Brother HL-1070 - B/W Laser Printer, Service Manual

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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. 2.27
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