JPS6313497A - Underwater wide band frequency transmitter/receiver - Google Patents

Abstract

PURPOSE:To attain an extremely high efficiency and wide frequency band of acoustic wave by interposing an acoustic matching layer between a sound wave radiating plane and an acoustic rubber, and adhering the outermost layer of the rubber to a case. CONSTITUTION:A vertical resonater 1-a consists of a front mass 11, a ceramic 12, and a back mass 13, to the sound wave radiating plane of which, the acoustic matching layer 2 of a thickness of lambda/4 is adhered. The acoustic matching layer 2 is also adhered to the acoustic rubber 3, and the rubber 3 is adhered to the case 5. The thus formed frequency transmitter/receiver generates oscillation in the oscillation mode generated by respective vertical resonaters and in the oscillation mode generated by the acoustic matching layer, and the overall oscillation characteristic has a wide hand characteristic synthesizing said two modes. Additionally, the back mass 13, etc., does not need to be made in thickness of lambda/4, and accordingly, usable frequency length to the ceramic 12 can be increased within the extend of lambda/2 and further, the applied power can be also made larger.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an underwater broadband transducer, and more particularly to an underwater broadband transducer that is improved in efficiency, broadband, and size and weight.

[Conventional technology]

Ordinary ceramic resonator or two ceramic resonators
Longitudinal transducers, which utilize runsipan-type transducers sandwiched between two pieces of metal from the front and back, are arranged in multiple planes taking into account the desired directivity and other operational conditions, and these sound wave radiation surfaces are arranged as acoustic windows. Transducer/receiver types that are glued to are widely used in various operational fields. In this case, acoustic rubber (or PC rubber) whose acoustic impedance PC is similar to that of water or seawater is usually used as a member constituting the window through which the radiated sound waves pass, the so-called acoustic window. Here, P represents the density and C represents the speed of sound.

In addition, such a transducer is often required to have a wide band for operational purposes, but in that case, each longitudinal oscillator that constitutes the transducer is a Langevin type oscillator, and a back mass (back mass) is used. A common method is to reduce the mechanical Q (selectivity) by setting the mass) to 1/4 wavelength. The back mass referred to here refers to the rear part of the metal mass bonded to the front and rear of the ceramic in a lungi pan type vibrator, and the front mass is called the front mass in contrast to this back mass. It is also well known that Further, in consideration of efficient use of the Langevin type vibrator, a ported clamping structure is often used so that prestress (pre -5 stress) can be applied to the ceramic I.

In any case, this lunge/pan type resonator has been attracting attention because of its structural features that make it easily adaptable to wide-band resonators, and the basic longitudinal resonator for wide-band resonators is one with a backmass of 1/4 wavelength. It is used in many ways.

FIG. 2 is a sectional view showing an example of a conventional underwater broadband transducer. In the conventional underwater broadband transducer shown in FIG. 2, a portion of a plurality of Langevin type oscillators used as longitudinal oscillators are vertical oscillators 5-a and 5-b.

5-c, and these longitudinal oscillators are, for example, longitudinal oscillators 5-c.
- As shown in a, metal front mass 61 and back mass 6
3, the two-stage cylindrical ceramic 62 is bolted together to apply prestress. The end face of the front mass 61, which serves as a sound wave radiation surface, is bonded to the acoustic rubber 3, and the sound waves from the back mass 63 are prevented from being radiated by the sound insulation material 4, so that the entire vertical vibrator 5-a is It has a structure in which it is housed in a case 5 together with the vertical vibrator.

In order to widen the band of such a transducer, the back mass 63 is set to λ/4 (λ is the wavelength at the resonant frequency), the mechanical Q is made small, and the whole is vibrated at λ/2. Therefore, the total length of the front mass 61 and the ceramic 62 is also λ/4
becomes. The front mass 61 is 1. The dimensions of the ceramic 62 are set in consideration of the conditions under which bending vibration does not occur, and also in consideration of the applied voltage.

