JPH117283

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DESCRIPTION JPH117283
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
piezoelectric speaker used in, for example, telephones, mobile communication devices, and the
like.
[0002]
2. Description of the Related Art As shown in FIGS. 3 and 4, a conventional sounding body has a
case 5, an outer peripheral edge portion of a piezoelectric diaphragm 8 having a piezoelectric
element 2 attached to the central portion of a flat metal substrate 7. It had a structure to hold by
adhesion with 6.
[0003]
The above-mentioned conventional sounding body is mainly an apparatus used with a single
sound, and a toy, an acoustic communication apparatus, etc. used in any frequency band such as
melody, voice, etc. It was difficult to cope at the level.
[0004]
SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to
the present invention, the metal substrate of the piezoelectric diaphragm housed in the case is
concentrically grooved outward from the outer peripheral part of the bonding position of the
piezoelectric element. By using the machined one, oscillation in a wide frequency band and sound
pressure level can be improved to achieve the intended purpose.
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[0005]
According to a first aspect of the present invention, there is provided a piezoelectric diaphragm
having a piezoelectric element bonded to a central portion of a metal substrate, and cases
provided respectively on the front and back sides of the piezoelectric diaphragm. And processing
the groove concentrically outward from the outer peripheral part of the bonding position of the
piezoelectric element of the metal substrate, and processing the groove concentric with the
piezoelectric element in the metal substrate, the metal substrate The surface area can be
substantially increased without changing the size of the outer circumference of the.
As a result, the resonant frequency of the piezoelectric diaphragm is lowered, and when
configured as a piezoelectric sounding body, oscillation in a low frequency range is possible, and
a sound pressure level in a low frequency range can be secured.
[0006]
According to a second aspect of the present invention, there is provided a piezoelectric sounding
body in which a first groove formed on an outer peripheral portion of a piezoelectric element
attachment position is gently curved on the surface side of the piezoelectric element attachment
surface. As a result, the metal substrate in the portion where the groove that vibrates
substantially is formed becomes thinner than the thickness of the metal substrate in the portion
to which the piezoelectric element is attached.
Therefore, the resonance frequency of the piezoelectric diaphragm can be reduced, and
furthermore, the sound pressure level in the low frequency range can be secured.
[0007]
The invention according to claim 3 of the present invention is a piezoelectric sounding body
which uses a metal substrate subjected to concentric processing and then subjected to heat
treatment, and removes processing distortion of the metal substrate after the heat treatment. As
a result, it is possible to prevent the occurrence of the vibration unevenness of the piezoelectric
diaphragm when the piezoelectric sounding body is formed.
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[0008]
Hereinafter, an embodiment of the present invention will be described using the drawings.
1 and 2 are views showing a piezoelectric sounding body and a piezoelectric diaphragm
according to an embodiment of the present invention.
[0009]
As shown in FIG. 2, a metal substrate 1 made of iron-nickel alloy and concentrically grooved from
the outer peripheral portion to the outer edge portion of the bonding position of the piezoelectric
element 2 and from which the processing strain is removed at a temperature of 350 ° C. The
piezoelectric element 2 was attached to the central flat portion of the above with an adhesive,
and then lead terminals were soldered respectively to the metal substrate 1 and the piezoelectric
element 2 to form a piezoelectric diaphragm 3.
The first groove adjacent to the piezoelectric element 2 formed in the metal substrate 1 is
processed so as to be gently curved upward from the bonding surface of the piezoelectric
element 2. As shown in FIG. 1, the outer edge portion 4 of the piezoelectric diaphragm 3 is
adhesively held between a case 5 and a case 6 formed of an ABS resin and having a sound
emitting hole 5a formed on the bottom as shown in FIG. A piezoelectric speaker was constructed.
[0010]
When an electrical signal is input to the piezoelectric sounding body configured as described
above, the piezoelectric diaphragm 3 resonates, and the vibration is emitted as sound from the
sound emission hole 5a. However, unlike the conventional product, the present invention is a
metal substrate Since the groove processing is performed by concentrically curving 1, even if the
outer diameter is the same as that of the metal substrate 7 of the conventional product, the
surface area becomes large, and the metal substrate 1 of the curved portion is formed The
thickness can be reduced to stably follow a low frequency band signal, and the sound pressure
level can be improved. Furthermore, since the first groove adjacent to the piezoelectric element 2
is gently curved above the bonding surface of the piezoelectric element 2, the curved portion of
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the metal substrate 1 does not disturb the vibration of the piezoelectric element 2. When the first
curved portion of the metal substrate 1 is bent downward from the bonding surface of the
piezoelectric element 2, the first groove clamps the vibration of the piezoelectric element 2, and
as a result, the metal substrate 1 and the piezoelectric element 2 The resonance of the diaphragm
formed in the above is shifted to the high frequency side, which is contrary to the fact that the
transmission in the low frequency region, which is the object of the present invention, is
followed. Furthermore, since the processing distortion is removed by heat treatment after
processing the metal substrate 1, resonance unevenness at the time of resonance of the
piezoelectric diaphragm 3 does not occur, and stable broadband frequency characteristics can be
obtained. In order to withstand the long-term vibration of the piezoelectric diaphragm 3, the
thickness of the metal substrate 1 after processing should not be thinner than 2/3 of the
thickness before processing in order to withstand bending of the piezoelectric substrate 3 for a
long time. You need to In addition, the number and shape of concentrically curved grooves and
the depths of the grooves are designed in accordance with the required frequency characteristics,
and the vibration of the piezoelectric element 2 is not absorbed and clamped but the vibration of
the piezoelectric element 2 is Design considerations are needed to follow or amplify this
uniformly.
[0011]
As described above, according to the present invention, in the piezoelectric diaphragm in which
the metal substrate is processed concentrically in the form of concentric grooves outward from
the outer peripheral portion of the bonding position of the piezoelectric element, the
piezoelectric element is bonded to the central portion. By configuring the piezoelectric sounding
body to be used, it is possible to substantially increase the surface area without changing the size
of the outer periphery of the metal substrate. As a result, the resonance frequency of the
piezoelectric diaphragm is lowered, and oscillation in a low frequency range is possible, and a
sound pressure level in a low frequency range can be secured, and oscillation can be performed
in all frequency bands such as melody and voice. Can provide an excellent sound generator.
[0012]
Brief description of the drawings
[0013]
1 is a cross-sectional view of a piezoelectric speaker according to an embodiment of the present
invention.
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[0014]
Fig. 2 A perspective view of the same piezoelectric diaphragm
[0015]
Fig. 3 Cross section of the conventional piezoelectric sounding body
[0016]
Fig. 4 A perspective view of the same piezoelectric diaphragm
[0017]
Explanation of sign
[0018]
1 metal substrate 2 piezoelectric element 3 piezoelectric diaphragm 5 case 5a sound output hole
6 case
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