JPH11230304A - Piston pump and device using the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To obtain a torque limiter function at low cost with a simple structure. SOLUTION: A return spring which pushes the piston 75 back to the cam 77 and a cam 77 provided on the torque transmission member 39 and having a convex portion 89 and a concave portion 91 are provided on the torque transmitting member 39. 79
A friction clutch 43 disposed between the torque transmitting members 37 and 39; and an actuator 41 for pressing the friction clutch 43 by the hydraulic pressure of the cylinder 73. The hydraulic pressure of the cylinder 73 is guided to the top 105 of the piston 75. A bypass 103 was provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piston pump, and a power transmission device and a differential device using the same.

[0002]

2. Description of the Related Art FIG.
Such a coupling 201 is described.

[0003] The coupling 201 is connected to an output shaft 203 on the rear wheel side and is rotated by the driving force of the engine. An input shaft 205 and a rotating case 2 connected to the input shaft 205 are provided.
07, an output shaft 209 on the front wheel side, which is disposed inside thereof so as to be relatively rotatable, and a sprocket 2 connected to the output shaft 209.
11, a chain 213, a rotating case 207 and an output shaft 20
9 comprises a multi-plate clutch 215, an oil pump 217, a hydraulic actuator 219, a relief valve 221 and the like.

When the driving torque of the engine increases and a relative rotation occurs between the rear wheel-side rotating case 207 and the front wheel-side output shaft 209, the oil pump 217 is operated by the relative rotation, and the hydraulic actuator is actuated. The hydraulic pressure is sent to the motor 219 to fasten the multi-plate clutch 215 and the output shaft 209.
The driving force is transmitted to the front wheels via the sprocket 211 and the chain 213. The relief valve 221 is shown in FIG.
, A valve sheet 227 provided in a connection hole 225 between the pressure chamber 223 of the hydraulic actuator 219 and the outside.
And a ball 229 for closing the valve sheet 227.
And a coil spring 231 for pressing the ball 229 against the valve sheet 227. The coil spring 231 is opened by receiving the pressure of the pressure chamber 223, and protects the pressure chamber 223 from excessive pressure and has a torque limiter function. As a result, the drive torque exceeding the allowable value is not transmitted to the front wheels.

[0005]

However, as described above, the relief valve 221 requires processing of the connection hole 225 and the valve sheet 227.
No. 27 requires a high processing accuracy and therefore has a high processing cost. In addition, the use of the ball 229 and the coil spring 231 increases the number of parts and increases the cost.

Further, since the centrifugal force applied to the ball 229 acts in the opposite direction to the urging force of the coil spring 231, the input shaft 20
5 (rotation case 207) is greatly influenced by the rotation speed (vehicle speed), and there is a possibility that the above-mentioned torque limiter function, which is desired to be operated at the relative rotation speed between the front and rear wheels, does not work properly.

Accordingly, the present invention provides a piston pump whose torque limiter function can be obtained at a low cost with a simple structure and whose torque limiter function is not affected by centrifugal force, and a power transmission device using this piston pump. And a differential device.

[0008]

According to a first aspect of the present invention, a piston pump includes a pair of torque transmitting members arranged rotatably relative to each other, a cylinder and a piston disposed on one torque transmitting member side, and the other torque transmitting member. A cam provided on the member side and having a convex portion and a concave portion, a return spring for pushing the top of the piston back to the cam, and a piston pump provided on the cylinder and having an inlet and an outlet for oil accompanying the movement of the piston. And a bypass path for guiding the pressure on the discharge port side to the top of the piston is provided.

When a torque is input to one of the torque transmitting members, a differential rotation occurs due to the driving resistance of the other torque transmitting member, and each piston is pushed into the cylinder by the convex portion of the cam and then returned to the cam by a return spring. And is reciprocated.

When the piston pump is driven in this manner,
While allowing relative rotation (differential rotation) between the torque transmitting members by the rotation of the piston pump, torque is transmitted between the two torque transmitting members by the driving resistance (differential limiting force).

Since the driving resistance of the piston pump increases as the differential rotation speed increases, the torque transmission characteristic and the differential limiting characteristic are of a speed-sensitive type.

