JPH11278084A - Electrice drive device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a device and reduce noise concerning the electric drive device furnished with a pair of electric motors and a pair of differential gears to transmit motor output torque to left and right driven wheels. SOLUTION: A pair of ball type reduction gears 7L, 7R devised to transmit motive power by reducing its speed trough a ball 76 with a casing 70 as a reaction receiver from an input side cam plate 73 to an output side cam plate 74 is provided. Each of electric motors 6L, 6R and each of driven wheels 4L, 4R are respectively connected to an input shaft 71 and an output shaft 72 of each of the reduction gears 7L, 7R, the casing 70 of both of the reduction gears 7L, 7R is integrated, the casing 70 is made free to rotate, and each of differential gears is constituted by each of the reduction gears 7L, 7R. A starting assist is carried out by driving both of the electric motors 6L, 6R in the same direction in a state where rotation of the casing 70 is constrained, and the turning assist is carried out by driving both of the electric motors 6L, 6R in a state where constraint of the casing 70 is released in the opposite directions to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric drive device provided between left and right driven wheels of a vehicle having one of a front wheel and a rear wheel driven by an engine and the other being a driven wheel.

[0002]

2. Description of the Related Art Conventionally, as this type of electric drive device,
According to Japanese Patent Application Laid-Open No. 9-79348, a pair of electric motors and a pair of planetary gear type differentials are provided, and each electric motor is connected to a sun gear of each differential via a reduction gear train. , Connect each driven wheel to the carrier of each differential,
Further, there is known a structure in which the ring gears of both differential devices are connected to each other so that the rotation of the ring gear can be restrained by a brake means.

In this apparatus, when both electric motors are driven in the same direction with the brake means turned on, and the sun gears of the two differentials are rotated in the same direction via a reduction gear train, the ring gear reacts. As a receiver, the carriers of both differential devices rotate in the same direction, and the output torque of both electric motors is transmitted to both driven wheels as driving force in the same direction. Thus, when starting on a slippery road surface, both driven wheels are driven by driving both electric motors in the same direction with the brake means on,
Start assist can be performed. When the brake means is turned off and both electric motors are stopped after starting,
The ring gear idles, and no reverse drive torque is transmitted from the driven wheel side of the electric motor.

When both electric motors are driven in opposite directions while the brake means is turned off to rotate the sun gear of one differential gear forward and the sun gear of the other differential gear reversely, one of the differential gears is rotated. The reaction force in the reverse direction acts on the ring gear via the planetary gears of the driving device, and the reaction force in the forward direction acts on the ring gears via the planetary gears of the other differential device. In contrast, the carrier of one differential device rotates in the forward direction, and the carrier of the other differential device rotates in the reverse direction. That is, the output torque of one electric motor is transmitted to one driven wheel as a driving force, and the output torque of the other electric motor is transmitted to the other driven wheel as a braking force. Therefore, when the vehicle turns, the electric motor on the turning outer wheel is rotated forward and the electric motor on the inner wheel is rotated in reverse to apply a driving force to the outer wheel driven wheels and a braking force to the inner wheel driven wheels to perform turning assist. be able to.

[0005]

In order to reduce the weight and cost of the electric drive device, it is desired to use a small motor used for a cell motor or the like as the electric motor. In this case, it is necessary to increase the reduction ratio of the transmission mechanism between the electric motor and the driven wheel. However, if a planetary gear type differential is used as in the above-described conventional example, the differential Since the reduction ratio of the device cannot be made so large, the reduction ratio of the reduction gear train must be increased, and the electric drive device is enlarged by the reduction gear train, and further, noise caused by gear backlash is reduced. It is easy to occur.

Incidentally, a ball type speed reducer is known as a speed reducer capable of obtaining a large reduction ratio (Japanese Utility Model Application Laid-Open No. 5-37).
No. 13). This speed reducer has a casing, and an input side and an output side cam plate arranged in the casing so as to face each other in the axial direction, and power is received from the input side cam plate to the output side cam plate by receiving the casing as a reaction force receiver. It is configured to be transmitted at a reduced speed via a ball. When the casing is rotatable, transmission of the reverse drive torque from the output shaft of the speed reducer to the input shaft is prevented by idling of the casing, and the casing also functions as a differential device.

