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DESCRIPTION JP2007228127

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DESCRIPTION JP2007228127
PROBLEM TO BE SOLVED: In a conventional piezoelectric speaker, sound pressure
characteristics at 1 kHz to 10 kHz are not good. SOLUTION: A plurality of piezoelectric element
chips, a piezoelectric resin portion made of an organic resin filled on the side surface side
excluding the electrode surface of the piezoelectric element chip, and a peripheral resin portion
of only the organic resin around the piezoelectric resin portion A first frame to be bonded to the
surrounding resin portion, and a conductive resin film formed on the both sides of the
piezoelectric resin portion, and a first By forming the vibration material between the second
frame provided outside and the first frame, the sound pressure characteristic is improved.
[Selected figure] Figure 1
Piezoelectric speaker
[0001]
The present invention relates to a piezoelectric speaker using a plurality of piezoelectric element
chips, and more particularly to a piezoelectric speaker capable of improving sound pressure
characteristics.
[0002]
In general, the speaker mechanically vibrates the voice cone and reproduces voice by flowing an
electrical electrical signal to a voice coil connected to a voice cone which plays a role of a
diaphragm.
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However, the conventional electromagnetic speaker has problems such as generation of a
leakage flux around it. In recent years, with the increasing demand for smaller and lighter and
thinner audio devices such as televisions and surround sound, extremely thin and lightweight
piezoelectric speakers have been developed. This piezoelectric speaker is disclosed, for example,
in Patent Documents 1, 2, 3 and the like, and is composed of an epoxy resin and a large number
of lead zirconate titanate (PZT) piezoelectric element chips, a conductive electrode film, etc. The
piezoelectric element chip and the organic resin are used, and the piezoelectric effect of the
piezoelectric element and the elasticity of the organic resin are utilized. JP-A-62-247700 JP-A2000-324598 JP-A-2003-348692
[0003]
However, in the above-described conventional piezoelectric speaker, for example, the sound
pressure characteristics at 1 kHz to 10 kHz are not good. The present invention has been created
in order to effectively solve the above problems.
[0004]
According to the present invention, a piezoelectric resin portion made of an organic resin filled
on the side surface side excluding a plurality of piezoelectric element chips and the electrode
surface of the piezoelectric element chip, and a peripheral resin portion of only the organic resin
around the piezoelectric resin portion And a first frame to be joined to the surrounding resin
portion, and a piezoelectric resin composite formed by the above method, a conductive electrode
film provided on both sides of the piezoelectric resin portion, and a first frame And a vibration
material is formed between a second frame provided on the outer side of the second frame and
the first frame. The piezoelectric resin composite can be approximated to a curved surface
selected from one or more of a part of a cylindrical curved surface, a part of a conical curved
surface, a part of a spherical curved surface, and a part of an ellipsoid curved surface. It is a
piezoelectric speaker characterized by having.
[0005]
In addition to lead zirconate titanate (PZT), other composite ceramics can be used as the
piezoelectric element chip. Specifically, it is also possible to use lead zinc niobate titanate (PZNT)
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or magnesium niobate lead titanate (PMNT) whose piezoelectric strain constant is about three
times larger than that of PZT. In order to ensure a good piezoelectric effect, the pair of electrode
surfaces of the individual piezoelectric element chips need to be substantially parallel. Usually, in
a piezoelectric element chip, a surface having a large area is used as an electrode surface, and the
thickness of the piezoelectric element chip is the distance between the electrode surfaces.
Therefore, the distance between the electrode surfaces, that is, the thickness of the piezoelectric
element chip needs to be the same. The piezoelectric element chip in the present invention may
have any shape as long as the electrode surfaces are parallel and the distance between the
electrode surfaces is approximately the same. For example, the shape of the piezoelectric element
chip may be a shape selected from one or more of a cylindrical body, a rectangular solid, and a
triangular cylindrical body, and a piezoelectric resin composite in which the rectangular solid and
the triangular cylindrical body are mixed is also possible. Industrially, piezoelectric element chips
having the same rectangular parallelepiped shape are recommended.
