JPS5928120B2 - piezoelectric electroacoustic transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a piezoelectric electroacoustic transducer using a monomorph piezoelectric vibrator. There is a piezoelectric electroacoustic transducer that utilizes the bending vibration of a child, but in order to use it as a car horn, the output sound pressure must be similar to that of a dog, and the tone must be audibly suitable for the purpose.

A conventional monomorph piezoelectric vibrator has a structure in which a diaphragm and a piezoelectric element are directly bonded, and the output sound pressure is about 105 dB at a distance of 1 m in front.

On the other hand, if an attempt is made to obtain a large output sound pressure by increasing the input excitation voltage, there is a problem that the piezoelectric element will be damaged.

Therefore, as shown in FIG. 1, by interposing a metal disk 2 between a diaphragm 1 and a circular piezoelectric element 3,
A piezoelectric vibrator has been proposed in which the mechanical impedance is matched, the piezoelectric element 3 is not damaged, and the output sound pressure is high.

However, with this type of structure, there is only one resonance point as shown in Figure 2, so if you operate it at this resonance frequency to obtain maximum output, the tone will be extremely monotonous and high-pitched, which is similar to car horns, etc. It was inappropriate to use it for

Therefore, there is a method of amplitude modulating at a frequency of 200 to 500 H2 to improve the tone, but even with this method, if the piezoelectric vibrator does not have a resonance point corresponding to the sideband frequency of the amplitude modulated wave, the desired The present invention was made to solve the above problem, and it is possible to improve the frequency characteristics of the piezoelectric vibrator by changing the shape of the metal plate interposed between the piezoelectric element and the diaphragm. It is an object of the present invention to provide a piezoelectric electroacoustic transducer that has an audibly appropriate tone color by adjusting the characteristics.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 shows an embodiment of the present invention, in which 14 is a piezoelectric vibrator according to the present invention, 11 is a circular diaphragm,
12 is a metal plate.

The metal plate 12 has an outer diameter that is intermediate between that of the diaphragm 11 and the piezoelectric element 13, and is cut out around the periphery so as to have a shape other than a circle.

13 is a circular piezoelectric element made of porcelain such as zircon or lead titanate which is polarized in the thickness direction.

Then, a diaphragm 11, a metal plate 12, a piezoelectric element 13
are joined with their centers aligned.

Next, the relationship between the metal plate 12 and the resonant frequency fr will be discussed.

Generally, the resonance frequency fr of the bending vibration of a disc-shaped piezoelectric element is I am in awe of this.

Here, t is the thickness of the piezoelectric vibrator, r is the radius, E is Young's modulus, ρ is the density, Iσ is Poisson's ratio, α is a constant determined by the vibration mode, etc.

Therefore, the appearance of the metal plate 12 is
Since it is related to the Young's modulus E1 and the density ρ, the metal plate 12
If the shape of is changed, the value of 5 changes, and the resonant frequency fr changes.

FIG. 4 shows the frequency characteristics of the piezoelectric vibrator 14 shown in FIG. 3, which has bimodal physical properties with two resonance frequencies, frl and fr2.

Therefore, since the tone color output is performed at two output frequencies of the resonance frequency frl and fr2, an audibly appropriate tone color is obtained, and the output sound pressure is also uniform.

As described above, according to the present invention, the opposing sides are arranged in an arc shape between the circular diaphragm and the circular piezoelectric element, and the other opposing sides are interposed with a metal plate with a notch. Since the output sound pressure can be obtained and the frequency characteristic becomes a bimodal characteristic, a timbre output in which a plurality of timbres are overlapped can be obtained, and an audibly appropriate timbre can be obtained.

The present invention has been variously explained above with reference to preferred embodiments, but the present invention is not limited to these embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. That's true.

[Brief explanation of drawings]

Fig. 1 is a plan view of a conventional piezoelectric vibrator, Fig. 2 is a frequency characteristic diagram of the piezoelectric vibrator shown in Fig. 1, and Fig. 3 is a plan view showing an embodiment of the piezoelectric vibrator according to the present invention. 4 are frequency characteristic diagrams of the piezoelectric vibrator shown in FIG. 3. DESCRIPTION OF SYMBOLS 1...Diaphragm, 2...Metal disk, 3...Piezoelectric element, 11...Diaphragm, 12...Metal plate, 13 ...Piezoelectric element, 14...Piezoelectric vibrator, 15...
・The center point of the piezoelectric element.

Claims (1)

[Claims] 1. In a piezoelectric electroacoustic transducer in which a metal plate is interposed between a piezoelectric element and a diaphragm, the piezoelectric element and the diaphragm are formed into a circular shape, and the metal plate is cut out except for the opposing periphery of the disc. A piezoelectric electroacoustic transducer characterized in that it is formed into a shape, and is formed by bonding a piezoelectric element, a diaphragm, and a metal plate, and has bimodal frequency characteristics.