| 主权项 |
1. An image forming apparatus, comprising:
an image bearer having a surface to bear a toner image; a transfer device configured to contact the surface of an image bearer to form a transfer nip; and a transfer bias power source configured to output a transfer bias to transfer the toner image from the image bearer onto a recording medium interposed between the transfer device and the image bearer in the transfer nip, wherein the transfer bias power source is configured to output an alternately switching voltage that alternates between a transfer-directional voltage having a polarity to transfer the toner image from the image bearer onto the recording medium and a return-directional voltage having an opposite polarity to the polarity of the transfer-directional voltage, and wherein the transfer bias power source is configured to reduce a target value of Vdc as an image area ratio of a toner image to be printed increases, and to increase the target value of Vdc as the image area ratio reduces, where Vdc is an average value of the alternately switching voltage during printing. |
