A porous structure flexoelectric hydrophone and method of fabrication

Abstract

The present application relates to the field of underwater acoustic detection equipment, and discloses a porous structure flexoelectric hydrophone and a manufacturing method, which comprises a porous BTO ceramic element, a clamp, a first wire, a second wire and a packaging shell.The clamp comprises a clamp upper cover and a clamp lower seat.The outer edge of the porous BTO ceramic element is clamped and fixed between the clamp upper cover and the clamp lower seat to form a circular structure with a periphery fixed support.The one end of the first wire is clamped between the outer edge of the top surface of the porous BTO ceramic element and the bottom surface of the clamp upper cover, and the one end of the second wire is clamped between the outer edge of the bottom surface of the porous BTO ceramic element and the top surface of the clamp lower seat.The packaging shell comprises a first shell and a second shell.The clamp is integrally fixed and assembled in the second shell, and the other end of the first wire and the second wire penetrates through the second shell and is led outwards.The first shell and the second shell are mutually buckled and sealedly connected to form a closed inner cavity.The present application improves the sensitivity of the hydrophone in the prior art.

Description

Technical Field

[0001] This invention relates to the field of underwater acoustic detection equipment, specifically to a porous flexible hydrophone and its manufacturing method. Background Technology

[0002] Underwater acoustic detection technology is a core support for marine resource exploration, national defense security early warning, marine ecological monitoring, and underwater engineering inspection. Hydrophones, as key sensing components of underwater acoustic detection systems, directly determine the accuracy and range of underwater target identification, signal transmission, and environmental perception. Based on their working principles, hydrophones can be divided into active and passive hydrophones. Active hydrophones rely on an external power source for signal conversion, inevitably generating self-noise and consuming relatively high power, making them unsuitable for long-term unattended marine detection. In contrast, passive hydrophones generate signal conversion entirely from external acoustic energy excitation, requiring no external power supply, and possess significant advantages such as simple structure, extremely low power consumption, and no self-noise interference.

[0003] Currently, the most widely used passive hydrophones are piezoelectric hydrophones, which achieve force-to-electric conversion based on the piezoelectric effect. However, piezoelectric hydrophones are limited by the Curie temperature; above this temperature, the piezoelectric effect disappears, resulting in poor temperature stability. Furthermore, their sensitivity is positively correlated with size, requiring larger device volumes for low-frequency detection, which contradicts the trend towards miniaturization and integration in underwater acoustic detection equipment. Therefore, a flexoelectric hydrophone based on the flexoelectric effect is proposed. The flexoelectric effect is a force-to-electric coupling phenomenon induced by strain gradient polarization. Unlike the piezoelectric effect, the flexoelectric effect is ubiquitous in all dielectric materials and is not limited by the Curie temperature. Moreover, the flexoelectric effect exhibits a significant size effect; the smaller the device size, the larger the strain gradient, and the higher the force-to-electric conversion efficiency. This allows flexoelectric hydrophones to maintain high sensitivity while achieving miniaturization. These advantages have led to increasing attention being paid to flexoelectric hydrophones based on the flexoelectric effect. However, the relatively low sensitivity of traditional disc-structured flexoelectric hydrophones makes it difficult to meet the requirements for low-frequency weak signal detection. Therefore, it is particularly important to design a flexural hydrophone with high sensitivity. Summary of the Invention

[0004] In order to overcome the defects of the prior art, the purpose of this invention is to provide a porous flexible hydrophone and a manufacturing method thereof, so as to solve the technical problem of how to improve the sensitivity of hydrophones in the prior art.

[0005] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a porous flexible hydrophone, comprising a porous BTO ceramic element, a clamp, a first wire, a second wire, and a package housing; The clamp includes a clamp top cover and a clamp bottom base; The outer edge of the porous BTO ceramic element is clamped and fixed between the upper cover of the fixture and the lower seat of the fixture to form a peripherally fixed circular structure. One end of the first wire is clamped between the outer edge of the top surface of the porous BTO ceramic element and the bottom surface of the upper cover of the fixture, and one end of the second wire is clamped between the outer edge of the bottom surface of the porous BTO ceramic element and the top surface of the lower seat of the fixture. The encapsulation housing includes a first housing and a second housing; The clamp is fixedly assembled inside the second housing, and the other ends of the first and second wires pass through the second housing and extend outward; the first housing and the second housing are interlocked and sealed to form a closed inner cavity.

[0006] Preferably, the upper and lower surfaces of the porous BTO ceramic element are sputtered and coated with chromium / gold electrode layers, and several circular through holes are uniformly opened in the middle of the porous BTO ceramic element.

[0007] Preferably, an annular clamping groove is provided on the upper side of the lower fixture, the depth of which is equal to the thickness of the porous BTO ceramic element, and the porous BTO ceramic element is embedded in the clamping groove.

[0008] Preferably, the upper cover of the clamp has a first wire hole and a first lead hole, and the lower base of the clamp has a second wire hole and a second lead hole; The first wire hole and the second wire hole are vertically aligned, and the first lead hole and the second lead hole are vertically aligned. The first wire passes through the first wire hole, the first lead hole, and the second lead hole in sequence and extends to the lower part of the fixture.

[0009] Preferably, the upper cover of the clamp is provided with a plurality of first bolt holes evenly distributed along the circumference, and the lower seat of the clamp is provided with second bolt holes that correspond one-to-one with the first bolt holes evenly distributed along the circumference; the inner wall of the second housing is integrally formed with a plurality of support columns evenly distributed along the circumference, and after the upper cover of the clamp and the lower seat of the clamp are clamped together, they are locked and fixed to the support columns by bolts passing through the first bolt holes and the second bolt holes.

[0010] Furthermore, an elongated hole is made on the top surface of the support column, and a fixing groove is made on the side of the support column. The nut is placed inside the fixing groove, and the bolt passes through the elongated hole and engages with the nut thread to lock the upper cover of the clamp and the lower seat of the clamp.

