Sharp AL-1551 (serv.man4) Service Manual ▷ View online
AL-1551 OPERATIONAL DESCRIPTIONS 7-2
2. Scanner section
A. How to scan documents
The scanner has sensors that are arranged in a line. These sensors
scan a certain area of a document at a time and deliver outputs
scan a certain area of a document at a time and deliver outputs
sequentially. When the line is finished, the next line is scanned, and this
procedure is repeated.
The figure below shows the case where the latter two sections of an
The figure below shows the case where the latter two sections of an
image which are scanned are shown with solid lines and the former two
sections which are being transmitted are shown with dotted lines.
The direction of this line is called "main scanning direction," and the
The direction of this line is called "main scanning direction," and the
scanning direction "sub scanning direction."
In the figure below, one line is divided into 4 sections. Actually, however,
one line is divided into thousands of sections. For scanning, the light
one line is divided into thousands of sections. For scanning, the light
receiving element called CCD is used.
The basic resolution indicates the scanner capacity. The basic resolution
is expressed in dpi (dot/inch) which shows the number of light emitting
is expressed in dpi (dot/inch) which shows the number of light emitting
elements per inch on the document.
The basic resolution of this machine is 400dpi.
In the sub scanning direction, at the same time, the motor that drives the
In the sub scanning direction, at the same time, the motor that drives the
optical system is controlled to scan the image at the basic resolution.
B. Basic structure of scanner section
The scanner unit performs scanning in the digital optical system.
The light from the light source (Xenon lamp) is reflected by a document
The light from the light source (Xenon lamp) is reflected by a document
and passed through three mirrors and reduction lenses to the CCD
element (image sensor) where images are formed. This system is known
as the reduction image sensor system. Photo energy on the CCD
as the reduction image sensor system. Photo energy on the CCD
element is converted into electrical signals (analog signals). (Photo-
electric conversion). The output signals (analog signals) are converted
into digital signals (A/D conversion) and passed to the MCU (main
into digital signals (A/D conversion) and passed to the MCU (main
control/image process section). The resolution at that time is 400dpi.
The mirror unit in the scanner section is driven by the mirror motor.
The MHPS is provided to detect the home position of the copy lamp unit.
The MHPS is provided to detect the home position of the copy lamp unit.
1
2
3
4
5
5
4
3
2
1
Sub scanning direction
Sensor scanning area
Main
scanning
direction
scanning
direction
Original
Image data sent to the ICU PWB
To MCU PWB
1
Copy lamp (Xenon lamp)
2
Reflector
(light conversion plate)
(light conversion plate)
3
No. 1 mirror
4
No. 2 mirror
5
No. 3 mirror
6
Lens
7
No. 2/3 mirror unit
8
Copy lamp unit
9
CCD
10 Mirror motor
11 MHPS
(Mirror home position sensor)
(6)
(5)
(4)
(3)
(2)
(1)
(10)
(11)
(9)
(8)
(7)
( "# $%&'
AL-1551 OPERATIONAL DESCRIPTIONS 7-3
3. Laser unit
The image data sent from the MCU (image process circuit) is sent to the
LSU (laser unit), where it is converted into laser beams.
A. Basic structure
The LSU unit is the writing section of the digital optical system.
The semiconductor laser is used as the light source, and images are
The semiconductor laser is used as the light source, and images are
formed on the OPC drum by the polygon mirror and f
θ
lens, etc.
The laser beams are passed through the collimator lens, the cylindrical
lens, the polygon mirror, the f
lens, the polygon mirror, the f
θ
lens, and the mirror to form images on the
OPC drum in the main scanning direction. The laser emitting PWB is
provided with the APC (auto power control) in order to eliminate
fluctuations in the laser power. The BF PWB works for measurement of
fluctuations in the laser power. The BF PWB works for measurement of
the laser writing start point.
Makes the laser scanning speeds at both ends of the drum same as
each other.
each other.
B. Laser beam path
C. Composition
Effective scanning width:216mm (max.)
Resolution:600dpi
Beam diameter: 75um in the main scanning direction, 80um in the sub
scanning direction
scanning direction
Image surface power:0.20 ±0.03mW (Laser wavelength 780 - 795nm)
Polygon motor section:Brushless motor 20.787rpm
No. of mirror surfaces:6 surfaces
No. of mirror surfaces:6 surfaces
4. Fuser section
No
Component
Function
(1) Semiconductor laser
Generates laser beams.
(2) Collimator lens
Converges laser beams in parallel.
(3) Polygon mirror,
polygon motor
Reflects laser beams at a constant rpm.
(4) BD (Mirror, lens, PWB) Detects start timing of laser scanning.
(5) f
θ
lens
Converges laser beams at a spot on the
drum.
drum.
Makes the laser scanning speeds at both
ends of the drum same as each other.
(Refer to the figure below.)
ends of the drum same as each other.
(Refer to the figure below.)
