Acoustic-electric conversion structure

Abstract

The invention relates to the technical field of ultrasonic transducers, in particular to an acoustic-electric conversion structure which comprises a backing, a matching layer and piezoelectric ceramics, the backing comprises a first containing space and a first opening communicated with the first containing space, the inner wall of the side, facing the first opening, of the first containing space is a first connecting face, and the inner wall of the side, facing the first opening, of the first containing space is a second connecting face; the matching layer is arranged at the first opening of the backing and used for sealing the first opening, the piezoelectric ceramic comprises an emitting surface and a back surface, and the emitting surface and the back surface are arranged on the two opposite sides of the piezoelectric ceramic respectively. According to the acoustic-electric conversion structure, the cavity is formed in the first connecting face, connected with the back face of the piezoelectric ceramic, of the backing, the piezoelectric ceramic can be effectively bound by the backing, the emission intensity of a product is guaranteed, acoustic impedance mismatch is formed through the huge difference between the acoustic impedance of air in the cavity and the acoustic impedance of the piezoelectric ceramic, and the acoustic-electric conversion effect is improved. And the sound energy transmitted into the cavity is reflected back to the piezoelectric ceramic, so that the sensitivity of the piezoelectric ceramic is improved.

Description

Technical Field

[0001] The invention relates to an ultrasonic transducer, and in particular to an acoustic-electric conversion structure applied to an air-medium piezoelectric ceramic ultrasonic transducer. Background Art

[0002] With the development of ultrasonic technology, air-to-air ultrasonic application technology has been widely used in many fields, such as ultrasonic ranging, object recognition, traffic detection, etc. Among them, air-to-air ultrasonic transducers have become key components due to their advantages such as non-contact, no need for coupling agents, and easy real-time online detection. At present, among air-to-air ultrasonic transducers, piezoelectric ceramic transducers are the most widely used, with the characteristics of simple structure, reliable performance, and adaptability to harsh environments.

[0003] Air-mediated piezoelectric ceramic ultrasonic transducers can not only be used to generate ultrasonic waves, but also receive ultrasonic waves and detect them using the principle of sound wave reflection. In this process, the piezoelectric ceramic transducer generates a piezoelectric reverse effect through voltage excitation, generates vibrations and radiates sound waves into the air. When sound waves propagate in the air and encounter obstacles, they are reflected. The reflected waves are captured by the transducer again and amplified by the circuit. However, after the circuit excitation stops, the piezoelectric ceramic transducer will still produce attenuated vibrations, which will affect the accuracy of signal reception. For this reason, a backing is usually added to the transducer structure to increase the damping effect, speed up the vibration attenuation process, reduce the vibration elimination time, and improve the accuracy of signal reception. The backing of existing air-mediated piezoelectric ceramic ultrasonic transducers is usually made by a dispensing process to form a colloid backing on the back of the piezoelectric ceramic.

[0004] However, the dispensing process has the disadvantage of numerous and complex process parameters, and it is difficult to accurately control the shape and size of the backing, resulting in poor consistency in product performance. In order to overcome this defect, some manufacturers have switched to a process that is easier to control the shape and size of the backing to form a backing of a specific shape and size to improve the designability of product performance. In order to meet the process requirements for controlled molding of the backing, the backing materials used in these new processes are usually harder than the gelatin backing. However, although this hard backing can more effectively shorten the vibration elimination time, it also strengthens the constraint on the vibration of the piezoelectric ceramic, causing the emission intensity of the product to attenuate. Therefore, it is urgent to propose an acoustic-to-electric conversion structure for use in an air-medium piezoelectric ceramic ultrasonic transducer to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide an acoustic-to-electric conversion structure for an air-medium piezoelectric ceramic ultrasonic transducer, which shortens the vibration elimination time and reduces the influence of the backing on the emission intensity of the product by constructing a cavity on the backing that matches the piezoelectric ceramic.

[0006] The technical solution adopted by the present invention to solve the above problem is: an acoustic-electric conversion structure, comprising:

[0007] The backing includes a first accommodating space and a first opening communicating with the first accommodating space, wherein the first accommodating space includes a first connecting surface facing the first opening.

[0008] A matching layer is disposed at the first opening to close the first opening.

[0009] The piezoelectric ceramic comprises an emitting surface and a back surface, wherein the emitting surface and the back surface are respectively arranged on two opposite sides of the piezoelectric ceramic, the piezoelectric ceramic is arranged in the first accommodating space, the back surface is connected to the first connecting surface, and the emitting surface is connected to the matching layer.

[0010] A cavity is provided at the first connecting surface on the backing, and an orthographic projection of the cavity on the first connecting surface and an orthographic projection of the back surface on the first connecting surface have an overlapping area, and the overlapping area is greater than zero.

[0011] Preferably, when the overlapping area is larger than the orthographic projection area of ​​the back surface on the first connecting surface, the peripheral side of the piezoelectric ceramic is fixedly connected to the inner wall of the first accommodating space.

[0012] Preferably, the piezoelectric ceramic is in the shape of a disc, and the emitting surface and the back surface are respectively located at two opposite ends of the piezoelectric ceramic.

[0013] Preferably, the piezoelectric ceramic is in the shape of a rectangular sheet, and the emitting surface and the back surface are respectively located on two opposite sides of the piezoelectric ceramic.

[0014] Preferably, a geometric center of an outline shape of an orthographic projection of the cavity on the first connecting surface coincides with a geometric center of an outline shape of an orthographic projection of the back surface on the first connecting surface.

[0015] Preferably, the backing is made of a plastic material through a press molding process, so that the backing is covered on the outside of the matching layer and the piezoelectric ceramic during the press molding process, so that the matching layer and the piezoelectric ceramic are integrally formed with the backing, and the matching layer and the piezoelectric ceramic are connected to the backing.

[0016] Wherein, during the molding process of the backing material, the pressure applied to the backing material is at least 0.15 MPa.

[0017] Preferably, the backing is formed by an injection molding process, and the backing is formed into one piece with the matching layer and the piezoelectric ceramic during the injection molding process.

[0018] Preferably, the acoustic-to-electric conversion structure further includes:

[0019] A circuit board is arranged on the backing, and the circuit board is electrically connected to the piezoelectric ceramic.

[0020] A wiring harness is electrically connected to the circuit board.

