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JP2012244596

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DESCRIPTION JP2012244596
The present invention provides an alarm speaker capable of reducing the change in physical
properties such as elastic modulus even in a high temperature environment and maintaining the
sound pressure with less deterioration of characteristics even when used for a long time. An
alarm speaker 1 includes a speaker unit 3 housed in a housing 2 and outputting an alarm sound
of a predetermined frequency band. The speaker unit 3 includes a piezoelectric plate 31 that
vibrates by a piezoelectric effect in response to driving vibration, and a diaphragm 32 driven by
the piezoelectric plate 31. The diaphragm 32 is formed of aluminum. The housing 2 includes a
sound hole 231 for outputting the sound wave output from the speaker unit 3 to the external
space, and a cavity 211 which is a space between the diaphragm 32 and the sound hole 231.
[Selected figure] Figure 1
Alarm speaker
[0001]
The present invention relates to an alarm speaker that outputs an alarm sound.
[0002]
In general, various techniques are adopted for a speaker apparatus used for a television receiver,
a personal computer, etc., in order to suppress peaks and dips in sound pressure frequency
characteristics.
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1
For example, Patent Document 1 discloses a technique for flattening the frequency
characteristics by providing a braking mechanism for suppressing sound waves on the side wall
of an acoustic tube. According to the figure, the speaker device described in Patent Document 1
uses a speaker unit provided with a cone-shaped diaphragm.
[0003]
JP-A-9-307985
[0004]
There is a diaphragm of a speaker unit using a resin film.
The diaphragm of the resin film has a relatively large internal loss and suppresses the sharpness
of the resonance, so it has the effect of contributing to the flattening of the frequency
characteristics.
[0005]
On the other hand, not the speaker apparatus that requires the above-described flattening of the
frequency characteristics, but also an alarm speaker specialized for the output of the alarm sound
is provided. The warning speaker may be exposed to a severe temperature environment as in a
vehicle. For example, the environment of a speaker device mounted on a vehicle may become
very hot in summer, and the elastic modulus of the diaphragm may change due to the softening
of the resin film, and as a result, the sound pressure may change. . In addition, when used in a
severe temperature environment, the resin film degrades over time, and the elastic modulus of
the diaphragm changes, which causes a problem that the sound pressure decreases in long-term
use.
[0006]
The present invention has been made in view of the above-described problems, and an object of
the present invention is to provide an alarm speaker capable of maintaining sound pressure even
when used for a long time.
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2
[0007]
The alarm speaker according to the present invention includes a speaker unit including a
diaphragm driven by a piezoelectric effect and outputting an alarm sound in a predetermined
frequency band, and a housing for housing the speaker unit, the housing being output from the
speaker unit And a cavity which is a space between the diaphragm and the sound hole, the
diaphragm being made of metal.
[0008]
In this alarm speaker, it is preferable that the diaphragm is a cone type whose diameter is
increased in the direction in which the sound wave is output, and a curved surface having a
center of curvature outside the diaphragm is formed.
[0009]
In this alarm speaker, the diaphragm is preferably made of aluminum.
[0010]
According to the configuration of the present invention, since the diaphragm is formed of metal,
changes in physical properties such as elastic modulus are small even in a high temperature
environment, and deterioration in characteristics is small and sound pressure can be maintained
even when used for a long time It has the advantage of
[0011]
(A) is a front view which shows embodiment, (b) is the sectional view on the AA line in the figure
(a).
FIG.
FIG.
It is the BB sectional drawing in FIG. 1 (a).
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3
It is a perspective view which shows the external appearance same as the above.
It is sectional drawing to which the principal part same as the above was expanded. FIG.
[0012]
The alarm speaker described below is configured to output a sound in a frequency band used as
an alarm sound when a notification signal instructing to turn on from the outside is input. The
warning speaker is used, for example, for a device mounted on a vehicle and outputting a
warning sound when a notification signal indicating an abnormality of the vehicle is input.
[0013]
As shown in FIGS. 1 to 5, the alarm speaker 1 includes a housing 2 in which the dimension in the
direction of outputting the alarm sound is smaller than the dimension in the other direction.
Hereinafter, the direction in which the alarm sound is output from the housing 2 is taken as the
thickness direction of the housing 2. That is, the left and right direction in FIG. 1B is the
thickness direction of the housing 2.
