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JPS61245800

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DESCRIPTION JPS61245800
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
method of adjusting frequency characteristics of a piezoelectric transducer, which easily adjusts
frequency characteristics among acoustic characteristics of a handset used for a telephone, an
interphone or the like. Prior Art FIG. 6 shows a cross-sectional structural view of a conventional
piezoelectric transducer. In the figure, al is a front air chamber plate, which also serves as a
sound hole 32 to fix the outer circumference of the transducer and the outer case. A front air
chamber 33 is formed between the piezoelectric vibrator 34 and the front air chamber plate 31.
The piezoelectric vibrator 34 has a structure in which a metal plate and a ceramic piezoelectric
body are bonded with an adhesive. A back air chamber plate 35 forms a back air chamber 39
with the piezoelectric vibrator 34. In addition, the back air chamber plate 36 is fixed to the
terminals 38 for input and output of electric signals, and a small hole 37 connecting the thin
back air chamber 39 and the outside is provided, and this small hole 37 is Covering. The input /
output terminal 38 is connected to one electrode of the ceramic piezoelectric body of the
piezoelectric vibrator 34 and the metal plate, respectively. The acoustic characteristics of the
piezoelectric transducer are determined by the resonance frequency, resonance resistance,
capacitance, volume of back air chamber 39, size of small hole 37, air resistance of acoustic
resistance material 400, front air chamber 33 of piezoelectric vibrator 34. There are factors such
as the volume, the size of the sound hole 32, and the fixed state of the piezoelectric vibrator 34.
Since the acoustic characteristics of the handset used in the telephone are strictly limited, the
size of the piezoelectric vibrator 34, the allowable range of the resonance frequency and the
capacitance of the conventional piezoelectric transducer are narrowly limited, the acoustic
resistance material 4o In order to equalize the air permeability of the metal mold, expensive
dimensional mesh is used, the dimensional accuracy of the resin molded article and the metal
machined article is increased, and the manufacturing conditions are strictly defined. Problems to
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be Solved by the Invention The conventional piezoelectric transducer requires high-precision
parts and severe manufacturing conditions, which increases the cost, and causes problems such
as a decrease in yield in manufacturing process i. . The present invention provides a way to solve
these problems by introducing a simple adjustment process. Means for Solving the Problems In
the present invention, the back air chamber volume and the small holes of the back air chamber
plate are newly designed to eliminate the acoustic resistance material and adjust the diameter
and length of the small holes. By adopting the method, the wide distribution of the acoustic
characteristics is intended to suppress the system and to reduce the cost and improve the yield,
even if parts of general accuracy are used. In the present invention, the acoustic resistance
material covering the small holes provided in the back air chamber plate is removed to realize
suppression of the spread of the frequency characteristics, and the small holes provided in the
back air chamber volume and the back air chamber plate Was designed to the optimal value.
Since the acoustic resistance material is one of the causes of variation, the variation suppression
effect is large by removing this.
Furthermore, the variation of the resonance frequency determined by the dimensions and the
fixed state of the piezoelectric vibrator appears as the variation of acoustic characteristics. If the
resonant frequency of the piezoelectric vibrator deviates significantly from the target value, the
piezoelectric vibrator and the back air chamber can be viewed as one by adjusting the diameter
or the length of the minute hole provided in the back air chamber plate. Can be adjusted to the
desired value. By this operation, it is possible to suppress the variation of the frequency
characteristic of the series converter. Embodiment 1 FIG. 1 shows an embodiment of the present
invention. The basic configuration is the front air chamber 3. Piezoelectric vibrator 4. The back
air chamber 9 is the same as the conventional one, but only the minute holes 7 are provided in
the back air chamber plate 6 and no acoustic resistance material is used. The diameter and
length of the micropores 7 are designed using the central value of the distribution of the
resonant frequency of the piezoelectric vibrator 4, but when the resonant frequency is high, the
flatness of the frequency characteristic is lost. The frequency characteristics of the receiver as
shown in FIG. The sound pressure level rises sharply near KH2. When such a frequency
characteristic is shown, it can be flattened as shown by a broken line B in the frequency
characteristic of FIG. 2 by enlarging the diameter of the hole as shown by the broken line in FIG. .
When the resonance frequency is low, the frequency characteristics are as shown in FIG. 3
(before adjustment) (but after the micropores 7 are closed with an epoxy resin, silicon fess, etc., a
hole of a smaller diameter is made. The frequency characteristics can be flattened as shown after
adjustment in FIG. In FIG. 3, "m" indicates the characteristics before adjustment, and "B" indicates
the characteristics after adjustment. Embodiment 2 FIG. 4 shows another embodiment of the
present invention. The method of adjusting the frequency characteristic is a method of cutting or
filling the length of the hole in a manner to be broken or suspended in a line in the minute hole 1
o in FIG. 4. When the resonance frequency of the piezoelectric transducer 4 is high, flattening of
the frequency characteristic can be realized by deleting the length of the minute hole 1 o as
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shown by the broken line in FIG. 4. Conversely, when the resonant frequency of the piezoelectric
vibrator 4 is low, the frequency characteristics can be flattened by closing the minute holes 10
with resin or the like and increasing the length of the holes and then opening a person. The
frequency characteristics can also be flattened by simultaneously performing the operations
shown in the first embodiment and the second embodiment. Although the frequency
characteristic as a receiver has been described here, the same can be applied to a transmitter.
The frequency characteristics of the piezoelectric transducer can be easily adjusted by changing
the diameter and / or the length of the minute holes provided in the back air chamber plate as
shown in this embodiment. As shown in FIG. 5, compared with the conventional case where the
frequency characteristic is not adjusted, the effect of the adjustment method of this embodiment,
which is B, can significantly improve the range of the frequency characteristic variation,
compared to the distribution range of the present embodiment. is there.
Effects of the Invention As described above, according to the present invention, a converter that
has conventionally been discarded outside the standard can be regenerated, and yield can be
improved. In addition, it is unnecessary to make the accuracy of parts too strict, which can lower
the cost of parts.
[0002]
Brief description of the drawings
[0003]
1 and 4 are cross-sectional views of the piezoelectric transducer of the present invention, and
FIG. 2 is a frequency characteristic diagram of the receiver comparing before and after
adjustment of the adjustment method of the present invention, and FIG. Fig. 6 is a comparison
chart of distribution characteristics of frequency characteristics as a piezoelectric receiver before
and after performing adjustment by the adjustment method of the present invention, Fig. 6
comparing frequency characteristics before and after adjustment by another adjustment method
of the present invention; The figure is a cross-sectional view of a conventional piezoelectric
transducer.
1 ...... front air chamber plate, 2 ...... sound hole, 3 ...... front air chamber, 4 ...... piezoelectric
vibrator, 6 ..... · Back air chamber plate, 6 · · · · · · · Lead wire, 7, 1 o · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · back air chamber.
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