| 摘要 |
PURPOSE:To suppress an early decline of the stored pressure of an auxiliary liquid pressure source by providing a check valve on the passage between the downstream side of a control valve and a boost chamber to prevent the operating liquid which is fed from the auxiliary liquid pressure source into the boost chamber from being leaked when a main liquid pressure source fails. CONSTITUTION:A throttle valve 20 and a control valve 21 are formed at the sliding section of a power piston 2 and a spool 15, and the throttle valve 20 squeezes the passage between an inlet port 29 and an outlet port 30 which couples with a main liquid pressure source, while the control valve 21 controls a coupling with the passage 15f which connects to the inlet port 29 and the boost chamber 17. A valve body 51 is put at a stepped opening on the side of the boost chamber 17 of the passage 15f, and it is pressed to the stepped opening by a spring 52. On the other hand, an auxiliary liquid pressure source 12 is connected to a groove 2h of a power piston 2, and is coupled with the boost chamber 17 by a movement of the spool 15. |
