| 摘要 |
PROBLEM TO BE SOLVED: To provide a developing device configured to apply a bias formed by superimposing an AC bias on a DC bias to a developing roller, while preventing separation of external additive from toner and reduction of the external additive in the developing device as much as possible.SOLUTION: In development on sheets P1, P2, P3, a developing bias formed by superimposing an AC bias on a DC bias to a developing roller 83, to supply toner from the developing roller 83 to a photoreceptor drum 321. In sheet intervals B1, B2, toner smaller in amount than in development is carried on the developing roller 83, as development preparation operation. In the AC bias of the developing bias, a peak-to-peak voltage during the development preparation operation is set lower than a peak-to-peak voltage during development. A difference &Dgr;V1 between the DC bias during the development preparation operation and a background part potential is set larger than a difference &Dgr;V2 between the DC bias during the development and a background part potential of the photoreceptor drum 321. |
