Patent ID: 8909081

Claim:
An image forming apparatus comprising: an image carrier which carries a toner image; a transfer member which pinches and feeds a record medium in cooperation with the image carrier; a transfer voltage applying device which applies a bias voltage to the transfer member; a voltage controller which performs constant voltage control on the transfer voltage applying device; a transfer contribution current detecting device which detects a transfer contribution current value that contributes to transfer of the toner image from the image carrier to the record medium, the transfer contribution current including a current induced by a voltage applied to a transfer Nip where the transfer of the toner image occurs; an antistatic member which is arranged downstream in a record medium feeding direction from the transfer member and for removing static electricity from the record medium; and an antistatic voltage applying device which applies an AC voltage to the antistatic member, wherein: the transfer contribution current detecting device measures current values during a current detection time, which corresponds to an integral multiple of a period of the AC voltage applied to the antistatic member, and detects the transfer contribution current value from the measured values; and the voltage controller controls the bias voltage applied to the transfer member based on the transfer contribution current value detected by the transfer contribution current detecting device such that the transfer contribution current value will be kept within a predetermined range.