US Patent 7766604 Fuel pump

Fuel pump (10)comprises a casing (18) and an impeller (20). A group of concavities (20a) are formed in an upper or a lower face of the impeller. A groove (24) communicating a discharge hole (25) is formed in a inner face of the casing. The groove has an opening portion (27e) that directly communicates with the discharge hole. The opening portion is shaped so as to extend in the rotation direction of the impeller, within a span 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. The opening portion is be formed so as to extend in the rotation direction of the impeller beyond the position (29b) where the inner peripheral edge connects therewith.