Patent ID: 8457508

Claim:
An image forming apparatus, configured to execute a developing operation for forming a developer image and to form an image comprising the developer image on a recording medium, the image forming apparatus comprising: an image carrier configured to carry an electrostatic latent image formed thereon; a developing housing configured to accommodate a developer for developing the electrostatic latent image into a developer image; a developer carrier, which is held by the developing housing, and which is configured to carry the developer in the developing housing and to supply the developer to the image carrier; a developing bias supply part configured to supply a developing bias to the developer carrier; a remaining quantity calculation part configured to calculate a remaining quantity of the developer in the developing housing; a deterioration degree storage part configured to store a relationship between the remaining quantity of the developer in the developing housing and a deterioration degree of the developer caused by each of a series of developing operations; a deterioration quantity calculation part configured to, every time the remaining quantity calculation part calculates the remaining quantity of the developer: determine the deterioration degree of the developer based on the relationship stored in the deterioration degree storage part, and calculate a deterioration quantity of the developer by adding each of the determined deterioration degrees; and a developing bias setting part configured to set a value of the developing bias corresponding to the deterioration quantity calculated by the deterioration quantity calculation part, wherein the deterioration degree of the developer is a value previously stored in the deterioration degree storage part in relation to the remaining quantity of the developer in the developing housing, and wherein the developing bias supply part is configured to supply the developing bias set by the developing bias setting part to the developer carrier.