Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2000-05-25
2001-11-06
Pendegrass, Joan (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S028000
Reexamination Certificate
active
06314250
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus that forms an electrostatic latent image on an electrophotographic photosensitive member through an electrophotographic process, and visualizes the electrostatic latent image with a developer contained in a developing device, and more particularly, to an electrophotographic image forming apparatus having developer amount detecting means capable of sequentially detecting the remaining amount of developer contained in a developer containing portion, a process cartridge and a developing device.
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 that 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 that 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 that makes the electrophotographic photosensitive member and process means that acts on the electrophotographic photosensitive member into a cartridge that is detachably mountable to a main body of the electrophotographic image forming apparatus. The process cartridge system can remarkably improve 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.
One type of the electrophotographic image forming apparatuses of the above process cartridge system includes a developer amount presence and absence detecting device that informs the user of a fact that the developer has been completely consumed.
The details will be further described.
FIG. 18
shows an example of an image forming apparatus A to which a conventional process cartridge B is mounted. A developing device
10
that constitutes developing means in the process cartridge B, includes a developer container
11
having a developing portion
13
that supplies a developer T to a latent image formed on a photosensitive drum
1
serving as an image bearing member to visualize the latent image and a hopper portion
14
provided for the purpose of reserving and storing the developer T. Then, the developer T within the hopper portion
14
is fed to the developing portion
13
from the interior of the hopper portion
14
by the gravity and an agitating device
15
or the other developer feeding means.
In the developing portion
13
, a developing roller
12
that serves as a cylindrical developer bearing member for feeding the developer T up to a developing position opposite to the photosensitive drum
1
is disposed in the vicinity of the photosensitive drum
1
. The developer T is stuck and held on the surface of the developing roller
12
, and the developer T is fed up to the developing position opposite to the photosensitive drum
1
by the rotation of the developing roller
12
.
The amount and height of the developer T are regulated and uniformly coated on the developing roller
12
by developer regulating means
17
such as a doctor blade while the developer T is being fed. The developer T is rubbed by the developing roller
12
, the developer regulating means
17
or the developer T per se so that the developer T is charged during a process where the developer T is fed onto the developing roller
12
.
Then, the developer T fed to a portion of the developing roller
12
opposite to the photosensitive drum
1
by the developing roller
12
, that is, to a developing position, is transferred onto the photosensitive drum
1
by an appropriate developing bias voltage applied between the photosensitive drum
1
and the developing roller
12
by a developing bias power supply
54
that serves as bias applying means, and an electrostatic latent image on the photosensitive drum
1
is then developed to form a toner image.
The developer T that has not been used for development is fed while it remains on the developing roller
12
, and then again contained in the developing portion
13
.
On the other hand, a recording medium P set in a sheet feeding cassette
20
is conveyed to a transfer position by a pickup roller
21
and conveying means
22
having a conveying roller pair, 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
1
is transferred onto the recording medium P by application of a voltage.
The recording medium P to which the toner image has been transferred is conveyed to fixing means
5
by a conveying guide
23
. The fixing means
5
includes a driving roller
5
c
and a fixing roller
5
a
having a heater
5
b
therein which applies a heat and a pressure to the recording medium P which is passing through the fixing means
5
to fix the transferred toner image onto the recording medium P. Thereafter, the recording medium P is externally discharged from the apparatus.
The photosensitive drum
1
after the toner image thereon has been transferred onto the recording medium P by the transfer roller
4
, is subjected to a succeeding image forming process after the developer remaining on the photosensitive drum
1
has been removed by cleaning means
6
. The cleaning means
6
scrapes off the residual developer on the photosensitive drum
1
by an elastic cleaning blade
7
disposed so as to be abutted against the photosensitive drum
1
and collects the residual developer into a waste developer reservoir
8
.
As described above, in the developing device
10
, because the developer T is consumed every time the developing operation is repeated, it is necessary to monitor the presence and absence of the developer T in the developing portion
13
at any time so as to prevent the shortage of the developer T.
Under the above circumstances, the conventional developing device
10
includes a developer amount detecting device as means for detecting the residual amount of the developer, and the developer amount detecting device includes an antenna electrode
18
for detection of the residual amount of the developer, which is disposed horizontally in the interior of the developing portion
13
in order to detect the residual amount of the developer T.
The developer amount detecting device further includes a developer amount measuring circuit
50
which is equipped with a capacitance detecting circuit
52
as means for measuring a capacitance between the antenna electrode
18
and the developing roller
12
. The capacitance detecting circuit
52
is connected with the antenna electrode
18
. With this structure, the developing bias voltage which is applied to the developing roller
12
by the developing bias power supply
54
is detected by the antenna electrode
18
to measure the capacitance between the antenna electrode
18
and the developing roller
12
.
The developer amount measuring circuit
50
also includes a reference capacitance
53
as means for setting a capacitance that 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 that is a reference in measure
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Pendegrass Joan
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