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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 separator
pawls are teflon coated to reduce friction with the roller and prevent a
smear on the paper caused by the separator pawl.
Separator pawl
PPD2
Pressure roller
Paper guide
Thermal fuse
Heater lamp
AL-1551 OPERATIONAL DESCRIPTIONS 7-4
(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 purposes.
Saftey device
(Thermal breaker, thermal
fuse)
Triac (in the
power supply unit)
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
copy paper, the upper heat roller and the discharging brush.
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 th e signal f r om the
main PWB, the triac is
controlled on and o ff.
(power supply PWB )
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