JPH09215093A - Piezoelectric speaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric speaker which simplifies structure, is compact and light in weight and efficiently reproduces super high frequency sounds over a wide range through higher order wave vibrations with satisfactory frequency characteristics and directional characteristics. SOLUTION: A diaphragm 1 is composed of plural parallel gutter-shaped curved surfaces 1a, 1b..., the respective gutter-shaped curved surfaces 1a, 1b... are bonded on adjacent sides and form a bonding part 11a, and sides 11b and 11b opposite to the bonding part 11a are supported by a frame 3. A piezoelectric element 2, which is supported at a peripheral part by the frame 3, is fitted to the bonding part 11a of the diaphragm 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a simple structure, a small size, a light weight, and a shape in which a high-order vibration wave can be easily carried. The present invention relates to the structure of a piezoelectric type loudspeaker that is reproduced by.

[0002]

2. Description of the Related Art Conventionally, a piezoelectric type sounding body is roughly divided into two types structurally. In both cases, an electro-mechanical vibration converting mechanism is a metal that also serves as an electrode, as in Conventional Example 1 shown in FIG. A piezoelectric ceramic thin plate 2b is attached to one surface of the plate 2a, and the other electrode plate 2c is attached to the other surface, or a unimorph type piezoelectric element 2'having a known structure, or a conventional example 2 shown in FIG. As described above, a bimorph type piezoelectric element 2 in which another piezoelectric ceramic thin plate 2b and an electrode plate 2c are formed on the other surface of the metal plate 2a is used.

An example of a conventional structure of a speaker unit as a sounding body uses the piezoelectric element 2 or the piezoelectric element 2'as a vibrating plate directly. However, since the piezoelectric element itself has a low conversion efficiency, the structure shown in FIG. In the structure of the conventional example 1 shown in FIG. 1, a resonator 5 having a resonance frequency equal to the resonance frequency of the piezoelectric element 2 ′ and having a sound emission hole 5 a formed on the front surface of the piezoelectric element 2 ′ is coupled and the resonance is performed. The sound of the frequency is amplified by resonance and the conversion efficiency is improved.

The above-mentioned piezoelectric speaker is small in size for emitting a sound of a single frequency but relatively high in efficiency, but has a narrow reproduction frequency band, and is suitable for reproducing a wide band sound as a speaker. Therefore, the sounding body of the conventional example 2 shown in FIG. 22, that is, the piezoelectric speaker, has been put into practical use for the purpose of eliminating such a drawback. The structure will be described with reference to FIG. 1. The piezoelectric element 2 is attached to the apex portion of a conical diaphragm 7 whose peripheral portion is supported by the frame 6, and the conductor 21a connected to the metal plate 2a is connected to the piezoelectric element 2. , And an electric signal is applied through the lead wire 21b connected to the electrode plate 2c, the piezoelectric element 2 bends and vibrates in a direction perpendicular to the surface, and the cone-shaped diaphragm 7 vibrates by reaction and radiates sound. With this structure, the acoustic energy is directly radiated from the cone-shaped diaphragm 7, so the conversion efficiency is slightly higher,
In addition, since there is no resonator on the front side, the reproduction band is widened and it can be used as a speaker.

[0005]

Among the above, the prior art example 1 shown in FIG. 21 radiates only a single-frequency sound, so it can be used as a narrow-band signal sound generator. Not suitable for use as a speaker.

The conventional example 2 shown in FIG. 22 can be used as a speaker for reproducing a range to some extent, but the cone type diaphragm 7 that emits sound is conventionally used in the mass control band. Since it is for the purpose, it has relatively high rigidity, and since it vibrates together with the piezoelectric element 2, it reproduces at a certain high efficiency at the lowest resonance frequency, but the mass of the vibration system increases in the frequency band higher than that. Therefore, the efficiency is low, and the efficiency is remarkably reduced in the band above the high resonance frequency, so only the lowest resonance frequency is reproduced at a high level, and the frequency characteristics are not flat in the other bands, and the reproduction is performed. There was a drawback that the range was not very wide.

