JPH11309852A - Driver and driving method for ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eject a stabilized quantity of ink from a nozzle by applying a voltage of such order as causing no flight of ink from a nozzle between a diaphragm and a drive electrode during nonoperation time other than ink flight operation thereby removing residual charges completely from an ink jet head. SOLUTION: When ink is flied by operating an ink jet head 31 through a diaphragm drive control circuit 93, i.e., at the time of ink flight operation, a power supply control means 91 supplies power for applying a DC pulse voltage to the ink jet head 31. During an interval after ink is flied before next pulse is outputted, i.e., nonoperation time other than ink flight operation, switching is made to an AC power supply 94 in order to apply a low voltage high frequency AC voltage to the ink jet head 31. Consequently, residual charges on the diaphragm and drive electrode of the ink jet head 31 are discharged through the AC power supply 94.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for driving an ink jet head using an electrostatic actuator, and more particularly to a method for completely removing residual charges of an ink jet head and discharging a stable amount of ink from a nozzle. The present invention relates to a method and an apparatus for driving an ink-jet head which can be driven.

[0002]

2. Description of the Related Art With the recent trend toward color printing, demand for a printer using an ink jet head capable of obtaining a clear print image has rapidly increased. As the ink jet head, a bubble jet method, a PZT (piezoelectric element) method, and the like are generally known as a method of flying ink, and are commercialized.

In recent years, an ink jet head using an electrostatic actuator, which can be manufactured in a process similar to a semiconductor manufacturing process and is easily miniaturized, has been receiving attention.

An ink jet head using this electrostatic actuator deforms the diaphragm by applying a voltage between a diaphragm provided in a pressurizing chamber for pressurizing ink and a drive electrode provided in opposition to the diaphragm. (The diaphragm is attracted to and brought into contact with the drive electrode side.) The deformation causes the ink to flow into the pressurizing chamber, and uses the restoring force when the diaphragm returns to its original shape when the voltage is suddenly turned off. Then, the ink is made to fly from the pressurizing chamber to the outside.

The details of the ink jet head using this electrostatic actuator are described in “A LOW POWER,
SMALL, ELECTROSTATICALLY-D
RIVE COMMERCIAL INKJETHE
AD "(Seiko Epson Corporation).

[0006]

However, in the ink jet head having such a configuration, a pulsed DC voltage is continuously applied between the diaphragm and the driving electrode during the operation thereof. Due to long-term use, polarization occurs in the dielectric existing in the diaphragm and the drive electrode, which makes it impossible to control the amount of flexure of the diaphragm to the desired amount of flexure. There is a problem that the ink cannot be ejected. This problem becomes significant when the vibrating plate is made of a semiconductor material.

As a technique for solving such a problem, for example, there is a technique disclosed in Japanese Patent Application Laid-Open No. 7-214770 and a technique disclosed in Japanese Patent Application Laid-Open No. 8-72237.

In the technique disclosed in Japanese Patent Application Laid-Open No. Hei 7-214770, when a voltage is applied between a diaphragm and an individual electrode for a certain period of time by a charging circuit and ink is caused to fly, the voltage is stored by a discharging circuit. Discharge the charge rapidly,
This prevents charge accumulation.

The technique disclosed in Japanese Patent Application Laid-Open No. 8-72237 is to short-circuit the high-potential side and the low-potential side of the power supply when the head is not operating, thereby preventing charge accumulation.

However, even with such a technique, it is not possible to sufficiently discharge the electric charges since all of them need to be discharged instantaneously.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and has been made in consideration of the above circumstances, and has been made in view of the above circumstances. It is an object of the present invention to provide a head driving method and a head driving method.

[0012]

The present invention for achieving the above object is constituted as follows. The invention according to claim 1 includes a nozzle, a pressure chamber communicating with the nozzle, a vibration plate provided in the pressure chamber, and a drive electrode provided to face the vibration plate. A non-operation other than the ink flying operation of the ink-jet head, such that an AC voltage is applied between the vibration plate and the driving electrode to such an extent that ink does not fly from the nozzles. A method for driving an ink-jet head, characterized in that:

According to a second aspect of the present invention, in the method of driving an ink jet head according to the first aspect, the frequency of the AC voltage applied between the diaphragm and the driving electrode is such that the ink of the ink jet head has The frequency is higher than the frequency of the pulse applied to the drive electrode during the flying operation.

