| 摘要 |
A residual toner collecting device efficiently collects residual toner remaining untransferred on a photoconductive element of an electrophotographic copier by cleaning the photoconductive element. A scavenger roller and a flat counterelectrode, which constitute the collecting device, are supplied with dc bias voltages which are different in polarity. The polarities of the dc bias voltages are switched each to the opposite polarity only for a predetermined part of the period between a start of movement of the photoconductive element and a stop of the movement. Further, an ac bias voltage is applied to at least one of the scavenger roller and the counterelectrode superposed on the dc bias voltage for the predetermined period. The predetermined period is a period during which cleaning the photoconductive element is not required.
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