In view of the above, the present invention provides a vibrating plate shape, a coupling structure of the vibrating plate and a piezoelectric element, and a mounting structure of the vibrating plate and the piezoelectric element to a frame in order to solve the drawbacks of the conventional example. With improved ingenuity, the frequency characteristics are flat,
It is an object of the present invention to provide a piezoelectric speaker that reproduces a wide band efficiently and has a low manufacturing cost.

[0008]

A piezoelectric speaker according to the present invention for achieving the above object will be described with reference to FIGS. 1 to 3 showing a first invention and FIGS. 4 to 6 showing a second invention. In the first invention, the plurality of gutter-shaped curved surfaces 1a, 1b, which join the adjacent sides in the parallel direction to form the joint 11a,
, And the film-shaped diaphragm 1 attached to the frame 3 by being adhered to the frame 3 at the outer side portions 11b, 11b on the opposite side of the joined portion 11a and the peripheral portion of the frame 3
A bimorph type or unimorph type piezoelectric element 2 adhered to and supported by the piezoelectric element 2 and a joint part 11a of the diaphragm 1 is a piezoelectric speaker unit 10 adhesively bonded to the piezoelectric element 2. It is a piezoelectric speaker.

The second aspect of the present invention is to form a plurality of gutter-shaped curved surfaces 1a, 1b, which are joined portions 11a by joining adjacent sides in the parallel direction.
, And the film-shaped diaphragm 1 attached to the frame 3 by being adhered to the frame 3 at the outer side portions 11b, 11b on the opposite side of the joined portion 11a and the peripheral portion of the frame 3
A piezoelectric speaker unit 20 comprising a bimorph type or unimorph type piezoelectric element 2 adhered to and supported on a piezoelectric element 2, and a joint portion 11a of the diaphragm 1 is adhesively coupled to the piezoelectric element 2 via a coupling rod 4. It is a piezoelectric speaker characterized by comprising.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In a piezoelectric loudspeaker having such a structure, a rectangular diaphragm 1 having a good area factor as viewed from the sound wave emission direction is adopted as compared with a normal circular diaphragm. Therefore, the sound pressure is improved over the entire sound range, and particularly, the band near the lowest resonance frequency can be reproduced with high efficiency.

Further, the rising angle α of the joint 11a where the diaphragm 1 of the speaker unit 10 of the first embodiment according to the first invention shown in FIGS. 1 to 3 is connected to the piezoelectric element 2 is steep. The rigidity with respect to the vibration direction is high, the high resonance frequency becomes high, and it has the effect of widening the reproduction frequency band to the higher side, and unlike the point junction in the conical diaphragm, the coupling with the piezoelectric element 2 is performed. Since the part is linear and has a large area, the electroacoustic conversion efficiency is improved, and the reproduction level becomes high even at the high resonance frequency, that is, the high limit frequency of the reproduction band. Moreover, the piezoelectric speaker is excellent in tone color with low manufacturing cost.

Further, since the diaphragm 1 has a gutter-shaped curved surface shape, the inclination angle of the diaphragm continuously changes from the rising angle α of the joint portion 11a toward the diaphragm peripheral direction, and the gutter-shaped curved surface is also formed. Since the parts in the longitudinal direction vibrate in the same phase, it is possible to continuously reproduce at a high level even in the band between the lowest resonance frequency and the high resonance frequency as compared with the case of the conical shape. Also, in the case of a single speaker unit, the directivity characteristic is broad in the direction perpendicular to the joint portion 11a of the diaphragm.

Also, in the speaker unit 20 according to the second aspect of the present invention shown in FIGS. 4 to 6, the diaphragm 1 has the joint portion 11a.
At the intermediate point of the above, the outer peripheral edge portion is connected to the center of the piezoelectric element 2 fixed to the frame 3 by the connecting rod 4. The peripherally fixed piezoelectric element vibrates in a mode similar to a circular membrane, and is not constrained along the diameter, so that it vibrates efficiently, and in particular, the central portion has the maximum amplitude. Therefore, this embodiment has high electroacoustic conversion efficiency.

