Toshiba e-STUDIO 206, Service Manual

Page: 163 / 238

11
© February 2007 TOSHIBA TEC CORPORATION All rights reserved e-STUDIO166/206
DRUM RELATED SECTION
11 - 3
11.3 Functions
1) Drum
The drum is made of a cylindrical aluminum base coated with thin film of organic photoconductive
substance.
The photoconductive object becomes insulative (the electrical resistance is high) when it is not
exposed to the light and electrically conductive (the electrical resistance is low) when it is exposed to
the light. This object is called a photoconductor.
2) Main charger
The main charger in this equipment consists of a metal rod with U-shaped section, insulated blocks
at both ends of the rod and a needle electrode attached between them.
When a high voltage is applied to the needle electrode, the air around it is charged (ionized). The
ionized air then flows into the drum causing it to be charged. This phenomenon is called “corona dis-
charge”. At the same time, a control bias is applied to the main charger grid to control the charging
amount.
In a dark place, negative charge is evenly applied onto the drum surface by the corona discharge
and this grid. In addition, a cleaner is installed to clean up the dust attached on the needle electrode.
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Needle electrode
The needle electrode has aligned needles and their points perform the corona discharge. These
points (electrodes) discharge toward the drum in one direction to realize the more efficient dis-
charging comparing to the charger wire which discharges in a radial direction. Therefore, the
needle electrode enables to reduce the ozone amount.
Fig. 11-2
Needle electrode
Main charger
Charge