JP4205658B2 - Hydraulic power transmission device - Google Patents

Description

The present invention relates to a hydraulic power transmission device that distributes torque in accordance with the rotational difference between the front and rear wheels of a four-wheel drive vehicle, and in particular, from the four-wheel drive that cuts off excessive torque generated during sudden start and sudden braking. The present invention relates to a hydraulic power transmission device having a mechanism for switching to two-wheel drive.

  An FF type four-wheel drive vehicle equipped with a conventional hydraulic power transmission device is shown in FIG. In FIG. 11, the power from the engine 100 is transmitted to the left and right front wheels 102L and 102R by the front propeller shaft 101, and at the same time is transmitted from the hydraulic power transmission device 103 to the left and right rear wheels 105L and 105R by the rear propeller shaft 104.

  The conventional hydraulic power transmission device 103 includes a housing connected to the front propeller shaft 101 and a rotor connected to the rear propeller shaft 104, and the housing forms a cam surface having two or more cam ridges on the inner surface. The rotor is rotatably arranged in the housing, and a plurality of piston chambers are formed in the rotor in the axial direction so as to face the cam surface, and a suction and discharge communication path is provided on the opposite side of the cam surface of the piston chamber. Is provided.

Each of the piston chambers of the rotor receives the pressure of the return spring so that the piston can be reciprocated and is driven by the cam surface when a rotational speed difference occurs between the front propeller shaft 101 and the rear propeller shaft 104. . An orifice is formed for each piston chamber on the open end face side of the communication passage formed in each piston chamber of the rotor.
JP-A-5-047442 Japanese Patent No. 2952139

  By the way, in such a conventional hydraulic power transmission device, when the vehicle is suddenly started or suddenly braked, the rotational speed difference temporarily increases to generate excessive torque, which is commensurate with this excessive torque. As described above, not only the hydraulic power transmission device but also the strength of the vehicle drive system must be increased, and there is a problem of increasing the size and cost of the device.

  Therefore, in the conventional hydraulic power transmission device, a torque limiter valve that supports the check ball in a closed state by a spring is provided in the middle of the high pressure oil passage from the piston chamber to the low pressure side, and a predetermined high pressure exceeding the spring load is provided. When receiving, the flow path is opened by a check ball and drained from the piston chamber to suppress excessive torque.

  However, as a torque limiter mechanism for such a conventional hydraulic power transmission device, for example, a torque limiter valve needs to be individually provided in each of a plurality of piston chambers provided in the rotor. There is a problem of becoming.

  The torque characteristics of the conventional hydraulic power transmission device are as follows. When a four-wheel drive vehicle is equipped with an anti-skid brake system (hereinafter referred to as “ABS”), all the wheels of the four-wheel drive vehicle rotate at the same speed during sudden braking. There is a problem that accurate ABS control cannot be performed.

  The ABS operates by detecting sudden braking exceeding a certain deceleration acceleration, generates a pseudo vehicle speed from the difference in wheel speed of each wheel, and sets the brake hydraulic pressure so that the wheel speed becomes 90%, for example, with respect to this pseudo vehicle speed. The slip ratio is controlled so as to obtain the maximum friction coefficient.

  However, in the case of a four-wheel drive vehicle using a hydraulic power transmission device, if there is a difference in rotational speed between the front drive shaft and the rear drive shaft due to power transmission from the wheel side during deceleration by sudden braking, Even if an attempt is made to control the slip ratio by changing the wheel speed so that the maximum friction coefficient can be obtained independently by the ABS control, for example, the front and rear wheels can be controlled by ABS control. The torque transmission by the transmission device causes interference that suppresses changes in wheel speed due to ABS, and accurate ABS control cannot be performed.

  In order to avoid interference with the ABS due to such a hydraulic power transmission device, it is desirable to switch from four-wheel drive to two-wheel drive during ABS operation. Switching to wheel drive has been realized.

  However, when switching from four-wheel drive to two-wheel drive by electric control means, a mechanism for switching from four-wheel drive to two-wheel drive by an electric actuator is added to the hydraulic power transmission device. Therefore, there is a problem that the structure is complicated and the cost is significantly increased.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic power transmission device that has a simple structure and suppresses excessive torque at the time of sudden start or sudden braking and that can avoid interference with ABS.

