JPS6096094A - Piezo-electric type electroacoustic transducer - Google Patents

Abstract

PURPOSE:To suppress unnecessary peak acoustic pressure at a high band by setting the fixed part at peripheral part of a piezo-electric vibrator to the non- circular shape, and suppressing efficiently the higher resonance. CONSTITUTION:Basically, the fixed part 15 at peripheral part of a piezo-electric vibrator 6 consisting of a metallic diaphragm 1 combining a ceramic piezo-electric body 2 is set to the non-circular shape as shown by the oblique lines. Concretely, the shape of stepped part 5 of a case 4 having a sound releasing hole 3 at the upper surface is set to an oval shape. The actual lines in the figure show an acoustic pressure frequency characteristic when the ratio of the long diameter and the short diameter of the oval is 1.05/1, and the broken lines show an acoustic pressure frequency characteristic when the ratio of the long diameter and the short diameter is 1.25/1. The smaller the ratio of the long diameter and the short diameter is, the larger the unnecessary acoustic pressure peak at the high band is. As the ratio goes to larger, the unnecessary acoustic pressure peak at the high band goes to smaller. The ripple goes to larger in the unnecessary reproducing band up to 3.4kHz. Practically, the ratio of the long diameter and the short diameter is preferable to exists in the range of 1.05/1-1.25/1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a piezoelectric electroacoustic transducer used in telephone handsets and the like.

Conventional configuration and its problems Piezoelectric electroacoustic transducers using piezoelectric vibrators constructed by laminating a ceramic piezoelectric body to a metal diaphragm are widely used as piezoelectric buzzers and piezoelectric sounding bodies. Recently, they are being used as telephone receivers and transmitters.

Generally, this piezoelectric vibrator is constructed as shown in FIGS. 1 and 2. That is, a circular flat ceramic piezoelectric body 2 having electrodes made of silver or the like formed on both sides is bonded to one side of a diaphragm 1 made of a circular flat metal using an adhesive.

Further, the electrode of the ceramic piezoelectric body 2 (-J) and the diaphragm 1 are electrically connected.

A piezoelectric electroacoustic transducer using this piezoelectric vibrator is constructed as shown in FIG.

That is, a step 5 is provided inside the case 4 having the sound emitting hole 3 on the top surface, and the diaphragm 1 of the piezoelectric vibrator 6 is attached to the step 5.
A back air chamber plate 8 having supporting protrusions 7 on the outer periphery is incorporated into the bottom surface of the case 4, and the back air chamber plate 8
The peripheral edge of the diaphragm 1 was fixed by the support ridges 7 and the stepped portion 5 of the case 4.

Further, an acoustic leak hole 9 is provided in the center of the back air chamber plate 8, and an acoustic resistor 10 is attached to the acoustic leak hole 9 so as to block it. Terminals 11 and 12 are provided, and the input terminal 11 has a lead wire 13 connected to the electrode of the ceramic piezoelectric body 2 of the piezoelectric vibrator 6, and the input terminal 12 has a lead wire 14 connected to the diaphragm 1. is connected.

Note that the case 4 has a stepped portion 5. Although the support ridges 7 are provided on the back air chamber plate 8 to serve as a fixed part for the piezoelectric vibrator 6, a fixing ring may be used separately from the case 4 and the back air chamber plate 8 to serve as the fixed part.

In the conventional piezoelectric electroacoustic transducer of this type, the fixed part of the piezoelectric vibrator 6, the step part 5 and the supporting protrusion 7 in the example, have a circular ring shape, and the shape of the receiver of the telephone using this is circular. The frequency characteristics of the sound pressure level are generally measured by attaching the coupler to a coupler of a predetermined volume, and the characteristics are required to be located in the shaded area shown in FIG. 4, for example. 1s,
3.4K Hz or higher must be attenuated by 18 dB10at or higher.

