Target Potential Correction In Each Mode - Canon ImageRunner iR8500 Series Service Manual

Chapter 8
In a low humidity environment,
the resistance of paper
decreases and, on the other
hand, the transfer efficiency
increases; as such, the laser
power is reduced to prevent
excess deposit of toner.
In a high humidity environment,
the moisture of paper decreases
the transfer efficiency; as such,
the laser power is increased to
increase the density.
3. Density Adjustment during printing (scanner input)
195˚C
WMUP
Potential sensor
Laser
Grid bias
Potential determined
F-8-22

8.3.11 Target Potential Correction in Each Mode

iR85+
The laser power/developing bias determined in relation to potential control is corrected for the following operating mode, and the result is used as the target
value specific to each:
During operation in high
humidity mode
8-14
Lighter
Darker
195˚C
WMUP
Potential sensor
Laser
Grid bias
Potential determined
F value
Lighter 1
3
5
Density
7
9
Darker
The laser power/Vdc is corrected
according to the F setting.
Potential control
sequence started.
WMUPR
VD VL
Pw
Vg
Vg
Pw
Vdc
Purpose
To prevent decreases in density (caused by a
lower developing efficiency because of moist
toner or a lower transfer efficiency caused by
moist paper).
Laser power
correction
value
Extra low humidity
Low humidity
Density
Normal humidity
High humidity
Extra high humidity
The laser power/Vdc is corrected
to suit the environment.
Potential control
sequence started
WMUPR
VD VL
Pw
Vg
Vg
Pw
Vdc
F-8-21
Laser power Vdc
correction value correction value
x 0.8
-20V
x 1.0
x 1.2
x 1.5
200˚C
STBY
T-8-8
Correction
Corrects the laser power/developing
bias according to the environment.
Vdc VD
correction correction
value value
-5%
+20V
+5%
+30V
200˚C
STBY
0008-8689