In order to achieve this object, the present invention is configured as follows. The present invention
A housing connected to a first shaft of two shafts for individually driving a front wheel and a rear wheel, and having a cam surface having two or more cam peaks on an inner surface;
The piston chamber is connected to the second shaft and rotatably accommodated in the housing, and a plurality of piston chambers are formed in an axial direction facing the cam surface, and the piston chamber is located on the opposite side of the piston chamber from the cam surface. A suction communication passage that communicates with each other and an annular suction communication groove that communicates each suction communication passage, and a suction discharge communication passage that communicates with a piston chamber having an orifice as a flow resistance generating means and each suction discharge communication passage. A rotor provided with an annular suction / discharge communication groove;
Each of the plurality of piston chambers is reciprocally accommodated by receiving a return spring and is driven by a cam surface during relative rotation between the first shaft and the second shaft;
It is fixed to the housing on the end face side where the suction communication groove and suction / discharge communication groove of the rotor are formed, and closes the suction / discharge communication groove and opens a common suction port that connects the suction communication groove to the external low-pressure chamber. A washer member;
And a hydraulic power transmission device that transmits torque according to the rotational speed difference between the first shaft and the second shaft.

The present invention relates to such a hydraulic power transmission device as a torque limiter mechanism that limits an excessive torque generated with a rapid increase in the rotational speed difference to a predetermined value.
A relief washer member arranged coaxially on the outside of the washer member and movable in the axial direction;
A drain communication path provided for each piston chamber and communicating each piston chamber with a rotor end face against which a relief washer member is pressed;
The relief washer member is pressed against the rotor end face to close the drain communication path, and when the force applied by the hydraulic pressure to the relief washer member through the drain communication path exceeds a predetermined spring load, the relief washer member is moved backward to drain. A relief spring that drains the piston chamber into the low pressure chamber by opening the communication passage;
And a weight member that rotates integrally with the housing and locks the relief washer member down to the open position of the drain communication path by inertia force when the housing stops or starts rotating.

  Here, the weight member is a cylindrical member that is rotatably disposed on the inner peripheral surface of the housing outside the rotor. A taper groove is formed on the end surface of the cylindrical member, and a part of the weight member is protruded by fitting with the relief washer member. The ball is fitted into the taper groove, and the drain washer is opened by pushing down the relief washer member via the taper groove and the ball by the inertia force when the housing stops or starts rotating.

  The taper groove of the weight member causes the ball to move due to the angle of one taper surface that generates a pressing force that presses the relief washer member through the ball by the inertial force of the weight member when suddenly starting, and the inertial force of the weight member during sudden braking. The angle of the other taper surface that generates the pressing force for pressing the relief washer member is set to a different angle.

The relief springs are a plurality of coil springs arranged in the circumferential direction of the relief washer member. The relief spring may be a wave spring that is arranged coaxially with the relief washer member and undulates in the circumferential direction.

  According to the present invention, the torque limiter mechanism has a simple structure in which a relief washer member functioning as a valve member is movably disposed by the support of a spring on the end surface of the drain communication passage communicating with the piston chamber of the rotor. When excessive high pressure is applied due to a sudden increase in the rotational speed difference during sudden start or sudden braking, the relief washer member retracts to open the drain communication path and drain the high-pressure oil, keeping the generated torque at the specified torque. In addition, transmission of excessive torque can be prevented.

  In particular, the torque limiter mechanism of the present invention is provided as a common mechanism for a plurality of piston chambers, and the structure can be simplified and the cost can be reduced as compared with the case where a check ball valve is provided for each piston chamber.

Also, the four-wheel drive is switched to the two-wheel drive by moving the relief washer member to the open position of the drain communication path by the inertia force of the weight member generated by the stop of the housing due to the wheel lock during sudden braking when the ABS is operated. Interference with ABS can be suppressed.

  FIG. 1 is a sectional view showing an embodiment of a hydraulic power transmission device according to the present invention, and FIG. 2 shows an end view seen from the right side of FIG.