In addition, the characteristic of the diaphragm of the first aspect of the present invention is that the high resonance frequency is increased and the reproduction frequency band is widened to the higher side, and between the lowest resonance frequency and the high resonance frequency. In the case of a single speaker unit, the function of continuously reproducing at a high level even in the band of, and the function of broadening in a direction perpendicular to the joint portion 11a of the diaphragm are obtained at a low manufacturing cost. A feature of the present invention is to provide a piezoelectric speaker with excellent tone color conversion efficiency.

FIG. 20 shows the frequency characteristics of the piezoelectric speaker unit of the first embodiment 1 of the present invention. As shown, the playback frequency band is typically 3rd as shown in the figure.
Due to the next harmonic, the maximum limit of the normal high frequency speaker is 20
Since it can reproduce up to a high frequency of 50 KHz, which is much higher than KHz, it is used for a tweeter of a composite type speaker.

[0016]

FIG. 1 shows the configuration of an embodiment of the piezoelectric speaker of the present invention.
~ It will be described in detail with reference to FIG. 1 is a top view of the first embodiment, FIG. 2 is a side sectional view, FIG. 3 is a perspective view of the first embodiment, FIG. 4 is a partial side sectional view of the second embodiment, FIG. 5 is a top view, and FIG. Similarly, a partial cross-sectional view of the other side surface of the second embodiment, FIG. 7 is an exploded view showing a manufacturing process of the first embodiment, FIG. 8 is a schematic perspective view of a diaphragm molding die of the first and second embodiments, FIG. 9 is an exploded view of another manufacturing process of the first embodiment.

FIG. 10 is a top view of one modification of the first and second embodiments of the present invention, FIG. 11 is a side view thereof, and FIG. 12 is a top view of another modification of the speaker of the present invention. FIG. 13 is a side view thereof, and further, as various application examples using the first embodiment, the second embodiment and the modification thereof, FIG.
Is an external view of the speakers mounted on the front and back sides at right angles, FIG. 15 is an exploded perspective view thereof, and FIG. 16 is an external view of the speakers mounted on the same plane with their respective angles turned at right angles. FIG. 17 is a top view thereof, FIG. 18 is a top view of a speaker in which the speaker unit of the present invention is attached to the outside of a radial square surface in the same direction, and FIG. 19 is a speaker unit of the present invention attached to the outside of a radial triangular surface in the same direction. It is a top view of the speaker.

1 to 3 showing the structure of the piezoelectric speaker unit 10 of the first embodiment, and FIG. 7 showing the disassembled state.
In the present embodiment, reference numeral 1 is a diaphragm of the speaker of the present invention. In this embodiment, the outer shape of a 38-micron-thick polyimide or polyetherimide film A is cut out into a square shape to form a joint portion 11a.
It is bent (B) around the center line, and both sides are adjacent to the gutter-shaped curved surfaces 1a and 1b, and if necessary, heated and shaped. Then, the outer peripheral portions 11b and 11b are formed on both edges (C).

Alternatively, the above-mentioned film A is pressed by the hot pressing molds 25 and 26 shown in FIG.
Two gutter-shaped curved surfaces 1a and 1b, which are formed by cutting the periphery, are manufactured, and as shown in FIG. 9, the edges to be the joints 11a are bonded by an adhesive in another step, and both ends thereof are bonded. It can be obtained by molding the outer peripheral portions 11b and 11b on the edges. Further, the pressing shape of the above-mentioned hot pressing molds 25 and 26 is press-molded in one shot on both sides adjacent to the gutter-shaped curved surfaces 1a and 1b, like the shape (C) of the diaphragm 1 in FIG. You can also

On the line passing through the center of the bimorph type piezoelectric element 2 (or the unimorph type piezoelectric element 2 ') of the speaker of the present invention, the bonding portion 11a of the diaphragm 1 is adhered over the entire length. Has been done. Therefore, since the connecting portion with the piezoelectric element 2 is linear and has a large bonding area, the reproduction level becomes high even at the high resonance frequency, that is, at the high limit frequency of the reproduction band. The piezoelectric element 2 is an outer frame 3 that constitutes the frame 3.
It is attached to the frame 3 in a state of being sandwiched between an attachment frame 3b and a holding frame 3c provided inside a.

