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The present invention relates to a piezoelectric electroacoustic transducer and a casing of an
acoustoelectric transducer, and more particularly to a piezoelectric electroacoustic transducer
such as a piezoelectric buzzer. The prior art casing method such as a piezoelectric buzzer is a
method of bonding a piezoelectric vibrator to a case with an adhesive, the front case is made of
metal such as aluminum, the back case is housed together with the piezoelectric vibrator, The
method of fixing by bending the end of the metal case was used. FIG. 6 shows a piezoelectric
electroacoustic transducer manufactured according to the prior art. The piezoelectric vibrator 14
is configured by bonding a ceramic piezoelectric body 16 to a metal diaphragm 15 with an
adhesive. The silver electrode on the bonding surface of the ceramic piezoelectric body 16 is
soldered to a lead wire on the metal diaphragm 15 and is connected to one of the terminals 23,
and the other electrode of the ceramic piezoelectric body 16 is directly soldered to the lead wire
It is connected to the other terminal 23 '. The front case 19 is made of metal and has a sound
release hole 17 so that the peripheral portion of the piezoelectric vibrator 14 is held by the
spacer 2Q. The rear case 21 is made of resin, fixes the terminal 23.23 ', and has an acoustic leak
hole 22. In the assembly, the piezoelectric vibrator 14 and the spacers 20. After the rear case 21
is stored, the opening end of the front case 19 is bent and fixed by caulking 25. Problems to be
Solved by the Invention In the row shown in FIG. 5, since the front case 19 has the same
potential as the diaphragm 15, the front case 19 has a structure that easily discharges when a
high voltage approaches from the outside. For this reason, in order to make it difficult to cause
discharge, the front case 19 may be used as a resin case of an insulator, and there is a drawback
that it is difficult to support and fix the piezoelectric vibrator. In this case, in this case, a structure
is used that fixes with an adhesive or holds by fitting, but the cost increases due to the increase
in the number of parts and the number of steps, and the support fixing condition of the
piezoelectric vibrator becomes unstable There was a problem with The present invention is
intended to provide a piezoelectric electroacoustic transducer that can solve this problem. Means
for Solving the Problems The present invention comprises a piezoelectric vibrator, a front case
and a rear case, the piezoelectric vibrator is held between both cases, and both cases are welded
by ultrasonic vibration. Here, the front case and the rear case are both made of thermoplastic
resin and have ring-shaped projections for supporting and fixing the periphery of the
piezoelectric vibrator, and at least one of the outer peripheral portions of the cases has a
cylindrical convex portion and The case has a melting point, and both cases melt and adhere the
melting point by ultrasonic vibration.
Function According to the invention, front cases fused together. The periphery of the
piezoelectric vibrator can be securely fixed by the ring-shaped protrusion provided on the rear
case. Embodiment (Example 1) FIG. 1 shows the cross-sectional structure of a piezoelectric
electroacoustic transducer according to the present invention. The piezoelectric vibrator 2 is the
same as that shown in the conventional row, and the ceramic piezoelectric body 3 is attached to
the metal vibrating plate 4, and each electrode and the terminal 11.11 'are connected by a lead
wire. Front case 1 is mu BS. Polycarbonate, polypropylene, PB?. A thermoplastic resin such as
PieT, a complex obtained by adding an inorganic substance to this, and the like can be used. The
front case 1 has a sound release hole 5. A ring-shaped protrusion 61 A cylindrical protrusion 7 is
formed. A front air chamber 9 is formed between the piezoelectric vibrator 2 and the front case
1. The rear case 13 uses the same thermoplastic resin as the front case 1. A leakage hole 12 and
a ring-shaped protrusion 6 ? 1 cylindrical protrusion 7 ? are formed in the rear case 13, and a
back air chamber is formed between the leak hole 12 and the piezoelectric vibrator 2. Terminals
11.11 'are fixed to the rear case. The front case 1 and the rear case 13 are bonded by applying
ultrasonic vibration with a frequency of 40 K 1-IZ and an amplitude of 2 o to 30 ?m. In this
case, the ultrasonic vibration application time was 0.5 seconds. When the resonance
characteristic of the piezoelectric electroacoustic transducer was measured, the target value was
obtained. (Embodiment 2) FIG. 2 shows another embodiment 11FI according to the present
invention. The cylindrical convex portion 7 provided on the outermost periphery of the front case
1 is lengthened, the melting margin 8 is provided on the outer peripheral portion of the rear case
13, and the ultrasonic vibration horn 26 is struck against the melting portion 8 and vibrated. . As
a result, sufficient welding strength can be obtained in 0.3 seconds for applying ultrasonic
vibration, and it is possible to reduce the adverse effect on the piezoelectric vibrator.
Embodiment 3 FIG. 3 shows another embodiment of the present invention. Thickness of grooveshaped thin portions 1 'and 13' formed between the ring-shaped protrusion 6.6 'formed on the
front case 1 and the rear case 13 and the cylindrical convex portions 7 and 7' at the outermost
periphery The thickness of the front case 1 is made thinner than the thickness of the central
portion of the front case 1 so that the amount of ultrasonic waves leaking to the ring-shaped
bumps 6, 6 'is suppressed. The resonance characteristic obtained the target value. Embodiment 4
FIG. 4 shows another embodiment according to the present invention. The inner side surface of
the cylindrical convex portion at the outermost periphery of the front case 1 is formed obliquely
to widen the base. Similarly, the inner side surface of the back surface 1130 cylindrical convex
portion 7 'is formed obliquely. By this, ultrasonic vibration is incident from the outer surface of
the back case 1.3 and is concentrated on the melting margin 8 and becomes large ultrasonic
energy, and welding is completed in a short time which is easy to melt, and the influence on the
piezoelectric imaging element 2 Can be kept small.
Further, the excess ultrasonic energy is diffused through the cylindrical convex portion 7 of the
front case 1 and the influence on the piezoelectric vibrator 2 is small. Although four lines have
been described as the above example, it is also possible to reduce ultrasonic vibration to be
applied to the piezoelectric vibrator by making the four examples combined. According to the
piezoelectric electroacoustic transducer of the present invention, since the thermoplastic resin is
used for the front case, the insulation property by the external high voltage is high and the
discharge is difficult to occur, so that the semiconductor circuit to be connected is easily
protected. Since the front case and the rear case are directly welded using ultrasonic vibration,
the number of parts is small and the number of man-hours can be shortened, which is
industrially valuable.
Brief description of the drawings
FIG. 1 is a cross-sectional view of a piezoelectric electro-acoustic transducer according to the
present invention, FIGS. 2 to 4 are cross-sectional views of a piezoelectric electro-acoustic
transducer according to another embodiment of the present invention, and FIG. FIG. 2 is a crosssectional view of a shaped electro-acoustic transducer.
1 и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и 'ring-raised ring
7,7'. ииииииииииииииииииииииииииииии Rear case Name of Agent Attorney Nakao Toshio Other 1 person Figure 1
Figure 3 Figure 4 Figure 5
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description, jps626596
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