| 摘要 |
PURPOSE:To prevent the side surface of a rider ring groove formed on a piston from wear by providing a back-up ring between both side surfaces or one side surface of the rider ring and the piston. CONSTITUTION:Several rider rings 3 of 4 ethylene fluoride resin are provided on the outer periphery of a piston 1 and formed on the both end sides with grooves 1b for providing back-up rings 4. Said groove 1b is deeper than a rider ring groove 1a to enlarge the contact area of the side surface. In this groove 1b is incorporated the back-up ring 4 of 4 ethylene fluoride resin and between these back-up rings 4 is incorporated the rider ring 3 by shrinkage fit. The proper clearance between the rider ring 3 and the back-up ring 4 is provided in consideration of thermal expansion. |
