Electrophotography – Image formation – Transfer
Reexamination Certificate
2001-10-15
2003-03-25
Brase, Sandra (Department: 2852)
Electrophotography
Image formation
Transfer
C399S302000, C399S303000
Reexamination Certificate
active
06539194
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus which uses an electrostatic image recording method, an electrophotographic image recording method or the like. More particularly, the invention relates to an image forming apparatus which includes a plurality of image forming means, and performs image formation using an intermediate transfer member or a transfer-material bearing member.
2. Description of the Related Art
FIG. 7
is a cross-sectional view illustrating a principal portion of a conventional image forming apparatus.
An image forming apparatus
1
P includes an image forming unit
10
including laterally arranged stations a, b, c and d each having substantially the same configuration, a feeding unit
20
, an intermediate transfer unit
30
, a fixing unit
40
, and a control unit (not shown).
The respective units will now be described in detail.
The image forming unit
10
includes photosensitive drums
11
a
,
11
b
,
11
c
and
11
d
, each serving as an image bearing member. Each of the photosensitive drums
11
a
-
11
d
is supported for rotation around its axis, and is rotatably driven in the direction of an arrow. Primary chargers
12
a
,
12
b
,
12
c
and
12
d
, optical systems
13
a
,
13
b
,
13
c
and
13
d
, and developing units
14
a
,
14
b
,
14
c
and
14
d
are disposed around the outer circumferences of the photosensitive drums,
11
a
,
11
b
,
11
c
and
11
d
in the direction of rotation, respectively. The primary chargers
12
a
-
12
d
provide a uniform amount of charges on the surfaces of the photosensitive drums
11
a
-
11
d
, respectively. The optical systems
13
a
-
13
d
form electrostatic latent images on the photosensitive drums
11
a
-
11
d
by exposing the photosensitive drums
11
a
-
11
d
, respectively, using a light beam, such as a laser beam or the like, modulated in accordance with a recording image signal. Then, the electrostatic latent images are developed by the developing units
14
a
-
14
d
which accommodate developers (toners) having four colors, i.e., yellow, cyan magenta and black, respectively. Cleaning devices
15
a
,
15
b
,
15
c
and
15
d
are disposed at portions downstream from image primary transfer regions Ta, Tb, Tc and Td for transferring the developed images onto an intermediate transfer member (an intermediate transfer belt
31
, to be described later), respectively. Toner particles remaining on the photosensitive drums
11
a
-
11
d
(those not transferred onto the intermediate transfer member
31
) are scraped off by the cleaning devices
15
a
-
15
d
, to clean the surfaces of the photosensitive drums
11
a
-
11
d
, respectively.
According to the above-described process, image formation by the toners having the respective colors is performed.
The feeding unit
20
includes a cassette
21
a
and a manual feed tray
27
for accommodating sheets of a recording material P, pickup rollers
22
and
26
for individually feeding sheets of the recording material P from the cassette
21
a
and the manual feed tray
27
, respectively, pairs of rollers
23
and a feeding guide
24
for feeding a sheet of the recording material P fed from the corresponding one of the pickup rollers
22
and
26
to registration rollers
25
a
and
25
b
, and the registration rollers
25
a
and
25
b
for conveying the sheet of the recording material P to a secondary transfer region in synchronization with the timing of image formation by the image forming unit
10
.
The intermediate transfer unit
30
includes an intermediate transfer belt
31
made of PET (polyethylene terephthalate), PVdF (polyvinylidene fluoride) or the like. The intermediate transfer belt
31
moves around a driving roller
32
for transmitting a driving force to the intermediate transfer belt
31
, a tension roller
33
for providing the intermediate transfer belt
31
with an appropriate tension by urging it by means of a spring or the like, and a driven roller
34
facing a secondary transfer region Te via the intermediate transfer belt
31
. A primary transfer plane A is formed between the tension roller
33
and the driving roller
32
. The driving roller
32
comprises a metal roller having a urethane-rubber or chloroprene-rubber coating a few mm thick on a surface thereof, in order to prevent slip relative to the intermediate transfer belt
31
. The driving roller
32
is rotatably driven by a pulse motor (not shown). Primary transfer devices
35
a
-
35
d
are provided at the primary transfer regions Ta-Td where the photosensitive drums
11
a
-
11
d
face the intermediate transfer belt
31
, respectively, at positions behind the intermediate transfer belt
31
. A secondary transfer device
36
is provided at a secondary transfer region Te where the driven roller
34
faces the intermediate transfer belt
31
, so as to face the driven roller
34
via the intermediate transfer belt
31
. A cleaning device
50
for cleaning the image forming surface of the intermediate transfer belt
31
is provided on the image transfer belt
31
at a portion downstream from the secondary transfer region Te. The cleaning device
50
includes a cleaner blade
51
made of polyurethane rubber or the like, and a waste-toner box
52
for accommodating waste toner.
The fixing unit
40
includes a fixing roller
41
a
incorporating a heat source, such as a halogen-lamp heater or the like, a roller
41
b
pressed against the fixing roller
41
a
, a guide
43
for guiding the sheet of the recording material P to a nip portion constituted by a pair of the rollers
41
a
and
41
b
, internal discharging rollers
44
for guiding the sheet of the recording material P discharged from the nip portion further to the outside of the apparatus, and external discharging rollers
45
. Reference numeral
46
represents a casing.
Next, the operation of the above-described image forming apparatus will now be described.
When an image-forming-operation start signal is provided, sheets of the recording material P are individually fed from the cassette
21
a
by the pickup roller
22
. A sheet of the recording material P thus fed is conveyed to the registration rollers
25
a
and
25
b
after passing through the feeding guide
24
by the pair of feeding rollers
23
. At that time, the registration rollers
25
a
and
25
b
are stopped, and the leading edge of the sheet of the recording material P contacts the nip portion. Thereafter, the registration rollers
25
a
and
25
b
start to rotate at the timing at which the image forming unit
10
starts image formation. The start of rotation of the registration rollers
25
a
and
25
b
is set to coincide with arrival of the sheet of the recording material P and the toner image being subjected to primary transfer on the intermediate transfer belt
31
in the image forming unit
10
at the secondary transfer region Te.
In the image forming unit
10
, when an image-forming-operation signal is provided, the toner image formed on the photosensitive drum
11
d
at the most upper-stream portion in the direction of rotation of the intermediate transfer belt
31
according to the above-described process is subjected to primary transfer at the primary transfer region Td by the primary transfer device
35
d
where a high voltage is applied. The toner image subjected to primary transfer is conveyed to the subsequent primary transfer region Tc. At the primary transfer region Tc, image formation is performed while being delayed by the time of conveyance of the toner image between the adjacent image forming units from the preceding image formation at the primary transfer region Td, and the subsequent toner image is transferred in a state of being adjusted to the preceding toner image. Toner images of the four colors are transferred onto the intermediate transfer belt
31
in a state of being adjusted with one another by repeating the above-described process, and the resultant four-color image subjected primary transfer proceeds to the secondary transfer region Te.
When the sheet of the recording material P enters
LandOfFree
Image forming apparatus including transfer belt having first... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image forming apparatus including transfer belt having first..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming apparatus including transfer belt having first... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3049857