JP4420336B2 - Hydraulic power transmission device - Google Patents

Description

The present invention relates to a hydraulic power transmission device that distributes torque according to a rotational difference between front and rear wheels of a four-wheel drive vehicle.

  FIG. 6 shows an FF four-wheel drive vehicle equipped with a conventional hydraulic power transmission device. In FIG. 6, 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 disposed 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 piston chamber from the cam surface. 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. . A washer member is fixed to the housing on the opening end face side of the communication passage formed in each piston chamber of the rotor, and an arcuate annular groove is separately formed on the washer member at a position facing the slope of each cam crest. In addition, the communication passage is opened, and an orifice communicating with the external low-pressure chamber is formed in each annular groove.

  In such a hydraulic power rotating device, a torque corresponding to the difference in rotational speed between the front drive shaft 101 and the rear drive shaft 104 is generated. In other words, when a rotational speed difference occurs between the front drive shaft 101 and the rear drive shaft 104, the rotor rotates relative to the cam surface of the housing to reciprocate the piston, and the pressure oil discharged from the piston passes through the communication path. A high pressure is generated in the piston chamber by the flow resistance when passing through the orifice formed in the washer member, thereby generating torque.

  FIG. 7 is a characteristic diagram of the torque T with respect to the rotational speed difference ΔN of the conventional hydraulic power transmission device, and this characteristic is determined according to the opening cross-sectional area of the orifice.

Here, if the flow rate of oil passing through the orifice is Q and the torque is T, the following relational expression exists between the two.
T = f (Q ² )
JP-A-5-047442 Japanese Patent No. 2952139 JP 2000-310191 A

  However, the torque characteristic of such a conventional hydraulic power transmission device is that when a four-wheel drive vehicle is equipped with an anti-skid brake system (hereinafter referred to as “ABS”), the four-wheel drive vehicle is not Have substantially the same rotational speed, and 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.

An object of the present invention is to provide a hydraulic power transmission device that can avoid interference with an ABS with a simple structure.

In order to achieve this object, the present invention is configured as follows. The hydraulic power transmission device of the present invention is
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 cams on an inner surface;
It is connected to the second shaft and is housed in the housing so as to be rotatable and opposed to each other. A plurality of piston chambers are formed in the axial direction facing the cam surface. A rotor provided with a communication passage for discharge;
Each of the plurality of piston chambers is reciprocally stored by receiving a return spring and is driven by the cam surface during relative rotation between the first shaft and the second shaft;
It is fixed to the housing on the opening end face side of the communication passage formed in each piston chamber of the rotor, and an annular groove is separately formed at a position corresponding to the slope of each cam crest to open the communication passage. A washer member formed with an orifice as a flow resistance generating means communicating with an external low pressure chamber in the groove;
And a hydraulic power transmission device that transmits torque according to the rotational speed difference between the first shaft and the second shaft.

In the present invention for such a hydraulic power transmission device,
A cam crest that becomes a discharge process of each piston when generating a drive torque corresponding to a rotational speed difference due to a positive relative rotation between the first shaft and the second shaft upon receiving power transmission from the engine side The opening cross-sectional area of the plurality of first orifices formed on the washer member relative to one of the slopes is set to a predetermined value,
When generating a coast torque according to the rotational speed difference due to the reverse relative rotation between the first shaft and the second shaft upon receiving the power transmission from the wheel side, the cam crest of the cam crest that becomes the discharge process of each piston The opening cross-sectional area of the plurality of second orifices formed on the washer member relative to the other slope is set to be larger than a predetermined value.

  Here, the first orifice and the second orifice are alternately formed in arcuate grooves formed separately in the circumferential direction of the washer member.

In the hydraulic power transmission device of the present invention, when the drive torque is generated, the first orifice is a discharge port and the second orifice is a suction port. When coasting torque is generated, the first orifice is a suction port and the second orifice is It is a discharge port.

According to the present invention, during normal running, the hydraulic power transmission device transmits power from the engine side to generate drive torque corresponding to the rotational speed difference. On the other hand, during sudden braking when the ABS operates, power is transmitted from the wheel side. By generating a coast torque according to the difference in rotational speed, using the fact that the rotational direction of the rotor with respect to the cam surface is reversed in the drive torque and the coast torque,
The opening cross-sectional area of the orifice (second orifice) used when generating the coasting torque is set larger than the orifice (first orifice) used when generating the drive torque to keep the generated torque low and to minimize interference with the ABS.

The structure for this purpose is a simple structure in which the opening cross-sectional area of the orifice used when the coast torque is generated is large, and a small size and light weight can be achieved at low cost.

