Patent ID: 6985684

Claim:
An image forming apparatus comprising at least: a rotary, a rotary driving motor for rotating the rotary, a plurality of development units each of which is mounted to said rotary such that the development unit is replaceable at a replacement position and has a development roller for carrying developer-and an input gear, a development unit driving motor for driving said development roller, a development unit driving gear which is disposed outside said rotary such that the development unit driving gear can be selectively meshed with said input gear of one of said plurality of development units and to which the driving force of said development unit driving motor is transmitted, and a control device for controlling the drive of said rotary driving motor and said development unit driving motor, wherein: during the image forming operation, said development rollers of the respective development units are set at the development position relative to a photoreceptor by turns according to the rotation of said rotary and, at the development position, said input gear of each of the respective plurality of development units are meshed with said development unit driving gear so as to drive said development rollers with the driving force of said development unit driving motor by turns, thereby achieving multi-color development, said image forming apparatus further comprising a rotary driving motor control means which controls said rotary driving motor for the rotation of said rotary during the non-image forming operation such that the rotational speed of said rotary in a contact region where said input gear collides with said development unit driving gear is lower than the rotational speed of said rotary in a region other than said contact region, and the rotational speed of-said rotary in the region other than said contact region during the rotation of said rotary in the non-image forming operation is set to be lower than the maximum speed of said rotary rotating during the image forming operation.