Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2001-02-20
2002-11-19
Lee, Susan S. Y. (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S152000, C347S263000, C399S107000, C399S110000
Reexamination Certificate
active
06483527
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus of a copying machine, a printer and the like, and more particularly, to an image forming apparatus for forming a color image using a plurality of image forming parts.
2. Related Background Art
As shown in
FIGS. 12A and 12B
, there is a conventional full color image forming apparatus of the in-line type which has a plurality of photosensitive drums arranged in line. There are mainly two kinds of such full color image forming apparatuses. One is an image forming apparatus
200
A of the horizontal arrangement type which has a plurality of photosensitive drums horizontally arranged in line as shown in FIG.
12
A and the other is an image forming apparatus
200
B of the vertical arrangement type which has a plurality of photosensitive drums vertically arranged in line as shown in FIG.
12
B. Their features are that the image forming apparatus
200
A of the horizontal arrangement type is short in height but requires a large area for installation, while that the image forming apparatus
200
B of the vertical arrangement type requires a small area for installation but is tall in height.
In an in-line full color image forming apparatus, parallelism of each photosensitive drum
201
and accuracy in position between a scanner unit
202
and the drum are, always considered to be very important in light of an image color aberration.
Conventionally, as the image forming apparatus
200
B of the vertical arrangement type shown in
FIG. 14
, the photosensitive drum
201
is positioned by being abutted to a drum support block
204
mounted on each of right and left side plates
203
a
and
203
b
with accuracy.
The scanner unit
202
is positioned by being mounted on a scanner stand
205
so as to bridge the right and left side plates
203
a
and
203
b
and being secured on the scanner stand
205
by screws with accuracy.
In a conventional color printer, the most important problem has been a tilt aberration of each color in a printed image. As shown in
FIG. 13
, when black (Bk) and magenta (M) are recorded in superposed relation, a tilt between the photosensitive drums of the colors and a tilt of the scanner unit from the photosensitive drum directly appear on the image as the tilt aberration G. Namely, when the parallelism of four photosensitive drums is lost, the tilt aberration G of each color occurs on the printed image. In addition, when parallelism of an optical axis of the scanner unit and an axis of each photosensitive drum is lost, the tilt aberration G of each color occurs on the printed image likewise.
Conventionally, as shown in
FIG. 14
, in order to obtain accuracy in position of a plurality of the photosensitive drums
201
and the scanner units
202
, the drum support blocks
204
are used in all four parts to assure parallelism of the photosensitive drums. For the scanner unit
202
, parallelism of the scanner stand
205
is strictly defined or the plate is thickened in order to strengthen rigidity or the like so as to improve accuracy and strength of components.
In case where improving accuracy of the component is not sufficient, during assembly, a master tool which has an assured positional relationship is used to adjust a position of the scanner stand
205
whereto the drum support block
204
and the scanner
202
are mounted. There is another means such that the position is adjusted by an adjustment mechanism which can make fine adjustment to the assembly. Generally used as an adjustment method is a mechanical adjustment mechanism using a cam or a lever.
In the above described means, however, there is a limit in strictly defining the accuracy of the component and assuring the position. It is generally said that amount of color aberration accepted in the color printer is 100 &mgr;m, and the color aberration in this configuration should be within tens of &mgr;m in spite of various factors of the color aberration. For this reason, each component has to be manufactured in the accuracy of some &mgr;m, which requires impracticable measurement defining in the drum support block
204
and the scanner stand
205
.
Further, assembly by adjustment and fine adjustment in position cause an increase in cost and requires time-consuming adjustment, which is a serious disadvantage for products such as printers to be mass produced.
SUMMARY OF THE INVENTION
The present invention is made in view of the above problems and an object of the present invention is to provide an image forming apparatus which forms images with good quality.
An another object of the present invention is to provide an image forming apparatus with high accuracy in mutual position of a plurality of image forming portions.
A still another object of the present invention is to provide an image forming apparatus comprising:
a plurality of image bearing members;
a plurality of image writing means for writing an image onto: each of said image bearing member; and
a frame for supporting a plurality of said image bearing members and a plurality of said image writing means, said frame having a plurality of first holding parts which hold both ends of each of said image bearing body and a plurality of second holding parts which hold both ends of each of said image writing means.
Further objects of the present invention will become more apparent upon a reading of the following detailed description with reference to the drawings.
REFERENCES:
patent: 5552857 (1996-09-01), Ishikawa
patent: 5758243 (1998-05-01), Haneda et al.
patent: 6236820 (2001-05-01), Nakazato et al.
patent: 6278471 (2001-08-01), Uchiyama et al.
patent: 6396524 (2002-05-01), Cooper et al.
Irei Yoshiharu
Kaneko Tamotsu
Matsuoka Isao
Miyamoto Takayuki
Nakao Jun
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Lee Susan S. Y.
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