Metallic acoustic matching layer and transducer

Abstract

To release heat generated by a piezoelectric vibrator to an acoustic medium, and suppress variations in acoustic impedance of an acoustic matching layer even when heated.SOLUTION: A metal acoustic matching layer that is made of metal and transmits sound waves to an acoustic medium includes an input end that inputs a sound wave, an output end that emits sound waves facing the acoustic medium, a mass portion formed with a predetermined thickness from the output end, and an acoustic impedance transforming portion having therein a filling material in contact with the mass portion, and the filling material is made of a material different from the material of the acoustic impedance transformation portion and the mass portion.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a transducer that transmits acoustic waves through an acoustic matching layer. [Background technology]

[0002] In acoustic devices such as fish finders, sonars, and acoustic communication devices, it is necessary to increase the power of the acoustic output to improve acoustic performance. In order to increase the power of an acoustic device, it is sufficient to increase the input electrical signal to the piezoelectric transducer that converts the electrical signal into mechanical vibration. However, as the mechanical vibration increases, the piezoelectric transducer also generates more heat, degrading the acoustic characteristics.

[0003] Although a method of directly cooling the piezoelectric transducer with an acoustic medium or the like is conceivable, the acoustic impedance of the acoustic medium of underwater acoustic devices, water (acoustic impedance: 1.5 Mrayls), is different from that of the piezoelectric transducer (acoustic impedance: 20-30 Mrayls), and so sound waves are reflected at the interface with the acoustic medium. In order to suppress reflection at this interface, a technique is known in which an acoustic matching layer is inserted between the acoustic medium, such as water, and the piezoelectric transducer (for example, Patent Documents 1 and 2). A material that provides an acoustic impedance between the water and the piezoelectric transducer is inserted into the acoustic matching layer, and a composite material in which a filler such as a metal or oxide is mixed into a resin-based material is widely used.

[0004] Patent Document 1 discloses a technique that employs a metal matching layer for heat dissipation and an acoustic medium for cooling. Patent Document 2 discloses a technique that fills a first acoustic matching layer made of a number of tapered columns with a second acoustic matching layer having a different acoustic impedance for acoustic impedance matching, gradually changing the acoustic impedance from the piezoelectric transducer to the acoustic medium. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 62-155000 [Patent Document 2] Japanese Patent Application Publication No. 11-89835 Summary of the Invention [Problem to be solved by the invention]

[0006] The acoustic matching layer is made of a material that provides acoustic impedance between the acoustic medium, water, and the piezoelectric transducer, and composite materials that contain fillers such as metals or oxides mixed into resin-based materials are widely used. However, compared to metals, resins have a large change in volume and elasticity with temperature, so the acoustic impedance determined by density and sound speed also changes with temperature, which makes it difficult to achieve acoustic matching when outputting high power sound.

[0007] The above-mentioned Patent Document 1 merely describes that the metal material of the acoustic matching layer has a smaller acoustic impedance than the piezoelectric transducer, and furthermore, the metal acoustic matching layer is only considered on the premise that existing bulk metals are used. Therefore, the metal materials that can be used are limited, there is little freedom in design, and it is not possible to achieve a wide bandwidth of acoustic characteristics.

[0008] In addition, in Patent Document 2, the tip of the first acoustic matching layer that radiates sound waves to the acoustic medium is narrowed, which causes a problem of poor acoustic radiation efficiency. In addition, the materials of the first and second acoustic matching layers in Patent Document 2 are determined only by the acoustic impedance parameter, but there is a problem that a broadband cannot be achieved under certain conditions, particularly when a metal is used for the first acoustic matching layer.

[0009] The present invention has been made in consideration of the above problems, and has an object to dissipate heat generated in a piezoelectric vibrator to an acoustic medium and to suppress fluctuations in the acoustic impedance of an acoustic matching layer even when heated. [Means for solving the problem]

[0010] The present invention is a metallic acoustic matching layer made of metal and transmitting sound waves to an acoustic medium, comprising an input end for inputting sound waves, an output end facing the acoustic medium and radiating sound waves, a mass portion formed with a predetermined thickness from the output end, and an acoustic impedance converting portion having a filler material therein that contacts the mass portion, wherein the filler material is made of a material different from the materials constituting the acoustic impedance converting portion and the mass portion. Effect of the Invention

[0011] Therefore, by adopting a metal for the acoustic matching layer, the present invention can realize stable acoustic characteristics even at high temperatures by dissipating heat generated by the piezoelectric transducer to the acoustic medium and suppressing the fluctuation of the acoustic impedance of the acoustic matching layer even when heat is applied. Also, by changing the shape of the acoustic impedance conversion section, it is possible to adopt various types of metal materials to achieve acoustic matching with the acoustic medium, increasing the degree of freedom in design and facilitating the widening of the acoustic bandwidth.

