Importance

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Abstract

A pump apparatus includes: a spool valve including a first land portion, a second land portion, and a third land portion; a first pressure chamber into which an upstream pressure of the metering orifice is introduce; a second pressure chamber into which a downstream pressure of the metering orifice is introduced; a third pressure chamber into which the pressure of the discharge passage is introduced; a fourth pressure chamber into which a low pressure is introduced; and a first fluid pressure chamber side communication passage which is formed in the pump housing which is arranged to selectively supply the pressure of the third pressure chamber and the pressure of the fourth pressure chamber to the first fluid pressure chamber in accordance with the movement of the spool valve.

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First Claim