JP2021154785A - Suspension structure for in-wheel motor drive device - Google Patents

Abstract

To provide a structure which reduces vibration in a vertical direction that occurs when an in-wheel motor drive device drives a drive wheel.SOLUTION: A suspension device comprises: a shaft 57 which is provided on any one of a suspension member connected to an in-wheel motor drive device and a vehicle body side member; an outer cylinder 54 which is provided on the other one, and through which the shaft 57 passes; a rolling element 55 which is provided between the shaft 57 and the outer cylinder 54; and an elastic part 56 which is interposed between the suspension member and the vehicle body side member.SELECTED DRAWING: Figure 3

Description

The present invention relates to a suspension device for an in-wheel motor drive device that is provided on wheels of an electric vehicle such as an electric vehicle or a hybrid vehicle and drives the wheels.

Conventionally, for example, a suspension device described in Japanese Patent Application Laid-Open No. 2002-181121 is known as a suspension device for connecting a driving wheel to a vehicle body. The suspension device described in Patent Document 1 includes a liquid-filled anti-vibration device incorporated in the inner end of the lower arm in the vehicle width direction. According to the liquid-filled vibration isolator described in Patent Document 1, vibration in the left-right direction can be suppressed and low-frequency road noise transmitted to the vehicle body can be reduced.

Japanese Unexamined Patent Publication No. 2002-181121

An electric vehicle in which an in-wheel motor drive device is provided inside a drive wheel and the in-wheel motor drive device and the vehicle body are connected by a suspension device is known. In such an electric vehicle, unlike a driven wheel and a drive wheel driven by a drive shaft, a problem peculiar to an in-wheel motor drive device arises. That is, when the in-wheel motor drive device accelerates or decelerates the wheels, the wheels move up and down, and the vertical vibrations associated therewith occur. Further, vibration due to torque fluctuation of the in-wheel motor drive device or torque unevenness, for example, cogging torque, occurs. When such vibration is transmitted to the vehicle body through the suspension device, the ride quality is impaired, such as deterioration of in-vehicle noise. According to the prior art, vibration propagation in the left-right direction is suppressed, but rotational vibration around the lower arm swing axis due to vertical movement of the wheel cannot be vibration-proofed.

An object of the present invention is to provide a structure for reducing vibration generated when an in-wheel motor drive device accelerates or decelerates a drive wheel.

For this purpose, the suspension structure for an in-wheel motor drive device according to the present invention has a shaft provided on either one of a suspension member and a vehicle body side member connected to the in-wheel motor drive device, and a shaft provided on the remaining other. It includes an outer cylinder to be passed through, a bearing provided between the shaft and the outer cylinder, and a vibration isolator inserted between the suspension member and the vehicle body side member.

According to the present invention, since the vertical vibration is generated by the bearing, it is possible to suppress the transmission of the vertical vibration generated when the in-wheel motor drive device is driven to the vehicle body side member. The shape and structure of the vibration isolator are not particularly limited. The anti-vibration device is, for example, a cushion-like device, for example, an elastic body such as rubber. The structure of the bearing is not particularly limited, and may be, for example, a slide bearing in which the inner ring and the outer ring are in sliding contact, or a rolling bearing in which a plurality of rolling elements are arranged in the annular space between the inner ring and the outer ring. good. The suspension member may be, for example, an A-shaped arm that is swingably connected to the vehicle body side member in the vertical direction, or one of a plurality of links that are swingably connected to the vehicle body side member. do.

The arrangement of the anti-vibration device is not particularly limited. As one aspect of the present invention, the vibration isolator is a tubular bush having an elastic body that absorbs vibration, and is arranged coaxially with the bearing.

As a preferable aspect of the present invention, the suspension member and the vehicle body side member are connected at two places with a space in the front-rear direction of the vehicle, and of these connection points, the one closer to the axle passing through the center of the wheel hub of the in-wheel motor drive device. A shaft, an outer cylinder, a bush, and a bearing are arranged at the connecting portion of the bearing, and the center line of the bearing extends in the front-rear direction of the vehicle. The shaft, outer cylinder, bush, and bearing of the present invention may be arranged at both of the two locations. As another aspect, the suspension member and the vehicle body side member may be connected at only one place, or at three or more places.

