Patent ID: 6929458

Claim:
An internal gear oil pump rotor assembly, comprising: an inner rotor having “Zi” external teeth with trochoid tooth profiles; and an outer rotor having “Zo” internal teeth which are engageable with the external teeth, wherein the oil pump rotor assembly is used in an oil pump which further includes a casing having a suction port for drawing fluid and a discharge port for discharging fluid are formed, and which conveys fluid by drawing and discharging fluid by volume change of cells formed between the inner rotor and the outer rotor produced by relative rotation between the inner rotor and the outer rotor engaging each other, and wherein the number of teeth “Zi” of the inner rotor is set to be equal to or fewer than “6”, and a ratio Si/So is set so as to satisfy the following inequalities: 0.8≦Si/So≦1.3, where Si is a cross-sectional area of one external tooth which is formed outside a root circle that is formed along the bottoms of the external teeth of the inner rotor, and So is a cross-sectional area of one internal tooth which is formed inside a root circle that is formed along the bottoms of the internal teeth of the outer rotor.