Image forming apparatus and image adjusting method

1. An image forming apparatus comprising:

an image carrying member;

a latent image forming unit to form an electrostatic latent image on the image carrying member;

a developing unit to form a toner image by developing the electrostatic latent image on the image carrying member;

a forcible discharge unit to forcibly discharge the toner from the developing unit;

a toner supplying unit to supply toner after the forcibly discharging; and

a fog-detection unit to detect fog of the image,

wherein the forcible discharge unit forcibly discharges the toner from the developing unit based on a detected result of the fog-detection unit.

2. The image forming apparatus of claim 1 , wherein the fog-detection unit comprises an image density sensor to detect the fog of the image formed on the image carrying member or on a transfer member.

3. The image forming apparatus of claim 1 , comprising a condition control unit to control image forming conditions, and having an image quality adjustment mode for controlling the forcible discharge of toner based on the detected result of the fog of the image, wherein the condition control unit sets an image forming condition for occurrence of fog in the image quality adjustment mode.

4. The image forming apparatus of claim 1 , wherein the forcible discharge unit forcibly discharges the toner by a quantity corresponding to a fog level detected by the fog-detection unit.

5. The image forming apparatus of claim 1 , comprising a humidity sensor to detect environmental humidity, and a density control unit to control toner density in a developer based on the detected result of the humidity sensor.

6. The image forming apparatus of claim 1 , comprising a number-of-sheets counter to count the number of image-formed sheets, and a density control unit to control toner density in a developer based on a counted value of the number-of-sheets counter.

7. The image forming apparatus of claim 1 , wherein the developing unit comprises a developer carrying member which rotates with facing the image carrying member, to develop the electrostatic latent image on the image carrying member, and the image forming apparatus comprises a power source to apply a direct-current component of a developing bias voltage to the developer carrying member.

8. The image forming apparatus of claim 7 , wherein the direct-current component of the developing bias voltage is controlled so that a fog margin in the fog detection of the image is narrower than that in the image forming.

9. The image forming apparatus of claim 1 , comprising an intermediate transfer member on which the toner image formed on the image carrying member is transferred.

10. The image forming apparatus of claim 9 , wherein the fog detection is performed by using the toner image transferred on the intermediate transfer member.

11. The image forming apparatus of claim 1 , wherein the forcible-discharge unit forms a toner image for forcible discharge on the image carrying member.

12. The image forming apparatus of claim 11 , wherein the forcible-discharge unit controls forcibly discharged toner quantity by controlling an area or a density of the toner image made by the forcibly discharged toner on the image carrying member.

13. The image forming apparatus of claim 1 , wherein the image forming apparatus comprises a toner density sensor to detect a toner density in the developing unit, and the toner supplying unit supplies toner based on a detected result of the toner density sensor.

14. An image adjusting method comprising:

adjusting a developing bias voltage applied on an image carrying member;

developing an image on the image carrying member by toner in a developing unit, to form a toner image;

detecting fog by using the toner image;

discharging the toner forcibly from the developing unit based on a result of fog detection; and

supplying toner after the discharging the toner forcibly.

15. The image adjusting method of claim 14 , wherein the image adjusting is performed at every predetermined number of sheets of image formation.

16. The image adjusting method of claim 14 , wherein the image adjusting is performed at every image formation job.

17. The image adjusting method of claim 14 , wherein the image adjusting is performed when an image forming apparatus is turned on.

18. The image adjusting method of claim 14 , wherein the discharging the toner forcibly includes forming a toner image for forcible discharge on the image carrying member.

19. The image adjusting method of claim 14 , wherein the detecting fog is performed by detecting a toner density of the toner image.

20. The image adjusting method of claim 14 , wherein the supplying toner is performed based on a toner density in the developing unit.