Image forming apparatus which removes a surface potential of an

Abstract

An image forming apparatus which utilizes an intermediate transfer member. Plural toner images, for example of different colors, can be superimposed on the intermediate transfer member, and then can be transferred to a paper sheet. A discharging device is provided for discharging a charge applied to the intermediate transfer member. Further, a value of a voltage provided by this discharging device and/or a voltage provided for a transfer bias is proportional to an actual surface potential on the intermediate transfer member, which is proportional to the number of times toner images have been formed on the intermediate transfer member prior to transfer to the paper sheet. For example, if a full color toner image is formed on the intermediate transfer member, which may result from four operations of transferring individual toner images onto the intermediate transfer member, a voltage provided by the discharger and/or by a transfer bias device will be higher than that if only a monocolor image has been formed on the intermediate transfer member. Further, the image forming apparatus can be operable to form images on thicker paper, and in this instance a drive speed of devices in the image forming apparatus can be reduced, and a voltage applied to a pre-charger can also accordingly be reduced. The image forming apparatus can also include a cleaning device from the intermediate transfer belt, and the functions of both the intermediate transfer member discharging device and a cleaning device can be combined in one brush roller.