JP2000004499A - Piezoelectric diaphragm and piezoelectric acoustic component using the piezoelectric diaphragm - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a piezoelectric acoustic component that is easily configured to be a surface mount type with excellent acoustic conversion efficiency and used for a sound source of plural sounds. SOLUTION: Three slits 2c1-2c3 are formed in parallel with a top plate being a metallic plate 2 that is drawn as a cap and plural rectangular piezoelectric plates 3, 4 are adhered face to face to parts among the slits to configure plural unimorph diaphragms 1. The slits 2c1-2c3 of the diaphragm 1 are sealed by a flexible sealing material, a lower end of a circumferential wall of the metallic plate 2 is adhered to a base 10 to form an acoustic space between the metallic plate 2 and the base 10. Surface electrodes of piezoelectric plates 3, 4 connect with input electrodes 11, 12 by wires 7, 8 and the metallic plate 2 connects with an earth electrode 13. The diaphragm 1 is covered in a contactless state and a cover 20 with sounding holes 21 is fixed on the base 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric acoustic component such as a piezoelectric buzzer or a piezoelectric receiver.

[0002]

2. Description of the Related Art Hitherto, piezoelectric acoustic components have been widely used as a piezoelectric buzzer or a piezoelectric receiver that generates an alarm sound or an operation sound in electronic devices, home appliances, mobile phones, and the like.

A piezoelectric acoustic component of this type is disclosed in, for example,
As described in JP-A-107593 and JP-A-7-203590, a unimorph type diaphragm is formed by attaching a circular metal plate to a single-sided electrode of a circular piezoelectric plate, and the periphery of the metal plate of the diaphragm is formed. In general, the structure is such that the portion is supported in a circular case and the opening of the case is closed with a cover.

[0004]

However, when such a circular diaphragm is used, there has been a problem that the acoustic conversion efficiency is low and it is difficult to construct a surface mount type. Further, the conventional piezoelectric acoustic component is generally used as a sound source of a single sound, and a plurality of sounds such as a scale and a complicated sound such as a beat sound cannot be generated.
Therefore, in order to generate a plurality of sounds, it is necessary to provide a plurality of diaphragms, which leads to an increase in cost and a disadvantage of a large size.

It is an object of the present invention to provide a small-sized piezoelectric vibrating plate which has good sound conversion efficiency and can be used as a sound source for a plurality of sounds. Another object of the present invention is to provide a piezoelectric acoustic component that can be easily configured in a surface mount type using the above-described piezoelectric vibration plate.

[0006]

In order to achieve the above-mentioned object, the invention according to claim 1 is directed to a metal plate having three parallel metal plates.
By providing more than one slit, by joining face-to-face piezoelectric plates of rectangular and different dimensions in the area between each slit,
Provided is a piezoelectric vibrating plate comprising a plurality of vibrating plates that generate different sounds.

[0007] When a rectangular piezoelectric plate is face-to-face bonded to a portion between slits provided in a metal plate, a portion sandwiched between the slits of the metal plate forms a vibrating portion. When a predetermined frequency signal is input between the metal plate and the surface electrode of the piezoelectric plate, the piezoelectric plate expands and contracts in the length direction, and the vibrating part flexes and vibrates in response to this,
Pronounce. At this time, both ends in the length direction of the rectangular piezoelectric plate become nodes of vibration, and the center part in the length direction becomes an antinode of vibration. FIG.
As shown in the figure, in a conventional disk-shaped diaphragm, since the peripheral portion is fixed by a case or the like, it is difficult to bend and displace, and the maximum displacement point P is only the center point.
Although the displacement volume is small, the structure according to the present invention increases the displacement volume because the maximum displacement point P exists along the center line in the longitudinal direction of the piezoelectric plate. Since this displacement volume becomes energy for moving air, the sound conversion efficiency can be increased. Even if the peripheral portion of the metal plate is fixed to a substrate, a case, or the like, the portion sandwiched by the slits can be freely displaced, so that the sound conversion efficiency does not decrease. Further, since the portion where the piezoelectric plate is fixed can be freely displaced by the slit, a lower frequency can be obtained as compared with a conventional disk-shaped diaphragm. Conversely, if the same frequency is obtained, the size can be reduced.

Further, when a metal plate is connected to the ground and an optimum frequency signal is input to each piezoelectric plate to the surface electrode of the piezoelectric plate,
Each piezoelectric plate can be separately excited to generate a sound of a different frequency. By electrically driving the respective diaphragm portions independently or simultaneously, it is possible to freely generate a sound like a musical scale or a beat sound. Adjacent diaphragm portions are separated by slits, so that vibration of the diaphragm portions does not adversely affect adjacent diaphragm portions.
Therefore, a plurality of diaphragms can be arranged in a small area at high density.

