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DESCRIPTION JP2004040728

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DESCRIPTION JP2004040728
An object of the present invention is to apply a piezoelectric speaker device to a door mount
speaker for vehicle installation, and attach the speaker to the lower part of the door to make the
high-frequency directional characteristic favorable. Another object of the present invention is to
provide a speaker device that can meet the demand for a thin, lightweight vehicle audio device.
According to a first aspect of the present invention, a first diaphragm and a second diaphragm
coupled to each other, and the first diaphragm and the second diaphragm are respectively
attached to the first diaphragm and the second diaphragm. The first and second piezoelectric
elements are provided, and the vibration directions of the first and second diaphragms are not
parallel to each other. [Selected figure] Figure 2
Piezoelectric speaker device
[0001] The present invention relates to a piezoelectric speaker device using a piezoelectric
element. [0002] Conventionally, dynamic speakers and piezoelectric speakers are known as
speaker devices. For example, in a dynamic speaker, a drive coil fixed to a diaphragm having a
cone shape is disposed in the magnetic gap of the magnetic circuit, and the electromagnetic
driving force of the coil obtained by the DC magnetic field in the magnetic gap is used as
mechanical vibration to the diaphragm. By transmitting the vibration, the diaphragm can
acoustically convert this mechanical vibration to emit sound. On the other hand, a piezoelectric
speaker utilizes the piezoelectric effect of a piezoelectric substance such as Rochelle salt or
barium titanate. For example, Japanese Patent Laid-Open No. 2000-354297 discloses a cone
diaphragm at the center of the piezoelectric element. There is disclosed a speaker device in which
is fixed. Unlike a dynamic speaker device, a piezoelectric speaker does not require a magnetic
circuit, so that a lightweight speaker device can be obtained. As disclosed in the above-mentioned
publication, the piezoelectric speaker device has a performance particularly suitable as a tweeter
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(speaker for high sound). By the way, in a dynamic type speaker device for door mounting of an
on-vehicle audio device, since the dynamic type speaker device is attached to the lower part of
the door, the human being on which the sound of the high range is taken The sensitivity to highpitched voices to humans is lowered, and the problem is that the user can not enjoy realistic
voices. It is sufficient to move the dynamic speaker device attached to the lower part of the door
in the direction of the person who got on the vehicle, but there are problems with the structure
of the door, the space in the car, the cost and the like. Further, when the dynamic type speaker
device is attached to the upper part of the door, the directivity is improved, but there is a
problem that it is generally difficult to attach to the upper part of the door due to the structural
limitation of the door and the structural limitation of the vehicle. According to a first aspect of
the present invention, a first diaphragm and a second diaphragm coupled to each other, the first
diaphragm, and the first diaphragm are combined. A first piezoelectric element and a second
piezoelectric element respectively attached to the second diaphragm, and the vibration directions
of the first diaphragm and the second diaphragm are not parallel to each other It is characterized
by DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A first
embodiment of a piezoelectric speaker device according to the present invention will be
described below with reference to FIG.
FIG. 1 (a) is a cross-sectional view showing the piezoelectric speaker device of the first
embodiment, FIG. 1 (b) is a top view showing the diaphragm 2 of the first embodiment, and FIG.