As a more preferable aspect of the present invention, the bearings are arranged at the connecting portion near the axle and the connecting portion away from the axle at the rear of the vehicle, and the bushes are provided on the two bearing portions, respectively, and the axle is provided with respect to the hardness in the vertical direction. The bush closer to is harder than the bush farther away from the rear of the vehicle. According to this aspect, steering stability is improved. By making the axes of the bearing and the bush substantially parallel to the straight line connecting the centers of the two bushes, the prying against the vertical movement of the wheel is minimized.

The tubular bush may be provided between the inner ring and the shaft of the bearing, or may be provided between the outer ring and the outer cylinder of the bearing. As one aspect of the present invention, the bush is interposed between the outer cylinder and the bearing. According to this aspect, since the diameter of the bearing is increased, many rolling elements can be incorporated and the contact surface pressure can be reduced.

As one aspect of the present invention, the bearing is a roller bearing. Cylindrical roller bearings have low contact surface pressure and good durability. As another aspect of the present invention, the bearing is a needle roller bearing or another type of rolling bearing.

As described above, according to the present invention, it becomes difficult to transmit the vibration generated when the in-wheel motor drive device accelerates / decelerates the drive wheels to the vehicle body. Therefore, the ride quality of the electric vehicle is improved.

It is a top view which shows the suspension structure for an in-wheel motor drive device which becomes one Embodiment of this invention. It is a front view which shows the embodiment. It is sectional drawing which shows the vibration isolation device and the bearing part of the same embodiment. It is a vertical cross-sectional view which shows the vibration isolation device and the bearing part of the same embodiment. It is a top view which shows the suspension structure for an in-wheel motor drive device which becomes another embodiment of this invention. It is a top view which shows the suspension structure for the in-wheel motor drive device which becomes still another Embodiment of this invention. It is a schematic diagram which shows the suspension device which connects an in-wheel motor drive device and a member on a vehicle body side. FIG. 7 is a schematic view showing a vertical force during acceleration. FIG. 8 is a schematic view showing a vertical force during deceleration.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view showing a suspension structure for an in-wheel motor drive device according to an embodiment of the present invention. FIG. 2 is a front view showing the embodiment. FIG. 3 is a side view showing the in-wheel motor drive device of the same embodiment. As shown in FIG. 1, the suspension structure of the present embodiment includes a road wheel W, a tire T, an in-wheel motor drive device 10, a subframe 30, and a suspension device 40.

The road wheel W is known to have a rim portion and spoke portions, and a tire T is mounted on the outer periphery of the rim portion. The tire T and the road wheel W form the wheels of the electric vehicle. The rim portion rises inward in the vehicle width direction from the outer peripheral edge of the spoke portion, and the road wheel W partitions the inner space area.

The in-wheel motor drive device 10 is arranged in the inner space region of the road wheel W, and has a wheel hub bearing portion 11, a motor portion 12, and a deceleration portion 13. The wheel hub bearing portion 11 is a rolling bearing that rotatably supports the wheel hub 14, and receives a load borne by the tire T such as a vehicle weight. The wheel hub 14 projects outward from the wheel hub bearing portion 11 in the vehicle width direction (outboard side), and the spoke portions of the road wheel W are attached and fixed. The axis O represents the center of rotation (axle) of the wheel and passes through the center of the wheel hub 14 of the wheel hub bearing portion 11. When the wheel goes straight at a steering angle of 0 °, the axis O extends parallel to the vehicle width direction. When the road wheel W and the in-wheel motor drive device 10 steer, the axis O extends in the vehicle width direction, but inclines with the steering angle.