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide an electric drive device for a vehicle which can be reduced in size and noise by using a ball type speed reducer.

[0008]

Means for Solving the Problems In order to solve the above problems,
In the present invention, an electric drive device provided between left and right driven wheels of a vehicle having one of a front wheel and a rear wheel driven by an engine and the other as a driven wheel, and a pair of electric motors;
A casing provided with a pair of differentials interposed between the two electric motors and the left and right driven wheels, and an input side and an output side cam plate disposed in the casing so as to face each other in the axial direction; And a pair of ball type speed reducers configured so that power is reduced and transmitted via balls from the input side cam plate to the output side cam plate with the casing as a reaction force receiver, and each ball type speed reducer is provided. By connecting the electric motors and the driven wheels to the input shaft and the output shaft of each ball type speed reducer by freely rotating the casing of the speed reducer, each of the differential devices And the casings of the two ball type speed reducers are connected to each other so that the rotation of the casing can be restricted by the brake means.

According to the present invention, when both electric motors are driven in the same direction while the casing is restrained by the braking means, the output torque of each electric motor is increased by the input side cam plate, the ball and the output side of each ball type speed reducer. The driving force is transmitted to each driven wheel via the cam plate, and the starting assist is performed.
Then, after the start, the restraint of the casing by the brake means is released and both electric motors are stopped. However, according to this, the casing idles and the reverse drive torque from each driven wheel side is not transmitted to each electric motor. In addition, while the restraint of the casing is released, both electric motors are driven in opposite directions to rotate the input side cam plate of one ball type speed reducer in the forward direction and the input side cam plate of the other ball type speed reducer. When the ball is rotated in the reverse direction, a reverse reaction is applied to the casing of one ball type speed reducer in the reverse direction, and a reaction in the normal direction is applied to the casing of the other ball type speed reducer. The output side cam plate of the ball type speed reducer rotates in the forward direction, and the output side cam plate of the other ball type speed reducer rotates in the reverse direction. Thus, the output torque of one electric motor is transmitted to one driven wheel as a driving force, and the output torque of the other electric motor is transmitted to the other driven wheel as a braking force, and turning assist is performed.

Here, unlike the planetary gear type differential, the ball type speed reducer does not generate noise due to backlash and has a large reduction ratio. There is no need to interpose a gear train with a large reduction ratio between them. Thus, the size of the electric drive device can be reduced and noise can be reduced.

In the ball type speed reducer, an axial thrust force acts on the output side cam plate via the ball at the time of power transmission. Therefore, it is necessary to increase the thickness of the bearing portion of the output side cam plate of the casing of the ball type speed reducer to secure rigidity against thrust force. As a result, if an independent casing is provided for each ball type speed reducer, the shaft length of the electric drive device becomes longer. On the other hand, the casing of both ball type speed reducers is constituted by a common casing, and the output side cam plate of one ball type speed reducer and the output side cam plate of the other ball type speed reducer are shafted in the common casing. If a thrust bearing is interposed between both output side cam plates, a thrust force acting on both output side cam plates can be mutually received by both output side cam plates via the thrust bearing, It is not necessary to provide a bearing portion for receiving the thrust of the output cam in the casing. Thus, the shaft length of the electric drive device can be shortened to further reduce the size. Further, it is not necessary to separately provide a thrust bearing for the output side cam plate for each ball type speed reducer, so that the number of parts can be reduced and the cost can be reduced.

[0012]

FIG. 1 shows a front wheel drive vehicle in which left and right front wheels 3L, 3R are driven by an engine 1 via a transmission 2, and an electric motor is provided between left and right rear wheels 4L, 4R as driven wheels. An expression driving device 5 is provided.

As shown in FIG. 2, the electric drive device 5 includes a pair of left and right electric motors 6L and 6R and a pair of left and right ball type speed reducers 7L and 7R. Each of the ball type speed reducers 7L and 7R includes a casing 70, a hollow input shaft 71 supported in the casing 70, an output shaft 72 inserted through and supported by the input shaft 71, and an eccentric distance e formed in the input shaft 71. An input side cam plate 73 pivotally supported on the outer periphery of the eccentric cam 71a,
An output-side cam plate 74 fixed to the output shaft 72 and supported in the casing 70 so as to face the input-side cam plate 73 in the axial direction, and a ball type for regulating the rotation of the input-side cam plate 73 with respect to the casing 70. An Oldham mechanism 75 is provided.

