| 摘要 |
PURPOSE:To perform high-precision image density control by detecting a leak current generated between a no-image part on a photosensitive body and a developing roll and storing the value in a memory, and correcting the value with a coefficient based upon its form size in a copying process. CONSTITUTION:The developing roll 10 is applied with a developing bias and the photosensitive body 1 and developing roll 10 contact each other across a developer which has sufficient electric resistance, so the leak current during developing bias application is about 0.2-0.05muA. When an original is copied, the size of the original is detected and a difference in consumption due to a difference in original size between the last copying and current copying is corrected during the supplying of toner as much as toner consumed in the last copying operation. The deficiency stored in the memory is outputted to a driving motor 13a in the next copying operation and toner matching including the deficiency is supplied from a toner bottle 12 to a developing device 4. Consequently, even when the size of an original to be copied is different, a copy of invariably stable image density is taken. |
