Sharp AL-2020 (serv.man2) Service Manual ▷ View online
AL-2040 COPY PROCESS 6 - 3
Step-3: Developing (DC bias)
A bias potential is applied to the MG roller in the two component
magnetic brush developing method, and the toner is charged neg-
ative through friction with the carrier.
magnetic brush developing method, and the toner is charged neg-
ative through friction with the carrier.
Non-image area of the drum surface charged with negative poten-
tial repel the toner, whereas the laser exposed portions where no
negative charges exist, attract the toner. As a result, a visible
image appears on the drum surface.
tial repel the toner, whereas the laser exposed portions where no
negative charges exist, attract the toner. As a result, a visible
image appears on the drum surface.
Toner is attracted over the shadowed area because of the develop-
ing bias.
ing bias.
Step-4: Transfer
The visible image on the drum surface is transferred onto the print
paper by applying a positive charge from the transfer corona to the
backside of the print paper.
paper by applying a positive charge from the transfer corona to the
backside of the print paper.
Step-5: Separation
Since the print paper is charged positively by the transfer corona, it
is discharged by the separation corona. The separation corona is
connected to ground.
is discharged by the separation corona. The separation corona is
connected to ground.
Step-6: Cleaning
Toner remaining on the drum is removed and collected by the
cleaning blade. It is transported to the waste toner collecting sec-
tion in the cleaning unit by the waste toner transport roller.
cleaning blade. It is transported to the waste toner collecting sec-
tion in the cleaning unit by the waste toner transport roller.
S
N
N
:Carrier (Magnetized particle)
:Toner (Charge negative by friction)
(N) (S) Permanent magnet
:Toner (Charge negative by friction)
(N) (S) Permanent magnet
(provided in three locations)
MG roller
DC
400V 8V
About DC 5.2kV
AL-2040 COPY PROCESS 6 - 4
Step-7: Optical discharge (Semiconductor laser)
Before the drum rotation is stopped, the semiconductor laser is
radiated onto the drum to reduce the electrical resistance in the
OPC layer and eliminate residual charge, providing a uniform state
to the drum surface for the next page to be printed.
radiated onto the drum to reduce the electrical resistance in the
OPC layer and eliminate residual charge, providing a uniform state
to the drum surface for the next page to be printed.
When the electrical resistance is reduced, positive charges on the
aluminum layer are moved and neutralized with negative charges
on the OPC layer.
aluminum layer are moved and neutralized with negative charges
on the OPC layer.
Charge by the Scorotron charger
Function
The Scorotron charger functions to maintain uniform surface
potential on the drum at all times, It control the surface potential
regardless of the charge characteristics of the photoconductor.
potential on the drum at all times, It control the surface potential
regardless of the charge characteristics of the photoconductor.
Basic function
A screen grid is placed between the saw tooth and the photocon-
ductor. A stable voltage is added to the screen grid to maintain the
corona current on the photoconductor.
ductor. A stable voltage is added to the screen grid to maintain the
corona current on the photoconductor.
As the photoconductor is charged by the saw tooth from the main
corona unit, the surface potential increases. This increases the
current flowing through the screen grid. When the photoconductor
potential nears the grid potential, the current turns to flow to the
grid so that the photoconductor potential can be maintained at a
stable level.
corona unit, the surface potential increases. This increases the
current flowing through the screen grid. When the photoconductor
potential nears the grid potential, the current turns to flow to the
grid so that the photoconductor potential can be maintained at a
stable level.
Process controlling
Function
The print pattern signal is converted into an invisible image by the
semiconductor laser using negative to positive (reversible) devel-
oping method. Therefore, if the developing bias is added before
the drum is charged, toner is attracted onto the drum. If the devel-
oping bias is not added when the drum is charged, the carrier is
attracted to the drum because of the strong electrostatic force of
the drum.
semiconductor laser using negative to positive (reversible) devel-
oping method. Therefore, if the developing bias is added before
the drum is charged, toner is attracted onto the drum. If the devel-
oping bias is not added when the drum is charged, the carrier is
attracted to the drum because of the strong electrostatic force of
the drum.
To avoid this, the process is controlled by adjusting the drum
potential and the grid potential of the Scorotron charger.
potential and the grid potential of the Scorotron charger.
Basic function
Voltage added to the screen grid can be selected, high and low. To
make it easily understood, the figure below shows voltage transi-
tion at the developer unit.
make it easily understood, the figure below shows voltage transi-
tion at the developer unit.
Start
1) Because the grid potential is at a low level, the drum potential
is at about -400V. (Carrier may not be attracted though the car-
rier is pulled towards the drum by the electrostatic force of -
400V.
rier is pulled towards the drum by the electrostatic force of -
400V.
2) Developing bias (-400V) is applied when the photoconductor
potential is switched from LOW to HIGH.
3) Once developing bias (-400V) is applied and the photo con-
ductor potential rises to HIGH, toner will not be attracted to the
drum.
drum.
Stop
The reverse sequence takes place.
Retaining developing bias at an abnormal occurrence
Function
The developing bias will be lost if the power supply was removed
during print process. In this event, the drum potential slightly
abates and the carrier makes deposits on the drum because of
strong static power. To prevent this, the machine incorporates a
function to retain the developing bias for a certain period and
decrease the voltage gradually against possible power loss.
during print process. In this event, the drum potential slightly
abates and the carrier makes deposits on the drum because of
strong static power. To prevent this, the machine incorporates a
function to retain the developing bias for a certain period and
decrease the voltage gradually against possible power loss.
