To prevent degradation of a developer to maintain an image quality and an image density for a long period of time.
An image forming apparatus is provided with a developing tank 20 storing the developer therein, a developer carrying part 21 which generates a travelling wave electric field to carry the developer and supplies the developer to a photoreceptor drum, a supply roller 23 which supplies the developer from the developing tank 20 to the developer carrying part 21, and a recovery roller 25 or the like which recovers the developer from the developer carrying part 21 to the developing tank 20. The quantity of the developer carried is increased or reduced in accordance with the density of an image to improve the image quality as well as the image density. In the case of development of a void area, the quantity of the developer carried is set to 0 to completely prevent fog or the like of the void area, and thus the image quality is improved furthermore. Since the developer is efficiently carried, degradation of the developer caused by repeated carrying and recovery is suppressed to maintain the image quality and the image density for a long period of time.
IWAKURA YOSHIE
MURAKAMI SUSUMU
KONO SATOSHI
TOMII MINORU
KUBO TAKASHI
