Electrophotographic recording apparatus configured to switch a bias voltage in a developing unit

摘要

In an electrophotographic image recording apparatus of the type using a single-ingredient type developer, i.e., toner, a latent image is electrostatically formed on a photoconductive drum or similar image carrier. A developing unit has a developing roller for conveying the toner deposited thereon, and an intermediate roller for conveying the toner transferred thereto from the developing roller and depositing it on the latent image to thereby produce a corresponding toner image. An image transfer unit transfers the toner image to a cut sheet. During the development of an area of the image carrier other than a latent image area, at least one of biases assigned to the developing roller and intermediate roller, respectively, is switched over to thereby form an electric field different in direction from an electric field assigned to the formation of the toner image between the two rollers. As a result, the toner existing on the intermediate roller is collected by the developing roller. This successfully prevents the toner from depositing on the intermediate roller except when required, and frees the image transfer unit from the deposition of the toner.