The piston pump of the present invention is provided with a bypass so as to guide the discharge pressure of the piston pump to the top of the piston on the cam side. Therefore, the piston is determined by the product of the discharge pressure and the pressure receiving area. A reaction force is applied, and this reaction force acts in a direction opposite to the urging force of the return spring.

Accordingly, when the discharge pressure rises as the relative rotation speed of each torque transmitting member increases, and this reaction force exceeds the urging force of the return spring, the return spring remains bent. Then, the piston stops moving, jumps over the convex portion of the cam surface, and the piston and the cam idle.

In this way, a limiter function for maintaining the discharge pressure of the piston pump at a constant value when the relative rotation speed of the torque transmitting member exceeds a predetermined value is obtained.

Further, the cylinder of the piston pump is protected from excessive pressure by the limiter function.

This limiter function, which can be obtained by merely providing a bypass passage, is different from the conventional relief valve 221 in that the valve sheet 227 requiring high processing accuracy is not required, and the processing cost is low. Since the ball 229 and the coil spring 231 are not required, the number of parts is not increased and the cost can be reduced accordingly.

Further, since oil is used as the working fluid of the piston pump, a large discharge pressure and a large torque transmission function (differential limiting function) can be obtained at a small relative rotation speed as compared with a configuration using air, for example.

According to a second aspect of the present invention, there is provided the piston pump according to the first aspect, wherein the piston is disposed so as to move in the axial direction, and an effect equivalent to that of the first aspect is obtained.

In addition to this, since the piston is arranged to move in the axial direction, the limiter function of the piston pump is released from the influence of the centrifugal force and operates only by the relative rotation speed unlike the conventional example.

According to a third aspect of the present invention, there is provided a power transmission device which operates by receiving pressure from a piston pump, a friction clutch disposed between respective torque transmitting members thereof, and the piston pump. An actuator, and a pressing member that presses the friction clutch by the pressing force of the actuator. The differential between the two torque transmitting members is limited by the driving resistance of the piston pump and the friction resistance of the friction clutch. It is characterized in that torque is transmitted between transmission members.

In this power transmission device, the piston pump and the friction clutch according to the first or second aspect are provided between the torque transmission members, and the friction clutch is engaged by applying an operating pressure from the piston pump to the actuator. As a result, the frictional resistance of the friction clutch is added to the driving resistance of the piston pump, and the torque transmission function (differential limiting function) is greatly enhanced.

For example, in a four-wheel drive vehicle in which a driving force is transmitted to one of a front wheel and a rear wheel via this power transmission device, and the other wheel is constantly driven by an engine, the vehicle is driven by the engine while traveling on a rough road or the like. When the wheel of the vehicle rotates idle and differential rotation occurs between the front and rear wheels, the driving force is transmitted to the wheel on the grip side by this power transmission device, and the escape property and the running performance are improved.

When the differential rotation speed between the front and rear wheels exceeds a predetermined value, the increase in the transmission torque of the power transmission device is stopped by the torque limiter function of the piston pump, and excessive torque is applied to the wheels on the power transmission device side. Is prevented from being applied.

Therefore, in such a four-wheel drive vehicle, the propeller shaft and the drive shaft on the power transmission device side can be made thinner to some extent to reduce the weight.

Further, since oil is used as the working fluid of the piston pump, the operation response of the power transmission device accompanying the occurrence of the differential rotation is fast, so that the maneuverability and running performance of the vehicle are improved.
The effect of improving stability and the like is great.

Further, in the configuration in which the piston of the piston pump is moved in the axial direction, a predetermined torque limiter function which operates only by the relative rotation speed between the torque members is obtained, being free from the influence of the engine rotation speed (vehicle speed).

According to a fourth aspect of the present invention, there is provided the power transmission device according to the third aspect, wherein the friction clutch is a multi-plate clutch, and the same effects as those of the third aspect are obtained.

In addition to the above, the multi-plate clutch is compact and has a large torque capacity, and the torque capacity and the torque transmission function (differential limiting function) of the power transmission device are adjusted by changing the number of clutch plates. can do.

The invention of claim 5 is the invention of claim 3 or claim 4.
In the power transmission device described above, the cam of the piston pump is formed on the pressing member, and an effect equivalent to the configuration of the third or fourth aspect is obtained.

In addition, by forming the cam of the piston pump on the pressing member, a dedicated cam member is not required, and the number of parts and cost are reduced accordingly.

