Fuser Unit Control Circuit; Configuration - Toshiba e-STUDIO182 Service Manual

12.5 Fuser Unit Control Circuit

12.5.1

Configuration

In this equipment, the surface temperature of the fuser roller is controlled by turning ON/OFF 2 heater
lamps (center and side) which have different heat-generating positions with the command from the SoC
on the MAIN board. The surface temperature of the fuser roller is detected by 3 thermistors (center,
side and edge) and then the information of the temperature is transmitted to the SoC and each control
circuit. Based on the detected temperature, the SoC transmits the control signal of the heater lamp to
the control circuit (TRC: Triac) of each heater lamp on the switching regulator. The power supply to
each fuser roller is thus controlled by driving TRC. The SoC detects the overheating of the fuser roller.
In case that the surface temperature of the fuser roller has exceeded the specified temperature, the
SoC turns the heater lamp OFF.
If the SoC does not function for some reason and the fuser roller is abnormally overheated as the
result, a forcible power-OFF circuit transmits a relay-OFF signal to the switching regulator to shut off the
power supply to the heater lamp by opening the relay. In addition, if these control circuits do not
function with thermistor abnormality or other reasons and the fuser roller is abnormally overheated as
the result, thermostat shut off the power supply to the heater lamps to protect the equipment.
Fuser unit
Fuser thermostat
Front
Fuser roller
Center heater lamp
Side heater lamp
Center Side
thermistor thermistor
A/D
converter
e-STUDIO182/212/242
FUSER / EXIT UNIT
Switching regulator
Rear
Center heater lamp
control circuit
Side heater lamp
control circuit
Edge
thermistor
Center heater lamp
control signal
SoC
Side heater lamp
control signal
Relay-OFF signal
Forcible power-off
circuit
Fig. 12-2
12 - 6
Noise
( TRC1 )
( TRC2 )
Relay
MAIN board
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L
N
filter
Main switch
AC line
DC line