| 摘要 |
PURPOSE:To prevent a defective image from being formed owing to lateral vibration by detecting the lateral vibration of the image carrier belt in the time of detection by sensors for a detection mark which varies at right angles to a rotating direction. CONSTITUTION:The detection mark 95 varies in rotation-directional length at right angles to the rotating direction and the lateral vibration of the image carrier belt 11 is detected from the time of detection by the sensors 72 and 725 for the detection mark 95. The detection mark 95 is detected by the sensors 72 and 725 to detect the rotation-directional position of the image carrier belt 11. The time of detection of the detection mark 95 by the sensors 72 and 725 varies according to whether or not the image carrier belt 11 vibrates laterally since the length of the detection mark 95 varies in the lateral direction, so that the lateral vibration of the image carrier belt 11 is detected when the detection time or its change value exceeds a normal value. Consequently, the lateral vibration of the image carrier belt is detected with the simple constitution and the defective image is prevented from being formed. |
