JP3079175B2 - Piezoelectric element and hydrophone using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric element having a cylindrical structure in which a flexible strip-shaped polymer piezoelectric substance is spirally wound around a certain central axis, and using the piezoelectric element.
In particular, the present invention relates to a flexible hydrophone excellent in applicability as a towable sonar.

[0002]

2. Description of the Related Art As an example of a cylindrical piezoelectric element, a towed sonar is known (Japanese Patent Application Laid-Open No. 55-76962).
No. 57-60992, JP-A-2-278178, etc.). This is a hydrophone linear array that is mainly arranged in a straight line at predetermined intervals in order to receive engine sound, screw sound, cavitation sound, etc. generated by a ship, and is adapted to the frequency band of the transmitted sound wave. In order to detect the target vessel by phasing the output phase of each receiver, this hydrophone linear array is usually towed by the vessel via a rope or the like on which electric wires are arranged. Take the form to do.

Conventionally, a ceramic piezoelectric element formed into a hollow cylinder, for example, a PZT piezoelectric element, has been used as a sound wave detecting element used in such a towed sonar.

When this kind of hollow cylindrical piezoelectric element is used as a sound wave transmitter, sound waves are radiated isotropically in the radial direction, that is, at the same sound pressure regardless of the frequency.
On the other hand, a receiver is one in which the receiving sensitivity does not change even when the element is rotated around the central axis in the longitudinal direction. In other words,
There is a characteristic that the transmission / reception sensitivity in the radial direction has no directivity.

On the other hand, in the field of ultrasonic processing, an electrostrictive element such as barium titanate magnet has been used in a cylindrical form to obtain a large displacement. Also, U.S. Pat.
No. 108 discloses a relay using a bimorph that is cut out from a hollow cylinder of a ceramic piezoelectric body and formed into a spiral shape.

[0006]

The conventional cylindrical ceramic piezoelectric element described above achieves an isotropic sensitivity characteristic regardless of the frequency of a sound wave as a sound wave transmitter / receiver, and a large displacement occurs in an electrostrictive element. Although it has the advantage that it can be obtained, it includes the following problems. (1) Although it is rigid, it is vulnerable to impact and is cumbersome to handle. For example, storage is not easy in a long element because of poor flexibility. (2) It is not easy to manufacture large-diameter and long products. (3) In a structure in which a large number of receivers are linearly arranged, as in the above-described hydrophone linear array, mechanical properties such as bending and strength and specific gravity are non-uniform due to the joints. It is liable to be damaged due to the impact caused by the motion of the flying vehicle transmitted through the rope, the bending stress caused by the water flow, etc., and the characteristics may be deteriorated.

Another problem is that the operability of unwinding or winding the hydrophone linear array together with the rope is extremely poor.

It is also conceivable to solve the above-mentioned problems of the hollow cylindrical ceramic piezoelectric element, particularly the problems caused by the rigidity of the ceramic, by using a polymer piezoelectric element having excellent flexibility. However, it is not easy to make a polymer piezoelectric body into a seamless cylindrical piezoelectric element due to the difficulty of forming electrodes on it, and even if it is a polymer piezoelectric body, it is flexible. Does not improve much. On the other hand, the conventional spiral element cut out from a ceramic hollow cylinder has the drawback that it is weak and fragile to impact, in addition to the fact that it is not easy to manufacture particularly large diameter and long ones, and in terms of flexibility Are several steps inferior to polymer piezoelectrics.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a piezoelectric element in which the above-mentioned problems of the conventional hollow cylindrical ceramic piezoelectric element have been improved, and a flexible hydrophone using the same.

[0010]

According to the study of the present inventors, a flexible band-shaped piezoelectric element is spirally wound to have a substantially cylindrical shape to maintain isotropy of sensitivity. However, it has been found that a remarkable improvement on the above-mentioned problems of the hollow cylindrical ceramic piezoelectric element can be obtained.

