JP2000291688A - Driving force transmitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the responsiveness of a driving force transmitting device by rolling a ball by the operation of a cam mechanism caused by the increase and decrease of the frictional engagement force when a pilot clutch mechanism is frictionally engaged, and acting the frictional force caused by the rolling of the ball in the moving direction of a clutch plate forming the pilot clutch mechanism. SOLUTION: A cam mechanism 10e is formed by a first cam member 19 connected to an inner shaft 10b integrally rotatably and axially movably, a ball 18 integrally rotatably held by an inner clutch plate 14a of a pilot clutch mechanism 10d, and a second cam member 17 holding the ball 18 with the frist cam member 19, and the ball 18 is rotatably fitted in a retainer 16 axially movably mounted on the inner clutch plate 14a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving force transmitting device disposed between rotating members that can rotate relative to each other and transmitting torque between these rotating members.

[0002]

2. Description of the Related Art As one type of a driving force transmitting device, as disclosed in Japanese Patent Application Laid-Open No. 3-282019, friction is provided between inner and outer rotating members located coaxially and relatively rotatable relative to each other. A main clutch mechanism that transmits torque between the two rotating members by engagement, an electromagnetic pilot clutch mechanism that operates by energization and frictionally engages, and a pilot clutch that is located between the main clutch mechanism and the pilot clutch mechanism. There is a driving force transmission device including a cam mechanism that converts a frictional engagement force of a clutch mechanism into a pressing force on the main clutch mechanism.

In the driving force transmission device, a magnetic path is formed by energizing an electromagnetic coil of an electromagnet constituting a pilot clutch mechanism, and the pilot clutch mechanism operates by a magnetic induction action to operate the main clutch mechanism. , So that torque is transmitted between the two rotating members.

[0004]

In the driving force transmitting device disclosed in the above publication, the inner plate of the pilot clutch is spline-engaged with the cam mechanism so as to be movable in the axial direction. Or, when separated, friction occurs in the direction opposite to the direction of movement of the pilot clutch in the spline engagement portion, and this frictional force causes hysteresis in the transmission torque characteristic and deteriorates the responsiveness of the driving force transmission device. Had become.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to address the above problems. An invention according to claim 1 of the present invention is a main clutch mechanism that is disposed between inner and outer rotating members coaxially and relatively rotatably positioned and transmits torque between these rotating members by frictional engagement, An electromagnetic pilot clutch mechanism that operates and frictionally engages by energization, and a cam that is located between the main clutch mechanism and the pilot clutch mechanism and converts a frictional engagement force of the pilot clutch mechanism into a pressing force on the main clutch mechanism; In the driving force transmission device provided with a mechanism, the cam mechanism includes a first cam member integrally rotatably coupled to one of the rotating members and movably in an axial direction, and a clutch plate of the pilot clutch mechanism. A ball held so as to be integrally rotatable, and a second cam member for holding the ball together with the first cam member. And it is characterized in Rukoto.

According to a second aspect of the present invention, in the driving force transmission device according to the first aspect, the ball is provided in a retainer provided on a clutch plate of the pilot clutch mechanism so as to be movable in an axial direction. And is fitted so as to be rollable.

[0007]

In the driving force transmitting device according to the first aspect of the present invention, when the pilot clutch mechanism frictionally engages, the cam mechanism operates and the ball rolls due to the increase or decrease in the frictional engagement force. Since the frictional force caused by the rolling of the ball acts in the moving direction of the clutch plate constituting the pilot clutch mechanism, the responsiveness of the driving force transmission device is improved and the hysteresis of the transmission torque characteristic is reduced.

Further, in the driving force transmission device according to claim 2 of the present invention, the retainer can be moved by the frictional force between the ball and the retainer. For this reason, the movement of the clutch plate constituting the pilot clutch mechanism is performed smoothly, and the above-described operation and effect become more remarkable.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment according to the present invention will be described below with reference to the drawings. The driving force transmission device 10
As shown in FIG. 1, is disposed in a driving force transmission path to a rear wheel side in an FF (front engine / front drive) -based four-wheel drive vehicle.

In the four-wheel drive vehicle, the transaxle 21 has a transmission and a transfer integrally, and outputs the driving force of the engine 22 to both axle shafts 24a via the front differential 23 to drive the front wheels 24b. And output to the first propeller shaft 25. First propeller shaft 25
Are connected to the second propeller shaft 26 via the driving force transmission device 10, and these two propeller shafts 25,
When the motor 26 is connected so as to be capable of transmitting torque, the driving force is transmitted to the rear differential 27 and is output from the differential 27 to both axle shafts 28a to drive both rear wheels 28b.