According to a third aspect of the present invention, there is provided a nozzle, a pressure chamber communicating with the nozzle, a diaphragm provided in the pressure chamber, and a drive electrode provided to face the diaphragm. A driving device for applying a pulsed DC voltage between the vibration plate and the driving electrode, and after the vibration plate driving device starts operating. AC voltage applying means for applying an AC voltage that does not cause ink to fly from the nozzles, between the diaphragm and the drive electrode, except until the ink flying operation ends. Drive unit for inkjet head.

According to a fourth aspect of the present invention, in the ink jet head driving device according to the third aspect, the frequency of the AC voltage applied by the AC voltage applying means is:
The frequency is higher than the frequency of the pulsed DC voltage applied by the diaphragm driving means.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a driving apparatus for an ink jet head for applying a voltage between two electrodes (a first electrode and a driving electrode provided on a diaphragm) provided on an electrostatic actuator. In addition, when the ink jet head is not operating except when the ink jet head applies a DC voltage between the two electrodes to fly the ink, or conversely, when the ink jet head is not operating other than the ink flying operation, the ink is not large enough to fly between the two electrodes. The gist is that an AC voltage having a high frequency is applied to prevent accumulation of residual charges.

Hereinafter, an ink jet head driving device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view for explaining a schematic configuration of an ink jet printer on which an ink jet head driving device of the present invention is mounted.

The ink jet printer 1 is used for paper or OH
It prints on a recording sheet 2, which is a recording medium such as a P sheet, and includes an inkjet head scanning system and a recording sheet feeding system.

The inkjet head scanning system includes a head unit 3 having a single or multiple ink jet printheads (for example, three, four, or seven colors), and a carriage 4 for holding the head unit 3.
A scan shaft 5 and a guide shaft 6 for reciprocating the carriage 4 in parallel with the recording surface of the recording sheet 2.
A pulse motor 7 for reciprocatingly driving the carriage 4 along the guide shaft 6;
And a timing belt 9 for changing the reciprocating motion of the idle pulley.

The recording sheet feeding system includes a recording sheet 2
, Which also serve as a guide plate for guiding the recording sheet 2 along the transport path, a paper pressing plate 11 for pressing the recording sheet 2 between the platen 10 to prevent floating, and a discharge roller 12 for discharging the recording sheet 2; A discharge holding roller 13;
The head unit 3 includes a maintenance device 14 for cleaning the nozzle surface of the head unit 3 that discharges ink and recovering a defective ink discharge from a good state, and a paper feed knob 15 for manually conveying the recording sheet 2.

The recording sheet 2 is fed to a recording section where the head unit 3 and the platen 10 face each other by a sheet feeding device such as a manual feed or a cut sheet feeder (not shown). At this time, the rotation amount of a paper feed roller (not shown) is controlled, and the conveyance to the recording unit is controlled.

The print head of the head unit 3 includes:
An electrostatic actuator is used as an energy source for flying ink. The electrostatic actuator uses an electrostatic force (Coulomb force) acting between a diaphragm and an electrode provided opposite to each other to sharply displace the diaphragm. This displacement changes the volume of the pressurized chamber filled with ink. Due to the change in the volume of the pressurizing chamber, ink is ejected from nozzles provided in the pressurizing chamber, and recording on the recording sheet 2 is performed.

The carriage 4 is driven by a pulse motor 7, an idle pulley 8, and a timing belt 9 to record the recording sheet 2.
Is scanned in the horizontal direction (main scanning), and the head unit 3 attached to the carriage 4 records an image for one line. Each time printing of one line is completed, the printing sheet 2 is fed in the vertical direction (sub-scan), and printing is performed on the next line.

The image is recorded on the recording sheet 2 in this manner, and the recording sheet 2 that has passed through the recording section is contacted with a discharge roller 12 disposed downstream of the recording sheet 2 at a constant pressure by a discharge press roller. 13 and discharged.

FIG. 2 is a perspective view for explaining the configuration around the carriage 4 including the print head 31 for one color of the head unit 3 shown in FIG.

