Canon GP160, Service Manual

Page: 102 / 797

COPYRIGHT © 1999 CANON INC. CANON GP160 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 6 IMAGE FORMATION SYSTEM
6-4
III. TRANSFER CHARGING ROLLER BIAS CONTROL
A. Overview
This unit employs the roller direct transfer charging system. There are 4 types of
transfer charging roller bias, their respective roles and timings are explained below.
1. Transfer bias
Positive voltage is applied by this bias, which transfers the toner from the photosen-
sitive drum to the paper.
2. Cleaning bias
Because a direct transfer system is employed, there are times when, because of
jams, etc., the toner on the drum adheres to the transfer charging roller. In order to clean
this toner off, negative voltage is applied at the times below, causing the toner which has
adhered to the transfer charging roller to return to the photosensitive drum. The output
of this negative voltage is as follows:
• During forward rotation
• During part of backward rotation
3. Reference bias
Due to fluctuations in the environment, or the transfer charging roller’s resistance,
there is the possibility that the transfer effectiveness will fluctuate. In order to minimise
image deterioration caused by this, the transfer charging roller bias applied voltage level
is compensated.
The reference bias is applied when the start key is pushed, and the voltage level
compensated.
4. Paper interval bias
When performing continuous printing, the bias value is lowered to prevent the toner
between the paper adhering to the transfer charging roller.