| 摘要 |
PURPOSE:To obtain an always fogfree image, by changing bias voltage to be applied to a control grating in accordance with a repeated use number of a photoreceptor or a developer, and converting polarity of toner charge attached to the photoreceptor into the opposite one. CONSTITUTION:A rotation number of a drum or a sleeve roller is measured in accordance with use number total 21 of a photoreceptor or use number total 22 of a developer. An output value of bias voltage source 23 is gradually changed to change potential of control grating 24 of corona discharger 17 prior to transfer. As a result, when the use number of the photoreceptor or the developer rises, the bias voltage rises in accordance with its rise, an accelerating electric field of corona discharge reverse in polarity to a charged toner is always active, thus permitting a fogging toner to be converted in polarity, and an always fogfree copy image to be obtained without being transferred by it. |
