Electric fuel pump device

Abstract

An electric fuel pump for pumping a liquid fuel from a tank to an engine. The pump device has a regenerative pump section and an electric motor section for driving the regenerative pump section. The regenerative pump section includes a pump casing having a first inner surface and a second inner surface axially opposing to and spaced from each other to define therebetween a pump chamber, a shaft adapted to be rotatingly driven by the electric motor section and an impeller accommodated by the pump chamber and mounted on the shaft for rotation therewith but axially movably relatively thereto. The impeller has one axial end surface opposing to the first inner surface with a first gap formed therebetween, and the other axial end surface opposing to the second inner surface of the pump casing with a second gap formed therebetween. The first inner surface and the second inner surface of the pump casing has axial thrust generating surfaces which are so shaped as to gradually decrease the first and the second gaps towards the downstream sides as viewed in the direction of flow of fuel introduced into these gaps. In consequence, axial thrust forces are generated by wedging action of the fuel introduced into the gaps so that the impeller is kept out of contact with the inner surfaces of the pump casing during operation of the pump device.