JPH01130699A - Piezoelectric speaker - Google Patents

Abstract

PURPOSE:To obtain a flat frequency characteristic and a high sound pressure by supporting the peripheral part of a diaphragm made of a foaming resin material through a support piece having an elasticity on a frame and disposing a ring shape oscillation absorbing body having the elasticity on the peripheral part of the metal plate of a piezoelectric sounding body. CONSTITUTION:A diaphragm 13 is composed of the foaming resin material, the peripheral part is supported on the frame 14 through the support piece 15 having the elasticity and the elastic ring shape oscillation absorbing body 18 is disposed on the peripheral part of the metal plate 17 of the piezoelectric sounding body having a piezoelectric body 16 and the metal plate 17 concentrically bonded to the surface of the piezoelectric body. Thereby, a split oscillation generated on the peripheral part of the metal plate can be absorbed to obtain the flat frequency characteristic, add the mass of the metal plate by, the oscillation absorbing body and reproduce a low frequency. Since the peripheral part of the diaphragm is supported by the elastic support piece, a distortion is reduced even at the time of a large input, the diaphragm is light and has the suitable rigidity and comparatively large internal loss, so that a sound pressure peak can be effectively absorbed.

Description

[Detailed description of the invention] [Production] "Bori choan taina The present invention relates to a piezoelectric speaker using a piezoelectric sounding body.

As shown in FIG. 5, the conventional piezoelectric speaker 1 has a diaphragm 3 fixed to a frame 2, and the center of the piezoelectric sounding body 4 touches the support member 5 at the center of the diaphragm 3. Supported through. The piezoelectric sounding body 4 includes a metal plate 6 and a pair of piezoelectric bodies 7 having a smaller diameter than the metal plate 6 and concentrically attached to both surfaces of the metal plate 6. The diameter ratio of the metal plate 6 and the piezoelectric body 7 is
Assuming that the diameter of the metal plate 6 is 11 and the diameter of the piezoelectric body 7 is 22, they are selected so as to satisfy the first equation in order to maximize the vibration efficiency of the piezoelectric sounding body 4.

l Also, the material of the diaphragm 3 includes thin sheet metal, thin sheet resin,
Paper, film, etc. are used.

However, in such a center-supported piezoelectric speaker, a resonance point in the primary vibration mode occurs at the periphery of the metal plate 6. Therefore, a large amount of vibration occurs at the peripheral edge of the metal plate 6, thereby producing a sharp sound pressure peak.

Moreover, as mentioned above, the metal plate 6 and the piezoelectric body 7.

The diameter ratio is 0. -7 to about 0.8, therefore, the outer peripheral portion consists of only the metal plate 6, which has lower rigidity than the portion to which the piezoelectric body 7 is bonded. Moreover, in a center-support type piezoelectric speaker, the outer circumference of the metal plate 6 is not constrained in any way, and therefore, the lack of rigidity at the outer circumference causes divided vibration at each frequency, which also causes sharp sound pressure peaks. This causes the sound quality to deteriorate.

Another problem with the conventional piezoelectric speaker 1 is that the material of the diaphragm 3 causes deterioration in sound quality. In other words, when metal or resin is used as the material for the diaphragm 3, although it has high rigidity, it is difficult to obtain high sound pressure due to its weight, and the resonance frequency unique to the material is within the audible body range. , a large sound pressure peak occurs at that frequency, leading to deterioration of sound quality.

Furthermore, when paper or film is used as the material for the diaphragm 3, it lacks rigidity and the diaphragm itself is difficult to make piston movements, resulting in uneven frequency characteristics. In this case, although the sounding body is rigid, the resonance point of the sounding body is strong, and this also has the problem of producing a strong sound pressure peak near the resonance frequency of the sounding body.

The present invention was made in view of the above problems, and an object of the present invention is to provide a piezoelectric speaker that can obtain flat frequency characteristics, high sound pressure, and further improve sound quality. .

