Importance

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Abstract

A pump unit includes a variable capacity pump, and a balanced piston mechanism having a piston body, connected to an operation section of a variable swash plate, provided inside a cylinder, capable of sliding in an axial direction. The balanced piston mechanism has first, second and third pressure receiving chambers provided in the cylinder. Primary side and the secondary side working fluid pressures of an actuator switching valve are respectively introduced to the first receive pressure chamber and the second pressure receiving chamber, and a set pressure that has been previously set, corresponding to a working fluid differential pressure arising before and after passing through the actuator switching valve, in a steady state of the operating position of the actuator switching valve is introduced to the third pressure receiving chamber.

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First Claim