JPH10108297A - Piezoelectric sounding body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric sounding body that has provision for requirements of lowering a frequency as an acoustic characteristic and in which the sound pressure characteristic is improved. SOLUTION: A surrounding part of a diaphragm 5 of a piezoelectric element 7 is supported with a container case 19 using an adhesive 18 in the piezoelectric sounding body 20, a spherical spacer 11 whose the diameter is 50-1000μm is mixed in the adhesives 18 so as to provide a node support structure (pint support structure) to the container case 19. Thus, the entire piezoelectric element 7 contributes to the amplitude of the vibration by using a contact point with the spherical spacer 11 as node in the vibration mode of the piezoelectric element 7 and a high sound pressure is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric sounding body used in a portable telephone or an electronic sound buzzer, and more particularly to a piezoelectric sounding body which improves a sound pressure characteristic by improving a vibration mode of a piezoelectric element. In particular, the present invention relates to a piezoelectric sounding body having an improved support structure for a piezoelectric element in a storage case.

[0002]

2. Description of the Related Art In the advanced information age, piezoelectric sounders have been replaced by conventional electromagnetic speakers as speakers and microphones in mobile phones and other information devices and electronic devices, and electronic buzzers used in household electrical appliances. In recent years, demand has been remarkably expanding.

This piezoelectric sounding body has an extremely simple structure utilizing the piezoelectric effect of a piezoelectric material, is suitable for miniaturization, thinning, and cost reduction, and is a sounding body suitable for the above-mentioned applications.

Hereinafter, an example of the structure of a conventional piezoelectric sounding body will be described with reference to a sectional view of FIG.

[0005] The piezoelectric element 1 vibrates utilizing the piezoelectric effect of generating a polarization by applying a pressure or a tension or the like to a ferroelectric or the like and generating an electrostatic charge on an end face or the electrostriction effect of generating a mechanical stress when an electric field is applied. An energy / electrical energy conversion element formed of a ferroelectric ceramic, such as PZT (lead zirconate titanate) porcelain, as a piezoelectric material 2 in the form of a thin disk, and having two main surfaces having electrical conductivity of, for example, silver or the like. Good electrodes 3 and 4 are formed by coating.

The piezoelectric element 1 is made of a material such as brass and has a diameter larger than that of the piezoelectric element 1 and is formed in the shape of a thin disk. One main surface 5a or both main surfaces 5a and 5b are provided.
Further, the piezoelectric element 7 is formed by being fixed with one electrode 4 interposed therebetween.

The piezoelectric element 1 having the structure shown in FIG. 6 in which the piezoelectric element 1 is fixed to only one main surface 5a is a unimorph, and the two main surfaces 5a, 5a
The one in which the piezoelectric elements 1 are fixed to b is called a bimorph.

At this time, although not shown, the electrodes 3 and 4 of the piezoelectric element 1 in the piezoelectric element 7 are soldered with insulating coating conductors for transmitting and receiving electric signals to and from the outside. It is led out of a storage case 9 serving as a housing base of the element 1.

The storage case 9 is generally made of a synthetic resin or the like, and the peripheral portion of the vibrating plate 5 is held on the inner wall of the storage case 9 with an adhesive so that the piezoelectric element 7 can vibrate. There is no particular limitation on the shape, size, and structure of the inner wall that holds the peripheral portion of the diaphragm 5, but, for example,
The storage case 9 shown in FIG.
A, 9B are formed such that the opening end surfaces thereof are fitted to each other, and the peripheral portion of the diaphragm 5 is held by an adhesive 8 while sandwiching the peripheral portion of the diaphragm 5 in an annular groove formed in the fitting portion. ing. In addition,
Reference numeral 6 denotes a sound emission hole.

While the above-described piezoelectric sounding body 10 is suitable for thinning and miniaturization, the reduction in size of the piezoelectric element conflicts with the demand for lowering the frequency of the acoustic characteristics.

When the entire peripheral portion of the vibration plate 5 of the piezoelectric element 7 is completely fixed to the inner wall of the storage case 9, the substantial vibration mode is changed as shown in FIG. Without vibrating, as shown by the broken line, the vibration mode is such that the amplitude in the vicinity of the periphery is not sufficiently obtained and only the central portion vibrates, and the sound pressure (proportional to the displacement volume of the piezoelectric element 7) decreases. .

As described above, the conventional piezoelectric sounding body has a problem that it is difficult to respond to a demand for lowering the acoustic characteristics and the sound pressure is small.

[0013]

SUMMARY OF THE INVENTION Therefore, the invention of claim 1 of the present invention improves the vibration mode by devising a supporting structure of the peripheral portion of the diaphragm of the piezoelectric element by using a spherical spacer, An object of the present invention is to provide a piezoelectric sounding body having improved sound pressure characteristics.

