Patent ID: 8297913

Claim:
A fuel pump comprising a casing and an impeller, wherein: the impeller is substantially disk shaped having an upper surface and a lower surface, and rotates in only one direction within the casing around a rotational axis; a group of concavities is formed in each of the upper and lower surfaces of the impeller, and is arranged on a circle around the rotational axis of the impeller; a first groove is formed in an inner surface of the casing, faces the group of concavities formed in the lower surface of the impeller, and extends from an upstream end to a downstream end along a rotational direction of the impeller; a second groove is formed in the inner surface of the casing, faces the group of concavities formed in the upper surface of the impeller, and extends from an upstream end to a downstream end along the rotational direction of the impeller; a fuel intake hole is formed in the casing and passes through the casing from the exterior of the casing to the upstream end of the first groove; a fuel discharge hole is formed in the casing and passes through the casing from the downstream end of the second groove to the exterior of the casing; a plurality of impeller depressions is formed in at least the lower surface of the impeller, located on at least one of the inside and the outside of the group of concavities, and arranged on a circle around the rotational axis of the impeller; in a cross-section along a circumferential direction of the impeller, each of the impeller depressions has its deepest portion in a rear half thereof with respect to the rotational direction of the impeller; and the impeller has no depression having its deepest portion in a front half thereof with respect to the rotational direction of the impeller.