Patent ID: 8385794

Claim:
A belt device, comprising: an endless belt bearing a toner image having a plurality of different colors superimposed one on another; a plurality of rollers on which the belt is mounted and including a drive roller connected to a specified drive source and rotating the belt; a meandering correcting member correcting the meandering of the belt in a width direction of the belt; a sensor detecting the position of an end surface of the belt in the belt width direction; an adjusting mechanism adjusting the movement of the meandering correcting member; and a controller controlling the adjusting mechanism based on the position detection of the belt end surface by the sensor, wherein: the controller controls the adjusting mechanism so that the belt end surface approaches a specified target position and lies within a specified position range including the specified target position, and when a(t) denotes the belt end surface position, 2 q denotes the magnitude of the fluctuation, r denotes the specified target position and p denotes an arbitrary constant, the specified position range is a range from +p×q+r to −p×q+r, and the controller feedback controls the adjusting mechanism to satisfy a relationship of −p×q+r≦a(t)≦+p×q+r.