| 摘要 |
PURPOSE:To obtain the one component dry toner developing device where stable image density without any fogging can be obtained by solving the problem of the ratio of the toner of the reverse polarity inside the developing device from increasing in accordance with image printing. CONSTITUTION:The device is provided with a control means 13 controlling developing voltage of a developing roll 2, a driving means driving the developing roll 2 and a photosensitive drum 8, not shown in diagram. The voltage control means 13 impresses developing bias of the same polarity as the surface potential of the photosensitive drum to the developing roll 2 when forming the image, electrifies the photosensitive body 8a to the surface potential which is equivalent to that at the time of image formation when forming non-image and impresses voltage of a smaller absolute value than developing bias or voltage of the reverse polarity as the surface potential of the photosensitive body 8a to the developing roll 2 in a state when exposure is not carried out. The driving means drives at least the photosensitive body 8a and the developing roll 2 when forming non-image. Thus, since the toner of the reverse polarity is ejected from the developing device when forming non-image, there it no fogging when the image is formed and the stable image density can be obtained. |