As shown in FIG. 2, the driving force transmitting device 10 includes an outer housing 10 which is an outer rotating member.
a, an inner shaft 10b serving as an inner rotating member, a main clutch mechanism 10c, a pilot clutch mechanism 10d,
And a cam mechanism 10e.

The outer housing 10a comprises a bottomed cylindrical case 11a, and a cover 11b screwed into the opening of the case 11a to cover the opening in a liquid-tight manner. The case 11a is formed of a non-magnetic material such as an aluminum alloy. The cover body 11b is made of a magnetic part 11b1, 1 made of a magnetic material such as an iron-based material.
1b3 and a non-magnetic portion 11b2 formed of a non-magnetic material such as a cylindrical stainless steel at a radially intermediate portion between the two magnetic portions 11b1 and 11b3 are integrally formed. A rear end of the first propeller shaft 25 is connected to a front end of the case portion 11a so as to transmit torque.

The inner shaft 10 b includes a cover body 11.
b through the center of the outer housing 10a in a liquid-tight manner.
And is rotatably supported by the case 11a and the cover 11b in a state where the movement in the axial direction is restricted. The distal end of the second propeller shaft 26 is inserted into the inner shaft 10b, and is connected to transmit torque.

The main clutch mechanism 10c is a wet-type, multi-plate type friction clutch and includes a number of clutch plates (an inner clutch plate 12a, an outer clutch plate 1).
2b), and is disposed on the back wall side of the case portion 11a. Each of the inner clutch plates 12a constituting the friction clutch is spline-fitted to the outer periphery of the inner shaft 10b and assembled so as to be movable in the axial direction, and each of the outer clutch plates 12b is connected to the outer housing 1
The outer case 0a is spline-fitted to the inner periphery of the case portion 11a and is movably mounted in the axial direction. The inner clutch plates 12a and the outer clutch plates 12b are alternately positioned, abut against each other and frictionally engage with each other,
They are separated from each other and become free.

The pilot clutch mechanism 10d includes an electromagnet 13, a friction clutch 14, and an armature 15. The electromagnet 13 has a ring shape, and includes an electromagnetic coil 13a and a yoke 13 that supports the electromagnetic coil 13a.
b. The electromagnet 13 is attached to the cover 11.
In the annular recessed part 11b4 of b, a small clearance is set between the annular recessed part 11b4 and the cover body 11b, and it is rotatably mounted.

The friction clutch 14 includes a plurality of clutch plates (an inner clutch plate 14a and an outer clutch plate 14b). As shown in FIG. 3, each inner clutch plate 14a has a circular hole 14 at its inner peripheral edge.
a1 are provided at equal angular intervals, and a cylindrical retainer 16 is mounted in each of the round holes 14a1 so as to be movable in the axial direction. Further, each outer clutch plate 14b is connected to the case 11a of the outer housing 10a.
Are spline-fitted to the inner periphery of the shaft so as to be movable in the axial direction. Each of the inner clutch plates 14a and each of the outer clutch plates 14b are alternately positioned, abut against each other and frictionally engage with each other, and are separated from each other to be in a free state.

In each of the inner clutch plates 14a and the outer clutch plates 14b, a plurality of circumferentially extending elongated holes are formed at predetermined circumferential intervals to prevent short-circuiting of magnetic flux. These long holes are located at positions that can face the front end surface of the nonmagnetic portion 11b2 of the cover body 11b.

The armature 15 has an annular shape, and is spline-fitted to the inner periphery of the case portion 11a of the outer housing 10a so as to be movable in the axial direction. The armature 15 is attached to the cover body 11b with the friction clutch 14 interposed therebetween. It is located opposite.

As shown in FIGS. 2, 3 and 5, the cam mechanism 10e includes a piston 19 as a first cam member,
It is composed of a thrust plate 17 as a cam member and a ball 18. The ball 18 is rotatably fitted in a retainer 16 provided in the round hole 14a1 of the inner clutch plate 14a so as to be movable in the axial direction, and is held between both cam members (piston 19 and thrust plate 17). Have been. An annular ball groove 17a is formed on the end surface of the thrust plate 17, a cam groove 19a is formed on the end surface of the thrust plate 17 at equal angular intervals, and the ball 18 is sandwiched between the two grooves 17a, 19a. ing.

