| 摘要 |
PURPOSE:To provide surface pressure distribution on an upper and a lower surface, by a method wherein projection parts, circumferentially integrally connected to each other, are formed on at elast either the upper or the lower end in the direction of an axis of the external projection part of a spacer expander. CONSTITUTION:A side rail pressure collect part 25 is formed such that it comprises at least either of upper and lower ends 25a in the direction of an axis of an external projection part 22 of a spacer expander 2 and projection parts 25b, integrally connected to at least either of the upper and the lower end and cut away from at least a coupling member 24 by press-cut and other like method. This increases a pressure collecting area on the spacer expander and a side rail 3, enables uniform maintenance of surface pressure distribution on the upper and the lower surface of the ring groove of a piston 6 by means of the side rail 3, and permits production of a sufficient sealing effect. |