(1)
(2)
(3)
(4)
(5)
: Laser beam
path for BF PWB
a
≠ b ≠ c
a
b
c
d = e = f
d
e
f
f
θ
LENS
) "# $%&'
AL-1551 OPERATIONAL DESCRIPTIONS 7-4
A. General description
General block diagram (cross section)
Top view
(1) Heat roller
A teflon roller is used for the heat roller and a silicone rubber roller is
used for the lower heat roller for better toner fusing performance and
paper separation.
(2) Separator pawl
Three separator pawls are used on the upper heat roller. The separator
pawls are teflon coated to reduce friction with the roller and prevent a
pawls are teflon coated to reduce friction with the roller and prevent a
smear on the paper caused by the separator pawl.
(3) Thermal control
1) The heater lamp, thermistor, main PWB, DC power supply PWB, and
triac within the power supply unit are used to control the temperature
in the fuser unit.
in the fuser unit.
To prevent against abnormally high temperature in the fuser unit, a
thermal breaker and thermal fuse are used for safety purposes.
2) The surface temperature of the upper heat roller is set to 165 -
190°C. The surface temperature during the power save mode is set
to 100°C.
3) The self-check function comes active when one of the following
malfunctions occurs, and an "H" is displayed on the multicopy
window.
a. When the heat roller surface temperature rises above 240°C.
b. When the heat roller surface temperature drops below 100°C during
the copy cycle.
c. Open thermistor
d. Open thermal fuse
e. When the heat roller temperature does not reach 190°C within 27
second after supplying the power.
(4) Fusing resistor
Fusing resistor
This model is provided with a fusing resistor in the fusing section to
improve transfer efficiency.
Since the upper heat roller is conductive, when using copy paper that
contains moisture and the distance between the transfer unit and the
fusing unit is short, the transfer current may find a path to ground via the
fusing unit is short, the transfer current may find a path to ground via the
copy paper, the upper heat roller and the discharging brush.
Separator pawl
PPD2
Thermal fuse
Thermistor
Heat roller
Paper guide
Pressure roller
Heat roller
Thermistor
Thermal fuse
Heater lamp
Separator pawl
Saftey device
(Thermal breaker, thermal
fuse)
(Thermal breaker, thermal
fuse)
Triac (in the
power supply unit)
Level o f the thermisto r is
con trolled by the main PWB.
con trolled by the main PWB.
With th e signal from the
main PWB , the triac is
main PWB , the triac is
con trolled on and o ff.
(power supply PWB )
Heated by the heater
lamp.(950W)
lamp.(950W)
The surface temperature
of the upper heat roller is
sensed by the thermistor.
of the upper heat roller is
sensed by the thermistor.
* "# $%&'
AL-1551 OPERATIONAL DESCRIPTIONS 7-5
5. Paper feed section and paper transport
section
A. Paper transport path and general operations
Paper feed is made in two ways; the tray paper feed and the manual
paper feed. The tray is of universal-type, and has the capacity of 250
paper feed. The tray is of universal-type, and has the capacity of 250
sheets.
The front loading system allows you to install or remove the tray from the
front cabinet.
front cabinet.
The general descriptions on the tray paper feed and the manual paper
feed operation are given below.
(1) Cassette paper feed operation
1) The figure below shows the positions of the pick-up roller, the paper
feed clutch sleeve, and the paper feed latch in the initial state without
pressing the COPY button after lighting the ready lamp.
The paper feed latch is in contact with the projection of the clutch
The paper feed latch is in contact with the projection of the clutch
sleeve.
2) When the COPY button is pressed, the main drive motor starts
rotating to drive each drive gear.
The pick-up drive gear also is driven at that time. Since, however, the
paper feed latch is in contact with the projection of the clutch sleeve,
rotation of the drive gear is not transmitted to the pick-up roller, which
rotation of the drive gear is not transmitted to the pick-up roller, which
does not rotate therefore.
3) After about 0.1 sec from when the main motor start rotating, the tray
paper feed solenoid (PFS) turns on for a moment.
This disengages the paper feed latch from the projection of the
clutch sleeve, transmitting rotation of the pick-up drive gear to the
clutch sleeve, transmitting rotation of the pick-up drive gear to the
paper feed roller shaft, rotating the pick-up roller to feed the paper.
4) After more than half rotation of the pick-up roller, the paper feed latch
is brought in contact with a notch on the clutch sleeve, stopping
rotation of the pick-up roller.
(1)
Scanner unit
(9)
Drum
(2)
Copy lamp
(10)
Transfer unit
(3)
Lens unit
(11)
Pickup roller
(4)
LSU (Laser unit)
(12)
Manual paper feed tray
(5)
Paper exit roller
(13)
Manual paper feed roller
(6)
Main charger
(14)
PS roller unit
(7)
Heat roller
(15)
Paper feed roller
(8)
Pressure roller
(2)
(4)
(1)
(3)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(13)
(12)
(14)
(15)
OFF
PFS
OFF
RRS
OFF
PFS
OFF
RRS
+ "# $%&'
Click on the first or last page to see other AL-1551 (serv.man4) service manuals if exist.