JPS63257400A - Piezoelectric speaker - Google Patents

Abstract

PURPOSE:To obtain picture quality with less distortion by adhering a piezoelectric vibrator and a film to the circumferential ridge of the piezoelectric vibrator. CONSTITUTION:The piezoelectric vibrator 16 is arranged at the midpoint of the film 20 and adhered to the inner circumferential ridge 20e of the film 20 at its circumferential part 16a by means of an adhesives or the like. The piezoelectric vibrator 16 is supported by the film 20 at the circumferential part 16a, then the load of the circumferential part 16a is large and the free motion hardly takes place in comparison with the midpoint and the circumferential part 16a acts like a vibration node. Thus, no irregular vibration takes place and the frequency characteristic is smooth without any dips and notches. Thus, excellent sound quality with less distortion is attained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a piezoelectric speaker using a piezoelectric vibrator.
It has improved sound quality compared to the conventional one.

[Conventional technology]

Piezoelectric speakers using piezoelectric vibrators can be made thinner than dynamic speakers, so they can be incorporated into small televisions, radios, and the like. However, conventional piezoelectric speakers do not provide sufficient sound quality.

The structure of a conventional piezoelectric speaker is shown in FIGS. 2 and 3.

The piezoelectric speaker shown in Fig. 2 has a circular diaphragm 12 made of gold B% or the like.
Ceramic with a smaller diameter than this in the center! ! A piezoelectric vibrator 16 is constructed by pasting a first grade piezoelectric element 14, and the peripheral edge of the diaphragm 12 is directly supported by a ring-shaped support member 26 (
In this application, the term "support" is used to include the case of fixing.

). By applying an audio signal or the like between the upper and lower surfaces of the piezoelectric element 14, the piezoelectric vibrator 16 vibrates,
Sound waves are emitted.

In the piezoelectric speaker shown in FIG. 3, a piezoelectric vibrator 16 in which a piezoelectric element 14 is attached to a diaphragm 12 is attached to a film 2o made of plastic or the like having a larger diameter than the piezoelectric vibrator 16, and the peripheral edge of the film 20 is attached to a supporting member 20. It was supported by

[Problem that the invention seeks to solve]

In the piezoelectric speaker 1o shown in FIG. 2, the diaphragm 12 made of gold B or the like is directly supported by the support member 26, so the frequency characteristics in the open back state as shown in FIG. 6 are as shown by the solid line in FIG. The sound quality was harsh, with severe undulations, no extension in the low range, and an emphasis on the high range.

Furthermore, the frequency characteristics in the sealed back state as shown in FIG. 7 were as shown by the dotted line in FIG. 4, with the high frequency being more emphasized. For this reason, the frequency characteristics are affected by the back space of the mounting case, and for example, when the back is W! When used in a closed ultra-thin case, sufficient sound quality could not be obtained.

In the piezoelectric speaker shown in FIG. 3, the diaphragm 12 is
Since the film 20 is supported by the support member 26 through the film 20, the undulations are compensated for by the internal loss of the film 20, and the frequency characteristics in the open back state are as shown by the solid line in FIG. 5, which is similar to the piezoelectric speaker in FIG. Compared to , the low range is extended and a softer sound can be obtained.

However, since the film 2o is adhered to the entire surface of the piezoelectric vibrator 16, the supporting position (vibration fulcrum) of the piezoelectric vibrator 16 by the film 2o is unclear, and as shown in FIG. The sound quality was distorted and distorted.

In addition, the frequency response with the back sealed is that there is no extension in the low range as shown by the dotted line in Figure 5, and it is not sufficient to use it in an ultra-thin layer case with the back sealed like the piezoelectric speaker in Figure 2. I couldn't get the sound quality.

The present invention aims to solve the problems in the conventional technology and provide a piezoelectric speaker that provides good sound quality with little distortion.

Means for Solving Problem C] This invention is an improvement on the film-attached piezoelectric speaker shown in FIG. The film is attached to the periphery of the piezoelectric vibrator (in other words, the piezoelectric vibrator has a central portion where no film is attached).