The motor unit 12 is an electric motor and drives the wheel hub 14. The speed reduction unit 13 decelerates the output rotation of the motor unit 12 and transmits it to the wheel hub 14. Regarding the position in the vehicle width direction, the wheel hub bearing portion 11 is arranged on the outside in the vehicle width direction (outboard side) of the in-wheel motor drive device 10, and the motor portion 12 is arranged on the inside in the vehicle width direction (inboard side) to decelerate. The portion 13 is arranged at the central portion in the vehicle width direction. As shown by the broken line in FIG. 1, the wheel hub bearing portion 11, the outer portion of the motor portion 12 in the vehicle width direction, and the deceleration portion 13 are housed in the inner space region of the road wheel W. On the other hand, as shown by the solid line in FIG. 1, the inner portion of the motor portion 12 in the vehicle width direction protrudes from the inner space region of the road wheel W.

With respect to the vehicle front-rear direction position, the motor unit 12 is arranged offset from the axis O in the vehicle front-rear direction, and is arranged in front of the vehicle in the present embodiment. The speed reduction unit 13 is a parallel shaft gear speed reducer. The arrangement and structure of the motor unit 12 and the deceleration unit 13 are not limited to this embodiment.

The suspension device 40 is a strut type suspension device, and has a strut 41 and a lower arm 48 as suspension members. The strut 41 is a suspension member arranged above the axis O, extends in the vertical direction, the lower end 42 of the strut is connected to the upper part of the in-wheel motor drive device 10, and the upper end of the strut (not shown) is attached to the vehicle body. The vehicle body is a member on the vehicle body side when viewed from the strut 41. The vehicle body side member means a member connected to the vehicle body side from the viewpoint of the member to be described.

The strut 41 is a shock absorber that expands and contracts in the vertical direction, and has a nested damper and a coil spring that surrounds the upper end region (damper inner cylinder) of the damper. The upper end of the coil spring (not shown) supports the upper coil spring seat provided at the upper end of the strut (upper end of the inner cylinder of the damper) (not shown). The lower end of the coil spring is supported by a lower coil spring seat (not shown). The lower coil spring seat is fixed to the outer cylinder of the damper that occupies the lower end region of the strut 41. The lower end of the damper outer cylinder includes the lower end 42 of the strut. The in-wheel motor drive device 10 is connected to a tie rod of a steering steering device (not shown), and is steered around a steering axis Kp extending in the vertical direction. The strut 41 is arranged inside the road wheel W in the vehicle width direction.

The lower arm 48 is a swing arm connected to the lower part of the in-wheel motor drive device 10 via a ball joint 49 at the outer end 48p in the vehicle width direction. The in-wheel motor drive device 10 can steer around the upper end of the strut (not shown) and the steering axis Kp (FIG. 2) which is a straight line passing through the ball joint 49.

The lower arm 48 has two inner ends 48q and 48r in the vehicle width direction. The inner ends 48q and 48r in the vehicle width direction are separated in the vehicle front-rear direction, and elastic bushes 51 and 52 are provided, respectively. The inner end 48q in the vehicle width direction in front of the vehicle is arranged close to the axis O when traveling straight (when not steering). On the other hand, the inner end 48r in the vehicle width direction behind the vehicle is separated from the axis O when traveling straight (when not steering). As shown in FIG. 1, when viewed in the vertical direction, the distance from the axis O when traveling straight (when not steering) to the elastic bush 52 (rear bush) on the rear side is from the axis O when traveling straight (when not steering). It is larger than the distance to the elastic bush 51 (front bush) on the front side. In the present embodiment, when viewed in the vertical direction, the axis O when traveling straight (when not steering) intersects the elastic bush 51 on the front side. The arrangement of the ball joint 49 is the same as that of the outer end 48p in the vehicle width direction. As a modification not shown, the axis O when traveling straight (when not steering) may be separated from both elastic bushes 51 and 52 in front of the vehicle when viewed in the vertical direction, or between both elastic bushes 51 and 52. It may be located in.

The lower arm 48 is a suspension member arranged below the axis O. The lower arm 48 is rotatably connected to the subframe 30 on the vehicle body side via elastic bushes 51 and 52. The lower arm 48 can swing in the vertical direction with the inner ends 48q and 48r in the vehicle width direction as base ends and the outer ends 48p in the vehicle width direction as free ends. FIG. 2 schematically shows a state of bouncing upward with a virtual line.

