| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of effectively reducing contamination of a charging roller even with a developer using two or more kinds of external additives having different particle sizes and triboelectric charging series to suppress an increase in surface resistance, realizing an extended life of the charging roller. <P>SOLUTION: A surface of a cleaning brush roller 13 rotating in abutment with a charging roller 12 is ranked, in a triboelectric charging series, on a positive polarity side than first and second external additives contained in a developer. At least while the cleaning brush roller 13 cleans one turn of the charging roller 12, control means performs control so that the cleaning brush roller 13 and charging roller 12 constitute a first circumferential speed ratio. Further, at least while the cleaning brush roller 13 cleans one turn of the charging roller 12, the control means performs control so that the cleaning brush roller 13 and charging roller 12 constitute a second circumferential speed ratio. <P>COPYRIGHT: (C)2012,JPO&INPIT |
