JPH0511711B2 - - Google Patents
Info
- Publication number
- JPH0511711B2 JPH0511711B2 JP15641286A JP15641286A JPH0511711B2 JP H0511711 B2 JPH0511711 B2 JP H0511711B2 JP 15641286 A JP15641286 A JP 15641286A JP 15641286 A JP15641286 A JP 15641286A JP H0511711 B2 JPH0511711 B2 JP H0511711B2
- Authority
- JP
- Japan
- Prior art keywords
- transducer
- fiber
- composite material
- piezoelectric ceramic
- reinforced composite
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 239000000919 ceramic Substances 0.000 claims description 25
- 239000000463 material Substances 0.000 claims description 14
- 239000003733 fiber-reinforced composite Substances 0.000 claims description 13
- 239000000835 fiber Substances 0.000 claims description 7
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 5
- 239000004917 carbon fiber Substances 0.000 claims description 5
- 239000003365 glass fiber Substances 0.000 claims description 5
- 239000004760 aramid Substances 0.000 claims description 3
- 229920006231 aramid fiber Polymers 0.000 claims description 3
- 230000005855 radiation Effects 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 239000002131 composite material Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000005684 electric field Effects 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 239000011208 reinforced composite material Substances 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 229920006332 epoxy adhesive Polymers 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229920001084 poly(chloroprene) Polymers 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000002604 ultrasonography Methods 0.000 description 1
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は広帯域で無指向性を有するハイパワー
水中超音波トランスジユーサに関するものであ
る。DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a broadband, omnidirectional, high-power underwater ultrasonic transducer.
（従来技術）
従来、無指向性を有するトランスジユーサとし
て、周知の如く第３図に示すようなラジアルモー
ドで動作する円筒状圧電セラミツクトランスジユ
ーサが広く用いられている。第３図に示すトラン
スジユーサは、内外表面に銀あるいは金焼きつけ
電極３１，３２が形成され、この電極３１，３２
間に直流高電界を加えて矢印に示す如く、肉厚方
向に放射状に分極処理が施されている。このトラ
ンスジユーサは電気端子３３，３４から交流電圧
を印加することにより、直径が一様に伸縮する、
所謂径拡がり振動モード（ラジアル・エクステン
シヨナル・モード）で中心軸０−０′に関して二
重矢印で示すように円筒の外表面から無指向性の
音響放射が行われる。(Prior Art) Conventionally, a cylindrical piezoelectric ceramic transducer that operates in a radial mode as shown in FIG. 3 has been widely used as a non-directional transducer. The transducer shown in FIG. 3 has silver or gold baked electrodes 31, 32 formed on the inner and outer surfaces.
A high direct current electric field is applied between them, and polarization is performed radially in the thickness direction as shown by the arrows. This transducer uniformly expands and contracts in diameter by applying an alternating current voltage from the electrical terminals 33 and 34.
In a so-called radial extensional vibration mode, omnidirectional acoustic radiation is performed from the outer surface of the cylinder as shown by the double arrow with respect to the central axis 0-0'.
（発明が解決しようとする問題点）
従来の円筒状圧電セラミツクトランスジユーサ
は、中心軸に対して無指向性の音響放射を行うこ
とができるが、以下のような問題点がある。(Problems to be Solved by the Invention) Conventional cylindrical piezoelectric ceramic transducers can radiate sound omnidirectionally with respect to the central axis, but they have the following problems.