Since the diaphragm 1 has a gutter-shaped curved surface shape, the inclination angle of the diaphragm 1 is the rising angle α of the joint portion 11a.
It continuously changes from the top to the top, and since the longitudinal part of the gutter-shaped curved surface vibrates in the same phase, it is continuous even in the band between the lowest resonance frequency and the high resonance frequency as compared with the case of the conical shape. And can be played back at a high level.
Therefore, the frequency characteristic during this period becomes flat at a high level.
As described above, the joint portion 1 connected to the piezoelectric element 2
Since the rising angle α of 1a is steep, the rigidity is large in the vibration direction, and since the diaphragm 1 is composed of a plurality of trough-shaped curved surfaces 1a and 1b, its high resonance frequency is increased and the reproduction frequency band is increased. Becomes wider.

Further, since the rectangular diaphragm 1 is adopted as viewed from the radiation direction of the sound wave, the diaphragm area is large and the minimum resonance occurs when the outer dimensions are the same (rectangular piece length = circular diameter). It is possible to reproduce in a band near the frequency with higher efficiency than that of a conventional circular (conical) diaphragm speaker.

Further, the diaphragm 1 used in the speaker of the present invention is easier to manufacture when a rectangular diaphragm is obtained than when it is a conical diaphragm. Further, when the outer dimensions (diameter and one side) are the same, the price per unit area of the acoustic radiation surface viewed from the sound radiation direction is relatively low.

In the piezoelectric speaker unit 20 of the second embodiment whose structure is shown in FIGS. 4 to 6, the diaphragm 1, the piezoelectric element 2, and the frame 3 have the same shape as that of the first embodiment.
The difference is that the joint portion 11a is coupled to the center of the piezoelectric element 2 via the coupling rod 4. Since the diaphragm 1 is driven by the portion of the piezoelectric element 2 having the largest amplitude, the second embodiment has a characteristic that the conversion efficiency is high.

10 and 11 are a front view and a side sectional view of a modified example of the first embodiment. The vibrating plate 1 of this modified example is composed of a gutter-shaped curved surface 1a, a gutter-shaped curved surface 1b, and a gutter-shaped curved surface 1c.
Consisting of two gutter-shaped curved surfaces, the length of each gutter-shaped curved surface,
The diaphragm 1 has the same width and the same radius of curvature, and therefore has the same sound pressure frequency characteristics of each curved surface, and is suitable as a piezoelectric speaker that emits a large output. The vibrating plate 1 is linearly bonded to the piezoelectric element 2 at a position apart from the center on the surface of the piezoelectric element 2 by the two joint portions 11a and 11a.

Further, in another modification shown in FIGS. 12 and 13, the sizes of the gutter-shaped curved surfaces 1d and 1f at both ends are large, and the size of the central gutter-shaped curved surface 1e is the gutter-shaped curved surface. 1
d, the sound pressure frequency characteristic of each curved surface is changed by making it smaller than the gutter-shaped curved surface 1f. In this case, the radiation sound of the central trough-shaped curved surface 1e can be set to a higher range than the radiation sounds of the other trough-shaped curved surfaces 1d and 1f. On the other hand, the gutter-shaped curved surfaces 1d and the gutter-shaped curved surfaces 1f at both ends having a large size have a large radiation area, and thus are suitable for low-frequency range reproduction. In the other modified example, the diaphragm 1 and the piezoelectric element 2 are also adhesively bonded in a linear shape at two locations apart from the center of the piezoelectric element 2, as in the above-described modified example.

As described above, in the other modified examples shown in FIGS. 12 and 13, the gutter-shaped curved surface portion 1 having different shape dimensions is used.
Since d, 1e, and 1f are combined, the vibration modes of the respective parts are different and the frequency characteristics are also different. As a result, the reproduction band is wider as a whole, the directional characteristics are broad, and the frequency characteristics are It has the effect of being flat. In particular, the size of the central trough-shaped curved surface 1e is small, which is suitable for reproduction in the super high range.

Further, the dimension between the outer peripheral portions 11b, 11b is made larger than the length (diameter) of the joint portion of the piezoelectric element 2 to increase the surface area of the vibration plates 1a, 1b, (1c) and the conversion efficiency. Can be set to a high value for high output. in this way,
The speaker using the piezoelectric speaker unit of the present invention has an advantage that the sound pressure frequency characteristic and the directional characteristic can be freely selected and radiated depending on the intended use.

