Patent ID: 8478157

Claim:
An image forming device that performs an image forming operation in one of a color mode for forming a color image with developers of a plurality of colors including black, a monochrome mode for forming a monochrome image with black developer, and a continuous mode for forming in succession a plurality of monochrome images on a plurality of recording media comprising: a plurality of photosensitive members for the respective colors; a plurality of developing rollers for the respective colors, each configured to supply the developer to the corresponding photosensitive member to form a developer image on the photosensitive member; a transfer member disposed in confrontation with the plurality of photosensitive members, the transfer member being configured to transfer the developer images from the photosensitive members onto a recording medium; a plurality of collecting members for the respective colors, each configured to collect excrescences that remain on the corresponding photosensitive member after the developer image is transferred onto the recording medium; a reverse-transfer unit configured to perform a reverse-transfer operation on at least one of the collecting members so as to transfer the excrescences collected by the at least one of the collecting members back onto at least one of the photosensitive members and further onto the transfer member; a control device configured to control the reverse-transfer unit and the at least one of the collecting members, in the continuous mode the control device controlling the reverse-transfer unit to perform, every time an image formation for one recording medium is completed, the reverse-transfer operation such that the excrescences are transferred from the at least one of the photosensitive members onto the transfer member at a timing in a medium interval, the medium interval being an interval between when a preceding recording medium is past a first confronting position between the photosensitive member and the transfer member and when a subsequent recording medium reaches the first confronting position, the subsequent recording medium following the preceding recording medium; and a switching unit that sets a contact state to a first contact state during the reverse-transfer operation in the continuous mode such that one of the developing rollers for black contacts one of the photosensitive members for black and that remaining ones of the developing rollers are separated from remaining ones of the photosensitive members.