JPH03147852A - Multi-throw type liquid discharge device - Google Patents

Abstract

PURPOSE:To obtain a multi-throw type liquid discharge device which ensure its activation regardless of a change in atmospheric temperature, can be assembled easily and allow its miniaturization and light-weight realization by arranging each internal electrode in such a manner that these electrode surround the internal wall of each through hole and a ceramic part around each through hole and providing external electrodes consisting of common electrodes formed so that these electrodes cover external lateral faces connecting the both ends of the ceramic element. CONSTITUTION:Internal electrodes 35, 36 and external electrodes 38a to 38d, 39a to 39d are arranged in such a manner that these electrodes are opposed to each other through ceramic parts 37a, 37b consisting of piezoelectric ceramics. Thus a constitution in which paired piezoelectric elements are arranged on the top of each through hole for liquid discharge 33a to 33d. Consequently, the internal electrodes 35, 36 are connected to the negative potential of one of the internal electrodes 35, 36 commonly. In the meantime, the volume of the specified through holes for liquid discharge 33a to 33d is caused to change by connecting the external electrodes 38a to 38d, 39a to 39d to the negative potential of the other internal electrode. Thus the liquid can be discharged from the specified through holes for discharge 33a to 33d. Consequently, the through holes 33a to 33d are arranged side by side in a single ceramic element 32 and also piezoelectric elements are constituted in one piece.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multiple liquid ejecting device such as that used in an inkjet printer head, and in particular, to a liquid ejecting device that uses the piezoelectric effect of a piezoelectric element to eject liquid. Relates to something configured to dispense.

[Conventional technology]

2. Description of the Related Art Conventionally, a structure using a piezoelectric element has been known as an inkjet ejection structure at the end of an inkjet printer. - An example is explained with reference to FIG.

In the structure shown in FIG. 2, a plurality of grooves 1a to IC are formed in a base 1 made of a rigid material such as glass or ceramics. A diaphragm 2 made of metal is attached to the upper surface of the base 1 so as to open the bottoms of the grooves 1a-1c. On the upper surface of the diaphragm 2, piezoelectric elements 33 to 3C are attached to portions corresponding to the grooves 1a to IC, respectively.

The piezoelectric elements 3a to 3C have a structure in which electrodes are formed on a piezoelectric plate, and are driven by applying a voltage to the electrodes.
The diaphragm portions above the grooves 1a to 1c are bent and deformed, thereby changing the volume of the grooves 13 to 1c and ejecting inkjet.

Another example of a conventional inkjet ejecting device is one in which electrodes are formed on the inner and outer circumferential surfaces of a cylindrical piezoelectric ceramic, and by applying a voltage to the electrodes, the inner diameter of the element is deformed and ink is ejected. A device using a piezoelectric element is known. In this case, a head was constructed by incorporating several dozen of the above piezoelectric elements for one printer.

[Technical problem to be solved by the invention] In the first conventional example explained with reference to FIG. 2, metal plates having different coefficients of thermal expansion are attached to a base 1 made of glass, ceramics, etc. Therefore, there is a risk of peeling when the ambient temperature changes, which poses a problem in terms of reliability.

In addition, when pasting the piezoelectric elements 3a to 3C to the diaphragm 2, it is necessary to paste each piece accurately at the correct position above the valley grooves 1a to IC, and this pasting requires a lot of work. It required

Furthermore, it is necessary to electrically connect each of the piezoelectric elements 3a to 3c one by one, which requires complicated work when electrically connecting.

On the other hand, in conventional examples that incorporate many cylindrical piezoelectric elements,
Since each piezoelectric element is composed of an independent element, assembly requires complicated work and costs are considerably high. Not only that, but because the head was made up of a combination of independent elements, the head had to be quite large.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a multiple liquid ejection device that operates reliably regardless of changes in ambient temperature, is easy to assemble, and has a structure that can be made smaller and lighter. It's about providing something.

