JPH07217545A - Piston type hydraulic pressure device - Google Patents

Abstract

PURPOSE:To store working liquid in a clearance groove, to perform lubrication of a slide gap by means of the stored working liquid, and to improve wear resistance and seizure resistance by forming the clearance groove in a part of the inner peripheral surface of a cylinder bore, in a swash type piston type hydraulic pressure device. CONSTITUTION:A plurality of cylinder bores 11 are arranged on the same pitch circle from the center of a cylinder block 10 rotated around a rotation center shaft A. One end of a piston 12 slidably fitted in each cylinder bore 11 is brought into slide contact with A swash 30 through a shoe 31. The piston 12 is reciprocated along the swash 30 to suck and discharge working liquid. In a so formed piston pump, a clearance groove 11c to spread a slide gap is formed between the inner peripheral surface 11a on the release end side of the cylinder bore 11 and the inner peripheral surface 11b of the cylinder bore 11 brought into slide contact with the outer peripheral surface 12b on the tip side of the piston 12. This constitution facilitates discharge of a foreign matter in working liquid through the clearance groove 11c and improves lubricity of a slide surface.

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 piston pump which reciprocates a piston in accordance with the rotation of a cylinder block to suck and discharge fluid, and a piston which reciprocates by fluid pressure to reciprocate the piston. The present invention relates to a swash plate type piston type hydraulic device such as a swash plate type piston motor for converting a cylinder into rotation of a cylinder block.

[0002]

2. Description of the Related Art As a piston type hydraulic device of this type which has been conventionally used as a power transmission mechanism for industrial machines and vehicles,
Swash plate type piston pumps and piston motors are known. FIG. 5 is a vertical cross-sectional view showing an example of a commonly used swash plate type piston pump, and FIG. 6 is a perspective view showing a partial cutaway of a main part thereof, which is rotatably incorporated in the apparatus main body 1. A plurality of cylinder bores 11 are provided on the same pitch circle from the center of the cylinder block 10 in parallel with the rotation center axis A that is the main axis of the cylinder block 10. With the rotation of the moving cylinder block 10, each piston 12 reciprocates in the cylinder bore 11 to suck and discharge the fluid.

In such a swash plate type piston pump,
The one end of each piston 12 revolves while slidingly contacting the swash plate 30 to cause the piston 12 to reciprocate. At this time, in the discharge process, the piston 12 is pressed against the swash plate 30 by the discharge pressure. Then, in the suction process, the shoe plate 32, which is in sliding contact with the swash plate 30, pulls the piston shoe 31 mounted on the one end spherical portion 12a of the piston 12 to extend along the surface of the swash plate 30.

Since each piston 12 makes a stroke motion in the suction direction during the half revolution during revolution, and a stroke motion in the remaining half revolution during the revolution, the cylinder 12 is slidably contacted with the cylinder block 10 of the main assembly 1 of the apparatus. A valve plate 4 having fluid supply and fluid discharge kidney ports 41, 42 on a pitch circle corresponding to the cylinder bore 11 of the block 10.
It is possible to obtain a continuous pumping action by fixing 0 and making one surface 40a thereof slidably contact the end surface 10a of the cylinder block 10.

The structure of the piston motor is almost the same as that of the piston pump, and the operating principle is opposite. That is, the piston reciprocates by the pressure of the working fluid supplied into the cylinder bore of the cylinder block, and the movement of this piston is converted into the rotation of the cylinder block.

However, in such a piston type hydraulic device, an external force is applied to the piston in a radial direction orthogonal to the sliding direction, and the piston always slides in the cylinder bore in an oblique state. FIG. 7 is an explanatory view showing an external force acting on the piston 12 of the swash plate type piston pump (FIG. 5) described above, in which the piston 12 has a reaction force F1 perpendicular to the plate surface from the swash plate 30 and an oil pressure against it. I am receiving F2.

Since the direction of the reaction force F1 is oblique to the axial direction of the cylinder bore 11, a component force F3 in the direction orthogonal to the axial direction is generated at one end of the piston 12. As a result, the piston 12 is tilted counterclockwise in the cylinder bore 11 into a one-sided contact state, the piston 12 receives reaction forces F4 and F5 from the cylinder block 10, and a particularly large load is applied to the tip of the piston 12 and the open end of the cylinder bore 11. To work.

