| 摘要 |
PROBLEM TO BE SOLVED: To provide a piston ring which exerts characteristics corresponding to a light oil lubrication type diesel engine that uses a fuel such as light oil as a lubricant. SOLUTION: A piston ring (1) comprises an expander (6) on the inner peripheral side of a piston ring body (5). The expander (6) is formed by incorporating a circumferential length adjusting mechanism (8) in a coil spring (7) formed in a ring. The circumferential length adjusting mechanism (8) comprises a rod (9) of which a flange (9a) is provided at the central part, and a left side support part (10a) and right side support part (10b) for supporting the rod (9). A shape memory member (11) of shape memory alloy which is formed in coil is arranged between the left side support part (10a) and the flange (9a). A bias spring (12) is arranged between the right side support part (10b) and the flange (9a). Thus, the pressurizing force of the expander(6) in radial direction against the piston ring body (5) is smaller in a high temperature state than in a low temperature state. COPYRIGHT: (C)2008,JPO&INPIT
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