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Fusing Section Main Unit Theory of Operation
2-114
II Composition/Operation
16.4.5 Abnormally high temperature detection control
• The temperatures of the Heating Roller and Fusing Pressure Roller are monitored using
the Heating Roller Thermistor (TH1) and Fusing Pressure Roller Thermistor (TH2) while
the machine remains active. If an abnormally high temperature is detected, “abnormally
high temperature 0520/0521” is displayed.
A. Detection start timing
• The Power Switch is turned ON.
B. Detection termination timing
• The Power Switch is turned OFF.
C. Detection conditions
• The temperature detected by the Heating Roller Thermistor (TH1) becomes 230°C or
more.
• The temperature detected by the Heating Roller Thermistor (TH1) is 220°C or more and,
at the same time, the temperature gradient for a 1-sec. period exceeds 11°C.
• The temperature detected by the Fusing Pressure Roller Thermistor (TH2) becomes
196°C or more during a predetermined period of time after a door has been opened or
an error or malfunction has occurred.
• The temperature of the Fusing Pressure Roller (after correction) becomes 220°C or
more.
16.4.6 Open-circuited Heating Roller Thermistor (incorrect installation) detection
control
• The temperature detected by the Heating Roller Thermistor (TH1) during a warm-up
cycle is monitored and, if an abnormal temperature is detected, “warm-up failure 0500” is
displayed.
A. Detection start timing
• At the start of the low temperature start control
• At the start of the warm-up control
B. Detection termination timing
• The temperature detected by the Heating Roller Thermistor (TH1) reaches the control
temperature (warm-up control temperature).
• A predetermined period of time elapses after the start of control.
C. Detection conditions
• The temperature detected by the Heating Roller Thermistor (TH1) increases by less than
3°C for the period of time that begins when the low temperature start control is started
and ends when 2 sec. elapse thereafter.
• The temperature detected by the Heating Roller Thermistor (TH1) increases by less than
7°C for the period of time that begins when the low temperature start control is started
and ends when 3 sec. elapse thereafter.
• The difference between the maximum and minimum temperatures detected by the Heat-
ing Roller Thermistor (TH1) for the 3-sec. period after the warm-up cycle has been
started is less than 5°C.
• The difference between the maximum and minimum temperatures detected by the Heat-
ing Roller Thermistor (TH1) for the 3-sec. period after the warm-up cycle has been
started is 50°C or more.
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