  In FIG. 1, a hydraulic power transmission device 10 according to the present invention has a cylindrical housing 12 that is open to the left and right, and a cam 14 is fixed to a right side inside the housing 12 by a stopper ring 15.

  The cam 14 is provided with a cam surface 16 in which peaks and valleys are alternately formed along the circumferential direction on the inner surface side which is the left end surface. In this embodiment, the number of peaks formed on the cam surface 16 is four, for example. A rotor 18 is rotatably incorporated on the left side of the cam 14. The rotor 18 has a shaft hole 20 and a spline hole 22 following the shaft hole 20, and a bearing 24 is disposed in the shaft hole of the left housing 12.

  For example, the front drive shaft side is connected to the shaft hole 20 and spline hole 22 of the rotor 18 and the bearing 24. On the other hand, a rear drive shaft is connected to the housing 12 side.

  The rotor 18 has a plurality of piston chambers 26 that are open on the cam 14 side in the circumferential direction. A piston 28 is incorporated in the piston chamber 26 so as to be reciprocally movable. A return spring 32 is disposed behind the piston. A ball 30 is disposed at the tip of the piston and is in contact with the cam surface 16. In this embodiment, the number of pistons 28 provided on the rotor 18 is seven.

  An orifice 38, a suction communication path 34, and a drain communication path 44 are provided from the inner peripheral side at the rear portion of the piston chamber 26, that is, on the side opposite to the cam surface 16. The orifice 38 communicates with a suction / discharge communication groove 40 formed in an annular shape on the end face of the rotor 18, and seven orifices 38 are communicated with the suction / discharge communication groove 40. An annular suction communication groove 42 is formed on the end surface of the rotor 18 between the suction / discharge communication groove 40 and the suction communication path 34.

  A washer member 36 is disposed on the left side of the rotor 18. The washer member 36 is fixed to the end surface of the housing 12 by a fixing pin (not shown), and the suction / discharge communication groove 40 and the suction communication groove 42 are sealed by close contact with the end surface of the rotor 18.

  A relief washer member 48 is arranged coaxially on the outside of the washer member 36. The relief washer member 48 is incorporated in a ring groove 46 formed in the housing 12 so as to be movable in the axial direction. A spring accommodating hole 54 is formed at the rear (left side) of the relief washer member 48, and a relief spring 55 is incorporated therein to press the relief washer member 48 against the end face of the rotor 18 with a predetermined spring load.

  A drain communication path 44 opens from the piston chamber 26 to the end face of the rotor 18 with which the relief washer member 48 abuts. For this reason, the relief washer member 48 closes the drain communication path 44 by pressing the end face of the rotor 18 by the spring force of the relief spring 55.

  Cutouts 48a are formed at a plurality of locations on the outer peripheral side of the relief washer member 48, and balls 52 are incorporated therein. A cylindrical weight member 50 is incorporated on the right side of the ball 52 so as to be rotatable with respect to the housing 12.

  The weight member 50 is fitted with the ball 52 by a tapered groove which will be clarified in the description after being formed on the end face on the relief washer member 48 side. For this reason, the weight member 50 is engaged with the housing 12 via the relief washer member 48 and the ball 52 and rotates integrally.

  The torque limiter mechanism in the hydraulic power transmission device 10 of the present invention includes a drain communication path 44, a relief washer member 48, a relief spring 55, a ball 52, and a weight member 50.

  This torque limiter mechanism performs a relief operation when an unnecessarily high pressure is generated due to high-speed movement of the piston 28 due to a rapid increase in the rotational speed difference between the housing 12 and the rotor 18 when the vehicle is suddenly started or suddenly braked. I do. That is, the hydraulic pressure in the piston chamber 26 is applied to the relief washer member 48 via the drain communication passage 44, and pushes the relief washer member 48 in the direction in which the relief spring 55 is compressed.

