Underwater sound low-frequency transducer structure and manufacturing method

Abstract

The invention provides a deepwater-resistant low-frequency transducer structure and a manufacturing method. The deepwater-resistant low-frequency transducer structure comprises transducer array elements, a front-end bracket, a rear-end bracket, a heavy back lining filler and a transducer shell, the low-frequency transducer structure for underwater sound can be used in a standing wave tube, and is suitable for the arraying application of the transducer low-frequency longitudinal array in the design of a high-voltage-resistant structure. According to the pouring method adopted by the invention, the filling of the rear heavy backing of the transducer array element is not limited by the size, and the rear heavy backing is seamlessly attached to the rear end of the transducer array element, so that the transducer can bear higher pressure. The overall structure has the advantages of being resistant to high pressure, compact in structure, capable of effectively restraining rear-end sound radiation, capable of improving front-end radiation energy and the like.

Description

Technical Field

[0001] The present invention belongs to the field of underwater acoustic wave sensing communication, and specifically relates to a structure and manufacturing method of an underwater acoustic low-frequency transducer, and more particularly to a deep water resistant technical solution. Background Art

[0002] A low-frequency underwater acoustic transducer is a device used for underwater acoustic wave sensing and communication. It is of great significance in military and engineering applications such as underwater communication, sonar detection, and underwater intelligence gathering. Low-frequency underwater acoustic transducers usually operate in a frequency range of several hundred hertz to several thousand hertz. This frequency has a longer propagation distance in water and stronger penetration ability, making it suitable for long-distance communications and deep-water environments. In the development of the field of underwater acoustic transducers, in order to open up the deep-sea direction, low-frequency transducers are developing in the direction of lower frequencies, more pressure-resistant structures, and smaller sizes. For example, patent document CN108766412A discloses a pressure-resistant underwater acoustic cylindrical transducer array, including an upper cover shell, a cylindrical component and a lower cover shell, wherein the upper cover shell and the lower cover shell are respectively fixedly connected to the upper and lower ends of the cylindrical component; the cylindrical component includes an aluminum inner tube, a base array frame, a rubber outer wall and a plurality of transducer array elements, the base array frame is an annular cylinder, and a plurality of mounting holes adapted to the transducer array elements are arranged on the base array frame, and a plurality of the transducer array elements are respectively arranged in one of the mounting holes; the base array frame is sealed between the aluminum inner tube and the rubber outer wall.

[0003] In the research of underwater acoustic transducers, standing wave tubes are of great significance for the performance testing of various underwater acoustic transducers. Standing wave tubes are usually cylindrical pipe structures. The transducers are installed in the pipes. The acoustic performance of low-frequency transducers is verified by receiving signals from the transducers. In standing wave tubes, since the sound field environment is pipe-type, low-frequency transducers are required to have higher forward radiation efficiency and energy.

[0004] In underwater acoustic transducers, conventional longitudinal arrays have excellent forward radiation capabilities, and their structures are easy to arrange and pressure-resistant. Based on these advantages, longitudinal array transducers are consistent with the characteristics of underwater acoustic low-frequency transducers used in standing wave tubes. In the engineering applications of traditional longitudinal arrays, in order to meet the requirements of array arrangement, the longitudinal arrays are usually equipped with installation nodes. In traditional structural design, the nodes are generally designed at the rear cover plate, and then each transducer longitudinal array is fixed to a mounting plate or mounting structure through the nodes to meet the positioning requirements. The position of the nodes has a greater impact on the vibration mode, and usually a smaller size means that the structure is more pressure-resistant. Under the requirements of densely packed dimensions in space, the setting of nodes usually takes up more space, which also brings more inconvenience to installation, and its installation accuracy is difficult to guarantee. How to effectively use space has become the key to the optimization of low-frequency transducer structure.

[0005] In the field of underwater acoustics, the research on the back-end backing of the transducer is also an important direction for studying transducers. The back-end backing plays a role in sound insulation and sound absorption for the transducer. The radiation at the back end will lose more energy of the transducer, thereby affecting the sound radiation efficiency of the transducer. The back-end backing material of the transducer is generally some composite material or foam material used to block sound propagation. However, due to the strong penetration of low-frequency sound waves, the back baffle design of low-frequency transducers is more difficult. Ordinary materials, whether metal or non-metal, cannot play a significant role in sound insulation, especially when the transducer is small in size. In a limited space, the traditional baffle cannot effectively suppress the low-frequency transducer. Therefore, seeking a material structure with a small size that can effectively suppress back radiation is also of great significance to the development of low-frequency transducer structures for underwater acoustics.