[0011] Preferably, the lower edge of the first housing is provided with an annular mounting groove, and the upper edge of the second housing is provided with an annular mounting protrusion. The depth of the mounting groove is equal to the height of the mounting protrusion. The mounting groove and the mounting protrusion are aligned and fitted to achieve a fast assembly of the first housing and the second housing. The first housing is made of polyimide sound-permeable material, and the second housing is made of permalloy shielding material.

[0012] Preferably, a flow guide hole is provided on the side wall of the second housing, and a third lead hole is provided at the center of the bottom surface of the second housing; The enclosed cavities of the first and second housings are filled with castor oil that matches the acoustic impedance of the water, and the castor oil is injected into the cavities through a guide hole; the lead-out ends of the first and second wires pass through the third lead hole and are connected to the external electrode.

[0013] Furthermore, the assembly joints between the first and second housings, the flow guide holes, and the third lead hole are all sealed with epoxy resin.

[0014] Secondly, the present invention also provides a method for manufacturing a porous flexible hydrophone, for obtaining the aforementioned porous flexible hydrophone, comprising the following steps: Cylindrical flexible electric ceramic preforms were prepared by high-pressure sintering. After the preforms were fixed, they were cut into thin slices by diamond wire cutting machine. The thin slices were polished on both sides and ultrasonically cleaned with anhydrous ethanol. A chromium / gold composite electrode layer is deposited by magnetron sputtering on the upper and lower surfaces of a flexoelectric ceramic sheet, and then a number of uniformly distributed circular through holes are etched by ultraviolet laser to produce a porous BTO ceramic element. The fixture upper cover and fixture lower base are CNC milled using PEEK material. The first bolt hole, the first wire hole, and the first lead wire hole are machined on the fixture upper cover, and the second bolt hole, the second wire hole, the second lead wire hole, and the annular clamping groove matching the thickness of the porous BTO ceramic element are machined on the fixture lower base. The first hemispherical shell made of polyimide is injection molded and the groove is machined for assembly; the second cylindrical shell made of permalloy is integrally molded, and the second shell is machined and assembled with protrusions and multiple support columns, and the support columns are provided with elongated holes and fixing grooves. The second shell is also machined with guide holes and third lead holes. The first wire is inserted into the first wire hole, and the second wire is inserted into the second wire hole. The porous BTO ceramic element is placed into the clamping groove of the fixture lower seat, and the fixture cover is fastened to press the first wire and the second wire against the upper and lower outer edges of the porous BTO ceramic element, respectively. The fixture is placed coaxially on the support column of the second housing, and bolts are passed through the first bolt hole, the second bolt hole, the elongated hole, and the nut in the fixing groove to lock and fix it. The first wire passes through the first lead hole and the second lead hole in sequence and then comes out from the third lead hole together with the second wire. The assembly groove of the first housing and the assembly protrusion of the second housing are aligned and fastened, and castor oil matching the underwater acoustic impedance is filled into the inner cavity of the housing through the guide hole. Finally, epoxy resin is used to seal the housing seam, the guide hole and the third lead hole to complete the hydrophone fabrication.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: This invention provides a porous flexible hydrophone. The complete hydrophone body structure comprises a porous BTO ceramic element, a clamp, two wires, and a separate encapsulated housing. The clamp's upper and lower covers hold the porous BTO ceramic element's outer edge, forming a peripherally fixed circular structure. Two wires, positioned on the upper and lower surfaces of the element, facilitate signal extraction. The entire clamp is then fixed inside a second housing, and the first housing is fastened to form a closed internal cavity assembly. Based on the porous BTO ceramic element as the core sensing component, the disc-shaped peripherally fixed mounting method fully releases the deformation space of the porous ceramic, compared to solid, non-porous ceramic... The ceramic disc can achieve a larger strain gradient, improving the flexural polarization response capability and ensuring the hydrophone has a high-sensitivity hardware foundation from the underlying structure. The modular assembly architecture, which uses clamps to hold components and separates and snaps together the encapsulation shell, separates the core sensitive components, clamping and positioning structure, and shielding and sound-permeable encapsulation structure into independent and quickly disassembled combination units. In the event of damage to the core components, the encapsulation shell can be disassembled and the clamps released to replace the components individually, without scrapping the entire hydrophone. This effectively reduces device maintenance costs and extends the service life of the whole device. At the same time, the completely sealed shell structure can provide a stable water environment working space for the internal sensitive components.

[0016] Furthermore, the porous BTO ceramic element has chromium / gold electrode layers on its upper and lower surfaces and uniformly distributed circular through holes in the center. The chromium / gold composite electrode layer can form a conductive circuit with stable conductivity and strong adhesion on the surface of the ceramic element. Under the action of underwater acoustic pressure, the flexural polarization charge generated by the ceramic can be completely and with low loss conducted to the upper and lower conductors, avoiding signal attenuation caused by electrode detachment and conductive circuit breakage. The uniformly distributed circular through holes in the center of the element will change the mechanical properties of the ceramic disk, greatly improve the deformation freedom of the central area of ​​the disk, reduce the overall equivalent bending stiffness of the ceramic element, and generate a larger strain gradient under the same underwater acoustic pressure excitation, significantly enhancing the internal flexural polarization intensity of the ceramic. The hydrophone can output a higher amplitude electrical signal, directly achieving a significant improvement in sensitivity. The uniform arrangement of through holes can also ensure uniform deformation throughout the disk, avoiding signal distortion caused by local stress concentration.

[0017] Furthermore, the lower fixture is equipped with an annular clamping groove whose depth matches the thickness of the porous BTO ceramic element. The ceramic element is embedded inside the clamping groove. During assembly, the clamping groove can achieve radial and vertical dual restraint on the porous BTO ceramic element, preventing radial displacement and warping of the element inside the fixture. This ensures that the outer edge of the ceramic element can be completely and uniformly pressed by the upper fixture cover and the lower fixture, maintaining stable peripheral support constraints. This prevents local clamping failure and uneven deformation due to component misalignment, ensuring long-term stable sensitivity of the hydrophone. At the same time, the groove structure can quickly position the ceramic element, simplifying the assembly alignment process and improving assembly efficiency.

