Confidential
3-34
(3) Control of the Fusing Temperature
Each roller of the fusing unit is controlled to maintain the appropriate temperature so that
toner will be fixed correctly onto the print paper.
<Basic Structure of Temperature Control (Fig.3-35)>
FLS: Thyristor to control the on/off operation of power supply to the
heat lamp.
THS1 / THS2: Thermostat to shut down the circuit for safety when it will be too
hot within the fusing unit FU.
TH: Temperature sensor to detect the surface temperature of the heat
roller (HR).
RY: Relay to prevent the further heating when it will be hotter than
the set point within the fusing unit FU.
GA/CPU: Process circuit to process the temperature signal
(micro computer).
CM1: Sensor circuit for temperature signal (for ACOFF signal).
CM2: Sensor circuit for temperature signal (for HON signal).
CM3: Sensor circuit for temperature signal (for processing).
Q: Sensor circuit for shut-down by the thermistor
(for THERR signal).
HR: Back-up roller.
<Signal Functions>
HON-N: To turn on/off the heater in side the fusing roller.
ACOFF: To turn off the relay RY1 when it is sensed too hot.
THERR: To detect the shut-down by the thermistor.
AD: To convert the temperature sensing signal to AD.
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