[0012] The details of at least one implementation of the subject matter disclosed herein are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the disclosed subject matter will become apparent from the following disclosure, drawings, and claims. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective cross-sectional view showing an example of a transducer according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a cross-sectional view illustrating an example of a vibrator according to a first embodiment of the present invention. [Diagram 3] FIG. 2 is a perspective view showing an example of a filler according to the first embodiment of the present invention. [Figure 4] FIG. 2 is a perspective view showing an example of an acoustic impedance converting portion according to the first embodiment of the present invention. [Diagram 5] FIG. 2 is a cross-sectional view showing a main part of a vibrator according to a first embodiment of the present invention. [Figure 6] FIG. 1 shows a bending vibration model according to the first embodiment of the present invention. [Figure 7] FIG. 1 shows the first embodiment of the present invention and is a diagram illustrating a vibration model. [Figure 8] 1 is a graph showing an example of the relationship between the acoustic transmittance of the acoustic impedance converting portion and the frequency depending on whether or not a mass portion is present, according to the first embodiment of the present invention. [Figure 9] 1 is a graph showing the relationship between the acoustic transmittance of the acoustic impedance converting portion and the frequency depending on the thickness of the mass portion according to the first embodiment of the present invention. [Figure 10] 1 is a graph showing the relationship between the acoustic transmittance and frequency of the acoustic impedance converting portion depending on the presence or absence of a filler, according to the first embodiment of the present invention. [Figure 11] 4 is a graph showing an example of the shape of the horn according to the first embodiment of the present invention. [Figure 12] 1 is a graph showing Example 1 of the present invention, illustrating the relationship between the acoustic transmittance of the acoustic impedance converter and the frequency depending on the shape of the acoustic impedance converter. [Figure 13] 1 is a graph showing Example 1 of the present invention, illustrating the relationship between the sound velocity ratio between the filler and the acoustic impedance converting portion and the upper limit frequency. [Figure 14] 1 is a graph showing Example 1 of the present invention, illustrating the relationship between the specific acoustic impedance ratio of a filler and an acoustic impedance converting portion and the upper limit frequency. [Figure 15] FIG. 11 is a cross-sectional view showing an example of a vibrator according to a second embodiment of the present invention. [Figure 16] 11 is a graph showing a relationship between the acoustic transmittance and the frequency of an acoustic impedance converting portion according to a second embodiment of the present invention. [Figure 17] FIG. 11 is a perspective view of a filler according to a third embodiment of the present invention. [Figure 18] FIG. 11 is a perspective view of a filler according to a fourth embodiment of the present invention. [Figure 19] FIG. 11 is a perspective view of a transducer according to a fifth embodiment of the present invention. [Figure 20] FIG. 13 is a perspective view of a transducer according to a sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. EXAMPLES

[0015] 1 shows a first embodiment of the present invention, and is a perspective cross-sectional view showing an example of a transducer 1 using a plurality of transducers 2 each having an acoustic matching layer made of a metal material and a filler. The transducer 1 of this embodiment outputs a sound wave into water as an acoustic medium to detect and measure the distance to an object.

[0016] The transducer 1 has multiple transducers 2 arranged in a lattice pattern inside a watertight case 100 formed in the shape of a rectangular box and connected to an underwater cable 101.The transducers 2 are vibrated by an electrical signal input from the underwater cable 101, and sound waves are output to an acoustic medium.

[0017] The watertight case 100 has an opening at the top in the figure, and the end faces of the transducers 2 are arranged in a lattice pattern facing the opening. The opening of the watertight case 100 contacts an acoustic medium (water, seawater) via a vibration transmission member (not shown), and outputs sound waves generated by the transducers 2 to the acoustic medium.

[0018] The transducers 2 arranged in a lattice have sound-proofing material 102 made of resin or the like arranged between adjacent transducers 2 to suppress transmission of vibration between the adjacent transducers 2. The underwater cable 101 is connected to a control device (not shown). In the illustrated example, the transducers 2 are formed in a rectangular column shape, but the shape of the transducer 2 is not limited to this and may be cylindrical or the like.

[0019] Fig. 2 is an axial cross-sectional view of the transducer 2 shown in Fig. 1. The transducer 2 is composed of a backing 5, a piezoelectric transducer 4, and a metal acoustic matching layer 3, in that order from the bottom surface on the side of the watertight case 100 shown in Fig. 1.

[0020] The backing 5 is composed of a member that supports the piezoelectric vibrator 4. The piezoelectric vibrator 4 is sandwiched between electrodes 41 and 42, and vibrates in response to an electric signal applied to the electrodes 41 and 42, converting it into an acoustic signal. A metal acoustic matching layer 3 is disposed on the upper surface of the electrodes 42 that sandwich the piezoelectric vibrator 4.

[0021] The metal acoustic matching layer 3 is composed of a columnar member whose bottom surface on the piezoelectric vibrator 4 side is an input end 3A for inputting sound waves, and whose top surface in the figure faces the acoustic medium 9 and radiates sound waves is an output end 3B. The metal acoustic matching layer 3 has the function of transmitting an acoustic signal (vibration) received at the input end 3A to the output end 3B, and matching the acoustic impedance at the output end 3B with that of the acoustic medium 9. The metal acoustic matching layer 3 is formed of a metal such as an aluminum alloy, for example.

[0022] In order to set the acoustic impedance to a predetermined condition, the metal acoustic matching layer 3 has three layers inside: a space 33 filled with a filler 6, a mass section 32 having a predetermined thickness t from the output end 3B, an acoustic impedance conversion section 30 covering the space 33, and a base section 31 connecting the acoustic impedance conversion section 30 to the input end 3A on the piezoelectric transducer 4 side.

[0023] The metal acoustic matching layer 3 may be formed by forming three layers, the base 31, the acoustic impedance converting section 30 having the space 33, and the mass section 32, separately, filling the space 33 with the filler 6, and then bonding the three layers together. Alternatively, the base 31, the acoustic impedance converting section 30 filled with the filler 6, and the mass section 32 may be integrally formed using a 3D printer capable of switching materials.

[0024] As the filler 6 filled in the space 33, for example, a composite material such as syntactic foam in which hollow microspheres made of glass, metal, polymer, etc. are solidified with resin can be used.