Now, the above-mentioned broadband transducer is commonly used in large quantities, but in addition to this, an acoustic matching layer with a thickness of λ/4 is bonded to the radiation surface of a single vibrator to form two resonance modes. Attempts have been made to widen the band.
Volume 5, No. 12.

P530-533. (December 1952), and recently, suggestions for improving the content of this document have been highly efficient.

"A Study of Broadband Underwater Ultrasonic Transducers" targeting broadband piezoelectric transducers (Takeshi Inoue et al.).

Institute of Electronics and Communication Engineers material US85-22. August 27, 1985
(Japanese). This λ/4 acoustic matching layer has a matching member such as epoxy resin interposed between the vibrator radiation surface and the load medium for generating a second vibration mode, and the vibrator has bandpass characteristics due to multiple vibration modes. The purpose is to increase bandwidth by adding

[Problem that the invention seeks to solve]

However, the conventional broadband transducer described above has the following problems.

In other words, in a transducer in which a necessary number of Langevin type vibrators are housed in a case, wide band is ensured by setting the backmass to λ/4. In this case, the basic problem is that there is a large difference between the acoustic impedance of the sound wave emitting surface of the vibrator and the acoustic impedance of the acoustic rubber used for the acoustic window, and therefore efficiency cannot be achieved and the band is inevitably narrow. Under these conditions, if the backmass is set to λ/4 length to achieve a wide band, the dimensions will become very large, and the weight will also become very large. Superimpose. This means that compared to ceramic parts, which have a sound speed of about 3000 to 3500 m/s, the sound speed of metals such as aluminum used for normal front mass and back mass is about 5000 m/s, and furthermore, the density difference between the two This is self-evident if we take this into account.

On the other hand, in the case of a resonator that uses an acoustic matching layer with a thickness of λ/4, it is of course possible to impart broadband characteristics to the resonator itself, but the resonator is usually rarely used as a single unit. In most cases, the device is housed in a case, as shown in FIG. 2, and transmits and receives sound waves through an acoustic window. This is done in consideration of operational environment resistance, so-called weather resistance, robustness, and operability when the transducer is used as a transducer. Therefore, conventional transducers with acoustic matching layers are However, there is a problem in that it cannot withstand use in a practical environment as it is.

An object of the present invention is to eliminate the above-mentioned drawbacks, and to interpose at least one quarter-wavelength acoustic matching layer between the sound wave emitting surface of the longitudinal transducer group and the acoustic rubber in a layered adhesive state. An object of the present invention is to provide an underwater wideband transducer that is significantly improved in efficiency and wideband by providing an acoustic window with a structure in which rubber itself is bonded to the case, and which can be significantly reduced in size and weight.

[Means for solving problems]

The underwater broadband transducer of the present invention is of a type in which a sound wave radiation surface of a group of vertical transducers is bonded to an acoustic window, in which at least one quarter-wavelength acoustic matching layer is sequentially applied to the sound wave radiation surface. The acoustic rubber is laminated and bonded to the outermost layer of acoustic rubber, and the acoustic rubber is bonded to the longitudinal transducer group housing case to form an acoustic window.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the underwater broadband transducer of the present invention. The embodiment shown in FIG.
An example is shown in which the sound bottle combination layer of /4 wavelengths is 1'+I'i, but it is of course possible to form a plurality of layers, and the acoustic matching effect increases accordingly, as will be described later. However, this selection can be made arbitrarily by taking into account the trade-off with the external dimensions, weight, and other operational requirements of the transducer to be constructed.

The embodiment shown in FIG. 1 includes longitudinal vibrators 1-a and 1-b.

1-.C2 acoustic matching layer 2. Acoustic gono・3. It is formed by adding the sound insulating material 4, case 5, etc.

The longitudinal oscillators 1-a, 1-b, and 1-c are shown as representatives of a part of vertical oscillators arranged in a plane. ceramic 12
, a back mass 13, and an acoustic matching layer 2 having a thickness of λ/4 is adhered to the sound wave emitting surface thereof. This acoustic matching layer 2 uses epoxy resin, and its acoustic impedance PC is the acoustic impedance of the sound wave radiation surface of the vertical vibrator 1-a, and the sound that uses a neoprene-based synthetic material. a
The acoustic impedance of the rubber 3 is set to take approximately an intermediate value.

