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DESCRIPTION JPH0678397

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DESCRIPTION JPH0678397
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
piezoelectric sounding body containing a piezoelectric diaphragm configured to convert an audio
signal to a voltage value by being applied to a telephone, and more particularly, The invention
relates to a novel piezoelectric sounding body improved such that flat frequency-sound pressure
characteristics can be obtained by suppressing the occurrence of a sharp peak of sound pressure
level due to resonance action in frequency-sound pressure characteristics of the piezoelectric
sounding body It is.
[0002]
2. Description of the Related Art Reflecting the recent advanced information age, various
communication means have been diversifying, and in particular, telephones having various
functions have been developed, especially indoors etc. In order to avoid limitation on the call
location in the country, there is an eye to the spread of wireless telephones, so-called cordless
telephones, in which the transmitting / receiving unit and the telephone main body are separated
and independent and configured to transmit and receive voice by wireless communication. There
is something to watch. Furthermore, the demand for mobile phones that can be freely carried
outside and have a telephone line is also expanding.
[0003]
In the cordless telephone and mobile phone, an electronic circuit function for converting voice
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into a radio signal, a power supply unit, etc. are incorporated in the handset, as compared to the
case where the handset and the telephone main body are connected by a connection line. At the
same time, it is necessary to make the handset body small and thin.
[0004]
In order to cope with this, instead of the electromagnetic speaker utilizing the electromagnetic
action, a piezoelectric element utilizing the piezoelectric effect capable of making the
transmitting part and the receiving part of the handset small and thin in shape is used. There is.
[0005]
A conventional example of a piezoelectric speaker to which the piezoelectric element is applied
will be described with reference to FIG.
[0006]
In the piezoelectric sounding body 10, a piezoelectric element 21 having an electrostrictive effect
that produces a mechanical stress when a pressure or tension is applied to a ferroelectric or the
like causes a polarization to generate an electrostatic charge at the end face or an electric field. It
is formed in a thin disk shape using ferroelectric ceramics such as PZT (lead zirconate titanate)
porcelain as a material.
[0007]
On both main surfaces of the piezoelectric element 21, for example, electrodes 23a and 23b
having good electrical conductivity such as silver are formed in a film form.
[0008]
The piezoelectric element 21 on which the electrodes are formed is made of brass, SUS (stainless
steel) or the like, and has a larger diameter than that of the piezoelectric element 21 and is
formed on the diaphragm main surface 22a of the diaphragm 22 formed in a thin disk shape.
The piezoelectric diaphragm 20 is configured by being fixed with the one electrode 23b
interposed therebetween.
[0009]
At this time, an insulation coated conducting wire for transmitting and receiving an electrical
signal to the outside at one end of the other electrode 23a of the piezoelectric diaphragm 20
attached to the piezoelectric element 21 and one end of the diaphragm 22. Solder connection is
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made to the external connection terminals 26a and 26b disposed on the storage lid 12 covering
the opening portion of the storage case 11 which is fixed by the solders 24a and 24b and
becomes the housing base of the piezoelectric diaphragm 20, for example. It shall be done.
[0010]
Here, the storage lid 12 is not a component of the piezoelectric sounding body 10, and generally
has a storage lid as a piezoelectric sounding body, and itself has an opening part closed (capsule
structure) and a storage lid. Both include the one that is closed by bringing the opening part into
contact with the handset main body to be attached (a half open structure) (this example is a
piezoelectric sounding body of a capsule structure having a storage lid).
Further, the method of leading the insulating coated wire to the outside is not limited to the
above example, but there is a method of leading according to the application and mounting
method.
[0011]
The storage case 11 is made of aluminum or a synthetic resin or the like, and has a side wall
having an annular or polygonal shape, a storage opening 13 for storage and attachment of the
piezoelectric diaphragm 20 one of which is fully opened, and the storage By having the opening
relative wall portion 19 opposed to the opening portion 13, the cross section is processed and
formed into a substantially concave shape.
A sound release hole 27 is provided in the relative wall portion 19.
[0012]
Further, a braking hole 14 is opened substantially at the center of the storage lid 12, and a sound
pressure adjusting film 18 formed in a mesh shape is coated on the inside of the storage lid 12
with the braking hole 14, and further bonding By being fixed by an agent or the like, the sound
pressure to the piezoelectric vibration of the piezoelectric diaphragm 20 can be adjusted.
[0013]
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A mounting step 15 is provided substantially at the center of the inner wall surface of the storage
case 11 along the entire inner surface, and the piezoelectric diaphragm 20 in the present
embodiment is a storage opening 13 for storing the piezoelectric element 21. It is stored in the
storage case 11 via the storage opening 13 so as to face the side, and the peripheral portion 22b
of the diaphragm 22 of the piezoelectric diaphragm 20 is abutted in the mounting step 15, and
further, For example, it is coated and fixed over the entire circumference of the mounting step 15
with a silicone-based sealing adhesive 16.
