General Description; Paper Feed Section And Paper Transport Section; Paper Transport Path And General Operations - Sharp AL-2020 Service Manual

A. General description
General block diagram (cross section)
Thermal fuse
Thermistor
Heat roller
Top view
Thermistor
Heat roller
Separator pawl
(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 sep-
arator 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.
To prevent against abnormally high temperature in the fuser
unit, a thermal breaker and thermal fuse are used for safety pur-
poses.
Safety device
(thermal breaker, thermal
fuse)
Triac (in the
power supply unit)
Separator pawl
PPD2
Separator pawl
Pressure roller
Paper guide
Thermal fuse
Heater lamp
Heated by the heater
lamp. (950W)
The surface temperature
of the upper heat roller is
sensed by the thermistor.
Level of the thermistor is
controlled by the main PWB.
With the signal from the
main PWB, the triac is
controlled on and off.
(power supply PWB)
AL-2020/2035/2040/2050/2060 OPERATIONAL DESCRIPTIONS 7 - 4
2) The surface temperature of the upper heat roller is set to 160 -
200°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
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 copy paper, the upper heat roller and the discharg-
ing brush.
5. Paper feed section and paper
transport section
A. Paper transport path and general operations
4 3
14
1 Scanner unit
2 Copy lamp
3 LSU (Laser unit)
4 Paper exit roller
5 Main charger
6 Heat roller
7 Pressure roller
Paper feed is made in two ways; the tray paper feed and the man-
ual 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.
The general descriptions on the tray paper feed and the manual
paper feed operation are given below.
5 2
1
6
7
8
9
10
13 12 11
8 Drum
9 Transfer unit
10 Pickup roller
11 Manual paper feed tray
12 Manual paper feed roller
13 PS roller unit
14 Paper feed roller