[0006] In the pressure-resistant structural design of underwater acoustic transducers, since transducers have the requirement of watertight packaging to ensure normal operation, the pressure-resistant design is generally divided into structural hard support and structural adaptive support. The internal pressure of the structural hard support transducer is normal pressure, so the shell structure design needs to fully support its external pressure, usually water pressure. In this case, when the external water pressure is high, the shell usually needs sufficient wall thickness or local reinforcement to prevent the transducer from losing stability or yielding, but this method greatly increases the weight, size and cost of the transducer. Structural adaptive support refers to the internal and external pressures of the transducer being balanced or close to balanced through its own deformation or adjustment, thereby greatly reducing the capacity requirements of the shell support. Pressure compensation and elastomer filling can achieve this effect. When elastomer filling is required to meet the requirements of ultra-high pressure resistance, we need to optimize the structure so that the liquid filling material can fill the complex internal space of the transducer, because any cavity in the structure will cause damage to the structure under high pressure.

[0007] In view of the technical problems existing in the prior art, the present invention proposes a deep-water resistant low-frequency transducer structure and manufacturing method, utilizes the advantages of the longitudinal array transducer array elements, seeks a new array positioning structure in the production of the transducer, and a new method for preparing the low-frequency transducer backing material to meet the design requirements of high pressure resistance, compact structure, and effective suppression of rear radiation. Summary of the invention

[0008] In view of the defects in the prior art, the object of the present invention is to provide a deep-water resistant low-frequency transducer structure and a manufacturing method.

[0009] According to the present invention, an underwater acoustic low-frequency transducer structure is provided, comprising: a transducer array element, a front-end bracket, a rear-end bracket, a heavy backing filling and a transducer housing;

[0010] The transducer assembly consisting of the transducer array element, the front end bracket, the rear end bracket, and the heavy backing filling is arranged in the transducer housing;

[0011] There are multiple transducer array elements, and the multiple transducer array elements are densely arranged to form a transducer;

[0012] The front end bracket and the rear end bracket are respectively arranged at two ends of the transducer housing;

[0013] One side of the filling edge of the heavy backing is in contact with the transducer array element, and the other side is flush with the edge of the rear end bracket.

[0014] Preferably, the number of the transducer array elements is multiple;

[0015] The material of the heavy backing filling is based on epoxy resin and is mixed with a plurality of steel balls.

[0016] Preferably, the steel balls are mainly made of a mixture of three sizes, including: a first steel ball, a second steel ball, and a third steel ball, and the diameters of the first steel ball, the second steel ball, and the third steel ball are increased in length.

[0017] Preferably, the underwater acoustic low-frequency transducer structure further comprises: a watertight filling layer, a watertight connector, and a watertight filling gate;

[0018] The transducer housing is a stainless steel cylindrical barrel structure, one end of the transducer housing is connected to a watertight connector, the side connected to the watertight connector is defined as the rear end, a rear end bracket is provided on the periphery of the rear end of the transducer housing, and the rear end bracket is connected to the rear end of the transducer housing through a mounting hole provided at the rear end of the transducer housing; the front end bracket and the rear end bracket are provided with holes;

[0019] The rear end of the transducer housing is provided with a watertight filling pouring port, and the watertight filling layer is filled between the heavy backing filling and the transducer housing through the watertight filling pouring port;

[0020] The transducer array element transmits the signal to the watertight connector via the signal line.

[0021] Preferably, the transducer array element is a cylinder without a mounting node, and is made of a front cover plate, a rear cover plate and a plurality of piezoelectric ceramics through mold shaping, curing and stacking; the front cover plate of the transducer array element is radially positioned by the front end bracket, and the rear cover plate is radially positioned by the rear end bracket 4.

[0022] Preferably, the coaxiality of the front cover plate and the rear cover plate is no more than 0.1 mm; the surfaces of the front cover plate and the rear cover plate are smooth and free of adhesive residue; and the number of piezoelectric ceramics is 40.

[0023] Preferably, the front bracket and the rear bracket are made of polypropylene material, and the structure is a cylindrical irregular porous structure.

[0024] Preferably, the diameter of the first steel ball is 10 mm, the diameter of the second steel ball is 3 mm, and the diameter of the third steel ball is 1 mm.

