HP Color LaserJet CM2320 - Multifunction Printer - Page 102

Fuser protective function
The protective function detects an abnormal temperature rise of the fuser and interrupts power supply
to the fuser heater. The following protective components prevent an abnormal temperature rise of the
fuser heater.
●
DC controller: The DC controller monitors the detected temperature of the thermistors. It
deactivates the fuser heater control signal and releases the relay to interrupt the power supply to
the fuser heater under the following conditions.
◦
Main thermistor: 253°C (487.4°F) or higher
◦
Sub thermistor 1: 273°C (523.4°F) or higher
◦
Sub thermistor 2: 273°C (523.4°F) or higher
●
Fuser heater safety circuit: The fuser heater safety circuit monitors the detected temperature of
the thermistors. It releases the relay to interrupt the power supply to the fuser heater under the
following conditions.
◦
Main thermistor: 320°C (608°F) or higher
◦
Sub thermistor 1: 295°C (563°F) or higher
◦
Sub thermistor 2: 295°C (563°F) or higher
●
Thermal fuse: The thermal fuse blows to interrupt power supply to the fuser heater if the thermal
fuse temperature reaches 228°C (442°F) or higher.
Fuser failure detection
The DC controller determines a fuser unit failure, deactivates the fuser heater control signal, releases
the relay to interrupt power supply to the fuser heater, and then notifies the formatter of a failure state
when it encounters the following conditions.
●
Start-up failure conditions
◦
The main thermistor temperature does not reach 50°C (122°F) within a specified period of
heater startup during the wait period.
◦
The main thermistor temperature does not reach the targeted temperature within a specified
period after the temperature once reaches 50°C (122°F) from the heater startup during the
wait period.
◦
The main thermistor temperature does not reach the targeted temperature within a specified
period under the heater temperature control during the initial rotation period.
●
Abnormal low temperature conditions
◦
The main thermistor temperature remains at 100°C (212°F) or lower for a specified period
under the heater temperature control during the print period.
90 Chapter 5 Theory of operation ENWW