INTERNAL GEAR PUMP

PROBLEM TO BE SOLVED: To improve mechanical efficiency and inhibit the lowering of volumetric efficiency in an internal gear pump in which a difference in the number of teeth between an inner rotor and an outer rotor is one and reduce cavitation erosion by inhibiting the generation of cavitation even when the rotation speed of the pump is increased in that case. SOLUTION: Among clearances between the closest approach portions of the respective teeth of the inner rotor 1 and the outer rotor 2 formed before and after a chamber 8 in a rotor rotation direction on an intake port 4, the clearance at the maximum position is set at 0.3 mm or more, relationship between a thickness t and an outer diameter D of the outer rotor 2 is defined as t/D ≤ 0.35, so that liquid is also drawn from the chamber preceding a chamber in an initial stage of the intake. Flow speed of the liquid drawn into the chamber when the mechanical efficiency is improved by setting the outer diameter of the outer rotor to be small and the thickness to be large is inhibited from increasing. COPYRIGHT: (C)2008,JPO&INPIT