JPH01243700A - Piezoelectric loudspeaker - Google Patents

Abstract

PURPOSE:To improve the acoustic characteristic by forming a recessed part on a frame member to be provided in the recessed part to be formed into a plate-shaped member at a specific interval, setting the recessed part in a rear end space on the recessed part and installing a piezoelectric transducing element. CONSTITUTION:A frame member 6, to which a piezoelectric transducing element 2 making a recessed part (a through hole) 61 into a rear end space 64 is ad hered, is provided in the recessed part 44 of a plate-shaped member 4 at a specific interval and the rear end pressure of the piezoelectric transducing element 2 is adjusted by the recessed part 61 of the frame member 6. The piezoelectric transducing element 2 generates a free vibration with making the frame member 6 as a supporting point, the vibration vibrates the air of the front end side of the piezoelectric transducing element 2, simultaneously the vibration is transmitted to the plate-shaped member 4 through the frame member 6 and vibrates the frame member 6 and the plate-shaped member 4. Thus, the acoustic characteristic is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in the container structure of a piezoelectric speaker using a piezoelectric element.

[Conventional technology]

Conventionally, piezoelectric speakers have been used as electroacoustic transducers that convert electrical signals into acoustic vibrations using piezoelectric elements.

Piezoelectric speakers convert electrical signals into acoustic vibrations by directly driving a diaphragm using the electrostrictive effect of piezoelectric elements, so they are thin, flat, compact, and have low power consumption, which electrodynamic speakers do not have. Although it has excellent characteristics, it has been used in a limited range of applications such as melodic alarms and toys because of the acoustic characteristics due to the structure in which the diaphragm is directly driven by a piezoelectric element.

[Problem to be solved by the invention]

By the way, when a piezoelectric element is used in a speaker, conventional methods have been used such as simply fixing it to a part of the device, so the outer case vibrates together with the piezoelectric element and becomes a resonator that induces unnecessary vibrations. etc., lacked fidelity. In particular, due to the structure of the piezoelectric element, the edge of the diaphragm is fixed to the installation member, etc., so the structure of the installation space and the mounting member are directly connected to the diaphragm, which may affect the sound quality etc. is known empirically.

Therefore, an object of the present invention is to provide a piezoelectric speaker in which the structure of a container in which a piezoelectric conversion element is installed is improved.

[Means to solve the problem]

As shown in FIG. 1, in the piezoelectric speaker of the present invention, a recess 44 is formed in a plate member 4, a frame member 6 is installed with a predetermined gap 60 on the inner wall of the recess 44, and the frame member 6 is The piezoelectric transducer 2 is fixed onto the recess (through hole 61) formed in the recess (through hole 61), with the recess (through hole 61) serving as a back space 64.

Further, in the piezoelectric speaker of the present invention, the plate-like member 4 and the frame member 6 can be made of foamable synthetic resin.

[For production]

The frame member 6 to which the piezoelectric transducer 2 is fixed is installed with a constant gap 60 in the recess 44 of the plate member 4, and the back pressure of the piezoelectric transducer 2 is determined by the recess (through hole 61) of the frame member 6. will be adjusted accordingly. Then, the piezoelectric transducer 2 generates free vibration using the frame member 6 as a support point, and the vibration is transmitted to the piezoelectric transducer 2.
The vibration is transmitted to the plate member 4 through the frame member 6, causing the frame member 6 and the plate member 4 to vibrate. Therefore, by including the plate-like member 4 in the acoustic conversion member in this way, it is possible to better represent the characteristics of the reproduced sound such as a human voice and improve the reproducibility.

By forming the plate member 4 and the frame member 6 from foamable synthetic resin, the low frequency characteristics are improved.

〔Example〕

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

This piezoelectric speaker uses a piezoelectric transducer 2 as an electroacoustic transducer, and a disk-shaped piezoelectric element 22 made of ceramic or the like is fixed to the center of a circular diaphragm 21 that also serves as an electrode. At the same time, an electrode 23 made of a conductive metal layer is provided on the surface of the piezoelectric element 22 by metallization treatment or the like. The piezoelectric transducer 2 has a sandwich structure consisting of a diaphragm 21 and an electrode 23 with the piezoelectric element 22 at the center.

The diaphragm 21 and the electrode 23 have leads 24.
25 are connected by electrical connection means such as soldering, and electrical signals to be converted into acoustic vibrations are applied through leads 24.25.

A plate-like member 4 is installed as a container for accommodating this piezoelectric transducer 2. This plate-like member 4 is made up of a thick book cover, and an intermediate member is placed on a back member 41 as a support. 42 is installed, and a surface member 43 is installed thereon. This plate-like member 4 includes a back member 41 made of strong cardboard, an intermediate member 42 made of a synthetic resin sheet, and a surface member 43.
is constructed from a foamable synthetic resin board, and a surface shielding board made of cardboard or the like is used.

A recess 44 of an arbitrary shape is formed in the temple plate-like member 4 with a depth that reaches the intermediate member 42. In this embodiment, the recess 44 has an irregular shape of 61 formed by slightly cutting off the corners of a rectangle. It is formed. This recess 44 has a portion set on the speaker side and the other portion set as an accommodation space 46 for a drive circuit 45 such as a radio.