According to a second aspect of the present invention, a projection is provided on the periphery of the diaphragm itself and is supported at the tip thereof. An object of the present invention is to provide a piezoelectric sounding body that achieves an improvement.

According to a third aspect of the present invention, in addition to the configuration of the projections of the vibration plate of the piezoelectric element in the piezoelectric sounding body of the second aspect, the arrangement of these projections is made to provide uniform and uniform point support. It is an object of the present invention to provide a piezoelectric sounding body in which a sound pressure characteristic is further improved as a vibration mode without deviation.

According to a fourth aspect of the present invention, a point supporting structure of the piezoelectric element in the piezoelectric sounding body according to the third aspect of the present invention is achieved by a simpler structure. It is an object of the present invention to provide a piezoelectric sounding body in which a plurality of protruding protrusions are provided, and the protrusions are bent substantially perpendicularly on both main surfaces to realize a point support structure.

According to a fifth aspect of the present invention, in addition to the projection structure of the diaphragm of the piezoelectric element in the piezoelectric sounding body of the fourth aspect, a plurality of these projections are provided at equal intervals along the periphery of the diaphragm. In addition, since the convex portions are alternately bent substantially perpendicularly to both principal surfaces, a uniform point support structure is provided, thereby further improving the sound pressure characteristics as a vibration mode without deviation. It is an object to provide an intended piezoelectric sounding body.

[0018]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a piezoelectric sounding body in which an adhesive holding a peripheral portion of a diaphragm of a piezoelectric element in a storage case is provided. Is mixed with a spherical spacer having a diameter of 50 μm to 1000 μm.

Here, the spherical spacer refers to a spacer that is in the adhesive and can be supported between the storage case and the peripheral portion of the diaphragm to support the piezoelectric element at points.

With such a configuration, unlike the vibration mode in which the peripheral portion of the vibration plate of the piezoelectric element is completely fixedly supported, the vibration mode having a large amplitude and a large sound pressure is realized by a simple support structure. .

By mixing the spherical spacer into the adhesive in advance, the process of assembling the piezoelectric sounding body can be performed in exactly the same manner as in the prior art, and the sound pressure characteristics can be improved simply and at low cost.

Further, in the above-described simple support structure for the piezoelectric element storage case, the protrusions are provided on both sides of the piezoelectric element in the periphery of the diaphragm of the piezoelectric element along the circumference. The present invention is also realized by the invention described in claim 2 of the present invention.

Here, it is sufficient that the protrusion is a small protrusion having a point or a line whose tip is not a flat surface, and any structure in which only the tip of the protrusion contacts the storage case in the adhesive and is supported. Is enough.

Such projections can be easily formed by pressing the peripheral portion of a vibrating plate (generally a thin metal plate) of the piezoelectric element at the same time as or before or after the punching of the vibrating plate. Thus, the sound pressure characteristic can be realized at a very low cost in the same manner as described above.

In particular, in the case of a structure in which a plurality of the protrusions on the vibration plate of the piezoelectric element of the piezoelectric sounding body are provided alternately and evenly along the periphery of both main surfaces of the vibration plate, as in the invention according to claim 3. Since the piezoelectric element is uniformly supported on the storage case without any deviation, the sound pressure characteristics are further improved.

According to a fourth aspect of the present invention, in the piezoelectric sounding body, a plurality of radially projecting projections are provided on a peripheral edge of a vibration plate of the piezoelectric element, and the projections are formed on both main surfaces. And is bent substantially vertically.

Here, the above-mentioned convex portion means any shape having a plurality of convex portions whose peripheral edge is not smooth when the diaphragm is formed.

The diaphragm is formed in this manner, and the protrusion is bent substantially perpendicularly to both main surfaces of the diaphragm, so that only the tip of the bent protrusion is formed in the same manner as the above-mentioned projection. A simple support structure for supporting the element is obtained.

Here, the arrangement of the convex portions in the bending direction is not particularly limited, but the bent convex portions may be partially offset only on one main surface, or the convex portions may be uneven. If they are not provided at intervals, the support to the storage case will be uneven and the vibration will be unstable.

In view of the above, in the invention of claim 5 of the present invention, a plurality of the protrusions are provided at equal intervals along the periphery of the diaphragm, and the protrusions are alternately arranged substantially perpendicularly on both main surfaces. Since the piezoelectric element is uniformly supported on the storage case without any deviation, the sound pressure characteristic is further improved.

