A deep water longitudinal vibration underwater acoustic transducer with acoustic low pass filter structure

Abstract

The application provides a deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure and belongs to the technical field of deep-water transducers. The problem that the electric-acoustic performance of the longitudinal vibration underwater acoustic transducer is greatly deteriorated after an oil-filled cavity is introduced is solved. The transducer comprises a front cover plate, a piezoelectric crystal stack, a rear cover plate, an oil-filled cavity, an oil-filled slit and a pressure-resistant shell, the front cover plate and the rear cover plate are connected with two ends of the piezoelectric crystal stack respectively, the front cover plate, the piezoelectric crystal stack and the rear cover plate are all installed in the pressure-resistant shell, the annular gap between the rear cover plate and the pressure-resistant shell is the oil-filled slit, the annular gap between the piezoelectric crystal stack and the pressure-resistant shell is the oil-filled cavity, and the bottom of the pressure-resistant shell is provided with an oil filling hole. The transducer is mainly used for longitudinal vibration underwater acoustic transducers with low-frequency broadband characteristics in underwater working environments.

Description

Technical Field

[0001] This invention belongs to the field of deep-water transducer technology, and in particular relates to a deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure. Background Technology

[0002] As one of the core components of a sonar system, the performance of the transducer directly affects the quality of the sonar system. Longitudinal vibration underwater acoustic transducers are widely used in mid-to-high frequency bands for underwater positioning, countermeasures, communication, and navigation due to their mature technology, simple structure, and high reliability. As the operating depth of underwater platforms increases, the transducers mounted on the platforms are required to have deep-water pressure resistance. Currently, in deep-water environments, longitudinal vibration underwater acoustic transducers usually adopt a liquid-filled structure design to achieve deep-water operation by balancing the internal and external pressures of the transducer. However, the liquid-filled structure design introduces additional impedance of the liquid cavity into the transducer vibration system, resulting in a reduction in effective acoustic power. In addition, the reverse vibration of the transducer's radiating surface is transmitted to the sound field through the liquid cavity, forming sound wave cancellation, which leads to a decrease in the transducer's electroacoustic response, a reduction in the effective operating bandwidth, and ultimately a significant reduction in the working performance of the sonar system.

[0003] Currently, in order to suppress the deterioration of electroacoustic performance, low-impedance reflective material is usually laid at the bottom of the liquid cavity, or compliant material is added to the oil-filled liquid cavity to reduce the impact of the liquid cavity. However, when the working water depth exceeds several hundred meters, the low-impedance reflective layer and compliant material fail, resulting in a significant deterioration of electroacoustic performance. Summary of the Invention

[0004] In view of this, the present invention aims to propose a deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure to solve the problem that the electroacoustic performance of the longitudinal vibration underwater acoustic transducer deteriorates significantly after being introduced into an oil-filled cavity.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure, comprising a front cover plate, a piezoelectric crystal stack, a rear cover plate, an oil-filled cavity, an oil-filled slit, and a pressure-resistant shell. The front cover plate and the rear cover plate are respectively connected to both ends of the piezoelectric crystal stack. The front cover plate, the piezoelectric crystal stack, and the rear cover plate are all installed inside the pressure-resistant shell. The annular gap between the rear cover plate and the pressure-resistant shell is an oil-filled slit. The annular gap between the piezoelectric crystal stack and the pressure-resistant shell is an oil-filled cavity. An oil-filling hole is provided at the bottom of the pressure-resistant shell.

[0006] Furthermore, the front cover plate and the rear cover plate are provided with threaded holes for installing prestressed bolts, which pass through the front cover plate and the piezoelectric crystal stack and connect to the rear cover plate.

[0007] Furthermore, the upper end of the front cover is sealed with a watertight layer.

[0008] Furthermore, both the front cover and the rear cover are bonded to the piezoelectric crystal stack using epoxy resin adhesive.

[0009] Furthermore, the piezoelectric crystal stack comprises several stacked piezoelectric material blocks, with an electrode sheet bonded between each adjacent block.

[0010] Furthermore, the rear cover plate is made of a material with a density of 7850 kg / m³. 3 Alloy steel.

[0011] Furthermore, the front cover is made of a material with a density of 2730 kg / m³. 3 An aluminum alloy with a Young's modulus of 69 GPa.