  FIG. 1 is a cross-sectional view showing an embodiment of a hydraulic power transmission device according to the present invention, and FIG. 2 shows a cross-section AA of FIG. 1 is a cross section taken along the line BB of FIG.

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

  The cam 14 is provided with a cam surface 16 having a cam crest formed in the circumferential direction on the inner surface side serving as the left end surface. In this embodiment, the number of cam crests formed on the cam surface 16 is, for example, four. A rotor 18 is rotatably mounted on the left side of the cam 14. The rotor 18 has a shaft hole 20 and a spline hole 22 communicating with the shaft hole 20, and a bearing 24 is arranged on the left side.

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

  The rotor 18 has a plurality of circumferentially formed piston chambers 26 opened on the cam surface 16 side. A piston 28 is reciprocally incorporated in the piston chamber 26, and a return spring 32 is disposed behind the piston 28. The ball 30 is disposed at the tip of the piston 28 and is in contact with the cam surface 16.

  A communication hole 34 is provided in the rear portion of the piston chamber 26, that is, on the side opposite to the cam surface 16, and the communication hole 34 is used as a suction path and a discharge path for the piston chamber 26.

  A washer member 36 is disposed on the left side of the rotor 18. The washer member 36 is positioned and fixed to the housing 12 by a lock pin 44. On the end surface of the washer member 36 on the rotor 18 side, opening grooves 38 are separately formed at eight locations in the circumferential direction divided into 45 ° divided ranges corresponding to the cam inclined surfaces.

  Each of the opening grooves 38 provided in the washer member 36 is formed with an orifice through which oil discharged from the piston chamber 26 in the discharge process of the piston 28 flows into the low pressure chamber on the left side. In the present invention, the first orifice 40 having a small opening cross-sectional area and the second orifice having a large opening cross-sectional area are formed every other opening groove 38 formed by dividing the washer member 36 in eight circumferential directions. Forming. In the cross-sectional view of FIG. 1, the first orifice 40 having a small opening cross-sectional area provided in the opening groove 38 facing the communication hole 34 from the upper piston chamber 26 is shown.

  An accumulator chamber 46 is formed on the upper left side of the housing 12, and an accumulator piston 48 is incorporated therein. A temperature switch 50 is incorporated in the lower left portion of the housing 12, and when the internal oil temperature reaches a predetermined temperature, the temperature switch 50 operates to close the suction path from the low pressure chamber to the piston chamber 26, and the piston 28. The oil suction is stopped in response to the reciprocating motion of the vehicle, so that the four-wheel drive is switched to the two-wheel drive.

  Details of the arrangement of the opening groove 38 of the washer member 36 and the state of the first and second orifices provided in the opening groove 38 are shown in FIG. In FIG. 2, eight opening grooves 38 are separately formed on the inner peripheral side of the washer member 36. In the opening groove 38, the first orifice 40 and the second orifice 42 are alternately formed in every other four locations.

  The first orifice 40 is an orifice that becomes a discharge port in the discharge process of the piston 28 when receiving power from the engine during normal operation, and the first orifice 40 is an orifice for generating a so-called drive torque.

  A second orifice 42 is formed between the first orifices 40. The opening area of the second orifice 42 is set to be larger than that of the first orifice 40, and the torque generated with respect to the rotational speed difference is kept low.

  The second orifice 42 generates a coast torque when receiving torque from the wheel side due to a sudden braking that activates the ABS. In the present invention, the second orifice 42 avoids interference with the ABS that operates during the sudden braking. Therefore, the opening cross-sectional area of the second orifice 42 is increased to suppress the generated coast torque to a low level.

  Note that the suction slits 56 disposed at intervals of 90 ° with respect to the opening grooves 38 disposed at intervals of 45 ° allow the suction of oil from the low-pressure chamber in the piston chamber 26 to be performed by the first orifice 40 or the second orifice. However, since the suction amount is insufficient only by suction from these orifices, the suction slit 56 is used to supplementarily suck oil at an initial position corresponding to the peak of the cam crest to compensate for this. Is provided.

  FIG. 3 is an explanatory view of the positional relationship between the discharge and suction steps of the opening groove and the first and second orifices with respect to the rotor rotation when the housing is driven and coasted in the hydraulic power transmission device of the present invention. .

  FIG. 3A shows the reciprocating motion of the piston 28 with respect to the movement of the cam surface 16 when the hydraulic power transmission device 10 receives power transmission from the engine side and rotates relative to it during normal travel. When driving to receive power transmission from the engine side in FIG. 3A, the cam surface 16 moves relative to the left as shown by the arrow as a relative rotation surface when the rotor 18 side is fixed.

