JPH07251504A - Ink jet printing head - Google Patents

Abstract

PURPOSE:To form a printing image of high quality on a printing medium while enhancing the jet characteristics of ink by providing a variable means selectively changing the magnitude of the hydromechanical conductance in an ink supply passage. CONSTITUTION:In an ink jet printer, a cell 1 is formed of a metal stainless plate 1a and has the chamber surrounded by a resin spacer 1b and the first diaphragm 6 driven by a first piezoelectric element 4 and is filled with the ink 8a supplied from an ink storage chamber 8 through an ink supply passage 2. Jet orifices 3 are formed to the front of the cell 1 by etching. A movable means consisting of a second piezoelectric element 5 and a second diaphragmn 7 is further provided to the cell 1. The inner pressure of the cell 1 is raised by the expansion of the first diaphragmn 6 and the cross-sectional area of the ink supply passage 2 is reduced by the expansion of the second diaphragm 7 and the jet characteristics of ink are made variable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer head.

[0002]

2. Description of the Related Art Hard copy of computer information and video images (images permanently read by the naked eye)
In general, the need for color printers has increased as the quality of image information and the ease of access of such printers have increased.

There are various methods (printing methods) for printing on a printing medium, and the current main color printing methods are an electrophotographic method of developing a charge latent image formed by exposure with toner and a fine hole method of ink. There are an ink jet system ejected from a sheet, a thermal transfer system in which a sheet-like ink is transferred by heating, a thermal sublimation system in which a sheet-like ink is sublimated by heating to print an image, and a film printer system in which a silver halide photograph is directly drawn with light.

Among such printing methods, there are ink jet methods called on-demand type and continuous type. The on-demand type is a system that ejects ink only when a signal is input, and the continuous type is a system that always generates ink fog and controls the direction of ink fog scattering by a deflection electrode. is there. The on-demand type is provided as a relatively inexpensive printer because of its simple mechanism and is widely used.
In many cases, three-color or four-color printer heads realize colorization. There is also a phase change type ink jet system which is not only a liquid as an ink, but is also a solid at room temperature and is heated and liquefied before being ejected and re-solidified on a printing medium.

As a method of ejecting ink, a generally popular one at present is a thermal method of ejecting ink by utilizing the expansion force of bubbles vaporized by heating, or a cell filled with ink by a piezoelectric body. A piezo method that compresses and ejects ink. All of these printing methods are characterized by ejecting ink using a pressing force, are inexpensive and easy to maintain, and are therefore widely used in inkjet printer heads.

[0006]

However, in the above-mentioned conventional ink jet printer head, since the ejection force of the ink is weak, the shape of the ejected ink is small and well-shaped when the ink of high viscosity (ink that hardly diffuses) is used. If the ink does not become dull and has low viscosity, bleeding occurs. Therefore, there is a problem in that the quality of the printed image is inferior.

When high-viscosity ink is used, the shape of the ejected ink is small and well-shaped by increasing the pressure for ejecting the ink. Moreover, since the viscosity of the ink is high, the printed image is less likely to bleed. It is generally known that there is a problem that the ejection pressure of ink is lowered.

That is, due to the structure of the ink jet printer head, the cells filled with the ejected ink naturally have ejection holes for ejecting the ink and ink supply passages for supplying the ink into the cells. When the ink in the cell is ejected, the rising pressure generated in the cell escapes to the outside through the ink supply flow path, so that a so-called backflow phenomenon of ink occurs and there is a problem that the ejection pressure of the ink decreases. .

There are various ink ejection pressures, such as a method of directly pressurizing a cell filled with ink or a method of expanding the ink or bubbles on the ejection hole side and supporting the reaction force with the internal pressure of the cell. However, in any case, if it is desired to effectively use the pressure increase generated in the cell when the ink is ejected only for ejecting the ink, it is necessary to make it difficult for the pressure to escape to the ink supply channel. . In other words, for example, the flow passage cross-sectional area of the ink supply flow passage is reduced or the flow passage length is increased so that the ink does not easily flow in the ink supply flow passage.
That is, it is necessary to reduce the hydrodynamic conductance.

In the ink supply channel having the small conductance, ink is supplied into the cells by a so-called capillary phenomenon, so that the time required to supply the ink into the cells (so-called refill time) is reduced. There was a problem of becoming long.

As a result, the ink is not smoothly filled in the cells, and it is impossible to speed up the ejection of the ink (increase the ejection pulse or the driving frequency of the ejection) particularly in continuous intermittent printing, which is effective. There was a problem that it was not possible to configure a simple printer.

When the refill time cannot catch up with the high-speed pulse ejection, the ink amount in the cell decreases, and when the ink amount in the cell becomes insufficient, the ink ejection amount for each pulse also decreases due to the decrease in the cell internal pressure. However, if bubbles are generated in the cells, the amount of ejected ink becomes non-uniform, so that it is still difficult to secure the density of the printed image. In addition, the shape of the ejected ink is not small and well-shaped, and as a result, the problem that the printed image is blurred or unclear cannot be solved.

