JPS6210476Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is suitable for use in swash plate type rotary fluid machines, especially cylinder barrel rotating swash plate type hydraulic pistons, low pressure, low swash plate tilting angles such as pumps, motors, compressors, etc.
Concerning improved durability under high-speed rotation conditions.

1 to 3 are diagrams schematically showing conventional examples of a swash plate type rotary fluid machine.

FIG. 1 shows an example in which the center of gravity of the piston, including the piston and the piston shoe, on the axial line is always located within the sliding surface of the bush.

In Figures 2 and 3, when the tilt angle of the swash plate is zero, the center of gravity on the axis of the piston including the piston and the piston shoe is within the sliding surface of the bush, respectively.
An example is shown outside the sliding surface.

A cylinder barrel 2 is integrally fixed around the main shaft 1, a plurality of bushing holes 3a are bored in the axial direction on the same circumference in the cylinder barrel 2, and the bushing holes 3a are fitted into the bushing holes 3a from one side. a cylinder or bush 3, a piston 4 which is slidably inserted into the bush 3 on one side, and a piston bush 5 which is rotatably attached to a ball portion on the other side of the piston 4.
, a shoe retainer 6 in which the piston shoe 5 is attached to the swash plate 7 such that the piston shoe 5 is slidably in contact with the swash plate 7 , a casing 11 on one side of which the swash plate 7 is attached so as to be tiltable; A valve 8 that periodically communicates with the other side and the other side of the bushing hole 3a of the cylinder barrel 2 is connected to a port plate 9.
It is integrally fixed to the head 10 via.

As shown in FIGS. 1 to 3, in the conventional example, the center of gravity positions a and b on the axis of the piston 4, in which the piston shoe 5 is attached to the ball portion of the piston 4, are at the tilt angle of the swash plate 7. A feature of the conventional example is that when is zero, the end of the sliding surface of the bushing 3 that slides on the piston 4 does not coincide with the end (b).

The effects and drawbacks of the conventional example will be explained below.

A swash plate type pump with two rotations of cylinder barrel and piston 4 with a diameter of approximately 20 mm or more has a maximum oil pressure of 350 kg/cm ² , a maximum rotation speed of 4000 rpm, and a maximum tilt angle of swash plate 7 of 20°. things are used.
However, recent hydraulic pumps are diversifying and tending to be automatically controlled ^. The intersection angle with the swash plate 7 is called the tilt angle of the swash plate 7.), and is often used under conditions such as high rotation speed (2000 to 4000 rpm).

Under the above conditions, the side force of the piston 4 is mostly exerted by centrifugal force, so that the piston 4 and the bush 3 slide in small reciprocating motions at substantially the same circumferential position of the bush 3. As a result, an oil film cannot be sufficiently formed on the sliding surface portion, resulting in micro-movement wear, that is, fretting.

In the conventional hydraulic piston pump, when the tilting angle of the swash plate 7 is zero, that is, at the neutral position, the center of gravity positions a and b on the axis of the piston 4, with the piston shoe 5 attached to the ball portion, are as shown in FIG. cylinder barrel 2
In the case where it is located within the sliding surface of the bushing 3 in the
As shown in the figure, the bush 3 inside the cylinder barrel 2
In some cases, it is located outside the sliding surface. The center of gravity positions a and b are located inside and outside the sliding surface of the bush 3, respectively, throughout the entire stroke at a low tilting angle.

In the former case, in the sliding part A of Fig. 2,
In the latter case, the lubricating oil is difficult to enter into the sliding parts A in FIG. 3, and fretting is likely to occur.

As mentioned above, when used at low pressure, low tilt angle, and high rotation speed, conventional piston 4 tends to suffer from fretting, and if this condition continues, the sliding surface between piston 4 and bushing 3 will seize. This had a serious drawback, leading to serious damage to the main parts of the pump.

The purpose of this invention is to prevent piston seizure by preventing fretting under conditions of low pressure (~10Kg/ ^cm2 or less), low tilt angle (~6° or less), and high rotation speed (~2000rpm or more). An object of the present invention is to provide a swash plate type rotary fluid machine that can eliminate the problem.

In order to prevent fretting from occurring under the above operating conditions of the piston, (i) the contact positions of the sliding parts should always be easily changed from each other, and (ii) oil should be kept between the sliding surfaces as much as possible. Wedge or Squeeze to make it easier to enter.
It is important to exercise in a way that produces the following effects. In order to achieve these (i) and (ii), in the present invention, the inner and outer ends of the cylinder are substantially rounded, and the center of gravity in the axial direction of the piston to which the piston shoe is attached is adjusted. The swash plate is characterized in that it is arranged so as to coincide with the outer end position of the inner surface of the cylinder where edge cutting begins when the tilt angle of the swash plate is zero, that is, the end of the sliding surface of the cylinder.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof illustrated in FIG. 4 of the accompanying drawings.

