| 摘要 |
PROBLEM TO BE SOLVED: To accept lubricant and securely aluminum plating by a piston on a flank face by providing a recessed section extended to the surrounding on the flank face apart from combustion pressure of a nitride piston ring. SOLUTION: In a piston ring provided with a recessed section extended to the surrounding at least on a flank face apart from combustion pressure, the flank face is formed into a recessed type when viewed on a cross section so as to accept lubricant and prevent aluminum plating from an aluminum piston. Moreover, a lubricant reservoir can be additionally provided in this annular recessed section so that the piston ring receives cushion action when it receives inclination stress and is not exposed to all friction due to a piston groove of the aluminum piston. Preferably, this recessed section is 2 to 3μm recessed section extended in substantially central part so that the most advantageous result is obtained.
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