The concave portion 44 has a shape corresponding to the shape thereof, and
A frame member 6 made of foamable synthetic resin or the like having a thickness corresponding to the depth is installed with a constant gap 60 between it and the wall surface of the recess 44. This frame member 6 has a second
As shown in the figure, a through hole 61 is formed as a concave portion having a similar shape to the piezoelectric transducer 2, and a stepped portion 62 is provided on the upper side of the through hole 61 to increase the diameter for inserting the piezoelectric transducer 2. A portion 63 is formed.

Therefore, as shown in FIG. 3, the piezoelectric transducer 2 is
It is attached to the stepped portion 62 of the large-diameter portion 63 on the frame member 6 with an adhesive or the like, and a back space 64 is formed by a through hole 61 in the back surface thereof. Although not shown, a shielding member made of cardboard, a synthetic resin sheet, or the like is installed on the surface of this plate-like member 4.

According to such a configuration, the piezoelectric transducer 2 is connected to the frame member 6
and generates acoustic vibrations using the frame member 6 as a support point in response to an electric signal applied between the leads 24 and 25. The back pressure is applied to the cylindrical back space 6 defined by the through hole 61 formed in the frame member 6 and the intermediate member 42.
Adjusted by 4. Further, since the frame member 6 is installed inside the recess 44 of the plate member 4 with a certain gap 60 between it and the inner wall thereof, the vibration of the piezoelectric transducer 2 causes the frame member 6 to vibrate. Vibration is transmitted from the frame member 6 to the plate member 4 through the air in the gap 60, the back member 41, and the intermediate member 42, and an appropriate damper effect is obtained.

In addition, in the embodiment, the case where the plate member 4 and the frame member 6 were formed of foamable synthetic resin was explained, but paper, metal,
It may be formed of wood or other synthetic resin.

In addition, if the frame member 6 is sufficiently thick, the through hole 61 may be replaced with a cylindrical recess to adjust the back pressure in the same way.

〔Experimental result〕

The piezoelectric transducer 2 is made of sintered two-component ceramic of lead titanate and lead zirconate, and has a diameter of 28.5 mm and a thickness of 0.0 mm.
A 5 m+a piezoelectric element 22 was formed, and this was fixed to a brass plate with a diameter of 40 mm and a thickness of 0.20 ann as the diaphragm 21. The surface member 43 and frame member 6
As a comparative example, a piezoelectric transducer 2 was attached to a plate-like member 4 shown in FIG. 1 made of foamable synthetic resin, and a similar piezoelectric transducer 2 was attached to a conventional circular support frame.

According to experiments, the piezoelectric speaker according to the present invention has a characteristic A.
,In the comparative example, a frequency characteristic of characteristic B is obtained, and in the comparative example, a sharp level drop point P, ,P, ,P, ,P, ,P=,P+, sudden level drop in each region from the bass to the treble range is obtained. While the level rising point P11 and pH appear, in the piezoelectric speaker of the present invention, the level falling points Pi, Pt, P
+. Although there is a decrease in the level at points P,
There is no extreme level drop in ,P, ,P,,P,.
It has been improved to have smoother characteristics. In particular, it can be seen that the level in the bass range is enhanced, the peak point in the treble range is suppressed, and the level is enhanced from the bass range to the middle range.

When a human voice was reproduced and the reproduced sound was evaluated for each speaker with these characteristics, it was found that the piezoelectric speaker of the present invention has excellent sound quality and timbre reproducibility, and is able to reproduce natural human voices. Moreover, it was confirmed that it has excellent acoustic characteristics such as easy listening.

〔Effect of the invention〕

As explained above, according to the present invention, a recess is formed in the frame member that is installed with a certain gap in the recess formed in the plate member, and the recess is used as a back space above the recess for piezoelectric conversion. With the element installed, the piezoelectric transducer generates free vibration using the frame member as a support point, and the back pressure is adjusted by the recessed part of the frame member. As a result, the characteristics of reproduced sounds such as human voices are well expressed. Reproducibility can be improved.

Furthermore, if the plate-like member and the frame member are made of foamable synthetic resin, the low-frequency characteristics can be improved, and the reproducibility of human voices and the like 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 the piezoelectric speaker shown in FIG.
FIG. 3 is a sectional view taken along the line ■--■ of the piezoelectric speaker shown in FIG. 1, and FIG. 4 is a diagram showing electroacoustic conversion characteristics. 2...Piezoelectric conversion element 4...Plate member 44...Recess -6...Frame member 60...Gap 61...Through hole (recess) Patent applicant Nippon Chemi-Con Co., Ltd.

Claims (2)

[Claims] (1) A recess is formed in a plate-like member, a frame member is installed with a certain gap on the inner wall of the recess, and a recess is set in the back space above the recess formed in the frame member, and a piezoelectric transducer is installed. Piezoelectric speaker with fixed. (2) The piezoelectric speaker according to claim 1, wherein the plate member and the frame member are made of foamable synthetic resin.