Protective Functions; Outline; Failure Detection - Canon ImageRUNNER 1022iF Service Manual

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3hole punch paper

*1: Target fixing temperature at startup. When the initial temperature of the fixing unit is high, the target temperature is lowered. In the continuous copy mode, the

target temperature is lowered.

*2: Number of sheets controlled at the initial target temperature. If it is exceeded, the target temperature is lowered. The prescribed number of sheets varies with

the paper size.

8.3 Protective Functions

8.3.1 Outline

/ / / / iR1018 / iR1018J / / iR1022A / iR1022F / iR1022i / iR1022iF /

This circuit is installed on the DC controller PCB. It is used to monitor abnormal rise of the fixing temperature at all times. If the main thermistor's output voltage

is held below about 0.78 V (about 235 deg C or higher) for at least 1 second or the sub-thermistor's output voltage is held blow about 0.39 V for 0.15 seconds or

longer due to the rise in the fixing heater temperature, the relay is turned off and the fixing heater is turned off irrespective of the relay drive signal (RLYD).

If the temperature of the fixing heater increases abnormally, on the other hand, to exceed about 228 deg c, the temperature fuse will melt to cut the power to the

fixing heater.

8.3.2 Failure Detection

/ / / / iR1018 / iR1018J / / iR1022A / iR1022F / iR1022i / iR1022iF /

The CPU on the DC controller PCB will identify a fault in the fixing assembly if any of the following conditions (a through d) occurs; as a result,

- it will cut the power to the fixing heater.

- it will cause the relay drive signal (RYLD) to go '1' to turn off the relay and, at the same time, will communicate the presence of a fault to the image processor PCB.

a. Detection of thtermistor short circuit (excessively high temperature)

This failure is detected when the main thermistor has continuously detected a temperature equal to or higher than 235 deg C for 1 second or longer during temper-

ature control.

This failure is detected when the sub-thermistor has continuously detected a temperature equal to or higher than 300 deg C for 0.15 second or longer during tem-

perature control.

b. Detection of open thermistor (excessively low temperature)

This failure is detected when the main thermistor has continuously detected a temperature lower than 20 deg C for 0.5 second or longer during temperature control.

This failure is detected when the sub thermistor has continuously detected a temperature lower than 35 deg C for 0.15 second or longer after the end of start up.

This failure is detected when the sub-thermistor cannot detect a temperature equal to or higher than 75deg C even if 2.29 to 20 seconds have lapsed since start of

power supply to the fixing heater.

c. Detection of Drive circuit failure (zero-cross error)

This failure is detected when the number (cycle) of zero-cross inputs that have been counted every second has been outside the range (45-65 Hz) twice.

d. Detection of startup failure

This failure is detected when the main thermistor has detected a temperature lower than 45 deg C 2.29 seconds after start of power supply to the fixing heater.

This failure is also detected when the main thermistor temperature is lower than 150 deg C and the rise in the main temperature per second is less than 12 deg C or

Cassette

Manual

Duplex

Fixing mode

pickup

feed tray

pickup

Yes

Heavy paper

Yes

Plain

Power supply PCB