Electrophotography – Control of electrophotography process – Having temperature or humidity detection
Reexamination Certificate
2001-03-30
2002-12-24
Pendegrass, Joan (Department: 2852)
Electrophotography
Control of electrophotography process
Having temperature or humidity detection
C399S066000
Reexamination Certificate
active
06498907
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine and the like for performing image formation in accordance with an electrophotographic method or an electrostatic recording method.
2. Related Background Art
As an electrophotographic multi-color or full-color image forming apparatus, there is proposed a so-called tandem type image forming apparatus which forms a color image by arranging a plurality of photosensitive drums in one row and sequentially superimposing a toner image of each color formed on each photosensitive drum onto an intermediate transfer member (intermediate transfer belt) or onto a transfer material.
FIG. 11
is a schematic block diagram showing an example of a conventional electrophotographic tandem type full-color image forming apparatus.
This image forming apparatus is provided with four image forming stations (image forming units), i.e., an image forming station
1
Y for forming an image of a yellow color, an image forming station
1
M for forming an image of a magenta color, an image forming station
1
C for forming an image of a cyan color, and an image forming station
1
K for forming an image of a black color, and these four image forming stations are arranged in one row at predetermined intervals.
In each of the image forming stations
1
Y,
1
M,
1
C and
1
K, photosensitive drums
2
a,
2
b,
2
c
and
2
d
are provided as image bearing members. Around the respective photosensitive drums
2
a,
2
b,
2
c
and
2
d
are provided charging rollers
3
a,
3
b,
3
c
and
3
d,
developing devices
4
a,
4
b,
4
c
and
4
d,
primary transfer rollers
5
a,
5
b,
5
c
and
5
d,
and drum cleaning devices (cleaning blades)
6
a,
6
b,
6
c
and
6
d.
Further, exposing devices
7
a,
7
b,
7
c
and
7
d
are respectively provided above portions between the charging rollers
3
a
,
3
b
,
3
c
and
3
d
and the developing devices
4
a
,
4
b
,
4
c
and
4
d
. Yellow toner, magenta toner, cyan toner and black toner are respectively contained in the respective developing devices
4
a
,
4
b
,
4
c
and
4
d.
In this conventional example, each of the photosensitive drums
2
a
,
2
b
,
2
c
and
2
d
is a negative charge organic photoconductor and has a photoconductive layer (not shown) on a drum base body (not shown) made of, e.g., aluminum. Each photosensitive drum is driven to rotate at a predetermined process speed by a drive device (not shown).
The charging rollers
3
a
,
3
b
,
3
c
and
3
d
(charging means) are respectively brought into contact with the photosensitive drums
2
a
,
2
b
,
2
c
and
2
d
by a predetermined pressure force and uniformly charge the surfaces of the respective photosensitive drums
2
a
,
2
b
,
2
c
and
2
d
by charging bias applied from a charging bias power supply (not shown) so as to provide a predetermined polarity and potential.
The developing devices
4
a
,
4
b
,
4
c
and
4
d
cause the toner to adhere to electrostatic latent images formed on the respective photosensitive drums
2
a
,
2
b
,
2
c
and
2
d
and develop (realize visible images) them as toner images.
Each of the primary transfer rollers
5
a,
5
b,
5
c
and
5
d
(primary transferring means) is constituted by coating a core with an elastic member having a medium-resistance (volume resistivity: 1×10
4
to 1×10
7
&OHgr;cm), and it comes into contact with each of the photosensitive drums
2
a
,
2
b
,
2
c
and
2
d
through the intermediate transfer belt
8
(an intermediate transfer member) at each primary transfer position. Primary transfer bias power supplies (high-voltage power supplies)
9
a
,
9
b
,
9
c
and
9
d
are respectively connected to the primary transfer rollers
5
a
,
5
b
,
5
c
and
5
d.
The exposing devices (laser scanner devices)
7
a
,
7
b
,
7
c
and
7
d
form electrostatic latent images according to image information on the surfaces of the respective photosensitive drums
2
a
,
2
b
,
2
c
and
2
d
charged by the respective charging rollers
3
a
,
3
b
,
3
c
and
3
d
by outputting from a laser output section (not shown) laser beams modulated in accordance with time series electric digital pixel signals of image information respectively input from a host computer (not shown) and image-exposing the surfaces of the respective photosensitive drums
2
a
,
2
b
,
2
c
and
2
d
through reflection mirrors
10
a
,
10
b
,
10
c
and
10
d.
The intermediate transfer belt
8
is stretched around a drive roller
11
, a secondary transfer opposite roller
12
and a support roller
13
and rotated (moved) in a direction indicated by an arrow (clockwise direction) by drive of the drive roller
11
. The secondary transfer opposite roller
12
is brought into contact with a secondary transfer roller
14
through the intermediate transfer belt
8
to form a secondary transfer position M. As the intermediate transfer belt
8
, one having a volume resistivity of 1×10
8
to 1×10
12
&OHgr;cm is preferable, and one consisting of urethane based resin, fluorine-based resin, nylon-based resin or polyimide-based resin, one consisting of an elastic material such as silicone rubber or Hydrin rubber, or one obtained by dispersing carbon or conductive powder in these materials and performing the resistivity adjustment can be used. In this conventional example, a single-layer endless belt having a thickness of 0.1 mm obtained by dispersing carbon in polyimide and adjusting the volume resistivity to 1×10
9
&OHgr;cm was used as the intermediate transfer belt
8
.
The secondary transfer roller
14
is constituted by coating a core with a foam layer of, e.g., EPDM, NBR, Hydrin rubber having a medium-resistance value (volume resistivity: 1×10
6
to 1×
10
&OHgr;cm) and provided at a position opposed to the secondary transfer opposite roller
12
with the intermediate transfer belt
8
and a transfer material P such as paper sandwiched therebetween so as to be capable of contacting with and being separated from them. Further, to the secondary transfer roller
14
are connected a current detector
17
for applying and controlling the later-described secondary transfer bias, a power supply
18
, and a controller
19
.
The belt cleaning device (cleaning blade)
15
for removing and collecting transfer residual toner remaining on the surface of the intermediate transfer belt
8
is provided at the outside of the intermediate transfer belt
8
. Further, a fixing device
16
having a fixing roller
16
a
and a pressure roller
16
b
is provided downstream of a secondary transfer position M in the direction for conveying the transfer material P where the secondary transfer opposite roller
12
and the secondary transfer roller
14
come into contact with each other.
The image forming operation by the above-described image forming apparatus will now be described.
When an image forming operation start signal is sent, transfer material (paper) P is fed one by one from a cassette (not shown) and conveyed to a registration roller (not shown). At this time, the registration roller (not shown) is stopped and the leading end of the transfer material P is in the standby mode immediately before the secondary transfer position M.
On the other hand, in the respective image forming stations
1
Y,
1
M,
1
C and
1
K, when the image forming operation start signal is sent, the respective photosensitive drums
2
a
,
2
b
,
2
c
and
2
d
driven to rotate at a predetermined process speed (0.117 in/see) are uniformly charged so as to have a negative polarity by the charging rollers
3
a
,
3
b
,
3
c
and
3
d
, respectively. The exposing devices
7
a
,
7
b
,
7
c
and
7
d
respectively convert color-separated image signals input from a host computer (not shown) into optical signals in the laser output section (not shown), and the modulated laser beams (the converted optical signals) are respectively scan-exposed through the reflection mirrors
10
a
,
10
b
,
10
c
and
10
d
onto the respective charged phot
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