第３図から明らかな如く、従来のトランスジユ
ーサはすべて圧電セラミツクスからできている。
圧電セラミツクスは密度が約8.0×103Kg／m3で、
径拡がりモードに関係する音速が3000〜3500ｍ／
secであるため、固有音響インピーダンス（密度
と音速の積で定義される）が24×106〜28×106
MKSraylsと媒質である水の固有音響インピーダ
ンスの20倍近くあり極めて大きい。このため水と
トランスジユーサとの間で音響インピーダンスの
ミスマツチングが生じ、得られる帯域幅は15パー
セントからせいぜい30％と制限されたものにな
る。従つて、例えば従来のトランスジユーサをソ
ーナーシステムに用いた場合、狭帯域特性のため
にパルスの尾引きが長くなり距離分解能が劣化す
るといつた欠点があつた。一般に、パルスの尾引
きの小さなコンパクトなパルス応答特性を得よう
とすると広帯域のトランスジユーサが必要不可決
なものとなる。円筒状圧電セラミツクトランスジ
ユーサはおいて広帯域のものを得ようとする目的
で、水とのインピーダンス整合を改善するために
はトランスジユーサの機械インピーダンスを小さ
くすること（これは音響放射面積当たりのトラン
スジユーサの質量を小さくすることに相当する）
が必要であり、従来肉厚を薄くすることが専ら行
われてきた。しかしながら、トランスジユーサの
肉厚を薄くすると圧電セラミツクスの加工が難か
しくなること、及び機械的強度が著るしく劣化す
ることにより、ハイパワー音響放射が不可能とな
るといつた問題があつた。 As is clear from FIG. 3, all conventional transducers are made of piezoelectric ceramics.
Piezoelectric ceramics has a density of approximately 8.0×10 3 Kg/m 3 ;
The sound speed related to diameter expansion mode is 3000 to 3500 m/
sec, so the specific acoustic impedance (defined as the product of density and speed of sound) is 24×10 6 to 28×10 6
The characteristic acoustic impedance of MKSrayls is nearly 20 times that of water, which is the medium, and is extremely large. This results in an acoustic impedance mismatch between the water and the transducer, which limits the available bandwidth to 15% to no more than 30%. Therefore, for example, when a conventional transducer is used in a sonar system, the narrowband characteristic causes a long pulse tail and degrades the distance resolution. Generally, in order to obtain a compact pulse response characteristic with little pulse trailing, a broadband transducer is essential. In order to obtain a broadband cylindrical piezoelectric ceramic transducer, it is necessary to reduce the mechanical impedance of the transducer (this means that the mechanical impedance of the transducer is small) to improve the impedance matching with water. (equivalent to reducing the mass of the jusa)
Conventionally, the focus has been on reducing the wall thickness. However, when the wall thickness of the transducer is made thinner, processing of the piezoelectric ceramic becomes difficult, and the mechanical strength deteriorates significantly, making high-power acoustic radiation impossible.
本発明の目的は、広帯域で高効率の音響放射特
性を有し、かつハイパワー送波が可能な無指向性
トランスジユーサを実現することである。 An object of the present invention is to realize an omnidirectional transducer that has wide-band, highly efficient acoustic radiation characteristics and is capable of high-power transmission.
（問題点を解決するための手段）
本発明に従つたトランスジユーサの基本構成
は、径拡がり振動モードで動作する圧電セラミツ
ク円筒振動子と、一方向にのみ繊維が配された繊
維強化複合材料からなるシートからなり、該繊維
強化複合材料でできたシートは該圧電セラミツク
円筒振動子の円周方向に、繊維の方向が円筒の中
心軸に一致するように、被覆したものである。ま
た、必要に応じて炭素繊維、ガラス繊維あるいは
アラミド繊維を該繊維強化複合材料シートの上か
ら強く巻きつけても良い。即ち、本発明に従つた
トランスジユーサは、圧電セラミツク円筒振動子
とその上に多重に巻かれた中心軸方向に対する剛
性の大きな繊維強化複合材料からなるシートが一
体となつて一様な径拡がり振動モードで動作する
無指向性の水中超音波トランスジユーサである。(Means for Solving the Problems) The basic structure of the transducer according to the present invention is a piezoelectric ceramic cylindrical vibrator that operates in a diameter-expanding vibration mode, and a fiber-reinforced composite material in which fibers are arranged only in one direction. The sheet made of the fiber-reinforced composite material is coated in the circumferential direction of the piezoelectric ceramic cylindrical vibrator so that the direction of the fibers coincides with the central axis of the cylinder. Furthermore, if necessary, carbon fibers, glass fibers, or aramid fibers may be tightly wound over the fiber-reinforced composite material sheet. That is, the transducer according to the present invention has a piezoelectric ceramic cylindrical resonator and a sheet made of a fiber-reinforced composite material having high rigidity in the direction of the central axis, which is wound multiple times on the piezoelectric ceramic cylindrical resonator, and has a uniform diameter expansion. It is an omnidirectional underwater ultrasound transducer that operates in vibration mode.
（作用）
本発明に従つた無指向性のハイパワー水中超音
波トランスジユーサの代表的な一例を第１図に示
す。第１図に示したトランスジユーサの斜視図に
おいて、１１，１１′は円筒状圧電セラミツク振
動子であり、２１は円筒の中心軸方向に繊維が配
列された繊維強化複合材料でできたシートを振動
子１１，１１′の外表面に有機接着剤を介して多
重に巻きつけたものである。振動子１１，１１′
は従来の第３図に示した円筒状圧電セラミツクト
ランスジユーサと同様に径拡がり振動を行い、１
１と１１′は同相で駆動される。効率的な音響放
射を行うために、繊維強化複合材料シートからな
る円筒１２は、振動子１１，１１′と一体となつ
て径拡がり振動モードで振動することが必要不可
決である。トランスジユーサが一様な径拡がり振
動をするために、円筒１２は中心軸０−０′方向
に関する剛性が極めて大きいことが望まれる。本
トランスジユーサに用いる繊維強化複合材料から
なるシート２１は第２図に示すように、繊維の方
向（矢印で示す）が円筒の中心軸に一致するよう
に（第２図のＺ軸）配列されなければならない。
また、円筒状圧電セラミツク振動子１１，１１′
に巻きつけやすいように、第２図のｘ軸方向に対
しては可撓性のある方がトランスジユーサを作製
しやすい。このような材料として、ガラス繊維強
化複合材料（Ｇ−FRP）、炭素繊維強化複合材料
（Ｃ−FRP）が好適である。第２図に示したこの
ような複合材料からなるシート２１は、円周方向
に関しては繊維が入つていないため、径振動モー
ドに関してはマトリツクスとなつているプラスチ
ツクスの音速となる。これは圧電セラミツクスの
音速よりかなり小さい。(Function) FIG. 1 shows a typical example of a non-directional high-power underwater ultrasonic transducer according to the present invention. In the perspective view of the transducer shown in FIG. 1, 11 and 11' are cylindrical piezoelectric ceramic vibrators, and 21 is a sheet made of a fiber-reinforced composite material in which fibers are arranged in the direction of the central axis of the cylinder. The outer surfaces of the vibrators 11 and 11' are wrapped in multiple layers with an organic adhesive interposed therebetween. Vibrator 11, 11'
The cylindrical piezoelectric ceramic transducer shown in FIG.
1 and 11' are driven in phase. In order to efficiently radiate sound, it is essential that the cylinder 12 made of a fiber-reinforced composite material sheet vibrate in a diameter-expanding vibration mode together with the vibrators 11, 11'. In order for the transducer to vibrate with uniform diameter expansion, it is desirable that the cylinder 12 has extremely high rigidity in the direction of the central axis 0-0'. As shown in FIG. 2, the sheet 21 made of fiber-reinforced composite material used in this transducer is arranged so that the fiber direction (indicated by the arrow) coincides with the central axis of the cylinder (Z-axis in FIG. 2). It must be.
In addition, cylindrical piezoelectric ceramic vibrators 11, 11'
It is easier to fabricate a transducer if it is flexible in the x-axis direction in FIG. 2 so that it can be easily wrapped around the transducer. As such materials, glass fiber reinforced composite materials (G-FRP) and carbon fiber reinforced composite materials (C-FRP) are suitable. Since the sheet 21 made of such a composite material shown in FIG. 2 has no fibers in the circumferential direction, the radial vibration mode has the sonic velocity of the plastic matrix. This is considerably lower than the sound speed of piezoelectric ceramics.
