Electrophotography – Image formation – Development
Reexamination Certificate
2000-05-11
2002-07-02
Braun, Fred L. (Department: 2852)
Electrophotography
Image formation
Development
C399S111000, C399S285000
Reexamination Certificate
active
06415127
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing apparatus used in an image forming apparatus such as an electrophotographic copying machine and an electrophotographic printer.
2. Related Background Art
In the image forming apparatus of an electrophotographic system, an electrostatic latent image formed on an image bearing member is developed by a developing apparatus and is visualized as a toner image. In an image forming apparatus for forming a color image by overlapping toner images of plural colors, an image forming apparatus using an intermediate transfer member as shown in
FIG. 15
is proposed and practically used to form a color image having no color shift. In this image forming apparatus, the image can be formed by using the intermediate transfer member irrespective of sizes and thicknesses of a transfer member, etc. and media flexibility is also improved.
An image forming process in the image forming apparatus in
FIG. 15
will be explained. The image forming apparatus is connected to a host device
112
such as a personal computer and a work station, and receives image data through a video interface by a print request from the host device
112
. These image data are decomposed into four colors of yellow, magenta, cyan and black, and charge, exposure and development processes are sequentially performed in each color with respect to a photosensitive drum
110
so that toner images are formed. These toner images are overlapped and transferred to the intermediate transfer member (intermediate transfer drum)
105
of a drum shape. Thereafter, these toner images are transferred together to a recording material such as paper as a recording medium so that a full color image is formed on the recording material.
The photosensitive drum
110
as a first image bearing member is rotated at a predetermined circumferential speed in an arrow direction. A surface of this photosensitive drum
110
is uniformly charged by a charging roller
102
as a charging means. The charging roller
102
comes in press contact with the surface of the photosensitive drum
110
with predetermined pressing force, and charges the photosensitive drum
110
while the charging roller
102
is driven and rotated by the rotation of the photosensitive drum
110
. Next, a scanning operation is performed by an exposure means
103
on/off-controlled in accordance with image data of a first color (e.g., yellow), and an electrostatic latent image of the first color is formed on the surface of the photosensitive drum
110
. This electrostatic latent image of the first color is developed by a developing apparatus
104
Y storing yellow toner among plural developing apparatuses
104
and is visualized as a yellow toner image. The developing apparatuses
104
(
104
Y to
104
K) will be described later.
The toner image of the first color formed on the photosensitive drum
110
is transferred to a surface of the intermediate transfer drum
105
(primary transfer). The intermediate transfer drum
105
as a second image bearing member comes in press in contact with the photosensitive drum
110
with constant pressing force, and is rotated in an arrow direction in
FIG. 15
at a circumferential speed approximately equal to that of the photosensitive drum
110
. The toner untransferred but left on the surface of the photosensitive drum
110
in the primary transfer is scraped by a cleaning blade
106
a
of a cleaner
106
coming in press contact with the photosensitive drum
110
and is stored into a waste toner container
106
b.
The above processes are also repeated with respect to magenta, cyan and black. Every time a magenta toner image of a second color, a cyan toner image of a third color and a black toner image of a fourth color are obtained, the toner images are sequentially transferred onto the intermediate transfer drum
105
. Thus, a full color image obtained by overlapping the toner images of the four colors is formed on the intermediate transfer drum
105
.
The full color image on the intermediate transfer drum
105
is electrostatically transferred together to a recording material P fed from a paper cassette
108
, etc. by a secondary transfer roller
109
(secondary transfer). Thereafter, the recording material P is sent to a fixing apparatus
107
and the four toner images are fixed. Thereafter, the recording material P is discharged from a discharging portion to the exterior of the apparatus so that a predetermined desirable print image is obtained.
The developing apparatuses
104
(
104
Y,
104
M,
104
C,
104
K) in the above image forming apparatus are not particularly limited, but dry type one-component developing apparatuses are variously proposed as one of the developing apparatuses and are practically used. This is because the developing apparatus can be generally made compact and simplified in structure by a dry type one-component developing method. However, a problem exists in that it is difficult to form a thin layer of toner as a one-component developer on a developer bearing member in any of the developing apparatuses of the dry type one-component system.
However, developments with respect to thin layer forming method and apparatus of toner are indispensable since improvements of resolution and clearness of the image, etc. are required at present. Therefore, some measures with respect to this problem are proposed.
For example, as shown in Japanese Patent Application Laid-Open No. 54-43038 (1979), a developing blade (an elastic regulating member) made of rubber or a metal abuts on the developer bearing member and toner passes through an abutting portion between this developing blade and the developer bearing member and is regulated. Thus, a toner thin layer is formed on the developer bearing member and sufficient frictional charged charges (triboelectricity) are given to the toner by friction in the abutting portion. This dry type one-component developing apparatus and the thin layer forming method do not limit the toner (one-component toner) as a one-component developer at all.
In the case of magnetic toner, a developing apparatus as shown in
FIG. 16
is proposed. In this developing apparatus
104
, toner is supplied and borne onto a developing sleeve
121
(developer bearing member) by magnetic force of a magnet
113
of a roller shape arranged within the developing sleeve
121
. The toner passes through an abutting portion between the developing sleeve
121
and a developing blade
122
and is regulated so that a toner thin layer is formed on the developing sleeve
121
. In the case of nonmagnetic toner, it is necessary to separately arrange a toner supply member for supplying the toner onto the developing sleeve. This is because no nonmagnetic toner is supplied by magnetic force.
Therefore, a developing apparatus as shown in
FIG. 17
is proposed as the developing apparatus using nonmagnetic toner. In this developing apparatus
104
, a toner supply roller
123
is arranged in a position of a developing sleeve
121
on its upstream side from a developing blade
122
in a rotating direction of this developing sleeve
121
within a developing container
126
storing nonmagnetic toner T as a one-component developer. The toner supply roller
123
is constructed by using a foam body formed by polyurethane foam, sponge, etc., or a fur brush abutting on the developing sleeve
121
. The toner T is supplied and borne onto the developing sleeve
121
by rotating this toner supply roller
123
in an arrow direction.
The toner borne onto the developing sleeve
121
is sent to an abutting portion of the developing sleeve
121
and the developing blade
122
as the developing sleeve
121
is rotated. The toner is regulated and formed as a thin layer in this abutting portion. Thereafter, the toner is carried to a developing portion opposed to the photosensitive drum
110
and is used to develop an electrostatic latent image on the photosensitive drum. The toner unconsumed in the development but left on the developing sleeve
121
is returned to the interio
Hashimoto Kouji
Kobayashi Tetsuya
Sasame Hiroshi
Watanabe Yasunari
Yamamoto Shinya
Braun Fred L.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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