| 摘要 |
According to the invention, a constant current output is applied to a backup roller or a secondary transfer member, and the cleaning bias is controlled according to the measurement obtained by monitoring the voltage generated at that time. Cleaning biases of a plus polarity and a minus polarity are alternately applied to the backup roller to recover the toner adhered on the secondary transfer roller to the intermediate transfer belt. The cleaning bias is controlled according to the combined resistance of the secondary transfer section which is varied with not only the environment of the image forming apparatus, but also the condition of use and various factors to recover the toner adhered to the secondary transfer roller to the intermediate transfer belt without fail, thereby preventing smudges on the back of sheet paper or smudges on images.
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