[Means for solving technical problems]

The present invention is a multiple liquid ejection device that utilizes the piezoelectric effect of the piezoelectric elements, in which a piezoelectric element is provided corresponding to each of a plurality of liquid ejection through holes, and has the following configuration. It is characterized by

That is, there is a ceramic body in which a plurality of through holes for liquid discharge that are open on both end faces are arranged in parallel; The ceramic body includes an internal electrode formed to surround the ceramic body, and an external electrode formed on the outer surface connecting both end surfaces of the ceramic body to face the internal electrode.

The ceramic part of the ceramic body sandwiched between the internal electrode and the external electrode is made of piezoelectric ceramic, and one of the internal electrode and external electrode is formed independently for each liquid discharge through hole. The other electrode is formed as a common electrode, so that a corresponding piezoelectric element is provided for each liquid ejection through hole.

In a structure in which internal electrodes are formed independently for each through-hole for liquid discharge, each internal electrode is arranged so as to surround the inner wall of each through-hole or the ceramic portion around each through-hole,
The external electrode is constituted by a common electrode formed to cover the outer surface connecting both end surfaces of the ceramic body.

On the other hand, in the case of a structure in which the internal electrode is a common electrode, this common electrode includes a plurality of drive electrode parts formed to surround a part of the ceramic part around each through hole, and a plurality of drive electrode parts formed to surround a part of the ceramic part around each through hole. and a connection electrode portion arranged to connect the drive electrode portions to each other. On the other hand, the external electrodes are formed independently for each of the liquid ejection through holes so as to face each of the drive electrode sections via the ceramic part made of piezoelectric ceramics.

[Function] Since a plurality of piezoelectric elements are configured using a single ceramic body corresponding to each liquid discharge through hole, manufacturing is easy and each liquid discharge through hole can be formed with high density. can be provided.

In addition, since it is constructed by forming electrodes and liquid discharge through holes in a single ceramic body, in other words, it is not made by bonding different materials with different coefficients of thermal expansion, so even if the ambient temperature changes, Less likely to cause scuffs, etc.

Furthermore, each piezoelectric element is configured to be electrically connected to each other at an internal electrode within the ceramic body or at an external electrode formed on the outer surface of the ceramic body, so that each piezoelectric element is driven. The electrical connections required for this are also easy to make.

Note that in a structure in which internal electrodes are independent for each through-hole for liquid discharge, especially in a structure in which each internal electrode is formed so as to surround the ceramic part around the through-hole for liquid discharge, Since the first ceramic part around the through hole is independent between adjacent liquid discharge through holes,
Crosstalk can be effectively suppressed.

Furthermore, in the structure in which the internal electrodes are common, the external electrodes are independently formed for each piezoelectric element on the external electrode side, so that electrical connection during driving is made easier.

[Explanation of Examples]

An embodiment applied to a structure used in an inkjet printer head will be described below.

FIG. 1 is a perspective view of a multiple liquid ejection device according to a first embodiment of the present invention. In this multiple liquid ejection device 11, a plurality of liquid ejection through holes 13a to 13d are arranged in parallel at a predetermined distance from each other so as to extend on both end surfaces of the ceramic body 12. In FIG. 1, liquid discharge through hole 13a-13
Although only one end W12a where one end of d is open is shown, the liquid discharge through hole 13 is also shown on the other end surface side.
A-+3d is open.

A plurality of independent internal electrodes 15a-15d are formed so as to surround ceramic parts 14a-14d having a donut-shaped cross section around each liquid discharge through hole 13a-13d.

On the other hand, in the ceramic body 12, the internal electrodes 15a-
The outer ceramic portion 16 of 15d is made of piezoelectric ceramics. An external electrode 17 is formed over the entire outer surface of the ceramic body 12 except for both end surfaces. Therefore, since each of the internal electrodes 15a to 15d and the external electrode 17 are configured to face each other via the ceramic portion 16, each liquid ejection through hole 13a-
It can be seen that a piezoelectric element is constructed every 13d.