That is, according to the present invention, a flexible strip-shaped polymer piezoelectric material provided with an electrode layer facing the surface is spirally wound around a certain central axis, and the surface electrode layer is extended from the central axis. An object of the present invention is to provide a piezoelectric element having a self-supporting helical structure disposed substantially parallel to a direction.

Further, according to the present invention, a band-shaped piezoelectric element obtained by laminating a pair of band-shaped polymer piezoelectric bodies with a center electrode layer interposed therebetween so that the polarization directions thereof are opposite to each other is spirally wound and arranged. Another object of the present invention is to provide a hydrophone having a self-supporting helical structure and a structure capable of extracting an electric output generated between a surface electrode formed on both surfaces of the band-shaped piezoelectric element and the central electrode layer. Where polymer piezoelectric
Or with regard to the piezoelectric element, "self-supporting helical structure"
As is clear from the examples described later, the product piezoelectric element
Or in a hydrophone
A spiral wound support inside the body or piezoelectric element
A spiral-shaped structure, which is maintained without.

[0013]

As described above, the piezoelectric element of the present invention is formed into a substantially cylindrical shape by winding the strip-shaped piezoelectric element, and thus has not only good isotropic sensitivity characteristics but also the above-mentioned hollow shape. Significant improvements are obtained over the lack of flexibility and impact resistance, which were the main problems with cylindrical ceramic piezoelectric elements.

In the piezoelectric body constituting the polymer piezoelectric element, deformations associated with output include expansion and contraction in the plane direction (biaxial), thickness change (uniaxial), and volume compression / expansion change. Among them, it is generated by mechanical stress applied to a towed sonar or the like, and the source of noise is expansion and contraction in the plane direction. In the hydrophone of the present invention, noise due to such expansion and contraction in the plane direction is generated. Is effectively canceled out by using a band-shaped piezoelectric element obtained by laminating a pair of polymer piezoelectric bodies via a central electrode layer so that the polarization directions of the polymer piezoelectric bodies are opposite to each other, and does not substantially cause harmful noise. On the other hand, by adopting a cylindrical structure in which such a band-shaped piezoelectric element is spirally wound and arranged, the overall flexibility is not impaired, and the sound pressure of the sound wave from the object to be measured is reduced by that of the polymer piezoelectric material. It is effectively detected as a deformation in the thickness direction or a change in volumetric compression / expansion.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the piezoelectric element and hydrophone of the present invention will be described below with reference to the drawings.
This will be described in more detail.

FIG. 1 is a partially cutaway front view of a spiral piezoelectric element according to an embodiment of the present invention, which is configured as a receiver (hydrophone) of a towed sonar, and FIG. 2 is a cross-sectional view in a thickness direction of the piezoelectric element taken along a cutout plane II-II.

Referring to FIG. 1 and FIG. 2, a band-shaped piezoelectric element 10 constituting this spiral piezoelectric element is formed by forming surface electrodes 2a and 2b on both sides of a band-shaped piezoelectric body 1 having flexibility. The spiral piezoelectric element according to the present invention has a shape in which the strip-shaped piezoelectric element 10 is spirally wound around a certain central axis O. Lead wires 8a and 8b were connected to the surface electrodes 2a and 2b by soldering 7, respectively, and an electric output generated between the surface electrodes was provided at the right end of the spiral piezoelectric element when receiving a sound wave. Terminals A and B so that they can be extracted between terminals AB, and when transmitting sound waves, etc.
From the piezoelectric body 1.

The width (d) and the helical pitch (p) of the band-shaped piezoelectric element 10 are appropriately selected according to the characteristics required for the piezoelectric element, but are generally about 2 to 50 mm, preferably 5 to 20 mm. <P / d ≦ 3 is preferable. If the width is less than 2 mm, cutting tends to occur at the time of spiral winding, and if it exceeds 50 mm, it becomes difficult to form a spiral shape. When p / d ≦ 1, the band-shaped piezoelectric elements 10 may partially overlap, or electrical noise may be generated due to contact between the surface electrodes 2a or between the surface electrodes 2a-2b. On the other hand, if p / d> 3, the area efficiency of the element is reduced. The number of turns of the spiral constituting the spiral piezoelectric element is preferably one or more, particularly three or more, so as to secure the above-mentioned isotropic sensitivity characteristics.

