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CHAPTER II -20
2.4 Drum Unit
2.4.1 Photosensitive Drum
Generates the latent electrostatic image and develops the image on the drum surface.
2.4.2 Primary Charger
Forms a uniform charge on the drum surface.
(1) Corona wire
Generates the ion charge on the drum.
(2) Grid
Spreads the ion charge evenly over the drum surface.
2.4.3 Developer Roller
Develops the latent electrostatic image on the drum surface by the addition of the toner.
2.4.4 Transfer Roller
Transfers the toner image to the paper from the drum surface.
2.4.5 Cleaner Roller
Removes and recycles the toner remaining on the drum surface.
2.4.6 Erase Lamp
Discharges the electrostatic latent image on the drum.
2.5 Print Process
2.5.1 Charging
The drum is charged to approx. +1000V by an ion charge which is generated by the primary
charger. The charge is generated by ionization of the corona wire, which has a DC bias
from high-voltage power supply applied to it. The flow of the ion charge is controlled by the
grid to ensure it is distributed evenly on the drum surface. The drum sleeve is regulated to
approx. 280V by the voltage regulator.
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Fig. 2.25
The primary charge uses a corona wire, but since the drum is positively charged, only less
than 1/10 of the usual quantity of ozone is generated compared with the negatively charged
drum. The level of ozone expelled from the printer is therefore not harmful to the human
body. Applicable safety standards have been complied with.
Passive Type
Voltage Regulator
Grid
Voltage
Regulator
Corona wire
HVPS
1000V
280V
Aluminum drum sleeve
Organic Photoconductor layer
Drum