Patent ID: 7706723

Claim:
An image forming apparatus, comprising: a plurality of image carriers configured to form a plurality of color images; a drive mechanism configured to drive the plurality of image carriers simultaneously, the drive mechanism including a single drive unit for driving the plurality of image carriers; a plurality of drive force transmission gears provided for each of the plurality of image carriers, respectively, the gears configured to transmit a driving force from the single drive unit to the plurality of image carriers; a phase difference detector configured to detect a phase difference in drive speed among the plurality of image carriers; and a plurality of shift units provided for each of the plurality of drive force transmission gears, respectively, and each of the shift units configured to mesh or unmesh a respective one of the drive force transmission gears to the drive mechanism, each of the shift units being activated to correct the phase difference in drive speed among the plurality of image carriers based on a detection result obtained by the phase difference detector, wherein each of the shift units meshes with the drive mechanism independently of the other shift units such that each of the shift units corrects the phase difference independently of each of the other shift units.