JPS62170785A - Rotary swash plate type axial piston pump - Google Patents

Abstract

PURPOSE:To lessen dead volume by parallelly providing an inlet check valve and an outlet check vale in the member engaging with a cylinder in which a pressure piston is slidably inserted. CONSTITUTION:An axial piston pump 20 has a pressure piston 4, a cylinder 8 and a swash plate 9, and an inlet check valve 2 and an outlet check valve 3 are parallelly provided in the direction in which a pressure piston 4 is slid in a spacer 18 independently of a cylinder 8 each other. Accordingly, the pressure piston 4 can slide to almost the end surface of the spacer 18, and the dead volume can be lessened up to the required minimum.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a rotating swash plate type axial piston pump,
By making it possible to open and close both the suction check valve and the discharge check valve in the axial direction, it is possible to
The present invention relates to a rotating swash plate type axial piston pump suitable for generating f/(!#).

[Conventional technology]

A conventional rotary swash plate type axial piston pump is described, for example, in Mechanical Design, Vol. 20, No. 6 (1976), p. 38. In FIGS. 6(a) and 6(b), among the suction and discharge check valves provided in the cylinder 8', one discharge check valve 3' is oriented in the axial direction, and the other suction check valve 2' is oriented in the axial direction. It was arranged perpendicular to the axial direction.

[Problem that the invention seeks to solve]

However, the above structure has a large dead volume, which will be described later, and is not suitable for an ultra-high pressure generation mechanism. The reason is explained below. Hydraulic oil is low.

In the case of medium pressure, it can be regarded as an incompressible fluid, but in the case of an ultra-high pressure hydraulic system of, for example, 3000 kg-f/cJ, the volumetric strain is 10% as shown in Figure 5.
Compressibility becomes a major problem.

However, the compression ratio β is defined by the following equation.

Here, dv/dP: rate of change in volume due to pressure change.

■o: When the piston is at the dead center The volume of oil in the pressure chamber is be.

From formula (1), ΔP=-ΔV/V o...(2)
β, and in order to increase the pressure, the compressibility β of the oil and the volumetric strain ΔV/Vo become issues. Here, the compression ratio β is a constant determined by the pressure of the hydraulic oil.

The volumetric strain is determined by the pressure piston 4' shown in FIG. 6(a).
The volume of fluid (displaced volume) ΔV that is displaced during the stroke S from the bottom dead center to the top dead center, and the amount that exists in the pressure chamber 25 when the piston 4' is at the top dead center as shown in FIG. 6(b). is the ratio of the volume of fluid Vo to the volume Vo of the fluid. In addition, the dead volume (volume that is not swept) mentioned above is Vo/Δ
V, that is, the volume inside the chamber 25 shown in FIG. 6(b). Therefore, to increase the pressure, it is necessary to increase the volumetric strain ΔV/VoO value. That is, if the displacement volumes ΔV are equal, the structure must be such that the volume Vo of oil in the pressure chamber 25 is small.

Returning to the foregoing, the pump described above had a structure in which the volume Vo of the fluid existing in the pressure chamber 25 was increased.

The present invention solves these problems and provides a rotating swash plate type axial piston pump with a small dead volume.

[Means for solving problems]

In order to achieve the above object, the present invention provides a rotating swash plate type axial piston pump in which suction and discharge check valves suck and discharge fluid through a pressurizing piston. The pistons are arranged in parallel within a member that engages with a cylinder into which the pistons are slidably inserted.

[Effect]

According to the above-mentioned configuration, the dead volume is kept to the necessary minimum by arranging check valves for suction and discharge in parallel to the direction in which the piston slides in the member that engages with the cylinder into which the piston is inserted. It can be made smaller. This not only makes it possible to reliably generate ultra-high pressure, but also simplifies the processing process and improves sealing performance.

〔Example〕

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

In Figures 1 to 3, the axial piston pump 2
0 is a cylinder block 1, a suction check valve 2, a discharge check valve 3, a pressurizing piston 4, a force transmitting piston 5,
It is composed of a piston shoe 6, a rotating shaft 7, a cylinder 8, a swash plate 9, a discharge flange 10, a casing 21, and the like. The casing 21 includes a plurality of divided bodies 11, 12,
13, 14, 15, and 16, and these divided bodies are integrally fixed with bolts or the like. Casing 2
A swash plate 9 is connected to a rotating shaft 7 located on the left side inside the housing 1, and the rotating shaft 7 is rotatably supported by a casing 21 via a bearing 17.22.

Further, the cylinder block 1 located on the right inside the casing 21 is supported by the casing 21.

A plurality of cylinders 8 are bored in the cylinder block 1 so as to have central axes parallel to the rotating shaft 7. The pressure piston 4 is fitted into the cylinder 8 via a sleeve 8' so as to be reciprocatable in the axial direction.

