| 摘要 |
A projection (21b4) provided at a tip portion of an inner lip portion (21b) of a first cup seal (21) comes in contact with a second side wall (20c) of a recessed portion (20) and a large axial force is exerted in the axial direction on a first tapered inner peripheral surface (21b1) of the first cup seal (21) from a rear side tapered surface (4b2) of a primary piston (4). This makes it possible to reliably hold the first cup seal (21) in the axial direction by utilizing the axial force. Therefore, the first cup seal (21) can be suppressed from moving in the axial direction. In particular, the projection (21b4) of the first cup seal (21) comes in contact with a tapered surface (20c′) of the second side wall (20c) to obtain a further increased axial force, and the first cup seal (21) can be held more reliably. |
