Variable displacement vane pump

A variable displacement vane pump comprising:

• a rotor linked to a driving shaft;
• a plurality of vanes provided so as to be able to reciprocate in a radial direction relative to the rotor;
• a cam ring having an inner circumferential surface on which tip ends of the vanes slide by rotation of the rotor;
• pump chambers defined by the rotor, the cam ring, and pairs of the adjacent vanes;
• a suction passage configured to guide working fluid to the pump chambers;
• a first fluid pressure chamber and a second fluid pressure chamber defined in an outer-circumferential accommodating space on outer side of the cam ring, the first fluid pressure chamber and the second fluid pressure chamber being configured to make the cam ring eccentric with respect to the rotor by pressure difference between the first fluid pressure chamber and the second fluid pressure chamber;
• a control restrictor configured to impart resistance to a flow of the working fluid discharged from the pump chambers;
• a flow-amount control valve operated in accordance with an upstream-downstream differential pressure of the control restrictor, the flow-amount control valve being configured to control flow amount of the working fluid discharged from the pump chambers;
• a variable control valve operated by the working fluid that has passed through the control restrictor, the variable control valve being configured to control an amount of eccentricity of the cam ring with respect to the rotor by controlling pressure difference between the first fluid pressure chamber and the second fluid pressure chamber;
• and
• a return passage connected to the flow-amount control valve, the return passage being configured to circulate a part of the working fluid discharged from the pump chambers through the suction passage.