| 摘要 |
An improvement of the inner periphery of a power piston which is connected to a valve body of a booster is disclosed. The inner periphery of the power piston comprises a radial portion which is disposed in abutment against an end face of a step formed on the valve body, an annular groove located radially outward of the radial portion, and a step formed at the boundary between the radial portion and the annular groove. The provision of the annular groove and the step assures sufficient strength around the inner periphery of the power piston without requiring an increased wall thickness of the power piston. |
