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JP2006165923

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2006165923
An object of the present invention is to provide a piezoelectric ultrasonic transducer capable of
emitting ultrasonic waves with narrow directivity and high sound pressure while keeping the
structure simple and maintaining its thinness. In a piezoelectric ultrasonic transducer having thin
film electrodes formed on both main surfaces and having a piezoelectric element polarized in the
thickness direction disposed on one side of a diaphragm, the vibration field on the vibration field
side of the diaphragm Adopting the configuration with a concave cross section shape and using a
concave configuration like the conventional configuration, without using a resonator as in the
conventional configuration, while maintaining narrow directivity characteristics, higher sound
pressure can be achieved toward the sound emitting side of the piezoelectric ultrasonic
transducer. It enabled it to emit ultrasonic waves. [Selected figure] Figure 1
Piezoelectric ultrasonic transducer
[0001]
The present invention relates to a piezoelectric ultrasonic transducer in which a plate-like
piezoelectric element having electrodes formed on both principal surfaces is attached to one side
of a diaphragm, and more specifically, narrow directivity characteristics of ultrasonic radiation.
The present invention relates to a piezoelectric ultrasonic transducer in which the structure of a
diaphragm is improved for the purpose of improving sound pressure.
[0002]
In recent years, technological progress in the field of ultrasound has been remarkable, and with
this trend, demands for high performance and miniaturization and thinning of the ultrasound
transducer itself are increasing more and more.
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[0003]
Hereinafter, the conventional piezoelectric ultrasonic transducer 24 will be described using the
cross-sectional view of FIG. 4 (see, for example, Patent Document 1).
The piezoelectric element 1d is formed by forming thin film electrodes on both main surfaces of
a plate having a piezoelectric effect, and generates a mechanical stress by applying a voltage
signal to both electrodes.
Although the main driving portion of the drip-proof ultrasonic transducer is described as an
example in this drawing, the basic structure and operation principle of the piezoelectric
ultrasonic transducer are the drip-proof ultrasonic transducer. There is no change without
limitation.
[0004]
The piezoelectric element 1d is bonded to a diaphragm 3d which is a part of a conductive
housing 2d, and the thin film electrode formed on the bonding surface side includes the
diaphragm 3d, the housing 2d, and the bonding electrode 4d. It is conducted to the wiring 5d. In
addition, the thin film electrode formed facing the bonding surface of the piezoelectric element
1d is conducted to the wiring 7d through the bonding electrode 6d. When an electrical AC signal
in the ultrasonic region is applied to the electrodes on both main surfaces of the piezoelectric
element 1d through the two wires 5d and 7d, as described above, the piezoelectric film is
piezoelectric at the same frequency as the applied electrical AC signal due to mechanical stress.
Stretching movement occurs in the longitudinal direction of the element 1d.
[0005]
Here, since the diaphragm 3d has no piezoelectric effect and no mechanical stress is generated,
the piezoelectric element 1d and the diaphragm 3d are integrated to induce bending vibration in
the vertical direction. Then, when the diaphragm 3d is bent and fixed while being fixed by the
peripheral support, the electric AC applied from the surface (hereinafter referred to as a radiation
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surface) opposite to the end face to which the piezoelectric element 1d of the diaphragm 3d is
bonded. Ultrasonic waves of the same frequency as the signal are emitted.
[0006]
However, in the conventional piezoelectric ultrasonic transducer 24 as shown in FIG. 4, since the
radiation surface of the diaphragm 3d is a flat surface, the ultrasonic waves generated by the
bending vibration are easily diffused radially, and the radiation It becomes difficult to maintain
the convergence to the front in the direction of the axis 9d. Therefore, it is not suitable for the
application which requires the narrow directivity characteristic of an ultrasonic wave.
Furthermore, the sound pressure of the ultrasonic wave to the front in the direction of the
radiation axis 9d becomes low as the convergence to the front in the direction of the radiation
axis 9d is low as described above.