Here, the thrust plate 17 is rotatably supported by a thrust bearing 20 interposed between the thrust plate 17 and the cover body 11b while being restricted in the axial direction.
Further, the piston 19 is spline-fitted to the outer periphery of the inner shaft 10b and is integrally rotatable, and is attached so as to be able to press the main clutch mechanism 10c. In addition,
After the cam mechanism 10e is assembled, the two cam members 19, 17
The axial dimension of the retainer 16 is set smaller than the axial clearance between the cam members 19 and 17 so that the retainer 16 can move in the axial direction between the two.

The energization of the electromagnetic coil 13a of the electromagnet 13 takes in signals such as accelerator opening, vehicle speed, differential speed, and steering angle, and controls the current value according to the running state of the vehicle. Further, the driver may be able to switch to each of the driving modes described below by operating a switch. In this case, the switch is disposed near the driver's seat in the passenger compartment.

In the driving force transmission device 10 having such a configuration, the electromagnet 1 constituting the pilot clutch mechanism 10d is used.
When no current is supplied to the third electromagnetic coil 13a, no magnetic path is formed, and the friction clutch 14 is in a non-engaged state. Therefore, the pilot clutch mechanism 10d is in a non-operating state, the retainer 16 constituting the cam mechanism 10e can rotate integrally with the piston 19 via the ball 18, and the main clutch mechanism 10c is in the non-operating state. is there. Thus, the vehicle constitutes a two-wheel drive mode.

On the other hand, when the electromagnetic coil 13a of the electromagnet 13 is energized, a magnetic path is formed in the pilot clutch mechanism 10d, and the electromagnet 13 attracts the armature 15.
For this reason, the armature 15 presses the friction clutch 14 to frictionally engage, and a pilot torque is generated in the pilot clutch mechanism 10d. As a result, relative rotation occurs between the retainer 16 and the ball 18 and the piston 19, and the cam mechanism 10e operates.

Here, based on FIGS. 6, 7 and 8,
The operation of the cam mechanism 10e will be described. In these figures, retainer 16, ball 18 and piston 1 are shown.
9 schematically shows a slope of a cam groove 19a formed in FIG.

FIG. 6 shows a state where the ball 18 is stationary without rolling on the slope of the cam groove 19a. At this time, the force a generated by the pilot torque acts on the slope of the cam groove 19a via the retainer 16 and the ball 18 on the lower side in the figure. This force a generates a force b that pushes the slope of the cam groove 19a by the ball 18 in the normal direction. The axial component of this force b acts as a cam thrust c,
This cam thrust c and the reaction force P due to the rigidity of the clutch plates 12a and 12b of the main clutch mechanism 10d are balanced. That is, when P = c = a / tan θ, the ball 18 is stationary with respect to the cam groove 19a.

FIG. 7 shows the state of the electromagnetic coil 13a from the state of FIG.
This shows a state in which the pilot torque is increased by increasing the amount of power to the motor. At this time, the ball 18 is
Rolling on the slope a, the piston 19 presses the main clutch mechanism 10c. As the amount of current increases, FIG.
As shown in (a), the force a ′ (= a + Δa) generated by the pilot torque increases, whereby the ball 1
8, the force b 'pushing the slope of the cam groove 19a and the cam thrust c' increase. Then, as shown in FIG.
The clutch plate 12a of the main clutch mechanism 10d,
An imbalance occurs between the reaction force P and the cam thrust c ′ due to the rigidity of 12b, and the ball 18 rolls to a position where they become equal. Here, P = a / tan θ ′ = (a′−Δa) / tan θ ′ c ′ = a ′ / tan θ ′ Therefore, the imbalance amount of the axial force is c′−P = Δa / tan θ ′ Becomes The component force in the slope direction of the cam groove 19a of c'-P generates a moment T for rolling the ball 18, and the ball 1
By the rolling of 8, a frictional force F is generated between the ball 18 and the retainer 16. This friction force F is directed rightward in the drawing,
That is, it acts in a direction to engage the pilot clutch mechanism 10d.

