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JPH1132394

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DESCRIPTION JPH1132394
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
piezoelectric electroacoustic transducer used as, for example, a piezoelectric handset, a
piezoelectric speaker, or a piezoelectric sounder, and more specifically, an improved support
structure in a case of a piezoelectric diaphragm. The present invention relates to a piezoelectric
electroacoustic transducer.
[0002]
2. Description of the Related Art Conventionally, piezoelectric electroacoustic transducers are
widely used as piezoelectric handsets, piezoelectric speakers, piezoelectric sounders and the like.
An example of this type of piezoelectric electroacoustic transducer is disclosed in Japanese
Examined Patent Publication No. 8-32111.
[0003]
The piezoelectric electroacoustic transducer disclosed in the above prior art will be described
with reference to FIG. As shown in FIG. 5, the piezoelectric-type electroacoustic transducer 51
has a structure in which a piezoelectric diaphragm 55 is housed in a case 54 composed of a case
main body 52 and a lid 53. The case body 52 has a top plate portion 52b provided with a sound
output hole 52a, and a cylindrical portion 52c connected to the top plate portion 52b. A first step
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52d is formed on the inner wall of the cylindrical portion 52c, and a case-side support surface
52e is provided in the step 52d in parallel with the top plate 52b. The piezoelectric diaphragm
55 is fixed to the case-side support surface 52e using an adhesive 56 having elasticity. Further,
on the lower surface side of the piezoelectric diaphragm 55, the piezoelectric diaphragm 55 is
bonded to the inner wall of the cylindrical portion 52c by the elastic adhesives 57, 57.
[0004]
The piezoelectric diaphragm 55 has a structure in which a piezoelectric ceramic plate 55b having
a diameter smaller than that of the metal plate 55a is bonded to the lower surface of the metal
plate 55a. Electrodes (not shown) are formed on the upper and lower surfaces of the
piezoelectric ceramic plate 55b. A first lead (not shown) is connected to the electrode on the
lower surface of the piezoelectric ceramic plate 55b, a second lead (not shown) is connected to
the metal plate 55a, and the first and second leads are drawn out of the case 54. It is done.
[0005]
A second step 52f is formed on the inner wall of the cylindrical portion 52c near the opening on
the opposite side to the top plate 52b of the cylindrical portion 52c. The lid member 53 is
adhesively fixed to the case main body 52 (an adhesive is not shown) so as to fit in the second
step 52f.
[0006]
As described above, the case main body 52 has the top plate 52b having the sound emission hole
52a and the cylindrical portion 52c having the first and second steps 52d and 52f, and has a
relatively complicated shape. Have. Therefore, the case main body 52 is usually made of a
synthetic resin molded product.
[0007]
In the piezoelectric-type electroacoustic transducer 51, depending on the application, it is
strongly required that the frequency of the generated sound is as designed. Therefore, in the
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piezoelectric type electroacoustic transducer 51, it is required that the variation of the resonant
frequency of the piezoelectric diaphragm 55 to be used is small and the variation of the resonant
frequency due to the fixing structure of the piezoelectric diaphragm 55 to the case 54 is small.
[0008]
However, in the conventional piezoelectric-type electroacoustic transducer 51, the case-side
support surface 52e of the case main body 52 is not necessarily parallel to the top plate 52b, so
that there is a problem that the frequency of the generated sound varies. That is, when the case
side support surface 52e of the case main body 52 is parallel to the metal plate 55a of the
piezoelectric diaphragm 55, as shown in FIG. 6A, the upper surface of the metal plate 55a is the
case side support surface 52e and When the surface is sufficiently adhered and the piezoelectric
diaphragm 55 is adhered and fixed by the adhesive 56, the variation of the resonance frequency
hardly occurs.
[0009]
On the other hand, as shown in FIG. 6 (b), the case-side support surface 52e of the case main
body 52 is inclined so as to become higher toward the inside, or as shown in FIG. 6 (c), The
resonance frequency is different in the case where the case-side support surface 52e is inclined
so as to be lower toward the inside. That is, in the case of the state shown in FIG. 6 (b), the
resonance frequency is lowered because the piezoelectric diaphragm 55 is mechanically
supported at the portion A near the outer peripheral edge thereof, while FIG. When the
piezoelectric diaphragm 55 is supported at the inner end B of the case-side support surface 52e
as shown in FIG.
[0010]
Therefore, in the conventional piezoelectric-type electroacoustic transducer 51, there is a
problem that the frequency of the generated sound varies due to the variation in the inclination
of the case-side support surface 52e. In particular, the case main body 52 is often made of a
synthetic resin molded product because the shape is relatively complicated, but in the case of a
synthetic resin molded product, the variation of the case side support surface 52e may be
reduced. It was difficult and therefore the resonance frequency was more likely to vary.