1 (c) is a first FIG. 1D is a circuit diagram showing a network circuit used when driving the
piezoelectric speaker device of the first embodiment. As shown in FIG. 1A, in the piezoelectric
speaker device according to the first embodiment, a disc-shaped first piezoelectric element 100
and a disc having a smaller diameter than the first piezoelectric element 100 are used. -Shaped
second piezoelectric element 101, cone-shaped first diaphragm 1 attached to the center of first
piezoelectric element 100, and cone-shaped attached to the center of second piezoelectric
element 101 A second diaphragm 2 is provided. The first diaphragm 1 and the second
diaphragm 2 can be made of paper, a thin resin sheet or the like. Further, the diaphragms 1 and
2 are configured by integrally molding or by separately forming each diaphragm and bonding
them by bonding or the like. The first piezoelectric element 100 and the second piezoelectric
element 101 are piezoelectric elements having capacitive impedance utilizing the piezoelectric
effect of a piezoelectric substance such as Rochelle salt or barium titanate. A cone-shaped second
diaphragm 2 is attached to the central portion of the second piezoelectric element 101, and a
portion of the outer peripheral edge (the lower portion in FIG. 1A) is a predetermined portion of
the first diaphragm 1. It is combined with or formed integrally with the first diaphragm 1 at a
position close to the portion (the lower portion in FIG. 1A). The periphery of the first diaphragm
1 is attached to and fixed to the attachment member 3. In addition, since the first diaphragm 1 is
attached to the attachment member 3 via the flexible edge member 1a, in particular, the edge
member 1a is easily elastically deformed. Therefore, the vibration of the first diaphragm 1 is not
inhibited. FIG. 1 (b) is a top view of the diaphragm 2 as viewed from the direction of the alternate
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long and short dash line 4 of the second diaphragm 2 coupled or integrally formed with the
diaphragm 1. That is, it is a view seen from the axial direction perpendicular to the disc surface
of the second piezoelectric element 101 through the central portion of the second diaphragm 2,
and it can be seen that the second diaphragm 2 is circular. Further, FIG. 1C is a top view of the
first diaphragm 1 as viewed from the direction of the alternate long and short dash line 5. That
is, it is a view seen from the axial direction perpendicular to the disc surface of the first
piezoelectric element 100 through the central portion of the first diaphragm 1, and it can be seen
that the first diaphragm 1 is circular. Since the diaphragm 2 is viewed obliquely from the
direction of the alternate long and short dash line 5, the diaphragm 2 is drawn in an elliptical
shape in FIG. 1 (c).
The first piezoelectric element 100 and the second piezoelectric element 101 may be driven via
the network circuit shown in FIG. 1 (d). An audio signal is added to the electrode of the first
piezoelectric element 100 through a low pass filter in which an inductor L is connected in series.
For this reason, an audio signal of a low band is applied to the first piezoelectric element 100,
and an audio signal of the entire area is applied to the second piezoelectric element 101. Next,
the operation of the piezoelectric speaker device according to the first embodiment will be
described. When an audio signal is supplied to the first piezoelectric element 100 and the second
piezoelectric element 101, the central portion of the first piezoelectric element 100 supported by
the mounting member 3 is in the left-right direction in FIG. It deforms to vibrate in the direction
parallel to 5. Further, the second piezoelectric element 101 is deformed so as to vibrate in a
direction parallel to the dashed line 4. The first diaphragm 1 is driven by the amplitude of the
first piezoelectric element 100, and the first diaphragm 1 efficiently emits mainly low-pitched
sound. Further, the second diaphragm 2 is driven by the amplitude of the second piezoelectric
element 101, and the second diaphragm 2 efficiently emits mainly high-pitched voice in a
direction parallel to the dashed dotted line 4 Ru. That is, the attachment member 3 is attached to
the side door inner wall of the car itself or the side door inner wall of the car, so that the upper
left direction of the dashed dotted line 4 in FIG. It will be pointing in the direction. Therefore, the
high-pitched sound emitted from the second diaphragm 2 attached to the second piezoelectric
element 101 efficiently reaches the human ear. Since the directivity is narrow in the high tone
range, by configuring the vibrating surface of the speaker to face the head of a person sitting in a
car as in this embodiment, the high tone range can be efficiently heard, and therefore, it is better.
I can hear the voice. In addition, since the piezoelectric speaker is lighter than the conventional
dynamic speaker, it is suitable for an on-vehicle application where weight reduction is required.
In the first embodiment, the first piezoelectric element 100 is made to receive a bass region by
using a network circuit. In this circuit, a high pass filter (capacitor or the like) may be provided in
the network circuit in order to make the second piezoelectric element 101 more positively
receive the high-pitched area. As described above, if the piezoelectric speaker device of the
present embodiment is applied to a door mount speaker for vehicle installation, the high sound
area of the speaker can be attached to the lower portion of the door. It is emitted towards.
