JPH04136488A - Piston for compressor provided with piston ring - Google Patents

Abstract

PURPOSE:To provide satisfactory sealability and prevent shortage of an oil film between a piston ring and a cylinder bore by fastening the piston ring on the bottom side of a ring groove, and forming oil reservoirs on an outer peripheral surface of the piston ring. CONSTITUTION:A piston ring 5 formed of circular plate-like PTFE is bend-laid and the resultant outer peripheral surface is a surface 51 on which a plurality of oil reservoirs 510 of circular recessions are scooped out. In order to fit the piston ring 5 to a piston 2, the ring 5 is bend-laid from the bottom side 212 to the head side 211 of a ring groove 21 such that the surface 51 is faced to the side of a cylinder bore 10. The piston ring 5 is then widened by a back pressure applied to a gap C4, while lubricating oil moving from the bottom side 212 to a gap C3 is effectively held by the oil reservoirs 510, keeping in contact with the cylinder bore 10. Shortage of an oil film in respect to the cylinder bore 10 is prevented even if a compressor is operated under a severe condition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piston for a compressor having a piston ring, and more specifically to a piston for a reciprocating compressor fitted with an endless type resin piston ring. Regarding.

[Prior Art] Among the reciprocating compressors, such as crank type, swash plate type, and rocking swash plate type, in which a piston reciprocates within a cylinder pore to compress fluid, the swash plate type compressor for vehicle air conditioning shown in Fig. 13 is used. This will be explained using a machine as an example. In this compressor, when the piston 2 disposed in the cylinder bore 10 of the cylinder block 1 reciprocates within the cylinder bore 10, the piston 2 is moved in order to prevent refrigerant gas from leaking through the sliding gap. A piston ring 3 is fitted around the outer periphery. piston ring 3
is made of synthetic resin with excellent heat resistance and abrasion resistance, and there are two types: slit type and endless type. The conventional endless type resin piston ring 3 has a 14th
As shown in the figure, it is formed into a flat annular shape with a smooth surface 31 in the normal state, and as shown in Fig. 15, the jig (
(not shown) is expanded in the radial direction and inserted into the outer circumference of the piston 2, and then, using the bending of the annular part and elastic restoring force, the ring groove is opened so that the surface 31 is on the cylinder bore 10 side. 21 is bent from the head side 211 to the bottom side 212 (see, for example, Japanese Patent Laid-Open No. 57-24469).

[Problems to be Solved by the Invention] By the way, in the piston 2 having the conventional piston ring 3 described above, as shown in FIG. Even if there is an elastic restoring force in the area between the groove 21 and the bottom wall, there is a gap C1, that is, the piston ring 3 is fitted in the ring groove 21 in a floating state, and the gap C1 is maintained.
The piston ring 3 is expanded by the back pressure acting on the piston ring 3, thereby sealing the compressed fluid.

However, in the piston 2 having such a piston ring 3, the piston ring 2 tends to rotate in the circumferential direction during reciprocating stroke within the cylinder pore 10, and the piston ring 2 is abraded between the ring groove 21 and lacks durability. Something happened.

In addition, in this piston 2, when the compressor is started, sufficient back pressure does not act on the gap C1, so the outer circumferential surface 3
1 and the cylinder pore 10, the sealing performance was likely to be impaired.

Furthermore, in this piston 2, since the surface 31, which is the outer peripheral surface after the piston ring 3 is bent, is formed smoothly, it is difficult to operate the compressor at high speed for a long time, to start it at a low temperature, or to avoid fluid shortages. When operating under these conditions, an oil film tends to run out between the surface 31 and the cylinder pore 10, which causes the piston ring 3 to wear out or melt, resulting in damage to the piston 2 and the cylinder pore 10. There was a risk that creases or seizures would easily occur between the cylinder pores 10.

The present invention aims to achieve excellent sealing performance in a reciprocating compressor piston having an endless type resin piston ring, and also to prevent the oil film from running out between the cylinder pore and the piston. It is something to do.

[Means for Solving the Problems] In order to solve the above-mentioned problems, a compressor piston having a piston ring of the present invention is provided by expanding a resin piston ring, which is normally formed into a flat annular shape, in a radial direction. A piston for a compressor is provided that is inserted into an outer peripheral portion and then fitted into a ring groove using the bending of an annular portion and elastic restoring force, wherein the piston ring after fitting is located at the bottom of the ring groove. A novel method is adopted in which the sides are tightly attached and an oil reservoir is formed on the outer peripheral surface.

The piston ring can be tightly attached to the bottom side of the ring groove by bending the flat annular piston ring from the bottom side toward the head side when the piston ring is normally fitted into the ring groove.

