Electrophotography – Control of electrophotography process – Of plural processes
Reexamination Certificate
2001-01-31
2002-09-24
Chen, Sophia S (Department: 2852)
Electrophotography
Control of electrophotography process
Of plural processes
C358S296000
Reexamination Certificate
active
06456803
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus such as a copier or a printer using the electrophotographic process or the electrostatic recording process.
2. Related Background Art
FIG. 9
of the accompanying drawings schematically shows the construction of a color image forming apparatus. This color image forming apparatus has a digital color image reader portion in the upper portion thereof, and a digital color image printer portion in the lower portion thereof.
In the digital color image reader portion, and original
30
is placed on an original supporting glass table
31
, and a reflected optical image from the original
30
exposed and scanned by an exposure lamp
32
is condensed on a full color sensor
34
by a lens
33
to thereby obtain a color resolved image signal.
The color resolved image signal is processed by a video processing unit, not shown, via an amplifying circuit, not shown, and is delivered to the digital color image printer portion.
In the digital color image printer portion, a photosensitive drum
1
which is an image hearing member is supported for rotation in the direction of arrow R
1
. Around this photosensitive drum
1
, there are disposed a pre-exposure lamp
11
, a corona charger
2
, a laser beam exposing optical system
3
, a potential sensor
12
, four developing devices
4
y,
4
c,
4
m,
4
bk,
a density detecting sensor
13
as density detecting means, a transferring apparatus
5
and a cleaning device
6
.
The color resolved image signal from the digital color image reader portion is inputted to the laser beam exposing optical system
3
, and the color resolved image signal is converted into an optical signal by a laser output portion, not shown, whereafter a laser beam is reflected by a polygon mirror
3
a,
and is converted into an optical image E passing through a lens
3
b
and a mirror
3
c
and linearly scanning (raster scanning) the surface of the photosensitive drum
1
.
During the image formation in the digital color image printer portion, the photosensitive drum
1
is first rotated in the direction of arrow R
1
, and the surface thereof is deelectrified by the pre-exposure lamp
11
, where after it is uniformly charged by the corona charger
2
, and the optical image E is applied to this charged surface for each resolved color to thereby form an electrostatic latent image.
Next, a predetermined developing device is operated for each resolved color to thereby develop and visualize the electrostatic latent image on the photosensitive drum
1
, and an image by a toner as a developer having resin as a base substance is formed on the photosensitive drum
1
.
Here, the developing devices
4
y,
4
c,
4
m
and
4
bk
are adapted to be selectively moved toward the photosensitive drum
1
in conformity with respective resolved colors by the operation of eccentric cams
24
y,
24
c,
24
m
and
24
bk.
Further, the toner image as developer image on the photosensitive drum
1
are transferred to a recording material as a sheet supplied from a recording material cassette
7
to a position opposed to the photosensitive drum
1
through a conveying system and the transferring apparatus.
The transferring apparatus
5
has, in the present example, a transferring drum
5
a,
a transferring charger
5
b,
an adsorbing charger
5
c
for electrostatically adsorbing the recording material, an adsorbing roller
5
g
opposed to the adsorbing charger
5
c,
an inner side charger
5
d
and an outer side charger
5
e,
and a recording material carrying sheet
5
f
formed of a dielectric material is cylindrically integrally extended in the opening area of the peripheral surface of the transferring drum
5
a
journalled so as to be rotatively driven.
As the recording material carrying sheet
5
f,
use is made of a dielectric material sheet such as polycarbonate film.
As the transferring drum
5
a
is rotated, the toner image on the photosensitive drum
1
are transferred onto the recording material carried on the recording material carrying sheet
5
f,
by the transferring charger
5
b.
As described above, a desired number of color images are transferred to the recording material adsorbed and conveyed by the recording material carrying sheet
5
f,
and finally a full color image is formed on the recording material.
In the case of a four-color mode, when the transfer of the toner images of four colors to the recording material is completed in this manner, the recording material is separated from the recording material carrying sheet
5
f
by the action of a separating pawl
8
a,
a separating push-up roller
8
b
and a separating charger
5
h,
and the toner images and fixed on the recording material through a heat roller fixing device
9
and the recording material is discharged onto a tray
10
.
Also, after the transfer, the photo-sensitive drum
1
has the residual toners on its surface removed by the cleaning device
6
, and thereafter is again used for the image forming process.
When images are to be formed on both surfaces of the recording material, immediately after the recording material has been discharged from the fixing device
9
, a conveying path changeover guide
19
is driven, and the recording material is guided to a reversal path
21
a
via a sheet discharge vertical path
20
, whereafter the recording material is once stopped, and is caused to leave in a direction opposite to the direction in which it has been fed in with the trailing end thereof when fed in as the leading end by the reverse rotation of reversing rollers
21
b,
and the recording material is reversed and stocked in an intermediate tray
22
. Thereafter an image is again formed on the other surface of the recording material by the image forming process.
Also, the recording material carrying sheet
5
f
on the transferring drum
5
a
is contaminated by the scattering and adherence of powder from the photosensitive drum
1
, the developing devices
4
, the cleaning device
6
, etc., the adherence of the toners during the jam of the recording material, and sometimes the adherence of oil on the recording material during the image formation on the both surfaces of the recording material, but is cleaned by the action of a fur brush
14
and a backup brush
15
opposed to the fur brush
14
with the recording material carrying sheet
5
f
interposed therebetween, and an oil removing roller
16
and a backup brush
17
opposed to the oil removing roller
16
with the recording material carrying sheet
5
f
interposed therebetween, and thereafter is used again for the image forming process. Such cleaning is effected during pre-rotation and during post-rotation, and is effected whenever jam occurs.
In the present example, design is made such that the eccentric cam
25
of the transferring drum is operated and a cam follower
5
i
made integral with the transferring drum
5
a
is operated, whereby the gap between the recording material carrying sheet
5
f
and the photosensitive drum
1
can be set to a predetermined spacing at predetermined timing. For example, it is a construction in which during standby or during the OFF of power source, the spacing between the transferring drum
5
a
and the photosensitive drum
1
is made great and the rotation of the transferring drum
5
a
can be made independent of the rotative driving of the photosensitive drum
1
.
Also, each developing device is provided with first and second agitating and carrying means designed to carry the toner in opposite directions. Also, a developing sleeve is disposed above the first agitating and carrying means.
In the above-described series of image forming operations, the developing device operates as follows. When the photosensitive drum
1
is rotated and the electrostatic latent image thereon arrives at a developing position, a developing bias comprising AC and DC superimposed one upon the other is applied from a developing bias voltage source to the developing sleeve, and the developing sleeve is rotated by a developing sleeve driving device, not s
Ogata Takao
Suzuki Kazuo
Zaima Nobuhiko
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