JPH1056689A - Piezoelectric sounding body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an adverse effect caused by sticking of adhesive agent by forming a wall so as to prevent the adhesive agent from flowing out and being stuck onto a diaphragm by providing ring-shaped irregularities at the peripheral part of an area to be applied with the adhesive agent for fixing the piezoelectric diaphragm into a housing case. SOLUTION: In a piezoelectric sounding body 20 in structure fixing a peripheral part 16 of a piezoelectric diaphragm 15 fixing a piezoelectric element 1 forming electrodes 3 and 4 on both the sides of a piezoelectric member 2 onto a main face 15a through an adhesive agent 8 to a housing case 9, in the area of the peripheral part 16 to apply the adhesive agent 8, irregularities 17 are provided around in the form of parallel rings from a peripheral terminal to the inner terminal of an adhesive agent applying area X. Thus, the fixing of the piezoelectric diaphragm is strengthened by securing a wider contact areas between the peripheral part 16 of the piezoelectric diaphragm 15 and the adhesive agent 8, the irregularities 17 become the wall for preventing the adhesive agent 8 from flowing out onto the piezoelectric diaphragm, and the adverse influence upon acoustic characteristics are prevented.

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 cellular phone, an electronic sound buzzer, and the like, and more particularly, to an inner side of an adhesive used for fixing a piezoelectric diaphragm to a storage case. More specifically, the present invention relates to a piezoelectric sounding body that prevents intrusion of the adhesive and avoids an influence on a sound pressure characteristic of an adhesive.

[0002]

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 Description of the Related Art In the advanced information age, piezoelectric sounding bodies have been replaced by conventional electromagnetic speakers as speakers and microphones in mobile phones and other information devices and electronic devices, and electronic sounds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

This piezoelectric sounding body has a very simple structure utilizing the piezoelectric effect of a piezoelectric material, is suitable for miniaturization, thinning, and cost reduction, and is 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.

The piezoelectric element 21 vibrates using a piezoelectric effect in which a polarization is generated when a pressure or a tension or the like is applied to a ferroelectric or the like to generate an electrostatic charge on an end face or an electrostriction effect in which a mechanical stress is generated 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 in a thin disk shape, and having good electrical conductivity of, for example, silver on both main surfaces thereof. Electrodes formed by coating.

[0006] The piezoelectric element 21 is made of a material such as brass and has a larger diameter than the piezoelectric element 21 and is formed in a thin disk shape on one main surface 22a or both main surfaces. The piezoelectric element 20 is formed by being fixed with one electrode interposed therebetween. Note that a piezoelectric element fixed to only one main surface is called a unimorph, and a piezoelectric element fixed to both main surfaces is called a bimorph.

At this time, although not shown, the piezoelectric element 20
The one end of the other electrode attached to the piezoelectric element 21 and the one end of the piezoelectric vibrating plate 22 are solder-fixed with an insulated conductor for transmitting and receiving an electric signal to / from the outside. It is assumed that the piezoelectric element 20 is led out of the storage case 11 serving as a housing base of the piezoelectric element 20.

The storage case 11 is a fixed body which is generally made of a synthetic resin or the like and which fixes the periphery of the piezoelectric element 20 to the inner wall of the storage case so that the piezoelectric vibration plate can vibrate. The structure of the inner wall for fixing the piezoelectric vibrating plate is not limited.
In No. 1, the upper and lower peripheral portions were fixed with an adhesive while sandwiching the peripheral portion of the piezoelectric vibrating plate in a concave portion provided along the inner wall formed at the inner wall fitting portion of the storage cases A and B divided into upper and lower portions. Has a structure.

Although the above-described piezoelectric sounding body is suitable for thinning and miniaturization, the reduction in size of the piezoelectric vibrating plate contradicts the reduction in frequency.

[0010] Therefore, it is desirable to expand the vibration region by making the bonding region of the peripheral portion where the adhesive of the piezoelectric vibration plate is applied and fixed to the storage case as narrow as possible.

[0011]

However, FIG. 6A is a perspective view of the piezoelectric element 7 and FIG. 6B is an enlarged sectional view of the periphery of the piezoelectric diaphragm fixed to the storage case 9. As described above, the main surface of the conventional piezoelectric vibration plate 5 is generally a flat surface as a whole, and the adhesive 8 (viscous fluid) applied to the peripheral portion of the piezoelectric vibration plate 5 is applied to the bonding area x of the piezoelectric vibration plate 5. Flows out from the inside (the center side where the piezoelectric element 1 is located)
When hardened, it sticks to the vibrating surface and inhibits elastic displacement, thereby adversely affecting the acoustic characteristics.

