Controlling The Fixing Mechanisms - Canon LBP-2000 Service Manual

CHAPTER 2
C. Controlling the Fixing Mechanisms
1. Outline
Static
Pressure
eliminating brush
roller
Fixing roller
The fixing roller, pressure roller, and delivery roller of the fixing assembly are driven by the main
motor (M101). The fixing roller is heated by a single fixing heater (H101; 800 W). The surface
temperature of the fixing roller is monitored by the main thermistor and the sub thermistor; the
main thermistor is used to check the middle of the fixing roller while the sub thermistor is used to
check the right edge of the fixing roller.
When the surface temperature increases, the resistance of TH101 will decrease, causing the
voltage of the main thermistor (TH1) and the sub thermistor signal (TH2) to decrease.
The DC controller PCB controls the fixing heater drive signal (/FSRDRV) based on the voltage
level of the TH1 signal and the TH2 signal, thereby controlling the surface temperature of the
fixing assembly to remain a specific level.
The FSRDRV signal is generated in relation to the zero-cross (/ZEROXI) signal from the zero-
cross circuit found on the power supply PCB.
If the sub thermistor detects an increase in temperature at the end (thermistor reading of
210°C) as caused by the use of small paper in continuous printing, the Printer starts down se-
quence.
The Printer is equipped with sleep mode for energy conservation, and it turns off the fixing
heater (H101) while it remains in sleep mode (power saving mode).
2 - 12
Separation
claws
Static
eliminating brush
Fixing heater Main thermistor (middle)
Sub thermistor (right)
Figure 2-2-5
Delivery roller
/FSRDRV
/ZEROXI
M101
TH1/TH2
Thermal switch