[0007]
Then, the piezoelectric ultrasonic transducer 25 of a structure as shown in FIG. 5 is known as one
means of solving such a problem and improving a narrow directivity characteristic and a high
sound pressure. This piezoelectric ultrasonic transducer 25 is a piezoelectric ultrasonic
transducer 24 shown in FIG. 4 in that a light and small resonator 16 having a mortar shape is
mounted on the central portion of the radiation surface of the diaphragm 3e. However, the other
basic structure and drive principle are completely the same.
[0008]
In this configuration, when the flexural vibration as described above is induced to the diaphragm
3e, the vibration amplitude becomes largest at the central part of the radiation surface of the
diaphragm 3e, but the resonator 16 mounted at the central part of the radiation surface Is so
light and compact that this vibrational amplitude can not be suppressed. Therefore, the mounted
resonator 16 also vibrates up and down with an amplitude substantially equal to the vibration at
the central portion of the radiation surface of the diaphragm 3e, and not only the diaphragm 3e
but also the resonator 16 itself is It has an action of emitting a sound wave.
[0009]
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As a result, compared with the case where the resonator 16 is not provided, not only the
ultrasonic wave can be emitted with a wider vibration area, but also the ultrasonic wave of larger
sound pressure from the portion of the resonator 16 with a large vibration amplitude. It will be
able to radiate. Furthermore, since the resonator 16 has a mortar shape, it is possible to enhance
the convergence of ultrasonic vibration in the direction of the radiation axis 9e. Therefore, it is
possible to improve the narrow directivity which is important as an ultrasonic transducer and the
sound pressure to the front of the radiation axis 9e.
[0010]
JP-A-2000-241532 (page 3, FIG. 1)
[0011]
However, since the piezoelectric ultrasonic transducer 25 provided with the resonator 16 as
shown in FIG. 5 requires extra thickness for the resonator 16, the thickness reduction as the
ultrasonic transducer is pursued. Their presence is a particularly big challenge when
[0012]
Furthermore, the resonator 16 used in the piezoelectric ultrasonic transducer 25 needs to be
made of a light and thin member as much as possible, and the bonding area with the radiation
surface of the diaphragm 3e has a minimum area. It is difficult to maintain the structural
strength of the ultrasonic transducer because it is necessary to
[0013]
In addition to this, by providing the resonator 16, it becomes easy to induce split vibration
accompanying the complication of the shape of the vibrating portion, and there is also a
possibility of having a plurality of unexpected and unnecessary resonance points.
If there are a plurality of resonance points associated with such divided vibration, vibration such
as reduction of vibration amplitude or instability of vibration mode in the vicinity of the
resonance point (that is, the frequency to be driven) originally required by the piezoelectric
ultrasonic transducer. It becomes a factor to inhibit the characteristics, and it becomes difficult to
maintain good sound pressure frequency characteristics.
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[0014]
In order to achieve the above object, the piezoelectric ultrasonic transducer of the present
invention adopts the following configuration.
[0015]
The piezoelectric ultrasonic transducer according to the present invention is a piezoelectric
ultrasonic transducer in which thin film electrodes are formed on both main surfaces and a
piezoelectric element polarized in the thickness direction is disposed on one side of the
diaphragm. The cross-sectional shape on the side of the sound field vibration in the radial
direction is a bowl-shaped concave shape.
[0016]
Further, a piezoelectric ultrasonic transducer according to the present invention is characterized
in that the diaphragm is provided with a plurality of the above-mentioned concave shapes.
[0017]
Furthermore, the piezoelectric ultrasonic transducer according to the present invention is
characterized in that the bottom of the concave shape described above is shifted from the center
position of the rim of the concave shape.
[0018]
Furthermore, in the piezoelectric ultrasonic transducer according to the present invention, in the
plurality of concave shapes in which the axis connecting the bottom of the concave shape
described above and the center position of the rim of the concave shape is provided in the
diaphragm, It is characterized in that it is set in different directions.
[0019]
In the piezoelectric ultrasonic transducer according to the present invention, the cross-sectional
shape of the vibration radiation direction of the diaphragm is a bowl-shaped concave shape, and
the bottom of the concave shape and the center position of the rim of the concave shape vibrate
The arrangement on the vertical axis of the plate eliminates the need for mounting a resonator
for emitting ultrasonic waves from the radiation surface with a wider vibration area as in the
ultrasonic vibrator of the conventional configuration. Thus, it is possible to emit an ultrasonic
wave of higher sound pressure to the sound emitting side of the piezoelectric ultrasonic
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transducer while maintaining the narrow directivity characteristic.
