Electrophotography – Image formation – Development
Reexamination Certificate
1999-08-23
2003-04-08
Braun, Fred L (Department: 2852)
Electrophotography
Image formation
Development
Reexamination Certificate
active
06546220
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that is applicable, for example, as a color printer, a color copying machine or a color facsimile. More specifically, the present invention relates to a color electrophotographic apparatus for forming color images by electrophotography, and to an image forming unit used in the same.
DESCRIPTION OF THE PRIOR ART
A conventional image forming apparatus is disclosed, for example, in Publication of Unexamined Patent Application (Tokkai) No. Hei 7-36246.
The following is an explanation of a conventional color image forming apparatus as disclosed in the same publication, with reference to FIG.
43
. As shown in
FIG. 43
, an intermediate transfer belt unit
101
includes an intermediate transfer belt
102
, a primary transfer roller
103
, a secondary transfer roller
104
, a cleaner roller
105
, and a waste toner reservoir
106
. Color images can be superimposed on the transfer belt
102
. In the middle of the main body of this image forming apparatus, a group of image forming units
108
is provided. Four image forming units
107
Bk,
107
Y,
107
M and
107
C for black, yellow, magenta and cyan, each unit being of sector shape in cross section, are arranged circularly to form the group of image forming units
108
. When an image forming unit
107
Bk,
107
Y,
107
M or
107
C is installed properly in the color image forming apparatus, mechanical driving systems and electrical connection systems are coupled between the image forming units
107
Bk,
107
Y,
107
M and
107
C and other portions of the color image forming apparatus via mutual coupling members, so that both sides are mechanically and electrically connected. The image forming units
107
Bk,
107
Y,
107
M and
107
C are supported by a supporter and collectively rotated by a motor, so that they can revolve around a non-rotatable cylindrical shaft
109
. For image formation, the image forming units
107
Bk,
107
Y,
107
M and
107
C are successively moved by rotation to an image forming position
110
, where they oppose the primary transfer roller
103
spanning the intermediate transfer belt
102
. The image forming position
110
is also the exposure position for exposure with a laser signal beam
111
.
Inside this image forming apparatus, a laser exposing device
112
is arranged horizontally below the group of image forming units
108
. The laser signal beam
111
passes through a light path opening
113
between the image forming units
207
M and
207
C, and through an opening provided in the shaft
119
, and enters a mirror
114
, which is fixed inside the shaft
119
. The laser signal beam
111
reflected by the mirror
114
enters the black image forming unit
107
Bk positioned at the image forming position
110
through an exposure opening
115
. Then, the laser signal beam
111
passes through a light path between a developing device
116
and a cleaner
117
, arranged on the upper and the lower side in the image forming unit
107
Bk, enters an exposure portion on the left side of a photosensitive member
118
, and scans for exposure along the direction of the axis of the photosensitive member
118
. The toner image formed on the photosensitive member
118
is transferred to the intermediate transfer belt
102
. Then, the group of image forming units
108
rotates 90 degrees, so that the yellow image forming unit
107
Y moves into the image forming position
110
. An operation similar to the above formation of the black image is performed to form a yellow toner image overlaying the black toner image previously formed on the intermediate transfer belt
102
. Similar operations as explained above are performed using the magenta and cyan image forming units
107
M and
107
C to compose a full color image on the intermediate transfer belt
102
. After the full color image on the intermediate transfer belt
102
is completed, a recording paper is conveyed by a secondary transfer roller
104
and a tertiary transfer roller
119
, and the color image is simultaneously transferred onto the recording paper. The recording paper onto which the color image has been transferred is conveyed to a fuser
120
, which fuses the color image on the recording paper.
The above relates to an image forming apparatus as disclosed in Tokkai Hei 7-36246 etc., but these prior art examples do not disclose particular structures for retaining the image forming units precisely and reliably in the image forming apparatus, so that there is a need for the realization of such technological means.
Moreover, a color image forming apparatus for forming a color image with four image forming units by superimposing toner images on an intermediate transfer belt is known from Tokkai Hei 9-304996.
The following is an explanation of the conventional color image forming apparatus disclosed in this publication, with reference to
FIGS. 44 and 45
.
FIG. 44
is a cross sectional view showing a positioning and driving mechanism for a photosensitive member in a conventional color image forming apparatus.
FIG. 45
is a perspective view of the same.
As shown in
FIGS. 44 and 45
, flanges
402
are attached to both end portions of a drum-shaped photosensitive member
401
, and one photosensitive member shaft
403
is attached to both flanges
402
. A concave tapered surface
404
is formed on the right end of the photosensitive member shaft
403
, and a coupling plate
406
having eight tongues
405
is attached around the photosensitive member shaft
403
forming the concave tapered surface
404
. Thus, the photosensitive member
401
can be rotated by rotating the coupling plate
406
.
The photosensitive member driving mechanism, which is provided at the apparatus main body, comprises a driving shaft
411
, a coupling plate
412
rotating together with the driving shaft
411
, a driving gear
413
, and a driving motor. On the tip of the driving shaft
411
, a convex tapered surface
414
is formed, which mates with the convex tapered surface
404
formed on the right end of the photosensitive member shaft
403
.
The coupling plate
412
is provided with eight coupling tongues
418
, which mesh with the coupling plate
406
on the side of the photosensitive member
401
. The coupling plate
412
is fixed in rotation direction to the driving shaft
411
by a pin
415
, but the coupling plate
412
is movable in the axial direction within a predetermined distance. Thus, the coupling plate
412
retreats temporarily when the tips of the coupling tongues
418
abut the tips of the coupling tongues
405
. The coupling plate
412
is forced by a compression spring
416
to abut a tip stopper
417
, which holds it in a certain position.
The driving shaft
411
is supported rotatably and displaceably in the thrust direction by bearings
422
that are fixed to a hosing-side plate
420
and a driving base plate
421
. A driving shaft gear
413
meshing with a motor-side gear
423
is attached to the driving shaft
411
between the housing-side plate
420
and the driving base plate
421
. A compression spring
424
is inserted between the bearing
422
and the driving shaft gear
413
, and this compression spring
424
biases the driving shaft
411
in a direction separating it from the photosensitive member
401
. By moving a thrust bearing
425
, the driving shaft
411
can be moved against the force of the compression spring between a separated position and a coupling position
When the image forming unit in the image forming position is being changed, the driving shaft
411
is positioned in a separated position, where it is separated from the photosensitive member shaft
403
. Then, during the image forming operation, the driving shaft
411
is positioned in a coupling position, where the concave tapered surface
401
is coupled with the convex tapered surface
414
, as shown in FIG.
44
. In this coupling position, the coupling tongues
405
mesh with the coupling tongues
418
, so that a driving force can be transmitted.
The above relates to a color image forming apparatus as discl
Asakura Kenji
Katakabe Noboru
Yoshikawa Masanori
Braun Fred L
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
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