The vehicle body subframe 30 is a vehicle body side member when viewed from the lower arm 48. 1 and 2 show a structure relating to the left front wheel of the electric vehicle, but the right front wheel (not shown) is also configured symmetrically with the left front wheel and is connected to the right side of the subframe 30 in the vehicle width direction. The subframe 30 is connected to a main frame of a vehicle body (not shown).

3 and 4 are cross-sectional views showing the elastic bush of the same embodiment. The elastic bushes 51 and 52 are provided inside the cylindrical inner ends 48q and 48r in the vehicle width direction, respectively, and include a metal inner cylinder 53 and an outer cylinder 54, a metal rolling element 55, and a cylindrical rubber or the like. It has an elastic portion 56 and a shaft 57, and extends in the front-rear direction of the vehicle. The axis Xb represents the central axis of the elastic bush 51 and passes through the center of the axis 57. The axis Xb represents the center of rotation of the bearing composed of the inner cylinder 53, the outer cylinder 54, and the rolling element 55. In this embodiment, the extended axis Xb of the elastic bush 51 passes through the other elastic bush 52. As a result, when the lower arm 48 swings around the inner ends 48q and 48r in the vehicle width direction, the elastic bush 52 is less likely to be twisted.

The rolling elements 55 are needle-shaped rollers, and a plurality of rolling elements 55 are arranged in the annular space of the inner cylinder 53 and the outer cylinder 54 at intervals in the circumferential direction. Both ends of the outer cylinder 54 are folded inward to form a collar portion 54b. Each flange portion 54b regulates the rolling element 55 from coming out in the extending direction of the shaft 57. The outer cylinder 54 is inserted and fixed in the center hole of the inner end 48q in the vehicle width direction. Needle roller bearings having inner rings, outer rings, and needle rollers have a smaller cross-sectional area than cylindrical roller bearings, and are therefore suitable for incorporation into elastic bushes 51 and 52 in terms of space and weight. Further, the needle roller bearing has a type without an inner ring and a type without an outer ring, and the outer cylinder 54 of the elastic bushes 51 and 52 to be incorporated can be used as a rolling surface, and the number of parts is reduced. As a modification (not shown), the rolling element 55 may be a single-row or double-row cylindrical roller.

An elastic portion 56 is inserted and fixed in the central hole of the inner cylinder 53. A pipe-shaped shaft 57 is inserted and fixed in the central hole of the elastic portion 56. Both ends of the shaft 57 project from the elastic portion 56. The shaft 57 is attached and fixed to the subframe 30 by passing a bolt through the center hole or the like. The elastic portion 56 contains a vibration isolator having an appropriate hardness and acts as a vibration isolator that reduces vibration transmission from the in-wheel motor drive device 10 to the subframe 30.

That is, the elastic bush 51 is an assembly of a rolling bearing and a rubber bush. The shaft 57 on the innermost diameter side is rotatably supported by the outer cylinder 54 on the outermost diameter side. Further, the elastic portion 56 suppresses the transmission of vibration between the outer cylinder 54 and the shaft 57.

The elastic bush 52 has an outer cylinder, a shaft, and a cylindrical elastic portion inserted and fixed between them. The outer cylinder of the elastic bush 52 is fixed to 48r. The shaft of the elastic bush 52 is, for example, a pipe through which a bolt or the like (not shown) is passed and fixed to the subframe 30. Thus, the elastic bushes 51 and 52 are interposed between the lower arm 48 as a suspension member and the subframe 30. The vibration transmitted from the in-wheel motor drive device 10 to the lower arm 48 is damped by the elastic portions of the elastic bushes 51 and 52, making it difficult to transmit to the subframe 30.

Next, the problems peculiar to the in-wheel motor will be described.

