Automatic Bias Control - Canon Color imageCLASS MF9170c Service Manual

Chapter 7

7.4.2 Automatic Bias Control

imageCLASS MF9170c / imageCLASS MF9150c / imageCLASS MF8450c
Depending on the individual difference or deterioration condition of the transfer roller, attraction roller, and ETB, differences and changes occur in the resistance
value of each unit. In this condition, a transfer failure may occur when an expected level of bias is not applied to each roller.
This control is executed to apply the optimum level of bias to each roller based on the measured voltage of each roller.
The DC controller sends a constant current to the transfer roller (Bk) and attraction roller when starting print operation and measures the voltage at that point. Based
on the measured voltage, it extracts the optimum transfer and attraction biases.
In the subsequent print operation, the optimum transfer and attraction biases are applied to stabilize the image quality.
Transfer roller (Bk)
ETB
Constant current
Photosensitive drum (Bk)
a. Transfer roller voltage detection
7-20
Current
Attraction roller
V Voltage
detection
Constant current
F-7-25
ETB
ETB engaged roller
Current
V Voltage
b. Attraction roller voltage detection
0019-8977
detection