Electrophotography – Image formation – Photoconductive member
Reexamination Certificate
2001-12-12
2004-03-23
Tran, Hoan (Department: 2852)
Electrophotography
Image formation
Photoconductive member
C399S343000
Reexamination Certificate
active
06711368
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, etc., and more specifically, to an image forming apparatus with a blade-shaped abutment member which includes an image carrying member having a photosensitive layer and a photosensitive layer carrying member carrying thereon the photosensitive layer, and in which a latent image is formed on the image carrying member in an image forming area thereof in accordance with image information and developed to provide a toner image, which is then transferred to a transfer material, whereupon the residual toner attached to the image carrying member is removed by the abutment member.
2. Description of the Related Art
FIG. 10
is a cross sectional view illustrating the relation between a cylindrical (drum-shaped) photoreceptor (cylindrical photoreceptor) and a cleaning part for removing the toner, which is not transferred but remains on the photoreceptor, from the photoreceptor, in an image forming apparatus such as a copying machine, etc., applying electrophotography. There are two types of cleaning parts, one using a cleaning blade and the other using a roller in the form a fur brush. Practically, the main stream of the cleaning parts is a technique of using a cleaning blade
81
as shown in
FIG. 10
because it is at low costs, easy to design, excellent in the scraping function, and so on. A photoreceptor
70
in
FIG. 10
is used for repeatedly performing the processes of charging, image exposure, development, transfer, cleaning, etc., while being rotated in a direction of an arrow RR. Among these processes, a cleaning part
80
is used for removing the toner remaining on the photoreceptor
70
after the transfer process, and plays an important role of forming a clear copy image.
In the example as described above, the cleaning part
80
uses a plate-like cleaning blade
81
for removing toner. In this case, the cleaning blade
81
is mounted in such a manner that one
81
a
of opposite edges
81
a
,
81
b
of one side of the cleaning blade
81
is in abutment with a surface of the photoreceptor
70
. Thus, in the cross sectional view of
FIG. 10
, the cleaning blade
81
is mounted in such a manner that an angle &phgr;, which is formed between the cleaning blade
81
and the tangent line of the photoreceptor
70
at a location at which the cleaning blade
81
abuts against the photoreceptor
70
, become an acute angle. This angle &phgr; is set such that the toner, which remains on the photoreceptor
70
without being transferred, can be efficiently scraped off and dropped into a collection part
82
in opposition to the rotation of the photoreceptor
70
in the direction of the arrow RR.
The cleaning part of the above-mentioned known image forming apparatus has an excellent cleaning characteristic through the use of the cleaning blade, but is apt to produce a large friction between the cleaning blade and the photoreceptor. As a result, there would arise a problem that those portions of the cleaning blade
81
in the vicinity of edges
81
a
,
81
b
thereof which are in abutment with the photoreceptor
70
are easily inverted or turned over (hereinafter also referred to as curling) due to the large friction, as shown in FIG.
11
. Referring to
FIG. 11
, the portions of the cleaning blade
81
in the vicinity of the edges
81
a
,
81
b
thereof are turned over or curled up, so the edge
81
b
, instead of the edge
81
a
which has abutted against the photoreceptor
70
before occurrence of the turned-over or curling state, comes to be pressed against the surface of the photoreceptor
70
, from which it will be understood that it is difficult to scrape off the toner remaining on the photoreceptor therefrom.
As a proposal for solving the problem of the known image forming apparatus as described above, there are inventions disclosed in Japanese Patent Application Laid-Open No. Hei 3-1979 and Japanese Patent Application Laid-Open No. Hei 7-319359 for instance. In the invention disclosed in Japanese Patent Application Laid-Open No. Hei 3-1979, the photoreceptor is prevented from being curled up by applying a lubricant such as an organic solvent dispersing liquid of lubricating minute powder such as Kynar, etc., to the surface of the photoreceptor at the initial stage of using the image forming apparatus. The lubricant is gradually removed from the photoreceptor as the operating time elapses, and does not serve for a lubricating function, but it is intended for toner to succeed the role of the lubricant in place thereof, thereby preventing curling of the photoreceptor.
In the above case, however, there is another problem in that if the lubricant, which is attached to the photoreceptor by application of the organic solvent dispersing liquid, is prevented from being detached from the photoreceptor so as to sustain the intended effect of the lubricant, an adverse influence resulting therefrom would appear to an image to be formed, giving rise to an image defect. Additionally, in this case, the photoreceptor includes an image forming area in which an image is formed according to image information. and a developing area which is wider than the image forming area and in which development is carried out by toner, and hence the toner used for development is supplied to the cleaning blade in a portion of the cleaning blade corresponding to the developing area, so that there would be little fear that a large friction might be generated between the cleaning blade and the photoreceptor. However, toner is not sufficiently supplied to the portions of the cleaning blade corresponding to those portions of the photoreceptor which lie outside the developing area thereof, thus causing a further problem that a large friction is created between the cleaning blade and the photoreceptor, from where the edges of the cleaning blade come to be easily turned over.
In the invention disclosed in Japanese Patent Application Laid-Open No. Hei 7-319359, there is proposed a technology of preventing the problem encountered with the above-mentioned invention, i.e., the turning over or curling in the portions of the cleaning blade, which lie outside the width of the developing area of the photoreceptor. In this proposal, development holding members are arranged at opposite ends of the cleaning blade, and intended to serve the purpose that the toner lying outside the width of developing area on a transfer belt is wiped off so as to adjust the toner to a suitable amount when the amount of toner is excessive, and the toner wiped off is made to attach to the transfer belt when the amount of toner lying outside the width of the developing area is too small, thereby making it possible to supply the toner to the entire surface of the cleaning blade. However, there arises a further problem that if non-image patterns continue at the opposite ends of the width of each image in the formation of images on the photoreceptor, toner would not be accumulated on the development holding members, thus resulting in a situation that there easily takes place curling of the cleaning blade.
SUMMARY OF THE INVENTION
The present invention is intended to solve the problems as referred to above, and has for its object to provide an image forming apparatus which is capable of preventing a cleaning blade from being curled up or turned over with the passage of an operation time thereof or due to the shapes of patterns forming images even when a cleaning blade, which is low in cost, easy to design and excellent in a toner scraping function, is used as a cleaning device.
In order to solve the above-mentioned problems, the present invention resides in an image forming apparatus which includes: an image carrying member (photoreceptor) having a photosensitive layer and a photosensitive layer carrying member (original pipe) carrying the photosensitive layer; a latent image forming device for forming a latent image on the image carrying member in accordance with image information; a developing device for forming a toner image
Kabushiki Kaisha Toshiba
Tran Hoan
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