4 to 6 are longitudinal sectional side views showing the main parts of the embodiment of the present invention. FIG. 4 shows a situation where the tilting angle of the swash plate is zero, that is, the piston is located at the center of the stroke, FIG. 5 shows a situation where the piston is located at the top dead center, and FIG. 6 shows a situation where the piston is located at the bottom dead center.

Components having the same reference numerals in FIGS. 1 to 3 showing the conventional example and those in FIGS. 4 to 6 showing the embodiment of the present invention have almost the same structure, and a description thereof will be omitted.

The present invention differs from the conventional example in that the inner and outer ends of the piston shoe cylinder, that is, the bush 3, are substantially rounded, and the piston shoe 5
When the tilt angle of the swash plate 7 is zero, the center of gravity position c on the axis of the piston 4 rotatably attached to the ball part is,
It is arranged so as to coincide with the outer end position of the inner surface of the bush where the corner chamfering begins, that is, the end point C of the sliding surface of the cylinder that slides on the piston 4.

Under operating conditions of low pressure, low tilt angle and high rotational speed,
Since a side force acts on the piston 4 approximately in the direction of centrifugal force, that is, in the radial direction from the axis of the main shaft 1, the sliding movement between the piston 4 and the bushing 3 is a minute reciprocation at approximately constant points in the circumferential direction of the bushing 3. Repeat. Therefore, the atmosphere is likely to cause fretting, but in this invention, as shown in Figure 4,
When the swash plate 7 is in the neutral position where the tilt angle is zero, that is, when the piston 4 is at the center of its stroke, the center of gravity position c on the axis of the piston 4, in which the piston shoe 5 is attached to the ball, is aligned with the piston 4. It coincides with the sliding surface end C of the sliding bush 3.

Furthermore, when the piston 4 is at the top dead center, the centrifugal force causes the piston 4 to tilt and move relative to the bushing 3, as shown in FIG. The point of contact between the two constantly changes to the tinged part. Therefore the aforementioned requirements
(i) will be satisfied. On the other hand, when the piston 4 is at the bottom dead center, the piston 4
and bushing 3 are in line contact and slide. This state is the same as before, but at this time, in this invention, the above-mentioned requirement (ii) is met.
A squeezing effect occurs. In particular, the squeezing effect becomes large when the inclination of the axis of the piston 4 with respect to the axis of the bushing 3 changes from the state shown in FIG. 5 to the states shown in FIGS. 4 and 6.

In this way, in the piston 4 of the present invention, the swash plate 7
During one rotation of the piston, the axial contact point of the piston changes. In addition, due to changes in the inclination between the axis of the piston 4 and the axis of the bushing 3 as shown in Figures 5 and 6, it is expected that an oil film will be formed due to the squeezing effect on the sliding surface and that lubricating oil will enter. . Therefore, fretting is less likely to occur between the piston 4 and the bushing 3, and seizure of the piston 4 can also be prevented.

The reason why the operating conditions of the piston 4 are limited here is that in the high pressure, high tilt angle, and high rotation range, the direction of the side face of the piston 4 changes significantly during one rotation, and the lubrication between the piston 4 and the bushing 3 is reduced. This is because it is easier for oil to enter, so fretting is generally less likely to occur and seizure is not a problem.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway side view of a conventional swash plate-type rotary fluid machine in which the center of gravity on the axis of the piston is always located within the sliding surface of the bushing. When the center of gravity on the axis of the piston is within the sliding surface of the bushing, Figure 3 is a sectional view of the main part of the conventional example. Figures 4 to 6 are views similar to Figure 2 of the conventional example that is outside the sliding surface, and Figures 4 to 6 are views similar to Figure 2 of the main parts of the embodiment of the present invention, but each shows a different operating state. FIG. 1... Main shaft, 2... Cylinder barrel, 3... Bush, 3a... Bush hole, 4... Piston, 5...
...Piston shoe, 6...Shu retainer, 7...
... Swash plate, 8 ... Valve, 9 ... Port plate,
10... Head, 11... Casing, A... Sliding part, B, C... Sliding surface end, a, b, c... Center of gravity position.

Claims (1)

[Scope of utility model registration request] A swash plate type rotary fluid machine in which a piston shoe attached to the outer end of a piston whose inner end is inserted into an axially extending cylinder bored in a cylinder barrel that rotates around its axis comes into sliding contact with a swash plate. In the above, the inner and outer ends of the cylinder are substantially rounded, and the center of gravity position c in the axial direction of the piston 4 to which the piston shoe 5 is attached is
A swash plate type characterized in that, when the tilt angle of the swash plate 7 is zero, the slanting plate 7 is arranged so as to coincide with the outer end position of the inner surface of the cylinder where the chamfering starts, that is, the end C of the sliding surface of the cylinder. Rotating fluid machine.