[0014]
The housing 2 accommodates a speaker unit 3 that outputs an alarm sound, a circuit unit 4 that
generates a drive signal for making the speaker unit 3 sound, and a battery 5 as a power source.
In the internal space of the housing 2, a speaker housing 21 in which the speaker unit 3 is
disposed, and a circuit housing 22 in which the circuit unit 4 and the battery 5 are disposed are
provided.
[0015]
A sound hole 231 for outputting an alarm sound to the outside opens in the front wall 23 which
is one side in the thickness direction of the housing 2. A cavity 211 is formed in a portion
surrounded by the speaker unit 3 and the front wall 23 in the speaker storage unit 21.
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Furthermore, in the housing 2, a connector 6 to which a notification signal is input from the
outside is provided on a side wall of a portion provided with the circuit housing portion 22.
[0016]
When the notification signal is input to the circuit unit 4 through the connector 6, the circuit unit
4 outputs a drive signal to the speaker unit 3 to drive the speaker unit 3 to generate an alarm
sound. The alarm sound output from the speaker unit 3 passes through the cavity 211 and is
output from the sound hole 231 to the outside of the housing 2. The cavity 211 is provided to
increase the sound pressure of a frequency band used as an alarm sound by utilizing resonance.
[0017]
In the following, the vertical direction is defined according to FIG. The housing 2 has an outer
shell formed by a case body 25 whose rear surface is open and a cover 27 which closes the rear
surface of the case body 25. The outer peripheral shape of the housing 2 projected from the
front is U-shaped with the lower part opened upward, and in the upper part with a semicircular
shape opened downward. That is, the housing 2 has a shape in which the outer peripheral shape
in the front view as a whole is a reverse U shape and a straight line between the open ends of the
U shape.
[0018]
The case body 25 has a peripheral wall projecting rearward from the periphery of the front wall
23 of the housing 2 to the entire periphery, and a partition wall 24 that divides the internal
space of the housing 2 vertically into two from the rear surface of the front wall 23 It is provided
in a projecting manner. The partition wall 24 is continuous with the peripheral wall (hereinafter
referred to as “upper peripheral wall”) of the upper portion of the case main body 25, and the
upper peripheral wall of the case main body 25 and the partition wall 24 form a wall
surrounding the cavity 211 described above. Ru.
[0019]
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The projecting dimension of the partition wall 24 from the front wall 23 is smaller than the
projecting dimension of the peripheral wall from the front wall 23, and the upper peripheral wall
of the case main body 25 has a shoulder (symbols without symbols) continuous with the rear end
of the partition wall 24 ) Is formed. A stepped portion 251 is formed on the upper peripheral
wall of the case body 25 in front of the shoulder, and a stepped portion 241 continuous to the
stepped portion 251 is formed on the partition wall 24. The stepped portions 241 and 251 are
formed such that the inner size of the portion surrounded by the upper peripheral wall of the
case main body 25 and the partition wall 24 is narrower on the front side of the stepped portions
241 and 251 than on the rear side.
[0020]
By the way, inside the case main body 25, the middle frame 26 supported by the shoulder
formed on the upper peripheral wall of the case main body 25 and the rear end edge of the
partition wall 24 is disposed. The middle frame 26 includes a support plate 260 supported by the
upper peripheral wall and the partition wall 24 of the case main body 25, and a separation wall
262 protruding rearward from the peripheral edge of the opening formed at the central portion
of the support plate 260. Continuously in one piece. On the front surface of the outer peripheral
portion of the support plate 260, in a state where the middle frame 26 is attached to the case
main body 25, the holding convex portion 261 opposed to the step portions 241 and 251 is
provided protruding all around the support plate 260 .
[0021]
On the other hand, the cover 27 is formed in a plate shape, and the peripheral portion is
supported by the rear end edge of the peripheral wall provided in the case main body 25. A
support rib 271 is provided on the front of the cover 27 so as to surround the rear end of the
separation wall 262 of the middle frame 26. A gap is formed between the support rib 271 and a
part of the separation wall 262, and the speaker unit 3 and the circuit unit 4 are electrically
connected through the gap (see FIG. 4).
