Patent ID: 8718501

Claim:
An image forming apparatus, comprising: a latent image bearer configured to bear a latent image; a developing device configured to develop a latent image on the latent image bearer with toner; a nip creating member contacting the latent image bearer configured to create a transfer nip therebetween; a transfer current providing device configured to provide a prescribed target amount of transfer current to the nip creating member, said transfer current transferring the toner image from the latent image bearer onto one of the nip creating member and a recording sheet conveyed by the nip creating member, an image area rate obtaining device configured to obtain an image area rate of the latent image borne on the image bearer in the vicinity of an exit of the transfer nip; a determiner configured to determine a prescribed target amount of transfer current to be provided to the nip creating member based on one of at least two first and second algorithms, each of said at least two first and second algorithms representing a relation between the image area rate of the latent image borne on the image bearer in the vicinity of an exit of the transfer nip and a prescribed target amount of transfer current; and a process controller configured to execute a first transfer step, in which the toner image on the latent image bearer is transferred onto one of the nip creating member and the recording sheet for the first time, and a second transfer step, in which the toner image on the latent image bearer is transferred onto one of the nip creating member and the recording sheet already bearing a prescribed toner image thereon, wherein said first algorithm is utilized in the second transfer step when the image area rate falls within a typical range from the lower limit (a %) to the upper limit (b %), said first algorithm decreasing the prescribed target amount as the image area rate increases within the typical range, and wherein said second algorithm is utilized in the second transfer step in which the transfer current is applied when the toner image passes through the transfer nip based on the image area rate in a range corresponding to a predetermined line in a sub-scanning direction in the vicinity of the exit of the transfer nip and when the image area rate is less than the lower limit (a %) of the typical range, said second algorithm decreasing the target amount to be less than that obtained by the first algorithm when the image area rate is the lower limit (a %), wherein said lower limit (a %) is more than zero and said higher limit (b %) is greater than the lower limit (a %), and wherein the second algorithm controls the transfer current using the image area rate of a transfer station that transfers the toner image.