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[3] DEVELOPING SECTION
1. Basic outline
(1) Two-component developer
Developer is composed of tow components; toner and carrier.
Carrier functions as a media to attract toner to electrostatic latent
images on the OPC drum.
As the toner is mixed with the carrier, the friction changes it to posi-
tive or negative.
Developer characteristics changes due to deterioration to degrade
print quality. Therefore developer must be replaced periodically.
(2) Two-component magnetic brush developing
A rotatable non-magnetic sleeve is provided on the magnet roller and
rotated.
Carrier forms a magnetic brush on the sleeve surface by the mag-
netic force to attract toner to electrostatic latent images on the OPC
drum.
(3) Developing bias
Since the reverse developing system is employed, toner is attracted
to the area (light potential area) where laser beams are radiated.
Though it is the light potential area, the OPC drum is negatively
charged. To attract negatively charged toner to the OPC drum, a
higher (absolute value) bias must be applied to the MG roller. There-
fore, the amount of attracted toner can be varied by the level of the
developing bias voltage.
The developing bias serves to prevents against attachment of exces-
sive toner by setting it lower (in absolute value) than the surface
potential (dark potential) when making white background.
2. Basic composition
1
No.
Name
1
Developing magnet roller
2
Developing doctor blade
3
Developing stirring roller
4
Developing transport roller
5
Developing toner density
sensor
3. Basic operation
When the power switch of the machine is turned on, the machine
starts warming up. After about one minute, the main motor rotates.
The drive power of the developing unit is transmitted from the main
motor through the main drive unit to the developing drive unit.
Change in the mixing ratio of toner and carrier is sensed by the toner
density sensor in the developing unit as the change in magnetic
permeability, and outputted to the analog input pin of the main PWB
CPU of the main body.
The CPU monitors the input voltage level, and controls the main
motor and toner motor to supply, transport, and stir toner until the
proper density is obtained.
3 – 1
2
4
3
5
Forms the magnetic brush of
carrier by the magnetic force.
Used of regulation of the
magnetic brush height.
Stirs carrier in the developing
unit to distribute toner uniformly.
Transports toner supplied from
the toner hopper unit to the
stirring section.
Detects the toner density in the
developer.
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