Developing Section; General Descriptions; Basic Composition - Sharp SF-1020 Service Manual

2. Developing section

1) General descriptions

(1) Two-component developer
The developer is composed of toner and carrier.
Carrier serves as a medium for attaching toner onto the electrostatic
image on the photoconductor drum.
By stirring toner and carrier, they are rubbed to be charged positive
(+) and negative (–) respectively.
Since developer will deteriorate to degrade copy quality, it should be
replaced regularly.
(2) Two-component magnetic brush development
The rotatable non-magnetic sleeve is provided over the magnet roller
and is rotated.
Carrier forms a magnetic brush on the sleeve surface by magnetic
force to attach toner onto the electrostatic image on the photoconduc-
tor drum.
(3) Developing bias
When the photoconductor is charged and exposed to light (ex-
posure), the surface potential (voltage) of the photoconductor will not
be lost completely. (The residual potential remains.)
Toner is attracted to the photoconductor by this residual potential,
dirtying the photoconductor. As a result, a dirty copy of white back-
ground is generated.
To prevent against this, a voltage of the same polarity and higher than
the residual potential is applied to the MG roller, preventing toner from
being attached to the photoconductor surface.
MG roller
Toner
Carrier
Developing bias voltage
(4) DV harness
The toner density sensor, the developing bias, and the developing
unit identification resistance harness.
(For details, refer to [6] DISASSEMBLY AND ASSEMBLY.)
(Viewed from the rear of develoing unit)
DV harness connector
Residual potential < DV BIAS
DV BIAS
-200V
(Details of DV harness connector)
For color identification
GND
Resistor
*For toner density sensor
GND
*Resistance value is identified by color

2) Basic composition

2
1
3
No. Name
1
Magnet roller
2 Developing doctor blade
3
Developing MIX roller
4 Toner transport roller
5 Toner density sensor
5 – 2
For bias
4
5
Forms a magnetic brush of carrier
by magnetic force.
Limits the height of the magnetic
brush.
Stirs carrier in the developing unit
and distributes toner evenly.
Transport toner sent from the
toner hopper unit to the stirring
section.
Senses toner density
developer.
VB
in