Abstract: A centrifugal pump of the vortex-flow type includes a pump housing defining therein an arcuate pump chamber in surrounding relationship with a central sealed chamber, and a disc-like impeller rotatably and axially movably assembled within the pump housing and having opposite end faces each forming a close clearance with a corresponding internal end wall of the pump housing between the sealed and pump chambers, the impeller having on either end face of the rim portion thereof a plurality of circumferentially equally spaced vane grooves which cooperate with the pump chamber to produce a discharge pressure therein and being formed with at least one pressure balancing hole extending axially therethrough in the interior of the sealed chamber.

Abstract: A motor-driven fuel pump including a motor section provided with a driving motor, and a pump section arranged below the motor section and provided with an impeller to be driven by the driving motor. A plurality of pressure compensation hollows are formed on opposite surfaces of a sealing portion of the impeller, and a plurality of communication holes are formed through the sealing portion for communicating the pressure compensation hollows. In another aspect, a plurality of pressure compensation passages are provided to be communicated to a higher pressure side of either a pump chamber defined around outer peripheral vanes of the impeller and a fuel well for receiving a fuel leaked along a sealing portion of the impeller.