Patent ID: 8478150

Claim:
An image forming apparatus comprising: a photoconductive drum rotatably supported, and rotating by receiving a drive force from a drive source; a first voltage application portion outputting an AC voltage; a developing roller carrying toner to be charged, connected to the first voltage application portion, and feeding toner to the photoconductive drum; a contact member making contact with the photoconductive drum to remove residual toner; a detection portion detecting occurrence of electric discharge between the developing roller and the photoconductive drum; and a developing unit feeding toner to the developing roller, and supporting the developing roller opposite the photoconductive drum with a gap secured in between, the developing unit feeding toner to the developing roller with prescribed timing and for a prescribed time during electric discharge detection in which, while the photoconductive drum rotates and the first voltage application portion stepwise varies a peak-to-peak voltage of an AC voltage applied to the developing roller, a voltage at which electric discharge occurs between the photoconductive drum and the developing roller is detected.