In order to realize the above-described structure for supporting the piezoelectric element with respect to the storage case of the diaphragm, it is important that the periphery of the diaphragm is movable, assuming that the adhesive has a certain degree of elasticity even after being fixed. For example, an adhesive containing a silicone resin as a main component is used.

[0032]

Embodiments of the present invention will be described in detail with reference to the drawings. The same members as those in the related art are designated by the same reference numerals.

FIG. 1 is a sectional view showing an embodiment of a piezoelectric sounding body according to claim 1 of the present invention.

FIG. 2 is a perspective view including a partial cross section for explaining an embodiment of the diaphragm of the piezoelectric element of the piezoelectric sounding body according to the second and third aspects of the present invention.

FIG. 3 is a sectional view showing an embodiment of a piezoelectric sounding body on which the above-mentioned diaphragm is mounted.

FIG. 4 is a perspective view showing an embodiment of the piezoelectric element of the piezoelectric sounding body according to claims 4 and 5 of the present invention.

FIG. 5 is a sectional view showing an embodiment of a piezoelectric sounding body on which the above-mentioned piezoelectric element is mounted.

In FIG. 1, a piezoelectric sounding body 20 is composed of a piezoelectric element 1 in which electrodes 3 and 4 are formed on both surfaces of a piezoelectric material 2.
A piezoelectric element fixed to one main surface 5a (or both main surfaces 5a, 5b) of the piezoelectric element 7 and a peripheral portion of the vibration plate 5 held in a storage case 19 by an adhesive 18;
A spherical spacer 11 having a diameter of 50 μm to 1000 μm is mixed in an adhesive 18 holding a peripheral portion of the diaphragm 5 in a storage case 19.

Although the basic configuration of the storage case 19 is the same as that of the conventional example shown in FIG. 6, the storage case 19 is formed at a fitting portion where the open end faces of the storage cases 19A and 19B are vertically fitted. The width Y of the annular groove 12 is wide.

The spherical spacer 11 is, for example, a metal particle, a ceramic particle, a resin particle or the like. The configuration is such that the peripheral portion of the diaphragm 5 is located in the gap and is supported via the spherical spacer 11 without directly contacting the storage case 19.

Here, it is important to use an adhesive having elasticity as the adhesive 18, for example, an adhesive containing a silicone resin as a main component.

As a result, when the piezoelectric element 7 vibrates while bending up and down, the spherical spacer 11 becomes a fulcrum and the peripheral edge of the diaphragm becomes movable in the adhesive 18.
As shown in FIG. 7 (b), a knot support structure is provided.
The lowering of the primary resonance frequency is realized, and a large amplitude (sound pressure) is obtained. Of course, the resonance frequency depends on the diameter, thickness, elastic modulus, and the like of the piezoelectric element and the diaphragm of the piezoelectric element. However, the above-described node support structure has a lower sound than the peripheral fixed support structure in which the peripheral portion of the piezoelectric element diaphragm is fixed. Clearly the pressure properties are excellent.

Next, as a means for realizing the above-described node supporting structure, a structure for forming a node on the diaphragm itself of the piezoelectric element 17 can be provided to the storage case.

As shown in the piezoelectric vibrating plate 15 of FIG. 2 and the piezoelectric sounding body 30 of FIG. 3, the vibrating plate 15 of the piezoelectric element 17 is a circular metal plate (thickness 20 mm) of brass, phosphor bronze, stainless steel, aluminum or the like.主 100 μm)
It is characterized in that protrusions 16, 16 are provided on both main surfaces along the circumference in the peripheral portion of 5a, 15b (the area that fits in the groove 12 of the storage case).

As shown in FIG. 3, the tips of the projections 16, 16 are configured to make point contact with the upper and lower surfaces in the groove 12 of the storage case 19, and the projections are previously punched before assembly. It can be easily formed by hitting.

As a result, the piezoelectric element 17 is
At 6, the point supporting structure is realized, and the vibration mode of the node support is realized.

Of course, the periphery of the vibration plate 15 of the piezoelectric element 17 may be bonded with the above-mentioned elastic adhesive 28 if necessary.

In this case, even if the piezoelectric element 1 is bonded,
The peripheral edge of the diaphragm 15 of the seventh embodiment is movable, and serves as a node support structure.

Next, as shown in FIG. 7C, a peripheral structure of the vibration plate of the piezoelectric element 27 is used as a support structure that can obtain a large amplitude in the same manner as the above-described node support structure of the vibration plate of the piezoelectric element. End supporting structures are conceivable.

This is to prevent the peripheral portions of the upper and lower main surfaces of the vibration plate of the piezoelectric element 27 from being fixed, as shown in FIG.
Is a perspective view showing a shape of the piezoelectric element 27 (to which the piezoelectric element 1 is adhered) before bending.