FIG. 8 shows the state of the electromagnetic coil 13a from the state of FIG.
This shows a state in which the amount of power to the motor is reduced and the pilot torque is reduced. At this time, as shown in FIG. 8A, the force a ″ (= a−Δa) generated by the pilot torque acting downward in the figure decreases with the decrease in the amount of energization, whereby the ball 18 The force b ″ pushing the slope of the groove 19a and the cam thrust c ″ decrease. Then, as shown in FIG.
The reaction force P due to the rigidity of the a and 12b overcomes the cam thrust c "to roll the ball 18, and a friction force F is generated between the ball 18 and the retainer 16 to the left (in the direction separating the pilot clutch) in the figure.

As a result, the main clutch mechanism 10c frictionally engages in accordance with the frictional engagement force of the friction clutch 14 to transmit torque between the outer housing 10a and the inner shaft 10b. For this reason, the vehicle constitutes a four-wheel drive drive mode in which torque can be transmitted between the uncoupled state and the directly coupled state between the two propeller shafts 25 and 26 according to the value of the current applied to the electromagnetic coil 13a of the electromagnet 13. I do.

When the current applied to the electromagnetic coil 13a of the electromagnet 13 is increased to a predetermined value, the armature 15 is strongly attracted and the frictional engagement force of the friction clutch 14 is increased.
Increase the relative rotation between retainer 16 and piston 19. As a result, the ball 18 increases the pressing force on the piston 19 to bring the main clutch mechanism 10c into the connected state. For this reason, the vehicle has two propeller shafts 25, 26.
Constitute a drive mode of four-wheel drive directly connected.

Thus, in the driving force transmitting device 10, as shown in FIGS.
And the frictional force F between the retainers 16 acts in the moving direction of the pilot clutch mechanism 10d, so that the responsiveness of the transmission torque characteristic of the driving force transmission device 10 is improved and the hysteresis thereof is reduced.

Next, a second embodiment according to the present invention will be described with reference to the drawings. As shown in FIG. 1, the driving force transmission device 10 is disposed in a driving force transmission path to the rear wheel side of the four-wheel drive vehicle (the first propeller shaft 25 and the second propeller shaft 26).

As shown in FIG. 9, the driving force transmitting device 10 includes an outer housing 10 which is an outer rotating member.
a, an inner shaft 10b as an inner rotating member, a main clutch mechanism 10c as a friction clutch, and a pressing force generating means 10f for pressing the main clutch mechanism 10c.
, And transmits a torque corresponding to the differential rotation speed, and further includes a pilot clutch mechanism 10d and a cam mechanism 10e as lock means 10g.

The outer housing 10a comprises a cylindrical outer case 11a having a bottom, and a cover 11b which is screwed into one end opening of the outer case 11a to cover the opening. The inner shaft 10b has a cover. The body 11b extends through the center of the body 11b in a liquid-tight manner and extends into the outer case 11a. The body 11b is rotatably supported with its movement in the axial direction restricted. A first propeller shaft 25 is connected to a distal end portion of the outer case 11a of the outer housing 10a so as to be able to transmit torque, and the inner shaft 10b
Has a second propeller shaft 26 inserted into its bore.
Are connected so that torque can be transmitted.

The main clutch mechanism 10c is a wet type multi-plate friction clutch having a large number of clutch disks 12a and clutch plates 12b.
a is spline-fitted to the outer peripheral side of the inner shaft 10b and is mounted so as to be movable in the axial direction, and each clutch plate 12b is spline-fitted to the inner peripheral side of the outer case 11a and is assembled so as to be movable in the axial direction. It is attached. The clutch discs 12a and the clutch plates 12b are alternately positioned, abut against each other and frictionally engage with each other, and are separated from each other to be in a free state.

The pressing force generating means 10f includes a piston 10f
1, a high viscosity fluid sealed in a rotor 10f2 and a fluid chamber R, wherein a piston 10f1 is rotatable in a liquid-tight manner around the inner shaft 10b in an outer housing 10a and is movable in an axial direction. It is attached to the outer case 11a so as to be axially movable in a liquid-tight manner and to be integrally rotatable. Piston 1
0f1 forms a recess provided in the inner surface of the inner wall of the outer case 11a in the fluid chamber R in this state.

The rotor 10f2 has a plurality of protrusions extending in the radial direction, and is accommodated in the fluid chamber R while being fixed to the outer periphery of the inner shaft 10b.

The locking means 10g comprises a pilot clutch mechanism 10d, a cam mechanism 10e, and a piston 19. Here, the lock means 10g will be described focusing on the differences from the first embodiment. The electromagnetic coil 13a of the electromagnet 13 that constitutes the pilot clutch mechanism 10d is an on-of-off disposed near the driver's seat.
Normally (off), the current is cut off, and a predetermined current required for bringing the main clutch mechanism 10c into a completely connected locked state flows by a switch operation (on). I have.

