In-wheel motor system for a steering wheel

An in-wheel motor system for mounting a direct drive motor to a steering wheel comprises a first knuckle 4 which is connected to the non-rotary side of a geared motor 3 by a connection member I0 having elastic bodies and direct-moving guides for limiting movement to a vertical direction and locked in a steering direction by upper and lower suspension arms 5a and 5b and a second knuckle 7 which is connected to a steering rod 8 and fitted with a brake unit 9 and a wheel 2 through a hub 6. This second knuckle 7 is connected to the above first knuckle 4 in such a manner that it can turn on a king pin axis J in the steering direction and to the output shaft of the above geared motor 3 by a connection shaft 20 having constant velocity joints 21 and 22 at both ends, thereby reducing an increase in steering torque.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an in-wheel motor system for a steering wheel for use in a vehicle having direct drive wheels as steering wheels.

2. Description of the Prior Art

In recent years, in a vehicle driven by a motor such as an electric car, an in-wheel motor system which incorporates a motor composed of a knuckle as a frame dress-up part and a drive motor in wheels has been employed due to its high space efficiency and drive force transmission efficiency (for example, U.S. Pat. No. 2,676,025, JP-A 9-506236 and JP-A 10-305735) (the term “JP-A” as used herein means an “unexamined published Japanese patent application”).

However, since the motor is fixed to a knuckle which is a frame dress-up part of the vehicle in the above in-wheel motor system of the prior art, when an in-wheel motor is used in the steering wheel, the motor turns in a steering direction together with the wheel at the time of steering. That is, as the inertia moment on the steering axis of the steering wheel provided with the in-wheel motor increases due to the mass of the motor, not only does the steering torque becomes large but also the resonance in the steering direction easily occurs.

In a vehicle having a suspension mechanism such as a spring, it is known that as the mass of unsprung parts such as a wheel, knuckle and suspension arm so called “unsprung mass” increases, variations in the ground contact force of a tire become larger and the road holding properties become worse when the vehicle runs on a rough road. In the in-wheel motor of the prior art, as the motor is fixed to the knuckle as described above, the above unsprung mass increases by the mass of the motor with the result that variations in the ground contact force of the tire become larger and the road holding properties become worse.

It is an object of the present invention which has been made in view of the above problems of the prior art to provide an in-wheel motor system for a steering wheel which can reduce an increase in the steering torque of a steering wheel provided with an in-wheel motor.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided an in-wheel motor system for mounting a direct drive motor to a steering wheel, comprising a first knuckle which is connected to the non-rotary side of the direct drive motor and locked in a steering direction and a second knuckle which is connected to a steering rod and to the first knuckle in such a manner that it can turn on a king pin axis in the steering direction and fitted with a brake unit and the steering wheel. Thereby, as the in-wheel motor does not turn in the steering direction at the time of steering, the steering torque of the steering wheel can be reduced without fail.

According to a second aspect of the present invention, there is provided an in-wheel motor system for a steering wheel, wherein the non-rotary side of the motor is connected to the first knuckle by elastic bodies and dampers, or elastic bodies having a spring or damper function. Thereby, the motor is float mounted to a frame dress-up part to function as the weight of a dynamic damper, thereby making it possible to improve the ground contact performance of the tire and riding comfort.

According to a third aspect of the present invention, there is provided an in-wheel motor system for a steering wheel, wherein the non-rotary side of the motor is supported by direct-moving guides and a buffer member in the vertical direction of a vehicle. Thereby, variations in the ground contact pressure of the tire at the time of driving on a rough road and the road holding properties of the vehicle can be improved.

According to a fourth aspect of the present invention, there is provided an in-wheel motor system for a steering wheel, wherein the non-rotary side of the motor is supported by direct-moving guides and a buffer member in the horizontal direction of a vehicle in addition to the vertical direction. Thereby, variations in the longitudinal force of the tire can be reduced and the tire performance can be stabilized.

According to a fifth aspect of the present invention, there is provided an in-wheel motor system for a steering wheel, wherein the output shaft of the motor and a wheel support hub mounted to the second knuckle are interconnected by constant velocity joints. Thereby, even when the motor shaft becomes eccentric from the wheel shaft by steering drive force can be transmitted from the motor to the wheel without fail.