従つて、径拡がり振動モードに関して、本発明
に従つて円筒１２をＧ−FRPあるいはＣ−FRP
としたトランスジユーサは、従来の圧電セラミツ
ク円筒単体でできたトランスジユーサより寸法が
小さく実現できることになり、小型化の点で有利
となる。さらに、本発明に従つたトランスジユー
サは単位音響放射面積当りの実効的な質量が従来
のトランスジユーサより相当小さくなるので、水
との音響インピーダンス整合が著るしく改善さ
れ、広帯域のトランスジユーサが実現できる。 Therefore, regarding the radial expansion vibration mode, according to the present invention, the cylinder 12 is made of G-FRP or C-FRP.
The size of the transducer thus constructed can be smaller than that of a conventional transducer made of a single piezoelectric ceramic cylinder, which is advantageous in terms of miniaturization. Furthermore, since the transducer according to the invention has a significantly lower effective mass per unit acoustic radiation area than conventional transducers, the acoustic impedance matching with water is significantly improved, making it possible to provide a broadband transducer. Usa can make it happen.
周知の如く、圧電セラミツクスは張力に対して
脆く、圧縮力に対し強い。このため、ハイパワー
トランスジユーサを実現するためには圧電セラミ
ツクスに圧縮バイアス応力をかけて使用した方が
有利となる。本発明に従つたトランスジユーサで
は、円筒状圧電セラミツク振動子１１，１１′の
外側に複合材料シートをある程度の張力を伴つて
巻きつけるが、このとき振動子１１，１１′に一
定の最適なバイアス応力を量産時において安定し
て与えることは難かしい。この対策として必要に
応じてガラス繊維、炭素繊維あるいはアラミド繊
維を、円筒１２の表面に巻きつけることによつ
て、圧電振動子１１，１１′に圧縮応力を供給す
ることは極めて有効である。 As is well known, piezoelectric ceramics are brittle under tension and strong against compression. Therefore, in order to realize a high-power transducer, it is advantageous to apply compressive bias stress to piezoelectric ceramics. In the transducer according to the present invention, a composite material sheet is wound around the outside of the cylindrical piezoelectric ceramic vibrators 11, 11' with a certain degree of tension. It is difficult to stably apply bias stress during mass production. As a countermeasure against this problem, it is extremely effective to supply compressive stress to the piezoelectric vibrators 11 and 11' by wrapping glass fibers, carbon fibers, or aramid fibers around the surface of the cylinder 12 as necessary.
（実施例）
本発明に従つたトランスジユーサの一実施例を
同じく第１図に示す。第１図において１１，１
１′は円筒状圧電セラミツク振動子で内外面に銀
焼きつけ電極が形成されている。この電極を用い
て直流高電界（4KV／mm）を100℃の油中で印加
することによつて分極処理がなされ、振動子１
１，１１′は周知の如く横効果31モードで径拡が
り振動を行う。この場合、振動子１１，１１′は
同相で駆動される。(Embodiment) An embodiment of a transducer according to the present invention is also shown in FIG. 11,1 in Figure 1
1' is a cylindrical piezoelectric ceramic vibrator with silver baked electrodes formed on its inner and outer surfaces. Using this electrode, polarization treatment is performed by applying a direct current high electric field (4KV/mm) in oil at 100℃, and the oscillator 1
1 and 11' perform radial expansion vibration in the transverse effect 31 mode, as is well known. In this case, the vibrators 11 and 11' are driven in phase.
