Patent ID: 8023872

Claim:
A belt device for use in an image forming apparatus, the belt device comprising: an endless belt member that runs in a predetermined direction; a first detecting unit that detects a widthwise displacement of the belt member indicative of an amount of displacement in a width direction of the belt member; a correcting unit that corrects displacement of the belt member in the width direction during a period starting from turning power on and ending with completion of drive preparation of the belt member, based on the widthwise displacement detected by the first detecting unit; a second detecting unit that includes an arm member positioned outside from a widthwise end of the belt member and apart from the widthwise end at a normal position by a threshold, and that detects whether the belt member has displaced in the width direction from the normal position by an amount that is greater than the threshold; and a belt stopping unit that, during the period starting from turning power on and ending with completion of drive preparation of the belt member, stops running of the belt member only when the second detecting unit detects that the belt member has displaced by an amount that is greater than the threshold.