Basic function
Normally, the developing bias voltage is retained for a certain time
before the drum comes to a complete stop if the machine should
stop before completing the normal print cycle. The developing bias
can be added before resuming the operation after an abnormal
interruption. Therefore, carrier will not make a deposit on the drum
surface.
before the drum comes to a complete stop if the machine should
stop before completing the normal print cycle. The developing bias
can be added before resuming the operation after an abnormal
interruption. Therefore, carrier will not make a deposit on the drum
surface.
Semiconductor laser
0
START
STOP
Print potential
Toner attract
potential
potential
2)
3)
1)
Low
4)
High
Drum potential
Developing bias
Time
AL-2040 OPERATIONAL DESCRIPTIONS 7 - 1
[7] OPERATIONAL DESCRIPTIONS
1. Outline of operation
The outline of operation is described referring to the basic configuration.
(Basic configuration)
(Outline of copy operation)
Setting conditions
1) Set copy conditions such as the copy quantity and the copy
density with the operation section, and press the COPY but-
ton. The information on copy conditions is sent to the MCU.
ton. The information on copy conditions is sent to the MCU.
Image scanning
2) When the COPY button is pressed, the scanner section starts
scanning of images.
The light from the copy lamp is reflected by the document and
passed through the lens to the CCD.
The light from the copy lamp is reflected by the document and
passed through the lens to the CCD.
Photo signal/Electric signal conversion
3) The image is converted into electrical signals by the CCD cir-
cuit and passed to the MCU.
Image process
4) The document image signal sent from the CCD circuit is pro-
cessed under the revised conditions and sent to the LSU
(laser unit) as print data.
(laser unit) as print data.
Electric signal/Photo signal (laser beam) conversion
5) The LSU emits laser beams according to the print data.
(Electrical signals are converted into photo signals.)
6) The laser beams are radiated through the polygon mirror and
various lenses to the OPC drum.
Printing
7) Electrostatic latent images are formed on the OPC drum
according to the laser beams, and the latent images are devel-
oped to be visible images (toner images).
oped to be visible images (toner images).
8) Meanwhile the paper is fed to the image transfer section in
synchronization with the image lead edge.
9) After the transfer of toner images onto the paper, the toner
images are fused to the paper by the fusing section. The cop-
ied paper is discharged onto the exit tray.
ied paper is discharged onto the exit tray.
(Outline of printer operation)
The print data sent from the PC are passed through the NIC PWB
(in case of network connection) and the MCU to the LSU. The pro-
cedures after that are the same as above 5) and later.
(in case of network connection) and the MCU to the LSU. The pro-
cedures after that are the same as above 5) and later.
(Outline of scanner operation)
The scan data are passed through the MCU to the PC according
to the conditions requested by the operations with the operation
panel.
to the conditions requested by the operations with the operation
panel.
Operation
section
Scanner section
CCD
MCU (Main control/image process section)
USB
PC
Laser beam
Paper exit
Fusing section
Paper transport section
Manual paper
feed section
Cassette paper
feed section
Printer section
LSU (Laser unit)
Laser diode, Polygon mirror lens
Laser diode, Polygon mirror lens
Process section
NIC PWB
Network
(print only)
PC
AL-2040 OPERATIONAL DESCRIPTIONS 7 - 2
2. Scanner section
A. Scanner unit
The scanner unit in the digital copier scans images.
It is composed of the optical unit and the drive unit. The optical unit
performs scanning in the main scan direction with the light receiv-
ing elements (color CCD). The drive unit performs scanning in the
sub scanning direction by moving the optical unit.
performs scanning in the main scan direction with the light receiv-
ing elements (color CCD). The drive unit performs scanning in the
sub scanning direction by moving the optical unit.
B. Optical system
Two white lamps are used as the light source.
Light radiated from the light source is applied to the document on
the document table. The reflected light from the document is
reflected 4 times by No. 1 - No. 3 mirrors and passed through the
reduction lens to form images on the light-receiving surface of 3-
line CCD.
the document table. The reflected light from the document is
reflected 4 times by No. 1 - No. 3 mirrors and passed through the
reduction lens to form images on the light-receiving surface of 3-
line CCD.
The light-receiving surface of the color CCD is provided with 3 line
scanning sections for RGB. Separate images scanned in each
color section are overlapped to complete color scanning. (When
PC scanning)
scanning sections for RGB. Separate images scanned in each
color section are overlapped to complete color scanning. (When
PC scanning)
The resolution is 600dpi.
When copying, only the green component is used to print with the
printer.
printer.
The color component for printing can be switched to red or blue by
the service simulation.
the service simulation.
(Spectrum characteristics of the lamp)
(Spectrum characteristics of the color CCD)
(Optical unit)
C. Drive system
The drive system is composed of the scanner motor, the pulley
gear, the idle pulley, the idle gear, the belt 473, the belt 190, and
the shaft.
gear, the idle pulley, the idle gear, the belt 473, the belt 190, and
the shaft.
The motor rotation is converted into reciprocated movements of
the belt 473 through the idle gear, the pulley gear, the belt 190,
and the idle pulley to drive the optical unit.
the belt 473 through the idle gear, the pulley gear, the belt 190,
and the idle pulley to drive the optical unit.
100
75
50
45.4
100.0
50.2
25
380
480
580
680
780
Wavelength [nm]
Sensitivity
1
Table glass
2
Optical unit
3
Lens
4
Mirror 1
5
Mirror 2
6
Mirror 3
7
CCD PWB
8
Lamp
9
Reflector
10
Original
Spectral sensitivity characteristics (Standard characteristics)
Relative sensitivity
Wavelength [nm]
8
9
9
8
10
1
7
5
3
4
2
6
7
9
3
4
6
2
8
5
1
3
1
Scanner motor
2
Pulley gear
3
Idle pulley
4
Belt 473
5
Belt 190
6
Optical unit
7
Shaft
8
Idle gear
9
Table glass
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