In this configuration in which a cam is formed on a pressing member having a small mass, unlike the configuration in which a cam is provided on a casing member having a large mass, the cam is simultaneously processed when the pressing member is forged. In addition to this, the processing cost is greatly reduced, and the heat treatment of the cam is greatly reduced because the pressing member having a small mass is easily heat-treated.

Further, the casing without the cam can be easily processed and heat-treated. For example, the cost can be reduced by casting.

The invention of claim 6 is the invention of claims 3 to 5
The power transmission device according to any one of claims 1 to 3, wherein an orifice is provided in a pressing member of the actuator, and oil passed through the orifice is supplied to a friction clutch, and then the piston pump is returned via a return oil passage. The oil is circulated by being guided to the suction port of (1), and the same effect as the configuration of claims 3 to 5 is obtained.

In addition, since the pressurized oil supplied to the actuator circulates through the power transmission device, the sliding portion between the piston top and the cam of the piston pump and the friction clutch are used. Sufficient lubrication, seizure is prevented, and durability is greatly improved.

Further, since the friction clutch is stabilized by sufficient lubrication, the torque transmission function (differential limiting function) of the power transmission device is stabilized.

Further, by circulating the oil, the temperature of the oil partially raised by the friction clutch, the piston pump or the like is averaged, and the above-mentioned function of the power transmission device is further stabilized.

Further, for example, in any of the oil circulation paths,
If a centrifugal filter is formed or a magnet filter that adsorbs metal abrasion powder is disposed, abrasion powder from a friction clutch, a piston pump, or the like is effectively removed, and the oil is kept clean. This prevents abnormal wear of the piston pump, especially the sliding part between the piston and the cam, and malfunctions of the suction valve and discharge valve due to the abrasion powder. improves.

A differential device according to a seventh aspect of the present invention includes a differential case that is rotationally driven by the driving force of the engine, a differential mechanism that distributes the rotation of the differential case to the wheels, and a differential rotating member of the differential mechanism. A power transmission device according to any one of claims 3 to 6, which is disposed between a pair of torque transmission members, wherein a differential force is generated by driving resistance of a piston pump and friction resistance of a friction clutch. Is limited.

In this differential device, when the power transmission device according to any one of claims 3 to 6 is provided between a pair of torque transmission members that are differential rotation members of a differential mechanism, when differential rotation occurs, The friction clutch is fastened by the piston pump, and the differential of the differential mechanism is limited by the differential limiting force due to the driving resistance of the piston pump and the friction resistance of the friction clutch.

Further, even if the differential speed exceeds a predetermined value, the cylinder of the piston pump is protected from excessive pressure by the above-mentioned limiter function.

In addition, since oil is used as the working fluid of the piston pump, the response to the generation of the differential limiting force due to the generation of the differential rotation is fast, so that the controllability, running performance and stability of the vehicle are improved. Is big.

In the configuration in which the piston of the piston pump is moved in the axial direction, the effect of the engine speed (vehicle speed) is released, and a differential limiting function and a limiter function that operate only by the differential speed can be obtained.

[0043]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. Coupling 1 of this embodiment
The (power transmission device) is configured by using a piston pump 3, and the coupling 1 has the features of claims 3, 4, and 6, and the piston pump 3 has the features of claims 1 and 2. FIG. 1 shows the coupling 1, and the left side thereof corresponds to the front of the four-wheel drive vehicle of FIG. 5 using the coupling 1.

In this four-wheel drive vehicle, the driving force of the engine 5 is transmitted from the transmission 7 to the transfer 9 and is distributed from the transfer 9 to the front wheel side and the rear wheel side.

The driving force on the rear wheel side is transmitted to the rear differential 13 via the propeller shaft 11, and the driving force on the front wheel side is transmitted to the front differential 19 via the propeller shaft 15, the coupling 1 and the transmission shaft 17. .

The rear differential 13 distributes the transmitted driving force to the left and right rear wheels 25 and 27 via the rear axles 21 and 23.
Further, the coupling 1 includes rear wheels 25 and 27 as described later.
When the sides are idling, they are connected and transmit the driving force to the front differential 19 via the transmission shaft 17, and the front differential 19 transmits the transmitted driving force via the front axles 29 and 31 to the left and right front wheels 3.
Distribute to 3, 35.