In the multiple liquid ejection device 11 of the first embodiment, a potential of one polarity is applied to the external electrode 17, and any internal electrode 15a
By applying a potential of the other polarity to ~15d, any piezoelectric element can be driven, thereby deforming the desired through-holes 13a-13d and ejecting an inkjet.

As is clear from the above structure, in this multiple liquid discharging device 11, not only the through holes 13a to 13d for liquid discharging are arranged in parallel in the single ceramic body 12, but also the through holes 13a-13d are arranged in parallel. A piezoelectric element corresponding to each of the liquid discharge through holes 13a to 13d is constructed using the actual ceramic body 12. Therefore, since independent piezoelectric elements are not assembled later, there is no need to perform complicated assembly work, and a plurality of piezoelectric elements and liquid discharge through holes can be formed at high density.

Furthermore, since only ceramics and electrode materials are used, there is no need to bond different materials together as in the conventional example shown in FIG. Therefore, even if the ambient temperature changes,
Peeling is less likely to occur.

Next, a method for manufacturing the multiple liquid ejection device shown in FIG. 1 will be explained. First, as shown in FIG. 3, a slurry 22 of ceramics such as alumina or lead zirconate titanate (PZT) is stored in a container 21. A fixed jig made of a conductive material is placed in the slurry 22. Carbon cores 24a to 24d, one end of which is fixed to the fixture 23, are immersed.

Incidentally, the carbon cores 24a to 24d are scattered by a firing process to be described later, and are used to form the liquid discharge through holes 13a to 13d of the first embodiment. Therefore, carbon cores are prepared according to the number of through holes for liquid discharge.

Next, a DC voltage is applied between the fixing jig 23 and the container 21 to charge the ceramic slurry 22, and move the ceramics toward each of the carbon cores 24a to 24d, which is one electrode. Deposit ceramic slurry around ~24d.

Next, the carbon cores 24a to 24d are pulled up from the slurry 22, and the attached ceramic slurry is dried.

By going through the above steps, as shown in FIG. 4, a circular ceramic layer 2 is formed around the carbon cores 24a to 24d.
5a to 25d can be formed.

Next, after drying the cylindrical ceramic layers 25a to 25d shown in FIG. 4, a metal layer serving as an internal electrode is formed on the outer surface thereof. The metal layer can be formed, for example, by immersing Ceramic N25a to 25d in a conductive paste made of Ag-Pd. Formation of this metal layer can also be performed by other methods such as applying a conductive paste.

Next, the plurality of carbon cores 24a to 24d on which the ceramic layers 25a to 25d and metal layers are formed are integrated with piezoelectric ceramics and fired at a temperature of 100 to 1200°C, as shown in FIG. A sintered ceramic body 12 is obtained.

In addition, each carbon core 24a to 24 is made of piezoelectric ceramic.
When integrating d, carbon cores 248 to 24d having ceramic layers 25a to 25d and metal layers formed on the outer surface are added to a slurry mainly composed of piezoelectric ceramics.
It can be obtained by immersing a piezoelectric ceramic, or by molding a piezoelectric ceramic using an appropriate mold so that each of the carbon cores 24a to 24d is disposed inside.

During such molding before firing, it is preferable to leave a part of the metal layer that will become the internal electrode exposed on both end surfaces of the ceramic body 12 shown in FIG. This is to facilitate electrical connection with the outside when driving.

Note that, as is clear from FIG. 5, the carbon cores 24a to 24d are not shown in the sintered ceramic body 12. This is because the carbon cores 24a to 2
This is because 4d burns out and scatters.

Next, a conductive paste mainly composed of Ag is applied to the outer surface of the ceramic body 12, and then baked at a temperature of 700 to 8 oo'C to form the external electrode 17 shown in FIG. 1. In this way, the liquid ejecting device 11 of the first embodiment can be obtained.

As is clear from the description of the manufacturing process described above, in the liquid ejection device 11 of this embodiment, a multiple liquid ejection device in which a plurality of liquid ejection through holes 13a-136 are arranged in parallel is obtained by a relatively simple process. be able to. Moreover, the complicated work of accurately positioning and fixing the piezoelectric element on the groove, as in the conventional example, can be omitted. Therefore, it is possible to obtain a multiple liquid ejection device that is excellent in mass productivity.