The input side cam plate 73 has a groove 73a formed along the hypo (inversion) cycloid curve HS shown in FIG. 3, and the output side cam plate 74 has an epi (abduction) shown in FIG. A groove 74a is formed along the cycloid curve ES, and a ball 76 is interposed between the cam plates 73, 74 so as to engage with the grooves 73a, 74a. The hypocycloid curve HS is a curve obtained by inverting a circle having a radius e along a circle CA having a radius larger than the radius of the reference circle C by the eccentric distance e, and the epicycloid curve ES is This is a curve obtained by abducting a circle having a radius e along a circle CB having a radius smaller by e than the radius of the reference circle C. The number of waves of the epicycloidal curve ES is an even number from the number of waves of the hypocycloidal curve HS. The radius of the reference circle C and the eccentric distance e are set so as to be smaller.

When the input shaft 71 is rotated, the input cam plate 73 revolves in a circle having a radius e without rotating by the action of the Oldham mechanism 75. When the input cam plate 73 revolves by the number of waves of the hypocycloid curve HS, the output cam plate 74 is rotated via the ball 76 by the difference in the number of waves between the hypocycloid curve HS and the epicycloid curve ES. In the illustration, the number of waves in the pyrocycloid curve HS is 12, and the epicycloid curve E
The number of S waves is 10, and the reduction ratio is 12: (12-1).
0) = 6: 1. Note that the illustrated one is merely an example, and the reduction ratio can be further increased.

The input shaft 71 of each ball type speed reducer 7L, 7R
A gear 71b is attached to the outer end of the
1b is meshed with a gear 6a on the output shaft of each electric motor 6L, 6R, and each rear wheel 4L, 4R is connected to the output shaft 72 of each ball type speed reducer 7L, 7R. , 6R output torque of each of the left and right ball type reduction gears 7
L and 7R are transmitted to the left and right rear wheels 4L and 4R.

In this embodiment, the casings of the left and right ball type speed reducers 7L and 7R are constituted by a common casing 70, and the output side cam plate 74 of the left ball type speed reducer 7L.
And the output side cam plate 74 of the ball type reduction gear 7R on the right side in the casing 70 in the axial direction.
A thrust bearing 77 is interposed between 4, 74.
According to this, the thrust force acting on each output side cam plate 74 via the ball 76 during power transmission is mutually received by the both output side cam plates 74, 74 via the common thrust bearing 77.

The casing 70 is rotatable,
This rotation can be restrained by the brake means 8. The brake means 8 is composed of a dog clutch composed of a movable dog 8a spline-engaged with the outer periphery of the casing 70 and a fixed dog 8b opposed to the movable dog 8a. 8b to engage and disengage the casing 70.

The electric motors 6L, 6R are supplied with electric power from the battery 11 via the motor drivers 10L, 10R controlled by the controller 9, and the controller 9 also controls the energization of the solenoid 8c. The controller 9 performs start assist control when the front wheels 3L and 3R slip when starting, and performs turn assist control when the vehicle turns.

In the start assist control, the solenoid 8c is energized to restrict the rotation of the casing 70 by the brake means 8, and the electric motors 6L and 6R are driven in the same direction. According to this, the input side cam plates 73, 73 of the two-ball type speed reducers 7L, 7R revolve in the same direction, and the balls 76
Output side cam plate 7 of both ball reducers 7L, 7R via
4, 74 are decelerated and rotated in the same direction. At this time, a reaction force acts on the casing 70 via the ball 76, the input side cam plate 73, and the Oldham mechanism 75 in a direction opposite to the rotation direction of the output side cam plate 74. As a result, the output torque of both electric motors 6L, 6R is transmitted as driving force to both rear wheels 4L, 4R, and starting is assisted.

