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JPH09215093

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPH09215093
[0001]
The present invention has a simple structure, a small size, a light weight, and a shape easily
accessible to high-order vibration waves, efficiently super-high frequency sound, good frequency
characteristics and directivity characteristics, and a wide band. The present invention relates to
the structure of a piezoelectric speaker to be reproduced by the
[0002]
2. Description of the Related Art Piezoelectric type sounding bodies are conventionally divided
roughly into two types of structures, and as an electro-mechanical vibration conversion
mechanism, as in the prior art 1 shown in FIG. A unimorph type piezoelectric element 2 'of a
known structure in which a piezoelectric ceramic thin plate 2b is adhered to one side of a plate
2a and the other electrode plate 2c is adhered to the other side, or a prior art example 2 shown
in FIG. As in the above, a bimorph type piezoelectric element 2 is used in which another
piezoelectric ceramic thin plate 2b and an electrode plate 2c are formed on the other surface of
the metal plate 2a.
[0003]
One example of the structure of a speaker unit as a conventional sounding body utilizes the
piezoelectric element 2 or the piezoelectric element 2 'directly as a diaphragm, but since the
conversion efficiency is low if the piezoelectric element as it is, the conventional structure shown
in FIG. In the structure of Example 1, the resonator 5 having a resonance frequency equal to the
resonance frequency of the piezoelectric element 2 'and having the sound emission hole 5a
formed therein is coupled to the front surface of the piezoelectric element 2'. Is amplified by
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resonance to enhance the conversion efficiency.
[0004]
The above-mentioned piezoelectric speaker is small and relatively efficient but narrow in
reproduction frequency band to emit sound of a single frequency, and is not suitable for
reproducing wide-band sound as a speaker. In order to eliminate such a defect, the sound
generator, that is, the piezoelectric speaker of Conventional Example 2 shown in FIG. 22 has been
put to practical use.
The structure will be described with reference to the figure. The piezoelectric element 2 is
attached to the top of the conical diaphragm 7 whose peripheral portion is supported by the
frame 6, and the lead 21a connected to the metal plate 2a When the electric signal is applied
through the conducting wire 21b connected to the electrode plate 2c, the piezoelectric element 2
bends and vibrates in the direction perpendicular to the surface, and the cone-shaped diaphragm
7 vibrates by reaction to emit sound.
With this structure, the acoustic energy is directly radiated from the cone-shaped diaphragm 7 so
that the conversion efficiency is slightly high, and since there is no resonator on the front, the
reproduction band is broadened, and it can be used as a speaker Become.
[0005]
Among the above, the conventional example 1 shown in FIG. 21 only emits sound of a single
frequency, so that it can be used as a narrow band sound generator. Not suitable for use as a
speaker.
[0006]
The conventional example 2 shown in FIG. 22 can be used as a speaker for reproducing the
sound range to some extent, but the cone-shaped diaphragm 7 that emits sound is intended to be
conventionally used in the band of mass control. Therefore, the rigidity is relatively high, and it is
regenerated with a certain degree of efficiency at the lowest resonance frequency because it
vibrates integrally with the piezoelectric element 2, but the efficiency is high because the mass of
the vibration system is increased in the frequency band higher than that. Since the efficiency is
significantly reduced in the low frequency band above the high resonance frequency,
substantially only the lowest resonance frequency is reproduced at a high level, the frequency
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characteristic is not flat in the other bands, and the reproduction frequency band is not very
high. There was a drawback that said it was not wide.
[0007]
Therefore, the present invention devises and improves the shape of the diaphragm, the coupling
structure of the diaphragm and the piezoelectric element, and the attachment structure of the
diaphragm and the piezoelectric element to the frame, in order to eliminate the disadvantages of
the prior art. In addition, another object of the present invention is to provide a low-cost
piezoelectric type speaker which has flat frequency characteristics and efficiently reproduces a
wide band.
[0008]
A piezoelectric speaker according to the present invention for achieving the above object will be
described based on FIGS. 1 to 3 showing the first invention and FIGS. 4 to 6 showing the second
invention. In the first aspect of the present invention, a plurality of wedge-shaped curved
surfaces 1a, 1b,... Are used as the joint portion 11a by joining adjacent sides in the parallel
direction, and the other side opposite to the joint portion 11a A diaphragm 1 in the form of a film
attached and attached to the frame 3 by the outer side parts 11b and 11b, and a bimorph or
unimorph piezoelectric element 2 supported by attaching the peripheral part to the frame 3 The
piezoelectric speaker is characterized in that it comprises a piezoelectric speaker unit 10 in
which a joint portion 11 a of the diaphragm 1 is adhesively bonded to the piezoelectric element
2.