[0012] Furthermore, the watertight layer is prepared by filling with vulcanized rubber or epoxy resin materials.

[0013] Furthermore, the liquid filling the oil-filled cavity and the oil-filled slit is an insulating material.

[0014] Furthermore, the distance between the rear cover plate and the pressure-resistant housing is no more than 1 mm.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention forms an acoustic low-pass filter structure through an oil-filled cavity and an oil-filled slit. This structure utilizes the structural characteristics of the longitudinal vibration transducer itself. Through the oil-filled slit formed between the rear cover plate and the pressure-resistant shell, it is equivalent to mechanically connecting an acoustic impedance structure in series at the end of the oil-filled cavity. At this time, according to the principle of acoustic low-pass filtering, the vibration of the cavity with a resonant frequency higher than the filter cutoff frequency is effectively suppressed. Thus, without changing the original structure of the longitudinal vibration transducer, this invention avoids introducing new additional structures or materials into the transducer structure, maintaining the advantages of simple structure, easy assembly process, and high reliability of the longitudinal vibration transducer.

[0016] 2. The acoustic low-pass filter of the present invention has an acoustic impedance derived from the thermal viscosity loss of the liquid in the slit. The magnitude of the acoustic impedance depends on the thermal viscosity characteristics of the filling liquid and the structural dimensions of the transducer itself. Compared with traditional solutions, the present invention is not limited by hydrostatic pressure, and the transducer with the acoustic low-pass filter structure can operate at full ocean depth.

[0017] 3. This invention employs an acoustic low-pass filter structure formed by an oil-filled cavity and an oil-filled slit, which greatly suppresses the degradation of electroacoustic performance caused by the oil-filled cavity. Through the design of the oil-filled slit, the acoustic low-pass filter structure can restore the underwater acoustic performance of the longitudinal vibration transducer after the degradation caused by oil filling to a level comparable to that of the unfilled underwater acoustic performance. While maintaining the deep-water pressure resistance of the longitudinal vibration transducer, it also has high electroacoustic response and wide operating frequency band underwater acoustic performance. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of a deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure according to the present invention. Figure 2 This is a schematic diagram of the equivalent circuit of the acoustic low-pass filter of a deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure according to the present invention. Figure 3 The graph shows the vibration velocity comparison between the piezoelectric crystal stack and the oil-filled liquid cavity of the longitudinal vibration underwater acoustic transducer in the states of no oil filling, oil filling, and oil-filled slit introduction. Figure 4 A comparison of the conductivity curves of a longitudinally vibrating underwater acoustic transducer in the states of no oil filling, oil filling, and oil-filled slit introduction. Figure 5 A comparison of the transmitted voltage response curves of the longitudinal vibration underwater acoustic transducer in the states of no oil filling, oil filling, and oil filling slit introduction.

[0019] In the picture: 1-Front cover plate, 2-Piezoelectric crystal stack, 3-Rear cover plate, 4-Prestressed bolt, 5-Oil-filled cavity, 6-Oil-filled slit, 7-Pressure-resistant shell, 8-Watertight layer, 9-Oil-filled hole. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0021] Detailed Implementation Method 1: See Figure 1-5This embodiment describes a deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure, comprising a front cover plate 1, a piezoelectric crystal stack 2, a rear cover plate 3, an oil-filled cavity 5, an oil-filled slit 6, and a pressure-resistant housing 7. The front cover plate 1 and the rear cover plate 3 are respectively connected to both ends of the piezoelectric crystal stack 2. The front cover plate 1, the piezoelectric crystal stack 2, and the rear cover plate 3 are all installed inside the pressure-resistant housing 7. The annular gap between the rear cover plate 3 and the pressure-resistant housing 7 is the oil-filled slit 6, and the annular gap between the piezoelectric crystal stack 2 and the pressure-resistant housing 7 is the oil-filled cavity 5. The pressure-resistant housing 7 has an oil-filling hole 9 at its bottom. The front cover plate 1 and the rear cover plate 3 have threaded holes for installing prestressed bolts 4. The prestressed bolts 4 pass through the front cover plate 4 and the piezoelectric crystal stack 2 and are connected to the rear cover plate 3. After assembly, oil is filled into the interior through the oil-filling hole 9, forming the oil-filled cavity 5 and the oil-filled slit 6. The oil-filled cavity 5 and the oil-filled slit 6 form an acoustic low-pass filter structure.

