A high-stability underwater acoustic standard device and manufacturing method

Abstract

The present invention discloses a high-stability underwater acoustic standard device and its manufacturing method. The underwater acoustic standard device mainly consists of a sensitive element assembly, a support rod, upper and lower end caps, a sound-transmitting rubber sleeve, filling oil, a stainless steel compression ring, a waterproof shielded cable, etc. Multiple small-diameter piezoelectric ceramic tubes are selected as the sensitive elements, with a resonance frequency higher than twice the upper limit of the working frequency and operating away from the resonance frequency. The piezoelectric ceramic tubes are flexibly suspended inside the support rod through soft support pads to maintain a free vibration state. A sound-transmitting rubber sleeve is selected as the sound-transmitting window, and energy is transmitted through the filling oil to avoid direct contact between the sensitive elements and the sound-transmitting material. In terms of the manufacturing process, the sound-transmitting rubber sleeve and the upper and lower end caps are sealed by extrusion deformation of the stainless steel compression ring. After the filling oil is filled, the air bubbles inside the filling oil are removed by vacuum pumping. This structural form and manufacturing process ensure that the underwater acoustic standard device has good temperature, pressure, and time stability and is suitable as a calibration standard for underwater acoustic measurement standard devices.

Description

Technical Field

[0001] The present invention relates to the field of underwater acoustic measurement, and specifically belongs to a standard device for the assessment of underwater acoustic metrology standards, mainly a high-stability underwater acoustic standard device and its manufacturing method. Background Art

[0002] Before and after World War II, with the needs of military struggles and ocean development, the discipline of underwater acoustic engineering was born. After decades of continuous development, underwater acoustic engineering is now more and more widely used and has been integrated into all aspects of daily life. Its applications in the military mainly include various types of sonar systems, torpedo acoustic guidance, underwater mine acoustic fuzes, and underwater acoustic countermeasure equipment, etc. Its applications in civilian use mainly include marine communication, marine environment observation, oil and gas resource exploration, search for underwater objects, fishery resource investigation, etc. There are a large number of underwater acoustic devices for sound reception or transmission in the applications of underwater acoustic engineering. In order to accurately evaluate whether the acoustic performance of these underwater acoustic devices and their underwater acoustic systems and components meet the designed technical indicators and usage requirements, it is necessary to establish various underwater acoustic performance test systems. The National Defense Science and Technology Industry Underwater Acoustic Primary Metrology Station has established multiple sets of underwater acoustic metrology standard devices with a frequency range from low frequency to high frequency and a pressure range from normal pressure to high hydrostatic pressure. It is a relatively difficult task to measure the small uncertainty of the underwater acoustic metrology standard device and judge whether its operation status is normal, which requires the use of device assessment standards to achieve. The assessment standard for reception performance is generally called a standard hydrophone, the assessment standard for transmission performance is called a standard transmitter, and the standard that can achieve the assessment of both reception and transmission performance is called an underwater acoustic standard device. There have been many studies on standard hydrophones, such as "20Hz - 150kHz high-stability standard hydrophone" reported by Jia Youdi, Shen Jianxin, etc., and "100kHz - 500kHz piezoelectric composite standard hydrophone" reported by He Tao, Xu Zhuohua, etc. However, these standard hydrophones usually come with preamplifiers and can only be used for the assessment of reception performance and cannot be used for the assessment of transmission performance. Hua Minglong et al. proposed "15kHz - 25kHz underwater acoustic standard transmitting transducer" CN85200255. This transducer is short cylindrical and has a flat transmitting response within the working frequency range. Like common transmitting transducers, this transducer uses PZT-4 material and the surface sealing material is sound-transmitting rubber, and it works near the resonant frequency. Therefore, its performance varies with temperature and pressure much more than the measurement uncertainty of the standard device, and it is not suitable as the emission assessment standard of the standard device. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies existing in the prior art and provide a high-stability underwater acoustic standard device and its manufacturing method. The present invention designs and manufactures an underwater acoustic standard device with excellent reception and transmission performance and high stability, which is applied to the assessment of the reception and transmission performance of medium and low-frequency underwater acoustic standard devices and the accurate evaluation of their working conditions.

[0004] The present invention aims to improve the stability of underwater acoustic standards and meet the needs of transceiver performance assessment for underwater acoustic metrology standard devices. It discloses a structure and manufacturing method of a highly stable underwater acoustic standard using multiple small-diameter piezoelectric ceramic tubes as sensitive elements, with the sensitive elements flexibly suspended and filled with oil inside.

