JPH08200207A - Piston pump and piston motor - Google Patents

Abstract

PURPOSE: To provide a piston pump and piston motor which produce practically no lateral pressure to a cylinder, wear of the cylinder and the piston is less, produce less vibration and can be miniaturized. CONSTITUTION: A plurality of cylinders 9 are formed inside a cylinder block 8 and a piston 11 is stored inside the respective cylinders 9, while the cylinder block 8 is rotated relatively to a cam ring 12 by a shaft 6 and the can ring 12 and the shaft 6 is eccentrically arranged. A cam surface 12A formed in the interior of the cam ring 12 is made so that the distance between parts corresponding to the respective cylinders 9 and the cylinder 9 varies with respect to the axial direction of the cylinder 9 and a spherical mediation member 18 at least partially stored inside the cylinder 9 is interposed between the respective pistons 11 and the cam surface 12A of the cam ring 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston pump and a piston motor.

[0002]

2. Description of the Related Art In conventional piston pumps and piston motors, when a piston reciprocates in a cylinder, a force acting in a direction transverse to the reciprocating direction acts on the piston. There is a problem that lateral pressure is generated in the cylinder. According to FIG.
This problem will be described.

FIG. 17 is a schematic diagram of a conventional axial piston pump. In FIG. 17, 102 is a cylinder block, and the cylinder block is a rotating shaft 104.
And is rotatable about the axis of rotation. In the cylinder block 102, a plurality of cylinders 106 in a direction parallel to the rotation axis are evenly arranged in the circumferential direction at positions that are separated from the center of rotation of the rotation axis 104 by an appropriate distance in the radial direction. Each cylinder 106 has a piston 1
08 is accommodated, and the piston 108 can reciprocate in the direction of the rotating shaft 106. Each cylinder 106
A compression coil spring 110 is housed inside the piston 108 to the right, and the piston 108 is biased to the left by the coil spring 110. Reference numeral 112 denotes a valve plate, and the cylinder block 102 can slide and rotate with respect to the valve plate 112. Reference numeral 114 denotes a swash plate which is a cam member, and the swash plate 114 has a contact surface which is a cam surface inclined by an angle θ with respect to a plane orthogonal to the rotating shaft 104. The left end of each piston 108 urged by the coil spring 110 is in contact with the contact surface.

When the rotating shaft 104 is driven to rotate, the piston 108 in a state where the contact surface of the swash plate 114 gradually approaches with the rotation is pushed by the contact surface of the swash plate 114 and resists the extension force of the coil spring 110. Then, the piston 108 in a state where the contact surface of the swash plate 114 gradually moves away with the rotation is pushed by the extension force of the coil spring 110 and moves to the left.

The valve plate 112 is the piston 1 as described above.
During the reciprocating movement of 08, the fluid is sucked into the cylinder 106 corresponding to the piston moving leftward from the outside through the fluid circulation port, and the fluid is discharged from the inside of the cylinder 106 corresponding to the piston moving rightward. The fluid is discharged to the outside through the flow port.

By the way, as shown by the arrow in FIG. 17, during the reciprocating movement of the piston as described above, the swash plate 114 with respect to the piston 108, especially the piston moving to the right.
A force acts in a direction inclined with respect to the rotation axis direction. For this reason, the force (lateral pressure) indicated by the arrow in which the piston 108 laterally presses the cylinder 106 is generated.
This side pressure is generated by the piston 108 and the cylinder 106.
Wear is accelerated to cause fluid leakage between the cylinder and the piston, which lowers pump efficiency and causes vibration, which is not preferable. Therefore, conventionally, a long piston 108 is used to minimize the influence of lateral pressure.
Therefore, miniaturization of the device has been hindered.

The above-mentioned problems exist not only in the axial piston pump, but also in the radial piston pump, the axial piston motor, and the radial piston motor.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a piston pump and a piston motor in which a lateral pressure is not substantially generated in a cylinder.