  When the hydraulic pressure in the piston chamber 26 exceeds the drain set pressure determined by the spring load of the relief spring 55, the relief washer member 48 is pushed down from the end face of the rotor 18, opens the drain communication path 44, and opens the high pressure in the piston chamber 26 to the low pressure chamber 45. Drain the oil. By the high pressure oil drain from the piston chamber 26, it is possible to limit the excessive torque generated in the hydraulic power transmission device to a predetermined limit torque at the time of sudden start or sudden braking.

Here, the hydraulic pressure of the piston chamber 26 is P, the opening cross-sectional area of the drain communication passage 44 is S, and the spring load of the relief spring 55 is F.
(S × P)> F
When the hydraulic pressure is obtained, the relief washer member 48 is operated to perform a drain operation for opening the drain communication path 44.

  Note that the opening cross-sectional area S of the drain communication passage 44 is the total cross-sectional area of the seven piston chambers 26, and even in the relief spring 55, as shown in FIG. It is the total load.

  In addition to the torque limiter function for limiting the transmission torque by suppressing the high pressure more than necessary due to the high-speed reciprocating movement of the piston 28 at the time of sudden start or sudden braking, the vehicle suddenly started or suddenly braked. The function of switching from the four-wheel drive to the two-wheel drive is provided by opening the drain washer 44 through the ball 52 by the inertia force (inertia) generated in the weight member 50 at that time.

  First, at the time of a sudden start, the housing 12 is accelerated to, for example, several tens of kilometers per hour from a stopped state, and at this time, the weight member 50 is left behind due to inertia, and the ball 52 is held by the tapered surface of the tapered groove. The relief washer member 48 is pushed down to open.

  Also, during sudden braking, for example, when the speed is reduced from 100 km / h to 0 km in a short time, the housing 12 that has been rotating at a high speed stops suddenly, so that the weight member 50 moves against the housing 12 by the inertial force generated by the rotation. The drain washer 44 is released from the relief washer member 48 via the ball 52 which is relatively moved and fitted in the tapered groove.

  Here, torque generation due to a difference in rotational speed between the housing 12 and the rotor 18 in the hydraulic power transmission device 10 of FIG. 1 will be described as follows. The piston 28 provided on the rotor 18 is a suction process in a process from the peak to the valley of the cam surface 16. Further, the discharge process is a process from the valley of the cam surface 16 toward the mountain.

  In the suction process of the piston 28, as shown in the piston 28 below the rotor 18, the piston 28 is moved to the right side by being pushed by the return spring 32, and the oil is discharged from the suction / discharge communication path 40 through the orifice 38. Further, the suction communication groove 42 is formed in the suction communication passage 34 at a position before and after the valley of the cam surface 16 via a suction opening 65 (see FIG. 2) formed in the washer member 36 which will be clarified later. In this way, oil that is insufficient only by the suction of the orifice 38 is replenished.

  On the other hand, in the discharge process as shown by the piston 28 on the upper side of the rotor 18, the oil sucked by the leftward movement of the piston 28 is discharged through the orifice 38 into the suction / discharge communication groove 40, and the orifice 38. A high pressure is generated in the piston chamber 26 by the flow resistance at the time of flowing through, and torque transmission is performed between the housing 12 and the rotor 18 by this high pressure.

  The oil discharged from the piston chamber 26 through the orifice 38 is also sucked from the suction / discharge communication groove 40 into the lower piston chamber 26 in the suction process at the same time through the orifice 38.

  Here, if the hydraulic pressure of the piston chamber 26 in the discharge process is high, and the hydraulic pressure of the piston chamber 26 in the suction process is low, the hydraulic pressure of the suction / discharge communication groove 40 is an intermediate pressure that is an intermediate value thereof. The suction / discharge communication groove 40 functions as an intermediate pressure chamber.

  Further, in the hydraulic power transmission device 10 of FIG. 1, an accumulator chamber 56 is formed in the upper left corner of the housing 12, and an accumulator piston 58 is housed therein. The accumulator chamber 56 communicates with the low pressure chamber 45 on the outer periphery of the rotor 18 and absorbs the volume change of the oil accompanying the temperature change. The left side of the accumulator piston 58 is open to the atmosphere, so that the low pressure chamber 45 is at atmospheric pressure. Further, seals 60 and 62 are incorporated on the left and right sides of the shaft portion of the rotor 18 to seal the internal oil in a sealed state.

