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.

1 . An oilless reciprocating air compressor comprising: 
 a cylinder made of Al or Al alloy;    a piston that reciprocates in the cylinder so that a gas sucked from an outside is compressed and discharged from the cylinder, said piston having an annular groove on an outer circumferential surface; and    a piston ring fitted in the annular groove of the piston and made of composite material of self-lubricating resin and heat-resistant material for increasing sliding performance, an inner surface of the cylinder having SiC coating.    
   
   
       2 . An oilless reciprocating air compressor as claimed in  claim 1  wherein the self-lubricating material of the piston ring comprises polytetrafluoroethylene and the heat-resistant material comprises graphite.  
   
   
       3 . An oilless reciprocating air compressor as claimed in  claim 1  wherein the piston is made of self-lubricating composite material.  
   
   
       4 . An oilless reciprocating air compressor as claimed in  claim 3  wherein the self-lubricating composite material comprises condensed polynuclear aromatic resin and graphite for increasing sliding performance.  
   
   
       5 . An oilless reciprocating air compressor as claimed in  claim 1  wherein the SiC coating is made by plating.  
   
   
       6 . An oilless reciprocating air compressor as claimed in  claim 1  wherein thickness of the SiC coating of a portion to which higher side thrust acts by the piston is greater than that at the other side.  
   
   
       7 . An oilless reciprocating air compressor as claimed in  claim 1  wherein a receiving projection in the annular groove of the piston is provided at a portion to which higher side thrust acts, the projection engaging in an abutment of the piston ring.