Intermediate-frequency broadband electroacoustic energy transmitting device and design method thereof

Abstract

The invention discloses an intermediate frequency broadband electro-acoustic energy emission device and a design method thereof, the device comprises a magnetostrictive rod and an excitation coil, the magnetostrictive rod generates axial telescopic deformation under the action of an alternating magnetic field, and the excitation coil generates axial telescopic deformation under the action of structural constraint and force transmission of a triangular frame. The axial deformation of each driving unit is synthesized at the central output assembly (central base), and the axial infinitesimal displacement of the magnetostriction rod is effectively converted into in-plane vibration or composite vibration output of the central output assembly by reasonably designing the geometric dimension and the connection mode of the triangular frame and the arrangement angle of each driving unit. Therefore, the force output capability and the structural stability of the transducer are improved. According to the invention, the structure is compact, the stress is symmetrical, the response speed is fast, high sound source level output and wide frequency band are realized with a small size, and the linearity is good.

Description

Technical Field

[0001] This invention relates to the field of electroacoustic transducer technology, and particularly to a medium-frequency broadband electroacoustic energy emitting device and its design method. Background Technology

[0002] Electroacoustic transducers are mainly used in underwater acoustics, ultrasonic processing, vibration generation, and other fields. Their core function is to convert electrical energy into mechanical vibration or sound wave radiation. Traditional electroacoustic transducers often use piezoelectric ceramics or magnetostrictive materials as the driving source. Among them, piezoelectric transducers, although technologically mature, often face problems such as limited material strain, low tensile strength, brittle fracture, and severe heat generation under high power in the mid-frequency range, especially in applications requiring high energy density and high output force. These limitations restrict their output capacity and reliability.

[0003] As a novel smart material, giant magnetostrictive materials possess significant advantages such as large strain values ​​(up to 1000-1500 ppm), high energy density, fast response speed, and large output force, making them particularly suitable for transducer designs with medium to high power and high energy density. However, some technical challenges remain in practical applications: First, the material is typically used in rod form, and although its axial expansion and contraction are large, they are still at the micrometer level, limiting direct driving efficiency; second, the output direction of a single driving unit is unidirectional, making it difficult to directly achieve complex vibration modes or large-amplitude in-plane motion; third, the overall transducer structure needs to operate under high preload to ensure material performance, which places higher demands on the symmetry, stiffness, and force transmission efficiency of the structure.

[0004] Existing giant magnetostrictive transducers mostly employ a single drive form with longitudinal vibration or a composite structure, or increase output by simply stacking multiple drive units in parallel. However, this often results in complex structures, large volumes, uneven stress distribution, and difficulties in vibration coupling and phase coordination between different units, easily introducing nonlinear distortion and affecting the transducer's bandwidth and linearity. Therefore, how to efficiently integrate the output of multiple giant magnetostrictive drive units within a compact space, effectively amplify or convert their minute axial displacements into the desired form of vibration output, while maintaining structural stiffness, symmetry, and dynamic stability, has become a key technical problem for improving the performance of this type of transducer. Summary of the Invention

[0005] To address the above problems, this invention provides a mid-frequency broadband electroacoustic energy emission device and its design method.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A mid-frequency broadband electroacoustic energy transmitting device includes a triangular shell (4), a central base (8) fixed in the middle of the triangular shell (4); three sets of super magnetostrictive oscillators are clamped and fixed between the triangular shell (4) and the central base (8) through a magnetically conductive base (5); the three sets of super magnetostrictive oscillators are arranged radially symmetrically; an AC excitation coil (9) is provided on the outer sleeve of the super magnetostrictive oscillator; the excitation coil (9) is electrically connected to a watertight head (10) installed on the triangular shell (4); cork is provided on the upper and lower sides of the triangular shell (4). The cork pad (3) is covered with a cover plate (1) on the outside of the cork pad (3). The outer periphery and middle part of the cover plate (1) are fixed to the triangular shell (4) and the central base (8) by connecting screws (2), respectively. The cover plate (1) and the cork pad (3) and the cork pad (3) and the triangular shell (4) are sealed by polyurethane sealant. The cavity inside the triangular shell (4) is filled with air or silicone oil. The super magnetostrictive oscillator is in a pre-compression state. The three sides of the triangular shell (4) form a side radiation surface (11).