Thus, the pilot clutch mechanism 10
In (d), when the electromagnetic coil 13a of the electromagnet 13 is energized, a magnetic field is generated between the yoke 13b, the friction clutch 14, and the armature 15, and the armature 15
And the friction clutch 14 is driven by the magnet 1
The piston 19 is pressed to the main clutch mechanism 10c by the action of the cam mechanism 10e, and the main clutch mechanism 10c is locked. The cam mechanism 10e is similar to that of the first embodiment, and is shown in FIGS.

In the driving force transmission device 10 having such a configuration, the electromagnet 1 constituting the pilot clutch mechanism 10d is used.
When the third electromagnetic coil 13a is in a non-energized state, the friction clutch 14 and the armature 15 are in a free state, and the retainer 16 of the cam mechanism 10e is in a state of being able to rotate integrally with the inner shaft 10b via the ball 18. Yes,
The functions of the friction clutch 14 and the cam mechanism 10e are restricted.

Therefore, in a vehicle equipped with the driving force transmission device 10, differential rotation occurs between the two propeller shafts 25, 26, and as a result, the outer housing 10
When the relative rotation occurs between the inner shaft 10a and the inner shaft 10b, the rotor 10f2 constituting the pressing force generating means 10f
Rotates relative to the outer housing 10a in the fluid chamber R, and the two propeller shafts 25, 26
A pressing force is generated according to the differential rotation speed between the two. This pressing force presses the piston 10f1 and the main clutch mechanism 1
0c, the main clutch mechanism 10c frictionally engages according to the differential rotation speed.

For this reason, the first propeller shaft 25 is
Outer housing 10a, main clutch mechanism 10c,
The second propeller shaft 2 via the inner shaft 10b
6, a torque corresponding to the differential rotation speed is transmitted from the first propeller shaft 25 to the second propeller shaft 26.

On the other hand, in the driving force transmission device 10, the electromagnet 1 constituting the pilot clutch mechanism 10d is used.
When the third electromagnetic coil 13a is energized, a magnetic field is generated between the yoke 13b, the friction clutch 14, and the armature 15, and the armature 15 and the friction clutch 14 are attracted to the electromagnet 13 by a magnetic induction action. As a result, the friction clutch 14 frictionally engages and connects the nut member 16 to the outer case 11a side, and the retainer 16 and the piston 19
Are in a state in which they can be relatively rotated. Thereby, the cam mechanism 10e functions effectively.

Therefore, in a vehicle equipped with the driving force transmission device 10, differential rotation occurs between the two propeller shafts 25, 26, and as a result, the outer housing 10
When a relative rotation occurs between a and the inner shaft 10b, a pressing force is generated by the pressing force generating means 10f. At this time, when the electromagnetic coil 13a of the electromagnet 13 is energized, a pressing force is also generated in the locking means 10g.

That is, in the locking means 10g,
When relative rotation occurs between the outer housing 10a and the inner shaft 10b, relative rotation occurs between the retainer 16 and the piston 19 due to the frictional engagement force of the friction clutch 14 to operate the cam mechanism 10e, thereby moving the piston 19 to the main clutch mechanism 10c. Press to the side. As a result, the main clutch mechanism 10c applies the pressing force generated by the pressing force generating means 10f to the locking means 1 located on the opposite side.
Due to the pressing force generated at 0 g, the locking state is obtained by being strongly pressed from both sides and firmly frictionally engaged to be completely connected.

Therefore, in the driving force transmission device 10, the electromagnet 1 constituting the pilot clutch mechanism 10d is used.
By turning on the electromagnetic coil 13a of the third propeller shaft 3, the locking means 10g is made effective, and both propeller shafts 25 and 26 are turned on.
If the differential rotation occurs during this time, the main clutch mechanism 10c is instantaneously locked to configure the vehicle in a complete four-wheel drive state, and the vehicle escapes from the wheel-off state, travels on a rough road, travels on sand. It is possible to improve the running performance under severe running conditions such as the above. Therefore, when a severe condition is encountered, the vehicle can be easily switched to a traveling performance suitable for the severe traveling condition. Further, in the driving force transmission device 10, the on-off switch is operated to switch from a four-wheel drive state in which torque is transmitted according to the differential rotational speed between the front and rear wheels to a complete four-wheel drive state. Since it is configured, an expensive control device is not required.