[0021] The shell comprises a second accommodating space, wherein the second accommodating space extends to one side of the shell to form a second opening, the backing is arranged in the second accommodating space, the inner wall of the second accommodating space is used to apply a resisting force pointing to the center of the second opening to the peripheral side of the backing, the Young's modulus of the shell is greater than the Young's modulus of the backing, and the orthographic projection line segment of the contact portion between the inner wall of the second accommodating space and the outer side of the backing in the extension direction of the second accommodating space and the orthographic projection line segment of the contact portion between the outer side of the matching layer and the inner wall of the first accommodating space in the extension direction of the second accommodating space overlap.

[0022] Preferably, the shell is formed of a plastic material on the outside of the backing through a molding process, so that the shell and the backing are formed in one piece.

[0023] Preferably, the shell is formed by an injection molding process, and the shell is formed as one piece with the backing during the injection molding process.

[0024] Beneficial effects of the embodiments of the present invention

[0025] The acoustic-to-electric conversion structure, by opening a cavity at the first connecting surface on the backing that is connected to the back side of the piezoelectric ceramic, can effectively restrain the backing on the piezoelectric ceramic, which not only ensures the emission intensity of the product, but also forms an acoustic impedance mismatch through the huge difference between the acoustic impedance of the air in the cavity and the acoustic impedance of the piezoelectric ceramic, and reflects the acoustic energy transmitted to the cavity back to the piezoelectric ceramic, thereby improving the sensitivity of the piezoelectric ceramic.

[0026] The acoustic-to-electric conversion structure uses a plastic material and a molding method to shape the backing, so that the matching layer and the piezoelectric ceramic are connected to the backing in an integrated manner, which significantly simplifies the manufacturing process of the acoustic-to-electric conversion structure, reduces the production steps, and improves production efficiency. In addition, the integrated molding process also effectively reduces the errors that may occur in the manufacturing process, ensures the close connection and structural stability between the components, thereby improving the consistency and reliability of the product. In addition, through the optimization of the molding process, the present invention only needs to adjust the product performance through the injection molding process parameters, which not only solves the problem of complicated backing design parameters and complex production process in the existing air-medium piezoelectric ceramic ultrasonic transducer, but also achieves the goal of quickly adjusting the transducer performance by simplifying the design and reducing the processing steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1It is a schematic cross-sectional view of an acoustic-to-electric conversion structure proposed in one embodiment of the present invention.

[0028] Figure 2 is a schematic cross-sectional view of a backing provided in one embodiment of the present invention Figure 1 .

[0029] Figure 3 It is a schematic cross-sectional view of an air-medium piezoelectric ceramic ultrasonic transducer proposed in one embodiment of the present invention.

[0030] Figure 4 It is a diagram of a sound wave propagation model for a two-layer medium proposed in one embodiment of the present invention.

[0031] Figure 5 It is a diagram of a sound wave propagation model for a three-layer medium proposed in one embodiment of the present invention.

[0032] Figure 6 is a schematic cross-sectional view of a backing provided in one embodiment of the present invention Figure 2 .

[0033] Figure 7 is a schematic cross-sectional view of a cavity-free backing proposed in one embodiment of the present invention.

[0034] Figure 8 is a schematic cross-sectional view of a cavity backing proposed in one embodiment of the present invention.

[0035] Fig. 9 1 is a vibration displacement curve diagram of an air-medium piezoelectric ceramic ultrasonic transducer under different working conditions proposed in one embodiment of the present invention.

[0036] Fig.10 1 is a maximum amplitude curve diagram of an air-medium piezoelectric ceramic ultrasonic transducer under the influence of different cavity lengths proposed in one embodiment of the present invention.

[0037] Fig.11 1 is a vibration displacement curve diagram of an air-medium piezoelectric ceramic ultrasonic transducer under the influence of different cavity lengths proposed in one embodiment of the present invention.

[0038] Fig.12 1 is a vibration displacement curve diagram of an air-medium piezoelectric ceramic ultrasonic transducer under the influence of different cavity heights proposed in one embodiment of the present invention.

[0039] Fig.13 1 is a maximum amplitude curve diagram of an air-medium piezoelectric ceramic ultrasonic transducer under the influence of different cavity heights proposed in one embodiment of the present invention.

[0040] Fig.14 It is an oscillographic curve diagram of a material of TPE and a hardness of 90A proposed in an embodiment of the present invention.

[0041] Fig.15 It is an oscillographic curve diagram of a material of TPE and a hardness of 75A proposed in an embodiment of the present invention.

[0042] Fig.16 It is an oscillographic curve diagram of a material of TPE and a hardness of 45A proposed in an embodiment of the present invention.

[0043] Fig.17 It is an oscillographic curve diagram of a material of PVC and a hardness of 75A proposed in an embodiment of the present invention.

[0044] Fig.18 It is a schematic cross-sectional view of an embodiment of the present invention in which the area of ​​the overlapping region between the orthographic projection of the cavity on the first connecting surface and the orthographic projection of the back surface on the first connecting surface is larger than the area of ​​the orthographic projection of the backing on the first connecting surface.

[0045] Among them: 100, backing; 110, first accommodating space; 120, first opening; 130, first connecting surface; 131, cavity; 200, matching layer; 300, piezoelectric ceramic; 310, back side; 320, emitting surface; 400, circuit board; 500, wiring harness; 600, housing. DETAILED DESCRIPTION

[0046] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0047] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description created by the present application, unless otherwise specified, "multiple" means two or more.

[0048] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0049] like Figure 1 to Figure 2 As shown. The acoustic-to-electric conversion structure includes a backing 100, a matching layer 200 and a piezoelectric ceramic 300. The backing 100 includes a first accommodating space 110 and a first opening 120 connected to the first accommodating space 110, and the inner wall of the first accommodating space 110 facing the first opening 120 is a first connecting surface 130. The matching layer 200 is arranged at the first opening 120 of the backing 100, and is used to close the first opening 120. The piezoelectric ceramic 300 includes an emitting surface 320 and a back surface 310, and the emitting surface 320 and the back surface 310 are respectively arranged on opposite sides of the piezoelectric ceramic 300, and the piezoelectric ceramic 300 is arranged in the first accommodating space 110, the back surface 310 is connected to the first connecting surface 130, and the emitting surface 320 is connected to one side of the matching layer 200. A cavity 131 is provided at the first connection surface 130 on the backing 100, and the orthographic projection of the cavity 131 on the first connection surface 130 is located within the range of the orthographic projection of the back surface 310 on the first connection surface 130. The acoustic-electric conversion structure, by providing the cavity 131 at the first connection surface 130 connected to the back surface 310 of the piezoelectric ceramic 300 on the backing 100, can effectively reduce the constraint of the backing 100 on the piezoelectric ceramic 300, not only ensuring the emission intensity of the product, but also forming an acoustic impedance mismatch through the huge difference between the acoustic impedance of the air in the cavity 131 and the acoustic impedance of the piezoelectric ceramic 300, reflecting the acoustic energy transmitted to the cavity 131 back to the piezoelectric ceramic 300, thereby improving the sensitivity of the piezoelectric ceramic 300.

