Electrophotography – Image formation – Transfer
Reexamination Certificate
2002-06-17
2004-12-21
Tran, Hoan (Department: 2852)
Electrophotography
Image formation
Transfer
C399S308000
Reexamination Certificate
active
06834176
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, or the like, which employs an electrophotographic or electrostatic recording method. In particular, it relates to an image forming apparatus of an indirect transfer type, in which an image made up of developer on an image bearing member is transferred onto an intermediary transfer member.
As for a typical electrophotographic image forming apparatus, an image forming apparatus such as the one shown in
FIG. 10
has been known.
The image forming apparatus
200
in
FIG. 10
is provided with an electrophotographic photoconductive member, in the form of a drum, that is, a photoconductive drum
1
, as an image bearing member. The photoconductive member
1
is rotationally supported and is rotationally driven by a driving means (unshown) in the direction indicated by an arrow mark in the drawing. Surrounding the photoconductive drum
1
are a charging means
2
, an exposing means
3
, a developing means
4
, and a cleaning means
10
. Further, placed next to the photoconductive drum
1
are an intermediary transfer belt
6
as an intermediary transferring member, and a primary transferring means
5
which is positioned in a manner to sandwich the intermediary transfer belt
6
between itself and photoconductive drum
1
.
The photoconductive drum
1
comprises an aluminum cylinder, and a layer of organic photoconductor (OPC) coated on the peripheral surface of the aluminum cylinder. The charge roller
2
comprises a metallic core, an electrically conductive rubber layer, and a surface layer, listing from the inward side. The electrical resistance of the surface layer is in the mid range. The charge roller
2
is placed in contact with the peripheral surface of the photoconductive drum
1
. The peripheral surface of the photoconductive drum
1
is uniformly charged by applying to the charge roller
2
a bias (charge bias), which is a combination of DC and AC biases. The exposing means
3
emits a beam of laser light in response to signals in accordance with the image formation data inputted into a laser driver, exposing the uniformly charged peripheral surface of the photoconductive drum
1
. As a result, an electrostatic latent image is formed on the peripheral surface of the photoconductive drum
1
.
The developing means
4
is a rotary developing means comprising developing devices
4
Y,
4
M,
4
C, and
4
K for developing the electrostatic latent images into toner images of yellow (Y), magenta (M), cyan (C), and black (B), respectively. When developing the electrostatic latent images into toner images different in color, the rotary developing means
4
is rotated so that the developing devices different in the color of the developer contained therein are moved one by one to the location, at which developing devices oppose the photoconductive drum
1
. As a result, the developers different in color are adhered to the peripheral surface of the corresponding photoconductive drum
1
in a manner to reflect the pattern of the corresponding electrostatic latent images on the peripheral surface of the photoconductive drum
1
, forming images made up of the developers (toner images).
The intermediary transfer belt
6
is stretched around four rollers: a driving roller
61
, a tension roller
62
, a follower roller
63
, and a primary transfer roller
5
, and is moved (rotationally driven) in the direction indicated by an arrow mark in the drawing. Each of the toner image, which are formed on the photoconductive drum
1
and are different in color, is sequentially transferred onto the intermediary transfer belt
6
by applying the primary transfer electric field to the primary transfer roller
5
as the primary transferring means disposed at a location at which the intermediary transfer belt
6
is pinched between the photoconductive drum
1
and primary transfer roller
5
. There is also the secondary transfer roller
8
as the secondary transferring means, which is disposed at a location where it opposes the follower roller
63
, with the intermediary transfer belt
6
pinched between the secondary transfer roller
8
and follower roller
63
. The toner images placed in layers on the intermediary transfer belt
6
are transferred all at once by applying the secondary transfer electric field to the secondary transfer roller
8
, onto a recording medium P.
The cleaning means
10
for the photoconductive drum
1
is disposed downstream from the primary transfer station T, in terms of the direction in which the photoconductive drum
1
is driven. It removes the transfer residual toner particles, that is, the toner particles which were not transferred onto the intermediary transfer belt
6
in the primary transfer station T and remained on the photoconductive drum
1
.
The cleaning means
11
for the intermediary transfer belt
6
is disposed on the downstream side of the secondary transfer station T′, in terms of the direction in which the intermediary transfer belt
6
is driven. It removes the residual toner particles, that is, the toner particles which were not transferred onto a recording medium P in the secondary transfer station T′ and remained on the intermediary transfer belt
6
.
The fixing means
9
(fixing device) has two rollers: a fixing roller
91
and a pressure roller
92
. It fixes the toner images to the recording medium P after they are transferred onto the recording medium P.
Next, the operation of the image forming apparatus
200
structured as described above will be described. First, the peripheral surface of the photoconductive drum
1
is uniformly charged by applying charge bias to the charge roller
2
while rotationally driving the photoconductive drum
1
in the direction indicated by the arrow mark in the drawing. Next, the photoconductive drum
1
is exposed by the exposing means
3
in accordance with the image formation data of the first color component, for example, yellow (Y) color component, forming an electrostatic latent image corresponding to the yellow component of an intended image. At this point of the image forming operation, the developing device rotary
4
is rotated to move the yellow component developing device
4
Y to the position at which the yellow component developing device
4
Y, which contains yellow toner as developer, opposes the photoconductive drum
1
. Then, a compound bias (development bias), which normally is a combination of DC and AC voltages, is applied to the developer bearing member (development roller) of the yellow component developing device
4
Y to adhere the yellow toner to the electrostatic image on the photoconductive drum
1
. As a result, a toner image is made up of yellow toner, on the peripheral surface of the photoconductive drum
1
. Then, the yellow toner image on the photoconductive drum
1
is transferred onto the intermediary transfer belt
6
by applying the primary transfer bias to the primary transfer roller
5
.
Similarly, the toner images corresponding to magenta (M), cyan (C), and black (K) color components, respectively, are sequentially formed on the photoconductive drum
1
, and are transferred in layers onto the intermediary transfer belt
6
. As a result, four toner images different in color are placed in layers on the intermediary transfer belt
6
.
Meanwhile, the recording medium P stored in a cassette
12
as a recording medium storing portion are consecutively supplied into the image forming apparatus
200
while being separated from the other recording medium P. Each recording medium P is conveyed to the secondary transfer station T′ by a conveyance roller pair
14
and a registration roller pair
15
in synchronism with the movement of the four color toner images on the intermediary transfer belt
6
.
In the secondary transfer station T′, the four color toner images layered on the intermediary transfer belt
6
are transferred all at once, by applying secondary transfer bias to the secondary transfer roller
8
, on
Saito Makoto
Tomizawa Takeshi
LandOfFree
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