Patent ID: 7625192

Claim:
An internal gear pump comprising: a pump casing; an outer rotor; an inner rotor disposed on an inner peripheral side of the outer rotor; a crescent disposed in a gap between the inner rotor and the outer rotor; outer cells formed by the crescent and the outer rotor; and inner cells formed by the crescent and the inner rotor, wherein a port projection portion projecting along a circumferential direction towards a finishing end portion of an inlet port so as to extend across an area, over which tooth top portions of the outer rotor pass, is formed in an outer peripheral side of a starting end portion of an outlet port, a section of an end of the port projection portion being a position at which the tooth top portions of the outer rotor start to separate from the surface of an arc-shaped convex surface side of the crescent, wherein a continuity area of a portion which continues along a circumferential direction between the port projection portion of the outlet port and a non-projection starting edge where the port projection portion is not formed, towards the finishing end portion of the inlet port, is formed substantially in an arc shape similar to an outer peripheral shape of the arc-shaped convex surface side on an outlet port side of the crescent, and wherein the continuity area having a projection length of the port projecting portion from the non-projecting starting edge until the port projection portion is set in such a manner that linking of the port projection portion of the outlet port in the pump casing to the outer cells due to gradual separation of the surface of the arc-shaped convex surface side of the crescent from the tooth top portions of the outer rotor, and linking of the non-projecting starting edge of the outlet port to the inner cells due to gradual separation of a concave surface of the arc-shaped surface side of the crescent from the tooth top portions of the inner rotor occur substantially simultaneously.