| 摘要 |
PURPOSE:To quicken a collection of a toner and to raise the collection efficiency by applying a bias voltage which is higher than a collection bias voltage at the time of development and also to which an AC voltage is superposed, to a toner supply/collection roller, at the time of collecting a toner. CONSTITUTION:The developing device which can switch a color of a toner by selecting any one toner supply part is provided with a collection bias voltage circuit applying a bias voltage which is higher than a collection bias voltage of the time of development, and also, to which an AC voltage is superposed, to a toner supply/collection roller 12 at the time of collecting a toner in order to switch the color of the toner. Accordingly, a collecting work of the toner on a developing sleeve at the time of switching the color of the toner is executed in a short time and also, surely, and even if the color is switched frequently, a distinct image of a desired color having no color mixture can be obtained. |
