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JPS54115095

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DESCRIPTION JPS54115095
Specification 10 Title of Invention
Piezoelectric buzzer
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric
buzzer in which the sound output is increased and the sound generation frequency is broadened.
In recent years, piezoelectric buzzers have been widely used as buzzers for various alarms. This is
because there are advantages such as thinness and low power consumption as compared with
the conventional electromagnetic type. This piezoelectric buzzer generally accommodates a socalled bimorph diaphragm in which a metal plate (b) and a piezoelectric plate (2) are joined as
shown in FIG. 1 in a case (7) having an opening (6) on the front surface That is, the diaphragm
generates a sound of 2 to 9 KHz which does not exceed the bending vibration by the alternating
voltage supplied from the excitation electric circuit (8). However, since the sound generation
frequency utilizes resonance of the diaphragm, it is uniquely determined by the shape and size of
the diaphragm, and there is no freedom of frequency selection, which causes a problem in
practical use. As an example, in recent years, attempts have been made to diversify the soundgenerated signal by producing several types of sounds of different frequencies using
conventional electromagnetic speakers and selecting them. It was considered difficult with the
piezoelectric buzzer. Furthermore, in recent years, the power supply voltage has a tendency to
decrease with the use of ICs in electric circuits, and since the conventional piezoelectric buzzer
has a low acoustic output, there has been a strong demand for its improvement. The present
invention proposes a piezoelectric buzzer which increases the sound output and broadens the
sound generation frequency except for the above drawbacks, and the effect is that the
piezoelectric is used as an Imo A · · · oscillator and a piezoelectric body is added. This can be
achieved by using a composite diaphragm in which a single diaphragm is opposed to and coupled
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via a coupling member. Next, an embodiment of the present invention will be described with
reference to the drawings. The bimorph diaphragm is fixed in the case 8 in the center's fixed
method and the peripheral fixing method. The case of application is shown in FIG. That is, a
bimorph diaphragm in which a hole is formed in the center and a piezoelectric plate (2) of an
annular disc having silver electrodes baked on both sides and a metal plate (1) is bonded with an
adhesive, and the same shape as the metal plate (1) The diaphragms (3) represented by the single
metal plate of the present invention are opposed to each other with the ring connector (4)
interposed therebetween to form a composite diaphragm, and the screws (5) are passed through
the central holes and the case (7) Insert and fix screw (5) in the center of the front of the case
with opening (6). In the figure, (8) is an electric circuit for excitation, (9) is a lead wire for
connecting the bimorph diaphragm and the electric circuit for excitation, and scream is a
terminal for power supply connection. The case where the peripheral fixation method is carried
out is shown in FIG.
A metal plate (1) and a piezoelectric plate (2) with silver electrodes baked on both sides were
bonded with an adhesive, but an I7 vibration plate and a diaphragm with a diameter slightly
smaller than that of the metal plate (1) In the same way, a composite diaphragm is constructed
by bonding 8 adhesive elements (4 interspersed with an adhesive to form a composite diaphragm
at the periphery of the opening, and fixed to the inner wall of the case with an adhesive). . Then,
the excitation electric circuit (8) and the bimorph oscillator are connected by leads II (9) and (9).
さらに11! FIG. 4 shows the case where the periphery of the diaphragm (3) is fixed to the
inner wall of the case (7) with an adhesive, as in another embodiment 5 of the peripheral fixing
method shown in FIG. The configuration of the composite diaphragm in this case is the same as
in FIG. 8, but the diameter of the metal plate (1) is smaller than that of the diaphragm (3), and the
case around the fitting plate (3) is a case The point fixed to the inner wall and the protrusion (1)
for supporting eight points on the diaphragm 1 ((3)) are different in shape and nine points.
Example 1 As a piezoelectric buzzer shown in FIG. 2, a phosphor bronze disk l having a diameter
of 25 and a thickness of 0.2 m, having a hole of gJmφ at its center, was used as a metal plate (1)
and silver electrodes were baked on both sides. An annular disc made of lead zirconate titanate
based porcelain with an outer diameter of 18 mm, an inner diameter of @m, and a thickness of
0.2 M is bonded as a piezoelectric plate (2) with an epoxy resin adhesive (brand name araldite) to
make a bimorph diaphragm The And the same shape as the metal plate (1). A diaphragm (3)
made of a single bronze bronze plate is made, and a Bakelite resin ring connector with an outer
diameter of 5 S, an inner diameter of 3 Ji + o, and a thickness of 1 m is made between the
bimorph diaphragm and the diaphragm (3) It was fixed to a case (7) having 6 holes 8 (6) of
diameter 8 * on the front side with 8NJItφ brass screw (5) with 4) interposed. The effect of
adding a single diaphragm (3) was compared and experimented with the piezoelectric buzzer (a)
according to the embodiment of the present invention and the piezoelectric buzzer (b) from
which the diaphragm (3) and the connector (4) were removed. . The results are shown in FIG. 5
and FIG. FIG. 5 is a graph showing the frequency characteristics of the measured electrical
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admittance for observing the resonance state of the diaphragm, but in the case of the
piezoelectric buzzer (a) of the present invention using a composite diaphragm, the bimorph
diaphragm The vibration corresponding to the main vibration of (a vibration corresponding to
the resonance of the added diaphragm (3) occurs in addition to the vibration (.eta.), While the
piezoelectric buzzer (b) of only the bimorph ) Only occurred. As a result, as shown in FIG. 6, in
the case of the piezoelectric buzzer (a) of the present invention, it is understood that the sound
goodness characteristics increase in appearance and a wide band characteristic is obtained.
