Electrophotography – Image formation – Development
Reexamination Certificate
2000-05-05
2003-02-18
Grainger, Quana M. (Department: 2852)
Electrophotography
Image formation
Development
C399S284000
Reexamination Certificate
active
06522855
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer and to a developing apparatus for a use in these apparatuses.
2. Discussion of the Background
Conventionally, as a developing apparatus for developing with two-component developer including toner and carrier, there is known a developing apparatus in which toner is taken into developer according to behaviors of the developer without a need for a toner density detecting device.
In such a developing apparatus, however, a toner feeding amount depends upon whether or not a behavior of the developer is active and whether or not the developer is abundant in respective places, thereby partially causing the toner density to be unstable, which easily results in fogging or an uneven image density.
Accordingly, in Japanese Patent Application No. 63-4282, for example, to prevent fogging or an uneven density on an image as described above, there is proposed a developing apparatus having two toner supplying regulating members as described below. A first toner supplying regulating member has a fixed end above a doctor blade, which is a developer regulating member for regulating a developer layer thickness on a developer bearing member. The first toner supplying regulating member extends toward a toner supplying tank which is a toner container section. A second toner supplying regulating member is arranged closer to the toner supplying tank than the first toner supplying regulating member. The second toner supplying regulating member extends from the upper portion of the developing apparatus downward, partitioning the developing apparatus into a developer container and a toner supplying tank. The lower free end of the second toner supplying regulating member is on an extension line of a free end of the first toner supplying regulating member or in the developer bearing member side.
In the above developing apparatus, a portion of the uppermost developer layer on the developer bearing member, where developer is relatively coarse and thereby toner is easily taken into, moves to a regulating position of the above doctor blade in a condition of a higher toner density than that of the developer layer on the developing bearing member in the vicinity of the surface of the developer bearing member. Such a movement of the portion of the uppermost developer layer on the developing bearing member, however, is prevented at the free end of the second toner supplying regulating member before the developer layer enters into the developer layer thickness regulating area enclosed by the first toner supplying regulating member, the developer bearing member surface, and the doctor blade. This prevents developer of an extremely high toner density from being supplied to the developer layer thickness regulating area, and only toner sufficiently charged by a friction with magnetic particles is conveyed to the developing area opposite to the image bearing member, such that a fogged strip (background soiling) on an image and an uneven image density in a direction perpendicular to a developer conveying direction with the developer bearing member or the like are prevented.
A developing apparatus previously proposed by the applicant of the present invention and disclosed in Japanese Patent Laid-open Publication No. 9-197833 is useful for dissolving the above-described disadvantages while achieving down-sizing and a lower cost of the apparatus.
The developing apparatus in Japanese Patent Laid-open Publication No. 9-197833 internally has a magnetic field generating device, a developer bearing member for bearing and conveying two-component developer including toner and magnetic carrier, a first regulating member for regulating an amount of developer born and conveyed by the developer bearing member, a developer container section for containing developer scraped off by the first regulating member, and a toner container section arranged adjacent to the developer container section for supplying toner to the developer bearing member. The developing apparatus changes a toner take-in condition of the developer on the developer bearing member by changing a contact condition between the developer and the toner according to a change of the toner density of the developer on the developer bearing member. The developer container section has a second regulating member arranged upstream of the first regulating member in the conveying direction of the developer on the developer bearing member, and the second regulating member is spaced from the developer bearing member so as to regulate a passage of an increase of the developer when the developer layer thickness is increased due to a rise of the toner density of the developer on the developer bearing member. According to this developing apparatus, the toner and the magnetic carrier in the developer are agitated by a cyclic motion of the developer in the developer container section so as to prevent a charged amount of the toner from being reduced, thereby avoiding an occurrence of an abnormal image such as an image having an uneven image density or fogging while achieving down-sizing and a lower cost of the apparatus by reducing the number of components.
FIG. 1
illustrates an example of a developing apparatus related to the above Japanese Patent Laid-open Publication No. 9-197833, and
FIG. 2
is an enlarged view of a main portion of the developing apparatus for assistance in explaining behaviors of the developer in the developing apparatus. The developing apparatus includes a developing sleeve
1
as a developer bearing member containing a permanent magnet as a magnetic field generating device, a first regulating member
2
for regulating a layer thickness of developer
22
, a developer containing case
4
as a developer containing member for forming a developer container section
3
for containing developer which is obstructed by the first regulating member
2
upstream of the first regulating member
2
in a rotary direction of the developer bearing member, and a toner hopper
6
arranged adjacent to the developer containing case
4
for containing toner. The toner hopper
6
is in communication with the developer container section
3
through a toner supplying path
7
as a toner supplying aperture. Inside the toner hopper
6
, there is provided an agitator
8
as a toner agitating member for conveying stored toner
5
to the toner supplying path
7
while agitating the toner
5
. Furthermore, at the lower end of the developer containing case
4
, there is provided a second regulating member
9
spaced from the developing sleeve
1
so as to regulate a passage of an increase of the developer
22
when a layer thickness of the developer
22
is increased due to a rise of the toner density of the developer
22
on the developing sleeve
1
.
In the developing apparatus illustrated in
FIGS. 1 and 2
, when a toner density of the developer
22
passing the first regulating member
2
is within a predetermined appropriate range, the developer
22
scraped off by the second regulating member
9
forms a developer stagnated portion
10
. Then, the developer stagnated portion
10
clogs the toner supplying path
7
, and taking-in of toner
5
from the toner hopper
6
into the developer containing section
3
is stopped in this condition. In the developer stagnated portion
10
, the developer
22
scraped off by the second regulating member
9
is received by a toner supplying stage
14
b
, which is provided integrally with a developing apparatus frame
14
. The toner supplying stage
14
b
is inclined downward to the developing sleeve
1
and has a predetermined length, thereby the developer
22
is prevented from dropping to the toner hopper
6
by a motion of the layer of the developer
22
. Accordingly, a constant amount of the developer
22
can always be maintained on the developer sleeve
1
and a self-regulation for constantly supplying toner to the developer
22
is achieved. When a toner density of the developer in the
Imamura Tsuyoshi
Katoh Shunji
Kawahara Shin-ichi
Sudo Kazuhisa
Tamaki Shinji
Grainger Quana M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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