To explain the material of each part, the flexible piezoelectric element 1 of the present invention is a polymer piezoelectric element in order to provide good flexibility as a whole spiral piezoelectric element or to form a long spiral piezoelectric element. Consist of body. Such a polymer piezoelectric body 1 can be easily formed into a spiral shape as shown in FIG. 1 by winding it after forming a strip having surface electrodes 2a and 2b.

The polymer piezoelectric body 1 is arbitrarily made of a generally known polymer piezoelectric material, but is composed of a vinylidene fluoride (VDF) homopolymer or a VD made of a copolymer or the like.
An F-based piezoelectric material or a vinylidene cyanide-vinyl acetate copolymer having relatively high heat resistance is preferably used. These polymer piezoelectric materials are formed into a film by melt extrusion or the like, and then subjected to uniaxial stretching or heat treatment at a softening temperature or lower, and polarization treatment by application of an electric field at a softening temperature or lower, as necessary. In addition, the polymer piezoelectric body 1 can generally take the form of a film or a sheet, and the thickness thereof is 20 to 2.
It is preferable that the size be selected in the range of about 000 μm, particularly 100 to 1000 μm. The thickness of the polymer piezoelectric body is 20
If it is less than μm, sufficient receiving sensitivity cannot be obtained.
Above μm, the flexibility of the film is impaired, and furthermore, a high voltage is required for polarization, so that an edge discharge is generated and polarization becomes extremely difficult.

The surface electrodes 2a and 2b are provided on the surface of the piezoelectric body 1 without deteriorating the flexibility of the entire spiral piezoelectric element.
It can be formed in a thickness range of 0.02 μm to 200 μm by vapor deposition, thermal spraying, plating (especially electroless plating) of a conductive material such as copper, aluminum, zinc, or the like, or bonding and attaching a metal foil. In particular, in combination with a polymer piezoelectric body, in order to provide good solderability and excellent transmission / reception sensitivity while maintaining good flexibility, the counter electrodes 2a and 2b are:
It is preferable to form a sprayed electrode layer having a thickness of 10 to 100 μm, particularly 20 to 50 μm.

The electrodes 2a, 2b of the spiral piezoelectric element of the present invention
It is preferable to apply an insulating coating to the surface of the substrate. As shown in FIG. 3 corresponding to FIG.
b can be formed as insulating coating layers 5a and 5b that selectively cover the spiral piezoelectric element. More preferably, the entire spiral piezoelectric element is embedded in an insulator 11 and solid (or hollow) as shown in FIG. It is preferable that the element is formed in a cylindrical shape to improve the robustness and handleability of the element. Such an insulating covering 5
a, 5b or 11 is plastic, ceramic,
It can be selected from an elastomer or the like according to the use situation. Above all, for the insulator 11, it is preferable to use an elastomer such as urethane rubber, silicone rubber, or butyl rubber in order to maintain the flexibility of the entire spiral piezoelectric element in addition to the robustness.

The external shape of the buried covering 11 is a cylinder (cylinder).
The shape is not limited to this, and other shapes may be used as long as the sensitivity does not have directivity. For example, the buried covering may be formed into an elliptic cylinder (cylindrical) shape to give a direction to bending stress. . In addition, at the center of the buried covering, other than electric wires, if necessary, electric parts such as a preamplifier, a strength member, a filler, or the like may be buried, or a cavity may be formed and disposed. it can.

