JPH0626447A - Hydraulic pump motor - Google Patents

Abstract

PURPOSE:To improve lubricating performance between a piston and a cylinder easily and prevent them from being seized in a hydraulic pump motor which is provided with a casing, a rotating shaft which is supported through a bearing in the casing, a cylinder block which is engaged with the rotating shaft and is equipped with plural cylinders at intervals in the circumferential direction, and pistons which are inserted into respective cylinders respectively and slide reciprocatingly in the cylinders. CONSTITUTION:Multiple grooves 20c which are shallower than a clearance between a piston 20 and a cylinder are formed at the circumferential surface of the piston 20 which slides in the cylinder, in the axial direction of the piston 20. It is thus possible to lead pressure oil to the respective grooves 20c, and from a lubricating oil film between the piston 20 and the cylinder easily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a swash plate type or swash shaft type hydraulic pump / motor.

[0002]

2. Description of the Related Art Generally, a hydraulic pump / motor reciprocates a piston in a cylinder. The gap between the cylinder and the piston needs to be kept at a constant size so that the leakage of pressure oil does not increase.

Next, an example of a conventional swash plate type hydraulic motor will be described with reference to FIGS.

The casing 1 is composed of a cylindrical main body casing 1a whose one side in the axial direction is closed, and a rear casing 1b fixed to the other side in the axial direction of the main body casing 1a. A swash plate 2 having a sliding contact surface 2a inclined with respect to the axis of the main body casing 1a is fixed to the inner side of the main body casing 1a in the axial direction. A valve plate 3 is fixed to the inner surface of the rear casing 1b so as to face the swash plate 2, and the valve plate 3 is formed with a pair of eyebrow ports 4,5 (5 is not shown). Has been done. The eyebrow ports 4 and 5 communicate with supply / discharge passages 6 and 7 (7 is not shown) formed in the rear casing 1b.

The casing 1 has a rotating shaft 8 bearings 9 and 10.
The rotary shaft 8 penetrates through the holes of the swash plate 2 and the valve plate 3. A cylinder block 11 is fitted on the rotating shaft 8, and a plurality of cylinders 12 are provided in the cylinder block 11 at intervals in the circumferential direction so as to face the swash plate 2 in the axial direction. The cylinder block 11 is adapted to rotate while being in sliding contact with the valve plate 3. Each cylinder 12 of the cylinder block 11 communicates with the eyebrow ports 4 and 5 of the valve plate 3 via the communication passages 13, 13 ...

A piston 14 is slidably accommodated in each cylinder 12 of the cylinder block 11, and a concave spherical surface portion 14 is provided on the tip side of each piston 14.
a is formed. In the axial direction of each piston 14, an oil passage 15 that opens at the center of the bottom of the concave spherical surface portion 14a is provided.

A piston shoe 16 as a sliding member is connected to the tip end side of each piston 14.
Each piston shoe 16 has a concave spherical surface portion 14 of the piston 14.
The spherical joint portion 16a fitted to a and the sliding contact surface 2a of the swash plate 2
It is composed of a disk portion 16b which slides on the top. An oil guide hole 17 for guiding pressure oil in the cylinder 12 is provided in the axial direction of the piston shoe 16. Each piston shoe 1
6 is a swash plate 2 as the cylinder block 11 rotates.
The swash plate 2 is abutted against the swash plate 2 by the piston shoe pressing plate 18 so as to slide on the sliding contact surface 2a.

The operation of the swash plate hydraulic motor described above will be described.

The pressure oil discharged from a hydraulic pump (not shown) sequentially passes through a supply passage provided in the rear casing 1b, one eyebrow port 4 of the valve plate 3 and a communication passage 13 of the cylinder block 11, and then the cylinder 12 Supplied within. The hydraulic pressure of the pressure oil supplied into the cylinder 12 acts in a direction to extend the piston 14 from the inside of the cylinder 12,
As a result of pushing, the piston shoe 16 is pressed against the swash plate 2. Since the swash plate 2 is inclined with respect to the axis of the piston 14, the piston shoe 16 is slidably attached to the sliding contact surface 2.
a on the piston 14 due to the reaction force of the pressing force.
Rotates the cylinder block 11, and the rotary shaft 8 rotates together with the cylinder block 11.

In the supply stroke in which the cylinder block 11 rotates and each communication passage 13 communicates with the eyebrow port 4 on one side, pressure oil is supplied into each cylinder 12 and the piston 14 extends from the inside of the cylinder 12. The piston 14 gives a rotational force to the rotating shaft 8. On the other hand, as the cylinder block 11 rotates, each communication passage 13 communicates with the eyebrow port 5 on the other side, and the piston 14 enters the cylinder 12 in the discharge stroke.
The piston 14 discharges the oil in the cylinder 12 to the discharge passage side through the communication passage 13 and the eyebrow port 5 sequentially.

During the operation of the above-mentioned motor, pressure oil in the communication passage 13 is introduced into the sliding surface between each cylinder 12 and the piston 14 through the gap between the cylinder 12 and the piston 14 to form an oil film. It is designed to lubricate the spaces.

