JPH08159237A - Rotary swash plate type axial piston pump and four-wheel drive vehicle using this pump - Google Patents

Abstract

PURPOSE: To provide a rotary swash plate type axial piston pump which is constituted to increase the allowable number of revolutions with an additional margin being not low and without increasing the size of a pump. CONSTITUTION: In a rotary swash plate type axial piston pump, each piston chamber 26 and a pressure chamber 30 on the piston side intercommunicate through a pressure introduction passage 29 on the piston side and a pressure introduction passage 31 on the shoe side. A plurality of pressure introduction passages 22 on the swash plate side individually extending from a position making slide contact with a shoe 28 for a piston to the back are formed in a rotary swash plate 23. The opening parts on the swash plate back side of the pressure introduction passages 32 on the swash plate side communicate with respective pressure chambers 33 on the swash plate side which are independent of each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary swash plate type axial piston pump which can be driven at high speed and a four-wheel drive vehicle using the piston pump.

[0002]

2. Description of the Related Art As a conventional rotary swash plate type axial piston pump, see, for example, "Theory and Practice of Piston Pumps and Motors" by Sadao Ishihara, published by Ohmsha Publishing Co., Ltd. (published May 20, 1979). Some are listed on page 91. As shown in FIG. 7, a rotary shaft 61 is rotatably supported by a pump housing 60, and a rotary swash plate 62 is coaxially fixed to the rotary shaft 61. The rotary swash plate 62 is housed in the housing 60, and the tips of the plurality of pistons 63 slidably contact the inclined surface 62 a of the rotary swash plate 62 via the piston shoes 64. The plurality of pistons 63 are arranged at equal intervals along the circumferential direction of the rotary swash plate 62, and are arranged so as to be capable of reciprocating in respective cylinder holes formed in the housing 60.

Each piston 63 is biased toward the rotary swash plate 62 by a spring and has a swash hole 65a at the tip thereof.
An oil passage 65 is formed in each piston 63 for sucking the working oil into each piston chamber 70 in the cylinder hole. A suction ball check valve 66 is inserted in the middle of the oil passage 65 to prevent backflow from the piston chamber 70 to the oblique hole,
Further, the piston chamber 70 is provided with the discharge ball check valve 6
7 to the discharge port 68.

The piston 63 and the swash plate are respectively provided between the inclined surface 62a of the rotary swash plate 62 and the piston shoe 64, and between the rear surface facing the inclined surface 62a and the inner wall surface of the housing 60. A thrust bearing 69 for supporting an axial load applied to 62 is provided. In the figure, 71 is an annular metal that receives the thrust bearing 69. Further, reference numeral 74 denotes an intake port through which hydraulic oil flows into the pump.

When the rotary swash plate 62 rotates in conjunction with the rotation of the rotary shaft 61, each piston 63 reciprocates while being regulated by the rotary swash plate 62. That is, when each piston 63 moves forward by the urging force of the spring 72,
When the working oil is sucked into the piston chamber 70 through the oil passage 65 and the suction ball check valve 66, and then is pushed back by the inclined surface 62a of the rotary swash plate 62 and moves backward, the operation inside the piston chamber 70 is performed. Oil is discharged through the discharge ball check valve 67. This is performed every time the rotating swash plate 62 makes one rotation.

When the piston 63 moves backward, the hydraulic oil in the piston chamber 70 is compressed, and the pressure is transmitted to the rotary swash plate 62 side through the piston 63 and the piston shoe 64. Of the load input to the swash plate 62, the radial load is supported by a radial bearing 73 provided on the rotary shaft 61 integrated with the rotary swash plate 62, and the axial load is arranged on the rear side of the swash plate 62. Supported by the thrust bearing 69.

[0007]

In the rotary swash plate type axial piston pump, the axial load becomes very large as the load increases, but in the conventional pump described above, the thrust bearing 69 supports the axial load. Therefore, the larger the axial load to be supported, that is, the higher the pressure generated in each piston chamber 70 is set, it is necessary to use a large-sized bearing as the thrust bearing 69. Causes the total length of the pump itself in the axial direction to be lengthened. Further, since the thrust bearing 69 has a low allowable rotation speed, the pump cannot be rotated at a high speed, and in order to cope with this, it is necessary to increase the specific discharge capacity by the lower rotation speed to earn a flow rate. , This leads to an increase in the size of the pump.

Such a pump having a low allowable rotation speed and a large size is difficult to be applied to an automobile or the like having severe layout restrictions and a high rotation speed. At this time, conventionally, as described in Japanese Utility Model Laid-Open No. 2-96483, a bearing shoe is provided in an annular shape along the circumferential direction of the swash plate on the back side of the rotary swash plate, and each piston chamber is provided. Pressure is introduced into the bearing shoe through a pressure introducing passage provided in the housing, and the axial load is supported by the pressure, and there is a type that corresponds to high-speed rotation of the rotating swash plate. Since it is necessary to form a plurality of pressure introducing passages, it is necessary to robustly form the housing, and there is a problem that the machining cost is increased because the pressure chambers are formed on the entire circumference corresponding to the bearing shoes.

The present invention has been made by paying attention to the above-mentioned problems, and a rotary swash plate type axial piston pump having a high permissible rotational speed with a small machining cost and without increasing the size of the pump, The purpose is to provide a four-wheel drive vehicle using the pump.

