JPH0585000B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an ultrasonic transducer used under high water pressure.

[Conventional technology]

The structure of a conventional transducer array will be explained based on FIG. In FIG. 2, 1 is an ultrasonic transducer (hereinafter referred to as a oscillator), 2 is Kirk rubber, 3 is a cable, and 4 is a rubber material, which is constructed as described above.

First, in order to operate as a transducer, the vibrator 1
A voltage is applied at a constant frequency to make it vibrate. Then, the vibrator 1 that is not surrounded by the Kirk rubber 2
Sound waves are emitted from the front of the opening. At this time, the sound waves are radiated with constant directivity. The emitted sound waves propagate through water, hit an object, are reflected, and return to the vibrator 1. Here, the sound wave is vibrator 1
When the sound waves are incident on the vibrator 1, the sound waves do not enter the sides of the vibrator 1 because the circumference thereof is surrounded by the Kirk rubber 2. Therefore, since the vibration is small, the voltage output is also small.

The reason why the reception sensitivity is high for sound incident from the front and low reception sensitivity for sound incident from the rear is that the characteristic acoustic impedance of the Kirk rubber 2 is resistant to acoustic media such as water. This is achieved because it is sufficiently low. As described above, Kirk rubber 2 has a low specific acoustic impedance, which is equivalent to a low Young's modulus.

[Problem that the invention seeks to solve]

Therefore, in conventional examples using Kirk rubber having such a small Young's modulus, there is a problem that the Kirk rubber loses its sound insulation properties in deep oceans because the Kirk rubber is compressed by hydrostatic pressure.

Additionally, as Kirk rubber is compressed and deformed, large strains are added to other components.
As a result, the rubber material may crack and lose its waterproof properties. Therefore, there is a problem in that the water pressure resistance of the conventional example shown in FIG. 2 is limited to a depth of about 100 to 200 meters.

Incidentally, in the above explanation, the operation and problems as a wave receiver have been described, but it goes without saying that similar problems occur when operating as a wave transmitter due to the principle of reversibility of a wave transmitter/receiver.

The present invention was made in order to solve the above problem, and its purpose is to manufacture an ultrasonic transducer whose solution to the above problem is disclosed in Japanese Patent Publication No. 59-20234. The object of the present invention is to provide a method that can be used with high reliability even in the deep ocean.

[Means and actions for solving problems]

To achieve this objective, the present invention forms a groove in a metal plate for bucking the vibrator, and forms the thickness of the metal plate to 1/9 to 14/36 of the wavelength of the internal sound wave, and similarly A sheet-shaped intermediate medium having a thickness of 1/9 to 14/36 of the wavelength of the internal sound wave is placed in the groove of the metal plate and fixed with adhesive, and then a vibrator is placed on the intermediate medium, and the vibrator is By pouring a liquid waterproof molding material made of the same material as the intermediate medium around the intermediate medium and heating and curing it, the waterproof molding material and the intermediate medium are integrated to cover the periphery and rear surface of the vibrator, and the vibrator is fixed. In this way, ultrasonic transducers are manufactured.

〔Example〕

A first embodiment of the present invention will be described below with reference to FIGS. 1, 3, and 4.

FIG. 1 is a sectional view showing a first embodiment of an ultrasonic transducer according to the present invention. In Fig. 1, 5 is a vibrator, 6 is a waterproof molding material made of rubber, etc., and 7 is a vibrator.
8 is a cable, 8 is an intermediate medium made of a sheet-like rubber material, and 9 is a metal plate. The metal plate 9 is provided on the rear surface of the vibrator 1 with the intermediate medium 8 interposed therebetween, and the thickness of the metal plate 9 and the intermediate medium 8 is 1/9 to 14/of the wavelength of the internal sound wave, respectively. Limited to 36. Note that the waterproof shield material 6 and the intermediate medium 8 are made of the same material.

Next, a method of manufacturing an ultrasonic transducer having such a configuration will be explained. First, a metal plate 9 is grooved and formed so that the thickness is 1/9 to 14/36 of the wavelength of the internal sound wave, and an intermediate medium 8 is formed. Adhere to the bottom part with a cyanoacrylate instant adhesive as shown in FIG.

Then, the vibrator 5 to which the cable 7 is connected is placed on the intermediate medium 8, and a liquid waterproof molding material 6 made of the same material as the intermediate medium 8 is poured around it and heated to harden. The transducer 1 is integrated with the medium 8 to cover the periphery and rear surface of the transducer 1, and the transducer 1 is fixed, and then the whole is further covered with a waterproof molding material 6 to form an ultrasonic transducer as shown in FIG. Manufacture.

The operation of the ultrasonic transducer manufactured in this way will be explained based on FIGS. 3 and 4.

