Variable displacement-type oil pump

A variable displacement oil pump comprising:

• a rotor that is driven and rotates by an internal combustion engine;
• a plurality of vanes that are accommodated at an outer periphery of the rotor so as to be able to extend and retract;
• a cam ring that defines a plurality of pump chambers by accommodating the rotor and the vanes at an inner circumferential side of the cam ring, and increases and decreases a volume variation of each of the plurality of pump chambers by an eccentric movement of the cam ring with respect to the rotor;
• an inlet portion that is formed in an inlet area where an inside volume of the pump chamber is increased;
• an outlet portion that is formed in an outlet area where the inside volume of the pump chamber is decreased;
• a forcing mechanism, having a pre-load provided, that forces the cam ring in a direction in which the volume variation of each of the plurality of pump chambers is increased;
• one or more control oil chambers that changes the volume variation of each of the plurality of pump chambers, the control oil chambers including at least a decrease side control oil chamber that exerts a force on the cam ring in a direction in which the volume variation of each of the plurality of pump chambers is decreased by being supplied with the oil discharged from the outlet portion;
• a drain mechanism that discharges the oil from specified one control oil chamber among the control oil chambers;
• an electrical control mechanism into which a downstream side oil discharged from the outlet portion and passing through an oil filter provided on a discharge passage connected to the outlet portion is introduced and which is able to regulate a discharge pressure, which is a hydraulic pressure of the oil discharged from the outlet portion, to a plurality of setting pressures by controlling supply and discharge of the oil discharged from the outlet portion to and from the specified one control oil chamber on the basis of an electric signal and adjusting an internal pressure of the specified one control oil chamber, the electrical control mechanism configured to, when not being energized, not introduce oil to the specified one control oil chamber;
• and
• a control valve into which the downstream side oil discharged from the outlet portion and passing through the oil filter and without passing through the electrical control mechanism is introduced as a control pressure, the control valve configured to, when a hydraulic pressure of the introduced oil exceeds a predetermined setting working pressure, adjust the internal pressure of the specified one control oil chamber by supplying the oil discharged from the outlet portion into the specified one control oil chamber or discharging the oil from the specified one control oil chamber.