Patent ID: 8876504

Claim:
A pump rotor for an internal gear pump, the pump rotor being formed by combining an inner rotor ( 2 ) having N teeth and an outer rotor ( 3 ) having (N+1) teeth and disposing the rotors eccentrically relative to each other, wherein a working position (G) of the inner rotor ( 2 ) and the outer rotor ( 3 ) is always located rearward of an eccentric axis (CL) in a rotating direction of the inner rotor, and wherein a maximum value φD max of a working pitch diameter φD of the inner rotor ( 2 ) and the outer rotor ( 3 ) satisfies the following relational expression: φ D max <1.7 e ·sin(π/180)/sin {π/(180 ·N )} (Expression 1) where e denotes an amount of eccentricity between the inner rotor and the outer rotor, and N denotes the number of teeth in the inner rotor.