| 摘要 |
A charger for charging the surface of a photoconductive drum by a contact charging method in an electrophotographic image forming apparatus includes: a charge roller for charging an unexposed surface of the photoconductive drum to a prescribed potential by contact with the surface of the photoconductive drum; a power supply connected to the charge roller, for supplying a variable DC charge voltage to the charge roller; a potential sensor installed around the photoconductive drum, for detecting a charge potential value of the unexposed surface of the photoconductive drum; and a controller for comparing the charge potential value detected by the potential sensor with a specified value, and changing the charge voltage generated by the power supply upon detecting any difference therebetween, so as to maintain the charge potential of the photoconductive drum at a constant value.
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