The surface electrodes 2a and 2b need not be provided over the entire surface of the long strip-shaped piezoelectric body 1. For example, as shown in FIG. 4 corresponding to FIG. 1, the surface electrodes 2a (and 2b—not shown) are provided apart from each other along the length direction of the strip-shaped piezoelectric body 1, and the piezoelectric body is provided in an intermediate blank portion. 1 may be configured to be exposed. As a result, functionally, two spiral piezoelectric elements 10a and 10b are formed for each region where the surface electrode 2a (2b) exists. Of these elements 10a and 10b, the front and back electrodes 2a and 2b of 10a are connected to terminals A1 and B1 via lead wires 81a and 81b connected by solder 7, respectively. It is taken out between terminals A1 and B1. On the other hand, the front and back electrodes 2a, 2
b is connected to terminals A2 and B2 via lead wires 82a and 82b, respectively, which are soldered, and a lead generated in the element 10b is taken out between the terminals A2 and B2. Lead wire 8
It is preferable to pass 1, 82 through a portion near the center axis of the spiral piezoelectric element (inside the spiral) as shown in the figure. The hydrophone having such a configuration is not limited to two, but is a hydrophone linear array in which a larger number of unit elements are functionally independent and are linearly connected in terms of structure. Conformity is ensured. In addition, since these connecting elements are integrally formed, bending,
It has the feature that mechanical properties such as strength and specific gravity are uniform, and has the advantage of being functionally equivalent to one element in terms of structural handling. Since the piezoelectric elements are functionally independent of each other, the connecting elements can transmit and receive at different frequencies, and one can be used as a transmitter and the other as a receiver.

Next, another preferred embodiment of the present invention will be described.

FIG. 5 is a partially cutaway front view of one embodiment of the hydrophone of the present invention, and FIG. 6 is a cutaway surface V of FIG.
FIG. 6 is a schematic cross-sectional view in the thickness direction of the piezoelectric element taken along I-VI. In these drawings, parts similar to those shown in FIGS. 1 to 4 are denoted by the same reference numerals.

Referring to FIGS. 5 and 6, a strip-shaped piezoelectric element 50 constituting this hydrophone has a pair of strip-shaped polymer piezoelectric bodies 1a and 1b arranged such that their polarization directions p are opposite to each other. It is attached to the central electrode layer 3 via the adhesive layers 4a and 4b. In addition, these polymer piezoelectric bodies 1a and 1b have surface electrodes 2a and 2b on the surface opposite to the central electrode layer 3, respectively.

In the hydrophone of the present invention, such a band-shaped piezoelectric element 50 is spirally wound around a central axis O as shown in FIG.
And the outputs (output terminals A and C) from 2b and 2b are short-circuited,
A voltage output between the output from the center electrode layer 3 (output terminal B) and the output from the center electrode layer 3 can be taken out by the detection means 5.

In order to prevent noise due to the above-described expansion and contraction stress in the plane direction and to ensure good detection characteristics of sound waves and excellent flexibility as a whole, the band-shaped piezoelectric element is
The central electrode layer 3 located at the center has a neutral axis and the stress deformation is vertically symmetrical. For example, the central electrode layer 3 is a metal foil electrode that governs the rigidity of the entire band-shaped piezoelectric element. It is preferable to form the surface electrodes 2a and 2b with a flexible vapor deposition electrode or, particularly, a metal spray electrode.

In the second embodiment, the central electrode layer 3
Has a higher rigidity as compared with the polymer piezoelectric bodies 1a and 1b and the surface electrodes 2a and 2b as described above, for example, copper,
Aluminum, tin, zinc, gold, silver, platinum, etc. thickness is 6 ~
It is preferably formed of a metal foil of about 200 μm, particularly 20 to 120 μm. However, as described above, a layer configuration in which the center electrode layer 3 serves as a neutral point and the upper and lower polymer piezoelectric materials are deformed symmetrically with respect to bending stress is preferably adopted. A material other than the above metal foil is also used.

The adhesive layers 4a and 4b can be formed by a conductive adhesive in which conductive particles are dispersed.
Even when a layer having a thickness of about 5 to 40 μm is formed by using an adhesive such as an epoxy resin, a urethane resin, a polyester resin, a butadiene resin, or an acrylic resin having higher adhesive strength, the output characteristics can be maintained satisfactorily.

