Patent ID: 8123459

Claim:
An impeller for a fuel pump having an outer pump chamber and an inner pump chamber being substantially coaxial with each other, the impeller comprising: a plurality of partition walls provided at least in a region corresponding to the inner pump chamber and arranged in the rotative direction, each of the plurality of partition walls partitioning inner vane grooves, which are adjacent to each other, wherein a rear surface is located at a rear side in a rotative direction of each of the inner vane grooves, at least a radially inner side of the rear surface inclines rearward in the rotative direction from a radially inner side to a radially outer side, a backward tilt angle α 2 defined between (i) a first imaginary line that connects a radially inner end of the rear surface with a radially outer end of the rear surface and (ii) a second imaginary line that extends in a radial direction from the radially inner end of the rear surface, satisfies a relationship of 30° α 2 ≦80°, wherein the rear surface at least partially inclines rearward in the rotative direction from one end side in a rotation axis direction to an other end in the rotation axis direction, the rear surface has a plurality of surfaces intersecting with each other, and the following condition is satisfied: an inclination angle β 1 is different from an inclination angle β 2 , where the inclination angle β 1 is defined between (a) a fifth imaginary line that connects an end at the one end side in an radially innermost side of the rear surface with an end at the other end side in the radially innermost side of the rear surface and (b) a sixth imaginary line that extends in a direction of a tangent toward the rear side in the rotative direction from the end of the rear surface at the one end side in the radially innermost side, and the inclination angle β 2 is defined between (c) a seventh imaginary line that connects an end at the one end side in a radially outermost side of the rear surface with an end at the other end side in the radially outermost side of the rear surface and (d) an eighth imaginary line that extends in a direction of a tangent toward the rear side in the rotative direction from the end of the rear surface at the one end side in the radially outermost side.