| 摘要 |
PURPOSE:To prevent unnecessary toner and carrier from being stuck on a photosensitive body when an image is visualized through the use of plural developing rollers by starting to apply a bias voltage to a developing sleeve when the tip of the electrified part of the photosensitive body reaches a developing region. CONSTITUTION:When the tip X1 of the electrified part X on an electrified photosensitive body 1 reaches a first developing region A1 between the photosensitive body 1 and a first developing sleeve 12, the application of the bias voltage to the sleeve 12 is started (a). At this time, the application of the bias voltage to a second developing sleeve 13 is not started. Then, the top end X1 of the electrified part X reaches a second developing region A2, accompanying with the rotation of the photosensitive body 1, but a voltage is started to be applied to the sleeve 13, at this time (b). Then, the rear end X2 of the electrified part X reaches the region A1, the application of the voltage to the sleeve 12 is released (c). Therefore, the carrier C on the sleeve 13 is prevented from being transferred and stuck to a base part Y2 opposite to the sleeve 13 (c). Continuously, when the rear end X2 of the electrified part X reaches the region A2, the application of the voltage to the sleeve 13 is released, as well (d). |