Further, in view of the above-mentioned problems of the prior art, the present invention provides a piston pump in which the wear of the cylinder and the piston is small, the fluid leakage between the cylinder and the piston is unlikely to occur, and the high efficiency can be maintained. An object is to provide a piston motor.

Further, in view of the above problems of the prior art, it is another object of the present invention to provide a piston pump and a piston motor in which the wear of the cylinder and the piston is small and the vibration is small.

Further, in view of the above problems of the prior art, it is another object of the present invention to provide a piston pump and a piston motor which can be miniaturized while maintaining high efficiency without substantially generating an upper pressure. To do.

[0012]

According to the present invention, in order to achieve the above object, a plurality of cylinders are formed in a cylinder block, and a piston is housed inside each of the cylinders. A cam surface rotatable relative to the cylinder block, and a cam surface of the cam member has a distance between a portion corresponding to each cylinder and the cylinder during the relative rotation. A piston pump, characterized in that it is formed so as to change with respect to the axial direction, and a spherical medium member is interposed between each piston and the cam surface of the cam member. It

In one aspect of the present invention, the plurality of cylinders are arranged in the cylinder block in a radial direction around a rotation center of the relative rotation. In one aspect of the present invention, the plurality of cylinders are arranged in the cylinder block around a rotation center of the relative rotation so as to face a direction of the rotation center. In one aspect of the present invention, each of the intermediate members is housed in a corresponding cylinder.

Further, according to the present invention, in order to achieve the above object, a plurality of cylinders are formed in a cylinder block, and a piston is housed inside each of the cylinders. The cam surface of the cam member is rotatable relative to the cylinder, and the cam surface of the cam member has a distance between the portion corresponding to each cylinder and the cylinder in the axial direction of the cylinder during the relative rotation. The plurality of cylinders are formed so as to change, and are arranged in the cylinder block in a radial direction around a rotation center of the relative rotation, and each of the pistons and a cam surface of the cam member. A piston pump, characterized in that an intervening member having a rotationally symmetric shape is interposed between the intermediary members in the direction of the rotation center of the relative rotation. That.

In one aspect of the present invention, the cylinder block is formed with a recess for accommodating each of the intermediate members at a position corresponding to each of the cylinders.

In the above aspect of the present invention, biasing means such as a compression spring that biases the piston toward the cam surface of the cam member is disposed in each cylinder.

Further, according to the present invention, in order to achieve the above object, a plurality of cylinders are formed in a cylinder block, and a piston is accommodated in each of the cylinders. The cam surface of the cam member is rotatable relative to the cylinder, and the cam surface of the cam member has a distance between the portion corresponding to each cylinder and the cylinder in the axial direction of the cylinder during the relative rotation. Provided is a piston motor, which is formed so as to change, and in which a spherical medium member is interposed between each piston and the cam surface of the cam member.

In one aspect of the present invention, the plurality of cylinders are arranged in the cylinder block in a radial direction around a rotation center of the relative rotation. In one aspect of the present invention, the plurality of cylinders are arranged in the cylinder block around a rotation center of the relative rotation so as to face a direction of the rotation center. In one aspect of the present invention, each of the intermediate members is housed in a corresponding cylinder.

Further, according to the present invention, in order to achieve the above object, a plurality of cylinders are formed in a cylinder block, and a piston is housed in each of the cylinders. The cam surface of the cam member is rotatable relative to the cylinder, and the cam surface of the cam member has a distance between the portion corresponding to each cylinder and the cylinder in the axial direction of the cylinder during the relative rotation. The plurality of cylinders are formed so as to change, and are arranged in the cylinder block in a radial direction around a rotation center of the relative rotation, and each of the pistons and a cam surface of the cam member. A piston motor, characterized in that an intermediate member having a rotationally symmetric shape is interposed between the intermediate member and the intermediate member around the direction of the center of rotation of the relative rotation. That.