However, in general, when the peripheral edge of the circular flat piezoelectric vibrator 6 is fixed in the shape of a circular ring, many higher-order resonances occur in addition to the basic resonance. Figure 6 shows an example of the sound pressure frequency characteristics of a single piezoelectric vibrator 6 whose peripheral part is fixed in a circular ring shape.
fl is the fundamental resonance frequency, and f , f , and f are the second, third, and fourth resonance frequencies, respectively. but,
In the case of a telephone handset, only the vicinity of the fundamental resonance is used, and higher-order resonances are not only unnecessary but also have a negative effect.

In other words, as shown by curve A in FIG. 4, sound pressure peaks (sensitivity peaks) B and C occur in unnecessary portions above 3.4 KHz, making it impossible to achieve the necessary high-frequency attenuation characteristics.

OBJECTS OF THE INVENTION An object of the present invention is to provide a piezoelectric electroacoustic transducer that can suppress unnecessary sound pressure peaks in high frequencies.

Structure of the Invention In order to achieve the above-mentioned objects, the present invention provides a piezoelectric vibrator constructed by bonding a ceramic piezoelectric body to a metal diaphragm in a case having a sound emission hole on the top surface. A back air chamber plate having an acoustic leakage hole on the bottom of the case is connected to the piezoelectric vibrator so as to have a constant spacing therebetween, and a fixed part on the periphery of the piezoelectric vibrator This configuration is intended to prevent the generation of high-order resonance of the piezoelectric vibrator and suppress unnecessary high-frequency sound pressure peaks.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to FIGS. 6 to 12 of the drawings.

First, the structure of the piezoelectric resonator and the structure of the piezoelectric electroacoustic transducer are substantially the same as those shown in FIGS. 1 to 3,
Here, only the fixed portion of the peripheral edge of the piezoelectric vibrator is characterized, so the characteristic portion will be explained.

Basically, as shown in FIG. 6, the fixed portion 15 at the peripheral edge of the piezoelectric vibrator 6, which is made of a metal diaphragm 1 combined with a ceramic piezoelectric body 2, is made non-circular as shown with diagonal lines. At the point.

Specifically, as shown in FIGS. 7 and 8, the stepped portion 6 of the case 4 having the sound emitting hole 3 on the upper surface has an elliptical shape.

Further, as shown in FIGS. 9 and 10, the support protrusion 7 of the back air chamber plate 8 may have an elliptical shape.

Note that the stepped portion 6 of the case 4. The shape of the supporting protrusion 7 of the back air chamber plate 8 may be oval instead of oval.

The ratio of the major axis and minor axis of this elliptical or oblong shape is 1.067
1 to 1.25/1 is desirable. The solid line in Figure 11 is the sound pressure frequency characteristic when the ratio of the major axis to the minor axis is 1.05/1, and the broken line is the sound pressure frequency characteristic when the ratio of the major axis to the minor axis is 1.25/1. The smaller the ratio, the larger the unnecessary sound pressure peaks in the high range9.The larger the ratio, the smaller the unnecessary sound pressure peaks in the high range, but the larger the ripple within the required reproduction band up to 3.4KHz, making it difficult to put into practical use. In other words, the ratio of the major axis to the minor axis is 1
．． The range of 0j571 to 1.25/1 is preferable.

In addition, the stepped portion 5 of the case 4. Although both of the supporting protrusions 7 of the back air chamber plate 8 may have a non-circular shape, a sufficient effect can be obtained even if only one of them is made non-circular.

Further, the fixed portion 15 at the peripheral edge of the piezoelectric vibrator 6 is not limited to the above-mentioned ellipse or ellipse, but may also be a flower shape made of continuous unevenness as shown in FIG. All non-circular shapes such as polygons are targeted and have the effect.

Further, in the above embodiment, the stepped portion 5 of the case 4. Back air chamber plate 8
Although the case 4 is cylindrical, the back air chamber plate 8 is also a simple disk, and the peripheral edge of the piezoelectric vibrator 6 is fixed with an ellipse or an oval shape. A non-circular support ring such as an ellipse may be placed above or below the piezoelectric vibrator 6 and fixed thereto.

