JPH03151575A - Axial piston machine - Google Patents

Abstract

PURPOSE:To prevent a spring from being twisted in a machine where a piston is pressed against a cam plate via a washer by a spring disposed inside a recessed portion formed in the piston by interposing a ball between the recessed portion and the washer. CONSTITUTION:A piston 25 is fitted into a cylinder formed in a freely rotating cylinder block in such a manner that the piston 25 freely reciprocates within the cylinder. In a recessed portion 24 formed in the piston 25 a washer 26 and a spring 7 are disposed in sequence from the bottom face of the piston 25, whereby the piston 25 is pressed against a cam plate. A recessed portion 27 serving as a positioning portion is formed at the center of the washer 26 in such a manner as being opposite to the recessed portion 24, and a ball 28 is held in the recessed portion 27. The ball 28 is pressed against the bottom face of the recessed portion 24 by the spring 7. The ball 28 restrains rotation of the piston 25 from being transmitted to the washer 26, thereby preventing the spring 7 from being twisted.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an axial piston machine consisting of an axial piston pump or a motor.

<Prior Art> Conventionally, there is an axial piston pump as shown in FIG. 4 (Japanese Utility Model Application No. 116082/1982). In this axial piston pump, a cylinder 3 is formed in the axial direction in a cylinder block 2 that is rotated by a rotating shaft 1, and a piston 5 is fitted into the cylinder 3 so as to be able to reciprocate. A washer 6 and a part of a spring 7 are disposed in a recess provided in the piston 5, and the spring 7 urges the piston 5 in a direction to protrude through the washer. On the other hand, an inclined plate 12 is attached to the tiltable swash plate 8 via a thrust bearing 11, and the inclination angle of the swash plate 8 is adjusted by a plunger 13. As the cylinder block 2 rotates, the piston 5 revolves around the rotation axis l, and the spring 7 presses the head of the piston 5 toward the inclined plate 12 via the washer 6. The swash plate 8 is reciprocated with a stroke corresponding to the inclination of the swash plate 8 to suck in fluid through the valve plate 9 and discharge it.

<Problems to be Solved by the Invention> By the way, in the conventional axial piston pump described above, when the piston 5 reciprocates while revolving around the rotating shaft 5, the following problem occurs. That is, since the inner surface of the knoll ring 3 is polished by a honing machine or the like, a mesh pattern is formed, and when the piston 5 reciprocates, it is guided by the pattern and tries to rotate. That is, the piston 5 tends to rotate while revolving around the rotation axis. On the other hand, since the sub and ring 7 are pressed against the cylinder block 2 at one end, they only revolve together with the cylinder block 2, and as the piston 5 rotates, the washer 6
Twisting is applied to the spring 7 via. That is,
As shown in FIG. 3, the piston 5 rotates in the direction of the arrow, whereas the spring 7 only revolves, so the spring 7 is twisted through the washer 6.
There were cases where it broke. Of course, the washer 6 is provided with a through hole 6a to guide hydraulic oil between the washer 6 and the bottom surface of the recess of the piston 5, thereby reducing friction between the washer 6 and the bottom surface of the recess of the piston 5. Although consideration has been taken to prevent torsional force from acting on the piston 7, there may be times when the hydraulic oil is not sufficiently distributed between the washer 6 and the bottom of the concave portion of the piston 5, such as during startup. When the viscosity of the spring 7 was low, the spring 7 often broke.

Therefore, an object of the present invention is to prevent the spring that urges the piston outward from being twisted even when the piston rotates, thereby preventing the spring from breaking.

<Means for Solving the Problems> In order to achieve the above object, the present invention includes a piston that is reciprocatably fitted into a cylinder formed in a rotatable cylinder block, and a recess formed in the piston.
In an axial piston machine in which a washer and a spring are arranged in order from the bottom side of the recess so that the spring presses the piston toward the swash plate, between the bottom of the recess of the piston and the center of the washer. It is characterized by having a ball interposed in it.

It is desirable that the washer is provided with a positioning part that positions the ball at the center.

Further, the present invention is characterized in that a hemispherical convex portion facing the bottom surface of the concave portion of the piston is integrally formed in the center portion of the washer.

Further, the present invention is characterized in that hemispherical convex portions are integrally formed in the center portions of both surfaces of the washer.

<Operation> When the piston reciprocates inside the cylinder as the cylinder block rotates, the ball is interposed between the washer and the bottom of the recess in the cylinder, so the piston exerts almost no force on the washer and spring. Therefore, no torsion force is applied to the spring, and breakage of the spring is prevented.

In addition, if the washer is provided with a positioning part such as a recess for positioning the ball at the center, the ball can be positioned at the center of the piston, and the piston will come into contact with the center of rotation at one point. Even when the ball and washer rotate, almost no rotational moment acts on the ball and washer.

In addition, if a hemispherical convex portion facing the bottom surface of the concave portion of the piston is integrally formed in the center of the washer, when installing the washer and spring into the concave portion of the piston,
Compared to the case where the ball and washer are separate, the washer and ball can be assembled more easily, reducing costs, and preventing defects due to assembly errors.

Further, when hemispherical convex portions are integrally provided in the center of both sides of the washer, the washer can be assembled without considering directionality, and mistakes in assembly are prevented.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

This embodiment differs only in the structure of the piston and washer from the conventional example shown in Fig. 4; however, the rotating shaft, cylinder block, cylinder, swash plate, thrust bearing, inclined plate, plunger, spring, etc. It has exactly the same structure as the example. Therefore, the explanation of the parts having the same structure as the conventional example will be omitted, and only the different parts will be explained with reference to FIG.

