Variable displacement vane pump

Abstract

A variable displacement vane pump includes: a control orifice that imparts resistance to a flow of working oil discharged from pump chambers; a flow-amount control valve that operates in accordance with an upstream-downstream differential pressure of the control orifice and controls a flow amount of the working oil discharged from the pump chambers; a variable control valve that is operated by the working oil that has passed through the control orifice and controls an amount of eccentricity of a cam ring with respect to a rotor by controlling a pressure difference between a first fluid pressure chamber and a second fluid pressure chamber; and a return passage that is connected to the flow-amount control valve and circulates a part of the working oil discharged from the pump chambers through a suction passage.

1 . 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.   
     
     
         2 . The variable displacement vane pump according to  claim 1 , further comprising
 a variable restrictor capable of changing resistance imparted to a flow of the working fluid that has passed through the control restrictor, wherein   the variable control valve is operated in accordance with the upstream-downstream differential pressure of the variable restrictor.   
     
     
         3 . The variable displacement vane pump according to  claim 2 , wherein
 an opening area of the variable restrictor is set such that the upstream-downstream differential pressure for operating the variable control valve is generated by allowing the working fluid to pass through the variable restrictor at a flow amount that is greater than a passing flow amount of the control restrictor for generating the upstream-downstream differential pressure for operating the flow-amount control valve.