[0025] The filler 6 is not limited to syntactic foam and may be a resin, metal or composite material as long as it satisfies the acoustic conditions (acoustic impedance and sound speed) described below. The metal acoustic matching layer 3 may be made of a desired metal material according to the acoustic conditions, such as iron, aluminum, or an alloy.

[0026] The configuration of the metal acoustic matching layer 3 includes a mass portion 52 formed at a predetermined thickness t from the output end 3B, and an acoustic impedance converting portion 30 having a filler 6 therein that contacts the mass portion 52, and the filler 6 is made of a material different from the materials constituting the acoustic impedance converting portion 30, the mass portion 32 and the base portion 31.

[0027] 3, the shape of the filler 6 (and space 33) in this embodiment is formed of a tubular member with an annular cross section having an apex 6A with a closed shape toward the input end 3A of the metal acoustic matching layer 3 and an open end 6B formed of an end face that opens toward the output end 3B on the acoustic medium 9 side. The shape of the filler 6 (and space 33) is not limited to a tubular member with an annular cross section, and can be formed of a plate-like member or a columnar member in addition to the tubular member.

[0028] In addition, the distance from the input end 3A to the apex 6A of the filler 6 of the base 31 may be set to a predetermined distance such as ¼ wavelength of the frequency to be mainly used.

[0029] Here, as shown in FIG. 4, the acoustic impedance conversion part 30 is formed as a horn-shaped (or funnel-shaped) member that covers the outer periphery of the filler 6 on the inner periphery of the cylindrical filler 6. The acoustic impedance conversion part 30 that covers the outer periphery of the filler 6 has a plane surrounded by the apex 6A of the filler 6 as an input part 30A, and a plane surrounded by the inner periphery of the open end 6B of the filler 6 as an output part 30B. The horn-shaped part of the acoustic impedance conversion part 30 can have an end face (output part 30B) on the output end 3B side as a horn throat, and an end face (input part 30A) on the piezoelectric vibrator 4 side as a horn mouth. The output part 30B of the acoustic impedance conversion part 30 on the inner periphery of the filler 6 and the acoustic impedance conversion part 30 that surrounds the outer periphery of the filler 6 are connected to a mass part 32.

[0030] The acoustic output (sound waves) generated by the piezoelectric vibrator 4 enters the acoustic impedance conversion section 30 from the base 31, passes through a path whose cross-sectional area gradually decreases from the input section 30A to the output section 30B, and then passes through the mass section 32 before being output to the acoustic medium 9.

[0031] As will be described later, the frequency characteristics output from the metal acoustic matching layer 3 to the acoustic medium 9 can be optimized depending on the horn-shaped shape of the acoustic impedance converting section 30 extending from the input section 30A to the output section 30B and the size of the mass section 32.

[0032] That is, by using metal for the acoustic matching layer, heat generated in the piezoelectric vibrator 4 is smoothly released to the acoustic medium 9, and fluctuations in the acoustic impedance of the metal acoustic matching layer 3 are suppressed even when heat is applied, thereby realizing stable acoustic characteristics even at high temperatures. Also, by changing the shape of the acoustic impedance conversion section 30 extending from the input section 30A to the output section 30B, various types of metal materials can be used for the metal acoustic matching layer 3 to achieve acoustic matching with the acoustic medium 9, increasing the degree of freedom in design and facilitating a wide acoustic bandwidth. The horn-shaped shape of the acoustic impedance conversion section 30 and the size of the mass section 32 will be described later.

[0033] Fig. 5 is an axial cross-sectional view showing a main part of the transducer 2 shown in Fig. 1. In Fig. 5, an example is shown in which the acoustic impedance converting part 30 functions as a leg part 300 supporting the mass part 32 facing the acoustic medium 9.

[0034] When an electrical signal is input between electrodes 41 and 42, the piezoelectric transducer 4 vibrates to generate sound waves, which are emitted from the input end 3A of the metal acoustic matching layer 3, through the acoustic impedance converter 30, and from the output end 3B to the acoustic medium 9.

[0035] When there is an acoustic impedance mismatch between the metallic acoustic matching layer 3 and the acoustic medium 9, the sound waves are reflected at the output end 3B, which serves as the boundary surface, and the efficiency of radiating the sound waves to the acoustic medium 9 decreases.

[0036] For this reason, the metal acoustic matching layer 3 in this embodiment is a metallic acoustic impedance conversion section 30 containing a filler 6, which matches the acoustic impedance between the metal acoustic matching layer 3 and the acoustic medium 9, smoothly radiating sound waves from the output end 3B, which serves as the boundary surface, to the acoustic medium 9, thereby improving the heat dissipation and acoustic characteristics of the piezoelectric vibrator 4.

[0037] The density of the metal constituting the metallic acoustic matching layer 3 is ρ A and the speed of sound is C A and the density ρ A and the speed of sound C A The product of these is the specific acoustic impedance z A The specific acoustic impedance z of the metallic acoustic matching layer 3 is A and the cross-sectional area S of the metallic acoustic matching layer 3. A The product of these is the acoustic impedance Z A However, the cross-sectional area S A is the area in the cross-sectional direction indicated by the arrow CC in FIG.

[0038] Next, the density, sound velocity, specific acoustic impedance, cross-sectional area, and acoustic impedance of the acoustic medium 9 such as water are respectively expressed as ρ B , C B , z B , S B , Z B Let us assume that.

[0039] If the cross-sectional area of ​​the narrowest portion (cross section D in the figure) of the acoustic impedance converting portion 30 in the path connecting to the mass portion 32 is S, the cross-sectional area S is expressed by the following formula (1).