Figure 3 is an explanatory diagram of the operation of the ultrasonic transducer shown in Figure 1, and Figure 4 is the front-rear ratio of incident sound from the front and rear.
FIG. 3 is a diagram showing FBR as a function of frequency.
When a sound wave is incident from the _rear as shown by the arrow in FIG. Sound wave B ₂ reflected at boundary b
When the metal plate 9 has a thickness of 1/4 wavelength, the waves are in phase and synthesized as strong reflected waves.

On the other hand, when the intermediate medium 8 has a thickness of 1/4 wavelength, the sound wave B ₃ transmitted through the boundaries c and b, reflected at the boundary a between the intermediate medium 8 and the vibrator 5, and re-reflected at the boundary b, and the boundary c , b and reaches the boundary a, the sound wave B ₄ is
At the boundary a, they are in opposite phase and cancel each other out.
Therefore, the vibration of the vibrator 5 due to the sound incident from behind becomes small, and therefore the wave receiving sensitivity is also low.

The above explanation is qualitative, and since transmission and reflection are actually performed multiple times at the boundaries a, b, and c, the phenomenon is a little more complicated.

According to the analysis conducted by the present inventor using a transmission line model, the front-back ratio FBR is equal to the open transmission coefficient due to sound incident from the rear. However, it is necessary that |Z _O /R _W tank ₀ l ₀ /2|≫|Z _B /R _W |>1. Z ₀ : Unique acoustic impedance of the vibrator 5, R _W : Unique acoustic impedance of the sound field medium, Z _B : Unique acoustic impedance when looking backward from boundary a, k ₀ : Wave number of the vibrator 5,
l ₀ : Thickness of vibrator 1.

The above conditions are satisfied at most frequencies in the first embodiment.

In the ultrasonic transducer shown in Fig. 1, backing has a two-layer structure consisting of an intermediate medium 8 having a 1/4 wavelength at a reference frequency and a metal plate 9 having a 1/4 wavelength. .

Here, when stainless steel is used as the metal plate 9, the open transmission coefficient, that is, the front-back ratio FBR is FBR=1/1+Ω ² √(1−27 ² ) ² +(0.92) ² .

Note that Ω=tan(π/2·/ ₀ ), :frequency Therefore, when the front-to-back ratio FBR is expressed as a function of frequency, it becomes as shown in FIG. In FIG. 4, the front-back ratio FBR is 20 dB or more in the range / ₀ = 4/9 to 14/9, which corresponds to 1/9 wavelength to 14/36 wavelength.

Next, a second embodiment of the present invention will be described based on FIG.

FIG. 5 is a perspective view showing a second embodiment of the method for manufacturing an ultrasonic transducer according to the present invention. In FIG. 5, 10 is a longitudinally vibrating vibrator, 11 is a waterproof molding material made of a rubber material, etc., 12 is an intermediate medium made of a sheet-like rubber material, and 13 is a metal plate. The metal plate 13 connects the vibrator 10 with the intermediate medium 12 interposed therebetween.
provided on the rear surface, and also includes the metal plate 13 and the intermediate medium 1.
2, the thickness is limited to 1/9 to 14/36 of the wavelength of the internal sound wave, respectively.

14 is a signal line, 15 is a housing case, 16
17 is a boot in the form of a covered cylinder; 17 is an oil; 18 is a cylindrical casing with an electronic circuit 19 built therein; a terminal board 22 with terminals 20 and 21 provided inside both ends;
23 is attached via an O-ring 24 so as to maintain watertightness, and a groove 25 for attaching the boot 16 is carved on the outer periphery of one end. 26 is a band; 27 is a fixing flange attached to the other end of the housing 18;
Fixed to another structure, e.g. to one side of the submersible,
Or, attach it as appropriate when joining the flange of a high water pressure multi-core cable. In addition, the terminal board 2
2 and 23 are made of hermetic seals with excellent watertightness.

Next, a method of manufacturing the ultrasonic transducer will be explained.
First, a vibrator array is formed by arranging the vibrators 10 in a row, backing them with a metal plate 13 with an intermediate medium 12 interposed on the rear surface, providing a signal line 14 on the front surface, and surrounding them with a housing case. 1
A liquid waterproof molding material 11 is poured through the molding material 5 and cured and fixed by heating.

Then, the signal line 14 is connected to a terminal plate 22 attached to the housing 18. Thereafter, the housing case 15 is housed in the boot 16 filled with oil 17, and the boot 16 is inserted into the mounting groove 25 of the housing 18.
and then tighten and fix it to the casing 18 with a band 26. As a result, the terminal board 22 attached to the housing 18
to seal the boot 16 and remove the oil 1 in the boot 16.
7. Make sure that seawater, etc. does not get mixed in.

