JP2002168172A - Axial piston type hydraulic machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an axial piston type hydraulic machine requiring no highly precise machining and having a less leakage amount and a wear loss. SOLUTION: The axial piston type hydraulic machine having a piston 8, a cylinder block 2, a swash plate 10, a valve plate 12 and a spindle 3 comprises elastic bodies 20, 30 provided on the outer periphery of the piston 8 or on the inner face of a bore 7 and pressure flow passages 21, 31 for deforming the elastic bodies 20, 30, the elastic bodies 20, 30 being deformed to produce a less amount of leakage when the bore 7 is at a high pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION A piston reciprocating in a bore of a cylinder block rotating with a main shaft, a swash plate fixed to a casing and slippered by a slipper connected to the piston, and a low viscosity supplied to the piston is eliminated. And a valve plate for controlling a working fluid, and an axial piston type fluid machine having an elastic body at an outer peripheral portion of a piston or an inner peripheral portion of a bore.

[0002]

2. Description of the Related Art Such prior art is widely used as a pump or a motor. First, a conventional axial piston type fluid machine will be described with reference to FIGS. 5 and 6 in order to better understand the present invention. A cylinder block 2 is mounted in the casing 1 so as to rotate integrally with a main shaft 3, and the main shaft 3 is rotatably supported on the casing 1 by bearings 4. To prevent leakage. The cylinder block 2 is rotatably supported by the casing 1 via a cylinder block bearing 6.

A plurality of bores 7 formed in the cylinder block 1 (hereinafter simply referred to as a bore 7 using a reference numeral 7) respectively accommodate a piston 8 so as to be movable in an axial direction (left and right directions in the drawing). A slipper 9 is attached to the piston 8c, and the slipper 9 slides on a slope 10a of a swash plate 10 fixed to the casing 1.

[0004] Each of the bores 7 communicates with a flow path 11 to the outside, and the flow path 11 is provided with a valve plate 12. As shown in FIG. 6, the valve plate 12 has an arc-shaped low-pressure port 12a and a similar high-pressure port 12b. In the figure, U is a top dead center, and D is a bottom dead center. When the cylinder block 2 rotates in the direction of the arrow X, it operates as a pump, and when it rotates in the Y direction, it operates as a motor.

In operation, when the main shaft 3 rotates, the cylinder block 2 also rotates, and accordingly, the piston 8 reciprocates in the bore 7 of the cylinder block 2 due to the swash plate 10. While the cylinder block 2 rotates in the X direction from the bottom dead center D to the top dead center U, the piston 8 moves rightward in the drawing, and sucks fluid from the low pressure port 12 a of the valve plate 12 into the bore 7 of the cylinder block 2. While the cylinder block 2 rotates in the X direction from the top dead center U to the bottom dead center D, the piston 8 moves to the left in the drawing, and discharges fluid from the high pressure port 12b of the valve plate 12. That is, it operates as a pump that sucks in and discharges fluid by utilizing the volume change due to the reciprocating motion of the piston 8.

On the other hand, when the cylinder block 2 is used as a motor, a pressurized fluid is supplied to the high pressure port 12b of the valve plate 12 to rotate the cylinder block 2, whereby the connected main shaft 3 rotates. The return fluid is the low pressure port 1 of the valve plate 12.
From 2a, it returns to the tank piping which is not illustrated.

As shown in FIG. 7, in such a fluid machine, a leak generated in a gap δ between the outer periphery of the piston 8 and the bore 7 of the cylinder block 2 has a great effect on efficiency. In the case where the pressure P1 in the bore 7 becomes higher than the pressure P2 in the gap, that is, in the case of a pump, the piston 8 is in the discharge stroke of the pressurized fluid, and in the case of the motor, the supplied pressurized fluid causes the piston 8 to swash the swash plate 10. Leaks when it is located on the high pressure side pressed against the pressure, and the amount of this leak is a function of the working fluid pressure and clearance at that time.