In order to shorten the refill time, it is conceivable to lower the viscosity of the ink or increase the conductance, but if the viscosity of the ink is lowered, the bleeding of the printed image on the printing medium may increase, There is also a problem that control of ink droplets becomes difficult.

Further, if the conductance is increased, as described above, the backflow phenomenon of the ink occurs due to the rise of the cell internal pressure at the time of ejecting the ink, and the backflow phenomenon cannot be maintained effectively. This hinders the supply of ink into the cells, and again, similar to the above, there is a problem due to insufficient ink filling of the cells.

The present invention has been made in view of the above problems, and its main object is to obtain an ink jet printer head having excellent ink ejection characteristics.

Another object of the present invention is to obtain an ink jet printer head capable of enhancing the jetting force of ink and making a printed image on a printing medium a high quality printed image.

Still another object of the present invention is to obtain an ink jet printer head capable of maintaining a high ejection pulse by shortening a time required for supplying ink into cells, a so-called refill time.

Still another object of the present invention is to provide an ink jet printer head which can easily adjust the hydrodynamic conductance in the ink supply flow path.

Still another object of the present invention is to provide an ink jet printer head which can increase the ratio of the pressure applied to the ejection hole side more than the ratio of the pressure applied to the ink supply channel side and is inexpensive in manufacturing cost. Is to get.

[0020]

In order to achieve the above object, an ink jet printer head according to a first aspect of the present invention communicates ink filled in a cell through an ink supply channel with the cell. An ink jet printer head for printing by ejecting from fine ejection holes is provided with variable means for selectively changing the magnitude of hydrodynamic conductance in the ink supply channel.

According to a second aspect of the present invention, there is provided an ink jet printer head according to the first aspect, wherein the varying means has a magnitude of the hydrodynamic conductance when ejecting ink from the ejection holes. The size is smaller than the magnitude of the hydrodynamic conductance when the ink is supplied into the cells.

According to a third aspect of the present invention, there is provided the ink jet printer head according to the first aspect, wherein the variable means has a large magnitude of the hydrodynamic conductance when the variable means ejects ink from the ejection holes. The size of the hydrodynamic conductance during non-operation is set smaller than the size of the hydrodynamic conductance during non-operation, and the hydrodynamic conductance is set larger than the size of the hydrodynamic conductance during non-operation when ink is supplied into the cell. It is a feature.

An ink jet printer head according to a fourth aspect of the present invention is the ink jet printer head according to any one of the first, second and third aspects, wherein the variable means is a flow path of the ink supply flow path. It is characterized in that it includes movable means for changing the cross-sectional area.

According to a fifth aspect of the present invention, there is provided an ink jet printer head according to the fourth aspect, wherein the movable means is a mechanical displacement means capable of moving forward and backward with respect to the inside of the ink supply passage. And an electromechanical conversion means for driving the mechanical displacement means on the basis of an electric signal.

In order to achieve the above-mentioned object, an ink jet printer head according to a sixth aspect of the present invention ejects ink filled in a cell through an ink supply channel from a fine ejection hole communicating with the cell. In an inkjet printer head for performing printing by causing the ink to be ejected from the ejection holes in the cells, a first diaphragm selectively bulged in the cells and a first diaphragm for driving the first diaphragm are driven. 1 piezoelectric element, a second diaphragm that selectively bulges into the ink supply channel, and a second piezoelectric element that drives the second diaphragm, and at least the ink is ejected from the ejection hole. It is characterized in that the second piezoelectric element is actuated when ejecting.

[0026]

In general, the ink jet printer head according to the present invention is mainly composed of cells, ejection holes, ink supply passages, and variable means. The cells are filled with ink supplied through an ink supply channel. Further, the ejection hole is formed in a fine diameter,
The ink is discharged to fill the inside of the cell while communicating with the cell. Further, the variable means selectively changes the magnitude of the hydrodynamic conductance in the ink supply flow path into the cell.

That is, in the present invention, the magnitude of the hydrodynamic conductance of the ink supply channel is not fixed but is appropriately changed by the movable means. This change in conductance is performed, for example, in synchronism with the ink ejection operation of the head, and at least when the internal pressure of the cell rises due to the ink ejection, if the conductance of the ink supply channel is reduced, it escapes from here. Since the pressure is reduced, the ejection pressure is prevented from decreasing, and the ink filled in the cells is ejected from the ejection holes at a predetermined ejection pressure. As a result, the shape of the ejected ink becomes small and uniform.

According to a second aspect of the present invention, there is provided an ink jet printer head according to the first aspect, wherein when the varying means ejects ink from the ejection holes, the magnitude of the hydrodynamic conductance is set. Is smaller than the magnitude of the hydrodynamic conductance when ink is supplied into the cell.