[0005] The object of the present invention is achieved through the following technical solutions. A highly stable underwater acoustic standard includes an upper end cover, a lower end cover, a sound-transmitting rubber sleeve, and a sensitive element assembly. The two ends of the sound-transmitting rubber sleeve are respectively connected to the upper end cover and the lower end cover to form a closed space, and the inside of the sound-transmitting rubber sleeve is filled with oil as a medium for energy transfer; multiple support rods are installed in this space and connected to the end faces of the upper end cover and the lower end cover. Multiple sensitive element assemblies for receiving and transmitting sound waves are arranged vertically and flexibly suspended on the support rods. The positive and negative electrodes of the multiple sensitive element assemblies are connected in parallel through wires and then connected to an electrical connector; a waterproof shielded cable is connected to the electrical connector, and the cable head is installed in the top cavity of the upper end cover and fixed by fastening screws.

[0006] The sensitive element assembly includes an upper cover plate, a piezoelectric ceramic tube, a support gasket, and a lower cover plate. The piezoelectric ceramic tube is arranged between the upper cover plate and the lower cover plate, and the support gasket passes through the piezoelectric ceramic tube and is flexibly suspended on the support rod.

[0007] The inside of the piezoelectric ceramic tube is air-decoupled, and its resonance frequency is higher than twice the upper limit of the working frequency.

[0008] Eight sensitive element assemblies are connected in parallel to form an equidistant linear array.

[0009] The acoustic impedance of the filled oil should match that of water.

[0010] The sound-transmitting rubber sleeve is sealed with the upper end cover and the lower end cover by extrusion deformation of a stainless steel compression ring.

[0011] The present invention also discloses a manufacturing method of a highly stable underwater acoustic standard, including the following steps:

[0012] 1. Install multiple support rods on the upper end cover, and sequentially install the assembled sensitive element assemblies inside the support rods, arrange them at equal intervals, fix them in the corresponding positions with glue, and cover the lower end cover;

[0013] 2. Connect the positive and negative electrodes of the multiple sensitive element assemblies together with wires and finally connect them to the electrical connector;

[0014] 3. Pass the sound-transmitting rubber sleeve through the lower end cover and cover it outside the support rods, align one end with the step left on the upper end cover, and align the other end with the step on the lower end cover; place the stainless steel compression ring at the connection position between the sound-transmitting rubber sleeve and the end cover, and use a crimping device to extrude and deform the stainless steel compression ring to achieve the seal between the end cover and the rubber sleeve;

[0015] 4. Select a suitable filling oil and inject it into the standard device through the oil filling hole inside the upper end cover. After it is full, evacuate it in the vacuum chamber and maintain it for a certain period of time until all the bubbles inside the standard device are discharged. Then tighten the oil filling seal screw, and rely on the sealing ring on its end face to achieve the sealing of the filling oil.

[0016] 5. Pass the watertight shielded cable through the cable head, reserve a certain length, strip off the outer skin, and leave the core wire. Use a mold to vulcanize to achieve watertightness. After the watertight shielded cable is connected to the electrical connector, the cable head is installed in the top cavity of the upper end cover and fixed with the fastening screw 13, and the production of the underwater acoustic standard device is completed.

[0017] The beneficial effects of the present invention are as follows:

[0018] a) The sensitive element uses a small-diameter piezoelectric ceramic circular tube. When transmitting and receiving, its resonance frequency is much higher than the upper limit of the working frequency. The change in the resonance frequency caused by the changes in temperature, pressure, and time has little effect on the transmitting and receiving performance, and the underwater acoustic standard device has high temperature, pressure, and time stability.

[0019] b) The piezoelectric ceramic circular tube is fixed inside the support gasket and then flexibly suspended on the support rod. The rubber gasket has a good decoupling effect, ensuring the free vibration state of the piezoelectric ceramic circular tube and improving the flatness of the receiving sensitivity response of the underwater acoustic standard device.

[0020] c) The sound transmission uses a sound transmission rubber sleeve filled with a filling oil with good stability. The sound transmission material has no direct contact with the piezoelectric ceramic circular tube, and the influence of the change in the performance of the sound transmission material with temperature and pressure is greatly reduced, thereby improving the temperature and pressure stability of the standard device.

[0021] d) By connecting multiple piezoelectric ceramic circular tubes in parallel to form a linear array, the transmitting voltage response of the underwater acoustic standard device is greatly improved; after parallel connection, the static capacitance increases, improving the cable-carrying capacity of the standard device. Description of the Drawings

[0022] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0023] Figure 2 Schematic diagram of the sensitive element assembly.