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In addition, since the piezoelectric speaker is thin and light, it is easy to attach it to a door, and
the speaker can meet the demand for weight reduction of an on-vehicle audio device. Second
Embodiment Hereinafter, a second embodiment of a piezoelectric speaker device according to the
present invention will be described with reference to FIG. FIG. 2 (a) is a cross-sectional view
showing the piezoelectric speaker device of the second embodiment, FIG. 2 (b) is a top view
showing the diaphragm 7 of the second embodiment, and FIG. 2 (c) is a second FIG. 2D is a
circuit diagram showing a network circuit used when driving the piezoelectric speaker device of
the second embodiment. As shown in FIG. 2A, in the piezoelectric speaker device of the second
embodiment, a disc-shaped first piezoelectric element 200 and a disc having a diameter smaller
than that of the first piezoelectric element 200 are used. , A first diaphragm 6 attached to the
central portion of the first piezoelectric element 200, and an edge member 6a provided on the
outer peripheral edge side of the first diaphragm 6 . The periphery of the outer periphery of the
edge member 6 a is attached to the attachment member 8. The mounting member 8 is
constituted by, for example, a door or other frame or casing of a car. The first diaphragm 6 is
disposed in the first direction in the direction (left direction in FIG. 2A) away from the surface of
the first piezoelectric element 200 to which the central portion of the first piezoelectric element
200 is attached. A cone portion 6b expanding from the central portion of the piezoelectric
element 200 and a direction formed by folding back from the outer peripheral edge of the cone
portion 6b and approaching the surface of the first piezoelectric element 200 (right direction in
FIG. 2A) , And the folding part 11 expanded from the outer periphery of the cone part 6b. The
first piezoelectric element 200 is attached to the central portion of the cone portion 6 b, that is,
the base end portion of the first diaphragm 6. In addition, a cone-shaped second diaphragm 7 is
attached to the central portion of the second piezoelectric element 201, and a part of the outer
peripheral edge (upper part in FIG. 2A) is a folded portion of the first diaphragm 1. It is combined
with or integrally formed with the first diaphragm 6 at a position close to a predetermined
portion (upper part in FIG. 1A) in FIG. The position of the center of gravity G of the whole of the
first piezoelectric element 200, the second piezoelectric element 201, the first diaphragm 6, the
second diaphragm 7 and the edge member 6a is in the direction of the dashed dotted line 10
(first Mounting in the axial direction perpendicular to the disc surface of the first piezoelectric
element 200 through the central portion of the diaphragm 6 of the first embodiment, so as to
substantially coincide with the surface 8 a of the mounting member 8 shown on the dashed line
12 Be
The first diaphragm 6 and the second diaphragm 7 can be made of paper, a thin resin sheet or
the like. In FIG. 2B, the diaphragm 7 bonded or integrally formed on the diaphragm 6 is directed
in the direction of the alternate long and short dash line 9 (the center of the second diaphragm 7
and the disc of the second piezoelectric element 201 It is a top view of the 2nd diaphragm 7 seen
from the axial direction perpendicular | vertical to a surface, and it turns out that it is circular.
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Further, FIG. 2C is a top view of the first diaphragm 6 as viewed from the direction of the
alternate long and short dash line 10, and it can be seen that the first diaphragm is also circular.
Since the diaphragm 7 is viewed obliquely from the direction of the alternate long and short dash
line 10, the diaphragm 7 is drawn in an elliptical shape in FIG. 2 (c). The first piezoelectric
element 200 and the second piezoelectric element 201 may be driven via the network circuit
shown in FIG. 2 (d). An audio signal is added to the electrode of the first piezoelectric element
200 through a low pass filter in which an inductor L is connected in series. For this reason, an
audio signal in the low band is mainly applied to the first piezoelectric element 200, and an audio
signal in the high band is mainly applied to the second piezoelectric element 201. Next, the
operation of the piezoelectric speaker device of the second embodiment will be described. When
an audio signal is supplied to the first piezoelectric element 200 and the second piezoelectric
element 201, the central portion of the first piezoelectric element 200 supported by the
mounting member 8 is in the left-right direction in FIG. It deforms to vibrate in the direction
parallel to 10. Further, the second piezoelectric element 201 is deformed so as to vibrate in a
direction substantially parallel to the dashed dotted line 7. The first diaphragm 6 is driven by the
amplitude of the first piezoelectric element 200, and the first diaphragm 1 efficiently emits
mainly low-pitched sound. Further, the second diaphragm 7 is driven by the amplitude of the
second piezoelectric element 201, and the second diaphragm 7 efficiently emits mainly highpitched sound in a direction substantially parallel to the dashed dotted line 9. Therefore, the
upper left direction of the alternate long and short dash line 9 in FIG. 2 (a) corresponds to the
head of a person riding a car by making the mounting member 8 the inner wall of the side door
of the car itself or attaching to the inner wall of the side door of the car. It will be pointing in the
direction. Therefore, the high-pitched sound emitted from the diaphragm 7 attached to the
second piezoelectric element 201 efficiently reaches the human ear. In the second embodiment,
the first diaphragm 6 includes the cone portion 6 b and the folding portion 11 that is folded back
from the cone portion 6 b and spreads in the direction opposite to the spreading direction of the
cone portion 6 b. The thickness can be reduced in the direction of.
