| 摘要 |
PROBLEM TO BE SOLVED: To improve the fuel economy and the steering stability of a vehicle by decreasing the discharge from a pump at its higher rotation or at the running of the vehicle in higher speed, and to prevent the pump from continuing to be relieved at the steering of a steering wheel without driving or the like. SOLUTION: A control spool 35 is provided for controlling the opening degree of a restriction passage 24 corresponding to the differential pressure between the front stage and the rear stage of a fixed restriction 42. At higher rotation of a pump 10, the control spool 35 restricts the restriction passage 24 to decrease the flow rate of working fluid to be supplied to a control valve 14. A directional control valve 23 is provided which is adapted to be switched over corresponding to the differential pressure between the front stage and the rear stage of the restriction passage 24. When the differential pressure between the front stage and the rear stage of the restriction passage 24 is low, the directional control valve 23 opens a spring chamber 31 of a flow control valve 34 to a bypass passage 18 on the lower-pressure side. |
