Electrophotography – Control of electrophotography process – Control of transfer
Reexamination Certificate
2001-11-08
2004-07-20
Braun, Fred L. (Department: 2852)
Electrophotography
Control of electrophotography process
Control of transfer
C399S303000
Reexamination Certificate
active
06766123
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus utilizing the electrophotographic process or the like, and particularly to an apparatus for charging a recording material before transfer.
2. Description of the Related Art
Various processes such as the electrophotographic process, the heat transfer process and the ink jet process have heretofore been adopted in image forming apparatuses. Of these, an image forming apparatus using the electrophotographic process has advantages in high speed, high quality of image and quietude.
FIG. 3
of the accompanying drawings schematically shows the construction of an example of the image forming part of a conventional image forming apparatus using the electrophotographic process.
The image forming apparatus of the electrophotographic type has, for example, a drum-shaped electrophotographic photosensitive body, i.e., a photosensitive drum
1
, as an image bearing body, and uniformly charges the surface of the rotating photosensitive drum
1
by primary charging means
2
, and thereafter effects exposure
12
in accordance with image information by exposing means
11
such as an LED or a laser to thereby form an electrostatic latent image on the surface of the photosensitive drum
1
. Thereafter, the electrostatic latent image is developed by a developing apparatus
8
by the use of a developer (a toner, or a toner with a carrier), and the toner is made to electrostatically adhere to the latent image, which is thus visualized as a toner image.
In synchronism with the formation of the toner image on such a photosensitive drum
1
, a transferring material P is conveyed from a sheet feeding cassette
15
by conveying means
14
, and the toner image on the photosensitive drum
1
is electrostatically transferred onto the transferring material P conveyed to a transferring position opposed to the photosensitive drum
1
by the conveying means
14
, by the action of transfer charging means
4
. Thereafter, the toner image transferred onto the transferring material P is fixed by being heated and pressurized by a fixing apparatus
21
, whereby a permanent image is obtained on the transferring material P.
On the other hand, any untransferred toner residual on the photosensitive drum
1
after transfer is removed by a cleaning blade provided in a drum cleaner
10
, and is collected into the container portion (waste toner container part) of the cleaner
10
. The photosensitive drum
1
having had its surface thus cleaned is repetitively used for image formation.
Now, in recent years, color image forming apparatuses using the electrophotographic process have spread. There are various types of color image forming apparatuses. Besides the well-known multiple transfer type and intermediate transferring member type, there are the multiple developing type in which development is repeated on the surface of an image bearing body to thereby superimpose and form toner images of plural colors, whereafter the toner images are collectively transferred, and the in-line type which has image forming means (process stations) of a plurality of different colors along a transferring material conveying belt and toner images of the plural colors are superimposed and transferred to a transferring material conveyed by the conveying belt.
The color image forming apparatus of the in-line type can be made higher in speed and has many advantages including the advantage in quality of image due to the low frequency of toner image transfer. In this in-line type, there has also been proposed a construction in which for the improvement in usability and the reduction in installation area, the process stations are arranged in a vertical direction and a transferring material is conveyed substantially vertically.
FIG. 4
of the accompanying drawings shows an example of the construction of a full color image forming apparatus of the conventional in-line type. This apparatus has an electrostatic sucking belt, i.e., a conveying belt
14
, as a transferring material conveying member, and the conveying belt
14
is passed over a drive roller
23
, a sucking opposed roller
22
and tension rollers
13
a
,
13
b
. The conveying belt
14
is rotatively driven in the direction of arrow by the drive roller
23
.
Process stations
31
Y,
31
M,
31
C and
31
Bk which are yellow (Y) magenta (M), cyan (C) and black (Bk) image forming parts are disposed along the peripheral surface of the conveying belt
14
, and a transferring material is sequentially conveyed to the respective process stations by the conveying belt
14
. Each process station
31
(
31
Y,
31
M,
31
C,
31
Bk) has a photosensitive drum
1
(
1
Y,
1
M,
1
C,
1
Bk), a primary charger
2
(
2
Y,
2
M,
2
C,
2
Bk), a developing apparatus
8
(
8
Y,
8
M,
8
C,
8
Bk) and a drum cleaner
10
(
10
Y,
10
M,
10
C,
10
Bk), and the photosensitive drum
1
, the charger
2
, the developing apparatus
8
and the drum cleaner
10
are integrally made into a process cartridge which is made detachably mountable with respect to the main body of the image forming apparatus.
A transferring blade
4
(
4
Y,
4
M,
4
C,
4
Bk) which is transfer charging means abuts against the photosensitive drum
1
with the conveying belt
14
interposed therebetween, and during the transfer of a toner image on the photosensitive drum
1
to the transferring material P, a transferring bias voltage is applied to the transferring blade
4
from a transferring bias power supply
32
(
32
Y,
32
M,
32
C,
32
Bk) connected thereto.
When in the foregoing, an organic semiconductive electrophotographic photosensitive member (OPC photosensitive member) of the negative polarity is used as the photosensitive drum
1
and the exposed portion of a latent image in which negative charges have been attenuated by the exposure of the photosensitive drum
1
is to be developed, use is made of a developer including a toner of the negative polarity. Accordingly, a transferring bias voltage of the positive polarity is applied from a transferring bias power supply
32
to the transferring blade
4
.
The transferring material P is conveyed from a sheet feeding cassette
15
toward the image forming part by a pickup roller
16
and sheet feeding rollers
17
and
18
, and is once nipped by and between a pair of registration rollers
19
a
and
19
b
which are roller-shaped synchronous rotary members, and thereafter is supplied to the transferring material sucking part of the conveying belt
14
by the pair of registration rollers
19
in synchronism with the image forming operation on the photosensitive drum
1
.
In the sucking part, a sucking roller
20
as sucking charging means is installed in opposed relationship with the sucking opposed roller
22
with the conveying belt
14
interposed therebetween, and the conveying belt
14
and the transferring material P are adapted to be nipped by and between the sucking roller
20
and the opposed roller
22
. A voltage (sucking bias voltage) is applied from a sucking bias power supply (high power supply), not shown, to the sucking roller
20
, whereby sucking charges are imparted to the transferring material P, and the transferring material P to which the charges have been imparted polarizes the conveying belt
14
, whereby the transferring material P is electrostatically sucked to the conveying belt
14
.
The transferring material P sucked to the conveying belt
14
in this manner passes through the respective process stations in succession, and yellow, magenta, cyan and black toner images on the respective photosensitive drums
1
are successively superimposed and transferred onto the transferring material P. Thereafter, the transferring material P is separated from the conveying belt
14
and is conveyed to a fixing apparatus
21
, where the fixing of the toner images of the four colors is effected, and a full color permanent image is thus obtained on the transferring material P. Any untransferred toner residual on the photosensitive drum
1
after the transfer is removed by the cle
Ebihara Shunichi
Saito Yoshiro
Braun Fred L.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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