(Function) According to this invention, since the film is attached to the circumferential R portion of the piezoelectric vibrator, the load on the circumferential edge of the piezoelectric vibrator increases, making it difficult to move freely compared to the central portion. (For this reason, the support position (vibration fulcrum) of the piezoelectric vibrator by the film becomes the peripheral edge position to which the film is attached, making it difficult to stop irregular distortion, and providing sound quality with less distortion.

In addition, as will not be shown in the examples described later, the surface of the piezoelectric vibrator may be exposed from the outside! By attaching a film that forms a FA cavity, its resonance effect will provide good bass sound quality even when the back is sealed, and even when used in an ultra-thin case with the back sealed. You can get good sound quality. The film forming this cavity can be constructed integrally or separately from the film supported by the above-mentioned support member. Also,
If this cavity is configured to have a substantially trapezoidal cross section, a cavity with a large volume can be obtained even if the height is low, and the resonance effect is improved. Furthermore, if a recess is formed in the center of the film forming the approximately trapezoidal cavity, irregular vibrations of the film on the upper surface of the trapezoid can be prevented and the sound quality can be further improved.

[Example 1] An example of the present invention is shown in FIG. The piezoelectric vibrator 16 is a circular diaphragm 12 made of special metal (brass, etc.) with a piezoelectric element 14 made of ceramic or the like having a smaller diameter placed in the center of the diaphragm 12.
It is constructed by pasting.

The film 20 is made of a thin, hard-to-deform material such as a resin film such as PET (polyethylene terephthalate, polyester, polycarbonate, or vinyl chloride), paper (synthetic paper, etc.), or paper coated.The thinner the film, the lower the sound. Easy, but difficult to process, so 30-5
A thickness of about 0 μm is appropriate. The film 20 is formed into a ring shape with a hole 22 having a diameter b1 approximately the same as that of the piezoelectric element 14 in the center thereof.

The piezoelectric vibrator 16 is arranged at the center of the film 20, and its peripheral edge 16a is attached to the inner peripheral edge 20e of the film 20 with an adhesive or the like.

The outer peripheral edge 20c of the film 20 is supported by the support member 26 in a tensioned state (taut state). By applying an audio signal or the like between the upper and lower surfaces of the piezoelectric element 14, the piezoelectric vibrator 16 vibrates and generates sound.

According to this piezoelectric speaker, since the piezoelectric vibrator 16 is supported by the film 20 at its peripheral edge 16a, the peripheral edge i5a
The load is large, making it difficult to move freely compared to the central portion, and as shown in FIG. 9, this peripheral portion 16a serves as a vibration fulcrum. Therefore, the film 20 shown in FIG.
Compared to the case where the piezoelectric vibrator 16 is affixed to the entire surface of the piezoelectric vibrator 16, irregular vibrations are less likely to occur, and its frequency characteristics have gentle undulations as shown in FIG. Therefore, good sound quality with little distortion can be obtained.

(Example 2) Another example of the present invention is shown in FIG. Further, a plan view thereof is shown in FIG. 12, and a rear view thereof is shown in FIG. 13, respectively.

The piezoelectric vibrator 16 is made by attaching the piezoelectric element 14 to the diaphragm 12. Lead wires 24 and 24 are connected to the piezoelectric element 14 and the diaphragm 12 for applying audio signals and the like between the upper and lower surfaces of the piezoelectric element 14. The piezoelectric vibrator 16 is attached to the film 20.

The film 20 has a circular shape, and a trapezoidal protrusion 20a is formed in the center thereof, and a step 20b is formed at a position on the outer periphery of the protrusion 20a. Further, the film 20 is supported in a tensioned state by having its peripheral edge portion 20c sandwiched between ring-shaped support members 26°26. The same materials as in the first embodiment can be used for the piezoelectric vibrator 16 and the film 20.

The piezoelectric vibrator 16 is arranged in the center of the film 20,
It is attached to the film 20 with an adhesive or the like. The piezoelectric vibrator 16 may be attached with the piezoelectric element 14 placed on the side facing the film 20, or may be placed and attached on the opposite side, but considering the drawing out of the lead wire 24, , 11th
It is easier to pull out if you place and paste it on the opposite side as shown in the diagram. The stepped portion 20b is formed at a position having approximately the same diameter as the piezoelectric vibrator 16, and plays a positioning role when arranging the piezoelectric vibrator 16.

