JPS63227199A - Piezoelectric sounding body - Google Patents

Abstract

PURPOSE:To obtain a sounding body high in sound pressure level by disposing a recessed part on the boundary of the fixed support part and the free part of the piezoelectric bimorph type sounding body or a free part adjacent thereto according to a dislocated boring and laminating. CONSTITUTION:Electrodes 13, 14 are respectively drawn to separate three directions on piezoelectric material green sheets 11, 12. A hole with diameter d=2Rpi/division number-gap (g) is opened on the position of a radius R on which a peripheral fixed body 15 is formed with 1/2P dislocated between the sheets 11, 12. On two upper and lower parts, the green sheet 21 having the hole with radius R is formed, laminated, temporarily fixed, a peeling film 31, a spacer 32 are laminated, pressed, integrated with the peripheral fixed body 15 to form the piezoelectric sounding body through removal of binder and burning. According to this constitution, the thickness of the sheet at the boundary part of a diaphragm part and the fixed body part is thinned substantially to one layer, the displacement in the diaphragm is large and the sounding body high in the sound pressure level is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric sounding body, particularly to a piezoelectric sounding body used as a piezoelectric buzzer or a piezoelectric speaker.

[Conventional technology]

A piezoelectric sounding body is obtained by bonding two pieces of piezoelectric material with electrodes formed on both sides.By connecting the electrodes so that they are opposite to each other with respect to the polarization direction, when an alternating current voltage is applied between the electrodes, the piezoelectric sounding body is bonded together. Since each of the piezoelectric materials expands and contracts oppositely to each other, warping occurs alternately in the vertical direction centering on the bonded surface. For this reason, if the outer periphery is fixed in a circular shape, the center will be displaced up and down due to this warp.
It becomes a vibrator that vibrates at the frequency of the applied alternating current signal, and when a signal of several kHz is applied, this vibration creates air compression waves and becomes a sounding body that produces sound.

[Problem that the invention seeks to solve]

In the above-described sounding body, if the amount of displacement of the center portion is large, the sound produced will be louder, so a structure with a large displacement of the center portion is desired. However, when the piezoelectric material is a ceramic sintered body, the material itself has no flexibility, so if the periphery is fixed, the movement of the center is also suppressed. As a result, a bimorph piezoelectric sounding element whose entire structure is made of ceramics and whose periphery is fixed becomes a sounding element with a low sound pressure level. FIG. 4 is a partially cutaway perspective view of a bimorph type sounding body, which is an example of a conventional piezoelectric sounding body. As shown in FIG. 4, the piezoelectric sounding body has a metal plate 41 at its center, piezoelectric materials 42 and 43 are pasted on both sides of the metal plate 41, and electrodes 44 are connected to each other so as to be opposite to each other with respect to polarization. It is something.

By pasting it on the metal plate 41 in this way,
In order to ensure the flexibility of this metal plate 41 part with the support body 45 of the peripheral fixed part, the warpage that occurs in the piezoelectric material 42 part displaces the whole, which becomes vibration and efficiently generates sound. However, such a sounding body attached to a metal plate requires a process of attaching piezoelectric material to the metal plate.
This method requires a process of connecting the electrodes, and also requires adhesion while perfectly aligning the top and bottom of the metal plate, which has the disadvantage that this alignment process is not easy and increases costs. The object of the invention is to eliminate these conventional drawbacks and to provide a highly efficient piezoelectric sounding element using a simple method that allows one piece to be fired.

[Means for solving problems]

The piezoelectric sounding body of the present invention is a piezoelectric bimorph type sounding body obtained by fixedly supporting a part of a laminate made of two layers of piezoelectric ceramics sandwiched between at least three layers of electrodes. At least one recessed part is formed in the free state part adjacent to the boundary part of the free state part, and this recessed part is used for drilling in one layer and subsequent lamination or upper and lower parts. Obtained by offset drilling between two layers and subsequent lamination.