In the present embodiment, the surface electrodes 2a and 2b of the piezoelectric element 50 are sprayed electrodes of silver, copper, aluminum, zinc or the like having a thickness of 10 to 100 μm, preferably 20 to 50 μm, or 0.02 to 0.1 μm. It is preferable to form a vapor deposition electrode of about 1 μm and maintain good flexibility. With this configuration, even when a metal foil electrode having relatively high rigidity is used as the center electrode layer 3, good flexibility is maintained as a whole of the belt-shaped piezoelectric element 50, and a spiral winding as shown in FIG. The structure becomes possible. Then, in combination with the spirally wound structure shown in FIG. 5, a cylindrical piezoelectric element 50 having good flexibility as a whole is obtained. This element has no significant difference in flexibility in the radial direction, and is excellent in operability during deployment and storage of the sonar.

Also in the case of using a laminated polymer piezoelectric material as in this embodiment, the surface electrodes 2a and 2b do not need to be provided over the entire surface of the long strip-shaped piezoelectric element 50, and are not shown in FIG. As described above, the piezoelectric elements 50 may be formed discontinuously with electrode blanks at predetermined intervals in the length direction. A hydrophone formed by spirally winding such a band-shaped piezoelectric element 50 is a hydrophone linear array in which a large number of element units shown in FIG. 5 are linearly connected, and compared with a conventional hydrophone array. Since they are integrally formed, they have a characteristic that mechanical properties such as bending, elongation, and strength and specific gravity are uniform. Thus, for example, it has excellent durability against tensile impact.

In the hydrophone of the present invention, the band-shaped piezoelectric element 50 as described above is also used for the embodiment of FIGS. It is also conceivable to adopt a configuration in which the outer surface of the body is wound in a spiral shape around a body rod or cylinder and an insulating coating is applied to the outer surface
You. However, in order to prevent the residual stress applied to the band-shaped piezoelectric element and to improve the measurement sensitivity, for example, once, the band-shaped piezoelectric element is wound around a rigid or elastic rod-shaped body and spirally shaped, The rod-shaped body is removed, and the spirally shaped band-shaped piezoelectric element 50 is embedded in the elastomer covering 11 made of urethane rubber, silicon rubber, butyl rubber, or the like .
A self-supporting spiral-shaped structure, which keeps the spiral shape without the body
It is said. Thus, a cylindrical rod-shaped hydrophone having good flexibility as a whole and good wave receiving sensitivity as shown in FIG. 5 is obtained.

On the other hand, the outer shape of the cover 11 is preferably cylindrical, but may be another shape. For example, the cover 11 may be formed into an elliptical column to give directionality to bending stress. It is possible. In the center of the cover 11, electric wires such as a signal line and a power supply line, electric components such as a depth gauge and a compass, a strength member, and a filler are buried, or a cavity is formed and arranged. You can also.

The band-shaped piezoelectric element 50 generally has a width of 2 to 50.
mm, preferably 5 to 20 mm, and has a desired length by being wound, for example, with a spacing of 1 to 20 mm (preferably spacing / width ≦ 1), a winding number of 1 or more, and a winding diameter of 8 to 50 mm. A hydrophone is obtained.

The individual hydrophone elements thus obtained are sequentially connected at intervals changed so as to be suitable for sound waves in a desired wavelength range, whereby a hydrophone suitable for use as a towable sonar is provided. An array is obtained.

In the above, the piezoelectric body 1 has a single layer or
Although the case of the layers has been exemplified, the piezoelectric body 1 may have a structure in which a larger number of piezoelectric bodies are stacked, and in this case, an intermediate electrode layer may be interposed between the piezoelectric layers.

In the above description, the spiral piezoelectric element of the present invention has been described mainly with respect to a receiver of a towing type sonar which is a preferred embodiment thereof. However, the spiral piezoelectric element using the band-shaped piezoelectric element 10 of the present invention is not limited to this, and may be used as a probe of an ultrasonic flaw detector or an ultrasonic thickness gauge for a cylindrical inspection object such as a pipe, or It can also be used as an oscillation (signal) element such as a probe of a sonic cleaner. At this time, the lead wires (signal lines) 8a, 8b, 8c,
81a, 81b, 82a, 82b and the like are used as power supply lines.

