| 摘要 |
PURPOSE:To restrain the undesirable expense of developer, to prevent contamination and to keep the title device clean by detecting the operating time of an image carrier and inhibiting development by a mechanical means in a specific time after the operation starts. CONSTITUTION:As the image carrier of a photosensitive body 1 turns, a pulse signal arises through a photocoupler 13, and is counted by an adding counter CUC to detect the operation time of the photosensitive body 1. In the specific time after the photosensitive body 1 starts operating, a solenoid 13A is brought non-excited by a developing device control circuit DC, and a magnetic roll 5 in a developer carrying roll 4 is accurately controlled so that its mid-position between poles N and S faces the photosensitive body 1. The development on the photosensitive body 1 facing a lower magnetic brush, is thus impossible; therefore, the developer is restrained from being used undesirably because the photosensitive body 1 is electrostatically charged in unstable mode, and its contamination is prevented to keep the image forming device clean. |
