JPH11210615A - Axial piston type pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an axial piston type pump with high capacity efficiency by controlling the inclination of a cylinder block to be a lowering factor of mechanical efficiency of a pump. SOLUTION: An axial piston type pump houses a cylinder block 3, a piston 2, a cam plate 4, a valve plate 5, a main shaft 6 and the like in a casing 1, rotates the cylinder block 3 in the casing 1 by the rotation of the main shaft 6 and reciprocates the piston 2 to perform suction and discharge of fluid by the reciprocating motion of the piston 2. A support mechanism to support the cylinder block 3 in the casing 1 so that it can rotate freely is constructed with a cylinder block bearing 8, a stretched bearing to support one end of the cylinder block 3 and an outside support bearing 11 or a shaft support bearing to support the other end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial piston pump having a piston, a cylinder block, a swash plate, a valve plate, and a main shaft, and using a low-viscosity fluid such as water as a working fluid.

[0002]

2. Description of the Related Art FIG. 7A is a sectional view showing the structure of an axial piston pump of this type, and FIG. 7B is a view of a valve plate 5 viewed from the direction of arrow A in FIG. As shown in FIG. 7A, the axial piston pump has a structure including a casing 1, a piston 2, a cylinder block 3, a swash plate 4, a valve plate 5, a main shaft 6, and the like. When the main shaft 6 rotates, the cylinder block 3 spline-connected to the main shaft 6 also rotates, the slipper 7 slides on the surface of the swash plate 4, and the piston 2 reciprocates in the cylinder block bore 3a. I have. Further, the valve plate 5 has a disk shape in which a low pressure port 5a and a high pressure side port 5b are formed in an arc shape with a line connecting the top dead center B and the bottom dead center C interposed therebetween.

While the cylinder block 3 rotates from the bottom dead center C to the top dead center B, the piston 2 moves rightward and the valve plate 5
From the low pressure port 5a of the cylinder block bore 3a
While the cylinder block 3 rotates from the top dead center B to the bottom dead center C, the piston 2 moves to the left and the valve plate 5
The fluid is discharged from the high pressure port 5b. That is, the axial piston type pump is a pump of a type in which a fluid is sucked and discharged using a volume change due to a reciprocating motion of the piston 2. The fluid sucked into the cylinder block bore 3a passes through the passage 2a in the piston 2, flows into the sliding surfaces of the swash plate 4 and the slipper 7, and acts as a lubricating liquid.

As described above, in the axial piston type pump, the cylinder block 3 rotates with the rotation of the main shaft 6, and the cylinder block is supported by a projecting bearing mechanism as shown in FIG. Is often used. In particular, in a pump of this system using a low-viscosity fluid such as water as a working fluid, a slide bearing by lubrication of the working fluid is used as the cylinder block bearing 8.
In FIG. 7A, reference numeral 9 denotes a bearing (ball bearing) that supports the main shaft 6, and reference numeral 10 denotes a shaft seal.

[0005]

In the axial piston pump having the above structure, there is a slight gap between the cylinder block 3 and the cylinder block bearing 8.
In actual operation, in many cases, the cylinder block 3 is driven by the load received by the piston 2 from the swash plate 4 or the cylinder block 3.
Under the influence of the pressure balance between the valve block 5 and the valve plate 5, the cylinder block 3 rotates inclining in this gap. In addition, this inclination is inclined in a direction in which the gap on the high pressure port 5b side of the valve plate 5 becomes larger (wedge shape).

FIG. 8 is a view showing a gap between the valve plate 5 (high pressure port 5b side) and the sliding surface of the cylinder block 3 when the cylinder block 3 is inclined. As shown in the figure, when the cylinder block 3 is inclined in the gap between the cylinder block 3 and the cylinder block bearing 8 as described above, a part of the discharge flow rate Q of the working fluid from the piston 2 is reduced by the valve plate 5 and the cylinder. It leaks through the gap h between the block 3. The leakage flow rate is a leakage loss and is a factor that lowers the volumetric efficiency of the pump.

