| 摘要 |
PURPOSE:To always place all pump chambers in an operating condition in the case of low pump rotational speed and to switch the condition to either the all pump chamber operating condition or the specific pump chamber stop condition in accordance with a load pressure only at high rotational speed time. CONSTITUTION:A suction side passage 22 and a communication path 23, connected to a specific pump chamber, are provided. A switching valve 1, switched so as to generate communication or interruption of a communication condition between these suction side passage 22 and communication path 23, is provided. This switching valve 1 is formed into a double structure system comprising a pump rotational speed sensing outer spool 13 actuated in accordance with a differential pressure generated before and after a control orifice 25 provided in a flow control valve 26 and a load pressure sensing inner spool 11 actuated in accordance with a rise of load pressure in a pressure chamber 27. Thus by forcing an all pump chamber operating condition generated regardless of the load pressure at low rotational speed time, a fluctuation of assist force is not generated, to obtain a good steering feeling. The switching valve can be miniaturized. |