[Effect]

The piezoelectric sounding body of the present invention is a bimorph-type laminate in which the vibrating part has three electrode layers. By connecting the electrode connection of the second layer of the bimorph forming part to the first layer of the laminate through a through hole so as to form a layer, the thickness at the position of the outer peripheral fixing part was reduced to one layer. state. As a result, the peripheral portion is thinner than in the case where conventional piezoelectric ceramic plates are laminated and fixed around the periphery, and this thinning makes it easier to move as a diaphragm despite being a ceramic body. Therefore, even if the same amount of power is supplied, the diaphragm of the present invention can be displaced efficiently, resulting in a sounding body with a high sound pressure level. Forming electrodes on a piezoelectric plate as in the case of configuring.

Piezoelectric sounding elements can be obtained through a simple process of simply laminating and firing them together, without requiring any steps such as pasting on a metal plate, attaching to a case support, or connecting electrodes to external terminals. It will be done.

〔Example〕

Next, the piezoelectric sounding body of the present invention will be explained with reference to the drawings.

FIG. 1 is a partially cutaway perspective view of a piezoelectric sounding body showing an embodiment of the present invention. The diaphragm is made of two layers of piezoelectric ceramics 11
and 12, electrodes 13 are formed in all three layers, upper, lower, and inner, and these electrodes are drawn out in three directions of the outer circumferential fixed body 15 by an external extraction electrode 14 and connected to an external electrode 16.

Grooves 17, which are the main part of the present invention, are located on both sides of the boundary between the fixed part of the two-layered piezoelectric ceramic outer circumferential fixed body 15 and the diaphragm, and these grooves are shifted by 1/2 pitch vertically. 9. FIG. 2 is a plan view showing an example of a pattern formed on a piezoelectric material green sheet to obtain a piezoelectric sounding element of the present invention, and an example of the hole punching state. material green sheet 11
Electrodes 13 and lead-out electrodes 14 are formed on the front and back sides of the piezoelectric green sheet 12 shown in FIG. 2(b), and are drawn out in three different directions. When the outer circumferential fixed body is formed, the piezoelectric green sheets 11 and 12 are shifted by 1/2P between the piezoelectric green sheets 11 and 12 by a pitch (here, 1./2 pitch angle). and diameter d
Drill a hole such that d=2・R・π/number of divisions−cap g. At this time, the number of divisions is such that the hole diameter d ranges from 1 rhyme to 4 rhymes, and the gap g is 0.5 in to ll.
Set as ll11.

The two piezoelectric green sheets obtained in this way are laminated and pressed as they are, subjected to a binder removal process, and then fired to create a simple diaphragm, which is used by incorporating it into a fixed part and case as a sounding body. However, these two green sheets 21 each have a hole with a radius of R on the top and bottom.
After stacking and temporarily fixing these, as shown in FIG. 3, the peeling film 31 and the spacer 32 are laminated and pressed together to obtain an integral piece with the outer peripheral fixing body, and the binder is removed. Through the process and firing process, it becomes a piezoelectric sounding body obtained by integral firing. Note that FIG. 3 is a side view showing an example of the structure when piezoelectric sounding bodies of the present invention are laminated.

The piezoelectric sounding element constructed in this way has a peripheral fixed part with a thickness equivalent to one layer of green sheet (20 μm to 50 μm), so this part has flexibility even though it is a ceramic sintered body. Since the vertical deflection caused by the central electrode-forming portion can be obtained in a state close to a free state, the decrease in efficiency due to the influence of peripheral fixation is much smaller, resulting in a sounding body with a high sound pressure level. Also,
Since the piezoelectric sounding body of the present invention can be obtained by simply drilling and printing green sheets, laminating them, removing the binder, and firing, there is no need to align and attach the metal plate and piezoelectric material, or take out the electrodes to the outside, as in the past. Since there is no need for any wiring or the like, and the manufacturing process for ordinary multilayer ceramic capacitors can be used as is, cost reduction effects can be easily obtained.

The piezoelectric green sheet used here is magnesium
Lead niobate Pb (Mg,..., ・Nb,...)03
An electrostrictive material powder mainly composed of an organic binder and °
The mixture is dispersed in a solvent to form a slurry.

This is made into a ceramic raw sheet having a uniform thickness of 20 μm to 200 μm by slip casting using a doctor blade.