  FIG. 2 is an end view of the housing 12 shown in FIG. 1 as viewed from the right. The washer member 36, the relief washer member 48, the weight member 50, and the piston 28 in FIG. Yes.

  In FIG. 2, a communication groove 68 is formed on the inner end face of the housing 12 from the inner periphery to the outer periphery at intervals of 45 °, and the communication groove 68 communicates the low pressure chamber 45 on the outer peripheral side with the low pressure chamber on the inner peripheral side. ing. A suction opening 65 formed in the washer member 36 is located at a position 45 ° apart between the communication grooves 68.

  The suction opening 65 of the washer member 36 is disposed at a valley position on the cam surface 16. At this position, the suction communication groove 42 on the end surface of the rotor 18 shown in FIG. The oil is supplied from the low pressure chamber. Further, accumulator chambers 56 are formed at four locations on the outer peripheral side of the housing 12, and a part of the accumulator chambers is opened inward.

  A washer member 36 and a relief washer member 48 shown in FIG. 1 are coaxially arranged in front of the inner end face of the housing 12, and a weight member 50 is arranged via a ball 52 in front of the relief washer member 48. Will be. The ball 52 is fitted into tapered grooves formed on the end face of the weight member 50, and the ball 52 is fitted into four tapered grooves in the circumferential direction.

  Further, the seven pistons 28 provided on the rotor 18 side change positions by rotating relative to the housing 12 in accordance with the rotational speed difference with the rotor 18, and are sucked in a rotation range from the peak of the cam surface 16 toward the valley. It becomes a process, and it becomes a discharge process in the range which goes to a mountain from a valley. Further, an orifice 38, a suction communication path 34, and a drain communication path 44 are opened from the inner peripheral side on the end face of the piston 28.

  FIG. 3 is an explanatory view showing the assembled parts of the relief washer member 48 and the weight member 50 of FIG. The relief washer member 48 has a rectangular notch 48a formed in the outer peripheral portion of the end surface on the weight member 50 side, and a ball 52 is incorporated therein. A washer member 36 is disposed inside the relief washer member 48, and a suction opening 65 is formed in the washer member 36.

  The washer member 36 is fixed to the inner end surface of the housing 12 by inserting a fixing pin into the pin hole 82, and the relief washer member 48 is arranged in a rotation direction with respect to the housing 12 by the arrangement of the fixing pin with respect to the outer arc-shaped cutout 48a. Is restricted and is movable only in the axial direction.

  The weight member 50 disposed on the right side of the relief washer member 48 includes a tapered groove 70 that fits the discharge portion of the ball 52.

  FIG. 4 shows the ball 52 on the relief washer member 48 side and the tapered groove 70 on the weight member 50 side of FIG. 3, and is in this positional relationship when the weight member 50 rotates integrally with the housing 12. .

  The triangular taper groove 70 formed on the end surface of the weight member 50 forms a drive taper surface 70a and a coast taper surface 70b. The angle of the drive taper surface 70a is as small as θ1, and the coast taper surface 70b The angle is as large as θ2. Here, the angle θ1 of the drive taper surface 70a is, for example, 14 °, and the angle θ2 of the coast taper surface 70b is, for example, 42 °.

  FIG. 5 is an explanatory view of the operating state of the relief washer member due to the inertial force of the weight member generated during driving and coasting. FIG. 5 (A) shows a driving time in which a rotational speed difference is generated by receiving a power rotation from the engine by suddenly starting the vehicle, and the relief washer member 48 is rapidly integrated with the housing 12 in the direction of arrow A by the sudden start. However, since the weight member 50 is in a stopped state, a rotation delay occurs with respect to the sudden rotation of the relief washer member 48 in the A direction, and an inertial force Fa associated therewith is generated in the opposite direction.

  For this reason, the ball 52 moves along the drive taper surface 70a of the tapered groove 70, and with the movement of the ball 52, the relief washer member 48 is pushed down in the direction of arrow C to open the drain communication path 44.