In one aspect of the present invention, the cylinder block is formed with a recess for accommodating each of the intermediate members at a position corresponding to each of the cylinders.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view showing a first embodiment of a radial piston pump according to the present invention, and FIGS. 2 and 3 are sectional views showing its assembled state.

In these figures, 2 is a casing body, and 3 and 4 are casing lids, which are joined by bolts and integrated to form a casing. A substantially cylindrical cavity having rotational symmetry about the XY direction is formed in the casing. A rotary shaft 6 in the XY direction is arranged in the cavity. The rotary shaft 6 is rotatably supported by the casing lid portion 3 via a bearing, and the end portion on the X direction side extends outside the casing. The rotary shaft 6 has a spline 6A at an end on the Y direction side in a portion inside the casing. In the following description, the axial direction, the radial direction, and the circumferential direction all refer to the directions related to the rotary shaft 6 unless otherwise specified.

An annular cylinder block 8 is disposed in the casing cavity. The cylinder block 8 has a spline hole 8A that engages with the spline 6A of the rotary shaft 6 at the center in the X direction. Eight cylinders 9 are radially formed on the cylinder block 8 along the radial direction of the rotary shaft 6. These cylinders are evenly arranged in the circumferential direction of the rotary shaft 6, that is,
Adjacent cylinders 9 form an angle of 45 degrees with each other. Each of these cylinders 9 is a cylinder block 8
Is open to the outer peripheral surface side. Also, the cylinder block 8
On the inner peripheral surface side of the fluid flow port 1 that can communicate with each cylinder 9.
0 is formed. A piston 11 is provided in each cylinder 9.
Is housed. Although not shown, each cylinder 9
A compression coil spring is housed in the piston 11
Is urged radially outward by the coil spring.
The cylinder block 8 is rotatably supported by the casing lid portion 3 via a bearing, and the end surface on the Y direction side is slidably brought into contact with the casing lid portion 4.

In the casing cavity, a cam ring 12 is arranged radially outward of the cylinder block 8. The cam ring 12 is urged in the B direction by an urging tool 14 attached to the casing body 2 and using a compression coil spring. The cam ring 12 is in contact with the tip of an adjusting screw 16 attached to the casing body 2 at a position facing the biasing tool 14.
Thereby, the position of the cam ring 12 in the AB direction can be set by appropriately screwing the adjusting screw 16 to adjust the tip position. 2 shown in FIGS. 2 and 3
1 (not shown in FIG. 1) is A of the cam ring 12.
The guide block is for moving in the B direction, and is locked by the tip of a locking screw 19 that is screwed into the casing body 2 from the outside. The cam ring 12 is formed with a guide groove 20 that engages with the guide block 21. The inner surface of the cam ring 12 is formed as a cylindrical cam surface 12A that is symmetrical about a rotational symmetry axis centered on the XY directions. By adjusting the adjusting screw 16, the cam surface 12A and the rotation center of the rotating shaft 6 (that is, the cylinder block 8).
The center of rotation of the pump is eccentric by a desired distance, and thereby the discharge amount of the pump can be adjusted.

In this embodiment, a spherical medium member 18 is interposed between the piston 11 in each cylinder 9 and the cam surface 12A of the cam ring 12. The medium member 18 has a diameter similar to that of the piston 11, and the cylinder 9
At least partially contained within. 4A and 4B are views showing the medium member 18 and the piston 11, in which FIG. 4A is a perspective view and FIG. 4B is an exploded perspective view.