[0010]

In order to achieve the above object, a rotary swash plate type axial piston pump of the present invention comprises:
The swash plate that rotates together with the rotary shaft and the slanted surface of the swash plate are slidably pressed through the piston shoes to respond to the rotation of the swash plate in the fixed cylinder hole. In a rotary swash plate type axial piston pump equipped with a plurality of pistons that stroke each other, a piston-side pressure introduction path that is provided in each piston and that can introduce the pressure of each piston chamber to the corresponding piston shoe position, and the piston The piston-side pressure chamber is formed of a concave portion formed in the sliding contact surface of each piston shoe with the swash plate and communicates with the side pressure introduction passage, and the concave portion is provided in the back surface facing the inclined surface of the swash plate. A swash plate side pressure chamber, and a swash plate side pressure introducing passage that is provided in the swash plate and connects the piston shoe sliding surface position of the swash plate and the swash plate side pressure chamber. There.

At this time, as described in claim 2, it is preferable that the swash plate side pressure chamber and the swash plate side pressure introducing passage are formed of a plurality of independent sets. Also,
A four-wheel drive vehicle according to the present invention includes a drive axle driven by a main motor, a fluid pressure supply unit having a fluid pressure pump that rotates in association with the drive axle and discharges a working fluid, and a driven wheel axle. Fluid pressure drive means having a fluid pressure motor that rotates in conjunction with each other, a first flow path that connects the discharge port of the fluid pressure supply means and the suction port of the fluid pressure drive means, and the suction port of the fluid pressure supply means In a four-wheel drive vehicle including a second flow path that communicates with the discharge port of the fluid pressure drive means, the fluid pressure pump of the fluid pressure supply means may be provided with the fluid pressure pump.
The rotary swash plate type axial piston pump described in 1) is adopted.

[0012]

With the above-described structure, in the invention described in claim 1 of the present invention, the pressure in each piston chamber is introduced into the piston side pressure chamber via the piston side pressure introducing passage provided in each piston. It As a result, a pressure corresponding to the pressure in the piston chamber is generated between the inclined surface of the swash plate and the piston shoe, and the sliding resistance between the two decreases in proportion to the pressure.

Further, since the piston side pressure chamber can face the opening on the inclined surface side of the swash plate side pressure introducing passage, the pressure introduced into the piston side pressure chamber is the swash plate side pressure. It can be introduced into the pressure chamber on the swash plate side through the introduction passage. Thereby, the pressure corresponding to the pressure of each piston chamber is introduced into the swash plate side pressure chamber, and the sliding resistance between the back surface of the swash plate and the housing inner wall surface facing the back surface is introduced. The sliding resistance between the two decreases in proportion to the applied pressure.

Therefore, when the rotary shaft of the pump or the swash plate rotates at high speed or the load of the pump increases, the pressure in each piston chamber rises, and the axial load transmitted to the swash plate via the piston increases. Follows the increase in pressure in the piston chamber, between the inclined surface of the swash plate and the piston shoe,
Also, the sliding resistance between the back surface of the swash plate and the inner wall of the housing becomes smaller according to the pressure in the piston chamber.

As described above, even if the axial load input to the swash plate becomes large due to the high speed rotation of the swash plate, the pressure proportional to the axial load is generated between the inclined surface of the swash plate and the piston shoe. , And between the back surface of the swash plate and the inner wall of the housing, the axial load can be supported while reducing the sliding resistance due to the rotation of the swash plate. Next, the invention described in claim 2 of the present invention is such that each swash plate side pressure chamber communicating with the swash plate side pressure introducing passage facing the piston side pressure chamber surely generates a desired pressure. The swash plate-side pressure chambers that communicate with the plate-side pressure introduction passages are individually provided.

This makes it possible to always introduce a predetermined pressure corresponding to the input axial load to the back pressure side of the swash plate. In addition, the invention described in claim 3 of the present invention has a high permissible rotational speed by the rotary swash plate type axial piston pump of claim 1 or 2 described above, and
Since it can be used under high load, pressure proportional to the axial load, such as when the drive wheel rotates at high speed, causes pressure between the inclined surface of the swash plate and the piston shoe, and between the back surface of the swash plate and the inner wall of the housing. Occurs, which reduces the sliding resistance due to the rotation of the swash plate.

[0017]

First, an embodiment of a rotary swash plate type axial piston pump according to the present invention will be described with reference to the drawings.
As shown in FIG. 1, the pump has a structure in which a rotary shaft 21 is rotatably supported by a pump housing 20 via a radial bearing 22. A rotary swash plate 23 is coaxially and integrally fixed to the rotary shaft 21. The rotary swash plate 23 is rotatably housed in the pump housing 20. On the inclined surface 23a side of the rotary swash plate 23, a plurality of pistons 24 are arranged at predetermined intervals along the circumferential direction of the swash plate 23 with their axes parallel to the rotary shaft 21. It is set up.

Each piston 24 is inserted into each cylinder hole 25 formed in the pump housing 20, and is restrained by the cylinder hole 25 so as to be reciprocally movable only in the axial direction. The piston 24 in the cylinder hole 25
The rear end side position constitutes a piston chamber 26. As shown in FIG. 2, a bottomed hole 24a extending in the axial direction is provided at the rear end portion of the piston 24, and a spring member 27 is provided in the bottomed hole 24a and the piston chamber 26. Each piston 24 is biased toward the swash plate 23 side by the spring member 27. The tip of the piston 24 is slidably pressed against the inclined surface 23a of the swash plate 23 via the piston shoes 28.

Each piston 24 has a piston chamber 26
A piston side pressure introducing passage 29 is formed axially penetrating from the bottom surface of the bottomed hole 24a toward the piston shoe 28. Further, a concave piston-side pressure chamber 30 is formed at a position of the piston shoe 28 that is in sliding contact with the inclined surface 23a of the swash plate 23, and the piston-side pressure chamber 30 and the piston-side pressure introduction The passage 29 communicates with the shoe side pressure introduction passage 31.

