INTERNAL GEAR PUMP

PROBLEM TO BE SOLVED: To create a tooth profile of an inner rotor of an internal gear pump without generating cusps at its each tooth tip.SOLUTION: A rolling circle is rolled on a base circle without slipping and a trochoid curve T is drawn by the trajectory of a fixed point separated by e from the center of the rolling circle. An envelope of a group of trajectory circles each having the center on the trochoid curve is made as the tooth profile of an inner rotor 2. The inner rotor is combined with an outer rotor to configure a pump rotor. When the profile curve of the inner rotor satisfies formula (1) and the minimum curvature radius of the trochoid curve T satisfies formula (2) respectively and if it is set such that K1=2 -C, and then, 0.5≤K1≤2 is satisfied, it prevents the generation of cusps s at both ends of each tooth tip of the tooth profile of the inner rotor 2.