As shown in FIG. 1, a ball 27, a disc-shaped washer 26, and a part of the spring 7 are arranged in a recess 24 with a flat bottom provided in a piston 25 with a hemispherical tip.

At the center of the washer 26 is a recess 2 as a positioning part.
A ball 28 is held in the recess 27 with the recess 27 facing the bottom surface of the recess 24. This ball 28 is pressed against the center of the bottom surface of the recess 24 by the spring 7 via the washer 26.

Therefore, even if the piston 25 rotates on its own axis as shown by the arrow while revolving around the rotation axis as the rotation axis (not shown) rotates, the ball 28 remains at one point at the center of the flat bottom surface of the recess of the piston 25. Washer 26
Almost no rotational force acts on the spring 7, thus preventing the spring 7 from breaking. Particularly during startup when the viscosity of the hydraulic oil is low, no rotational moment acts on the washer 26 as mentioned above, so breakage of the spring is prevented.

Further, since the washer is provided with a recess 27 to accurately position the ball at the center of the piston, that is, the center of the recess, rotational force will not act on the washer 26 even when the piston rotates. There is no.

FIG. 2 shows a second embodiment. In this embodiment, the washer and ball are integrated, whereas the ball and washer are separate structures in the embodiment shown in FIG. The piston 25 has exactly the same structure as the embodiment shown in FIG. The washer 36 is provided with hemispherical protrusions 38, 38 at the center of both sides.

Therefore, this washer 36 is pressed against the bottom surface of the recess by the spring 7, and contacts the center of the bottom surface of the recess 24 at one point by the tip of the convex portion 38. Therefore, even if the piston 25 rotates in the direction of the arrow, the piston 25
Since the convex portion 38 and the convex portion 38 contact each other at one point in the center, the washer 36
Therefore, no torsion force is applied to the spring 7, and breakage of the spring 7 is prevented.

Furthermore, since the washer 36 is integrally formed with the hemispherical convex portion 38, there is no problem of balls falling off when the washer 36 is assembled, compared to the embodiment shown in FIG. 1, and the assembly is easy. Further, since semispherical convex portions 38 and 38 are provided at the center of both sides of the washer 36, the washer 36
The washer 36 is attached to the piston 2 without considering the front and back sides of the
The washer 36 can be assembled into the recess 24 of No. 5, and the washer 36 can be assembled in the correct direction.

In the above embodiment, the convex portions 38° 38 are provided on both sides of the washer 36, but the convex portions may be provided on one side of the washer, and the side with the convex portions may be opposed to the bottom surface of the concave portion provided on the piston. good.

In addition, in the above embodiment, the structure of the swash plate is the same as the conventional example shown in FIG. 4, in which the swash plate is attached to the swash plate via a thrust bearing, but there is no thrust bearing or slant plate, and the piston is directly attached to the swash plate. It may be a structure in which they are in sliding contact.

<Effects of the Invention> As is clear from the above, according to the present invention, the ball is interposed between the bottom surface of the concave portion of the piston and the center portion of the washer, and the spring moves in the direction in which the piston protrudes through the ball and the washer. Since it is biased, even if the piston rotates while revolving, the rotation of the piston is difficult to be transmitted to the washer due to the presence of the ball, and therefore,
Breakage due to spring twisting is prevented.

Further, according to the present invention, since the washer is provided with a positioning part that positions the ball at the center, the ball can always be located at the center of the washer, making it difficult to transmit the rotational force caused by the rotation of the piston to the washer. can do.

Further, according to the present invention, since the hemispherical convex portion facing the bottom surface of the cylinder is integrally formed in the center of the washer,
Compared to a ball and washer that are separate structures, assembly is easier and the assembly can reduce the incidence of defects.

Further, according to the present invention, since semispherical convex portions are integrally formed in the center portions of both sides of the washer, the washer can be assembled into the concave portion of the piston without considering the direction of the washer. This allows you to prevent mistakes during assembly.

[Brief explanation of the drawing]

Figure 1.2 is a sectional view of the main parts of each embodiment of this invention, and Figure 3.
The figure is a cross-sectional view of the main parts of a conventional axial piston pump.
FIG. 4 is a sectional view of a conventional axial piston pump. 5.25... Piston, 6, 26.36... Wagonya, 28... Ball, 38... Convex part, 7... Spring. Figure 4

Claims (4)

[Claims] (1) A piston (25) is reciprocally fitted into a cylinder formed in a rotatable cylinder block (2), and a washer ( 26) and spring (7
) is arranged so that the piston (25) is pressed toward the swash plate by the spring (7).
6) An axial piston machine characterized in that a ball (28) is interposed between the central part of the machine. (2) The washer (26) has the ball (28)
The axial piston machine according to claim 1, further comprising a positioning part (27) for positioning around the axial piston machine. (3) A piston (25) is reciprocatably fitted into a cylinder formed in a rotatable cylinder block (2), and a washer ( 36) and spring (7
) is arranged so that the piston (25) is pressed toward the swash plate by the spring (7). An axial piston machine characterized by integrally forming a shaped convex portion (38). (4) A piston (25) is reciprocatably fitted into a cylinder formed in a rotatable cylinder block (2), and a washer ( 36) and spring (7
), and the spring causes the above piston (
25) is pressed against the swash plate, characterized in that hemispherical convex portions (38) are integrally formed in the center of both sides of the washer (36), respectively. .