Further, a force transmitting piston 5 is slidably inserted into the cylinder block 1, and one end thereof engages with the swash plate 9 via a piston shoe 6. It is engaged with the piston 4. The suction check valve 2 and the discharge check valve 3 are independent from the cylinder 8, and the space 24 indicates a suction port.

Next, the operation of the pump of the present invention will be explained.

When the rotating shaft 7 is rotated by a drive motor (not shown), the swash plate 9 and the cylinder block 1 provided on the end face thereof rotate.

At this time, since the swash plate 9 is rotated at an angle with respect to the rotation axis 7 direction by a swash plate angle adjustment mechanism (not shown), the pressure piston 4 is rotated through the piston shoe 6 and the force transmission piston 5. It reciprocates within the sleeve 8'. The fluid sucked from the suction boat 24 by the reciprocating motion of the pressurizing piston 4 is sent to the pressure chamber 19 via the suction check valve 2, and after being pressurized by the pressurizing piston 4, the fluid is fed to the pressure chamber 19 via the suction check valve 2. 3 to the discharge boat 23.

The suction and discharge strokes of the pump are performed by the above-mentioned operations, but in the case of this embodiment, as shown in FIGS. 4(a) and 4(b), the cylinder 8, the suction check valve 2, and the discharge stroke Since the check valve 3 and the check valve 3 are provided independently from each other, and both the check valves 2 and 3 are not provided inside the cylinder 8, the pressurizing piston 4 can stroke until it comes close to the end face of the spacer 18. Yes, the volumetric strain Δ
Since the value of V/Vo can be increased, the pressure can be increased. That is, since it rotates obliquely with respect to the direction within the spacer 18, the pressurizing piston 4 is connected to the cylinder 8 via the piston shoe 6 and the force transmitting piston 5.
reciprocate inside. This reciprocating movement of the pressurizing piston 4 causes suction from the suction boat 24. The fluid is sent to the pressure chamber 19 via the suction check valve 5, pressurized by the pressurizing piston 4, and then discharged to the discharge port 23 via the discharge check valve 3.

The suction and discharge processes of the pump are performed by the above-mentioned operations, but in the case of this embodiment, the cylinder 8 and the suction check 2
and the discharge check valve 3 are independent of each other, that is, both check valves 2 and 3 are not provided inside the cylinder 8 as in the conventional case, so the pressurizing piston 4 can be rotated until it touches the end face of the spacer 18. It is possible to do so.

In addition, both check valves 2 and 3 are arranged so that they do not interfere with the end face of the cylinder 8, and the area of the flow path of the discharge port 23 is kept to the minimum range, so the dead volume is small and it is possible to generate ultra-high pressure. is effective.

As shown in FIG. 4(b), since the volume Vo of the fluid existing in the pressure chamber 19 can be made smaller than in the past, the dead volume can be reduced to the necessary minimum, and ultra-high pressure can be reliably maintained. It is possible to generate

Further, by arranging the two check valves in the axial direction, the machining process is greatly simplified compared to the conventional case where the check valves are arranged in the axial direction and in the direction perpendicular to the axial direction. That is, when the hole for the check valve is provided only in the axial direction, machining becomes easier.

On the other hand, if a check valve is placed perpendicular to the axial direction as in the past, a hole must be drilled in that direction, but this hole must be drilled through from the outside of the cylinder block. This makes the hole quite long and difficult to machine. Furthermore, from the perspective of sealing pressure oil, if the hole is perpendicular to the axial direction as in the past, a cylindrical face seal will be used, which provides a more reliable seal than the end face seal as in the present invention. It is difficult.

〔Effect of the invention〕

According to the present invention, since the check valves for suction and discharge are arranged in the axial direction, the dead volume can be reduced to the necessary minimum, so that ultra-high pressure can be reliably generated.

[Brief explanation of drawings]

Fig. 1 shows the rotary swash plate type axial piston of the present invention Fig. 4 (
a) and FIG. 4(b) are explanatory diagrams of the dead volume in the present invention. FIG. 4(a) is a state diagram when the piston is at the bottom dead center, and FIG. 4(b) is a state diagram when the piston is from the bottom dead center. FIG. 5 is an explanatory diagram of fluid density change due to pressure. FIG. 6(a) and FIG. 6(b) are explanatory diagrams of conventional dead volume. a), Figure 4(b)
). 2... Suction check valve, 3... Discharge check valve, 4... Pressurizing piston, 18... Spacer, 19
...Pressure chamber, 23...Discharge boat, 24...Suction boat.

Claims (2)

[Claims] 1. In a rotary swash plate type axial piston pump that sucks and discharges fluid through a pressurizing piston using suction and discharge check valves, the suction and discharge check valves are installed in a cylinder into which the pressurizing piston is slidably inserted. A rotary swash plate type axial piston pump characterized in that the pump is arranged in parallel within a member that engages with the axial piston pump. 2. The rotating swash plate type axial piston pump according to claim 1, wherein the member that engages with the cylinder is a spacer.