JPS6119984A - Piston device for swash plate type piston pump and motor - Google Patents

Abstract

PURPOSE:To aim at the promotion of prevention against unusual wear, etc., by supporting an outer ring on a cylinder block between a piston and an inner wall of a cylinder, while installing an inner ring interposingly in a spherical bearing contacted slidingly with an outer circumferential wall of the piston, and keeping off any local contact between the piston and the cylinder. CONSTITUTION:A outer ring 6 of a spherical bearing 6 is locked to a concave part 2b formed in a cylinder opening part of a cylinder block 1 by means of press fit and the like. On the other hand, a piston 3 is slidably inserted into a hole 6c installed in the center of an inner ring 6a which is self-alogned to a clearance with the outer ring 6b by a spherical part and comes into contact with the circumference of the piston 3 with the surface pressure distributed to width A of the inner ring 6a. Therefore, sliding motion at a transmission part of force F1 becoming the most severe condition is solvable whereby seizure and unusual wear are preventable from occurring, while a pump and motor is usable at higher pressure and a larger tilting angle than ever before.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a piston device for a swash plate type piston pump motor.

[Background of the invention]

FIG. 4 is a sectional view showing an example of a conventional swash plate type piston pump/motor.

In FIG. 4, reference numeral 1 denotes a cylinder block, and the cylinder block 1 is spline-coupled to a drive shaft (not shown) so that it rotates in synchronization with the rotation of the drive shaft. A plurality of cylinders 2 are bored in the cylinder block l at equal intervals in the axial direction, and each cylinder 2
A piston 3 is inserted into each inner VC so as to be able to reciprocate. The tip 3a of the piston 3 has a spherical shape, and is engaged with the shoe 4, so that the piston 3 is swingably supported by the shoe 4. Reference numeral 5 denotes a swash plate, which faces the cylinder block 1 while being inclined at a predetermined angle, and the shoe 4 is in contact with the surface of the swash plate 5.

In the swash plate type piston pump/motor configured in this way, when the cylinder block 1 rotates, the piston 3
The shoe 4 engaged with the tip 38 slides on the swash plate 5. Since the swash plate 5 is inclined with respect to the axis of the cylinder block 1, the piston 3 reciprocates within the cylinder 2 while the cylinder block 10 is rotating, and operates as a pump or a motor. At this time, high pressure is generated in cylinder 2°
Therefore, the piston 3 is pressed against the swash plate 5 via the shoe 4, and the piston 3 receives a force FP due to the pressure between the cylinders 2 and an axial force F from the swash plate 5 via the shoe 4 as shown in the figure. , a radial force FR generated according to the inclination of the swash plate 5, and forces F and F generated between the piston 3 and the cylinder 2 to balance the nuclear force FR. Of these resultant forces, F, and Ft&! It changes according to the stroke amount of the piston 30, and the position where the piston 3 is most removed from the cylinder 2, that is, the top dead center of the stroke where the distance from the open end of the cylinder 2 to the shoe 4 is the longest.
＼ becomes the maximum value.

By the way, a slight gap is provided between the piston 3 and the cylinder 2 in order for the piston 3 to reciprocate within the cylinder 2. Therefore, as shown in FIG. The portion that transmits this becomes a local contact portion between the opening 2a of the cylinder 2 and the outer circumferential surface of the piston 3, resulting in a very high contact surface pressure. This is power F! The same applies to the contact portion between the rear end portion 3b of the piston 3 and the inner circumferential wall of the cylinder 2, which transmits the same.

If the piston 3 reciprocates inside the cylinder 2 under high contact surface pressure, seizing may cause abnormal wear and shorten the life of the pump/motor, making it impossible to use it at high pressure. Otherwise, various problems may occur, such as not being able to provide a large tilting angle.This problem is clear from the balance of forces shown in FIG.

=FR+F, that is, p+>pg, so F
, is most likely to occur at the contact portion between the opening 2a of the cylinder 2 and the outer circumferential surface of the piston 3, where .

[Purpose of the invention]

An object of the present invention is to provide a swash plate type piston pump/motor that eliminates the drawbacks of the prior art described above and can prevent local contact between the bistoy and the cylinder, thereby extending the life (and increasing the energy density). There is a particular thing.

[Summary of the invention]

In order to achieve this object, the present invention is characterized in that a spherical bearing is interposed between the piston and the cylinder.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 is a sectional view of essential parts showing a first embodiment of a piston device for a swash plate type piston pump/motor according to the present invention, in which 6 is a spherical bearing, and parts corresponding to those in FIG. 4 are denoted by the same reference numerals. It is attached.

