| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus such as a color printer which detects soil on a position detecting mark on a transfer belt at an appropriate stage and informs a user of the result of the detection. <P>SOLUTION: A threshold value 1 for judging the detected length (detection length) of the position detecting mark on the transfer belt and a threshold 2 smaller than the threshold 1 are set. During a printing operation, the detection length of the position detecting mark is detected by a sensor. When the value of the detected detection length is greater than the threshold 2, judgment is further made whether the detection length is smaller than the threshold 1 or not. When the detection length is smaller than the threshold 1, judgment is made that soil has the level that must be counted, and a soil detection counter is increased by +1. When the soil detection counter exceeds a prescribed value, a user is informed that the position detecting mark has been soiled. When the detection length is the threshold 2 or below, judgment is made that a soil has reached a level of which a user needs to be informed. Consequently, the user is informed that the position detecting mark has been soiled. <P>COPYRIGHT: (C)2008,JPO&INPIT |