  In response to such rotation of the cam surface 16 during driving, the piston 28 on the rotor 18 side moves differently on the slope 60 on the right side of the cam crest 58 and the slope 62 on the left side. First, the piston 28 in contact with the right inclined surface 60 moves down the inclined surface 60 of the cam crest 58 by the leftward movement (actual rotation) of the cam surface 16 during driving, and the piston chamber 26 is in the suction process. It becomes.

  Since the second orifice 42 having a large opening cross-sectional area is formed in the opening groove 38 provided opposite to the inclined surface 60 of the cam crest 58, the oil passes through the second orifice 42 from the low pressure side to the piston chamber 26. Inhaled. In the second orifice 42 of FIG. 3A, the thickness of the opening cross-sectional area is represented by the thickness of the arrow line.

  On the other hand, the piston 28 in contact with the slope 62 on the left side of the cam crest 58 is pushed up by the movement (rotation) of the cam surface 16 during driving, and the piston 28 is in the discharge process. Therefore, the oil from the piston chamber 26 is discharged to the low pressure chamber through the first orifice 40 having a small opening cross-sectional area by pushing up the piston 28.

  FIG. 4A shows an opening groove when the housing is fixed and the rotor side is rotated and the rotor rotation direction is shown as counterclockwise with respect to the relative rotation of the housing and the rotor during driving, as in FIG. 38 shows a discharge process and a suction process in FIG.

  Here, the position of the suction slit 56 corresponds to the position of the cam valley 59 in FIG. 3A, and the position rotated 45 ° therebetween becomes the position of the cam peak 58, and the process from the cam peak toward the cam valley is the suction. The process, the process from the cam valley to the cam peak is the discharge process.

  In FIG. 4A, during driving, pistons 28 at positions corresponding to every other open groove 38 indicated by diagonal lines are in the discharge process, and pistons 28 at positions corresponding to open grooves 38 indicated by blank spaces between them are sucked. In the process, the second orifice 42 having a large opening cross-sectional area is a suction process, and the first orifice 40 having a small opening cross-sectional area is a discharging process.

  Therefore, in the hydraulic power transmission device 10 according to the present invention at the time of driving, the oil discharged by the discharge process of the piston 28 flows into the piston chamber 26 due to the flow resistance when flowing through the first orifice 40 having a small opening cross-sectional area. A high pressure is generated, thereby generating a drive torque.

  FIG. 3B shows the movement of the piston by the relative rotation between the cam surface 16 and the rotor during coasting that receives power transmission from the wheel side due to sudden braking, with the rotor side fixed and the cam surface 16 side rotating. Represents.

  At the time of sudden braking in which the ABS is operated, the rotation direction of the cam surface 16 is opposite to the direction of the drive shown in FIG. For this reason, the piston 28 is pushed up by the slope 60 on the right side of the cam crest 58 and the discharge process is performed. On the other hand, the piston 28 that contacts the slope 62 on the left side of the cam crest 58 returns to the suction process.

  For this reason, during coasting, the discharge oil from the piston chamber 26 of the piston 28 which is a discharge process by the inclined surface 60 of the cam crest 58 flows into the low pressure chamber through the second orifice 42 having a large opening cross-sectional area. Since the opening cross-sectional area of the two orifices 42 is larger than the first orifice 40, the coast torque generated at this time is smaller than that during the driving shown in FIG.

  Here, the torque generated in the hydraulic power transmission device 10 of the present invention is proportional to the square of the flow rate flowing through the orifice, so that the flow rate of the second orifice 42 is halved relative to the flow rate of the first orifice 40. If the opening cross-sectional area is set in this way, the coast torque can be reduced to a quarter of the drive torque.

  FIG. 4B shows the opening groove 38 of the second orifice 42, which is a discharge process, with diagonal lines in the state in which the relative rotation of the housing and the rotor during coasting is shown in the rotor rotation direction with the housing fixed.

  As shown in FIG. 3B, the piston 28 process from the cam valley 59 toward the cam peak 58 is a discharge process with respect to the clockwise rotation direction of the rotor by the relative rotation at the time of coasting in FIG. A high pressure is generated in the piston chamber 26 due to the flow resistance when the oil discharged from the piston 28 flows through the second orifice 42 having a large opening cross-sectional area located at, and a torque proportional to the square of the flow rate at this time is generated. .

