Patent ID: 7756431

Claim:
An image formation apparatus comprising: a photoconductor; a charging section that applies a bias voltage comprising an AC voltage superposed on a DC voltage and charges the photoconductor; a controller that controls at least one of the AC voltage and an AC current applied by the charging section; and a detector that detects an amount of discharge occurring between the photoconductor and the charging section, wherein the controller controls at least one of the AC voltage and the AC current so that the amount of discharge detected by the detector becomes a singularity in change of the amount of discharge, and the controller determines whether the amount of discharge becomes the singularity or not by comparing the amount of discharge at three levels including a first level, a second level and a third level, the first level being a given AC voltage level or a given AC current level, the second level being obtained by adding the first level and a given value, the third level being obtained by subtracting the given value from the first level.