| 摘要 |
PROBLEM TO BE SOLVED: To conduct good cleaning by applying a low cleaning bias to a transfer roller in a relatively short period during the cleaning of a transfer carrier belt. SOLUTION: A charging voltage to be applied to charging rollers 10M and 10Y of process stations 8M and 8Y is set to -800 V so that the surface potentials of photoreceptor drums 9M and 9Y become -300 V. Then, a -1,800 V voltage (a cleaning bias) is applied to transfer rollers 13M and 13Y, a prescribed potential differenceΔ1,500 V which is required for cleaning is secured and negative polarity toner on a transfer carrier belt 7 is inverse transferred onto the drums 9M and 9Y. Since the surface potentials of the drums 9M and 9Y after passing a transfer section are boosted to -1,000 V, the surface potentials are lowered to -150 V through photoirradiation conducted by exposure destaticizers 21M and 21Y. Then, the charging voltage of -800 V is applied again so as to make to surface potentials to -300 V and a certain potential cycle is repeated.
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