Further, the acoustic matching layer 2 is bonded to an acoustic rubber 3, and the acoustic rubber 3 is further bonded to a case 5.
The acoustic window structure composed of the acoustic matching layer 2 and the second
The acoustic window constructed by a single acoustic rubber 3 shown in the figure is also much more robust. Note that the case 5 is made of metal and has a cylindrical shape in this embodiment.

Now, in the transducer formed in this way, two vibration modes occur: a vibration mode due to each longitudinal vibrator and a vibration mode due to the acoustic matching layer, and the overall vibration characteristics have broadband characteristics that are a combination of the two vibration modes. It becomes like this. Generally, n+1 vibration modes are generated, which is the number nK1 of acoustic matching layers to be interposed.

FIG. 3 is a vibration mode characteristic diagram showing an example of complex vibration mode characteristics when an acoustic matching layer is used. FIG. 3 shows the characteristics of complex vibration when the acoustic matching layer is one layer, and this is expressed by a first vibration mode a caused by the ceramic and a second vibration mode b caused by the acoustic matching layer. As mentioned above, generally, when n acoustic matching layers are used, n+1 vibration modes appear. Value Ve/Vx indicated by a, b
is the vibration velocity distribution of the acoustic matching layer normalized by the vibration velocity of the end face of the ceramic, that is, the sound wave emission surface. What Figure 3 means is that these oscillators have a phase of π with respect to each other.
This means that it is a dual mode oscillator in which two different resonance modes (180 degrees) exist in close proximity. Regarding the phase relationship, if the acoustic matching layer is doubled, there will be three resonance modes, and among these, the first and third modes have the same phase, and the second mode differs only in π. Odd mode in-phase and even mode anti-phase occur alternately.

In any case, creating multiple vibration modes and vibrating in multiple resonance modes will immediately lead to an expansion of the bandwidth. Additionally, the acoustic matching layer used for this purpose is formed of a plurality of layers having an acoustic impedance that gradually decreases from the sound wave emitting surface of the vertical vibrator to the sound θS rubber of the outermost layer. In this case, impedance matching between the load and the vertical vibrator can be achieved.

In this way, it is possible to achieve a wide band through the use of the tone b matching M of λ/・1, so the pack mass 13 etc.
It is not necessary to set the thickness to 4, and it is sufficient to have a thickness that is almost close to the front mass 11 etc., that is, a thickness that can suppress the generation of unnecessary bending vibrations. In this way, the usable length that can be provided to the ceramic block 12 out of the total λ/2 is increased accordingly, and the applied power can also be increased.

A numerical example is as follows. That is, as -V/1j of the conventional vertical vibrator shown in Fig. 2, 30KHz
The total length is approximately 57ff at the frequency used! ! ! The back mass length of λ/4 of I is about 34 IrIm, and the ceramic has a length of about 11-1, so the fo 7 photo mass length is about 12 marks. In this embodiment, the front mass and back mass are both 8 nn, and the ceramic is approximately 30 mm, reducing the total length to approximately 46 nnh. Along with this, the length of 5 layers of λ/4 epoxy resin 9 (Bz) is required, but the thickness of the acoustic rubber can be compressed to about 13nvn by using a window configuration in combination with an acoustic matching layer. Overall, in addition to reducing the weight by reducing the back mass, the overall length has been shortened by more than 10 meters, and the ceramic part can now be approximately three times as long.

