Patent ID: 7263321

Claim:
An image forming apparatus comprising: a transfer belt adapted to allow a plurality of toner images of different colors to be sequentially superimposed and transferred onto a surface thereof so as to form a color toner image; a plurality of image-forming units disposed along said transfer belt and each adapted to form a toner image with a corresponding one of said colors and transfer said toner image onto said transfer belt; a transfer device for transferring the color toner image on said transfer belt to a recording sheet at a secondary transfer position; a drive roller for rotationally driving said transfer belt; a tension roller disposed between said secondary transfer position and one of said image forming units located on a downstreammost side of said transfer belt in a rotation direction thereof, said tension roller allowing said transfer belt to be laid thereacross in a tensioned condition in cooperation with said drive roller, said tension roller being adapted to be changed in position in response to a biasing force to apply a tension to said transfer belt; and a speed detector for detecting a rotation speed of said tension roller and outputting a roller rotation speed signal.