Determining The Optimum Grid Bias; Grid Bias Corrective Control - Canon ImageRunner 600 Service Manual

CHAPTER 6 IMAGE FORMATION SYSTEM
B.

Determining the Optimum Grid Bias

A grid bias is selected so that the surface potential of the drum will be identical to the target
potential (the primary charging bias is fixed).
The relationship between the surface potential of
the drum (VD) and the gird bias is obtained based
on measurements taken several times.
Potential sensor
Primary charging
bias (DC)
Grid bias
C.

Grid Bias Corrective Control

If an optimum grid bias cannot be selected after measuring the surface potential of the drum
several times, a corrective control sequence is started to determine the optimum grid bias.
Measurement is continued while varying the level of
the grid bias so as to attain the target VD.
VD1
Target VD
VD-NG
195˚C
WMUP
Potential
sensor
Primary charging
bias (DC)
Grid bias
Figure 6-205 Sequence of Operations (corrective control)
6-8
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VD3
VD2
Charging
characteristic curve
VD1
500V 600V 700V
Grid bias
195˚C
WMUP
Measurement
Measurement
(VD2)
(VD1)
500 V
Potential control
sequence started
Figure 6-204 Sequence of Operations
VD3
VD2
WMUPR
500V 600V 700V Vg
Potential control
sequence started
If the target VD is attained basde on this
measurement, control is ended; otherwise,
corrective control will start.
WMUPR
Measurement
(VD3)
Vg
600 V 700 V
If the measurement is identical to the target VD,
control is ended. Measurements are taken as many
as 8 times; at times, an approximate level (to the
target VD) may be used.
VD-NG VD1 VD2 VD3
Vg1 Vg2 Vg3
Corrective control
sequence started
CANON imageRUNNER 600 REV.1 JAN. 2000 PRINTED IN U.S.A.
200˚C
STBY
Measurement
(targetVD)
A grid bias (VG) needed to attain the
target VD is selected.
200˚C
STBY
VD8
Vg8
The grid bias (vg) needed to
attain the target VD is
determined.