| 摘要 |
<P>PROBLEM TO BE SOLVED: To restrain the deterioration of image quality caused by toner remaining on a developing roller. <P>SOLUTION: The CPU 21 of a copying machine is functionally equipped with a potential control part 214 controlling a DC bias power source 631 disposed on a collecting roller so that the potential of the collecting roller can be set to be collection potential that is the potential of the collecting roller at which the toner can be collected from the developing roller only in a period that the developing roller rotates about once when an average printing rate is equal to or under a predetermined threshold (3% in this case). <P>COPYRIGHT: (C)2008,JPO&INPIT |
