Oil pump

An oil pump comprising:

• a housing including a pump receiving chamber;
• a pump constituting section including a cam profile surface provided within the pump receiving chamber, a rotor received radially inside the cam profile surface, and a plurality of vanes which are provided on an outer circumference side to be moved into and out of the rotor, and which form a plurality of operation chambers between the cam profile surface and an outer circumference of the rotor;
• a discharge opening portion formed in the pump receiving chamber, and opened to operation chambers of the plurality of the operation chambers in which volumes are decreased in accordance with a rotation of the rotor, in a direction of a rotation axis of the rotor;
• and
• a suction opening portion which is formed in the pump receiving chamber, which is opened to operation chambers of the plurality of the operation chambers in which volumes are increased in accordance with the rotation of the rotor in the direction of the rotation axis of the rotor, and which includes a termination end portion of the suction opening portion in the rotation direction of the rotor,
• the termination end portion including a termination end inner circumference portion, a termination end outer circumference portion provided radially outside the termination end inner circumference portion, and positioned radially outside the cam profile surface, a curved surface portion connecting the termination end inner circumference portion and the termination end outer circumference portion, and a cross portion at which the curved surface portion is crossed with the cam profile surface, and which is positioned at a position at which a radial length of a vane of the plurality of the vanes that confronts the suction opening portion is shorter than a half of an entire length of the vane, wherein
• the pump constituting section further includes a cam ring configured to be moved within the pump receiving chamber, wherein the cam profile surface is formed on an inner circumference surface of the cam ring, the rotor and the vanes are provided to the inner circumference surface of the cam ring, and the termination end outer circumference portion extends in an arc shape in parallel to the cam profile surface.