[0018] Furthermore, the upper cover and lower base of the fixture are respectively provided with aligned wire holes and lead holes. The first wire passes through two sets of channels and extends to the bottom of the fixture. The upper and lower aligned wire holes can accurately constrain the wire ends to fit against the upper and lower outer edges of the ceramic element, ensuring that the wire is in close contact with the electrode layer and avoiding contact resistance introduced by the contact gap, which would cause loss of electrical signal. The upper and lower aligned lead holes provide a regular through-path for the wire, allowing the wire to be smoothly led out from inside the fixture. During the assembly process, the wire will not be bent or squeezed and damaged. At the same time, the layered channel structure separates the electrode contact section from the external lead section, so that the electrode contact area on the surface of the ceramic element will not be disturbed when assembling and disassembling the fixture, preventing electrode wear and detachment, and ensuring the continuity and stability of signal transmission.

[0019] Furthermore, the upper and lower covers of the fixture are equipped with corresponding bolt holes, and the inner wall of the second housing is provided with circumferentially distributed support columns. After the fixture is clamped, it is locked and fixed to the support columns by bolts. The circumferentially distributed bolt holes can provide uniform clamping force along the outer edge of the ceramic element, ensuring that the entire outer periphery of the element is pressed synchronously, forming a complete and continuous peripheral fixed boundary condition, avoiding deformation gaps caused by insufficient local clamping force, which would reduce sensitivity. The support columns are integrally formed inside the second housing, which can directly bear the installation load of the entire fixture, combining the fixture and the shielding housing into a whole, simplifying the internal positioning structure of the housing. At the same time, the detachable connection method of bolt locking allows the entire fixture and ceramic element to be completely removed from the housing by loosening the bolts, which is convenient for individual inspection and replacement of multi-hole BTO ceramic elements without discarding the entire packaging housing, thus reducing the cost of device use.

[0020] Furthermore, the support column has an elongated slot on its top surface and a fixing groove on its side for placing nuts. Bolts pass through the elongated slot and engage with the nuts to lock the clamps. The fixing groove on the side of the support column can pre-accommodate the nuts, eliminating the need to lift the nuts from inside the housing during assembly. A single person can complete the bolt tightening operation, simplifying the assembly process. The elongated slot has an adjustment margin along its length, allowing for slight adjustments to the radial mounting position of the clamps on the support column during clamp assembly. This design is compatible with multi-hole BTO ceramic components and matching clamps of different outer diameters, eliminating the need to re-mold and process a second housing. The same set of encapsulation housings can accommodate various customized size-sensitive components, significantly reducing the mold and processing costs for mass production and customized modifications.

[0021] Furthermore, the first housing is provided with an assembly groove, and the second housing is provided with an assembly protrusion with a height equal to the depth of the assembly groove. The two are aligned and fitted together. At the same time, the two housings are made of different functional materials. The groove and protrusion structure with matching depth and height can achieve precise coaxial alignment. After fastening, a tight annular contact surface is formed, which improves the sealing performance of the housing and prevents water leakage in the water environment. The first housing made of polyimide has excellent sound transmission performance. External water sound pressure can be transmitted to the internal porous BTO ceramic element without attenuation, without shielding the water sound excitation and losing sensitivity. The second housing made of permalloy has excellent electromagnetic shielding capability, which can isolate the interference of external electromagnetic fields on the transmission of electrical signals of ceramic electrodes, eliminate signal noise caused by electromagnetic noise, improve the signal-to-noise ratio of the hydrophone output signal, and effectively detect sensitivity.

[0022] Furthermore, the second housing is equipped with a flow guide hole and a third lead hole at the center of the bottom surface. The sealed inner cavity is filled with castor oil that matches the underwater acoustic impedance. The wires are connected to the external electrodes through the third lead hole. The flow guide hole serves as a dedicated channel for filling the medium. After assembly, castor oil can be easily injected into the inner cavity of the sealed housing. The castor oil matches the underwater acoustic impedance, which can eliminate the acoustic impedance mismatch loss caused by the air layer inside the housing. The underwater acoustic pressure can be efficiently transmitted to the porous BTO ceramic element, avoiding acoustic energy reflection loss and ensuring high sensitivity output. Two wires are led out from the third lead hole at the center of the bottom surface. The wiring is neat and separates the signal lead-out end from the underwater acoustic incident side, avoiding wire obstruction and interference with the acoustic signal transmission, and stabilizing the external transmission path of the electrical signal.

[0023] Furthermore, the housing seams, flow guide holes, and third lead hole are all sealed with epoxy resin. After curing, epoxy resin has stable properties of being waterproof, insulating, and resistant to water immersion. It can completely seal the housing assembly gaps, medium filling holes, and lead hole, preventing external water from seeping into the sealed inner cavity and corroding the ceramic electrodes, wires, and clamps. At the same time, it isolates external moisture and impurities, extending the service life of the core sensitive components and internal structure. The sealing structure can also fix the medium inside the lead and flow guide hole, avoiding castor oil leakage during operation that could lead to acoustic impedance matching failure, and continuously maintaining the hydrophone's stable and highly sensitive detection performance.

