Image forming device

Details Image forming device Image forming device

2001-06-26

2002-05-28

Gordon, Raquel Yvette (Department: 2853)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

Reexamination Certificate

active

06394587

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an image forming device such as a copier, facsimile, printer or the like. More particularly, the invention relates to an image forming device wherein toner is caused to travel from a toner carrier toward an electrode disposed on the backside of an image receiving member and be deposited on the image receiving member thereby effecting image formation, with the toner deposition being controlled by a toner passage controller based on image signals.
BACKGROUND ART
In recent years, advances in the performance of personal computers and in network technology have brought about a strong demand for printers and copiers with high processing capabilities that can handle a large amount of documents including color documents. However, image forming devices that can output black and white and color documents with satisfactorily high quality and processing speed are still under development.
An image forming technology known as a “toner jet™” method includes causing toner to fly onto an image receiving member such as a recording sheet or an image carrying belt by the action of an electric field.
Image forming devices of this type are disclosed, for example, in Japanese Published Examined Patent Application No. 44-26333, U.S. Pat. No. 3,689,935 (Japanese Published Examined Patent Application No. 60-20747), Japanese Published Unexamined Patent Application No. 9-500842. As one example of these devices, the one disclosed in Japanese Laid-open Patent Application No. 10-100780 will be described with reference to FIG.
17
.
In
FIG. 17
, reference numeral
31
denotes a grounded toner carrier for conveying charged toner. A control blade
32
is provided for charging toner and adjusting same in one to three layers on the toner carrier
31
. Reference numeral
33
denotes a supply roller for supplying toner to the toner carrier
31
and charging the toner. Reference numeral
34
denotes a toner passage controller, in which toner passage holes
35
are formed, surrounded by control electrodes
36
. Voltage is applied from a control power source
37
to the control electrodes
36
in accordance with image signals. Reference numerals
38
and
39
represent a backside electrode and a power source for same, respectively. An image receiving member
40
such as recording paper is conveyed on the backside electrode
38
.
With the supply roller
33
and the toner carrier
31
in operation, a uniform toner layer is formed on the toner carrier
31
by the control blade
32
. In this state, voltage is applied to the backside electrode
38
, and while the image receiving member
40
is moved, voltage is applied to the control electrodes
36
in synchronism therewith based on image signals, from the control power source
37
, which is, for example, a driving IC or the like. Thereupon, the toner on the toner carrier
31
passes through the toner passage holes
35
in accordance with the image signals and adheres to the image receiving member
40
, whereby a desired image is formed on the image receiving member
40
.
In order to form a fine image of for example 600 pi (i.e., at a density of 600 dots per inch) on the entire surface of the image receiving member
40
, it is necessary to line up the toner passage holes
35
in the toner passage controller
34
at a corresponding pitch. Since this is obviously not achieved in a single row, the toner passage holes
35
and the control electrodes
36
are lined up in a large number of rows (eight rows in the example), as shown in FIG.
18
. The toner passage holes
35
and the control electrodes
36
are both circular, and connection electrodes leading to the control electrodes
36
extend toward both sides with respect to the moving direction of the toner carrier
31
so as to avoid interference between them. The connection electrodes are connected to the leads of corresponding driving ICs for outputting control voltage.
Such construction has the problem of high cost in view of the large number of toner passage holes
35
and corresponding driving ICs. Moreover, there is the problem known as white line noise (hereinafter referred to as “WLN”) wherein grey or white streaks are produced in the image, because most of the toner on the toner carrier
31
is consumed at the first row of the toner passage holes
35
and the toner density decreases in the direction in which the toner passage holes
35
are arranged, i.e., in the direction perpendicular to the moving direction of the toner carrier
31
.
In view of these problems, it has been proposed to provide deflection electrodes
41
a,
41
b
in addition to the control electrodes
36
around the toner passage holes
35
as shown in
FIG. 19
so as to deflect the flying toner, thereby enabling a plurality of dots to be deposited through one toner passage hole
35
(“New multiplexing method makes TonerJet even more low cost manufacturing” by Ove Larson, Journal of Electrophotography, Vol. 36, No. 2, p. 46-49, 1997).
Referring to
FIGS. 19 and 20
, below the control electrodes
36
shown in
FIG. 20A
, deflection electrodes
41
a,
41
b
are arranged in pairs on right and left sides of the toner passage holes
35
as shown in FIG.
20
B. Voltage is selectively applied to the deflection electrode
41
a,
41
b,
or to both of them, so as to determine toner landing positions
42
a
to
42
c
as shown in FIG.
19
B. Voltage application to the deflection electrode
41
a,
41
b,
or to both of them is switched over as the image receiving member
40
is moved. Accordingly, the deflection electrodes
41
a,
41
b
are arranged at an angle such that tan &thgr; is ⅓ (18.4) with respect to the center lines through the toner passage holes
35
as shown in
FIG. 20B
to compensate for the movement of the image receiving member
40
. Voltage is applied first to the deflection electrode
41
a
or
41
b
which is offset toward the upstream side with respect to the travelling direction of the image receiving member
40
.
With this construction, the pitch P with which the toner passage holes
35
are arranged is 254 &mgr;m, ensuring sufficient aperture area of the toner passage holes
35
, whereby the control of flying toner is performed reliably. The toner passage holes
35
need be provided only in two rows as shown in the drawings for forming an image of 600 dpi, leading to a considerable reduction in cost.
The device shown in
FIG. 17
adopts a structure wherein the image receiving member
40
is a recording sheet or the like, on which an image is formed directly. In the case of forming a color image, it is difficult to synchronize the timing of image formation of various colors because of the variations in the conveyance of the recording paper, because of which image quality can decrease. Therefore, in some cases it is preferable to use an intermediate image carrying belt as the image receiving member
40
and to transfer the image formed thereon onto the recording paper or the like, as disclosed in Japanese Laid-open Patent Application No. 10-100780.
Referreing now to
FIG. 21
, reference numeral
43
denotes an endless image carrying belt serving as the image receiving member
40
, made of a resin film of about 10
10
&OHgr;/cm resistance into which a conductive filler has been dispersed, and wound around a pair of two rollers
44
a,
44
b.
Reference numeral
45
denotes a pick-up roller for feeding recording sheets
46
one by one from a paper supply tray. Reference numeral
47
represents a timing roller for synchronizing the supplied recording paper
46
with an image position. Reference numeral
48
represents a transfer roller for transferring a toner image formed on the image carrying belt
43
onto the recording paper
46
. The transfer roller
48
is pressed against the roller
44
a with the image carrying belt
43
interposed therebetween and voltage is applied thereto for the transfer of images. Reference numeral
49
denotes a fixing device for fixing the toner image transferred onto the recording paper
46
by applying heat and pressure thereto.
In such image forming devic

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