Patent ID: 7264440

Claim:
A fuel pump, comprising a casing and a substantially disc-shaped impeller rotating within the casing; wherein a group of concavities is formed in both upper and lower faces of the impeller in an area located inwardly from an outer circumference of the impeller by a first distance, the area extending along the circumferential direction of the impeller, a groove is formed in both upper and lower inner faces of the casing in an area directly facing the group of the concavities, each concavity extends for a second distance in the radial direction of the impeller from an inner end to an outer end, adjacent concavities are separated by a partitioning wall, the pair of upper and lower concavities are partially separated by a partitioning wall, and bottom portions of the pair of upper and lower concavities are connected over a region extending outwardly from a point which is separated from the inner end of the concavities by a distance not exceeding one eighth of the second distance at the concavities whose inner ends directly face and align with an inner end of the groove formed in the casing and whose outer ends directly face and align with an outer end of the groove formed in the casing.