When the in-wheel motor drives the wheels, a front-rear force is generated at the ground contact point between the wheels and the road surface. FIG. 7 schematically shows the structure of a suspension device that connects an in-wheel motor to a vehicle body when viewed from the outside in the vehicle width direction of an electric vehicle. This suspension device has a general structure, and has an extending damper 43 that expands and contracts straight in the vertical direction, and a lower arm 48. The damper 43 does not extend strictly vertically, and is inclined at a predetermined trad angle so that the lower end is in front of the vehicle and the upper end is in the rear of the vehicle. The axis Xd represents the center line of the damper 43.

As shown in FIG. 7, when viewed from the outside in the vehicle width direction, the reference line Lb extending orthogonal to the axis Xd and extending to the rear of the vehicle intersects the outer end 48p of the lower arm 48 in the vehicle width direction extending parallel to the swing axis of the lower arm 48. The intersection of the reference lines Lc is called the swing instantaneous rotation center Pd of the suspension device. The straight line passing through the ground contact point Ps of the circular tire T (wheel) and the flat road surface S and the swinging momentary rotation center Pd is defined as the reference line Lf. The reference line Lf and the road surface S form an angle θ.

8 and 9 are schematic views showing a front-rear force F when the in-wheel motor drives the wheels in the forward direction and a vertical force Ftan θ acting on the in-wheel motor in FIG. 7. The vertical force Ftan θ acting on the wheels becomes unsprung vibration applied to the unsprung member of the suspension device, and is propagated to the vehicle body via the lower arm 48 to worsen the noise inside the vehicle. There are similar concerns about torque unevenness in in-wheel motors. In the prior art, vibration propagation in the vehicle width direction is suppressed, but rotational vibration around the swing axis of the lower arm 48 due to vertical movement of the wheels cannot be vibration-proofed.

According to the present embodiment, since the lower arm 48 and the subframe 30 are connected via the elastic bush 51 having a built-in bearing, the elastic bush 51 even if the wheels (tire T and road wheel W) move up and down. There is no resistance around the axis Xb of the elastic bush 51 due to the bearing of the above, and it is possible to suppress the transmission of vertical vibration to the subframe 30 and the vehicle body.

Further, the vertical vibration is suppressed without softening the hardness of the elastic portion 56 of the elastic bush 51. The elastic bush 51 may have the same hardness as the conventional one and does not affect the steering stability.

Further, due to the bearing of the elastic bush 51, the torsional moment of the elastic bush 51 is not generated in the elastic bush 51 as in the conventional case, and the torsional moment of the elastic bush 51 is not applied to the lower arm 48. Therefore, the lower arm can be made thinner and lighter, which contributes to the reduction of the unsprung weight of the suspension device and the increase of the output of the in-wheel motor drive device 10.

As a modification (not shown), the elastic bush 52 may also have a built-in bearing like the elastic bush 51.

Next, other embodiments of the present invention will be described. FIG. 5 is a plan view showing another embodiment of the present invention. Regarding the other embodiments, the configurations common to the above-described embodiments are designated by the same reference numerals and the description thereof will be omitted, and the different configurations will be described below. In another embodiment, the suspension device 60 has two links 61, 62 instead of the lower arm 48 described above. The outer ends 61p and 62p of the links 61 and 62 in the vehicle width direction are connected to the lower portion of the in-wheel motor drive device 10 via a common ball joint 49. The link 61 in front of the vehicle extends along the axis O. It should be understood that along the axis O here is the vicinity of the axis O. The vehicle width direction inner end 61q of the link 61 is the same as the vehicle width direction inner end 48q described above, and is connected to the subframe 30 via the elastic bush 51.

The link 62 is arranged behind the link 61, the outer end 62p in the vehicle width direction is arranged in the front of the vehicle, and the inner end 62q in the vehicle width direction is arranged in the rear of the vehicle and extends diagonally. It should be understood that the diagonal here is an inclined posture with respect to the axis O. The vehicle width direction inner end 62q of the link 62 is the same as the vehicle width direction inner end 48r described above, and is connected to the subframe 30 via the elastic bush 52.