[0007] In a further improvement, the super magnetostrictive oscillators are positioned at a 120° angle to each other.

[0008] In a further improvement, the super magnetostrictive oscillator is formed by alternating bonding of permanent magnets (6) and super magnetostrictive rods (7), and both ends of the super magnetostrictive oscillator are permanent magnets (6).

[0009] In a further improvement, the super magnetostrictive oscillator is composed of two super magnetostrictive rods (7) and three permanent magnets (6) arranged and glued alternately; the length of the AC excitation coil (9) is less than the length of the super magnetostrictive oscillator; the length of the super magnetostrictive oscillator is greater than the length of the installation space of the super magnetostrictive oscillator by 0.1-0.5 mm.

[0010] Further improvements include a magnetostrictive rod (7) with a diameter of 20 mm and a length of 55 mm, and a permanent magnet (6) with a diameter of 20 mm and a length of 10 mm; both the magnetostrictive rod (7) and the permanent magnet (6) are slit-cut.

[0011] Further improvements include: the magnetic base (5) is made of DT4C electrical pure iron material; the permanent magnet (6) is made of neodymium iron boron material; the super magnetostrictive rod (7) and the permanent magnet (6) are bonded and fixed with adhesive, which is EPO-TEKH74 series epoxy resin adhesive; the triangular shell (4) and the central base (8) are made of aluminum alloy material; the cover plate (1) is made of titanium alloy material and is electroplated on the surface; and the sealant is polyurethane.

[0012] In a further improvement, the three corners of the triangular shell (4) are all rounded, and the three side radiation surfaces (11) are all concave arcs.

[0013] Further improvements include ensuring that the size of the intermediate frequency broadband electroacoustic energy emitting device does not exceed 450mm*450mm*65mm.

[0014] A design method for the above-mentioned mid-frequency broadband electroacoustic energy emission device involves adjusting the thickness of the side radiation surface (11) according to the resonant frequency. When it is necessary to increase the resonant frequency, the thickness of the side radiation surface (11) is increased; when it is necessary to decrease the resonant frequency, the thickness of the side radiation surface (11) is decreased.

[0015] Further improvements are made by adjusting the thickness of the magnetic base (5) according to the working depth of the mid-frequency broadband electroacoustic energy emission device, thereby adjusting the preload of the super magnetostrictive oscillator so that at the working depth, the super magnetostrictive rod (7) works in the linear region of its magnetostrictive characteristic curve and is at the optimal working point with the largest slope of the strain-magnetic field strength curve.

[0016] Advantages of this invention: 1. The transducer unit of this invention optimizes the energy transfer path and vibration synthesis mechanism through innovative mechanical structure design. Its impedance curve changes slowly near the resonance point, with a wide bandwidth. The -3dB bandwidth measured at a water depth of 30m exceeds 500Hz, and the output waveform has good linearity.

[0017] 2. The transducer unit of the present invention has a unit volume ≤0.013m³, a weight ≤15kg, and a maximum size ≤450mm*450mm*65mm, especially a height ≤65mm, which is conducive to the miniaturization and convenient deployment of the transducer.

[0018] 3. Thanks to the high energy density of the super magnetostrictive rod material, the transducer unit of this invention can achieve a sound source level of over 195dB with only a small current of 10A, demonstrating superior performance.

[0019] 4. The transducer unit of this invention, through reasonable mechanical structure and prestress design, has good linearity near the resonance point and high output waveform quality. Attached Figure Description

[0020] Figure 1 This is an overall structural diagram of the mid-frequency broadband electroacoustic energy emission method.

[0021] Figure 2 This is an overall assembly diagram of a mid-frequency broadband electroacoustic energy emission method.

[0022] Figure 3 This is an internal structural diagram of a mid-frequency broadband electroacoustic energy emission method.

[0023] Figure 4 This is a potting mold diagram for a mid-frequency broadband electroacoustic energy emission method.