[0008] For this purpose, various techniques for suppressing the leakage amount have been proposed. However, if the gap δ is reduced, the friction loss between the bore and the outer periphery of the piston increases.
Is known in which a resin having excellent lubricating properties (low friction and low abrasion) is coated on the inner peripheral surface under a low-viscosity fluid or such a resin is fitted. However, in the related art, since a resin is used, it is difficult to perform high-precision processing and clearance management as compared with metal in view of its properties.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an axial piston type fluid machine which does not require high-precision machining, can reduce a leakage amount, and has a small friction loss.

[0010]

According to the present invention, there is provided a swash plate in which a piston reciprocating in a bore of a cylinder block rotating with a main shaft and a slipper fixed to a casing and sliding with a piston are connected. A valve plate for controlling a low-viscosity working fluid supplied to and removed from the piston, and an axial piston type fluid machine having an elastic body on the outer periphery of the piston. In order to expand the elastic body radially outward, a pressurized flow path communicating with the bore is formed in the outer peripheral portion of the piston.

Further, according to the present invention, a piston which reciprocates in a bore of a cylinder block which rotates together with the main shaft and a swash plate which is fixed to a casing and slides with a slipper connected to the piston, and supply to the piston are eliminated. And a valve plate for controlling a low-viscosity working fluid, and an elastic body at the inner periphery of the bore with a force corresponding to the working pressure of the fluid in the axial piston type fluid machine having an elastic body at the inner periphery of the boss. In order to expand radially inward, a pressurizing flow path communicating with the working fluid flow path is formed in the inner peripheral portion of the bore.

Therefore, when the bore in the cylinder block communicates with the high pressure port of the valve plate, that is, when the pressure in the bore becomes high, the elastic body is actuated by the force of the working fluid applied from the pressurized fluid. It expands radially outward or inward. As a result, the gap between the outer circumferential surface of the piston and the inner circumferential surface of the bore is closed by the elastic body, so that the amount of the high-pressure working fluid leaking through the gap in the bore is suppressed. Therefore, the volumetric efficiency is improved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. Components corresponding to the above-mentioned prior art are denoted by the same reference numerals, and redundant description is omitted.

According to the present invention, a cylindrical elastic body 20 is provided on the outer peripheral portion of the piston 8. The elastic body 20 is preferably made of, for example, a Teflon (registered trademark) -based resin having excellent lubricating properties under a low-viscosity fluid. A plurality of (four in the illustrated example) radially extending pressurized flow paths 21 are formed in the hollow portion 8d of the piston 8. In addition,
Reference numeral 22 denotes a flow path leading to the slipper 9.

In the illustrated example, the upper piston 8 in the drawing communicates with the low pressure port 12a of the valve plate 12, and the lower piston 8 communicates with the high pressure port 12b of the valve plate 12. Therefore, since a high pressure is generated in the bore 7, the pressure causes the elastic body 20 to expand radially outward through the pressurizing flow path 21, thereby forming the expansion portion 22. Due to the expansion portion 22, the gap δ between the piston 6 and the bore 7 is reduced, and the amount of leakage can be reduced.

As described above, according to the present invention, in the case of a pump or a motor, the piston diameter changes due to the deformation of the elastic body by a force corresponding to the operating pressure at that time, and an appropriate radial gap δ can be obtained. it can. As described above, since the gap δ is small in the high-pressure region and large in the low-pressure region, the leakage amount is small and the friction loss is small. In addition, since the outer diameter of the piston changes according to the pressure, the management of the radial gap δ can be relatively easily performed, and a level of manufacturing precision that is difficult to process is not required.

FIG. 2 shows the experimental results of the embodiment shown in FIG. 1. The horizontal axis indicates the supply pressure (MPa), and the vertical axis indicates the leakage amount (cm ³ / s). In this experiment, the supply pressure was changed while the piston was stationary, and the amount of leakage from around the piston at that time was measured. The symbol □ indicates the case of the present invention, and the black circle indicates the conventional example. As can be seen from the figure, in the conventional example, the leakage amount increases almost in proportion to the pressure, but according to the present invention, it can be seen that the leakage amount substantially disappears.