In addition, since the center of gravity G is attached so as to substantially coincide with the
surface 8 a of the mounting member 8 in the direction of the alternate long and short dash line
10, the first and second diaphragms 6, 7 etc. It is not necessary to provide a separate suspension.
Therefore, the piezoelectric speaker device can be directly attached to the iron plate of the door
without using the attachment member 8, so that the installation space of the piezoelectric
speaker of the second embodiment can be reduced and the attachment can be easily performed.
Become. In addition, since the piezoelectric speaker is lighter than the conventional dynamic
speaker, it is suitable for an on-vehicle application where weight reduction is required.
Furthermore, as described above, since directivity is high in the high sound range, by configuring
the vibration surface of the speaker to face the head of a person sitting in a car as in this
embodiment, the high sound range can be efficiently heard. You will be able to hear better voices.
In the second embodiment, the first piezoelectric element 200 is made to receive the low band by
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using a network circuit. In this circuit, a high pass filter (capacitor or the like) may be provided in
the network circuit in order to make the second piezoelectric element 201 more positively
receive the high-pitched area. As described above, in the piezoelectric speaker device according
to the present embodiment, the first diaphragm 6 is constituted by the cone portion and the
folded portion formed by folding the first diaphragm 6, and the first piezoelectric element 200 is
formed at the central portion of the cone portion. Directly attached to the first diaphragm 6 with
a minimum number of members, since they are attached from the inner side of the first
diaphragm 6 to the base end portion of the first and second piezoelectric elements 200 and 201
and the second Since the diaphragm 7 can be stably supported, thinning, weight reduction and
cost reduction can be achieved. Third Embodiment Hereinafter, with reference to FIG. 3, a third
embodiment of a piezoelectric speaker device according to the present invention will be
described. FIG. 3 (a) is a cross-sectional view showing the piezoelectric speaker device of the
third embodiment, FIG. 3 (b) is a top view showing diaphragms 22a and 22b of the third
embodiment, and FIG. 3 (c) is a third 3 (d) is a circuit diagram showing a network circuit used
when driving the piezoelectric speaker device of the third embodiment. FIG. As shown in FIG. 3A,
in the piezoelectric speaker device according to the third embodiment, a disc-shaped first
piezoelectric element 300, a second piezoelectric element 301 on a disc, and The first diaphragm
22a, the first diaphragm 22b, the cone-shaped diaphragm 21a, the edge member 21b, and the
mounting member 23 are provided.