[0024] Reference numerals: sensitive element assembly 1, lower end cover 2, support rod 3, upper end cover 4, filling oil 5, sound transmission rubber sleeve 6, wire 7, electrical connector 8, stainless steel compression ring 9, oil filling seal screw 10, watertight shielded cable 11, cable head 12, fastening screw 13, upper cover plate 14, piezoelectric ceramic circular tube 15, support gasket 16, lower cover plate 17. Detailed Embodiments

[0025] The following will introduce the present invention in detail in conjunction with the drawings and embodiments:

[0026] As shown Figure 1 in the figure, a high-stability underwater acoustic standard mainly includes a sensitive element assembly 1, a lower end cap 2, a support rod 3, an upper end cap 4, filling oil 5, a sound-transmitting rubber sleeve 6, a wire 7, an electrical connector 8, a stainless steel compression ring 9, an oil-filling and sealing screw 10, a watertight shielded cable 11, a cable head 12, a fastening screw 13, etc. Both ends of the sound-transmitting rubber sleeve 6 are respectively connected to the upper end cap 4 and the lower end cap 2 to form a closed space, and the filling oil 5 is filled inside the sound-transmitting rubber sleeve 6 as a medium for energy transfer; multiple support rods 3 are installed in this space and connected to the end faces of the upper end cap 4 and the lower end cap 2. Multiple sensitive element assemblies 1 for receiving and transmitting sound waves are arranged vertically and flexibly suspended on the support rods 3. The positive and negative electrodes of the multiple sensitive element assemblies 1 are connected in parallel through the wire 7 and then connected to the electrical connector 8; the watertight shielded cable 11 is connected to the electrical connector 8, and the cable head 12 is installed in the top cavity of the upper end cap 4 and fixed by the fastening screw 13.

[0027] As shown Figure 2 in the figure, the sensitive element assembly is the core of electro-acoustic conversion. When the standard is used for reception, the sensitive element converts the sensed sound signal into an electrical signal; when the standard is used for transmission, the power amplifier excitation signal acts on the sensitive element assembly to generate high-frequency vibration and transmit sound waves underwater. The sensitive element assembly 1 includes an upper cover plate 14, a piezoelectric ceramic circular tube 15, a support gasket 16, and a lower cover plate 17. The piezoelectric ceramic circular tube 15 is arranged between the upper cover plate 14 and the lower cover plate 17, and the support gasket 16 passes through the piezoelectric ceramic circular tube 15 and is flexibly suspended on the support rod 3. The upper and lower cover plates are used for sealing the two end faces of the piezoelectric ceramic circular tube and decoupling the internal air layer. The piezoelectric ceramic circular tube is a small-diameter circular tube and operates away from the resonance frequency. Usually, the upper limit of the working frequency of the standard is lower than 1 / 2 of the resonance frequency of the element. The support gasket is made of rubber material and has a through hole with the same diameter as the piezoelectric ceramic circular tube. After the piezoelectric ceramic circular tube is fixed inside the support gasket, it is flexibly suspended inside the support rod, and the piezoelectric ceramic circular tube is in a free vibration state. During implementation, the upper cover plate 14 and the lower cover plate 16 are respectively bonded to the two end faces of the piezoelectric ceramic circular tube 15. After curing and forming, the assembly is installed inside the support gasket 16 and fixed with glue, thus completing the production of the sensitive element assembly.

[0028] The lower end cap is processed from a material with a relatively large density, such as copper or stainless steel. There is a through hole at the bottom of the lower end cap for hanging a counterweight to keep the standard perpendicular to the water during operation. There is a step at the upper end of the lower end cap, and its height is equivalent to that of the sound-transmitting rubber sleeve. One end of the sound-transmitting sleeve is installed at the step position, and the end cap and the sound-transmitting rubber sleeve are sealed by squeezing and deforming the stainless steel compression ring.

[0029] The support rod is a high-strength metal rod, which is used to install the sensitive element assembly and plays a protective role. The diameter of the support rod is related to the highest operating frequency, generally less than 1 / 10 of the wavelength of the highest operating frequency, and should be as far away from the piezoelectric ceramic tube as possible.

[0030] The upper end cap is made of copper or stainless steel with a relatively large density. There is a step at the lower part of the upper end cap, and its height is equivalent to that of the sound-transmitting rubber sleeve. One end of the sound-transmitting sleeve is installed at the step position, and the stainless steel compression ring is used to squeeze and deform to achieve the seal between the end cap and the sound-transmitting rubber sleeve. An electrical connector is installed inside the upper end cap, and an oil-filling threaded through-hole is reserved. The top cavity is closely matched with the size of the cable head, and the radial "O" - ring seal on the cable head is used to achieve watertightness.

