Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2001-07-19
2004-12-14
Pham, Hai (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S011000, C347S015000
Reexamination Certificate
active
06830305
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an ink jet recording head driving method and a circuit therefor which drives an ink jet recording head incorporating a piezoelectric actuator. More particularly, the present invention relates to an ink jet recording head driving method and a circuit therefor, capable of enhancing the gray scale quality of characters and picture images by changing a diameter of micro ink droplets, which are discharged from nozzles, by use of gray scale information of printing data, and thus changing a size of dots formed on a recording medium such as paper and OHP (overhead projector) film.
BACKGROUND ART
An ink jet printer is provided with a plurality of nozzles and records characters and image pictures on a recording medium such as paper or OHP film by selectively discharging equal-sized micro ink droplets, which are fitted to a recording resolution, from each of the nozzles. Particularly, a drop on demand type ink jet printer, which records characters and image pictures by discharging only the ink droplets necessitated for recording characters and image pictures from nozzles, has been extensively used at home and offices since it is easily miniaturized and colorized as well as generates little noise. In order to attain higher-quality characters and image pictures by use of the aforementioned ink jet printer, a gray scale printing is effective, which changes the size of dots formed on a recording medium by modulating a diameter of micro ink droplets discharged from nozzles according to gray scale information of printing data.
FIG. 16
is a block diagram showing an example of electric configuration of an ink jet recording head driving circuit applied to the aforementioned conventional ink jet printer (hereafter, referred to as “first prior art”).
FIG. 17
is a sectional view showing an example of mechanical configuration of relevant part of an ink jet recording head
1
.
FIG. 18
is a plan view showing an example of mechanical configuration of relevant part of an ink jet printer.
The ink jet recording head
1
of the example has a laminated structure comprising a nozzle plate
3
provided with a plurality of nozzles
2
(orifices), a pressure generating chamber plate
5
which is provided concavely with a plurality of pressure generating chambers
4
,
4
, . . . having one-to-one correspondence to each of the nozzles
2
and filled with ink supplied from an ink tank (not shown) through both an ink pool (not shown) and an ink outlet
5
a
, a plurality of diaphragms
6
,
6
, . . . having one-to-one correspondence to the pressure generating chambers
4
and forming a bottom plate for each of the pressure generating chambers
4
and a plurality of piezoelectric actuators
7
,
7
, . . . attached to each of the diaphragms
6
respectively. Electrodes
8
and
9
are mounted at both edges of each of the piezoelectric actuators
7
. One of the electrodes
8
and
9
is earthed through an electrode line
10
and the other is connected to a switching unit
24
shown in FIG.
16
through the electrode line
10
. This ink jet recording head is a drop on demand type multi head and, in particular, referred to as a Kyser type within the head. According to such an ink jet recording head, when drive waveform signals are applied from the switching unit
24
to arbitrarily combined piezoelectric actuators
7
,
7
, . . . according to printing data, the piezoelectric actuators
7
,
7
, . . . displace the corresponding diaphragms
6
. Accordingly, the volume of the pressure generating chamber
4
therein ink is filled is rapidly changed and thus an ink droplet
11
is discharged from the corresponding nozzle
2
.
As shown in
FIG. 18
, according to the ink jet printer of the aforementioned example, the ink jet recording head
1
is mounted on a head guide axis
12
so that it is sidable in the right and left direction in the figure, and is driven by a head drive motor (not shown). Meanwhile, a recording medium
13
such as paper or OHP film is moved in the up and down direction in the figure by a feed roller
14
driven by a feed motor (not shown). Hereafter, moving direction of the ink jet recording head
1
is referred to as a main scanning direction, and that of a recording medium
13
as a sub-scanning direction.
An ink jet recording head driving circuit shown in
FIG. 16
is schematically configured comprising a control unit
21
, a drive waveform storage means
22
, a waveform generating unit
23
and a switching unit
24
. The control unit
21
, according to commands supplied from outside, controls a head drive motor which drives the ink jet recording head
1
and a feed motor which drives a feed roller
14
. At the same time, the control unit
21
supplies a nozzle selecting data DSN to the switching unit
24
at every discharging period which denotes an adequate period when the ink drop
11
should be discharged from each the nozzle
2
. A nozzle selecting data indicates an appropriate piezoelectric actuator
7
out of a plurality of piezoelectric actuators
7
,
7
, . . . whereto drive waveform signals comprising waveform shown in
FIG. 19
should be applied. Incidentally, at the adequate timing, the control unit
21
supplies a discharging start command which denotes a command to start discharging the ink droplet
11
from each nozzle
2
to the waveform generating unit
23
. The drive waveform storage means
22
is, for example, composed of ROM and the like and stores drive waveform information on drive waveform signals which should be applied to a plurality of piezoelectric actuators
7
,
7
, . . . .
The waveform generating unit
23
comprises waveform generating circuits
25
, power amplifying circuits (not shown) and the like. After the waveform generating circuit
25
generates drive waveform signals on the basis of drive waveform information which is read out from a drive waveform storage means
22
, the power amplifying circuit amplifies power, and then the amplified drive waveform signals are supplied to the switching unit
24
on the basis of a discharging start command sent from the control unit
21
. The switching unit
24
comprises such as nozzle selecting circuits
26
and switches
27
,
27
, . . . composed of transfer gates, for example, and provided to be corresponding to piezoelectric actuators
7
,
7
, . . . . On the basis of the nozzle selecting data DSN supplied from the control unit
21
, the switching unit
24
turns on any one of the switches
27
, and applies drive waveform signals supplied from the waveform generating unit
23
to the corresponding piezoelectric actuators
7
.
In the ink jet printer with the aforementioned configuration, the control unit
21
controls a head drive motor which drives the ink jet recording head
1
and a feed motor which drives a feed roller
14
according to commands provided from outside. At the same time, the control unit
21
supplies a nozzle selecting data DSN to the switching unit
24
at every discharging period and supplies a discharging start command to the waveform generating unit
23
.
Accordingly, the ink jet recording head
1
is moved in the main scanning direction, while the recording medium
13
is moved in the sub-scanning direction. After the waveform generating circuit
25
generates drive waveform signals on the basis of drive waveform information read out from the drive waveform storage means
22
, a power amplifying circuit amplifies power signals. Thus, the amplified drive waveform signals are supplied to the switching unit
24
on the basis of a discharging start command sent from the control unit
21
. The nozzle selecting circuit
26
turns on any one of the switches
27
on the basis of the nozzle selecting data DSN supplied from the control unit
21
. In this way, drive waveform signals supplied from the waveform generating unit
23
are applied to the piezoelectric actuators
7
.
As a result, the ink droplet
11
is discharged from the nozzle
2
corresponding to a piezoelectric actuator
7
whereto drive waveform signals are applied. As shown in
FIG. 20
, in
Dickstein, Shaprio, Morin & Oshinsky, LLP.
Fuji 'Xerox Co., Ltd.
Nguyen Lam
Pham Hai
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