Patent ID: 7149443

Claim:
An image forming apparatus comprising in the casing of the apparatus; a belt member which is a photosensitive belt or an intermediate transfer belt or a transfer material carrying belt, a driving roller for driving said belt member, a follower roller, a tension roller for tensioning said belt member, the tension roller being located at the position remoter than the position of said follower roller from said driving roller, the distance between said driving roller and said follower roller being longer than that between said follower roller and said tension roller, and the belt being approximately linear in shape between said driving roller and follower roller; an image detecting means located at a position below and facing the belt member between said driving roller and follower roller for detecting the toner image on said belt member; and a contact member contacting an upper, inside surface of the belt member at the position facing said image detecting means across the belt member to push the belt member toward said image detecting means.