Determining The Optimum Developing Bias; Potential Control For Transparency Mode - Canon ImageRunner iR8500 Series Service Manual

Potential sensor
Developing bias
(DC)
Laser

8.3.8 Determining the Optimum Developing Bias

iR105i/iR105+ / iR9070 / iR85+ / iR8070
An optimum developing bias (Vdc) is computed based on the optimum drum surface potential (VD).
Potential sensor
Laser
Grid bias
Potential determined

8.3.9 Potential Control for Transparency Mode

iR105i/iR105+ / iR9070 / iR85+ / iR8070
To prevent detachment of toner in high density areas on transparencies, the contrast is decreased to limit the amount of toner deposit. To enable the decrease
in contrast, potential control for transparency mode is executed to select a target value.
Measurement is continued by varying the
level of the laser output so as to attain
the target VL.
VL1
VL3
Target VL
VL2
VL-NG
195˚C
WMUP
Reference
output
Corrective control sequence
started
Vdc is computed based on this VD;
Vdc = VD - Vback (120 V)
195˚C
WMUP
If the measurement is identical to the
target VL, control is ended.
Measurements are taken as many
as 8 times; at times, an approximate
(to the target VL) may be used.
WMUPR
VL1 VL2 VL3
VL-NG
-10% -20% Pw Pw1 Pw2 Pw3
The laser output needed to
attain the target VL is
determined.
F-8-14
Vg
Photosensitive drum
WMUPR
VD VL
Optimum grid Optimum laser output
bias determined
determined
Pw
Vg Vg
Pw
Potential control sequence started
F-8-15
200˚C
STBY
VL8
Pw8
Potential sensor
VD
Vdc
Developing
cylinder
200˚C
STBY
Vdc
Chapter 8
0006-9613
0006-9615
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