IMAGE FORMING APPARATUS AND CONTROL METHOD

PROBLEM TO BE SOLVED: To provide an image forming apparatus that carries out stable sheet conveyance with an inexpensive configuration in a monochrome image forming mode that operates faster than a full-color image forming mode.SOLUTION: An image forming apparatus is configured to include a high output motor as a motor for a black cartridge 7d, and low output motors as motors for color cartridges 7a to 7c. In a monochrome image forming mode that operates faster than a full-color image forming mode, the image forming apparatus separates developing rollers of the color cartridges 7a to 7c from a photoreceptor drum so as not to be driven, and contacts only photoreceptor drums 1a to 1d with an electrostatic conveying belt 11 so as to be rotated and driven.