The present invention relates to a piezoelectric material having a piezoelectric body and a metal plate having a diameter larger than that of the piezoelectric body and concentrically attached to the surface of the piezoelectric body. A piezoelectric speaker comprising a sounding body, a diaphragm that supports the piezoelectric sounding body via a support member and vibrates to output sound by driving the piezoelectric sounding body, and a frame that supports the diaphragm, wherein the diaphragm is It is made of a foamed resin material, and its peripheral edge is supported by the frame via an elastic support piece, and an elastic annular vibration absorber is provided on the peripheral edge of the metal plate of the piezoelectric sounding body. It is characterized by

According to the above configuration, the periphery of the metal plate of the piezoelectric sounding body has
An annular vibration absorber having elasticity is provided. This makes it possible to absorb split vibrations occurring at the peripheral edge of the metal plate, and to obtain flat frequency characteristics. Furthermore, each time a vibration absorber is provided on a metal plate, the mass of the metal plate is added by the amount of the vibration absorber, and therefore the resonant frequency is lowered, making it possible to reproduce low frequencies.

Furthermore, since the peripheral edge of the diaphragm is supported by an elastic support piece, compliance is increased, distortion is small even when an adult is exerting force, and low-frequency signals can also be faithfully reproduced. Furthermore, since the diaphragm is made of a foamed resin material, it is possible to obtain a diaphragm that is lightweight, has appropriate rigidity, and has a relatively large internal loss, and can effectively absorb the sound pressure peak of the power generation sounding body. Can be done.

, LUwj1 FIG. 1 is a cross-sectional view of a piezoelectric speaker 10 according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken from the section line ■-■ in FIG. 1. This piezoelectric speaker 10 includes a piezoelectric sounding body 11, a diaphragm 13 that centrally supports the piezoelectric sounding body 11 via a support member 12, and vibrates and outputs sound by driving the piezoelectric sounding body 11, and a diaphragm 13 that supports the diaphragm 13. frame 14
and has. The diaphragm 13 is fixed to the frame 14 via an elastic support piece 15. The elastic support piece 15 is made of, for example, urethane foam, rubber, or leather.

The support member 12 has a cylindrical shape, and its upper end is formed to have a large diameter in consideration of adhesion to the diaphragm 13. However, the shape is not limited to this, and an inverted conical shape can also be used.

In this embodiment, the piezoelectric sounding body 11 is of a bimorph type, and has a pair of circular piezoelectric bodies 16 made of PZT or the like and a circular metal plate 17, with the piezoelectric body 16 sandwiching the metal plate 17. configured in the state. The metal plate 17 has a larger diameter than the piezoelectric body 16, and has a larger diameter than the piezoelectric body 16.
and metal plate 17 are attached concentrically. Therefore, the outer periphery of the metal plate 17 extends radially outward from the outer periphery of the piezoelectric body 16. An annular vibration absorber 18 is attached to the lower surface of the peripheral edge 17a of the metal plate 17.

This vibration absorber 18 has elasticity and is made of, for example, foamed plastic or rubber.

By providing the vibration absorber 18 on the periphery of the metal plate 17 in this way, even if the outer periphery of the metal plate 17 becomes the resonance point of the primary vibration mode and attempts to vibrate greatly, in the center-supported piezoelectric speaker 10, the vibration is absorbed. Vibrations are absorbed by the body 18.

Therefore, sound pressure peaks are suppressed, and a flat sound pressure-frequency characteristic can be obtained. Further, by adding the vibration absorber 18, it is possible to absorb the divided vibration caused by the insufficient rigidity of the outer circumferential extension portion 17a of the metal plate 17, and obtain flat frequency characteristics. Furthermore, the addition of the mass of the vibration absorber 18 increases the apparent mass of the metal plate 17 as a vibrating body, which lowers the resonance frequency, making it possible to reproduce from low frequencies. A wide frequency band can be obtained.

FIG. 3 is a graph showing the sound pressure-frequency characteristics of a piezoelectric speaker equipped with the vibration absorber 18 and a piezoelectric speaker not equipped with the vibration absorber 18 by the inventor of the present invention. In FIG. 3, line ml shows the case where the vibration absorber 18 is provided, and line m2 shows the case where the vibration absorber 18 is not provided. As is clear from FIG. 3, it is understood that by providing the vibration absorber 18, the sound pressure peak peculiar to the piezoelectric sounding body 11 can be suppressed, and a flat frequency characteristic can be obtained.

The material of the diaphragm 11 is foamed resin, such as foamed polystyrene. Foamed resin is lighter than resin plates or metal plates, and if the dimensional ratio and density are selected within the ranges described below,
It is a material that is rigid and effective as a diaphragm. Furthermore, since the internal loss is greater than that of materials such as resin plates, metal plates, paper, and films, the sound pressure peaks characteristic of piezoelectric sounding bodies are also suppressed.

