Patent ID: 8033796

Claim:
A motor-mounted internal gear pump comprising: a pump part which sucks and discharges a liquid; and a motor part which drives the pump part, the pump part including: an inner rotor with teeth on its outer surface and an axial hole penetrating its center; an outer rotor with teeth on its inner surface to mesh with the teeth of the inner rotor; a pump casing which houses the inner rotor and the outer rotor; and an internal shaft which is inserted into the axial hole and pivotally supports the inner rotor, the pump casing including: flat inner surfaces facing opposite end faces of the teeth of the inner rotor and opposite end faces of the teeth of the outer rotor, with small gaps between the inner surfaces and the end faces, the motor part including: a rotator located inside the pump casing and integral with the outer rotor; and a stator which applies a revolving magnetic field to the rotator to rotate it, wherein the internal shaft includes a cylindrical bearing which has an outside diameter smaller than the inside diameter of the axial hole of the inner rotor and is longer than the widths of the teeth of the inner rotor, and a fitting part which extends from end faces of the bearing and has an outside diameter smaller than the outside diameter of the bearing; the pump casing includes two pump casing members as separate members forming the flat inner surfaces; the fitting part of the internal shaft is fitted into fitting holes made in the flat inner surfaces of the two pump casing members; the two pump casing members are connected with each other outside the, outside diameter of the outer rotor with the flat inner surfaces in contact with said end faces of the bearing; and wherein the two casing members are made of synthetic resin and one of them has a cylindrical can axially extending outward from a flat inner surface thereof, and the can is softer than the flat inner surface in terms of axial rigidity; and the casing members are connected at a tip side of the can.