[0040]

number

[0041] In addition, regarding the propagation of the sound waves generated by the piezoelectric vibrator 4, the ratio in decibels between the sound pressure in the metal acoustic matching layer 3 measured at point A in Figure 5 and the sound pressure in the acoustic medium 9 measured at point B in Figure 5 is defined as the acoustic transmittance.

[0042] 5, the acoustic impedance converting portion 30 surrounding (sandwiching) the filler 6 (space 33) can be treated as legs 300 supporting a mass portion 32 that radiates sound waves to an acoustic medium 9. As shown in Fig. 6, sound waves transmitted from the piezoelectric vibrator 4 via the base portion 31 to the legs 300 cause the mass portion 32 supported by the ends of the legs 300, 300 to undergo bending vibration.

[0043] Here, Fig. 8 shows an example of the acoustic transmittance when a mass portion 32 is provided at the end of the leg portion 300 as shown in Fig. 6, and when sound waves are emitted from the end of the leg portion 300 without providing the mass portion 32. Fig. 8 is a graph showing an example of the relationship between the acoustic transmittance and frequency of the acoustic impedance converting portion 30 depending on whether or not the mass portion 32 is provided.

[0044] In the graph shown, the specific acoustic impedance z of the acoustic medium 9 B = 1.5 Mrayls, the specific acoustic impedance z of the acoustic impedance converter 30 in the metal acoustic matching layer 3 A =16.7Mrayls, speed of sound C A = 6230 m / s, specific acoustic impedance z of filling material 6 R = 1.5 Mrayls, sound velocity C of filling material 6 r Here is an example where =6230m / s.

[0045] As shown in Figure 8, compared to the case where sound waves are radiated from the acoustic impedance conversion unit 30 without providing a mass unit 32 (without a mass unit in the figure), providing a mass unit 32 supported by the legs 300 of the acoustic impedance conversion unit 30 (with a mass unit in the figure) makes it possible to improve the acoustic transmittance.

[0046] The configuration in which the legs 300, 300 surrounding the filler 6 support the mass section 32 can be considered equivalent to the spring 8 supporting the mass 7 as shown in Fig. 7. The inventors of the present application have studied the frequency characteristics of the spring-mass vibration system by changing the thickness t of the mass section 32 shown in Fig. 5. Fig. 9 is a graph showing the relationship between the acoustic transmittance of the acoustic impedance conversion section 30 and the frequency according to the thickness t of the mass section 32.

[0047] In the example of Fig. 9, the thickness t of the mass portion 32 was changed between 1 mm and 10 mm to study the effect of resonance in the operating frequency range of the transducer 1. As shown in the figure, by changing the thickness t of the mass portion 32, there exists a thickness t at which the acoustic transmittance within the operating frequency range is improved due to the effect of spring-mass resonance. For example, when the thickness t = 10 mm or when the thickness t = 4 mm, the acoustic transmittance within the operating frequency range is increased.

[0048] The spring-mass resonance frequency is determined by the thickness t of the mass portion 32 of the mass element and the acoustic impedance converting portion 30 (leg portion 300) which is a spring element. Therefore, by appropriately setting the thickness t and the spring constant of the leg portion 300, the spring-mass resonance frequency can be set within the operating frequency range, thereby improving the acoustic transmittance.

[0049] Furthermore, by changing the thickness t of the mass portion 32, there exists a thickness t at which the acoustic transmittance within the operating frequency range deteriorates due to the influence of bending resonance. For example, when the thickness t is 1 mm, the acoustic transmittance suddenly decreases and deteriorates at the bending resonance frequency within the operating frequency range.

[0050] The bending resonance frequency is determined by the mass and thickness t of the mass portion 32, and the width (spacing of the leg portions 300) of the mass portion 32. Therefore, the mass and thickness t of the mass portion 32 and the dimensions, shape, or material of the leg portions 300 (filler 6 or space 33) may be appropriately changed so that the bending resonance frequency falls outside the operating frequency range.

[0051] Next, the relationship between the space 33 and the filler 6 will be described. Fig. 10 is a graph showing the relationship between the acoustic transmittance and frequency of the acoustic impedance converter 30 depending on the presence or absence of the filler 6. In the illustrated example, the solid line shows the case where syntactic foam is used as the filler 6, and the dashed line shows the case where no material is filled in the space 33.

[0052] By filling the space 33 of the acoustic impedance converter 30 with the filler 6, it is possible to maintain a good acoustic transmittance within the operating frequency range, compared to when the space 33 is used as a cavity. If the space 33 is used as a cavity, the acoustic transmittance deteriorates in the high frequency region within the operating frequency range. For this reason, the acoustic transmittance is improved by filling the space 33 with the filler 6.

[0053] Next, the shapes of the filler 6 and the acoustic impedance converting portion 30 will be described. As shown in Fig. 3, the filler 6 is made of a cylindrical member (composite material) having an apex 6A closed toward the input end 3A of the metal acoustic matching layer 3 and a bottom surface open toward the output end 3B. The space 33 is also made of the same shape as the filler 6.

[0054] The acoustic impedance conversion section 30 inside the cylindrical filler 6 comprises a planar input section 30A with a large diameter facing the input end 3A, and a planar output section 30B with a small diameter facing the output end 3B, as shown in Figure 4.

[0055] Acoustic impedance converting section 30 inside filler 6 becomes a horn-shaped section from output section 30B to input section 30A, with output section 30B corresponding to the throat of the horn and input section 30A corresponding to the horn-shaped mouth.

