Canon Color iR C3480, Service Manual

Page: 235 / 774

Chapter 7
7-12
The developing bias is used to retain toner over the static image formed on the surface of the photosensitive drum.
The bias is generated by the 2 circuits of HVT1: developing AC high-voltage generation circuit and DC high-voltage generation circuit.
The developing AC high-voltage generation circuit is used to generate the AC bias applied to the developing cylinder, producing 2 types of biases for color and Bk
(DEV_AC_YMC, DEV_AC_Bk).
The developing DC high-voltage generation circuit is used to generate the DC bias applied to the developing cylinder, producing 2 types of biases for color and Bk
(DEV_DC_YMC, DEV_DC_Bk).
The AC and DC biases thus generated are combined at such times as specified for application to the developing cylinder.
The level of the developing bias varies in keeping with the instructions from the DC controller.
7.2.4 Generation of the Primary Transfer Bias
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Color iR C3380G / Color iR C2880G / Color iR C3380i / Color iR C3380 / Color iR C2880i / Color iR C2880 / iR C3480 / iR C3480i / iR C3080 / iR C3080i / iR
C2550
The primary transfer bias is used to transfer toner from the surface of the photosensitive drum to the ITB.
The bias is generated by the primary transfer DC high-voltage generation circuit of HVT2. The circuit is used to provide a DC bias for application to the primary
transfer roller, producing 4 independent biases for individual colors (TR1_Y, TR1_M, TR1_C, TR1_Bk). These DC biases are applied to the primary transfer roller
at such times as specified.
The level of the primary transfer bias varies according to the instructions from the DC controller.
The DC controller, on the other hand, switches the voltage level of the primary transfer bias for constant voltage control according to the primary transfer current
feedback signal (TR1S) arriving from the primary transfer high-voltage generation circuit.
7.2.5 Generation of the Secondary Transfer Bias
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Color iR C3380G / Color iR C2880G / Color iR C3380i / Color iR C3380 / Color iR C2880i / Color iR C2880 / iR C3480 / iR C3480i / iR C3080 / iR C3080i / iR
C2550
The secondary transfer bias is used to transfer toner from the ITB to paper.
The bias may be either DC positive bias or DC negative bias generated by the DC high-voltage generation circuit of HVT2. The DC positive bias is applied to the
secondary transfer roller at time of toner transfer, while the DC negative bias is applied to the secondary transfer roller at time of cleaning.
The high-voltage power supply circuit applies these secondary transfer biases (TR2) to the secondary transfer roller in keeping with a specific printing sequence as
follows:
- Print Bias (DC positive bias)
It is a bias used to transfer toner from the ITB to paper as part of printing sequence. It is a DC positive bias and is applied to the secondary transfer roller.
- Sheet-to-Sheet Bias (DC negative bias)
It is a bias used to return the residual toner from the secondary transfer roller to the ITB after forming a patch image or between sheets during continuous printing.
The machine applies both DC positive and negative biases to the secondary transfer roller in turns.
- Cleaning bias (DC positive /DC negative bias):
It is a bias used to return the toner sticking to the secondary transfer roller after the formation of a patch image or at power-on. It actually consists of a DC positive
bias and a DC negative bias applied alternately to the secondary transfer roller.
The level of the secondary transfer bias varies in keeping with the instructions from the DC controller.
The DC controller, on the other hand, switches the level of the secondary transfer bias in keeping with the secondary transfer current feedback signal (TR2S) arriving
from the secondary transfer DC high-voltage generation circuit for constant voltage control.
7.3 Image Stabilization Control
7.3.1 Overview of Image Stabilization
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Color iR C3380G / Color iR C2880G / Color iR C3380i / Color iR C3380 / Color iR C2880i / Color iR C2880 / iR C3480 / iR C3480i / iR C3080 / iR C3080i / iR
C2550
To ensure an ideal image against the deterioration of parts associated with imaging otherwise occurring as a result of changes in the environment or in the machine,
the following mechanisms are used: