Electrophotography – Image formation – Development
Reexamination Certificate
2000-12-21
2002-09-10
Royer, William J. (Department: 2852)
Electrophotography
Image formation
Development
C399S299000, C399S302000, C399S303000
Reexamination Certificate
active
06449451
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus utilizing the electrophotographic recording method, such as a laser printer, a copier or a facsimile apparatus, and particularly to an image forming apparatus provided with a plurality of image bearing members and suitable for use in the in-line method wherein images formed on the image bearing members are sequentially superimposed on the same transferring member to thereby form images of a plurality of colors.
2. Related Background Art
Various color image forming apparatuses utilizing the electrophotographic recording method to form images of a plurality of colors have heretofore been devised and some of them have been put into practical use.
The image forming apparatuses of the electrophotographic recording type are excellent in that the recording speed can be made high, over image forming apparatuses of other recording types such as the ink jet type in which ink droplets are directly blown against recording paper to thereby form an image, and the silver salt photographic type in which image exposure is effected on a photosensitive chromophoric material to thereby effect recording, and are achieving distinction from those other recording types for the market needs desiring a higher speed.
As a typical example of color image forming apparatuses utilizing the electrophotographic recording method, there is, for example, a color image forming apparatus of a type containing a rotatable developing apparatus therein. The color image forming apparatus of this type is provided with a rotatable body (rotatable developing apparatus) therein, and has an apparatus construction in which developing devices of four colors, e.g. yellow, magenta, cyan and black, are disposed along the rotational peripheral surface of the rotatable body, whereby electrostatic latent image bearing bodies (photosensitive bodies) are sequentially developed with developers (toners) of the respective colors.
In the image forming apparatus adopting such a rotatable developing apparatus, the step of visualizing electrostatic latent images for the respective colors formed on a common photosensitive body as toner images at a predetermined developing position by the respective developing devices, and transferring such toner images onto sheet-like recording paper (transferring material) such as paper each time the toner image is obtained is repeated. By the repetition of such transferring step, toner images of a plurality of colors are formed.
Also, as another example, there has been devised an apparatus of a type in which toner images of respective colors are sequentially selectively superimposed on the surface of a photosensitive body to thereby form toner images of a plurality of colors on the surface of the photosensitive body, whereafter the toner images are collectively transferred to recording paper.
There is also an image forming apparatus of the so-called in-line type in which by the use of a plurality of photosensitive bodies, toner images of respective colors are discretely formed by developing devices of the respective colors, and the toner images are sequentially transferred from the respective photosensitive bodies onto a transferring member and the transferring member is conveyed to thereby form toner images of a plurality of colors.
There is also a type in which toner images of respective colors are sequentially superimposed not directly on recording paper but on an intermediate transferring member (transferring member) to thereby form toner images of a plurality of colors, whereafter the toner images are collectively transferred to the recording paper.
The above-described typical types of the color image forming apparatus utilizing the electrophotographic recording method have both merits and demerits, but from the viewpoint of the higher speed progressing conjointly with the recent market needs, the in-line type is at advantage and many products have been put into practical use by this type.
FIG. 9
of the accompanying drawings is a side view schematically showing an example of the image forming apparatus adopting the in-line type, more particularly the main internal construction of an image forming apparatus of a four-drum multiple transfer type (hereinafter referred to as the in-line color printer).
The in-line color printer
400
has photosensitive drums which are electrostatic latent image bearing members disposed in opposed relationship with developing devices containing toners of respective colors therein and successively disposed in the direction of conveyance of a transferring member, and sequentially transfers toner images of the respective colors developed on the respective drums by the developing devices to recording paper conveyed by a transferring belt or the like, and obtains a full color image by toners of four colors, i.e., yellow, magenta and cyan which are three primary colors, plus black.
In
FIG. 9
, an endless transferring belt
406
is passed over a driving roller
407
and a driven roller
410
, and is rotated in the direction of arrow, and four photosensitive drums
401
a
to
401
d
are disposed in series in opposed relationship with the transferring belt
406
. Generally, to obtain a high quality of image in the apparatus of this type, it is important to reduce the color misregistration among the images of a plurality of colors formed by superimposition, and it is preferable to make the station spacings among a plurality of image forming means (image forming stations), in other words, the spacings among the photosensitive bodies, equal to each other, and the disposition accuracy thereof is important.
It is also effective for the reduction in color misregistration to make the circumferential length of the driving roller and the spacings among the photosensitive bodies equal to each other.
Also, the image forming stations
409
a
,
409
b
,
409
c
and
409
d
for forming images of respective colors are comprised of photosensitive drums
401
a
to
401
d
, charging apparatuses
402
a
to
402
d
, exposing apparatuses
403
a
to
403
d
, developing devices
404
a
to
404
d
and cleaning apparatuses
405
a
to
405
d
, and these are disposed around the respective photosensitive drums.
In the image forming stations
409
a
,
409
b
,
409
c
and
409
d
, developer images of the respective colors are superimposed on a recording material conveyed on the transferring belt
406
by yellow (Y), magenta (M), cyan (C) and black (Bk) developers to thereby form a multicolored image. Also, the image forming stations of the respective colors have constructions substantially similar to one another with the exception that the developers of different colors are contained in the developer containing portions of the developing devices
404
a
to
404
d.
The image forming operation will hereinafter be described. A laser beam (information light including predetermined image information) modulated in conformity with image data from a host apparatus such as a personal computer is applied from the exposing apparatuses
403
a
to
403
d
to the surfaces of the photosensitive drums
401
a
to
401
d
uniformly charged by charging rollers which are charging apparatuses
402
a
to
402
d
, whereby desired electrostatic latent images are obtained for the respective colors. These latent images are reversal-developed on the predetermined developing regions of the rotational peripheral surfaces of the photosensitive drums by the developing devices
404
a
to
404
d
disposed in opposed relationship with the aforementioned predetermined developing regions and containing toners of the respective colors therein, and are visualized as toner images. These toner images are electrostatically multiplexly transferred in order of Y, M, C and Bk in transferring nip portions by the transferring apparatuses
408
a
to
408
d
to recording paper P fed by a paper feeding mechanism, not shown, i.e., the recording paper P conveyed by a conveying mechanism and entering from the right as viewed in
FIG. 9
, and a resultant
Suzuki Jun
Tsuruya Satoshi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Royer William J.
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