JPS6221120Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a piezoelectric alarm device that generates sound by bending and vibrating a piezoelectric vibrator using an electric circuit.
The objective is to provide a piezoelectric alarm that emits an audible sound of high volume and low frequency. Note that the piezoelectric alarm device that is loud and sensitive to low frequencies is one that has a sound pressure of approximately 115 dB at a distance of 1 meter in front of the vehicle, such as a car horn, and has a fundamental frequency of several hundred Hz, or something similar to that. Refers to something that has excellent performance.

Conventional piezoelectric alarms are generally known as piezoelectric buzzers, but the sound level generated is at most 1m in front.
100db, and the resonant frequency of the tone is 2KHz
It is a simple harmonic sound of ~4KHz. Therefore, until now, there has been no piezoelectric alarm device that can be put to practical use as a horn for automobiles.

In order to achieve the above objectives, this invention improves the sound generation structure for sound pressure, and utilizes the beat phenomenon created by each simple harmonic audible sound by bending and vibrating two piezoelectric vibrators for tone. This is how it was done. An embodiment of this invention will be described with reference to the drawings. In the figure, reference numerals 1 and 2 are composite piezoelectric vibrators (hereinafter simply referred to as vibrators) that efficiently convert radial vibration energy of a piezoelectric element into acoustic energy. The vibrators 1 and 2 are composed of piezoelectric elements 3 and 4 made of porcelain such as zircon and lead titanate that are polarized in the thickness direction, and bending vibrations in the thickness direction that efficiently perform radial expansion and contraction due to the electrostrictive effect of the piezoelectric elements 3 and 4. It consists of metal plates 5 and 6 for increasing sound pressure, and diaphragms 7 and 8 for sound pressure amplification, which are bonded together with an adhesive via the metal plates 5 and 6, respectively. In an electroacoustic exchanger having such a structure, the inserted metal plates 5 and 6 serve as mechanical impedance matching devices, so that even relatively small piezoelectric elements 3 and 4 can drive large diaphragms 7 and 8. becomes. In this embodiment, the diaphragms 7 and 8 are drawn and curved at the peripheral portions in order to prevent the acoustic output from being diminished due to the tilting phenomenon. The difference between the vibrators 1 and 2 is that the diaphragm 7 and the diaphragm 8 are slightly different in size, and this is a feature of this invention. Reference numeral 9 denotes an electric circuit that vibrates the vibrators 1 and 2 at their respective natural bending frequencies. Reference numeral 10 designates a reflector for amplifying sound pressure. This reflector 10 has a recess formed in the center of the front surface, and after storing the electric circuit 1 in the recess, the recess is closed by filling the recess with a filler. The shape of the reflector 10 may be a flat plate or a horn shape, but it is preferable to have a shape similar to the diaphragm as shown in the figure, that is, a curved shape in which the peripheral portion is concave toward the front. 12 is a support that connects the vibrator 1 and the reflector 10, and 13 is a support that connects the vibrator 1 and the vibrator 2, which is bonded to the nodal portion of the vibrator when it resonates. It is usually made of an elastic material such as a sponge material.

In the above component, the first vibrator 1 has a reflector 1 with an appropriate interval determined by the bending frequency so that the curved shape of the peripheral portion becomes concave toward the front surface.
0 via a support 12, and the second vibrator 2 is arranged so that the curved shape of the peripheral portion thereof becomes concave toward the front surface and with an appropriate interval determined by the flexural frequency. The first vibrator 1 is disposed in front of the first vibrator 1 via a support 13 so as to also serve as a reflector for the second vibrator 2.