When the spiral piezoelectric element of the present invention is used as a probe for inspecting a cylindrical object to be inspected,
In order to maintain good acoustic contact between the test object and the piezoelectric element, it is preferable to seal the periphery of the element with a flexible tube or balloon and provide a means for sucking and discharging liquid inside the element. .

[0041]

EXAMPLE 1 A hydrophone was manufactured according to the embodiment shown in FIGS.

First, a copolymer of vinylidene fluoride (VDF) / trifluoroethylene (TrFE) having a molar ratio of 75/25 (number average molecular weight = 1.75 × 10 ⁵ , manufactured by Kureha Chemical Industry Co., Ltd.) was diced. Extrude the sheet at a temperature of 265 ° C.
After heat treatment at 25 ° C. for 13 hours, under an electric field of 75 MV / m,
A polarization treatment was performed for a total of 1 hour including a holding time of 5 minutes at 123 ° C. and a rising / falling time to obtain a polymer piezoelectric film having a thickness of 500 μm. After surface treatment, an electric wire spraying machine (DK metal spraying machine E, manufactured by Kato Metallicon Co., Ltd.)
Spraying under the condition of air pressure of 5 kg / cm ² and voltage of 15 V using a zinc spray electrode 2 having a thickness of about 40 μm.
a and 2b were formed.

Next, the piezoelectric element having the laminated structure shown in FIG.
D) The slit-shaped piezoelectric element 10 was obtained by slitting.

This band-shaped piezoelectric element 10 is wound around a brass rod having a diameter of 7 mmφ, and is wound and fixed with tape.
After the heat treatment at 1 ° C. for 1 hour, the resultant was gradually cooled to room temperature, and the band-shaped piezoelectric element was helically shaped and the brass bar was removed. As the brass rod used in the hammering step, a brass rod smaller in diameter than the brass rod used in the next shaping step is preferably used.

Subsequently, a shaping tool in which plate-shaped screw blades were spirally attached at a pitch of 15 mm to a brass rod having a diameter of 10 mm was prepared. 5 mm), and left at room temperature for 10 minutes or more to mold. Thus, a shaped spiral piezoelectric element having a length of 120 mm was obtained, and then the shaping tool was withdrawn except for about half of the element, and was axially aligned with a jig in a Teflon mold frame having a diameter of 20 mm. After insertion, fully degassed polyurethane resin (“TYPE3318 / 2” manufactured by Zeon Corporation)
023 / DOA = 50/40/10 ”(weight ratio) was poured into about half of the mold frame, and after heating and curing at 60 ° C. for 6 hours, the jig, mold frame and shaping tool were removed.
Then, lead wires 8a and 8b connected to terminals A and B are joined to one end of the spiral piezoelectric element by solder 7, returned to the mold frame again, and the remaining uncoated portion is cast with the above polyurethane resin. By curing, a hydrophone (about 135 mm in length) was obtained in which the band-shaped piezoelectric element 10 wound and formed spirally and embedded in the insulating cover 11 as shown in FIG.

In order to test the performance of the hydrophone thus obtained as a receiver, the above-mentioned slit band-shaped piezoelectric element and a hydrophone formed in a spiral shape and embedded in a urethane elastomer measuring the hydrostatic piezoelectric constant d _h of were compared with each other.

The measurement results are shown in Table 1 below. From the table, it can be seen that in the piezoelectric element of the present invention, the wave receiving sensitivity before shaping is maintained even after shaping. Here, the hydrostatic pressure piezoelectric strain constant d _h was determined by the following method.

A sample is immersed in silicon oil placed in a pressure vessel.
Immersed in the container and pressurized from a nitrogen gas source to pressure P (Newton (N)
/ M^Two ) While adding the charge Q (coulomb) of the sample.
(C)) is measured. And a gauge pressure of 2 kg / cm^Two
The amount of charge increase dQ with respect to the pressure rise dP in the vicinity is obtained,
It was calculated by the following equation.

D _h = (dQ / dP) / A The unit is C / N. Here, A is the electrode area (m ² )
It is.

