Impeller and motor

1. An impeller comprising:

a hub having an outer circumferential surface, the hub being rotated about a center axis extending in an up-down direction; and

a plurality of inclined blades that are disposed on the outer circumferential surface of the hub at intervals in a circumferential direction,

the inclined blades being inclined relative to the center axis and arranged such that a front edge of each of the inclined blades in a rotating direction is positioned on an upper side than a rear edge thereof,

the outer circumferential surface of the hub including:

a first outer circumferential surface including a portion arranged at a position overlapping the inclined blade in a direction of the center axis, the position being present above a joined portion of the outer circumferential surface to the inclined blade;

a second outer circumferential surface including a portion arranged at a position overlapping the inclined blade in the direction of the center axis, the position being present rearward of the first outer circumferential surface in the rotating direction and below the joined portion of the outer circumferential surface to the inclined blade; and

a connecting portion that connects an end of the first outer circumferential surface on a rear side in the rotating direction and an end of the second outer circumferential surface on a front side in the rotating direction to each other,

wherein the connecting portion is arranged forward of the front edge of the inclined blade in the rotating direction,

the first outer circumferential surface is a curved surface having a curvature radius that gradually increases downward from above,

a tangential plane at an arbitrary point on the second outer circumferential surface is positioned parallel to the center axis or farther away from the center axis on an upper side than on a lower side, and

a distance from the center axis to an arbitrary first point, which is positioned at the end of the first outer circumferential surface on the rear side in the rotating direction, is equal to or longer than a distance from the center axis to a second point, which is positioned at the end of the second outer circumferential surface on the front side in the rotating direction and at a same position as the first point in the direction of the center axis.

2. The impeller according to claim 1 , wherein the connecting portion is positioned between the rear edge of the inclined blade on the front side in the rotating direction of the hub and the front edge of the inclined blade on the rear side in the rotating direction of the hub.

3. The impeller according to claim 1 , wherein the connecting portion includes an inclined surface having a distance from the center axis in a radial direction, the distance gradually decreasing from a first outer circumferential surface side toward a second outer circumferential surface side.

4. The impeller according to claim 3 , wherein the inclined surface includes a first inclined portion having a convex shape relative to the outer circumferential surface.

5. The impeller according to claim 3 , wherein the inclined surface includes a second inclined portion having a concave shape relative to the outer circumferential surface.

6. The impeller according to claim 3 , wherein the inclined surface includes:

a first inclined portion that is in continuity with the first outer circumferential surface, and that has a convex shape relative to the outer circumferential surface; and

a second inclined portion that is in continuity with each of the first inclined portion and the second outer circumferential surface, and that has a concave shape relative to the outer circumferential surface.

7. The impeller according to claim 3 , wherein the inclined surface includes:

a first inclined portion that is in continuity with the first outer circumferential surface, and that has a convex shape relative to the outer circumferential surface;

a second inclined portion that is in continuity with the second outer circumferential surface, and that has a concave shape relative to the outer circumferential surface; and

a third inclined portion that is in form of a flat surface, and that is arranged between the first inclined portion and the second inclined portion to be in continuity with the first inclined portion and the second inclined surface, respectively.

8. The impeller according to claim 1 , wherein the connecting portion has a joining surface that is perpendicular to a tangential direction of the first outer circumferential surface at an end joining to the first outer circumferential surface, and that is perpendicular to a tangential direction of the second outer circumferential surface at an end joining to the second outer circumferential surface.

9. The impeller according to claim 1 , wherein the second outer circumferential surface is a surface having a distance from the center axis, the distance gradually increasing from the front side in the rotating direction toward the rear side in the rotating direction.

10. A motor comprising:

a stator;

a rotor supported rotatably relative to the stator; and

the impeller according to claim 1 , the impeller being fixed to the rotor.