Patent ID: 7632083

Claim:
A pump rotor used in an internal gear pump including: an inner pump rotor having outer gear teeth; an outer pump rotor having inner gear teeth that mesh with the outer gear teeth; and a casing having a pumping-in port through which a fluid is pumped in, and a pumping-out port through which the fluid is pumped out, the pump rotor pumping in and pumping out the fluid by volume change of cells formed between gear tooth surfaces of the rotors so as to carry the fluid when the rotors mesh with each other and rotate, wherein the pump rotor is formed from a sintered material of Fe—Cu—C and has a density not less than 6.6 g/cm 3 and not more than 7.1 g/cm 3 and has a porosity of not less than 10% and not greater than 20%, and at least an outer circumferential surface of the outer pump rotor and both end surfaces perpendicular to rotation axes of the rotors are non-grinded surfaces and have ten point height of irregularities Rz not less than 4 μm and not more than 10 μm.