| 摘要 |
A charging member comprised of a conductive shaft and conductive fibers planted thereon is brought into contact with a charged member with a photoconductor provided on the surface thereof. The conductive shaft is applied with a combined voltage of d.c. voltage and a.c. voltage having a peak-peak value lower than two times the discharge starting threshold voltage that is determined by the surrounding atmosphere around the charged member. While the charging member and the charged member rotate at different surface velocity, the charged member is charged through the contact area in which impedance is low due to the influence of a.c. voltage, so that a stable surface potential close to the d.c. voltage may be charged onto the charged member. Further, it is effective that the frequency f of the a.c. voltage will be so set up as to suffice a relation: f>Vp/2R, where f is a frequency of the applied a.c. voltage, Vp(mm/s) is a moving velocity of the charged member, and R(mm) is a particle size of a developer used. Moreover, it is effective that another charging member is provided on the downstream side of the aforementioned charging member.
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