Patent ID: 7565095

Claim:
A belt device comprising: a plurality of rollers including: a drive roller configured to be supplied with a driving force; and a follow roller that follows rotation of the drive roller; a belt looped around the plurality of rollers, the belt having an inner peripheral surface facing inside of a loop of the belt and an outer peripheral surface opposite the inner peripheral surface, the belt having a first widthwise edge and a second widthwise edge opposite the first widthwise edge in a widthwise direction; an urging member that applies tension to the belt in a circumferential direction orthogonal to the widthwise direction; a widthwise-movement restricting member disposed on the inner peripheral surface on a first widthwise edge side, the widthwise-movement restricting member restricting widthwise movement of the belt in a direction toward a second widthwise edge side; and an expansion-contraction restricting member disposed on the second widthwise edge side on at least one of the inner peripheral surface and the outer peripheral surface, the expansion-contraction restricting member restricting expansion-contraction of the belt so that a circumferential length in the second widthwise edge side is shorter than a circumferential length in the first widthwise edge side when the belt is applied with tension in the circumferential direction.