Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2000-08-04
2002-05-28
Chen, Sophia S. (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S030000, C399S061000
Reexamination Certificate
active
06397018
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developer amount detecting method, a developing device, a process cartridge and an electrophotographic image forming apparatus.
In the present specification, the electrophotographic image forming apparatus is directed to, for example, an electrophotographic copying machine, an electrophotographic printer such as an LED printer or a laser beam printer, an electrophotographic facsimile machine and an electrophotographic word processor.
The process cartridge makes at least one of charging means, developing means and cleaning means and an electrophotographic photosensitive member integrally into a cartridge which is detachably mountable to a main body of the electrophotographic image forming apparatus, or makes at least the developing means and the electrophotographic photosensitive member integrally into a cartridge which is detachably mountable to a main body of the electrophotographic image forming apparatus.
2. Related Background Art
Up to now, in an image forming apparatus using an electrophotographic image forming process, there has been applied a process cartridge system which makes the electrophotographic photosensitive member and process means that operates on the electrophotographic photosensitive member into a cartridge which is detachably mountable to a main body of the electrophotographic image forming apparatus. The process cartridge system can remarkably be improved in the operability since the maintenance of the apparatus can be conducted by a user per se not depending on a service man. For that reason, the process cartridge system has been widely employed in the electrophotographic image forming apparatus.
In the electrophotographic image forming apparatus of the above process cartridge system, a user replaces the cartridge mounted on the apparatus by a fresh one. Therefore, it is a great convenience to provide the electrophotographic image forming apparatus with a function of informing the user that a developer within the process cartridge is completely depleted.
FIG. 54
shows an example of a conventional image forming apparatus A on which a process cartridge B is mounted. A developing device
9
, which constitutes developing means by a process cartridge B. includes a developing chamber
9
A that supplies a developer T to a latent image formed on a photosensitive drum
7
and visualizes the latent image and a developer container
11
A that contains the developer T therein. The developer T within the developer container
11
A is fed to the developing chamber
9
A by gravity and an agitating device
9
e
or other developer feeding means.
In the developing chamber
9
A, a developing roller
9
a,
which serves as a cylindrical developer bearing member for feeding the developer T up to a developing position opposite to the photosensitive drum
7
, is disposed in the vicinity of the photosensitive drum
7
. The developer T is attracted and held on the surface of the developing roller
9
a,
and the developer T is fed up to the developing position opposite to the photosensitive drum
7
due to the rotation of the developing roller
9
a.
The amount and height of the developer T are regulated and uniformly coated on the developing roller
9
a
by developer regulating means
9
d
such as a doctor blade while the developer T is being fed.
The developer T is rubbed by the developing roller
9
a,
the developer regulating means
9
d
or the developer T per se so as to be electrically charged during a process where the developer T is fed onto the developing roller
9
a.
Then, the developer T which has been fed to a portion of the developing roller
9
a
opposite to the photosensitive drum
7
, that is, to a developing position by the developing roller
9
a
is transferred onto the photosensitive drum
7
due to an appropriate developing bias voltage applied between the photosensitive drum
7
and the developing roller
9
a
by a developing bias power supply
54
which serves as bias applying means, and an electrostatic latent image on the photosensitive drum
7
is then developed to form a toner image.
The developer T, which has not been used for development, is fed while it remains on the developing roller
9
a,
and then permitted to be again contained in the developing portion.
On the other hand, a recording medium
2
set in a sheet feed cassette
3
a
is conveyed to a transfer position by a pickup roller
3
b,
a pair of conveying rollers, a registration roller (not shown) and so on in synchronism with the formation of the toner image. A transfer roller
4
is disposed as transfer means at the transfer position, and the toner image on the photosensitive drum
7
is transferred onto the recording medium
2
by application of a voltage.
The recording medium
2
onto which the toner image has been transferred is conveyed to fixing means
5
. The fixing means
5
includes a fixing roller
5
b
having a heater
5
a
therein and a driving roller
5
c,
and applies heat and pressure to the recording medium
2
, which is passing through the fixing roller
5
b
to fix the transferred toner image onto the recording medium
2
. Thereafter, the recording medium
2
is discharged to the outside of the apparatus.
The photosensitive drum
7
from which the toner image has been transferred onto the recording medium
2
by the transfer roller
4
is subjected to a succeeding image forming process after the developer remaining on the photosensitive drum
7
has been removed by cleaning means
10
. The cleaning means
10
scrapes off the residual developer on the photosensitive drum
7
by an elastic cleaning blade
10
a
disposed so as to be abutted against the photosensitive drum
7
and collects the residual developer thus scrapped off into a waste developer reservoir
10
b.
As described above, in the developing device
10
, the developer T is depleted every time the developing operation is repeated. And if there is a shortage of developer, there may occur a defect such as a deterioration of the image density or a lack of the image. For that reason, it is necessary to monitor the presence/absence of the developer T in the developing chamber
9
A and the develop container
11
A so as to prevent the shortage of the developer T.
Under the above circumstances, the conventional developing device
9
includes a developer amount detecting device as means for detecting the residual amount of the developer. The developer amount detecting device includes a bar-shaped antenna electrode
35
for detection of the residual amount of the developer which is disposed horizontally in the interior of the developing chamber
9
A as a member for the electrode to detect the residual amount of the developer T.
The developer amount detecting device further includes a developer amount measuring circuit
50
. The developer amount measuring circuit
50
is equipped with a capacitance detecting circuit
52
as means for measuring a capacitance between the antenna electrode
35
and the developing roller
9
a.
The capacitance detecting circuit
52
is connected with the antenna electrode
35
. With this structure, the developing bias voltage which is applied to the developing roller
9
a
by the developing bias power supply
54
is detected by the antenna electrode
35
to measure the capacitance between antenna electrode
35
and the developing roller
9
a.
The developer amount measuring circuit
50
also includes a reference capacitance
53
as means for setting a capacitance which is a reference for comparison and a capacitance detecting circuit
51
as means for measuring the reference capacitance
53
. The reference capacitance
53
and the developing bias power supply
54
are connected to each other, and the developing bias voltage is detected through the reference capacitance
53
, to thereby obtain the capacitance which is a reference in measurement of a unknown capacitance.
The developer amount detecting device compares an output of the capacitance detecting circuit
51
with an output of the capacitance detecti
Ikemoto Isao
Karakama Toshiyuki
Matsumoto Hideki
Sakurai Kazushige
Watanabe Kazushi
Canon Kabushiki Kaisha
Chen Sophia S.
Fitzpatrick ,Cella, Harper & Scinto
Ngo Hoang
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