Patent ID: 8088496

Claim:
A piston ring including a piston ring body and a surface coating film formed on at least one of upper and lower surfaces of the piston ring body, wherein, the surface coating film comprises a most outside surface layer including a heat-resistant resin and a metal powder contained in the heat-resistant resin and a base bottom layer formed close to the piston ring body and including a heat-resistant resin and the metal powder contained in the heat-resistant resin, in which the base bottom layer includes a metal powder containing rate not more than that contained in the most outside surface layer, the metal powder is a powder selected from a group consisting of copper system powder, nickel powder, nickel alloy powder, lead system powder, and tin system powder, the heat-resistant resins forming the base bottom layer and the most outside surface layer further include either one of molybdenum disulfide, tungsten disulfide, or graphite, the containing rate of the metal powder contained in the base bottom layer is a positive amount not more than 40 mass %, the containing rate of the either one of molybdenum disulfide, tungsten disulfide, or graphite contained in the base bottom layer is a positive amount not more than 5 mass %, the containing rate of the metal powder contained in the most outside surface layer is 40 to 80 mass %, and the containing rate of the either one of molybdenum disulfide, tungsten disulfide, or graphite contained in the most outside surface layer is 2 to 10 mass %.