Canon MF720 Series Service Manual page 50

NOTE:
• With MF8200 series, this control is not executed since detection of temperature by the Sub Thermistor is not performed.
• Tempreture of Sub Thermistor: T1 < T2 < T3 < T4
● Reduction of Throughput by Feeding Small Size Paper
NOTE:
When paper size is specified by user, paper interval is increased from the 2nd sheet of the job.
When a sensor detects that the paper size is small, paper interval is increased from 3rd or 4th sheet of the job.
Based on the combination of detection result of the Pre-registration Detection Sensor and detection result of paper length (L),
paper interval extension time is determined according to the table shown below.
Category
1
2
3
Pre-registration Detec-
tion Sensor
ON
OFF
■ Fixing temperature control
The fixing control circuit controls temperatures of the fixing heater to attain the respective target temperatures.
The figure below shows this circuit schematically.
The DC controller monitors the fixing heater temperature detection signal (MAINTH) to output the respective fixing heater drive
signals (FSRD+, FSRD-) depending on the detected temperatures. The fixing heater drive circuit controls the fixing heater based
on the output signal to attain the target temperature in the fixing heater.
1. Start-up temperature control
This controls the fixing heater warm-up to the target temperature.
Different temperatures are targeted depending on elapsed time after the last print job, paper types or the environment.
Plain paper (environment temperature is 18 deg C or lower),
Plain paper (environment temperature is higher than 18 deg C), heavy paper 3, label paper
Paper length (L)
-
L >/= 270 mm
L < 270mm
Fixing assembly
Fixing film unit
FU1
TH
Pressure
roller
FU1 Temperature fuse
TH Thermistor
Fixing control circuit
Paper type
heavy paper 1, heavy paper 2
Others
Paper interval extension time (seconds)
1
0 (Not extended)
10
8
Fuse
FU901
Relay
RL901 drive
circuit
FSRD+
ixing heater
FSRD-
drive circuit
MAINTH
42
2. Technical Explanation
2
8
4
/RLD+
/RLD-
DC controller
Fixing heater
safety circuit
3
6
2