In the vicinity of the carriage 4, an ink cartridge 403 containing ink and having a vent 404, a casing 401 containing the ink cartridge 403, a casing lid 405, and the ink cartridge 403 are detachably attached to the print head 31. Ink supply pipe 402 to be supplied to the casing 401, a hook 406 for fixing the casing lid 405 to the casing 401 when the casing lid 405 is closed, a lid stopper 407, and the ink cartridge 4.
A pressing spring 408 is provided to hold the ink cartridge 403 in the casing 401 between the casing lid 405 and the ink cartridge 403 while urging the ink cartridge 403 in a direction opposite to the direction in which the ink cartridge 03 is stored (the direction of the arrow D3).

When the carriage 4 having such a configuration is moved in the scanning direction (the direction of the arrow D1), the recording sheet 2 is main-scanned. Also, recording sheet 2
Is sent in the sub-scanning direction (the direction of arrow D2).
Will be printed.

[Embodiment 1] FIG. 3 shows Embodiment 1 of the present invention.
FIG. 3 is a cross-sectional view illustrating a structure of an inkjet head in FIG. The inkjet head 31 includes a nozzle 54 provided on a side surface in the drawing, a pressure chamber 51 having a vibration plate 55 for changing the internal pressure of the nozzle 54 to discharge ink from the nozzle 54, and supplies ink to the pressure chamber 51. An ink supply chamber 52 for storing ink, an inlet 53 for guiding the ink in the ink supply chamber 52 to the pressurizing chamber 51, and a space 71 at a position facing the first electrode 56 provided on the vibration plate 55. It has a drive electrode 72 that is a second electrode that is separated.

The space 71 between the first electrode 56 and the drive electrode 72 is 0.3 μm in the first embodiment. The first electrode 56 provided on the diaphragm 55 is an impurity conductive layer formed by diffusing boron as described later. The first electrode 56 is used in the first embodiment.
Are grounded, and the drive electrode 72 is connected to the wiring 80.
Thereby, a voltage from a diaphragm drive control circuit described later is applied.

When a voltage is applied between the first electrode 56 and the drive electrode 72 of the ink-jet head 31 having the above-described structure, the electrostatic force generated between the two electrodes causes the electrostatic head shown in FIG.
As shown in (2), the diaphragm 55 is attracted to the drive electrode 72 side and bends from the state of the solid line to the state of the dotted line. When the diaphragm 55 is bent in this manner, the volume of the pressurizing chamber 51 increases, and the ink in the ink supply chamber 52 flows into the pressurizing chamber 51 through the inlet 53. When the application of the voltage is stopped from this state, the shape of the diaphragm 55 is restored to the original shape,
By applying pressure to the pressure chamber 51 by the restoring force at this time, ink droplets are ejected from the nozzles 54.

In the first embodiment, since the first electrode 56 formed on the diaphragm 55 is grounded, a positive potential is applied to the drive electrode 72 as a drive voltage. The force F acting on the diaphragm 55 by this drive voltage is F = 1
/ 2 · {εrε0 S (V / d) ² }.

Where εr is the first electrode 56 and the second electrode 56
The relative dielectric constant between the electrode (drive electrode) 72, ε0 is the relative dielectric constant of vacuum, S is the area of the electrode, V is the drive voltage, and d is the distance between the first electrode 56 and the second electrode (drive electrode) 72. Distance.

Next, a method of manufacturing the above-described ink jet head will be briefly described. The inkjet head 31 used in the first embodiment is manufactured by using a so-called semiconductor device manufacturing process, a micro machine manufacturing process, or the like, and various methods are available. Here, an example will be described. I do. Needless to say, even an inkjet head manufactured by a method other than the manufacturing method described here can be driven by the driving device according to the present invention.

The ink jet head 31 shown in FIG.
Is composed of three components. Referring to this figure, a channel plate 50 composed of a pressure chamber 51, an ink supply chamber 52, an inlet 53, a nozzle 54, and a vibration plate 55
And a top plate 6 that covers the upper side of the channel plate 50 in the figure.
0 and diaphragm 5 provided in channel plate 50
5 is provided with a glass substrate 70 on which a space 71 is provided at a position facing the drive electrode 5 and a drive electrode 72 is disposed.

