| 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 50 is put in a stepped opening on the side of a chamber 16 of a hole 15k constituting the passage 15f, which is closed by the valve body 50 when the spool 15 is moved and the opening is pressed. The valve body 50 is inserted in a valve body holder 13a formed at one end of an output rod 13, and is pushed to the right shown in the figure by a spring 51. 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. |
