Oilless reciprocating air compressor

Abstract

In an oilless reciprocating air compressor, a piston reciprocates in a cylinder to compress a gas sucked from the outside and the compressed gas is discharged to the outside. The piston has an annular groove on the outer circumference, and a piston ring made of self-lubricating resin composite material is placed in the annular groove. The inner surface of the cylinder has SiC coating to increase the life of the piston ring, thereby allowing the compressor to be used at high pressure and high temperature efficiently to increase durability.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to an oilless reciprocating air compressor. [0002] In U.S. Pat. No. 5,117,742, a piston in an oilless reciprocating air compressor is made of resin and has an annular groove on the outer circumference. A piston ring made of resin is fitted in the annular groove, and the piston reciprocates in a cylinder. [0003] In the oilless reciprocating air compressor, it is not necessary for lubricating oil to be fed into a piston ring, a piston or a cylinder. Lubricating oil is not introduced into a compression chamber in the cylinder, and is not contained in compressed air discharged from the compressor. Thus, oilless reciprocating air compressors are widely used in medical, food or oxygen-feeding field that do not like oil in compressed air, or among users who are troubled in feed and maintenance of lubricating oil. [0004] When the resin piston is employed, the cylinder is made from Al or Al alloy flattening, casting or die cast...

AI Technical Summary

Benefits of technology

[0027] In view of the disadvantages, it is an object of the invention to provide an oilless reciprocating air compressor operable at high-pressure and high-temperature of 2 to 3 MPa over 1 MPa to prevent generation of small resin pieces from a piston ring which slidably reciprocates in a cylinder to keep sealing capapility of the piston ring for a long time, to prevent abnormal sounds caused by leakage and to prevent heat from transmitting to a bearing of a piston, further avoiding damages or fauling during reciprocation of the piston ring or piston to greatly extend the life of the piston ring to keep its performance for a long time.

Problems solved by technology

As shown by an arrow in FIG. 3, leakage occurs through the space to decrease compression efficiency and to cause noise.

Accordingly, sealing capability of the resin piston ring 20 becomes poor to decrease discharge performance of the oilless reciprocating air compressor.

Furthermore leakage is likely to generate abnormal sound.

High temperature air on a compression chamber thermally gives adverse effects to a bearing of the piston, thereby decreasing the lives of the piston pin 16, the end of the connecting rod 17 and the bearing.

In high-pressure and high-temperature operation, the piston ring is abnormally worn to decrease sealing capability and is then worn locally to breakage.

However, as operation continues, the piston-ring small pieces in the labyrinth groove increase to come into the piston-ring groove, so that desired purposes cannot be attained after a certain time passes.

Metal plating such as Ni or Cr is applied to the inner surface of the cylinder, but coating of Ni and Cr decreases sliding performance and seizure resistance.

Especially in high-pressure and high-temperature operation, it does not improve the life of the piston ring.

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