Electrophotography – Image formation – Transfer
Reexamination Certificate
2000-08-30
2002-02-19
Royer, William J. (Department: 2852)
Electrophotography
Image formation
Transfer
Reexamination Certificate
active
06349192
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to image forming apparatus such as copiers and laser printers employing an electrophotographic system or electrostatic recording system and, more particularly, to configurations of an intermediate transfer module and a secondary transfer module.
2. Description of the Related Art
In general, conventional image forming apparatus such as copiers and laser printers employing an electrophotographic system or electrostatic recording system as described above have a configuration in which image exposure is performed on a surface of a photosensitive drum to form an electrostatic latent image; the electrostatic latent image formed on the surface of he photosensitive drum is developed by a developing device to form a toner image in a predetermined color, and the toner image is directly transferred on to and fixed on recording paper or temporarily transferred to an intermediate transfer body and is thereafter transferred on to the recording paper at a time to form an image.
When a color image is formed by an image forming apparatus as described above, as shown in
FIG. 27
, a configuration may be employed in which a latent image forming step of performing image exposure on a surface of a single photosensitive drum
200
with an image exposure device
201
to form an electrostatic latent image associated with a predetermined color and a developing step of developing the latent image with a developing device
202
for the associated color are repeated for a predetermined number of colors; toner images T having the predetermined colors sequentially formed on the surface of the photosensitive drum
200
are subjected to primary transfer on to an intermediate transfer belt
203
on a multiplex basis; and the toner images are subjected to secondary transfer from the intermediate transfer belt
203
on to recording paper
204
at a time to form a color image.
Image forming apparatus as described above include so-called tandem type image forming apparatus having plural (e.g., four) photosensitive drums each associated with a predetermined color and having a configuration in which toner images in predetermined colors sequentially formed on surfaces of the respective photosensitive drums are subjected to primary transfer on to an intermediate transfer belt on a multiplex basis; and the toner images are thereafter subjected to secondary transfer from the intermediate transfer belt on to recording paper at a time to form a color image.
For example, as shown in
FIG. 29
, a tandem type image forming apparatus as described above has four image forming units, i.e., a black image forming unit
300
K for forming an image in black (K), a yellow image forming unit
300
Y for forming an image in yellow (Y), a magenta image forming unit
300
M for forming an image in magenta (M) and a cyan image forming unit
300
C for forming an image in cyan (C). The four image forming units
300
K,
300
Y,
300
M and
300
C arc horizontally arranged at constant intervals from each other. Below the image forming units
300
K,
300
Y,
300
M and
300
C for black (K), yellow (Y), magenta (M) and cyan (C), an intermediate transfer belt
301
for transferring toner images sequentially formed by the respective image forming units in an overlapping relationship with each other is provided such that it is driven by plural rolls
311
through
314
including driving rolls for rotation in the direction indicated by the arrow. For example, the intermediate transfer belt
301
is configured in the form of an endless belt by forming a synthetic resin film made of polyimide or the like having flexibility in the form of a belt and by connecting both ends of the synthetic resin film formed in a belt-like configuration by means of welding or the like.
All of the image forming units
300
K,
300
Y,
300
M and
300
C for black (K), yellow (Y), magenta (M) and cyan (C) have the same configuration, and toner images in black (K), yellow (Y), magenta (M) and cyan (C) are sequentially formed by the respective four image forming units
300
K,
300
Y,
300
M and
300
C as described above. The image forming units
300
K,
300
Y,
300
M and
300
C for the respective colors have a photosensitive drum
302
, and a surface of the photosensitive drum
302
is uniformly charged by a scorotron
303
for primary charging and is thereafter scanned and exposed by laser light for image formation from an image exposure device
304
in accordance with image information to form electrostatic latent images. The electrostatic latent images formed on the surface of the photosensitive drums
302
are developed into visible toner images by developing devices
305
of the respective image forming units
300
K,
300
Y,
300
M and
300
C with toners in respective colors, i.e., black, yellow, magenta and cyan, and the visible color images are transferred on to the intermediate transfer belt
301
by a transfer charger
306
in an overlapping relationship with each other. The toner images in black, yellow, magenta and cyan transferred on to the intermediate transfer belt
301
on a multiplex basis are transferred at a time on to transfer paper
307
by a secondary transfer roll
315
urged into contact with an opposite roll
314
and are thereafter subjected to a fixing process at a fixing device
308
to form a color image.
Reference numbers
309
and
310
in
FIG. 29
represent a photosensitive body cleaner and an intermediate transfer belt cleaner, respectively.
However, the above-described related art has problems as described below. In an image forming apparatus having a configuration as described above, for example, when the intermediate transfer belt is pulled out from the body of the apparatus, the intermediate transfer belt must be spaced from the photosensitive drum. Most image forming apparatus as shown in
FIG. 27
have a configuration in which an intermediate transfer belt
203
is spaced from a photosensitive drum
200
by pushing a surface of the intermediate transfer belt
203
with a push-down member
205
and by retracting a primary transfer roll
206
downward, as shown in FIG.
28
. In this configuration, a secondary transfer roll
207
is also retracted downward.
In this case, however, since the push-down member
205
must be urged against a surface of the intermediate transfer belt
203
, a problem arises in that the intermediate transfer belt
203
can be damaged. In the case of a tandem type image forming apparatus, since an intermediate transfer belt
301
is long and four photosensitive drums
302
C,
302
M,
302
Y and
302
K are in contact with the intermediate transfer belt
301
as shown in
FIG. 30
, it is very difficult to provide a configuration in which the intermediate transfer belt
301
is spaced from the four photosensitive drums
302
C,
302
M,
302
Y and
302
K by a push-down member.
In order to allow an intermediate transfer belt to be pulled out from the body of the apparatus while avoiding such problems, a configuration may be employed in which an intermediate transfer belt is held at two positions, i.e., a position where it transfers an image from a photosensitive drum and a position where it is spaced from the photosensitive drum and pulled out and in which a secondary transfer portion has two or more positions including a position where it transfers an image on to recording paper and a position where it is pulled out. When the intermediate transfer belt of such an image forming apparatus is pulled out from the body of the apparatus, the secondary transfer portion must be moved to the pull-out position and the intermediate transfer belt must be thereafter moved to the spaced pull-out portion.
However, the above-described configuration has a problem in that the intermediate transfer belt can be subjected to damage that reduces image quality and the apparatus can be broken in the worst case because the intermediate transfer belt and secondary transfer portion rub and scratch each other when the operation of moving the secondary transfer portion t
Hayashi Yukio
Iseki Shuji
Kawabata Takashi
Miyamoto Yoko
Niwa Minoru
Fuji 'Xerox Co., Ltd.
Morgan & Lewis & Bockius, LLP
Royer William J.
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