JPH08270557A - Piston for high pressure gas compressor - Google Patents

Abstract

PURPOSE: To extend the life of a piston ring and reduce the leakage amount of gas by adjusting push-press force against the cylinder inner surface of each piston ring of a piston having a plurality of piston rings to the weakest possible uniform push-press force, and reducing the abrasion of the piston ring. CONSTITUTION: In a piston for high pressure gas compressor which is provided with a plurality of annular piston ring grooves 5 on the outer circumferential part of a cylindrical piston 2 which is reciprocatingly slide-moved on a cylinder 1 inner surface, and in which piston ring 8 is fitted to each piston ring groove 5, a communicating hole 12 communicated from the top end part of respective piston 2 with a compressing chamber is arranged from a plurality of piston ring grooves 5 which are positioned near the top end part of piston 2 in the piston groove 5, and also gas communicating resistance of the communicating hole 12 is enlarged toward the communicating hole communicated with the piston ring grooves 5 which are positioned far from the top side of the piston top end.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston of an oilless reciprocating compressor for compressing natural gas or the like into a high pressure.

[0002]

2. Description of the Related Art Conventionally, an oil-free reciprocating compressor has been used in order to prevent lubricating oil from being mixed into compressed gas when compressing natural gas or the like to a high pressure. However, in order to operate the compressor without lubrication, a plurality of piston ring grooves are fitted with piston rings made of a material having a low coefficient of friction such as Fluoro resin. However, even if a fluororesin ring is used, when the compressor is operated without lubrication, the ring wears greatly and the life of the piston ring is short.As the piston ring wears, the gap between the piston ring notches opens and the leakage area increases. Increase, the amount of gas leakage increases, and the efficiency of the compressor decreases.

Further, among the plurality of piston rings, the piston ring on the top side near the compression chamber at the tip of the piston increases the pressing force of the piston ring against the inner surface of the cylinder due to the pressure of the compressed gas flowing into the inner back surface of the piston ring. However, the wear is particularly accelerated. Japanese Patent Fair 3-573
In Japanese Patent No. 212, the groove bottoms of a plurality of piston ring grooves are communicated with each other through a through hole, whereby the compressed gas flowing into the back surface of the top side piston ring is dispersed to the back surface of the second and subsequent piston rings, A method is disclosed for uniformly reducing the pressure on the back of each piston ring to reduce wear on the top piston ring.

[0004]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention In order to prevent wear of the piston ring of the conventional oil-free reciprocating compressor described above, the piston ring that is fitted in the communicating piston ring groove is merely connected to each other. The back pressure becomes equal, but the pressure of the gas that leaks from the compression chamber side through the gap between the piston and cylinder gradually decreases as it passes through each piston ring, and the gas pressure acting from the outside of each piston ring Is not constant, even if the gas pressure acting from the rear surface of the piston ring is made uniform by the through hole, the pressing force against the inner surface of the cylinder of the piston ring is never constant.

Therefore, according to the present invention, the pressing force of the piston having a plurality of piston rings against the inner surface of the cylinder of each piston ring is adjusted to be as weak and uniform as possible to reduce the wear of the piston ring and extend the life of the piston ring. An object of the present invention is to provide a piston of an oil-free reciprocating compressor that can be extended and reduce gas leakage.

Still another object of the present invention is to provide a structure of a piston which reduces wear on the top and bottom rider rings of the piston of the oilless reciprocating compressor.

[0007]

Means for Solving the Problems As a result of intensive studies by the present inventors in order to achieve the above object, as a result, a communication hole communicating from a plurality of piston ring grooves on the top side close to the compression chamber to the compression chamber on the top side. The pistons are formed by changing the thickness and / or the length of each communication hole so that the gas flow resistance of each communication hole becomes larger as the communication hole communicating with the piston ring groove farther from the tip of the piston. The inventors have found that the pressing force of the ring on the inner surface of the cylinder can be kept uniform and low, and have completed the present invention.

That is, the present invention provides a high-pressure gas compressor having a plurality of annular piston ring grooves on the outer circumference of a cylindrical piston that slides back and forth on the inner surface of the cylinder, and piston rings are fitted in the respective piston ring grooves. In the piston for use in the piston ring groove, a plurality of piston ring grooves close to the tip of the piston are provided with communication holes that respectively communicate from the tip of the piston to the compression chamber, and the piston ring far from the top side of the piston tip is formed. A gist of a piston for a high-pressure gas compressor is characterized in that a communication hole that communicates with a groove is formed so that a gas flow resistance of the communication hole increases.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a piston for a high pressure gas compressor according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of essential parts of an example of a high pressure gas compressor piston of the present invention.