[0024] Figure 5 This is a modal simulation diagram of a mid-frequency broadband electroacoustic energy emission method.

[0025] Figure 6 This is a simulation diagram of prestressing at a water depth of 30m for a medium-frequency broadband electroacoustic energy emission method.

[0026] Figure 7 This is a schematic diagram of the simulation curve of the sound source level at a water depth of 30m for the mid-frequency broadband electroacoustic energy emission method.

[0027] Figure 8 This is a schematic diagram of the measured sound source level at a water depth of 30m using the mid-frequency broadband electroacoustic energy emission method.

[0028] Figure 9 This is a schematic diagram of the measured waveform at a 30m water depth sound source level for the mid-frequency broadband electroacoustic energy emission method. Detailed Implementation

[0029] The technical solution of the present invention will be specifically described below through specific embodiments and in conjunction with the accompanying drawings.

[0030] refer to Figures 1 to 4 This embodiment provides a specific mid-frequency broadband electroacoustic energy transmitting device (i.e., transducer).

[0031] like Figure 1 and Figure 2 As shown, the transducer has a flat triangular shape and a highly compact structure. Its external frame mainly consists of a cover plate 1, three high-strength connecting screws 2, a triangular shell 4, and a central base 8. The three connecting screws 2, as the main load-bearing components, pass sequentially through corresponding mounting holes in the cover plate 1, the cork pad layer 3, the triangular shell 4, and the central base 8, thus compressing all core components into a rigid whole. The cork pad layer 3, placed between the cover plate 1 and the triangular shell 4, primarily serves to dampen vibrations and buffer stress, thereby improving the transducer's acoustic performance. The cover plate 1 is made of corrosion-resistant titanium alloy and has an electroplated surface to adapt to underwater working environments.

[0032] like Figure 3 As shown, the core driving part of this invention is located between the triangular shell 4 and the central base 8. The triangular shell 4 itself serves as the three sides of a triangular frame, and together with the central base 8, forms a stable force transmission structure. Between the triangular shell 4 and the central base 8, three sets of supermagnetostrictive oscillators are circumferentially and uniformly spaced at 120-degree intervals.

[0033] Each set of magnetostrictive oscillators is specifically constructed as follows: two cylindrical magnetostrictive rods 7 and three cylindrical permanent magnets 6 are arranged alternately along the axial direction and precisely bonded together with EPO-TEKH74 series high-strength epoxy resin adhesive. To ensure the symmetry of the magnetic circuit and the uniform application of preload, both ends of the oscillator are permanent magnets 6. In this embodiment, the magnetostrictive rods 7 are made of rare-earth magnetostrictive material Terfenol-D, with a diameter of 20 mm and a length of 55 mm; the permanent magnets 6 are made of neodymium iron boron (NdFeB) material, also with a diameter of 20 mm and a length of 10 mm. To reduce high-frequency eddy current losses, the cylindrical surfaces of all magnetostrictive rods 7 and permanent magnets 6 are axially slit.

[0034] Each magnetostrictive oscillator is fitted with an excitation coil 9. The length of the coil is carefully designed to be slightly less than the total length of the oscillator to ensure that the alternating magnetic field it generates can act efficiently and uniformly on the magnetostrictive rod 7. The leads of the three excitation coils 9 converge to a watertight head 10 and are connected in parallel to facilitate unified power supply and control from an external drive power source.

