| 摘要 |
A variable displacement vane pump includes a drive shaft; a rotor formed with slots; vanes received by the slots; a cam ring which can become eccentric and cooperates with the rotor and vanes to define pump chambers; suction and discharge ports opened to the pump chambers; a sealing member dividing a space on an outer circumferential surface of the cam ring into first and second fluid pressure chambers; a metering orifice formed on a discharge passage connected with the discharge port; and a pressure control section adapted to control a pressure which is introduced into the first or second fluid pressure chamber. The pressure control section includes a high pressure chamber into which an upstream pressure of metering orifice is introduced, a medium pressure chamber into which a downstream pressure of metering orifice is introduced, and a low pressure chamber connected with a reservoir tank. The vane pump further includes a relief valve adapted to drain the downstream pressure of metering orifice to the reservoir tank; and a variable metering mechanism configured to narrow an area of the metering orifice at least when the relief valve is opened.
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