| 摘要 |
A charging apparatus includes a charging device for electrically charging a photosensitive member; a bias applying device for applying to the charging member a charging bias voltage comprising a DC voltage component and a AC voltage component, wherein the bias applying device effect a constant voltage control with a constant AC component of the charging bias voltage; a AC detector for detecting a AC detected current when the charging member is supplied with a test bias voltage; a DC detector for detecting a DC detected current when the charging member is supplied with the test bias voltage; and a controller for controlling a charging bias voltage to be applied to the charging member; wherein the control means determines a peak-to-peak voltage Vo when a change rate of detected DC current provided by sequentially applying the test bias voltages having different peak-to-peak voltages in order of increasing or decreasing peak-to-peak voltage becomes not more than a predetermined level, and the control means sets a peak-to-peak voltage of the charging bias voltage on the basis of a detected AC current when a peak-to-peak voltage Vp larger than the peak-to-peak voltage Vo and a detected AC current when a peak-to-peak voltage Vq not larger than the peak-to-peak voltage Vo.
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