Therefore, the present invention according to claim 1 of the present invention provides a piezoelectric sounding body having an uneven wall provided with an uneven wall so that the adhesive applied to the periphery of the piezoelectric vibrating plate does not flow into the inside of the vibrating plate. It is intended to provide the body.

According to the second aspect of the present invention, in addition to the object of the first aspect, in particular, a large number of "walls" can be provided in an area narrower than mere unevenness, and the diaphragm is made thinner. It is another object of the present invention to provide a piezoelectric sounding body which has an advantage that a means for forming a "wall" of a simple bend can be employed as compared with the case of providing unevenness.

[0014]

In order to achieve the above object, according to the first aspect of the present invention, a piezoelectric element having electrodes formed on both surfaces of a piezoelectric material is fixed to one or both main surfaces. In the piezoelectric sounding body in which the peripheral portion of the piezoelectric vibration plate is fixed to the storage case with an adhesive, at least a region on both main surfaces of the piezoelectric vibration plate to which the adhesive is applied is provided with irregularities in a parallel ring shape from a peripheral edge. It is characterized by having been established.

Here, as the unevenness, since the thickness of the pressure transmitting diaphragm is as thin as about 20 to 100 μm, the unevenness has a height of 0.1 to 0.4 mm. , 0.
About 2 to 6 sets of parallel rings are provided at a pitch of 1 to 0.4 mm (in the case of a circular piezoelectric vibrating plate, concentric rings are provided).

When the piezoelectric vibrating plate is formed in this manner, the above-mentioned irregularities are provided from the peripheral edge of the piezoelectric vibrating plate to the entire area where the adhesive is applied. And the adhesive applied to the bonding area in the peripheral part of the piezoelectric vibrating plate becomes a wall due to the unevenness and does not flow into the inside. However, the width required for fixing the piezoelectric vibration plate to the storage case is small, which is effective for miniaturization, and the adhesive is fixed to the inside of the vibration of the piezoelectric vibration plate to deprive the elasticity of the piezoelectric vibration plate. The possibility of adversely affecting the vibration is avoided.

Here, the cross-sectional shape of the irregularities is not particularly limited, but the thinner the piezoelectric vibrating plate, the better the acoustic characteristics (sound pressure characteristics and frequency characteristics). It is necessary to take into account the fact that the area of the piezoelectric vibrating plate becomes smaller due to the size reduction and that the vibrating surface must be secured as much as possible, and that the bonding area (bonding applied surface) to the storage case is required to be narrow. Comes out.

In this regard, it is difficult to provide literally irregularities (thicknesses of the irregularities are locally thinner than the thickness of the diaphragm) in the peripheral portions of both main surfaces of the piezoelectric diaphragm ( If the lid is too thin, vibration intensity cannot be secured.)

According to the second aspect of the present invention, in addition to the effect of preventing the adhesive from flowing out due to the unevenness, the adhesive for the piezoelectric vibration plate is applied so that the cross-sectional shape of the unevenness becomes a plurality of continuous triangular waves. A piezoelectric sounding body characterized in that the peripheral portion to be formed is bent, and is sufficient even if the application surface of the adhesive is limited to a small area (that is, even if the width of the application area in the radial direction is narrowed). A plurality of irregularities (walls) can be provided while securing the bonding area with the adhesive (the height can be adjusted to reduce the pitch), and the thickness of the piezoelectric diaphragm is not changed locally. The formation of a triangular wave (wall) with a constant thickness (that is, without reducing the strength of the piezoelectric diaphragm) can be easily realized by means of bending.

[0020]

Embodiments of the present invention will be described in detail with reference to 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 (a) of the piezoelectric element of the piezoelectric sounding body and an enlarged cross-sectional view (b) for explaining the state of the piezoelectric diaphragm adhered and fixed to the storage case.

FIG. 3 is a sectional view showing an embodiment of a piezoelectric sounding body according to claim 2 of the present invention.

FIG. 4 is an enlarged sectional view for explaining the peripheral shape of the piezoelectric diaphragm of the piezoelectric sounding body.

In FIG. 1, a piezoelectric sounding body 20 includes a peripheral portion 16 of a piezoelectric vibration plate 15 in which electrodes 3 and 4 formed on both surfaces of a piezoelectric material 2 are fixed to one main surface 15a. 2 is fixed by an adhesive 8, and particularly, as shown in FIG.
At least a region 15a and 15b (approximately corresponding to the peripheral portion 16) on which the adhesive 8 is applied are provided with irregularities 17 (only the concave portion is indicated by reference numeral 17 for convenience) from the peripheral edge in a parallel ring shape. I do.

