Patent ID: 7871238

Claim:
A fuel pump comprising a casing and a substantially disc-shaped impeller rotating within the casing, wherein a first group of concavities and a second group of concavities are formed in a concentric pattern in an intake side face of the impeller, and the second group of concavities is located outside of the first group of concavities in a radial direction, a third group of concavities is formed in a discharge side face of the impeller, and the third group of concavities communicates with the second group of concavities, a first groove, a second groove and a communicating groove are formed in an inner face of the casing facing the intake side face of the impeller, the first groove extending continuously in a direction of rotation of the impeller from an upper flow end to a lower flow end in an area facing the first group of concavities, the second groove extending continuously in the direction of rotation of the impeller from an upper flow end to a lower flow end in an area facing the second group of concavities, and the communicating groove communicating with the lower flow end of the first groove and with the upper flow end of the second groove, and a third groove is formed in an inner face of the casing facing the discharge side face of the impeller, the third groove extending continuously in the direction of rotation of the impeller from an upper flow end to a lower flow end in an area facing the third group of concavities, wherein no group of concavities communicating with the first group of concavities is formed in the discharge side face of the impeller, and wherein the first group of concavities does not pass through from the intake side face to the discharge side face of the impeller.