Driving device and image forming device

摘要

There is described an image-forming apparatus having a rotation system constituted by a driving roller, a driven roller and a transfer belt, threaded on both the driving roller and the driven roller. The apparatus includes: a motor to drive the rotation system, a rotational axis of the motor being coupled to the driving roller directly or through a power transmission element disposed between them; a first rotational-velocity controlling section to control a first rotational velocity of the motor; a velocity detecting section to detect a second rotational velocity of the driving roller or the driven roller; and a second rotational-velocity controlling section to also control the first rotational velocity of the motor, based on a detected signal detected by the velocity detecting section. The second rotational-velocity controlling section employs either a feedback controlling method or a feed-forward controlling method to control the first rotational velocity.