  FIG. 5 is a graph showing the relationship of torque T to rotational speed difference ΔN during driving and coasting in the hydraulic power transmission device of the present invention. In FIG. 5, a characteristic curve 64 is a characteristic of drive torque in a drive using the first orifice having a small opening cross-sectional area, and a sufficiently large torque T is generated with respect to an increase in the rotational speed difference ΔN.

  On the other hand, a characteristic curve 66 is a characteristic of coast torque generated by the flow rate flowing through the second orifice 42 having a large opening cross-sectional area used at the time of sudden braking when the ABS is operated. The value is suppressed to a sufficiently small generated torque with respect to the characteristic curve 64 in the case of the first orifice 40.

  For this reason, during sudden braking when the ABS operates, the coast torque determined by the characteristic curve 66 of FIG. 5 is generated by the flow rate flowing through the second orifice 42 having a large opening cross-sectional area, and the generated coast torque is small. When controlling the wheel speed by adjusting the brake fluid pressure so as to maintain an ideal slip ratio, for example, 90%, with respect to the pseudo vehicle speed generated by the ABS based on the wheel speed, the hydraulic power transmission device of the present invention It is possible to avoid as much as possible that the wheel speed controlled by the ABS due to the generation of the coasting torque interferes with the ABS as the same wheel speed.

  In the present invention, the structure for suppressing the torque generated during sudden braking when the ABS operates is a simple configuration in which the opening cross-sectional area of the orifice provided in the washer member 36 for flowing the oil discharged from the piston chamber to the low pressure side is increased. Compared to the case of switching from four-wheel drive to two-wheel drive during sudden braking by conventional electrical control, the structure is extremely simple, and as a result, a mechanism that avoids interference with ABS is provided. However, the configuration of the apparatus is simple, can be reduced in size and weight, and can be realized at low cost.

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

Sectional drawing which showed one Embodiment of this invention AA sectional view of FIG. Explanatory drawing of the positional relationship between the discharge and suction steps and the first and second orifices with respect to the movement of the cam surface relative to the relative rotation as seen when the rotor is fixed during driving and coasting Explanatory drawing of the positional relationship between the discharge and suction steps of the opening groove with respect to the rotor rotation and the first and second orifices when the housing is fixed while driving and coasting The graph which showed the torque characteristic with respect to the rotational speed difference by this invention Illustration of a four-wheel drive vehicle equipped with a hydraulic power transmission device Graph showing torque characteristics against rotational speed difference with conventional devices

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 26: Piston chamber 28: Piston 30: Ball 32: Return spring 34 : Communication hole (suction / discharge path)
36: washer member 38: opening groove 40: first orifice 42: second orifice 44: lock pin 46: accumulator chamber 48: accumulator piston 50: temperature switch 52, 54: seal 56: suction slit 58: cam crest 59: cam Valley 60, 62: Slope

Claims (3)

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 rotor provided with a communication path for suction and discharge in
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,
An annular groove and a valley of the cam crest, which are arranged in an arcuate shape at a position opposite to the slope of each cam crest, arranged fixed to the housing on the opening end face side of the communication passage formed in each piston chamber of the rotor. with a separate suction groove communicating with the outside of the low-pressure chamber in a position relative separation formed to open the communicating passage section, to form an orifice as flow resistance generating means communicating with said low pressure chamber to the annular groove A washer member;
A hydraulic power transmission device that transmits torque according to a rotational speed difference between the first shaft and the second shaft;
When a drive torque corresponding to a rotational speed difference due to a positive relative rotation between the first shaft and the second shaft is generated in response to power transmission from the engine side, the piston becomes a discharging step. The opening cross-sectional area of the plurality of first orifices formed in the washer member relative to one slope of the cam crest is set to a predetermined value,
The cam serving as a discharge step of each piston when receiving a power transmission from the wheel side and generating a coast torque according to a rotational speed difference caused by a reverse relative rotation between the first shaft and the second shaft. A hydraulic power transmission device, wherein an opening cross-sectional area of a plurality of second orifices formed in the washer member relative to the other slope of the mountain is set larger than the predetermined value. 2. The hydraulic power transmission device according to claim 1, wherein the first orifice and the second orifice are alternately formed in arcuate grooves formed separately in a circumferential direction of the washer member. Hydraulic power transmission device.
2. The hydraulic power transmission device according to claim 1, wherein when the drive torque is generated, the first orifice is a discharge port and the second orifice is a suction port, and when the coast torque is generated, the first orifice is reversed. A hydraulic power transmission device, characterized in that it is a suction port and the second orifice is a discharge port.

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