A variable displacement pump includes a control valve formed with a
high-pressure chamber for introducing therein high-pressure fluid on the
upstream side of a metering orifice, a pressure chamber for introducing
therein pressure fluid on the downstream side of the metering orifice, a
low-pressure chamber arranged between the high-pressure and pressure
chambers for introducing therein low-pressure fluid, and a communication
passage for providing fluid communication between one of the
high-pressure and low-pressure chambers and a first fluid-pressure
chamber of the pump. First and second recessed grooves are formed in the
outer-peripheral surface of a spool of the control valve to provide fluid
communication between the low-pressure and high-pressure chambers through
the communication passage of the control valve when the spool carries out
selective switching between the high-pressure and low-pressure chambers
to supply fluid to the communication passage, thus restraining abrupt
pressure rise in the first fluid-pressure chamber.