１２は中心軸０−０′方向に炭素繊維を配した
Ｃ−FRP円筒であり、厚さ0.5mmのＣ−FRPシー
トを５重に巻いたものである。この場合、圧電振
動子１１，１１′に圧縮応力が加わるように、Ｃ
−FRPシートの内側にエポキシ系接着剤を塗布
して、シートに張力を加えながら強固に巻かれて
いる。従つて、円筒１２は中心軸０−０′方向に
関する撓み変形に対しては高い剛性を示し、円筒
状圧電セラミツク振動子の径拡がり振動モードに
呼応して、トランスジユーサ全体として二重矢印
で示す如く、一様な径拡がり振動モードで振動す
ることができるわけである。さらに、本実施例に
おいては、振動子１１，１１′は一様な圧縮バイ
アス応力を加えて、動作時の機械的強度を増大さ
せる目的で、円筒１２の外表面をガラス繊維で緊
密に巻いた。 12 is a C-FRP cylinder in which carbon fibers are arranged in the 0-0' direction of the central axis, and C-FRP sheets with a thickness of 0.5 mm are wound five times. In this case, C
- Epoxy adhesive is applied to the inside of the FRP sheet, and the sheet is tightly rolled while applying tension. Therefore, the cylinder 12 exhibits high rigidity against bending deformation in the direction of the central axis 0-0', and in response to the radial expansion vibration mode of the cylindrical piezoelectric ceramic vibrator, the transducer as a whole exhibits a double arrow shape. As shown, it is possible to vibrate in a uniform diameter expansion vibration mode. Furthermore, in this embodiment, the outer surface of the cylinder 12 of the vibrator 11, 11' is tightly wrapped with glass fiber in order to apply uniform compressive bias stress and increase mechanical strength during operation. .
本実施例における円筒振動子１１，１１′は全
く同一形状のもので、肉厚は５mm、高さは３cmで
ある。本トランスジユーサの高さは12cm、外径は
10cmである。本実施例のトランスジユーサは、周
知の如く、トランスジユーサの上下面をFRP円
板で蓋をして、ネオプレンゴムで全体をモールド
することにより水密を保持することができ、この
状態で、中心周波数9.5KHzで動作し、送波及び
受波感度においていずれも40％を超える比帯域幅
を実現することができる。さらに、本トランスジ
ユーサが、振動子１１，１１′に対してバイアス
応力印加機構を有すること、及び水との音響整合
が向上したことにより、トランスジユーサ単位質
量当たりの音響放射パワーにおいて、従来の円筒
状圧電セラミツクトランスジユーサを大きく上ま
わることが可能である。 The cylindrical vibrators 11 and 11' in this embodiment have exactly the same shape, and have a wall thickness of 5 mm and a height of 3 cm. The height of this transducer is 12cm, and the outer diameter is
It is 10cm. As is well known, the transducer of this embodiment can be kept watertight by covering the upper and lower surfaces of the transducer with FRP disks and molding the entire body with neoprene rubber. It operates at a center frequency of 9.5KHz and can achieve a relative bandwidth of over 40% in both transmitting and receiving sensitivities. Furthermore, this transducer has a bias stress applying mechanism to the transducers 11 and 11', and has improved acoustic matching with water, so that the acoustic radiation power per unit mass of the transducer is lower than that of the conventional transducer. cylindrical piezoelectric ceramic transducer.
（発明の効果）
以上詳述した如く、本発明に従えば広帯域でか
つハイパワー特性に優れた水中超音波トランスジ
ユーサを提供することができる。(Effects of the Invention) As detailed above, according to the present invention, it is possible to provide an underwater ultrasonic transducer having a wide band and excellent high power characteristics.