If the conductance of the ink supply channel is smaller than that when ink is supplied into the cell, the pressure generated in the cell due to the ink ejection operation is less likely to escape from the ink supply channel when the ink is ejected. Since the decrease of the cell internal pressure is prevented, it is possible to effectively use the pressure for ejecting the ink. Therefore, the ejection pressure of the ink is maintained at a predetermined value, and the print image on the print medium can be a high-quality print image.

On the other hand, when the ink is supplied to the cells, the conductance of the ink supply channel is made larger than that at the time of swelling, so that the ink is supplied sufficiently smoothly.
A sufficient amount of ink is filled in the cell in a short time. As a result, it is possible to prevent the printing characteristics from being deteriorated due to the ink shortage in the cells due to the ink ejection operation.

In the ink jet printer head according to a third aspect of the present invention, in the ink jet printer head according to the first aspect, the varying means sets the magnitude of the hydrodynamic conductance when ejecting ink from the ejection holes. Is made smaller than the magnitude of the hydrodynamic conductance during non-operation, and conversely, when the ink is supplied into the cells, the hydrodynamic conductance is made larger than the magnitude of the hydrodynamic conductance during non-operation.

That is, the magnitude of the conductance of the ink supply channel can be adjusted to at least three types by the variable means. If the first conductance is defined as the steady state when the non-operating state is set, the second conductance is set to have a smaller magnitude (the degree of ease of ink flow) than the first conductance when the ink is ejected. Further, when ink is supplied, its size is larger than the first conductance (the degree of ease of ink flow).
Is set as a large third conductance.

When the ink is ejected, the variable means brings the ink supply flow path into the second conductance (smallest size) state. Therefore, the internal pressure of the cell, which should be increased with the ink ejection, is discharged from the ink supply flow path. The ink ejection pressure is maintained at a predetermined value without escaping. In this way, since the ejection pressure is always maintained at a predetermined value and the ink ejection operation is performed,
The shape of the ejected ink is small and regular.

Further, when the ink is supplied to the cells, the ink supply flow path is in the third conductance (largest size) state, so that a sufficient amount of ink is supplied to the cells in a short time. . In particular, when ink is continuously supplied immediately after ejection, or when this is repeated at high speed, the ink supply flow path can be greatly changed from the second conductance state to the third conductance state. Holding the pressure in the cell at
It is possible to synergistically achieve both effects of improving the conductance of the supply channel when supplying ink.

This third conductance state can be increased independently of the conductance of the ink supply flow path in the first conductance state, and as a result, the flow of ink into the cell during supply can be made sufficiently smooth in a short time. Can be done.

As described above, according to the present invention, the ink ejection pressure can be kept stable, the ink can be supplied to the cells sufficiently smoothly, and the so-called refill time can be shortened. For this reason, intermittent ejection at a high pulse rate can be performed extremely stably.

An ink jet printer head according to a fourth aspect of the present invention is the ink jet printer head according to any one of the first, second and third aspects.
The variable unit has a configuration including a movable unit that changes a flow passage cross-sectional area of the ink supply flow passage.

The movable means adjusts the conductance of the ink supply flow passage by changing the flow passage cross-sectional area. In this case, at least when the ink is ejected (increase in cell internal pressure), the flow passage cross-sectional area is made small to reduce the conductance so that the backflow phenomenon of ink to the ink supply flow passage is hard to occur. In other words, the mechanism is not particularly limited as long as it functions like a variable throttle valve provided in the ink supply flow path.

Here, the movable means continuously changes the flow passage cross-sectional area in a stepless manner if it changes the flow passage cross-sectional area of the ink supply flow passage, or changes the flow passage cross-sectional area different from each other. It is possible to use any mechanism such as a mechanically changing mechanism or a mechanism for switching between full open and full closed (conductance is set to 0) like an opening / closing means.

The one in which the cross-sectional area can be changed steplessly allows the conductance to be finely adjusted, and the one in which the cross-sectional area can be changed stepwise or the open / close type can relatively perform the operation corresponding to the jetting or the supplying. Speed can be increased with a simple structure.

As another modification of the movable means, in addition to changing the cross-sectional area of a single supply channel, a plurality of supply channels are provided to selectively change the number of channels communicating with the cell. It is also possible to change the cross-sectional area of the supply channel as a whole by switching.

In this case, the individual flow passage cross-sectional areas may be the same, or different flow passage cross-sectional areas may be provided, and the selective change of the flow passage cross-sectional areas allows fine adjustment of the change in the total flow passage cross-sectional area (conductance). There is.

As a means for changing the conductance, it is possible to employ a flow path length changing means for changing the length of the ink supply flow path. For example, it is possible to adopt a configuration in which a plurality of ink supply channels having different lengths are provided and some of them are selectively combined with an on-off valve.

Also in this case, the conductance of the ink supply channel is selectively changed to prevent the drop of the ink ejection pressure, shorten the refill time at the time of ink supply, and cope with a high pulse rate. Become.

According to a fifth aspect of the invention, there is provided an ink jet printer head according to the fourth aspect, wherein the movable means comprises mechanical displacement means and electromechanical conversion means.