[0020]
Therefore, it becomes possible to realize thinning as an ultrasonic transducer by a simple
member configuration consisting only of the diaphragm and the piezoelectric element without
mounting the above-described resonator.
[0021]
In addition, by not mounting the above-described resonator, it is possible to eliminate the
structural weakness that has been a problem in the conventional configuration.
[0022]
Furthermore, with the configuration in which the resonator is removed from the ultrasonic
transducer, the shape of the vibrating portion is simplified, and unnecessary resonance points
associated with the divided vibration can be eliminated.
From this, in the vicinity of the resonance point originally required by the piezoelectric ultrasonic
transducer, factors that inhibit the vibration characteristics such as a decrease in vibration
amplitude and destabilization of the vibration mode are removed, and good sound pressure
frequency characteristics are obtained. You will be able to maintain.
[0023]
In addition, a plurality of concave shapes are formed on the radiation surface of one diaphragm,
and for each of the concave shapes, the center position of the bottom of the concave shape and
the rim of the concave shape is on the vertical axis of the diaphragm. By adopting the shifted
configuration, it is possible to emit high sound pressure ultrasonic waves with narrow directivity
characteristics in a plurality of arbitrary directions by a set of drive mechanisms consisting of the
piezoelectric element and the diaphragm.
[0024]
First, an example of the configuration of the piezoelectric ultrasonic transducer in the first
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embodiment of the present invention and the operation thereof will be described.
FIG. 1 shows a configuration example of a piezoelectric ultrasonic transducer 21 according to the
present invention.
The same members in the configuration of the present invention will be described using the same
reference numerals as the background art.
[0025]
As shown in the sectional view of FIG. 1, the piezoelectric ultrasonic transducer 21 of the present
invention comprises a piezoelectric element 1a formed by forming thin film electrodes on both
main surfaces of a plate having a piezoelectric effect, and the piezoelectric element 1a.
Conducting and adhering to the diaphragm 3a which is a part of the conductive case 2a, the thin
film electrode formed on the bonding surface side of the piezoelectric element 1a is conducted to
the wiring 5a through the bonding electrode 4a, and piezoelectricity The thin film electrode
formed opposite to the adhesive surface of the element 1a is electrically connected to the wiring
7a through the adhesive electrode 6a as in the background art, but the piezoelectric ultrasonic
transducer 21 of the present invention is It is characterized in that the cross-sectional shape of
the radiation surface of the plate 3a is a bowl-shaped concave shape.
[0026]
Furthermore, an example is shown in which the bottom of this concave shape is made coincident
with the center position of the rim of the concave shape in the vertical axis direction of the
drawing.
[0027]
Next, the function and operation of the piezoelectric ultrasonic transducer according to the
present invention will be described.
When an electrical alternating current signal of ultrasonic frequency is applied to the
piezoelectric ultrasonic transducer 21, the piezoelectric element 1 a and the diaphragm 3 a are
integrated integrally in the vertical direction, as described in the background art. It is induced.
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[0028]
By this flexural vibration, an ultrasonic wave is generated from the radiation surface of the
diaphragm 3a. The concave shape of the radiation surface is a mortar shape, and the ultrasonic
waves generated from each part of the radiation surface are of the radiation surface. By radiating
in each normal direction, as shown by the arrow 8a, the ultrasonic waves radiated from the entire
radiation surface are all axes connecting the bottom of the concave and the center position at the
rim of the concave. That is, the light is propagated in the direction of focusing on the radiation
axis 9a corresponding to the vertical axis described above.
[0029]
Therefore, as compared with the background art in which the radiation surface is a plane, it is
possible to reduce the diffusion effect of the emitted ultrasonic waves, and as a result, an
ultrasonic transducer with a narrow directivity characteristic is realized. be able to.
