Variable displacement oil pump

A variable displacement oil pump comprising:

• a pump structural unit adapted to be driven by an internal combustion engine for varying a volume of each of a plurality of working chambers and for discharging oil, drawn into an inlet portion, from a discharge portion;
• a variable-volume mechanism configured to vary a variation of the volume of each of the working chambers, wherein the chambers open into the discharge portion, by a displacement of a moveable member included in the pump structural unit;
• a first biasing member for forcing the movable member in a biased direction that the variation of the volume of each of the working chambers increases;
• a control chamber configured to change a displaced position of the moveable member by introducing the oil, discharged from the discharge portion, into the control chamber;
• a directional control valve including a spool having a pressure-receiving section for receiving a discharge pressure from the discharge portion and slidably installed in a close-fitting bore into which a communication passage opens and which communicates with the control chamber, a second biasing member for forcing the spool in one sliding direction opposite to another sliding direction of the spool corresponding to a direction of action of the discharge pressure acting on the pressure-receiving section of the spool, a movable support slidably located at a position being axially opposite to the spool, sandwiching the second biasing member between the spool and the movable support, the movable support being configured to be forced in a same axial direction as the another sliding direction of the spool by the second biasing member, and a pressure-receiving chamber defined between the movable support and a bottom of the close-fitting bore, the directional control valve being configured to selectively switch between an oil-discharge from the control chamber and an oil-introduction from the discharge portion to the control chamber by a sliding movement of the spool resulting from a relative pressure force between a biasing force created by the discharge pressure and a biasing force of the second biasing member;
• and
• a control mechanism disposed between the discharge portion and the directional control valve and configured to control the sliding movement of the spool by electrically controlling switching between a supply mode at which the discharge pressure is supplied from the discharge portion to the pressure-receiving chamber via the control mechanism and a drain mode at which fluid communication between the discharge portion and the pressure-receiving chamber is blocked and an oil-discharge from the pressure-receiving chamber via the control mechanism is permitted, thereby displacing the movable support.