As described above, each of the piezoelectric loudspeakers of the present invention has a high efficiency in the band near the lowest resonance frequency, and continuously in the band between the lowest resonance frequency and the high frequency resonance frequency. It can be played back at a high level, has a wider playback band, and has a flat frequency characteristic, so it has the characteristics of a super tweeter, and is extremely useful when combined with a woofer, squawker, or tweeter. It is possible to make a multi-way speaker excellent in high-frequency reproduction.

The configuration of each of the above-described embodiments and modifications of the piezoelectric speaker of the present invention is not limited to the structure of the above embodiment. For example, as the material of the diaphragm 1, in addition to the above-mentioned polyimide and polyetherimide, any moldable material having appropriate rigidity and internal loss such as plastic film, aluminum or aluminum alloy, paper, cloth, etc. may be used. be able to. Therefore, there is a convenience that processing can be easily performed. In the case of the modified speaker unit, the gutter-shaped curved surfaces do not necessarily have to have the same size and curvature, and need not be symmetrical with respect to the center line.

The piezoelectric speaker unit 10 according to the first embodiment and the piezoelectric speaker unit 2 according to the second embodiment described above will be described below.
An application example using 0 and each modified speaker unit will be described.

First, as shown in FIGS. 14 and 15, a speaker using a speaker unit in which the diaphragms 1 having a trough-shaped curved surface are placed back to back with a piezoelectric element 2 interposed therebetween is a bidirectional speaker. In addition, the directional characteristics can be changed in the case of a speaker in which the front and back speaker units are arranged at right angles to each other in the axial direction, for example, as shown in FIG. Of course, it is also possible to arrange a plurality of them on the same plane in the same direction to make the directivity sharp and to radiate the super treble in a specific direction perpendicular to the plane.

Further, as shown in FIGS. 16 and 17, a large number of piezoelectric type speaker units 10, 10, ... (Or piezoelectric type speaker units 20, 20 ,. The multi-unit loudspeakers arranged side by side in a direction can increase electroacoustic conversion efficiency by substantially increasing the diaphragm area, and can sharpen directivity to concentrate sound at a desired place. As a modification of this application example, an array of speaker units is
For example, if there is only one column in the vertical direction, it is possible to easily adopt a so-called three-dimensional sound radiation method that radiates super high frequencies in the horizontal direction with broad directional characteristics as in the case of tone distortion.

Furthermore, as shown in FIGS.
The piezoelectric type speaker unit 10, 10, ... (or the piezoelectric type speaker unit 20, 20, ..., Or its modification speaker) is mounted on a flat plate to form a polygonal columnar support 8 such as a triangular prism or a quadrangular prism. , Or a polyhedron support (not shown), and arranged in a polyhedron shape so as to radiate in three, four, or more directions, and incorporated to form a spherical radiator that vibrates a respiratory ball. It has many advantages such as being able to easily.

As described above, the speaker of the present invention has a simple structure, a lightweight composition material, and a small number of constituents.
Overall cost is low and assembly is very easy,
Even in the case of the application speaker of the multi-unit driving type as described above, the advantages of overall lightweight, easy assembly, and low cost are not lost.

Further, it is not necessary that the gutter-like curved surface portions of the diaphragm 1 have the same shape or the same shape symmetrically as shown in the drawings, or the same shape and shape symmetrically. As long as the requirements are met, the action of the present invention is exhibited, and the effects described below are exhibited, the invention can be appropriately modified and carried out.

[0037]

As described above, the piezoelectric loudspeaker according to the present invention basically has the effect of the conventional rectangular trough-shaped curved surface diaphragm as a loudspeaker, and has a structure unique to the original loudspeaker of the present invention. The following effects can be expected as unique effects based on this.