Next, regarding the density of foamed resin that can be suitably used as a diaphragm, if the density is too high, the weight will increase and the sound pressure will decrease, and if it is too low, the rigidity will be insufficient. According to experiments, the density is 0. 005~0. 0
It was confirmed that a value of 25 g/cnl was appropriate. Regarding the dimensional ratio of the diaphragm, the thickness of the diaphragm is t,
Diameter of the diaphragm (if the diaphragm is square, the diagonal length)
Letting D be 5≦□≦20 (2) It was confirmed that a relatively flat sound pressure-frequency characteristic can be obtained by setting the range. FIG. 2 shows measured values of sound pressure-frequency characteristics at various size ratios. In the figure,
Line m3 indicates line mO when the size ratio is less than 5 within the range shown in equation (2) above. As can be understood from the figure, line ml has low sound pressure at low frequencies,
A peak occurs in the audible band. In line m5, there is an excessive difference in sound pressure between the low frequency range and the high frequency range, and the frequency characteristics are poor.

On the other hand, line m3 has sufficient sound pressure in the low frequency range, does not have a large peak in the audible range, and exhibits relatively flat characteristics.

In the examples, foamed polystyrene is used as the foamed resin, but foamed polyethylene may also be used (or a copolymer of foamed polystyrene and foamed polyethylene may also be used).

Further, in the embodiment, the support member 12 is formed separately from the diaphragm 13, but they may be formed integrally.

Furthermore, although a bimorph type piezoelectric sounding body 11 is used in the embodiment, it goes without saying that a unimorph type can also be used.

Hahahaha Dust Power Comes As described above, according to the present invention, the following effects are achieved.

(Since an elastic annular vibration absorber is provided at the periphery of the metal plate of the piezoelectric sounding element, it is possible to absorb vibrations occurring at the outer periphery of the metal plate that constitutes the piezoelectric sounding element. Flat frequency characteristics can be obtained.In addition, by providing a vibration absorber, the apparent mass of the metal plate that is the vibrating part increases, which lowers the resonant frequency, making it possible to reproduce from low frequencies. It is possible to widen the frequency band to be reproduced.

(b) Since the diaphragm is made of foamed resin, it is easy to design the diaphragm with an optimal density and dimension ratio, which effectively suppresses the sound pressure peak of the piezoelectric sounding element, which has a relatively large internal loss. It is possible to achieve effects such as being able to absorb a lot of energy, having appropriate rigidity and allowing easy piston movement, and also being able to obtain high sound pressure due to the lightweight nature of the foam.

(C) Since the peripheral part of the diaphragm is supported by the frame via an elastic support piece, compliance is increased, distortion is small even when an adult is exerting power, and low-frequency signals can also be faithfully reproduced. Can be done.

[Brief explanation of the drawing]

The first is a sectional view of a piezoelectric speaker 10 according to an embodiment of the present invention, FIG. 2 is a sectional view taken from the cutting plane line ■-■ in FIG. 1, and FIG. A graph showing the sound pressure-frequency characteristics of the diaphragm 13 and one without it, FIG. 4 is a graph showing the sound pressure-frequency characteristics of three types with different dimensional ratios of the diaphragm 13, and FIG. 5 is a graph showing the sound pressure-frequency characteristics of the conventional piezoelectric speaker. FIG. 10... Piezoelectric speaker, 11... Piezoelectric sounding body, 12
...Support member, 13...Vibration plate, 14...Frame, ■Elastic support piece, 16...Piezoelectric body, 17...
- Metal plate, 18... Vibration absorber. Patent applicant: Murata Manufacturing Co., Ltd. Figure 2 Figure 3 Figure 4 Notification table (Hz)

Claims (1)

[Claims] A piezoelectric sounding body having a piezoelectric body and a metal plate having a diameter larger than that of the piezoelectric body and concentrically attached to the surface of the piezoelectric body; A piezoelectric speaker including a diaphragm that supports the diaphragm and vibrates to output sound by driving a piezoelectric sounding body, and a frame that supports the diaphragm, wherein the diaphragm is made of a foamed resin material and has an elastic periphery. A piezoelectric speaker, characterized in that the piezoelectric speaker is supported by the frame via a support piece, and further includes an elastic annular vibration absorber provided at a peripheral edge of the metal plate of the piezoelectric sounding body.