TWI597990B - Speaker - Google Patents

Description

speaker

About the invention of the speaker.

Among the speakers for headphones, what is well known is a device for docking a piezoelectric element with a vibrating plate.

At this time, it is very important that the piezoelectric element and the vibrating plate as a whole reduce the internal decay rate. The linear distortion of the sound can be controlled by minimizing the attenuation of the wave energy generated by the vibration. In addition, since the attenuation rate is frequency dependent, it is important to reduce the attenuation rate at the frequency at which the attenuation rate is the largest.

In the electric speaker device, as a metal material excellent in sound quality, a material that can suppress energy loss inside the metal is favored. In other words, lightweight and hard materials are best. Representative high-quality metals are titanium and tantalum. These metals are used in advanced audio equipment in the coil-driven electric speaker device, which can improve the acoustic characteristics of the diaphragm itself.

On the other hand, regarding the attachment of the piezoelectric element to the speaker on the metal plate, since the metal plate is attached to the piezoelectric element, bending vibration can occur. According to this configuration, in order to reduce the distortion rate of the output sound, it is necessary to optimize the characteristics of the metal plate and the shape of the piezoelectric element.

In view of this, the present invention has been made in an effort to provide a speaker that can effectively solve the above problems.

The present invention has been made in an effort to provide a speaker in which a metal plate is attached to a piezoelectric element and outputs a sound distortion rate.

Adjusting the area ratio of the metal plate to the piezoelectric element enables low distortion. In general, if the metal plate is a lightweight/hard material, even if the piezoelectric element is attached to the entire surface of the metal plate, the sound transmission of the metal plate outputs a low-distortion sound. On the other hand, if the metal plate is not lightweight and the texture is soft, after the piezoelectric element is attached to the entire surface of the metal plate, especially in the peripheral region of the metal plate, the vibration of the piezoelectric element cannot be sufficiently transmitted, and thus Produces distortion. On the contrary, if the metal plate is not attached to the piezoelectric element, especially if the metal plate is lightweight or hard, it will be distorted because of the sound conduction in the metal plate that is not radiated into the space. . Therefore, the area of the piezoelectric element relative to the metal plate should be larger when the metal plate is a lighter/hard material, and should be smaller when it is not a lighter or soft material.

One of the features of the speaker of the present invention is that in a speaker in which a piezoelectric element is attached to a metal plate and vibrated by a piezoelectric element but a bending vibration of the metal plate, E(kN/mm2) (N is a unit of force Newton) ) indicates the longitudinal elastic modulus of the metal plate, the density is expressed in ρ (g/cm 3 ), the area of the metal plate on the attaching surface is represented by Sm, and the area of the piezoelectric element is represented by Sp, and the formula X = (Sp / Sm) • (ρ The value of X in /E) is between 0.01 and 0.08.

Due to this feature, the metal plate is lightweight and hard (ρ/E small) material, the area ratio (Sp/Sm) of the metal plate and the piezoelectric element is increased, and the metal plate is not lightweight. Soft (ρ/E large) When the material is reduced in area, it becomes a speaker with a low distortion rate. In addition, according to the experiment of the patent applicant, the value of X is most suitable between 0.02 and 0.07, and the distortion rate is small between 0.01 and 0.08 (refer to the following example).

Here, the "longitudinal elastic coefficient" means the elastic modulus in the thickness direction of the metal plate.

The value of X is optimized.

The third feature of the speaker of the present invention is that the metal plate and the piezoelectric element have a substantially similar shape on the attachment surface, and the positions of the center of gravity of the metal plate and the piezoelectric element are substantially identical.

With this feature, the piezoelectric element is mounted at a position away from the edge of the metal plate. The distortion of the edge of the metal sheet is reduced.

The fourth feature of the speaker of the present invention is that it has a through hole penetrating the piezoelectric element and the metal plate.

According to this feature, the metal plate and the piezoelectric element are bonded to each other based on the perforations, and have various resonance frequencies. The frequency characteristics become smooth and the distortion occurring at a specific frequency is alleviated.

According to the present invention, it is possible to provide a product in which a metal plate is bonded to a piezoelectric element and a sound distortion rate is low.

1‧‧‧Metal sheet

2‧‧‧Piezoelectric components

3‧‧‧Perforation

4‧‧‧Maximum distortion rate

Figure 1 is an explanatory view showing a speaker of the present invention;

2 is an explanatory diagram showing a relationship between an X value and a distortion rate;

Fig. 3 is an explanatory diagram showing the relationship between the X value and the maximum distortion rate.

Figure 1 shows the speaker of the present invention. The piezoelectric element 2 is attached to the metal plate 1. The area of the metal plate 1 on the attaching surface is Sm, and the area of the piezoelectric element 2 is Sp. The area Sp of the piezoelectric element 2 attached to the metal plate 1 is of course equal to or smaller than the area Sm of the metal plate 1. That is, (Sp/Sm) ≤ 1.

