JPH01293099A - Piezoelectric speaker - Google Patents

Abstract

PURPOSE:To enhance the expression capability of delicate sound such as a human voice or music, etc., by forming plural cavity parts formed in pipe shape on a back plane member. CONSTITUTION:The plural cavity parts 52 formed in the pipe shape connected in an up-and-down direction are formed on the back plane member 42 and a front plane member 44, and they are formed with matrials with high rigidity. And on the the back plane part of a piezoelectric-crystal element 46, the cavity part 52 facing with a through hole 60 forms a back plane space BS essentially by connecting a large number of cavity parts 52 formed in the pipe shape in the up-and-down direction along with spread by the cavity part 52 opened adja cently not in a narrow range formed only by the circular through hole 60, and an ideal back plane state can be obtained. In such a way, the back plane pressure of the piezoelectric-crystal element 46 at the time of performing electical-acoustic transducing can be adjusted by the back plane space BS having sufficient spread, and also, back plane sound can be transmitted to the cavity part 52 of the back plane member 42, which oscillates the back plane member 42 and enhances the expression capability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric speaker whose acoustic characteristics are improved by a container structure in which a piezoelectric transducer is installed.

[Conventional technology]

Conventionally, piezoelectric speakers have been used as electrical pass/fail converters that convert electrical signals into acoustic vibrations using piezoelectric transducers. Piezoelectric speakers convert electrical signals into acoustic vibrations by directly driving a diaphragm using the electrostrictive effect of piezoelectric elements, so they have excellent features that electrodynamic speakers do not have, such as being flat, compact, and low power consumption. It also has unique acoustic characteristics due to the structure in which the diaphragm is directly driven by a piezoelectric element, so it has been used in a limited range of applications such as melodic alarms and toys.

Furthermore, since piezoelectric speakers are simply attached to a part of equipment such as a radio, the outer case vibrates with the piezoelectric transducer and becomes a resonator that induces unnecessary vibrations. It was lacking in precision. In particular, due to its structure, the piezoelectric transducer is fixed to the installation member using the edge of the diaphragm, so the structure of the installation space and the mounting member are directly connected to the diaphragm, which may affect the sound quality. known to give.

Therefore, in order to improve the acoustic characteristics by changing the structure of the container in which the piezoelectric transducer is installed, for example, as shown in FIG.
As the plate member 2, a laminate having a three-layer structure of a back member 4, an intermediate member 6, and a front member 8 is used. A recess 10 is formed. In each of the four parts 10, a frame member 12 made of foamable synthetic resin or the like has a thickness corresponding to the depth and shape of the four parts, and a certain gap 14 is provided between the four parts 10 and the wall surface of the recessed part 10. A circular through hole 16 is formed in the frame member 12, and a step portion having a small diameter is provided in the middle thereof, and a piezoelectric transducer 18 is fixed to this step portion. An acoustic transducer circuit 20 for driving the piezoelectric transducer 18 is installed in the recess 10 adjacent to the frame member 12 .

In this piezoelectric speaker, acoustic vibration is generated in the piezoelectric transducer 18 using the frame member 12 as a support point, and the back pressure is closed by the through hole 16 of the frame member 12, the intermediate member 6, and the diaphragm 19 of the piezoelectric transducer 18. adjusted by the rear space.

The vibration of the piezoelectric transducer 18 causes the frame member 12 to vibrate, and the vibration is transmitted from the frame member 12 to the plate member 2.
Since the energy is transmitted through the gap 14, the back member 4, and the intermediate member 6, an appropriate damping effect can be obtained by the air present in the transmission path. As a result, this piezoelectric speaker provides an effective acoustic conversion level in the mid-range frequency range representing the characteristics of the human voice. [Problems to be Solved by the Invention] Therefore, although this piezoelectric speaker is effective for voice telegrams that convey simple messages, etc., it is necessary to provide a gap 14 between the frame member 12 and the front member 8. In addition to the required structural complexity, the effective frequency range was narrow, and the acoustic characteristics also left room for improvement.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a piezoelectric speaker that expands the reproducible frequency range and makes it possible to express delicate human voices and music.

Another object of the present invention is to provide a piezoelectric speaker whose acoustic characteristics are improved by using simple synthetic resin members for the back and front members on which piezoelectric transducers are installed.