[0022]
With the configuration described above, the internal space of the housing 2 surrounded by the
case main body 25 and the cover 27 is partitioned by the partition wall 24 and the middle frame
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26. A space surrounded by the upper peripheral wall of the case main body 25, the partition wall
24, the middle frame 26, and the cover 27 forms the cavity 211 while accommodating the
speaker unit 3 as the above-described speaker accommodation portion 21. The space surrounded
by the remaining peripheral wall of the case main body 25, the partition wall 24, the middle
frame 26, and the cover 27 accommodates the circuit portion 4 and the battery 5 as the circuit
accommodation portion 22 described above.
[0023]
In the front wall 23 of the case main body 25, a plurality of (four in the illustrated example)
sound holes 231 are formed in the outer peripheral portion of the region corresponding to the
cavity 211 surrounded by the upper peripheral wall and the partition wall 24. . As described
above, the upper peripheral wall of the case main body 25 and the partition wall 24 form a wall
that surrounds the cavity 211 in a circular shape. The sound holes 231 are arranged at equal
intervals on the circumference along the wall. In the present embodiment, in the front view of the
housing 2, four sound holes 231 are formed vertically and horizontally. Further, an annular
control rib 232 is provided on the rear surface of the front wall 23 so as to project rearward
along the inner peripheral edge of the sound hole 231.
[0024]
The speaker unit 3 includes a piezoelectric plate 31 using a piezoelectric bimorph as a drive unit
that generates a vibration upon receiving a drive signal, and includes a diaphragm 32 that
vibrates with the piezoelectric plate 31 to generate an alarm sound. That is, the diaphragm 32 is
coupled to one surface of the piezoelectric plate 31 in the thickness direction, and the
piezoelectric plate 31 drives the diaphragm 32 by the piezoelectric effect. For example, PZT (lead
zirconate titanate) is used as a piezoelectric material that forms a piezoelectric bimorph.
[0025]
The diaphragm 32 is formed of a thin metal material, and is formed in a cone shape in which the
diameter increases in the thickness direction of the piezoelectric plate 31 as it is separated from
the piezoelectric plate 31. That is, the diaphragm 32 is a rotating body having a center line along
the thickness direction of the piezoelectric plate 31, and the shape in which the distance from the
piezoelectric plate 31 changes in an exponential function or an elliptic curve in the direction
10-05-2019
7
along the center line. Is formed. In other words, the diaphragm 32 forms a curved cone having a
center of curvature on the side opposite to the center line (outside of the diaphragm 32).
[0026]
The cone-shaped diaphragm 32 has an advantage that the sharpness of the resonance is
relatively small, and even if the resonance frequency of the diaphragm 32 does not match the
resonance frequency of the piezoelectric plate 31, the reduction of the sound pressure hardly
occurs. There is. Therefore, the speaker unit 3 can reduce variation in sound pressure among
products, and can secure a required sound pressure with high yield. Further, as described later,
since the cone-shaped diaphragm 32 is held so that the outer peripheral portion is bent, it has a
feature that concentration on the diaphragm 32 is difficult to occur. That is, in an environment
where scattering material from the outside is likely to collide, such as when mounted on a
vehicle, if a dome-shaped diaphragm is used, the diaphragm may be depressed by the scattering
material to affect the sound pressure, but the cone type In the diaphragm 32 of the above, since
the deformation due to the scattering object is hard to occur, the influence on the sound pressure
is small.
[0027]
Furthermore, since the diaphragm 32 is formed of a metal material, there is almost no change in
physical properties such as elastic modulus even when used in a high temperature environment
such as when mounted on a vehicle, and furthermore, high temperature and low temperature are
repeated. It is hard to produce the deterioration by something. That is, there is little change in
sound pressure due to temperature environment or aging, and it can be used for a long time. As
the metal material forming the diaphragm 32, a material having high rigidity and high sound
velocity is suitable. By using the diaphragm 32 having such characteristics, loss of sound energy
is small, and high sound pressure can be obtained at the resonance frequency. Although this
embodiment selects aluminum as this kind of metal material, it is also possible to use other
metals, such as titanium and a magnesium alloy.
