Print Process - Brother FAX-2820 Service Manual

3.2.4.7

Print process

Charging
The drum is charged to approximately 900V 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 the
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 aluminum drum sleeve in the exposure
drum is grounded.
Current
circuit
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.
Exposure stage
After the drum is positively charged, it is exposed to the light emitted from the laser unit.
Laser detector
Laser diode
< Laser exposure unit >
1. The laser beam radiated from a laser diode inside the laser unit are concentrated into a
constant width by a slit in the CO lens cell and then reflected by a polygon mirror rotating at
high speed.
2. The laser beam reflected by the polygon mirror are refracted by the theta lens and radiated
from the right through to the left end of the reflection mirror as the polygon mirror rotates.
At this time, blur of the vertical direction of the laser beam by inclination of a polygon mirror
is corrected by passing a TORIC lens.
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Corona wire
Drum
Toric lens
CO lens
Aluminum drum sleeve
Organic photoconductor layer
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Grid
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HVPS
Paper
Laser beam
f θ lens
Polygon mirror
Motor
3 - 1 3
Exposure
drum
Laser beam
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