Basic Process And Composition; Model - Sharp AR-5132 Service Manual

2. Basic process and composition

•
This machine employs the scorotron system to charge the
photoconductor surface uniformly to a certain level. The conven-
tional corona charger mechanism is employed which is composed
of the corona wire and the saw tooth plate (stainless plate of
0.1mm thick).
In corona charging, oxygen molecules in the air are ionized to form
ozone. This mechanism suppresses the generation of ozone.
•
The process separation mechanism is employed for serviceability.
•
The one-touch stopper mechanism prevents against high voltage
leakage caused by drop of the corona charger unit.
( 5.25KV)
MC
Fuse bulb
DL
Process
control
sensor
SC
AC 5.2KV
(DC 400V)
Drive system view
(1) Details of image forming process
Step 1: Charging
Main charger high voltage transformer (MHVG)
Grid voltage
Standard mode
Photo mode
TSM mode
Printer mode
A uniform negative charge is applied to the OPC drum surface by
negative corona discharge of the main charger.
The OPC drum surface potential is controlled by the screen grid
voltage to be virtually the same level as the grid voltage.
•
When the drum surface potential is lower than the grid voltage,
electric charges generated by discharging of the main charger are
passed through the screen grid to keep charging until the drum
surface potential reaches the same level as the grid voltage.
•
When the drum surface potential reaches about the same level as
the grid voltage, electric charges generated by discharging of the
main charger flow through the electrode of the screen grid to the
high voltage unit grid voltage output circuit. Therefore the drum
surface potential is kept at the same level as the grid voltage.
LD
785nm
EXP
Drum mark
sensor
Toner
Carrier
Developing bias
400V
TC
I t 180µA
( 5.3KV)
Developing bias
voltage
–490V –400V
–490V –400V
–440V –350V
–460V –400V
Step 2: Exposure (laser beams)
Laser beams are generated in the LSU according to the print signal
from the ICU and radiated to the drum surface. The resistance of the
are of OPC layer where laser beams are radiated reduces to dis-
charge negative charges, forming electrostatic latent images on the
drum surface.
DV
unit
Exposure (laser beam)
Non image
area
Step 3: Developing (Bias –400V)
The electrostatic latent images on the drum surface are made visible
images. This model uses the two-component magnetic brush
developing system to supply the bias voltage of –400V to carriers
(MG roller), and toner is negatively charged by friction with carriers.
Since the non-image area on the drum is negatively charged greater
than the developing bias, the negatively charged toner is repulsed
from the drum. The image area on the drum is exposed by laser
beams and its potential is decreased. Then negative toner is attached
to it by the DV bias.
2 – 3
Screen grid
Grid voltage output section
Exposure
OPC
layer
Pigment
layer
Aluminum
layer
Image Non image
(drum)
area area
Carrier
Toner
S
N
N
N
S
Main charger output
section
High voltage
unit
Image
area
-400V