Canon ImageRunner iR8500 Series, Service Manual, Page: 347 / 1122

Chapter 8
8-7
8.3 Potential Control
8.3.1 Outline
0006-9576
iR105i/iR105+ / iR9070 / iR85+ / iR8070
The potential is controlled for the following:
[1] Determining the optimum grid bias. (VD control)
[2] Determining the optimum laser output. (VL control)
[3] Determining the optimum developing bias (DC). (Vdc control)
Figure shows the construction of the control system:
F-8-6
8.3.2 Basic Sequence
0006-9585
iR105i/iR105+ / iR9070 / iR8070
Figure shows the basic sequence (timing) of operations related to potential control.
F-8-7
Primary charging wire
Potential sensor
Grid wire
Laser light
Developing cylinder
DC controller PCB
Laser driver PCB
High-voltage DC PCB
DC bias
DC bias
DC bias
Control
signal
Control
signal
D
e
te
c
tio
n
s
ig
n
a
l
J502
J3
11
12
13
14
4
3
2
1
0 V
24 VU
POT-DT
POT-ON
Potential control PCB
Drum surface
potential reading When '1', the potential
sensor turns on.
WMUPR
WMUP STBY
195˚C 200˚C
Drum motor(M0)
Primary
charging bias
(DC)
Developing bias
AC bias (AC)
Developing bias
(DC)
Grid bias
Laser
Potential stabilization sequence
Fixed value
Optimum grid bias
determined Optimum laser output
determined
Potential control
Potential control is as when the main power switch is turned on.
A series of charging operations is executed to
stabilize the potential of the drum.
To prevent stray toner, the developing bias
is turned off for non-image areas.
Optimum laser output
determined
Transparency mode
potential control