1 to 3, reference numeral 22 denotes a valve member, which is a fluid suction pipe 24 and a fluid discharge pipe 26 extending through a mounting plate 4A fixed to the casing lid portion 4. And the valve member 22 is thus fixed in position with respect to the casing. The valve member 22 is
It has a fluid suction opening 28 that communicates with the fluid suction pipe 24 and a fluid discharge opening 30 that communicates with the fluid discharge pipe 26. The fluid suction opening 28 and the fluid discharge opening 30 are notches formed in the X-direction half of the valve member 22 in the Q-direction and P-direction half, respectively. The valve member 22 is Y
The half portion on the direction side is held by the casing lid 4, and the outer peripheral surface on the X direction side slidably contacts the inner peripheral surface on the Y direction side of the cylinder block 8. Then, when the cylinder block 8 rotates, the fluid flow port 10 of each cylinder 9 runs through the fluid suction opening 28 and the fluid discharge opening 30.

The rotary shaft 6 and the cylinder block 8 are shown in FIG.
It is driven and rotated clockwise in FIG. 2, as indicated by the white arrow inside. As a result, the intermediate member 18 and the piston 11 are moved inward by the cam surface 12A of the cam ring 12 until each cylinder 9 moves from the position (1) shown in FIG. 2 to the position (4). The fluid in the cylinder 9 (the fluid between the piston 11 and the fluid flow port 10 such as oil) is pushed out to the fluid flow port 10 through the fluid discharge port 30 and the fluid discharge pipe 26. In addition, until each cylinder 9 moves from the position (5) shown in FIG. 2 to the position (8), the extension force of the coil spring in the cylinder 9 causes the piston 11 and the intermediate member 18 to move outside. The fluid is sucked into the cylinder 9 from the fluid suction pipe 24 through the fluid suction opening 28.

The portion of the casing cavity other than the inside of the cylinder is also filled with fluid, and the fluid in these casing cavities realizes the lubricating action.

As described above, in the radial piston pump of this embodiment, since the spherical medium member 18 is arranged between each piston 11 and the cam surface 12A of the cam ring 12, the medium member 18 cams. Although the direction of the force received from the surface 12A is a direction orthogonal to the cam surface and is strictly different from the directions of the cylinder 9 and the piston 11,
Since only the force from the medium member 18 in the directions of the cylinder 9 and the piston 11 is applied to the piston 11 that is in surface contact with the cylinder 9, even if the length of the piston 11 is short, the lateral pressure is substantially applied to the cylinder 9. Therefore, the wear of the cylinder and the piston is small, the fluid leakage between the cylinder and the piston is unlikely to occur, the pump efficiency is maintained high, the vibration is small, and the size can be reduced.

FIG. 5 is an exploded perspective view showing a second embodiment of the radial piston pump according to the present invention, and FIGS. 6 and 7 are sectional views showing the assembled state thereof. In these drawings, the same members as those in FIGS. 1 to 4 are designated by the same reference numerals.

In the present embodiment, the casing body 2
The inner portion of the double-sided portion also serves as the cam member, and the cam surface 12A is formed on the inner surface thereof. Further, in this embodiment, the number of cylinders 9 is 9, and the shape of the cam surface 12A is such that the same pattern is repeated every 90 degrees with respect to the circumferential direction of the rotary shaft 6. That is, while the rotary shaft 6 and the cylinder block 8 make one rotation, each cylinder 9
In, the suction and the discharge are repeated at every rotation angle of about 45 degrees. Therefore, in this embodiment, the valve member 2
The structure 2 is different from that of the first embodiment, and four fluid suction openings 28 and four fluid discharge openings 30 are provided.

Further, in this embodiment, the medium member 18 has a cylindrical shape rotationally symmetrical about the direction of the center of rotation of the rotary shaft 6, that is, the XY direction. A recess 8B for accommodating the intermediate member 18 is formed on the outer peripheral surface of the cylinder block 8 at a position corresponding to each cylinder 9. The intermediate member 18 has a diameter equivalent to the width of the recess 8B and is at least partially accommodated in the recess 8B. 8A and 8B are views showing the medium member 18 and the piston 11, where FIG. 8A is a perspective view and FIG. 8B is an exploded perspective view.

Also in this embodiment, the same operational effect as that of the first embodiment of the radial piston pump can be obtained.