According to a sixth aspect of the present invention, there is provided an in-wheel motor system for a steering wheel, wherein the rotary portion of the motor and the wheel are interconnected by a flexible coupling having at least two direct-moving guides connected to each other in such a manner that their moving directions cross each other in the axial direction of the motor and a constant velocity joint-like coupling which has the center of its movement on a king pin axis. Thereby, even when a hollow type direct drive motor which cannot directly transmit the revolution of the motor to the hub due to its structure is used as the in-wheel motor, drive force can be transmitted from the motor to the wheel without fail.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described hereinunder with reference to the accompanying drawings.

FIG. 1is a diagram showing the constitution of an in-wheel motor system for a steering wheel according to Embodiment 1. InFIG. 1, reference numeral1denotes a tire,2a wheel composed of a rim2aand a wheel disk2b,3ageared motor comprising an electric motor3A and a planetary speed reducer3B in a motor case3C,4a first knuckle which is fitted with the above geared motor3and connected to upper and lower suspension arms5aand5b,6awheel support hub which is connected to the wheel2at its rotation axis,7a second knuckle which is connected to a steering rod8and to the first knuckle4in such a manner that it can turn on a king pin axis J in the steering direction. A brake unit9and the above wheel2are mounted to the second knuckle7through the above wheel support hub6.

That is, the in-wheel motor system for a steering wheel of the present invention is constituted such that the knuckle consists of the first knuckle4locked in the steering direction and the second knuckle7mounted to the wheel2and connected to the steering rod8, the geared motor3is mounted to the above first knuckle4, and the first knuckle4and the second knuckle7are rotatably interconnected in the steering direction. Denoted by5cis a suspension member composed of a shock absorber or the like.

More specifically, the above geared motor3is an inner rotor type in-wheel motor in which a non-rotary case3afor supporting the stator3S of the electric motor3A is connected to the motor case3C and a rotary case3bfor supporting a rotor3R is connected to the planetary speed reducer3B. The above motor case3C is connected to the above first knuckle4by a connection member10having elastic bodies11and direct-moving guides12for limiting movement to the vertical direction arranged on a hollow disk-like plate13as shown inFIG. 2(a), and the output shaft (motor output shaft) of the above planetary speed reducer3B is connected to the above second knuckle7by a connection shaft20having constant velocity joints21and22at both ends.

Each of the direct-moving guides12for limiting movement to the vertical direction comprises a guide rail12phaving a projecting portion extending in the vertical direction and a guide member12qhaving a recessed portion to be mated with the above guide rail12p. To slide the above guide rail12pand the guide member12qsmoothly, a plurality of steel balls12rmay be put between the projecting portion of the above guide rail12pand the recessed portion of the guide member12q.

The geared motor3is mounted to the first knuckle4which is supported by the upper and lower suspension arms5aand5band locked in the steering direction as described above, and the first knuckle4is connected to the second knuckle7which is linked to the wheel support hub6and the steering rod8in such a manner that it can turn on the king pin axis J in the steering direction. Therefore, the geared motor3which is an in-wheel motor does not turn in the steering direction together with the wheel2at the time of steering unlike the prior art. Consequently, the steering torque does not increase, thereby making it possible to reduce the steering torque of the steering wheel without fail.

Since the second knuckle7connected to the wheel support hub6and the output shaft of the geared motor3are interconnected by the connection shaft20having constant velocity joints21and22at both ends in this embodiment, drive force can be transmitted from the motor3to the wheel2even at the time of steering without fail.

Further, since the above first knuckle4and the motor case3C to which the non-rotary case3afor supporting the stator3S of the above geared motor3is fixed are interconnected by the connection member10having the elastic bodies11and the direct-moving guides12for limiting movement to the vertical direction in this embodiment, the geared motor3is float mounted to an unsprung portion which is a frame dress-up part of the vehicle. Therefore, the mass of the motor is separated from the unsprung mass of the vehicle and functions as the weight of a so-called dynamic damper, whereby it cancels unsprung vibration at the time of driving on a rough road, thereby making it possible to reduce variations in the ground contact force of the tire and to improve the road holding properties of the vehicle. A vibration load on the geared motor3at the time of driving on a bad road can be reduced.

According to Embodiment 1, the knuckle consists of the first knuckle which is connected to the non-rotary side of the geared motor3by the connection member10having elastic bodies11and direct-moving guides12for limiting movement to the vertical direction and locked in the steering direction by the upper and lower suspension arms5aand5band the second knuckle7which is connected to the steering rod8and fitted with the brake unit9and the wheel2through the hub6, the second knuckle7is connected to the first knuckle4in such a manner that it can turn on the king pin axis J in the steering direction, and the above second knuckle7and the output shaft of the above geared motor3are interconnected by the connection shaft20having constant velocity joints21and22at both ends. Therefore, even at the time of steering, the rotation of the geared motor3in the steering direction can be suppressed, the steering torque of the steering wheel can be greatly reduced, and drive force can be transmitted without fail.