In order to suppress the inclination of the cylinder block 3, there is a measure to increase the length of the cylinder block bearing 8 in the thrust direction (axial direction).
The cylinder block bearing 8 and the cylinder block 3
Since the area of the sliding surface between them increases, the mechanical loss due to the friction between the two increases, which causes a problem that the mechanical efficiency of the axial piston pump decreases.

The present invention has been made in view of the above points, and an object of the present invention is to provide an axial piston type pump capable of suppressing the inclination of the cylinder block 3 which causes a reduction in mechanical efficiency of the pump and obtaining a high volumetric efficiency. Aim.

[0009]

According to the first aspect of the present invention, a cylinder block, a piston, a swash plate, a valve plate, a main shaft, and the like are housed in a casing, and the casing is rotated by rotation of the main shaft. An axial piston type pump in which a cylinder block rotates and a piston reciprocates and a piston reciprocates to suck and discharge a fluid, a supporting mechanism for rotatably supporting the cylinder block in a casing is provided at one end of the cylinder block. And a peripheral support bearing or a shaft support bearing for supporting the other end.

[0010] The invention described in claim 2 is the same as the claim 1.
The axial piston type pump described in (1) is characterized in that a groove is provided in the axial direction on the cylinder block sliding surface of the outer peripheral support bearing or the shaft support bearing.

[0011] The invention according to claim 3 is based on claim 1.
Or in the axial piston type pump according to 2,
The outer peripheral support bearing or the shaft support bearing is made of a resin material.

The invention described in claim 4 is the first invention.
Or in the axial piston type pump according to 2,
The outer peripheral support bearing or the shaft support bearing is made of a ceramic material.

The invention described in claim 5 is the first invention.
Or in the axial piston type pump according to 2,
The sliding surface of the cylinder block of the outer peripheral support bearing or the shaft support bearing is coated with ceramic.

[0014] The invention according to claim 6 is the first invention.
Or in the axial piston type pump according to 2,
The sliding surface of the cylinder block of the outer peripheral support bearing or the shaft support bearing is coated with titanium nitride (TiN).

The invention described in claim 7 is the first invention.
Or in the axial piston type pump according to 2,
The sliding surface of the cylinder block of the outer peripheral support bearing or the shaft support bearing is coated with diamond-like carbon (DLC) material.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the structure of an axial piston pump according to the present invention. In FIG. 1, portions denoted by the same reference numerals as those in FIG. 7 indicate the same or corresponding portions, and thus description thereof will be omitted.

This axial piston type pump comprises a casing 1, a piston 2, a cylinder block 3, a swash plate 4, a valve plate 5, a main shaft 6, and the like. A low viscosity fluid such as water is used as a working fluid in FIG. It is the same as the pump, but differs in that a cylinder block bearing 8 which is an overhang bearing and an outer peripheral support bearing 11 are used together as a support mechanism for rotatably supporting the cylinder block 3 in the casing 1. As shown, the outer peripheral support bearing 11 is arranged to support the outer periphery of the cylinder block 3 on the valve plate 5 side, and the cylinder block bearing 8 is arranged to support the outer periphery of the cylinder block 3 on the side opposite to the valve plate 5.

When only the overhanging bearing 9 is used as the support mechanism for the cylinder block 3 as in the prior art, due to restrictions on the processing accuracy and the processing method at the time of manufacture, the radial direction of the cylinder block 3 and the cylinder block bearing 8 is limited. There was a limit to the minimum gap. As described above, the leakage of the working fluid through the gap between the valve plate 5 and the cylinder block 3 due to the inclination of the cylinder block 3 in this gap causes a reduction in pump efficiency.

Therefore, as shown in FIG. 1, the inclination of the cylinder block 3 can be reduced by using the cylinder block bearing 8 which is an overhang bearing and the outer peripheral support bearing 11 together. FIGS. 2A and 2B are conceptual diagrams showing comparative examples in which the outer peripheral support bearing 11 is not used and in which the outer peripheral support bearing 11 is used. FIGS. d) shows the case where the outer peripheral support bearing 11 is used together. The gap width between the cylinder block 3, the cylinder block bearing 8 and the outer peripheral support bearing 11 is H
b, the inclination angle of the cylinder block 3 when the outer peripheral support bearing 11 is not used is θa,
When the inclination angle of the cylinder block 3 when
Then, θa> θb, and the inclination angle of the cylinder block 3 can be suppressed by installing the outer peripheral support bearing 11.