The mechanical displacement means operates so as to be able to move forward and backward with respect to the inside of the ink supply flow path. The electromechanical conversion means drives the forward / backward movement of the mechanical displacement means based on an electric signal.

That is, when an electric drive signal is applied to the electromechanical converting means, the electromechanical converting means produces a corresponding mechanical output, whereby the mechanical displacing means enters the ink supply flow path. It moves forward and backward.

When the mechanical displacement means enters into the ink supply channel, the cross-sectional area of the ink supply channel becomes small, so that the conductance of the ink supply channel becomes a relatively small value.
On the contrary, when the mechanical displacement means exits from the ink supply channel, the cross-sectional area of the ink supply channel becomes larger than that at the time of entering and the conductance becomes a relatively large value.

An ink jet printer head according to a sixth aspect of the present invention is a cell, an ink supply channel, an ink ejection hole, a first diaphragm, a first piezoelectric element, a second diaphragm, and a second diaphragm. It is mainly composed of two piezoelectric elements and control means for these piezoelectric elements.

The cell is filled with ink supplied through the ink supply channel. The ink supply channel supplies the ink from the ink storage means into the cell. The ink ejection hole communicates with the cell and ejects the ink in the cell.

Here, the first piezoelectric element and the first diaphragm instantaneously increase the pressure in the cell in order to eject the ink in the cell from the ejection hole.

Further, the second piezoelectric element and the second diaphragm cause the fluid conductance of the ink supply flow path when ink is ejected from the ejection holes more than when ink is supplied into the cells. Make it smaller.

That is, the first diaphragm is bulged toward the inside of the cell in principle when the first piezoelectric element is activated. As a result, the volume in the cell is reduced and the internal pressure is increased. Due to this increase in internal pressure, the ink filled in the cells is ejected from the ejection holes.

Further, in principle, the second diaphragm is bulged toward the inside of the ink supply channel when the second piezoelectric element is activated. As a result, the cross-sectional area of the ink supply channel becomes smaller, and the conductance becomes smaller.

Further, when the second piezoelectric element is operated by the control means at least when the ink is ejected (when the first piezoelectric element is operated), the conductance of the ink supply channel is increased when the internal pressure of the cell rises. Becomes smaller, and the ink (pressure) is prevented from flowing back and escaping from there, and as a result, the ink can be ejected at a stable ejection pressure.

In general, the operation amount of the first and second piezoelectric elements can be adjusted by the applied voltage value. Therefore, by controlling this voltage, the ink ejection pressure and the cross-sectional area of the ink supply channel are finely adjusted. You can also do it.

When the direction of the applied voltage is reversed, the amount of operation in the opposite direction can be obtained. Therefore, by switching the applied voltage between positive, zero, and negative, three operations can be performed during positive operation, non-operation, and negative operation. It is possible to control the movable amount in stages.

The adjustment of these operations and the adjustment during the operations may be performed by the control means.

[0059]

1 (A) and 1 (B) are schematic configuration diagrams of an ink jet printer head according to a first embodiment of the present invention. As shown in FIGS. 1A and 1B, the ink jet printer head according to this embodiment includes a cell 1, an ink supply channel 2, an ejection hole 3, a first piezoelectric element 4, and a second piezoelectric element 4.
The piezoelectric element 5, the first diaphragm 6, the second diaphragm 7, and the control drive circuit 9 are mainly configured. Note that FIG. 1A is a schematic configuration diagram of the inkjet printer head according to the first embodiment when not operating.
FIG. 6B is a schematic configuration diagram during operation of the inkjet printer head according to the first embodiment.

The cell 1 is composed of a metallic stainless plate 1a and is composed of a chamber surrounded by a resin spacer 1b and a first diaphragm 6. Then, the inside thereof is filled with the ink 8a (commercially available non-aqueous black ink) supplied from the ink storage 8 through the ink supply flow path 2. A jet hole 3 is provided on the front side of the cell 1 by etching. The spacer 1b is
It is formed by applying a photosensitive adhesive resin to the metallic stainless steel plate 1a and then patterning by exposure.

The first piezoelectric element 4 is a laminated type PZT.
A piezoelectric element plate 4a, a silver electrode 4b for fixing the piezoelectric plate,
4c and is connected to the control drive circuit 9 (control means).

The second piezoelectric element 5 (electro-mechanical conversion means) is also composed of a laminated type PZT piezoelectric element plate 5a and silver electrodes 5b and 5c for fixing the piezoelectric plate, and the control drive circuit 9 is provided. It is connected.

The first diaphragm 6 and the second diaphragm 7 are formed of an aluminum thin plate, and are bonded to the holes formed by patterning and etching the metallic stainless plate 1a with an adhesive resin, and the first piezoelectric element 4 is formed. Is connected to the second piezoelectric element 6.

The control drive circuit 9 (control means) includes the first
Voltage is applied to the piezoelectric element 4 and the second piezoelectric element 5 of
The first piezoelectric element 4 and the second piezoelectric element 5 are mechanically strained (bent) in a specific direction, and the first piezoelectric element 4 and the second piezoelectric element 5 are synchronously driven.