Further, as shown in FIGS. 2 and 3, the rotary swash plate 23 has a plurality of swash plate side pressure introducing passages extending individually from the position where it can slidably contact the piston shoe 28 toward the rear surface 23b. 32 is provided. Further, the swash plate rear side opening of each swash plate side pressure introduction passage 32 communicates with the independent swash plate side pressure chamber 33. Each swash plate side pressure chamber 33,
Each of them is composed of a recess formed on the back surface 23b of the rotary swash plate 23. The swash plate side pressure introduction passage 32 and the swash plate side pressure chamber 33 are provided at predetermined intervals along the circumferential direction of the swash plate 23.

The pitch between the swash plate side pressure introducing passages 32 is set smaller than the pitch between the pistons 24, and the inclined surface 23a of the swash plate 23 in each swash plate side pressure introducing passage 32 is set. The side opening area is the piston 24
It is set to be smaller than the working piston side pressure chamber 30.
Furthermore, the inclined surfaces 23 of the plurality of swash plate side pressure introduction passages 32
The a-side opening position is provided only on the inclined surface 23a of the swash plate 23 where the piston 24 retracts.

A ring-shaped metal 34 is fixed to the inner wall of the pump housing 20 facing the back surface 23b of the swash plate 23 at a position facing the swash plate side pressure chamber 33. The rear surface 23b of the metal plate 23 is adapted to slide on the metal 34. The piston chambers 26 communicate with the inlet / outlet ports 35 provided in the piston housing 20, respectively. Each inlet / outlet port 35 is connected to the tank 36 by the suction side pipe 3
7 and a discharge side pipe 38 connected to a predetermined hydraulic fluid supply unit 39. A check valve 40 for suction is inserted in each branch pipe 37a to each inlet / outlet port 35 in the inlet side pipe 37 to prevent backflow from the inlet / outlet port 35 to the main side of the inlet side pipe 37. Has been done.

Similarly, check valves 41 for discharge are respectively inserted in the branch pipes 38a to the respective inlet / outlet ports 35 in the discharge side pipe 38, so that the inlet / outlet ports are connected from the main side of the discharge side pipe 38. Backflow to 35 is prevented. In addition,
In FIG. 1, 43 is an oil seal. Also, 44
Is a passage for discharging hydraulic oil and is connected to the tank 36.

Next, the operation of the rotary swash plate type axial piston pump having the above construction will be described. The rotating shaft 21
When the rotating swash plate 23 is rotated, the integrated rotating swash plate 23 rotates at the same number of rotations, and each piston 24 starts reciprocating motion in response to the rotation of the rotating swash plate 23. Then, each piston 24 advances to the swash plate 23 side every time the rotary swash plate 23 makes one rotation, so that the working fluid is transferred from the suction side pipe 37 to the piston chamber 26 through the suction check valve 40. The piston is sucked, continuously pushed by the swash plate 23 and retracted from the swash plate 23, so that the hydraulic fluid in the piston chamber 26 is compressed and the pressure in the piston chamber 26 becomes equal to or higher than a predetermined value. The hydraulic fluid in the chamber 26 is discharged to the discharge side pipe 38 via the check valve 41 for discharge and supplies the hydraulic fluid to a predetermined hydraulic fluid supply section 39.

At this time, when the pressure in the discharge side pipe 38 is low and the pump is almost unloaded, the piston 2
The pressure in each piston chamber 26 when 4 is retracted is not so high. That is, since the reaction force transmitted to the swash plate 23 side via the piston 24 is small, the axial load transmitted to the swash plate 23 is small. In this state, each piston side pressure chamber 30 is passed through each pressure introducing passage 29, 31, 32.
Since the pressure introduced into the swash plate side pressure chamber 33 is small,
The swash plate 23 rotates in a state of sliding contact with the annular metal 34, but since the axial load is also small, the sliding resistance received by the rotary swash plate 23 is small.

Further, when the load of the pump becomes high such as the pressure in the discharge side pipe 38 becomes high, the pressure in each piston chamber 26 rises individually when each piston 24 retracts, and the reaction force proportional to the pressure. Is transmitted to the swash plate 23 side through the piston 24. At this time, since the pressure in the piston chamber 26 is always introduced into the piston side pressure chamber 30 via the piston side pressure introducing passage 29, when the pressure rises in the piston chamber 26, the piston follows the piston side pressure chamber 30. The pressure in the side pressure chamber 30 also rises, and the sliding resistance between the shoe 28 and the inclined surface 23a of the swash plate 23 is reduced by an amount corresponding to the pressure.

Further, the piston-side pressure chamber 30 has the swash plate 2
3, the pressure of the piston side pressure chamber 30 is introduced into the swash plate side pressure chamber 33 via the swash plate side pressure introduction passage 32. The pressure also rises in the swash plate side pressure chamber 33, and the sliding resistance between the back surface 23b of the swash plate 23 and the metal 34 (the inner wall surface of the pump housing 20) is reduced.

As a result, of the loads transmitted to the swash plate 23 side via the piston 24, for the axial load, a pressure corresponding to the axial load is introduced into the swash plate side pressure chamber 33. As a result, a predetermined pressure is generated in the swash plate side pressure chamber 33, thereby supporting the axial load. That is, fluid bearings capable of generating pressure according to the load input to the swash plate 23 are formed between the swash plate 23 and the piston 24 shoe 28 and between the swash plate 23 and the metal 34. This enables the pump to be used under high load and high rotation.

