Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-07-28
2002-06-25
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06409314
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to an image forming apparatus and an image forming method each for use in a copier, facsimile, printer, or the like and particularly for effecting recording by ejecting a toner as a developer onto a recording sheet.
2. Background Art
As the capabilities of personal computers have increased in recent years, a large quantity of documents are handled in offices, while a copier, a facsimile, and a printer having high processing abilities have been used widely due to the advancement of network technology. On the other hand, color documents tend to increase because of rapid prevalence of an inkjet printer and the like. However, an engine capable of outputting monochrome and color documents which are satisfactory both in printing speed and in image quality is still under development, so that the advent of such an engine as mentioned above is expected in this field.
As a conventional image forming apparatus, there is one using a direct marking method wherein an image is formed directly on paper. For example, the image forming apparatus disclosed in Japanese Unexamined Patent Publication No. SHO 63-136058 is aproposal of an apparatus of toner ejection type which is one of direct marking methods.
Below, an example of the foregoing conventional image forming apparatus will be described with reference to the appended drawings.
FIG. 17
is a sectional view showing a schematic structure of the conventional image forming apparatus. In
FIG. 17
, a toner
105
as a developer is filled in a developer hopper
104
, and the toner
105
is guided to the position of a toner layer regulating blade
103
in contact with a toner transport roller
101
by the rotating action of a toner supply roller
102
and of the toner transport roller
101
.
As shown in
FIG. 17
, a flexible printed circuit
110
is disposed under the developer hopper
104
in such a manner as to cover an opening
104
a
. A backside electrode
111
is provided in opposing relation to the flexible printed circuit
110
. A direct-current power source
112
is connected to the backside electrode
111
. In the structure, a recording sheet
122
from a sheet supply roller
120
passes over the backside electrode
111
to be guided to a heat roller
123
.
FIG. 18
is a detailed diagram showing, under magnification, a part of the flexible printed circuit
110
of FIG.
17
. In
FIG. 18
, part (a) is a vertical sectional view of the flexible printed circuit
110
and part (b) is a plan view of the flexible printed circuit
110
when viewed from the toner transport roller
101
. It is to be noted that the part (a) of
FIG. 18
is a sectional view taken along the line A-A′ of the part (b) of FIG.
18
.
As shown in the part (a) of
FIG. 18
, the flexible printed circuit
110
has image signal electrodes
115
provided on the top surface (surface opposed to the toner transport roller
101
) of a flexible printed circuit base
110
a
. The image signal electrodes
115
are provided in such ring-shaped configurations as to surround the top-face openings of apertures
116
which are through holes formed in the flexible circuit base
110
a
, and are electrically connected to signal voltage control means
117
.
As shown in the part (b) of
FIG. 18
, the flexible printed circuit
110
has the apertures
116
and the image signal electrodes
115
corresponding to the apertures
116
which are arranged in plural numbers along the width of the recording sheet
122
and is disposed such that a line drawing in a direction along the width of the recording sheet
22
is formed.
Next, a description will be given on the operation of the conventional image forming apparatus thus constituted.
As shown in
FIG. 17
, the toner
105
is supplied from the toner supply roller
102
to the toner transport roller
101
which is grounded and the toner
105
is formed into a thin layer having a uniform film thickness by the toner layer regulating blade
103
. The thin-layer toner
105
thus formed is a non-magnetic material having an amount of charge of −10 &mgr;/g and an average particle diameter of 8 &mgr;m.
The toner layer formed on the outer circumferential surface of the toner transport roller
101
is transported to a proximate position at a distance of about 30 &mgr;m from the image signal electrodes
115
(the part (a) of
FIG. 18
) of the flexible printed circuit
110
. At this time, when a voltage of +300 V is applied to the image signal electrodes
115
by the image signal voltage control means
117
, the toner
105
passes through the apertures
116
and jumps in the direction of the recording sheet
122
. A voltage of +1000 V is applied to the backside electrode
111
and the toner
105
that has jumped is attracted to the backside electrode
111
to land on the recording sheet
122
, thereby forming dots.
If the voltage to the image signal electrodes
115
is switched to 0 V, the jumping of the toner
105
from the toner transport roller
101
is suppressed and the landing of the toner
105
on the recording sheet
122
is inhibited, so that non-dot parts (blank) are formed. An image is recorded on the recording sheet
122
by controlling the voltage applied to the image signal electrodes depending on the positions of the apertures
116
.
However, the conventional image forming apparatus as described above had the following problems.
If the voltage to the image signal electrodes
115
is switched to 0 V during the non-dot part (the blank) formation, the jumping of the toner
105
from the toner transport roller
101
is suppressed. However, the toner
105
jumping between the image signal electrodes
115
and the recording sheet
122
is scattered to land on the periphery of the dots formed on the recording sheet
122
, so that the image formed on the recording sheet
122
is in a fogged state.
Moreover, in the conventional image forming apparatus required the same number of image signal voltage control means
117
for applying the voltage to the image signal electrodes
115
as the corresponding number of image signal electrodes
115
. In the case where each of the image signal voltage control means
117
is constituted with a change-over switch,
2560
or more switches are necessary to control the flexible printed circuit
110
which covers, e.g., the transverse length (about 8.53 inches) of A
4
size at a recording density of 300 dpi. If the recording density is 600 dpi, 5000 or more switches become necessary.
In developing an image forming apparatus of toner ejection type using the flexible printed circuit
110
, therefore, it has been a significant challenge in this field to effect high-density recording with a minimum number of switches in terms of production cost. In the case of thus reducing the number of switches, however, an increase in the complexity of the wiring pattern of the flexible printed circuit
110
may lead to higher cost. To achieve reasonable cost, therefore, the number of switches has to be reduced, while a simpler wiring pattern is used.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image forming apparatus and an image forming method which have solved the foregoing challenge. In accordance with this invention, there can be formed homogeneous dots free from fog at an image by optimizing a voltage applied to electrodes for an image signal. It is another object of the present invention to provide an image forming apparatus and an image forming method whereby a stable image resistant to environmental and secular changes is formed at reduced manufacturing cost.
Still another object of the present invention is to provide an image forming apparatus and an image forming method which enable the formation of dots high in density and smaller in diameter. Yet another object of the present invention is to provide an image forming apparatus and an image forming method which enable the modulation of dot density and the changing of dot diameter.
To attain the aforesaid objects, an image forming apparatus according
Aizawa Masahiro
Fukano Akira
Kitaoka Yoshitaka
Kumon Akira
Matsuo Hiroyuki
Akin Gump Strauss Hauer & Feld L.L.P.
Gordon Raquel Yvette
Matsushita Electric - Industrial Co., Ltd.
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