[0024] This invention also provides a method for manufacturing a porous flexible hydrophone. A ceramic substrate is prepared through high-pressure sintering, diamond wire cutting, and double-sided polishing and cleaning, resulting in a ceramic sheet with uniform thickness and a smooth, defect-free surface. The substrate flatness ensures the accuracy of subsequent electrode sputtering and through-hole etching, avoiding uneven deformation caused by substrate defects. Radio frequency magnetron sputtering is used to prepare chromium / gold composite electrodes, and ultraviolet laser etching is used to create uniform through-holes. This allows for precise control of electrode thickness, through-hole size, and arrangement, stably achieving the low bending stiffness and high strain gradient mechanical and electrical properties of the porous ceramic. The batch-produced components exhibit high sensitivity consistency. A PEEK material CNC milling fixture is then used to integrally form a permalloy cylindrical shell and a polyimide acoustic shell. Standardized precision machining ensures the matching of assembly dimensions for each component, resulting in a long... The waist-shaped hole matching process enables the housing to adapt to multiple component specifications, reducing the need for customized modification processing. The step-by-step assembly process first completes the precise clamping and positioning of ceramic components and fixtures, and then the whole assembly is installed onto the housing support column. This allows for early detection of electrode contact and component clamping defects during the assembly stage, avoiding rework after the whole machine is packaged. Finally, the entire assembly is sealed with epoxy after filling the dedicated guide hole with castor oil that matches the water acoustic impedance. The media filling and sealing processes are separated, which ensures that the internal cavity is fully filled with media without air bubbles and can seal all water-permeable and leakage points in one go. The whole method has a smooth process connection and controllable processing accuracy, which can stably mass-produce flexible hydrophones with high sensitivity, detachable maintenance, and compatibility with multiple component specifications. The production yield is high, and the later maintenance and component replacement operations are convenient, effectively reducing the total life cycle production cost. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the porous flexible electric ceramic element structure in an embodiment of the present invention; Figure 2 This is a schematic diagram of the fixture disassembly in an embodiment of the present invention; Figure 3 This is a structural breakdown diagram of the packaging shell in an embodiment of the present invention; Figure 4 This is a structural breakdown diagram of the porous flexible electro-hydraulic device in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure in an embodiment of the present invention where the clamp is fixed to the second housing; Figure 6 This is a three-dimensional structural schematic diagram of the porous flexible hydrophone in an embodiment of the present invention; Figure 7 This is a cross-sectional view of the porous flexible electro-hydraulic device in an embodiment of the present invention; Figure 8 This is a simulation diagram showing the relationship between the radius of the circular through-hole and the surface charge in a porous flexural ceramic element according to an embodiment of the present invention. In the diagram: 1. Porous BTO ceramic element; 2. Circular through hole; 3. Fixture; 4. Fixture top cover; 5. Fixture bottom; 6. First bolt hole; 7. Second bolt hole; 8. First wire hole; 9. Second wire hole; 10. First lead hole; 11. Second lead hole; 12. Clamping groove; 13. Encapsulation housing; 14. First housing; 15. Second housing; 16. Assembly groove; 17. Assembly protrusion; 18. Support column; 19. Long slotted hole; 20. Fixing groove; 21. Guide hole; 22. Third lead hole; 23. First wire; 24. Second wire. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0027] The purpose of this invention is to provide a porous flexible hydrophone and its manufacturing method, which solves the technical problems of low sensitivity, high maintenance cost and difficulty in customized modification of existing hydrophones. By improving the deformation response capability of the device through a porous ceramic structure and optimizing the overall assembly structure and manufacturing process, the invention achieves the effects of high sensitivity, long life, low cost mass production and customized adaptation of hydrophones.

[0028] The present invention will now be described in further detail with reference to the accompanying drawings: Example 1 See Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 as well as Figure 7In one embodiment of the present invention, a porous flexible hydrophone is provided, comprising a porous BTO ceramic element 1, a clamp 3, a first wire 23, a second wire 24, and a housing 13. The clamp 3 includes a clamp top cover 4 and a clamp bottom base 5. The outer edge of the porous BTO ceramic element 1 is clamped and fixed between the clamp top cover 4 and the clamp bottom base 5 to form a peripherally fixed circular structure. One end of the first wire 23 is clamped between the outer edge of the top surface of the porous BTO ceramic element 1 and the bottom surface of the clamp top cover 4, and one end of the second wire 24 is clamped between the outer edge of the bottom surface of the porous BTO ceramic element 1 and the top surface of the clamp bottom base 5. The housing 13 includes a first housing 14 and a second housing 15. The clamp 3 is integrally fixedly assembled inside the second housing 15. The other ends of the first wire 23 and the second wire 24 extend outwards through the second housing 15. The first housing 14 and the second housing 15 are interlocked and sealed to form a closed inner cavity, providing a stable working environment for the internal core components.

[0029] The porous BTO ceramic element 1 has chromium / gold electrode layers sputtered onto its upper and lower surfaces, which can stably conduct polarization charges and reduce signal transmission loss. Several uniformly sized circular through-holes 2 are evenly distributed in the center of the porous BTO ceramic element 1. In this embodiment, there are seven circular through-holes 2, each with a diameter of 3 mm and a spacing of 4 mm between adjacent holes. The overall diameter of the porous BTO ceramic element 1 is 22 mm, and its thickness is 0.2 mm. This porous structure significantly increases the deformation freedom of the central region of the ceramic element, reduces the equivalent bending stiffness, generates a larger strain gradient under hydroacoustic pressure excitation, effectively enhances the flexural polarization intensity, and improves the detection sensitivity of the hydrophone.

[0030] The fixture 3 is precision-machined from insulating, environmentally friendly, high-strength, and high-temperature-resistant PEEK engineering plastic, and has an overall ring-shaped split structure. The lower fixture 5 has an annular clamping groove 12 on its upper side. The depth of the clamping groove 12 is equal to the thickness of the porous BTO ceramic element 1, specifically 0.2mm. The inner diameter of the annular clamping groove 12 is 16mm, and the outer diameter is 22mm. The porous BTO ceramic element 1 is embedded inside the clamping groove 12, enabling precise positioning and limiting fixation of the element, preventing assembly misalignment and warping, and ensuring the stability of the surrounding support structure. The upper fixture cover 4 has an overall inner diameter of 16mm, an outer diameter of 32mm, and a thickness of 2mm. The specifications of the lower fixture 5 are consistent with those of the upper fixture cover 4.