FIG. 9 is an exploded perspective view showing the first embodiment of the axial piston pump according to the present invention.
11 and 12 are sectional views of the assembled state. In these figures, the same members as those in FIGS. 1 to 8 are designated by the same reference numerals.

In the present embodiment, the cylinder block 8 is fixed to the rotary shaft 6, and the rotary shaft 6 is rotatably supported by the casing lid portion 4 via a bearing and has an end on the Y direction side. The part extends out of the casing.
Further, the center portion of the end portion of the cylinder block 8 on the X direction side is also rotatably supported by the casing lid portion 3 via a bearing. Thus, the rotary shaft 6 and the cylinder block 8 can be integrally rotated relative to the casing 8.

Seven cylinders 9 are formed in the cylinder block 8 in parallel along the direction of the center of rotation of the rotary shaft 6. These cylinders are evenly arranged in the circumferential direction of the rotary shaft 6. Each of these cylinders 9 is open at the end surface of the cylinder block 8 on the Y direction side. Also,
On the end surface of the cylinder block 8 on the X direction side, a fluid flow port 10 that communicates with each cylinder 9 is formed. A piston 11 is housed in each cylinder 9. Although not shown, a compression coil spring is housed in each cylinder 9 and the piston 11 is biased in the Y direction by the coil spring, as described in the conventional example of FIG. There is.

The casing lid portion 3 also has a function as a valve member. That is, a fluid suction pipe 24 and a fluid discharge pipe 26 are connected to the casing lid portion 3, while the inner surface of the casing lid portion 3 serves as a sliding contact surface with the cylinder block 8. At the radial position where the fluid flow port 10 is located, there are formed a fluid suction opening 28 and a fluid discharge opening 30 which are formed like grooves in the circumferential direction in the vicinity of a half circumference, respectively.
8 and the fluid discharge opening 30 are respectively connected to the fluid suction pipe 24.
And the fluid discharge pipe 26. Therefore, when the cylinder block 8 rotates, the fluid flow port 1 of each cylinder 9
0 runs through the fluid intake opening 28 and the fluid discharge opening 30.

A swash plate (cam member) 52 having a variable tilt angle is arranged in the casing cavity. The swash plate 52 has an A
A rotation support shaft in the B direction is provided, and the support shaft is rotatably supported by two support members 54 fixed to the casing body 2. The swash plate 52 has a cam surface 52A having a flat surface on the X direction side, and has a first screw member 56 for rotational driving on the surface on the Y direction side. Then, a second screw member 58 that engages with the first screw member 56 is rotatably attached to the inner surface side of the casing lid portion 4. A rotary operation member 60 spline-engaged with the second screw member 58 is inserted from the outside of the casing into the casing body 2. Thus, by appropriately rotating the operation member 60, the second screw member 58 is rotated, and thereby the swash plate 52 is rotated around the rotation axis via the first screw member 56. Swash plate cam surface 5
The inclination angle of 2A (that is, the angle formed with the plane orthogonal to the direction of the rotation center of the rotation shaft 6) is adjusted. Thereby, the discharge amount of the pump can be adjusted.

In this embodiment, the spherical medium member 18 is interposed between the piston 11 and the cam surface 52A in each cylinder 9. The intermediate member 18 has a diameter similar to that of the piston 11 and is at least partially housed in the cylinder 9.

Also in this embodiment, the same effect as that of the first embodiment of the radial piston pump can be obtained.

FIG. 14 is an exploded perspective view showing a second embodiment of the axial piston pump according to the present invention, and FIG.
16 and 16 are a partially omitted front view and a sectional view of the assembled state, respectively. In these figures, FIG.
The same members as those in 3 are designated by the same reference numerals.

