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JPS59107698

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DESCRIPTION JPS59107698
[0001]
The present invention relates to a piezoelectric acoustic transducer such as a piezoelectric
speaker using a piezoelectric diaphragm, and to a protection method for preventing the
characteristic deterioration of the piezoelectric diaphragm. FIG. 1 shows a cross-sectional view of
an existing piezoelectric speaker. (1) is a disk-shaped piezoelectric diaphragm, which is made of
ceramic material or the like at the center of one surface of a metal substrate (2) such as brass. A
material plate (3) is bonded, and an electrode film is further provided on the other surface of the
piezoelectric material plate (3). (4) is a cone paper, the top of which is coupled to the center of
the piezoelectric diaphragm (1). (5) is a bottomed frame made of resin which is an insulating
material, and the peripheral portion of the above-mentioned corn paper is adhered to the
opening side. (6) is an insulating + 'l terminal plate consisting of a flat portion of the outer
surface integrally formed with the frame (5), (7) is a terminal fixed by caulking to the terminal
plate (6) , Two are juxtaposed. (8) (8) is a lead wire for applying an acoustic signal to the
piezoelectric material plate (3) of the piezoelectric diaphragm (1), and the lead wire (8) of J is a
metal substrate <2> The other lead wire (8) is connected to the electrode film of the piezoelectric
material plate (3) and the other terminal-by connecting the one terminal (7) to the other terminal
(7) (9) (9). Similarly, they are connected by soldering (9) (9). In the piezoelectric speaker having
the above-described configuration, the acoustic signal input to both terminals (7) and (7) of the
terminal plate (6) is a piezoelectric material of the piezoelectric diaphragm <1) through the lead
wires (8) and (8). As a result of being applied to both sides of the plate (3), the piezoelectric
diaphragm (1) is bent and moved by the electrostrictive effect of the piezoelectric material plate
(3) to vibrate the 1-on paper (4) to make an audible one It is a) to get. However, if such an
acoustic transducer is left for a long period of time (by leaving the body (and depending on the
temperature change of the outside air, the H-type diaphragm (1) has its metal substrate (2) and
piezoelectric material plate ( It causes the occurrence of warpage due to the difference in
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expansion coefficient with 3). For this reason, on the contrary, a potential difference due to the
piezoelectric phenomenon is generated on both surfaces of the piezoelectric material plate (3),
and this piezoelectric material plate (3) acts in the direction to break its own polarization, and the
electrostrictive effect of the piezoelectric material plate <3) It will deteriorate. As a result, at the
time of incorporating an acoustic transducer to be rejected into an acoustic device such as a
radio, there arises a disadvantage that the defective sound 1 gl transducer with reduced acoustic
reproduction capability may be obtained. The present invention has been made to solve the
above problems, and a method of protecting a piezoelectric sound W converter provided with
shorting means for shorting between both terminals for applying an acoustic signal to a
piezoelectric diaphragm. To provide
Each of FIGS. 2 to 4 shows an embodiment in which a piezoelectric speaker is taken as an
example of an acoustic transducer according to the present invention, and in FIG. 1 is j at the
same reference numeral as FIG. In the embodiment of FIG. 2, the feature of the present invention
is that both sides of the piezoelectric material plate and the terminal plate constituting the
piezoelectric diaphragm combined with cone paper and stored in the play A (5) (6) The lead
wires of two trees electrically connecting the two upper terminals (7) and (7) respectively to the
soldered holes of the terminals (7) and (7) (9) (9) Provide two wood extension leads (8 ') (8')
extending through the frame to the outside of the frame (5) and twisting these two extension
leads together (8 '> (8')) Therefore, the two terminals ^ (7) and (7) are short-circuited. A
piezoelectric speaker provided with shorting means for shorting between the two terminals (7)
and (7) as described above is stored in this short-circuited state, and when the piezoelectric
speaker is actually incorporated into an acoustic device such as a radio The above-mentioned
extended lead S twisted! l (8 ') (8') is cut off, and while the acoustic bag picker is stored alone, 4terminals <7) (7) of the terminal plate (6), ie, the piezoelectric material plate (2) Since both
surfaces are short-circuited by the extended lead wire (8 ') of the lead wire (8), this piezoelectric
material plate (2) is generated due to the warp of the piezoelectric material plate (2) due to the
temperature change. The charge is neutralized. As a result, since the polarization breakage of the
piezoelectric material plate (2) is suppressed, the reduction of the sound reproduction capability
of the piezoelectric speaker is prevented. In addition, after both terminals (7) and (7) of the
piezoelectric speaker are connected to the electric circuit of the acoustic device, this electric
circuit holds the terminals (7) and (7) in a short-circuited state. In the embodiment of FIG. 3, the
feature of the present invention is the terminal plate (6) in which two terminals (7) and (7) for
inputting an acoustic signal to the piezoelectric speaker are arranged in parallel. The conductive
adhesive tape (10) is pasted over the both terminals (7) and (7) on the top, and these terminals
(7) and (7) are short-circuited. The conductive adhesive tape is made of a copper foil with a
pressure sensitive adhesive or an aluminum s foil, for example, a product number 1245 or 1267
manufactured by Scotch. When the acoustic transducer is incorporated into an acoustic device,
the conductive adhesive tape (10) is peeled off. Further, FIG. 4 shows an embodiment of a single
terminal plate used for a piezoelectric speaker, wherein (a) is a front view and (b) is a two-sided
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section. .