[0031] The filling oil is the filling liquid between the sound-transmitting rubber sleeve and the piezoelectric ceramic tube. Its function is to achieve the energy transfer between the piezoelectric ceramic tube and the sound-transmitting rubber sleeve. There are three requirements for the selection of the filling oil material. First, acoustic performance: the acoustic impedance of the filling liquid should match that of water to avoid acoustic wave focusing or divergence. Second, chemical stability: it should have no corrosion to the sound-transmitting rubber and piezoelectric ceramics. Third, physical properties: it should have an appropriate viscosity, the viscosity changes little with temperature, and the liquid expansion coefficient is low. Usually, silicone oil with good stability is selected.

[0032] The sound-transmitting rubber sleeve is formed by vulcanization using a mold, and its thickness is usually 3 - 5 mm. The sound-transmitting rubber sleeve needs to meet the requirement that the sound wave can pass through the material layer without reflection and loss. Its characteristic impedance matches that of water, the attenuation constant is very low, and it has a low water permeability, so it can work underwater for a long time. Usually, it is made of neoprene or butyl rubber material.

[0033] The wire is used for the electrical connection between 8 sensitive element assemblies and the connection between the sensitive element assembly and the cable connector. The standard device needs to be used for transmission, and the wire should meet the current and voltage requirements during transmission.

[0034] The electrical connector is used for the electrical connection between the oil-filled part of the standard device and the rear end. A 2-core small-size electrical connector is selected. One end is connected to the positive and negative poles of the piezoelectric ceramic tube, and the other end is connected to the core wire of the watertight shielded cable.

[0035] The stainless steel compression ring is mainly used for the seal between the sound-transmitting rubber sleeve and the end cap. Before deformation, its inner diameter is the same as the outer diameter of the rubber sleeve. The crimping equipment is used to make it squeeze and deform, thereby causing the rubber sleeve to deform and achieving the watertightness between the rubber sleeve and the end cap.

[0036] The watertight shielded cable transmits the electrical signal converted by the piezoelectric ceramic tube to the signal acquisition end during reception. When used for transmission, the excitation signal is applied from the power amplifier end to the piezoelectric ceramic tube. A shielded watertight cable is selected. The metal shield layer is used to shield the electromagnetic signals in space and reduce electromagnetic interference.

[0037] The specific manufacturing method is as follows:

[0038] 1. Install 6 support rods 2 on the upper end cap 4, and sequentially install the assembled sensitive element assemblies 1 inside the support rods 2, arranging them at equal intervals, fixing them in corresponding positions with glue, and covering the lower end cap 2;

[0039] 2. Connect the positive and negative poles of 8 sensitive element assemblies 1 together with wires 7 respectively, and finally connect them to the electrical connector 8;

[0040] 3. Pass the sound-transmitting rubber sleeve 6 through the lower end cap 2 and cover it outside the support rod 3. One end is aligned with the step left on the upper end cap 4, and the other end is aligned with the step of the lower end cap 2; Place the stainless steel compression ring 9 at the connection position of the sound-transmitting rubber sleeve 6 and the end cap, and use a crimping device to squeeze and deform the stainless steel compression ring 9 to achieve the seal between the end cap and the rubber sleeve;

[0041] 4. Select an appropriate filling oil 5 and inject it into the standard device through the oil filling hole inside the upper end cap 4. After it is full, evacuate it in a vacuum chamber and maintain it for a certain period of time until all the bubbles inside the standard device are discharged. Tighten the oil filling sealing screw 10, and rely on the sealing ring on its end face to achieve the filling oil seal;

[0042] 5. Pass the watertight shielded cable 11 through the cable head 12, leave a certain length and peel off the outer skin, leaving the core wire. Use a mold to vulcanize to achieve watertightness. After the watertight shielded cable 11 is connected to the electrical connector 8, the cable head 12 is installed in the top cavity of the upper end cap 4 and fixed with a fastening screw 13, then the manufacturing of the underwater acoustic standard device is completed.

[0043] The present invention selects a sound-transmitting rubber sleeve as the sound-transmitting window, and transmits energy through the filling oil, avoiding direct contact between the sensitive element and the sound-transmitting material. In terms of the manufacturing process, the sound-transmitting rubber sleeve and the upper and lower end caps are sealed by squeezing and deforming the stainless steel compression ring. After the filling oil is full, the air bubbles inside the filling oil are removed by evacuating. This structural form and manufacturing process ensure that the underwater acoustic standard device has good temperature, pressure and time stability, and is suitable as the assessment standard for underwater acoustic metrology standard devices.

