Patent attributes
The positioning of an image read sensor for accurately reading the toner image on the belt member becomes easy. The image read sensor 21 is located on the supporting frame 26 provided to the casing of the image forming apparatus so that it faces the belt member such as an intermediate transfer belt 45 between the driving roller 46 and follower roller 48 when the belt unit is mounted to the casing of the apparatus. The supporting frame 26 is provided with shaft supporting recesses 27. The shaft member is supported for rotation in the belt unit such that it contacts the inside surface of the belt member and pushes the belt member outward at the position it faces the image read sensor across the belt member when the belt unit is mounted to the casing of the apparatus.
