Axial fan and fan assembly

1. An axial fan comprising:

a stationary portion; and

a rotating portion supported to be rotatable with respect to the stationary portion; wherein

the rotating portion includes:

a shaft positioned along a central axis extending from an inlet of the axial fan to an outlet of the axial fan;

a rotor magnet provided in an annular shape around the central axis;

a rotor holder including a cylindrical inside surface configured to hold the rotor magnet; and

an impeller directly or indirectly fixed to an outer circumferential surface of the rotor holder;

the stationary portion includes:

an armature located radially inside of the rotor magnet;

a bearing member configured to rotatably support the shaft;

a base portion configured to support the bearing member and the armature;

a tubular housing extending in an axial direction radially outside of the impeller; and

a plurality of support ribs, each of which is configured to join the housing and the base portion to each other, the plurality of support ribs is located upstream of the impeller in the axial direction;

the impeller includes:

a cup-shaped blade support portion configured to cover the rotor holder; and

a plurality of blades arranged in a circumferential direction radially outside of the blade support portion to generate a downward air flow, downward being from the inlet of the axial fan to the outlet of the axial fan, in the axial direction during rotation;

the rotating portion includes a first balance correction portion located between the blade support portion and the rotor holder in the radial direction, and configured to allow a change in a circumferential mass distribution;

the impeller includes:

a second balance correction portion which is: located below the first balance correction portion in the axial direction, located below the rotor holder and a junction of each blade with the blade support portion in the axial direction, and configured to allow a change in a circumferential mass distribution;

a first cone portion located below the second balance correction portion in the axial direction and decreasing in diameter with a height decreasing downward in the axial direction; and

the impeller includes a cylindrical portion including a cylindrical outer circumferential surface and located between the first cone portion and the second balance correction portion.

2. The axial fan according to claim 1 , wherein the impeller further includes a second cone portion increasing in diameter with increasing height in the axial direction which is located above the second balance correction portion and below the junction of each blade with the blade support portion in the axial direction.

3. The axial fan according to claim 2 , wherein an angle of inclination of a straight line that joins an upper end edge and a lower end edge of the first cone portion with respect to the central axis is greater than an angle of inclination of a straight line that joins an upper end edge and a lower end edge of the second cone portion with respect to the central axis.

4. The axial fan according to claim 1 , wherein a tangent to a radially outer surface of the first cone portion crosses the second balance correction portion.

5. The axial fan according to claim 1 , wherein

the second balance correction portion includes a plurality of hole portions arranged in the circumferential direction; and

each of the plurality of hole portions is open downwardly in the axial direction.

6. The axial fan according to claim 1 , wherein a lower end of the housing is positioned at a level lower than a level of a lower end of the first cone portion in the axial direction.

7. The axial fan according to claim 1 , wherein the housing includes, circumferentially around the first cone portion, an exhaust pipe portion including an inner circumferential surface increasing in diameter with decreasing height in the axial direction.

8. The axial fan according to claim 1 , wherein the housing includes:

a lower housing member which radially overlaps with the first cone portion; and

an upper housing member which radially overlaps with the blades.

9. The axial fan according to claim 1 , wherein

the impeller is a resin-molded article;

the first cone portion includes a bottom surface in the axial direction that is circular in a plan view; and

the first cone portion includes a gate mark in the bottom surface.

10. A fan assembly comprising:

an outlet side fan which is the axial fan according to claim 1 ; and

an inlet side fan which is an axial fan located above the outlet side fan in the axial direction; wherein

a housing of the inlet side fan and the housing of the outlet side fan together define a continuous wind channel.

11. The fan assembly according to claim 10 , wherein a rotation direction of an impeller of the inlet side fan and a rotation direction of the impeller of the outlet side fan are different from each other.

12. The fan assembly according to claim 10 , wherein the fan assembly is configured to supply a cooling air flow to an interior of a room in which a plurality of electronic devices are installed.

13. The axial fan of claim 1 , further comprising:

an inlet above the plurality of support ribs in the axial direction; and

an outlet below the cone portion in the axial direction.