Image forming apparatus

1. An image forming apparatus comprising:

an image holding member in which a toner image is held;

a transfer member configured to transfer the toner image to a transfer material;

a cleaning unit configured to remove waste toner remaining on the image holding member;

a waste toner receiving member configured to receive the waste toner removed by the cleaning unit; and

a full state detection unit comprising a waste toner amount detection unit disposed in the waste toner receiving member to detect an amount of waste toner and configured to detect whether the waste toner is fully filled in the waste toner receiving member by using the waste toner amount detection unit,

wherein the waste toner amount detection unit is movable in a buried state in which the waste toner amount detection unit is positioned under a surface of the waste toner received in the waste toner receiving member, in a non-buried state in which the waste toner amount detection unit is positioned above the surface of the waste toner, and in a loaded state in which the waste toner amount detection unit contacts the surface of the waste toner, and

the full state detection unit detects whether the waste toner is fully filled in the waste toner receiving member when the waste toner amount detection unit is positioned in the loaded state switched from the non-buried state.

2. The image forming apparatus of claim 1 , wherein the transfer member is movable, and the waste toner amount detection unit switches to the buried state, the non-buried state, or the loaded state in cooperation with movement of the transfer member.

3. The image forming apparatus of claim 2 , further comprising:

an actuator configured to provide a rotation force; and

a connection portion disposed between the actuator and the transfer member and configured to deliver the rotation force of the actuator to the transfer member,

wherein by the rotation force of the actuator, the transfer member moves in an away state in which the transfer member is spaced apart by a predetermined distance from the image holding member and in a close state in which the transfer member is closer to the image holding member than in the away state.

4. The image forming apparatus of claim 2 , further comprising:

a case on which the image holding member is fixedly installed; and

a cover configured to open and close the case and on which the transfer member is mounted,

wherein by opening and closing of the cover, the transfer member moves in an away state in which the transfer member is spaced apart by a predetermined distance from the image holding member and in a close state in which the transfer member is closer to the image holding member than in the away state.

5. The image forming apparatus of claim 1 , wherein the transfer member is movable in an away state in which the transfer member is spaced apart by a predetermined distance from the image holding member and in a close state in which the transfer member is closer to the image holding member than in the away state, and

in the full state detection unit, the waste toner amount detection unit switches from the buried state to the non-buried state to correspond to movement of the transfer member from the close state to the away state, and switches from the non-buried state to the loaded state to correspond to movement of the transfer member from the away state to the close state.

6. The image forming apparatus of claim 5 , wherein the full state detection unit is configured to be pressurized in contact with the transfer member when the transfer member moves from the close state to the away state, and

the full state detection unit is configured to be released from the contact pressurization by the transfer member when the transfer member moves from the away state to the close state.

7. The image forming apparatus of claim 6 , wherein the full state detection unit comprises a rotatable shaft on which the waste toner amount detection unit is mounted and a link portion that protrudes from the shaft toward the transfer member and is contactable to the transfer member.

8. The image forming apparatus of claim 5 , further comprising:

a control unit configured to control operations of the transfer member and the full state detection unit.

9. The image forming apparatus of claim 8 , wherein the control unit is configured to perform non-buried control for switching the waste toner amount detection unit from the buried state to the non-buried state by moving the transfer member from the close state to the away state;

to perform loading control for switching the waste toner amount detection unit from the non-buried state to the loaded state by moving the transfer member from the away state to the close state after performing the non-buried control; and

to perform determination control for determining whether the waste toner is in a full state after performing the loading control.

10. The image forming apparatus of claim 9 , further comprising a waste toner stirring unit configured to flatten the waste toner received in the waste toner receiving member.

11. The image forming apparatus of claim 10 , wherein the control unit performs flattening control for flattening the waste toner by operating the waste toner stirring unit after performing the loading control and before performing the determination control.

12. The image forming apparatus of claim 10 , wherein the waste toner stirring unit operates in cooperation with movement of the transfer member.

13. The image forming apparatus of claim 8 , wherein the control unit is configured to control image formation when the waste toner amount detection unit is in the buried state.

14. The image forming apparatus of claim 1 , wherein the waste toner amount detection unit has a trapezoid cross section and has a top surface, a bottom surface having a wider width than the top surface, and a pair of inclined surfaces connecting the top surface with the bottom surface.

15. The image forming apparatus of claim 14 , wherein an angle between the inclined surface and the bottom surface of the waste toner amount detection unit is greater than a first angle of repose that is an angle between a bottom surface and an inclined surface of the waste toner received in the waste toner receiving member.

16. The image forming apparatus of claim 1 , wherein the waste toner amount detection unit comprises an outer frame portion forming a first opening portion and a split-beam portion disposed in the first opening portion to divide the first opening portion into a plurality of second opening portions.

17. The image forming apparatus of claim 16 , wherein a total area of the second opening portions is greater than and equal to about 0.1 mm 2 and less than and equal to about 300 mm 2 .

18. The image forming apparatus of claim 16 , wherein at least one of the outer frame portion and the split-beam portion has a trapezoid cross section including a pair of inclined surfaces, and an angle between the pair of inclined surfaces is a second angle of repose that is an angle between inclined surfaces of the waste toner received in the waste toner receiving member.

19. The image forming apparatus of claim 1 , wherein the waste toner receiving member is rotatable.