Sharp AM-300 (serv.man7) Service Manual ▷ View online
AM-300DE
3 – 10
8. Print process
8.1. Image forming process
Normal paper is used as print paper. A laser beam is used to expose
on the OPC surface to form latent electrostatic images, which are
developed into visible images (toner images) and are transferred on
paper. The basic operation is composed of the five processes: charg-
ing, exposure, development, transfer, and cleaning.
on the OPC surface to form latent electrostatic images, which are
developed into visible images (toner images) and are transferred on
paper. The basic operation is composed of the five processes: charg-
ing, exposure, development, transfer, and cleaning.
8.2. System diagram (1)
8.3. System diagram (2)
Fig. 7
Main
charger
brush
charger
brush
Separation
electrode
electrode
Transfer
charge
roller
charge
roller
Developing roller
Supply roller
Photoconductor
drum (OPC)
drum (OPC)
Laser Scanning Unit
Laser
beam
beam
DC: +3600V (D6 Cathode)
DC: -950V
AC: -570V <--> -1330V
DC: -500V
DC: +400V
DC: -280V
Paper
Toner
MC
TC
SV
DV
DC: -220V
Heat roller
Pressure roller
Heater lamp
FU-EARTH
Print
print
Cleaning
cleaning
Paper
100MOHM
100V
4.7MOH M 4.7MOHM
Transfer Charger
Roller Voltage
Roller Voltage
Development
Roller
Voltage
Roller
Voltage
Main Charger
brush Voltage
brush Voltage
High Voltage Power Supply Unit
Supply
Roller
Voltage
Roller
Voltage
CONTROL PWB
16bit CPU
IC21
IC21
57
56
TCON
MCON
PWMSIN
Constant
voltage
control
circuit
voltage
control
circuit
PWM
control
circuit
control
circuit
Logic
circuit
circuit
Oscillation
circuit
circuit
B51
Transformer
Transformer
High Voltage PWB Unit
Constant
voltage
control
circuit
voltage
control
circuit
Oscillation
circuit
circuit
Feedback circuit
Feedback circuit
B1
Transformer
Transformer
HV(+)
Rectifier
circuit
Rectifier
circuit
HV(-)
Rectifier
circuit
Rectifier
circuit
HV(-)
Rectifier
circuit
Rectifier
circuit
Constant
voltage(+)
circuit
voltage(+)
circuit
Constant
voltage(-)
circuit
voltage(-)
circuit
Short
circuit
circuit
Short
protection
circuit
protection
circuit
SV
DV
MC
TC
110M
Ω
250M
Ω
FU-EARTH
LASER MFP
Transfer Roller
Supply Roller
Developing Roller
Charger Roller
Heat Roller
Pressure Roller
Doctor
OPC DRUM
Separation electrode
Fig. 8
AM-300DE
3 – 11
8.4. Image forming process diagram
Main charger
brush
Scanning
mirror
Mirror
Lens
Laser diode
Toner
Paper exit
Fusing
Heater lamp
Separation
electrode
Separation
Transfer
Transfer roller
High voltage circuit
Paper feed roller
Paper tray
Paper
High voltage
circuit
Cleaning, Charge
Exposure
Development
cleaning
Developing
roller
High voltage
circuit
Heat roller
Pressure roller
Fig. 9
AM-300DE
3 – 12
8.5. Functions and operations of major parts
8.5.1 OPC drum unit
The OPC drum is charged and latent electrostatic images are formed
on it and developed into visible toner images.
on it and developed into visible toner images.
a. OPC drum
Latent electrostatic images are formed and developed into toner
images on the OPC drum.
images on the OPC drum.
Organic Photo Conductor is used. The OPC surface is charged nega-
tively by the main charger brush.
tively by the main charger brush.
When the OPC is exposed to laser beam, the electric resistance of the
exposed section falls and electric charge is generated in the OPC. As
a result, electric charge on the OPC surface is removed. This principle
is used to form latent electrostatic images.
exposed section falls and electric charge is generated in the OPC. As
a result, electric charge on the OPC surface is removed. This principle
is used to form latent electrostatic images.
b. Main charger brush
The main charger brush charges the OPC drum surface. It is com-
posed of brush fiber, and is in the shape of a roller. A high voltage of
AC 760V (P-P) and DC-950V are applied to charge the brush.
posed of brush fiber, and is in the shape of a roller. A high voltage of
AC 760V (P-P) and DC-950V are applied to charge the brush.
The main charger brush is in contact with the OPC drum. BY applying
electric charge to the OPC drum, the OPC drum is charged to about
DC-900V.
electric charge to the OPC drum, the OPC drum is charged to about
DC-900V.