The diameter of the protrusion 20a of the film 20 (the diameter of the trapezoidal bottom) is
The diameter is approximately equal to the diameter of the piezoelectric element 14. Therefore, the piezoelectric vibrator 16 is connected to the film 20 at its peripheral edge 16a.
will be affixed to.

When the piezoelectric vibrator 16 is attached to the film 20, a cavity 28 having a trapezoidal cross section and sealed or substantially sealed from the outside is formed between the piezoelectric vibrator 16 and the film protrusion 20a. This cavity 28 creates a resonance effect. Due to this resonance effect, the frequency characteristics are changed to 1! as shown in FIG. [Even in this condition, there is less decrease in low frequencies and increase in high frequencies compared to the open back condition. Therefore, sufficient sound quality can be obtained even when used in an ultra-thin case with the back sealed (good sound quality can be obtained from either side). In addition,
Since the cavity 28 is trapezoidal, a large cavity volume can be obtained even at a lower height than when the cavity 28 is shaped like a sphere, and a large resonance effect can be obtained.

Further, the piezoelectric vibrator 16 has a peripheral edge 16a that is connected to the film 2.
0, the vibration occurs with the piezoelectric vibrator center edge 16a as a fulcrum as shown in FIG.
Because it supports the vibration of ! Vibration is further prevented and sound quality with less distortion can be obtained. Furthermore, the high frequency range is lower than that without the void 1128, resulting in a softer sound quality.

Furthermore, the piezoelectric speaker shown in FIG. 11 can be installed in a device with ff1l on the outside in the drawing, and the support member 26 can be airtightly fixed to the device to obtain a waterproof structure.

Note that the stepped portion 20b of the film 20 not only has a positioning function but also contributes to improving sound quality. That is, the frequency characteristic without the stepped portion 20 is as shown by the dotted line in FIG. 16, whereas when the stepped portion 20 is present, the frequency characteristic is as shown by the solid line in the same figure.

According to this, with the stepped portion 20b, the frequency characteristics have less ups and downs, the characteristic that the low range is extended and the ts range is reduced is reduced by (:1), and the clarity of the real voice is improved.

Further, a trapezoidal film portion 20a forming the cavity 28
A ring-shaped recess 32 is formed in the center of the upper surface as shown in FIG. 17(a), or a conical recess 3 is formed as shown in FIG. 17(b).
0, the abnormal vibrations on the upper surface of the film portion 20a are reduced, and the frequency characteristics become less undulating as shown in FIG. 18, thereby improving the sound quality. Also,
As shown in FIG. 17(C), press the concave portion 31 into
The sound quality is further improved by attaching it to the center of the

Further, by forming a partial notch 12a in the diaphragm 12 as shown in FIG. 20, the peak of the frequency characteristics can be suppressed.

Further, by providing grains (fine irregularities) on the surface of the film 20, internal loss is increased and sound quality is further improved.

[Example 3] In Example 2, the part of the film 20 that supports the piezoelectric vibrator 16 and is fixed to the support member 26 and the part 20a of the film 20 that forms the cavity 20 are integrally molded. Film 20A in Figure 19.

It can also be configured separately like 20B. The film 2OA has a trapezoidal cross section, and its peripheral edge 20d is adhered to the upper surface of the peripheral edge 16a of the piezoelectric vibrator 16 to form a cavity 28. The film 20B is formed into a donut shape, and its inner peripheral edge 20d is adhered to the lower surface of the peripheral edge 16a of the piezoelectric vibrator 16. In addition, the outer peripheral edge 20
c is supported by the support member 26 in a tensioned state.

According to this piezoelectric speaker, since the piezoelectric vibrator 16 is attached and supported by the films 20e and 20d at its peripheral edge 16a, good sound quality can be obtained as in the second embodiment. Note that it is also possible to attach the film 2OA to both the upper and lower surfaces of the piezoelectric vibrator 16.