Of the loads transmitted to the swash plate 23 side via the piston 24, the radial load is transmitted from the swash plate 23 to the rotary shaft 21 and supported by the radial bearing 22. However, the contribution of the pressure increase in the piston chamber 26 to the radial load is small. Further, in order to introduce the pressure of the piston chamber 26 into the swash plate side pressure chamber 33, the piston side pressure chamber 30 needs to face the opening of the swash plate side pressure introduction passage 32. On the piston 2
By setting the pitch between the swash plate side pressure introduction passages 32 smaller than the pitch between the four, the time interval in which the shoe side piston side pressure chamber 30 does not face the swash plate side pressure introduction passage 32 is shortened. ing. Further, as described above, following the rotation of the rotary swash plate, the piston side pressure chamber of each piston shoe intermittently opposes the opening of each swash plate side pressure introduction passage. By appropriately adjusting the pitch of the openings of the pressure introducing passages, it is possible to always set some of the openings of the swash plate side pressure introducing passages so as to be able to face the piston side pressure chambers, so there is no problem.

Further, it is the position of the inclined surface 23a of the swash plate 23 facing the backward direction of the piston 24 that a load larger than a predetermined load is applied via the piston 24. There is no problem as long as the swash plate side pressure introduction passage 32 and the swash plate side pressure chamber 33 are provided only in the portion.
Here, for example, in the case where only one swash plate side pressure chamber is provided on the back side of the swash plate and a plurality of swash plate side pressure introducing passages are connected to the one swash plate side pressure chamber, the plurality of Even if a predetermined pressure is introduced with the piston side pressure chamber facing some of the swash plate side pressure chambers, the pressure leaks from the swash plate side pressure introduction path that does not face the piston side pressure chamber, A desired pressure may not be generated in the swash plate side pressure chamber.

However, in this embodiment, since the swash plate side pressure introducing passages 32 and the swash plate side pressure chambers 33 are independent, the pressure introduced into one swash plate side pressure chamber 33 is different from the other pressure. It does not escape through the swash plate side pressure introduction passage 32. in this way,
Between the swash plate 23 and the piston 24 shoe 28, and the swash plate 2
A fluid bearing which can be supported by a pressure corresponding to a load input to the swash plate 23 is formed between the metal plate 3 and the metal 34. This eliminates the need for a thrust bearing for receiving an axial load input to the rotary swash plate 23, and employs a fluid bearing capable of generating a supporting pressure according to the load, so that the rotational speed of the pump used. Even if is set to a high value, it is possible to prevent the pump from increasing in size.

Further, since the pressure introducing passage for introducing pressure to the fluid bearing is not provided in the pump housing 20,
It is not necessary to make the pump housing 20 more robust than before. In addition, since the pressure introducing paths 29, 31, 32 for introducing the pressure are also configured with the shortest distance,
The processing cost is also small. In the above embodiment, the swash plate side pressure introducing passages 32 and the swash plate side pressure chambers 33 are made to correspond to each other in a one-to-one manner, but a plurality of swash plate side pressure introducing passages 32 are provided. It may have a one-to-many configuration in which the plate-side pressure chambers 33 communicate with each other. However, as described above, only one swash plate side pressure introducing passage 32 is connected to one swash plate side pressure chamber 33.

The working fluid leaking from each swash plate pressure introducing passage 32 is returned to the tank 36 side through the passage 44.
Next, an embodiment will be described in which the rotary swash plate type axial pump is applied to a fluid pressure pump in a four-wheel drive vehicle based on a front wheel drive vehicle. FIG. 4 is a schematic configuration diagram. In the figure, 1 is an engine as a main prime mover, and the rotational driving force of the engine 1 is input to a front wheel side differential device 3 via a transmission 2, and an output side of the differential device 3 serves as a drive axle. A front wheel 5 is connected via a front axle 4 of the.

The front wheel side differential device 3 is rotationally driven by a ring gear 3b formed in a differential gear case 3a being meshed with a gear 2a connected to the output side of the transmission 2. A pinion 3d is attached to a pair of pinion shafts 3c formed in the differential gear case 3a, a pair of side gears 3e meshes with these pinion 3d, and the front axle 4 is connected to these side gears 3e.

Further, the differential gear case 3a
A second ring gear 3f is formed in parallel with the ring gear 3b. The second ring gear 3f is connected to the rotary shaft 6a of the fluid pressure pump 6 that constitutes the drive side fluid pressure drive means via a gear 3g that meshes with the second ring gear 3f.
The fluid pressure pump 6 is a rotary swash plate type axial piston pump having the above-described configuration, in which suction side pipes connected to respective inlet / outlet ports are connected to a strainer 7a arranged in a reservoir tank 7. With the second
It is connected to the tank port T of the electromagnetic directional control valve 9 for forward / backward switching through a low pressure pipe 8L forming a flow path. In addition, the discharge side pipe connected to each of the inlet / outlet ports is the first
It is connected to the pump port P of the electromagnetic directional control valve 9 for forward / backward switching through a high pressure pipe 8H forming a flow path.

In the following description, as components of the rotary swash plate type axial piston pump as the fluid pressure pump of the present embodiment, the members not shown in FIG. 4 are the corresponding members of the pump used in the above description. Description will be given by attaching the same reference numerals as the attached reference numerals. Here, in the rotary swash plate type axial piston pump 6, the suction side and the discharge side are not interchanged depending on the rotation direction of the rotary shaft 6a, as can be seen from the above-described structure and operation. The discharge flow rate is proportional to the increase in the vehicle speed until the vehicle speed reaches a set vehicle speed higher than the vehicle speed at which the maximum transmission torque starts to decrease, as indicated by a solid line S ₁ in FIG. 5, for example. Is set at a maximum discharge flow rate above a set vehicle speed that does not require a four-wheel drive state.