Note that the dimensions of the piston ring in the normal state can be determined by the type of resin, the outer diameter of the piston, the diameter of the ring groove, the depth of the ring groove, etc. so that the piston ring is tightly fitted in the ring groove after fitting.

Further, the shape of the oil reservoir may be a recess or a through hole, and the number, size, pitch, etc. can be optimally selected depending on the type of compressor used.

[Function] In the compressor piston having the piston ring of the present invention,
Since the piston ring is tightly fitted on the bottom side of the ring groove, it is difficult for the piston ring to rotate in the circumferential direction during reciprocating stroke, reducing wear between the inner peripheral surface and the bottom wall of the ring groove. To prevent. In addition, the piston ring mounted in the V state in a tight state is elastically deformed so that the thickness on the bottom side is less than the thickness on the head side, and on the head side it contacts the cylinder bore without a gap due to the elastic restoring force. Therefore, this piston performs a sealing action suitably even during startup when back pressure is insufficient.

Moreover, in this piston, the piston ring is thicker on the bottom side than on the head side, and the oil reservoir on the outer circumferential surface is in sliding contact with the cylinder bore, so the lubricating oil moving from the bottom side is removed. The oil reservoir effectively retains the oil and prevents the oil film from running out between the inner surface of the cylinder pore and the inner surface of the cylinder pore even when the compressor is operated under severe conditions.

[Example] Hereinafter, an example in which the present invention is embodied in a piston of a swash plate compressor will be described with reference to the drawings. However, since the swash plate compressor is basically the same as the conventional one (see FIG. 13), the same reference numerals are given to it and detailed description thereof will be omitted.

(Example 1) First, as shown in FIG. 1 or FIG. 2, the piston ring 5 in a normal state will be described. This piston ring 5
is made of PTFE formed into a flat annular shape, and an oil reservoir 510 consisting of a plurality of circular recesses is bored in the surface 51 which becomes the outer peripheral surface after being bent. This piston ring 5 is obtained by cutting out a flat plate-shaped PTFE into an annular shape, in which an oil reservoir 510 has been previously formed in a pattern by a method such as hot pressing. This piston ring 5 is normally
Inner diameter id = 13mm, outer diameter Od = 28mm 1 plate thickness t = 3
mm, and the plate width W=10 mm. Further, the oil reservoir 510 is formed with a pitch of 1 mm, a pitch of 0.1 mm, and a depth of 0.3 mm.

On the other hand, the piston 2 into which the piston ring 5 is fitted is
As shown in Fig. 3, outer diameter 0D = 31 mm, diameter ID of ring groove 21 = 26.2 mm, depth T of ring groove 21 =
It is formed to have a thickness of 2.4 mm.

To fit the piston ring 5 onto the piston 2, use a jig (not shown) to expand it in the radial direction and insert it into the outer circumference of the piston 2, and then bend the annular part. Using the elastic restoring force, the surface 51 is aligned with the cylinder bore 10.
The ring groove 21 is bent from the bottom side 212 to the head side 211 so as to be on the side.

In this way, the piston ring 5 after fitting is tightly attached at the bottom side 212 of the ring groove 21 (arrow in the figure), as shown in FIG. 4, so that the thickness of the bottom side 212 is reduced due to elastic deformation. The thickness is lower than that of the head side 211, and a gap C3 is created between the bottom side 212 and the cylinder pore 10. Also, this piston ring 5
In order to apply an elastic restoring force on the head side 211, the oil reservoir 510 is connected to the cylinder bore 10 without creating a gap between the oil reservoir 510 and the cylinder bore 10 on the head side 211.
A gap C4 is created between the ring groove 21 and the bottom wall of the ring groove 21.

Compressor piston 2 with piston ring 5 of this embodiment
In this case, the piston ring 5 is placed on the bottom side 21 of the ring groove 21.
2, the piston ring 5 is hard to rotate in the circumferential direction during the reciprocating stroke, and wear between the inner circumferential surface and the bottom wall of the ring groove 21 can be prevented. can.

This piston 2 also has a piston ring 5 on the head side 2.
Since the cylinder pore 11 is brought into contact with the cylinder pore 10 without any gap, the sealing action can be suitably performed even at the time of startup. Moreover, in this piston 2, the piston ring 5 is expanded by the back pressure acting on the gap C4, and the many oil reservoirs 510 effectively hold the lubricating oil moving from the bottom side 212 direction to the gap C3, so that the cylinder pore Since it is in sliding contact with the cylinder pore 10, it is possible to prevent the oil film from running out between the cylinder pore 10 and the inner surface of the cylinder pore 10 even when the compressor is operated under severe conditions.

