| 摘要 |
PROBLEM TO BE SOLVED: To stably accurately detect the residual amount of developer with respect to an image forming device provided with a developing system capable of obtaining appropriate image density and a distinct image having no fogging even in the case of using small-grain-size toner, and changing the components of AC voltage such as peak-to-peak voltage, frequency and duty ratio according to some conditions. SOLUTION: The time when pre-rotation is performed being a stage other than an image forming stage is set as a toner residual amount detecting stage. In the residual amount detecting stage, toner residual amount is detected by impressing the AC voltage whose duty ratio on a (V-) side is made constant, that is, 50% on the developing sleeve of a developing device regardless of the change of the duty ratio of the AC voltage at the time of controlling the image density. In the image forming stage, the image density is controlled by changing the duty ratio of the developing bias to a ratio in accordance with the desired image density. |