A movable means is constituted by the second piezoelectric element 5 and the second diaphragm 7, and the first piezoelectric element 4, the first diaphragm 6 and the second piezoelectric element 5 and the second diaphragm 7 are arranged. The variable means is constituted by. Further, the first piezoelectric element 4 constitutes an electromechanical conversion means, and the first diaphragm 6 constitutes a mechanical displacement means.

As shown in FIGS. 2A and 2B, the dimensions of each part of the ink jet printer head according to this embodiment are as follows. Cell 1: Length 5 mm Width 3 mm Height 0.3 mm Ink supply channel 2: Length 2 mm Width 3 mm Height 0.12 mm First piezoelectric element 4: Length 1.5 mm Width 1.8 mm Height 1
mm Second piezoelectric element 5: length 0.7 mm width 1.8 mm height 1
mm First diaphragm 6: length 1.8 mm, width 2 mm Second diaphragm 7: length 1 mm, width 2 mm

In the ink jet printer head according to the present embodiment configured as described above, as shown in FIG. 1 (B), the control drive circuit 9 is connected to the first piezoelectric element 4 and the second piezoelectric element 5. When a voltage (rectangular AC wave of about 50V) is applied to the electrodes 4b, 4c and 5b, 5c, this first
Of the piezoelectric element 4 and the second piezoelectric element 5 of
A mechanical strain (deflection) occurs in the inward direction and in the spacer 1b direction.

The first piezoelectric element 4 and the second piezoelectric element 5 are the first diaphragm 6 and the second diaphragm 7 connected to the first piezoelectric element 4 and the second piezoelectric element 5, respectively.
To force the cells to bulge toward the inside of the cell 1 or toward the spacer 1b.

That is, the bulging of the first diaphragm 6 reduces the volume in the cell 1 to increase the internal pressure of the cell. Further, the second diaphragm 7 reduces the flow passage cross-sectional area of the ink supply flow passage 2 due to the swelling thereof.

Ink 8a filled in the cell 1
Is pressurized by the swelling operation of the first diaphragm 6, the pressure is transmitted to the ejection hole 3 side and the ink supply passage 2 side. At this time, the flow passage cross-sectional area of the ink supply passage 2 is Is reduced by the bulging of the second diaphragm 7, so that the internal pressure is prevented from escaping from there.
Most of the increased pressure of the ink 8a in the cell 1 is consumed for ejecting the ink from the ejection hole 3, and the ink is ejected from the ejection hole 3 at a stable pressure.

That is, the ink in the cells whose internal pressure has risen due to the swelling operation of the first diaphragm 6 flows out more toward the ejection holes 3 than at the ink supply flow path 2 side. As a result, the pressure drop of the ink 8a in the cell 1 at the time of ink ejection is suppressed, the backflow phenomenon of ink is prevented, and the ejection pressure becomes sufficiently stable and ejected from the ejection hole 3 as compared with the conventional device. The shape of the ink 8a is always small and regular, and it is possible to provide a stable print on the print medium, and it is possible to improve the quality of the print image.

As a concrete example according to the present invention,
While increasing the drive frequency of the control drive circuit 9, the second piezoelectric element 5 is driven and the second piezoelectric element 5 is not driven.
When the ejection of the ink 8a is observed with a stroboscopic photograph or the like, when the second piezoelectric element 5 is not driven, uniform and stable ink droplet formation was observed only up to about 7 kHz. It was confirmed that when the second piezoelectric element 5 was driven, uniform and stable ink droplets were formed up to about 12 kHz.

When ink droplets ejected at a frequency of 4 kHz were measured, when the second piezoelectric element 5 was driven, the droplets had a diameter of about 55 μm, whereas the second piezoelectric element 5 had a diameter of about 55 μm. If the element 5 is not driven, the diameter is about 80 μm
When the second piezoelectric element 5 is driven, the movement speed of the ejected droplets is about 7 m / s.
In contrast, when the second piezoelectric element 5 was not driven, it was only about 5 m / s.

When the ejection of the ink 8a ends, the application of the voltage applied from the control drive circuit 9 to the first piezoelectric element 4 and the second piezoelectric element 5 is stopped, and the first piezoelectric element 4 is stopped. The mechanical strain generated in the element 4 and the second piezoelectric element 5 is restored, and along with this, the first diaphragm 6 and the second diaphragm 7 are also returned to the original flat plate state.

As a result, the conductance of the ink supply flow path 2 returns from the small value to the original value, and at the same time, the ink is sucked into the cell, and the ink is supplied into the cell 1 through the ink supply flow path 2. The ink 8a is re-supplied from the ink reservoir 8. The re-supply amount of ink at this time is an amount corresponding to the ink 8a ejected from the ejection hole 3.

