| 摘要 |
PURPOSE:To reduce variance in the surface potential of a photosensitive body which moves at a high speed and to perform control with high accuracy by charging electrostatically the difference between the surface potential of the photosensitive body which is obtained by the electrostatic charging of an upstream-side scorotron and a set surface potential by a downstream-side electrostatic charging device. CONSTITUTION:The photosensitive drum 10 while rotating is charged electrostatically by the upstream-side scorotron 20 and a current corresponding to the surface potential of the photosensitive body 12 flows to a control grid 22. The difference between the surface potential of the photosensitive body 12 and the set potential is calculated by the differential amplifier 41 of a controller 40, and the output corresponding to the difference is supplied to an amplifier 42, so that an amplified signal is supplied to a transformer 50. The transformer 50 applies the corona wire 31 of the downstream- side corotron 30 with a voltage required to eliminate the difference between the set surface potential of the photosensitive body 12 and the surface potential of the photosensitive body 12 which is charged actually by the upstream-side scorotron 20. The corona wire 31 of the corotron 30 further charges the photosensitive body 12, so that the surface potential of the photosensitive body 12 reaches the preset value.
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