[0009]
In the second invention, a plurality of wedge-shaped curved surfaces 1a, 1b,... Are used as joined
portions 11a by joining adjacent sides in a parallel direction, and the outer side portion 11b
opposite to the joined portions 11a joined , 11b and the film-like diaphragm 1 attached to the
frame 3 by adhesion, and the bimorph or unimorph piezoelectric element 2 supported by
adhering the periphery to the frame 3; The piezoelectric speaker unit 20 is characterized in that
the piezoelectric speaker unit 20 is bonded to the piezoelectric element 2 via a coupling rod 4
and bonded.
[0010]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the piezoelectric speaker of
such a configuration, a rectangular diaphragm 1 having a good area factor as viewed from the
direction of sound wave radiation is employed as compared to a normal circular diaphragm.
Therefore, the sound pressure is improved over the entire sound range, and in particular, the
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band near the lowest resonance frequency can be reproduced with high efficiency.
[0011]
Further, since the rising angle α of the joint portion 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, On the other hand, the rigidity is high, the high
frequency resonance frequency is high, and the reproduction frequency band is broadened to the
high side, and unlike the point junction in the conical diaphragm, the junction with the
piezoelectric element 2 Since the area is large and the area is large, 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.
In addition, the piezoelectric speaker is excellent in timbre and inexpensive in manufacturing
cost.
[0012]
Furthermore, since the diaphragm 1 has a wedge-shaped curved surface shape, the inclination
angle of the diaphragm changes continuously from the rising angle α of the joint 11a toward the
diaphragm peripheral direction, and the longitudinal direction of the wedge-shaped curved
surface Since the parts vibrate in phase, it is possible to continuously reproduce at a high level 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 also becomes broad in the
direction perpendicular to the bonding portion 11 a of the diaphragm.
[0013]
Further, in the speaker unit 20 according to the second invention shown in FIGS. 4 to 6, the
piezoelectric element 1 has a piezoelectric element whose outer peripheral portion is fixed to the
frame 3 by the connecting rod 4 at the middle point of the joint portion 11a. It is coupled to the
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center of the element 2.
The peripherally fixed piezoelectric element vibrates in a circular film-like mode and vibrates
efficiently because it is not constrained along the diameter, and in particular, the central portion
has a maximum amplitude.
Therefore, this embodiment has a high electroacoustic conversion efficiency.
[0014]
In addition, it is a feature of the diaphragm according to the first aspect of the invention
described above that the high frequency resonance frequency is increased and the reproduction
frequency band is broadened to the high side, and even the band between the lowest resonance
frequency and the high frequency resonance frequency. In the case of a speaker unit having a
single high-level reproduction and directivity characteristics as well, it has an additional effect of
becoming broad in the direction perpendicular to the junction 11a of the diaphragm, and further,
it is excellent in timbre with low manufacturing cost. And a piezoelectric speaker having high
conversion efficiency.
[0015]
FIG. 20 shows the frequency characteristics of the piezoelectric speaker unit according to the
first embodiment of the present invention described above.
As shown, the reproduction frequency band can be reproduced to a high frequency of 50 KHz,
which is much higher than the 20 KHz high limit of a typical high-pitched speaker, by the
typically illustrated third harmonic. Used as a speaker tweeter.
[0016]
DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of an embodiment of the
piezoelectric speaker according to the present invention will be described in detail with reference
to FIGS.
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1 is a top view of Example 1, FIG. 2 is a cross-sectional view of a side, FIG. 3 is a perspective view
of Example 1, FIG. 4 is a side partial cross-sectional view of Example 2, FIG. 5 is a top view, FIG.
Similarly, FIG. 7 is an exploded view showing a manufacturing process of Example 1, FIG. 8 is a
schematic perspective view of a molding die of the diaphragm of Example 1 and Example 2, FIG.
FIG. 9 is an exploded view of another manufacturing process of the first embodiment.
[0017]
10 is a top view of one of the above-mentioned first embodiment and the second embodiment of
the present invention, FIG. 11 is a side view thereof, FIG. 12 is a top view of another variation of
the speaker of the present invention, FIG. FIG. 14 is an external view of a speaker attached to the
front and back sides of a plane with its directions changed at right angles as various applications
using the first embodiment, the second embodiment and the modification thereof. FIG. 15 is an
exploded perspective view of the speaker, FIG. 16 is an external view of a speaker mounted with
its sides turned at right angles on the same plane, FIG. 17 is a top view thereof, and FIG. FIG. 19
is a top view of a speaker in which the speaker unit of the present invention is mounted in the
same direction on the outside of a radial triangular surface.