According to a second aspect of the present invention, the metal plate of the piezoelectric vibration plate according to the first aspect is drawn so as to have a top plate portion and a peripheral wall portion, and the slit is provided in the top plate portion.
The slit is sealed with a flexible sealing material, and the lower end of the peripheral wall of the metal plate is adhesively fixed to a substrate having a plurality of input electrodes and a ground electrode, so that the gap between the metal plate and the substrate is reduced. An acoustic space is formed, and the surface electrodes of the piezoelectric plates face-to-face bonded to the top plate are individually connected to the input electrodes of the substrate, and the metal plate is connected to the ground electrode of the substrate. If a cover that covers in a non-contact state and has a sound emission hole is adhered and fixed on the substrate, a surface-mounted piezoelectric acoustic component serving as a sound source of a plurality of sounds can be obtained.

In this case, since the metal plate is formed in a cap shape, an acoustic space can be easily formed between the metal plate and the substrate by fixing the lower end of the peripheral wall portion to the flat substrate. . Moreover, by forming the slit on the top plate,
A large mounting area (vibration area) for the piezoelectric plate can be secured, and the sound conversion efficiency can be further increased.

The slit of the metal plate is sealed with a sealing material in order to prevent air leakage, but since this sealing material has flexibility, it does not hinder the displacement of the portion sandwiched between the slits.
Therefore, independent sound can be generated without being affected by the vibration of the adjacent diaphragm portion. As the sealing material, a material having flexibility such as silicone rubber is desirable.

Further, since the cover for covering the diaphragm in a non-contact state is adhered and fixed on the substrate, the periphery of the diaphragm can be made substantially closed. Then, by arranging the input electrode and the ground electrode provided on the substrate to the side edge or the back surface of the substrate, it is possible to easily configure the surface-mounted component.

[0013]

2 to 6 show a piezoelectric buzzer as an example of a piezoelectric acoustic component according to the present invention. The piezoelectric buzzer generally includes a unimorph-type diaphragm 1, a substrate 10,
And a cover 20.

The vibrating plate 1 is composed of a metal plate 2 formed in a cap shape, and two rectangular piezoelectric plates 3 and 4 electrically and mechanically face-to-face bonded on the metal plate 2. . The metal plate 2 is made of a material having both good conductivity and spring elasticity, such as phosphor bronze and 42Ni. 4 metal plates
In the case of 2Ni, since the thermal expansion coefficient is close to that of ceramic (PZT or the like), a more reliable one can be obtained. FIG.
As shown in, the metal plate 2 are integrally formed by drawing processing has a top plate portion 2a and a peripheral wall 2b, the three parallel slits 2c ₁ ~2c ₃ is formed in the top plate 2a , one piezoelectric plate 3 is part 2d between slits 2c ₁ and 2c ₂
And the other piezoelectric plate 4 has slits 2c ₂ and 2c ₃
Between portions 2e. Slit 2c ₁ ~2
The length L of the c ₃ is longer than the interval W of the slit 2c ₁ ~2c _3, equal to the length L and width W of each length x and width y of the piezoelectric plates 3 and 4 is a slit 2c ₁ ~2c ₃ or Slightly shorter. Note that the magnitude relationship between the length L and the width W and the magnitude relationship between the length x and the width y may be opposite to the above.

The piezoelectric plates 3 and 4 are made of a piezoelectric ceramic such as PZT, and have electrodes 3a and 3b and electrodes 4a and 4b formed on the front and back surfaces thereof. 2e is electrically connected by facing bonding with a conductive adhesive or the like. The back electrode 3
b and 4b are omitted, and the back surfaces of the piezoelectric plates 3 and 4 are directly bonded to the metal plate 2 via a conductive adhesive or the like, so that the metal plate 2
May also be used as the back electrodes 3b and 4b.

At least one of the length x, width y and thickness t of the piezoelectric plates 3 and 4 is set to be different. Therefore, the resonance frequencies of the two piezoelectric plates 3 and 4 are different from each other. The piezoelectric plates 3 and 4 are connected to the slits 2c ₁ to
Site 2d between 2c _3, after bonding to 2e, the slits 2
c _{1 to} 2c ₃ are sealed with a flexible sealing material 5 such as silicone rubber. In addition, the sealing step of the sealing material 5 includes:
This may be performed after the diaphragm 1 is bonded to the substrate 10 as described later.

The diaphragm 1 is bonded and fixed to an insulating substrate 10 made of a glass epoxy substrate or the like, and an acoustic space 6 is formed between the diaphragm 1 and the substrate 10. Note that the acoustic space 6 does not need to be completely sealed, and for example, a braking hole or the like may be appropriately provided in the substrate 10 to communicate with the outside. Substrate 1
0 denotes a first electrode 11 and a second electrode 12 which are input electrodes.
And a third electrode 13 serving as a ground electrode. The first electrode 11 is formed so as to extend from the upper surface on one end side of the substrate 10 to the back surface side via the side edge, and the second electrode 12
Similarly, it is formed so as to extend from the upper surface on the other end side of the substrate 10 to the rear surface side via the side edge. The third electrode 13 is formed so as to surround the central portion of the substrate 10 in a headband shape.