FIGS. 3 and 4 show another embodiment of the present invention. In FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals. In this embodiment, a cylindrical elastic body 30 is provided on the inner peripheral surface of the bore 7 by fitting or coating. From the space between the valve plate 12 and the bore 7 of the pressurizing flow path 11, a plurality of (two in the illustrated example) pressurizing flow paths 31 communicate with a circular groove 32 provided near the center of the bore 3. The number and direction of the pressurized flow channels 31 can be arbitrarily designed.

Accordingly, similarly to the above-described embodiment, the elastic body 30 on the high pressure side is deformed by the pressurized fluid from the pressurized flow path 31 so as to have an expanded portion indicated by reference numeral 33, thereby reducing the amount of leakage. it can.

FIG. 4 is a view taken along the line AA of FIG. 3, and has six bores 7 in the illustrated example, and an elastic body 30 is provided on each inner peripheral surface thereof. Each of the pressurized flow paths 31 is perforated in the cylinder block 2, and unnecessary portions thereof are closed by plugs P.

[0022]

As described above, according to the present invention, since the elastic body is deformed by the pressurized fluid from the pressurized flow path, the higher the pressure, the larger the amount of deformation. As a result, the gap between the piston and the bore is increased. Can be reduced, and the amount of leakage decreases. Therefore, the efficiency of the axial piston type fluid machine can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram showing the effect of the present invention.

FIG. 3 is a sectional view showing another embodiment of the present invention.

FIG. 4 is a view taken in the direction of the line AA in FIG. 3;

FIG. 5 is a sectional view of a conventional axial piston type fluid machine.

FIG. 6 is a plan view of the valve plate as viewed in a direction B in FIG. 5;

FIG. 7 is a diagram for explaining the amount of leakage.

[Description of Signs] 1 ... Casing 2 ... Cylinder Block 3 ... Main Shaft 4 ... Bearing 5 ... Shaft Seal 6 ... Cylinder Block Bearing 7 ... Bore 8 ... Piston 9 ... Slippers 10 ... Swash plate 10a ... Slope 11 ... Flow path 12 ... Valve plate 12a ... Low pressure port 12b ... High pressure port 20,30 ... Elastic body 21,31 ... Pressurized channels 22, 23 ... Expanded parts 32 ... Circular grooves

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Atsushi Yamaguchi 79-5, Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa Prefecture Inside the Department of Production Engineering, Faculty of Engineering, Yokohama National University (72) Inventor Yutaka Otaka 79, Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa No. 5 Yokohama National University Faculty of Engineering Department of Production Engineering F-term (reference) 3H070 AA01 BB04 BB06 CC06 CC21 CC29 CC31 DD09 DD28 3H071 AA03 BB01 CC11 CC28 CC31 DD01 3H084 AA08 AA16 BB07 BB16 BB23 CC02 CC12 CC59

Claims (2)

[Claims] 1. A swash plate, in which a piston reciprocating in a bore of a cylinder block rotating together with a main shaft, a swash plate fixed to a casing and slippers connected to the piston slide, and a low-viscosity operation supplied to and removed from the piston. In an axial piston type fluid machine having a valve plate for controlling fluid and having an elastic body at the outer periphery of the piston, the elastic body at the outer periphery of the piston is radially expanded outward by a force corresponding to the operating pressure of the fluid. Therefore, a pressurized flow passage communicating with the bore is formed in the outer peripheral portion of the piston. 2. A swash plate, in which a piston reciprocating in a bore of a cylinder block rotating together with a main shaft, a swash plate fixed to a casing and slippers connected to the piston slide, and a low-viscosity operation supplied to and removed from the piston. A valve plate for controlling the fluid, the axial piston type fluid machine having an elastic body in the inner peripheral part of the bore, the elastic body in the inner peripheral part of the bore is radially inward by a force corresponding to the operating pressure of the fluid. An axial piston type fluid machine characterized in that a pressurizing flow passage communicating with a working fluid flow passage is formed in an inner peripheral portion of a bore for expansion.