First, the formation of the channel plate 50 will be described. Before forming the channel plate 50,
Using a silicon substrate wrapped to about 00 μm, an oxide film 101 is formed on the entire surface of the silicon substrate 100 by a thermal oxidation method, as shown in FIG. 5A. And
On the oxide film 101 on the upper surface of the silicon substrate 100 in the figure,
By known photolithography and dry etching, the pressure chamber 51, the ink supply chamber 52, the inlet 5
An opening for defining the shape of the nozzle 3 and the nozzle 54 is provided, and the etching mask 101a is formed as shown in FIG.

Next, the silicon substrate 100 having the etching mask 101a formed by the patterned oxide film 101 is anisotropically etched with a KOH solution. The silicon substrate 100 used here has a substrate surface having a (110) plane or a (100) plane.
In the anisotropic etching using the KOH solution, the etching is automatically stopped when the (111) plane of the silicon substrate is exposed. Therefore, when the etching mask 101a is formed, the opening of the portion to be the nozzle 54 or the inlet 53 is opened. By adjusting the size of, the etching depth in these portions can be set to a desired depth. The depth of the pressure chamber 51 and the ink supply chamber 52 is adjusted to about 6.5 μm by adjusting the etching time together with the size of the opening of these parts, so that the thickness of the part to be the diaphragm 55 becomes about 6.5 μm. To do. The pressurization chamber 51 and the ink supply chamber 52 are etched by the KOH solution.
An appropriate taper is formed by exposing the (111) plane in the side wall portion. After that, the oxide film used as the etching mask is removed.

In this manner, as shown in FIGS. 5C and 6, the pressurizing chamber 51, the ink supply chamber 52, the inlet 53, the nozzle 54, and the diaphragm 55
00 is formed. Channel plate 5 formed here
As shown in FIG. 6, a plurality of pressurizing chambers and a plurality of nozzles are formed in the number 0 so that a plurality of ink droplets can be ejected from one head.
6 is a plan view of the surface of the silicon substrate on which the pressurizing chamber 51, the ink supply chamber 52, the inlet 53, the nozzle 54, and the like are formed. FIG. 5 is a cross-sectional view taken along line AA of FIG. It is the drawing shown in order of process.

Then, on the back side of the silicon substrate 100, the diaphragm 55 and the first
A resist pattern in which a portion (not shown) for making electrical contact with the electrode 56 is opened is formed by photolithography, and boron is ion-implanted into the diaphragm 55 and the contact portion, as shown in FIG. 5C. First electrode 5
6 and an impurity diffusion layer serving as a contact line are formed. Thereafter, an oxide film is formed on the entire surface of the silicon substrate 100 by a thermal oxidation process, so that an insulating film 57 is formed on the surface of the vibration plate 55 (the back surface side of the silicon substrate). This insulating film 57 is for preventing a short circuit with the drive electrode 72.

Next, the glass substrate 7 provided with the drive electrodes 72
The formation of 0 will be described. In this glass substrate 70,
When bonded to the state shown in FIG. 3 using a borosilicate glass substrate, the diaphragm 55 of the channel plate 50
Is formed in a portion where is located by a predetermined depth by etching, an ITO film is formed to form a contact line connected to the inside of the recess and the recess, and the drive electrode 72 is formed in the recess by lift-off. A contact line connected to the drive electrode 72 is formed on the surface of the glass substrate. At this time, in the case of a head having a plurality of pressure chambers and nozzles, a drive electrode and respective contact lines are formed for each pressure chamber.

Thereafter, the entire surface on which the electrodes are formed is covered with SiF.
An H film is formed to a thickness of about 2 μm. The SiFH film is not patterned and is provided on the entire surface of the substrate to form a protective film, thereby preventing the drive electrodes from being deteriorated due to the influence of ambient humidity.

The depth at which the recess is formed depends on the first electrode 56 in the space 71 when the drive electrode 72 is formed.
The distance from the (insulating film surface) to the opposing drive electrode 72 (SiFH film surface) is 0.1 to 1 μm, preferably 0.1 to 1 μm so as to enable driving at a lower driving voltage.
The thickness is set to 0.5 μm. In the first embodiment, as described above, the concave portion is formed so that the space 71 is 0.3 μm.

Note that this space 71 is replaced with a silicon substrate 100 instead of forming a recess in the glass substrate 70.
The vibrating plate 55 may be dug from the back surface (the lower side in the figure) of the silicon substrate 100 as much as the space 71 is formed by etching. In this case, the drive electrode 72 and its contact line are formed of ITO without forming a recess in the glass substrate 70.

