Patent ID: 8391759

Claim:
A belt device comprising: a belt member that is stretched over a plurality of rollers including a first roller, a second roller and a third roller arranged from upstream to downstream in this order and moves in a predetermined moving direction; a plurality of image carriers in contact with the belt member, each image carrier carrying respectively each toner image for each color; a secondary transfer roller provided at a position opposing the third roller such that the belt member is nipped therebetween forming a secondary transfer nip so that a toner image formed on the belt member is transferred onto a recording sheet that is conveyed to a position of the secondary transfer nip; a movable roller that detaches the belt member from the plurality of image carriers; a detecting unit that detects deviation of the belt member in a belt width direction of the belt member; and a preventing member that is arranged near to the detecting unit, and that prevents deviation of the belt member in a direction other than the moving direction and the belt width direction, wherein the first roller corrects deviation of the belt member in the width direction based on a result detected by the detecting unit; the plurality of image carriers and the movable roller are provided downstream of the first roller in the belt conveying direction and upstream of the second roller, and are provided to contact the belt member; and the detecting unit and the preventing member are provided at a position downstream of the second roller in the belt conveying direction and upstream of the third roller in the belt conveying direction.