The first diaphragm 22a, the second diaphragm 22a, and the diaphragm 21a can be made of
paper, a thin resin sheet, or the like. The peripheral portion of the cone diaphragm 21 a is
attached to and fixed to the attachment member 23. In addition, since the diaphragm 21a is
attached to the attachment member 23 via the flexible edge member 21b, the edge member 21b
is particularly easily elastically deformed. Therefore, the vibration of the diaphragm 21a is not
inhibited. FIG. 3 (b) shows the first diaphragm 22a bonded or integrally formed on the cone
diaphragm 21a in the direction of the dashed dotted line 24a (the center of the first diaphragm
22a is passed through the first piezoelectric element The top view of the diaphragm 22a viewed
from the axial direction perpendicular to the disc surface of 300 and the direction of the dashed
dotted line 24b of the diaphragm 22b bonded to the diaphragm 21a (the central portion of the
second diaphragm 22b It is the top view of diaphragm 22b seen from the axial direction
perpendicular | vertical to the disc surface of the 2nd piezoelectric element 301). In this
embodiment, the diaphragms 22a and 22b have an elliptical shape. 3C shows the diaphragm
21a, the first and second diaphragms 22a, and the diaphragm as viewed from the direction of the
alternate long and short dash line 25 (the drive direction passing through the center of the cone
diaphragm 21a). It is a top view of 22b. As shown in the figure, the first and second diaphragms
22a and 22b are attached to the upper and lower positions of the cone diaphragm 21a. In
addition, since the diaphragm 22a and the diaphragm 22b are viewed obliquely from the
direction of the dashed dotted line 25, in FIG. 3 (c), the diaphragms 22a and 22b are flatter than
in FIG. 3 (b). It will be drawn in an oval shape. The first piezoelectric element 300 and the second
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piezoelectric element 301 are driven via the network circuit shown in FIG. 3 (d). An audio signal
is added to the electrode of the first piezoelectric element 300 via a low pass filter in which an
inductor L is connected in series. For this reason, an audio signal in the low band is mainly
applied to the first piezoelectric element 300, and an audio signal in the high band is mainly
applied to the second piezoelectric element 301. Next, the operation of the piezoelectric speaker
device according to the third embodiment will be described. When an audio signal is supplied to
the first piezoelectric element 300 and the second piezoelectric element 301, the central portion
of the first piezoelectric element 300 supported by the first diaphragm 22a is a dashed line 24a
in FIG. 3A. Deforms to vibrate in parallel with Further, the second piezoelectric element 301 is
deformed so as to vibrate in a direction parallel to the dashed dotted line 24b.
The second diaphragm 22b is driven by the amplitude of the second piezoelectric element 301,
and the second diaphragm 22b efficiently emits mainly high-pitched sound in a direction parallel
to the dashed dotted line 24b. That is, the mounting member 23 is mounted on the side door
inner wall of the car itself or the side door inner wall of the car, so that the upper left direction of
the dashed dotted line 24b in FIG. It will be pointing in the direction. Therefore, the high-pitched
sound emitted from the diaphragm 22b attached to the second piezoelectric element 301
efficiently reaches the human ear. Since high directivity is high in the high range, by configuring
the vibrating surface of the speaker to face the head of a person sitting in a car as in this
embodiment, the high range can be efficiently heard, and thus, it is better. You will be able to
hear the voice. On the other hand, the first diaphragm 22a is driven by the amplitude of the first
piezoelectric element 300, and the first diaphragm 22a efficiently emits mainly low-pitched
sound in a direction parallel to the dashed dotted line 24a. Ru. That is, the mounting member 23
is attached to the side door inner wall of the car itself or to the inner wall of the side door of the
car, thereby pointing to the leg of a person riding on the vehicle in the lower left direction of the
dashed dotted line 24a in FIG. It becomes a direction. The piezoelectric element 300 emits sound
exclusively for the low frequency range. The low-range sound is not highly directional, so it can
be heard well in the car even if it is directed downward. In addition, since the piezoelectric
speaker is lighter than the conventional dynamic speaker, it is suitable for an on-vehicle
application where weight reduction is required. In the third embodiment, the first piezoelectric
element 300 is made to receive the low band by using a network circuit. In this circuit, a high
pass filter (such as a capacitor) may be provided in the network circuit in order to allow the
second piezoelectric element 301 to more positively receive the high sound area. As described
above, if the piezoelectric speaker device of the present embodiment is applied to a door mount
speaker for vehicle installation, the high sound area of the speaker may be attached to the lower
part of the door. It is emitted towards. Moreover, since the piezoelectric speaker is thin and light,
it is easy to attach it to the door, and the speaker can meet the demand for weight reduction of
the on-vehicle audio device. -4th Embodiment-Hereinafter, 4th Embodiment of the piezoelectric
type speaker apparatus by this invention is described with reference to FIG.