The electromagnetic directional control valve 9 for switching between forward and backward movement is
The input / output port A is connected to the inflow port 10a of the swash plate type variable displacement motor 10 as a fluid pressure motor described later, and the input / output port B is the outflow port 1 of the swash plate type variable displacement motor 10.
0b. When the solenoid 9a is in the non-energized normal position, the pump port P communicates with the input / output port A and the tank port T communicates with the input / output port B, and the solenoid 9a connects the pump port P at the offset position in the energized state. The input / output port B and the tank port T are connected to the input / output port A, respectively.

That is, at the normal position, the high-pressure oil in the high-pressure pipe 8H is fed to the inflow port 10a of the swash plate type variable displacement motor 10.
The low-pressure pipe 8L is connected to the outflow port 10b so that the rotary shaft 1
0c is rotationally driven in the rotational direction during forward traveling. Conversely, at the offset position, the high-pressure oil in the high-pressure pipe 8H is fed to the variable displacement motor 1
The low-pressure pipe 8L is connected to the outflow port 10a of 0 (inflow port when moving forward) and the inflow port 10b (outflow port when moving forward) a.
The rotary shaft 10c is driven to rotate in the direction of rotation during reverse travel.

The electromagnetic directional control valve 9 is built in a swash plate type variable displacement motor 10, which will be described later, and the output port A,
B is the variable displacement motor 10 without passing through each pipe.
Are connected to the inflow / outflow ports 10a and 10b. Further, the energization of the solenoid 9a of the electromagnetic directional control valve 9 is connected to the DC power source 9c via a shift position detection switch 9b which is turned on only when the solenoid 9a is selected to be reverse by a shift lever (not shown). As a result, it is controlled to be in a non-energized state when traveling forward and to be energized when traveling backward.

As shown in FIG. 6, the swash plate type variable displacement motor 10 has a rotating shaft 10c with respect to the motor housing 100.
Are rotatably supported by bearings 111. A cylindrical cylinder block 101 disposed in the housing 100 is coaxially fitted to the rotary shaft 10c by serration. In the cylinder block 101, a plurality of pistons 102 are arranged at equal intervals along the rotation direction of the cylinder block 101. Each piston 102 is slidably supported by the cylinder block 101 in a direction parallel to the axis of the cylinder block 101.

A swash plate 103 is arranged in the housing 100 at a position facing the right end surface of the cylinder block 101. The swash plate 103 includes a disc portion 103a,
A protruding portion 103b protruding from the upper end of the disc portion 103a
And an inclination angle thereof is swingable around a predetermined swing axis P. The swing shaft P is a rotary shaft 10c.
Is offset by a predetermined amount ε in the direction in which the swash plate 103 approaches the facing surface of the cylinder block 101.

A shoe 108, which is capped at the right end of each piston 102, is slidably brought into contact with the facing surface of the swash plate 103 by a shoe holder 109. This shoe holder 109
Are pressed against the swash plate 103 side via the needle 112 by the pressing spring 110 arranged on the inner peripheral surface of the cylinder block 101. Further, the swash plate 103 is biased by the biasing means 113 in the direction in which the inclination angle is reduced. The urging means 113 is used for the protrusion 10 of the swash plate 103.
The protrusion 103 of the swash plate 103 is brought into contact with the left end face of 3b.
b is arranged in the fluid pressure chamber 113b of the cylinder device having a control piston 113a as a main body, which is capable of pressing the swash plate 103 in the right direction, that is, in the direction of reducing the inclination angle of the swash plate 103.
The spring member 113c that can be biased to the 3 side and the fluid pressure chamber 11
A communication pipe 113d that connects 3b to a low pressure portion in the swash plate type variable displacement motor 10, for example, the low pressure pipe 8L side or opens to the atmosphere, and an orifice 113e that is a throttle interposed in the middle of the communication pipe 113d. , And the control piston 113a is biased toward the swash plate 103 side by the elastic force of the spring member 113c. The cylinder tube body of the cylinder device is formed by a part of the pump housing 100.

Further, a stopper 114 projects from the inner surface of the pump housing 100 toward the swash plate 103, and when the swash plate 103 has a predetermined inclination angle, that is, a set maximum inclination angle, the stopper 114 is provided. The swash plate 103 is contacted with the swash plate 103 to regulate the inclination of the swash plate 103. The stopper 114
May be composed of a screw member or the like so that the amount of protrusion to the swash plate 103 can be adjusted.

On the other hand, a valve plate 115 fixed to the housing 100 is provided on the left end surface of the cylinder block 101.
Are in sliding contact with each other, and the valve plate 115 and each piston 1
A communication hole 117 is formed between the bore 116 that houses 02. As shown in FIG. 3, in the valve plate 115, an inflow port 10a (outgoing port at the time of reverse travel) is provided in the left half and an outflow port 10b (incoming port at the time of reverse travel) in the right half along the movement trajectory of the communication hole 117. Are formed.

The maximum specific discharge amount of the swash plate type variable displacement motor 10 (the specific discharge amount when the swash plate 103 has the maximum inclination angle) is larger than the specific discharge amount of the piston pump 6. Is set. Further, the suction port 6b of the rotary swash plate type axial piston pump 6 described above.
A relief valve 11 that determines the upper limit of the discharge pressure of the piston pump 6 as a torque limiting unit is interposed between the discharge port 6c and the discharge port 6c. Further, the piston pump 6 and the electromagnetic switching valve 9
Between the high-pressure pipe 8H and the low-pressure pipe 8L are communicated with each other by the communication pipe 12, and with respect to the communication pipe 12,
A check valve 13 that allows the flow of fluid from the low-pressure pipe 8L side to the high-pressure pipe 8H side is provided, and with respect to the second communication pipe 14 arranged in parallel with the communication pipe 12,
A fixed orifice 15 is connected in parallel with the check valve 13.