Next, a third embodiment according to the present invention will be described with reference to the drawings. As shown in FIGS. 10 and 11, the third embodiment differs from the first and second embodiments only in the cam mechanism 10e and the peripheral portion thereof. Will be described, and description of other components will be omitted.

In the third embodiment, the retainer 16 is formed in a disk shape, and its outer periphery is spline-connected to the inner periphery of each inner clutch plate 14a of the friction clutch 14. A plurality of round holes 16a are formed in the retainer 16 at equal angular intervals and in the axial direction, and a ball 18 is rollably fitted in each round hole 16a. The inner periphery of the retainer 16 is rotatable with respect to the inner shaft 10b.

Each ball 18 has a piston 19 as a first cam member and a thrust plate 1 as a second cam member.
7. In the first and second embodiments, the cam groove 19a is formed only in the first cam member (piston 19), but here, the cam grooves 19a, 17a are formed in both cam members (piston 19 and thrust plate 17). The ball 18 is formed between the cam grooves 19a and 17a. After the cam mechanism 10e is assembled, the axial dimension of the retainer 16 is larger than the axial clearance between the cam members 19 and 17 so that the retainer 16 can move in the axial direction between the cam members 19 and 17. It is set small. The operation of the cam mechanism 10e is the same as that of the first and second embodiments, and the description is omitted here.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a vehicle equipped with a driving force transmission device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the driving force transmission device.

FIG. 3 is a front view of an inner clutch plate, a retainer, and a ball constituting a pilot clutch mechanism of the driving force transmission device.

FIG. 4 is a partially enlarged cross-sectional view of the driving force transmission device.

FIG. 5 is a sectional view of the driving force transmission device taken along line AA of FIG. 4;

FIG. 6 is an operation diagram of a cam mechanism in the driving force transmission device.

FIG. 7 is an operation diagram of a cam mechanism in the driving force transmission device.

FIG. 8 is an operation diagram of a cam mechanism in the driving force transmission device.

FIG. 9 is a cross-sectional view of a driving force transmission device according to a second embodiment of the present invention.

FIG. 10 is a partially enlarged cross-sectional view of a driving force transmission device according to a third embodiment of the present invention.

FIG. 11 is a front view of a retainer of the driving force transmission device.

[Explanation of symbols]

Reference numeral 10: driving force transmission device, 10a: outer housing, 1
0b: inner shaft, 10c: main clutch mechanism,
10d: pilot clutch mechanism, 10e: cam mechanism,
10f ... pressing force generating means, 10f1 ... piston, 10f
2 ... rotor, R ... fluid chamber, 10g ... locking means, 11a
... Case part, 11b ... Cover body, 12a ... Inner clutch plate, 12b ... Outer clutch plate, 13 ...
Electromagnet, 13a: electromagnetic coil, 14: friction clutch, 1
4a: inner clutch plate, 14b: outer clutch plate, 14a1: round hole, 15: armature, 16
... Retainer, 16a ... Round hole, 17 ... Thrust plate (second cam member), 17a ... Cam groove, 18 ... Ball, 1
9: piston (first cam member), 19a: cam groove, 20
... Thrust bearing, 21 ... Transaxle, 22
... Engine, 23 ... Front differential, 24a
.. Axle shaft, 24b front wheel, 25 first propeller shaft, 26 second propeller shaft, 27 rear differential, 28b rear wheel.

Claims (2)

[Claims] A main clutch mechanism disposed between inner and outer rotating members coaxially and relatively rotatable to each other to transmit torque between these rotating members by frictional engagement;
An electromagnetic pilot clutch mechanism that operates and frictionally engages by energization, and a cam that is located between the main clutch mechanism and the pilot clutch mechanism and converts a frictional engagement force of the pilot clutch mechanism into a pressing force on the main clutch mechanism; And a driving force transmission device having a mechanism.
A first cam member coupled integrally to one of the rotating members and movably in an axial direction;
A driving force transmission device comprising: a ball held rotatably integrally with a clutch plate of the pilot clutch mechanism; and a second cam member that holds the ball together with the first cam member. 2. The driving force transmission device according to claim 1, wherein the ball is rotatably fitted in a retainer provided on a clutch plate of the pilot clutch mechanism so as to be movable in an axial direction. A driving force transmission device characterized by the above-mentioned.