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FIG. 4 (a) is a cross-sectional view showing the piezoelectric speaker device of the fourth
embodiment, FIG. 4 (b) is a top view showing the diaphragms 37 and 38 of the fourth
embodiment, and FIG. FIG. 4D is a top view showing the piezoelectric speaker device of the
fourth embodiment, and FIG. 4D is a circuit diagram showing a network circuit used when
driving the piezoelectric speaker device of the fourth embodiment. As shown in FIG. 4A, in the
piezoelectric speaker device according to the fourth embodiment, a disc-shaped first piezoelectric
element 401, a disc-shaped second piezoelectric element 400, and Of the first diaphragm 38 in
the form of a cone attached to the first piezoelectric element 401, the second diaphragm 37 in
the form of a cone attached to the second piezoelectric element 400, the diaphragm 36, and the
diaphragm 36. And an edge member 36a provided on the outer peripheral side. The periphery of
the outer periphery of the edge member 36 a is attached to the attachment member 39. The
mounting member 39 is constituted by, for example, a door or other frame or casing of a car.
Similarly to the second embodiment shown in FIG. 2, the cone-shaped diaphragm 36 includes a
cone portion 36 b and a folding portion 43 folded back from the cone portion 36 b and
spreading in the direction opposite to the spreading direction of the cone portion 36 b. The first
and second diaphragms 38 and 37 are bonded or integrally formed on the diaphragm 36. The
first and second diaphragms 38 and 37 and the diaphragm 36 can be made of paper, a thin resin
sheet or the like. FIG. 4B shows the second diaphragm 37 in the direction of the alternate long
and short dash line 41 (an axial direction perpendicular to the disc surface of the second
piezoelectric element 400 through the center of the second diaphragm 37). The top view of the
diaphragm 37 and the first diaphragm 38 in the direction of the alternate long and short dash
line 42 (axial direction perpendicular to the disc surface of the first piezoelectric element 401
through the center of the first diaphragm 38) It is the top view of the diaphragm 38 seen from
FIG. In this embodiment, the diaphragm 37 and the diaphragm 38 are elliptical. FIG. 4C is a top
view of the diaphragm 36 as viewed from the direction of the dashed dotted line 40 (the driving
direction passing through the central portion of the diaphragm 36). As shown in the figure, the
diaphragm 36 is circular, and the first and second diaphragms 38 and 37 are attached to the
upper and lower positions of the cone diaphragm 36. In addition, it is understood that the cone
portion 36 b and the folded portion 43 of the diaphragm 36 are circular. Since the diaphragm 37
and the diaphragm 38 are viewed obliquely from the direction of the alternate long and short
dash line 40, in FIG. 4C, the diaphragms 37 and 38 have a flatter oval shape than that in FIG. 4B.
It will be drawn. The first piezoelectric element 401 and the second piezoelectric element 400
may be driven via the network circuit shown in FIG. 4 (d).
An audio signal is added to the electrode of the first piezoelectric element 401 through a low
pass filter in which an inductor L is connected in series. For this reason, the audio signal of the
low band is mainly applied to the first piezoelectric element 401, and the audio signal of the low
band to the high band is mainly applied to the second piezoelectric element 400. Next, the
operation of the piezoelectric speaker device according to the fourth embodiment will be
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described. When an audio signal is supplied to the first piezoelectric element 401 and the second
piezoelectric element 400, the central part of the first piezoelectric element 401 is deformed so
as to vibrate in a direction substantially parallel to the dashed dotted line 42. Further, the second
piezoelectric element 400 is deformed so as to vibrate in a direction substantially parallel to the
dashed dotted line 41. The first diaphragm 38 is driven by the amplitude of the first piezoelectric
element 401, and when there is a low pass filter, the second diaphragm 38 efficiently emits
mainly low-pitched sound. Further, the first diaphragm 37 is driven by the amplitude of the
second piezoelectric element 400, and from the first diaphragm 37 sound from the low tone
range to the high tone range is emitted in a direction substantially parallel to the dashed dotted
line 41. That is, the mounting member 39 is mounted on the side door inner wall of the car itself
or the side door inner wall of the car, so that the upper left direction to which the dashed dotted
line 41 in FIG. Point in the direction of Therefore, high-pitched sound emitted from the
diaphragm 37 attached to the second piezoelectric element 400 efficiently reaches the human
ear. In the low frequency range, the vibration directions of the diaphragms 37 and 38 are vectorcombined and emitted in the direction parallel to the dashed dotted line 40. In the fourth
embodiment, the diaphragm 36 which is coupled to or integrally formed with the first and
second diaphragms 401 and 400 and supported by the mounting member 39 has a cone portion
36 b and a folded portion 43 formed by being folded therefrom. The thickness can be reduced in
the direction of the alternate long and short dash line 40 by making the configuration. For this
reason, when the attachment member 39 is directly attached to the iron plate of the car door, the
installation space of the piezoelectric speaker of the fourth embodiment is reduced, and the
attachment can be easily performed. In addition, since the piezoelectric speaker is lighter than
the conventional dynamic speaker, it is suitable for an on-vehicle application where weight
reduction is required. Furthermore, as described above, since the directivity is narrow in the high
sound range, by configuring the vibration surface of the speaker to face the head of a person
sitting in a car as in this embodiment, the high sound range can be efficiently heard. It became
possible to hear better voices.