This ceramic raw sheet is punched out to a specified size, and holes for forming grooves are formed using a punch and a die. Next, an electrode paste is printed on the processed piezoelectric green sheet including the holes using a screen printer.

The green sheets with holes and electrode patterns obtained in this way were stacked and heated at a temperature of around 100℃.
A laminate is obtained by pressing at a pressure of about 50 kg/cm2. Next, after cutting this laminate into predetermined dimensions as necessary, first the organic matter present in the cavity pattern and ceramic green sheet is slowly heated in an oxidizing atmosphere in the first debinding step to decompose and decompose it. make it disappear Normally, these organic substances are completely decomposed and oxidized by 500°C to 600°C, but if the temperature is suddenly raised to the decomposition temperature, the laminate will be damaged, so it should be heated at 25°C/hour or slower. Raise the temperature at the temperature increase rate to 500°
By maintaining the temperature at C to 600°C for a sufficiently long time, the organic matter is completely eliminated.

After this, the piezoelectric sounding body described above is obtained by firing at a temperature of 900° C. to 1200° C″c.

In this example, the grooves were formed by drilling holes at different positions between the upper and lower piezoelectric green sheets, but this could also be done by drilling holes at twice the pitch in the piezoelectric green sheets on only one side. The thickness of the fixed portion obtained later is only the thickness of one layer of the Habo piezoelectric material green sheet, so it does not restrict the movement of the diaphragm, and it becomes an efficient sounding body that can be formed in one piece. The point is that a groove is formed at the boundary between the free state portion that is displaced as a diaphragm and the fixed body portion that supports and fixes it, and this groove provides a thinning effect. For example, in a rectangular bimorph diaphragm, both ends are configured as supporting parts, but grooves may be formed at the boundary between the fixed parts at both ends and the diaphragm inside. In the case of a sheet, holes similar to those described above may be formed.

〔Effect of the invention〕

As is clear from the above description, the piezoelectric sounding body of the present invention is produced by forming holes in a single layer of sheets laminated at the boundary between the free state portion that is displaced as a diaphragm and the fixed body portion that supports the diaphragm. Even though the diaphragm is a ceramic sintered body that can be made into a thin one-layer structure with grooves formed and the thickness at this boundary part is approximately one layer, the diaphragm and the fixed body are integrated. The displacement of the diaphragm becomes closer to the free state, and the displacement of the diaphragm becomes larger, which has the effect of producing a sounding body with a high sound pressure level9.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of a piezoelectric sounding body showing an embodiment of the present invention, and FIG. 2 is a plan view showing an example of a pattern formed on a piezoelectric green sheet to obtain a piezoelectric sounding body of the present invention and the state of drilling holes. 3 is a side view showing an example of a structure when piezoelectric sounding bodies of the present invention are laminated, and FIG. 4 is a partially cutaway perspective view of a bimorph type sounding body showing an example of a conventional piezoelectric sounding body. be. 11.12... Piezoelectric ceramics (piezoelectric green sheet), 13.44... Electrode, 14... Extracting electrode, 15... Outer periphery fixing body, 16... External electrode, 17...
... Vortex, d... Hole diameter for groove formation, R... Radius at the position of the fixed body, P... Pinch (pitch angle) for groove formation, g... Gap between grooves , 21...Green sheet, 31...Peeling film, 32...Spacer, 41...Metal plate, 42.43...Piezoelectric material, 45...
...Support. Figure 7 “Gay Mando” Ceramics

Claims (2)

[Claims] (1) In a piezoelectric bimorph type sounding body obtained by fixedly supporting a part of a laminate consisting of two layers of piezoelectric ceramics sandwiched between at least three layers of electrodes, the fixed support part and the free part are separated. A piezoelectric sounding body characterized in that at least one concave portion is formed at a boundary portion or a free state portion adjacent thereto. (2) A patent claim characterized in that the concave portion is obtained by drilling a hole in one layer and then laminating the layer, or by punching a hole at a mutually shifted position between the upper and lower layers and then laminating the layer. A piezoelectric sounding body according to range (1).