[Reference example]

Although not included in this invention, if a circular film 20 is pasted on the entire surface of the piezoelectric vibrator 16 as shown in FIG. 21, and a film 21 forming a cavity 28 is further pasted thereon,
A resonance effect by the cavity 28 and a supporting effect (prevention of irregular vibration) of the piezoelectric vibrator peripheral edge IZ16a by the film 21 can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, since the film is attached at the peripheral edge of the piezoelectric vibrator, the support position (vibration fulcrum) of the piezoelectric vibrator by the film is at the peripheral edge where the film is attached. As a result, irregular distortion is less likely to occur, and sound quality with less distortion can be obtained.

In addition, as shown in the above embodiment, if a film that forms a cavity that is sealed from the outside is attached to the surface of the piezoelectric vibrator, its resonance effect will improve the bass sound even when the back is densely packed. Good sound quality is obtained, and sufficient sound quality can be obtained even when used in a very square case with a sealed back. Further, if this cavity is configured to have a substantially trapezoidal cross section, a cavity with a large volume can be obtained even if the height is low, and the resonance effect is improved. Furthermore, if a recess is formed in the center of the film forming the approximately trapezoidal cavity, irregular vibrations of the film on the upper surface of the trapezoid can be prevented and the sound quality can be further improved.

In the above embodiments, the present invention is applied to a circular speaker, but it can be applied to piezoelectric speakers of various shapes such as oval and square.

[Brief explanation of drawings]

FIG. 1 is a top view showing an embodiment of the present invention. FIGS. 2 and 3 are cross-sectional views showing conventional piezoelectric speakers, respectively. FIG. 4 is a frequency characteristic diagram of the piezoelectric speaker of FIG. 2. FIG. 5 is a frequency characteristic diagram of the piezoelectric speaker of FIG. 3. FIG. 6 is a diagram showing the state of use with the back side open. FIG. 7 is a diagram showing the state of use in the back-height IM1. FIG. 8 is a cross-sectional view showing a state in which the piezoelectric vibrator of the piezoelectric speaker shown in FIG. 3 is irregularly distorted. FIG. 9 is a sectional view showing the #i dynamic state of the piezoelectric speaker of FIG. 1. FIG. 10 is a frequency characteristic diagram of the piezoelectric speaker of FIG. 1. FIG. 11 is a sectional view showing another embodiment of the present invention, and is a sectional view taken along the line A--A in FIG. 12. FIG. 12 is a plan view of the piezoelectric speaker of FIG. 11. FIG. 13 is a bottom view of the piezoelectric speaker of FIG. 11. FIG. 14 is a frequency characteristic diagram of the piezoelectric speaker of FIG. 11. FIG. 15 is a sectional view showing the vibration state of the piezoelectric speaker of FIG. 11. FIG. 16 is a diagram showing a change in frequency characteristics due to the stepped portion 20b of the film 20 of the piezoelectric speaker shown in FIG. 11. FIG. 17 is a sectional view showing a state in which a recess is formed in the film portion 20a forming the cavity 28 of the piezoelectric speaker shown in FIG. FIG. 18 is a diagram showing a change in frequency characteristics due to the concavity &i in FIG. 17. FIG. 19 is a sectional view showing another embodiment of the invention. FIG. 20 is a bottom view showing the diaphragm 12 with a partial notch 12a formed therein. FIG. 21 is a sectional view showing a reference example. 12... Vibration plate, 14... Piezoelectric element, 16... Piezoelectric vibrator, 26... Supporting member, 20... Film,
20b...Stepped portion, 28...Cavity, 30.32...
recess.

Claims (5)

[Claims] (1) A piezoelectric vibrator made by pasting a piezoelectric element on a diaphragm is pasted on a film having a peripheral edge extending outward from the piezoelectric vibrator, and the peripheral edge of the film is supported on a support member. What is claimed is: 1. A piezoelectric speaker comprising: the piezoelectric vibrator and a film attached to each other at a peripheral edge of the piezoelectric vibrator. (2) The piezoelectric speaker according to claim 1, wherein a film forming a cavity that is sealed or substantially sealed from the outside is adhered to the surface of the piezoelectric vibrator. (3) The piezoelectric speaker according to claim 2, wherein the film forming the cavity is integrally molded with the film supported by the support member. (4) The piezoelectric speaker according to claim 2 or 3, wherein the cavity has a substantially trapezoidal cross section. (5) The piezoelectric speaker according to claim 4, wherein a recess is formed in the center of the film forming the cavity.