[0050] The side of the matching layer 200 facing the first accommodating space 110 is fixedly connected to the emitting surface 320 of the piezoelectric ceramic 300 in a fitting manner, and the material of the matching layer 200 can be a polymer or composite material with good acoustic properties to ensure that the sound waves can be effectively transmitted to the piezoelectric ceramic 300. At the same time, the thickness and material properties of the matching layer 200 can be adjusted according to the design requirements of the acoustic-to-electric conversion structure to optimize the transmission efficiency of the sound waves. During the manufacturing process, the matching layer 200 is fixed at the first opening 120, and the connection between the matching layer 200 and the first opening 120 should be processed by a manufacturing process or a seal should be provided to ensure the stability and airtightness of the structure. In this embodiment, the matching layer 200 plays a role in improving the efficiency of the transmission of sound energy to the air.

[0051] The piezoelectric ceramic 300 is arranged on the side of the matching layer 200 facing the first accommodating space 110, and the back surface 310 is fixedly connected to the first connecting surface 130 in the first accommodating space 110 in a fitting manner, and the piezoelectric ceramic 300 uses the piezoelectric positive / reverse effect to generate sound energy, and receives sound energy and converts it into an electrical signal for judgment. The function of the piezoelectric ceramic 300 is to deform and generate sound waves under the action of electrical signals, or to convert received sound wave signals into electrical signals. In this embodiment, in order to reduce the vibration and displacement generated by the piezoelectric ceramic 300 during operation, the side of the piezoelectric ceramic 300 away from the matching layer 200 is fixedly connected, and the piezoelectric ceramic 300 and the matching layer 200 are bonded as a whole.

[0052] The design of the cavity 131 is the key innovation of the present invention. The cavity 131 is located on the first connecting surface 130 and is defined as being recessed in a direction away from the first opening 120. The orthographic projection of the cavity 131 on the first connecting surface 130 and the orthographic projection of the back surface 310 on the first connecting surface 130 have an overlapping area, and the overlapping area is greater than zero. As for the shape of the cavity 131, Figure 2 and Figure 6 As shown, in the specific implementation, it is embodied as a concave curved groove and a cylindrical groove. This embodiment constructs a cavity 131 on the first connecting surface 130, which not only optimizes the reflection performance of the sound wave, but also further reduces the influence of the backing 100 on the emission intensity of the transducer by reducing the direct mechanical constraints on the piezoelectric ceramic 300. In addition, the backing 100 can also adjust the sensitivity and vibration elimination time of the product by controlling the size and shape of the cavity 131.

[0053] Furthermore, when the overlapped area is larger than the orthographic projection area of ​​the back surface on the first connecting surface 130, Fig.18 As shown, the circumferential side of the piezoelectric ceramic 300 is fixedly connected to the inner wall of the first accommodating space 110, and the circumferential side of the piezoelectric ceramic 300 can be connected to the circumferential inner wall of the first accommodating space 110 by bonding, thereby ensuring that the piezoelectric ceramic 300 is fixed outside the cavity 131 and preventing the piezoelectric ceramic 300 from falling into the cavity 131.

[0054] Further, if Figure 8As shown, in order to further optimize the emission intensity and reflectivity of the sound wave, the present embodiment restricts the geometric relationship between the cavity 131 and the piezoelectric ceramic 300. Specifically, the area corresponding to the orthographic projection of the cavity 131 on the first connection surface 130 is within the range of the orthographic projection of the back surface 310 on the first connection surface 130, that is, the area of ​​the orthographic projection of the cavity 131 on the first connection surface 130 is smaller than the area of ​​the orthographic projection of the back surface 310 on the first connection surface 130, thereby ensuring that the piezoelectric ceramic 300 can be set up on the first connection surface 130. This design ensures that the piezoelectric ceramic 300 can obtain sufficient support when working, while limiting the influence range of the cavity 131. The shape of the piezoelectric ceramic 300 is embodied as a disc, a rectangular disc, etc. in a specific embodiment. The relationship between the contour shape of the orthographic projection of the piezoelectric ceramic 300 on the first connecting surface 130 and the contour shape of the orthographic projection of the cavity 131 on the first connecting surface 130 is embodied in the specific embodiment that the geometric center of the contour shape of the orthographic projection of the piezoelectric ceramic 300 coincides with or deviates from the geometric center of the contour shape of the orthographic projection of the cavity 131.

[0055] Furthermore, for example, the first accommodating space 110 is a circular groove structure with a radius of L1, the cavity 131 is a concave curved groove, and its orthographic projection shape on the first connecting surface 130 is a circle with a radius of L2, and L1 is greater than L2, the piezoelectric ceramic 300 is a disc, and the geometric shape of the contour shape of the orthographic projection of the piezoelectric ceramic 300 on the first connecting surface 130 coincides with the geometric shape of the contour shape of the orthographic projection of the cavity 131 on the first connecting surface 130. This geometric design ensures that the piezoelectric ceramic 300 can be partially suspended above the cavity 131, while the other part directly contacts the first connecting surface 130. This layout not only enhances the stability of the piezoelectric ceramic 300, but also optimizes the propagation path of the sound wave, so that the emission intensity and reflectivity of the sound wave are optimally balanced. Figures 7 to 9 As shown, through simulation experiments, it is verified that when the geometric relationship between the cavity 131 and the piezoelectric ceramic 300 meets the above requirements, the emission intensity and reflectivity of the sound wave can be significantly improved. Specifically, when the radius of the piezoelectric ceramic 300 is between the radius of the cavity 131 and the radius of the first accommodating space 110, the distribution of the sound wave on the piezoelectric ceramic 300 is more uniform, avoiding unnecessary energy loss, and at the same time, the presence of the cavity 131 provides an enhancement effect of a reflective surface, further improving the performance of the device.

