| 摘要 |
PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing delay of cleaning operation for a secondary transfer roller using a developing bias power supply in common. SOLUTION: In the image forming apparatus, a toner image formed on an image carrier by being supplied with toner from a developing roller to which controlled bias voltage is applied is primarily transferred onto an intermediate transfer body, and then it is secondarily transferred onto a recording sheet by transfer voltage applied to the secondary transfer roller, and toner adhering to the peripheral surface of the secondary transfer roller is reversely transferred to the intermediate transfer body by application of the bias voltage as cleaning voltage. In the apparatus, a power path is switched so that the controlled bias voltage can be applied to the secondary transfer roller, and when the absolute value of the bias voltage is smaller than a threshold, the absolute value is made potential equal to or above the threshold. When the potential is changed, the secondary transfer roller is separated from the intermediate transfer body in a predetermined section, and when the potential is not changed, the secondary transfer roller is prevented from being separated therefrom. COPYRIGHT: (C)2010,JPO&INPIT
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