After the ejection of the ink 8a is finished, the voltage applied from the control drive circuit 9 to the first piezoelectric element 4 and the second piezoelectric element 5 for the pressurizing operation in the cell 1 is performed. You may apply a voltage of the opposite polarity to, in this case,
The first piezoelectric element 4 and the second piezoelectric element 5 are replaced with ink 8
It can be distorted in the direction opposite to that when jetting a. This is the so-called piezoelectric inverse effect.

In this case, the first diaphragm 6 and the second diaphragm 7 are opposite to those when the ink 8a is ejected due to the reverse strain of the first piezoelectric element 4 and the second piezoelectric element 5. To increase the cross-sectional area of the ink supply flow path 2 and strengthen the suction of ink into the cell 1.

Here, since the second diaphragm 7 is largely recessed, the ink supply flow path 2 from the ink reservoir 8 is discharged.
The ink 8a re-supplied into the cell via the ink flows quickly, and the time required for refilling the ink is shortened.
Of course, the backward operation of the piezoelectric element may be performed only by the second piezoelectric element 5.

In the first embodiment described above,
Although it has been described that the control driving circuit 9 synchronously drives the first piezoelectric element 4 and the second piezoelectric element 5, the present invention is not limited to this. For example, the second piezoelectric element 5 may be moved in the direction of the spacer 1b. While being distorted, the first piezoelectric element 4 is driven a plurality of times to eject the ink 8a, and when the amount of the ink 8a in the cell 1 becomes small,
The control drive circuit 9 may be applied with a voltage having a polarity opposite to that at the time of ink ejection to control the supply of the ink 8a. Of course, the first piezoelectric element 4 and the second piezoelectric element 5
It is needless to say that the operation may be set to a steady state (when not operating), a pressurizing operation, and an ink supply operation (piezoelectric inverse effect), and the series of operations may be continuously driven and controlled.

Further, in the first embodiment, the first
The ink 8a in the cell 1 was ejected using the bending force of the piezoelectric element 4 and the second piezoelectric element 5 of FIG. As shown in, by directly utilizing the expansion of the piezoelectric bodies 20 and 21 fixed by the fixing plate 11, the ejection force of the ink 8a can be further strengthened. It should be noted that FIG. 3A is a schematic configuration diagram when the inkjet printer head is not operating in this case, and FIG. 3B is a schematic configuration diagram when the inkjet printer head is operating.

Further, in the first embodiment, the variable means is constituted by the second piezoelectric element 5 and the second diaphragm 7 to change the cross-sectional area of the ink supply channel and to prevent the backflow phenomenon of ink. Although it is difficult to cause it, the present invention is not limited to this, and the conductance is set to 0 by completely closing the ink supply flow path 2 such as a valve or a shutter opening / closing device. There is no particular limitation on the configuration such as a thing.

FIG. 4 is a vertical sectional view showing a schematic structure of an ink jet printer head according to the second embodiment of the present invention. The biggest difference from the first embodiment shown in FIG. 1 is that the first spacer 14a and the second spacer 14 are provided in the cell.
b, two cells of a first cell 12a and a second cell 12b are formed, and two inks of a first ink supply channel 13a and a second ink supply channel 13b having different lengths are provided. The point is that the supply flow path is formed. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 4, in the ink jet printer head according to the second embodiment, a first spacer 14a having a thin blade taper at one end and protruding is provided at substantially the center of the head. The second spacer 14b is provided on the rear surface side.

The first piezoelectric element 4 and the first diaphragm 6 are provided on the lower surface side of the head, and the second piezoelectric element 5 and the second diaphragm 7 are provided on the upper surface side of the head. A jet hole 3 is formed on the front side of the head.

The portion surrounded by the first spacer 14a, the first diaphragm 6 and the ejection hole 3 is the first portion.
Cell 12a of the first spacer 14a and the second spacer 14a
The second cell 12b, which directly communicates with the ink storage case 8, is located between the second cell 12b and the spacer 14b.

Due to the gap between the first spacer 14a and the second diaphragm 7, the first cell 12a is formed.
And a second cell 12b are connected to each other to form a first ink supply channel 13a, and the first spacer 14 is formed.
Below the tip of the thin blade tapered protrusion of a, the flow path length is almost zero.
The second ink supply channel 13b is formed.

In the ink jet printer head according to the second embodiment constructed as described above, the first
Since the spacer 14a is provided, the head itself becomes large, but it is possible to form two ink supply channels, that is, the first ink supply channel 13a and the second ink supply channel 13b. Can improve the response of the refill.

Of the two ink supply flow paths, the flow path cross-sectional area of the second ink supply flow path 13a, which has a relatively long flow path length, is set to the second piezoelectric element 5 and the second diaphragm 7 of the second ink supply flow path 13a. The first spacer 14 of the first piezoelectric element 4 and the first diaphragm 6 is selectively reduced by bulging in the direction of the first spacer 14a (direction of arrow B).
It is possible to prevent the backflow phenomenon of the ink due to the pressurizing operation due to the swelling in the a direction (direction of the arrow A) and to prevent the drop of the ejection pressure, and the ink 8a filled in the cells 12a. Can be jetted at a stable pressure. The second ink supply channel 13b has a channel length of almost 0, and the second cell 12 is provided on the upstream side thereof.
Since b exists, the backflow phenomenon of the ink from the second ink supply flow path 13b hardly occurs when the ink is ejected.