Fig. 1(A) shows a circular metal plate 1 and a piezoelectric element 2, and Fig. 1(B) shows a square metal plate 1 and a piezoelectric element 2. As shown in the figure, the shapes of the metal plate 1 and the piezoelectric element 2 can be arbitrarily designed. Moreover, since the metal plate 1 and the piezoelectric element 2 are substantially similar in shape, and the positions of the centers of gravity of the two are substantially uniform, it is in compliance with the expectation of reducing the edge distortion of the metal plate.

A perforation 3 can also be provided on the metal plate 1 and the piezoelectric element 2. The perforations 3 penetrate the metal plate 1 and the piezoelectric element 2. Therefore, the diaphragm can have a plurality of resonance frequencies due to the length of the section in which the diaphragm is divided. Further, since the perforation 3 also penetrates the piezoelectric element 2, the resonance frequency of the metal plate 1 (the resonance frequency of the metal plate 1 and the piezoelectric element 2 as a whole) also becomes diverse. The frequency characteristics become smooth and the distortion occurring at a specific frequency is alleviated.

Figure 2 shows the relationship between the X value and the distortion rate. It is an experimental result when the metal plate 1 is made of brass (ρ/E=0.087), the metal plate 1 and the piezoelectric element 2 are circular, the center position of the metal plate 1 is the same as that of the piezoelectric element 2, and the perforation 3 is not provided. The distortion ratios at X=0.005, X=0.009, X=0.04, and X=0.085 at different frequencies are shown. The horizontal axis is the frequency and the vertical axis is the distortion rate.

The distortion rate varies with frequency. Looking at the maximum distortion rate, X=0.005 (indicated by 4a in the figure) has the highest distortion rate, and X=0.04 (indicated by 4c in the figure). The distortion rate is the smallest, X=0.009 (used in the figure) The distortion rate is at an intermediate value when 4b is expressed) and X=0.085 (indicated by 4d in the figure).

Figure 2 is another experimental example. As can be seen from the figure, even when the material of the metal plate 1, the shape of the metal plate 1 and the piezoelectric element 2, and the shapes of the two are not similar, the value of the maximum distortion rate is the smallest when X=0.04 to 0.06.

Figure 3 shows the relationship between the X value and the maximum distortion rate. The horizontal axis is X and the vertical axis is the maximum distortion rate. The figure shows the average of multiple experimental results. In addition, 4a to 4d in Fig. 2 are embodied.

According to Fig. 3, the maximum distortion rate is less than 2% when X = 0.01 to 0.08. At this time, the tone of the instrument is a high-quality sound that can be fully discerned. In addition, the maximum distortion rate is about 1% at X = 0.02 to 0.07, and the value is the smallest.

Here, observe the increase in the maximum distortion rate when X < 0.01 and X > 0.08. This is necessary to adjust Sp/Sm and obtain high sound quality when X=0.01~0.08. For example, when the metal plate 1 is made of lightweight and hard titanium (ρ/E = 0.042), it is preferable that the ratio of Sp/Sm can be close to 1 (the piezoelectric plate is placed on almost the entire surface of the metal plate). When the metal plate 1 is made of soft silver (ρ/E = 0.104), high sound quality can be obtained by reducing the ratio of Sp/Sm (Sp/Sm < 0.76).

As described in detail above, the speaker of the present invention can achieve a low distortion rate by adjusting the area ratio of the metal plate 1 and the piezoelectric element 2. Further, the maximum distortion rate can also be reduced by providing the through holes 3 penetrating the metal plate 1 and the piezoelectric element 2. At this time, the same is true when the maximum distortion rate is reduced at X=0.01~0.08.

In view of the above, the present invention can be used in the production of high-quality speakers for the majority of audio equipment manufacturers.

The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

1‧‧‧Metal sheet

2‧‧‧Piezoelectric components

3‧‧‧Perforation

Claims (4)

A speaker that attaches a piezoelectric element to a metal plate, through a vibration of the piezoelectric element, but in a speaker in which the metal plate is bent and vibrated, and represents a longitudinal direction of the metal plate with E (kN/mm 2 ) (N is a unit of force Newton) The modulus of elasticity, the density is expressed by ρ (g/cm3), the area of the metal plate of the attachment surface is represented by Sm, and the area of the piezoelectric element is represented by Sp. The formula X = (Sp/Sm) • (X/() A speaker with a value between 0.01 and 0.08. The speaker of claim 1, wherein the value of X is between 0.02 and 0.07. The speaker according to claim 1, wherein the attachment surface, the metal plate and the piezoelectric element have the same shape, and the positions of the center of gravity of the metal plate and the piezoelectric element are identical. The speaker unit of claim 1, wherein the piezoelectric element and the metal plate have perforations for penetrating the piezoelectric element and the metal plate.