Patent ID: 7058322

Claim:
An image forming apparatus comprising: an image carrier that carries a toner image; transfer means which includes a transfer member forming a transfer nip portion together with said image carrier and which can apply a transfer bias to said transfer member to transfer the toner image carried on said image carrier to a toner image transfer area of a print material passing through said transfer nip portion; control means for controlling a transfer bias set value set in order to apply a predetermined transfer bias to said transfer member; and size sensing means for sensing a size of the print material; wherein if the size of the print material sensed by said size sensing means is smaller than a predetermined size, said control means switches a first transfer bias set value to a second bias set value smaller than the first transfer bias set value while the toner image transfer area of the print material is passing through said transfer nip portion, and if the size of the print material sensed by said size sensing means is larger than the predetermined size, said control means switches the first transfer bias set value to the second transfer bias set value smaller than the first transfer bias set value after the toner image transfer area of the print material has gassed through said transfer nip portion.