| 摘要 |
PROBLEM TO BE SOLVED: To restrain fluctuation of image-forming characteristic caused by cumulative operations of a process cartridge. SOLUTION: When the amount of cumulative operation gets large, a DC bias Vdc of a developing sleeve 31 is varied according to cumulative electrifying time, so that the sensitivity fluctuation of a photosensitive drum 1, that is, the change of bright potential V1 which is to be corrected. When the image forming characteristic fluctuated in a direction where developing characteristic is increased by the cumulative operation of the process cartridge, image- formation which is closer to the reference values of an image is performed, by making initial variation large and timing of variation short from gradually asymptotic characteristic. |