As can be seen from the figure, a plurality of radially projecting projections 26 are provided on the peripheral edge of the diaphragm 25 of the piezoelectric element 27, and these projections are further provided as shown in FIG. 26 is bent substantially perpendicularly to both main surfaces 25a and 25b.

In particular, in FIG. 4B, eight piezoelectric elements 27 are arranged at equal intervals along the periphery of the vibration plate 25 and eight are alternately bent.

In the piezoelectric sounding body 40 using the piezoelectric element 27 having the above structure, as shown in the sectional view of FIG. Mode is realized. It should be noted that the adhesive may be adhered in the same manner as described above.

It is to be noted that the above-mentioned projections 26 are supported if at least two projections are provided on each main surface side of the vibration plate 25 of the piezoelectric element 27. However, it is preferable to obtain a stable vibration mode. To achieve uniform and even support, FIG.
As shown in (b), four or more convex portions 26 should be alternately arranged on each main surface side at equal intervals. However, for example, a large number of convex portions 26 may be provided so that the shape before bending shown in FIG.

The shape of the convex portion 26 is not limited to a square shape as shown in FIG. 4, but may be a shape which is completely point-supported, for example, a triangle or a semicircle.

[0056]

According to the first, second and fourth aspects of the present invention, the holding of the piezoelectric element with respect to the storage case has a simple support structure, so that a large vibration mode can be obtained and a low frequency range can be obtained. The acoustic characteristics can be improved, and the sound pressure characteristics can be improved.

The third and fifth aspects of the present invention, in addition to the effects of the second or fourth aspect of the present invention, provide a uniform support structure for the piezoelectric element, thereby further improving the sound pressure characteristics. Can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a piezoelectric sounding body according to claim 1 of the present invention.

FIG. 2 is a perspective view including a partial cross section for explaining an embodiment of a diaphragm of a piezoelectric element of a piezoelectric sounding body according to claims 2 and 3 of the present invention.

FIG. 3 is a cross-sectional view showing an embodiment of a piezoelectric sounding body on which the diaphragm is mounted.

FIG. 4 is a perspective view showing an embodiment of a piezoelectric element of a piezoelectric sounding body according to claims 4 and 5 of the present invention.

FIG. 5 is a cross-sectional view showing an embodiment of a piezoelectric sounding body on which the piezoelectric element is mounted.

FIG. 6 is a sectional view showing a structure of a conventional piezoelectric sounding body.

7A is a schematic diagram illustrating a vibration mode of a piezoelectric element of a conventional piezoelectric sounding body, and FIG. 7B is a schematic diagram illustrating a vibration mode of a node support structure of the piezoelectric element of the piezoelectric sounding body. ,
(C) is a schematic diagram showing a vibration mode of the edge support structure of the piezoelectric element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Piezoelectric material 3, 4 Electrode 5, 15, 25 Vibrating plate 7, 17, 27 Piezoelectric element 8, 18, 28 Adhesive 9, 19 Storage case 10, 20, 30, 40 Piezoelectric body 11 Spherical spacer 16 , 17 protrusion 12 groove 26 protrusion

Claims (5)

[Claims] 1. A piezoelectric element having electrodes formed on both surfaces of a piezoelectric material fixed to one or both main surfaces of a vibration plate, and a peripheral portion of the vibration plate of a piezoelectric element is held in a storage case with an adhesive. In the piezoelectric sounding body, a diameter of 50 μm to 1000 μm is contained in an adhesive holding a peripheral portion of the diaphragm in a storage case.
A piezoelectric sounding body characterized in that a spherical spacer is mixed therein. 2. A piezoelectric element having electrodes formed on both surfaces of a piezoelectric material fixed to one or both main surfaces of a vibration plate, and a peripheral portion of the vibration plate of a piezoelectric element is held in a storage case with an adhesive. In a piezoelectric sounding body, a projection is provided on both main surfaces along a circumference at a peripheral portion of the diaphragm. 3. The piezoelectric sounding body according to claim 2, wherein a plurality of protrusions are provided alternately and evenly along peripheral portions of both main surfaces of the diaphragm. 4. A piezoelectric element having electrodes formed on both surfaces of a piezoelectric material fixed to one or both main surfaces of a vibration plate, and a peripheral portion of the vibration plate of a piezoelectric element is held in a storage case with an adhesive. In a piezoelectric sounding body, a plurality of protrusions projecting in a radial direction are provided on a peripheral edge of the vibration plate, and the protrusions are bent to both main surfaces. 5. The piezoelectric sound generation device according to claim 4, wherein a plurality of projections are provided at equal intervals along the periphery of the diaphragm, and the projections are alternately bent on both main surfaces. body.