Axial fan and refrigerator

1. An axial fan comprising:

an impeller rotatable about a rotation axis extending in a vertical direction;

a motor to rotationally drive the impeller;

a housing radially outside the impeller and the motor;

an intake port provided at an upper portion of the housing in the vertical direction; and

an exhaust port provided at a lower portion of the housing in the vertical direction, wherein

an inner wall surface of the housing includes a groove recessed radially outward and extending in the vertical direction, the groove being defined by a channel with two sidewalls and a bottom wall;

wherein at least a first end of the groove in the vertical direction extends to one end of the housing in the vertical direction;

the inner wall surface of the housing includes a first wall including a gap defined between the first wall and a radially outer edge of the impeller;

the groove is provided at the first wall;

a circumferential width of the groove is narrower than a circumferential width of the first wall;

an inner wall surface of the at least one first wall and a circumferential edge of the exhaust port overlap with each other in an axial view parallel to the vertical direction; and

the groove is provided in a center of one side of the inner wall surface.

2. The axial fan according to claim 1 , wherein at least a portion of the groove overlaps with the impeller in the radial direction.

3. The axial fan according to claim 1 , wherein the first end of the groove increases in depth toward the end of the housing in the vertical direction.

4. The axial fan according to claim 3 ,

wherein

the first end of the groove is adjacent to the intake port.

5. The axial fan according to claim 1 , wherein edges connected to the inner wall surface and positioned on two sides of the groove in the circumferential direction are curved.

6. The axial fan according to claim 1 , wherein an edge at the first end of the groove and at the end of the housing is curved.

7. The axial fan according to claim 1 , wherein the inner wall surface of the housing includes an additional gap between a second wall of the housing and the radially outer edge, the gap being narrower than the additional gap.

8. The axial fan according to claim 7 , wherein an inner surface of the first wall is part of a substantially cylindrical shape centered on the rotation axis.

9. The axial fan according to claim 7 , wherein the additional gap between the second wall and the impeller increases toward one end in the vertical direction.

10. The axial fan according to claim 7 ,

wherein an outer wall surface of the housing has a substantially rectangular shape in a cross sectional view perpendicular to the vertical direction, and

wherein the first wall and the second wall are provided on the inner wall surface that is one side of the substantially rectangular shape.

11. The axial fan according to claim 1 , wherein the groove includes a hole passing through the housing in the radial direction.

12. A refrigerator comprising the axial fan according to claim 1 .

13. An axial fan comprising:

an impeller rotatable about a rotation axis extending in a vertical direction;

a motor to rotationally drive the impeller;

a housing radially outside the impeller and the motor;

an intake port provided at an upper portion of the housing in the vertical direction; and

an exhaust port provided at a lower portion of the housing in the vertical direction;

wherein

the housing includes a hole passing therethrough in the radial direction;

an inner wall surface of the housing includes a first wall including a narrow gap with a radially outer edge of the impeller and a second wall including a wide gap with the radially outer edge;

the hole is provided at a center of the first wall in the circumferential direction;

the second wall is provided at two opposing sides of the first wall in the circumferential direction; and

an inner wall surface of the at least one first wall and a circumferential edge of the exhaust port overlap with each other in an axial view parallel to the vertical direction.

14. The axial fan according to claim 13 , wherein the hole overlaps in the radial direction with at least part of the impeller.

15. The axial fan according to claim 13 , wherein a radially inner edge of the hole is curved.

16. A refrigerator comprising the axial fan according to claim 13 .