In addition, by making the bottom of the concave shape of the radiation surface coincide with the
center position of the rim of the concave shape in the vertical axis direction of the drawing, the
structure of the whole radiation surface is the bottom of the concave shape and the concave
Axisymmetric with respect to a radiation axis 9a connecting the center position of the rim of the
shape.
Therefore, the amplification action generated by superposing ultrasonic waves generated from
each part of the radiation surface becomes strong, and ultrasonic waves with very high sound
pressure can be generated.
[0030]
Therefore, in the piezoelectric ultrasonic transducer 21 according to the present invention, by
making the cross-sectional shape of the radiation surface of the diaphragm 3a into a concave
shape of a mortar shape, the focusing property of the ultrasonic radiation is enhanced. Narrow
directivity characteristics and high sound pressure can be realized without having to place the
child 16 on purpose.
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Therefore, it is possible not only to simplify the entire member configuration but also to
contribute significantly to the thinning of the ultrasonic transducer by not providing the
resonator 16.
[0031]
Further, the piezoelectric ultrasonic transducer 21 of the present invention can eliminate the
structural strength weakness that has been a problem in the conventional configuration by the
member configuration in which the resonator 16 is not mounted. .
[0032]
Not only that, in the piezoelectric ultrasonic transducer 21 of the present invention, it is possible
to substantially eliminate divisional vibration accompanying the complication of the shape of the
vibrating portion by providing the resonator 16 shown in FIG.
Therefore, it is possible to reduce the number of such unnecessary resonance points and
maintain the vibration characteristics such as the vibration amplitude and the stability of the
vibration mode in the vicinity of the resonance point originally required by the piezoelectric
ultrasonic transducer. Become.
That is, good sound pressure frequency characteristics as an ultrasonic transducer can be
realized.
[0033]
Next, another configuration example of the piezoelectric ultrasonic transducer in the second
embodiment of the present invention and the operation in the configuration example will be
described.
FIG. 2 shows a configuration example of a piezoelectric ultrasonic transducer 22 according to the
present invention.
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[0034]
The piezoelectric ultrasonic transducer 22 in FIG. 2 is replaced with the configuration example of
the piezoelectric ultrasonic transducer 21 shown in FIG. 1 above, and the bottom of the concave
shape and the center position of the rim of the concave shape are used. , And in a direction
perpendicular to the diaphragm 3b.
Other configurations are similar to those shown in the first embodiment.
[0035]
By adopting the above-mentioned configuration, not only the advantage of enabling ultrasonic
radiation with narrow directivity characteristics and high sound pressure but also the thinness of
the above-described members while maintaining the simple configuration, the bottommost
portion in the concave shape Piezoelectric ultrasonic vibration that allows arbitrary high
directivity sound radiation with narrow directivity characteristics in the direction of the radiation
axis 9b by arbitrarily setting the radiation axis 9b connecting with the center position of the rim
in concave and concave shape You will be able to provide children.
[0036]
In this manner, the center position of the concave bottom and the edge of the mouth are shifted
on the vertical axis of the diaphragm 3b, so that the direction of the radial axis 9b connecting the
center of the bottom of the concave and the edge of the rim Is offset from the vertical axis
direction of the diaphragm.
Therefore, the ultrasonic waves generated from the concave radiation surface are propagated so
as to be focused in the direction of the radiation axis 9b.
That is, in the piezoelectric ultrasonic transducer 22 of the present invention, the narrow
directivity characteristic of the emitted ultrasonic wave can be arbitrarily controlled in the
direction inclined from the vertical axis direction of the diaphragm 3b by a very simple structure.
become able to.
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[0037]
Next, a third embodiment of the present invention, an example of the configuration of a
transducer to which a plurality of piezoelectric ultrasonic transducers 22 shown in FIG. 2 are
applied, and the operation in the configuration example will be described.
[0038]
FIG. 3 is a perspective view showing still another structural example of the piezoelectric
ultrasonic transducer in the present invention, and a diaphragm 3c to which the piezoelectric
element 1c is attached, and a plurality of concave shapes on the radiation surface of the
diaphragm 3c. In this embodiment, in this embodiment, a piezoelectric type in which the concave
bottom 10 and the center position 11 at the concave edge of the concave are shifted on the
vertical axis of the diaphragm 3c. 7 shows an exemplary configuration of the ultrasonic
transducer 23.
