Driving device for driving endless metal belt and image forming apparatus

A driving device, comprising:

• an endless metal belt having a strip shape;
• a plurality of rotational members for bearing the metal belt to allow the metal belt to run circularly;
• and
• a polisher disposed so as to come in contact with widthwise opposite end edges of the metal belt for polishing the opposite end edges of the metal belt in running, the polisher having a shape that avoids interference with the rotational members, wherein:
• at least a first of the plurality of rotational members has a pair of opposite surfaces, and a circumferential surface for bearing the metal belt thereon,
• the circumferential surface has, in cross sectional view perpendicular to a circumferential direction of the metal belt, a convex shape projecting radially outward,
• the circumferential surface has a widthwise central region coming in contact with the metal belt, and a widthwise peripheral region that is not in contact with the metal belt, and
• the polisher is disposed near the first rotational member along the widthwise opposite end edges of the metal belt at a farther downstream position in a rotational direction of the first rotational member than a position where the metal belt starts changing from a straight form into a curved form by contacting the first rotational member.