Controlling The Transfer Corona Current - Canon NP6045 Service Manual

Q156
Micro- D/A
processor converter
DC controller PCB
In this condition, the high-voltage transformer sends high voltage that suits the output
of the primary charging level control signal (HVTPC) to the primary charging assembly.
If an excess corona current flows from the primary charging assembly because of
changes in the environment, the return current to the comparator circuit increases,
causing the output to decrease. This in turn decreases the corona current from the
primary charging assembly so that the current is controlled to a specific level at all times.
In the photo mode, a target value lower than the dark area potential (V
used for normal copying mode by about 80 V is used. As such, potential control is
executed during copying in photo mode for the first time after the power switch is turned
on to control the primary corona current.

3. Controlling the Transfer Corona Current

The transfer efficiency representing the transfer of toner from the photosensitive
drum to copy paper is affected by changes in the environment (temperature, humidity).
To limit changes occurring in the density caused by changes in the environment, the
transfer current is varied according to the temperature and humidity measured by the
environment sensor.
COPYRIGHT © 1997 CANON INC.
J114 J202
HVTPC
-A5 -6
J202
DCON
-1 Switching
J114 J202
HVTTC
-A6 -5
J114
-A10
Comparator circuit
Figuire 4-109
CANON NP6045 REV. 1 MAR. 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 4 IMAGE FORMATION SYSTEM
Variable
+
width pulse
--
oscillator
circuit
Primary high-voltage
circuit
Variable
width pulse
+ oscillator
--
circuit
Transfer high-voltage
HVT
Humidity (%)
Figure 4-110
Primary charging
T502
Drive
circuit
transformer
T501
Drive
Transfer charging
circuit
transformer
) target value
D
assembly
Photo-
sensitive
drum
assembly
4-11