Image forming apparatus having a transfer device for transferring a toner image and having a bias voltage controller

摘要

The image forming apparatus of the present invention, in which a toner image formed in an image forming section is transferred onto a transfer medium (sheet-like material) consisting of at least one of paper sheets and resin sheets, comprises a bias voltage supply for supplying a transfer bias voltage to a toner image transfer device, an environmental state detecting device for detecting at least one of temperature and humidity in the vicinity of the toner image forming section, and a bias voltage controller for switching the on/off state of the bias voltage output from the bias voltage supply as well as the magnitude and polarity of the bias voltage into a predetermined magnitude and polarity at a predetermined timing in accordance with the presence or absence of the transfer medium, the kind of the transfer medium and the environmental condition detected by the environmental state detecting device. The image forming apparatus of the particular construction permits transferring the toner image formed on the image carrier onto the sheet-like material with a high transfer efficiency without giving rise to the memory image by the transfer bias voltage.