A conductive adhesive is applied to the lower end of the peripheral portion 2b of the metal plate 2 by transfer or the like, and is adhered onto the substrate 10 to fix the metal plate 2 to the substrate 10, Electrical connection with the third electrode 13 is performed at the same time. Note that the metal plate 2 includes the first electrode 11 and the second electrode 12.
In order to prevent electrical continuity, it is desirable to form an insulating film on the first electrode 11 and the second electrode 12 corresponding to, for example, the bonding portion of the metal plate 2 by a method such as printing. Further, the upper surface of the vibration plate 1, that is, the surface electrodes 3a and 4a of the piezoelectric plates 3 and 4, respectively.
Are connected to the first electrode 11 and the second electrode 12 of the substrate 10 via the coated metal wires 7 and 8, respectively. The reason why the coated metal wires 7 and 8 are used is to prevent the wires 7 and 8 and the metal plate 2 from being short-circuited. The connection position of the wires 7 and 8 to the surface electrodes 3a and 4a is desirably at a longitudinal end portion that serves as a node of vibration of the piezoelectric plates 3 and 4.

A cover 20 that covers the vibration plate 1 in a non-contact state is adhesively fixed on the substrate 10. A sound emission hole 21 is formed in the ceiling surface of the cover 20, and a buzzer sound can be emitted from the hole 21 to the outside. The material of the cover 20 may be a metal or a resin. When the metal cover 20 is used, the metal cover 20 and the third electrode 1
3 may be conducted.

In the case of the piezoelectric buzzer having the above structure, the resonance frequency is affected by the thickness, material, adhesive and the like of the metal plate 2, but the length x, width y, and thickness t of the piezoelectric plates 3 and 4 are determined. Is determined dominantly. As described above, at least one of the length x, the width y, and the thickness t is used, and two piezoelectric plates 3 and 4 having different dimensions are electrically driven independently. Can be composed. As an example, one vibrating plate to which the piezoelectric plate 3 is bonded is approximately 440H.
z, and the other diaphragm to which the piezoelectric body 4 is adhered is approximately 1,
When driven at 000 Hz, it is possible to generate a sound like a time signal of NHK (Japan Broadcasting Corporation).

If two frequencies are generated simultaneously, a beat sound can be generated. That is, when the piezoelectric plates 3 and 4 are driven at the same time, the two vibrating plate portions mainly composed of the piezoelectric plates 3 and 4 share the acoustic space 6 and the sound emission hole 21, so that about 440 Hz And about 1,00
A beat sound having a difference frequency of 0 Hz (about 560 Hz) as a main component can be obtained.

The metal plate 2 and the third electrode 13 of the substrate 10
A conductive adhesive was used to make the connection between the metal plate 2 and the substrate 10 with a normal insulating adhesive, and then the solder, the conductive adhesive, or the lead was used. The metal plate 2 and the third electrode 13 may be connected using a wire or the like. In short, the method of connecting the metal plate 2 and the first electrode 13 is not limited to the above embodiment, and any method can be used.

FIG. 7 shows a second embodiment of the piezoelectric diaphragm according to the present invention. In this piezoelectric vibration plate, a large number of parallel slits 32a to 32o are formed in a top plate portion 31 of a large metal plate 30 drawn in a cap shape, and piezoelectric plates having different dimensions are formed in portions between these slits. 33a to 33n are bonded face to face. In this embodiment, each of the piezoelectric plates 33a to 33a to
The length, width, thickness, etc. of 33n are gradually changed so as to have a frequency suitable for the musical scale, for example, and slits 32a to 32o are formed.
Are changed in accordance with the lengths of the piezoelectric plates 33a to 33n. Lead wires 34a to 34n for signal input are individually connected to the surface electrodes of the piezoelectric plates 33a to 33n. In addition, the metal plate 30 is connected to a ground part.

If an electric signal is input from each of the lead wires 34a to 34n and each of the piezoelectric plates 33a to 33n is driven independently, a single-tone keyboard adapted to the musical scale can be formed. If two arbitrary piezoelectric plates are driven at the same time, an arbitrary beat sound can be generated, and an advanced musical instrument can be constructed. As described above, since a large number of piezoelectric plates 33a to 33n can be arranged side by side with the slits 32a to 32o therebetween, the piezoelectric bodies 33a to 33n can be arranged at high density in a small space, and a small and sophisticated multi-frequency sounding body can be provided. Obtainable.

