| 摘要 |
An image forming apparatus includes: photosensitive members; an endless belt facing the photosensitive members; developing rollers respectively supplying, to the photosensitive members, developer of different colors which is charged to a first polarity; cleaning rollers adjacent to the photosensitive members; a separating mechanism separating the developing roller from the photosensitive member in a single color printing. If in a multi color printing, a control unit applies a cleaning bias whose polarity is a second polarity opposite to the first polarity and which holds a first electric potential to each cleaning roller. If in the single color printing, the control unit executes a bias reduction control in which a cleaning bias applied to the cleaning roller not used in the single color printing is given the second polarity and is made to hold a second electric potential whose absolute value is smaller than that of the first electric potential.
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