As shown in FIGS. 6 and 7, the piston is provided with annular groove oil reservoirs 14b and 14c on its outer peripheral surface 14 and as shown in FIG. 8 without an oil reservoir. And are used.

[0013]

By the way, the cylinder 1
In a conventional hydraulic pump / motor that relies on the introduction of pressure oil into the gap between the two and the piston 14 for lubrication between the two and the piston 14, when the rotational speed is high and the pressure is low, Since the piston 14 is pressed against the cylinder 12 by the centrifugal force, even if there is a gap between the cylinder 12 and the piston 14, an oil film is less likely to be formed in this pressed part, so a seizure phenomenon occurs. To do.
Generally, a hydraulic pump / motor has a maximum rotation speed when the pressure is low, and therefore the maximum rotation speed is limited by the seizure limit between the cylinder 12 and the piston 14.

The present invention has been made in view of the above-mentioned problems of the prior art, and a hydraulic pump / motor capable of easily improving the lubricity between the cylinder and the piston and increasing the maximum rotation speed. The purpose is to provide.

[0015]

The features of the means adopted by the present invention in order to achieve the above-mentioned object are that a groove shallower than the clearance between the piston and the cylinder is formed on the outer peripheral surface of the piston sliding in the cylinder. This is because a plurality of lines are provided in the axial direction of the piston.

[0016]

The lubricating oil film is easily formed between the piston and the cylinder by introducing the pressure oil for lubrication into each groove formed on the outer peripheral surface of the cylinder that slides.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Will be described.

In the first embodiment shown in FIGS. 1 and 2, the groove 2 shallower than the gap between the piston 20 and the cylinder 12 is provided at three locations on the outer peripheral surface of the piston 20 sliding in the cylinder 12.
A plurality of 0c are provided in the axial direction. That is,
The groove 20c is provided between the oil sumps 20a and 20b and the oil sump 20.
It is provided on the left side of a and the right side of the oil sump 20b. A piston shoe 16 is connected to the piston 20. The circumferential width of each groove 20c is determined by the cylinder 12
It may be arbitrarily set within a range in which the contact surface pressure between the piston 20 and the piston 20 does not become extremely large.

In the second embodiment of FIG. 3, the groove 20c is provided with an oil sump 2
It is provided at two locations between 0a and 20b and on the right side of the oil sump 20b.

In the third embodiment shown in FIG. 4, the groove 20c is connected to the oil reservoir 2
It is provided at one place on the right side of 0b.

In the fourth embodiment shown in FIG. 5, a piston 20 having no oil sump is provided with a groove 20c while leaving a part of the piston shoe 16 side.

The basic operation of the hydraulic pump / motor of the present invention is the same as that of the conventional one, but since the groove 20c is provided, the leakage between the cylinder 12 and the piston 20 is
Since the number is slightly increased as compared with the conventional one, it is only necessary to select an appropriate one from the examples according to the usage conditions.

Since the hydraulic pump / motor of the present invention has the above-mentioned groove 20c, it rotates at a low pressure and at a high speed, and even if the piston 20 is pressed against the cylinder 12 by the centrifugal force, the groove 20c is discharged from Since the pressure oil is forcibly supplied, an appropriate oil film is easily formed between the cylinder 12 and the piston 20, and seizure between the cylinder 12 and the piston 20 is prevented.

[0024]

According to the present invention described above, an oil film is easily formed between the cylinder and the piston, wear of both is reduced, seizure can be prevented, and a decrease in efficiency is reduced. . Therefore, the life and reliability of the hydraulic pump / motor is improved.

[Brief description of drawings]

FIG. 1 is a side view showing a first embodiment of a piston according to the present invention,

2 is an enlarged cross-sectional view taken along the line AA of FIG.

FIG. 3 is a side view showing a second embodiment of the piston according to the present invention,

FIG. 4 is a side view showing a third embodiment of the piston according to the present invention,

FIG. 5 is a side view showing a fourth embodiment of the piston according to the present invention,

FIG. 6 is a sectional side view showing an example of a conventional hydraulic pump / motor,

FIG. 7 is a side view showing an example of a piston in a conventional hydraulic pump / motor,

FIG. 8 is a side view showing another example of a piston in a conventional hydraulic pump / motor.

[Explanation of symbols]

 1 casing 2 swash plate 3 valve plate 8 rotary shaft 11 cylinder block 12 cylinder 20 piston 20a oil sump 20b oil sump 20c groove

Claims (1)

[Claims] 1. A casing, a rotary shaft supported in the casing via bearings, a cylinder block engaged with the rotary shaft, and provided with a plurality of cylinders at intervals in the circumferential direction. A hydraulic pump equipped with a piston that is inserted into each cylinder and slides back and forth inside the cylinder.
In the motor, a hydraulic pump / motor is characterized in that a plurality of grooves, which are shallower than a gap between the piston and the cylinder, are provided on an outer peripheral surface of the piston that slides in the cylinder in the axial direction of the piston.