[0022] Through the oil-filled slit 6 formed between the rear cover plate 3 and the pressure-resistant shell 7, a pure acoustic impedance structure is mechanically connected in series at the end of the oil-filled cavity 5. By utilizing the principle of acoustic low-pass filtering, the vibration of the oil-filled cavity 5, whose resonant frequency is higher than the filter cutoff frequency, is greatly suppressed. This can restore the underwater acoustic performance of the longitudinal vibration transducer, which has deteriorated due to oil filling, to a level comparable to that of the unfilled transducer. While maintaining the deep-water pressure resistance of the longitudinal vibration transducer, it also has high electroacoustic response and wide operating frequency band underwater acoustic performance.

[0023] Furthermore, the size parameters of the oil-filled slit 6 formed between the rear cover plate 3 and the pressure-resistant housing 7 can be adjusted as needed, and the liquid filling the oil-filled cavity 5 and the oil-filled slit 6 can be replaced as needed.

[0024] In this embodiment, excellent acoustic impedance characteristics can be achieved with a distance of no more than 1 mm between the rear cover plate 3 and the pressure-resistant housing 7. The filling liquid in the oil-filled cavity 5 and the oil-filled slit 6 has a density of approximately 970 kg / m³. 3 Methyl silicone oil is an insulating material.

[0025] In this embodiment, the piezoelectric crystal stack 2 includes several stacked piezoelectric material blocks, with an electrode sheet bonded between each adjacent block. Specifically, the piezoelectric crystal stack 2 consists of 30 stacked piezoelectric ceramic rings, with annular copper electrode sheets bonded between adjacent ceramic rings using epoxy resin adhesive. The outer end of the electrode sheet has a sheet-like protrusion for welding a conductive wire.

[0026] In this embodiment, the rear cover plate 3 uses a density of 7850 kg / m³. 3 Made of high-density metal materials such as alloy steel, the front cover 1 uses materials with a density of 2730 kg / m³. 3Made of low-density, high-Young's modulus materials such as aluminum alloy with a Young's modulus of 69 GPa, the vibration velocity is amplified by the large mass ratio between the rear cover plate 3 and the front cover plate 1, so that the vibration energy of the piezoelectric crystal stack 2 is transmitted to the radiation surface, thereby achieving a high electroacoustic response.

[0027] In this embodiment, the watertight layer 8 is prepared by filling with vulcanized rubber or epoxy resin material.

[0028] Specifically, the watertight layer 8 is made of polyurethane material for potting. This material has good sound transmission performance, which facilitates the outward radiation of sound waves generated by the vibration of the front cover plate. At the same time, this material has good tensile toughness, which can maintain the watertightness of the pressure-resistant shell 7 in deep water environment while transmitting the hydrostatic pressure inward to the oil-filled cavity 5 to achieve pressure balance inside and outside the transducer.

[0029] In this embodiment, the prestressed bolt 4 can be adjusted in size according to requirements. The prestressed bolt 4 is made of aluminum alloy material. While maintaining the structural strength to apply sufficient prestress to the piezoelectric crystal stack 2, it is as lightweight as possible to avoid the structural stiffness and inertial mass of the bolt itself affecting the vibration characteristics of the longitudinal vibration transducer.

[0030] In this embodiment, as Figure 3 As shown, after the introduction of the oil-filled cavity 5, the transducer's vibration velocity curve has two resonance peaks in the working frequency band, and the vibration velocity of the piezoelectric crystal stack at 4kHz is opposite to that of the oil-filled cavity 5. When the acoustic low-pass filter structure is introduced, the transducer's vibration velocity curve recovers to a single resonance peak, and the amplitude is close to that when it is not filled with oil, which shows the suppression effect of the acoustic low-pass filter structure on the vibration of the oil-filled cavity 5.

[0031] In this embodiment, as Figure 4 As shown, when the acoustic low-pass filter structure is introduced, the longitudinal vibration resonance peak of the transducer reappears at 3kHz, demonstrating the effect of the acoustic low-pass filter structure on the additional impedance of the oil-filled cavity 5, so that the longitudinal vibration transducer has admittance characteristics similar to those when it is not filled with oil.