In the fourth embodiment, the first piezoelectric element 400 is made to receive the low band by
using a network circuit. Further, in this embodiment, since the sound outputted by the two
piezoelectric elements is added and emitted by vector synthesis in the low frequency, a low band
signal of the same band may be added to the two piezoelectric elements. . As described above, in
the piezoelectric speaker device according to the present embodiment, the first diaphragm is
disposed on the inside of the cone-shaped diaphragm 36 using the cone portion 36 b and the
diaphragm 36 of the folded portion 43 folded back therefrom. And a second piezoelectric
element 400 attached to the second diaphragm 37. As a result, the first diaphragm 38 having the
first piezoelectric element 401 and the second diaphragm 37 having the second piezoelectric
element 400 can be stably stabilized directly on the diaphragm 36 with the minimum number of
members. Since it can be supported, thinning, weight reduction and cost reduction can be
achieved. In the first to fourth embodiments, two piezoelectric speakers are attached. However,
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three or more piezoelectric speakers can be attached. In this case, it is also possible to share and
receive three or more frequency bands for each piezoelectric speaker. As described above,
according to the embodiment of the present invention, it is possible to configure a thin and
lightweight speaker device. Also, desired directional characteristics can be obtained. BRIEF
DESCRIPTION OF THE DRAWINGS FIG. 1 shows a first embodiment of a piezoelectric speaker
device according to the present invention. (A) is a cross-sectional view showing the piezoelectric
speaker device of the first embodiment, (b) is a top view showing the diaphragm 2 of the first
embodiment, (c) is a piezoelectric speaker of the first embodiment FIG. 6 (d) is a circuit diagram
showing a network circuit used when driving the piezoelectric speaker device of the first
embodiment. FIG. 2 shows a second embodiment of a piezoelectric speaker device according to
the present invention. (A) is a cross-sectional view showing the piezoelectric speaker device of
the second embodiment, (b) is a top view showing the diaphragm 7 of the second embodiment,
(c) is a piezoelectric speaker of the second embodiment FIG. 8D is a circuit diagram showing a
network circuit used when driving the piezoelectric speaker device of the second embodiment.
FIG. 3 shows a third embodiment of a piezoelectric speaker device according to the present
invention. (A) is a cross-sectional view showing the piezoelectric speaker device of the third
embodiment, (b) is a top view showing the diaphragms 22a and 22b of the third embodiment, (c)
is a piezoelectric of the third embodiment. FIG. 6 (d) is a circuit diagram showing a network
circuit used to drive the piezoelectric speaker device of the third embodiment.
FIG. 4 shows a fourth embodiment of a piezoelectric speaker device according to the present
invention. (A) is a cross-sectional view showing the piezoelectric speaker device of the fourth
embodiment, (b) is a top view showing the diaphragms 37 and 38 of the fourth embodiment, (c)
is the piezoelectric of the fourth embodiment FIG. 7D is a circuit diagram showing a network
circuit used when driving the piezoelectric speaker device of the fourth embodiment. [Description
of the code] 100, 200, 300, 401: first piezoelectric element 101, 201, 301, 400: second
piezoelectric element 1, 6, 22a, 38: first diaphragm 2, 7, 22b, 37: second diaphragm 3, 8, 23, 39:
mounting member 1a, 6a, 21b, 36a ,: edge member L: inductor G: center of gravity
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