[0056] In this embodiment, the acoustic impedance transforming section 30 inside the filler 6 is configured in a horn shape, and the shape of the horn from the output section 30B to the input section 30A is configured with a curved surface. The shape of the horn is determined according to the parameter T as shown in FIG.

[0057] The parameter T is a constant that indicates the shape of the side surface of the horn and varies between T = 1 and ∞. The relationship between the parameter T and the shape of the horn is as described in "Introduction to Electrical Acoustics, by Kawamura Masayasu, Shokodo, published on January 1, 1983, pages 70-71."

[0058] When the parameter T = ∞, the shape of the horn becomes conical as shown by the dashed line in Figure 11, the cross section in the axial direction becomes trapezoidal, and the side of the horn from the horn throat to the horn mouth becomes a straight inclined surface, forming a solid truncated cone.

[0059] When the parameter T=0, the shape of the horn becomes catenoidal as shown by the two-dot chain line in FIG. 11, and the curved periphery has the greatest curvature from the horn throat to the horn mouth, and the side of the acoustic impedance conversion section 30 becomes curved as shown in FIG. 4.

[0060] When the parameter T=0.5, the horn shape becomes hyperbolic, and the curvature from the horn throat to the horn mouth becomes smaller than that of the catenoidal shape, as shown by the solid line in Figure 11. Furthermore, when the parameter T=1, the horn shape becomes exponential, and the curvature from the horn throat to the horn mouth becomes smaller than that of the hyperbolic shape, as shown by the dashed line in Figure 11.

[0061] Using the above parameter T, the shape of the acoustic impedance transforming portion 30 inside the filler 6 shown in FIG. 4 is defined by the cross-sectional area S (Sx in FIG. 11) in the radial direction of the horn, and is expressed by the following equation (2).

[0062]

number

[0063] 11, x is the distance from the horn throat, and m is the horn's divergence constant, which is a parameter determined by the length and spacing of the acoustic impedance converter 30. The divergence constant m is set so that the sides of adjacent fillers 6 are closed at apex 6A. The divergence constant m is as described in the above-mentioned "Introduction to Electroacoustic Engineering."

[0064] 12 is a graph showing the relationship between the shape of the side surface of the acoustic impedance converter 30, the acoustic transmittance, and frequency. In the case of a conical shape with parameter T=∞, ripples are generated in the high frequency range, adversely affecting the acoustic transmittance in the operating frequency range.

[0065] In contrast, in the case of hyperbolic with parameter T=0.5 or exponential-on with T=1, it is possible to maintain good acoustic transmittance in the operating frequency range. Therefore, it is preferable to set the parameter T to 1 or less, configure the shape of the side surface of the acoustic impedance conversion section 30 inside the filler 6 with a convex curved surface toward the axis of the cylindrical filler 6, and set the aperture (area) of the input section 30A to be larger than the aperture of the output section 30B. This makes it possible to suppress ripples in the high frequency range and maintain good acoustic transmittance.

[0066] Next, the acoustic conditions of the filler 6 and the acoustic impedance conversion section 30 will be considered. The filler 6, which is made of a composite material such as syntactic foam, has a specific acoustic impedance z R is the specific acoustic impedance z of the acoustic medium 9 that emits the sound waves. B The filler 6 is a material with a sound velocity C close to R is the sound velocity C of the acoustic impedance conversion section 30 A Materials close to this are preferable.

[0067] 13 and 14 show the relationship between the filler 6, the acoustic impedance converter 30, and the acoustic medium 9. In the examples of FIGS. 13 and 14, the specific acoustic impedance z B= 1.5 Mrayls, the specific acoustic impedance z of the acoustic impedance conversion unit 30 (acoustic medium A) A =16.7Mrayls, speed of sound C A = 6230 m / s, specific acoustic impedance z of filling material 6 R = 1.8 Mrayls, sound velocity C of filling material 6 R Here is an example where = 2250 m / s.

[0068] FIG. 13 shows the sound velocity ratio (C R / C A 2 is a graph showing the relationship between the upper limit frequency and the frequency at which the transducer 2 can radiate the acoustic power to the acoustic medium 9.

[0069] FIG. 13 shows the sound velocity C A = 6230 m / s, specific acoustic impedance z of filling material 6 R The specific acoustic impedance z of the acoustic medium B Here is an example where the value is fixed at 1.5Mrayls.

[0070] In this embodiment, the sound velocity ratio (C R / C A ) to 0.35 or more, an upper limit frequency according to the frequency range to be used can be obtained, and good frequency characteristics can be realized. In contrast, in Patent Document 2, when a metal matching layer is used as the first matching layer, the region of Cr / Ca<0.35 is reached, and a wide frequency band of frequency characteristics cannot be expected.

[0071] FIG. 14 shows the specific acoustic impedance ratio (z R / z A ) and the upper limit frequency. In the illustrated example, the specific acoustic impedance z A = 16.7 Mrayls, sound velocity C of filling material 6 R The acoustic impedance conversion section 30 has the same sound velocity C A Here is an example where the speed is fixed at 6230 m / s.

[0072] In this embodiment, the specific acoustic impedance ratio (z R / z A ) to 0.75 or less, an upper limit frequency according to the frequency range used can be obtained, thereby realizing good frequency characteristics.

[0073] As described above, in the transducer 1 of this embodiment, a metal acoustic matching layer 3 is disposed on the end face where the vibrator 2 outputs sound waves to the acoustic medium 9, and the metal acoustic matching layer 3 is provided with an acoustic impedance conversion section 30, a filler 6, and a mass section 32, thereby realizing heat dissipation from the piezoelectric vibrator 4 and ensuring acoustic transmittance and frequency characteristics.

