Robot cleaner

1. A robot cleaner, comprising:

a main body having a suction port at a bottom surface thereof;

a pair of wheel assemblies disposed at both sides of the main body, and configured to move the main body;

a dust box installed on the bottom surface of the main body, and configured to collect dust sucked through the suction port;

a filter unit configured to filter air discharged from the dust box;

a suction fan configured to form a suction pressure on a suction channel defined by the suction port, the dust box and the filter unit; and

a battery disposed at a side of the dust box;

an agitator rotatably mounted to a lower part of the main body;

side brushes mounted so as to be rotatable with a rotation shaft extending in a vertical direction of the main body; and

a driving force transmission device configured to transmit a rotational force of the agitator to the side brushes,

wherein the dust box is disposed between the suction port and the filter unit with respect to a longitudinal direction of the main body.

2. The robot cleaner of claim 1 , wherein a balance weight facing the battery with the dust box therebetween is installed in the main body.

3. The robot cleaner of claim 1 , wherein the dust box is disposed between the pair of wheel assemblies.

4. The robot cleaner of claim 3 , wherein the battery is mounted between the pair of wheel assemblies.

5. The robot cleaner of claim 4 , wherein a length of the battery with respect to a vertical direction of the main body is longer than that with respect to a horizontal direction of the main body.

6. The robot cleaner of claim 1 , wherein the driving force transmission device comprises worms and worm gears.

7. The robot cleaner of claim 1 , wherein the suction fan comprises:

a plurality of wings configured to introduce air in an axial direction, and to discharge the air to a radial direction; and

a shroud having a suction port disposed in front of the wings in the axial direction, and having a discharge port formed in a ring shape in a circumferential direction of the wings.

8. The robot cleaner of claim 1 , wherein the filter unit comprises:

a filter case configured to form a part of the suction channel;

a first filter disposed on a suction port side of the filter case; and

a second filter disposed on a discharge port side of the filter case,

wherein one or more bypass holes are penetratingly formed on a side surface of the filter case.

9. The robot cleaner of claim 8 , wherein a flow rate through the bypass hole is set to be less than a flow rate through the first filter.

10. The robot cleaner of claim 8 , wherein the first filter comprises a mesh filter, and a mesh filter having mesh holes smaller than those of the mesh filter of the first filter is installed at the bypass hole.

11. A robot cleaner, comprising:

a main body having a suction port at a bottom surface thereof;

a pair of wheel assemblies disposed at both sides of the main body, and configured to move the main body;

a dust box installed on the bottom surface of the main body, and configured to collect dust sucked through the suction port;

a filter unit configured to filter air discharged from the dust box;

a suction fan configured to form a suction pressure on a suction channel defined by the suction port, the dust box and the filter unit;

a battery disposed at a side of the dust box;

an agitator rotatably mounted to a lower part of the main body;

side brushes mounted so as to be rotatable with a rotation shaft extending in a vertical direction of the main body; and

a driving force transmission device configured to transmit a rotational force of the agitator to the side brushes.

12. The robot cleaner of claim 11 , wherein the driving force transmission device comprises worms and worm gears.