When the vehicle speed increases to a predetermined speed after the start, the power supply to the solenoid 8c is stopped to release the restraint of the casing 70 by the brake means 8 and the electric motor 6
The driving of L and 6R is stopped. In this case, each rear wheel 4L, 4
Although the output side cam plates 74 of the ball type speed reducers 7L and 7R rotate integrally with R, the casing 70 rotates freely, so that the input side cam plate 73 on the eccentric cam 71a with the rotation of the output side cam 74. Rotates integrally with the casing 70, and the reverse drive torque from the rear wheels 4 </ b> L and 4 </ b> R is not transmitted to the input shaft 71. Accordingly, the electric motors 6L, 6R are prevented from being over-rotated by the reverse drive from the rear wheels 4L, 4R during running, and the durability of the electric motors 6L, 6R is ensured.

In the turning assist control, while the restraint of the casing 70 is released, of the left and right electric motors 6L and 6R, the motor on the turning outer wheel is driven in the forward direction, and the motor on the inner wheel is driven in the reverse direction. For example, during a right turn, the left electric motor 6L is driven in the forward direction, and the right electric motor 6R is driven.
Is driven in the reverse direction. According to this, the input side cam plate 73 of the left ball type speed reducer 7L revolves in the forward direction with respect to the casing 70, and the forward direction torque is transmitted to the output side cam plate 74, so that the right ball The input side cam plate 73 of the type speed reducer 7R revolves in the reverse direction with respect to the casing 70, and the reverse direction torque is transmitted to the output side cam plate 74. At this time, the casing 70 has a reaction force in the reverse direction due to the forward rotation torque of the output side cam plate 74 of the left ball type speed reducer 7L and a reverse direction rotation torque of the output side cam plate 74 of the right ball type speed reducer 7R. The reaction force in the forward direction acts, and the output side cam plate 7L of the left ball type speed reducer 7L is determined based on the rotation speed of the casing 70 based on the balance between the two reaction forces.
4, that is, the speed of the left rear wheel 4L is increased, and the output side cam plate 74 of the right ball type speed reducer 7R, ie, the right rear wheel 4R is decelerated. As a result, a driving force is applied to the left rear wheel 4L, which is the outer wheel, and a braking force is applied to the right rear wheel 4R, which is the inner wheel, to generate a yaw moment in the right turning direction, thereby assisting turning.

Here, if an inexpensive small motor used as a cell motor or the like is used as the electric motors 6L and 6R, the electric motors 6L and 6R may be connected to the electric motors 6L and 6R in order to obtain the driving force and braking force necessary for starting assistance and turning assistance. Wheel 4L, 4
It is necessary to increase the reduction ratio between R and R. However, since the ball-type reduction gears 7L and 7R can increase the reduction ratio, the input shafts 71 and 71 of the electric motors 6L and 6R and the ball-type reduction gears 7L and 7R. It is not necessary to interpose a gear example having a large reduction ratio between the electric drive device 5 and the electric drive device 5. Also, unlike the planetary gear type differential device, noise due to gear backlash is not generated, and the noise can be reduced together with the fact that a gear train having a large reduction ratio is not required.

It is also possible to provide a separate casing for each of the ball type speed reducers 7L and 7R and connect the two casings together.
L, 7R are constituted by a common casing 70, and the output side cam plates 74, 7 of both ball reducers 7L, 7R are formed.
If a common thrust bearing 77 is interposed between the four, the casing 70 does not need to have a bearing portion for receiving the thrust of the output side cam plate 74, the shaft length of the casing 70 is shortened, and the electric drive device 5 Can be further miniaturized. Further, it is not necessary to separately provide a thrust bearing for the output side cam plate 74 for each of the ball type speed reducers 7L and 7R, so that the number of parts can be reduced and the cost can be reduced.

FIG. 5 shows a second embodiment of the electric drive device 5, and the same members as those in the first embodiment are denoted by the same reference numerals. In this embodiment, the input side cam plate 73 of each of the ball type speed reducers 7L and 7R is fixed to the input shaft 71, and between the input side cam plate 73 and the output side cam plate 74,
With a fixed ball holding plate 78 interposed in the casing 70,
As shown in FIG. 6, a plurality of through holes 78a into which the balls 76 are loosely fitted are formed in the ball holding plate 78. As shown in FIG. 7, an elliptical groove 73 a ′ having a long diameter Ry and a short diameter Rx is formed in the input side cam plate 73, and the output side cam plate 74 has
As shown in FIG. 8, the groove 7 along the hypocycloid curve
4a 'are formed, and the ball 7 is inserted into both grooves 73a' and 74a '.
6 are engaged.