Also in the other embodiment shown in FIG. 5, similarly to the above-described embodiment shown in FIG. 1, the vertical vibration generated when the in-wheel motor driving device 10 is driven is suppressed from being transmitted to the subframe 30 and the vehicle body. can.

Next, still another embodiment of the present invention will be described. FIG. 6 is a plan view showing another embodiment of the present invention. Regarding the other embodiments, the configurations common to the above-described embodiments are designated by the same reference numerals and the description thereof will be omitted, and the different configurations will be described below. In still another embodiment, the rear end 48r of the suspension device 65 in the vehicle width direction incorporates the elastic bush 66 in place of the elastic bush 52 described above. The inner end 48r in the vehicle width direction of still another embodiment is formed in a cylindrical shape extending in the vehicle front-rear direction. The elastic bush 66 is the same as the elastic bush 51 described above. The axis of the elastic bush 66 on the rear side coincides with the axis Xb of the elastic bush 51 on the front side. Further, the hardness of the elastic portion 56 of the elastic bush 51 closer to the axis O is set to be harder than the hardness of the elastic portion 56 of the elastic bush 66 farther from the axis O.

In still another embodiment shown in FIG. 6, similarly to the above-described embodiment shown in FIG. 1, the vertical vibration generated when the in-wheel motor driving device 10 is driven is transmitted to the subframe 30 and the vehicle body. Can be suppressed.

Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to the illustrated embodiments. Various modifications and modifications can be made to the illustrated embodiment within the same range as the present invention or within the same range. For example, a part of the configurations may be extracted from the above-mentioned one embodiment, another part of the configurations may be extracted from the above-mentioned other embodiments, and these extracted configurations may be combined.

The present invention is advantageously utilized in electric vehicles and hybrid vehicles.

10 in-wheel motor drive, 11 wheel hub bearings,
12 Motor section, 13 Deceleration section, 14 Wheel hub,
48 lower arm, 30 subframe,
40, 60, 65 suspension system, 41 struts,
42 strut lower end, 43 damper,
48 Lower arm (suspension member),
48p, 61p, 62p Outer end in vehicle width direction,
48q, 48r, 61q, 62q Inner end in vehicle width direction,
49 ball joints, 51, 52, 66 elastic bushes,
53 inner cylinder, 54 outer cylinder, 54b collar, 55 rolling element,
56 elastic part, 57 axes, 61, 62 links,
Kp steering axis, O, Xb, Xd axis,
Pd swing momentary rotation center, Ps ground contact point, S road surface,
T tires (wheels), W road wheels.

Claims (6)

A shaft provided on either the suspension member or the vehicle body side member connected to the in-wheel motor drive device, and
An outer cylinder provided on the remaining other side through which the shaft is passed, and
A bearing provided between the shaft and the outer cylinder,
A suspension structure for an in-wheel motor drive device, comprising the suspension member and a vibration isolator inserted between the vehicle body side members. The suspension structure for an in-wheel motor drive device according to claim 1, wherein the vibration isolator is a tubular bush having an elastic body that absorbs vibration and is arranged coaxially with the bearing. The suspension member and the vehicle body side member are connected at two places at intervals in the front-rear direction of the vehicle.
Among these connection points, the shaft, the outer cylinder, the bush, and the bearing are arranged at the connection point closer to the axle passing through the center of the wheel hub of the in-wheel motor drive device.
The suspension structure for an in-wheel motor drive according to claim 2, wherein the center line of the bearing extends in the front-rear direction of the vehicle. The bearings are arranged at a connection point closer to the axle and a connection point away from the axle at the rear of the vehicle, respectively.
The bush is provided in each of the two bearing portions, and the bush is provided in each of the two bearing portions.
The suspension structure for an in-wheel motor drive according to claim 3, wherein the bush closer to the axle is harder than the bush farther from the rear of the vehicle in terms of hardness in the vertical direction. The suspension structure for an in-wheel motor drive according to any one of claims 2 to 4, wherein the bush is interposed between the bearing and the shaft. The suspension structure for an in-wheel motor drive according to any one of claims 1 to 4, wherein the bearing is a roller bearing.

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