If the applied voltage to each piezoelectric element is set to zero potential or the opposite polarity, the conductance of the first ink supply flow path 13a becomes large, so that the ink refilling is performed with good responsiveness, and further, the second Since the flow path length of the ink supply flow path 13b is formed to be substantially 0, the supplementary ink refill into the cell 12a can be stably performed without being affected by the change in the viscosity of the ink due to the temperature.

In the ink jet printer head according to the second embodiment, the functions described in the first embodiment, such as the control method of the control drive circuit 9 and the method of directly extending the piezoelectric element itself to the diaphragm, etc. , All features are applicable as well.

FIG. 5 is a vertical sectional view showing a schematic structure of an ink jet printer head according to the third embodiment of the present invention. The difference between this third embodiment and the first and second embodiments is that the piezoelectric element connected to the first diaphragm 6 and the second diaphragm 7 is a single piezoelectric element 15 in common. is there.

That is, although the same number of piezoelectric elements 4 and 5 and diaphragms 6 and 7 are provided in the first and second embodiments, in the ink jet printer head according to the third embodiment, As shown in FIG. 5, a point that one diaphragm 15 drives two diaphragms 6 and 7 is different from the first and second embodiments.

Thus, the first diaphragm 6 and the second diaphragm 6
By driving each of the diaphragms 7 by one piezoelectric element 15, it is not necessary to provide each piezoelectric element corresponding to the diaphragm, the structure of the head and the drive control system is simplified, and the manufacturing cost is low. Can be something. In FIG. 5, the same parts as those of the first and second embodiments are designated by the same reference numerals and the description thereof will be omitted. The cell structure of the ink jet printer head according to the third embodiment is almost the same as that of the first embodiment described with reference to FIG.

FIG. 6 is a vertical sectional view showing a schematic structure of an ink jet printer head according to the fourth embodiment of the present invention. The difference between the fourth embodiment and each of the above embodiments is that
This is the point that the function performed by the two diaphragms, the first diaphragm and the second diaphragm, can be performed by the single diaphragm 16.

That is, in each of the above embodiments, the first diaphragm pressurizes the inside of the cell, and the second diaphragm reduces the flow passage cross-sectional area of the ink supply flow passage to prevent ink backflow phenomenon. However, the ejection pressure was stabilized and the ejection force of the ink was maintained. However, in the ink jet printer head according to the fourth embodiment, as shown in FIG. Along with the pressurization, the flow passage cross-sectional area of the ink supply flow passage 2 is changed to prevent the ink backflow phenomenon, stabilize the ejection pressure, and maintain the ejection force of the ink. Of course, when the ink is refilled, the piezoelectric element 16 returns or deforms in the opposite direction, so that the conductance of the ink supply flow path 2 increases, as in the above-described embodiments.

As described above, by using one diaphragm, the head and the drive control system can be simplified and the manufacturing cost can be reduced. still,
In FIG. 6, the same parts as those in each of the above-described embodiments are designated by the same reference numerals and the description thereof will be omitted. The structure of the ink jet printer head according to the fourth embodiment is almost the same as that of the first embodiment described in FIG.

FIGS. 7A and 7B are vertical sectional views showing a schematic structure of an ink jet printer head according to a fifth embodiment of the present invention. This fifth embodiment and the above first to first
7A and 7B, each piezoelectric element 15 having a relatively long length is applied with a voltage applied to each of the adjacent piezoelectric elements 15 by voltages having polarities different from each other. The electrodes 16a, 16b, 16c for
The point is that strains in opposite directions are generated between the adjacent electrodes. The piezoelectric element 15 has a polarization shown in FIG.
It is formed so as to be in the direction of arrow P shown in FIG.

That is, the voltage from the control drive circuit 9 is applied to the electrodes 16a, 16b, 1 with the polarity as shown in FIG. 7B.
When applied to 6c, the piezoelectric element 15 causes a mechanical strain toward the inside of the cell at each of the electrodes 16a and 16c, and a mechanical strain away from the inside of the cell at the electrode 16b.

In this way, when the piezoelectric element 15 is deformed in the opposite directions between the adjacent electrodes, it is necessary to keep the electrode 16b at a zero potential and apply a voltage having a polarity different from that of the other electrodes 16a and 16c. However, by applying a reverse polarity voltage to the electrode 16b, a larger strain can be generated in the piezoelectric element 15, and the ejection pressure of ink can be increased.

On the other hand, if the polarities of the voltages shown in FIG. 7B are reversed and a voltage of this reverse polarity is applied to the piezoelectric element 15, the voltage element 15 is distorted in the direction opposite to that at the time of ink ejection.
In this case as well, the voltage applied to all electrodes may be set to zero potential, but by applying a reverse polarity voltage, the conductance of the ink supply flow path 2 can be further increased, and the refill time can be shortened. be able to. 7A is a schematic configuration diagram of the inkjet printer head according to the fifth embodiment when it is not operating, and FIG. 7B is a schematic configuration of the inkjet printer head according to the fifth embodiment when it is operating. It is a block diagram. The same parts as those in the first to fourth embodiments are designated by the same reference numerals and the description thereof will be omitted.