[0031] The upper cover 4 of the fixture has a first wire hole 8 and a first lead hole 10, and the lower base 5 of the fixture has a second wire hole 9 and a second lead hole 11. The first wire hole 8 and the second wire hole 9 are vertically aligned, and the first lead hole 10 and the second lead hole 11 are vertically aligned. In this embodiment, the diameter of the first wire hole 8, the second wire hole 9, the first lead hole 10, and the second lead hole 11 is 1mm. The distance between the first wire hole 8 and the second wire hole 9 and the center of the ring is 9.5mm, and the distance between the first lead hole 10 and the second lead hole 11 and the center of the ring is 13.5mm. The first wire 23 passes through the first wire hole 8, the first lead hole 10, and the second lead hole 11 in sequence and extends to the lower base 5 of the fixture. The regular alignment channel structure can ensure that the wire and the ceramic element electrode are in close contact, avoiding poor contact, wire bending and damage, and ensuring stable transmission of electrical signals.

[0032] The upper cover 4 of the clamp is evenly provided with several first bolt holes 6 along its circumference, and the lower seat 5 of the clamp is evenly provided with second bolt holes 7 that correspond one-to-one with the first bolt holes 6 along its circumference. In this embodiment, there are four first bolt holes 6 and four second bolt holes 7, each with a diameter of 3 mm, and they are evenly distributed circumferentially at a distance of 13.5 mm from the center. The inner wall of the second housing 15 is integrally formed with multiple support columns 18 that are evenly distributed circumferentially. In this embodiment, there are four support columns 18, each with a length of 14 mm, a width of 8 mm, and a height of 13 mm. After the upper cover 4 of the clamp is clamped to the lower seat 5 of the clamp, it is locked and fixed to the support columns 18 by M3 bolts passing through the first bolt holes 6 and the second bolt holes 7. The evenly distributed bolt holes can provide uniform clamping force, ensuring that the outer periphery of the ceramic component is clamped evenly and the force is stable.

[0033] The support column 18 has an elongated slot 19 on its top surface and a fixing groove 20 on its side. A nut is placed inside the fixing groove 20, and a bolt passes through the elongated slot 19 and engages with the nut's thread to lock the upper cover 4 and lower seat 5 of the clamp. In this embodiment, the elongated slot 19 has a depth of 13mm and is composed of a rectangular structure with a length of 9mm and a width of 3mm, combined with semi-circular structures with diameters of 3mm at both ends. The fixing groove 20 is located on the side of the support column 18, 2mm from the top surface, and has dimensions of 5.5mm in length, 2.4mm in width, and 13.5mm in depth. The elongated slot 19 provides adjustment allowance for assembly, accommodating multi-hole BTO ceramic components 1 and clamps 3 of different sizes, reducing the cost of customized device modification and mass production. The fixing groove 20 can limit and fix the nut, simplifying the assembly process and improving assembly efficiency.

[0034] The lower edge of the first housing 14 is provided with an annular mounting groove 16, and the upper edge of the second housing 15 is provided with an annular mounting protrusion 17. The depth of the mounting groove 16 and the height of the mounting protrusion 17 are equal, both being 2mm. The mounting groove 16 and the mounting protrusion 17 are aligned and fitted together to achieve a fastening assembly of the first housing 14 and the second housing 15. The first housing 14 is made of polyimide sound-permeable material and is manufactured using injection molding. It is a hollow hemispherical shape with an inner diameter of 40mm and a thickness of 6mm. The inner ring diameter of the mounting groove 16 is 44mm and the outer ring diameter is 48mm. Its excellent sound transmission performance ensures that the underwater acoustic signal is transmitted into the housing without attenuation. The second housing 15 is made of permalloy shielding material and is integrally formed by a cylindrical body and an upper annular mounting protrusion 17. The inner wall diameter of the cylindrical body is 40mm, the side wall thickness is 6mm, the bottom thickness is 3mm, and the height is 20mm. The inner ring diameter of the mounting protrusion 17 is 44mm and the outer ring diameter is 48mm. The permalloy material can effectively shield external electromagnetic field interference and improve the signal-to-noise ratio of the hydrophone output signal.

[0035] A 3mm diameter guide hole 21 is provided 2mm above the support column 18 on the side wall of the second housing 15, and a 3mm diameter third lead hole 22 is provided at the center of the bottom surface of the second housing 15. The closed inner cavity formed by the fastening of the first housing 14 and the second housing 15 is filled with castor oil that matches the underwater acoustic impedance. The castor oil is injected into the inner cavity through the guide hole 21, which can eliminate acoustic impedance mismatch loss and ensure that the underwater acoustic signal is efficiently transmitted to the porous BTO ceramic element 1. The lead-out ends of the first wire 23 and the second wire 24 pass through the third lead hole 22 to connect to the external electrode. The centralized lead structure has a neat wiring layout, which can avoid the lead wires from blocking and interfering with the acoustic signal transmission.

[0036] The assembly joints between the first housing 14 and the second housing 15, the flow guide hole 21, and the third lead hole 22 are all sealed with epoxy resin. The cured epoxy resin has excellent waterproof, insulating, and water immersion resistant properties, which can effectively seal all gaps and holes, prevent external water and impurities from seeping into the inner cavity and corroding the core components, and at the same time avoid internal castor oil leakage, maintain the sealing performance and working stability of the device for a long time, and extend the service life of the hydrophone.

