| 摘要 |
PURPOSE:To protect the quality of a copy by preventing a transfer sheet in the middle of copying from being left in a machine when a certain color toner is ended in case of color synthesis or double-surface copying. CONSTITUTION:The title device is constituted of photosensitive drum 9, 1st-3rd developing devices 12a-12c, photosensors 33-35 and a toner cartridge sensor 36, etc. By previously judging the number of remaining copying-enabled sheets obtained until the end of the toner of developing colors used in such a copying mode that the color synthesis or double-sided copying is performed by combining plural colors, the minimum remaining copying-enabled sheets of copies are formed when the minimum number of remaining copying-enabled sheets is smaller than the set number of sheets. Thereafter, necessary operations are promoted by moving the developing device where the toner is ended to a toner displacing position or replenishing position. Thus, the transfer sheet is not left in the machine because of the end of the toner and the transfer sheets can be protected, since only transfer sheets which satisfy the number of sheets obtained until the end of the toner of the developing color used in such a copying mode that the color synthesis or double-sided copying is performed by combining the plural colors, are previously supplied in the machine. |