As shown in FIG. 1, the coupling 1 comprises a piston pump 3, input side and output side torque transmitting members 37,
39, a hydraulic actuator 41 (actuator), a multi-plate clutch 43 (friction clutch) and the like.

A flange 45 is spline-connected to the input side torque transmitting member 37, and a screw hole 47 is provided in the flange 45 for connecting to the transmission shaft 17 side with a bolt.

The output side torque transmitting member 39 has a cover-4.
9 is fixed with a bolt 51, and a screw hole 5 for connecting the cover 49 to the propeller shaft 15 side with a bolt is provided.
3 are provided. Also, the torque transmitting member 39 and the cover
An O-ring 55 is disposed between the O-ring and the O-ring 49 to prevent oil leakage.

The torque transmitting member 37 includes a torque transmitting member 39.
Has penetrated into. The front end of the torque transmitting member 37 is supported by a torque transmitting member 39 via a bearing 57, and a seal 59 for preventing oil leakage is arranged between them. The rear end of the torque transmitting member 37 is covered with a cover 49 of the torque transmitting member 39 via a bearing 61.
It is supported by

Oil is sealed inside the torque transmitting members 37 and 39 and the cover 49.

As shown in FIG. 1, the hydraulic actuator 4
1 includes a pressing member 63 of the multi-plate clutch 43 and a hydraulic chamber 65 formed between the torque transmitting members 37 and 39 and the pressing member 63.
Between them, seals 67 and 69 for preventing oil leakage are arranged.

The multi-plate clutch 43 is disposed behind the pressing member 63 and between the torque transmitting members 37 and 39.
The pressing member 63 is provided with an orifice 71 that communicates the hydraulic chamber 65 with the multi-plate clutch 43 side.

The piston pump 3 includes a torque transmitting member 37
A plurality of cylinders 73 provided at equal intervals in the circumferential direction,
A piston 75 disposed in each cylinder 73 and a cam 77
A return spring 79, a suction port 81, a discharge port 83, and a one-way valve 85 provided in the discharge port 83.
And so on.

Each cylinder 73 is provided in the axial direction, and the piston 75 reciprocates in the axial direction. Each cylinder 73 communicates with a return oil passage 87 provided at the center of the torque transmitting member 37 via an inlet 81.

The cam 77 is composed of a convex portion 89 and a concave portion 91 provided on the torque transmitting member 39, and these convex portions 89 and concave portions 91 are formed alternately in the circumferential direction.

The return spring 79 is provided for each cylinder 7.
3 is held by a retainer 93 arranged on the inner circumference of
The piston 75 is connected to the convex portion 8 of the cam 77 via the retainer 93.
9 and depression 91.

The one-way valve 85 comprises a valve sheet 95 provided at the discharge port 83 and a ball 97. The discharge port 83 is provided in the hydraulic chamber 65 of the hydraulic actuator 41.
When a negative pressure is generated in the cylinder 73 of the piston pump 3, the ball 97 is sucked by the valve sheet 95 to close the discharge port 83, thereby preventing the oil from returning from the hydraulic chamber 65. .

The oil passage 87 of the torque transmitting member 37 is connected to the oil passage 87 via the suction port 81, the cylinder 73, the discharge port 83, the hydraulic chamber 65, the orifice 71 of the pressing member 63, the multi-plate clutch 43, and the bearing 61. To form an oil circulation path.

While the vehicle shown in FIG.
When the sides 5 and 27 idle, the torque transmission member 37 on the front wheel side
Differential rotation occurs between the (cylinder 73 and piston 75) and the rear wheel side torque transmitting member 39 (cam 77).

At this time, the piston 75 which has reached the position (the position 99 in FIG. 2) opposed to the convex portion 89 of the cam 77 is pushed into the cylinder 73 as shown in the upper half of FIG. , The suction port 81 is closed and a positive hydraulic pressure is generated.
With this oil pressure, the ball 97 moves from the valve sheet 95, the one-way valve 85 is opened and the oil pressure is applied to the hydraulic chamber 65 of the hydraulic actuator 41, and the pressing member 6
3, the multiple disc clutch 43 is engaged.