[0044] It can be understood that for those skilled in the art, equivalent replacement or change of the technical solution and inventive concept of the present invention should fall within the protection scope of the appended claims of the present invention.

Claims

1. A highly stable underwater acoustic standard device, characterized in that: It includes an upper end cover (4), a lower end cover (2), a sound-transmitting rubber sleeve (6) and a sensitive element assembly (1). The two ends of the sound-transmitting rubber sleeve (6) are respectively connected to the upper end cover (4) and the lower end cover (2) to form a closed space. Oil (5) is filled inside the sound-transmitting rubber sleeve (6) as a medium for energy transfer. A plurality of support rods (3) are installed in this space and connected to the end faces of the upper end cover (4) and the lower end cover (2). A plurality of sensitive element assemblies (1) for receiving and transmitting sound waves are arranged vertically and flexibly suspended on the support rods (3). The positive and negative electrodes of the plurality of sensitive element assemblies (1) are connected in parallel through wires (7) and then connected to an electrical connector (8). A watertight shielded cable (11) is connected to the electrical connector (8), and a cable head (12) is inserted into the top cavity of the upper end cover (4) and fixed by a fastening screw (13). The described sensitive element assembly (1) includes an upper cover plate (14), a piezoelectric ceramic circular tube (15), a support gasket (16) and a lower cover plate (17). The piezoelectric ceramic circular tube (15) is arranged between the upper cover plate (14) and the lower cover plate (17). The support gasket (16) passes through the piezoelectric ceramic circular tube (15) and is flexibly suspended on the support rod (3). Specifically, the support gasket (16) is made of rubber material and has a through hole with the same diameter as the piezoelectric ceramic circular tube (15). After the piezoelectric ceramic circular tube (15) is fixed in the through hole inside the support gasket, it is flexibly suspended inside the support rod (3) so that the piezoelectric ceramic circular tube (15) is in a free vibration state. The inside of the piezoelectric ceramic circular tube (15) is air-decoupled, and its resonance frequency is higher than twice the upper limit of the working frequency.

2. The highly stable underwater acoustic standard device according to claim 1, characterized in that: 8 sensitive element assemblies (1) are connected in parallel to form an equidistant linear array.

3. The highly stable underwater acoustic standard device according to claim 1, characterized in that: The acoustic impedance of the filled oil (5) should match the acoustic impedance of water.

4. The highly stable underwater acoustic standard device according to claim 1, characterized in that: The sound-transmitting rubber sleeve (6) and the upper end cover (4) and the lower end cover (2) are sealed by extrusion deformation with a stainless steel compression ring (9).

5. A method for manufacturing the highly stable underwater acoustic standard device according to claim 1, characterized in that: It includes the following steps: 1), Install a plurality of support rods (3) on the upper end cover (4). Sequentially install the assembled sensitive element assemblies (1) inside the support rods (3), arrange them at equal intervals, fix them in the corresponding positions with glue, and cover the lower end cover (2). 2), Use wires (7) to connect the positive and negative electrodes of the plurality of sensitive element assemblies (1) together respectively, and finally connect them to the electrical connector (8). 3), Pass the sound-transmitting rubber sleeve (6) through the lower end cover (2) and cover it outside the support rods (3). One end is aligned with the step left on the upper end cover (4), and the other end is aligned with the step of the lower end cover (2). The stainless steel compression ring (9) is placed at the connection position between the sound-transmitting rubber sleeve (6) and the end cover, and the stainless steel compression ring (9) is extruded and deformed by a crimping device to achieve the seal between the end cover and the rubber sleeve. 4), Select a suitable filling oil (5) and inject it into the standard device through the oil filling hole inside the upper end cover (4). After filling, evacuate it in a vacuum chamber and maintain it for a certain period of time until all the bubbles inside the standard device are discharged. Tighten the oil filling seal screw 10, and rely on the sealing ring on its end face to achieve the filling oil seal. 5), Pass the watertight shielded cable (11) through the cable head (12), reserve a certain length, strip the outer skin, leave the core wire, and achieve watertightness by vulcanization using a mold. After the watertight shielded cable (11) is connected to the electrical connector (8), the cable head (12) is installed into the top cavity of the upper end cover (4) and fixed using the fastening screw (13), then the production of the underwater acoustic standard device is completed.

Images