[0014]
However, according to the above-described conventional piezoelectric sounding body 10, the
diaphragm peripheral portion 22b of the piezoelectric diaphragm 20 is abutted along the entire
periphery of the mounting step portion 15, so that the silicone-based type is produced. Since it is
fixed by the sealing adhesive 16 of this type, the resonance phenomenon is completely achieved
although the peak phenomenon of the sound pressure at the resonance frequency inherent to the
piezoelectric diaphragm, so-called resonance action is suppressed to some extent. Is not resolved,
and resonance occurs at the frequency of the used voice band (especially in the high frequency
range around 3 to 4 kHz), which is determined by the dimensions of the diaphragm and the fixed
state around the diaphragm and the volume and shape of the storage case There is a problem
that the pressure level suddenly rises (see curve (a) in FIG. 3).
That is, there is a problem in that the conversation is disturbed because the voices suddenly and
loudly come into the ear while talking on a cordless telephone or mobile phone.
[0015]
The above problem is that the adjustment of the sound pressure by the damping holes 14 and
the sound pressure adjusting film 18 only results in a uniform decrease in the sound pressure
level, and the suppression of the resonance can not be sufficiently achieved.
[0016]
The present invention has been made in view of the above-described circumstances, and
suppresses abrupt fluctuations in frequency-sound pressure characteristics due to resonance
without compromising the sound pressure level, and flat frequencies over a wide range of used
voice bands. The present invention provides a piezoelectric speaker configured to obtain sound
pressure characteristics.
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[0017]
According to the present invention, a thin plate-like piezoelectric element is fixed to one main
surface of a storage case having a substantially concave cross section and a thin plate-like
vibration plate having a substantially concave cross section. A piezoelectric sounding body is
provided, characterized in that it has a structure including a piezoelectric vibrating plate whose
peripheral portion is fixed inside the storage case, and a resonance suppressing member fixed on
at least one main surface of the piezoelectric vibrating plate. In order to achieve the above object,
[0018]
In the present invention, the resonance suppressing member fixed on the main surface of the
piezoelectric diaphragm works to suppress the resonance action, and the occurrence of the peak
of the sound pressure level due to the resonance action The frequency range that can be heard as
a sound is approximately 100 Hz to 8 kHz, but the usual voice band used is 500 Hz to 4 kHz.
You can prevent it.
[0019]
In addition, the influence of the resonance suppression member on the piezoelectric vibration in
the entire use frequency band can be reduced by adjusting the position, mass and shape of the
resonance suppression member, and the whole sound pressure level is not impaired. The
suppression effect of the resonance suppression member appears prominently only near the
frequency at which the peak appears.
[0020]
Embodiments of the invention will be described in detail with reference to the drawings.
[0021]
FIG. 1 is a cross-sectional view showing an embodiment of a piezoelectric speaker according to
the present invention.
[0022]
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In FIG. 1, in the piezoelectric sounding body 50, a thin plate-like piezoelectric element 61 is fixed
to one main surface of a storage case 51 having a substantially concave cross section with one
end opened and a thin plate-like vibration plate 62 A feature is that the piezoelectric vibrating
plate 60 has a peripheral portion 62b of the plate 62 fixed inside the storage case 51, and a
resonance suppressing member 70 fixed on one main surface 62a of the piezoelectric vibrating
plate 60. Do.
[0023]
Further, in addition to the above-described structure, a storage lid 52 covering the opening 53 of
the storage case 51 serving as the housing base of the piezoelectric diaphragm 60 is fixed at the
opening edge 68 in the piezoelectric speaker 50. At one end of the other electrode 63a applied to
the electrode 61 and at the one end of the diaphragm 62, insulation coated conducting wires 65a
and 65b for exchange of electrical signals with the outside are fixed by solders 64a and 64b. In
addition, it is soldered to the external connection terminals 66a and 66b disposed on the storage
lid 12 so that input and output with the outside of the piezoelectric sounding body 50 are
possible.
[0024]
The main members of the piezoelectric speaker 50 will be described in detail below.
[0025]
The piezoelectric element 61 has a piezoelectric effect that generates polarization when a
pressure or tension is applied to a ferroelectric or the like to generate an electrostatic charge at
the end face or an electrostrictive effect that generates a mechanical stress when an electric field
is applied. It is formed in a thin disk shape with a thickness of 50 to 100 μm, using a material of
ferroelectric ceramics such as lead zirconate porcelain.
[0026]
On both main surfaces of the piezoelectric element 61, for example, a first electrode 63a and a
second electrode 63b having good electrical conductivity such as silver are formed in a thin film
form.
[0027]
The piezoelectric element 61 on which the electrodes are formed is made of brass or the like, has
a diameter larger than that of the piezoelectric element 61, and is formed in a thin disk shape
and has a thickness of about 50 μm. And the second electrode 63b, and together with the
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vibration plate 62, constitute a piezoelectric vibration plate 60.
[0028]
Next, the storage case 51 is made of a synthetic resin or the like, and has an annular or polygonal
side wall, a storage opening 53 one of which is fully open, and an opening relative wall facing the
storage opening 53. By having 59, the cross section is formed in a substantially concave shape.
[0029]
A sound emitting hole 57 is opened substantially at the center of the opening relative wall 59.
