Patent ID: 8606133

Claim:
An image forming apparatus comprising: an image carrier; a toner image forming unit that forms a toner image on the image carrier; a primary transfer unit that transfers the toner image on the image carrier to an intermediate transfer element; a secondary transfer unit that transfers the toner image on the intermediate transfer element to a recording medium; a toner adhesion amount detection unit that detects a toner adhesion amount of the toner image transferred to the intermediate transfer element; a process control unit that causes the toner image forming unit to form a predetermined toner pattern by a normal image forming operation on a surface of the image carrier at a predetermined timing, causes the primary transfer unit to transfer the predetermined toner pattern on the intermediate transfer element, causes the toner adhesion amount detection unit to detect a toner adhesion amount of the predetermined toner pattern, and adjusts at least one of a charging bias, an exposure amount, and a developing bias on the basis of the detection result so as to obtain a developing potential, which is a difference between a developing bias and a potential of an electrostatic latent image portion, so that a toner adhesion amount of a predetermined electrostatic latent image reaches a target toner adhesion amount; and a degree-of-toner-deterioration calculation unit that calculates a degree of toner deterioration from the toner adhesion amount detected by the toner adhesion amount detection unit, wherein the process control unit further causes the toner image forming unit to form a toner pattern for detecting a degree of toner deterioration on the image carrier, causes the primary transfer unit to transfer the toner pattern from the image carrier to the intermediate transfer element under a transfer condition such that transfer efficiency is lowered compared to a transfer condition at the time of image formation, causes the toner adhesion amount detection unit to detect toner adhesion amount of the toner pattern at multiple places, causes the degree-of-toner-deterioration calculation unit to calculate a degree of toner deterioration on the basis of a variation in data of the toner adhesion amount at the multiple places detected by the toner adhesion amount detection unit, and controls a ratio of the difference between a potential of a non-electrostatic latent image portion and the developing bias to the developing potential depending on the degree of toner deterioration calculated by the degree-of-toner-deterioration calculation unit.