Image forming apparatus

1. An image forming apparatus comprising:

a plurality of developing units to develop a visible image from an electrostatic latent image through a developer;

a transfer member provided to transfer the visible image developed by the plurality of developing units onto a printing medium and to rotate in a first direction;

a sensing unit including at least one sensor disposed opposite the transfer member, and at least one window disposed between the at least one sensor and the transfer member and corresponding to the at least one sensor, to sense the developer transferred onto the transfer member; and

a shutter device having a shutter movably provided with a displacement in the first direction of rotation of the transfer member,

wherein the shutter is to open and close the at least one window.

2. The apparatus according to claim 1 , wherein:

the shutter includes a first position at which the at least one window is closed and a second position at which the at least one window is opened; and

the shutter obliquely moves according to the displacement in the first direction and a displacement in a second direction perpendicular to the first direction between the first position and the second position.

3. The apparatus according to claim 1 , wherein the shutter device includes a shutter driving device having a cam gear, which is rotatably provided and converts rotation of the cam gear into movement of the shutter to open and close the at least one window, and

to drive the shutter.

4. The apparatus according to claim 3 , wherein the cam gear includes:

a gear body; and

a cam rail provided on one side of the gear body and configured to guide the movement of the shutter.

5. The apparatus according to claim 4 , wherein the shutter is guided by the movement of the cam rail and reciprocates in an oblique direction having the displacement in the first direction and a displacement in a second direction perpendicular to the first direction according to rotation of the cam gear.

6. The apparatus according to claim 4 , wherein the shutter includes:

a shutter body configured to open and close the at least one window; and

a guide pole provided on the shutter body to be movable along the cam rail.

7. The apparatus according to claim 6 , wherein:

the cam rail is formed such that a radial distance (r) from a center of the rotation of the cam gear to the cam rail varies according to rotation of the cam gear; and

the guide pole is guided by the cam rail by the rotation of the cam gear and moves based on the displacement in the first direction.

8. The apparatus according to claim 7 , wherein the shutter includes:

a first position at which the at least one window is closed; and

a second position at which the at least one window is opened,

wherein the shutter is positioned at the first position when the radial distance of the cam rail to which the guide pole is guided is r 1 ,

the shutter is positioned at the second position when the radial distance of the cam rail to which the guide pole is guided is r 2 , and

the r 1 is formed to be greater than the r 2 .

9. The apparatus according to claim 8 , wherein the shutter has the displacement in the first direction by the rotation of the cam gear and reciprocates a distance between the r 1 and the r 2 .

10. The apparatus according to claim 8 , wherein the cam rail includes:

a first cam rail having a radius of the r 1 ; and

a second cam rail having a radius of the r 2 .

11. The apparatus according to claim 10 , wherein the first cam rail extends longer than the second cam rail from the shutter body in an axial direction of the cam gear.

12. The apparatus according to claim 7 , wherein:

the cam rail is formed such that a height (h) in an axial direction of the cam gear varies according to rotation of the cam gear; and

the guide pole is provided to move according to the displacement in the first direction and the displacement in a second direction perpendicular to the first direction along the cam rail by the rotation of the cam gear.

13. The apparatus according to claim 12 , wherein the shutter includes:

a first position at which the at least one window is closed; and

a second position at which the at least one window is opened,

wherein the shutter is positioned at the first position when a radial distance of the cam rail to which the guide pole is guided is r 1 and a height in the axial direction is h 1 ,

the shutter is positioned at the second position when a radial distance of the cam rail to which the guide pole is guided is r 2 and a height in the axial direction is h 2 , and

the r 1 is formed to be greater than the r 2 , and the h 2 is formed to be greater than the h 1 .

14. The apparatus according to claim 13 , wherein the shutter obliquely moves according to the displacement in the first direction as much as a difference between the r 1 and r 2 and the displacement in the second direction as much as a difference between the h 1 and h 2 .

15. The apparatus according to claim 6 , wherein:

the shutter includes a first position at which the at least one window is closed and a second position at which the at least one window is opened; and

the shutter body is formed to entirely seal a surface located at a same level as the at least one window in a width direction of the transfer member from the sensor housing when the shutter is disposed at the first position.

16. The apparatus according to claim 3 , wherein:

the shutter driving device further includes:

a driving unit having a driving motor configured to generate a rotating force, and

a worm rotated by the driving motor; and

the cam gear further includes a worm wheel, which is meshed with the worm and rotated.

17. The apparatus according to claim 3 , wherein:

the sensing unit further includes a sensor housing which accommodates the at least one sensor;

the shutter includes a first position at which the at least one window is closed and a second position at which the at least one window is opened; and

the shutter is moved from the first position to the second position by the shutter driving device, and moved from the second position to the first position by an elastic restoring force of an elastic member provided between the sensor housing and the shutter.

18. The apparatus according to claim 1 , wherein:

the sensing unit further includes a sensor housing which accommodates the at least one sensor, and a second direction perpendicular to the first direction is a longitudinal direction of the sensor housing; and

the sensor housing includes:

a plurality of guide rails which are:

separated from each other in the second direction so that the shutter performs parallel movement, and

formed to obliquely move the shutter the displacement in the first direction and a displacement in the second direction.

19. An image forming apparatus comprising:

a plurality of developing units to develop a visible image from an electrostatic latent image through a developer;

a transfer member provided to transfer the visible image developed by the plurality of developing units onto a printing medium;

a sensing unit having at least one sensor, on which a window is formed, disposed opposite the transfer member and a sensor housing in which the at least one sensor is accommodated, to sense the developer transferred onto the transfer member; and

a shutter device having a shutter which opens and closes the window, and a shutter driving device which drives the shutter, and to open and close the sensing unit,

wherein the shutter driving device includes:

a driving unit which generates a driving force; and

a cam gear which is rotated by receiving the driving force from the driving unit and operates the shutter; and

the cam gear includes:

a gear body; and

a cam rail having a first cam rail having a radius of r 1 from a center of rotation of the cam gear and a second cam rail having a radius of r 2 smaller than the r 1 , and provided on one side surface of the gear body to restrict the shutter so that the shutter reciprocates according to a moving component of a moving direction of the transfer member.

20. An image forming apparatus comprising:

a plurality of developing units to develop a visible image from an electrostatic latent image through a developer;

a transfer member provided to transfer the visible image developed by the plurality of developing units onto a printing medium;

a sensing unit having a plurality of sensors and a plurality of windows,

the plurality of sensors being opposite the transfer member and disposed to be separated from each other in a first direction, and

the plurality of windows provided between the plurality of sensors and the transfer member and corresponding to the plurality of sensors, and

the sensing unit to sense the developer transferred onto the transfer member; and

a shutter device having a shutter formed to be movable according to a displacement in a second direction perpendicular to the first direction,

wherein the shutter opens and closes the plurality of windows.