| 摘要 |
PURPOSE:To prevent a piston from nodding motion without a piston ring exerting large pressure to the inner peripheral surface of a cylinder by forming an expander ring disposed along the inner periphery of the piston ring so that a small reacting force acts in the direction of piston pins but a large reacting force acts in the direction perpendicular to the piston pin direction. CONSTITUTION:An expander ring 5 repeatedly bent in an wave form is disposed aling the inner periphery of a piston ring 4 fitted into a ring groove 3 in a piston 2 so that the piston ring 4 is, at its inner periphery, resiliently held through the expander ring 5. Crest shaped portions having a relatively large radius R1 of curvature are formed in the direction of piston pins, or the X-X direction but crest shaped portions having a relatively small radius R2 of curvature are formed in the direction perpendicular to the piston pin direction, or the Y-Y direction so that the expander 5 has a relatively small reacting force in the X-X direction but has a relatively large reacting force in the Y-Y direction, thereby the piston 2 is prevented from nodding motion without the piston ring 4 exerting large pressure to the inner peripheral surface of a cylinder 1. |