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[0011]
An object of the present invention is to provide a piezoelectric electroacoustic transducer capable
of generating a sound of a desired frequency with high accuracy.
[0012]
According to a first aspect of the present invention, a piezoelectric diaphragm, a case for
supporting and storing the piezoelectric diaphragm near its periphery, and the piezoelectric
diaphragm being supported. A piezoelectric electro-acoustic transducer comprising an adhesive
bonding a piezoelectric diaphragm to a case in a portion, wherein an angle of the case-side
support surface to the piezoelectric diaphragm in a portion where the piezoelectric diaphragm is
supported by the case is θ It is characterized in that 60 ° ≧ θ ≧ 3 °.
[0013]
Preferably, the angle θ is 45 ° 2θ ≧ 3 °, as described in claim 2.
Although the structure of the case for housing the piezoelectric diaphragm in the piezoelectric
type electroacoustic transducer according to the present invention is not particularly limited,
according to a specific aspect of the present invention, as described in claim 3 In the case, the
case has a top plate portion and a cylindrical portion connected to the top plate portion, and the
case main body in which a step is formed on the inner peripheral surface of the cylindrical
portion, and the side opposite to the top plate portion of the case main body And a lid member
attached to the case main body so as to close the opening portion, and at least a part of the step
surface intersecting the inner peripheral surface of the cylindrical portion at the portion where
the step is provided It is a piezoelectric electroacoustic transducer according to claim 1 or 2,
which is a case-side support surface.
[0014]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A specific structural example of the
piezoelectric electroacoustic transducer of the present invention will be described below with
reference to the drawings.
[0015]
First Embodiment FIG. 1 is a cross-sectional view for explaining a piezoelectric type
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electroacoustic transducer according to a first embodiment of the present invention.
[0016]
The piezoelectric electroacoustic transducer 1 has a structure in which the piezoelectric
diaphragm 5 is housed in a case 4 composed of a case body 2 and a lid 3.
In the present embodiment, the case body 2 is made of a synthetic resin molded product, and has
a top plate portion 2b having at least one or more sound release holes 2a, and a cylindrical
portion 2c connected to the top plate portion 2b.
The end of the cylindrical portion 2c opposite to the top plate 2b is open.
[0017]
Further, a first step 2 d is formed on the inner wall of the cylindrical portion 2 c.
In the portion where the first step 2 d is provided, a case-side support surface 2 e facing the
outer peripheral edge of the piezoelectric diaphragm 5 is formed. Further, a second step 2 f is
formed below the first step 2 d. The second step 2 f is provided to attach the lid 3.
[0018]
The piezoelectric diaphragm 5 has a structure in which a piezoelectric ceramic plate 5b having a
smaller area than the metal plate 5a is bonded to the lower surface of the metal plate 5a. In the
present embodiment, the planar shape of the metal plate 5a constituting the piezoelectric
diaphragm 5 is circular, and the planar shape of the piezoelectric ceramic plate 5b is also
circular. However, the planar shape of the piezoelectric diaphragm 5 and the planar shape of the
piezoelectric ceramic plate 5b are not particularly limited to a circle, and may be another shape
such as a square or a rectangle.
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[0019]
In addition, the piezoelectric diaphragm 5 is not limited to one in which a piezoelectric ceramic
plate is bonded to a metal plate, and may have a structure in which a piezoelectric ceramic layer
is formed directly on one side of the metal plate A piezoelectric diaphragm may be used.
[0020]
In the present embodiment, electrodes (not shown) are formed on the upper and lower surfaces
of the piezoelectric ceramic plate 5b.
Then, lead wires are respectively connected to the metal plate 5a and the electrodes formed on
the lower surface of the piezoelectric ceramic plate 5b. These lead wires are drawn out of the
case 4 and connected to a circuit for driving the piezoelectric diaphragm 5, although not
particularly shown.
[0021]
The electrode (not shown) on the upper surface of the piezoelectric ceramic plate 5b may be
omitted. The piezoelectric diaphragm 5 is bonded to the case main body 2 using an adhesive 6
having elasticity in the vicinity of the outer peripheral edge of the metal plate 5a. That is, the
piezoelectric diaphragm 5 is in contact from below with the case-side support surface 2 e
inclined to be higher toward the inside from the lower side, and the piezoelectric diaphragm 5 is
in the case by the adhesive 6 at this abutting part. It is fixed to the main body 2. The present
embodiment is characterized in that the angle θ is in the range of 3 to 60 ° when the case-side
support surface 2 e is at an angle θ formed with the metal plate 5 a of the piezoelectric
diaphragm 5.
