JP2001320798A - Piezoelectric diaphragm for acoustic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize mechanical characteristics of a piezoelectric diaphragm in an acoustic device using the piezoelectric diaphragm. SOLUTION: In the piezoelectric diaphragm 10 for acoustic device formed by attaching the piezoelectric diaphragm 10, in which ceramic layer 14 is stuck onto both side faces of a metallic thin sheet 12 formed into a prescribed shape, to acoustic diaphragms 22 and 32 through attachment members 24 and 36, a plurality of small holes 12a penetrated from one side face of the metallic thin board 12 to the other side face are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an acoustic device using a piezoelectric diaphragm.

[0002]

2. Description of the Related Art A piezoelectric vibrating plate in which ceramic layers are attached to both sides of a thin metal plate is supported and attached to the acoustic vibrating plate at the center or the periphery thereof, and the vibration of the piezoelectric vibrating plate is acoustically vibrated. 2. Description of the Related Art A loudspeaker or an acoustic device that transmits sound to a plate, transmits vibration from an acoustic diaphragm to surrounding air, and emits sound has been known.

[0003]

The piezoelectric diaphragm repeatedly bends in response to an audio signal applied to its ceramics layer, and its vibration is transmitted to the acoustic diaphragm via the center support member. The sound propagates from the acoustic diaphragm to the surrounding air. Therefore, in an acoustic device using a piezoelectric diaphragm,
The followability or response of the piezoelectric diaphragm to the audio signal has a significant effect on the reproduced sound. However, in the prior art, the effect of the mechanical characteristics of the piezoelectric diaphragm on the sound reproduced by the acoustic device has not been sufficiently considered.

An object of the present invention is to solve such problems of the prior art, and an object of the present invention is to optimize the mechanical characteristics of a piezoelectric diaphragm in an acoustic device using the piezoelectric diaphragm.

[0005]

The present invention according to claim 1 has the gist of the invention.

[0006]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. The piezoelectric vibration plate 10 includes a circular metal thin plate 12 made of a metal thin plate such as aluminum, stainless steel, brass, or the like, and a ceramic layer 14 attached to both sides of the metal thin plate 12 with an appropriate adhesive. Consisting of The ceramic layer 14 can be formed of a ferroelectric ceramic material such as barium titanate or lead zirconate titanate. In FIG. 1, the ceramic layer 14 is formed on substantially both sides of the thin metal plate 12 except for the peripheral portion. Although not particularly shown, the ceramic layer 14 may be formed only on one side.

[0007] In the prior art, the metal thin plate 12 is formed of a simple plate-like member, and its mechanical properties depend on the physical properties of the material, particularly elasticity and bending stiffness, and the dimensions, particularly diameter and thickness. Had been decided. On the other hand, in the present embodiment, the thin metal plate 12 has a plurality of small holes 12a penetrating from one side surface to the other side surface. By forming the small holes 12a as in the present embodiment, the metal thin plate 12 can be formed without changing the material, thickness, and diameter of the metal thin plate 12.
It is possible to make the mechanical properties, particularly the bending stiffness or flexibility thereof, a desired value. As an example, the piezoelectric diaphragm 1
0 is a thin metal plate 12 having a diameter of 50 mm and a thickness of about 0.1 mm.
Small holes 12a having a diameter of 1.5 mm can be formed in 50 or more, preferably 100 or more, more preferably 200 or more, and in some cases 300 or more. The small hole 12a
Can be easily formed by, for example, superposing a plurality of metal thin plates 12 and performing electric discharge machining in a small hole.

Next, an example of an acoustic device using the piezoelectric vibrating plate 10 according to the above embodiment will be described with reference to FIG.
In FIG. 2, an acoustic device 20 includes a housing 22 as an acoustic diaphragm, for example, a mobile phone or a cordless telephone slave unit,
On one side of a desired position of a housing, such as a normal telephone handset, in particular on the inner surface of said housing, a piezoelectric diaphragm 10 is provided.
An annular projection 24 is provided as a mounting member for attaching the projection. The piezoelectric vibrating plate 10 is supported and fixed to the protruding portion 24 at the peripheral edge thereof. One or a plurality of through-holes 22a (two through-holes 22a are shown as an example in FIG. 2) penetrating the housing 22 may be provided in a region of the housing 22 surrounded by the protrusions 24. Further, the projection 24 may be formed by a single annular projection, or may be formed by a plurality of projections arranged on the circumference.

By applying an audio signal to the ceramic layer 14 of the piezoelectric vibrating plate 10, the piezoelectric vibrating plate 10 repeatedly bends back and forth, and the vibration is transmitted from the peripheral edge of the piezoelectric vibrating plate 10 via the projection 24 to the housing. Vibration is transmitted to the body 22 and then propagated from the housing 22 to the surrounding air.