[0035] The oscillator is fixed and pre-tightened via a pair of magnetically conductive bases 5. The magnetically conductive bases 5 are machined from DT4C electrical pure iron, possessing excellent magnetic permeability and mechanical strength. The permanent magnets 6 at both ends of each oscillator contact one magnetically conductive base 5. The back of the magnetically conductive base 5 is designed with guide bosses, or "guide rails," which precisely mate with the grooves on the triangular shell 4 and the central base 8. The key pre-stress application mechanism is as follows: Before assembly, the free length of a single magnetostrictive oscillator, including the magnetically conductive base, is designed to be slightly larger than the net height between the inner cavity of the triangular shell 4 and the corresponding mounting surface of the central base 8, with the difference controlled within the range of 0.1-0.5 mm. Due to the "excessive length" of the oscillator, the magnetically conductive bases 5 are compressed, thereby applying a precise axial mechanical pre-stress to the internal 7. This pre-tightening force is superimposed on the external hydrostatic pressure generated by the transducer's operating water depth, constituting the total pre-stress. By designing different "interference fits," the mechanical prestress can be adjusted so that, at the working depth, the supermagnetostrictive rod 7 operates in the linear region of its magnetostrictive characteristic curve and is near the optimal operating point where the slope of the strain-magnetic field strength curve is maximum, thus achieving maximum energy conversion efficiency and good linearity. The effectiveness of this design can be verified through finite element simulation, such as... Figure 6 The simulation analysis results of the 30-meter water depth prestressing show that the designed structure has qualified strength.

[0036] To ensure the long-term reliability and watertightness of the transducer in deep-water environments, potting is required after mechanical assembly and electrical connections are completed. For example... Figure 4As shown, the entire assembly is placed in the cavity of a dedicated potting mold 12, and then polyurethane potting compound is injected through the potting ports on both side covers. After curing, a robust watertight barrier is formed between the internal electronic components of the transducer and the external environment (the gaps between the covers, cork, and housing are all sealed with polyurethane). The potting compound also further secures the internal components, improves heat dissipation, and suppresses stray vibrations.

[0037] The cavity formed by the cover plate and the triangular shell 4 is filled with air or silicone oil to adjust the internal acoustic impedance or dissipate heat. The thickness of the radiating surface 11 on the side of the shell is designed to be 8.5 mm; this thickness, together with the acoustic properties of the material, determines the resonant frequency of the transducer. Modal simulation analysis is used to determine this. Figure 5 As shown, the structure exhibits a clear and pure in-plane breathing vibration mode at approximately 2600 Hz, which is precisely the operating mode utilized in this invention. Both simulation and field measurements indicate that the resonant frequency increases slightly with the increase of the thickness of the radiating surface 11.

[0038] Working principle: When an alternating current of the same phase and frequency is applied to the three parallel excitation coils 9 through the watertight head 10, an alternating magnetic field is generated in each coil. This alternating magnetic field is superimposed with the static bias magnetic field provided by the permanent magnet 6, and together they act on the supermagnetostrictive rod 7, causing it to undergo periodic axial stretching deformation magnetostrictive effect. Since the three drive units are arranged symmetrically at 120 degrees, and their two ends are rigidly connected to the stationary triangular shell 4 and the movable central base 8, the axial micro-displacements ΔL in the three directions will be vector-synthesized at the central base 8. This synthesis forces the central base 8 to generate a reciprocating vibration mainly located in the plane, which in turn drives the entire triangular shell 4, especially the three side radiation surfaces 11, to perform synchronous bending vibration, thereby radiating sound waves into the water. This "triangular synthesis" mechanism cleverly converts and amplifies the axial micro-displacement of the material itself into an effective in-plane vibration output, achieving high energy density and high output force.

[0039] Performance verification: Figure 7 The simulated sound source level curve of the transducer under a water depth of 30 meters is shown, demonstrating high output and wide bandwidth in the target frequency band. Figure 8 and Figure 9The figures show the frequency response curve and time-domain waveform of the sound source level measured at a depth of 30 meters. The experimental results demonstrate that the transducer requires only approximately 10A of drive current near the resonant frequency to achieve a sound source level exceeding 195dB, proving its high energy density characteristics. Simultaneously, the measured waveform exhibits low distortion and good linearity, validating the effectiveness of the prestressed design and triangular symmetrical structure. The overall dimensions of the transducer are controlled within 450mm * 450mm * 65mm, making it compact, lightweight, and easy to deploy and apply.

[0040] The above is only one specific implementation method of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing the protection scope of the present invention.

