Patent ID: 7853161

Claim:
An image forming apparatus comprising: a photoreceptor; a development roller carrying and supplying toner to the photoreceptor; and a power supply applying an alternating voltage comprising a development phase and a recovery phase to the development roller at non-image forming times, wherein a development duty, which shows a ratio of the development phase to a time of a cycle of the alternating voltage, and a frequency f of the alternating voltage are set in such a way that a time period in the development phase is larger than a time taken for the normally charged toner on the development roller to fly to a point located midway between the development roller and the photoreceptor and is smaller than a time taken for arriving at the photoreceptor, and a time period in the recovery phase is larger than sum of a time taken for the normally charged toner arrived at the point located midway between the development roller and the photoreceptor to arrive at the photoreceptor, a time taken for the normally charged toner arrived at the photoreceptor to return to the development roller, and a time taken for the oppositely charged toner beaten out by the normally charged toner returned to the development roller to fly from the development roller to the photoreceptor.