Patent ID: 7766604

Claim:
A fuel pump comprising a casing and a impeller rotating within the casing, wherein a group of concavities is formed in an upper or a lower face of the impeller, and concavities forming the group are repeated in a circumferential direction of the impeller, a groove communicating with a discharge hole is formed in a inner face of the casing, the groove extending continuously in a direction of rotation of the impeller in an area facing the group of concavities of the impeller, the groove having an opening portion that directly communicates with the discharge hole, the opening portion is shaped so as to extend in an arcuate shape in the rotation direction of the impeller from its upstream end to its downstream end, the opening portion being disposed from its upstream end to its downstream end within an area extending from a position corresponding to substantially the central position of the concavities of the impeller, in the radial direction thereof, to a position corresponding to substantially the outer peripheral edge of the concavities of the impeller, and not being disposed from its upstream end to its downstream end, within an area extending from a position corresponding to substantially an inner peripheral edge of the concavities of the impeller, in the radial direction thereof, to the position corresponding to substantially the central position of the concavities of the impeller, the inner peripheral edge of the groove, on the side communicating with the discharge hole, slants in the downstream end from a position corresponding to substantially the inner peripheral edge of the concavities of the impeller towards a position corresponding to substantially the central position of the concavities of the impeller, in the radial direction thereof, to connect with the opening portion, and the opening portion is formed so as to extend in an arcuate shape in the rotation direction of the impeller towards the downstream side past the position where the inner peripheral edge connects therewith.