Color image forming apparatus

Details Color image forming apparatus Color image forming apparatus

2000-02-29

2001-02-13

Lee, Susan S. Y. (Department: 2852)

Incremental printing of symbolic information

Electric marking apparatus or processes

Electrostatic

C399S049000, C399S301000, C399S302000

Reexamination Certificate

active

06188418

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a color image forming apparatus having a color deviation detecting function in a registration mechanism of color image forming apparatus of tandem engine type.
BACKGROUND OF THE INVENTION
In a conventional image forming apparatus of electrophotographic type, a uniform electric charge of about 1 millicoulomb per square centimeter is applied on the surface of a photosensitive drum. This surface of a photosensitive drum is exposed depending on the image information, and the electric charge of its irradiated portion only is released to the photosensitive drum substrate, and an image (electrostatic latent image) is formed as a result of distribution of electric charge. This electrostatic latent image is developed by coloring charged particles (toner particles), and a powder image is formed (toner development). The powder image is transferred onto a sheet material or the like. The transferred powder image is fused and fixed by heat or other energy, and an image is formed.
Recently, on the other hand, the image by the image forming apparatus of electrophotographic type is becoming colorful. As the color image forming apparatus, a color image forming apparatus of tandem engine type is proposed. This color image forming apparatus includes a plurality of image forming stations having a photosensitive drum. The plurality of image forming stations are image forming stations for forming cyan image, magenta image, yellow image, and, preferably, black image on each photosensitive drum. The powder image formed on each photosensitive drum is overlaid on an intermediate transfer material at transfer position of each color powder image, and transferred and synthesized. In the color image forming apparatus of tandem engine type, the image can be formed at high speed because each image is formed parallel in each color.
In the case of color image forming apparatus, however, each powder image formed in a different image forming station may be deviated in position due to positioning error between image forming stations, resulting in color deviation. To develop a color image forming apparatus of high quality, such color deviation is a serious problem, and the technique for correcting color deviation (registration) is required.
FIG. 8
is a block diagram of a conventional color image forming apparatus, and
FIGS. 9A
, B, C, D, E are diagrams showing types of color deviation in a general color image forming apparatus.
As shown in
FIG. 8
, a conventional color image forming apparatus comprises four image forming stations Pa, Pb, Pc, Pd arranged parallel in contact with the top of an intermediate transfer belt
7
which is rotated by drive rollers
14
a,
14
b.
Each image forming station has photosensitive drums
1
a,
1
b,
1
c,
1
d
contacting with the intermediate transfer belt
7
mounted on the color image forming apparatus main body respectively. Around the photosensitive drums
1
a,
1
b,
1
c,
1
d,
chargers
2
a,
2
b,
2
c,
2
d
are disposed for providing each photosensitive drum with an electrostatic charge. On the top of the image forming stations Pa, Pb, Pc, Pd, there is an exposure unit
3
which is a scanning optical system for forming an electrostatic latent image by exposing the light depending on the image information to the photosensitive drums
1
a,
1
b,
1
c,
1
d
charged by the charger unit. The exposure unit
3
includes an exposure unit
3
K for the photosensitive drum
1
a,
an exposure unit
3
C for the photosensitive drum
1
b,
an exposure unit
3
M for the photosensitive drum
1
b,
and an exposure unit
3
Y for the photosensitive drum
1
d.
A color deviation detector
13
is disposed near the drive roller
14
a.
Each one of the photosensitive drums
1
a,
1
b,
1
c,
1
d
is surrounded by:
developing units
4
a,
4
b,
4
c,
4
d
for developing the electrostatic latent image formed by exposure by coloring toner particles, and forming a powder image,
transfer units
5
a,
5
b,
5
c,
5
d
for transferring and synthesizing by overlaying each powder image formed by the developing units
4
a,
4
b,
4
c,
4
d
on the intermediate transfer belt
7
at the transfer position of each color powder image, and
cleaning units
6
a,
6
b,
6
c,
6
d
for cleaning and removing the residual toner particles on the surface of the photosensitive drums
1
a,
1
b,
1
c,
1
d
after the powder images are transferred on the ntermediate transfer belt
7
by the transfer units
5
a,
5
b,
5
c,
5
d.
The intermediate transfer belt
7
moves in the direction of arrow A shown in
FIG. 8
, and the photosensitive drums
1
a,
1
b,
1
c,
1
d
rotate in the direction of arrow B shown in
FIG. 8
without sliding on the intermediate transfer belt
7
.
In the conventional color image forming apparatus having such constitution, the image forming operation is described below.
First, at the image forming station Pa, the surface of the photosensitive drum
1
a
is uniformly charged with an electrostatic charge by the charger
2
a.
An electrostatic latent image corresponding to the image information of black component is formed on the photosensitive drum
1
a
by the exposure unit
3
K.
This electrostatic latent image is developed on the photosensitive drum la as a powder image by black toner particles by the developing unit
4
a.
This powder image is transferred on the intermediate transfer belt
7
as a black toner image by the transfer unit
5
a.
The surface of the photosensitive drum
1
a
after transfer process is cleaned by the cleaning unit
6
a,
and residual toner particles are removed to be ready for next image formation.
Parallel to the timing of forming the black toner image, at the image forming station Pb, the surface of the photosensitive drum
1
b
is uniformly charged with an electrostatic charge by the charger
2
b,
and
An electrostatic latent image corresponding to the image information of cyan component is formed on the photosensitive drum
1
b
by the exposure unit
3
C.
This electrostatic latent image is developed on the photosensitive drum
1
b
as a powder image by cyan toner particles by the developing unit
4
b,
and
It is laid over the black toner image formed on the intermediate transfer belt
7
, and a synthetic toner image is formed.
Similarly, thereafter, a magenta toner image is overlaid by the image forming station Pc, and a yellow toner image by the image forming station Pd sequentially on the intermediate transfer belt
7
. In this way, the synthetic toner image is formed by overlaying four color toner images on the intermediate transfer belt
7
.
After completion of formation of the synthetic toner image, a sheet material
9
of paper or the like is supplied in between the intermediate transfer belt
7
and a transfer roller
11
from a paper feed cassette
10
through a paper feed roller
8
. The transfer roller
11
is disposed at a position contacting with the intermediate transfer belt
7
for inserting the sheet material
9
between it and the intermediate transfer belt
7
. When the sheet material
9
is supplied, the synthetic toner image is transferred on the sheet material
9
. Then, after being heated and fixed by a fixing unit
12
, a color image is formed on the sheet material
9
.
In such image forming apparatus of tandem engine type, however, color deviation may occur in the following cases:
1) Unstable temperature when turning on the power.
2) Exchange of image forming stations Pa, Pb, Pc, Pd.
3) Setting condition of the image forming apparatus.
4) Deviation of mounting of the image forming stations Pa, Pb, Pc, Pd and scanning optical system due to temperature changes in the apparatus.
FIGS. 9A
to E depict modes of color deviation.
FIG. 9A
shows deviation of sub-scanning position by moving parallel to the moving direction A of the intermediate transfer belt
7
. In the diagram, Ra indicates a correct position, and Ea shows a deviated position, schematically.
FIG. 9B
shows deviation of main scanning position by moving parallel to the scanning direction of the exposure unit
3
(the directi

Affiliated with

Also associated with

Rating

Color image forming apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Color image forming apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Color image forming apparatus will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2583913