On the other hand, a gear 16 is attached to the rotary shaft 10c of the swash plate type variable displacement motor 10, and the differential gear case 17 of the rear wheel side differential device 17 is attached to the gear 16.
The ring gear 17b formed on a is meshed. The rear wheel side differential device 17 has substantially the same configuration as the front wheel side differential device 3 described above, and is different from the differential gear case 1 in FIG.
A pair of pinion shafts 17c is formed in 7a, and a pair of side gears 17e meshes with the pinion 17d attached to the pair of pinion shafts 17c. A rear axle 18 is connected to the side gears 17e, and a rear wheel 19 is connected to the rear axle 18.

Next, the operation of the above embodiment will be described. now,
When the vehicle stops on a high friction coefficient road such as a dry road surface and starts forward traveling from the braking state in which the engine 1 is in the idling state, the vehicle can be started by switching the shift lever (not shown) to the forward traveling state. Can be At this time, since the shift position detection switch 9b on the reverse traveling side is maintained in the off state, the solenoid 9a of the forward / reverse switching electromagnetic direction switching valve 9 is maintained in the non-energized state.
The switching position holds the normal position shown in FIG.

In this state, by releasing the brake pedal and stepping on the accelerator pedal, the rotational force of the engine 1 is transmitted to the front wheel side differential device 3 via the transmission 2 and the front wheel side differential device 3 is operated. The forward movement of the vehicle is started by rotationally driving the front wheels 5 in the forward direction. Then, in the rotary swash plate type axial piston pump 6, when the rotary shaft 6c is rotationally driven, the rotary swash plate 23, which is integrated with the rotary shaft 6c, moves from the state in which the rotational speed is zero to the rotary shaft 6c. Following the rotation, the rotation speed becomes a speed corresponding to the speed of the vehicle, and the piston pump 6 discharges the hydraulic fluid at a discharge flow rate corresponding to the rotation speed. At this time, the load from each piston 24 to the rotary swash plate 23 increases as the rotation speed increases, but as described above, the load between the rotary swash plate 23 and the piston shoe 28 increases as the load increases. Rotating swash plate 2
3 and the metal 34 (inner wall of the pump housing 20) each have a smaller sliding resistance according to the load, and the rotating swash plate 23 can rotate at high speed in a low friction state. It can rotate at different rotation speeds.

The discharged hydraulic oil is supplied to the inflow port 10a of the swash plate type variable displacement motor 10 through the high pressure pipe 8H and the forward / reverse switching electromagnetic directional switching valve 9, but the rear wheel 19 is started when the vehicle starts. Is also rotationally driven in the same direction as the front wheels 5 and at the same rotational speed, the rotary shaft 10c of the swash plate type variable displacement motor 10 also rotates via the rear wheel side differential device 17,
As a result, the hydraulic oil is sucked and discharged from the inflow port 10a.

At this time, in the swash plate type variable displacement motor 10, the maximum specific discharge amount of the swash plate type variable displacement motor 10 in the state where the swash plate 103 has the maximum inclination angle is V,
When the rotation speed of the rotary shaft 10c of the swash plate variable displacement motor 10, that is, the rotation speed of the driven axle is N _R , the maximum discharge amount per unit time in the swash plate variable displacement motor 10 is V × N _R. It is shown and increases in proportion to the rotational speed of the driven axle 18. On the other hand, the discharge amount from the piston pump 6, that is, the inflow flow rate Q supplied to the swash plate type variable displacement motor 10 is also the speed of the rotating shaft 6a, that is, the rotating speed N of the drive axle.
It is an amount proportional to _F.

Since the maximum specific discharge amount of the swash plate type variable displacement motor 10 is set larger than the specific discharge amount of the piston pump 6, the front wheel 5 and the rear wheel 19 rotate at substantially the same number of revolutions. In this state, Q <V × N _R. Therefore, since the swash plate 103 has an inclination angle smaller than the maximum inclination angle, the swash plate 103 is not in contact with the stopper 114 and is in a swingable state.

Therefore, the swash plate 103 is automatically adjusted to have an inclination corresponding to the flow rate of the supplied hydraulic oil, and the swash plate type variable displacement motor 10 has a flow rate substantially equal to the inflow rate supplied from the piston pump 6. Discharge. That is, in the above state, when the inflow flow rate supplied from the piston pump 6 increases in accordance with the vehicle speed as indicated by the broken line S ₂ in FIG. 5, the discharge flow rate from the swash plate type variable displacement motor 10 also follows the figure. 4 Increase as shown by the solid line S ₁ .

As a result, the pressure in the high-pressure pipe 8H does not rise and remains substantially zero, and the swash plate type variable displacement motor 10 does not transmit the driving torque to the driven axle, that is, the rear wheel 19. Therefore, the vehicle is a forward drive vehicle (two-wheel drive vehicle).
Drive forward in the same state as. In this traveling state, since the swash plate type variable displacement motor 10 discharges the same amount as the discharge amount from the piston pump 6, the forced suction does not occur. Therefore, the occurrence of cavitation in the swash plate type variable displacement motor 10 is avoided.

Next, the case of starting on a low friction coefficient road such as an icy road or a snowfall road will be described. As described above, first, the front wheels 5 are rotationally driven, but the front wheels 5, which are the driving wheels, slip due to the low friction coefficient road, so that the rotational speed N _F of the front wheels 5 is the rotational speed N of the rear wheels 19. _The rotation speed becomes higher than that of _R , and a predetermined rotation speed difference occurs between the front wheel 5 and the rear wheel 19.