FIG. 6 is a sectional view showing a liquid ejecting device according to a second embodiment of the present invention. In the liquid ejection device 31 of the second embodiment,
A plurality of liquid discharge through holes 33a to 33d are formed in the ceramic body 32 at a predetermined distance apart. Ceramic portions 34a to 34d are arranged around each of the liquid discharge through holes 33a to 33d.

On the other hand, a pair of internal electrodes 35, 36 configured as common electrodes are formed within the ceramic body 32. Each internal electrode 35.36 is connected to each through hole 33a to 33d.
Driving electrode portions 35a to 35d, 36a to 35a are formed so as to cover part of the ceramic parts 34a to 34d around the
36d, drive electrode parts 35a to 35d, 36a to 36
It has connection it electrode parts 5e to 35g and 36e to 36g that electrically connect d. That is, in the liquid ejection device 31 of this embodiment, each of the liquid ejection through holes 33a to 33d
According to the shape of the surrounding ceramic parts 34a~
Drive electrode portions 35a to 35d and 36a to 36d, each having a semicircular cross section, are formed so as to cover a portion of 34d. And each drive electrode part 35a-35d, 36a-
36d are mutually connected electrode parts 35e to 35g, 36e to 3
6g. ``Ceramic portions 37a and 37b made of piezoelectric ceramics are formed on the outside of the internal electrodes 35 and 36. The outer surface of each ceramic portion 37a and 37b is connected to the drive electrode portion 35a of the internal electrode 3536 as shown in the figure.
~35d, 36a ~ According to the cross-sectional shape of ~36d,
Each of the liquid discharge through holes 33a to 33d is raised so that its cross section has a semicircular shape. In this raised part, independent external electrodes 38a to 38d, 39a to 39d are provided for each liquid discharge through hole 33a to 33d.
is formed.

Therefore, in this embodiment, the internal electrodes 35, 36 and each of the external molds Fj 38a to 38d, 39a to 39d are ceramic portions 37a, 37b made of piezoelectric ceramics.
Since the piezoelectric elements are arranged so as to face each other via the liquid ejection through holes 33a to 33d, a structure is realized in which a pair of piezoelectric elements are arranged above each of the liquid discharge through holes 33a to 33d. Therefore, the internal electrode 35
．． 36 are commonly connected to the potential of one polarity, and the external electrode 3
By appropriately connecting 8a to 38d and 39a to 39d to the other polarity potential, a desired liquid discharge through hole 33a is formed.
33d can be varied to discharge liquid from desired liquid discharge through holes 33a to 33d.

In the second embodiment as well, a plurality of liquid discharge through holes 33a to 33d are arranged in parallel in a single ceramic body 32, and a plurality of piezoelectric elements are arranged in a single ceramic body 32. It is integrally constructed. Therefore, like the first embodiment shown in FIG. 1, it is possible to form a plurality of liquid ejection elements with high density, and unlike the conventional example shown in FIG. 2, different materials are not bonded together. Therefore, accidents such as peeling are unlikely to occur even if the ambient temperature fluctuates.

Next, a method for manufacturing the liquid ejection device 31 of the second embodiment will be described.

First, as shown in FIG. 7, a conductive paste 42 is applied onto a rectangular green sheet 41 made of a ceramic material such as alumina or lead zirconate titanate. Although the conductive paste 42 is applied to the entire surface in FIG. 7, it is not necessarily necessary to apply it to the entire surface because the conductive paste 42 is used to constitute the internal electrodes 35 and 36.

For example, the connection electrode parts 35e to 35g, 360 to
36g may be formed only in a part of the ceramic green sheet 41 between one long side 41a and the other long side 41b.

As the conductive paste 42, a material mainly composed of platinum, palladium, or an alloy thereof can be used as appropriate.

Next, as shown by the arrow in FIG. 7, a rectangular green sheet 43 mainly made of piezoelectric ceramics such as lead zirconate titanate is laminated on the main surface of the side on which the conductive paste 42 is formed. , a flat plate type laminate is obtained.

