| 摘要 |
PROBLEM TO BE SOLVED: To provide a color copying machine capable of preventing the unnecessary sticking of a developer to a photoreceptor, when the developer on a developing roller is brought into contact with or separated from the photoreceptor, even if the characteristic of the photoreceptor is changed or the potential by electrification of the photoreceptor is switched at every developing unit. SOLUTION: The color copying machine provided with a revolver rotating motor and a developing revolver driving part 506 for moving a desired developing unit to a developing position, developing bias supply for applying a developing bias to the developing roller and a developing bias control driving part 502, is provided with a potential sensor 204 detecting the potential by electrification of the photoreceptor and a control part 500 controlling the developing bias control driving part 502, to switch the developing bias applied when the developer on the developing roller is brought into contact with or separated from the photoreceptor, to the developing bias for generating an electric field for making the movement of the developer on the developing roller to the side of the photoreceptor harder than that by the developing bias used in forming an image, based on the results of the detection of the potential sensor 204. |
