 14 and the differential is engaged, with the denominator being the torque transmitted to the wheel on the high torque side (e.g., the right rear wheel 14).

[0051] The torque offset ratio increases with the increase of the differential limiting force. The magnitude of the torque offset ratio can be adjusted by, for example, the helix angle, pressure angle, tip circle diameter, axial length, and surface roughness of the tip surfaces 631a and 632a of each gear of the first half-shaft gear 61, the second half-shaft gear 62, the first pinion 631, and the second pinion 632. In a typical open differential, the torque offset ratio is less than 1.3, for example, around 1.1 to 1.2.

[0052] Next, refer to Figures 5 to 9 An example is given to how the differential limiting force on the differential device 33 on the rear wheel side helps to improve driving stability.

[0053] Figure 5 This indicates that the embodiment has Figure 1This diagram illustrates the vehicle behavior of vehicle 1 (shown in the diagram) and vehicle 1A (a comparative example where the rear-wheel differential 33 is replaced with an open differential instead of an LSD) during a driving test on a test track 8 with a left curve 81. In this driving test, with the road surface friction coefficient of the test track 8 set to 0.3 (equivalent to a snowy road surface), vehicles 1 and 1A entered the left curve 81 from the straight section 80 at the same speed, and regenerative braking was applied to the left and right front wheels 11 and 12 and the rear wheels 13 and 14 within the left curve 81. The torque bias ratio of the rear-wheel differential 33 in vehicle 1 is 2.0. The torque bias ratio of the rear-wheel differential in vehicle 1A is 1.2.

[0054] Figure 5 In the diagram, the behavior and trajectory of vehicle 1 are represented by solid lines, while the behavior and trajectory of vehicle 1A are represented by dashed lines. Figures 6 to 9 This is a chart representing the steering angles of vehicles 1 and 1A, the converted wheel speeds of the front wheels 11 and 12 and the rear wheels 13 and 14, the wheel torque, and the yaw rate of vehicles 1 and 1A, all along a common time axis. Figures 6 to 9 In the chart, T1 on the time axis represents the moment when regenerative braking begins by disengaging the accelerator pedal 16. Wheel torque is the torque acting on the wheels; torque in the acceleration direction is positive, and torque in the deceleration direction is negative.

[0055] Figure 6 In the diagram, the steering angle of vehicle 1 is represented by a solid line, while the steering angle of vehicle 1A is represented by a dashed line. Figure 7 and Figure 8 In the chart, the wheel speed of the left rear wheel 13 of vehicle 1 and its wheel torque are represented by a thin solid line; the wheel speed of the right rear wheel 14 of vehicle 1 and its wheel torque are represented by a thick solid line; the wheel speed of the left rear wheel 13 of vehicle 1A and its wheel torque are represented by a thin dashed line; and the wheel speed of the right rear wheel 14 of vehicle 1A and its wheel torque are represented by a thick dashed line. Figure 9 In the diagram, the yaw rate of vehicle 1 is represented by a solid line, while the yaw rate of vehicle 1A is represented by a dashed line.

[0056] like Figure 5 As shown, vehicle 1A loses control while turning and spins backward relative to its direction of travel, while vehicle 1 exhibits more stable behavior. This is because, in vehicle 1, as... Figure 8 As shown in the chart, the difference in wheel torque between the left rear wheel 13 and the right rear wheel 14 is relatively large, and the right rear wheel 14, which is located on the outside of the turn, has a greater negative wheel torque than the left rear wheel 13.

[0057] The left-right difference in wheel torque is caused by the load difference between the left and right rear wheels 13 and 14 during cornering and the differential limiting force of the differential device 33, which reduces the rotational speed difference between the left and right rear wheels 13 and 14. Its function is to cause the vehicle 1 to produce a yaw rate opposite to the cornering direction. Furthermore, as... Figure 9 As shown in the chart, the overall yaw rate of vehicle 1 is reduced, and oversteer is suppressed. In addition, the left rear wheel 13, located on the inside of the turn, has a smaller wheel torque, so the road grip has room to generate lateral tire force, which also suppresses oversteer.

[0058] In contrast, in vehicle 1A, although there is a difference in wheel torque between the left and right rear wheels 13 and 14, the difference is smaller than that in vehicle 1. Therefore, the difference in wheel torque between the left and right rear wheels 13 and 14 cannot be fully used to suppress oversteer, resulting in a significant disruption in vehicle behavior.

[0059] Furthermore, if the torque offset ratio is too large, the difference in torque between the left and right wheels will be too great, which can easily cause the outer wheel to slip during cornering. Therefore, the torque offset ratio is preferably 2.8 or less. Moreover, in order to ensure the vehicle's driving stability under various road conditions, the torque offset ratio is preferably set to 2.5 or less.

