Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2002-09-19
2004-05-18
Chen, Sophia S. (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S053000
Reexamination Certificate
active
06738585
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Patent Application No. 2002-6753, filed Feb. 6, 2002 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 image forming apparatus and a method thereof, and more particularly, to an image forming apparatus for and a method of controlling an image concentration.
2. Description of the Related Art
FIG. 1
illustrates an overall arrangement of a conventional image forming apparatus disclosed in U.S. Pat. No. 4,564,287. Referring to
FIG. 1
, the conventional image forming apparatus includes a photosensitive drum
1
, a primary charger
2
, a secondary charger
3
, an entire surface exposure lamp
4
, a potentiometer
7
, a developing roller
5
of a developing unit, a transfer charger
28
, a cleaner blade
35
, and a discharger
29
.
The photosensitive drum
1
is pre-discharged by the pre-discharge charger
29
, and then, an entire surface of the photosensitive drum
1
is uniformly charged. A reflected light beam illuminated by an original exposure lamp
11
and reflected from an original image
10
is radiated on the photosensitive drum
1
through mirrors
12
and
13
. In this case, an AC corona discharge or corona discharge having an opposite polarity to that of the primary charger
2
is performed by the secondary charger
3
to form an electrostatic latent image on the photosensitive drum
1
in accordance with the original image
10
.
The entire surface of the photosensitive drum
1
is then exposed by the entire surface exposure lamp
4
, so that the electrostatic latent image having a high contrast is formed. This latent image is then toner developed by the developing roller
5
.
The transfer charger
28
is then operated to transfer the developed image to a recoding paper sheet (not shown). A blank exposure lamp
6
preventing an adhesion of excessive toner to the photosensitive drum
1
is disposed above the secondary charger
3
to form light color areas and dark color areas on the photosensitive drum
1
under a control with standard image formation conditions.
The potentiometer
7
measuring a surface potential of the photosensitive drum
1
is disposed between the entire surface exposure lamp
4
and the developing roller
5
. A signal from the potentiometer
7
is supplied to an A/D converter
9
through a potential measurement circuit
8
and is converted into a digital signal by the A/D converter
9
. This digital signal is supplied to a microcomputer
15
.
An output from the microcomputer
15
is supplied to a D/A converter
16
and is connected to a light control circuit
17
, a first high voltage control circuit
18
, a second high voltage control circuit
19
, a transfer control circuit
24
, a pre-discharge control circuit
25
, and a DC development bias control circuit
20
. In an operation section
40
various key-in operations and display operations are performed.
The light control circuit
17
controls the original exposure lamp
11
through a lamp regulator
14
. The first and second high voltage control circuits
18
and
19
are connected to the primary charger
2
and the secondary charger
3
through first and second high voltage transformers
21
and
22
, respectively, to control respective charges of the primary and secondary chargers
2
and
3
. The transfer control circuit
24
is connected to the transfer charger
28
through the transfer high voltage transformer
26
.
The pre-discharge control circuit
25
is connected to the pre-discharge charger
29
through a pre-discharge high voltage transformer
27
. An output from the DC development bias control circuit
20
is connected to an AC development bias control circuit
23
, and an output from the AC development bias control circuit
23
is applied to the developing roller
5
. A standard white board
38
is used to control a light amount of the original exposure lamp
11
.
In the above conventional image forming apparatus, the surface potential of the photosensitive drum
1
is measured by the potentiometer
7
, and a development bias of the developing roller
5
and charge potentials of the primary and second chargers
2
,
3
are adjusted in accordance with a result of measurement of the surface potential of the photosensitive drum
1
. However, since only the surface potential of the image forming apparatus is measured in prior art, a variation in an image concentration caused by a variation in the thickness of the photosensitive body cannot be measured, and thus a uniform image concentration cannot be achieved.
SUMMARY OF THE INVENTION
To solve the above and other problems, it is an object of the present invention to provide an image forming apparatus for preventing a decrease in an image concentration caused by a variation in a thickness of a photosensitive body.
Additional objects and advantageous of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the above and other objects, according to an embodiment of the present invention,] there is provided an image forming apparatus. The apparatus includes a photosensitive body on which an electrostatic latent image for an image is formed, a charger charging the photosensitive body, a developing unit developing the electrostatic latent image of the photosensitive body, a measuring unit measuring a charge current flowing through the photosensitive body from the charger, a comparator comparing the charge current with a reference current, and a controller controlling a developing unit control variable so as to compensate for a variation in a thickness of the photosensitive body according to an output of the comparator.
According to an aspect of the present invention, the developing unit control variable is a development bias of the developing unit or a development vector, which is a difference between the development bias and an exposure potential of an exposure unit.
In order to achieve the above and other objects, according to another embodiment of the present invention, there is provided a method of compensating for the development mass per area caused by the thickness of the photosensitive body of the image forming apparatus. The method includes measuring a charge current I
i
of the photosensitive body, comparing the measured charge current I
i
with a first reference current I
rmin
of the photosensitive body, comparing the measured charge current I
i
with a second reference current I
rmax
in a case that the measured charge current I
i
is larger than the first reference current I
rmin
, and replacing the photosensitive body with a new one in a case that the measured charge current I
i
is larger than the second reference current I
rmax
, and performing an operation of the developing unit control variable and controlling the developing unit in an opposite case that the measured charge current I
i
is smaller than the second reference current I
rmax
.
In the replacing of the photosensitive body with the new one, a command replacing the photosensitive body is transferred to a display.
According to another aspect of the present invention, in order to compensate for a variation in development mass per area caused by the thickness of the photosensitive body, the development mass per area is compensated by measuring the charge current of the photosensitive body and correcting the development bias in a case that the measured charge current is larger than a minimum reference current, and a high quality image can be obtained during a life span of a new photosensitive body by informing a user whether the photosensitive body has to be replaced in a case that the measured charge current is larger than a maximum reference current.
REFERENCES:
patent: 4564287 (1986-01-01), Suzuki et al.
patent: 5160967 (1992-11-01), Tonegawa
patent: 5943526 (1999-08-01), Kodama
patent: 5943
Shin Kyu-cheol
Song In-yong
Chen Sophia S.
Staas & Halsey , LLP
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