Next, the top plate 60 is formed by forming an ink supply port for introducing ink from an ink cassette above the pressurizing chamber 52 using the same borosilicate glass substrate.

The channel plate 50, the glass substrate 70, and the top plate 60 formed as described above are anodically bonded to form a sandwich structure as shown in FIG.
Wiring is connected to the contact line formed by the impurity diffusion layer formed on the vibration plate 55 and the contact line formed on the glass substrate 70, thereby completing the ink jet head.

In the first embodiment, silicon is used as the material of the channel plate 50, but other materials such as glass, ceramics, metal, resin, and photosensitive resin may be used. It is also possible to use a material that can form a complicated shape.

FIG. 7 is a block diagram of a control system for controlling the operation of the ink jet printer 1. In this figure, a part related to the operation control of the inkjet head scanning system is particularly described.

The printer control means 90 in the figure is a means for generally controlling the operation of the ink jet printer 1. The power supply control unit 91 is a unit that supplies power to the printer control unit 90 and a diaphragm drive control circuit 93 described later.

The pulse motor 7 is a motor for driving the print head 3 (see FIG. 1) to reciprocate along the guide shaft 6. The operation of the pulse motor 7 is controlled by a head drive control circuit 92. The head drive control circuit 92
The operation is controlled by a command from the printer control means 90.

The diaphragm drive control circuit 93 outputs a pulsed DC voltage with the power supplied from the power supply control means 91 when the ink jet head 31 is operated to fly ink, that is, during the ink flying operation. On the other hand, the AC voltage is output from the AC power supply 94 until the next pulse is output after the ink is jetted, that is, during non-operation other than the ink jetting operation.

The AC power supply 94 is connected to the ink jet head 3.
1 is a power supply that generates a low-voltage high-frequency AC voltage to be applied to the power supply 1. The ink-jet head 31 is a head configured as described above (see FIG. 3). The drive electrode 72 of the ink-jet head 31 has a drive electrode 72, as shown in FIG. The pulse drive DC voltage (for example, 40
V) is applied. On the other hand, during a non-operation period other than this period, for example, 3 KHz to 1 MH output from the AC power supply 94.
An AC voltage having a frequency of z (for example, 5 V) is applied.

Here, the reason why the AC voltage is set to a low voltage of about 5 V during the non-operating period is that the diaphragm 55 also repeatedly vibrates in the vertical direction in FIG. 3 (in this case, the AC voltage is applied. Therefore, as shown in FIG. 4, not only the deflection in the direction of the driving electrode but also the deflection in the pressure chamber 51 side), the width of this vibration proportional to the applied voltage value ( This is because it is necessary to control the distance) so that the ink does not fly out of the nozzle 54.

The reason why the lower limit of 3 KHz or more is set for the frequency of the AC voltage is that the period of the pulse output from the diaphragm drive control circuit 93 is taken into consideration. That is, assuming that the cycle of the pulse output from the diaphragm driving control circuit 93 is 1 KHz in the present embodiment, as shown in FIG. 8, after the pulse for driving the diaphragm 55 is output, Unless an AC voltage of at least one cycle or more is applied until the pulse is output, the effect of removing the residual charge cannot be obtained.

Incidentally, in the present invention, the non-operation time other than the ink flying operation means, as shown in FIG. 8, until a certain time elapses after the DC voltage is applied to the drive electrode 72 (T in FIG. 8). ) Or any period from the time when the carriage 4 stops to the time when the carriage 4 stops during the operation of the carriage 4 until the ink flies from the nozzle 54 and a certain time elapses.

The driving apparatus according to the present embodiment is configured as described above. The specific operation will be described below. First, when a print signal is output from the printer control means 90 in FIG. 7, a pulse drive voltage as shown in FIG. 8 is output from the diaphragm drive control circuit 93 which has received this signal. While the drive voltage is being output, the first electrode 56 of FIG. 3 is grounded, and a voltage of about 40 V is applied to the drive electrode 72. As a result, the diaphragm 55 is moved by the electrostatic force acting between the electrodes 56 and 72 as shown in FIG.
The diaphragm 55 comes into contact with the drive electrode 72 as shown in FIG. With the deformation of the vibration plate 55, ink flows from the ink supply chamber 52 into the pressure chamber 51 via the inlet 53.

