Canon LBP351 Series, Service Manual

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Fixing System
Overview/Configuration
■ Overview
Fixing Delivery Assembly consists of the Fixing Assembly for fixing toner on the print paper and the Delivery Assembly for
delivering print paper on which toner is fixed to the Delivery Outlet (Face-down Tray, Face-up Tray).
■ Main Parts in the Fixing Assembly
This circuit is for controlling the temperature of the Fixing Assembly.
The Fixing Assembly of this machine uses an on-demand fixing method, and consists of the following parts:
DC controller
Fixing heater
drive circuit
Fixing heater
safety circuit
Relay
CPU
Power Supply PCB
TH1
TP1
H1
TH2
Pressure roller
Fixing sleeve
FIXING HEATER
DRIVE signal
FIXING HEATER TEMPERATURE signal
• Fixing Heater (H1):
Ceramic Heater for heating the Fixing Film
• Thermistors (TH1 and TH2):
Thermistors for detecting the fixing temperature
2 contact-type thermistors are used in this Fixing Assembly.
• Main Thermistor (TH1):
This thermistor is in contact with the center of the Fixing Heater and detects the temperature of the Fixing Heater.
(Contact type)
• Sub Thermistor (TH2):
This thermistor is in contact with the edge of the Fixing Heater and detects the temperature of the Fixing Heater. (Contact
type)
• Thermoswitch (TP1):
Thermoswitch for preventing the abnormal temperature rise of the Fixing Heater.
This thermoswitch is a contact-type thermoswitch, and is installed at the center of the Fixing Heater.
If the temperature of the Fixing Heater has risen abnormally, the contact point opens to stop the power supply to the Fixing
Heater.
Temperature control of the Fixing Assembly which consists of these parts is performed by the fixing control circuit and Fixing
Heater safety circuit according to the command of the CPU on the DC Controller.
Various Control Mechanisms
■ Fixing Temperature Control
● Heater Temperature Control
This control detects the surface temperature of the Fixing Heater and controls the drive signal of the Fixing Heater so that the
temperature of the Fixing Heater becomes the target temperature.
The temperature is detected by the Main Thermistor, and the DC Controller controls the temperature to become the target
temperature using the Fixing Heater drive (FSRD1/FSRD2).
The following shows this control circuit:
2. Technical Explanation (Device)
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