Patent ID: 8909079

Claim:
An image forming apparatus comprising: an image carrier movable in a predetermined moving direction and to carry a toner image; a first rotary body to contact an outer surface of the image carrier; a second rotary body pressed against an inner surface of the image carrier to form a transfer nip between the outer surface of the image carrier and the first rotary body; and a transfer bias generator to output to the second rotary body a transfer bias including a direct current component and an alternating current component for application to the image carrier to transfer the toner image from the image carrier onto a recording medium conveyed through the transfer nip, the transfer bias generator including: a transfer bias supply operatively connected to the second rotary body to supply the transfer bias including at least the alternating current component thereto; and a controller operatively connected to the transfer bias supply to detect a toner adhesion amount at a predetermined region of the image carrier located immediately upstream from the transfer nip and having a predetermined length in the moving direction of the image carrier, the transfer bias generator outputting at least the alternating current component under one of constant voltage control and constant current control and changing a target output value of the alternating current component separately from the direct current component from a non-zero value to another non-zero value according to the toner adhesion amount detected by the controller.