The piston 75 (position 101 in FIG. 2), which has reached the position facing the concave portion 91 of the cam 77, is formed by the return spring 79 as shown in the lower half of FIG.
In the process, the suction port 81 is opened, and a negative hydraulic pressure is generated in the cylinder 73. When a negative oil pressure is generated, the ball 97 is sucked by the valve sheet 95, the one-way valve 85 is closed, and oil is sucked into the cylinder 73 from the suction port 81.

While the oil is being sucked and discharged in each cylinder 73, the oil returns to the oil circulation path.

Since the suction port 81 is provided inside the cylinder 73 in the radial direction, the return of the oil is promoted by the centrifugal force.

As described above, when the piston pump 3 operates and the multi-plate clutch 43 is engaged, the driving force of the engine causes the driving force of the engine to couple the coupling 1 due to the driving resistance of the piston pump 3 and the friction resistance of the multi-plate clutch 43. Through front differential 1
9 to the front wheels 33, 35.

As described above, when the rear wheels 25 and 27 idle on a rough road or the like, the coupling 1 is connected and the vehicle is driven in a four-wheel drive state. The running performance and the escape performance in the road are improved.

Also, as on a good road, the rear wheels 25, 27
When the vehicle is not running idle, the rear wheels 25 and 27 and the front wheels 3
Since there is no large differential rotation between the motors 3 and 35, the piston pump 3 is not driven, the multi-plate clutch 43 is released and the coupling 1 is disconnected, and the vehicle enters the rear-wheel drive two-wheel drive state. , The front wheels 33 and 35 are brought into a rotating state.

Also, when making a sharp turn at a low speed, such as when entering a garage, the coupling of the coupling 1 is loose because the differential rotation between the front and rear wheels is small. Therefore, the tight corner breaking phenomenon is not caused. Does not occur.

A bypass 103 is provided between the torque transmitting members 37 and 39.

The bypass passage 103 communicates the hydraulic chamber 65 of the hydraulic actuator 41 with the top 105 side (cam 77 side) of the piston 75.

As shown in FIG. 3, the hydraulic pressure of the hydraulic chamber 65 is applied to the top portion 105 of the piston 75 by the bypass passage 103, and the piston 75 receives a force 107 which is a product of the hydraulic pressure and the sectional area.

This force 107 acts in the direction opposite to the urging force 109 of the return spring 79 that pushes the piston 75 back to the cam 77 during operation of the piston pump 3.

Accordingly, when the rotational speed of the torque transmitting members 37 and 39 increases as the rear wheels 25 and 27 idle, the force 107 applied to the piston 75 exceeds the urging force 109 of the return spring 79. , The return spring 79 remains bent, the piston 75 stops moving and the cam 7
7 jumps over the projection 89.

In such a state, the discharge pressure of the piston pump 3 stops increasing and is maintained at a constant value.

The balance between the forces 107 and 109 is determined by the idling of the rear wheels 25 and 27 (torque transmitting members 37 and 39).
Is set so that the rise of the discharge pressure is stopped when the differential rotation speed exceeds a predetermined value.

Thus, when the differential rotation speed of the torque transmitting members 37 and 39 exceeds a predetermined value, a torque limiter function for maintaining the discharge pressure of the piston pump 3 at a constant value operates.

FIG. 4 is a graph showing the change in the transmission torque (T) of the coupling 1 and the change in the discharge pressure (P) of the piston pump 3 when the differential rotation speed (△ N) of the torque transmission members 37 and 39 changes. 111.

When a differential occurs in the torque transmitting members 37 and 39 as indicated by an arrow 113 in the graph 111, the coupling 1 starts transmitting torque, and the differential rotation speed (△ N)
As the pressure rises, the transmission torque (T) and the discharge pressure (P) rise rapidly.

When the differential speed (△ N) further increases and exceeds a predetermined value, and the force 107 becomes larger than the urging force 109, the above-described torque limiter function is activated and the graph 111 is activated.
As shown by the arrow 115, the transmission torque (T) and the discharge pressure (P) are kept constant, so that the propeller shaft 15, the transmission shaft 17, and the drive shafts 29, 31 on the front wheels 33, 35 are excessively large. Torque is prevented from being applied.

Thus, the coupling 1 using the piston pump 3 is constituted.

As described above, in this coupling 1,
The torque limiter function of the bypass 103 provided in the piston pump 3 prevents an excessive torque from being applied to the front wheels 33 and 35.