[0101]

As described above, according to the present invention, since the variable means for selectively changing the magnitude of the hydrodynamic conductance in the ink supply passage in the cell is provided, the ink ejection characteristic is made excellent. The effect is that you can.

The present invention also has the effect that the jetting force of ink can be stabilized and the printed image on the printing medium can be maintained at a high quality printed image.

The present invention also has the effect that the time required to supply ink into the cells, the so-called refill time, can be shortened to eject ink at a high pulse rate.

Further, the present invention has an effect that the hydrodynamic conductance in the ink supply channel can be changed with a simple structure.

Further, according to the present invention, it is possible to prevent the ink from flowing back to the ink supply channel side when the ink is ejected and to escape, and to effectively use the pressure generated in the cell when the ink is ejected for the ejection. There is also.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of an inkjet printer head according to an embodiment of the present invention, and FIG. 1A is a schematic configuration diagram of the inkjet printer head according to the first embodiment when not operating. , (B) are schematic configuration diagrams during operation of the inkjet printer head according to the first embodiment.

FIG. 2 is an explanatory diagram showing the dimensions of each part of the inkjet printer head according to the first embodiment shown in the previous figure (FIG. 1), FIG. 2A is a longitudinal sectional view of the inkjet printer head, and FIG. FIG. 4 is a bottom view of the inkjet printer head.

FIG. 3 is a vertical sectional view showing a schematic configuration of an inkjet printer head according to a modified example of the first embodiment of the present invention shown in the previous figure (FIG. 1), and FIG. 3A is an inkjet printer according to this modified example. FIG. 9 is a schematic configuration diagram of the head when the head is not operating, and FIG. 9B is a schematic configuration diagram of the inkjet printer head according to the modification when the head is operating.

FIG. 4 is a vertical sectional view showing a schematic configuration of an inkjet printer head according to a second embodiment of the present invention.

FIG. 5 is a vertical sectional view showing a schematic configuration of an inkjet printer head according to a third embodiment of the present invention.

FIG. 6 is a vertical sectional view showing a schematic configuration of an inkjet printer head according to a fourth embodiment of the present invention.

FIG. 7 is a vertical sectional view showing a schematic configuration of an inkjet printer head according to a fifth embodiment of the present invention. (A)
FIG. 7B is a schematic configuration diagram of the inkjet printer head according to the fifth embodiment when the inkjet printer head is not operating, and FIG. 9B is a schematic configuration diagram of the inkjet printer head according to the fifth embodiment when the inkjet printer head is operating.

[Explanation of symbols]

 1: Cell 1a: Metallic stainless steel plate 1b: Spacer 2: Ink supply flow path 3: Jet hole 4: First piezoelectric element 5: Second piezoelectric element 6: First diaphragm 7: Second diaphragm 8: Ink storage 8a: Ink 9: Control drive circuit

Claims (6)

[Claims] 1. An ink jet printer head for printing by ejecting ink filled in a cell through an ink supply channel from a minute ejection hole communicating with the cell, wherein a hydrodynamic conductance in the ink supply channel is provided. An ink jet printer head, comprising variable means for selectively changing the size of the ink jet printer. 2. The variable means, when ejecting ink from the ejection holes, makes the magnitude of the hydrodynamic conductance smaller than the magnitude of the hydrodynamic conductance when ink is supplied into the cells. The inkjet printer head according to claim 1, wherein: 3. The variable means, when ejecting ink from the ejection holes, makes the magnitude of the hydrodynamic conductance smaller than the magnitude of the hydrodynamic conductance when the ink is not in operation, 2. The ink jet printer head according to claim 1, wherein the fluid conductance when supplying ink is made larger than the magnitude of the fluid conductance when not operating. 4. The ink jet printer according to claim 1, wherein the variable unit includes a movable unit that changes a flow passage cross-sectional area of the ink supply flow passage. head. 5. The movable means comprises a mechanical displacement means capable of advancing and retreating with respect to the inside of the ink supply flow path, and an electromechanical conversion means for driving the mechanical displacement means based on an electric signal. The inkjet printer head according to claim 4, wherein 6. An ink jet printer head for printing by ejecting ink filled in a cell through an ink supply channel from a minute ejection hole communicating with the cell, wherein ink in the cell is ejected from the ejection hole. A first diaphragm that selectively swells into the cell for ejecting; a first piezoelectric element that drives the first diaphragm; and a first diaphragm that selectively swells into the ink supply channel. A second diaphragm, and a second piezoelectric element that drives the second diaphragm,
And at least when ejecting ink from the ejection holes,
An ink jet printer head, characterized in that the second piezoelectric element is actuated.