| 摘要 |
A contact charging device includes a charging roller and a power source, the charging roller having a conductive core, a conductive elastic layer and a coating layer and rotating as being in contact with a photoreceptor drum made up of a conductive body and a photoconductor, and the power source applying between the core and the body a bias voltage in which an ac voltage has been superimposed on a dc voltage. The charging roller and the photoreceptor drum form an oscillation system of a characteristic frequency fm which oscillates due to static adsorptive force. The characteristic frequency fm is calculated from each parameter of the oscillation system, and a frequency fac of a superimposed ac voltage or twice the value of the frequency fac is set to fall within a range of fac<=0.5 fm or fac>=1.5 fm so as to suppress both resonance of the oscillation system and relatively large oscillation when taking viscosity damping resistance into consideration. A highly reliable contact charging device capable of surely preventing charging noise can be provided by adopting the highly universal condition of suppressing oscillation as obtained by an efficient method.
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