[0018]
In FIGS. 1 to 3 showing the structure of the piezoelectric speaker unit 10 of the first embodiment
and FIG. 7 showing the disassembled state, 1 is a diaphragm of the speaker of the present
invention. In this embodiment, a 38 micron thick polyimide or The outer shape of the
polyetherimide film A is cut out in a square and bent around the center line to be the joint
portion 11a (B), and both sides are heated and shaped if necessary adjacent to the bowl-like
curved surfaces 1a and 1b .
Then, the outer side portions 11b and 11b are formed at both end edges (C).
[0019]
Alternatively, the film A described above is pressed by the hot-pressing molds 25 and 26 shown
in FIG. 8 to be heat-formed, and two pieces obtained by cutting the periphery are formed as
single wedge-shaped curved surfaces 1a and 1b. As shown in FIG. 9, the edge which will be the
joint portion 11a is bonded with an adhesive as shown in FIG. 9, and the outer side portions 11b
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and 11b can be formed on both end edges thereof.
Further, the pressing shapes of the above-described hot pressing dies 25 and 26 are formed by
one-shot pressing on both sides adjacent to the wedge-shaped curved surfaces 1a and 1b as
shown in the shape (C) of the diaphragm 1 of FIG. It can also be done.
[0020]
The joint 11a of the diaphragm 1 is bonded over the entire length on a line passing through the
center of the bimorph piezoelectric element 2 (or the unimorph piezoelectric element 2 ') of the
speaker according to the present invention. . Therefore, since the junction with the piezoelectric
element 2 is linear and the junction area is large, the reproduction level is high even at the highresonance frequency, that is, the high-frequency limit frequency of the reproduction band. The
piezoelectric element 2 is attached to the frame 3 in a state of being held between an attachment
frame 3 b and a presser frame 3 c provided inside the outer frame 3 a constituting the frame 3.
[0021]
Further, since the diaphragm 1 has a wedge-shaped curved surface shape, the inclination angle
of the diaphragm 1 changes continuously from the rising angle α of the joint portion 11a to the
top, and the longitudinal direction of the wedge-shaped curved surface is the same. Since it
vibrates in phase, it is possible to continuously reproduce at a high level in the band between the
lowest resonance frequency and the high resonance frequency as compared with the case of the
conical shape. Therefore, the frequency characteristic during this period becomes flat at a high
level. As described above, since the rising angle α of the joint portion 11a coupled to the
piezoelectric element 2 is steep, the rigidity is large in the vibration direction, and the diaphragm
1 is formed of a plurality of wedge-shaped curved surfaces 1a and 1b. Because of that, the high
frequency resonance frequency becomes high and the reproduction frequency band becomes
wide.
[0022]
Also, as viewed from the radiation direction of the sound wave, the rectangular diaphragm 1 is
adopted, so the diaphragm area is large in the case of the same external dimensions (the length
of one square of the square length of the circle) and it is near the lowest resonance frequency.
The band can be reproduced more efficiently than a conventional circular (conical) diaphragm
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speaker.
[0023]
Furthermore, the diaphragm 1 used in the speaker according to the present invention is easier to
manufacture than the conical diaphragm in obtaining a square diaphragm.
Further, when the external dimensions (diameter and one side) are the same, the cost per unit
area of the acoustic radiation surface viewed from the sound radiation direction is relatively
inexpensive.
[0024]
The piezoelectric speaker unit 20 of the second embodiment whose structure is shown in FIGS. 4
to 6 has the same shape as the first embodiment but the diaphragm 1, the piezoelectric element
2 and the frame 3 have the same shape as the first embodiment. Except that they are connected
to the center of the piezoelectric element 2 via the connecting rod 4. The second embodiment is
characterized in that the conversion efficiency is high because the diaphragm 1 is driven by the
portion with the largest amplitude of the piezoelectric element 2.
[0025]
10 and 11 are a front view and a side sectional view of a modification of the first embodiment.
The diaphragm 1 of this modification includes three wedge-shaped curved surfaces such as a
wedge-shaped curved surface 1a, a wedge-shaped curved surface 1b, and a wedge-shaped curved
surface 1c, and the length, width, and radius of curvature of each wedge-shaped curved surface
Is the same, so that the sound pressure frequency characteristics of the respective curved
surfaces are all equal to each other in the diaphragm 1, which is suitable as a piezoelectric
speaker that emits a large output. The diaphragm 1 is bonded by bonding at a position away
from the center of the piezoelectric element 2 and the surface of the piezoelectric element 2 by
bonding portions 11 a and 11 a at two places.