[0074] By bringing the metal acoustic matching layer 3 into contact with the piezoelectric vibrator 4, it is possible to efficiently dissipate heat from the piezoelectric vibrator 4, and it is possible to maintain the acoustic characteristics while increasing the output of the piezoelectric vibrator 4. This makes it possible to provide a high-output transducer with stable acoustic characteristics even at high temperatures, and when the acoustic medium 9 is water or seawater, it becomes possible to capture distant objects. EXAMPLES

[0075] Fig. 15 is a cross-sectional view of a transducer 2 showing a second embodiment. In the second embodiment, a plurality of mass portions 32, 320 are provided in the metallic acoustic matching layer 3 of the transducer 2 to further improve the frequency characteristics, and the same elements as those in Fig. 2 of the first embodiment are given the same reference numerals and redundant explanations will be omitted.

[0076] The metal acoustic matching layer 3 of the present embodiment is configured by adding a filler 60 (second filler) and a mass portion 320 (second mass portion) between the mass portion 32 (first mass portion) of the above-mentioned Example 1 and the output end 3B of the metal acoustic matching layer 3, and the other configurations are the same as those of the above-mentioned Example 1.

[0077] Filler 60 is a cylindrical member configured in the same shape as open end 6B of filler 6 (first filler), and the inside of filler 60 is filled with a composite material such as syntactic foam, similar to filler 6. Filler 6 and filler 60 are arranged coaxially and are spaced apart by the thickness t1 of mass portion 32.

[0078] A cylindrical space 330 is formed in the metal acoustic matching layer 3 to accommodate the filler 60. The filler 60 is desirably made of the same material as the filler 6.

[0079] Thickness t1 of mass portion 32 is the distance from open end 6B of filler 6 to the bottom surface of filler 60, and thickness t2 of mass portion 320 is the distance from the top surface of filler 60 in the figure to output end 3B.

[0080] Fig. 16 is a graph showing the relationship between acoustic transmittance and frequency depending on the presence or absence of mass section 320. The solid line in the figure shows the frequency characteristics when mass section 320 is added to mass section 32 shown in Fig. 15, and the dashed line in the figure shows the frequency characteristics when mass section 320 is not added.

[0081] By arranging multiple fillers 6, 60 coaxially within the metal acoustic matching layer 3 and providing a mass section 32 between the fillers 6, 60 and a mass section 320 between the filler 60 and the output end 3B, the acoustic transmittance in the high frequency region within the operating frequency range can be improved.

[0082] 16 shows an example in which the thickness t1 of the mass part 32 is 5 mm, and the thickness t2 of the mass part 320 is 10 mm. The thicknesses of the mass part 32 and the mass part 320 can be set appropriately depending on the materials of the metal acoustic matching layer 3 and the fillers 6 and 60, and the frequency range used.

[0083] When producing the metal acoustic matching layer 3, the acoustic impedance converting portion 30, the base portion 31, the mass portion 32, the mass portion 320 and the space 330 are each formed separately, and the spaces 33, 330 are filled with the fillers 6, 60, respectively, before the various portions are joined together. EXAMPLES

[0084] FIG. 17 is a perspective view of a filler 6X showing a third embodiment. The filler 6X is made of a bullet-shaped columnar member instead of the cylindrical member of the first embodiment. The filler 6X is disposed inside the acoustic impedance conversion section 30 with the apex 6A facing the piezoelectric transducer 4 and the bottom surface 6C facing the output end 3B. Although not shown, the space inside the acoustic impedance conversion section 30 is also configured in the same shape as the filler 6X. The other configurations are the same as those of the first embodiment.

[0085] The sound waves output from the piezoelectric vibrator 4 pass through the acoustic impedance converter 30, whose cross-sectional area gradually decreases from the apex 6A to the bottom surface 6C, and then pass through the mass portion 32 and are radiated to the acoustic medium 9. By configuring the shape of the side surface of the filler 6X to be the same as the horn shape of the first embodiment, the acoustic characteristics can be improved. EXAMPLES

[0086] FIG. 18 is a perspective view of a filler 6Y showing a fourth embodiment. The filler 6Y is formed as a plate-like member having a cross section of the bullet-shaped columnar member of the third embodiment. The filler 6Y is disposed inside the acoustic impedance conversion section 30 with the apex 6A facing the piezoelectric transducer 4 and the bottom surface 6C facing the output end 3B. Although not shown, the space inside the acoustic impedance conversion section 30 is also configured in the same shape as the filler 6Y. The other configurations are the same as those of the first embodiment.

[0087] The sound waves output from the piezoelectric vibrator 4 pass through the acoustic impedance converter 30, whose cross-sectional area gradually decreases from the apex 6A to the bottom surface 6C, and then pass through the mass portion 32 to be radiated to the acoustic medium 9. By configuring the shape of the side surface of the filler 6Y to be the same as the horn shape of the first embodiment, the acoustic characteristics can be improved. EXAMPLES

[0088] 19 is a cross-sectional perspective view of a transducer 1 showing a fifth embodiment. The transducer 1 of this embodiment is similar to the first embodiment in other respects, except that an acoustic window 104 and insulating oil 103 are added to the first embodiment.

[0089] An acoustic window 104 is grounded at the opening of the watertight case 100 to seal the inside of the watertight case 100. Insulating oil is filled between the acoustic window 104 and the transducer 2 and between the acoustic window 104 and the sound-insulating material 102.