After the pressure chamber 51 is sufficiently filled with ink, the drive voltage is turned off as shown in FIG. For this reason, no electrostatic force acts between the two electrodes 56 and 72, and the diaphragm 55 returns to the original state rapidly by its own restoring force, and the ink changes with the volume change of the pressurizing chamber 51 at this time. Fly from the nozzle 54.

Next, the diaphragm driving control circuit 93 waits until the ink flies from the nozzle 54 and the vibration of the diaphragm 55 is attenuated, switches to the AC power supply 94, and switches the first electrode 56.
A low voltage (5) as shown in FIG.
V) Apply high frequency (about 3 KHz to 1 MHz) AC voltage. By applying this AC voltage, both electrodes 65, 72
Is discharged through the AC power supply 94. That is, the AC voltage is applied except during the period from the time when the diaphragm drive control circuit 93 starts operation and the pulse-like DC voltage is applied to the drive electrode 72 to the time when the ink flying operation ends. Become. The application of the AC voltage is continued until the next drive pulse (DC voltage) is output from the diaphragm drive control circuit 93. Then, the same operation as described above is repeated.

When the AC voltage is constantly applied to the diaphragm 55 when the head is not operating, the diaphragm 55 is constantly oscillating so as to undulate. This has the effect of stirring the ink inside, and the residual charge is always removed, so that a stable amount of ink can be ejected from the nozzles.

The timing for applying the DC voltage to the drive electrode 72 is preferably based on the timing at which the applied AC voltage becomes 0 V at which the applied AC voltage shifts in the + direction. If the timing is set as described above, the diaphragm 55 can be smoothly bent from the vibration operation of the diaphragm 55 (by the DC voltage).

[Second Embodiment] A second embodiment is different from the first embodiment only in the structure of the ink jet head from the structure of FIG. 3 shown in the first embodiment. The same is true. FIG. 9 is a cross-sectional view illustrating the configuration of the inkjet head used in the second embodiment.

This ink jet head 32 is the same as the ink jet head 31 used in the first embodiment except for the position of the nozzle for discharging ink droplets, which is provided on the upper side in the figure. That is, the ink jet head 32 is provided with a nozzle 58 provided on the upper side in the figure, a pressurizing chamber 51 provided with a vibrating plate 55 for varying the internal pressure for discharging ink from the nozzle 58, and ink to the pressurizing chamber 51. An ink supply chamber 52 for storing ink for supply, an inlet 53 for guiding the ink in the ink supply chamber 52 to the pressurizing chamber, and a diaphragm 55
Electrode 7 separated by a space 71 at a position facing the
Consists of two.

Then, as in the first embodiment, diaphragm 55
Is formed with a first electrode 56 formed by diffusing boron. By applying a voltage between the first electrode 56 and a driving electrode 72 as a second electrode, the diaphragm 55 is formed. The ink droplets are ejected from the nozzles 58 by deforming and changing the pressure in the pressure chamber 51.
The first electrode 56 is grounded in the first embodiment, and a voltage from the diaphragm drive control circuit similar to that shown in the first embodiment is applied to the drive electrode 72 via the wiring 80. It has become so.

Incidentally, such an ink jet head 3
2 is manufactured by mounting the nozzle 5 on the top plate 60 (about 150 μm thick).
8 is formed by a known Ni electroforming method.
Except that the ink supply port 90 is formed from the side, it is the same as the manufacture of the inkjet head 31 described above.

In actual use, the ink-jet head 32 is used so that the nozzles 58 face downward so that underprinting is performed on recording paper. As described above, by providing the nozzle 58 at the upper side in the drawing, that is, at the position opposing the diaphragm 55, the ink head pressure (pressure) in the pressurizing chamber 51 due to the deformation of the diaphragm 55 is different from the ink ejection direction. Since the directions are the same, the ink discharge is assisted, and the same discharge speed can be obtained with a smaller amount of deformation of the diaphragm 55 than the structure of the first embodiment described above. Further, by providing the nozzles 58 at the position facing the vibration plate 55, when a plurality of nozzles are provided in one head, the pressure applied to each nozzle becomes equal.

