| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a durable conventional type master cylinder by effectively preventing locally concentrated damages to a cup seal for extending a life of the seal. SOLUTION: When a piston 5 moves toward an operational position, the piston 5 turns in the winding direction of a coil spring 19 as the coil spring 19 is compressed, contact pressure between an outer circumference lip part 31 of the cup seal 10 and an inner circumference wall of a cylinder bore 3 is greater than contact pressure between in inner circumference lip part 32 and the piston 5, and the cup seal 10 does not turn together with the piston 5. When the piston 5 moves toward a non-operational position, the piston 5 turns in the reverse direction of the winding direction of the coil spring 19 as the coil spring 19 restores, the contact pressure between the inner circumference lip part 32 and the piston 5 is greater than the contact pressure between the outer circumference lip part 31 and the inner circumference wall of the cylinder bore 3., and the cup seal turns together with the piston 5.</p> |
