Patent ID: 8861996

Claim:
An image forming apparatus comprising: a primary transfer belt and a photosensitive drum which are a plurality of rotation members for performing image formation and rotate in contact with each other; a first driving motor which drives said primary transfer belt; a second driving motor which drives said photosensitive drum; an obtaining unit which obtains pieces of motor driving information about driving states of one of said first driving motor and said second driving motor at a plurality of different relative driving speeds while a relative driving speed of said second driving motor with respect to a driving speed of said first driving motor is changed to one of the plurality of different relative driving speeds; a driving speed determination unit which determines a target driving speed based on the pieces of motor driving information obtained by said obtaining unit such that a relative speed difference between a circumferential speed of said primary transfer belt and a circumferential speed of said photosensitive drum is reduced; a control unit which controls a driving speed of at least one of said first driving motor and said second driving motor in image formation based on the determined target driving speed; a plurality of developing units which are arranged for a plurality of photosensitive drums corresponding to different colors and are brought into contact with and separated from said respective photosensitive drums; and a memory which stores, as reference motor driving information, motor driving information obtained by said obtaining unit from said first driving motor in advance in a state where said primary transfer belt and said photosensitive drums are in contact with each other and said developing units are in contact with said photosensitive drums, wherein said control unit causes said obtaining unit to re-obtain motor driving information in a state where said control unit makes said primary transfer belt and said photosensitive drums contact each other and separates said developing units from said photosensitive drums, and wherein said control unit controls the driving speed in image formation using, as the target driving speed, the driving speed of at least one of said first driving motor and said second driving motor when motor driving information re-obtained by said obtaining unit coincides with the reference motor driving information stored in said memory.