Patent ID: 8185002

Claim:
An image forming apparatus comprising: an image forming unit that forms at least a pattern image; an annular belt that moves circularly and carries the pattern image formed by the image forming unit; a detection unit that detects a state of a surface of the belt, including the pattern image carried on the belt; a tension increase unit that increases a tension of the belt, at a detection position where the detection unit detects the pattern image, each time when the detection unit detects the pattern image, as compared with the tension of the belt at the detection position before the detection unit detects the pattern image; a drive roller that drives the belt; and a cleaning member that cleans the belt, wherein: the detection unit is opposed to the belt between a support position where the belt is supported on the drive roller and a cleaning position where the belt is contacted with the cleaning member, in a circulating direction of the belt; and the tension increase unit controls the cleaning member to decrease a resistance force of the cleaning member in the circulating movement of the belt as compared with the resistance force of the cleaning member before the detection unit detects the pattern image.