In this embodiment, the casing lid portion 4
The cam member 62 is integrally formed on the inner surface of the, and the surface on the X direction side is the cam surface 62A. Further, in the present embodiment, the shape of the cam surface is such that the same pattern is repeated every 180 degrees in the circumferential direction of the rotary shaft 6. That is, the rotary shaft 6 and the cylinder block 8
In each cylinder 9, the rotation angle is about 9
The suction and the discharge are repeated every 0 degree.
Therefore, in the present embodiment, the casing lid portion 3 is provided with two fluid suction openings 28 and two fluid discharge openings 30, and correspondingly, the fluid suction pipes 2 are provided.
4 and the fluid discharge pipes 26 are also provided in twos each.

In this embodiment, the spherical medium member 18 is interposed between the piston 11 and the cam surface 62A in each cylinder 9. The intermediate member 18 has a diameter similar to that of the piston 11 and is at least partially housed in the cylinder 9. Further, in FIG. 14 and FIG.
A compression coil spring 64 housed in each cylinder 9 is shown. The piston 11 is biased in the Y direction by the coil spring 64. Also, FIG. 15 and FIG.
In the figure, a supporting means 70 for fixing and supporting the casing is shown.

Also in this embodiment, the same effect as that of the first embodiment of the axial piston pump can be obtained.

The embodiment of the piston pump in which the rotary shaft 6 is driven and rotated to suck the fluid from the fluid suction pipe 24 and discharge the fluid from the fluid discharge pipe 26 has been described above. A piston motor for rotating the rotary shaft 6 as an output shaft by removing the compression coil spring as the urging means and introducing the high pressure fluid from one of the fluid suction pipe 24 and the fluid discharge pipe 26 and discharging the fluid from the other Can be configured. Also in such a piston motor, the same effects as those described in each of the embodiments of the piston pump can be obtained.

[0047]

As described above, according to the present invention, an intermediate member having a rotationally symmetrical shape is provided between the piston and the cam surface around the direction of the center of rotation of the relative rotation between the cylinder block and the cam member. Because of the interposition, only the force from the medium member in the direction of the cylinder and the piston is applied to the piston, and therefore, even if the length of the piston is short, the side pressure is not substantially applied to the cylinder, and the cylinder and the piston (EN) Provided are a piston pump and a piston motor which are less likely to wear due to galling, less likely to cause fluid leakage between the cylinder and the piston, maintain high efficiency, generate less vibration, and can be downsized.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a first embodiment of a radial piston pump according to the present invention.

2 is a cross-sectional view of the radial piston pump of FIG. 1 in an assembled state.

3 is a cross-sectional view of the radial piston pump of FIG. 1 in an assembled state.

FIG. 4 is a diagram showing a medium member and a piston of the radial piston pump of FIG.

FIG. 5 is an exploded perspective view showing a second embodiment of the radial piston pump according to the present invention.

6 is a sectional view of the radial piston pump of FIG. 5 in an assembled state.

7 is a cross-sectional view of the radial piston pump of FIG. 5 in an assembled state.

8 is a diagram showing a medium member and a piston of the radial piston pump of FIG.

FIG. 9 is a first axial piston pump according to the present invention.
FIG. 3 is an exploded perspective view showing the embodiment of FIG.

FIG. 10 is a sectional view of the axial piston pump of FIG. 9 in an assembled state.

11 is a cross-sectional view of the axial piston pump of FIG. 9 in an assembled state.

12 is a sectional view of the axial piston pump of FIG. 9 in an assembled state.

13 is a perspective view of a swash plate of the axial piston pump of FIG.

FIG. 14 is an exploded perspective view showing a second embodiment of the axial piston pump according to the present invention.

15 is a partially omitted front view of the axial piston pump of FIG. 14 in an assembled state.

16 is a cross-sectional view of the axial piston pump of FIG. 14 in an assembled state.

FIG. 17 is a schematic configuration diagram of a conventional axial piston pump.