[0022]
If the angle θ is less than 3 °, the support portion of the piezoelectric diaphragm 5 by the caseside support surface 2e is likely to vary in the radial direction of the piezoelectric diaphragm 5,
and the frequency of the generated sound tends to vary. When the angle exceeds 60 °, it
becomes difficult to securely fix the piezoelectric diaphragm 5 to the case body 2 using the
adhesive 6. Preferably, the angle θ is in the range of 3 ° to 45 °, and the piezoelectric
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diaphragm 5 can be fixed to the case body 2 more securely. Note that, since the adhesive 6 has
elasticity, it is pointed out that the support portion of the piezoelectric diaphragm 5 is not the
inner end of the adhesive 6 but the contact portion between the piezoelectric diaphragm 5 and
the case main body 2 .
[0023]
In the second step 2 f, the shape of the lid 3 is selected to correspond to the shapes on both sides
of the step 2 f. That is, the lid 3 has an annular projecting portion 3a, and the annular projecting
portion 3a is provided such that the outer wall of the annular projecting portion 3a is fitted to
the inner wall of the cylindrical portion 2c above the step 2f. . Further, the outer diameter of the
lid member 3 is determined such that the outer portion of the annular projecting portion 3a
abuts on the lower portion of the cylindrical portion 2c than the step 2f. The lid 3 is fixed to the
case body 2 using an adhesive (not shown).
[0024]
FIG. 2 shows the resonance characteristics (solid line) of the piezoelectric electroacoustic
transducer of the present embodiment, and in FIG. 2, for comparison, in the conventional
piezoelectric electroacoustic transducer, the case side support surface is shown in FIG. The
resonance characteristic (broken line) in the case of being inclined in the opposite direction as in
(c) is also shown.
[0025]
As is clear from FIG. 2, compared to the piezoelectric electroacoustic transducer of the present
embodiment, as shown in FIG. 6C, the case in which the case-side support surface is inclined
downward as it extends inward. That is, when the piezoelectric diaphragm is supported at the
inner end of the case-side support surface, it is understood that the resonance frequency is high.
[0026]
As described above, in the piezoelectric-type electroacoustic transducer 1 of the present
embodiment, since the angle θ is in the range of 3 to 60 °, variation in resonance frequency
can be suppressed.
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This will be described based on a specific experimental example.
[0027]
The piezoelectric electroacoustic transducer 1 is manufactured according to the following
specifications, except that the angle θ of the case side support surface 2e with respect to the
piezoelectric diaphragm 5 is variously changed to produce a plurality of piezoelectric
electroacoustic transducers, and resonance is produced. The frequency was measured.
The results are shown in FIG.
[0028]
Details of the produced piezoelectric resonator ... For the piezoelectric diaphragm 5, a metal plate
5a of diameter 19.4 mm × thickness 0.10 mm made of 42 Ni alloy, piezoelectric ceramic plate
5b of diameter 14 mm × thickness 0.10 mm (electrodes on both sides ) Were used in
combination. In addition, the case main body is made of synthetic resin, using an outer diameter
21.5 mm × height 5.5 mm, an opening diameter 18.8 mm at the lower end × height 4.0 mm of
the inner space, and the case side support What changed the inclination of the surface 2e
variously was prepared. The lid 3 had an outer diameter of 21.4 mm and a height of 1.2 mm, and
the inner space of the annular projecting portion 3 a had a diameter of 18.5 mm and a height of
0.7 mm. Further, as the adhesive 6, one made of a silicone adhesive having elasticity was used.
[0029]
FIG. 3 shows a change in resonance frequency when the inclination angle of the case side
support surface 2e is changed in the range of 0 ° to 50 °. In FIG. 3, ten piezoelectric
electroacoustic transducers 1 are manufactured at each inclination angle, and the maximum
value is indicated by □, the minimum value is indicated by Δ, and the average value is indicated
by ♦ among the resonance frequencies.
[0030]
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As apparent from FIG. 3, it can be seen that the resonance frequency is constant at approximately
2.5 KHz when the inclination angle is 3 ° or more. Therefore, by setting the inclination angle θ
of the case-side support surface 2e to 3 ° or more, the support can be reliably supported in the
vicinity of the outer peripheral surface of the piezoelectric diaphragm. It can be understood that
[0031]
Second Embodiment FIG. 4 is a schematic cross-sectional view for explaining a piezoelectric
electroacoustic transducer according to a second embodiment of the present invention. In the
piezoelectric-type electroacoustic transducer 11 of this embodiment, the piezoelectric diaphragm
5 is supported by the case side support surface 2 e and the lid material side support surface 3 b
provided on the lid material 3, and fixed by the adhesive 6. It is done. The other points are the
same as those of the piezoelectric electroacoustic transducer 1 according to the first
embodiment.