[0056] In this embodiment, by further limiting the geometric relationship between the cavity 131 and the piezoelectric ceramic 300, it is ensured that the piezoelectric ceramic 300 can be effectively set up on the first connecting surface 130, thereby optimizing the acoustic wave emission intensity and reflectivity. This geometric design not only improves the stability of the piezoelectric ceramic 300, but also verifies through simulation experiments that the acoustic wave propagation effect under specific geometric conditions is optimal, ensuring the high performance and reliability of the product. Through reasonable structural design, the present invention realizes the optimization of the acoustic-electric conversion structure and further enhances the market competitiveness of the product.

[0057] refer to Figures 7 and 8 In order to verify the influence of different materials (hard glue and soft glue) of the backing 100 of the gas dielectric piezoelectric ceramic 300 ultrasonic transducer and the presence or absence of the cavity 131 on the product performance, the simulation experiment was conducted to verify the following results: Fig. 9 As shown, from Fig. 9 The simulation results in the experiment combined with the sound pressure formula show that different injection molding material backings 100 can adjust the emission intensity of the transducer, and the presence of the cavity 131 can reduce the influence of the backing 100 on the emission intensity of the transducer, and even enhance the emission intensity and sensitivity of the transducer. The material parameters of different backings 100 in the simulation experiment are shown in Table 1. It should be noted that the hard glue corresponds to the injection molding backing 100 in this experiment, and the soft glue corresponds to the traditional glue backing 100.

[0058]

[0059] Table 1

[0060] Further, refer to Figures 7 and 8 In order to verify the influence of the size of the cavity 131 in the gas dielectric piezoelectric ceramic 300 ultrasonic transducer on the product performance, the simulation experiment was conducted to verify the following results: Figures 10 to 13 As shown, from Figures 10 to 13 The simulation results in the above combined with the sound pressure formula show that the length of the cavity 131 has a significant effect on adjusting the emission intensity of the ultrasonic transducer. Figure 10 to Figure 11 As shown in FIG. 1 , once the cavity 131 appears, the amplitude of the transducer will increase significantly. However, after the cavity 131 appears, the change in the height H1 of the cavity 131 has little effect on the emission intensity of the transducer. Figure 12 to Figure 13 The parameters of different cavities 131 of the same material backing 100 in the simulation experiment are shown in Table 2. It should be noted that the hard glue corresponds to the injection molding backing 100 in this case, while the soft glue corresponds to the traditional glue backing 100.

[0061]

[0062] Table 2

[0063] It should be noted that in Table 2, when the size of the cavity 131 L2>L1, the corresponding situation is that the orthographic projection of the cavity 131 on the first connection surface 130 and the orthographic projection of the back surface 310 on the first connection surface 130 have an overlapping area, and the overlapping area is larger than the orthographic projection area of ​​the back surface on the first connection surface 130. When the size of the cavity 131 meets this condition, Fig.10 Character Fig.11 As shown, the vibration displacement and the maximum vibration amplitude of the transducer are optimal, that is, the emission intensity of the piezoelectric ceramic 300 is the highest.

[0064] In one embodiment, in order to further adjust the emission intensity and sensitivity of the product while ensuring the consistency of the product. The backing 100 is made by a molding process, and the backing 100 is integrally formed with the matching layer 200 and the piezoelectric ceramic 300 during the molding process, so that the matching layer 200 and the piezoelectric ceramic 300 are connected to the backing 100. The molding process of the backing 100 is embodied as an injection molding process in a specific embodiment. Taking the injection molding process as an example, the backing 100 is molded by the injection molding process, and the backing 100 is integrally formed with the matching layer 200 and the piezoelectric ceramic 300 during the injection molding process.

[0065] Furthermore, in this embodiment, the molding process is a press molding process, and the backing 100 is made of a plastic material through a press molding process, so that the backing 100 is coated on the outside of the matching layer 200 and the piezoelectric ceramic 300 during the press molding process, so that the matching layer 200 and the piezoelectric ceramic 300 are integrally molded with the backing 100, and the matching layer 200 and the piezoelectric ceramic 300 are connected to the backing 100. During the molding process of the backing 100, the pressure (injection molding pressure) applied to the backing 100 material is at least 0.15 MPa.

[0066] From the perspective of making the matching layer 200 and the piezoelectric ceramic 300 more firmly connected to the backing 100, the pressurized molding process has the advantages of enhancing the interface adhesion, reducing interface voids and defects, improving material fluidity, promoting chemical bonding, and preventing delamination and separation, as follows:

[0067] Enhanced interfacial adhesion: The pressure molding process can promote the backing 100 material to more tightly cover the matching layer 200 and the piezoelectric ceramic 300 during the molding process by applying pressure. The pressure helps the mutual penetration and bonding between the material molecules, so that the interfacial adhesion between the matching layer 200 and the piezoelectric ceramic 300 and the backing 100 is significantly enhanced. This strong interfacial adhesion is crucial to ensure the integrity and reliability of the structure.

[0068] Reducing interface voids and defects: During the pressurization process, the applied pressure can effectively remove the air and micro-voids between the materials, thereby reducing the voids and micro-defects at the interface. This void-free connection not only increases the physical contact area between the matching layer 200 and the piezoelectric ceramic 300 and the backing 100, but also increases the interface strength and reduces the mechanical weakness caused by interface defects.

[0069] Improve material fluidity: The pressure can make the material flow better in the mold, so that all mold cavities can be fully filled and the material is evenly distributed on the contact interface. The uniform material distribution ensures the close fit between the matching layer 200, the piezoelectric ceramic 300 and the backing 100, avoiding the loose connection caused by insufficient or uneven material distribution.

[0070] Promoting chemical bonding: The pressure forming process is usually accompanied by a certain temperature control while applying pressure. This combination of temperature and pressure can promote the chemical bonding between the backing 100 material and the matching layer 200 and the piezoelectric ceramic 300, such as the formation of covalent bonds or hydrogen bonds, thereby enhancing the bonding strength of the interface. The enhancement of chemical bonding means that the tensile strength and peeling resistance of the joint are greatly improved.

