Electrophotography – Image formation – Photoconductive member
Reexamination Certificate
2002-12-09
2004-10-12
Grimley, Arthur T. (Department: 2852)
Electrophotography
Image formation
Photoconductive member
Reexamination Certificate
active
06804486
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application No. 2001-77577, filed Dec. 8, 2001, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an active steering system and a method thereof by which a belt can be steered so that additional registration correction is not needed which is used in an image forming apparatus, and a method of seeking a balance point at which the belt is driven most stably.
2. Description of the Related Art
In a system using a belt, a problem of weaving necessarily occurs during the driving of the belt. In particular, in an image forming apparatus of an electrophotography type such as printers, copiers, and facsimiles, weaving of the belt used as a photosensitive medium or transfer medium mainly causes mis-registration so that an image in a main scanning direction is deviated.
When the weaving of the belt used as the photosensitive medium or transfer medium occurs, mis-registration occurs where positions at a starting of the respective lines not being aligned within a page occurs. During formation of a color image, color mis-registration can occur so that color dots are not accurately overlapped. Thus, in the image forming apparatus adopting the belt as the photosensitive medium or transfer medium, a steering technology to control the position of the belt in a main scanning direction (a widthwise direction) is very important to prevent the weaving of the belt.
As shown in
FIG. 1
, a conventional registration system to control belt steering and scanning start points detects belt edge signals using laser beams emitted from four scanners
5
a
,
5
b
,
5
c
, and
5
d
and uses the belt edge signals, to prevent weaving of the belt and adjusts a deviation of the image due to the weaving of the belt. The four scanners
5
a
,
5
b
,
5
c
, and
5
d
scan the laser beams modulated according to image data onto a photoreceptor belt
1
supported by a plurality of rollers and endlessly circulating, to form an electrostatic latent image.
Referring to
FIG. 1
, in the conventional registration system, a belt edge sensor
3
includes four photodetectors
3
a
,
3
b
,
3
c
, and
3
d
, which are installed on an edge of the photoreceptor belt
1
to be overlapped. The four photodetectors
3
a
,
3
b
,
3
c
, and
3
d
receive the laser beams scanned by the scanners
5
a
,
5
b
,
5
c
, and
5
d
, respectively, and detect belt edge signals. Because part of the laser beams emitted from the scanners
5
a
,
5
b
,
5
c
, and
5
d
are blocked by the photoreceptor belt
1
, the photodetectors
3
a
,
3
b
,
3
c
, and
3
d
receive only remaining portions of the laser beams which are not blocked by the photoreceptor belt
1
. Thus, an amount of light received by the photodetectors
3
a
,
3
b
,
3
c
, and
3
d
changes according to a position of the photoreceptor belt
1
in the main scanning direction. The belt edge signals detected by the photodetectors
3
a
,
3
b
,
3
c
, and
3
d
convey information about the position of the photoreceptor belt
1
.
The belt edge signals detected by the photodetectors
3
a
,
3
b
,
3
c
, and
3
d
are compared with a signal indicating a previous position of the photoreceptor belt
1
at a belt edge synthesizer
7
. The belt edge synthesizer
7
generates a belt edge signal to change an image data start position of a corresponding line according to a change in position of the photoreceptor belt
1
. The synthesized belt edge signal is converted into an image scan start signal
114
indicating an image data start position of a corresponding line at a scanner control/synchronization module
9
. The image scan start signal changes a start position of the image for each line according to the weaving of the photoreceptor belt
1
so that the image can always maintain a predetermined distance from the edge of a print paper and multi-color dots are arranged to be overlapped at the same position of the photoreceptor belt
1
. In
FIG. 1
, reference numeral
11
denotes a computer for controlling a laser drive using the image scan start signal and a signal output from a controller
13
to control the overall image forming apparatus so that the laser beam can be output modulated using signals from the laser drive
108
,
110
, and
112
and the image scan start signal
114
from the scanner control/synchronization module
9
according to the image data.
Meanwhile, the belt edge signal passing through the belt edge synthesizer
7
is input to a belt steering controller
15
. The belt steering controller
15
drives a belt steering motor (not shown) according to the belt edge signal so that the edge of the photoreceptor belt
1
can be driven at the center of the photodetectors
3
a
,
3
b
,
3
c
, and
3
d.
The conventional registration system having the above structure controls the position of the photoreceptor belt
1
in the main scanning direction using a result obtained from Equation 1.
(Equation 1)
Y=K
p
×(the present belt position−the central position of photodetectors)+K
D
×(the present belt position−the previous belt position)
Here, KP is a proportional coefficient and KD is a differential coefficient. The Y value obtained from Equation 1 is used as a driving step number of a belt steering motor. When the belt steering motor drives a steering roller by a predetermined step according to the Y value, the steering roller is slant. Accordingly, a direction of movement of the photoreceptor belt
1
in the main scanning direction changes.
FIGS. 2 and 3
are graphs showing results of tests using the conventional registration system by changing the KP and KD values.
FIG. 2
is a graph showing the output of a photodetector measuring an amount of change of the belt edge when KP and KD are 1 and 15, respectively.
FIG. 3
is a graph showing the output of the photodetector when KP and KD are 0.5 and 10, respectively. To obtain the results of
FIGS. 2 and 3
, a product “PD S6967” having a length of 5 mm manufactured by HAMAMATSU is used as the photodetector. The maximum output voltage is set to 5 volts such that 1 volt corresponds to 1 mm in the weaving width of the belt. The photodetector is installed at the position separated 6 seconds from the belt steering apparatus. A 32 inches long sheet is used by being attached to the photoreceptor belt
1
. Here, a step of a seam is about 330 &mgr;m, a parallelism thereof is 51 &mgr;m, and a drive speed of the belt is 3.2 inch/sec. To reduce an effect due to any defect of the photoreceptor belt
1
, an output of the photodetector is accumulated for ten seconds.
Maximum weaving widths obtained from the above test conditions are 460 &mgr;m and 291 &mgr;m, respectively, as shown in
FIGS. 2 and 3
. The amounts of weaving with respect to the movement speed of the photoreceptor belt
1
are 3 &mgr;m/sec and 2 &mgr;m/sec, which means that, in the case of continuous printing, mis-registration of 300 &mgr;m (corresponding about 6 dots in the case of 600 dpi) or more from the edge of the paper to the image can be generated. Thus, when the conventional registration system is adopted, the scanning start point must be controlled in addition to the belt steering.
Because since the conventional registration system includes four photodetectors
3
a
,
3
b
,
3
c
, and
3
d
which receive laser beams scanned by scanners
5
a
,
5
b
,
5
c
, and
5
d
to form the image by color, and because calculations for the belt steering and color registration correction is performed at the belt edge synthesizer
7
using the belt edge signal for each color detected by the four photodetectors
3
a
,
3
b
,
3
c
, and
3
d
, the structure of the system is complicated and complicated calculations must be performed at the belt edge synthesizer
7
.
When there is a defect at the edge of the photoreceptor belt
1
or the step of the seam generated by connecting the photoreceptor belt
1
, a belt error signal is detected as
Lee Beom-ro
Lee Do-soo
Gleitz Ryan
Grimley Arthur T.
Samsung Electronics Co,. Ltd.
Staas & Halsey , LLP
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