First, let's talk about the sound pressure in the above configuration.
The first vibrator 1 has improved structure of the vibrator itself, the effect of the reflector 10, and the fact that the outer diameter of the second vibrator 2 is smaller than that of the first vibrator 1. Although the second vibrator 2 is disposed so as to cover the front surface), the sound pressure emitted from the first vibrator 1 is large enough to achieve the original purpose. (The value is almost the same as when the second oscillator 2 is not placed in the front.) The second oscillator 2 is a structural improvement of the oscillator itself, and the first oscillator 1 acts as a reflector. Due to the action and effect, the sound pressure emitted by the second vibrator 2 is large and its value is almost the same as the sound pressure emitted by the first vibrator 1 (despite the diameter of the diaphragm being smaller than the first vibrator 1). They are equivalent.
The fact that the respective sound pressures are approximately at the same level has an important meaning for the timbre described below. Regarding timbre, the first vibrator 1 and the second vibrator 2 have different natural frequencies because their diaphragms have different diameters. The sound produced by each element alone is a high-frequency simple harmonic sound. However, when they vibrate simultaneously, due to the beat phenomenon produced by each simple harmonic sound, the human hearing senses the sound as a low-frequency sound with a difference in frequency. Furthermore, what is important here is that the sound pressures emitted from the two vibrators are approximately at the same level. If these levels are different, as the distance from the sound source increases, the beat phenomenon will not be felt and the sound will become a simple harmonic sound with a higher sound pressure level. However, according to the present invention, as mentioned above, the sound pressure levels emitted from the two vibrators are almost the same, so no matter where they are from the sound source, the sound is perceived as a low difference in their respective vibration frequencies. .

To give a numerical example of the present invention, the piezoelectric elements 3 and 4 are made of zircon-lead titanate porcelain with an outer diameter of 36 mmφ and a thickness of 0.5 mm, polarized in the thickness direction, and the metal plates 5 and 6 are made with an outer diameter of 50 mmφ and a thickness of 0.5 mm. 0.5mm brass plate,
Diaphragm 7 has an outer diameter of 92mmφ and a flat plate part of 50mmφ.
(peripheral part is curved), 0.3mm thick brass plate, outer diameter 86mmφ as diaphragm 8, flat plate part 50mmφ
(The peripheral part has a curved shape), a brass plate with a thickness of 0.3 mm is used, and these are adhered with epoxy adhesive to constitute the transducers 1 and 2. ), a first vibrator 1 is arranged on the front surface of the oscilloscope with a support 12 having a thickness of 5 mm interposed therebetween, and a second vibrator 2 is disposed on the front surface of the
is placed between the first vibrator 1 and the support 13 with a thickness of 3 mm, the electric excitation input of 2 W is 1 m.
The maximum sound pressure in front is when only the first vibrator 1 is used.
It reached 114db, 113db when only the second vibrator 2 was driven, and about 117db when driven at the same time. Furthermore, their respective natural frequencies are 2800Hz and 3100Hz, so the human hearing senses it as a low frequency sound of 3100Hz - 2800Hz = 300Hz.

As mentioned above, this invention improves the sounding structure and makes use of the beat phenomenon created by the two vibrator's flexural vibrations, so it is also very effective in piezoelectric alarms. It has the excellent effect of being able to emit an audible sound that is both loud and low-frequency. Therefore, the use of the piezoelectric alarm device can be extended to fields such as automobile horns, which is an extremely excellent practical effect.

[Brief explanation of the drawing]

The drawings show one embodiment of the piezoelectric alarm according to the present invention, and FIG. 1 is a plan view thereof, FIG. 2 is a sectional view taken along line A-A' in FIG. 1, and FIG. Figure 2
It is a sound pressure waveform diagram of the piezoelectric alarm device shown in the figure. DESCRIPTION OF SYMBOLS 1... First piezoelectric vibrator, 2... Second piezoelectric vibrator, 3... First piezoelectric element, 4... Second piezoelectric element, 5... First metal plate, 6... Second metal plate, 7...first diaphragm, 8...second diaphragm, 10...reflector.

Claims (1)

[Scope of utility model registration request] a first piezoelectric vibrator that integrates a piezoelectric element, a metal plate, and a first diaphragm; and a second piezoelectric vibrator that is slightly smaller in size than the piezoelectric element, metal plate, and first diaphragm.
It consists of a second piezoelectric vibrator integrated with a diaphragm and a reflector for amplifying sound pressure, a first piezoelectric vibrator is disposed in front of the reflector, The second piezoelectric vibrator is connected to the first piezoelectric vibrator so that the vibrator serves as a reflector for the second piezoelectric vibrator.
A piezoelectric alarm device characterized in that a piezoelectric vibrator is disposed in front of the piezoelectric vibrator.