[0071] Prevent delamination and separation: Since the connection formed by the compression molding process is tighter and more uniform, this strong bond can effectively prevent delamination or separation problems during subsequent use. Especially when subjected to mechanical stress or temperature changes in the working environment, the strong connection of compression molding can maintain the integrity of the structure and extend the service life of the product.

[0072] In summary, the pressurized molding process achieves a high-strength, defect-free, uniform connection between the matching layer 200, the piezoelectric ceramic 300, and the backing 100 by applying pressure, thereby greatly improving the stability and reliability of the entire acoustic-to-electric conversion structure. This process not only improves the firmness of the connection, but also effectively prevents various failure modes that may occur at the interface.

[0073] It should be noted that the pressure applied by the pressurized molding process is greater than the external environmental pressure, which has the advantages of ensuring material fluidity and mold filling, improving interface bonding strength, eliminating bubbles and unevenness, preventing external environmental factors from affecting molding quality and ensuring structural integration. In short, the pressure requirement of the pressurized molding process is greater than the external environmental pressure in order to ensure that the material can fully flow, fill and bond in the mold to achieve a high-quality sound-to-electricity conversion structure and ensure the performance and reliability of the product.

[0074] During the injection molding process of the backing 100 in this embodiment, the backing 100, the matching layer 200 and the piezoelectric ceramic 300 are connected through a one-time molding process. The advantage of this process is that the backing 100 can be fixed to other components while being molded, which not only reduces the assembly steps, but also avoids the cumulative errors caused by multiple processing. By reasonably controlling the injection molding process parameters, such as injection pressure, temperature and cooling rate, the connection strength between the backing 100 and the matching layer 200 and the piezoelectric ceramic 300 can be further optimized to ensure the stability and reliability of the entire acoustic-to-electric conversion structure. In addition, the injection molding process can ensure the precise molding of the cavity 131, avoiding the dimensional errors and consistency problems that may occur in the traditional process. The high efficiency of the injection molding process not only improves the production speed, but also ensures the consistency of each batch of products, thereby effectively reducing the production cost and improving the yield rate. In addition, injection molding also provides technical support for the flexible adaptability of transducers in different application scenarios. In this way, it effectively overcomes the problems of single material selection and difficult to control transducer performance in the existing technology, and provides a technical solution that can flexibly adjust the performance of the transducer, thereby achieving the effect of optimizing the sound-to-electric conversion performance and improving the adaptability of the product.

[0075] Further, in this embodiment, the material of the backing 100 can be selected from thermoplastics, thermosetting plastics or other polymer materials suitable for injection molding process with good plasticity. By selecting different injection molding materials, the backing 100 can have different mechanical properties and electrical properties, thereby imposing different degrees of constraints on the working environment of the piezoelectric ceramic 300. For example, the use of a material with higher hardness can increase the constraint force on the piezoelectric ceramic 300 and reduce its displacement during operation, thereby improving the stability of the transducer. The selection of a relatively soft or elastic material can reduce the constraint force and make the piezoelectric ceramic 300 vibrate more freely. Alternatively, a material with a smaller acoustic impedance is selected to increase the reflectivity of sound waves, thereby making the piezoelectric ceramic 300 more sensitive. In addition, the selection of the injection molding process also provides a wide range of possibilities for adjusting the performance of the transducer. By selecting different materials and controlling the molding process, the characteristics of the backing 100 can be precisely controlled. For example, the vibration characteristics of the piezoelectric ceramic 300 can be affected by adjusting the modulus, damping coefficient and thermal expansion coefficient of the material, thereby achieving fine adjustment of the transducer performance without changing other structural designs.

[0076] In this embodiment, the material of the backing 100 is embodied as TPE and PVC in the specific implementation, wherein the hardness of the TPE material can be selected as 90A, 75A or 45A, and the hardness of the PVC material is 75A. According to the experimental results shown in the figure, the horizontal axis of the oscillogram represents time, and the vertical axis represents echo energy. The experiment shows that different materials and hardness have a significant impact on echo energy, as follows:

[0077] TPE(90A): Fig.14 As shown, the echo energy is large and the waveform decays quickly, which is suitable for scenarios that require fast response and can reduce residual vibration in a shorter time.

[0078] TPE(75A): Fig.15 As shown, the echo energy is relatively balanced and has a moderate decay time, which is suitable for application scenarios that require a balance between response speed and energy transmission.

[0079] TPE(45A): Fig.16 As shown, the echo energy is the strongest, but the decay speed is relatively slow, which is suitable for occasions requiring high-sensitivity detection and helps to enhance the sensitivity and signal receiving ability of the sensor.

[0080] In summary, TPE (90A) is a relatively hard material. The image shows that the echo energy is large, but the decay rate is the fastest. The backing 100 made of this material provides a greater mechanical constraint on the contact surface with the piezoelectric ceramic 300, which helps to reduce the displacement and distortion of the piezoelectric ceramic 300 during vibration, and is suitable for scenes that require a fast response. However, due to the faster energy decay, the sensitivity of the piezoelectric ceramic 300 in detecting weak signals may be reduced.

[0081] TPE (75A) is a medium-hardness material. The image shows that the echo energy is relatively balanced, the attenuation speed is moderate, and a good balance is achieved between hardness and sensitivity. It can maintain moderate energy attenuation while ensuring structural stability, and is suitable for application scenarios that require a balance between response speed and sensitivity. In certain application scenarios, the sensitivity or response speed of the transducer may not be as good as the backing 100 made of extremely hard or extremely soft materials.

[0082] TPE (45A) is a relatively soft material. The image shows that the echo energy is the strongest, but the decay speed is the slowest. The backing 100 made of this material provides less mechanical constraints on the piezoelectric ceramic 300, allowing the piezoelectric ceramic 300 to have greater vibration freedom, thereby improving the sensitivity of the transducer and being suitable for detecting weak signals. However, due to the slow energy decay, the residual vibration may be longer, thus affecting the clarity and detection speed of the transducer signal.

[0083] TPE materials with higher hardness (90A) provide stronger mechanical constraints on piezoelectric ceramics, which are suitable for fast response applications, but may slightly reduce sensitivity. TPE materials with medium hardness (75A) provide a balance between sensitivity and response speed, and are suitable for applications that require a comprehensive consideration of both. TPE materials with lower hardness (45A) have minimal constraints on piezoelectric ceramics, allowing greater vibration freedom and improving sensitivity, but the residual vibration time is longer, which may affect the response speed.

