Electrophotography – Control of electrophotography process – Of plural processes
Reexamination Certificate
2000-05-03
2003-02-25
Chen, Sophia S. (Department: 2852)
Electrophotography
Control of electrophotography process
Of plural processes
C399S092000, C399S299000, C399S302000
Reexamination Certificate
active
06526237
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus utilizing an electrophotographic method, such as a copying machine, a printer, a facsimile or the like.
2. Description of the Related Art
In conventional color image forming apparatuses such as copying machines, printers or the like, an intermediate transfer method is used where toner images formed in a plurality of image forming sections are sequentially superimposed on an intermediate transfer body and then transferred onto a recording medium altogether.
An example of an embodiment of an image forming apparatus utilizing this intermediate transfer method will be explained using FIG.
6
. First, electrostatic latent images are formed on a plurality of photographic photosensitive drums
101
a,
101
b,
101
c,
and
101
d
by using light, magnet, electric charge or the like, and then respective toners having respective colors are provided from respective developers
102
a,
102
b,
102
c,
102
d
to form toner images, thereby developing (visualizing) the electrostatic latent images.
An intermediate transfer belt
103
as an intermediate transfer body is arranged to be suspended by a drive roller
105
, a driven roller
106
and a tension roller
107
so as to be disposed opposite each of the photosensitive drums
101
a,
101
b,
101
c,
and
101
d
along a straight, horizontal plane, and the toner images formed on the surfaces of the photosensitive drums
101
a,
101
b,
101
c,
and
101
d
are sequentially transferred onto the intermediate transfer belt
103
in a superimposed manner by the action of primary transfer blades
104
a,
104
b,
104
c
and
104
d,
as primary transfer means, disposed on an opposite side of the intermediate transfer belt
103
from the respective photosensitive drums
101
a,
101
b,
101
c,
and
101
d.
A secondary transfer roller
108
is disposed on a side of the intermediate transfer belt
103
opposite the driven roller
106
, as a secondary transfer means, and sheets P composed of papers, synthetic resins or the like serving as recording media are suitably fed from sheet cassettes
109
a,
109
b,
or a manual feed tray
110
to a position between the intermediate transfer belt
103
and the secondary transfer roller
108
where the toner images transferred on the intermediate transfer belt
103
are re-transferred onto the sheets P by the action of the secondary transfer roller
108
.
The sheets P on which the toner images have been transferred are subjected to permanent fixation through heating and pressurizing treatments by a fixing device
111
, including upper and lower fixing rollers
111
a,
111
b,
and then delivered out of the apparatus. Using the photosensitive drums
101
a,
101
b,
101
c
and
101
d
as image forming means of Yellow, Magenta, Cyan and Black in a sequential order can give full color images; or using any one of the photosensitive drum
101
a,
101
b,
101
c,
or
101
d
can give a single color image (e.g., black).
The image forming apparatus with the above-mentioned intermediate transfer method is structured so that toner images transferred from the photosensitive drums
101
a,
101
b,
101
c
and
101
d
as intermediate transfer bodies onto the intermediate transfer belt
103
are read (detected) using an image reading means
112
, and that based on image information detected/read, image quality improvement is promoted.
The image reading means
112
, for instance, reads the image density of a toner image formed on the intermediate transfer belt
103
, and then, based on the information thus obtained, image forming conditions or primary transfer conditions are changed; or relative output image positions of respective photosensitive drums
101
a,
101
b,
101
c
and
101
d
are detected based on the positions of the respective color toner images formed on the intermediate transfer belt
103
, and then, in order to correct the amount of slippage with respect to the position accuracy, the image forming timing or the image forming positions of the photosensitive drums
101
a,
101
b,
101
c
and
101
d
are thereby corrected.
In the aforementioned conventional example, however, the fixing device
111
where the toner image on the sheet P is heated, melted and fixed on the sheet P heats up its surrounding environment because the fixing device
111
is required to generate quite a huge amount of heat to perform its function. Heat thus generated from the fixing device
111
thermally affects various parts arranged around the fixing device, and especially in the case where the heat reaches the intermediate transfer belt
103
, thermal expansion of the belt is generated in the vicinity of the fixing device
111
, thermal contraction occurs as the belt moves away from the fixing device
111
, and rotation of the intermediate transfer belt
103
makes this phenomenon repeating.
Accompanied by the heat stretching and contraction of the intermediate transfer belt
103
as mentioned above, toner images used for detection on the intermediate transfer belt
103
(detection toner images) become stretched and contracted, and especially in the case where toner images with a plurality of colors are superimposed on the intermediate transfer belt
103
a,
color slippage problem in terms of position arises.
Also, the heat capacity of the intermediate transfer belt
103
becomes smaller because of its structural function, so the appearance of influences by the aforementioned heat stretching and contraction are easily observed, and consequently there is posed a problem of lowered image quality, such as color slippage or the like.
In addition, a problem arises where, when the heat of the intermediate transfer belt
103
affects the image reading means
112
, this causes optical parts such as optical lenses constituting the image reading means
112
to generate thermal expansion or distortion, thereby lowering the image reading accuracy.
Furthermore, when detection toner images are detected on a peripheral surface of the intermediate transfer belt
103
winding around a roller which supports and suspends the intermediate transfer belt
103
, the fixing heat causes a change in the roller diameter, resulting in a lowering of the detecting accuracy.
The same problems as mentioned above occur in image forming apparatuses utilizing conveyance belts for carrying and conveying recording materials in order to sequentially transfer toner images from respective photosensitive drums onto the recording materials.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image forming apparatus capable of improving a detecting accuracy of a detecting means which detects toner images formed on a movable body.
Other objects of the present invention will be apparent by reading the following detailed description of the preferred embodiments.
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patent: 5701569 (1997-12-01), Kanazawa et al.
patent: 5740492 (1998-04-01), Deki et al.
patent: 5842080 (1998-11-01), Ashibe et al.
patent: 5991558 (1999-11-01), Emi et al.
patent: 6038423 (2000-03-01), Tagawa et al.
patent: 6188418 (2001-02-01), Hata
patent: 6285849 (2001-09-01), Shimada et al.
patent: 03-255473 (1991-11-01), None
patent: 09-327943 (1997-12-01), None
patent: 10-020579 (1998-01-01), None
patent: 10-282809 (1998-10-01), None
patent: 10-293432 (1998-11-01), None
patent: 11-052637 (1999-02-01), None
Canon Kabushiki Kaisha
Chen Sophia S.
Fitzpatrick ,Cella, Harper & Scinto
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