Patent attributes
To correct a bias voltage of each roller upon estimating a toner potential precisely even where toner's characteristics change due to, e.g., changes of environmental condition, changes over time, supplements of the toner, replacement of an EP cartridge, or the like, on an image forming apparatus according to this invention, the toner potential is estimated upon measuring a DB current in a prescribed period from a time that a development starting point on the developing roller starts development to a time that the development starting point comes in contact with a toner supplying roller. Alternatively, where the measured DB current is equal to or less than a fixed amount, a period for a warming-up processing is extended. Alternatively, where the toner is judged as supplemented upon detection of the remaining toner amount, a prescribed warming-up processing is made before the measurement for the DB current. Further alternatively, where the toner is judged as supplemented upon the detection of the remaining toner amount, a bias voltage of each roller set upon corrected based on the toner potential estimated based on the DB current is further corrected.