[0037] This embodiment provides a porous flexible hydrophone, comprising a complete hydrophone body structure consisting of a porous BTO ceramic element 1, a clamp 3, two wires, and a split-type encapsulation housing 13. The clamp upper cover 4 and clamp lower seat 5 clamp the outer edge of the porous BTO ceramic element 1 to form a peripherally fixed circular structure. Two wires placed on the outer edges of the upper and lower surfaces of the element are used for signal extraction. The entire clamp 3 is then fixed inside the second housing 15 and fastened to the first housing 14 to form a closed inner cavity assembly structure. Based on the porous BTO ceramic element 1 as the core sensing component, the disc-shaped peripherally fixed installation fully releases the deformation space of the porous ceramic, compared to traditional methods. The non-porous ceramic disk can achieve a larger strain gradient, improving the flexural polarization response capability and ensuring the hydrophone has a high-sensitivity hardware foundation from the underlying structure. The modular assembly architecture adopts a clamp 3 to hold the components and a separate and snap-fit ​​package shell 13. The core sensitive components, clamping and positioning structure and shielding sound-transparent packaging structure are separated into independent and quickly disassembled combination units. If the core components are damaged in the future, the package shell 13 can be disassembled and the clamp 3 can be released to replace the components individually without scrapping the entire hydrophone. This effectively reduces the device maintenance cost and extends the service life of the whole device. At the same time, the shell structure with a completely closed inner cavity can provide a stable water environment working space for the internal sensitive components.

[0038] Example 2 This invention also provides a method for manufacturing a porous flexible hydrophone, based on the above-described porous flexible hydrophone, comprising the following steps: Step 1: Prepare BTO ceramic sheets.

[0039] Cylindrical BTO ceramic preforms were sintered using a rapid high-pressure sintering method. The preforms had a diameter of 22 mm and a height of 8 mm. Epoxy resin was used to fix the preforms onto the aluminum alloy fixture of a diamond wire EDM machine. The machine's rotation speed was set to 250 rad / min, and the cutting speed to 0.2 mm / min. The preforms were then cut into several 22 mm diameter, 0.2 mm thick BTO ceramic sheets using the diamond wire EDM machine. The upper and lower surfaces of the cut BTO ceramic sheets were then polished sequentially with 800-grit, 1200-grit, and 2000-grit diamond polishing pastes. The polished sheets were then ultrasonically cleaned with anhydrous ethanol for 15 minutes.

[0040] Step 2: Preparation of porous BTO ceramic elements 1.

[0041] A radio frequency magnetron sputtering instrument was used to deposit 10 nm thick chromium and 30 nm thick gold electrode layers on the upper and lower surfaces of the BTO ceramic wafer, respectively. The RF magnetron sputtering instrument current was set to 15 mA and the sputtering time was 180 s. A 355 nm ultraviolet laser was then used to etch the surface of the BTO ceramic wafer, resulting in a porous BTO ceramic element 1 with seven 3 mm diameter circular through-holes 2. The seven circular through-holes 2 are evenly distributed in the middle of the BTO ceramic wafer, with a distance of 4 mm between adjacent through-holes 2. The overall thickness of the porous BTO ceramic element 1 is 0.2 mm and its diameter is 22 mm. Figure 1 As shown.

[0042] Step 3: Prepare the fixture 3 for the porous BTO ceramic element 1.

[0043] The fixture 3 is made of insulating, environmentally friendly, high-strength, and high-temperature resistant PEEK engineering plastic, which is precision milled using a high-precision CNC milling machine. The fixture 3 consists of a fixture upper cover 4 and a fixture lower base 5. The fixture upper cover 4 is generally circular, with an inner ring diameter of 16mm, an outer ring diameter of 32mm, and an overall thickness of 2mm. A first wire hole 8 with a diameter of 1mm is provided at a distance of 9.5mm from the center of the ring, a first lead wire hole 10 with a diameter of 1mm is provided at a distance of 13.5mm from the center of the ring, and four first bolt holes 6 with a diameter of 3mm are evenly provided circumferentially at a distance of 13.5mm from the center of the ring. The lower fixture 5 is also generally annular, with an inner ring diameter of 16mm, an outer ring diameter of 32mm, and an overall thickness of 2mm. A second wire hole 9 with a diameter of 1mm is located 9.5mm from the ring center, and a second lead wire hole 11 with a diameter of 1mm is located 13.5mm from the ring center. Four second bolt holes 7 with a diameter of 3mm are evenly distributed circumferentially at a distance of 13.5mm from the ring center. The upper side of the lower fixture 5 has an annular clamping groove 12 with an inner ring diameter of 16mm, an outer ring diameter of 22mm, and a depth of 0.2mm. Figure 2 As shown.

[0044] Step 4: Prepare the encapsulation housing 13 of the porous flexible hydrophone.

[0045] The encapsulation housing 13 of the porous flexible hydrophone is divided into a first housing 14 and a second housing 15. The first housing 14 is made of polyimide sound-permeable material and is manufactured by injection molding. The first housing 14 is a hollow hemispherical shape with an inner diameter of 40 mm and a thickness of 6 mm. The lower outer periphery of the first housing 14 has an annular mounting groove 16 with an inner ring diameter of 44 mm, an outer ring diameter of 48 mm, and a depth of 2 mm. The second housing 15 is made of permalloy, which can effectively shield electromagnetic interference. The second housing 15 is an integrally formed cylindrical body with an inner wall diameter of 40 mm, a side wall thickness of 6 mm, a bottom thickness of 3 mm, and a height of 20 mm, and an annular mounting protrusion 17 with an inner ring diameter of 44 mm, an outer ring diameter of 48 mm, and a height of 2 mm on the upper outer periphery of the cylindrical body. The inner wall of the second housing 15 is integrally formed with four circumferentially evenly distributed cuboid support columns 18, each 14mm long, 8mm wide, and 13mm high. The top surface of each support column 18 has a long, oblong hole 19 with a depth of 13mm, composed of a rectangle 9mm long and 3mm wide and two semicircles with a diameter of 3mm. A rectangular fixing groove 20, 5.5mm long, 2.4mm wide, and 13.5mm deep, is formed on the side of each support column 18 2mm from the top surface. A 3mm diameter guide hole 21 is located 2mm above each support column 18. A third lead hole 22 with a diameter of 3mm is located in the center of the bottom surface of the second housing 15. Figure 3 As shown.

[0046] Step 5: Packaging preparation of the porous flexible hydrophone.