[0026]
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Further, in the other modified examples shown in FIGS. 12 and 13, the dimensions of the ridged
curved surface 1d and the ridged curved surface 1f at both ends are increased, and the
dimensions of the central ridged curved surface 1e are formed by the ridged curved surface 1d.
The sound pressure frequency characteristics of the respective curved surfaces are changed by
making them smaller than the curved surface 1f. In this case, the radiation sound of the central
wedge-shaped curved surface 1e can be made into a sound range higher than the radiation
sound of the other wedge-shaped curved surfaces 1d and 1f. On the other hand, since the curved
surface 1d and the curved surface 1f on both ends of the large-sized end are large in radiation
area, they are suitable for bass region reproduction. In the other modified example as well, the
diaphragm 1 and the piezoelectric element 2 are adhesively bonded in a linear manner at two
places apart from the center of the piezoelectric element 2 as in the above-described modified
example.
[0027]
Thus, in the other modifications shown in FIGS. 12 and 13, since the wedge-shaped curved
surface portions 1d, 1e, 1f having different shapes and sizes are combined, the vibration modes
of the respective portions are different, and the frequency characteristics thereof are different. As
a result, the reproduction band is wider as a whole, the directivity characteristic is also broad,
and the frequency characteristic is flat. In particular, the size of the central wedge-shaped curved
surface 1e is small, and is suitable for reproduction of the super high range.
[0028]
In addition, the dimension between the two outer side portions 11b and 11b is made larger than
the length (diameter) of the bonding portion of the piezoelectric element 2, and the surface area
of the diaphragms 1a, 1b and (1c) is increased to enhance the conversion efficiency. Can also be
used for high output. As described above, the speaker using the piezoelectric speaker unit of the
present invention has an advantage of being able to freely select and radiate the sound pressure
frequency characteristic and the directivity characteristic according to the usage.
[0029]
As described above, each embodiment and modification of the piezoelectric speaker according to
the present invention are highly efficient in the band near the lowest resonance frequency, and
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continuously high in the band between the lowest resonance frequency and the high resonance
frequency. It has the characteristics of a super tweeter because it can be played back, and
furthermore, the playback band is wider and the frequency characteristic is flat, and it can be
used for ultra-high tone playback in combination with a woofer, squawker or tweeter. It can be
an excellent multi-way speaker.
[0030]
The configuration of each embodiment and modification of the piezoelectric speaker according to
the present invention described above is not limited to the configuration of the above
embodiment.
For example, as the material of the diaphragm 1, any material can be used as long as it is a
moldable material having appropriate rigidity and internal loss, such as plastic film, aluminum or
aluminum alloy, paper, cloth, etc. be able to. Therefore, there is a convenience that can be easily
processed. Further, in the case of the modified speaker unit, the dimensions, the curvatures, and
the like of the respective wedge-shaped curved surfaces do not necessarily have to be the same,
and are not necessarily symmetrical with respect to the center line.
[0031]
Hereinafter, application examples using the piezoelectric speaker unit 10 of the first
embodiment, the piezoelectric speaker unit 20 of the second embodiment, and the modified
speaker units of the second embodiment will be described.
[0032]
First, as shown in FIGS. 14 and 15, a speaker using a speaker unit in which the diaphragms 1 of
the above-described wedge-shaped curved surface are arranged back to back with the
piezoelectric element 2 in between is a bidirectional speaker. In the case of a speaker as shown in
the figure, for example, in which the front and back speaker units are arranged at right angles to
each other in the axial direction, the directivity characteristic can be changed.
Of course, it is possible to arrange plural pieces in the same direction on a plane to sharpen the
directivity, and to concentrate and radiate super high sound in a specific direction perpendicular
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to the plane.
[0033]
Further, as shown in FIGS. 16 and 17, a large number of piezoelectric speaker units 10, 10,... (Or
piezoelectric speaker units 20, 20,... Or modified speakers thereof) are arranged in the same
plane at right angles to each other on the same plane. The arranged multi-unit speaker can
increase the electroacoustic conversion efficiency by the increase of the diaphragm area
substantially, and can make the directivity sharp and concentrate the sound at a desired place. As
a modification of this application example, if the arrangement of the speaker units is, for
example, only one line in the vertical direction, a so-called three-dimensional sound radiation
system which radiates super high sound in the horizontal direction as in the tone zone and with
broad directivity characteristics. Things are easily possible.
