| 摘要 |
PROBLEM TO BE SOLVED: To provide a developing device that achieves stable non-development of toner from a developing roller to a magnetic roller, and suppresses adhesion of toner to the developing roller; and an image forming apparatus including the developing device.SOLUTION: During developing operation and non-developing operation, a developing bias is applied to a developing roller 83. The developing bias is formed by superimposing an AC bias on a DC bias. By the developing bias applied to the developing roller 83, an external additive is separated from toner, and consumed at a photoreceptor drum 321 side. When the printing rate of a toner image formed on the photoreceptor drum 321 is higher than a predetermined threshold, a consumption condition changing unit 94 reduces Vpp of the AC bias applied to the developing roller 83 during the non-developing operation, so as to suppress the consumption of the external additive to the photoreceptor drum 321 side. |
