| 摘要 |
PROBLEM TO BE SOLVED: To prevent the zero of a pump discharge amount and the deterioration of an operation oil by heat generation at the non-operation time of an actuator, without using an expensive variable capacity pump with a complicated structure. SOLUTION: An operation oil pressure passage 7 for introducing an operation oil discharged from a fixed capacity pump 4 to an actuator 1 is installed. On the way of this operation oil pressure passage 7, a check valve 8 for allowing the flow of the operation oil to the actuator 1 and obstructing the flow of an opposite direction is installed. An accumulator 9 which can maintain the pressure in the operation oil pressure passage 7 in the more downstream side than the check valve 8 to a prescribed pressure is installed. A control device 10 for controlling the flow in amount to the drain passage 11 of the operation oil discharged to the operation oil pressure passage 7 at the more downstream side than the check valve 8 is installed when the pressure in the operation oil pressure passage 7 reaches the prescribed pressure and a control oil pressure passage 15 for introducing the operation oil of the operation oil pressure passage 7 in the more downstream side than the check valve 8 is communicated with this control device 10. |