Therefore, the propeller shaft 15 and the transmission shaft 1
7 and the drive shafts 29 and 31 can be made thinner to some extent, and the weight can be reduced.

The limiter function obtained only by providing the bypass 103 is the same as that of the conventional relief valve 22.
Unlike the first embodiment, particularly high machining accuracy is not required, the machining can be performed at low cost, and the ball 229 and the coil spring 231 can be used.
Since this is unnecessary, the number of parts does not increase and the configuration can be made at a lower cost.

Further, since oil is used as the working fluid of the piston pump 3, the coupling 1 is connected with a slight differential rotation as compared with a configuration using air, for example, so that the maneuverability and traveling performance of the vehicle are improved. The effect of improving stability and the like is great.

Further, since the piston 75 is arranged to move in the axial direction, unlike the conventional example, the torque limiter function is released from the influence of the centrifugal force (engine speed: vehicle speed). An operating predetermined torque limiter function is obtained.

The multi-plate clutch 43 is compact and has a large torque capacity. In addition, the torque transmission function (differential limiting function) of the coupling 1 can be adjusted by changing the number of clutch plates. Drivability, running performance, stability, and the like of the vehicle can be further improved.

Also, by forming an oil circulation path inside the coupling 1, the sliding portion between the top portion 105 of the piston 75 and the cam 77, the clutch plate of the multi-plate clutch 43, etc. are sufficiently lubricated. Seizure is prevented and durability is greatly improved.

Also, with sufficient lubrication, the multiple disc clutch 43
, The torque transmission function (differential limiting function) of the coupling 1 is stabilized.

The multi-plate clutch 43 and the piston pump 3
For example, the oil temperature that has been partially increased by averaging is averaged by the circulating oil, and the above-described function of the coupling 1 is further stabilized.

If a centrifugal filter or a magnet filter is provided in any of the oil circulation paths, the multi-plate clutch 43 and the piston pump 3 can be used.
In addition to removing the abrasion powder from the oil and the like, the oil is kept clean, and the abrasion powder causes abnormal wear of the sliding portion between the piston 75 and the cam 77, clogging of the suction port 81, malfunction of the one-way clutch 85, etc. Is prevented, and the function of the coupling 1 is normally maintained.

Next, a second embodiment of the present invention will be described with reference to FIG. The coupling 117 (power transmission device) of this embodiment is configured using a piston pump 119. The coupling 117 has the features of claims 3, 4, 5, and 6, and the piston pump 119 has the features of claims 1 and 2. It has two features. FIG. 6 shows this coupling 117, and the left side of FIG.
In front of the four-wheel drive vehicle.

In the description of FIG. 6 and the second embodiment, members and the like having the same functions as those of the coupling 1 of the first embodiment are denoted by the same reference numerals, and the same functional members are repeatedly described. Omitted.

The coupling 117 is arranged on the front wheel side of the four-wheel drive vehicle, similarly to the coupling 1 of the first embodiment.

The coupling 117 is a piston pump 1
19, the input side and output side torque transmitting members 37, 3
9, a hydraulic actuator 41, a multi-plate clutch 43 and the like.

As shown in FIG. 6, this coupling 117
In the figure, the cam 121 of the piston pump 119 is provided on the pressing member 63 of the hydraulic actuator 41, the cylinder 73 is opened on the pressing member 63 side, and the one-way clutch 85 is provided on the opposite side.

The cam 121 is composed of convex portions 123 and concave portions 125 provided alternately on the pressing member 63 in the circumferential direction. The return spring 79 presses the piston 75 against these convex portions 123 and concave portions 125. .

Further, between the torque transmitting members 37 and 39,
A bypass 127 is provided, and the piston pump 1
The discharge pressure of 19 is guided to the hydraulic chamber 65 of the hydraulic actuator 41 through the bypass passage 127.

When the vehicle shown in FIG.
When the differential rotation occurs between the torque transmitting members 37 and 39 due to the idling of the sides 5 and 27, the urging force 1 of the return spring 79 is increased.
In response to 09, the piston 75 reciprocates along the convex portion 123 and the concave portion 125 of the cam 121, and the piston pump 119 operates.

When the piston pump 119 operates, the multi-plate clutch 43 is engaged, the coupling 117 is connected, the vehicle is driven in a four-wheel drive state, the front wheels 33 and 35 are driven, and the running performance on rough roads and the like is improved. The escape property is improved.