[0032] In this embodiment, as Figure 5 As shown, when the longitudinal vibration transducer changes from an unfilled state to an oil-filled state, the transmitted voltage response shows a "deep pit" at the original unfilled longitudinal vibration resonance. When the acoustic low-pass filter structure is introduced, the "deep pit" of the transmitted voltage response of the longitudinal vibration transducer disappears, and the peak value of the longitudinal vibration resonance at 3kHz is similar to the peak value when it is unfilled. This shows that the deep-water longitudinal vibration transducer with the acoustic low-pass filter structure can maintain good underwater acoustic performance.

[0033] Working principle: When an alternating electrical signal is applied to the piezoelectric crystal stack 2, it generates longitudinal stretching vibration, which drives the front cover plate 1 to radiate sound waves forward and at the same time drives the rear cover plate 3 to vibrate backward, driving the methyl silicone oil liquid behind it. The volume of the oil-filled cavity 5 provides the acoustic quality, while the extremely narrow oil-filled slit 6 generates a large flow resistance, i.e., acoustic resistance, to the liquid flow. The two are connected in series to form an acoustic low-pass filter structure.

[0034] This filter filters the vibration velocity of the rear cover plate 3. Low-frequency components can pass relatively easily, but when their energy is finally transferred to the heavy pressure-resistant shell 7, the radiation into the water is weak due to impedance mismatch. Meanwhile, harmful high-frequency vibration components are strongly attenuated when attempting to pass through the high-flow-resistance oil-filled slit 6, thus failing to effectively excite the pressure-resistant shell 7 to generate strong high-frequency vibrations. Therefore, from the perspective of the final underwater acoustic radiation effect, the high-frequency resonance caused by the vibration of the rear cover plate 3 is significantly suppressed, making the overall transducer's emission voltage response curve flatter, widening the effective operating bandwidth, while maintaining good pressure resistance and structural reliability.

[0035] The specific embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure, characterized in that: The device includes a front cover plate (1), a piezoelectric crystal stack (2), a rear cover plate (3), an oil-filled cavity (5), an oil-filled slit (6), and a pressure-resistant housing (7). The front cover plate (1) and the rear cover plate (3) are respectively connected to the two ends of the piezoelectric crystal stack (2). The front cover plate (1), the piezoelectric crystal stack (2), and the rear cover plate (3) are all installed inside the pressure-resistant housing (7). The annular gap between the rear cover plate (3) and the pressure-resistant housing (7) is the oil-filled slit (6). The annular gap between the piezoelectric crystal stack (2) and the pressure-resistant housing (7) is the oil-filled cavity (5). The pressure-resistant housing (7) has an oil-filled hole (9) at the bottom.

2. The deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure according to claim 1, characterized in that: The front cover plate (1) and the rear cover plate (3) are provided with threaded holes for installing prestressed bolts (4), which pass through the front cover plate (4) and the piezoelectric crystal stack (2) and are connected to the rear cover plate (3).

3. A deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure according to claim 1, characterized in that: The upper end of the front cover plate (1) is sealed with a watertight layer (8).

4. A deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure according to claim 1, characterized in that: Both the front cover plate (1) and the rear cover plate (3) are bonded to the piezoelectric crystal stack (2) with epoxy resin adhesive.

5. A deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure according to claim 1, characterized in that: The piezoelectric crystal stack (2) includes several stacked piezoelectric material blocks, with an electrode sheet bonded between each adjacent block.

6. A deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure according to claim 1, characterized in that: The rear cover plate (3) is made of a material with a density of 7850 kg / m³. 3 Alloy steel.

7. A deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure according to claim 1, characterized in that: The material of the front cover plate (1) has a density of 2730 kg / m³. 3 An aluminum alloy with a Young's modulus of 69 GPa.

8. A deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure according to claim 3, characterized in that: The watertight layer (8) is prepared by filling with vulcanized rubber or epoxy resin materials.

9. A deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure according to claim 1, characterized in that: The liquid filling the oil-filled cavity (5) and the oil-filled slit (6) is an insulating liquid.

10. A deep-water longitudinal vibration underwater acoustic transducer with an acoustic low-pass filter structure according to claim 1, characterized in that: The distance between the rear cover plate (3) and the pressure-resistant shell (7) is no more than 1 mm.

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