The motor case3C which is the non-rotary portion of the geared motor3is mounted to the above first knuckle4by the connection member10having elastic bodies11and direct-moving guides12for limiting movement to the vertical direction so that the mass of the motor functions as the weight of a dynamic damper, thereby making it possible to reduce variations in the ground contact force of the tire and to improve the road holding properties of the vehicle.

In the above Embodiment 1, the in-wheel motor is the geared motor3. Even when a hollow type direct drive motor3Z constituted such that a stator3S is mounted on a first annular case (non-rotary case)3awhich is open on the outer side in the radial direction, a rotor3R is mounted on a second annular case (rotary case)3bwhich is open on the inner side in the radial direction and arranged concentric to the above non-rotary case3aon the outer side in the radial direction of the non-rotary case3awith a predetermined space between it and the above stator3S, and the above non-rotary case3aand the rotary case3bare rotatably interconnected by a bearing3jis mounted as shown inFIG. 3andFIG. 4, the knuckle consists of a first knuckle4Z which is connected to the non-rotary side of the above motor3Z by a shock absorber30and locked in the steering direction by upper and lower suspension arms5aand5band a second knuckle7Z which is connected to the steering rod8and fitted with the brake unit9and the wheel2through a hub6Z, and the second knuckle7Z is connected to the first knuckle4Z in such a manner that it can turn on the king pin axis J in the steering direction. Thereby, the above motor3Z can be float mounted to an unsprung portion which is a frame dress-up part of the vehicle, and drive force can be transmitted from the above motor3Z to the wheel2at the time of steering without fail.

As shown inFIG. 5, the above shock absorber30comprises two plates34and35which are interconnected by springs32and32and a damper33movable in the vertical direction of the vehicle and whose moving directions are limited to the vertical direction of the vehicle by direct-moving guides31. That is, since the shock absorber30is constituted such that the two springs32and32which expand and contract in the vertical direction of the vehicle and the damper33which expands and contracts in the vertical direction of the vehicle are installed on the knuckle attachment plate34connected to the first knuckle4Z and that spring receiving portions36are installed at positions above or below the above springs32and a damper attachment portion37is installed at a position above the damper33on the motor attachment plate35connected to the non-rotary case3aof the motor3Z, the above motor attachment plate35and the knuckle attachment plate34can be guided in the vertical direction of the vehicle and the above motor3Z can be restricted to the vertical moving direction while attenuation force is generated. Thereby, the motor3Z can be float mounted to an unsprung portion which is a frame dress-up part of the vehicle and accordingly, the mass of the above motor3Z is separated from the unsprung mass of the vehicle and functions as the weight of a so-called dynamic damper. Therefore, unsprung vibration at the time of driving on a rough road is canceled, thereby making it possible to reduce variations in the ground contact force of the tire and to improve the road holding properties of the vehicle.

The hollow type direct drive motor3Z cannot transmit the revolution of the motor to the hub6Z directly due to its structure. In this embodiment, a flexible coupling50which can be eccentric from the shaft of the motor in the vertical direction and a constant velocity joint-like coupling40which can turn in the steering direction are used to interconnect the motor rotary portion and the wheel2so as to transmit the drive force of the above motor3Z to the wheel2.

That is, since the shaft of the above motor3Z becomes eccentric from the shaft of the wheel in the vertical direction, the flexible coupling50which can be eccentric from the shaft in the vertical direction is used to transmit drive force. As the above flexible coupling50and the wheel2must be made free from each other in the steering direction at this point, the constant velocity joint-like coupling40which has the center of its movement at the intersection point between the king pin axis J and the wheel shaft is installed between the above flexible coupling50and the wheel2.

Thereby, drive force can be transmitted from the motor3Z to the wheel2without increasing the steering torque at the time of steering.