[0060] (Effects of the implementation method)

[0061] According to the embodiments of the present invention described above, the differential rotation of the left and right rear wheels 13 and 14 is suppressed by the differential limiting force of the differential device 33, thereby easily generating regenerative braking force for the electric motors driving the left and right rear wheels 13 and 14. Furthermore, in situations such as Figure 5 When decelerating during a turn, the differential can suppress oversteer and stabilize vehicle behavior. In particular, in this embodiment, since the differential 33 is a mechanical differential, there is no action delay as in cases using electronic control components such as electromagnetic clutches, and an appropriate differential limiting force can be generated immediately according to the vehicle's driving state.

[0062] (Postscript)

[0063] The present invention has been described above based on embodiments, but these embodiments do not limit the invention as defined in the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are necessary for solving the problems of the invention. Additionally, the present invention may be implemented with appropriate modifications, such as omitting parts of the structure or adding or replacing structures, without departing from its spirit. Moreover, it may be implemented in modifications, for example, as follows.

[0064] In the above embodiment, the case where the front wheel differential 23 is an open differential is described, but it is not limited to this. The front wheel differential 23 may also be configured as an LSD with differential limiting function, similar to the rear wheel differential 33. Furthermore, as the drive source for the front wheel, an engine utilizing fuel such as gasoline may be used instead of the electric motor 21. Moreover, the drive device of the present invention may also be used as the drive device for a rear-wheel drive two-wheel drive vehicle that only drives the rear wheels.

[0065] Furthermore, in the above embodiment, a set of pinions 63 was described by meshing two second pinions 432 with a first pinion 631 to form a set of pinions 63. However, this is not a limitation; a set of pinions can also be formed by meshing one pinion meshing with the first half-shaft gear 61 and another pinion meshing with the second half-shaft gear 62. In this case, the pinion meshing with the first half-shaft gear 61 and the other pinion meshing with the second half-shaft gear 62 are meshed at a position where they are not radially parallel to the first half-shaft gear 61 and the second half-shaft gear 62.

[0066] Label Explanation

[0067] 1…vehicles

[0068] 11, 12... Front wheels

[0069] 13, 14... Rear wheels

[0070] 2…Drive mechanism on the front wheel side

[0071] 3… Rear wheel drive unit

[0072] 31… Electric motor

[0073] 33… Differential device

[0074] 5… Differential housing

[0075] 511…First retaining hole

[0076] 511a…Inner surface

[0077] 512…Second retaining hole

[0078] 512a…Inner surface

[0079] 61…First half-shaft gear

[0080] 62…Second half-shaft gear

[0081] 631…First pinion

[0082] 632…Second pinion

[0083] 631a, 632a... Tooth tip

[0084] 632b, 632c... end face

[0085] O… Rotation axis

Claims

1. A vehicle drive unit mounted on a vehicle, wherein, during deceleration, the vehicle performs regenerative braking on at least one of the left and right front wheels and the left and right rear wheels, wherein the vehicle drive unit drives the left and right rear wheels, wherein, The vehicle drive unit includes an electric motor and a differential device, the differential device distributing the driving force output from the electric motor to the left and right rear wheels. The differential device uses a differential limiting force corresponding to the regenerative braking force generated by the electric motor to limit the differential rotation of the left and right rear wheels.

2. The vehicle drive unit according to claim 1, wherein, The differential device is a mechanical differential device without electronic control components.

3. The vehicle drive unit according to claim 2, wherein, The torque bias ratio of the differential device is 1.4 or higher.

4. The vehicle drive unit according to claim 3, wherein, The torque bias ratio of the differential device is 2.8 or less.

5. The vehicle drive unit according to any one of claims 2 to 4, wherein, The differential device has: A pair of half-shaft gears output driving force to the left and right rear wheels; The first pinion meshes with one of the pair of half-shaft gears; The second pinion meshes with the other of the pair of half-shaft gears; and The differential housing houses the pair of half-shaft gears, the first pinion, and the second pinion, and is supplied with the driving force output from the electric motor. The first pinion and the second pinion are supported on the differential housing in such a way that they can rotate around a rotation axis parallel to the rotation axis of the differential housing, and the first pinion and the second pinion mesh within the differential housing.

6. The vehicle drive unit according to claim 5, wherein, A first retaining hole for receiving the first pinion and a second retaining hole for receiving the second pinion are formed on the differential housing. When the left and right rear wheels rotate differentially, the tooth tip surface of the first pinion slides on the inner surface of the first retaining hole, and the tooth tip surface of the second pinion slides on the inner surface of the second retaining hole.

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