Electric Circuit Description; Fuser Unit Control Circuit - Toshiba e-STUDIO2330C Service Manual

16.5 Electric Circuit Description

16.5.1

Fuser unit control circuit

[ 1 ] Configuration
In this equipment, 3 heater lamps (center, side, and sub*) which have different heat-generating
positions are installed in the heat roller to heat up the fuser belt. Also, one heater lamp (pressure roller
lamp) is installed in the pressure roller. The fusing temperature is controlled by turning ON/OFF these
heater lamps with the command from the ASIC on the LGC board.
The surface temperature of the fuser belt is detected by a thermistor (fuser belt front thermistor) and 2
thermopiles (fuser belt center and rear thermopiles: non-contact type sensors), and the surface
temperature of the pressure roller is detected by 2 thermistors (pressure roller center and rear
thermistors). And then the information of these temperatures is input to the ASIC through an A/D
converter.
Based on the detected temperature, the ASIC transmits the control signal of the heater lamp to the
drive circuit (TRC: Triac) of each heater lamp on the switching regulator via the heater lamp control
circuit. The power supply to each heater lamp is thus controlled by driving TRC.
The forcible power-OFF circuit detects the overheating of the fuser belt and pressure roller by each
thermistor/thermopile. In case that the surface temperature of the fuser belt or the pressure roller has
exceeded the specified temperature, the forcible power-OFF circuit transmits an overheat detection
signal to the ASIC and the heater lamp control circuit and transmits a reset signal to the relay in the
power supply unit to turn the relay OFF forcibly.
In addition, if these control circuits do not function due to thermistor abnormality or for other reasons
and the fuser belt or the pressure roller is abnormally overheated as the result, 3 thermostats (fuser belt
center and rear thermostats, pressure roller thermostat) shut off the power supply to the heater lamps
to protect the equipment.
*: e-STUDIO4520C only
Fuser unit
Center heater lamp
Side heater lamp
Sub heater lamp (e-STUDIO4520C only)
Fuser belt
front thermistor
Pressure roller thermostat
Pressure roller lamp
Pressure roller
center thermistor
LGC board
A/D
converter
Overheat detection signal
Forcible power-off circuit
e-STUDIO2330C/2820C/2830C/3520C/3530C/4520C
FUSER UNIT / PAPER EXIT SECTION
Fuser belt center Fuser belt rear
thermostat thermostat
Heat roller
Fuser belt Fuser belt
center rear
thermopile thermopile
Pressure roller
Pressure roller
rear thermistor
+5VSW
Heater lamp
ASIC
control circuit
Fig. 16-2
16 - 6
Switching regulator
Relay
Center heater lamp
driving circuit
( TRC1 )
Side heater lamp
driving circuit
( TRC2 )
Sub heater lamp
driving circuit
( TRC4 )
Pressure roller lamp
driving circuit
( TRC3 )
Center heater lamp control signal
Side heater lamp control signal
Sub heater lamp control signal
Pressure roller lamp control signal
Reset signal
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