Electrophotography – Image formation – Development
Reexamination Certificate
2001-02-27
2003-04-01
Braun, Fred L' (Department: 2852)
Electrophotography
Image formation
Development
C399S285000
Reexamination Certificate
active
06542710
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing apparatus preferably usable for an image forming apparatus such as an electrophotographic copier and an electrophotographic printer. Here, the developing apparatus can be installed in a cartridge and the cartridge is adapted to include a developing cartridge and processing cartridge which are attachable to and detachable from a main body of an image forming apparatus. The developing cartridge is a single body of the developing apparatus and configured as attachable to and detachable from the main body of the image forming apparatus and the processing cartridge is adapted to be configured by integration of a photosensitive body with at least one of the developing apparatus, an electrifying apparatus, and cleaning means and by making it attachable to and detachable from the main body of the image forming apparatus.
2. Related Background Art
Conventionally, electrophotography is adapted to use photoconductive substance, form an electric latent image on an electrophotographic photosensitive body by various methods, then develop the latent image with a developer (toner) to make a visualized image, and in a necessary occasion, transfer the image visualized by the toner to a recording medium such as paper, followed by fixing with heat and pressure to yield an image forming matter.
At present, improving an image resolution and definition are strongly required and thus, developing a thin toner layer forming method and an apparatus thereof become necessary. For this requirement, some measures have been proposed.
In addition, in the recent years, a contact one component developing method was proposed, in which development is carried out with a configuration, in which a surface layer of the photosensitive body is pressed by using a semiconductive developing roller or the developing roller, of which surface has a dielectric layer, as a developer carrying body.
Here,
FIG. 14
shows an example of the image forming apparatus of the contact one component developing system. This system is the system by which development is carried out by contacting the electrophotographic photosensitive body
21
with the developing roller
25
and using a one component developer.
First, the electrophotographic photosensitive body
21
is evenly electrified by an electrifying roller
22
which is the electrifying means for forming a latent image on the photosensitive body
21
by a laser light from an exposing unit
3
, which is the static latent image forming means. Subsequently, this latent image is visualized as a toner image by the developing apparatus
24
. Following this step, the toner image developed is transferred to a transfer material
13
by a transfer roller
9
. The transfer material
13
is carried to a fixing device
12
, where heat and pressure are applied thereto to fix the toner image, and then, the transfer material is discharged to the outside of the apparatus. On the other hand, toner
28
not transferred to the transfer material
13
and remaining on the photosensitive body
21
is removed by a cleaning blade
23
, which is the cleaning means, that is contained in a waste toner containing container
29
.
The developing apparatus
24
has a developer container
20
containing nonmagnetic toner
28
as the one component developer, the developing roller
25
which is the developer carrying body installed in an opening part thereof, an elastic blade
27
which is a regulating member in which the free end makes contact with the developing roller
25
, and an elastic roller
26
which is a developer carrying member contacted by pressure from a position upstream from the elastic blade
27
in a rotating direction of the developing roller
25
, and by rotation of the elastic roller
26
in the direction of an arrow D. Toner
28
is supplied to the surface of the developing roller
25
. Toner
28
is carried according to rotation of the developing roller
25
, charged with an electric charge and made into a thin layer by friction between a contacting part of the elastic blade
27
and the developing roller
25
. The toner
28
that has been made into a thin layer is carried by the developing roller
25
and supplied to the contact part with the photosensitive body
21
to develop the static latent image. Following this step, toner
28
, which was not developed and which remained in the contact part of the photosensitive body
21
with the elastic roller
25
, is removed by the elastic roller
26
. On the other hand, as described above, a new toner
28
is supplied to the developing roller
25
by the elastic roller
26
to repeat the above described action.
In recent years, with a purpose to reduce high triboelectrification stability and fog, a system, for example, U.S. application Ser. No. 167,723 (filed on Oct. 7, 1998,), now U.S. Pat. No. 6,229,979, was proposed to use means to electrically electrify toner by using a toner electrifying roller as a developer charging member.
Here,
FIG. 15
shows an example of the developing apparatus using the toner electrifying roller. This developing apparatus
40
is adapted to install the toner electrifying roller
32
in the above described developing apparatus.
The developing apparatus
4
has the developer container
30
containing nonmagnetic toner
34
as the one component developer, the developing roller
35
which is the developer carrying body installed in an opening part thereof, the elastic blade
33
which is a regulating member of which the free and contacts with the developing roller
35
, and the elastic roller
36
which is the developer carrying member contacted by pressure from the upstream position from the elastic blade
33
in the rotating direction of the developing roller
35
, and by rotation of the elastic roller
36
in the direction of the arrow D. Toner
34
is supplied to the surface of the developing roller
35
. The toner electrifying roller
32
is located between the contact part of the photosensitive body drum
31
, the developing roller
35
, the contact part of the elastic blade
33
, and the developing roller
35
. The toner electrifying roller
32
contacts the developing roller
35
.
Toner
34
supplied to the surface of the developing roller
34
is carried according to rotation of the developing roller
35
to be charged with the electric charge and made to the thin layer by friction in the contacting part of the elastic blade
33
with the developing roller
35
. Further, electric charging by discharge of the toner electrifying roller
32
charges the toner with an electric charge. The charged toner
34
is carried by the developing roller
35
to the contact part with the photosensitive body
31
to develop the static latent image. Following the step, toner
34
, which was not developed and remained in the contact part of the photosensitive body
31
with the elastic roller
35
, is removed by the elastic roller
36
. On the other hand, as described above, the new toner
34
is supplied to the developing roller
35
by the elastic roller
36
to repeat the above described action.
However, in the case where such toner electrifying roller
32
is used, the following problem results: the toner electrifying roller
32
contacts the developing roller
35
and hence, toner
34
attaches to the toner electrifying roller
32
to decrease an electric charging performance of the toner electrifying roller
32
. Particularly, in the case where a voltage over a discharge starting voltage is applied to the toner electrifying roller
32
, the voltage applied increases and therefore, toner becomes easy to attach to the electrifying roller.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a developing apparatus in which a developer is prevented from attaching to a developer electrifying member.
Another object of the present invention is to provide a developing apparatus in which the developer attached to the developer electrifying member is returned to the developer carrying member.
A further object of the p
Ishii Yasuyuki
Kakeshita Tomomi
Uehara Shinji
Braun Fred L'
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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