| 摘要 |
PROBLEM TO BE SOLVED: To provide a piston ring which causes neither non-contact parts in all circumferences at room temperature, nor increase of surface pressure at an abutment portion under thermal load. SOLUTION: A substantially circular piston ring has an outer peripheral surface 3 slid relative to a cylinder, an inner peripheral surface 4 opposed to a piston, and an abutment portion 2 which splits the substantially circular form in a radial direction. A cutout portion 4a serving a part of the inner peripheral surface 4 is formed on the surface 4, within a specified range starting an end face of the abutment portion 2. Radial thickness in the specified circumferential length range is smaller than the radial thickness a1 at other portions.
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