[0050]

[Table 1]

This hydrophone could be easily bent by hand, and after repeating bending several times with a radius of curvature of about 8 cm, remeasurement showed no change in _dh constant. Thus, it can be seen that the piezoelectric element of the present invention has excellent flexibility.

Example 2 A hydrophone was manufactured according to the embodiment shown in FIGS.

First, in the same manner as in the first embodiment,
A μm polymer piezoelectric film was obtained, and one surface thereof was roughened.

Separately, a polyester-based adhesive (“Byron 30SS” manufactured by Toyobo Co., Ltd. and “Coronate L” manufactured by Nippon Polyurethane Co., Ltd.) was applied to both sides of a 35 μm thick copper foil having both surfaces roughened. 1 (weight ratio) mixture)
After coating at 0 μm, a pair of piezoelectric films cut out from the polymer piezoelectric film obtained as described above are attached so that their polarization characteristics are opposite to each other.
The adhesive was cured under the condition of 0 kg / cm ² to obtain a laminated body of 1a / 4a / 3 / 4b / 1b excluding the surface electrodes 2a and 2b in FIG.

Next, both surfaces of the laminate obtained above were roughened by sandblasting with an alumina-based abrasive having a grain size of # 60, and thereafter, an electric wire spraying machine (manufactured by Kato Metallicon Co., Ltd., D
Air pressure 5kg / c using K type metal spraying machine E type)
Spraying under conditions of m ² and voltage 15V, thickness about 40 μm
Of the zinc sprayed electrodes 2a and 2b.

Next, the piezoelectric element having the laminated structure shown in FIG.
D) was slit to obtain a band-shaped piezoelectric element 50.

Example 1 of this band-shaped piezoelectric element 50
With the same habit and type as in the above, length 120mm
The spiral shaped piezoelectric element 50 is formed in the same manner as in Example 1 and then embedded in polyurethane, and spirally wound and shaped as shown in FIG.
Was embedded in the urethane elastomer coating 11 to obtain a hydrophone (length: about 135 mm).

When the electrode take-out part (right end in FIG. 5) of the hydrophone thus obtained is shaken by hand with a pendulum, between terminals AB and between terminals AC and B (as shown in FIG. 6). Output was measured using a digital oscilloscope (DL-2240, manufactured by Yokogawa Electric Corporation). The oscillograph charts of the output waveforms are shown in FIG. 7 (between terminals AB) and FIG.
Between). In the figure, the vertical axis represents the output (20 mV / div.),
The horizontal axis is time (0.5 sec / div.).

As is clear from the comparison between FIG. 7 and FIG.
In the output between the terminals AC and B according to the structure of the present invention (FIG. 8), it can be seen that the deformation noise due to the expansion and contraction of the hydrophone is effectively canceled.

[0060] Also, measured in the same manner as strip piezoelectric element wherein slits, it a hydrostatic piezoelectric constant d _h Example 1 hydrophone was embedded in the vehicle and urethane elastomer in a spiral shape, Both were compared. The measurement results are shown in Table 2 below. From the table, as in the first embodiment, the wave receiving sensitivity before the shaping is maintained even after the shaping.

[0061]

[Table 2]

Subsequently, the same measurement was performed by fixing the hydrophone to a radius of curvature of 10 cm with a jig.
_{The h} constant did not change.

[0063]

As described above, according to the present invention, by adopting a structure in which a flexible band-shaped piezoelectric body is spirally wound, flexibility and remarkably improved flexibility as compared with a cylindrical piezoelectric element are obtained. A piezoelectric element having impact resistance and suitable as a sound wave transmitting / receiving element is provided.

Further, by adopting a band-shaped piezoelectric element having a structure in which a pair of band-shaped polymer piezoelectric bodies are bonded on opposite sides and a spirally wound structure of the band-shaped piezoelectric element, mechanical flexibility can be maintained while maintaining the overall flexibility. A hydrophone that prevents generation of noise due to the application of a mechanical stress and has good wave receiving sensitivity is provided.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of a hydrophone according to an embodiment of the piezoelectric element of the present invention, as viewed from the front.

