Patent ID: 7257340

Claim:
An image forming apparatus comprising: an image carrier that carries a toner image; a transfer member forming a transfer nip portion together with said image carrier, for transferring the toner image carried on said image carrier to a print material passing through the transfer nip portion; a sensor for detecting a position of a print material; a power source for applying a transfer bias to said transfer member; a controller for controlling the transfer bias outputted from said power source; and a detector for detecting a size of the print material, wherein said controller receives information relating to a size of the print material from the detector, wherein when transferring the toner image to a first print material, and when a position located a first length away from a trailing end of the first print material toward a leading end of the first print material in a conveying direction is passing through the transfer nip portion, said controller outputs a signal for decreasing an output voltage of said power source, when transferring the toner image to a second print material with the length in the conveying direction being shorter than the first print material, and when a position located a second length away from a trailing end of the second print material toward a leading end of the second print material in the conveying direction is passing through the transfer nip portion, said controller outputs a signal for decreasing the output voltage of said power source, and wherein the second length is longer than said first length.