Fixing System; Outline; Fixing Control Circuit - Canon LBP253 SM Manual

Fixing System

Outline

The fixing/delivery unit fixes the toner onto a print paper and delivers it to the delivery tray.
The operation of the fixing/delivery unit is explained in the following.
1. The print paper fed from the pick-up/feed unit is fused the toner by the fixing film and the pressure roller.
2. The print paper delivered from the fixing unit is delivered to the face-down delivery tray or the face-up delivery slot. When
the engine controller detects that the heater temperature reaches 50 deg C after the last rotation is completed, it drives the
main motor for 50 msec. and dislocates the nip part. This prevents the toner adhering to the pressure roller.
The fixing unit of this printer utilizes the on-demand fixing method. It is structured as shown below.
• Heater:
This fixing unit incorporates one heater.
Fixing heater (H1): To heat the fixing film (ceramic heater)
• Thermistor:
This fixing unit incorporates one thermistor.
Thermistor (TH1): Sit almost at the center of the fixing film. (contact type)
To control the temperature of the fixing film
• Thermal switch:
Thermoswitch (TP1): Sit almost at the center of the fixing film (contact type)
If the temperature of the heater rises abnormally high, the contact gets broken and cuts off the AC voltage supply to the
fixing heater to interrupt the power supply to the heater.
The temperature control of the fixing unit incorporated as above is operated by the fixing temperature control circuit according to
the command from the CPU (IC201) on the DC controller.
The followings describe the each circuit and function of the temperature control of the fixing unit.

Fixing control circuit

The fixing control circuit controls the temperature in the fixing unit. The printer uses an on-demand fixing method.
Thermistor
Fixing heater
Fixing heater
control circuit
Engine controller PCB
Fixing unit
Fixing film
Pressure roller
CPU
22
2. Technology
Thermoswitch