[0034]
Furthermore, as shown in FIGS. 18 and 19, an assembly in which piezoelectric speaker units 10,
10,... (Or piezoelectric speaker units 20, 20,.. Incorporating into a polygonal support 8 such as a
triangular prism or a quadrangular prism, or a polyhedral support (not shown), and arranging it
in a polyhedral shape so as to radiate in three directions, four directions or more, It has many
advantages, such as being easily incorporated to construct a vibrating spherical radiator.
[0035]
As described above, since the speaker of the present invention is simple in structure, light in
composition material, and small in number of components, the overall cost is low and the
assembly is extremely easy, and the application of the multiple unit drive as described above
Even as an example speaker, the advantages of overall light weight, easy assembly and low cost
are not lost.
[0036]
Also, the shape and size of the wedge-shaped curved surface portion of the diaphragm 1 need not
be all the same as in the drawings, or the same size and shape as in the symmetry, and has the
features described in the claims. As long as they exhibit the effects of the present invention and
have the effects described below, they can be modified as appropriate.
[0037]
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As described above, the piezoelectric speaker according to the present invention basically retains
the effect as a speaker of the conventional rectangular wedge-shaped curved diaphragm, and has
a unique structure unique to the speaker according to the present invention. The following
effects can be expected as specific effects based on:
[0038]
(1)
Since the diaphragm is made of a thin sheet-like material such as paper, metal, cloth or synthetic
resin, it is easy to obtain and easy to process such as cutting, bending, bonding and the like.
(2)The drive source can be manufactured using an inexpensive material such as a ceramic
vibrator, which can be manufactured inexpensively as a whole.
(3)In relation to the above (1) and (2), since the speaker unit is used as a vibrating element in
combination with a light material, the product speaker can be made lightweight, and mass
production can be performed inexpensively.
(4)It can be freely designed in an easy-to-form shape of the diaphragm.
(5)The formation of the diaphragm does not require equipment such as heating or embossing.
(6)The speaker assembly manufacturing process does not require large equipment and the
manufacturing space can be small. (7)It can be easily combined with other speakers, and it is
easy to combine with other speakers as a super toe speaker of a multi-way speaker because it
takes up no space. (8)Since the vertical and horizontal directional characteristics appear clearly,
it can be configured as a speaker having the optimal directional characteristics for the required
service area.
[0039]
As a result of the various effects described above, the piezoelectric speaker of the present
invention has a wide reproduction frequency band and can obtain relatively flat frequency
characteristics in a wide band between the lowest resonance frequency and the high resonance
frequency. Therefore, it has an overall effect of being able to provide a piezoelectric speaker with
high efficiency and excellent timbre at low cost.
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[0040]
Brief description of the drawings
[0041]
1 is a top view showing the structure of the first embodiment of the present invention.
[0042]
2 is a side cross-sectional view of Example 1 as well.
[0043]
FIG. 3 is a perspective view of the first embodiment.
[0044]
4 is a side elevation and partial sectional view of the second embodiment.
[0045]
5 is a top view of Example 2 as well.
[0046]
6 is a partial cross-sectional view of the other side of Example 2 as well.
[0047]
7 is an exploded view showing a manufacturing process of Example 1.
[0048]
8 is a schematic perspective view of the molding die of the diaphragm of Example 1, Example 2.
[0049]
9 is an exploded view of another manufacturing process of the embodiment 1;
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[0050]
10 is a top view of a modification of the embodiment of the present invention.
[0051]
11 is a side view of the same.
[0052]
12 is a top view of another modification of the embodiment of the present invention.
[0053]
13 is a side view of the same.
[0054]
14 is an external view of the application example speaker attached to the front and back both
sides of the plane of FIG.
[0055]
15 is an exploded perspective view of the same.
[0056]
FIG. 16 is an external view of another application example speaker mounted with its directions
turned at right angles on the same plane as the plane.
[0057]
17 is a top view of the same.
[0058]
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 the radial square plane in the same direction.
[0059]
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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 the radial triangular surface in the same direction.
[0060]
FIG. 20 is a frequency characteristic diagram of Embodiment 1 of the present invention.
[0061]
FIG. 21 is a side sectional view of the conventional example 1 speaker.
[0062]
FIG. 22 is a side sectional view of a conventional example 2 speaker.
[0063]
Explanation of sign
[0064]
Reference Signs List 1 diaphragm 2 piezoelectric element (bimorph type) 2 'piezoelectric element
(unimorph type) 3 frame 4 coupling rod 5 resonator 6 frame of prior art example 2 cone shaped
diaphragm 8 polygonal columnar support
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