  Thus, after the relief washer member 48 is moved to the open position by the inertial force Fa applied to the weight member due to sudden start, the open state is maintained until the vehicle is stopped. The release state of the relief washer member 48 due to the inertial force Fa at the sudden start of the weight member 50 is lower than the limit torque value when the pressure in the piston chamber 26 exceeds the drain set pressure determined by the relief spring 55. As a result, the four-wheel drive state is switched to the two-wheel drive state.

  FIG. 5B shows the operation during coasting when the vehicle is braked suddenly. At the time of coasting due to sudden braking, for example, the housing 12 due to sudden braking stops in a short time from the rotation of the housing 12 in a traveling state of 100 km / h, and the relief washer member 48 also stops accordingly.

  On the other hand, the weight member 50 tries to further rotate by the inertia force Fb with respect to the stop of the housing 12. For this reason, the ball 52 is pushed down by the coast taper surface 70 b, and the relief washer member 48 opens the drain communication path 44. For this reason, even during sudden braking, the drain communication path 44 is opened by the inertia force Fb of the weight member 50 to switch from the four-wheel driving state to the two-wheel driving state, and interference with the ABS can be avoided by sudden braking. .

  FIG. 6 is an explanatory diagram showing the discharge process and the suction process with respect to the relative rotation of the cam surface when the rotor during driving and coasting is fixed in the hydraulic power transmission device 10 of the present invention.

  FIG. 6 (A) shows a driving time, the cam surface 16 is moving in the right direction, and the piston 28 that contacts the right slope 78 from the crest 76 to the trough 74 of the cam surface 16 is in the suction process. The piston 28 in contact with the left slope 80 facing the mountain 76 is a discharge process.

  FIG. 6B shows a suction process and a discharge process during coasting accompanying sudden braking of the vehicle. During the coasting, the rotation direction of the cam surface 16 is a rightward movement opposite to that during driving. Therefore, during the coasting, the piston 28 that is in contact with the left slope 80 from the crest 76 of the cam surface 16 toward the trough 74 is in a suction process as opposed to during driving, and at the same time, from the crest 76 of the cam surface 16 to the trough 74. The piston 28 that comes into contact with the right inclined surface 78 toward the opposite side is in the discharge process as opposed to during driving.

  FIG. 7 is an explanatory diagram of a discharge process and a suction process with respect to the rotor rotation when the housing is driven and coasted in the hydraulic power transmission device of the present invention. FIG. 7A is an explanatory diagram at the time of driving in which the vehicle travels normally, and the rotation direction of the rotor 18 is a left rotation indicated by an arrow with respect to the housing in a fixed state.

  During this drive, the piston 28 is in the suction process in the range of 45 ° from the peak to the valley of the cam, and the piston 28 is in the discharge process in the range of 45 ° from the valley to the peak. It occurs alternately at intervals of °.

  FIG. 7B shows a suction process and a discharge process during coasting in sudden braking. During the coasting, the rotation direction of the rotor 18 when the housing 12 is fixed is clockwise as opposed to during driving. With respect to the clockwise rotation of the rotor 18 at the time of the coast, the piston 28 becomes a suction process in a range of 45 ° from the peak to the valley of the cam surface 16, and the piston 28 becomes a discharge process in a range of 45 ° from the valley to the peak. The suction process and the discharge process occur alternately at 45 ° intervals.

  Compared with driving, it can be seen that the discharging process during driving is a suction process during coasting, and the suctioning process during driving is switched to the discharging process during coasting.

  FIG. 8 is an enlarged cross-sectional view of the operating state of the torque limiter mechanism according to the present invention in FIG. 1. As shown in FIGS. 5 (A) and 5 (B), the ball is moved by the inertia force of the weight member 50 by sudden start or sudden braking. An operation state in which the relief washer member 48 is pushed down to the open position of the drain communication path 44 via 52 and locked is shown.

  When the relief washer member 48 is opened by the inertia force of the weight member 50, the piston chamber 26 is communicated with the low pressure chamber 45 via the drain communication passage 44, and no oil flows through the orifice 38. Torque transmission according to the rotational speed difference between the housing 12 and the rotor 18 does not occur, and the two-wheel drive state is substantially achieved.

