| 摘要 |
PROBLEM TO BE SOLVED: To provide a piston ring with a DLC film having a low friction property and exhibiting abrasion resistance.SOLUTION: In an internal combustion engine, a DLC film 2 in which two kinds of layers A and B having different hardness are alternately laminated in plural is coated on an outer peripheral sliding surface of a piston ring 1, an outermost layer of the film is the layer A having the higher hardness, the hardness difference of the two kinds of the layers is 500-1,700 HV, the layer having the higher hardness has a thickness equal to or greater than a thickness of the layer B having the lower hardness, and the thickness of the layer having the higher hardness is 5 nm or more, and the film as a whole has a thickness of 5.0 μm or more. The piston ring slides in low friction with a flake graphitic cast iron material for a cylinder liner as a mating sliding member through engine lubricating oil. |
