Canon iR C1020 Series, Service Manual

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Chapter 10
10-2
10.2 Various Control Mechanisms
10.2.1 Controlling the Temperature of the Fixing Unit
10.2.1.1 Fixing Temperature Control
0019-5047
The fixing temperature control is to detect the surface temperature of the fixing sleeve and the fixing heater, and to maintain the fixing heater temperature at targeted
value according to the detected results.
The fixing sleeve temperature is monitored by the fixing main thermistor (TH1) and the fixing heater temperature is monitored by the fixing sub thermistor (TH2).
Results are output to the DC controller as the fixing temperature detection signal (MAINTH, SUBTH).
CPU (IC1001) on the DC controller PCB monitors the voltage of the fixing temperature detection signals and outputs the fixing heater drive signal (FSRD) to the
fixing control circuit based on the voltage value.
The fixing control circuit controls the fixing temperature based on the fixing heater drive signal so that the heater can be maintained at the targeted temperature.
F-10-2
The fixing temperature controls are divided into the following 4 types.
Initial rotation temperature control
CPU firstly turns ON the fixing heater for a specified period at power-ON and then, drives the fixing motor.
In a low temperature status such as at initial operation, the fixing sleeve may get damaged when the paper is fed because the grease inside the fixing sleeve is not
yet smooth enough.
This control is to melt the grease inside the fixing sleeve by heating the fixing heater before the fixing motor drives and to lubricate the sleeve in order to prevent
the fixing sleeve from being damaged.
Fixing sub thermistor (TH2) is used to detect the temperature.
Start-up temperature control
CPU heats the fixing heater to the start-up temperature in order to warm the fixing assembly up to the required temperature for fixing.
The start-up temperature varies depending on the elapsed time since previous print completion, paper types, and environments.
Fixing sub thermistor (TH2) is used to detect the temperature.
Print temperature control
CPU maintains the temperature of the fixing sleeve at its targeted temperature during print operation.
CPU gradually switches the target temperature in one printing process depending on the number of print. The targeted temperature varies depending on the paper
types.
The fixing main thermistor (TH1) is used to detect the temperature.
Between-sheets temperature control
At the continuous printing in low-speed mode, the pressure roller may be overheating between sheets.
CPU reduces the temperature of hexing heater below the normal fixing temperature between sheets. The targeted temperature varies according to the between-sheets
intervals and the paper types.
The fixing main thermistor (TH1) is used to detect the temperature.
RL3902
RL3901
Fixing sleeve unit
Fixing main thermistor
: TH1
Fixing heater
safety circuit
Low-voltage
power PCB
Fixing relay PCB
CPU
(IC1001)
DC controller PCB
Fixing sub thermistor
: TH2
FSRD
Fixing unit
MAINTH
SUBTH
FLD+
RLD-
ZEROX
Fixing control circuit
Fixing heater
drive circuit
Relay drive
circuit
Zero crossing
circuit
RLD+
Fixing thermal switch: TP1A
Fixing heater: H1