JPH0370118B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a piston-type fluid machine such as a piston pump motor or a compressor, and particularly to a piston-type fluid machine suitable for preventing seizure between a cylinder and a piston. It is.

[Conventional technology]

FIG. 6 shows a conventionally commonly used piston type fluid machine.

The main shaft 1 is slidably fitted into the center of the cylinder barrel 2 via a spline 10. A plurality of cylinders 4 are bored on the same circumference of the cylinder barrel 2, and pistons 3 are slidably inserted into the cylinders 4, respectively. A bushing 5 is interposed between the cylinder 4 and the piston 3 to prevent seizure. The bush 5 is made of a material that does not seize easily, such as a copper alloy, and is fitted into the cylinder 4 by casting adhesive, press fitting, or the like. As shown in FIG. 7, a plurality of rows of circumferential grooves 5a are bored near the end of the bush 5 on the side where the piston 3 is inserted. The tip of the piston 3 is formed into a spherical shape and abuts on the spherical groove of the shoe 6. The swash plate box 7 is provided to be inclined to the main shaft 1, and a swash plate 8 is provided on the inclined surface. The shoe 6 is formed so that it can slide on the swash plate 8 along the circumferential direction while being guided by the spherical seat 11.

A port plate 9 is fixed to the main body side, and an inlet/discharge port 9a communicating with the main body side is formed in the port plate 9. This suction and discharge port 9
a is formed at a position communicating with the cylinder 4, respectively.

With the above configuration, when the main shaft 1 is rotated and the cylinder barrel 2 is rotated, the shoe 6 slides along the swash plate 8, and the piston 3 reciprocates accordingly. Therefore, suction and compression forces act within the cylinder 4,
A medium (fluid such as oil) is sucked into the cylinder 4 through the suction and discharge port 9a and is discharged.

As shown in FIG. 7, during operation, a lateral force W is applied to the center Os of the tip of the piston 3 as a reaction force from the swash plate 8.
works as shown.

Due to the action of this lateral force W, a bending moment acts on the piston 3, causing it to tilt as shown. Therefore, an inclined gap is formed between the inner surface of the cylinder 4, more precisely, the inner surface of the bush 5 and the piston 3. Therefore, the pressure distribution acting within this inclined gap is
As shown in the figure, the pressure does not become constant. That is, when the circumferential groove 5a is not formed in the bush 5, the pressure distribution will be as shown by the dotted line, and the side in which the centrifugal force of the cylinder 4 acts (the side where the gap narrows toward the open side of the cylinder 4) is as shown in the figure. The distribution is a convex curve as shown in the upper part (shown in A), and the opposite side (the side where the gap widens toward the open side of the cylinder 4) is a concave curve as shown in the lower part of the figure (shown in B). Become.

However, when the circumferential groove 5a is present, the pressure distribution curve becomes as shown by the solid line in the figure, and no pressure distribution occurs in the circumferential groove 5a.

Due to the pressure in the gap based on the above pressure distribution, a bending moment M is applied which is opposite to the direction of the bending moment due to the lateral force W, and presses the piston 3 in a direction away from the inner circumferential surface of the bush 5.

From the above, during high-pressure operation in which a large lateral force W acts on the piston 3, the presence of the circumferential groove 5a reduces the bending moment M mentioned above, causing the piston 3 to hit the bush 5 unevenly, which tends to cause seizure damage. Defects arise.

On the other hand, in normal cases, the medium in the cylinder 4 is supplied into the circumferential groove 5a and forms an oil film, etc.
Compared to a case without the circumferential groove 5a, it has the advantage of being more effective in preventing seizure and also being more effective against centrifugal force during rotation. Therefore, there has been a need for a simple structure that is effective in preventing seizure both at low pressure, high speed, and during high pressure operation.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above circumstances, and its object is to provide a piston-type fluid machine with a simple structure that has seizure resistance over the entire operating range.

[Means for solving problems]

In order to achieve the above object, the present invention utilizes a piston-type fluid machine in which a groove is formed in a part of the inner circumferential surface of a cylinder on which a piston slides in a direction in which centrifugal force is applied.