Furthermore, another object of the present invention is to provide a piezoelectric speaker in which pass/fail impedance on the side of the back space is reduced.

[Means to solve the problem]

In the piezoelectric speaker of the present invention, a recess is formed in a back member in which a plurality of pipe-shaped cavities are formed, and a piezoelectric transducer is installed by closing the recess. A front member is installed in which a shaped cavity is formed.

Further, in the piezoelectric speaker of the present invention, a synthetic resin plate having liners arranged on both sides of a corrugated center core can be used for the back member and the front member.

Further, in the piezoelectric speaker of the present invention, a highly rigid back reinforcement plate can be installed on the back side of the recessed portion of the back member.

[For production]

Since a plurality of pipe-shaped cavities are formed in the back member, the four cavities communicate with the four parts formed on the back side of the piezoelectric transducer, and holes are formed on the back side of the piezoelectric transducer according to the area of the back member. A wide back space is created. Moreover, since the front member in which the cavity is formed is installed on the front side of the piezoelectric transducer, the front space can also be widened. As a result, a wide space is formed on the back and front sides of the piezoelectric transducer by the front member and the front member to which the piezoelectric transducer is attached, and a natural vibration form is obtained for the piezoelectric transducer, ranging from low to high frequencies. The necessary acoustic conversion level can be achieved over a wide range of areas, and the characteristics of reproduced sounds such as delicate human voices and music can be expressed well and the reproducibility can be improved.

In addition, by using synthetic resin plates with liners on both sides of a corrugated center core for the back and front members, sufficient rigidity and elasticity can be obtained, resulting in excellent acoustics. Characteristics are realized.

If a highly rigid back reinforcing plate is installed on the back side of the concave portion of the back member, internal loss in the back space can be reduced.

〔Example〕

1 to 3 show embodiments of the piezoelectric speaker of the present invention.

A cover 22 formed into a flat rectangular parallelepiped and made of a plate-like member such as cardboard or a synthetic resin plate is installed as an exterior case of the piezoelectric speaker. This cover 22 is provided with a back plate 24 formed in a rectangular shape, and side plates 26, 28, 30, and 32 of the same width are formed on each side of this back plate 24. Fold-out piece 34.3 at the top of each side plate 26-32
6.38 are formed, and a front plate 40 having the same shape as the back plate 24 is formed on the side plate 32 so as to be bendable, facing the back plate 24. Then, the side plates 26 to 30 are bent at right angles in the same direction to the back plate 24, and the folded pieces 34 to 38 and the front plate 40 are bent so as to form parallel surfaces, and the folded pieces 34 to 38 are folded on top of each folded piece 34 to 38. , the front plate 40 is fixed with adhesive or the like. Therefore, the cover 22 forms a flat rectangular segment-like body consisting of a back plate 24, side plates 26 to 32, and a front plate 40 using the same members, and a space forming a flat rectangular parallelepiped is formed inside the cover 22.

Inside the cover 22, a back member 42 and a side member 44, which have the same shape as the back plate 24 and are laminated with a thickness corresponding to the height of the side plates 26 to 32, are installed. These back member 42 and front member 44
is provided with a planar mounting portion 48 for installing the piezoelectric transducer 46, and this mounting portion 48
A four part 50 for accommodating a driving means is formed on the lower side of the piezoelectric transducer 46, and an audio reproducing circuit and a power source for driving the piezoelectric transducer 46 are installed in this four part 50.

By the way, the back member 42 and the front member 44 have a second
As shown in the figure, a plurality of pipe-shaped cavities 52 that are continuous in the vertical direction are formed, and a material with high rigidity is used. This material includes, for example, liners 56a, 56b or liners 58a, 58 made of synthetic resin plates on both sides of a core 54 made of corrugated synthetic resin plates.
b are fixed together to form a honeycomb structure with continuous circular or rectangular cavities 52 in one direction, and are formed from hollow synthetic resin having a flat plate shape and a constant thickness.

A through hole 60 forming a concave portion on the back side of the piezoelectric transducer 46 is formed in the back member 42, and a through hole 62 having the same diameter as the piezoelectric transducer 46 is also formed in the front member 44 corresponding to the through hole 60. There is. The through hole 60 is set slightly smaller than the diaphragm 64 of the piezoelectric transducer 46, and the piezoelectric transducer 46 is attached to the edge thereof.
The diaphragm 64 can be attached.