[0090] The sound waves output from the vibrator 2 are radiated to the acoustic medium 9 via the insulating oil 103 and the acoustic window 104. By protecting the vibrator 2 with the acoustic window 104 and the insulating oil 103, the durability of the transducer 1 can be ensured. EXAMPLES

[0091] 20 is a cross-sectional perspective view of a transducer 1 showing a sixth embodiment. The transducer 1 of this embodiment is the same as that of the first embodiment except that a resin mold 105 is added to the configuration of the first embodiment.

[0092] The opening of the watertight case 100 is filled with a resin mold 105 to protect the end face of the vibrator 2 and the sound insulating material 102 from the acoustic medium 9. The sound waves output from the vibrator 2 are radiated to the acoustic medium 9 via the resin mold 105. By protecting the vibrator 2 with the resin mold 105, the durability of the transducer 1 can be ensured. <Conclusion>

[0093] In the transducer 1 and vibrator 2 of Examples 1 to 6, by using a metal acoustic matching layer, heat generated in the piezoelectric vibrator 4 is dissipated to the metal acoustic matching layer 3, and the acoustic impedance of the metal acoustic matching layer 3 hardly changes even when heat is applied, so that stable acoustic matching can be achieved even at high temperatures. This makes it possible to provide a high-output transducer 1 with stable acoustic characteristics regardless of temperature.

[0094] By changing the shape of the acoustic impedance converter 30 so that the cross-sectional area gradually decreases, acoustic matching with the acoustic medium 9 can be achieved regardless of the metal material, increasing the degree of freedom in design and facilitating a broadband design.

[0095] By providing one or more mass portions 32, 320 on the acoustic medium 9 side of the acoustic impedance converter 30, the acoustic radiation efficiency can be improved and a wider frequency band can be realized.

[0096] Inside the metal acoustic matching layer 3, by combining a filler 6 made of a material different from that of the acoustic impedance converting section 30, it is possible to obtain acoustic characteristics (acoustic transmittance and frequency characteristics) that are suitable for the metal acoustic matching layer 3.

[0097] That is, in the conventional example, two materials are specified within the range of acoustic impedance, but the inventors of the present application found that, particularly when the acoustic matching layer is made of metal, the sound speed ratio between the metal and the filler 6 contributes significantly to the characteristics. In the conventional example, there exist conditions under which the acoustic characteristics are significantly deteriorated, whereas in the transducer 1 of Examples 1 to 6, by specifying the sound speed ratio between the metal and the filler 6, it is possible to derive design conditions suitable for the metallic acoustic matching layer 3.

[0098] As described above, the acoustic matching layers of Examples 1 to 6 can be configured as follows.

[0099] (1) A metallic acoustic matching layer 3 made of a metal and transmitting sound waves to an acoustic medium 9, comprising: an input end 3A for inputting sound waves; an output end 3B facing the acoustic medium 9 for radiating sound waves; a mass portion 32 formed from the output end 3B with a predetermined thickness t; and an acoustic impedance converting portion 30 having a filler 6 therein that contacts the mass portion 32, wherein the filler 6 is made of a material different from the materials constituting the acoustic impedance converting portion 30 and the mass portion 32.

[0100] With the above configuration, by using a metal for the acoustic matching layer, the heat generated by the piezoelectric vibrator 4 is released to the acoustic medium 9, and the fluctuation in the acoustic impedance of the metal acoustic matching layer 3 is suppressed even when heat is applied, thereby realizing stable acoustic characteristics even at high temperatures. In addition, by changing the shape of the acoustic impedance conversion section 30, various types of metal materials can be used to achieve acoustic matching with the acoustic medium, increasing the freedom of design and facilitating a wide acoustic bandwidth.

[0101] (2) The metal acoustic matching layer according to (1) above, characterized in that the mass portion 32 is supported by the acoustic impedance conversion portion 30 that sandwiches the filler 6, and a spring-mass resonance frequency determined by the mass portion 32 and the acoustic impedance conversion portion 30 is set within a preset frequency range.

[0102] With the above-mentioned configuration, by setting the spring-mass resonance frequency within the frequency range to be used, it is possible to suppress the decrease in sound transmittance in the high frequency range and obtain good acoustic characteristics.

[0103] (3) The metal acoustic matching layer described in (1) above, wherein the mass portion 32 is configured with a predetermined thickness t between the output end 3B and the acoustic impedance converting portion 30, and the mass portion 32 is supported by the acoustic impedance converting portion 30 sandwiching the filler 6 therebetween, and a flexural resonance frequency determined by the mass portion 32, the acoustic impedance converting portion 30, and a width by which the mass portion 32 is supported by the acoustic impedance converting portion 30 is set outside a preset frequency range.

[0104] With the above-described configuration, by setting the bending resonance frequency outside the frequency range in which the device is used, it is possible to suppress the decrease in sound transmittance in the high frequency range and obtain good acoustic characteristics.

[0105] (4) The metallic acoustic matching layer according to (1) above, wherein the mass portion 32 is arranged in plurality between the output end 3B and the acoustic impedance converting portion 30.

[0106] With the above-described configuration, the spring-mass resonance frequency can be effectively utilized by the multiple mass portions, and the acoustic characteristics can be improved.

[0107] (5) The metallic acoustic matching layer according to (1) above, wherein the filler 6 has a specific acoustic impedance z R and the specific acoustic impedance z of the acoustic impedance converter 30. A The ratio of z R / z A is 0.75 or less, and the sound velocity C R and the sound velocity C of the acoustic impedance converter 30 A Ratio of C R / C A A metallic acoustic matching layer, characterized in that:

[0108] With the above-mentioned configuration, the sound velocity ratio (C R / C A By setting the ratio of the specific acoustic impedance (z) to 0.35 or more, it is possible to obtain an upper limit frequency according to the frequency range to be used, and to realize a good frequency characteristic. R / z A ) to 0.75 or less, an upper limit frequency according to the frequency range used can be obtained, thereby realizing good frequency characteristics.