Therefore, generally, in a swash plate type piston pump, a method of increasing the insertion length of the piston 12 into the cylinder bore 11 to make the inclination of the piston 12 gentle and to make the component force F2 as small as possible is adopted. .
However, when the insertion length of the piston 12 is increased, the length of the sliding contact surface with the cylinder bore 11 is increased, and it becomes difficult for the hydraulic fluid to be introduced into the sliding gap between the two, which hinders the formation of an oil film, and the internal pressure is particularly low. There is a risk of seizure in this state. In order to solve the above problems, in the conventional swash plate type piston pump, the sliding gap between the piston 12 and the cylinder bore 11 is increased to improve the lubrication state of the sliding contact surface between them.

[0009]

However, in such a conventional swash plate type piston pump, the sliding gap between the piston 12 and the cylinder bore 11 is increased to prevent seizure. As shown in FIG. 7, the foreign matter D in the working fluid is likely to enter the sliding gap between the two, wear and seizure are likely to occur due to the foreign matter being caught, and the foreign matter D is extremely sensitive to the inclusion of the foreign matter in the working fluid. There was a problem.

In order to solve this point, the piston 1 is conventionally used.
The production cost is increased by subjecting 2 to nitriding, carburizing, quenching, etc. to increase the surface hardness, and making the cylinder block 10 a gunmetal-based material with high seizure resistance, and inserting a gunmetal-based bush in the cylinder bore 11. The result was a sharp rise. At the same time, there were inconveniences that the operating conditions were significantly limited, such as lowering the operating pressure and tightening the control of the degree of contamination of foreign matter in the hydraulic fluid. The present invention has been made in view of the above points, and an object of the present invention is to reduce the influence of foreign matter in a hydraulic fluid and to improve wear resistance and seizure resistance.

[0011]

In order to achieve the above-mentioned object, the present invention is provided with a cylinder block which rotates in synchronism with the rotation of a main shaft, and a cylinder block which is parallel to the main shaft on the same pitch circle from the center of the cylinder block. Multiple cylinder bores, pistons slidably inserted in these cylinder bores, and a swash plate slidably contacting one end of these pistons and reciprocating the pistons in the cylinder bores as the cylinder block rotates. And a valve plate which is in sliding contact with one end surface of the cylinder block and has a fluid supply hole and a fluid discharge hole for the cylinder bore, the inner peripheral surface on the open end side of the cylinder bore and the piston To enlarge the sliding gap with the outer peripheral surface of the piston between the inner peripheral surface of the cylinder bore and the outer peripheral surface on the tip side of the piston. There is provided a piston-type hydraulic device formed a relief groove.

Further, in the same piston type hydraulic device as described above, the cylinder bore is provided between the outer peripheral surface of the piston on the tip end side and the outer peripheral surface of the piston which is in sliding contact with the inner peripheral surface of the open end side of the cylinder bore. There is also provided a piston type hydraulic device having an escape groove for expanding a sliding gap with the inner peripheral surface of the.

[0013]

By configuring the piston type hydraulic device according to the present invention as described above, even if the amount of hydraulic fluid in the cylinder bore introduced into the sliding gap between the piston and the cylinder bore at low pressure is reduced, The sliding gap is lubricated by the hydraulic fluid stored in the clearance groove formed on the inner peripheral surface of the cylinder bore or the outer peripheral surface of the piston, and wear resistance and seizure resistance are significantly improved.

Further, the improved lubricity makes it possible to reduce the sliding gap between the piston and the cylinder bore, prevent the entry of large foreign matter mixed in the working fluid, and allow the small foreign matter to slide. Even if the foreign matter enters the dynamic gap, the foreign matter is quickly discharged through the escape groove, so that the possibility of foreign matter being caught is significantly reduced, and wear resistance and seizure resistance are improved.