As shown in FIG. 3, the back plate 24 is fixed to the back side of the back member 42, and the back part of the through hole 60 is connected to the back plate 24.
4, and a recess is formed in the back member 42 with a through hole 60. Since the diaphragm 64 of the piezoelectric transducer 46 is fixed to the periphery of the through hole 60 of the back surface member 42 forming this concave portion using an adhesive, the transparentization 60 of the back surface member 42 allows the back surface side to be connected to the back surface plate 24, As a result of closing the front side with the piezoelectric transducer 46, a back space BS is formed by the back member 42 on the back side of the piezoelectric transducer 4G.

Further, the front member 44 is fixed to the diaphragm 64 of the piezoelectric transducer 46 with an adhesive, with its through hole 62 concentrically fixed to the diaphragm 64.
4 is fixed on the front member 42 together with the front member 44.

In the piezoelectric transducer 46, a piezoelectric element 66 made of ceramic or the like is fixed to the center of a circular diaphragm 64 that also serves as an electrode, and is solid and concentric with the diaphragm 64.
An electrode 68 made of a conductive metal layer is provided on the surface of the electrode 68 by metallization or the like. Vibration plate 64 and electrode 6
Leads 70 and 72 are connected to each of the leads 8 by a connecting means such as soldering, and are drawn out to the recess 50 side.

According to such a configuration, the piezoelectric transducer 46 generates acoustic vibrations using the liner 56a, which forms a part of the back member 42, as a support point in response to an electric signal applied between the leads 70 and 72, and also performs piezoelectric transduction. Between the front and back of the element 46 is a liner 5 on the joint surface side of the back member 42 and the front member 44.
6a, 58b. That is, the liners 56a and 58b constitute a shield plate that blocks the front side and the back side of the piezoelectric transducer 46.

A main back space BS is formed on the back surface of the piezoelectric transducer 46 by the through hole 60 of the back member 42, and a plurality of cavities 52 formed in the back member 42 are formed in this back space BS. I understand. In particular, through hole 6
0 has a circular shape, but the through hole 6 of the central core 54 forming the partition wall
Since the side facing the 0 side is cut diagonally, the hollow portion 52
is connected to the through hole 60. Therefore, the back surface of the piezoelectric transducer 46 does not have only a narrow circular through-hole 60, but also a large number of hollow sections 52 that are vertically pipe-shaped and expand with adjacent open hollow sections 52. Due to the connection, the cavity 52 facing the through hole 60 forms a substantial back space BS together with the through hole 60, and an ideal back space state is obtained. Therefore, the back pressure of the piezoelectric transducer 46 during electrical 'f5 acoustic conversion is adjusted by the sufficiently wide back space BS, and the back surface is also transmitted to the cavity 52 of the back member 42, It vibrates.

Further, although the through hole 62 of the front member 44 is closed by the front plate 40, the through hole 62 is closed on the front side of the piezoelectric transducer 46.
A front space FS is formed by connecting the plurality of cavities 52 in the front member 44 communicating with the side surface of the through hole 62, and this also causes the front sound pressure of the piezoelectric transducer 4G to be released.

In this piezoelectric speaker, a highly rigid back reinforcement plate is provided on the back side of the piezoelectric transducer 46, for example, as shown in FIG. A metal plate 74 having a diameter may be installed. In this way, even if the back plate 24 is made of a synthetic resin board or cardboard with low rigidity, its rigidity can be sufficiently reinforced by the metal plate 74, and the back pressure can be adjusted using the low range of sound twinpedance. It is possible to enhance the effect and suppress the attenuation of sound pressure.

In addition, although the case where the back member 42 and the front member 44 were formed from a synthetic resin board was demonstrated in the Example, they may be formed from paper, a laminated wood board, a metal plate, etc.

Further, in the embodiment, the diaphragm 64 of the piezoelectric transducer 46 is fixed on the liner 56a of the back member 42, and the diaphragm 64 is
A through hole 62 of the liner 58b of the front member 44 is formed around the periphery of the front member 44.
The liners 58b may be overlapped and fixed, and the piezoelectric transducer 46 may be placed between the liners 56a and 58b.

