JPS6029279Y2 - piezoelectric sounding body - Google Patents

Description

[Detailed description of the invention] This invention vibrates a piezoelectric diaphragm with a monomorph structure in which a piezoelectric ceramic plate and a thin elastic plate such as a metal plate are bonded together, or a piezoelectric diaphragm in a bimorph structure in which piezoelectric ceramic plates are bonded together. Another object of the present invention is to flatten the sound pressure-frequency characteristics of a piezoelectric sounding body having a structure that generates sound as a source.

A conventional piezoelectric sounding body has a structure in which a single piezoelectric diaphragm is held in a case 3, as shown in the cross section of its basic structure in Fig. 1, and Fig. 1a shows a case 3 that supports the periphery of the diaphragm. The structure shown in FIG. 1 is a structure that supports the vibration nodes of the diaphragm.

In the figure, 1 is a piezoelectric ceramic plate, 2 is a metal plate that is bonded to the piezoelectric ceramic plate 1 to form a piezoelectric diaphragm, and 4 is a signal voltage applied to an electrode (not shown) of the piezoelectric ceramic plate 1. This is the lead wire.

This piezoelectric sounding body has features such as extremely low power consumption, thinness, and light weight, and has recently been used in many devices as a buzzer that generates a single frequency sound.

However, in this conventional piezoelectric sounding body, the diaphragm has very sharp resonance characteristics, so as shown in Figure 2, the level becomes very high near the resonance frequency, and the level change depending on the frequency is usually very large. It is.

Therefore, when this sounding body is used as a melody or voice speaker, only sounds of specific frequencies are emphasized, which is a major drawback in reproducing natural sounds.

The present invention eliminates these conventional drawbacks and provides a piezoelectric sounding body that can flatten the frequency characteristics of sound pressure and reproduce natural melodies and voices.

The piezoelectric sounding body according to the present invention is characterized by the fact that multiple piezoelectric diaphragms are installed in one case.
A description will be given below with reference to FIG. 3 showing one embodiment.

In FIG. 3, 5 and 6 are piezoelectric ceramic plates, and 7 and 8 are metal plates bonded to the piezoelectric ceramic plates 5 and 6, respectively. The piezoelectric ceramic plate 6 and the metal plate 8 constitute a second piezoelectric diaphragm, and these two piezoelectric diaphragms have different resonant frequencies due to their different sizes, thicknesses, materials, etc. It is set as follows.

These two piezoelectric diaphragms are installed in the case 9 with predetermined intervals in the thickness direction and are supported around the periphery, and the case 9 has through holes 1 corresponding to the first and second piezoelectric diaphragms.
1 and 12 are provided.

Further, 10 is a lead wire for simultaneously applying a signal voltage to the electrodes of the piezoelectric ceramic plates 5 and 6.

In this configuration, the through holes 1i and 12 are provided corresponding to the first and second piezoelectric diaphragms, so that a dense space is not formed by the first and second piezoelectric diaphragms, and the first and second piezoelectric diaphragms do not form a dense space. The piezoelectric diaphragm 2 is vibrated without any restrictions.

Therefore, the first and second piezoelectric diaphragms vibrate independently depending on the signal voltage applied by the lead wire 10, and their resonance frequencies are different, so the overall sound pressure characteristics 2 are as follows: It is possible to add the sound pressure characteristics of a piezoelectric diaphragm.

That is, at frequencies where the sound pressure produced by the first piezoelectric diaphragm is low, the sound pressure is not compensated for by the second piezoelectric diaphragm, and conversely, at frequencies where the sound pressure produced by the second piezoelectric diaphragm is low, the sound pressure is compensated by the first piezoelectric diaphragm. It can compensate for sound pressure.

FIG. 4 shows another embodiment of the piezoelectric sounding body of the present invention, in which two piezoelectric diaphragms are each supported by a case 9 at their vibration nodes.

In FIG. 4, the same parts as in FIG. 3 are indicated by the same numbers.

In both Figures 3 and 4 above, the piezoelectric diaphragm is illustrated using a monomorph structure in which a piezoelectric ceramic plate and a metal plate are bonded, but the present invention is equivalent to a bimorph structure in which piezoelectric ceramic plates are bonded together. Needless to say, this effect can be obtained.

Further, in place of the metal plate, another thin elastic plate such as a film-like diaphragm may be used.

Furthermore, it is not necessary to use two piezoelectric diaphragms, and a large number of piezoelectric diaphragms with slightly different resonant frequencies may be used, and the more piezoelectric diaphragms are used, the smaller the change in level of sound pressure due to frequency can be.

When two piezoelectric diaphragms are used, the first resonance frequency of the second piezoelectric diaphragm is set between the first resonance frequency and the second resonance frequency at which the sound pressure of the first piezoelectric diaphragm decreases. It is most effective to do so.

An example of the sound pressure-frequency characteristics in this case is shown in FIG.

The piezoelectric sounding body of the present invention uses multiple piezoelectric diaphragms with different resonance frequencies, as shown in the characteristics shown in Figure 5, so they do not mutually compensate for the sound pressure, and the frequency of the sound pressure is significantly greater than that of conventional piezoelectric diaphragms. It is possible to reduce level changes, and when playing melodies and voices, it can be played back faithfully.
It is very useful in practice.

[Brief explanation of drawings]

Figures 1a and b are cross-sectional views of a conventional piezoelectric sounding element with peripheral support and node support, respectively; Figure 2 is a diagram showing an example of the sound pressure-frequency characteristics of a conventional piezoelectric sounding element; and Figure 3. The figure is a cross-sectional view showing one embodiment of the piezoelectric sounding element according to the present invention when peripherally supported, FIG. 4 is a cross-sectional view showing another embodiment of the present invention when the joint is supported, and FIG. FIG. 3 is a diagram showing an example of the sound pressure-frequency characteristics of the piezoelectric sounding body according to the invention. 5.6...Piezoelectric ceramic plate, 7. Death: Metal plate, 9: Case.

Claims (1)

[Scope of utility model registration request] A plurality of piezoelectric diaphragms having mutually different resonance frequencies are housed in the same case at intervals in the thickness direction, and through holes are formed in the same direction on opposing surfaces of the case of each of the plurality of piezoelectric diaphragms. A piezoelectric sounding body.