Claims

1. A mid-frequency broadband electroacoustic energy emitting device, characterized in that, The system includes a triangular shell (4), with a central base (8) fixed in the middle of the triangular shell (4); three sets of super magnetostrictive oscillators are clamped and fixed between the triangular shell (4) and the central base (8) through a magnetically conductive base (5); the three sets of super magnetostrictive oscillators are arranged radially and symmetrically; an AC excitation coil (9) is provided on the outer sleeve of the super magnetostrictive oscillator; the excitation coil (9) is electrically connected to a watertight head (10) installed on the triangular shell (4); cork pads (3) are provided on the upper and lower sides of the triangular shell (4). The outer side of the pad (3) is covered with a cover plate (1). The outer periphery and the middle part of the cover plate (1) are fixed to the triangular shell (4) and the central base (8) by connecting screws (2), respectively. The cover plate (1) and the cork pad (3) and the cork pad (3) and the triangular shell (4) are sealed by polyurethane sealant. The cavity inside the triangular shell (4) is filled with air or silicone oil. The super magnetostrictive oscillator is in a pre-compressed state. The three sides of the triangular shell (4) form a side radiation surface (11).

2. The intermediate frequency broadband electroacoustic energy emitting device as described in claim 1, characterized in that, The super magnetostrictive oscillators are arranged at a 120° angle between each other.

3. The intermediate frequency broadband electroacoustic energy emitting device as described in claim 1, characterized in that, The super magnetostrictive oscillator is formed by alternating bonding of permanent magnets (6) and super magnetostrictive rods (7), and both ends of the super magnetostrictive oscillator are permanent magnets (6).

4. The intermediate frequency broadband electroacoustic energy emitting device as described in claim 3, characterized in that, The super magnetostrictive vibrator is composed of two super magnetostrictive rods (7) and three permanent magnets (6) arranged and glued alternately; the length of the AC excitation coil (9) is less than the length of the super magnetostrictive vibrator; the length of the super magnetostrictive vibrator is greater than the length of the installation space of the super magnetostrictive vibrator by 0.1-0.5 mm.

5. The mid-frequency broadband electroacoustic energy emitting device as described in claim 4, characterized in that, The diameter of the super magnetostrictive rod (7) is 20 mm and the length is 55 mm. The diameter of the permanent magnet (6) is 20 mm and the length is 10 mm. Both the surface of the super magnetostrictive rod (7) and the permanent magnet (6) are cut.

6. The mid-frequency broadband electroacoustic energy emitting device as described in claim 3, characterized in that, The magnetic base (5) is made of DT4C electrical pure iron material; the permanent magnet (6) is made of neodymium iron boron material; the super magnetostrictive rod (7) and the permanent magnet (6) are bonded and fixed with adhesive, which is EPO-TEKH74 series epoxy resin adhesive; the triangular shell (4) and the central base (8) are made of aluminum alloy; the cover plate (1) is made of titanium alloy and is electroplated on the surface; the sealant is polyurethane.

7. The intermediate frequency broadband electroacoustic energy emitting device as described in claim 1, characterized in that, The three corners of the triangular shell (4) are rounded, and the three side radiation surfaces (11) are all concave arcs.

8. The intermediate frequency broadband electroacoustic energy emitting device as described in claim 1, characterized in that, The size of the intermediate frequency broadband electroacoustic energy emitting device does not exceed 450mm*450mm*65mm.

9. A design method for a mid-frequency broadband electroacoustic energy emitting device according to any one of claims 1-8, characterized in that, The thickness of the side radiating surface (11) is adjusted according to the resonant frequency. When it is necessary to increase the resonant frequency, the thickness of the side radiating surface (11) is increased; when it is necessary to decrease the resonant frequency, the thickness of the side radiating surface (11) is decreased.

10. The design method of the mid-frequency broadband electroacoustic energy emission device as described in claim 9, characterized in that, Adjust the thickness of the magnetic base (5) according to the working depth of the medium frequency broadband electroacoustic energy emission device, thereby adjusting the preload of the super magnetostrictive oscillator so that at the working depth, the super magnetostrictive rod (7) works in the linear region of its magnetostrictive characteristic curve and is at the optimal working point with the largest slope of the strain-magnetic field strength curve.

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