[0047] One end of the first wire 23 is passed through the first wire hole 8 of the upper cover 4 of the clamp, and one end of the second wire 24 is passed through the second wire hole 9 of the lower seat 5 of the clamp. The porous BTO ceramic element 1 is embedded into the annular clamping groove 12 of the lower seat 5, so that the outer periphery of the bottom surface of the porous BTO ceramic element 1 is tightly fitted with one end of the second wire 24. Then, the upper cover 4 of the clamp and the lower seat 5 are coaxially aligned and fastened, so that the outer periphery of the top surface of the porous BTO ceramic element 1 is tightly fitted with one end of the first wire 23. The clamped clamp 3 is placed on the support column 18 of the second housing 15, ensuring that the clamp 3 and the second housing 15 are coaxially set. M3 bolts are used to pass through the aligned first bolt hole 6 and second bolt hole 7 in sequence, and through the elongated hole 19 to cooperate with the M3 nut placed in the fixing groove 20 to fasten the porous BTO ceramic element 1, forming a circular structure with a fixed periphery. The other end of the first wire 23 passes through the first lead hole 10 and the second lead hole 11 in sequence, extending to the lower side of the fixture base 5. The free ends of the first wire 23 and the second wire 24 are connected to the external electrode through the third lead hole 22. The mounting groove 16 of the first housing 14 and the mounting protrusion 17 of the second housing 15 are aligned and fitted to securely connect the first housing 14 and the second housing 15. Castor oil, matching the underwater acoustic impedance, is filled into the inner cavity of the encapsulation housing 13 through the flow guide hole 21 until the castor oil completely fills the inner cavity, wraps the porous BTO ceramic element 1 and the fixture 3, and removes all the air from the inner cavity. Finally, the connection between the first housing 14 and the second housing 15, the third lead hole 22 and the flow guide hole 21 are sealed with epoxy resin to complete the encapsulation preparation of the porous flexible hydrophone. Figure 4-7 As shown.

[0048] To verify the correctness of the structure of this invention, the finite element simulation software COMSOL Multiphysics 6.1 was used to establish a finite element model of this invention. Then, the dimensions were optimized and the sensitivity of the porous structure flexural hydrophone and the disk structure flexural hydrophone were obtained.

[0049] The material parameters used in the modeling are shown in Table 1: Table 1 Material Parameters

[0050] 1. Optimized size design For a porous BTO ceramic element 1 of a given specification, the seven circular through holes 2 always correspond to an optimal value for their radii. By parametrically scanning the model, the relationship between the radius of the circular through holes 2 on the porous BTO ceramic element 1 and the surface charge Q can be obtained, as follows: Figure 8 As shown in the figure, the surface charge Q of the porous flexible hydrophone first increases and then decreases with the increase of the radius of the circular through-hole 2. For the porous flexible hydrophone, the optimal radius of the circular through-hole 2 is 1.5 mm.

[0051] 2. Charge sensitivity M of the flexural hydrophone q M refers to the ratio of the surface charge Q of a flexure hydrophone to the free-field sound pressure intensity p acting at the effective sound center of the flexure hydrophone at a specified operating frequency. q =Q / p. This is the core performance parameter characterizing the sound-to-electric conversion capability of a flexural hydrophone.

[0052] The free-field sound pressure intensity p is set to 100 Pa, and the operating frequency is set to 100 Hz. For the porous flexible hydrophone, its surface charge Q is 1.303 pC. The charge sensitivity M of the porous flexible hydrophone is calculated. q The surface charge Q of the disk-structured flexible hydrophone is 0.013 pC / Pa; while for a disk-structured flexible hydrophone of the same size, its surface charge Q is 0.103 pC. The calculated charge sensitivity M of the disk-structured flexible hydrophone is... q The value is 0.001 pC / Pa. Therefore, it can be seen that the sensitivity of the porous flexible hydrophone is 13 times that of the disc flexible hydrophone, which indicates that the porous flexible hydrophone can effectively improve the sensitivity.

[0053] In summary, the porous flexure electro-hydrophone and its manufacturing method provided by this invention, by setting a circular through-hole 2 on the disc structure, removes the rigid support in the central region of the solid disc, significantly increasing the deformation freedom of the central region of the disc and expanding the distribution range of the high strain gradient region. Simultaneously, the porous structure reduces the equivalent bending stiffness of the ceramic element. Under the same underwater acoustic pressure excitation, the porous BTO ceramic element 1 can produce a greater bending deformation. Greater deformation corresponds to a greater strain gradient. The flexure electro-electric effect is essentially driven by the strain gradient; the greater the strain gradient, the greater the flexure electropolarization intensity, thereby directly improving the output sensitivity of the hydrophone. The porous flexure electro-hydrophone provided by this invention can effectively improve the sensitivity of traditional disc-structure flexure electro-hydrophones. Furthermore, the core component can be individually disassembled and replaced after damage, eliminating the need for overall component scrapping, extending the service life of the hydrophone, and reducing maintenance costs. At the same time, the elongated hole 19 design within the encapsulation housing 13 can accommodate flexure electro-ceramic elements of different sizes, significantly reducing the cost of mass production and customized modifications.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A porous flexible electrohydraulic device, characterized in that, Includes a porous BTO ceramic element (1), a fixture (3), a first lead wire (23), a second lead wire (24), and a package housing (13); The clamp (3) includes a clamp top cover (4) and a clamp bottom seat (5); The outer edge of the porous BTO ceramic element (1) is clamped and fixed between the upper cover (4) of the clamp and the lower seat (5) of the clamp to form a peripherally fixed circular structure; One end of the first wire (23) is clamped between the outer edge of the top surface of the porous BTO ceramic element (1) and the bottom surface of the fixture cover (4), and one end of the second wire (24) is clamped between the outer edge of the bottom surface of the porous BTO ceramic element (1) and the top surface of the fixture base (5); The encapsulation housing (13) includes a first housing (14) and a second housing (15). The clamp (3) is fixedly assembled inside the second housing (15), and the other ends of the first wire (23) and the second wire (24) pass through the second housing (15) and lead outward; the first housing (14) and the second housing (15) are interlocked and sealed to form a closed inner cavity.

