| 摘要 |
PROBLEM TO BE SOLVED: To provide a piston ring capable of optimizing the tension distribution in the circumference direction. SOLUTION: In the piston ring 1 that has the piston ring body 2, the coil expander 3 arranged on the inner circumference of the above piston ring body and biases the above piston ring body toward the outer circumference, the above coil expander is provided with large diameter parts 8, 70 of the wire formed in a coil shape to contact with the inner circumference face 2a of the above piston ring body and a small diameter part 9, 71 to form the outer diameter of the above coil expander in a smaller diameter than the roll diameter of the above large diameter part. COPYRIGHT: (C)2007,JPO&INPIT
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