[0039]
And the radiation axes 12-15 which connect the center position of the lowest part in each
concave shape and the mouth edge part become the form which turned mutually mutually
different direction.
In the present drawing, although the external shapes of the piezoelectric element 1c and the
diaphragm 3c are rectangular, what is the external shape of these as long as the flexural
vibration of the diaphragm and the piezoelectric element as described above can be induced. It
may be a combination of shapes.
[0040]
As described above, with the configuration in which the concave bottommost portion 10 and the
center position 11 of the mouth edge portion are shifted on the vertical axis of the diaphragm 3c,
as in the piezoelectric ultrasonic transducer 22 shown in FIG. The direction of the radiation axis
12 connecting the concave bottom portion 10 and the center position 11 of the rim portion is
offset from the vertical axis direction of the diaphragm.
Therefore, the ultrasonic waves generated from the concave radiation surface will be propagated
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so as to be focused in the direction of the radiation axis 12.
That is, in the piezoelectric ultrasonic transducer 23 of the present invention, the narrow
directivity characteristic of the emitted ultrasonic wave can be controlled in a direction inclined
from the vertical axis direction of the diaphragm by a very simple structure. Become.
[0041]
Further, as described above, by providing the diaphragm 3c with a plurality of concave shapes
and directing the directions different from each other, a plurality of driving mechanisms
consisting only of the diaphragm 3c and the piezoelectric element 1c can be used. Thus, it is
possible to emit an ultrasonic wave with good narrowing characteristics and high sound pressure
in any direction.
[0042]
For example, in the case of an application where it is necessary to emit a plurality of ultrasonic
waves in different directions, for example, conventionally, a plurality of ultrasonic transducers
are combined to constitute an apparatus, and the radiation angle is adjusted. In the present
invention, only one ultrasonic transducer is used, and this can be done without such a
complicated operation.
In addition to that, in the piezoelectric ultrasonic transducer 23 according to the present
invention, it is possible to avoid the upsizing of the device which has been caused by combining a
plurality of ultrasonic transducers as in the prior art. .
[0043]
In the description of the piezoelectric ultrasonic transducer 23 described above, a mode in which
a plurality of ultrasonic speakers emit narrow directional sound waves in different directions has
been described, but for example, from a pair of speakers, the same direction The sound pressure
may be emitted in different directions from the other speakers so that the sound pressure
emitted in each direction may be intentionally changed.
[0044]
The sound pressure emitted from each speaker may be changed by optionally changing the
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diameter or depth of the concave shape constituting each speaker.
[0045]
Furthermore, in the embodiment described above, a configuration example in which a plurality of
piezoelectric ultrasonic transducers 22 shown in FIG. 2 are incorporated is shown, but a plurality
of piezoelectric ultrasonic transducers 21 shown in FIG. The transducer may be configured in the
same configuration.
In that case, although it becomes impossible to apply to the application etc. which need to radiate
a plurality of ultrasonic waves in different directions, a plurality of piezoelectric ultrasonic
transducers 21 directed in the same direction can Sound waves can be emitted from the radiation
surface.
[0046]
It is sectional drawing which shows the structure of the piezoelectric ultrasonic transducer |
vibrator in this invention.
It is sectional drawing which shows the other structure of the piezoelectric ultrasonic transducer
in this invention.
It is a perspective view which shows the further another structure of the piezoelectric ultrasonic
transducer | vibrator in this invention.
It is sectional drawing which shows the example of a structure of the conventional piezoelectric
ultrasonic transducer. It is sectional drawing which shows the structural example of the other
conventional piezoelectric ultrasonic transducer.
Explanation of sign
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[0047]
1a to 1e Piezoelectric element 2a, 2b, 2d Housing 3a to 3e Diaphragm 4a, 4b, 4d, 4e, 6a, 6b, 6d,
6e Bonding electrode 5a, 5b, 5d, 5e, 7a, 7b, 7d Wiring 9a, 9b, 9d, 9e, 12-15 Radiation axis 21-25
Piezoelectric ultrasonic transducer
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