Importance

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Abstract

A fluid pump unit has a flow control valve which returns a portion of a working fluid discharged from a pump assembly when rotation speed of a rotor increases to become greater than a predetermined value. The flow control valve includes an essentially cylindrical spool chamber defined in a pump case, and a valve spool movably housed within the spool chamber. The spool chamber has a pair of through openings on the side wall thereof which through openings are selectively open and closed by movement of the spool valve. The pump case is formed with a pair of drain passages which are respectively communicated with the through openings of the spool chamber independently of each other. When rotation speed of a rotor of the pump assembly becomes greater than a predetermined value, the spool valve opens the through openings to return a part of the discharged working fluid to an inlet passage through which working fluid is introduced from a fluid source into the pump assembly.

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First Claim