[0006]
As the organic resin, an epoxy resin, a polyurethane resin or the like is used. The frame of the
speaker may be a material that can fix and support the piezoelectric resin composite and the
vibration material. The vibration material may be a material selected from one or more of paper,
cloth, metal-based material and organic-based resin material. A sheet-like vibrating material
having a thickness of about 0.01 mm to 1 mm is often used. As the conductive electrode film, a
deposited film of a conductive material such as carbon, aluminum, gold, silver, copper or the like
excellent in conductive characteristics on a piezoelectric element chip, an organic resin film
containing the conductive material, or the deposited film And a composite of the organic resin
film is preferable. An organic resin film such as polyurethane resin, polyethylene resin or epoxy
resin is provided on the upper surface of one side or both sides of the conductive electrode film
to protect the conductive electrode film provided on the upper part of the piezoelectric resin
portion and improve the speaker output characteristics. Good thing.
[0007]
According to the piezoelectric speaker of the present invention, a piezoelectric resin composite
formed of a plurality of piezoelectric element chips, a piezoelectric resin portion made of an
organic resin, and a peripheral resin portion of only an organic resin, and both surfaces of the
piezoelectric resin portion A second frame provided on the outer side of the first frame, and a
first frame provided on the outer side of the first frame. The formation of the vibrating material
between the bodies improves the sound pressure characteristics at 1 kHz to 10 kHz.
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[0008]
Hereinafter, an embodiment of a piezoelectric speaker according to the present invention will be
described in detail.
[0009]
FIG. 1 is an enlarged sectional view of an essential part showing a piezoelectric speaker of the
present invention.
FIG. 2 is a cross-sectional view of the piezoelectric speaker shown in FIG.
As illustrated, the organic resin 12 is filled between a plurality of piezoelectric element chips 11
having the same rectangular parallelepiped shape, and around the piezoelectric resin section 13
and the piezoelectric resin section 13 in which many piezoelectric element chips 11 are coupled.
A piezoelectric resin composite 15A formed of a peripheral resin portion 14 made only of an
organic resin, conductive electrode films 17A and 17B provided on both sides of the piezoelectric
resin portion 13, and a first bonded to the peripheral resin portion 14 And a second frame 16B
provided on the outside of the first frame 16A, and a vibrating material 15B formed between the
first frame 16A and the second frame 16B. The piezoelectric speaker is configured by By forming
the vibrating material 15B between the first frame 16A and the second frame 16B, the sound
pressure characteristic can be improved.
[0010]
Furthermore, the details of the embodiment will be specifically described. A piezoelectric resin
composite 15A of a piezoelectric speaker is manufactured by the method disclosed in Japanese
Patent Application Laid-Open No. 2003-348692. The piezoelectric element chip 11 used is a lead
zirconate titanate (PZT) -based piezoelectric element, and is a rectangular solid of 2 mm in
length, 2 mm in width, and 0.2 mm in thickness. In addition, an epoxy resin is used as the organic
resin 12 to be filled in order to bond the plurality of piezoelectric element chips 11. Since a flat
surface of 2 mm long and 2 mm wide is used as the electrode surface of the piezoelectric element
chip 11, the thickness of the piezoelectric resin composite 15 A is about the same as that of the
piezoelectric element chip 11. FIG. 3 shows a front view of the produced piezoelectric resin
composite 15A, and FIG. 4 shows a side view (illustration of the piezoelectric element chip is
omitted). In FIG. 3, the opening angle, the radius of curvature and the width of the piezoelectric
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resin composite 15A are denoted by θ, R and D, respectively. Further, in FIG. 4, the length
dimension of the piezoelectric resin composite 15A is L.
[0011]
The piezoelectric element chips 11 are arranged in a lattice along the R-curved surface, with the
intervals between the piezoelectric element chips 11 being equal intervals of 0.4 mm on average.
That is, along the R curved surface of FIG. 3, in the direction of the angle θ, 14 pieces of the long
side position of the piezoelectric element chip 11 and the arc-shaped end of the piezoelectric
resin composite 15A have the same distance. The piezoelectric element chips 11 are arranged at
an equal interval of 0.4 mm on average. The arrangement in which the above 14 arrangements in
the θ direction are parallelly displaced at an equal interval of 2.4 mm on average in the L
direction in FIG. 4 is repeated along the R curved surface, and a total of 196 piezoelectric
element chips 11 are arranged. The dimensions of the obtained piezoelectric resin composite
15A are width D = 37 mm, length L = 38 mm, and average curvature radius R = 45 mm. The
dimensions of the piezoelectric resin portion 13 excluding the surrounding resin portion 14 from
the piezoelectric resin composite 15A were 33 mm in width, 34 mm in length, and 45 mm in
average radius of curvature. A portion of the piezoelectric resin composite 15A according to
Example 1 is shown in FIG. As shown in FIG. 5, a total of 196 piezoelectric element chips 11 are
arranged in a grid at an equal interval of 0.4 mm, 14 in the X direction (see FIG. 5) and 14 in the
Y direction (see FIG. 5). Ru.
