Image-forming device

Details Image-forming device Image-forming device

2002-05-10

2004-04-06

Gordon, Raquel Yvette (Department: 2853)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

Reexamination Certificate

active

06715858

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an image forming device applied to a copying machine, a facsimile, a printer and the like. Specifically, the invention relates to an image forming device for forming an image in a way that the travel of developer from a developer carrier to a backside electrode is controlled by a developer passing controller based on an image signal and developer is attached on an image receiving member located between the developer passing controller and the backside electrode.
BACKGROUND ART
Recently, there is a strong demand for a copying machine or a printer capable of handing a mass of documents including color documents, accompanied with the improvement in the performance of a personal computer and the progress of network technology. However, it is still under development and expected to realize an image forming device which is capable of outputting black and white or color documents with sufficient and high quality and has a high processing speed.
As one of such technologies, the image forming technology called as “toner jet (registered trademark)” where toner flies onto the image receiving member such as recording paper or an intermediate image carrying belt under the effect of electric field is known.
Such image forming devices are disclosed in Japanese Examined Patent Publication No. 44-26333, U.S. Pat. No. 3,689,935 (corresponding to Japanese Examined Patent Publication No. 60-20747) and Japanese Patent National Publication No. 9-500842. As one of examples, a prior art shown in Japanese Patent Application No. 10-100780 is explained in detail with reference to FIG.
17
.
In
FIG. 17
, a grounded toner carrier
131
holds charged toner and conveys it. A regulating blade
132
manages toner layers from a single to triple on the toner carrier
131
and also charges toner. A supplying roller
133
supplies toner to the toner carrier
131
and charges toner. A toner passing controller
134
has a toner passing hole
135
formed therein and a control electrode
136
around the hole. A voltage corresponding to an image signal is applied to the control electrode
136
from a control power source
137
. Reference numeral
138
is a backside electrode and reference numeral
139
is a backside electrode power source. Reference numeral
140
denotes an image receiving member such as recording paper conveyed on the backside electrode
138
.
In this structure, a uniform toner layer is formed on the toner carrier
131
with the regulating blade
132
by operating the supplying roller
133
and the toner carrier
131
, and conveyed. Under this state, a voltage is applied to the backside electrode
138
and the image receiving member
140
is moved. Then, the control power source
137
such as a driver IC applies a voltage corresponding to an image signal to the control electrode
136
in synchronization with the movement of the image receiving member
140
. Thereby, toner on the toner carrier
131
flies onto the image receiving member
140
while passing through the toner passing hole
135
corresponding to the image signal and attaches to it. Thus, a desired image is formed on the image receiving member
140
.
Here, in order to form a fine image such as 600 dpi (600 dots per inch) on the entire surface of the image receiving member
140
, the toner passing holes
135
have to be arranged in such a pitch on the toner passing controller
134
. However, it is difficult to arrange them in a single row. As shown in
FIG. 18
, the toner passing holes
135
and the control electrodes
136
are arranged in a plurality of rows (eight rows in the shown example). The toner passing hole
135
and the control electrode
136
are shaped in a circle. Connecting electrodes connecting with the respective control electrodes
136
are extended to the moving direction of the toner carrier
131
and on both sides thereof to avoid mutual interference and connected to lead terminals of driver ICs outputting control voltage, respectively.
FIG. 17
shows an example that the image receiving member
140
is made of recording paper and others and an image is formed directly on this means. However, there are variations of thickness of recording paper, change of its characteristics with humidity variation and deformation occurs easily during conveyance. In case of a color printer, it is difficult to synchronize timing of forming an image for every color because of variation in conveyance of recording paper. This causes poor image quality. In order to avoid it, as shown in Japanese Patent Application No. 10-100780, it is preferable that an intermediate image holding belt is used as the image receiving member
140
and an image formed on this belt is transferred to recording paper collectively.
Referring to
FIG. 19
, an endless image holding belt
143
as the image receiving member
140
is made of a film in which conductive filler is dispersed in a resin with its resistance of 10
10
&OHgr;cm and is rolled up between a pair of rollers
144
a
and
144
b
. A pickup roller
145
supplies a piece of recording paper
146
from a paper feed tray. A timing roller
147
synchronizes position of an image with the supplied recording paper
146
. A transfer roller
148
transfers a toner image formed on the image holding belt
143
to the recording paper
146
, sandwiches the image holding belt
143
with the roller
144
a
, and presses the belt toward the roller
144
a
. At the same time, the transfer roller receives transfer voltage. A fixation device
149
fixes the toner image on the recording paper
146
by heating and pressing the recording paper
146
where a toner image has been transferred.
The above image forming device, however, has the following problems in case when the widths of the control electrode rows and the toner passing hole rows in the longitudinal direction, where the toner passing hole and the control electrode around it are installed, are equal to or less than the maximum printing width of the image receiving member in a direction perpendicular to the moving direction of the image receiving member.
First, an image density is decreased or irregularity of the image density is yielded in the area at the right and left ends of a formed image.
Next, when the toner passing controller is shifted in the direction perpendicular to the moving direction of the image receiving member, the area where the control electrode opposed to the image receiving member does not exist, namely, the area where an image cannot be formed is generated.
In addition, when the toner passing controller is not located in parallel to the orthogonal line perpendicular to the moving direction of the image receiving member, an image forming area W
20
is limited to W
20
=W
10
cos &thgr; where the angle between the orthogonal line and the control electrode row is &thgr; and the width of the control electrode row in the longitudinal direction is W
10
.
The first problem will be explained hereafter with reference to FIG.
16
A and FIG.
16
B. FIG.
16
A and
FIG. 16B
are diagrams showing the vicinity of the end portion of the developer passing controller.
FIG. 16A
is a cross section of the vicinity of the end portion of the developer passing controller.
FIG. 16B
is an upper view of the vicinity of the end portion of the developer passing controller. In
FIGS. 16A and 16B
, reference numeral
1
is the developer carrier,
2
is the developer layer formed on the developer carrier
1
and
3
is the developer passing controller. Further, reference numerals
4
a
,
4
b
, and
4
c
are developer passing holes and
10
a
,
10
b
, and
10
c
are control electrodes installed around developer passing holes
4
a
,
4
b
, and
4
c
, respectively. The control electrode
10
c
is the control electrode at the outermost end of the control electrode rows. Further, an arrow in
FIG. 16A
shows the electric power lines formed between the control electrodes
10
a
-
10
c
and the developer carrier
1
when the developer carrier
1
is grounded and a positive voltage is applied to the control electrodes
10
a
-

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