  FIG. 9 is a graph showing torque limiter characteristics according to the present invention. In FIG. 9, in a state before the weight member 50 is actuated by inertial force, when the hydraulic pressure in the piston chamber 26 exceeds the drain set pressure determined by the relief spring 55, the relief washer member 48 is retracted and the drain connection is continued. The passage 44 is opened, and the torque in this case is limited to the limit torque T1.

  On the other hand, when the drain washer 44 is released from the relief washer member 48 via the ball 52 by the inertial force of the weight member 50, the limit torque T2 is lower than the limit torque T1 and can be regarded as substantially two-wheel drive. Limited to

  From the torque characteristics shown in FIG. 9, for example, the time change of the torque characteristics during sudden braking is as shown in FIG. FIG. 10 shows a case where sudden braking is applied at time t1, and the weight member is reached after reaching the limit torque T1 at time t2 according to the torque characteristics of FIG. 9 as the rotational speed difference between the housing and the rotor increases with sudden braking. When the relief washer member 48 is opened by the inertia force of 50, the torque T2 is decreased at time t3, and thereafter, the two-wheel drive state is maintained.

  The time change of the torque characteristic at the time of sudden braking in FIG. 10 is basically the same at the time of sudden start.

  Here, as shown in FIG. 4, the angle θ1 of the drive taper surface for switching to the two-wheel drive at the time of sudden start is small, and the coast taper surface 70b for switching to the two-wheel drive at the time of sudden braking. The reason why the angle θ2 is increased will be described as follows. First of all, at the time of sudden start, for example, even if it is quite a sudden start, the speed changes from 0 km to several tens of kilometers per hour, while at the time of sudden braking, the speed is suddenly from 100 kilometers to 0 kilometers per hour. Make a change.

  Therefore, in order to obtain the same time change in torque characteristics as shown in FIG. 10 at the time of sudden start and sudden braking, the angle θ1 of the drive taper surface 70a at the time of sudden start with a small inertia force is reduced. The relief washer member 48 can be pushed down to the open position with a small inertial force, and the coast taper surface 70b corresponding to the sudden braking that generates a large inertial force is increased by increasing the angle θ2 so that the sudden start with a large inertial force. The relief washer member 48 is moved to the open position with an equivalent torque characteristic.

  Of course, the respective angles θ1 and θ2 in the tapered groove 70 are appropriately determined as necessary in accordance with the traveling condition and vehicle performance of the vehicle.

  In the above embodiment, a case where a coil spring is provided at a plurality of locations as the relief spring 55 of the relief washer member 48 is taken as an example. However, as a relief spring, a spring plate material is waved in the circumferential direction instead of the coil spring. A formed wave spring can also be used.

  Since the wave spring is a single wavy ring-shaped leaf spring, the cost is lower than that of a plurality of coil springs, and the thickness of the ring groove 46 in FIG. 1 is deeply formed to match the amplitude width of the wave washer. It is only necessary to do this, and the processing and assembly can be simplified as much as it is not necessary to form the spring accommodating hole 54.

The present invention is not limited to the above-described embodiments, includes appropriate modifications that do not impair the objects and advantages thereof, and is not limited by the numerical values shown in the above-described embodiments.

Sectional drawing which showed one Embodiment of this invention End view of the housing of FIG. 1 viewed from the right Explanatory drawing which extracted and showed the assembly part of the relief washer member and weight member of FIG. Explanatory drawing of the taper groove | channel of the ball | bowl on the relief washer member side of FIG. 3, and a weight member Explanatory drawing of the operating state of the relief washer member due to the inertial force of the weight member generated during driving and coasting Explanatory drawing showing a straight line development of the suction and discharge process with respect to the relative rotation of the cam surface when the rotor is fixed during driving and coasting Explanatory drawing which showed the suction and discharge process with respect to rotor rotation which looked at fixing the housing at the time of drive and coast 1 is an enlarged cross-sectional view of the operating state of the torque limiter mechanism according to the present invention in FIG. The graph which showed the torque limiter characteristic by this invention Explanatory drawing showing the time change of torque characteristics during sudden braking Explanatory drawing of a four-wheel drive vehicle equipped with a conventional hydraulic power transmission device

