Canon PC720 Service Manual - Page 33

Primary, Charging, Image, Exposure

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COPYING PROCESS OM C. Primary Charging (step 1) A-Primary corona roller ti AC bias DC bias D. Image Exposure (step 2) Optical image Dark area Light area Figure 2-105 The surface of the photosensitive drum is charged to a uniform negative potential in preparation for the formation of static latent images. The copier uses its primary charging roller to directly charge the photosensitive drum (primary charging). The primary charging roller is made of conducting rubber, and an AC bias is applied to the roller in addition to a DC bias. An AC bias serves to keep the surface potential of the photosensitive drum uniform, eliminating the need for pre-exposure. The DC bias applied simultaneously with the AC bias, on the other hand, serves to maintain primary potential. Reference: A direct charging system provides such advantages as low application voltage and generates little, if any, ozone. Figure 2-106 In this step, the optical image of the original is projected to the photosensitive drum to neutralize the charges in the light area. COPYRIGHT © 1994 CANON INC. CANON PC720/740/150M0 REV.O AUG.1994 PRINTED IN JAPAN pmplatt AU JAPON) 2 - 3

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COPYING
PROCESS
OM
C.
Primary
Charging
(step
1)
D.
Image
Exposure
(step
2)
A
—Primary
corona
roller
ti
AC
bias
DC
bias
Figure
2-105
The
surface
of
the
photosensitive
drum
is
charged
to
a
uniform
negative
potential
in
preparation
for
the
formation
of
static
latent
images.
The
copier
uses
its
primary
charging
roller
to
directly
charge
the
photosensitive
drum
(primary
charging).
The
primary
charging
roller
is
made
of
conducting
rubber,
and
an
AC
bias
is
applied
to
the
roller
in
addition
to
a
DC
bias.
An
AC
bias
serves
to
keep
the
surface
potential
of
the
photosensitive
drum
uniform,
eliminating
the
need
for
pre
-exposure.
The
DC
bias
applied
simultaneously
with
the
AC
bias,
on
the
other
hand,
serves
to
maintain
primary
potential.
Reference:
A
direct
charging
system
provides
such
advantages
as
low
application
voltage
and
generates
little,
if
any,
ozone.
Optical
image
Dark
area
Light
area
Figure
2-106
In
this
step,
the
optical
image
of
the
orig-
inal
is
projected
to
the
photosensitive
drum
to
neutralize
the
charges
in
the
light
area.
COPYRIGHT
©
1994
CANON
INC.
CANON
PC720/740/150M0
REV.O
AUG.1994
PRINTED
IN
JAPAN
pmplatt
AU
JAPON)
2
-
3