Canon CLBP-460PS, Руководство по обслуживанию

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a. If the D-CPU detects a fixing heater failure
If the fixing unit is heated excessively or does not reach the prescribed temperature for some
reason or other, the D-CPU deactivates the relay to interrupt the power to the heater and stops
sending the signal that drives the fixing heater.
The DC controller notifies the video controller of the fixing unit failure.
The D-CPU assumes a fixing heater failure when the fixing unit temperature is as follows:
1) Abnormal low temperature
The fixing unit temperature reaches the target value, then becomes 120°C or less. (Open
thermistor or a broken fixing heater wire)
2) Abnormal high temperature
The fixing unit temperature exceeds 215°C during standby or printing. (Thermistor short)
3) Warmup error
The following occurs after the fixing heater drive starts. (Open thermistor or thermistor error)
• The temperature does not reach 40°C within 130 seconds after the fixing unit drive starts.
• The temperature does not reach 60°C within 80 seconds after it reaches 40°C.
• The temperature does not reach 80°C within 80 seconds after it reaches 60°C.
• The temperature does not reach 100°C within 80 seconds after it reaches 80°C.
• The temperature does not reach 120°C within 80 seconds after it reaches 100°C.
• The temperature does not reach 140°C within 80 seconds after it reaches 120°C.
• The temperature does not reach 160°C within 100 seconds after it reaches 140°C.
4) Thermistor broken wire
The thermistor broken wire is assessed, if the following occurs when the fixing unit temper-
ature is lower than 60°C in the initial condition after power-ON.
When the thermistor sensitivity (note) is on the low temperature side, the fixing unit tem-
perature is -5°C or less
The fixing unit temperature when the thermistor sensitivity is on the low temperature side
is the same as the fixing unit temperature when the thermistor sensitivity is on the high tem-
perature side. (Open thermistor or thermistor abnormality)
Note: Thermistor sensitivity switching
To maintain the precision of thermistor detection regardless of the low and high tem-
perature areas, the D-CPU uses the THERMISTOR SENSITIVITY SWITCHING signal
(THSEL signal) to switch the thermistor sensitivity between the mode in which the low-
temperature detection precision is high and the mode in which the high-temperature
detection precision is high. If the THSEL signal is “L”, the thermistor is in the low-tem-
perature detection mode, and if it is “H”, the thermistor is in the high-temperature detec-
tion mode.
b. If the fixing heater safety circuit detects an upper or lower fixing heater failure
The safety circuit in the power supply unit cuts the power to the upper and lower fixing heaters
if the fixing temperature rises abnormally.
This circuit operates as follows (see fig.2-2-12):
The fixing heater safety circuit in the power supply unit monitors the FIXING UNIT TEM-
PERATURE DETECTION signal (THI) input to pin 14. THI is generated from the UPPER FIXING
ROLLER TEMPERATURE DETECTION signal (THRU) and the LOWER FIXING ROLLER TEM-
PERATURE DETECTION signal (THRL). If the output voltage from the thermistor reaches about
1.4 V due to a fixing temperature rise, the fixing heater safety circuit makes the No.5 pin out-
put “L” and turns the relay (RL101) OFF. This turns the upper and lower fixing heaters OFF.
To reset this circuit, turn the power OFF, allow 30 minutes or more, then turn the power ON
again.
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CHAPTER 2