[0028]
The speaker unit 3 is attached to the housing 2 by holding the outer peripheral portion of the
diaphragm 32 between the step portions 241 and 251 provided on the case main body 25 and
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8
the support plate 260 of the middle frame 26. As shown in FIG. 6, a recessed groove 253 is
formed in the step portions 241 and 251 (the illustrated example shows the step portion 251),
and an elastic member 252 formed in an annular shape is fitted in the recessed groove 253. Be A
part of the elastic member 252 is exposed from the recessed groove 253. The outer peripheral
portion of the diaphragm 32 is sandwiched between the holding convex portion 261 of the
support plate 260 and the step portions 241 and 251. In this state, the elastic member 252
elastically contacts the outer peripheral portion of the diaphragm 32, and from the diaphragm
32 Transmission of vibration to the case body 25 is suppressed.
[0029]
Further, at a portion which is an outer peripheral portion of the diaphragm 32 and does not abut
on the holding convex portion 261, a bending portion 322 which is curved to be convex forward
is formed. The bending portion 322 has a function of suppressing transmission of vibration from
the diaphragm 32 to the case main body 25 and the middle frame 26. Therefore, the loss due to
the vibration energy being transmitted from the vibration plate 32 to the housing 2 is suppressed
by the bending portion 322 and the elastic member 252, and the vibration energy of the
vibration plate 32 is efficiently converted into a sound wave. Become.
[0030]
As described above, the cavity 211 is formed in front of the speaker unit 3 in the case main body
25, and the cavity 211 is partitioned by the control rib 232 into a central space and an outer
peripheral space. Further, the control rib 232 has a gap with the diaphragm 32, and the central
space and the outer peripheral space of the cavity 211 communicate with each other through the
gap. The outer peripheral space communicates with the external space of the housing 2 through
the sound hole 231. Accordingly, the sound wave output from the speaker unit 3 is output from
the sound hole 231 to the external space of the housing 2 from the central space of the cavity
211 through the gap and further through the outer peripheral space of the cavity 211.
[0031]
By providing the cavity 211 of the above structure in the housing 2, the sound pressure of the
alarm sound output from the speaker unit 3 is enhanced using the resonance based on the
principle of Helmholtz resonance. That is, as shown in FIG. 7, the frequency characteristic
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9
(characteristic A0) of only the piezoelectric plate 31 has a large degree of sharpness and a small
sound pressure, but the frequency characteristic (characteristic A1) of the combination of the
piezoelectric plate 31 and the diaphragm 32 is sharp The degree is small and the sound pressure
for the alarm sound is high. Furthermore, by combining the piezoelectric plate 31, the diaphragm
32, and the cavity 211, a higher sound pressure can be obtained for the alarm sound as shown
by the frequency characteristic (characteristic A2) in FIG.
[0032]
As described above, at the lower part of the housing 2, the circuit storage part 22 surrounded by
the peripheral wall at the lower part of the case main body 2, the partition wall 24, the middle
frame 26 and the cover 27 is formed. The battery 5 is accommodated in a space surrounded by
the peripheral wall and the partition wall 24 at the lower part of the case main body 2 in the
circuit accommodation portion 22, and the circuit portion 4 mounted on the circuit board is
accommodated in the remaining space. The battery 5 is a lithium battery which is a primary
battery with a large capacity. Furthermore, a plurality of terminal pins 61 are connected to the
circuit board. As shown in FIG. 2, a part of the terminal pin 61 is disposed inside the cylindrical
portion 62 continuously and integrally provided on the side wall of the housing 2, and the
cylindrical portion 62 and the terminal pin 61 form the connector 6.
[0033]
On the rear surface of the housing 2, a mount 7 for mounting the housing 2 to another member
using a mounting screw 8 is formed. The mounting base 7 is provided with a mounting groove
71 opened upward and backward, and the mounting groove 71 is formed in the lower part in the
shape of a dovetail whose front left width is wider than the rear left width. That is, the wide
portion 711 is formed at the front of the mounting groove 71 and the narrow portion 712 is
formed at the rear. The lateral width of the narrow portion 712 is formed about the diameter of
the leg of the mounting screw 8, and the lateral width of the wide portion 711 is formed about
the width of the head of the mounting screw 8. Further, the front-rear width of the wide portion
711 is formed to be about the thickness dimension of the head of the mounting screw 8.
Therefore, by inserting the head of the mounting screw 8 into the wide portion 711, the
mounting screw 8 is coupled to the housing 2. A square-head screw is used as the mounting
screw 8.
[0034]
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Reference Signs List 2 housing 3 speaker unit 32 diaphragm 211 cavity 231 sound hole
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11
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