Canon iR7086, Service Manual

Page: 252 / 735

Chapter 7
7-6
7.4.4 Grid Bias Corrective Control
0010-8042
iR7105 / iR7095 / iR7086
If the optimum grid bias cannot be determined at the end of drum surface potential measurement, the machine starts its compensatory control sequence to determine
the bias.
F-7-8
7.4.5 Determining the Optimum Laser Output
0010-8043
iR7105 / iR7095 / iR7086
The machine determines the optimum laser output so that the drum surface potential (light area potential VL) is identical to the target potential.
F-7-9
WMUPR WMUP STBY
193
198
Potential sensor
Primary charging bias(DC)
Grid bas
650 V
550 V
or
750 V
Vg
Vg1 Vg2 Vg3 Vg8
VD1
VD-NG
VD2
VD3
Continues to take measurements while varying
the value of the grid bias so that it will be closer
to the target VD.
Potential control
sequence started
Compensatory control
sequence started
VD-NG VD1 VD2 VD3 VD8
TargetVD
A grid bias (Vg) needed to attain the
target VD is determined.
When the measurement is identical to the target VD,
ends the control. The machine executes measurement a
maximum of 8 times, possibly using an approximate
target VD.
WMUPR
WMUP STBY
195
198
Potential sensor
Developing bias(DC)
Laser
60%
80% 60% or
80%
100%
100%
Measurement(VL2) Measurement(VL1orVL3) Measurement (target VL)
Pw
VL1
VL2
VL3
Laser output
The machine takes measurements multiple times
to determine the relationship between the drum
surface potential (VL) and the laser output.
If this measurement brings about
the target VL, ends the control;
otherwise, starts compensatory control.
After measuring VL2, measures VL3 if VL2
is grater than the target VL; if smaller,
measures VL1.
Turn on the lamp at 80% of the reference
output determined at time of shipment. Determines the laser output (P)
needed to attain the target VL.