Patent ID: 6801728
Filing Date: 2004-10-05
Classification: G03G

Abstract:
An image forming apparatus in which a toner image formed on a photosensitive member is transferred onto a transfer paper through an intermediate transfer medium which comprises a plurality of layers including a conductive layer and which moves from a primary transfer part to a secondary transfer part by rotation, said apparatus comprising:primary transfer means which primarily transfers said toner image from said photosensitive member onto said intermediate transfer medium in said primary transfer part by applying a primary transfer bias which is determined in advance upon said conductive layer of said intermediate transfer medium; secondary transfer means which secondarily transfers said toner image now on said intermediate transfer medium onto a transfer paper in said secondary transfer part; bias control means which changes an output value of said primary transfer bias in accordance with a predetermined bias change condition when secondary transfer is not ongoing; reference detecting means which detects a reference mark formed on said intermediate transfer medium and outputs a reference signal; and toner image formation control means which controls toner image formation on said photosensitive member based on said reference signal, wherein said bias control means changes said output value after an elapsed period which is determined in advance since outputting of said reference signal, so that said output value is changed when a non-image area, in medium, is passing said primary transfer part, and said elapsed period is set so that said output value is changed before said non-image area has finished passing said primary transfer part.