Image forming apparatus preventing change of size of image

摘要

An image forming apparatus has a movable image bearing member on which an unfixed image is formed, transfer device for transferring the unfixed image on the image bearing member onto a recording medium, fixing device for heating and fixing the unfixed image transferred by the transfer means on the recording medium. The fixing device has a driving rotatable member for conveying the recording medium. The recording medium during the transfer by the transfer device is conveyed by the driving rotatable member. The apparatus is provided with detecting device for detecting information regarding the peripheral velocity of the driving rotatable member, and control device for controlling the movement speed of the image bearing member on the basis of the result of the detection by the detecting device.