In FIG. 1, reference numeral 1 is a cylinder of a compressor, and a piston 2 is reciprocally driven along the inner surface of the cylinder. The front end side of the piston 2 of the cylinder 1 constitutes a compression chamber 3, and the outer circumference of the piston 2 extends from the top side of the front end of the piston to a top side rider ring groove 4, a plurality of piston ring grooves 5, and a bottom side rider ring groove 6. Are sequentially engraved in an annular shape, and a top-side rider ring 7, a plurality of piston rings 8 and a bottom-side rider ring 9 are fitted in each.
A top side vertical hole 10 is formed from the tip of the piston 2 along the axial direction of the piston 2, communicates with the compression chamber 3, and a bottom side vertical hole 11 is formed from the base end of the piston 2 along the axial direction of the piston 2. It is bored and communicates with the back surface of the piston 2. Top side communication holes 12 that communicate with the top side vertical holes 10 from the plurality of piston ring grooves 5 near the top side of the piston 2 are provided, and from the plurality of piston ring grooves 5 near the bottom side of the piston 2 respectively. A bottom side communication hole 13 that communicates with the bottom side vertical hole 11 is provided. Further, a rider ring communication hole 14 communicating from the bottom side rider groove 6 to the bottom side vertical hole 11 is provided.

The top-side communication hole 12 has a smaller inner diameter as the communication hole is farther from the tip of the piston 2 to increase the gas flow resistance. The top-side communication hole 12 that communicates from the top-side piston ring groove 5 to the top-side vertical hole 10 has a hole diameter that allows a larger gas inflow amount than the gas inflow amount from the outer peripheral portion of the piston 2 to flow outward. On the other hand, the bottom side communication hole 13 has a smaller inner diameter as it goes farther from the base end portion of the piston 2 to increase gas flow resistance. The inner diameter of the rider ring communication hole 14 is determined so that the gas flow resistance is sufficiently small.

The communication holes 12 are formed in the piston ring grooves 5 respectively.
Also, one may be provided for the bottom side rider ring groove 6, or two or more may be provided. In particular, it is preferable to provide a plurality of top-side communication holes 12 and a plurality of rider-ring communication holes 14 communicating with the top-side piston ring groove 5 and the bottom-side rider ring groove 6 at equal intervals. As a result, the pressing force can be kept uniform over the entire circumference of the ring. As shown in FIG. 1, it is desirable to provide the piston ring 8 on the bottom side of the bottom side rider ring 9, but the communication hole 12 is not provided from the piston ring groove 5 on the bottom side.

In order to further reduce the amount of leaked gas, it is necessary to reduce the gap between the cylinder 1 and the piston 2.
In order to keep the sliding resistance low even if the gap is reduced, it is desirable to coat the cylindrical surface of the outer circumference of the piston 2 with the solid lubricating film 15 having excellent wear resistance and excellent lubricity. Solid lubrication film 15
For example, polyimide-based synthetic resins, polytetrafluoroethylene resins, polyhexafluoropropylene resins, and other fluorine-based synthetic resins are preferably used. Further, instead of forming a uniform film of the above-mentioned lubricous synthetic resin and coating the surface of the piston 2, metal plating is performed in a plating solution in which the lubricant powder is suspended to embed the lubricant powder. It is also possible to form a plated layer to form the solid lubricating film 15. The thickness of these solid lubricating films 15 does not have to be uniform as a whole, but rather it is preferable to increase the film thickness of the portion where the wear rate is high.

[0014]

According to the piston for a high pressure gas compressor of the present invention,
The high-pressure gas leaking from the compression chamber 3 to the bottom of the piston 2 through the gap between the cylinder 1 and the piston 2 at the tip of the piston 2 leaks between the top side rider ring 7 and the inner surface of the cylinder 1, and is the top side. Reaches the outer circumference of the piston ring 8 but the top side communicating hole 12 on the other hand is the top side
A larger amount of compressed gas flows from the compression chamber 3 to the rear surface of the piston ring 8 through the passage, and the gas pressure on the rear surface of the piston ring 8 becomes slightly higher than the gas pressure on the outer surface of the piston ring 8. The ring 8 is pressed against the inner surface of the cylinder 1 with a weak pressing force.

In the next second piston ring 8 from the top side, the gas pressure leaking through the outer circumference of the piston ring 8 beyond the first piston ring 8 is transferred to the first piston ring 8. Although it is lower than the gas pressure of No. 2, the top side communication hole 12 communicating with the second piston ring 8 passes through a communication hole 12 thinner than the top side communication hole 12 communicating with the first piston ring groove 5. The reduced gas pressure acts on the back surface of the piston ring 8,
The gas pressure acting on the outer surface of the second piston ring 8 becomes slightly larger, and the piston ring 8 is pressed against the inner surface of the cylinder 1 with a weakly adjusted pressing force.

In this way, as the distance from the top side is gradually increased, the gas pressure having a small flow rate and a reduced pressure acts on the back surface of the piston ring 8 through the top side communication hole 12 having a large flow resistance, so that the piston ring 8 moves. The pressing force can be adjusted to a substantially constant weak pressing force, the wear rate of the piston ring 8 is reduced, the life of the piston ring 8 is extended, the amount of gas leakage is reduced, and the efficiency of the compression chamber 3 is increased. be able to.

