Variable displacement pump with a suction area groove for pushing out rotor vanes

A viable displacement pump comprising:

• a cam ring accommodated within a pump body;
• a rotor rotating within the cam ring and formed slits at regular intervals circumferentially;
• a plurality of vanes inserted retractably into the slits;
• two plates carrying the cam ring and the rotor on both sides of the cam ring and the rotor;
• and
• wherein a circular groove communicating to bottom portions of the slits is partitioned into a suction area groove and discharge grooves;
• wherein the discharge grooves are formed on a face of each of the both plates;
• wherein the discharge grooves are not connected to the suction area groove;
• wherein a pressure fluid is introduced into the circular groove to push out the vanes;
• wherein a pump suction portion is formed on at least one of the plates;
• and
• wherein pressure introduced into the suction area groove is higher than pressure at the pump suction port and at least pressure at the suction port is introduced into the suction area groove.