8.5.2 Developing unit
Latent electrostatic images formed by laser beam on the OPC drum
are developed to visible images by the developing unit. Toner is filled
in the developing unit.
are developed to visible images by the developing unit. Toner is filled
in the developing unit.
a. Developing roller
The developing roller is made of urethane and has a high electric
resistance. It is flexible and is in close contact with the OPC drum.
Toner on the developing roller is attached to latent electrostatic images
on the OPC drum to form visible images on the OPC drum.
resistance. It is flexible and is in close contact with the OPC drum.
Toner on the developing roller is attached to latent electrostatic images
on the OPC drum to form visible images on the OPC drum.
A voltage of DC-220V is applied the developing roller.
b. Doctor
The doctor is in close contact with the developing roller. It adjusts toner
quantity on the developer roller surface.
quantity on the developer roller surface.
The doctor is made of conductive material.
c. Toner supply roller
Toner is supplied to the developing roller by the sponge roller which is
connected to the developing roller.
connected to the developing roller.
d. Toner stirring plate
This plate stirs toner in the developing unit to transport it to the devel-
oping roller smoothly.
oping roller smoothly.
8.5.3 Transfer charger roller
The transfer charger roller is made of urethane and has a high electric
resistance. It is flexible and is in close contact with the OPC drum.
resistance. It is flexible and is in close contact with the OPC drum.
A high voltage of AC 760V (P-P) and DC +3600V are applied to
charge.
charge.
It positively charges paper transported from the paper feed section,
which transfers negatively charged toner on the OPC drum onto the
paper.
which transfers negatively charged toner on the OPC drum onto the
paper.
8.5.4 Separation electrode
This electrode is connected to the drum ground. It discharges paper
which was positively charged in the transfer section to reduce the
potential difference with the OPC drum to reduce static electricity
between the paper and the OPC drum, thus facilitating separation of
paper.
which was positively charged in the transfer section to reduce the
potential difference with the OPC drum to reduce static electricity
between the paper and the OPC drum, thus facilitating separation of
paper.
Fig. 10
1
Developing roller
6
Separation electrode
2
Doctor
7
OPC drum
3
Toner stirring plate
8
Discharge plate
4
Toner supply roller
9
Main charger brush
5
Transfer roller
Fig. 11
2
4
1
7
5
6
3
Optical unit(LSU)
Paper
Toner
9
8
OPC layer
CTL (Charge transfer layer)
Aluminum layer
CGL (Charge generation layer)
AM-300DE
3 – 13
8.6. Image forming operation
The main charger is a rotating brush roller.
The main charger removes residual toner from the OPC drum by its
rotating sweeping action and causes it to stick to the brush.
rotating sweeping action and causes it to stick to the brush.
At the same time, a high voltage of -950V is applied to the main
charger roller to generate a discharge of electricity between the roller
and the OPC drum, generating positive and negative charges. The
negative charges are attracted to the OPC drum, and evenly distrib-
uted on the OPC drum. (The OPC drum surface is evenly charged.)
charger roller to generate a discharge of electricity between the roller
and the OPC drum, generating positive and negative charges. The
negative charges are attracted to the OPC drum, and evenly distrib-
uted on the OPC drum. (The OPC drum surface is evenly charged.)
Positive and negative charges are generated in the OPC drum CGL
exposed with the laser beam.
exposed with the laser beam.
Positive charges generated in the CGL are attracted toward the OPC
drum surface (negative charges), and negative charges toward the
aluminum layer (positive charges).
drum surface (negative charges), and negative charges toward the
aluminum layer (positive charges).
Therefore, the positive and negative charges neutralize each other in
the laser-exposed area of the OPC drum surface and the aluminum
layer, decreasing the potential of the OPC drum surface.
the laser-exposed area of the OPC drum surface and the aluminum
layer, decreasing the potential of the OPC drum surface.
The area which is not exposed to laser beam has no change, and the
OPC drum surface remains negatively charged to keep a high poten-
tial. As a result, latent electrostatic images are formed on the OPC
drum.
OPC drum surface remains negatively charged to keep a high poten-
tial. As a result, latent electrostatic images are formed on the OPC
drum.
STEP 1 (Cleaning, Charg-
ing):
ing):
Residual toner the OPC drum is
stirred and negative charges are
scattered evenly on the OPC
drum. (The OPC drum surface is
evenly charged.)
stirred and negative charges are
scattered evenly on the OPC
drum. (The OPC drum surface is
evenly charged.)
Fig. 12
AC760V
(P-P)
(P-P)
DC-950V
Main
charger
brush
charger
brush
Residual
toner
toner
CTL
CGL
OPC drum
Aluminum layer (drum base)
STEP 2 (Exposure): Laser beam scanning light corresponding to
the print data is radiated on the OPC drum.
Fig. 13
CTL
CGL
CTL
CGL
Non-exposed area
Laser beam
Exposed area
Aluminum layer
(Drum base)
(Drum base)
Aluminum layer
(Drum base)
(Drum base)
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