[0012]
Next, a first frame 16A to be bonded to the piezoelectric resin composite 15A is prepared using
acrylic resin. The first frame 16A is a rectangular parallelepiped 47 mm long, 50 mm wide, and 5
mm thick, and an air gap of 37.2 mm long, 40.2 mm wide, and 5 mm high is provided at the
center. However, the inner 37.2 mm side is parallel to the outer 47 mm side, and the inner 40.2
mm side is in parallel with the outer 50 mm side. The piezoelectric resin composite 15A is placed
in the gap of the first frame 16A, and the two linear ends (length 38 mm) of the piezoelectric
resin composite 15A are the two upper sides (length) of the frame gap. 40.2 mm part), and the
meeting part is joined by epoxy resin 19A, 19a, 19B and 19b. The piezoelectric resin composite
15A joined to the first frame 16A was subjected to curing treatment at 60 ° C. for 1 hour. After
the curing process, the piezoelectric resin composite 15A joined to the first frame 16A is washed,
and the conductive aluminum electrode film by vacuum evaporation is formed on both sides of
the piezoelectric resin portion 13 where the electrode surface of the piezoelectric element chip
11 exists. 17A and 17B were provided. The thickness of the aluminum electrode films 17A and
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17B was almost the same and 0.4 μm on average.
[0013]
Next, a second frame 16B provided on the outside of the first frame 16A is prepared using an
acrylic resin. The second frame 16B is a rectangular parallelepiped 97 mm long, 100 mm wide,
and 5 mm thick, and a gap of 77 mm long, 80 mm wide, and 5 mm high is provided at the central
portion thereof. However, the side of the inner 77 mm is parallel to the side of the outer 97 mm,
and the side of the inner 80 mm is parallel to the side of the outer 100 mm. A sheet-like
composite vibration mainly made of paper is placed between the first frame 16A and the second
frame 16B by placing the piezoelectric resin composite 15A joined to the first frame 16A at the
center of the gap of the second frame 16B. The material 15B (thickness 0.2 mm) is formed in
parallel with the frame surface and in a planar shape. Here, the first frame 16A and the second
frame 16B are located on the same plane, and the distance between the outer periphery of the
first frame 16A and the inner periphery of the second frame 16B is 15 mm. . As can be seen from
FIGS. 1 and 2, the piezoelectric resin composite 15A has a form that can be approximated to a
part of a cylindrical curved surface, and the composite vibration material 15B has a form that is a
part of a plane. After the electrode films 17A and 17B and the audio signal source 18 were
connected by the lead wires 18A and 18B, an electrical sound signal was applied to the lead
wires, and the sound pressure characteristics were evaluated in the frequency range of 1 kHz to
10 kHz. The sound pressure characteristics of Example 1 were 34 to 62 relative sound pressure
dB.
[0014]
As a comparative example, a piezoelectric speaker was produced by the method disclosed in
Japanese Patent Application Laid-Open No. 2003-348692. The comparative example is a speaker
in which the second frame 16B and the composite vibration material 15B are removed from the
first embodiment. That is, a piezoelectric resin composite 25 was produced in the same manner
as in Example 1 and having a width D = 37 mm, a length L = 38 mm, and an average curvature
radius R = 45 mm. Next, a frame 26 to be bonded to the piezoelectric resin composite 25 is
prepared using acrylic resin. The frame 26 is a rectangular solid of 57 mm long, 60 mm wide,
and 5 mm thick, and a gap of 37.2 mm long, 40.2 mm wide, and 5 mm high is provided at the
center. However, the inner 37.2 mm side is parallel to the outer 57 mm side, and the inner 40.2
mm side is in parallel with the outer 60 mm side. The piezoelectric resin composite 25 is placed
in the void portion of the frame 26, and the two linear end portions (length 38 mm portion) of
the piezoelectric resin composite 25 are the two upper sides (length 40.x) of the frame void
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portion. The meeting portion is joined with epoxy resin 29A, 29a, 29B and 29b according to 2
mm part). A perspective view (illustration of the piezoelectric element chip is omitted) of a part of
the piezoelectric resin composite 25 joined to the frame 26 is shown in FIG.