第１図は本発明に基づく無指向性円筒状トラン
スジユーサの例を示す図。第２図は本発明のトラ
ンスジユーサに用いる繊維強化複合材料を示す
図。第３図は従来の無指向性円筒状圧電セラミツ
クトランスジユーサを示す図。
図において、１１，１１′は円筒状圧電セラミ
ツク振動子、１２は繊維強化複合材料でできたシ
ートを多重に巻いてなる円筒、０−０′は円筒の
中心軸、２１は複合材料でできたシート、３１，
３２は電極、３３，３４は電気端子である。
FIG. 1 is a diagram showing an example of an omnidirectional cylindrical transducer according to the present invention. FIG. 2 is a diagram showing a fiber-reinforced composite material used in the transducer of the present invention. FIG. 3 is a diagram showing a conventional omnidirectional cylindrical piezoelectric ceramic transducer. In the figure, 11 and 11' are cylindrical piezoelectric ceramic vibrators, 12 is a cylinder made of multiple sheets of fiber-reinforced composite material, 0-0' is the central axis of the cylinder, and 21 is a cylinder made of composite material. sheet, 31,
32 is an electrode, and 33 and 34 are electrical terminals.
Claims (1)
繊維が配された繊維強化複合材料からなるシート
を備え、該繊維強化複合材料でできたシートは、
該圧電セラミツク円筒振動子の外周面にその繊維
方向が円筒振動子の中心軸に一致するように被覆
されていることを特徴とする無指向性水中超音波
トランスジユーサ。 ２ 特許請求の範囲の第１項のトランスジユーサ
において、繊維強化複合材料シートの上から炭素
繊維、ガラス繊維、あるいはアラミド繊維を巻き
つけたことを特徴とする無指向性水中超音波トラ
ンスジユーサ。[Scope of Claims] 1. A sheet made of a fiber-reinforced composite material comprising a piezoelectric ceramic cylindrical vibrator and a fiber-reinforced composite material in which fibers are arranged only in one direction, and the sheet made of the fiber-reinforced composite material:
An omnidirectional underwater ultrasonic transducer characterized in that the outer circumferential surface of the piezoelectric ceramic cylindrical vibrator is coated so that the fiber direction coincides with the central axis of the cylindrical vibrator. 2. An omnidirectional underwater ultrasonic transducer according to claim 1, characterized in that carbon fibers, glass fibers, or aramid fibers are wrapped around a fiber-reinforced composite material sheet. .
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15641286A JPS6313498A (en) | 1986-07-02 | 1986-07-02 | Nondirectional underwater ultrasonic transducer |
| EP87305864A EP0251797B1 (en) | 1986-07-02 | 1987-07-02 | Non-directional ultrasonic transducer |
| DE87305864T DE3787677T2 (en) | 1986-07-02 | 1987-07-02 | Non-directional ultrasound transducer. |
| US07/069,057 US4823041A (en) | 1986-07-02 | 1987-07-02 | Non-directional ultrasonic transducer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15641286A JPS6313498A (en) | 1986-07-02 | 1986-07-02 | Nondirectional underwater ultrasonic transducer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6313498A JPS6313498A (en) | 1988-01-20 |
| JPH0511711B2 true JPH0511711B2 (en) | 1993-02-16 |
Family
ID=15627182
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15641286A Granted JPS6313498A (en) | 1986-07-02 | 1986-07-02 | Nondirectional underwater ultrasonic transducer |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6313498A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03279532A (en) * | 1990-03-28 | 1991-12-10 | Natl House Ind Co Ltd | Structure for attaching support beam for geese-flight type passageway bed |
| JPH07284197A (en) * | 1994-04-08 | 1995-10-27 | Nec Corp | Dipole radiating type low-frequency underwater sound wave transmitter |
| JPH10228773A (en) * | 1997-02-14 | 1998-08-25 | Hitachi Ltd | Dynamic ram |
| CN102972046B (en) | 2010-06-30 | 2016-08-03 | 日本电气株式会社 | Oscillation device and electronic equipment |
| CN103883076B (en) * | 2014-02-26 | 2016-02-10 | 长沙理工大学 | FRP presstressed reinforcing steel and preparation method thereof and related device is mixed based on piezoelectric ceramics |
-
1986
- 1986-07-02 JP JP15641286A patent/JPS6313498A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6313498A (en) | 1988-01-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term |