2. The porous flexible hydrophone according to claim 1, characterized in that, The porous BTO ceramic element (1) has chromium / gold electrode layers sputtered on its upper and lower surfaces respectively, and several circular through holes (2) are uniformly opened in the middle of the porous BTO ceramic element (1).

3. The porous flexible hydrophone according to claim 1, characterized in that, The lower fixture (5) is provided with an annular clamping groove (12) on its upper side. The depth of the clamping groove (12) is equal to the thickness of the porous BTO ceramic element (1). The porous BTO ceramic element (1) is embedded in the clamping groove (12).

4. A porous flexible hydrophone according to claim 1, characterized in that, The upper cover (4) of the clamp has a first wire hole (8) and a first lead wire hole (10), and the lower seat (5) of the clamp has a second wire hole (9) and a second lead wire hole (11). The first wire hole (8) and the second wire hole (9) are aligned vertically, and the first lead hole (10) and the second lead hole (11) are aligned vertically. The first wire (23) passes through the first wire hole (8), the first lead hole (10), and the second lead hole (11) in sequence and extends to the lower part of the fixture (5).

5. A porous flexible electrohydraulic device according to claim 1, characterized in that, The clamp cover (4) has a plurality of first bolt holes (6) evenly opened along the circumference, and the clamp base (5) has second bolt holes (7) evenly opened along the circumference, corresponding one-to-one with the first bolt holes (6); the inner wall of the second housing (15) is integrally formed with a plurality of support columns (18) evenly distributed along the circumference. After the clamp cover (4) and the clamp base (5) are clamped together, they are locked and fixed to the support columns (18) by bolts passing through the first bolt holes (6) and the second bolt holes (7).

6. A porous flexible electrohydraulic device according to claim 5, characterized in that, The top surface of the support column (18) has an elongated hole (19), and the side surface of the support column (18) has a fixing groove (20). The nut is placed inside the fixing groove (20), and the bolt passes through the elongated hole (19) and engages with the nut to lock the upper cover (4) of the clamp and the lower seat (5).

7. A porous flexible hydrophone according to claim 1, characterized in that, The lower edge of the first housing (14) is provided with an annular mounting groove (16), and the upper edge of the second housing (15) is provided with an annular mounting protrusion (17). The depth of the mounting groove (16) is equal to the height of the mounting protrusion (17). The mounting groove (16) and the mounting protrusion (17) are aligned and fitted to achieve a fast assembly of the first housing (14) and the second housing (15). The first housing (14) is made of polyimide sound-permeable material, and the second housing (15) is made of permalloy shielding material.

8. A porous flexible hydrophone according to claim 1, characterized in that, A flow guide hole (21) is provided on the side wall of the second housing (15), and a third lead hole (22) is provided at the center of the bottom surface of the second housing (15). The closed cavities of the first housing (14) and the second housing (15) are filled with castor oil that matches the acoustic impedance of the water. The castor oil is injected into the cavities through the guide hole (21). The leads of the first wire (23) and the second wire (24) pass through the third lead hole (22) and are connected to the external electrode.

9. A porous flexible hydrophone according to claim 8, characterized in that, The assembly joints of the first housing (14) and the second housing (15), the guide hole (21) and the third lead hole (22) are all sealed with epoxy resin.

10. A method for manufacturing a porous flexible hydrophone, characterized in that, The process for obtaining a porous flexible hydrophone according to any one of claims 1-9 includes the following steps: Cylindrical flexible electric ceramic preforms were prepared by high-pressure sintering. After the preforms were fixed, they were cut into thin slices by diamond wire cutting machine. The thin slices were polished on both sides and ultrasonically cleaned with anhydrous ethanol. A chromium / gold composite electrode layer is deposited by magnetron sputtering on the upper and lower surfaces of the flexoelectric ceramic sheet, and then a number of uniformly distributed circular through holes (2) are etched by ultraviolet laser to produce a porous BTO ceramic element (1). The fixture upper cover (4) and fixture lower seat (5) are machined by CNC milling using PEEK material. The first bolt hole (6), the first wire hole (8), and the first lead wire hole (10) are machined on the fixture upper cover (4), and the second bolt hole (7), the second wire hole (9), the second lead wire hole (11), and the annular clamping groove (12) matching the thickness of the porous BTO ceramic element (1) are machined on the fixture lower seat (5). A hemispherical first shell (14) made of polyimide material is injection molded and an assembly groove (16) is machined; a cylindrical second shell (15) made of permalloy material is integrally molded, and a protrusion (17) and multiple support columns (18) are machined on the second shell (15). An elongated hole (19) and a fixing groove (20) are opened on the support columns (18). A guide hole (21) and a third lead hole (22) are machined on the second shell (15). Insert the first wire (23) into the first wire hole (8) and the second wire (24) into the second wire hole (9); place the porous BTO ceramic element (1) into the clamping groove (12) of the lower seat (5) of the clamp, and fasten the upper cover (4) of the clamp so that the upper and lower outer edges of the porous BTO ceramic element (1) respectively press the first wire (23) and the second wire (24); place the clamp (3) coaxially on the support column (18) of the second housing (15), and pass the bolt through the first bolt hole (6), the second bolt hole (7), and the elongated hole (19) to fix it. The nut in the groove (20) is locked and fixed; the first wire (23) passes through the first lead hole (10) and the second lead hole (11) in sequence and is led out from the third lead hole (22) together with the second wire (24); the assembly groove (16) of the first housing (14) and the assembly protrusion (17) of the second housing (15) are aligned and fastened, and castor oil matching the water acoustic impedance is filled into the inner cavity of the housing through the guide hole (21); finally, epoxy resin is used to seal the housing joint, the guide hole (21) and the third lead hole (22) to complete the hydrophone preparation.

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