[0032]
That is, at the upper end of the annular projection 3 a of the lid 3, the lid-side supporting portion
3 b inclined so as to become lower toward the inside is provided, and the piezoelectric vibrating
plate 5 with respect to the lid-side supporting portion 3 b is provided. When the angle is θ2, θ2
is in the range of 3 to 60 °. Furthermore, also in the present embodiment, the angle θ with
respect to the piezoelectric diaphragm 5 of the case-side support surface 2 e on the case body 2
side is also set to 3 to 60 °.
[0033]
Therefore, as in the case of the first embodiment, even if the accuracy of the support surface 2e
of the case main body 2 is slightly dispersed, as long as the piezoelectric diaphragm 5 has a size
of 3 ° or more, the outer periphery of the metal plate 5a It will be supported surely near the
surface, and the variation of the resonant frequency can be suppressed. In addition, on the lid 3
side, if the inclination angle θ of the lid-side support surface 3b with respect to the piezoelectric
diaphragm is 3 ° or more, even if the accuracy of the lid 3 slightly varies, the variation of the
resonant frequency is It can be effectively prevented.
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[0034]
(Other Modifications) In the first and second embodiments, the piezoelectric vibrating plate 5 is
fixed by the adhesive 6 over the entire area of the outer peripheral edge of the metal plate 5a,
but in the present invention, the piezoelectric vibrating plate The vicinity of the outer periphery
of the need not be fixed by the adhesive over the entire circumference, and may be only partially
adhered.
[0035]
Further, the structure of the case for housing and supporting the piezoelectric diaphragm 5 is not
limited to the one having the illustrated case main body 2 and lid 3, and the piezoelectric
diaphragm 5 is fixed by an adhesive in the vicinity of the outer peripheral edge. As long as it can
be supported, an appropriately shaped case can be used.
[0036]
According to the first aspect of the present invention, the piezoelectric type electroacoustic
system is formed by housing the piezoelectric diaphragm in the case and fixing and supporting
the piezoelectric diaphragm in the vicinity of the outer peripheral edge using an adhesive. In the
converter, the angle θ of the case-side support surface with respect to the piezoelectric
diaphragm is in the range of 3 to 60 °. Therefore, even if the angle of the support surface is
slightly dispersed, the piezoelectric diaphragm is surely in close proximity to the outer peripheral
surface As a result, the variation in resonance frequency can be reduced.
Therefore, it is possible to stably provide a piezoelectric electroacoustic transducer capable of
generating sound of a desired frequency.
[0037]
In the invention according to claim 2, since the θ is in the range of 3 to 45 °, the variation of
the resonant frequency of the piezoelectric electroacoustic transducer can be further reduced,
and the piezoelectric diaphragm is stabilized. A supported piezoelectric electroacoustic
transducer can be provided.
[0038]
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In the invention according to claim 3, since the inclination angle θ of the case-side support
surface provided in the case main body with respect to the piezoelectric diaphragm is 3 ° or
more, even if the accuracy of the case main body is slightly dispersed. The piezoelectric
diaphragm can be reliably supported in the vicinity of the outer peripheral surface thereof.
Therefore, as in the first aspect of the invention, it is possible to provide a piezoelectric
electroacoustic transducer with less variation in resonance frequency.
[0039]
Brief description of the drawings
[0040]
1 is a schematic cross-sectional view for explaining a piezoelectric electro-acoustic transducer
according to a first embodiment of the present invention.
[0041]
2 is a diagram showing the resonance characteristics of the piezoelectric electroacoustic
transducer according to the first embodiment of the present invention and the conventional
piezoelectric electroacoustic transducer shown in FIG. 6 (c).
[0042]
3 is a diagram showing the relationship between the tilt angle of the case-side support surface to
the piezoelectric diaphragm and the resonance frequency.
[0043]
4 is a schematic cross-sectional view for explaining a piezoelectric electro-acoustic transducer
according to a second embodiment of the present invention.
[0044]
5 is a cross-sectional view showing an example of a conventional piezoelectric electro-acoustic
transducer.
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[0045]
FIGS. 6A to 6C are enlarged cross-sectional views showing the state of the support portion in the
case where the angle of the case-side support surface with respect to the piezoelectric diaphragm
varies in the conventional piezoelectric electroacoustic transducer.
[0046]
Explanation of sign
[0047]
DESCRIPTION OF SYMBOLS 1 ... Piezoelectric-type electroacoustic transducer 2 ... Case main
body 2b ... Top plate part 2c ... Tubular part 2d ... 1st level | step difference 2e ... Case side
support surface 2f ... 2nd level | step difference 3 ... Lid material 3b ... Lid material side support
Surface 4 ... Case 5 ... Piezoelectric diaphragm 5a ... Metal plate 5b ... Piezoelectric ceramic plate 6
... Adhesive
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