| 摘要 |
PURPOSE:To enable a jam of dust or the like to be removed by a pressure of oil, which is allowed to reversely flow in a throttle valve, by allowing the oil of the original pressure to flow into an oil tank via the throttle valve and a return flow path from a bypass flow path, when the throttle valve is blocked by the dust or the like. CONSTITUTION:A bypass flow path 12, opened into a static pressure pocket 4 via a solenoid valve 11, is provided. While a return flow path 15, opened into an oil tank 14 from a flow path between the first check valve 9 and a throttle valve 6 in a static pressure flow path 5, is provided. The return flow path 15 mounts the second check valve 16 and a filter 17 placing it in a side of the oil tank 14. The second check valve 16 uses a valve opened by the original pressure P1 and closed by an intermediate pressure P2. A pressure switch 19, connected to a hole opened into the static pressure pocket 4, is further provided. The pressure switch 19 is formed being a type of detecting the lower limit, in which an electric contact is turned on when a pressure in the static pressure pocket is in a preset value or less, and the pressure switch 19 is electrically connected with a control unit 20. |