When the ink jet head 32 is driven by the driving device described in the first embodiment,
When ejecting ink droplets, the pressure applied to each nozzle can be made more uniform, so that the variation in the dot diameter of the ink to be ejected can be reduced.
The driving voltage can also be reduced.

As described above, according to the driving apparatus of the present invention, when the ink jet head is not operated, the low-voltage high-frequency AC voltage is applied between the first electrode 56 and the driving electrode 72. Thus, the residual charge of the ink jet head can be completely removed, and a stable amount of ink can be ejected from the nozzles.

[0067]

According to the present invention configured as described above, the following effects can be obtained. According to the first aspect of the invention, when the inkjet head is not operating other than the ink flying operation, an AC voltage is applied between the vibration plate and the driving electrode to such an extent that the ink does not fly from the nozzle. The residual charge of the head is completely removed, and a stable amount of ink can be ejected from the nozzles.

According to the second aspect of the present invention, the frequency of the AC voltage applied between the diaphragm and the drive electrode is set to a frequency higher than the frequency of the pulse applied to the drive electrode during the ink jetting operation of the ink jet head. Therefore, it is possible to effectively remove the residual charges of the ink jet head.

According to the third aspect of the present invention, ink is supplied from the nozzle between the diaphragm and the drive electrode except during the period from the start of the operation of the diaphragm driving means to the end of the ink flying operation. Since an AC voltage that does not cause flying is applied, the residual charge of the inkjet head is completely removed, and a stable amount of ink can be ejected from the nozzles.

According to the fourth aspect of the present invention, the frequency of the AC voltage applied by the AC voltage applying means is higher than the frequency of the pulsed DC voltage applied by the diaphragm driving means. Can be effectively removed.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a schematic configuration of an ink jet printer.

FIG. 2 is a perspective view for explaining a configuration around a carriage including a print head for one color of the head unit shown in FIG. 1;

FIG. 3 is a cross-sectional view illustrating a structure of the inkjet head according to the first embodiment.

FIG. 4 is a diagram for explaining the operation of the diaphragm shown in FIG. 3;

FIG. 5 is a view for explaining a step of forming the channel plate shown in FIG. 3;

FIG. 6 is a top view of a channel plate.

FIG. 7 is a block diagram of a control system for controlling the operation of the inkjet printer.

FIG. 8 is a diagram for explaining the operation of the diaphragm drive control circuit shown in FIG. 7;

FIG. 9 is a cross-sectional view illustrating a configuration of an inkjet head used in the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 31 ... Ink jet head, 51 ... Pressurization chamber, 52 ... Ink supply chamber, 54, 58 ... Nozzle, 55 ... Vibration plate, 56 ... 1st electrode, 71 ... Space, 72 ... Drive electrode, 93 ... Vibration plate drive control circuit .

Claims (4)

[Claims] 1. An ink jet head comprising: a nozzle; a pressure chamber communicating with the nozzle; a vibration plate provided in the pressure chamber; and a drive electrode provided to face the vibration plate. A driving method, wherein at the time of non-operation other than the ink flying operation in the inkjet head, between the diaphragm and the driving electrode,
A method for driving an ink jet head, characterized in that an AC voltage that does not cause ink to fly from the nozzles is applied. 2. The method according to claim 1, wherein a frequency of the AC voltage applied between the diaphragm and the drive electrode is higher than a frequency of a pulse applied to the drive electrode at the time of the ink jet operation of the ink jet head. The method for driving an ink jet head according to claim 1, wherein: 3. An inkjet head comprising: a nozzle; a pressure chamber communicating with the nozzle; a vibration plate provided in the pressure chamber; and a drive electrode provided to face the vibration plate. A driving device, comprising: a diaphragm driving unit that applies a pulsed DC voltage between the vibration plate and the driving electrode; and from the start of the operation of the diaphragm driving unit to the end of the ink flying operation. A driving device for an ink-jet head, comprising: an AC voltage applying unit that applies an AC voltage that does not cause ink to fly from the nozzles, between the vibration plate and the drive electrode, except for the above. 4. A frequency of the AC voltage applied by the AC voltage applying means is higher than a frequency of a pulsed DC voltage applied by the diaphragm driving means. The driving device of the inkjet head according to the above.