Patent ID: 9639032
Date: 2017-05-02
CPC Classifications: G03G

Claim:
1. An image forming apparatus, comprising: an image bearer having a surface to bear a toner image to be printed; a transfer device that contacts the surface of the image bearer to form a transfer nip; and a transfer bias power source that outputs 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 outputs 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 the transfer bias power source reduces a target value of Vdc as an image area ratio of the toner image increases, the transfer bias power source increases the target value of Vdc as the image area ratio reduces, and the transfer bias power source increases the target value of Vdc as an edge ratio of the toner image increases, where Vdc is an average value of the alternately switching voltage during printing.