FIG. 3 is a view showing the structure of the outer peripheral support bearing. The outer peripheral support bearing 11 is cylindrical as shown, and the inner diameter thereof is formed slightly larger (2 Hb) than the outer diameter of the cylinder block 3. The outer peripheral support bearing 11 has a structure in which a groove is not provided in a sliding surface (inner surface) 11a with the cylinder block 3 as shown in FIG. 3 (a), and a structure in which the sliding surface 11a is formed as shown in FIG. 3 (b). A plurality (eight in the figure) of grooves 11b
There is also a structure in which the lubrication of the working fluid is improved to reduce the friction loss. The number of the grooves 11b is not limited to this.

The material of the outer peripheral support bearing 11 is made of resin (plastic material) or ceramics to enhance the anti-corrosion property when using water, and to improve the cylinder block 3 under water lubrication.
To reduce the friction loss when sliding with the material constituting the. Further, in order to suppress the friction loss on the sliding surface between the outer peripheral support bearing 11 and the cylinder block 3, the sliding surface is preferably coated with ceramics, titanium nitride (TiN), diamond-like carbon (DLC), or the like.
The cylinder block 3 is usually formed of a stainless steel material, but the sliding surface of the cylinder block 3 with the cylinder block bearing 8 and the outer peripheral support bearing 11 is also provided on the sliding surface with ceramics, titanium nitride (TiN), and diamond-like carbon (DLC). Etc. may be coated.

FIG. 4 is a sectional view showing another structure of the axial piston pump according to the present invention. In FIG.
Portions denoted by the same reference numerals as those in FIG. 7 indicate the same or corresponding portions, and thus description thereof will be omitted. This axial piston pump uses a cylinder block bearing 8 and a shaft support bearing 12 which are overhang bearings as a support mechanism for rotatably supporting the cylinder block 3 on a casing.

As shown in FIG. 6, the shaft support bearing 12 has a cylindrical portion 1 whose outer periphery is a sliding surface 12a with the cylinder block 3.
2b and the flange portion 12c are integrally formed,
The flange portion 12c is fixed to the casing, and the cylindrical portion 12b is fixed.
Is inserted into a shaft support bearing insertion hole 3b formed in the center of the cylinder block 3. Here, the axis of the shaft support bearing 12 and the axis of the main shaft 6 coincide with each other. In addition,
FIG. 6A is a longitudinal sectional view of the shaft support bearing 12, and FIG.
(C) is a side view, respectively.

As described above, by adopting a structure in which the cylinder block bearing 8 and the shaft support bearing 12 are used together as the support mechanism of the cylinder block 3, the inclination angle of the cylinder block 3 can be reduced. FIG. 5 is a conceptual diagram showing a comparative example in the case where the shaft support bearing 12 is not used and in the case where it is used together.
5A and 5B show the case where the shaft support bearing 12 is not used, and FIGS. 5C and 5D show the case where the shaft support bearing 12 is used together. Clearance width between outer peripheral surface of cylinder block 3 and cylinder block bearing 8 and shaft support bearing 12
When the gap width between the outer peripheral surface of the cylinder and the inner peripheral surface of the shaft support bearing insertion hole 3b is Hb, the inclination angle of the cylinder block 3 when the shaft support bearing 12 is not used is θa, and the shaft support bearing 12 is used together Assuming that the inclination angle of the cylinder block 3 is θb, θa> θb, and the inclination angle of the cylinder block 3 can be suppressed by installing the shaft support bearing 12.

As shown in FIG. 6B, the shaft support bearing 12 has a sliding surface (inner surface) of the cylindrical portion 12b with the cylinder block 3.
6 (a), a plurality of (eight in the figure) grooves 1 are formed on the sliding surface 12a as shown in FIG. 6 (c).
There is also a structure in which 2d is provided to improve the lubricity of the working fluid and reduce the friction loss. The groove 12d
The number is not limited to this.