[0015]
Next, curing and vacuum deposition were performed in the same manner as in Example 1. The
thickness of the aluminum electrode films 27A and 27B provided on both surfaces of the
piezoelectric resin portion 23 where the electrode surface of the piezoelectric element chip 21 is
present was substantially the same and 0.4 μm on average. After connecting the lead wires 28A
and 28B to the electrode films 27A and 27B, sound electric signals were supplied to the lead
wires, and the sound pressure characteristics were evaluated in the same manner as in Example
1 in the frequency range of 1 kHz to 10 kHz. The sound pressure characteristics of the
comparative example were 33 to 60 relative sound pressure dB.
[0016]
As Example 2, the round piezoelectric resin composite 35A was produced by the method
disclosed in Japanese Patent Laid-Open No. 2003-348692. The piezoelectric element chip 31
and the organic resin 32 used are the same as in the first embodiment. Since a flat surface of 2
mm long and 2 mm wide is used as the electrode surface of the piezoelectric element chip 31, the
thickness of the round piezoelectric resin composite 35 A is about the same as that of the
piezoelectric element chip 31. A side view of the manufactured round piezoelectric resin
composite 35A (piezoelectric element chips are not shown) is shown in FIG. In FIG. 7, the
diameter and the radius of curvature of the circular piezoelectric resin composite 35A are d and
r, respectively. Moreover, the principal part enlarged plan view of 35 A of round piezoelectric
resin composites is shown in FIG.
[0017]
The arrangement of the piezoelectric element chips 31 is a grid-like array along the r-curved
surface, with the intervals between the piezoelectric element chips 31 being equal intervals of
0.4 mm on average. That is, along the r-curved surface of FIG. 7, the distance between the
position of the long side of the piezoelectric element chip 31 and the bisector curve passing
through the center O of the r-curved surface (see FIG. 8) is 0.2 mm. In the X direction (see FIG. 8),
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sixteen piezoelectric element chips 31 are arranged at equal intervals of 0.4 mm on average. The
16 piezoelectric elements chips 31 are arranged by arranging the above 16 arrangements
parallelly moved at an equal interval of 2.4 mm on average in the Y direction (see FIG. 8) along
the r-curved surface. As a result of repeating this arrangement of parallel movement at an equal
interval of 2.4 mm on average on the curved surface of half of the r-curved surface, 16, 16, 14,
14, 12, 12, 12, 6, 6. A total of 96 piezoelectric element chips 31 are arranged in a grid at an
equal interval of 0.4 mm on average along the r-curved surface. The same arrangement as the
above arrangement is applied to the remaining half of the curved surface, and finally, the end of
the r-curved surface, the center, the end to the six, six, twelve, twelve, twelve, twelve, fourteen,
fourteen, sixteen, 16, 16, 16, 14, 14, 12, 12, 6, 6. A total of 192 piezoelectric element chips 31
have an interval between the piezoelectric element chips 31 along the r-curved surface. They are
arranged in a grid form so that they have equal intervals of 0.4 mm on average.
[0018]
The dimensions of the obtained round piezoelectric resin composite 35A are diameter d = 43 mm
and average curvature radius r = 43 mm. The dimensions of the piezoelectric resin portion 33
excluding the surrounding resin portion 34 from the round piezoelectric resin composite 35A
were 39 mm in diameter and 43 mm in average radius of curvature. Next, a first frame 36A to be
joined to the round piezoelectric resin composite 35A is formed of an acrylic resin cylindrical
body having a diameter of 53 mm and a thickness of 3 mm, and a gap of 43.2 mm in diameter
and a height of 3 mm is provided in the center. Made. Place the round piezoelectric resin
composite 35A in the void of the first frame 36A, align the outer peripheral end (diameter 43
mm) of the round piezoelectric resin composite 35A with the void upper side of the frame 36A,
and then join the joint It joined by epoxy resin 39A and 39B. The bonded state of the round
piezoelectric resin composite 35A and the first frame 36A is shown in FIG. 9 in the form of an
enlarged sectional view of the relevant part (excluding the cut surface, the piezoelectric element
chip is not shown). Next, curing and vacuum deposition were performed in the same manner as
in Example 1. The thickness of the aluminum electrode films 37A and 37B provided on both
sides of the piezoelectric resin portion 33 where the electrode surface of the piezoelectric
element chip 31 exists was substantially the same and 0.4 μm on average.