As a result, the displacement of the piston pump 6 per unit time relatively increases as the front wheel 5 slips, and the swash plate type variable displacement motor 10 follows the displacement.
On the side, the inclination of the swash plate 103 is automatically adjusted so that the same discharge amount is output. Then, the flow rate from the piston pump 6 per unit time exceeds the maximum discharge amount per unit time of the swash plate type variable displacement motor 10.
That is, when Q = V × N _R , the inclination angle of the swash plate 103 of the swash plate type variable displacement motor 10 is regulated by the stopper 114, and the discharge amount is fixed.

In addition, a rotation is made between the front wheel 5 and the rear wheel 19.
When the difference in number of turns becomes large, Q> V × N _RThe state of
The discharge flow rate from the ton pump 6 is the swash plate type variable displacement motor 1
The discharge flow rate of 0 is exceeded, and the resistance of the swash plate type variable displacement motor 10 is increased.
The resistance acts as a load and the operating oil pressure of the high-pressure pipe 8H rises.
That is, in this state, as shown by the broken line in FIG.
Even if the discharge flow rate from the piston pump 6 increases,
Because the rear wheels have different wheel speeds, the swash plate type variable displacement motor 1
The discharge flow rate from 0 is the discharge from the piston pump 6.
It is always lower than the flow rate, and the difference is the load.

Therefore, the swash plate type variable displacement motor 10 is
The driving torque corresponding to the supply pressure from the high-pressure pipe 8H is transmitted to the rear wheels 19 via the rear wheel side differential device 17, and the vehicle travels forward in the same state as the four-wheel drive skew. The torque transmitted to the rear wheel side is generated only when a predetermined rotational speed difference occurs between the front and rear wheels, and rapidly increases as the rotational speed difference increases, and the maximum torque is restricted by the pressure limitation by the relief valve 11. Become. This torque limiting action makes it possible to reduce the strength of the components such as the rear wheel side differential device 17 and the drive shaft as compared with the conventional four-wheel drive vehicle.
It is possible to reduce fuel consumption and cost.

In the four-wheel drive state, the load on the rotary swash plate type piston pump 6 also increases, the pressure in each piston chamber 26 rises, and the load on the rotary swash plate 23 also increases, but as described above, Rotating swash plate 23 and piston shoe 28
The sliding resistance between the rotary swash plate 23 and the metal swash plate 23 (inner wall of the pump housing 20) becomes smaller according to the pressure (load), and the rotary swash plate 23 moves at a high speed in a low friction state. It becomes rotatable and can rotate at a rotational speed according to the rotation of the drive wheel 5.

Further, the rise of the torque is determined by the high pressure pipe 8
The fixed orifice 15 provided in the communication pipe 12 that connects the H and the low pressure pipe 8L manages the amount of leakage from the high pressure pipe 8H to the low pressure pipe 8L, and the characteristics can be set arbitrarily by changing the pressure rise. is there. Since the fixed orifice 15 has a temperature characteristic associated with a change in the viscosity of the hydraulic oil, the leakage amount is reduced at a low temperature and the drive amount is more likely to be generated than at a high temperature. Therefore, the function as a four-wheel drive vehicle is required. It has the advantage that it tends to become a four-wheel drive vehicle in winter when there are many opportunities.

Further, when the slip of the front wheels 5 is reduced and the rotational speed difference between the front wheels 5 and the rear wheels 19 is reduced from the above-mentioned four-wheel drive state, the piston pump 6 supplies the swash plate type variable displacement motor 10 with the discharge. The amount decreases and the above two-wheel drive state is restored. Next, when the vehicle is moved backward, the shift lever is switched to the reverse position to turn on the shift position detection switch 9b, so that the solenoid 9a of the forward-reverse switching electromagnetic directional control valve 9 is energized.
The switching position is switched from the normal position to the offset position, whereby the hydraulic oil in the high-pressure pipe 8H is supplied to the reverse inlet port 10b of the swash plate type variable displacement motor 10 and the hydraulic oil discharged from the backward outlet port 10a flows. Road 12
By returning to the low-pressure pipe 8L side through, the rotating shaft 10c of the swash plate type variable displacement motor 10 is reversed from that during forward traveling, and the rear wheel 19 is rotated in reverse. Therefore, when the vehicle is moving backward, the transmission of the driving force is exactly the same as when driving the vehicle forward, and pressure is generated in the high-pressure pipe 8H only when the front wheel 5 slips and a predetermined rotational speed difference occurs between the front and rear wheels. The torque is transmitted to the rear wheel 19.

At this time, in the rotary swash plate type axial piston pump 6 on the front wheel side, as described above, the suction port 6b and the discharge port 6c of the pump are not interchanged even when the rotation direction is reversed, and the forward / reverse switching is performed. Since the electromagnetic directional control valve 9 is built in the swash plate type variable displacement motor 10, expensive high pressure piping can be used only for the high pressure piping 8H, and the relief valve 11, the check valve 13, the orifice 15 and the like can also be used. Since it suffices to provide the pump so that it can handle only one direction of flow, the oil passage configuration can be extremely simplified as compared with the case of using a pump of another system.

Further, in a vehicle equipped with an anti-skid control device based on a front-wheel drive vehicle, the rotation speed of the front wheel 5 becomes smaller than that of the rear wheel 19 during braking, and the piston pump 6
The supply flow rate from the swash plate type variable displacement motor 10 decreases, but the inclination of the swash plate 103 is automatically adjusted accordingly, and the discharge amount of the swash plate type variable displacement motor 10 is also adjusted.
The flow rate is equal to the supply flow rate from the above, the high pressure on the low-pressure pipe 8L side is avoided, and the driving torque is not generated. Therefore, there is an advantage that interference with the anti-skid control device can be reduced.

