Impeller and fluid pump having the same

1. 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.

2. The impeller according to claim 1 , wherein the backward inclining angle α satisfies the following relationship: 20°≦α.

3. A fluid pump comprising:

a motor portion;

the impeller according to claim 1 , the impeller being rotated by the motor portion; and

a case member that defines the pump passage, the impeller being rotatable in the case member.

4. A fluid pump comprising:

a case member that has an inlet port and a pump passage; and

an impeller that is rotatable in the case member, the impeller having a plurality of vane grooves along the pump passage extending along a rotative direction of the impeller, each vane groove defined by a back surface on a backside with respect to the rotative direction,

wherein at least a radially inner side of the back surface is inclined to a radially outer side 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 is inclined relative to a straight line, which extends radially outwardly from the radially inner end along a radius of the impeller, backwardly with respect to the rotative direction,

the impeller has a thickness-center with respect to a thickness direction of the impeller,

at least an inlet side of the back surface on a side of the inlet port is inclined from the thickness-center toward the inlet port with respect to the thickness direction forwardly with respect to the rotative direction,

the case member has a communication wall that defines a communication passage communicating the inlet port with the pump passage,

the communication wall has an inlet-side end and a passage-side end that are connected via an inclining straight line, which is gradually elevated from the inlet port toward the pump passage,

the inclining straight line and a second line segment, which extends from the thickness-center of the back surface to the inclining straight line through the inlet-side end of the back surface, define an angle ε forwardly with respect to the rotative direction, and

the angle ε satisfies the following relationship: 90°≦ε≦130°.

5. The fluid pump according to claim 4 , wherein the back surface is inclined from the thickness-center toward both sides with respect to the thickness direction forwardly with respect to the rotative direction.

6. The fluid pump according to claim 4 ,

wherein the inclining straight line, which extends from the inlet-side end toward the passage-side end, is elevated at a rising angle θ, and

the rising angle θ satisfies the following relationship: 10°≦θ≦30°.

7. The fluid pump according to claim 4 ,

wherein the back surface defines an inclining surface that is inclined from the thickness-center toward the thickness-ends forwardly with respect to the rotative direction,

the thickness-center connects with the thickness-ends via a third line segment in the inclining surface,

the third line segment and a straight line, which extends from the thickness-center along a circumferential direction forwardly with respect of the rotative direction, define a forward inclining angle β therebetween, and

the forward inclining angle β satisfies the following relationship: 40°≦β≦60°.

8. The fluid pump according to claim 4 , further comprising:

a motor portion that rotates the impeller for pressurizing fluid drawn from the inlet port into the pump passage that is defined along the plurality of vane grooves.

9. A fluid pump comprising:

a case member that defines a pump passage therein; and

an impeller, which is rotatable in case member to pressurize fluid in the pump passage along a rotative direction of the impeller,

wherein the impeller includes a plurality of partition walls along the rotative direction, adjacent two of the plurality of partition walls defining a vane groove therebetween,

each partition wall has a back surface on a backside with respect to the rotative direction,

at least a 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.

10. An impeller, which is rotatable in a fluid pump having a pump passage extending 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,

at least a 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 defining a backward inclining angle α being an acute angle with respect to a radius of the impeller,

the back surface is inclined from a thickness-center of the impeller toward both thickness-ends of the impeller forwardly with respect to the rotative direction,

the thickness-center and each of the thickness-ends are connected via a second line segment, which defines a forward inclining angle β being an acute angle with respect to a first straight line, which is tangent to a circumscribed circle of an outer circumferential periphery of the impeller, 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.

11. A fluid pump comprising:

a case member that has an inlet port and a pump passage; and

an impeller that is rotatable in the case member, the impeller having a plurality of vane grooves along the pump passage extending along a rotative direction of the impeller, each vane groove being defined by a back surface on a backside with respect to the rotative direction,

at least a radially inner side of the back surface is 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, which defines a backward inclining angle α being an acute angle with respect to a radius of the impeller,

the back surface on a side of the inlet port is inclined from a thickness-center of the impeller toward the inlet port forwardly with respect to the rotative direction,

the case member has a communication wall that defines a communication passage communicating the inlet port with the pump passage,

the communication wall has an inlet-side end and a passage-side end that are connected via an inclining straight line, which is gradually elevated from the inlet port toward the pump passage,

the inclining straight line defines an angle ε being one of a right angle and an obtuse angle with respect to a second line segment, which extends from the thickness-center of the back surface to the inclining straight line through the inlet-side end of the back surface, and

the angle ε satisfies the following relationship: 90°≦ε≦130°.