On the other hand, a braking hole 54 is opened substantially at the center of the storage lid 52,
and a sound pressure adjusting film 58 formed in a mesh shape is covered inside the storage
hole 52 with the damping hole 54, and further an adhesive By being fixed, the whole adjustment
of the sound pressure with respect to the piezoelectric vibration of the piezoelectric element 60
can be performed.
[0030]
Next, a mounting step 55 is formed substantially at the center of the inner wall surface of the
storage case 51 along the entire inner surface, and the mounting step 55 is formed of the
piezoelectric element 61 of the piezoelectric element 60. The diaphragm main surface 62c
opposite to the adhering surface is abutted at the peripheral portion 62b so as to face the
opening relative wall 59 side, and is fixed by, for example, a silicone-based sealing adhesive 56.
[0031]
Next, the resonance suppressing member 70 is a coin-shaped metal or ceramic having a weight
of 0.35 g, a diameter of 10 mm, and a thickness of about 0.6 mm.
The resonance suppressing member 70 is soldered on at least one main surface of the main
surface of the piezoelectric diaphragm 60 (on the main surface 62c of the diaphragm 62 and on
the first electrode 63a of the piezoelectric element 61), double-sided adhesive tape, or adhesive
(In this example, one on the first electrode 63a of the piezoelectric element 61).
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It is desirable that a plurality of fixed positions of the resonance suppressing member 70 be
disposed in the vicinity of the approximate center of the main surface or at symmetrical positions
from the center.
[0032]
FIG. 2 is a perspective view when the piezoelectric diaphragm 60 to which the resonance
suppressing member 70 of the piezoelectric sounding body 50 is fixed is housed in the housing
case 51 and the housing lid 52 is sealed in the opening.
[0033]
According to the piezoelectric sounding body 50 configured as described above, the mass of the
resonance suppressing member 70 fixed on the main surface of the piezoelectric diaphragm 60
produces a reaction of the action received from the large amplitude fluctuation due to the
resonance action of the diaphragm. It works to suppress amplitude fluctuation.
Therefore, it is possible to prevent the occurrence of the peak of the sudden sound pressure level
due to the resonance action over the use voice band (about 500 Hz to 4 kHz).
[0034]
FIG. 3 shows the frequency-sound pressure characteristics of the conventional piezoelectric
sounding body 10 having the same structure and the piezoelectric sounding body 50 according
to the present invention except the presence of the resonance suppressing member (0.35 g), the
vertical axis sound pressure (dB), the horizontal axis It is shown as a semi-logarithmic graph of
frequency (Hz).
[0035]
According to the experiment of the inventor, as shown in FIG. 3, the sound pressure
characteristic (a) of the conventional piezoelectric sounding body 10 has a large fluctuation in
the sound pressure level in the frequency band of 1 kHz to 4 kHz. , P2 like peaks have occurred.
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On the other hand, the sound pressure characteristic (b) of the piezoelectric sounding body 50
according to the present invention is substantially flat in the above frequency band, and the
sound pressure level is not deteriorated.
[0036]
The resonance suppressing member fixed to the piezoelectric diaphragm, which is a main
component of the present invention, is not limited to the coin shape as in the present
embodiment, and may be, for example, a ring shape without restriction.
Further, the material of the resonance suppression member is not limited to metal or ceramic,
and any other material having durability as a member may be used.
[0037]
Furthermore, as described above, the piezoelectric sounding body has a storage lid and is closed
by itself as an opening (capsule structure), and the opening of the handset main body to be
mounted without the storage lid. It is needless to say that the piezoelectric sounding body
according to the present invention is included in both of the structures, though both of those
which are closed by coming into contact with each other (semi-opened structure) are included.
[0038]
Since the piezoelectric sounding body according to the present invention is configured as
described above, the resonance suppressing member fixed to the diaphragm suppresses the
fluctuation of the sound pressure level due to the resonance action, so that the use voice band
Have an excellent effect that a substantially flat sound pressure characteristic can be realized.
[0039]
Brief description of the drawings
[0040]
1 is a sectional view showing an embodiment of a piezoelectric sounding body according to the
present invention
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[0041]
2 is a perspective view showing an embodiment of a piezoelectric sounding body according to
the present invention
[0042]
Fig. 3 Graph of frequency-sound pressure characteristics of the present invention and the
conventional piezoelectric speaker
[0043]
Fig. 4 A sectional view showing a conventional piezoelectric speaker
[0044]
Explanation of sign
[0045]
50 Piezoelectric Sounding Body 51 Storage Case 52 Storage Lid 53 Storage Opening 54 Brake
Hole 55 Mounting Step 56 Adhesive 57 for Sealing 57 Sound Output Hole 58 Sound Pressure
Adjustment Film 59 Opening Relative Wall 60 Piezoelectric Vibrator 61 Piezoelectric Element 62
Vibrator 62a Piezoelectric element attachment surface 62b Opposite principal surface 63a of
diaphragm peripheral portion 62c 62a First electrode 63b Second electrode 64a, 64b Insulating
coated conducting wire 65a, 65b Solder 66a, 66b External connection terminal 68 Case
attachment end 70 Resonance suppression member
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