| 摘要 |
A power steering apparatus of the present invention which includes a pump, a power cylinder, a control valve, an orifice arranged in a supply passage leading an operating fluid discharged from the pump to the control valve, a flow control valve, and a switching valve. A spring chamber of the flow control valve is connected to the supply passage downstream of the orifice, and is responsive to the pressure difference across the orifice for regulating the flow rate of an operating fluid to the control valve to an almost constant flow rate. The switching valve is actuated in response to the differential pressure across the orifice for switching the communication of the spring chamber between the downstream of the orifice and the reservoir. When the differential pressure across the orifice is relatively low, the switching valve brings the spring chamber into communication with the reservoir. With this configuration, an excessively high pressure is not maintained in the pump, and an increase in the temperature of the operating fluid which brings about seizure of the pump can be prevented.
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