Patent ID: 7522853

Claim:
A method for controlling a voltage of a charging member for charging uniformly a surface of a charge receptor member by applying a DC voltage superposed with an AC voltage, said method comprising: measuring a discharge onset voltage Vth for initiating a discharge to said charge receptor member by applying the DC voltage to said charging member; measuring a first detection current flowing into said charge receptor member when a first AC voltage of 2×Vth or larger is applied solely to said charging member; measuring a second detection current flowing into said charge receptor member when a second AC voltage is applied to said charging member, the second AC voltage being 2×Vth or larger and different from the first AC voltage; determining a relational expression between the AC voltage to be applied to said charging member and an AC current flowing into said charge receptor member in a range of 2×Vth or larger, based on the first and second AC voltages and on the measured first and second detection currents; and obtaining a third AC voltage to be applied to said charging member by substituting a predetermined standard AC current value into the determined relational expression, said predetermined standard AC current value being sufficient to uniformly charge said charge receptor member, wherein, when a third AC current, which flows into said charge receptor member under the third AC voltage actually applied to said charging member, is within a predetermined range with respect to the predetermined standard AC current value, the obtaining step includes setting the third AC voltage as the AC voltage to be applied to said charging member.