The reason why the peripheral fixed portion of the piezoelectric vibrator 6 is made non-circular is as follows.

The vibration mode when the circular piezoelectric vibrator 6 resonates is a deflection vibration mode with the center of the piezoelectric vibrator 6 as an antinode and the inside of the fixed part 16 as a node, and the resonance frequency is determined by the diameter of the fixed part 15. . Therefore, if the fixed part 16 is circular ring-shaped, it will cause a clear resonance at a specific frequency, and the fifth
As shown in the figure, the higher-order resonance level also increases.

However, if the fixed portion 16 is made non-circular as in the present invention, the fixed diameter of the piezoelectric vibrator 6 is not constant from the center but differs in the circumferential direction, so that the resonance energy is dispersed over a plurality of frequencies. Therefore, the fundamental resonance, which has the largest resonance energy, is not affected to any extent, but the resonance energy of higher-order resonances is dispersed, and second-order, third-order, and fourth-order resonances are less likely to occur.

The sound pressure frequency characteristics of the piezoelectric electroacoustic transducer of the present invention are as shown by the solid line in Figure 4, and unnecessary sound pressure peaks in the high range are significantly reduced compared to the conventional example shown by the broken line. , exhibiting flat and good high-frequency attenuation characteristics.

Effects of the Invention As described above, the piezoelectric electroacoustic transducer of the present invention has a non-circular fixed portion at the periphery of the piezoelectric vibrator, which effectively suppresses high-order resonance and eliminates unnecessary high-frequency sound pressure peaks. It has the effect of eliminating the occurrence of noise and creating a flat sound pressure frequency characteristic, and when used in telephone receivers and transmitters, it enables extremely clear transmission and reception, and has industrial value. It is a great thing.

[Brief explanation of drawings]

Figure 1 is a top view of a general piezoelectric vibrator, Figure 2 is a front view of the same, Figure 3 is a sectional view of a piezoelectric electroacoustic transducer using the same piezoelectric vibrator, and Figure 4 is the invention of the present invention. 5 is a sound pressure frequency characteristic diagram of a conventional piezoelectric electroacoustic transducer, FIG. 5 is a sound pressure frequency characteristic diagram of a single piezoelectric vibrator with a fixed structure of a conventional piezoelectric vibrator, and FIG. 6 is a sound pressure frequency characteristic diagram of a piezoelectric vibrator of the present invention. An explanatory diagram showing an example of a fixing structure of a piezoelectric vibrator in an electroacoustic transducer, FIG. 7 is a half-sectional front view of an example of a case used in the piezoelectric electroacoustic transducer, and FIG. 8 is a top view of the same. Fig. 9 is a top view of the same back air chamber plate, Fig. 10 is a half-sectional front view of the same, Fig. 11 is a sound pressure frequency characteristic diagram based on the ratio of the major axis to the minor axis of the same example, and Fig. 12 is a diagram of other examples. It is an explanatory view showing a fixing structure of a piezoelectric vibrator of an example. 1... Metal diaphragm, 2... Ceramic piezoelectric body, 3... Sound emission hole, 4... Case, 6...・Stepped portion, 6...Piezoelectric vibrator, 7...Support protrusion, 8...Back air chamber plate, 9
...Acoustic leak hole, 10...Acoustic resistor, 11.12...Input terminal, 13.14...
... Lead wire, 15 ... Fixed part. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 6
Fig. f Fig. 8/Fig. 9 Iθ Fig. 10 Fig. 7X12

Claims (1)

[Claims] A piezoelectric vibrator consisting of a ceramic piezoelectric body coupled to a metal diaphragm is installed in a case with a sound emission hole on the top surface at a constant distance from the top surface of the case, and acoustic leakage is prevented from occurring on the bottom surface of the case. A piezoelectric electroacoustic transducer comprising: a back air chamber plate having holes coupled to the piezoelectric vibrator at a constant interval; and at least one of the fixed portions of the peripheral edge of the piezoelectric vibrator is non-circular.