Electrophotography – Control of electrophotography process – Of plural processes
Reexamination Certificate
2001-06-20
2002-11-05
Chen, Sophia S. (Department: 2852)
Electrophotography
Control of electrophotography process
Of plural processes
C399S038000, C399S048000
Reexamination Certificate
active
06477338
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image formation apparatus for finally forming a toner image on paper under an image formation condition that can be controlled, and a toner amount measurement apparatus and a toner amount measurement method for measuring a toner amount.
2. Background of the Invention
Hitherto, an image formation apparatus such as printers, copiers, and facsimile machines adopting electrophotography has been known. In such an image formation apparatus, light is applied to the surface of a photosensitive body for forming an electrostatic latent image and toner is deposited on the electrostatic toner image for development and then the toner deposited on the electrostatic toner image on the surface of the photosensitive body is transferred onto paper by means of a transfer device, a transfer belt, etc., whereby a toner image is finally formed on the paper. In such an image formation apparatus, to form a high-quality toner image, the amount of toner deposited on the photosensitive body or the transfer belt is measured with a toner amount measurement apparatus and the image formation condition applied for forming a toner image is controlled in response to the measured toner amount. An optical measurement method is widely known as a measurement method of the amount of toner deposited on the photosensitive body.
Here, the principle of a toner amount measurement method in a general toner amount measurement apparatus will be discussed with reference to
FIGS. 1
to
4
.
The surface of a photosensitive body or a transfer belt on which toner is deposited generally has a mirror structure high in flatness; hitherto, such a surface characteristic has been used to measure the toner amount in the toner amount measurement apparatus. Hereinafter, photosensitive bodies, transfer belts, etc., for supporting toner will be collectively called toner supports.
FIG. 1
is a drawing to show the measurement principle of a toner amount measurement method using specular reflection.
In the toner amount measurement method using specular reflection, light L
1
of a predetermined strength is applied from a light source
2
such as a light emitting diode to the surface of a toner support
1
and is specularly reflected on the surface of the toner support
1
and reflected light L
2
is received by a photosensor
3
such as a photodiode, which then outputs a voltage responsive to the strength of the received reflected light L
2
.
The reflected light L
2
is blocked in the portion of the surface of the toner support
1
where toner is deposited, and as the reflected light L
2
is blocked, the light reception amount of the photosensor
3
is lowered accordingly and the output voltage is lowered.
FIG. 2
is a graph to show the relationship between the toner deposition amount and the output voltage of the photosensor in the toner amount measurement method using specular reflection.
The graph shows on the horizontal axis the amount of toner deposited on the surface of the toner support and on the vertical axis the output voltage of the photosensor. The output voltage of the photosensor corresponds to the light amount of the specularly reflected light on the surface of the toner support, as described above.
As a curve
5
inclined downward to the right in the graph shows, the output voltage of the photosensor is lowered with an increase in the toner deposition amount. Since such a curve is previously found, the amount of toner deposited on the surface of the toner support can be found based on the relationship indicated by the curve
5
and the output voltage of the photosensor.
By the way, as for color toner, if light is applied to color toner, scattered light occurs because of reflection on the surface and in the inside of the color toner. A toner amount measurement method using such scattered light is also known.
FIG. 3
is a drawing to show the measurement principle of the toner amount measurement method using scattered light.
Also in the toner amount measurement method using scattered light, light L
1
of a predetermined strength is applied from a light source
2
to the surface of a toner support
1
in a similar manner to that in
FIG. 1
; in the toner amount measurement method using scattered light, however, a photosensor
6
is provided at a position at a distance from the reflected light L
2
shown in FIG.
1
and scattered light L
3
caused by toner
4
deposited on the surface of the toner support
1
is received by the photosensor
6
, which then outputs a voltage responsive to the strength of the received scattered light L
3
.
FIG. 4
is a graph to show the relationship between the toner deposition amount and the output voltage of the photosensor in the toner amount measurement method using scattered light.
Like the graph of
FIG. 2
, the graph of
FIG. 4
shows the amount of toner on the horizontal axis and the output voltage of the photosensor on the vertical axis. The output voltage of the photosensor corresponds to the light amount of the scattered light caused by the toner.
As a curve
7
in the graph of
FIG. 4
shows, the output voltage of the photosensor is raised with an increase in the toner deposition amount. Since such a curve
7
is previously found, the amount of toner deposited on the surface of the toner support can be found based on the relationship indicated by the curve
7
and the output voltage of the photosensor.
Most image formation apparatus in related arts measure the toner amount using either of the measurement principles shown in
FIGS. 1 and 3
or measure the toner amount using both the measurement principles in combination.
By the way, with the toner amount measurement method using specular reflection, the measurement sensitivity is degraded if the surface of the photosensitive body or the transfer belt is completely covered with toner.
FIG. 5
is a graph to show the measurement sensitivity in the toner amount measurement method using specular reflection.
The graph shows the toner amount on a toner support on the horizontal axis and the light amount of specularly reflected light on the vertical axis. The inclination of the graph represents the measurement sensitivity.
As the toner amount increases, the inclination of the graph is lessened and in the toner amount exceeding 0.5 mg/cm
2
, the inclination of the graph is extremely small. Thus, when the toner amount exceeds 0.5 mg/cm
2
, if the toner amount changes, the light amount of the specularly reflected light scarcely changes and it is very difficult to measure the toner amount. However, the toner amount to be actually measured may extend to 0.5 mg/cm
2
or more on the photosensitive body, in which case the toner amount measurement method using specular reflection is not adequate.
On the other hand, with the toner amount measurement method using scattered light, the toner amount at up to 0.7 mg/cm
2
level can be measured. However, the toner amount measurement method using scattered light involves some problems. The first problem is that the method cannot be applied to measurement on black toner where scattered light does not occur. It is also desired that toner amount measurement be conducted on black toner like color toner; the fact that the amount of the black toner cannot be measured by the method involves a problem.
The second problem is that it is difficult to apply the toner amount measurement method using scattered light on the type of photo sensitive body currently mainstream for the reason described later.
FIG. 6
is a drawing to show the structure of a surface of the type of photosensitive body currently mainstream.
The surface of the photosensitive body has a structure wherein an undercoat layer
1
_
2
, a charge generation layer
1
_
3
, a charge transport layer
1
_
4
, and an overcoat layer
1
_
5
are laid up in order on an aluminum base material
1
_
1
. In the currently mainstream image formation apparatus, to form an electrostatic latent image on the photosensitive body having such a surface structure, laser light is applied to the photose
Hisano Tohru
Kitazawa Kazuki
Ohashi Shin-ichi
Watanabe Yoichi
Yoshida Kaoru
Chen Sophia S.
Fuji 'Xerox Co., Ltd.
Morgan & Lewis & Bockius, LLP
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