| 摘要 |
PURPOSE:To prevent fogging and improve picture quality by a bias voltage within a specific range to between the base body of a photosensitive body and a toner carrier, and expanding the allowable range of the background voltage of the photosensitive body. CONSTITUTION:The bias voltage VB shown by an expression is impressed to between the base body 38 of the photosensitive body 10 and a developing sleeve 13 as the toner carrier. Consequently, an actual development starting voltage V0' becomes V0'=V0+VB; when the potential VW of the background part is positive, the VW has the wide spreaded allowable range extending almost from a minimum VB-V0 to a maximum V0+VB. Therefore, the area wherein fogging does not occur is widened by the bias VB' so even if the VW varies owing to the characteristic variation with the temperature of the photosensitive body, etc., the variation is absorbed to enter a fogging-free state all the time, thus improving the picture quality. |
