Patent ID: 7860415

Claim:
An image forming apparatus for electrophotographically forming an image, comprising: an image forming section for printing the toner image on a recording medium to form an image, the image forming section including a photoreceptor having a photosensitive layer for forming an electrostatic latent image on a surface thereof, and a developing device including a developing roller for supplying a toner to the electrostatic latent image on the surface of the photoreceptor to form a toner image, and a developer tank for storing a two-component developer containing a toner; a toner concentration detecting section for detecting a toner concentration in the developer tank; a printing speed switching section for switching a speed of printing an image formed by the image forming section; a toner concentration calculating section for calculating a toner concentration in the developer tank from a detection result by the toner concentration detecting section, according to the speed of printing an image; a toner replenishment control section for replenishing the toner into the developer tank according to a calculation result by the toner concentration calculating section; a sensitivity switching section for switching a detecting sensitivity of the toner concentration detecting section depending on the print speed of an image; and a toner concentration correcting section that corrects the calculation result generated by the toner concentration calculating section based on a thickness of the photosensitive layer on the photoreceptor of the image forming section.