The above is a comparison with a conventional example in which the back mass is set to λ/4 to achieve a wide band.However, regarding another conventional example, that is, one in which an acoustic matching layer with a thickness of λ/4 is bonded to a longitudinal vibrator, this It can be used as is, or if weather resistance is taken into consideration, it can be simply glued to acoustic rubber. In other words, the acoustic rubber 3 of the conventional structure shown in FIG. 2 is divided into upper and lower halves as shown by dotted lines, with the upper part being the acoustic rubber and the lower part being the acoustic matching layer. Such structures usually have the problem that the acoustic matching layer, which uses epoxy resin, is exposed to the environment, has lower weather resistance than neoprene-based acoustic rubber, and is difficult to ensure perfect adhesion to the main case. becomes. The solution of this problem by merging processing is the gist of the present invention, an embodiment of which is shown in FIG. The fractional bandwidth of the transducer thus obtained can be easily 40 to 50% even as a single acoustic matching layer, and widening the band can be easily achieved. Specifically, this is 2 compared to the case where the back mass is λ/4.
This means that it is possible to increase the bandwidth by ~3 times or more.

Regarding the degree of acoustic impedance matching, possible design bandwidth, and optimal matching layer thickness in a transducer with such a structure, a multimode filter synthesis method was introduced, and the longitudinal oscillator was connected to its electrical terminal. The numerical value is determined by assuming that it is a multimode filter with loads connected to the input and output terminals. The gist of this synthesis method is that when the image impedance Zim when viewing the longitudinal oscillator from the load side of the longitudinal oscillator, which can be expressed by a 4-terminal network using a special circuit, is a real number based on the filter theory of image parameters, it passes through. A method of synthesizing a longitudinal oscillator with few ripples in the passband, which becomes a stopband when it is an imaginary number. If you are trying to secure it by C, determine the specific acoustic impedance and layer thickness of the acoustic matching layer so that Zim is equal to the load impedance ZL at the center frequency and Zim can take real values continuously over as wide a band as possible, The number of acoustic matching layers and the thickness of the acoustic rubber are ultimately determined through a trade-off between these conditions and operating conditions.

〔Effect of the invention〕

As explained above, according to the present invention, in an underwater broadband transducer in which the sound wave radiation surface of the vertical transducer group is bonded to the acoustic window, the acoustic impedance between the sound wave radiation surface and the acoustic rubber is approximately equal to that of the two. By interposing at least one acoustic matching layer made of a material having an intermediate value and then adhering the outermost layer of acoustic rubber to the case to form an acoustic window, it is possible to significantly increase efficiency and widen the band. This has the effect of realizing a small, lightweight, and robust underwater wideband transducer that can significantly increase input power.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the underwater wideband transducer of the present invention, Fig. 2 is a sectional view showing an example of a conventional underwater wideband transducer, and Fig. 3 is a composite diagram when an acoustic matching layer is used. FIG. 3 is a vibration mode characteristic diagram showing an example of vibration mode characteristics. '-a+ 1 b, 1-c・song・vertical holder, 2...
...Sound rim (gold layer, 3...Acoustic rubber, 4.
...Sound insulation material, ...°°° case, 6-a, 5
-b, 5-c-・-Longitudinal vibrator, 11.61...
・Front mass, 12.62... mark ・Ceramic, 13
．． 63... Backmass. Agent Patent Attorney Yen Hara 2'°゛日l-to7'-','-C---4f't't7r
"th hand/f ---------Front mass, '2 --- ---<Dorami Schiff/
3 --- --- Panic ゛1ζ' (Fig. 1 O-a, O-4, 6-(: ---- - - Ichimau C Tsuku 63 - - - - - Ba, Tsu 2 Mba 2nd Ve - - - Sera S Rough Doi 4th edition's Tobeme dynamic speed Vχ -
--- Spring matching layer (7) Velocity meeting α -----e-7s
So21: Yoru Muta 1 child Hioka mode each - 11 - sound igq
Bankin layer (Yorugyu 2 station Daigo~to Figure 3)

Claims (1)

[Claims] In an underwater wideband transducer in which a sound wave emitting surface of a group of vertical transducers is bonded to an acoustic window, at least one quarter-wavelength acoustic matching layer is sequentially formed from the sound wave emitting surface to the outermost layer of acoustic rubber. 1. An underwater broadband transducer comprising an acoustic window formed by laminating and bonding the acoustic rubber to the vertical vibrator group housing case.