[0019]
Next, a second frame 36B provided on the outside of the first frame 36A is prepared with an
acrylic resin. The second frame 36B is manufactured by providing an acrylic resin cylindrical
body having a diameter of 103 mm and a thickness of 5 mm at a central portion thereof and
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providing an air gap of 83 mm in diameter and 5 mm in height. The piezoelectric resin composite
35A joined to the first frame 36A is placed in the center of the gap of the second frame 36B, and
the composite vibration material 35B mainly made of paper is disposed between the first frame
36A and the second frame 36B. A thickness of 0.2 mm is formed. Here, the central axes of the
first frame 36A and the second frame 36B passing through the center of the gap coincide with
each other, and the distance between the first frame 36A and the second frame 36B on the
central axis is 5 mm. Are arranged to be The average of the tilt angles of the composite vibration
material 35B with respect to the frame plane was about 30 degrees. FIG. 10 shows an enlarged
cross-sectional view of the main part of the piezoelectric speaker (the piezoelectric element chip
and the aluminum electrode film are omitted) in a state where the composite vibration material
35B is formed between the first frame 36A and the second frame 36B. . It can be understood
from FIG. 10 that the round piezoelectric resin composite 35A has a form that can be
approximated to a part of a spherical surface, and the composite vibration material 35B has a
form that can be approximated to a part of a conical surface. After connecting lead wires 38A
and 38B to the electrode films 37A and 37B, sound electric signals were supplied to the lead
wires and sound pressure characteristics were evaluated in the same manner as in Example 1 in
a frequency range of 1 kHz to 10 kHz. The sound pressure characteristic of Example 2 was 36 to
65 relative sound pressure dB.
[0020]
As described above, the sound pressure characteristics of Example 1 and Example 2 according to
the present invention are superior to those of the comparative example. That is, by forming the
vibration material between the first frame and the second frame, the sound pressure
characteristics at 1 kHz to 10 kHz are improved. In addition, although Example 1 showed an
example of a part of cylinder curved surface as a shape of a piezoelectric resin composite and
Example 2 showed an example of a part of spherical curved surface, a part of other cone curved
surfaces, an ellipse The present invention is also applicable to a part of a body surface or the like.
That is, a form in which the piezoelectric resin composite can be approximated to a surface
selected from one or more of a portion of a cylindrical surface, a portion of a conical surface, a
portion of a spherical surface, and a portion of an ellipsoidal surface. The effect of the present
invention is not lost.
[0021]
It is a principal part expanded sectional view showing a piezoelectric speaker of the present
invention. It is AA arrow sectional drawing of the piezoelectric speaker shown in FIG. FIG. 2 is a
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front view of a piezoelectric resin composite in Example 1; 5 is a side view of the piezoelectric
resin composite in Example 1. FIG. FIG. 6 is an enlarged plan view of an essential part showing a
part of the piezoelectric resin composite in Example 1; It is a perspective view which shows a
part of piezoelectric resin complex and frame in a comparative example. FIG. 7 is a side view of
the piezoelectric resin composite in Example 2; FIG. 7 is an enlarged plan view of a main part of
the piezoelectric resin composite in Example 2. FIG. 7 is an enlarged sectional view of an
essential part of a piezoelectric resin composite and a frame in Example 2; FIG. 6 is an enlarged
cross-sectional view of a main part of the piezoelectric speaker in Example 2;
Explanation of sign
[0022]
11 Piezoelectric element chip, 12 organic resin, 13 piezoelectric resin portion, 14 peripheral
resin portion, 15A piezoelectric resin composite, 15B vibration material, 16A first frame, 16B
second frame, 17A conductive electrode film, 17B conductive electrode film, 18A lead wire, 18B
lead wire, 19A epoxy resin, 19a epoxy resin, 19B epoxy resin, 19b epoxy resin,
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