| 摘要 |
PROBLEM TO BE SOLVED: To further reduce energy consumption and to provide a steering feeling during high-speed traveling by providing a solenoid valve for fixing the variable restrictor of a load pressure responding valve in an open condition according to an electric signal. SOLUTION: In a neutral state of steering, the variable restrictor 45 of a load pressure responding valve 31 is opened, the spring room 23 side of a flow rate control valve 27 is opened to a low pressure side and hydraulic oil discharged from a pump 10 is returned more to the sucking side of the pump. When a load pressure is increased by a steering operation in this state, the load pressure feeling and responding valve 31 is actuated and the variable diaphragm 45 is closed. Thus, the supplying flow rate of hydraulic oil supplied to a control valve 14 is increased to a maximum supplying flow rate. However, during high-speed traveling or the like, a solenoid valve 50 is actuated and the variable restrictor 45 of the load pressure responding valve 31 is fixed in an open state and thus, the state of a reduction in the supplying flow rate of hydraulic oil supplied to the control valve 14 is maintained even when a load pressure increases. |