In the present embodiment, the feature of the present invention is that the two terminals (7) and
(7) juxtaposed to the terminal plate (6 ') J- made of an insulating material are integrally formed of
a metal plate. It is in the point which short-circuits between these both terminals (7) and (7)
according to having comprised. In addition, a caulking hole (11) for fixing the frame and the
terminal plate (6 ') together is provided at the center of the connection between the two
terminals (7) and (7). There are provided rising pieces (12) (12) which are formed between the
periphery of the hole (11) and each of the two terminals (7) (7). A piezoelectric speaker using a
terminal board (6 ') having such a terminal configuration can be used to connect two terminals
(7) and (7) at the time of being incorporated into an acoustic device. The rising piece (12> (12)
will be cut off. Next, the effects of the present invention will be described based on measured
values. A heat cycle test in which 20 ░ C and 60 ░ C were switched at an interval of 1 hour on a
piezoelectric speaker with 10 properly selected terminals left open was carried out for 50 zicles,
pressure! The capacitance of the diaphragm is reduced by 19.7% in average value to the initial
value before the test. The frequency characteristics of the piezoelectric speaker before the test in
this case are shown in FIG. 5 (a), and the characteristics after the shorting are shown in FIG. 5 (b).
When comparing (a) and (b) of FIG. 5, it is clear that the sound reproduction capability of the
piezoelectric speaker, that is, the sound pressure is reduced after the dissent. On the other hand,
when the same heat cycle test was carried out to the piezoelectric type speaker which carried out
the method of the present invention, the capacitance of the piezoelectric diaphragm was 23% in
average value compared to the initial value of Tess I и before. It has been reduced. The frequency
characteristics of the piezoelectric speaker before the test in this case are shown in FIG. 6 (a), and
the characteristics after the death 1- are shown in FIG. 6 (b). When comparing (a) and (b) in FIG.
6, even after such a test, the sound reproduction capability of the piezoelectric speaker, that is,
the decrease in sound pressure is hardly seen as t'J. . The test results show that the piezoelectric
speaker according to the method of the present invention largely suppresses the breakdown of
the polarization of the piezoelectric material plate, which is indicated by the rate of decrease of
the electrostatic capacitance of the piezoelectric diaphragm = 7-capacity. Understandable.
Incidentally, in the explanation of the following 1 ;, in particular, a piezoelectric material plate is
bonded to one side of a metal substrate. ??? ; ',' T: A piezoelectric speaker using a
piezoelectric vibrating plate of a luff structure has been shown as an example, but even in a
piezoelectric vibrating plate of a bimorph structure in which a piezoelectric material is laminated
on both sides of a metal substrate The present invention is effective for the piezoelectric speaker
using the bimorph structure b) because it is generated once due to the warp due to the warp, and
further, it can be applied to other piezoelectric acoustic transducers such as a buzzer and the like.
is there.
In the method of protecting a piezoelectric acoustic transducer according to the present
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invention, as is apparent from the description of F below, a terminal plate having two terminals
fixed for applying acoustic signals to both sides of a piezoelectric material plate of a piezoelectric
diaphragm. In addition, when the acoustic transducer is incorporated into an acoustic device, the
short circuit means is removed when the acoustic transducer is incorporated into an acoustic
device. The potential difference between the piezoelectric material plate and the piezoelectric
material plate caused by the warping of the piezoelectric diaphragm due to the temperature
change occurring during storage in the lt body can be eliminated by the short circuit means
described above. Therefore, the piezoelectric material plate can be protected from polarization
destruction! Since the distortion effect is secured, the reproduction capability of the acoustic
transducer can be well maintained, and the reliability of the acoustic transducer can be improved.
Furthermore, since the short circuit means used in the method of protecting a piezoelectric
acoustic transducer according to the present invention is formed by twisting the extended
portion of the lead wire from the piezoelectric diaphragm via both terminals on the terminal
board, a new It is possible to short-circuit with a simple operation without adding any parts, and
it is also easy to cut the extension of this lead wire. Further, since the short-circuiting means is
formed by sticking the conductive adhesive tape across the both terminals on the terminal plate,
the direction of work elongation can be measured by the tape which is easily removable. Further,
since the short-circuiting means is integrally formed of the two terminals and the connecting
portion for connecting the both terminals by the metal plate, not only can the two terminals be
reliably short-circuited, Since the two terminals are connected, mounting of the terminals
increases the efficiency of the work.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a cross-sectional view of an existing piezoelectric speaker, FIGS. 2 to 4 are external
views showing respective embodiments of a protection system of a piezoelectric acoustic
transducer according to the present invention, and FIG. 5 is an existing piezoelectric speaker FIG.
6 is a frequency characteristic diagram of a piezoelectric speaker adopting the method of the
present invention.
(1) ... Piezoelectric diaphragm, (4) ... cone paper, (5) ... flano 0, (6) (6 ') ... terminal board, (7> ...
terminal, ( 8) ... lead wire, (8 ') ... extended lead wire, (10) ... conductive adhesive tape, (12) ...
standing I-piece. 11-?ииии rI +-Makoto zo S ? (C1) ? (G) ff + wave ward (b) (b) ? ? 539
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