| 摘要 |
PROBLEM TO BE SOLVED: To make a surface pressure generated by a lip of a piston ring and an inner wall surface of a cylinder tube not so high, and to enhance an abrasion- resistance of the piston ring. SOLUTION: The piston part structure comprises a piston body 1, made of a metal and formed with an annular recessed part on an outer periphery and a piston ring 5 made of resin and provided on an outer periphery surface of the piston body; in the piston part structure, the inner circumference surface side of the piston ring is bitten into the annular recesses parts 1a-1c of the piston body. In a state with a ring member 6 comprising an elastic material being previously attached into at least one of the annular recessed part of the piston body, the inner periphery surface of the piston ring is made to bite into the annular recessed parts and an annular projection 5b is formed at the outer circumference side of the piston ring by an elastic force of the ring member.
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