The through hole 78a has a radius Rs = (Ry + Rx)
/ 2 circles, the number of which is even less than the number of waves in the groove 74a '. The groove 74a 'is formed such that the distance from the rotation center of the output side cam plate 74 is Ry at the wave peak of the groove 74a' and Rx at the wave trough.

In this case, the input side cam plate 73 is
When rotated by the number of waves of a ', the number of waves and the ball 7
The output cam plate 74 rotates by the number of differences from the number 6 (the number of through holes 78a).

The casings of the two-ball type speed reducers 7L and 7R are constituted by a common casing 70 as in the first embodiment, and the output-side cam plates 74 and 74 of the two-ball type speed reducers 7L and 7R are formed by a casing. A thrust bearing 77 is interposed between the two output side cam plates 74, 74 so as to be opposed to each other in the axial direction in the 70, thereby shortening the axial length of the casing 70 and eliminating the number of parts.

Also in the second embodiment, the brake means 8
When the electric motors 6L, 6R are driven in the same direction while the rotation of the casing 70 is restricted by the
Output torques of the electric motors 6L and 6R are transmitted to R as driving force, and start assist is performed. After the start, the restraint of the casing 70 is released and the driving of the electric motors 6L, 6R is stopped. According to this, the casing 70 idles with the rotation of the output side cam plate 74, and the rear wheels 4L, 4R
The reverse drive torque from the side is not transmitted to the input shaft 71. If both electric motors 6L and 6R are driven in opposite directions while the restraint of the casing 70 is released, a driving force is applied to one of the rear wheels 4L and 4R and a braking force is applied to the other.
Turning assist is performed.

Although the embodiment in which the present invention is applied to the rear wheel electric drive device in the front wheel drive vehicle has been described above, the present invention is similarly applied to the front wheel electric drive device as a driven wheel in the rear wheel drive vehicle. Applicable.

[0031]

As is apparent from the above description, according to the present invention, the starting assist function and the turning assist function can be obtained, and the apparatus can be downsized and the noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of use of the apparatus of the present invention.

FIG. 2 is a sectional view showing a first embodiment of the device of the present invention.

FIG. 3 is a diagram showing a shape of a groove formed in an input side cam plate of the first embodiment.

FIG. 4 is a diagram showing a shape of a groove formed in an output side cam plate of the first embodiment.

FIG. 5 is a sectional view showing a second embodiment of the device of the present invention.

FIG. 6 is a side view of a ball holding plate according to a second embodiment.

FIG. 7 is a side view of an input cam plate according to a second embodiment.

FIG. 8 is a side view of an output cam plate according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Engine 3L, 3R Front wheel (drive wheel) 4L, 4R Rear wheel (driven wheel) 5 Electric drive device 6L, 6R Electric motor 7L, 7R Ball type reduction gear 70 Casing 71 Input shaft 72 Output shaft 73 Input side cam plate 74 Output side cam plate 76 Ball 77 Thrust bearing

Claims (2)

[Claims] An electric drive device provided between left and right driven wheels of a vehicle having one of a front wheel and a rear wheel as a drive wheel driven by an engine and the other as a driven wheel, comprising: a pair of electric motors; And a pair of differentials interposed between the two electric motors and the left and right driven wheels, respectively, comprising: a casing; and input side and output side cams disposed in the casing so as to face each other in the axial direction. And a pair of ball-type speed reducers configured so that power is reduced and transmitted through the balls from the input side cam plate to the output side cam plate using the casing as a reaction force receiver. By connecting the electric motors and the driven wheels to the input shaft and the output shaft of each ball type speed reducer by rotating the casing of the type speed reducer, In addition to configuring the device, An electric drive device for a vehicle, wherein casings are connected to each other, and rotation of the casings can be restricted by brake means. 2. The casing of the two ball type speed reducers is constituted by a common casing, and the output side cam plate of one ball type speed reducer and the output side cam plate of the other ball type speed reducer are formed in a common casing. The electric drive device for a vehicle according to claim 1, wherein a thrust bearing is interposed between both output side cam plates in the axial direction.