Belt driving device and image forming apparatus using the same

摘要

An image forming apparatus of the present invention includes an endless belt (60) for conveying a recording medium. The belt is passed over four support rollers (61) each being formed with an annular guide groove that receives a guide (60a) formed on the belt. Assume that a biasing force F2 acts on one end of at least one support roller remote from the guide of the belt, and a biasing force F1 acts on the other side close to the guide member. Then, a relation of F1 < F2 < 1.5 x F1 holds. This frees the image transfer surface of the belt from slackening and creasing.