Fuser Section - Sharp AL-1000 Service Manual

AL-1000/1010

Fuser section

1. General description
General block diagram (cross section)
Thermal fuse
Thermistor
Heat roller
Top view
Thermistor
Heat roller
Separator pawl
A. Heat roller
A pressure roller is used for the heat roller and a silicone rubber
roller is used for the lower heat roller for better toner fusing per-
formance and paper separation.
Separator pawl
PPD2
Pressure roller
Paper guide
Thermal fuse
Heater lamp
B. 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 smear on the paper caused by the
separator pawl.
C. 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
purposes.
Safety device
(thermal breaker, thermal
fuse)
Triac (in the
power supply unit)
2. The surface temperature of the upper heat roller is set to
165˚C ∼ 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 fol-
lowing 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.
D. Fusing resistor
Fusing resistor
This model is provided with a fusing resistor in the fusing sec-
tion to improve transfer efficiency.
General descriptions are made in the following.
General descriptions
Since the upper heat roller is conductive when copy paper is
highly moistured and the distance between the transfer unit and
the fusing unit is short, the transfer current leaks through the
copy paper, the upper heat roller and the discharging brush.
7-4
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)