Various Control Mechanisms; Controlling The Temperature Of The Fixing Unit; Fixing Temperature Control - Canon Color imageCLASS MF9170c Service Manual

Chapter 9

9.2 Various Control Mechanisms

9.2.1 Controlling the Temperature of the Fixing Unit

9.2.1.1 Fixing Temperature Control

imageCLASS MF9170c / imageCLASS MF9150c / imageCLASS MF8450c
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.
Fixing unit
Fixing thermal switch: TP1A
Fixing heater: H1
Fixing sub thermistor
: TH2
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.
9-2
Fixing sleeve unit
Fixing main thermistor
: TH1
Low-voltage
power PCB
Zero crossing
circuit
RL3901
RL3902
Fixing heater
drive circuit
Fixing control circuit
Fixing relay PCB
MAINTH
SUBTH
F-9-2
DC controller PCB
ZEROX
RLD+
Relay drive
circuit
RLD-
FSRD
Fixing heater
safety circuit
FLD+
CPU
(IC1001)
0019-5047