[0025] A method for manufacturing an underwater acoustic low-frequency transducer structure provided by the present invention comprises:

[0026] Step S1: knock multiple transducer array elements into the rear bracket with a rubber hammer, and then knock the front bracket into the front cover to accurately position them;

[0027] Step S2: Tighten the front bracket and the rear bracket together with multiple M8 screws;

[0028] Step S3: After the transducer array element, the front bracket and the rear bracket are installed, a heavy backing is added to the current overall structure. The heavy backing is made of epoxy resin as a base, mixed with steel balls, cast and cured, and the casting is divided into two times;

[0029] Step S4: After adding the heavy backing filling, the transducer assembly consisting of the front bracket, the rear bracket, the transducer array element, and the heavy backing filling is placed into the polyurethane potting watertight filling mold required for the final molding;

[0030] Step S5: Fix the transducer housing and pour the polyurethane rubber into the transducer housing through the watertight filling pouring port according to the process specifications. The gaps between the rear bracket and the transducer array elements and the cavities between the transducer assembly and the transducer housing are completely filled. The pouring process needs to be carried out in a vacuum environment.

[0031] Preferably, step S3 of the method for manufacturing the underwater acoustic low-frequency transducer structure comprises:

[0032] Step S31: first lay the first steel ball, and then fill the gap with the second steel ball and the third steel ball;

[0033] Step S32: pouring epoxy glue until it is flush with the edge of the rear end bracket;

[0034] Step S33: After the transducer array element and the front bracket and the rear bracket are basically positioned, the second backing casting is performed;

[0035] The second backing casting includes: cleaning, sandblasting and coating the inner surface of the transducer housing with a coupling agent, and then installing the rear end bracket into the transducer housing; casting through the through hole at the back of the transducer housing and vacuum curing, and this casting also requires adding steel balls from the through hole; and obtaining the required heavy backing filling.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The back liner filling material used in the present invention is based on epoxy, mixed with steel balls of different specifications and proportions, and is obtained by filling and solidifying the material in a liquid state. The density can be adjusted according to specific needs; the process is controllable, which solves the technical problems that the material with higher density formed by the back liner after mechanical processing cannot be seamlessly fitted with the rear end of the array element, and the small cavity makes the structure unstable when the structure is subjected to greater pressure.

[0038] 2. The present invention has a compact structure, does not require node installation for positioning of large low-frequency longitudinal array elements, and has accurate positioning.

[0039] 3. The structure of the present invention is light in weight, small in diameter, and easy to install and use.

[0040] 4. The transducer structure of the present invention can withstand deep water pressure of not less than 60Mpa.

[0041] 5. The present invention reduces the rear radiation energy loss and improves the forward radiation energy through the heavy backing filling design.

[0042] 6. The backing filling volume of the present invention is small and the space utilization rate is high.

[0043] 7. The front bracket and the rear bracket of the present invention are light in weight and have a pressure-resistant structure. The generation of internal voids is avoided during watertight filling, and the overall structure meets high-pressure resistance requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0045] Figure 1 This is a structural appearance diagram of the deepwater resistant low-frequency transducer provided by the present invention.

[0046] Figure 2 This is a structural diagram of the deepwater resistant low-frequency transducer provided by the present invention.

[0047] Figure 3 This is a schematic diagram of the position relationship and installation of the deepwater resistant low-frequency transducer provided by the present invention.

[0048] Figure 4 A schematic diagram of a transducer array element provided by the present invention.

[0049] Figure 5 This is a schematic diagram of a transducer housing provided by the present invention.

[0050] Figure 6 This is a schematic diagram of the transducer front end bracket provided by the present invention.

[0051] Figure 7 This is a schematic diagram of the rear end bracket of the transducer provided by the present invention.

[0052] Figure 8 This is a schematic diagram of the preparation of the heavy backing filling of the transducer provided by the present invention.

[0053] Fig. 9 Schematic diagram of the watertight filling preparation of the transducer provided by the present invention.

