Electrophotography – Having particular structure – Modular or displaceable
Reexamination Certificate
2000-11-28
2002-11-05
Chen, Sophia S. (Department: 2852)
Electrophotography
Having particular structure
Modular or displaceable
Reexamination Certificate
active
06477346
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus using the electrophotographic method, and for example, to an image forming apparatus such as a copier, a printer or a facsimile apparatus.
2. Related Background Art
As an image forming apparatus capable of polychromatic printing such as a color printer or a color copier, there has heretofore been proposed a color image forming apparatus which has a plurality of units (process cartridges) provided with at least photosensitive drums and detachably mountable to the main body of an image forming apparatus, and an exposure device for exposing each photosensitive drum charged in conformity with image information and forming an electrostatic latent image, and in which toner images of respective colors formed on the respective photosensitive drums are sequentially superimposed and primary-transferred to an intermediate transfer member, whereafter the toner images of respective colors on the intermediate transfer member are collectively secondary-transferred to a recording material.
Here, a bad image, i.e., an image having color misregistration, occurring when the disposed state of the photosensitive drums is inclined with respect to their regular position will be described with reference to a typical perspective view and a plan view shown in
FIG. 12A
, consisting of FIGS.
12
A
1
and
12
A
2
, and
12
B, consiting of FIGS.
12
B
1
and
12
B
2
, respectively, of the accompanying drawings.
Consider a case where as shown in
FIG. 12A
, a photosensitive drum
501
is inclined by an amount of deviation &Dgr;x, i.e., an inclination a with respect to an ideal position (alternate long and two short dashes line) in a plane wherein photosensitive drums are juxtaposed. When a laser beam based on image information is scanned on this photosensitive drum
501
by an exposure device, the photosensitive drum is exposed as indicated by a heavy line L(Exp), and at a transfer position, as indicated by a heavy line L(Tr), an amount of deviation 2&Dgr;x, i.e., an image transferred from the photosensitive drum onto an intermediate transfer member
502
, becomes inclined by 2&agr; which is double the aforementioned inclination &agr;. Further, if the inclinations of a plurality of photosensitive drums differ from one another, the inclinations of the images transferred onto the intermediate transfer member
502
also differ from one another and the positions of the toner images of respective colors on the intermediate transfer member
502
do not become coincident with one another within an allowable range, and become color misregistration or color irregularity.
Also, when as shown in
FIG. 12B
, the length of the optical path from an exposure device (laser deflector) to the surface of the photosensitive drum
501
differs between the scanning starting side (one lengthwise end side of the photosensitive drum) and the scanning ending side (the other lengthwise end side of the photosensitive drum), even if the light emission timing of the laser beam is controlled to thereby conform the exposure starting positions of the laser beams of respective colors to one another and a modulation frequency for effecting the light modulation of the laser beams is changed to thereby make general magnifications (the width of the image and the width in the main scanning direction) coincident with each other, the inclination &bgr; of the photosensitive drum
501
with respect to the exposure direction leaves an amount of deviation &Dgr;z at the intermediate position of the image and appears as color misregistration. So, in order to eliminate these inclinations &agr; and &bgr;, that is, to eliminate the amounts of deviation &Dgr;x and &Dgr;y relative to the regular position of the photosensitive drum, it is necessary to accurately determine the position at which each photosensitive drum is disposed.
So, heretofore, in order to accurately position the plurality of photosensitive drums
501
in the main body of the image forming apparatus, there has been adopted a method as shown in
FIG. 13
of the accompanying drawings wherein the rotary shaft portions
511
of the plurality of photosensitive drums
501
are accurately fixed and supported in engagement holes
604
disposed in a common centering plate
601
comprising a single member, and the reference apertures
602
A and
602
B of the common centering plate
601
are fitted to positioning pins
603
A and
603
B provided on a front side plate
600
constituting the frame of the main body of the image forming apparatus to thereby accurately position the photosensitive drums.
In the above-described construction according to the prior art, however, the plurality of photosensitive drums
501
are accurately positioned by the common centering plate
601
which is a single member and therefore, high dimensional accuracy has been required when the engagement holes
604
are formed in the common centering plate
601
.
Further, when each photosensitive drum
501
(or process cartridge) is to be interchanged, it is necessary to once detach the common centering plate
601
, and in case of the assembly after the interchange, the shaft portions
511
of the plurality of photosensitive drums must be engaged with the engagement holes
604
in the common centering plate
601
at a time, and this has been a factor which makes the work of interchanging the photosensitive drums
501
, etc. difficult. Likewise, in the manufacturing process of the image forming apparatus, it has been a factor which makes the assembling work for the photosensitive drum difficult.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image forming apparatus in which the position of each rotary shaft or each bearing of a first image bearing member and a second image bearing member can be adjusted easily.
It is another object of the present invention to provide an image forming apparatus in which the position of each protruding portion provided on a first unit and a second unit can be adjusted easily.
Further objects of the present invention will become apparent by reading the following detailed description.
REFERENCES:
patent: 5218405 (1993-06-01), Wong
patent: 5745825 (1998-04-01), Okawa et al.
patent: 6175705 (2001-01-01), Harada et al.
patent: 6198891 (2001-03-01), Ishida et al.
patent: 6249661 (2001-06-01), Saito et al.
patent: 63-43173 (1988-02-01), None
patent: 8-87152 (1996-04-01), None
patent: 8-220972 (1996-08-01), None
Canon Kabushiki Kaisha
Chen Sophia S.
Fitzpatrick ,Cella, Harper & Scinto
Tran Hoan
LandOfFree
Image forming apparatus featuring a plurality of image... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image forming apparatus featuring a plurality of image..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming apparatus featuring a plurality of image... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2971277