[0109] (6) The metal acoustic matching layer according to (1) above, wherein the acoustic impedance conversion section 30 is configured in a horn shape from the end face connected to the mass section 32 toward the input end 3A, and the side surface of the horn shape is configured as a curved surface.

[0110] With the above configuration, by changing the shape of the acoustic impedance conversion part 30 into a horn shape so that the cross-sectional area gradually decreases, it becomes possible to achieve acoustic matching with the acoustic medium 9 regardless of the metal material, thereby increasing the freedom of design and facilitating a broadband design.

[0111] (7) The metallic acoustic matching layer according to (6) above, characterized in that the cross-sectional area S of the horn-shaped acoustic impedance converting section 30 forming the curved surface is expressed by the above formula (2) when the area of ​​the end face connected to the mass section 32 is S0, the distance from the end face is x, the spreading coefficient of the horn is m, and the parameter determining the shape of the horn is T.

[0112] With the above configuration, by changing the shape of the acoustic impedance conversion part 30 into a horn shape so that the cross-sectional area gradually decreases, it becomes possible to achieve acoustic matching with the acoustic medium 9 regardless of the metal material, thereby increasing the freedom of design and facilitating a broadband design.

[0113] (8) The metal acoustic matching layer according to (6) above, characterized in that the filler 6 is composed of a tubular member having an apex toward the input end 3A, a flat opening end on the acoustic medium 9 side, and a curved side surface.

[0114] With the above-mentioned configuration, the acoustic impedance conversion section 30 on the inner periphery of the cylindrical filler 6 has a horn shape and its cross-sectional area gradually decreases, making it possible for any metal material to acoustically match with the acoustic medium 9, increasing the freedom of design and facilitating a broadband design.

[0115] The present invention is not limited to the above-mentioned embodiment, and various modifications are included. For example, the above-mentioned embodiment is described in detail to easily explain the present invention, and is not necessarily limited to those having all the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, the addition, deletion, or replacement of other configurations can be applied to a part of the configuration of each embodiment, either alone or in combination. [Explanation of symbols]

[0116] 1 Transducer 2 Transducers 3 Metal acoustic matching layer 4 Piezoelectric vibrator 3A input terminal 3B Output end 5. Backing 6 Filling material 6A Top 6B Open end 30 Acoustic impedance conversion section 30A input section 30B output section 31 Base 32 parts by mass 33 Space 41, 42 electrode 100 Watertight case 101 Underwater Cable 102 Soundproofing material

Claims

1. A metallic acoustic matching layer that is made of a metal and transmits a sound wave to an acoustic medium, An input terminal for inputting a sound wave; an output end that faces an acoustic medium and radiates acoustic waves; a mass portion formed to a predetermined thickness from the output end; an acoustic impedance converting portion having a filler therein and in contact with the mass portion; having The filler is A metallic acoustic matching layer, which is made of a material different from the material constituting the acoustic impedance conversion portion and the mass portion.

2. 2. The metallic acoustic matching layer according to claim 1, The metal acoustic matching layer is characterized in that the mass portion is supported by the acoustic impedance conversion portion that sandwiches the filler, and a spring-mass resonance frequency determined by the mass portion and the acoustic impedance conversion portion is set within a predetermined frequency range.

3. 2. The metallic acoustic matching layer according to claim 1, The metal acoustic matching layer is characterized in that the mass portion is configured to have a predetermined thickness between the output end and the acoustic impedance conversion portion, and is supported by the acoustic impedance conversion portion which sandwiches the filler, and a flexural resonance frequency determined by the mass portion, the acoustic impedance conversion portion, and a width at which the mass portion is supported by the acoustic impedance conversion portion is set outside a predetermined frequency range.

4. 2. The metallic acoustic matching layer according to claim 1, The metallic acoustic matching layer is characterized in that a plurality of the mass portions are arranged between the output end and the acoustic impedance conversion portion.

5. 2. The metallic acoustic matching layer according to claim 1, The specific acoustic impedance z of the filler Ｒ and the specific acoustic impedance z of the acoustic impedance converter. Ａ The ratio z Ｒ / z Ａ is 0.75 or less, and the sound velocity C Ｒ and the sound velocity C of the acoustic impedance converter. Ａ Ratio C Ｒ / C Ａ 2. A metallic acoustic matching layer, characterized in that:

6. 2. The metallic acoustic matching layer according to claim 1, The acoustic impedance converter includes: A metallic acoustic matching layer having a horn shape extending from an end face connected to said mass portion toward said input end, said horn shape having curved sides.

7. The metallic acoustic matching layer according to claim 6, The cross-sectional area S of the horn-shaped acoustic impedance converting portion forming the curved surface is expressed as follows, assuming that the area of ​​the end face connected to the mass portion is S0, the distance from the end face is x, the expansion coefficient of the horn is m, and the parameter determining the shape of the horn is T: [0010] A metallic acoustic matching layer characterized by being represented by the formula:

8. The metallic acoustic matching layer according to claim 6, The filler is A metallic acoustic matching layer characterized in that it is composed of a tubular member having an apex toward the input end, a flat open end on the acoustic medium side, and a curved side surface.

9. A transducer having the metallic acoustic matching layer according to any one of claims 1 to 8, A transducer comprising a piezoelectric vibrator provided at an input end of the metallic acoustic matching layer.

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