The ultrasonic transducer manufactured in this way has its signal line 14 housed together with the transducer array in the oil-filled boot 16, so even if it is dropped into the sea under high water pressure, the compression difference between each component will be maintained. The tension caused by this is not applied to the signal line 14, and troubles such as disconnection do not occur. In addition, terminal plates 22 provided at both ends of the housing 18,
23, the signal wire 14 on the boot 16 side, the signal wire on the side of another structure (not shown) connected to the fixing flange 7, and the signal wire inside the casing 18 are completely isolated, so that they can be easily separated under high water pressure The signal wires 14, etc., are lowered into the sea without any excessive force being applied to them.

Although the electronic circuit 19 is provided in this embodiment, if this electronic circuit 19 is not required, the terminal board 22,
23 may be directly connected with a signal line.

〔Effect of the invention〕

As described above, according to the ultrasonic transducer according to the present invention, the thickness of the sheet-like intermediate medium and the metal plate are each 1/9 to 14/36 of the wavelength of the internal sound wave, and By installing a metal plate on the rear surface of the vibrator, etc., and pouring a waterproof molding material of the same quality as the intermediate medium around the vibrator and hardening it by heating,
Since the ultrasonic transducer is manufactured by integrating the waterproof molding material and the intermediate medium to cover the periphery and rear surface of the vibrator and fixing the vibrator, the following effects are achieved.

In other words, since an intermediate medium and a metal plate each having a thickness of 1/9 to 14/36 wavelength are used as the backing layer of the resonator, the front-to-back sensitivity ratio can be made over 20 dB, and furthermore, it is possible to Since the front-to-back ratio does not deteriorate even at depths of 100 to 300 ft, and the waterproof mold material does not crack, it is possible to obtain a highly reliable ultrasonic transducer for deep water.

Furthermore, since the dimensions of the intermediate medium can be sufficiently inspected before assembly, accurate dimensions can be maintained, and the intermediate medium can be bonded to a metal plate using a cyanoacrylate instant adhesive, etc.
This has the effect of making the thickness of the adhesive layer negligible.

In addition, in the manufacture of ultrasonic transducers, when an intermediate medium is formed by pouring liquid waterproof molding material between the transducer and the metal plate that is its backing layer and hardening it by heating, it is necessary to It is difficult to maintain an appropriate distance between the vibrator and the metal plate, making manufacturing difficult. In addition, the narrow distance between the vibrator and the metal plate causes air bubbles to form when pouring the liquid waterproof molding material, resulting in overheating. Although it has the disadvantage of deteriorating the performance of the sound wave transducer, the present invention has a vibrator placed on a sheet-like intermediate medium adhesively fixed in the groove of a metal plate, and a layer made of the same material as the intermediate medium surrounding the vibrator. By pouring a liquid waterproof molding material and heating and curing it, the waterproofing molding material and the intermediate medium are integrated, covering the periphery and rear surface of the vibrator and fixing the vibrator. It is easier to manufacture than the method of pouring molding material between the vibrator and forming an intermediate medium, and
Since there is no fear of bubbles being generated in the intermediate medium, it is possible to provide an ultrasonic transducer with excellent performance.

Moreover, if the present invention is applied to the second embodiment, the first embodiment
In addition to satisfying the same effects as those of the examples, there is an effect that performance can be sufficiently maintained even in applications under high water pressure.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the first embodiment of the present invention, Fig. 2 is a sectional view of the conventional example, Fig. 3 is an explanatory diagram of the operation of Fig. 1, and Fig. 4 shows the front-rear ratio FBR as a function of frequency. FIG. 5 is a perspective view showing a second embodiment of the present invention. 5, 10... Vibrator, 6, 11... Waterproof molding material, 7... Cable, 8, 12... Intermediate medium, 9, 1
3...Metal plate, 14...Signal line, 15...Housing case, 16...Boot, 17...Oil, 18...Casing.

Claims (1)

[Claims] 1. A groove is formed in a metal plate for bucking the vibrator, and the thickness of the metal plate is set to 1/ of the wavelength of the internal sound wave.
A sheet-like intermediate medium, which has a thickness of 9 to 14/36 and a thickness of 1/9 to 14/36 of the wavelength of the internal sound wave, is inserted into the groove of the metal plate and fixed with adhesive. A vibrator is stacked on a medium, and a liquid waterproof molding material made of the same material as the intermediate medium is poured around the vibrator and heated and hardened, so that the waterproof molding material and the intermediate medium are integrated and molded around the vibrator. and a method for manufacturing an ultrasonic transducer, characterized by covering the rear surface and fixing the vibrator.