[0015]

Embodiments of the present invention will be specifically described below with reference to the drawings. Parts corresponding to those in FIG. 5 are designated by the same reference numerals and detailed description thereof will be omitted. FIG. 1 is a partial vertical cross-sectional view showing the relationship between a piston and a cylinder bore in the first embodiment of the present invention, and the configuration of the other parts is similar to that shown in FIG.

In this first embodiment, the inner peripheral surface on the open end side (the right end side in the figure) of the cylinder bore 11 provided in the cylinder block 10 which rotates around the rotation center axis A which is the main shaft of the swash plate type piston pump. 11a and the inner peripheral surface 11b of the cylinder bore 11 with which the outer peripheral surface 12b on the tip side of the piston 12 slides.
Between (the same diameter as the inner peripheral surface 11a), these inner peripheral surfaces 11
A relief groove 11c having a larger diameter than a and 11b for expanding a sliding gap with the outer peripheral surface of the piston 12 is formed.

The following structure is similar to that of FIG.
The piston 12 is a spherical portion 12 formed at one end on the swash plate 30 side.
The shoe 31 is rotatably mounted in all directions on a, and the sliding contact surface 31a of the shoe 31 is brought into pressure contact with the sliding contact surface 30a of the swash plate 30. In this state, the rotation transmission shaft 20 (FIG. 5) moves the cylinder block 10 It is made to rotate around the rotation center axis A.

Since the first embodiment is constructed as described above, when the cylinder block 10 rotates about the rotation center axis A and the piston 12 moves to the left in the discharging process,
As shown in FIG. 2, a relatively small foreign matter D that has been mixed into the hydraulic fluid inside the cylinder bore 11 and has entered the sliding gap D.
1 is discharged through the escape groove 11c by the flow of the hydraulic fluid. Further, small foreign matters that have entered the sliding gap from the outside of the cylinder bore 11 in the discharge step are guided into the cylinder bore 11 through the escape groove 11c, and in the next discharge step, the passage 10b is formed.
Alternatively, it is discharged from the sliding gap that has entered. Further, the large foreign matter D2 is caused by the piston 12 and the cylinder bore 1.
There is no possibility of entering the sliding gap with 1, and the possibility of foreign matter being caught is greatly reduced by being discharged through the passage 10b.
Even when the working fluid in the cylinder bore 11 is difficult to be introduced into the sliding gap at low pressure, the working fluid in the clearance groove 11c provides good lubrication and improves wear resistance and seizure resistance.

Next, FIG. 3 is a partial longitudinal sectional view showing the relationship between the piston and the cylinder bore of the second embodiment of the present invention. In the second embodiment, the inner wall surface on the open end side of the cylinder bore 11 excluding the inner wall surface 11b on the side where the cylinder bore 11 slidably contacts the tip portion 12b of the piston 12 has a larger sliding gap with the piston 12 on the inner wall surface. Medium-diameter part 11 for expanding
c and a large-diameter portion 11d having a larger diameter than that of c are formed, and an inner peripheral surface 13a having the same diameter as the inner diameter of the inner peripheral surface 11b is formed on the large-diameter portion 11d.
The large-diameter portion 11c is fitted into the escape groove by press-fitting the bush 13 having a groove.

According to the second embodiment described above, in addition to the effects of the first embodiment, the machining of the cylinder bore 11 is further facilitated, and the material of the bush 13 is the cylinder block 10.
The hardness can be made high regardless of the material, and the wear resistance of the cylinder bore open end side inner peripheral surface 13a having a smaller sliding area than the inner peripheral surface 11b can be improved.

Further, FIG. 4 is a partial longitudinal sectional view showing the relationship between the piston and the cylinder bore of the third embodiment of the present invention. In the third embodiment, the piston outer peripheral surface 12c on the side where the tip end side of the piston 12 is in sliding contact with the inner peripheral surface 11b of the cylinder bore 11, and the base side of the piston 12 is the cylinder bore 11.
An escape groove 12e for enlarging the sliding gap with the cylinder bore 11 on the piston outer peripheral surface intermediate between the piston outer peripheral surface 12d on the side slidingly contacting the inner peripheral surface 11a on the open end side (the same as the inner peripheral surface 11b). Is formed.