Here, in the characteristic shown in FIG. 6, the output voltage from the excitation electric circuit
is fixed to 2v ′ ′, and the frequency is changed to measure the sound output. The above is the
case where one diaphragm (3) is added, but the number of sheets used can be increased
depending on the application, and the shape and size can be changed. This gives an arbitrary
frequency-characteristic. Example 2 As a piezoelectric buzzer shown in FIG. 8, a phosphor bronze
disc having a diameter of 84 m and a thickness of 02111 M was used as a metal plate (1), and a
silver electrode was baked on both sides. Piezoelectric ceramic is joined with an adhesive as a
piezoelectric plate (2) to make a bimorph diaphragm, and a disc made of polyester resin with a
diameter of 281,111 and a thickness of 02 silk is used as a diaphragm (3), diameter IJ) H%
thickness The composite diaphragm was made by supporting and adhesively supporting at 8
points with an lfi bakelite connector (4). The periphery of the metal plate (1) of this composite
diaphragm was adhered to the inner wall of the case having an opening (6) of 1 鱈 φ on the
front surface to make a piezoelectric buzzer (0). In addition, EndPage: 2 made of only a bimorph
diaphragm. 2 conventional type piezoelectric buzzers (A ψ was made, and sound output was
compared and tested. The results are shown in FIG. Also in this case, it is understood that the
piezoelectric buzzer (e) according to the present invention can obtain good acoustic output
characteristics, with the addition of the diaphragm. The reason why the sound output is
improved in this way is that the amplitude of the bending vibration oscillator propagates as
bending vibration to the additional vibration plate without the piezoelectric body through the
coupling portion, and the vibration amplitude Is increased. Therefore-even if the peripheral part
of the additional diaphragm is also fixed to the case at the same time, and it is coupled to the
bimorph diaphragm at only one point away from the central part, the same effect as above is
obtained. can get. Example 8 The piezoelectric buzzer shown in FIG. 4 has projections of diameter
158 and height 1 m at 8 equally spaced concentric points of 15 flφ (diaphragm made of
polyester resin of diameter 59 w and thickness 92 ag provided with chrysanthemum (3 An
adhesive was applied to the projections (4) to bond the bimorph diaphragm to a composite
diaphragm. Then, the peripheral portion of the diaphragm (3) was fixed to the inner wall of the
case and housed in the case (7) to make a piezoelectric buzzer (@). Also, a piezoelectric buzzer (f)
of the conventional structure shown in FIG. 1 without the diaphragm (3) was produced. The
results of testing their acoustic properties are shown in FIG. Also in this case, it can be seen that
the effect of the additional diaphragm appears remarkably and is discussed. It is apparent that
the same effect as described above can be obtained by projecting on the metal plate (1) of the
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bimorph diaphragm as opposed to the projection for bonding (four are attached to the
diaphragm (3) .
Although the above embodiment shows the case where all the members are circular, the present
invention is not limited to the circular but can be applied to bimorph diaphragms of other shapes
such as a square. Furthermore, the same effect can be obtained in a so-called asymmetric 1-luff
diaphragm using a metal plate and a piezoelectric plate one by one or a symmetrical bimorph
diaphragm using two piezoelectric bodies.
4. Brief description of the drawings. FIG. 1 is a longitudinal sectional front view showing a
conventional piezoelectric buzzer, FIG. 2 is a longitudinal sectional front view showing one
embodiment of the present invention, and FIG. 8 is a longitudinal sectional front view showing
another embodiment. Fig. 4 is a longitudinal sectional front view showing a modification of Fig. 8,
Fig. 5 line shows the electrical admittance frequency characteristics of the piezoelectric buzzer
(a) according to the present invention and the piezoelectric buzzer (b) of the conventional
structure. FIG. 6 is a chart showing acoustic characteristics in the same manner, FIG. 7 is a chart
showing wedge characteristics of the piezoelectric buzzer (e) of the present invention and the
conventional piezoelectric buzzer (d) in Example 2, FIG. It is a graph which shows the acoustic
characteristic of the piezoelectric buzzer (e) of this invention and the conventional piezoelectric
buzzer (0 in Example 8). In the figure, 1 · · · metal plate, 2 · · · piezoelectric plate, 8 · · · diaphragm,
4 · · u metal, 6 · · · screw · · · · · · · · · · · · · · · · · · · · · · · · · · Electrical circuit for excitation. Applicant:
Sumitomo Special Metals Co., Ltd. · ° police agent press 1) Yoshihisa '· Figure 1 Figure 2 Figure
3 Figure 4 End Page: 3 Figure 5 j (kl-1x) Figure 6 f (kHz) 7 f (kHz) 1-1! EndPage: 4
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