Next, as shown in FIG. 8, the laminate is press-molded using a mold 44. The mold 44 includes an upper mold 45 in which semi-cylindrical protrusions 45a to 45d are formed on the lower surface, and a lower mold 46 in which curved recesses 46a to 46d are formed in the upper surface.
It has guides 48 and 49. As shown in FIG. 8, by bringing the upper mold 45 and the lower mold 46 close together, the semi-cylindrical protrusion 4 is formed on the upper and lower surfaces of the laminate 50.
5a to 45d and curved concave portions 46a to 46d are provided.

Next, as shown in FIG. 9, the press-molded laminate 5
Carbon cores 51a to 51d corresponding to the diameter of the semi-cylindrical recess are placed in the semi-cylindrical recess on the upper surface side of the carbon core 51a to 51d.

Next, on top of the laminate 50 on which the carbon cores 51a to 51d shown in FIG. 9 are placed, the laminate before being formed by the press W44 in FIG. Press molding is performed using a press device 52 shown.

The press device 52 has a lower mold 53 having the same shape as the lower mold 46 of the press device 44 shown in FIG. It has 54. 55.56 is a guide. The upper mold 54 is the lower mold 53
Since it has the same shape as , a laminate 57 shown in FIG. 11 can be obtained by press molding using this press device 52 .

By firing this laminate 57 at a predetermined firing temperature, the carbon cores 51a to 51d are burnt out and scattered, and the liquid discharge holes shown in FIG. Holes 33e to 33g are formed.

Next, as shown in FIG. 6, an independent external electrode 38a
38d, 39a to 39d are formed corresponding to each liquid discharge through hole 33a to 33d.

The external electrodes 38a to 38d and 39a to 39d can be formed by printing and baking a conductive paste, or by a so-called transfer method.

In addition, when forming external electrodes by the transfer method, the external electrodes 38a to 38d, 39a to 39d are formed on the outer surface of the ceramic green sheet during press forming using the press device 52 shown in FIG. 10 prior to sintering. It is also possible to form the conductive material by laminating resin films on the top and bottom of a laminate and transferring them onto the laminate during press molding. In this case, a resin film exists between the upper mold 54, the lower mold 53, and the green sheets forming the laminate.

Therefore, it is possible to prevent the ceramic ivy green sheet from adhering to the upper mold 54 and the lower mold 53.

As described above, in the manufacturing process of the multiple liquid ejecting device of the second embodiment, a plurality of liquid ejecting sections can be easily constructed through a relatively simple series of steps. Moreover, by simply determining the spacing between the carbon cores, the positions of the through holes 33a to 33d for liquid discharge can be determined, and the shape of the mold of the press device 44, 52 shown in FIG. 8 and FIG. 1O can be selected. It can be seen that the positioning of each piezoelectric element portion and the formation of internal electrodes can be easily performed by simply performing the following steps.

In the liquid ejection devices of the first and second embodiments described above, the internal electrode is formed so as to surround at least a part of the periphery of the ceramic portion around the liquid ejection through hole, but the inner electrode of the through hole In this case, the method for forming the internal electrodes is to create a ceramic body in which through holes for liquid discharge are arranged in parallel by firing, and then apply a conductive paste to the inner walls of the through holes. Then, the carbon core may be formed by baking, or by applying a conductive paste to the surface of the carbon core, scattering the carbon core at the firing stage, and baking the same.

Further, although the liquid ejection devices of the first and second embodiments described above are illustrated in which four liquid ejection through holes are formed, other numbers of liquid ejection through holes may be formed. It goes without saying that the present invention can be applied to such cases. Furthermore, it should be pointed out that the cross-sectional shape of each liquid discharge through hole and the cross-sectional shape of the internal electrodes are not limited to the illustrated example and can be changed as appropriate.

Further, in the second embodiment, in addition to the carbon core, a core made of a material that burns out and scatters during firing, such as resin or wax, may be used.

