| 摘要 |
PURPOSE:To provide a uniform radial direction and surface distribution on an upper and a lower surface, by a method wherein an internal peripheral projection and an external peripheral projection are respectively formed on at least either upper or lower end in the direction of an axis of the internal and the external projection on a spacer expander. CONSTITUTION:A pad part, which has an internal peripheral projection 26b, circumferentially connected to at least either upper or lower end 26a in the direction of an axis of an internal projection and cut away from a coupling member 24, is formed to an internal projection 21 of a spacer expander 2. A side rail pressure collecting part, which has an external projection 25b, circumferentially integrally connected to either of upper and lower ends 25a in the direction of an axis of an external projection and cut away from the coupling member 24, is formed to the external projection of the spacer expander 2. This enables uniform maintenance of surface distribution on the upper and lower surface of the ring groove of a piston 6 by means of a side rail 3. |
