Air cleaner

1. An air cleaner comprising:

a fan that is configured to suction air in an axial direction and discharge air between the axial direction and a radial direction;

a fan motor that is configured to rotate the fan; and

an air guide unit that:

includes (i) a cylindrical outer wall and (ii) an inner wall that is located in a center portion of the outer wall and that defines a space that is configured to receive the fan motor;

defines an annular air flow path that is configured to receive air discharged by the fan and that is defined by an inner circumferential surface of the outer wall and an outer circumferential surface of the inner wall;

includes a plurality of guide ribs that are spaced apart from each other in a circumferential direction, that are located in the annular air flow path, that each have a curved plate shape that includes a positive pressure surface that pushes air and is concave and a negative pressure surface that is opposite the positive pressure surface and that is convex, and that each include a cutoff portion that connects a lower end of a respective guide rib to a side of the respective guide rib close to the outer wall; and

includes a plurality of flow guide protrusions that are spaced apart from each other in the radial direction, that protrude from the negative pressure surface, and that extend vertically,

wherein each cutoff portion defines a cut-off hole that joins the cutoff portion and the inner circumferential surface of the outer wall in a rotation direction.

2. The air cleaner of claim 1 , wherein each of the plurality of flow guide protrusions has a protruded height from the negative pressure surface that decreases from a lower end of the flow guide protrusion to an upper end of the flow guide protrusion.

3. The air cleaner of claim 2 , wherein each of the plurality of guide ribs has an upper end and a lower end that are oriented in the rotation direction of the fan as the upper end and the lower end progress in the radial direction.

4. The air cleaner of claim 1 , wherein the cutoff portion is inclined closer to the outer wall as it progresses from a lower end to an upper end.

5. The air cleaner of claim 1 , wherein the cutoff portion comprises:

a vertical portion that extends vertically from a lower end; and

a horizontal portion that extends in the radial direction from an upper end of the vertical portion to one side of the guide rib close to the outer wall.

6. The air cleaner of claim 1 , wherein each of the plurality of guide ribs includes a plurality of teeth that are located in an upper end of a respective guide rib and that are spaced apart from each other in the radial direction,

wherein each of the plurality of teeth has an upper end that is convex, and has a width in the radial direction that becomes wider as it progresses from the upper end to a lower end.

7. The air cleaner of claim 1 , wherein each of the plurality of guide ribs includes a bending portion that is located at a lower end of a respective guide rib and that is bent toward the negative pressure surface.

8. The air cleaner of claim 1 , wherein each of the plurality of guide ribs connects the inner circumferential surface of the outer wall and the outer circumferential surface of the inner wall.

9. The air cleaner of claim 1 , wherein the fan comprises:

a hub that is coupled to a rotation shaft of the fan motor and that extends with a radius that increases in a direction of air flow through the annular air flow path;

a shroud that is spaced apart from the hub, that extends in a direction in which the hub extends, and that includes a central portion that defines a suction port that is configured to suck air; and

a plurality of blades that are located between the hub and the shroud.

10. The air cleaner of claim 9 , comprising a fan housing that is configured to receive the fan,

wherein the outer wall is located above the fan housing, and

wherein a lower portion of the inner wall is located in an opened upper side of the hub.

11. The air cleaner of claim 1 , wherein the plurality of flow guide protrusions extend vertically from an upstream side to a downstream side in an air flow direction.