〔Effect of the invention〕

According to the present invention, a plurality of liquid ejection through holes and corresponding piezoelectric elements are configured in a single ceramic body, so that a multiple liquid ejection device can be made smaller, lighter, and more dense. It can be easily achieved.

Further, since the electrode material is simply arranged within a single ceramic body, peeling is unlikely to occur even if the ambient temperature changes. Therefore, it is possible to realize a multiple liquid ejection device with excellent reliability.

In addition, it is possible to omit the complicated assembly work that is required in the case of conventional examples in which multiple independent liquid ejection elements are combined, and it is possible to manufacture the product through a series of relatively simple steps, making it easier to manufacture. It becomes possible to reduce costs effectively.

Therefore, according to the present invention, for example, it is small and lightweight;
It becomes possible to obtain an inkjet printer head capable of high-speed printing.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a multiple liquid ejection device according to a first embodiment of the present invention, FIG. 2 is a sectional view for explaining an example of a conventional liquid ejection device, and FIGS. 3 to 5 are FIG. 3 is a schematic cross-sectional view showing a state in which a carbon core is immersed in a ceramic slurry, and FIG. A side view showing the state in which the ceramic layer has been heated, Figure 5 shows the sintered ceramic ξ
FIG. 6 is an end view of a multiple liquid ejection device according to a second embodiment of the present invention, and FIGS.
FIG. 7 shows the process of applying a conductive paste onto a green sheet and further laminating a green sheet made of piezoelectric material. A perspective view for explanation, FIG. 8 is a schematic front view showing the process of molding a green sheet in the first mold, and FIG. 9 shows a state in which the carbon core is placed in the molded laminate. 10 is a schematic front view for explaining the process of laminating and molding ceramic green sheets on the laminate shown in FIG. 9, and FIG. 11 is a front end face of the formed laminate. It is a diagram. In the figure, 11.31 is a multiple liquid ejection device, 12.
32 is a ceramic body, 12a, 32a are end faces, 13a~
13d, 33a to 33d are liquid discharge through holes, 14a
=14d, 34a to 34d are ceramic parts, 15a
-15d, 35.36 are internal electrodes, 35a to 35d,
36a to 36d are drive electrode parts, 35a to 35g, 36e
~36g is a connection electrode part, 16 is a ceramic part, 37 is a ceramic part made of a piezoelectric ceramic layer, 17.3
8a to 38d and 39a to 39d indicate external electrodes.

Claims (2)

[Claims] (1) A multiple liquid ejection device in which a piezoelectric element is provided corresponding to each of the plurality of liquid ejection through holes, and the liquid is ejected using the piezoelectric effect of the piezoelectric element, and the device has both end faces. a ceramic body in which a plurality of through-holes for liquid discharge are arranged in parallel, each opening in the ceramic body; an internal electrode formed to surround the ceramic body; and an external electrode formed on an outer surface connecting both end surfaces of the ceramic body so as to face the internal electrode; The ceramic portion sandwiched between the inner electrode and the outer electrode is formed of piezoelectric ceramic, and one of the inner electrode and the outer electrode is formed independently for each liquid discharge through hole, and the other is a common electrode. A multiple liquid ejecting device, in which a plurality of piezoelectric elements corresponding to each liquid ejecting through hole are provided. (2) The internal electrode is formed independently for each liquid discharge through hole, and each internal electrode is arranged so as to surround the inner wall of each through hole or the ceramic portion around each through hole. 2. The multiple liquid ejecting device according to claim 1, wherein the external electrode is a common electrode formed to cover an outer surface connecting both end surfaces of the ceramic body. (3) The internal electrode is arranged to electrically connect the plurality of drive electrode parts to each other and a plurality of drive electrode parts formed so as to surround a part of the ceramic part around each through hole. and a common electrode having a connection electrode part, and the external electrode is arranged independently for each liquid discharge through hole so as to face each of the drive electrode parts via a ceramic part made of piezoelectric ceramics. It is formed by
The multiple liquid ejection device according to claim 1.