Electrophotography – Cleaning of imaging surface – Blade
Reexamination Certificate
1999-12-03
2001-10-30
Grimley, Arthur T. (Department: 2852)
Electrophotography
Cleaning of imaging surface
Blade
C015S001510, C399S346000, C399S347000, C399S351000
Reexamination Certificate
active
06311037
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a cleaning method for an image-bearing member used in an image forming apparatus according to electrophotography, inclusive of an electrostatic copying machine and an electrostatic printer, and an electrophotographic image forming apparatus adopting such a cleaning method.
In recent years, as image forming apparatus functioning as an output terminal working on a computer network, a complex machine having all functions of output terminals inclusive of a copying machine, a printer and a facsimile machine has been demanded on the market.
A demand on such an electrophotographic image forming apparatus is an increased duty cycle, i.e., an increase in upperlimit number of sheets on which the apparatus is normally operated without a maintenance service of a service engineer having a professional knowledge. A factor determining the duty cycle is a life of the image-bearing member.
Also from the ecological viewpoint, the image forming apparatus is seriously required to reduce the waste materials, i.e., to reduce the number of consumed articles and prolong the life of consumed articles.
Further, along with the progress of digital technology in recent years, digital-mode image forming apparatus is becoming predominant from hitherto predominant analog-mode image forming apparatus, and such digital mode apparatus is strongly desired to be produced at a cost comparable to or even lower than that of the analog-mode apparatus.
Further, copying machines and printers have been hitherto predominantly produced as monochromatic machines but are progressively converted into full-color machines in respects of both originals and output files. Accordingly, the production cost and running cost of a digital mode apparatus as described above and capable of full-color printing, are required to be suppressed at a level comparable to those of a monochromatic apparatus, thus remarkably reducing entire costs for users.
More specifically, the life of the image-bearing member for electrophotography depends on the performance of a cleaning device for removing a residual developer (or toner) remaining on the image-bearing member after a transfer step. In a well-known image forming apparatus, it is difficult to transfer the developer (or toner) constituting a visible image on an image-bearing member completely onto a transfer (receiving) material during the transfer step, and a slight portion of the toner inevitably remains on the image-bearing member after the transfer step. Further, some powdery fraction of the transfer material can remain on the image-bearing member due to contact thereof with the image-bearing member. Unless the portion of the toner and transfer material remaining on the image-bearing member after the transfer step (which may be inclusively referred to as “transfer residual toner” hereinafter in some cases) are sufficiently removed prior to a subsequent image forming cycle on the image-bearing member, the quality of an image formed in the subsequent image-forming cycle is lowered due to interference with the transfer residual toner. For this reason, the transfer residual toner has to be sufficiently removed after each transfer operation.
As cleaning means for the above purpose, various devices have been proposed heretofore. For example, there has been proposed a cleaning device including a cleaning blade comprising a resilient material, such as rubber, and abutted against the image-bearing member for removing by scraping off the transfer residual toner by an edge of the cleaning blade. The cleaning device is simple in structure, can be produced at a low cost and yet exhibits excellent performance of removing the transfer residual toner. Accordingly, such a cleaning device using a cleaning blade has been widely commercialized.
FIG. 1
is a schematic side sectional view of a conventional cleaning device disposed in proximity to a rotatory cylindrical image-bearing member
51
having an axis extending in a direction perpendicular to the drawing paper. Around the image-bearing member
51
, a charger, a developing device and a transfer means are disposed though not shown in FIG.
1
.
The cleaning device comprises a casing
53
having an opening directed toward the image-bearing member
51
and a cleaning blade
52
of urethane rubber, etc., affixed at one edge thereof with the edge of the opening, so that the other edge of the blade
52
is abutted against the image-bearing member so as to scrape off the transfer residual toner remaining on the image-bearing member after the transfer zone.
A portion of the transfer residual toner scraped off by the cleaning blade
52
and resident on the image-bearing member
51
functions to reduce the friction between the cleaning blade
52
and the image-bearing member
51
, whereby a good cleaning performance can be attained without a turnover of the cleaning blade
52
.
FIG. 2
illustrates another known cleaning device
43
, which is disposed in proximity to a rotatable cylindrical image-bearing member
32
having a rotation axis extending in a direction perpendicular to the drawing paper. Similarly as in
FIG. 1
, a charger, a developing device, a transfer means, etc., are disposed around the cylindrical image-bearing member
32
though not shown in FIG.
2
. The image-bearing member
32
is rotated in the direction of an indicated arrow A by a drive mechanism (not shown).
The cleaning device
43
comprises a casing
44
having an opening facing the image-bearing member
32
. At the opening, a cleaning blade
45
of urethane rubber, etc., is affixed with its one end by means of a supporting member
46
. The cleaning blade
45
is supplied with a force exerted from a spring (elastic member)
49
via a fulcrum
50
so as to be abutted with the other end thereof against the image-bearing member
32
. The cleaning blade
45
is disposed in a counter direction with respect to the drive direction of the image-bearing member
32
, i.e., in a direction such that the direction from the root (supported position) of the cleaning blade
45
toward a point of contact thereof with the image-bearing member is almost opposite to the direction of movement of the image-bearing member contacting the blade
45
. The transfer residual toner occurring at a transfer position (not shown) on the image-bearing member is moved to the edge of the cleaning blade
45
to be scraped off thereby.
A portion of the transfer residual toner scraped off by the cleaning blade
45
is caused to remain on the image-bearing member
32
under the rotation of the image-bearing member
32
. The transfer residual toner remaining in a small amount is supplied to the edge of the cleaning blade
45
, whereby a good cleaning performance can be attained without turnover of the cleaning blade
45
. Thus, the transfer residual toner powder reduces the frictional force acting between the blade
45
and the image-bearing member
32
.
The presence of silica fine particles of ca. 0.01 &mgr;m in volume-average particle size (diameter) externally added to the developer for improving the flowability of the developer and stabilizing the abutment of the cleaning blade against the image-bearing member is effective for further reducing the abutting force acting at the abutting position.
However, as the amount of transfer residual toner varies depending on the image density of originals to be reproduced, it is difficult to always supply a constant amount of developer to the abutting position to stably retain the abutting state.
For example, in the case of forming a large number of images at a low image density, a smaller amount of developer is supplied to the abutting position. As a result, the effect of reducing the abutting force acting between the cleaning blade and the image-bearing member is liable to be insufficient, whereby the cleaning blade can be turned over toward the direction of movement of the image-bearing member, so that the function of scraping off the attached matter on the image-bearing member can be significantly lowered but an im
Hisakuni Hisataka
Kubo Norihiko
Nakayama Yuji
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Grimley Arthur T.
Ngo Hoang
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