In a running state in which the rear wheels 25, 27 do not run idle, as in the case of running on a good road, the operation of the piston pump 119 is stopped to disconnect the coupling 117, and the vehicle is driven by two wheels driven by rear wheels. State, and the front wheels 33 and 35 are in a rotating state.

The hydraulic chamber 65 is connected to the hydraulic chamber 65 through the bypass passage 127.
The top 105 of the piston 75
, A force 107 which is a product of the hydraulic pressure and the cross-sectional area is applied. When the differential rotation speed of the torque transmitting members 37 and 39 due to the idling of the rear wheels 25 and 27 increases, and this force 107 becomes larger than the urging force 109 of the return spring 79, the piston 75
Stops moving. Thus, the torque transmitting member 3
When the differential rotation speeds of the motors 7 and 39 exceed a predetermined value, the torque limiter function is activated to maintain the discharge pressure (P) of the piston pump 119 and the transmission torque (T) of the coupling 117 constant. , 35 is prevented from being applied with excessive torque to the propeller shaft 15, the transmission shaft 17, and the drive shafts 29, 31.

Thus, the coupling 117 using the piston pump 119 is constituted.

Since the coupling 117 has the cam 121 of the piston pump 119 formed on the pressing member 63 of the hydraulic actuator 41 as described above, a dedicated cam member is not required, and the number of parts and cost are reduced accordingly. Is reduced.

Also, the cam 12 is attached to the pressing member 63 having a small mass.
The formation of 1 facilitates simultaneous processing of the cam 121 when forging the pressing member 63 as compared with, for example, a configuration in which a cam is provided on a casing member having a large mass. In addition to being greatly reduced, the pressing member 63 having a small mass can be easily heat-treated.
1, the heat treatment cost is greatly reduced.

Further, the torque transmitting member 39 without the cam can be easily processed and heat-treated, and the cost can be reduced by, for example, casting.

In addition, the coupling 117 has the same effect as the coupling 1 of the first embodiment.

If the power transmission device of the present invention is arranged between the differential rotating members of the differential device, the piston pump is operated by the differential rotation, the friction clutch is engaged, and the driving resistance of the piston pump and the friction clutch Differential is limited by the frictional resistance of

When the differential rotation speed exceeds a predetermined value by the torque limiter function of the power transmission device, the cylinder of the piston pump is protected from excessive pressure.

Also, since oil is used as the working fluid of the piston pump, the response to the generation of the differential limiting force accompanying the differential rotation is fast, so that the effect of improving the steering, running, and stability of the vehicle is great. .

Further, in the configuration in which the piston of the piston pump is moved in the axial direction, the effect of the engine speed (vehicle speed) is released, and a differential limiting function and a limiter function that operate only by the differential speed can be obtained. (Invention of Claim 7) In the power transmission device of the present invention, any of the torque transmission members may be on the input side and may be on the output side.

Further, the friction clutch is not limited to the multi-plate clutch, but may be, for example, a cone clutch.

[0112]

According to the piston pump of the first aspect, when the relative rotation speed of each torque transmitting member exceeds a predetermined value, the discharge pressure is maintained at a constant value by the limiter function of the bypass passage, and the piston pressure is maintained by the limiter function. The pump cylinder is protected from excessive pressure.

Further, unlike the conventional example, this limiter function which can be obtained only by providing the bypass path does not require high processing accuracy, is low in processing cost, is not accompanied by an increase in the number of parts, and is reduced in cost accordingly. Can be configured.

Further, since oil is used as the working fluid of the piston pump, a large discharge pressure and a torque transmission function (differential limiting function) at a small relative rotation speed as compared with the configuration using air.
Is obtained.

According to the second aspect of the invention, the same effect as that of the first aspect is obtained, and since the piston moves in the axial direction, the limiter function is released from the influence of the centrifugal force and operates only by the relative rotation speed. .

In the power transmission device of the third aspect, since the piston pump and the friction clutch of the first or second aspect are provided between the torque transmitting members, the friction resistance of the friction clutch is added to the driving resistance of the piston pump. In addition, the torque transmission function (differential limiting function) is greatly enhanced.

Further, in a four-wheel drive vehicle using this power transmission device, the propeller shaft and the drive shaft on the power transmission device side can be made thinner to some extent to reduce the weight.

