Patent ID: 6771919
Filing Date: 2004-08-03
Classification: G03G

Abstract:
An image forming apparatus comprising:a plurality of image carriers; a plurality of driven transmission members each being affixed to a respective image carrier; image carrier driving means for causing said plurality of image carriers to rotate via said plurality of driven transmission members; a plurality of image forming means for forming an image on a respective image carrier; transfer medium driving means for causing a transfer medium to move via a plurality of image transfer positions assigned to said plurality of image carriers; a plurality of image transferring means each for transferring an image from a respective image carrier to said transfer medium, the images being transferred from said plurality of image carriers to a preselected position on said transfer medium being driven by said transfer medium driving means one above the other; wherein when the image is formed on said image carrier and then transferred to said transfer medium, a rotation speed variation of said image carrier identical with one rotation period of said image carrier and ascribable to variations including a variation of said driven transmission member occurs in a phase set such that the images are transferred from said image carriers to said transfer medium one above the other in accurate register; wherein the chase of the rotation speed variation of said image carrier is set in accordance with rotation speed variations of said image carriers measured, and wherein said image carrier driving means comprises: a plurality of drive sources each being configured to drive a particular group of image carriers; absolute rotation angle sensing means each for sensing an absolute rotation angle of a respective driven transmission member included in the particular group of image carriers; and drive control means configured to control said plurality of drive sources in accordance with outputs of said absolute rotation angle sensing means such that the images are transferred from said image carriers to said transfer medium in accurate register.