AN IMAGE FORMING APPARATUS

摘要

An image forming apparatus comprises a photoreceptor (15), a developing roller (4) for forming a layer of developer on a surface thereof to supply toner to the photoreceptor at a developing position. A bias supply (7) applies a bias voltage between the developing roller and a ground. A conductive line connects the developer layer with ground, and the toner density of the developer layer is detected by monitoring the current flowing through the conductive line. A voltage controller (10) prevents the surface voltage of the developer layer from falling below a predetermined level, at least during a developing operation, despite the current flowing into the conductive line. Accordingly, the formation of fog on a copy can be prevented because the surface voltage of the developer layer is maintained above the specified level at least during the developer operation.