[Effect]

By supplying the medium into the grooves formed only in the direction of centrifugal force on the inner circumferential surface of the cylinder, this prevents seizure due to centrifugal force during high-speed rotation and low-pressure operation. This is to prevent seizure during operation.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

In FIGS. 1 to 5, the same reference numerals as in FIG. 6 indicate the same items or items with the same function.

As shown in FIGS. 1 and 2, a plurality of rows of grooves 5b are formed on the inner circumferential surface of the bush 5 fitted into the cylinder 4.
is formed. This groove 5b is formed only in the E direction shown in FIG. 2, that is, the direction in which centrifugal force acts, and is formed along the circumferential direction at a position close to the piston insertion end of the bush 5 as shown in FIG. 3. is formed.

In Fig. 2, the case where the piston 3 engages with the cylinder 4 at the top dead center corresponds to the beginning of discharge, the middle stroke of discharge is in the F direction of the figure, and the bottom dead center corresponds to the end of discharge in the G direction. There is a point.

Next, the operation of this embodiment will be explained.

In Figure 2, when the cylinder 4 is engaged at the top dead center of the piston 3, a large lateral force W acts and a one-sided contact occurs (see Figure 7), but the piston speed is zero and seizure occurs. To prevent this, it is sufficient to consider only the influence of centrifugal force caused by the rotation of the cylinder barrel 2.
Pressure oil having the same pressure as in the cylinder 4 is supplied into the groove 5b and presses the piston 3, thereby preventing seizure due to centrifugal force. The groove 5b was formed near the end of the bush 5 on the insertion side of the piston 3 in consideration of the above-mentioned inclination of the piston 3 due to the lateral force W, and the position, size, number, etc. of the groove 5b are determined as appropriate depending on the capacity of the machine. are selected.

When the piston 3 engages with the cylinder 4 at an intermediate point F between the top dead center and the bottom dead center, a relatively high pressure is applied and the piston speed is also high. Therefore, uneven contact of the piston 3 occurs, making it easy to seize, but unlike the conventional technology, there is no circumferential groove 5a in this area, so the pressure distribution (dotted line) shown in FIG. 7 acts, and the lateral force W is resisted. A bending moment M of sufficient magnitude acts. Therefore, seizure due to uneven contact is prevented.

Furthermore, when the piston is at the bottom dead center, no lateral force or centrifugal force acts because it is the end stroke of the discharge.

As a result of the above, seizure can be reliably prevented in all ranges of high and low pressure and high speed rotation.

Further, this embodiment is a simple one in which the groove 5b is formed in the bush 5, and can be implemented easily and at low cost.

Figures 4 and 5 show other embodiments, in which grooves 5c connected in an inclined manner are formed in Figure 4, and grooves 5b arranged in parallel are connected by mutually communicating grooves in Figure 5. The groove 5d is shown. In either case, the same effects as in the above embodiment can be achieved.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the effect of improving seizure resistance over the entire operating range is achieved with a simple structure.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a cylinder axis showing an embodiment of the present invention, Fig. 2 is a sectional view taken along the - line in Fig. 1, Fig. 3 is a view taken in the direction of the arrow in Fig. 2, and Figs. 4 and 5 are A cross-sectional view corresponding to FIG. 3 of another embodiment, FIG. 6 is a cross-sectional view of the main part of the piston fluid machine of the prior art, and FIG. 7 is an explanatory cross-section explaining the lateral force acting on the piston and pressure distribution 8 is a cross-sectional view of FIG. 7. 1...Main shaft, 2...Cylinder barrel, 3...Piston, 4...Cylinder, 5...Button, 5a
...Circumferential groove, 5b, 5c, 5d...Groove, 6...Show, 7...Swash plate box, 8...Swash plate, 9...Port plate, 9a...Suction/discharge port, 10...Spline , 11... Spherical sitting.

Claims (1)

[Claims] 1. In a piston-type fluid machine in which a piston is reciprocated within a plurality of cylinders that are bored in the axial direction on the same circumference of a cylinder barrel that rotates around the axis, the inner periphery of the cylinder on which the piston slides. A piston-type fluid machine characterized by forming a groove in a part of the surface in the direction of centrifugal force.