Patent ID: 7597543

Claim:
An impeller, which is rotatable in a fluid pump to pressurize fluid in a pump passage along a rotative direction of the impeller, the impeller comprising: a plurality of partition walls that is arranged along the rotative direction, adjacent two of the plurality of partition walls defining a vane groove therebetween, wherein each partition wall has a back surface on a backside with respect to the rotative direction, the back surface having a radially inner side, at least the radially inner side of the back surface is radially outwardly inclined backwardly with respect to the rotative direction, the back surface has a radially inner end and a radially outer end, which are connected via a first line segment, the first line segment and a first straight line, which extends radially outwardly from the radially inner end along a radius of the impeller, define a backward inclining angle α therebetween, the impeller has a thickness-center and thickness-ends with respect to a thickness direction of the impeller, the back surface is inclined from the thickness-center toward both the thickness-ends forwardly with respect to the rotative direction, the thickness-center and each of the thickness-ends are connected via a second line segment, the second line segment and a second straight line, which extends from the thickness-center along the circumferential direction forwardly with respect of the rotative direction, define a forward inclining angle β therebetween, and the backward inclining angle α and the forward inclining angle β satisfy the following relationships: 15°≦α≦30°; β≦60°; and 1≦β/α≦4.