| 摘要 |
<p>An image transfer unit provided with a cleaning device for use in an electrophotographic copying machine comprises an electrically conductive transfer roller disposed in abutting relationship with a photosensitive member, an electrically conductive, rotatable cleaning device disposed in abutting relationship with the transfer roller, and electrical bias means connected with the cleaning device and having a switchable polarity. During a transfer step, a bias voltage of opposite polarity to that of the toner is applied to the transfer roller through the cleaning device. At this time, toner attaching to the transfer roller is electrostatically transferred onto the cleaning device. During a cleaning step, a bias voltage of the same polarity as the toner is applied to the cleaning device, whereby the toner attaching thereto is transferred back to the photosensitive member through the transfer roller. The toner which is transferred back to the photosensitive member is removed by separate cleaner provided.</p> |