FIG. 2 is a schematic cross-sectional view in the thickness direction of the band-shaped piezoelectric element taken along a cutaway plane II-II in FIG.

3 is a schematic cross-sectional view in the thickness direction of a strip-shaped piezoelectric element having an insulating coating layer corresponding to FIG.

FIG. 4 is a perspective view of a hydrophone having a connection element structure according to another embodiment of the piezoelectric element of the present invention, as viewed substantially from the front.

FIG. 5 is a partially cutaway perspective view of an embodiment of the hydrophone of the present invention, as viewed from the front.

FIG. 6 is a schematic cross-sectional view in the thickness direction of the band-shaped piezoelectric element taken along a cut surface VI-VI in FIG. 5;

FIG. 7 is an oscillograph chart showing a noise generation state due to mechanical deformation in a hydrophone using a polymer piezoelectric element according to a comparative example (structure for extracting output between AB).

FIG. 8 is an oscillograph chart showing a noise generation state due to mechanical deformation in a hydrophone using a polymer piezoelectric element according to an embodiment (AC-B output extraction structure).

[Explanation of symbols]

1, 1a, 1b: strip-shaped polymer piezoelectric material, 2a, 2b: surface electrode layer, 3: central electrode layer, 4a, 4b: adhesive layer, 5a, 5b: insulating coating layer, 6: voltage output detecting means, 7: Solder, 8a, 8b, 8c, 81a, 81b, 82a, 82b:
Lead wires 10, 10a, 10b, 50: spirally wound band-shaped piezoelectric element, 11: coating, O: central axis, A, B, A1, B1, A2, B2: terminal.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuyuki Yoshitake 1-34-5 Ehara-cho, Nakano-ku, Tokyo (72) Inventor Taku Sato 183-1 Harada, Nishikicho, Iwaki-shi, Fukushima (72) Inventor Kazumoto Suzuki Fukushima 1-9-3, Honcho, Ueda-cho, Iwaki-shi, Japan (72) Kenichi Nakamura, 4-3, Yosawa-sakuta, Nakoso-machi, Iwaki-shi, Fukushima Prefecture (56) References JP-A-1-208098 (JP, A) JP-A-2 -77676 (JP, A) JP-A-55-121799 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04R 17/00 330 H04R 1/44 330 H01B 7/10 H01L 41 / 08

Claims (7)

(57) [Claims] 1. A belt-shaped polymer piezoelectric body having an electrode layer opposed to a surface thereof is spirally wound around a certain central axis, and the surface electrode layer is disposed substantially parallel to an extension direction of the central axis. A piezoelectric element having a self-supporting spiral-shaped structure. 2. The piezoelectric element according to claim 1, wherein a plurality of pairs of the surface electrode layers are provided apart from each other in an extending direction of the polymer piezoelectric body. 3. The piezoelectric element according to claim 1, wherein the polymer piezoelectric body is a pair of polymer piezoelectric bodies stacked with a common central electrode layer interposed therebetween. 4. The piezoelectric element according to claim 1, wherein an outer surface of the surface electrode layer is covered with an insulating material. 5. A piezoelectric element having a self-supporting helical structure.
Embed in elastomeric coating, flexible circle as a whole
The piezoelectric element according to any one of claims 1 to 3, wherein the piezoelectric element has a cylindrical rod shape.
Child. 6. A strip-shaped piezoelectric element obtained by laminating a pair of strip-shaped polymer piezoelectric bodies with a common central electrode layer interposed therebetween so that the polarization directions thereof are opposite to each other, and are spirally wound and arranged.
A highly flexible hydrophone having a self-supporting helical structure and a structure capable of extracting an electric output generated between a surface electrode formed on both surfaces of the band-shaped piezoelectric element and the central electrode layer. 7. A self- supported, spirally wound arrangement
7. The hydrophone according to claim 6 , wherein the band-shaped piezoelectric element having a helical structure is embedded in the elastomer coating to form a cylindrical rod as a whole.