Also in this third embodiment, the same effect as that of the first embodiment can be obtained, and the relief groove 12e formed on the outer peripheral surface of the piston 12 has the outer peripheral surface 12 of the piston 12.
Since the machining can be performed in the same process as the outer diameter machining of c and 12d, the relief groove 12e can be machined at low cost without extra cost.

In each of the above-described embodiments, the case where the present invention is applied to the swash plate type piston pump has been described. However, the present invention is not limited to this, and the swash plate type piston having substantially the same structure as the swash plate type piston pump is described. It can be implemented on the motor without any trouble.

[0024]

As described above, in the piston type hydraulic device according to the present invention, the relief groove is formed in a part of the inner peripheral surface of the cylinder bore, so that at the time of low pressure, the sliding gap between the piston and the piston bore Even if it becomes difficult to introduce the hydraulic fluid, the sliding gap is sufficiently lubricated by the hydraulic fluid stored in the clearance groove, and the wear resistance and seizure resistance can be greatly improved.

The improved lubricity makes it possible to reduce the sliding gap between the piston and the cylinder bore, prevent the entry of large foreign matter mixed in the working fluid, and at the same time remove the small foreign matter. Even if it enters the dynamic gap, it is quickly discharged through the relief groove formed in the cylinder bore, so that it is less susceptible to foreign matter in the hydraulic fluid and can be used at high pressure.

In addition, when the relief groove is formed on the outer peripheral surface of the piston, the same effect as described above can be obtained, and the relief groove formed on the outer peripheral surface of the piston is machined in the same step when machining the outer diameter of the piston. Therefore, it is possible to supply at low cost without extra cost for processing the relief groove.

[Brief description of drawings]

FIG. 1 is a partial vertical sectional view showing the relationship between a piston and a cylinder bore in a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of the same operation.

FIG. 3 is a partial longitudinal sectional view showing the relationship between the piston and the cylinder bore in the second embodiment of the present invention.

FIG. 4 is a partial longitudinal sectional view showing the relationship between a piston and a cylinder bore in the third embodiment of the present invention.

FIG. 5 is a vertical sectional view of a conventional swash plate type piston pump.

FIG. 6 is a perspective view showing a part of the same with its main part broken away.

FIG. 7 is an explanatory diagram showing a force that similarly acts on the piston.

[Explanation of symbols]

 1: Device body 10: Cylinder block 11: Cylinder bore 11c: Relief groove 12: Piston 12e: Relief groove 20: Rotation transmission shaft 30: Swash plate A: Rotation center shaft (spindle)

Claims (2)

[Claims] 1. A cylinder block that rotates in synchronization with rotation of a main shaft, and a plurality of cylinder bores provided on the same pitch circle from the center of the cylinder block in parallel with the main shaft.
A piston slidably inserted in each of the cylinder bores; a swash plate slidably contacting one end of each of the pistons to reciprocate the piston in the cylinder bore as the cylinder block rotates; In a piston-type hydraulic device provided with a valve plate having a supply hole and a discharge hole of a fluid for slidingly contacting an end surface of the cylinder bore, an inner peripheral surface on an open end side of the cylinder bore and an outer peripheral surface on a tip end side of the piston. A piston-type hydraulic device, characterized in that an escape groove for expanding a sliding gap with the outer peripheral surface of the piston is formed between the inner peripheral surface of the cylinder bore and the sliding contact. 2. A cylinder block that rotates in response to rotation of a main shaft, and a plurality of cylinder bores provided on the same pitch circle from the center of the cylinder block in parallel with the main shaft.
A piston slidably inserted in each of the cylinder bores; a swash plate slidably contacting one end of each of the pistons to reciprocate the piston in the cylinder bore as the cylinder block rotates; In a piston type hydraulic device provided with a valve plate having a supply hole and a discharge hole for fluid to the cylinder bore, the end surface being slidably in contact with the outer peripheral surface on the tip side of the piston and the inner peripheral surface on the open end side of the cylinder bore. A piston-type hydraulic device, characterized in that an escape groove for expanding a sliding gap with an inner peripheral surface of the cylinder bore is formed between the outer peripheral surface of the piston and a sliding contact.