Patent ID: 7499655

Claim:
An image forming method for switching and using a decolorization toner or an ordinary toner and forming a toner image on a photosensitive drum, comprising: counting a using history of the decolorization toner; counting a using history of the ordinary toner; calculating a film thickness of the photosensitive drum based on both counting the using histories; calculating various image forming process conditions for making a charging characteristic of the photosensitive drum appropriate in consideration of the film thickness; detecting which one is in use of the decolorization toner and the ordinary toner; adjusting the image forming condition to the decolorization toner with the calculated various image forming process conditions when it is detected that the decolorization toner is in use; and adjusting the image forming condition to the ordinary toner with the calculated various image forming process conditions when it is detected that the ordinary toner is in use.