| 摘要 |
PURPOSE:To stably prevent color mixture and to always form a high quality color image even when a device is used for a long period and environment is changed by detecting the potential of a toner image part formed on a photo sensitive body and controlling a developing bias in the next stage so as to satisfy the conditions in which color mixture is not generated. CONSTITUTION:The potential of the toner image part formed on a photosensitive drum 1 by the processes of electrification, exposure, and development is detected by a surface potential meter 9 after the electrification, and the developing bias in the development process after at least a second and subsequent time is controlled. At this time, a voltage VA is controlled so as to satisfy {¦VT-VA¦/ d}<=2.25(V/mum), where d(mum) is an interval between the photosensitive drum l and the sleeve 41, VA(V) is the maximum voltage of the alternating voltage element of the developing bias at which the toner image on the photosensitive drum 1 is pulled back to the sleeve 41, and VT(V) is the potential of the toner image part on the photosensitive drum 1. |