[0084] PVC(75A): Fig.17 As shown in the figure, similar to TPE (75A), it exhibits moderate echo energy and moderate decay time, but due to different material properties, its application adaptability varies. It is suitable for occasions that require an optimal balance between cost and performance.

[0085] After the backing 100 is made of PVC (75A), because PVC (polyvinyl chloride) is a plastic material with good hardness and stability, it usually exhibits high damping and low elasticity. The image shows that the echo energy is slightly lower than TPE (75A), and the attenuation rate is relatively slow. The high damping of PVC material helps to reduce the vibration energy transfer of piezoelectric ceramics, thereby reducing the residual vibration time to a certain extent, which is beneficial to the stability and accuracy of the signal. It is suitable for scenarios with high requirements for signal stability. PVC has higher rigidity and lower elasticity, which may lead to a reduction in the vibration freedom of piezoelectric ceramics, thereby slightly reducing the sensitivity and signal transmission efficiency.

[0086] In summary: The elasticity of the backing 100 made of TPE (45A) material provides a better buffering effect during the vibration transmission of piezoelectric ceramics, which helps to achieve a better balance between sensitivity and stability, and is suitable for application scenarios that require medium sensitivity and fast response. The PVC (75A) material is suitable for scenarios that require high signal stability and low residual vibration due to its higher damping and lower elasticity, but its higher rigidity may limit the vibration freedom of the piezoelectric ceramics to a certain extent, thereby slightly reducing the sensitivity. The backing 100 made of PVC (75A) material is more suitable for scenarios that require higher signal stability, such as ultrasonic equipment that requires long-term continuous monitoring or works in a high-noise environment. This choice can ensure the reliability and consistency of the signal.

[0087] In the above-mentioned embodiment, the acoustic-to-electric conversion structure uses a plastic material to manufacture the backing 100 and uses a molding technology to integrally mold the matching layer 200 and the piezoelectric ceramic 300 with the backing 100, which effectively solves the problems of numerous design parameters of the backing 100, complicated production process and poor product consistency in the prior art. Specifically, the backing 100 is integrated with the matching layer 200 and the piezoelectric ceramic 300 through a molding process, which not only simplifies the production process and reduces the production steps, but also ensures that the transducer performance has a high consistency in the same batch of products, and the performance of the transducer can be quickly obtained by adjusting only a few design parameters of the backing 100, thereby achieving the effect of reducing production costs and improving product quality. The above-mentioned embodiments all comply with the virtual work principle and the strain energy principle, as follows:

[0088] Principle of virtual work: The work done by external forces is equal to the work done by internal stresses.

[0089] For linear elastic materials, the strain energy can be calculated using Hooke's law, where Where E is the Young's modulus of the material and ε is the deformation of the structure.

[0090] Under the same deformation amount, the lower the Young's modulus of the backing 100 material, that is, the "softer" the material, the less energy the piezoelectric ceramic 3002 consumes. Assuming that the matching layer 200 and other conditions are the same, more energy can be applied to the matching layer 200, that is, a greater sound pressure is generated.

[0091] Sound pressure calculation formula:

[0092]

[0093] Displacement: x = x;

[0094] speed:

[0095] Acceleration:

[0096] in:

[0097] ρ is the air density.

[0098] A is the vibration acceleration.

[0099] S d is the vibration area.

[0100] r is the test radius.

[0101] In order to improve the sensitivity of the transducer, that is, to increase the reflectivity of the sound waves reflected on the piezoelectric ceramic 300, the present application proposes an embodiment. The acoustic-to-electric conversion structure includes a backing 100 and a piezoelectric ceramic 300, both of which play an important role in the process of sound wave transmission. In order to optimize the sound wave reflection effect, the present invention specifically designs the acoustic impedance of the backing 100 to be less than the acoustic impedance of the piezoelectric ceramic 300, thereby enhancing the reflectivity of the sound wave. The material selection of the backing 100 is crucial. In order to make the acoustic impedance of the backing 100 less than the acoustic impedance of the piezoelectric ceramic 300, a material with a lower acoustic impedance, such as a polymer material, is selected in this embodiment. This material has a higher sound wave reflection performance and can provide a better sound wave reflection effect when the piezoelectric ceramic 300 transmits or receives sound waves. Specifically, when the sound wave propagates between the piezoelectric ceramic 300 and the backing 100, due to the difference in the acoustic impedance of the two, a stronger sound wave reflection will be generated at the interface. This design greatly enhances the sensitivity of the piezoelectric ceramic 300, making it perform better when detecting weak signals. By optimizing the acoustic impedance of the backing 100, not only the reflectivity of the sound wave can be improved, but also unnecessary sound wave loss can be reduced, thereby improving the working efficiency of the piezoelectric ceramic 300. In practical applications, the material and structural design of the backing 100 can be adjusted according to specific needs. For example, for different application scenarios, materials with different acoustic impedance characteristics can be selected to achieve the best sound wave reflection effect. In addition, the design of this embodiment can also ensure that the piezoelectric ceramic 300 maintains a high-sensitivity working state without being excessively disturbed by the outside world. The acoustic impedance design of the backing 100 enables more sound waves to be reflected back to the piezoelectric ceramic 300, thereby improving its signal detection capability. This is particularly important for those acoustic-to-electric conversion devices that require high precision and high sensitivity.

[0102] This embodiment selects a specific material so that the acoustic impedance of the backing 100 is less than the acoustic impedance of the piezoelectric ceramic 300, thereby significantly enhancing the reflectivity of the sound wave. This design effectively improves the sensitivity of the piezoelectric ceramic 300, making it more sensitive and accurate in the process of sound-to-electric conversion. This optimized design of materials and structures not only solves the problem of excessive sound wave loss in the prior art, but also improves the working efficiency and performance of the overall device, achieving the effect of enhancing the signal detection capability.