[Explanation of symbols]

 2 Casing body part 3, 4 Casing lid part 6 Rotating shaft 6A Spline 8 Cylinder block 8A Spline hole 8B Recess 9 Cylinder 10 Fluid flow port 11 Piston 12 Cam ring 12A Cam surface 14 Biasing tool 16 Adjusting screw 18 Mediating member 19 Locking Screw 20 Guide groove 21 Guide block 22 Valve member 24 Fluid suction pipe 26 Fluid discharge pipe 28 Fluid suction opening 30 Fluid discharge opening 52 Swash plate 52A Cam surface 54 Support member 56 First screw member 58 Second screw member 60 Rotation Operation member 62 Cam member 62A Cam surface 64 Compression coil spring 70 Casing support means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area F04B 9/04 C

Claims (14)

[Claims] 1. A plurality of cylinders are formed in a cylinder block, a piston is housed in each of the cylinders, and a cam member is provided which is rotatable relative to the cylinder block. The cam surface of the cam member is formed such that the distance between a portion corresponding to each cylinder and the cylinder changes in the axial direction of the cylinder during the relative rotation. A piston pump characterized in that a spherical medium member is interposed between the cam member and the cam surface. 2. The piston pump according to claim 1, wherein the plurality of cylinders are arranged in the cylinder block in a radial direction around a rotation center of the relative rotation. 3. The piston according to claim 1, wherein the plurality of cylinders are arranged in the cylinder block around a rotation center of the relative rotation so as to face a direction of the rotation center. pump. 4. The piston pump according to claim 1, wherein each of the intermediary members is housed in a corresponding cylinder. 5. A plurality of cylinders are formed in a cylinder block, a piston is accommodated in each of the cylinders, and a cam member is provided which is rotatable relative to the cylinder block. The cam surface of the cam member is formed such that a distance between a portion corresponding to each of the cylinders and the cylinder changes in the axial direction of the cylinder during the relative rotation. Inside the cylinder block, arranged around the rotation center of the relative rotation in a radial direction, and between the pistons and the cam surface of the cam member, the direction of the rotation center of the relative rotation is arranged. A piston pump, characterized in that an intermediate member having a rotationally symmetrical shape is interposed around the piston pump. 6. The cylinder block is formed with a recess for accommodating each of the intermediary members at a position corresponding to each of the cylinders.
The piston pump described in. 7. The urging means for urging the piston toward the cam surface of the cam member is arranged in each of the cylinders, according to any one of claims 1 to 6. Piston pump described. 8. The piston pump according to claim 7, wherein the urging means is a compression spring. 9. A plurality of cylinders are formed in a cylinder block, a piston is housed inside each of the cylinders, and a cam member is provided which is rotatable relative to the cylinder block. The cam surface of the cam member is formed such that the distance between a portion corresponding to each cylinder and the cylinder changes in the axial direction of the cylinder during the relative rotation. A piston motor, characterized in that a spherical medium member is interposed between the cam member and the cam surface. 10. The plurality of cylinders are arranged in the cylinder block in a radial direction around a rotation center of the relative rotation,
The piston motor according to claim 9. 11. The piston according to claim 9, wherein the plurality of cylinders are arranged in the cylinder block around a rotation center of the relative rotation so as to face a direction of the rotation center. motor. 12. The piston motor according to claim 9, wherein each of the intermediate members is housed in a corresponding cylinder. 13. A plurality of cylinders are formed in a cylinder block, a piston is housed in each of the cylinders, and a cam member is provided which is rotatable relative to the cylinder block. The cam surface of the cam member is formed such that a distance between a portion corresponding to each of the cylinders and the cylinder changes in the axial direction of the cylinder during the relative rotation. Inside the cylinder block, arranged around the rotation center of the relative rotation in a radial direction, and between the pistons and the cam surface of the cam member, the direction of the rotation center of the relative rotation is arranged. A piston motor, characterized in that an intermediate member having a rotationally symmetrical shape is interposed around the piston motor. 14. The piston motor according to claim 13, wherein the cylinder block is formed with a recess for accommodating each of the intermediate members at a position corresponding to each of the cylinders.