FIG. 6(a) shows an example of the above flexible coupling50. This flexible coupling50comprises a hollow disk-like plate (wheel side plate)51which is situated on the wheel2side and whose periphery is connected to the inner side of the above constant velocity joint-like coupling40, a hollow disk-like plate (motor side plate)53which is situated on the motor3Z side and connected to the rotary case3bof the motor3Z, and a hollow disk-like plate (intermediate plate)52which is connected to the above wheel-side plate51by a direct-moving guide54and to the above motor side plate53by a direct-moving guide55, the direct-moving guide54consists of guide members54aand guide rails54b, the direct-moving guide55consists of guide members55aand guide rails55bmovable in a direction perpendicular to the moving direction of the above direct-moving guide54, and all of the above direct-moving guides are mounted on the motor3Z side plate and the wheel2side plate and on the front and rear sides of the intermediate plate at the same positions at intervals of 90°. Although force for turning in the peripheral direction and force for expanding in the radical direction are applied to the above intermediate plate52as shown inFIG. 6(b), as the direct-moving guide54which moves in a direction perpendicular to the moving direction of the above direct-moving guide55is installed on the rear side (wheel2side) of the above direct-moving guide55of the above intermediate plate52, force for expanding the above intermediate plate52in the radial direction is balanced with the force for expanding in the radial direction of the above direct-moving guide54with the result that only torque is transmitted to the wheel side plate51. Therefore, torque input into the direct-moving guide55from the motor side plate53connected to the rotary case3bis transmitted to the wheel side plate51through the above intermediate plate52, whereby the drive force of the above motor3Z can be transmitted to the wheel2without fail.

A flexible coupling50A in which the above hollow disk-like plates51to53are interconnected by direct-moving guides56and57whose moving directions are perpendicular to each other as shown inFIG. 7may be used in place of the above flexible coupling50.

In the above Embodiment 2, the motor3Z is supported in the vertical direction of the vehicle by the shock absorber30. When a shock absorber30A constituted such that two springs32A and32A which expand and contract in the horizontal direction of the vehicle and a damper33A which expands and contracts in the horizontal direction of the vehicle are installed on a first plate34A connected to the first knuckle4Z, a second plate34B having spring receiving portions36A installed at positions above or below the above springs32A and a damper attachment portion37A installed at a position above the above damper33A on the first plate34A side and two springs32and32expanding and contracting in the vertical direction of the vehicle and a damper33expanding and contracting in the vertical direction of the vehicle on the motor attachment plate35side is interposed between the above first plate34A and the motor attachment plate35connected to the non-rotary case3aof the motor3Z, the above first plate34A and the above second plate34B are interconnected by a direct-moving guide31A for guiding the above plates34A and34B in the horizontal direction of the vehicle, and the above second plate34B and the motor attachment plate35having spring receiving portions36installed at positions above or below the above springs32and a damper attachment portion37installed at a position above the damper33are interconnected by a direct-moving guide31for guiding the above plates34B and35in the vertical direction of the vehicle as shown inFIG. 8is used in place of the above shock absorber30, the above motor3Z can be float mounted in the horizontal direction of the vehicle in addition to the vertical direction of the vehicle, whereby the above motor3Z functions as the weight of a dynamic damper not only in the vertical direction but also in the horizontal direction of the vehicle. Therefore, since unsprung vibration at the time of driving on a rough road can be canceled to reduce variations in the ground contact force of the tire, thereby making it possible to improve the road holding properties of the vehicle and also to reduce variations in the longitudinal force of the tire. As a result, the performance of the tire can be stabilized.

In the above embodiment, an outer rotor type in-wheel motor is mounted as the hollow type direct drive motor3Z. An inner rotor type in-wheel motor3Y as shown inFIG. 9may be mounted in place of the above motor3Z. InFIG. 9, reference symbol3cdenotes the non-rotary case of the in-wheel motor3Y to which the stator3S is mounted and3ddenotes a rotary case which is arranged on the inner side in the radial direction of the above non-rotary case3cand rotatably connected to the above non-rotary case3cby a bearing3jand to which the rotor3R is mounted.

INDUSTRIAL FEASIBILITY

As having been described above, according to the present invention, an in-wheel motor system for mounting a direct drive motor to a steering wheel comprises a first knuckle locked in a steering direction and a second knuckle which is connected to a steering rod and to the first knuckle in such a manner that it can turn on a king pin axis in the steering direction and fitted with a brake unit and a steering wheel, and the direct drive motor is mounted to the first knuckle. Since the in-wheel motor does not turn in the steering direction at the time of steering, an increase in inertia moment on the steering shaft can be greatly suppressed and the steering torque of the steering wheel can be reduced without fail.

Since the non-rotary side of the above motor is connected to the first knuckle by elastic bodies and dampers, or elastic bodies having a spring or damper function and the above motor functions as the weight of a dynamic damper, the ground contact performance of the tire and riding comfort can be improved.