Patent ID: 8639142

Claim:
An image forming apparatus, comprising: an image carrying member to carry a toner image; an intermediate transfer member to carry, on a moving surface thereof, the toner image transferred from the image carrying member; a nip forming member to come into contact with the intermediate transfer member to form a transfer nip, in which a surface of the nip forming member moves in the same direction as the moving direction of the intermediate transfer member, and the toner image on the intermediate transfer member is transferred onto a surface of a recording sheet conveyed to the transfer nip; a transfer current output device to output a transfer current to be applied between the intermediate transfer member and the nip forming member; a detection device comprising a resistance detection device configured to detect the electrical resistance of the recording sheet and an environment detection device configured to detect an environmental parameter correlated with the electrical resistance detected by the resistance detection device; a storage device to store, as an algorithm for calculating a target value of the transfer current according to a toner image area ratio in the transfer nip, a plurality of algorithms corresponding to different values for one of the electrical resistance and the environmental parameter; and a transfer current control device to perform a process of selecting, from the plurality of algorithms, an algorithm according to the result of detection the detection device, and using the selected algorithm to calculate the target value, the transfer current control device controlling an output value from the transfer current output device to cause a transfer current value to match the target value calculated with the selected algorithm based on the toner image area ratio in the transfer nip.