Patent ID: 8107839

Claim:
An image forming apparatus for charging a surface of a photoconductor to a specified potential using a charging roller, comprising: a bias applying device for applying a charging bias to the charging roller; a current detector for detecting a charging current when the charging bias is applied; a storage for storing a target charging current value which is a charging current value when the surface of the photoconductor is charged to a necessary surface potential; a bias corrector for correcting the charging bias; and a photoconductor information detector for detecting photoconductor information concerning the temperature of the photoconductor, wherein the bias corrector: conducts a first comparison in which a first charging current value detected by the current detector when the first charging bias as an initially set value was applied by the bias applying device is compared with the target charging current value stored in the storage and then conducts a first bias correction calculation in which a second charging bias is calculated based on the first comparison result, and repeatedly performs a second calculation a specified number of times to calculate a second charging bias based on the first comparison result and then conducts a second comparison in which a second charging current value detected by the current detector when the second charging bias was applied by the bias applying device is compared with the target charging current value in order to calculate a third charging bias based on the second comparison result; and conducts a second bias correction calculation to correct the third charging bias obtained as a result of the first bias correction calculation based on the photoconductor information detected by the photoconductor information detector.