[0054] The figure shows:

[0055] DETAILED DESCRIPTION

[0056] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0057] like Figure 2 As shown, an embodiment of the present invention provides a deepwater resistant low-frequency transducer structure, comprising: a transducer array element 1, a front end bracket 3, a rear end bracket 4, a heavy backing filling 5, and a transducer housing 2; further, the deepwater resistant low-frequency transducer structure also includes: a watertight filling layer 6, a watertight connector 7, and a watertight filling casting 9;

[0058] The transducer assembly consisting of the transducer element 1, the front end bracket 3, the rear end bracket 4, and the heavy backing filling 5 is arranged in the transducer housing 2; there are multiple transducer elements 1, and the multiple transducer elements 1 are closely arranged to form a transducer; the front end bracket 3 and the rear end bracket 4 are respectively arranged at the two ends of the transducer housing 1; one side of the edge of the heavy backing filling 5 is in contact with the transducer element 1, and the other side is flush with the rear end bracket 5; further, the number of the transducer elements 1 is 7, the center distance of the multiple transducer elements 1 is 48mm, the diameter of a single transducer element 1 is 45mm, and the length is 458mm; further, the low-frequency transducer provided in the embodiment of the present invention is commonly used in a sound tube with a diameter not greater than 200mm, so it is necessary to arrange as many transducer elements 1 as possible in a limited space.

[0059] Furthermore, the material of the heavy backing filler 5 is epoxy resin as the base, mixed with steel balls of different sizes and proportions, and filled and solidified in a liquid state, and the density is adjustable;

[0060] Further, the transducer housing 2 is a stainless steel cylindrical barrel structure with a size of φ176mm×425mm and an internal cavity of φ168mm×300mm. A watertight connector 7 is connected to one end of the transducer housing 2, and the side connected to the watertight connector 7 is defined as the rear end. A rear end bracket 4 is provided on the periphery of the rear end of the transducer housing 2. The rear end bracket 4 is connected to the rear end of the transducer housing 2 through a mounting hole provided at the rear end of the transducer housing 2. The rear end bracket 4 has a certain support property and can play a role in preventing collision and supporting the erection of the deep-water resistant low-frequency transducer structure.

[0061] The rear end of the transducer housing 2 is provided with a watertight filling pouring port 9, and the watertight filling layer 6 is filled between the heavy backing filling 5 and the transducer housing 2 through the watertight filling pouring port 9;

[0062] The front cover plate 100 of the transducer array element 1 is positioned in the radial direction by the front end bracket 3, and the rear cover plate 200 is positioned in the radial direction by the rear end bracket 4;

[0063] The front bracket 3 and the rear bracket 4 are opened according to the central moment requirement of the transducer array element 1;

[0064] Furthermore, during installation: first, knock the seven transducer array elements 2 into the rear bracket 4 with a rubber hammer, and then knock the front bracket 3 into the front cover 100 to accurately position it, and finally tighten the front bracket 3 and the rear bracket 4 with six M8 screws; specifically, Figure 6 , Figure 7 As shown, Figure 6 Six evenly spaced through holes are arranged at the outer edge of the middle front bracket 3 structure. Figure 7 Six evenly spaced threaded holes are provided at the outer edge of the structure of the middle and rear end brackets 4, and the two are tightened by six M8 screws during installation.

[0065] The transducer array element 1 is a cylinder without a mounting node, and the method of mounting the rear cover plate 200 on a fixed structure by fasteners is abandoned, which can solve the technical problem that the spatial array is compact and the transducer array element 1 is too long to be installed; further, the transducer array element 1 is made by molding, curing and stacking the front cover plate 100, the rear cover plate 200 and a plurality of piezoelectric ceramics; the coaxiality of the front cover plate 100 and the rear cover plate 200 is not greater than 0.1 mm; the surfaces of the front cover plate 100 and the rear cover plate 200 are smooth and free of glue residue.

[0066] The embodiment of the present invention is not limited to the number of piezoelectric ceramics, and the number of piezoelectric ceramics may be 40.

[0067] The length of the transducer array element 1 has little effect on the pressure resistance of the structure. Each transducer array element 1 leads to a pair of positive and negative wires, which need to be cleaned before use. The transducer array element 1 transmits the signal to the watertight connector 7 through the signal line. At the same time, this structure can make the polyurethane rubber in the structure cavity more fluid when the watertight filling layer 6 is poured, reducing the probability of bubble generation.

[0068] Further, the material of the front bracket 3 and the rear bracket 4 is polyurethane material, and the structure is a cylindrical special-shaped porous structure, which is used to position the transducer array element 1; specifically, the polyurethane material is a slightly amber non-transparent or translucent polymer, with excellent mechanical properties, high rigidity, wear resistance, high strength, and excellent mechanical properties even at high temperatures. The dimensional stability is very good between -100°C and 150°C. In the technical solution of the present invention, the polyurethane material contributes to the precise positioning technical effect of the structure of the present invention; further, in a use environment with high heat generation, the polyurethane molded with 20% glass fiber has a tensile strength of 103Mpa, which can meet the ultra-high pressure resistance requirements of the transducer; at the same time, the structure can make the polyurethane rubber in the structural cavity more fluid when the watertight filling layer 6 is poured, thereby reducing the probability of bubble generation.

