BELT DRIVING DEVICE AND IMAGE FORMING DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an image forming device with a flat belt B as a transfer carrying belt wound among transfer rollers 6a-6d corresponding to photosensitive drums 5 in yellow, magenta, cyanogen and black colors, respectively, a meandering control roller 28 having a meandering detection part 39 and a driving roller 11 for changing over the layouts of the belt B between a full-color mode for making the belt B contact four transfer rollers 6a-6d and a monochrome mode for making it contact the transfer roller 6d only corresponding to the black photosensitive drum 5, ensuring correction of the lopsided belt B and stabilizing a belt running condition by suppressing a change in rotating torque which the meandering detection part 39 receives with the change of the belt layout even if the position of a belt wound on the meandering control roller 28 is changed with the change of the belt layout. SOLUTION: An angleθand a position of the belt wound on the meandering control roller 28 are kept almost constant with the change-over of the belt layout by mounting a paper introducing roller 14 and the meandering control roller 28 on a movable frame 9.