Patent ID: 8837989

Claim:
A belt driving apparatus comprising: a movable belt member; a stretching member configured to stretch said belt member; a steering unit configured to stretch said belt member and to be inclined to steer said belt member in a widthwise direction substantially perpendicular to a direction of movement of said belt member, said steering unit including: a rotatable member contacting an inner surface of said belt member and configured to be rotatable with movement of said belt member around a rotational axis of said rotatable member, with the rotational axis extending in the widthwise direction, non-rotatable members contacting an inner surface of said belt member, provided at each opposite axial end of said rotatable member, and configured not to be rotatable with movement of said belt member, wherein when said belt member is moved toward a side in the widthwise direction, a width of the non-rotatable member contacting an inner surface of said belt member is increased in the side and is decreased in the other side so that a first frictional force arising from sliding in the side is larger than a second frictional force arising from sliding in the other side, a supporting member configured to support said rotatable member and said non-rotatable members, wherein said supporting member is inclined, by a difference between the first frictional force and the second frictional force, around an axis perpendicular to the rotational axis, and urging members each provided in said steering unit and configured to urge said belt member against the non-rotatable member in planar contact with a region of said belt member located inside an edge of said belt member with respect to the widthwise direction, each said urging member having a width extending in the widthwise direction.