Image forming apparatus and method with different print modes for monochrome and full colour images

摘要

The timing on when a secondary transfer roller abuts on an intermediate transfer belt is different, in a monochromatic print mode, from the timing in a color print mode. Specifically, in the monochromatic print mode, the secondary transfer roller abuts on the intermediate transfer belt at time T2 prior to the start of an exposure process for the first image at time T1. Then, the secondary transfer roller is separated from the intermediate transfer belt at completion of the secondary transfer of the final image. Therefore, the secondary transfer roller has already touched on the intermediate transfer belt at the start of the irradiation of a light beam for forming the first electrostatic latent image. The exposure process is performed with the secondary transfer roller kept in contact with the intermediate transfer belt, to prevent shock displacements of an exposure position of the light beam.