According to the fourth aspect of the present invention, the same effect as that of the third aspect is obtained, and a large torque capacity can be obtained by using a multi-plate clutch. The torque transmission function (differential limiting function) can be adjusted.

The invention of claim 5 is the invention of claim 3 or claim 4.
The same effect as the configuration described above is obtained, and the cam of the piston pump is formed on the pressing member, so that a dedicated cam member is not required, and the number of parts and cost are reduced.

Further, it is easy to simultaneously process the cam when forging the pressing member, so that the processing cost is greatly reduced. In addition, the pressing member having a small mass is easily heat-treated.
The heat treatment cost of the cam is greatly reduced.

The invention of claim 6 is the invention of claims 3 to 5
The same effect as that of the above configuration is obtained, and the sliding portion between the piston and the cam, the friction clutch, and the like are sufficiently lubricated by the oil circulating inside, the seizure is prevented, and the durability is greatly improved.

Further, since the slip of the friction clutch is stabilized by sufficient lubrication, the torque transmission function (differential limiting function) of the power transmission device is stabilized.

Further, by circulating the oil, the temperature of the oil is averaged, and the above function of the power transmission device is further stabilized.

According to the differential device of the seventh aspect, the differential can be limited by the power transmission device of the third to sixth aspects provided between the differential rotating members.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a piston and a cam used in the piston pump of the first embodiment.

FIG. 3 is a view showing a force applied to the top of a piston via a bypass and a biasing force of a return spring in each embodiment.

FIG. 4 is a graph showing changes in a transmission torque (T) and a discharge pressure (P) with respect to a differential rotation speed (ΔN) in each embodiment.

FIG. 5 is a skeleton mechanism diagram of a vehicle using the power transmission device of each embodiment.

FIG. 6 is a sectional view showing a second embodiment of the present invention.

FIG. 7 is a sectional view of a conventional example.

FIG. 8 is a sectional view of a main part of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 117 Coupling (power transmission device) 3, 119 Piston pump 37 Input side torque transmission member 39 Output side torque transmission member 41 Hydraulic actuator (actuator) 43 Multi-plate clutch (friction clutch) 63 Hydraulic actuator Pressing member 71 orifice 73 piston 75 cylinder 77 cam 79 formed on torque transmitting member 39 return spring 87 return oil passage 89, 123 cam convex portion 91, 125 cam concave portion 103, 127 bypass passage 105 top of piston 121 cam formed on the pressing member 63

Claims (7)

[Claims] 1. A pair of torque transmitting members disposed so as to be relatively rotatable, a cylinder and a piston disposed on one torque transmitting member side, and a convex portion and a concave portion provided on the other torque transmitting member side. A piston having a cam, a return spring that pushes the top of the piston back to the cam, and a piston pump provided in the cylinder and having an oil intake port and a discharge port along with movement of the piston. A piston passage provided to a top side of the piston pump. 2. The piston pump according to claim 1, wherein the piston is arranged to move in the axial direction. 3. A piston pump according to claim 1 or 2, a friction clutch disposed between respective torque transmitting members thereof, an actuator which is actuated by applying pressure from the piston pump, and an actuator which operates by applying pressure from the piston pump. A pressure member for pressing the friction clutch by the pressing force of the rotor, limiting the differential between the two torque transmission members by the driving resistance of the piston pump and the friction resistance of the friction clutch, and controlling the torque between the two torque transmission members. A power transmission device for transmitting power. 4. The power transmission device according to claim 3, wherein the friction clutch is a multi-plate clutch. 5. The power transmission device according to claim 3, wherein the cam of the piston pump is formed on the pressing member. 6. The invention according to claim 3, wherein an orifice is provided in a pressing member of the actuator, and oil passing through the orifice is
A power transmission device wherein oil is circulated by being guided to a suction port of a piston pump through a return oil passage after being applied to a friction clutch. 7. A differential case that is rotationally driven by a driving force of an engine, a differential mechanism that distributes rotation of the differential case to a wheel side, and a pair of torque transmitting members that are differential rotary members of the differential mechanism. And a power transmission device according to any one of claims 3 to 6, which is disposed between the power transmission device and the differential transmission is limited by a driving resistance of the piston pump and a friction resistance of the friction clutch. Differential device.