Fuel pump

Claim 1

In a fuel-pumping aggregate of the type having a housing accommodating drive means and pump means driven by said drive means and operated according to the peripheral principle, said pump means including a rotatable impeller having a central axis and an outer peripheral portion having a periphery, said outer peripheral portion being provided with a plurality of vanes uniformly spaced from each other, said housing having an inner wall, said outer peripheral portion extending towards said inner wall and being spaced therefrom so that a fuel-feeding passage is defined therebetween, said outer portion being immersed into said fuel feeding passage a distance corresponding to the height of each vane so that said inner housing portion in the region of said passage has an axial wall portion extended in the axial direction of the impeller and two lateral wall portions extended in the radial direction of the impeller, and wherein hydraulic characteristics of said pump means are defined by a first pump geometric characteristic R m =S/L lying within the range of approximately from 0.4 to 2 mm, wherein S is a cross-sectional area of a space enclosed between the inner wall of the housing and the periphery of said outer portion and L is the length of the periphery of said outer portion, the improvement comprising that hydraulic characteristics of said pump means are further defined by a second pump geometric characteristic R s =B/E and a third pump geometric characteristic R a =A 2 /A 1 which lie within the range of approximately 0.5 to 1.5, wherein B is the width of the impeller in the axial direction thereof, E is the height of each vane, A 1 is the sum of the cross-sectional areas of two lateral portions of said space, extended laterally of said outer portion of the impeller; and A 2 is the cross-sectional area of a remaining portion of said space, the cross-sectional area of each of said two lateral portions being defined by the product of the height of the vane and a distance t 1 , defined in said axial direction between the impeller and one of said lateral wall portions, and the cross-sectional area A 2 being defined by the product of a distance t 2 defined in said radial direction between an end radial face of the impeller and said axial wall portion, and the sum of the width of the impeller and two distances t 1 .