Patent ID: 8523513

Claim:
A fuel pump comprising: a casing; and a substantially disk-shaped impeller rotatably disposed within the casing, wherein a first group of concavities is formed in a lower surface of the impeller, and concavities forming the first group are arranged in concentric circles with respect to a rotational axis of the impeller; a second group of concavities is formed in an upper surface of the impeller, and concavities forming the second group are arranged in concentric circles with respect to a rotational axis of the impeller; a first groove is formed in a first inner surface of the casing, the first groove extending from an upstream end to a downstream end in an area that faces the first group of concavities; a second groove is formed in a second inner surface of the casing, the second groove extending from an upstream end to a downstream end in an area that faces the second group of concavities; an intake hole is formed in the casing, the intake hole passing from the exterior of the casing to the upstream end of the first groove; a discharge hole is formed in the casing, the discharge hole passing from the exterior of the casing to the downstream end of the second groove; at least one seal portion is disposed on at least one of the first inner surface, the second inner surface, the lower surface and the upper surface, the seal portion comprising a plurality of layers of thin film, the plurality of layers of thin film formed by an identical material; and a clearance is formed between the seal portion and a portion facing the seal portion.