Here, in order to suppress the friction loss on the sliding surface of the cylindrical portion 12b of the shaft support bearing 12 with the cylinder block 3, a resin, ceramics, titanium nitride (TiN), diamond-like carbon ( DLC) or the like. Also, cylinder block 3
Is usually formed of a stainless steel material, but the sliding surface of the cylinder block 3 with the shaft support bearing 12 (the inner peripheral surface of the shaft support bearing insertion hole 3b) is also formed of ceramics, titanium nitride (Ti).
N), diamond-like carbon (DLC) and the like.

In the axial piston type pump of the present invention shown in FIGS. 1 and 4, the length of the cylinder block bearing 8 as an overhanging bearing in the thrust direction is made shorter than that of the existing cylinder block bearing. In order to reduce the frictional loss, the countermeasures are taken to reduce the sliding area.

[0028]

As described above, according to the present invention,
Since the support mechanism for rotatably supporting the cylinder block in the casing is composed of an overhang bearing that supports one end of the cylinder block and an outer peripheral support bearing or a shaft support bearing that supports the other end, the inclination angle of the cylinder block is reduced. Can,
As a result, the clearance between the sliding surface of the valve plate and the sliding surface of the cylinder block is reduced, and leakage of working fluid is reduced.
In an axial piston pump using a low-viscosity fluid such as water as a working fluid, an excellent effect of improving pump efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structural example of an axial piston pump according to the present invention.

2 (a) and 2 (b) are conceptual diagrams showing comparative examples of a case where an outer peripheral support bearing is not used and a case where the outer peripheral support bearing is not used. FIGS. ) Shows the case where the outer peripheral support bearing is used together.

FIGS. 3A and 3B are diagrams showing examples of the structure of an outer peripheral support bearing.

FIG. 4 is a sectional view showing the structure of an axial piston pump according to the present invention.

5 (a) and 5 (b) are conceptual diagrams showing comparative examples of a case where a shaft support bearing is not used and a case where a shaft support bearing is not used. FIGS. ) Shows the case where a shaft support bearing is used together.

6 (a), 4 (b) and 4 (c) are views showing the structure of a shaft support bearing.

FIG. 7A is a cross-sectional view showing the structure of a conventional axial piston pump, and FIG.
It is the A arrow view of (a).

FIG. 8 is a view showing a gap between a valve plate and a sliding surface of the cylinder block when the cylinder block is inclined.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing 2 Piston 3 Cylinder block 4 Swash plate 5 Valve plate 6 Main shaft 7 Slipper 8 Cylinder block bearing 9 Bearing 10 Shaft seal 11 Peripheral support bearing 12 Shaft support bearing

Claims (7)

[Claims] 1. A cylinder block, a piston, a swash plate, a valve plate, a main shaft, and the like are accommodated in a casing. The rotation of the main shaft rotates the cylinder block in the casing and reciprocates the piston. An axial piston type pump that suctions and discharges a fluid by movement, comprising: a support mechanism that rotatably supports the cylinder block in a casing; an overhang bearing that supports one end of the cylinder block; and an outer peripheral support bearing that supports the other end. An axial piston pump comprising a shaft supporting bearing. 2. The axial piston pump according to claim 1, wherein a groove is provided in an axial direction on a cylinder block sliding surface of the outer peripheral support bearing or the shaft support bearing. 3. The axial piston pump according to claim 1, wherein the outer peripheral support bearing or the shaft support bearing is made of a resin material. 4. The axial piston pump according to claim 1, wherein the outer peripheral support bearing or the shaft support bearing is made of a ceramic material. 5. The axial piston pump according to claim 1, wherein the sliding surface of the cylinder block of the outer peripheral support bearing or the shaft support bearing is coated with a ceramic material. 6. The axial piston pump according to claim 1, wherein titanium nitride (TiN) is provided on a sliding surface of the cylinder block of the outer peripheral support bearing or the shaft support bearing.
Axial piston type pump characterized by coated material. 7. The axial piston pump according to claim 1, wherein a sliding surface of the cylinder block of the outer peripheral support bearing or the shaft support bearing is coated with diamond-like carbon (DLC) material. Piston type pump.