[0103] In one embodiment. Figure 3As shown, the acoustic-electric conversion structure not only includes a backing 100, a piezoelectric ceramic 300, a first connection surface 130 and a back surface 310, but also further includes a circuit board 400, a wiring harness 500 and a housing 600. The integration of these components makes the structure of the entire transducer more complete and the functions more complete. The circuit board 400 is cleverly arranged on the backing 100 and electrically connected to the piezoelectric ceramic 300. The design and layout of the circuit board 400 fully consider the signal processing requirements of the piezoelectric ceramic 300. Through reasonable circuit design, the circuit board 400 can effectively receive and process the electrical signal converted by the piezoelectric ceramic 300 and transmit the electrical signal to the piezoelectric ceramic 300, so as to apply voltage excitation to the piezoelectric ceramic 300. The installation position of the circuit board 400 is close to the piezoelectric ceramic 300, which reduces the loss in the signal transmission process and ensures the signal quality and response speed of the transducer. The wiring harness 500 is electrically connected to the circuit board 400, forming a signal transmission channel from the piezoelectric ceramic 300 to the external device. The design of the wiring harness 500 ensures the stability and reliability of signal transmission, and can maintain good signal transmission performance in a variety of application scenarios. In addition, the length and wiring method of the wiring harness 500 can be customized according to specific application requirements to adapt to the connection requirements of different devices, thereby improving the application flexibility of the transducer. The housing 600 is integrally formed on the outside of the backing 100 through an injection molding process, providing additional physical protection and structural support. The housing 600 not only protects the internal components from the external environment, but also enhances the mechanical strength and durability of the entire transducer through its structural design. The use of the injection molding process ensures that the housing 600 is tightly combined with the backing 100 to form an efficient and integrated overall structure. In addition, the housing 600 can also select suitable materials according to the specific use environment to enhance the protective performance, such as waterproof, dustproof or impact resistance.

[0104] In this embodiment, by introducing a circuit board 400, a wiring harness 500 and a housing 600, the overall design of the acoustic-to-electric conversion structure is further improved, so that the transducer not only has excellent signal processing and transmission capabilities, but also has excellent structural protection and application adaptability. The reasonable arrangement of the circuit board 400 and its close connection with the piezoelectric ceramic 300 ensure efficient transmission and processing of signals. The flexible design of the wiring harness 500 improves the connection convenience and adaptability of the device. The injection molding of the housing 600 makes the entire transducer structure more stable and durable, greatly improving the reliability and service life of the product. Through this series of designs, the present invention achieves comprehensive optimization of the transducer structure, meets the needs of various application scenarios, and enhances the market competitiveness of the product.

[0105] Further, the shell 600 includes a second accommodating space, which extends to one side of the shell 600 to form a second opening, and the backing 100 is arranged in the second accommodating space. The inner wall of the second accommodating space is used to apply a holding force directed to the center of the second opening to the peripheral side of the backing 100, and the Young's modulus of the shell 600 is greater than the Young's modulus of the backing 100, that is, the shell 600 has a stronger anti-deformation ability than the backing 100, and the contact part between the inner wall of the second accommodating space and the outer side of the backing is in the extension direction of the second accommodating space. The orthographic projection line segment on the outer surface of the matching layer 200 and the contact portion of the outer side of the matching layer 200 with the inner wall of the first accommodating space 110 overlap in the extension direction of the second accommodating space, so that the inner wall at the second opening of the shell 600 will be abutted and connected with the corresponding position of the backing 100, so that the inner wall of the first accommodating space 110 at the first opening 120 is abutted against the peripheral side of the matching layer 200, thereby fixing the matching layer 200 at the first opening 120 to prevent the matching layer 200 from being separated from the backing 100.

[0106] The operating principle of the air-medium piezoelectric ceramic 300 ultrasonic transducer using a novel acoustic-electric conversion structure in the above-mentioned embodiment is as follows: First, the circuit board 400 voltage excitation inputs the piezoelectric ceramic 300, causing the piezoelectric ceramic 300 to vibrate by the piezoelectric reverse effect. The matching layer 200, the backing 100 and the piezoelectric ceramic 300 have a connection area, so the piezoelectric ceramic 300 will drive the two to move. The housing 600 has a stable constraint effect on the system, causing the matching layer 200 and the backing 100 to deform. The acoustic energy is transmitted from the piezoelectric ceramic 300 through the matching layer 200 and the backing 100 in the vertical direction. The matching layer 200 improves the efficiency of the acoustic energy transmission to the air, thereby improving the sensitivity of the product. The cavity 131 uses the acoustic impedance mismatch between the air and the piezoelectric ceramic 300 to reflect the acoustic energy back to the piezoelectric ceramic 300, thereby improving the sensitivity of the product. At the same time, the cavity 131 reduces the contact area between the backing 100 and the piezoelectric ceramic 300, that is, it reduces the energy lost due to deformation of the backing 100, so that the energy generated by the piezoelectric ceramic 300 acts more on the matching layer 200, generating a larger displacement, that is, a larger sound pressure. At the end of the voltage excitation, the piezoelectric ceramic 300 and the matching layer 200 perform attenuated vibrations and enter the vibration elimination period. The backing 100 provides damping through its own characteristics, accelerates attenuation, and reduces the vibration elimination time. When the sound wave is reflected back to the matching layer 200, the piezoelectric ceramic 300 has a piezoelectric positive effect and generates an electrical signal, which is amplified and transmitted through the circuit board 400 and the wiring harness 500 to make a judgment on the difference between obstacles.

[0107] In the above embodiment, a new type of air-to-electric conversion structure of the piezoelectric ceramic 300 ultrasonic transducer is applied. The transmission coefficient and reflection coefficient of the sound waves emitted by the piezoelectric ceramic 300 ultrasonic transducer are shown in the following three-layer medium model: Figure 4 As shown, the two-layer medium model of the transmission coefficient and reflection coefficient of the piezoelectric ceramic 300 transmitting sound waves toward the cavity 131 and receiving the reflected sound waves is as follows Figure 5 As shown. A represents the medium is the piezoelectric ceramic 300, B represents the medium is the matching layer 200, C represents the medium is the air outside the transducer, D represents the medium is the air in the cavity 131, i1 represents the transmission wave of the piezoelectric ceramic 300 to the outside of the transducer, t1 represents the transmission wave of the piezoelectric ceramic 300 to the outside of the transducer after passing through the matching layer 200, r1 represents the reflection wave of the piezoelectric ceramic 300 to the outside of the transducer when the transmission wave i1 is transmitted to the matching layer 200, i2 represents the transmission wave of the piezoelectric ceramic 300 to the cavity 131, t2 represents the transmission wave of the piezoelectric ceramic 300 to the cavity after passing through the air layer in the cavity 131, and r2 represents the reflection wave of the piezoelectric ceramic 300 to the cavity 131 reflected back to the piezoelectric ceramic 300 by the air layer in the cavity 131.

