Develop QC 2235 Plus Service Manual page 109

QC 2235plus Theory of Operation Ver.1.0 Mar. 2004
D. Power Save
• Temperature control is provided with a decreased fusing temperature so that power con-
sumption in the standby state can be minimized.
Mode Heating Roller Set Temperature (°C)
Power Save
16.3.4 Protection against abnormal conditions
• The machine provides protection against abnormally high temperature of the Fusing Unit
in the following three steps.
1. When the Heating Roller Thermistor/1 detects 230 °C, or the Fusing Pressure Roller
Thermistor detects 190°C (before the temperature control) or 220°C (during the tem-
perature control), the machine displays the malfunction code representing an abnor-
mally high temperature and inhibits the initiation of a new copy cycle. (This is an
ordinary detection of a malfunction of an abnormally high temperature.)
2. A different protection is provided when the CPU overruns, becoming unable to detect
the malfunction of an abnormally high temperature. If the Heating Roller Thermistor/1,2
detects 235 °C, or the Fusing Pressure Roller Thermistor detects 167°C (before the
temperature control) or 220°C (during the temperature control), the heater relay of the
DC Power Supply is turned OFF through the Control Board and the power supply to
each of the heater lamps is shut down. If the detected temperature thereafter
decreases, the heater relay is turned ON again and supply of power to the heater
lamps is resumed. The sequence of these operations is repeated until the CPU recov-
ers from the overrun and becomes able to detect the malfunction of an abnormally high
temperature. This control allows the power supply to each of the heater lamps to be
shut down before the corresponding thermostat operates. It thereby suppresses dam-
age to the Fusing Unit itself.
3. If detection of the abnormally high temperature through approaches 1 and 2 above is
not possible due to a defective thermistor or other reason, the thermostat comes into
play to shut down the power supply to each of the heater lamps. The Heating Roller
Thermostat is rated at 210 °C, while the Fusing Pressure Roller Thermostat is rated at
180 °C. The ratings do not, however, represent the actual surface temperature of the
corresponding rollers, since the thermostats are installed in a non-contact fashion with
respect to each of the rollers. (Ordinary protection against high temperatures)
Pressure Roller Set Temperature (°C)
160
2-79
Fusing section
150