| 摘要 |
PROBLEM TO BE SOLVED: To surely prevent leakage of a negative pressure by attaching a seal member for sealing mutual fitting parts of a valve piston and an input plunger by bringing into close contact with a forward seal end surface of the input plunger when the valve piston is positioned in the retreat limit regulated by a stopper means. SOLUTION: A set load of a return spring 44 is set larger than a valve spring 36. At retreating time of the input plunger 18 by an input rod 20, a valve part 34a of a valve element 34 is displaced backward against a set load of the valve spring 36 by a valve piston 33 without compressing the return spring 44. A forward end surface of an outward flange 18a is formed as a seal end surface 51, and when the valve piston 33 is positioned in the retreat limit received by a stopper ring 45, a seal member 52 brought into close contact with the seal end surface 51 is attached to the front end of the valve piston 33 to thereby surely seal mutual fitting parts of the valve piston and the input plunger to contribute to improving operational responsiveness of a booster piston. |