Although the relief valve 11 is used as the transmission torque limiting means in the above embodiment, the present invention is not limited to this, and the delivery pressure of the piston pump 6 is input as the displacement control pressure. In accordance therewith, a suction throttle valve may be provided to control the opening degree of the suction passage on the suction port side of the piston pump 6 to be small when the discharge pressure becomes equal to or higher than a predetermined pressure. In this case, when the pump discharge flow rate becomes equal to or higher than the specified pressure, the pump suction amount decreases, so that the pump discharge pressure decreases and the torque can be limited. At the same time, when the relief valve 11 is used. However, when the intake throttle valve is provided, the discharge flow rate decreases, so that heat generation can be suppressed.

Further, in the above embodiment, the rear wheel side differential 1
Although the case where 7 is provided has been described, the present invention is not limited to this, and the rear wheel side differential device 17 is omitted, and instead, the swash plate type variable displacement motor 10 is individually provided to the left and right axles of the left and right rear wheels 19. In this case, when different loads are applied to the left and right wheels when the vehicle is turning, the swash plate type variable displacement motor 10 naturally discharges the discharge flow rate according to the difference. Because of the difference, the differential function equivalent to that of the differential device can be exhibited.

Further, in the above-mentioned embodiment, although the embodiment based on the front wheel drive vehicle is explained, the present invention is not limited to this, and also in the case where the rear wheel drive vehicle is based, the fluid pressure pump is used as the rear wheel. By arranging the swash plate type variable displacement motor 10 on the side of the front wheel, it is possible to obtain the same effects as those of the above embodiment. In the above embodiment, the fluid pressure motor is described as a fluid pressure motor in which the inclination of the swash plate is automatically changed depending on the flow rate. However, for example, a low pressure pipe or the like is formed with a differential pressure detection orifice or the like. Provided with differential pressure detection means,
Another known variable displacement motor that forcibly changes the inclination of the swash plate based on the detection value of the differential pressure detection means may be adopted.

[0066]

As described above, in the rotary swash plate type axial piston pump of the present invention, the swash plate can be rotatably supported via the pressure chamber capable of generating the pressure corresponding to the load from the piston. Therefore, it is possible to rotate the swash plate at high speed without using the thrust bearing. Therefore, a desired flow rate can be obtained without increasing the specific discharge capacity of the pump, and the pump can be downsized.

Further, since it is not necessary to provide the pressure introducing passage for guiding the pressure corresponding to the load from the piston to the pressure chamber in the pump housing itself and the pressure introducing passage is provided at the shortest distance, the machining allowance is small. There is also an effect. For this reason,
As described in claim 3, it is possible to use at a high rotational speed and a high load required as a fluid pressure pump for a four-wheel drive vehicle of an automobile, and to increase the size even when used as the fluid pressure pump. Since it does not, it can be installed in the vehicle.

[Brief description of drawings]

FIG. 1 is a sectional view showing a rotary swash plate type piston pump according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between each pressure introduction path and a pressure chamber in the embodiment according to the present invention.

FIG. 3 is a diagram showing positions of a swash plate side pressure introduction path and a swash plate side pressure chamber of an embodiment according to the present invention.

FIG. 4 is a schematic configuration diagram of a four-wheel drive vehicle according to an embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a wheel law and a discharge flow rate in a rotary swash plate type piston pump and a fluid pressure motor according to an embodiment of the present invention.

FIG. 6 is a sectional view showing a fluid pressure motor of an embodiment according to the present invention.

FIG. 7 is a cross-sectional view showing a conventional rotary swash plate type piston pump.

[Explanation of symbols]

 6 Rotating swash plate type piston 10 Fluid pressure motor 21 Drive shaft 23 Rotating swash plate (swash plate) 24 Piston 25 Cylinder hole 26 Piston chamber 28 Piston shoe 29 Piston side pressure introducing passage 30 Piston side pressure chamber 32 Swash plate side pressure introducing passage 33 Swash plate side pressure chamber 34 Metal

Claims (3)

[Claims] 1. A swash plate that rotates integrally with a rotating shaft,
And a plurality of pistons that are slidably pressed against the inclined surface of the swash plate through a piston shoe and stroke in the fixed cylinder hole in response to the rotation of the swash plate. In a plate-type axial piston pump, the piston-side pressure introduction passage that is provided in each piston and that can introduce the pressure in each piston chamber to the corresponding piston shoe position and the piston-side pressure introduction passage that communicates with the piston-side pressure introduction passage A piston-side pressure chamber formed of a concave portion formed on a slidable contact surface with the swash plate, a swash plate-side pressure chamber formed of a concave portion provided on a back surface facing the inclined surface of the swash plate, and the swash plate And a plurality of swash plate side pressure introduction passages that communicate the piston shoe sliding surface position of the swash plate and the swash plate side pressure chamber with each other. pump. 2. The rotary swash plate type axial piston pump according to claim 1, wherein the swash plate side pressure chamber and the swash plate side pressure introducing passage are formed of a plurality of independent sets. 3. A fluid pressure supply means having a drive axle that is driven by a main motor and transmits a drive force to drive wheels, a fluid pressure pump that rotates in conjunction with the drive axle, and discharges a working fluid; Fluid pressure drive means having a fluid pressure motor that rotates in conjunction with the axle of the driving wheel, a first flow path that connects the discharge port of the fluid pressure supply means and the suction port of the fluid pressure drive means, and the fluid pressure supply A four-wheel drive vehicle including a second flow path that connects the suction port of the means and the discharge port of the fluid pressure drive means, wherein the fluid pressure pump of the fluid pressure supply means includes the second passage. A four-wheel drive vehicle that employs the rotary swash plate type axial piston pump described in 1.