[0069] Furthermore, the front bracket 3 and the rear bracket 4 are lightweight and porous structures, which can reduce their volume, thereby reducing the dimensional impact of such non-metallic material structures on the overall structure due to thermal expansion and contraction;

[0070] Furthermore, after the transducer array element 1, the front end bracket 3, and the rear end bracket 4 are installed, a heavy backing filling 5 is added to the existing overall structure, and the epoxy-based mixed steel balls are cast and cured. The casting is divided into two times, which can prevent the appearance of cavities and make the structure more pressure-resistant; the steel balls are mainly made of a mixture of three sizes, including: a first steel ball 511, a second steel ball 522, and a third steel ball 533. The diameter of the first steel ball 511, the diameter of the second steel ball 522, and the diameter of the third steel ball 533 increase progressively; the diameter of the first steel ball 511 can be 10 mm, the diameter of the second steel ball 522 can be 3 mm, and the diameter of the third steel ball 533 is 1 mm.

[0071] like Figure 8As shown, during the first pouring process, the first steel ball 511 is laid first, and then the second steel ball 522 and the third steel ball 533 are filled in the gap, and finally the epoxy glue is slowly poured until it is flush with the edge of the rear end bracket 4; then vacuum and solidify to obtain a dense rigid composite material backing; after this solidification, the transducer array element 1 and the front end bracket 3 and the rear end bracket 4 are basically positioned; then, the second heavy backing pouring is carried out, and the inner surface of the transducer housing 2 is cleaned, sandblasted, coated with a coupling agent and other surface treatments, and the rear end bracket 4 is installed into the transducer housing 2, and poured again through the through hole behind the transducer housing 2 and vacuumed and solidified for the second time. This pouring also requires adding steel balls from the through hole. After two pourings, the heavy backing filling 5 required in this example is obtained, and the heavy backing refers to the backing filling of the double backing pouring.

[0072] After the heavy backing filling 5 is obtained, the transducer assembly consisting of the front bracket 3, the rear bracket 4, the transducer array element 1, and the heavy backing filling 5 is placed into the polyurethane potting watertight filling mold 8 required for the final molding. The watertight filling mold 8 is a half structure. Fig. 9 As shown, during installation, the transducer housing 2 is fixed, and the polyurethane adhesive is poured into the transducer housing 2 through the watertight filling pouring port 9 according to the process regulations. The adhesive fills the transducer housing 2 and the internal cavity of the transducer assembly through the gap between the rear end bracket 4 and the transducer array element 1. The pouring process needs to be carried out in a vacuum environment to ensure that no bubbles or cavities are generated in the transducer during the pouring process.

[0073] In summary, the present invention is a low-frequency transducer structure for underwater acoustics that can be used in a standing wave tube, and is suitable for the application of the array of low-frequency longitudinal arrays of transducers in the design of high-pressure-resistant structures. The casting method adopted by the present invention can make the heavy backing filling 5 at the rear of the transducer array element 1 not limited by size, and seamlessly fit with the rear end of the transducer array element 1, so that the transducer can withstand greater pressure. The overall structure has the technical effects of high pressure resistance, compact structure, effective suppression of rear-end sound radiation, and increased front-end radiation energy.

[0074] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0075] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A low-frequency underwater acoustic transducer structure, characterized in that: include: Transducer array element (1), front end bracket (3), rear end bracket (4), heavy backing filling (5) and transducer housing (2); The transducer assembly consisting of the transducer array element (1), the front end bracket (3), the rear end bracket (4), and the heavy backing filler (5) is arranged in the transducer housing (2); There are a plurality of transducer array elements (1), and the plurality of transducer array elements (1) are closely arranged to form a transducer; The front end bracket (3) and the rear end bracket (4) are respectively arranged at two ends of the transducer housing (1); One side of the edge of the heavy backing filler (5) is in contact with the transducer array element (1), and the other side is flush with the edge of the rear end bracket (5).

2. The underwater acoustic low-frequency transducer structure according to claim 1 is characterized in that: The number of the transducer array elements (1) is multiple; The material of the heavy backing filler (5) is based on epoxy resin and is mixed with a plurality of steel balls.

