Piston ring

Abstract

A piston ring is provided at its outer periphery with a sliding surface, wherein in a cross section thereof which is perpendicular to a radial direction of the piston ring, the sliding surface includes a first sliding surface which occupies a predetermined region from one end thereof, and a second sliding surface which occupies a region extending from one end to the other end of the first sliding surface, the first sliding surface is formed of hard film, the second sliding surface is not formed of hard film, and the second sliding surface exists at a position deviated inward from a phantom line extending from the first sliding surface toward the other end.

1 - 5 . (canceled) 
     
     
         6 . A piston ring provided at its outer periphery with a sliding surface,
 Wherein in a cross section thereof which is perpendicular to a radial direction of the piston ring,   the sliding surface includes a first sliding surface which occupies a predetermined region from one end thereof, and a second sliding surface which occupies a region extending from one end to the other end of the first sliding surface,   the first sliding surface is formed of hard film,   the second sliding surface is not formed of hard film, and   the second sliding surface exists at a position deviated inward from a phantom line extending from the first sliding surface toward the other end.   
     
     
         7 . The piston ring according to  claim 6 ,
 wherein the first sliding surface is formed by forming a recess in a base material of the piston ring, and by providing the recess with a hard film,   in the cross section of the piston ring which is perpendicular to the radial direction of the piston ring,   the recess includes a first surface extending from one of upper and lower surfaces of the base material toward the other one of the upper and lower surfaces in parallel to an outer peripheral surface of the piston ring, and a second surface extending from one end of the first surface toward the outer peripheral surface of the piston ring, and   the second surface forming the recess and the outer peripheral surface of the piston ring are in contact with each other at an angle of 10° to 30°.   
     
     
         8 . The piston ring according to  claim 6 , wherein the hard film forming the first sliding surface is a Cr—N type film or a Cr—B—N type film formed by a PVD method. 
     
     
         9 . The piston ring according to  claim 6 ,
 wherein the second sliding surface is formed of base material of the piston ring.   
     
     
         10 . The piston ring according to  claim 6 ,
 wherein the outer periphery has a barrel face shape or an eccentric barrel face shape.   
     
     
         11 . The piston ring according to  claim 7 ,
 wherein the hard film forming the first sliding surface is a Cr—N type film or a Cr—B—N type film formed by a PVD method.   
     
     
         12 . The piston ring according to  claim 7 ,
 wherein the second sliding surface is formed of base material of the piston ring.   
     
     
         13 . The piston ring according to  claim 7 ,
 wherein the outer periphery has a barrel face shape or an eccentric barrel face shape.