(Example 2) In the piston of this example, the shape of the oil reservoir of the piston ring is different from that of Example 1. The structure of the piston 2 is the same as the piston 2 having the piston ring 5 of the first embodiment. The piston ring 6 shown in FIG. 5 has an oil reservoir 610 formed of a plurality of through holes formed in an outer circumferential surface 61. The oil reservoir 610 is formed with a pitch of 2 mm and a pitch of 02 mm.

(Evaluation) A swash plate compressor was assembled using the piston with the piston ring 5.6 in Example 1.2 above and the piston with the conventional piston ring, and the volumetric efficiency of these was measured, and the gas amount Under 1/10 gas shortage conditions and -
The time until occurrence of seizure was measured under low temperature starting conditions of 5°C. The results are shown in Figures 6-8.

From these results, it can be seen that the compressor employing the piston of Example 1.2, which has excellent sealing properties, can compress at an initial stage with no significant difference from the conventional one, and can compress with excellent efficiency even after 1000 hours of operation.

In addition, the compressor that uses the piston of Example 1.2, which is less likely to run out of the oil film due to the lubricating oil held in the oil reservoir even under conditions of gas shortage and low-temperature start-up, is different from the compressor that uses the conventional piston. It can be seen that seizure is less likely to occur between the piston and cylinder bore than in the previous example.

(Other Embodiments) As a further embodiment, as shown in FIGS. 9 to 12, it is also possible to adopt an oil reservoir having a shape different from that of the piston ring 5.6 of Embodiment 1.2. Other configurations are Example 1
It is the same as the piston 2 with the piston ring 5. The piston ring 7 shown in FIGS. 9 and 10 has an outer peripheral surface 7
1, an oil reservoir 710 consisting of a plurality of rectangular recesses is bored.

Further, the piston ring 8 shown in FIGS. 11 and 12 has an oil reservoir 810 formed in the outer circumferential surface 81 formed of a plurality of linear recesses. These piston rings 7.8
Even if a piston is adopted, the same operation and effect as in Example 1.2 can be obtained.

[Effects of the Invention] As detailed above, in the compressor piston having the piston ring of the present invention, the piston ring after fitting is
Since the ring groove is tightly attached to the bottom side and an oil reservoir is drilled on the outer circumferential surface, excellent sealing performance can be achieved, and even when the compressor is operated under severe conditions, the cylinder bore remains intact. It is possible to effectively prevent the oil film from running out between the

Therefore, in a compressor that employs the piston of the present invention,
While maintaining excellent compression efficiency, piston rings are less likely to wear out or melt, and as a result, wrinkles or seizure between the piston and cylinder bore can be prevented for a long period of time.

[Brief explanation of drawings]

1 to 4 relate to Embodiment 1 of the present invention, FIG. 1 is a plan view of a piston ring, FIG. 2 is an enlarged sectional view taken along line A-A in FIG. FIG. 4 is an enlarged sectional view of the main parts of the compressor. FIG. 5 is an enlarged sectional view of the piston ring of Example 2. 6, 7, and 8 are graphs showing the characteristics of the pistons of Example 1.2 and Comparative Example. 9 to 12 relate to other embodiments, and FIG. 9 is a plan view of a piston ring;
10 is an enlarged sectional view taken along the line BB in FIG. 9, FIG. 11 is a plan view of the piston ring, and FIG. 12 is an enlarged sectional view taken along the line CC in FIG. 11. FIG. 13 is a longitudinal sectional view of the swash plate compressor. Figures 14 to 16 relate to conventional technology; Figure 14 is a plan view of a piston ring, Figure 15 is a sectional view showing how the piston ring is fitted into the piston, and Figure 16 is an enlarged view of the main parts of the compressor. FIG. 2...Piston 21...Ring groove 211...
・Head side 212...Bottom side 5.6.7.8...
・Piston ring 51.61.71.81...Outer peripheral surface 510.610, 710.810...Oil sump Patent applicant Toyota Industries Corporation Representative Patent attorney Hiroshi Okawa Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 14 Figure 15 Figure 16

Claims (1)

[Claims] (1) The resin piston ring, which is normally formed into a flat annular shape, is expanded in the radial direction and inserted into the outer circumference of the piston, and then fitted into the ring groove using the bending of the annular part and elastic restoring force. The piston ring for a compressor is provided with a piston ring characterized in that the piston ring after fitting is tightly attached to the bottom side of the ring groove and an oil reservoir is formed on the outer peripheral surface. Piston for compressor.