Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2002-12-24
2004-11-16
Braun, Fred (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S029000, C399S258000
Reexamination Certificate
active
06819883
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing device, for example, used in a copying machine, a printer, or a facsimile machine of an electro-photographic type, an electronic recording type, or the like, for developing an electrostatic image formed on an image bearing member by supplying developers (toners) from first and second developer bearing members.
2. Description of the Related Art
In recent years, image forming apparatuses such as a copying machine and a printer have been required to output a printed image at increasingly higher speeds.
However, in a known developing device of the image forming apparatus, when a toner supplied from a toner container is held on the surface of one developing roller and an electrostatic latent image is developed (i.e., is visualized) by jumping (i.e., accreting) the toner on the latent image formed on a photoreceptor in an electrostatic manner, the toner held on the surface of the developing roller which is rotating at a high speed because of the speedup requirement quickly deteriorates.
In addition, the speedup causes the developer borne on the developing roller to jump on the photoreceptor and develop the latent image in a short period of time, thereby leading to a loss in image quality.
To solve the above-described problems, a developing device having a plurality of developing rollers for developing a latent image at each roller has been proposed. With this developing device, the deterioration of the toner and the loss in image quality of the high-speed image forming apparatus can be suppressed.
For example, as shown in
FIG. 4
, a developing device
101
has a structure in which a toner container
102
for containing a toner t has an opening opposing a photosensitive drum
100
where two developing rollers
103
a
and
103
b
are disposed. The surfaces of the developing rollers
103
a
and
103
b
are coated with thin films of the toner t by two regulating blades
104
a
and
104
b.
In this developing device
101
, the toner t is supplied from a toner supplying container
106
to the toner container
102
via a toner conveying device
107
on the basis of the data of a toner amount detected by a toner-amount detecting sensor
105
.
Also, as shown in
FIG. 5
, the developing device
101
has another structure in which toner containers
102
a
and
102
b
have developing rollers
103
a
and
103
b
, respectively. In this developing device
101
, the toner t is supplied from the toner supplying container
106
to the toner containers
102
a
and
102
b
via corresponding toner conveying devices
107
a
and
107
b
on the basis of the data of toner amounts detected by corresponding toner-amount detecting sensors
105
a
and
105
b.
Although the known developing device
101
shown in
FIG. 4
having only one toner container
102
and one toner conveying device
107
has a reduced size advantage, when the amount of the toner t in the toner container
102
varies in the range H shown in the figure, a supply amount of the toner t supplied to the developing roller
103
a
is different from that supplied to the developing roller
103
b.
That is, as shown in
FIG. 6
, since a toner coating amount coated on the surface of the developing roller
103
a
disposed upstream with respect to the rotating direction of the photosensitive drum
100
varies depending on the amount of the toner t in the toner container
102
, the toner coating amount decreases as a supply amount of the toner t supplied to the developing roller
103
a
decreases, resulting in a loss in image quality of an output image.
On the other hand, in the developing device
101
shown in
FIG. 5
, since supply amounts of the toner t supplied to the toner containers
102
a
and
102
b
are adjusted by the corresponding toner conveying devices
107
a
and
107
b
, stable amounts of the toner t are coated on the surfaces of the developing rollers
103
a
and
103
b
. However, since the toner conveying devices
107
a
and
107
b
are disposed for supplying the toner t to the corresponding toner containers
102
a
and
102
b
, a space for housing two toner conveying devices is required, thereby resulting in an increased size of the developing device
101
.
In particular, since the image forming apparatus not only performing at a high speed but also having a reduced size has been required in recent years, a compact developing device having a plurality of developing rollers also has been desired.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a developing device which has a reduced size and stably supplies a developer or a toner.
A developing device comprises a first developer container for containing a developer; a first developer bearing member for bearing and conveying the developer in the first developer container; a second developer container for containing a developer; and a second developer bearing member for bearing and conveying the developer in the second developer container. An electrostatic image formed on an image bearing member is developed by supplying the developers from the first and second developer bearing members to the electrostatic image. The developing device further comprises developer supplying means for supplying the developer in a developer supplying container to the first developer container; and developer conveying means for conveying the developer in the first developer container to the second developer container in order to supply the developer to the second developer container.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.
REFERENCES:
patent: 4358196 (1982-11-01), Mugrauer
patent: 4848267 (1989-07-01), Slayton et al.
patent: 4922294 (1990-05-01), Nakagami et al.
patent: 5329340 (1994-07-01), Fukuchi et al.
patent: 5592270 (1997-01-01), Takai et al.
patent: 5652947 (1997-07-01), Izumizaki
patent: 05-204244 (1993-08-01), None
patent: 09-211952 (1997-08-01), None
Kawano Ryuji
Nakase Takahiro
Braun Fred
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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