In FIG. 1, the spherical bearing 6 has an inner ring 6a and an outer ring 6b.
Of these, the outer ring 6b is fixed to a recess 2b formed in the cylinder opening 2a of the cylinder block 1 by means such as press fitting. On the other hand, the piston 3 is slidably inserted into a hole 6C bored in the center of the inner ring 6a, and the inner ring 6a is aligned with the outer ring 6b at the spherical surface, so that the outer circumference of the piston 3 is aligned. The inner ring 6a contacts with a surface pressure distributed over the width A of the inner ring 6a. Therefore, in the transmission part of the force F, which is the most severe condition, it is possible to eliminate the sliding due to the high contact surface pressure that conventionally occurs, thereby reducing the life of the pump and motor such as seizure and abnormal wear. In addition to being able to eliminate defects without causing any negative effects.

It becomes possible to use the pump fist motor at a higher pressure and a larger tilt angle than in the past.

Note that the operation of this embodiment is similar to that of the conventional example described above, so a description thereof will be omitted.

FIG. 2 is a sectional view of essential parts showing a second embodiment of a piston device for a swash plate type piston pump/motor according to the present invention.

This embodiment differs from the first embodiment in that, in addition to the spherical bearing 6 described above, another spherical bearing 7 is also provided at the force F transmission section. In other words, the inner ring 7 constituting the spherical bearing 7
a is fixed to a stepped portion 3c formed on the rear end portion 3b of the piston 3 by means such as press fitting, and the outer circumference of the outer ring 7b is configured to come into sliding contact with the inner circumference of the cylinder 2.

In one embodiment configured in this way, it is possible to eliminate the high surface pressure part in the transmission part of the force F in addition to the transmission part of the force F, compared to the first embodiment. The pump motor can be used at higher pressures and with larger tilt angles.

FIG. 3 is a sectional view of essential parts showing a third embodiment of a piston device for a swash plate type piston pump/motor according to the present invention.

In this embodiment, the recess 2b is formed relatively long in the axial direction of the cylinder 2, and the above-mentioned spherical bearing 6 and another spherical bearing 8 are arranged at a predetermined interval in the recess 2b. be. That is, the outer ring 8 of the spherical bearing 8 is located deep inside the recess 2b.
At the same time, the outer ring 6b of the spherical bearing 6 is fixed by press fitting or the like to the opening side of the recess 2b via the sleeve 9, and the inner circumferences of the inner rings 6a, 8a of both spherical bearings 6, 8 are fixed to the piston 3. It is constructed so that it slides. Even in the embodiment configured in this manner, the high surface pressure portion in the transmission portion of the force F1 and the force F can be eliminated, as in the second embodiment described above.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to eliminate local contact between the piston and the cylinder, and therefore it is possible to eliminate problems that adversely affect the pump motor, such as burning and abnormal wear, and further, Pumps and motors can be used at high pressures and large tilt angles, making it possible to increase energy density.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the main parts of a piston device for a swash plate type piston pump/motor according to the present invention, and FIGS. 2 and 3 show other embodiments of the piston device for a swash plate type piston pump/motor according to the present invention. 4 and 5 are cross-sectional views showing a piston device of a conventional swash plate type piston pump/motor. 1... Cylinder block, 2... Cylinder, 2a... Opening, 2b... Recess, 3... Piston, 3c... ...Dan section, 4
... Shoe, 5 ... Swash plate, 6°7.8
......Spherical bearing, 6a, 7a, 8a...
Inner circle. 6b, 7b, 8b... Outer ring, 9... Sleeve. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. A rotatable cylinder block and a piston slidably inserted into a cylinder of the cylinder block, the piston being guided by a swash plate by rotation of the cylinder block, 1. A piston device for a swash plate type piston pump/motor that reciprocates within a cylinder, characterized in that a spherical bearing is interposed between the piston and an inner wall of the cylinder. 2. The swash plate type piston pump/motor according to claim 1, wherein the outer ring of the spherical bearing is supported by the cylinder block, and the inner ring of the spherical bearing is in sliding contact with the outer peripheral wall of the piston. piston device. 3. A piston device for a swash plate type piston pump/motor according to claim 1, characterized in that a plurality of the spherical bearings are provided at predetermined intervals.