Cleaner

1. A cleaner comprising:

a suction flow path configured to receive air from an outside of the cleaner;

a dust separation unit configured to receive the air through the suction flow path and to separate dust in the air;

a fan module configured to move the air in the suction flow path; and

a dust sensor configured to measure a concentration of dust in the suction flow path,

wherein the suction flow path comprises:

a first suction flow path that extends in a first direction parallel to a horizontal cross-section plane orthogonal to a rotation axis of the fan module, and

a second suction flow path that extends in a second direction parallel to the horizontal cross-section plane and connects the first suction flow path to the dust separation unit, the second direction defining an obtuse angle on the horizontal cross-section plane with respect to the first direction,

wherein the cleaner further comprises a flap door rotatably disposed in the second suction flow path and configured to open and close the second suction flow path based on an air pressure in the second suction flow path,

wherein a central axis of the first suction flow path extends on the horizontal cross-section plane in the first direction and intersects the flap door,

wherein the second suction flow path on the horizontal cross-section plane is defined between a first surface of the flap door and a second surface of the cleaner that does not intersect the central axis of the first suction flow path,

wherein the dust sensor is disposed along the first surface in the second suction flow path, and

wherein the dust sensor is disposed closer to the first suction flow path than to the flap door.

2. The cleaner of claim 1 , wherein the dust sensor comprises:

an emitter configured to emit light; and

a receiver configured to receive the light emitted from the emitter.

3. The cleaner of claim 2 , wherein the dust sensor further comprises a substrate that supports at least one of the emitter or the receiver.

4. The cleaner of claim 2 , wherein the emitter and the receiver are disposed in the second suction flow path and face each other across the second suction flow path.

5. The cleaner of claim 4 , further comprising a suction pipe that define the second suction flow path,

wherein the emitter is disposed at a first side of the suction pipe, and the receiver is disposed at a second end of the suction pipe facing the first side.

6. The cleaner of claim 2 , wherein the emitter and the receiver are disposed in the second suction flow path and face a same direction.

7. The cleaner of claim 6 , further comprising a suction pipe that define the second suction flow path,

wherein the emitter and the receiver are disposed on one side of the suction pipe and arranged adjacent to each other.

8. The cleaner of claim 2 , wherein the emitter and the receiver are disposed on one substrate.

9. The cleaner of claim 1 , further comprising a sensor cover that covers the dust sensor.

10. The cleaner of claim 9 , further comprising a suction pipe that defines the second suction flow path, wherein the sensor cover defines a portion of the suction pipe.

11. The cleaner of claim 9 , wherein the dust sensor comprises:

an emitter configured to emit light; and

a receiver configured to receive the light emitted from the emitter, and

wherein the sensor cover comprises:

an accommodation part that defines an opening configured to receive at least one of the emitter or the receiver, and

a window that covers the opening defined at the accommodation part, the window being configured to transmit light.

12. The cleaner of claim 11 , wherein the accommodation part includes an impermeable material.

13. The cleaner of claim 11 , wherein the sensor cover further includes a cover support that is connected to the accommodation part and extends outward from the accommodation part.

14. The cleaner of claim 13 , further comprising a suction pipe that defines the second suction flow path, wherein the cover support is coupled to the suction pipe.

15. The cleaner of claim 13 , further comprising a suction pipe that defines the second suction flow path, wherein the cover support contacts the suction pipe.

16. The cleaner of claim 13 , further comprising:

a suction pipe that defines the second suction flow path; and

a substrate that supports at least one of the emitter or the receiver,

wherein the cover support comprises a first surface that contacts the suction pipe, and a second surface that contacts the substrate.

17. The cleaner of claim 11 , further comprising a suction pipe that defines the second suction flow path, the suction pipe defining a sensor hole that receives the accommodation part.

18. The cleaner of claim 1 , wherein an extension line of the first suction flow path intersects the rotation axis of the fan module.

19. The cleaner of claim 1 , wherein the fan module comprises an impeller and a suction motor configured to rotate the impeller about the rotation axis.