FIG. 8 shows a third embodiment of the piezoelectric acoustic component according to the present invention.
An example will be described. In this embodiment, case 4 is the same as before.
0 and the cover 50. A concave portion 41 is formed in the case 40, and a step portion 42 is formed on an inner peripheral surface of the concave portion 41.
Are formed. The piezoelectric vibrating plate 60 is a flat metal plate 6.
One is provided with three parallel slits 62, and two piezoelectric plates 63 and 64 are electrically and mechanically face-to-face bonded to a portion between these slits 62. In addition, the slit 6
2 is sealed with a sealing material 65 such as silicone rubber. The peripheral edge of the vibration plate 60 is placed on the step portion 42 of the case 40 and is closely fixed by an adhesive or the like. Thus, an acoustic space is formed between the case 40 and the diaphragm 60. A cover 50 having a sound emission hole 51 is adhered to the upper surface of the case 40 to complete a piezoelectric acoustic component.

The metal plate 61 is connected to the outside and the piezoelectric plate 6
In order to connect the 3, 64 surface electrodes to the outside, lead wires (not shown) may be connected, or lead terminals may be used. Since both connection methods are known,
Here, the description is omitted.

In the embodiment shown in FIG. 8, the outer shapes of the case 40, the cover 50 and the diaphragm 60 can be arbitrarily changed. For example, the case 40 and the cover 50 may be circular, and the metal plate 61 may be a circular plate.

In the above-described first to third embodiments, the unimorph type vibration plate in which the piezoelectric plate is adhered to one side of the metal plate has been described. May be used.

[0029]

As is apparent from the above description, claim 1
According to the invention described in (1), since a plurality of diaphragms that generate different sounds are configured by providing slits parallel to each other on the metal plate and face-to-face joining a rectangular piezoelectric plate to a portion between the slits, The slit allows the diaphragm to bend and vibrate greatly, improving the sound conversion efficiency and easily obtaining a low frequency.

Further, since the size of the piezoelectric plate bonded to the portion between the slits is changed, the resonance frequency of each diaphragm can be changed, and a plurality of sounds can be easily generated. By electrically driving each diaphragm independently or simultaneously, it is possible to freely generate a musical scale, a beat sound, and the like.

Further, by arranging the piezoelectric plates in parallel with slits therebetween, a plurality of piezoelectric plates can be arranged at a high density in a small space, so that a small multi-frequency sounding body can be obtained.

According to the second aspect of the present invention, an acoustic space can be easily obtained by using a cap-shaped metal plate and a flat substrate, and the components can be simplified. By forming electrodes on the substrate,
A surface-mounted piezoelectric acoustic component serving as a sound source for a plurality of sounds can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a comparison diagram of a displacement distribution between a conventional example and the present invention.

FIG. 2 is a perspective view of a piezoelectric buzzer as an example of the piezoelectric acoustic component according to the present invention.

FIG. 3 is an exploded perspective view of the piezoelectric buzzer of FIG.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 2;

FIG. 5 is a sectional view taken along line VV of FIG. 2;

FIG. 6 is an exploded perspective view of a diaphragm and a substrate.

FIG. 7 is a sectional view of a second embodiment of the piezoelectric diaphragm.

FIG. 8 is an exploded perspective view of a third embodiment of the piezoelectric acoustic component.

[Explanation of symbols]

1 the diaphragm 2 metal plate 2c ₁ ~2c ₃ slits 3,4 piezoelectric plate 3a, 4a surface electrode 5 sealing material 6 acoustic space 7,8 conductive wires 10 substrate 11 first electrode (input electrode) 12 second electrode ( Input electrode) 13 Third electrode (earth electrode) 20 Cover 21 Sound emission hole

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kenji Kishimoto 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto F-term in Murata Manufacturing Co., Ltd. (Reference) 5D004 AA01 AA09 BB01 CC06 DD01 DD03 FF04 FF09 5J033 AA08 BB04 CC04 EE03 EE17 FF14 GG03 GG08 GG15 GG18 JJ01

Claims (2)

[Claims] 1. A plurality of diaphragms that generate different sounds by providing three or more slits parallel to each other on a metal plate and joining rectangular and different-sized piezoelectric plates face-to-face between the slits. A piezoelectric vibrating plate characterized by the following. 2. The metal plate of the piezoelectric vibrating plate according to claim 1 is drawn so as to have a top plate portion and a peripheral wall portion, and the top plate portion is provided with the slit, and the slit is made flexible. The lower end of the peripheral wall of the metal plate is bonded and fixed to a substrate having a plurality of input electrodes and a ground electrode to form an acoustic space between the metal plate and the substrate. ,
The surface electrodes of the piezoelectric plates face-to-face bonded to the top plate are individually connected to the input electrodes of the board, the metal plates are connected to the ground electrodes of the board, and the diaphragm is covered and released in a non-contact state. A piezoelectric acoustic component, wherein a cover having a sound hole is adhesively fixed on a substrate.