(1) Since the diaphragm is made of a thin sheet material such as paper, metal, cloth, synthetic resin, etc., it is easily available and can be easily processed by cutting, bending, bonding and the like. (2) The driving source can be manufactured at a low cost by using a material such as a ceramic vibrator that is easily available at low cost. (3) With respect to the above (1) and (2), since the speaker unit uses a light material in combination as a vibrating element, the product speaker can be made lightweight and mass-produced at low cost. (4) The diaphragm can be freely designed into a shape that is easy to mold. (5) No equipment such as heating or embossing is required for forming the diaphragm. (6) No large equipment is required in the speaker assembly manufacturing process, and the manufacturing space is small. (7) Since it can be easily combined with other speakers and does not take up space, it can be easily combined with other speakers as a super tweeter for multi-way speakers. (8) Since the vertical and horizontal directional characteristics clearly appear, it is possible to construct a speaker having optimum directional characteristics for a required service area.

As a result of the above-mentioned effects, the piezoelectric speaker of the present invention has a wide reproduction frequency band and obtains a relatively flat frequency characteristic in a wide band between the lowest resonance frequency and the high resonance frequency. Thus, the piezoelectric speaker having high efficiency and excellent tone color can be provided at a low cost, which has a comprehensive effect.

[Brief description of drawings]

FIG. 1 is a top view showing the structure of Example 1 of the present invention.

FIG. 2 is a side sectional view of the first embodiment as well.

FIG. 3 is also a perspective view of the first embodiment.

FIG. 4 is a partial side sectional view of the second embodiment.

FIG. 5 is a top view of Example 2 of the same.

FIG. 6 is a partial cross-sectional view of the other side surface of the second embodiment.

FIG. 7 is an exploded view showing the manufacturing process of the first embodiment.

FIG. 8 is a schematic perspective view of a diaphragm molding die according to the first and second embodiments.

FIG. 9 is an exploded view of another manufacturing process of the first embodiment.

FIG. 10 is a top view of a modification of the embodiment of the present invention.

FIG. 11 is a side view of the same.

FIG. 12 is a top view of another modification of the embodiment of the present invention.

FIG. 13 is a side view of the same.

FIG. 14 is an external view of an application example loudspeaker mounted on both front and back sides of a plane with their directions turned at right angles.

FIG. 15 is an exploded perspective view of the above.

FIG. 16 is an external view of another application speaker mounted on the same plane with their directions changed at right angles.

FIG. 17 is a top view of the above.

FIG. 18 is a top view of an application example speaker in which the speaker unit of the present invention is attached to the outside of a radial square surface in the same direction.

FIG. 19 is a top view of an application example speaker in which the speaker unit of the present invention is attached to the outside of a radial triangular surface in the same direction.

FIG. 20 is a frequency characteristic diagram of the first embodiment of the present invention.

FIG. 21 is a side sectional view of a conventional example 1 speaker.

FIG. 22 is a side sectional view of a conventional example 2 speaker.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vibration plate 2 Piezoelectric element (bimorph type) 2'Piezoelectric element (unimorph type) 3 Frame 4 Coupling rod 5 Resonator 6 Frame of Conventional example 2 Cone type vibration plate 8 Polygonal columnar support

Claims (2)

[Claims] 1. A joint portion formed by joining adjacent sides in a parallel direction.
(11a) is composed of a plurality of gutter-shaped curved surfaces (1a), (1b), ..., And an outer peripheral portion (11) opposite to the above-mentioned joined joint (11a).
b) and (11b), the film diaphragm (1) is attached to the frame (3) by adhesion, and the bimorph-type or unimorph-type piezoelectric plate is supported by adhering the peripheral part to the frame (3). element
2. A piezoelectric speaker comprising a piezoelectric speaker unit (10), which comprises (2) and a bonding portion (11a) of the diaphragm (1) adhesively bonded to the piezoelectric element (2). 2. A joint portion formed by joining adjacent sides in a parallel direction.
(11a) is composed of a plurality of gutter-shaped curved surfaces (1a), (1b), ..., And an outer peripheral portion (11) opposite to the above-mentioned joined joint (11a).
b) and (11b), a film-shaped diaphragm (1) attached to the frame (3) by adhesion, and a bimorph-type or unimorph-type piezoelectric plate whose peripheral part is attached and supported by the frame (3). element
(2) consisting of a piezoelectric loudspeaker unit (20) in which the joint portion (11a) of the diaphragm (1) is adhesively bonded to the piezoelectric element (2) via a coupling rod (4). Piezoelectric speaker characterized by.