Patent ID: 7697854

Claim:
An image forming apparatus comprising: an image forming section for forming an image by printing a toner image on a recording medium, the image forming section including a photoreceptor having a photosensitive layer for forming an electrostatic latent image, and a developing device having a developing roller for forming a toner image by supplying a toner to the electrostatic latent image on the surface of the photoreceptor and a developer tank for storing two-component developer containing a toner; a print speed switching section for switching image printing speeds of the image forming section; a toner concentration detecting section for detecting a concentration of the toner in the developer tank and outputting a detection result, an output value of the detection result being modified according to a control value inputted to the toner concentration detecting section; a memory portion for storing a correction value for the control value, which correction value is determined by an association between image printing speed and another predetermined correction parameter; a correcting section for correcting the control value based on image printing speed and another predetermined correction parameter; a toner concentration calculating section for calculating the concentration of the toner in the developer tank based on the detection result outputted by the toner concentration detecting section; and a detection result correcting section for, during a no-image forming period, retrieving for each image printing speed a detection result outputted by the toner concentration detecting section to which the corrected control value has been inputted, and modifying the corrected control value according to the detection result retrieved.