〔Experimental result〕

The piezoelectric transducer 46 has a piezoelectric element 66 with a diameter of 28.5 mm made by sintering a two-component ceramic of lead titanate and lead zirconate on a brass plate with a diameter of 40 mm as a diaphragm 64, and an electrode 68 on it. I installed it and used it. The first embodiment has this piezoelectric transducer 46 set in the container structure shown in FIG. 1, and the second embodiment has a metal plate 74 installed on the rear surface of the back member 42 as shown in FIG. In addition, a container having the structure shown in FIG. 7 was used as a comparative example.

According to experiments, as shown in FIG. 5, characteristic A.

is the case of the first example, and characteristic B represents the comparative example. In characteristic B, the effective frequency range is very narrow from 600 to 4000 Hz (with a sharp level drop point P2 near 10001 fz and a sharp level peak point P2 near 150011 f).
3 occurs, and a sharp level drop point P4 also occurs near 30001rz. On the other hand, in the characteristic A in the first embodiment, the effective frequency range is 30011z to 3
It has been expanded over a wide range up to 0,000 Hz, and 400
Although there is a level drop point P + near Hz and a level drop point P2' where the degree of level drop is more gradual than in the comparative example near 1000 Hz, there is no sharp level increase point like the level peak point P3, and the level is low. A gentle level of enhancement is obtained from the high range to the high range.

Further, as shown in FIG. 6, characteristic A2 is the case of the second embodiment, characteristic B is a comparative example, and characteristic A2 of the second embodiment in which the metal plate 74 is installed on the back side is the case of the first embodiment. The level drop at the level drop points P1 and P2 in is resolved,
In particular, it can be seen that the level in the midrange has been enhanced.

Therefore, when evaluating the reproduction of human voices and music, the piezoelectric speaker of the present invention has excellent reproducibility of sound quality and timbre, and is capable of reproducing delicate human voices and music, and is superior to natural sounds. It was confirmed that the sound was reproduced faithfully and with easy-to-hear sound quality, and that it had excellent acoustic characteristics.

[Effects of the Invention] As explained above, according to the present invention, since the plurality of pipe-shaped cavities are formed in the back member, the cavities are formed in the recesses formed on the back side of the piezoelectric transducer. A wide back space corresponding to the area of the back member is formed on the back side of the piezoelectric transducer, and a large space is formed on the front side of the piezoelectric transducer.
Since an opening is formed and a front member is installed with a cavity passing through the opening, the front space can be widened, and the vibration form of the piezoelectric transducer becomes natural, so delicate sounds such as human voices and music can be heard. You can improve your ability to express sounds.

Further, according to the present invention, the back member and the front member include
As a synthetic resin plate with liners arranged on both sides of a corrugated core, it can be easily constructed using, for example, a synthetic resin cardboard board, and excellent acoustic characteristics can be achieved.

Furthermore, according to the present invention, by installing a highly rigid back reinforcement plate on the back side of the recessed portion of the back member, internal loss in the back space can be reduced and acoustic characteristics can be improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the piezoelectric speaker of the present invention, FIG. 2 is an exploded perspective view of essential parts of the piezoelectric speaker shown in FIG. 1, and FIG. 3 is a perspective view of the piezoelectric speaker shown in FIG. 1. 4 is a sectional view of main parts of another embodiment of the piezoelectric speaker of the present invention, and FIG. 5 is a diagram showing the electroacoustic conversion characteristics of the piezoelectric speaker shown in FIGS. 1 and 7. , FIG. 6 is a diagram showing electroacoustic conversion characteristics in the piezoelectric speakers shown in FIGS. 4 and 7, and FIG. 7 is a diagram showing a conventional piezoelectric speaker. 42...Back member 44...Front member 46...Piezoelectric conversion element 52...Cavity portion 54...Central cores 56a, 56b, 58a, 58b...Liner 60...
・Through hole (four parts) 74...Metal plate (rear reinforcement plate)

Claims (3)

[Claims] 1. A recess is formed in the back member in which a plurality of pipe-shaped cavities are formed, and a piezoelectric transducer is installed by closing the recess, and a pipe-shaped cavity is formed on the front side of the piezoelectric transducer. A piezoelectric speaker with a front panel. 2. 2. The piezoelectric speaker according to claim 1, wherein the back member and the front member are made of synthetic resin plates having liners arranged on both sides of a corrugated core. 3. 2. The piezoelectric speaker according to claim 1, further comprising a highly rigid back reinforcing plate provided on the back side of the recessed portion of the back member.