3. The underwater acoustic low-frequency transducer structure according to claim 2 is characterized in that: The steel balls are mainly made of a mixture of three sizes, including: a first steel ball (511), a second steel ball (522), and a third steel ball (533). The diameters of the first steel ball (511), the second steel ball (522), and the third steel ball (533) are gradually increased in length.

4. The underwater acoustic low-frequency transducer structure according to claim 1 is characterized in that: Also includes: A watertight filling layer (6), a watertight connector (7), and a watertight filling gate (9); The transducer housing (2) is a stainless steel cylindrical barrel structure. One end of the transducer housing (2) is connected to a watertight connector (7). The side connected to the watertight connector (7) is defined as the rear end. A rear end bracket (4) is provided on the outer periphery of the rear end of the transducer housing (2). The rear end bracket (4) is connected to the rear end of the transducer housing (2) through a mounting hole provided at the rear end of the transducer housing (2). The front end bracket (3) and the rear end bracket (4) are provided with holes. The rear end of the transducer housing (2) is provided with a watertight filling pouring port (9), and the watertight filling layer (6) is filled between the heavy backing filling (5) and the transducer housing (2) through the watertight filling pouring port (9); The transducer array element (1) transmits the signal to the watertight connector (7) via a signal line.

5. The underwater acoustic low-frequency transducer structure according to claim 1 is characterized in that: The transducer array element (1) is a cylinder without a mounting node, and is mainly made of a front cover plate (100), a rear cover plate (200) and a plurality of piezoelectric ceramics which are formed by a mold, cured and stacked; the front cover plate (100) of the transducer array element (1) is positioned in the radial direction by a front end bracket (3), and the rear cover plate (200) is positioned in the radial direction by a rear end bracket 4.

6. The underwater acoustic low-frequency transducer structure according to claim 5, characterized in that: The coaxiality of the front cover plate (100) and the rear cover plate (200) is no greater than 0.1 mm; the surfaces of the front cover plate (100) and the rear cover plate (200) are smooth and free of adhesive residue; and the number of the piezoelectric ceramics is 40.

7. The underwater acoustic low-frequency transducer structure according to claim 1 is characterized in that: The front end bracket (3) and the rear end bracket (4) are made of polypropylene material and have a cylindrical, irregularly shaped porous structure.

8. The underwater acoustic low-frequency transducer structure according to claim 3 is characterized in that: The diameter of the first steel ball (511) is 10 mm, the diameter of the second steel ball (522) is 3 mm, and the diameter of the third steel ball (533) is 1 mm.

9. A method for manufacturing the underwater acoustic low-frequency transducer structure according to any one of claims 1 to 8, comprising: Step S1: knocking a plurality of transducer array elements (2) into the rear end bracket (4) with a rubber hammer, and then knocking the front end bracket (3) into the front cover plate (100) to accurately position them; Step S2: Use a plurality of M8 screws to tighten the front bracket (3) and the rear bracket (4); Step S3: After the transducer array element (1), the front bracket (3) and the rear bracket (4) are installed, a heavy backing filler (5) is added to the current overall structure. The heavy backing filler (5) is made by casting and curing with epoxy resin as the base and mixed with steel balls. The casting is divided into two times; Step S4: After adding the heavy backing filling (5), the transducer assembly consisting of the front bracket (3), the rear bracket (4), the transducer array element (1), and the heavy backing filling (5) is placed into the polyurethane potting watertight filling mold (8) required for the final molding; Step S5: fix the transducer housing (2), and pour the polyurethane rubber into the transducer housing (2) through the watertight filling pouring port (9) according to the process specifications, so that the gap between the rear end bracket (4) and the transducer array element (1) and the cavity between the transducer assembly and the transducer housing (2) are completely filled, and the pouring process needs to be carried out in a vacuum environment.

10. The method for manufacturing an underwater acoustic low-frequency transducer structure according to claim 9, characterized in that: The step S3 comprises: Step S31: first lay the first steel ball (511), and then fill the gap with the second steel ball (522) and the third steel ball (533); Step S32: pouring epoxy glue until it is flush with the edge of the rear end bracket (4); Step S33: After the transducer array element (1) and the front support (3) and the rear support (4) are basically positioned, a second backing casting is performed; The second backing casting comprises: cleaning, sandblasting and coating the inner surface of the transducer housing (2) with a coupling agent, and then installing the rear bracket (4) into the transducer housing (2); casting through the through hole at the back of the transducer housing (2) and vacuum curing, and this casting also requires adding steel balls from the through hole; and obtaining the required heavy backing filling (5).

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