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FUSER UNIT
13 - 3
(9) Fuser roller front thermistor (THM1)
This thermistor cannot be used for the temperature control of the fuser roller. It detects a
temperature abnormality at the side area of the fuser roller where the paper does not pass
through.
(10) Fuser roller center thermostat (THMO1) and Fuser roller side thermostat (THMO2)
These thermostats cut off the power supply to the IH coil (IH-COIL) when the fuser roller
becomes abnormally hot as the result of a problem such as a thermistors (THM1, 2 and 3)
malfunction. The thermostats (THMO1 and 2) of this equipment are used to prevent abnormal
operation, and when any abnormality is detected, they must be replaced altogether with the other
damaged parts of the fuser unit.
13.4 Fuser Control Circuit
13.4.1
Configuration
A forcible power OFF circuit is embedded in this equipment. This circuit detects the overheating of the
fuser unit with the thermistors installed on it. When the surface temperature of either the fuser roller or
the pressure roller has exceeded the specified value, the circuit sends the relay ON signal in order to
shut off the power supply throughout the unit.
Fig. 13-2
N
L
IH board
LGC board
+5VB
+5VSW
Temperature
control circuit
Coil output
Fuse
AC input
Noise
filter
Breaker
Power cable
IH power source / drive circuit
Control circuit
including CPU
Photocoupler
AC line
DC line
Power supply for photocoupler
Switching signal of power setting
Duty ratio changing signal
IH status signal
IH coil energization permitting signal
Main CPU
ASIC
IH coil
Fuser roller
Pressure
roller
Center
thermistor
Center thermostat
Side thermostat
Rear thermistor
Front thermistor
Pressure roller thermistor
Switching regulator
+5VSW
Relay
+5VSW