Explanation of symbols

10: Hydraulic power transmission device 12: Housing 14: Cam 15: Stopper ring 16: Cam surface 18: Rotor 20: Shaft hole 22: Spline hole 24: Bearing 25: O-ring 26: Piston chamber 28: Piston 30: Ball 32 : Return spring 34: Suction communication path 36: Washer member 38: Orifice 40: Suction / discharge communication groove 42: Suction communication path 44: Drain communication path 45: Low pressure chamber 46: Ring groove 48: Relief washer member 48 a: Notch 50: Weight Member 52: Ball 54: Spring storage hole 55: Relief spring 56: Accumulator chamber 58: Accumulator piston 60, 62: Seal 65: Suction opening 68: Communication groove 70: Tapered groove 70a: Tapered surface for drive 70b: Tapered surface for coast 74: Valley 76: Mountain 78: Right slope 80: Left slope 82: pin hole

Claims (5)

A housing connected to a first shaft of two shafts for individually driving a front wheel and a rear wheel, and having a cam surface having two or more cam peaks on an inner surface;
The piston chamber is connected to the second shaft and rotatably accommodated in the housing, and a plurality of piston chambers are formed in an axial direction facing the cam surface, and are opposite to the cam surface of the piston chamber. A suction communication passage that communicates with the piston chamber, an annular suction communication groove that communicates each suction communication passage, and an intake / discharge communication passage that communicates with the piston chamber having an orifice as a flow resistance generating means. A rotor provided with an annular suction / discharge communication groove communicating with the discharge communication path;
In each of the plurality of piston chambers, a plurality of pistons that are received by a return spring and reciprocally moved and driven by the cam surface during relative rotation between the first shaft and the second shaft,
The rotor is fixed to the housing on the end surface side where the suction communication groove and the suction / discharge communication groove are formed, and closes the suction / discharge communication groove and communicates the suction communication groove with an external low-pressure chamber. A washer member having a common inlet opening;
A hydraulic power transmission device that transmits torque according to a rotational speed difference between the first shaft and the second shaft;
As a torque limiter mechanism that limits an excessive torque generated with a rapid increase in the rotational speed difference to a predetermined value,
A relief washer member arranged coaxially on the outside of the washer member and movable in the axial direction;
A drain communication path that is provided for each piston chamber and communicates each piston chamber with the rotor end surface against which the relief washer member is pressed;
When the relief washer member is pressed against the rotor end surface to close the drain communication passage, and the force applied by hydraulic pressure to the relief washer member through the drain communication passage exceeds a predetermined spring load, the relief washer A relief spring that drains the piston chamber into the low pressure chamber by retreating a member to open the drain communication path;
A weight member that rotates integrally with the housing and locks the relief washer member down to an open position of the drain communication path by inertia force at the time of stopping or starting rotation of the housing;
A hydraulic power transmission device comprising:
2. The hydraulic power transmission device according to claim 1, wherein the weight member is a cylindrical member rotatably disposed on an inner peripheral surface of the housing outside the rotor, and a tapered groove is formed on an end surface of the cylindrical member. The relief washer member is fitted into the taper groove with a partially protruding ball fitted into the relief washer member, and the relief washer is inserted through the taper groove and the ball by an inertial force when the housing stops or starts rotating. A hydraulic power transmission device, wherein a member is pushed down to open the drain communication path.
2. The hydraulic power transmission device according to claim 1, wherein the tapered groove of the weight member generates a pressing force that presses the relief washer member via the ball by an inertial force of the weight member when suddenly starting. And the angle of the other tapered surface that generates a pressing force that presses the relief washer member through the ball by the inertia force of the weight member during sudden braking is set to a different angle. A hydraulic power transmission device characterized by that.
2. The hydraulic power transmission device according to claim 1, wherein the relief spring is a plurality of coil springs arranged in a circumferential direction of the relief washer member.
  2. The hydraulic power transmission device according to claim 1, wherein the relief spring is a wave spring that is arranged coaxially with the relief washer member and undulates in a circumferential direction. .

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