Since the metal thin plate of the conventional piezoelectric vibrating plate does not have a configuration corresponding to the small hole 12a according to the present embodiment, the mechanical properties of the metal thin plate of the piezoelectric vibrating plate, especially the bending rigidity, are low. , The choice of material and the diameter and thickness. However, when using this kind of acoustic device in the above-described mobile phone or cordless phone handset, a normal telephone handset, etc., particularly when used in a mobile phone,
Since the internal space is very limited, the diameter of the piezoelectric vibrating plate is limited to about 10 to 20 mm, and the bending rigidity of the thin metal plate becomes relatively high.

On the other hand, the thickness of the metal thin plate has been about 0.1 mm conventionally, but in order to obtain a desired bending rigidity corresponding to the diameter of the reduced metal thin plate. If the thickness is further reduced, the manufacturing cost will increase dramatically. In other words, in order to obtain a target bending rigidity, not only a thin plate which is not normally distributed but also a special order must be made, and the thickness of the metal thin plate must be changed every time the diameter changes. Further, in order to obtain a desired bending rigidity, the thickness of the metal thin plate is set to 0.01 mm.
This has to be controlled in units, which is difficult in practice.

According to the present embodiment, by appropriately selecting the size, number and arrangement of the small holes 12a, the desired mechanical properties, particularly the bending rigidity or the rigidity of the metal thin plate and thus the piezoelectric vibrating plate can be reduced at low cost. Flexibility can be obtained.

Next, an acoustic apparatus according to another embodiment of the present invention will be described with reference to FIG. In FIG. 3, in the acoustic device 30, the circular piezoelectric diaphragm 10 is attached to the acoustic diaphragm 32 via a mounting member 36 including a rod 36a, a nut 36b, and a bracket 36c at the center. Bracket 36c is preferably attached to acoustic diaphragm 32 with a suitable adhesive or double-sided tape. The acoustic diaphragm 32 is preferably a gypsum board, styrofoam, a suitable plastic material such as boron,
It is made of a composite material in which fibers such as silicon carbide, alumina, carbon, and aramid are preformed in a plastic matrix such as nylon, polyester, or epoxy. An annular vibration control piece 3 is provided on one side of the piezoelectric vibrating plate 10.
4 may be attached. The vibration control piece 34 is made of an elastic material, preferably, synthetic rubber, natural rubber, low density polyethylene,
It consists of an elastomeric material such as soft vinyl chloride plastic.

By applying an audio signal to the ceramic layer 14 of the piezoelectric vibrating plate 10, the peripheral portion of the piezoelectric vibrating plate 10 repeatedly bends back and forth, and the vibration is transmitted from the center of the piezoelectric vibrating plate 10 to the mounting member. Acoustic diaphragm 3 through 36
The vibration is then transmitted from the acoustic diaphragm 32 to the surrounding air.

The small holes 1 are formed in the metal thin plate 12 of the piezoelectric vibrating plate 10.
By providing 2a, it is possible to easily and at low cost obtain the desired mechanical properties of the metal thin plate 12 and thus the piezoelectric vibrating plate. Further, the vibration control piece 34 is
0, the vibration control piece 3
Numeral 2 serves as an inertial mass body. Therefore, at this time, since the vibration control piece 32 keeps stopping at the original position due to the inertial force, the center of the piezoelectric vibration plate 10 is easily moved in the front-rear direction. . Further, the vibration control piece 32 is
The function of suppressing a resonance effect of a specific frequency generated in the inside and ensuring a flat sound pressure level is achieved.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a piezoelectric diaphragm according to a preferred embodiment of the present invention.

FIG. 2 is an example of an acoustic device using the piezoelectric diaphragm of FIG.

FIG. 3 is another example of an acoustic device using the piezoelectric diaphragm of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Piezoelectric vibration plate 12 ... Metal thin plate 12a ... Small hole 14 ... Ceramic layer

Claims (4)

[Claims] 1. A piezoelectric vibrating plate for an acoustic device which is formed by attaching a piezoelectric vibrating plate having ceramic layers attached to both sides of a metal thin plate molded into a predetermined shape to an acoustic vibrating plate via an attachment member. A piezoelectric vibrating plate, wherein a plurality of small holes penetrating from one side surface to the other side surface of the metal thin plate are formed. 2. An acoustic device formed by attaching a piezoelectric vibrating plate having ceramic layers adhered to both sides of a metal thin plate molded into a predetermined shape to an acoustic vibrating plate via a mounting member, wherein the metal thin plate A plurality of small holes penetrating from one side surface to the other side surface are formed. 3. The mounting member comprises one or a plurality of protrusions annularly arranged on one side surface of the acoustic diaphragm, and the piezoelectric diaphragm is supported by the acoustic diaphragm at a peripheral portion thereof. The acoustic device according to claim 2, which is worn. 4. The acoustic device according to claim 2, wherein the piezoelectric diaphragm is supported and attached to one side surface of the acoustic diaphragm via the mounting member at a central portion thereof.