First, the piezoelectric vibrating plate 1 can be arranged even in the adhesive applied area x having the same width as the conventional one by the provision of the irregularities 17.
Thus, a large contact area between the peripheral portion 16 and the adhesive 8 can be ensured.

Second, when the adhesive 8 is applied, irregularities 17
Becomes a “pool” or a “wall”, and the adhesive 8 is placed inside the piezoelectric vibration plate 15 (the center side where the piezoelectric element 1 is disposed).
Outflow (intrusion) to the building is suppressed.

The irregularities 17 can be formed, for example, by forming grooves concentrically around the periphery of a conventional flat circular piezoelectric vibrating plate 5.

At this time, it is important to provide a plurality of irregularities (grooves) from the peripheral edge of the piezoelectric vibrating plate to the inner end of the adhesive application region x.

By the way, the piezoelectric sounding body has been reduced in size and thickness.
There is a strong demand for improved acoustic characteristics, and in order to meet this demand, piezoelectric diaphragms have also become tens of microns thick.

However, if the irregularities formed on the peripheral portion of the thin piezoelectric vibrating plate 15 have the groove shape as described above, the peripheral portion becomes a thinner portion, and the vibration intensity particularly at the inner groove portion may be weakened. Come up. (The acoustic characteristics are improved as the thickness becomes thinner, but it is a problem even if the thickness is too thin.) In addition, the size of the piezoelectric vibrating plate also becomes smaller due to the miniaturization, and the adhesive applied area x with the storage case to secure the area of the vibrating portion. Should be as small as possible.

In order to respond to this, in the embodiment shown in FIG. 3 and FIG. As described above, the peripheral portion of the piezoelectric vibration plate to which the adhesive is applied is bent.

In the triangular wave cross section as the irregularities, the thickness of the piezoelectric vibrating plate is constant up to the peripheral edge, and there is no problem that the thickness is too thin. Also, the pitch of the triangular waves can be adjusted to form a large number of irregularities and adhere. The area becomes wider than in the above-described embodiment.

In addition, since the unevenness can be formed by bending, the unevenness can be formed very easily.

The adhesive 8 is most preferably a silicone resin adhesive having a high elasticity.

Further, the shape of the storage case 9 and the structure for engaging with the piezoelectric vibrating plate are not particularly limited to the above-described embodiment, but the present invention is based on the premise that an adhesive is used.

[0037]

According to the first aspect of the present invention,
The effect of strengthening the fixing of the piezoelectric vibrating plate to the storage case and preventing the adhesive from flowing into the inside of the piezoelectric vibrating plate to prevent the acoustic characteristics from being affected is obtained.

Further, the invention described in claim 2 is the same as the claim 1.
In addition to the effects of the invention described above, an effect that only a small adhesive application area is required while securing strength is obtained as a measure corresponding to downsizing of the piezoelectric sounding body and thinning of the piezoelectric vibration plate.

[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.

FIGS. 2A and 2B are a perspective view of a piezoelectric element of the piezoelectric sounding body according to claim 1 of the present invention and an enlarged cross-sectional view for explaining a state of a piezoelectric vibrating plate adhered and fixed to a storage case. .

FIG. 3 is a sectional view showing an embodiment of a piezoelectric sounding body according to claim 2 of the present invention.

FIG. 4 is an enlarged cross-sectional view for explaining the peripheral shape of the piezoelectric diaphragm of the piezoelectric sounding body according to claim 2 of the present invention.

FIG. 5 is a sectional view showing the structure of a conventional piezoelectric sounding body.

FIG. 6 is an enlarged sectional view showing a peripheral portion of a piezoelectric vibrating plate bonded and fixed to a storage case in a conventional piezoelectric sounding body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Piezoelectric material 3, 4 Electrode 5, 15, 25 Piezoelectric vibrating plate 6 Sound emission hole 7 Piezoelectric element 8 Adhesive 9 Storage case 10, 20, 30, Piezoelectric sound generator 16 Peripheral part 17 Unevenness (groove) 27 Triangular wave ( Irregularities) 26 convex

Claims (2)

[Claims] 1. A piezoelectric sounding body comprising: a piezoelectric element having electrodes formed on both surfaces of a piezoelectric material fixed to one or both main surfaces; and a peripheral portion of a piezoelectric vibration plate fixed to a storage case with an adhesive. A piezoelectric sounding body characterized in that at least a region on both main surfaces of a piezoelectric vibrating plate to which an adhesive is applied is provided with concavities and convexities from a peripheral edge in a parallel ring shape. 2. The piezoelectric sounding body according to claim 1, wherein a peripheral portion of the piezoelectric vibrating plate to which an adhesive is applied is bent so that a cross-sectional shape of the unevenness becomes a plurality of continuous triangular waves.