Page 20 - MF3010Series Service Manual (Rev.0) (1)-017-045 (1)

2 Technical Overview > Fixing System > Various Control Mechanisms > Protective Functions
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2) Protection function by fixing heater safety circuit 6) Startup failure detection
Fixing Heater (H1) safety circuit monitors the Thermistor (TH1) temperature consistently. If temperature of the Fixing Assembly is 100 deg C or higher when the machine becomes in
When Thermistor (TH1) reaches approx 235 deg C, it determines that the Fixing Heater (H1) pickup enabled state after entering fixing low voltage inlet sequence, it is judged as startup
is overheating and the fixing heater safety circuit turns OFF the relay drive circuit to shut failure.
the power supply to the Fixing Heater (H1).
7) Thermistor high temperature detection 2
3) Protection function by Temperature Fuse (TP1) Temperature of the Thermistor (TH1) is monitored every 200 msec during Fixing Assembly
When the Fixing Heater (H1) temperature rises abnormally and Temperature Fuse (TP1) control. If the temperature is equal or higher than "detection temperature of Thermistor high
temperature reaches approx 226 deg C, Temperature Fuse (TP1) opens to shut the power temperature detection 2", increase the value of "high temperature detection counter" by 1
supply to the Fixing Heater (H1). (+1). If not, decrease the value by 1 (-1). When the value of "high temperature detection
counter" becomes +50, it is judged as a Thermistor high temperature failure. The default
● Failure detection and minimum value of "high temperature detection counter" is 0.
With this machine, 10 types of failure detection are available. The "detection temperature of the Thermistor high temperature detection 2" is set to 195

1) Initial startup failure detection deg C when the target control temperature is 180 deg C or less. When the target control
When temperature of the Fixing Assembly does not exceed 50 deg C within 1.48 sec after temperature is above 180 deg C, it is set to "target control temperature + approx. 15 deg
the start of temperature control performed at initial rotation, it is judged as initial startup C".
failure. 8) Thermistor low temperature detection 2)
2) Initial Thermistor open detection Temperature of the Thermistor (TH1) is monitored for every 200 msec when paper is at
When temperature of the Fixing Assembly does not exceed 35 deg C within 1.48 sec after fixing nip during the Fixing Assembly control. When the temperature is lower than 135 deg
the start of temperature control at warm-up rotation temperature control or at cleaning C (120 deg C), increase the value of low temperature detection counter by 1 (+1). When
mode, it is judged as Thermistor open failure. it is 135 deg C (120 deg C) or higher, decrease the value by 1 (-1). When the value of low
temperature counter becomes +150, it is judged as Thermistor low temperature failure. The
3) Short circuit of Thermistor/abnormal high temperature detection default and minimum value of low temperature detection counter is 0.
When temperature of the Fixing Assembly is 220 deg C or higher for 30 consecutive times
by monitoring the temperature for every 5 msec, it is judged as Thermistor short circuit 9) Frequency detection circuit error (230V models only)
failure. In addition, this function also doubles as abnormal high temperature detection When frequency measurement is not completed within 3255 msec after the completion of
function of the Fixing Assembly. previous frequency measurement, it is judged as frequency detection circuit error.
4) Abnormal low temperature detection 10) Thermistor high temperature detection 3
After temperature of the Fixing Assembly exceeds 50 deg C at least once, monitor Temperature of the Thermistor (TH1) is monitored every 5 msec, and if the temperature
temperature of the Thermistor (TH1) for every 5 msec. It is judged as heater abnormal is equal or higher than "detection temperature of Thermistor high temperature detection
low temperature when the following condition is detected 240 consecutive times: the 2 + approx. 15 deg C" more than 30 consecutive times, it is judged as a Thermistor high
temperature is 100 deg C or lower while paper is at fixing nip, or it is 55 deg C or lower temperature failure.
during paper interval temperature control or at cleaning mode.

5) Thermistor open detection
After temperature of the Fixing Assembly exceeds 50 deg C, monitor temperature of the
Thermistor (TH1) for every 5 msec. When it is detected that the temperature is lower than
20 deg C for 6 consecutive times, it is judged as Thermistor open failure.

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2 Technical Overview > Fixing System > Various Control Mechanisms > Protective Functions