[0108] The calculation formula for the transmission coefficient of the sound waves emitted by the air-medium piezoelectric ceramic 300 ultrasonic transducer using a new acoustic-electric conversion structure is as follows:

[0109]

[0110] in:

[0111] Z1=ρ1·c1

[0112] Z2=ρ2·c2

[0113] Z3=ρ3·c3

[0114] The meaning of other parameters:

[0115] ρ1, ρ2, ρ3 are the densities of medium 1, medium 2, and medium 3.

[0116] c1, c2, c3 are the sound speeds in medium 1, medium 2, and medium 3.

[0117] K2 is the wave number, Where f is the frequency of the sound wave.

[0118] L is the thickness of medium 2.

[0119] During the vibration elimination period, after the piezoelectric ceramic 300 receives the reflected sound wave, the sound wave is transmitted in the piezoelectric ceramic 300 and the cavity 131 so that the calculation formula of the transmission coefficient and the reflection coefficient model is as follows:

[0120]

[0121] Transmittance of sound waves T:

[0122]

[0123] in:

[0124] Z1=ρ1·c1

[0125] Z3=ρ3·c3

[0126] The meaning of other parameters:

[0127] ρ1, ρ3 are the densities of medium 1 and medium 3.

[0128] c1, c3 are the sound speeds in medium 1 and medium 3.

[0129] When the piezoelectric ceramic 300 is PZT-5H, the specific parameters of the piezoelectric ceramic 300, air and matching layer 200 are shown in Table 3, and when the matching layer 200 conforms to the quarter-wavelength theory, the transmittance of the two-layer medium and the three-layer medium is shown in Table 4. According to the table below, the transmittance of the sound energy to the air outside the transducer is much greater than the transmittance of the sound energy to the air in the cavity 131, because the intensity of the sound wave emitted by the piezoelectric ceramic 300 is constant, when the transmittance of the sound energy to the air in the cavity 131 is lower, the transmittance of the sound energy to the air outside the transducer is higher, therefore, it can be concluded from Table 4 that when the backing 100 is configured with the cavity 131, the emission intensity of the transducer is effectively enhanced.

[0130] Material Speed ​​of sound (m / s) Density (kg / m^3) Acoustic impedance (MRayl) PZT-5H 4620 7000 32.34 Air 340 1.293 0.00043962 Matching layer 200 2400 560 1.344

[0131] Table 3

[0132] Transmittance Two-layer medium 5.43733E-05 Three-layer medium 0.030993397

[0133] Table 4

[0134] The above contents described in this specification are merely examples of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, as long as they do not deviate from the contents of the present specification or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. An acoustic-electric conversion structure, It is characterized in that include: A backing, comprising a first accommodating space and a first opening communicating with the first accommodating space, wherein the first accommodating space comprises a first connecting surface facing the first opening; a matching layer, disposed at the first opening to close the first opening; A piezoelectric ceramic, comprising an emitting surface and a back surface, wherein the emitting surface and the back surface are respectively arranged on two opposite sides of the piezoelectric ceramic, the piezoelectric ceramic is arranged in the first accommodating space, the back surface is connected to the first connecting surface, and the emitting surface is connected to the matching layer; A cavity is provided at the first connecting surface on the backing, and an orthographic projection of the cavity on the first connecting surface and an orthographic projection of the back surface on the first connecting surface have an overlapping area, and the overlapping area is greater than zero.

2. According to the acoustic-to-electric conversion structure described in claim 1, when the overlapping area is greater than or equal to the orthographic projection area of ​​the back surface on the first connecting surface, the peripheral side of the piezoelectric ceramic is fixedly connected to the inner wall of the first accommodating space.

3. According to the acoustic-electric conversion structure described in claim 1, It is characterized in that The piezoelectric ceramic is in the shape of a circular sheet, and the emitting surface and the back surface are respectively located at two opposite ends of the piezoelectric ceramic.

4. According to the acoustic-electric conversion structure described in claim 1, It is characterized in that The piezoelectric ceramic is in the shape of a rectangular sheet, and the emitting surface and the back surface are respectively located on two opposite sides of the piezoelectric ceramic.

5. The acoustic-to-electric conversion structure according to claim 1, It is characterized in that A geometric center of an outline shape of an orthographic projection of the cavity on the first connecting surface coincides with a geometric center of an outline shape of an orthographic projection of the back surface on the first connecting surface.

6. An acoustic-to-electric conversion structure according to any one of claims 1 to 5, It is characterized in that The backing is made of a plastic material through a press-molding process, so that the backing is covered on the outside of the matching layer and the piezoelectric ceramic during the press-molding process, so that the matching layer and the piezoelectric ceramic are integrally formed with the backing, and the matching layer and the piezoelectric ceramic are connected to the backing; Wherein, during the molding process of the backing material, the pressure applied to the backing material is at least 0.15 MPa.

7. The acoustic-to-electric conversion structure according to claim 6, It is characterized in that The backing is formed by an injection molding process, and the backing is formed into one piece with the matching layer and the piezoelectric ceramic during the injection molding process.

8. The acoustic-to-electric conversion structure according to claim 7, It is characterized in that The acoustic-to-electric conversion structure further includes: A circuit board is disposed on the backing, and the circuit board is electrically connected to the piezoelectric ceramic; a wiring harness electrically connected to the circuit board; The shell comprises a second accommodating space, wherein the second accommodating space extends to one side of the shell to form a second opening, the backing is arranged in the second accommodating space, the inner wall of the second accommodating space is used to apply a resisting force pointing to the center of the second opening to the peripheral side of the backing, the Young's modulus of the shell is greater than the Young's modulus of the backing, and the orthographic projection line segment of the contact portion between the inner wall of the second accommodating space and the outer side of the backing in the extension direction of the second accommodating space and the orthographic projection line segment of the contact portion between the outer side of the matching layer and the inner wall of the first accommodating space in the extension direction of the second accommodating space overlap.

9. According to the acoustic-electric conversion structure of claim 8, It is characterized in that The shell is formed on the outside of the backing by a molding process using a plastic material, so that the shell and the backing are formed as one piece.

10. An acoustic-to-electric conversion structure according to claim 9, It is characterized in that The shell is formed by an injection molding process, and the shell is formed as a whole with the backing during the injection molding process.

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