BELT UNIT AND IMAGE FORMING APPARATUS

PROBLEM TO BE SOLVED: To introduce tension by the operation of driving an extended endless belt by continuously releasing the tension of the belt in order to prevent residual deformation from being generated in the extended endless belt.SOLUTION: The endless belt 20 is extended around a plurality of rollers 21, 22 and 23, the support shaft 28 of the second roller 22 supported so as to be movable is biased by a compression spring 24, and thereby tension is introduced into the belt. A rotation shaft 26 supported parallel to the support shaft of the second roller is provided with a pressing member 25 pressed against the second roller via the belt, thereby holding the second roller so as to be displaced in a direction in which the tension of the belt decreases. The pressing member is supported so as to be rotatable, and rotated accompanied by the movement of the belt in its circumferential direction, thereby releasing a pressing force exerted on the second roller.