On the other hand, the gas pressure is released from the rear surface of the bottom rider ring 9 by the flow path communicating from the bottom rider ring groove 6 through the bottom communication hole 13 and the bottom vertical hole 11 to the rear surface of the piston 2. Therefore, the pressure on the back surface of the piston ring 8 on the bottom side can be reduced, and the pressing force of the piston ring 8 on the bottom side against the inner surface of the cylinder 1 can be kept low, and wear of the piston ring 8 can be reduced. Since the gas pressure acting on the outer side of the piston ring 8 closer to the bottom side becomes smaller, the inner diameter of the bottom side communication hole 13 communicating with the groove of the piston ring 8 is increased to reduce the gas flow resistance, and the rear surface of the piston ring 8 is reduced. Lower the gas pressure of
By reducing the pressing force of the piston ring 8, the pressing force of each piston ring 8 can be kept substantially uniform and small.

Further, since a flow path is provided from the bottom side rider ring groove 6 to the rear side of the piston ring 8 through the rider ring communication hole 14, the gas pressure on the rear side of the bottom side rider ring is reduced, and the life of the bottom side rider ring 9 is extended. be able to.

[0019]

According to the piston for a high-pressure gas compressor of the present invention, the pressing force of each piston ring 8 of the piston 2 of the oil-free high-pressure gas compressor on the inner surface of the cylinder 1 is adjusted to a low, substantially uniform pressing force. Therefore, the wear rate of the piston ring 8 can be reduced, the life of the piston ring 8 can be extended, the amount of gas leakage can be reduced, and the efficiency of the compressor can be improved.

The solid lubricating film 1 is formed on the cylindrical surface of the outer circumference of the piston 2.
By providing 5, the sliding resistance can be kept small even if the gap between the piston 2 and the cylinder 1 is made small, so that the gap can be made small and the leakage area at the abutment portion of the piston ring 8 can be reduced. It can be made small, the amount of gas leakage can be reduced, and the compression efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an outline of an example of a piston for a high-pressure gas compressor of the present invention.

[Explanation of symbols]

 1 Cylinder 2 Piston 3 Compression chamber 4 Top side rider ring groove 5 Piston ring groove 6 Bottom side rider ring groove 7 Top side rider ring 8 Piston ring 9 Bottom side rider ring 10 Top side vertical hole 11 Bottom side vertical hole 12 Top side communication Hole 13 Bottom side communication hole 14 Rider ring communication hole 15 Solid lubricant film

Front page continuation (71) Applicant 592215583 Kaji Tech Co., Ltd. 6 Bodhi, Mihara-cho, Minamikawachi-gun, Osaka Prefecture (72) Inventor Atsunori Sugihara 1-5-20 Kaigan, Minato-ku, Tokyo Tokyo Gas Co., Ltd. (72) Invention Akira Kobayashi 4-1-2, Hirano-cho, Chuo-ku, Osaka City, Osaka Gas Co., Ltd. (72) Inventor, Manabu Hattori, 507, Shintakamachi, Tokai City, Aichi Prefecture, Toho Gas Co., Ltd. (72) Invention Tokio Yoshida 1-17-1, Chiyo, Hakata-ku, Fukuoka City West Gas Co., Ltd. (72) Inventor Shunsuke Otaka 6 Bodhi, Mihara-cho, Minamikawachi-gun, Osaka Prefecture Kaji Tech Co., Ltd.

Claims (5)

[Claims] 1. A piston for a high-pressure gas compressor, comprising a plurality of annular piston ring grooves on the outer periphery of a cylindrical piston that slides back and forth on the inner surface of a cylinder, and piston rings are fitted in the respective piston ring grooves. , A plurality of piston ring grooves close to the tip of the piston are provided with communication holes that respectively communicate from the tip of the piston to the compression chamber, and communicate with the piston ring groove far from the top side of the piston tip. A piston for a high-pressure gas compressor, wherein the communication hole is formed so that the gas flow resistance of the communication hole is increased. 2. A plurality of piston ring grooves of the piston, wherein a plurality of piston ring grooves near the base end portion of the piston are provided with communication holes respectively communicating with the piston rear surface at the base end of the piston, and a piston is provided. 2. The piston for a high-pressure gas compressor according to claim 1, wherein a communication hole communicating with the piston ring groove farther from the bottom side of the base end has a larger gas flow resistance in the communication hole. 3. A bottom side rider ring groove, in which a rider ring is fitted, is provided on the piston peripheral surface on the bottom side further than the piston ring groove on the bottom side of the piston, and the piston from the bottom side rider ring groove to the bottom side. The piston for a high-pressure gas compressor according to claim 2, wherein a rider ring communication hole communicating with the rear surface is provided. 4. A piston for a high-pressure gas compressor according to claim 1, wherein the cylindrical outer peripheral surface of said piston is coated with a wear-resistant and lubricating film. 5. The high-pressure gas compression method according to claim 1, wherein the wear-resistant and lubricious coating is a synthetic resin coating such as a polyimide-based or fluorine-based synthetic resin or a metal plating layer in which a lubricating powder is embedded. Machine piston.