阅读说明：本技术 一种低频弯张类声压水听器 (Low-frequency flextensional acoustic pressure hydrophone ) 是由 徐言哲 范桂芬 雷文 付明 吕文中 于 2019-12-12 设计创作，主要内容包括：本发明属于水声设备领域,公开了一种圆柱形弯张类声压水听器,包括由8片压电陶瓷圆环共轴叠加形成的压电晶堆,在压电晶堆的上方和下方还分别设置有上、下铝合金盖板,它们均通过过渡体与压电晶堆相连；在压电晶堆的侧面外部,还设置有铝合金外壳；铝合金外壳与上、下铝合金盖板连接用于包围形成包围空间,从而构成凹桶式的弯张换能器结构；此外,在铝合金外壳外部还设置有铝合金接收面；对于铝合金接收面在与中心轴线相垂直的平面上的投影,投影的外边缘呈圆形或正n边形。本发明通过对水听器内部各组件的结构及其设置方式、材料等进行改进,得到圆柱形或近圆柱形弯张类声压水听器,是种二维全指向性声压水听器,并且在低频段具有较高的接收灵敏度。(The invention belongs to the field of underwater acoustic equipment, and discloses a cylindrical flextensional acoustic pressure hydrophone which comprises a piezoelectric crystal stack formed by coaxially overlapping 8 piezoelectric ceramic rings, wherein an upper aluminum alloy cover plate and a lower aluminum alloy cover plate are respectively arranged above and below the piezoelectric crystal stack and are connected with the piezoelectric crystal stack through transition bodies; an aluminum alloy shell is arranged outside the side surface of the piezoelectric crystal stack; the aluminum alloy shell is connected with the upper aluminum alloy cover plate and the lower aluminum alloy cover plate and used for surrounding to form a surrounding space, so that a concave barrel type flextensional transducer structure is formed; in addition, an aluminum alloy receiving surface is arranged outside the aluminum alloy shell; for the projection of the aluminum alloy receiving surface on a plane vertical to the central axis, the outer edge of the projection is in a circular shape or a regular n-polygon shape. The cylindrical or nearly cylindrical flextensional sound pressure hydrophone is obtained by improving the structure, the arrangement mode, the material and the like of each component in the hydrophone, is a two-dimensional omnidirectional sound pressure hydrophone, and has higher receiving sensitivity in a low frequency band.)

1. A flextensional acoustic pressure hydrophone is characterized by comprising a piezoelectric crystal stack formed by coaxially overlapping 8 piezoelectric ceramic circular rings and a prestressed bolt positioned at the central axis of the 8 piezoelectric ceramic circular rings; an upper aluminum alloy cover plate and a lower aluminum alloy cover plate are respectively arranged above and below the piezoelectric crystal stack, and both the upper aluminum alloy cover plate and the lower aluminum alloy cover plate are connected with the piezoelectric crystal stack through transition bodies; the outer part of the side face of the piezoelectric crystal stack is also provided with an aluminum alloy shell which correspondingly forms the other side face; the aluminum alloy shell is connected with the upper aluminum alloy cover plate and the lower aluminum alloy cover plate to surround and form a surrounding space, the piezoelectric crystal stack is positioned in the surrounding space, and for a cross-sectional shape formed by the intersection of a plane passing through the central axis and the aluminum alloy shell positioned on one side of the central axis, the cross-sectional shape is in an arch shape, the projection length of the arch shape on the central axis is larger than the projection length of the arch shape on the direction vertical to the central axis, so that a concave-barrel type flextensional transducer structure is formed by utilizing the arch-shaped aluminum alloy shell;

in addition, an aluminum alloy receiving surface corresponding to the aluminum alloy outer shell is arranged outside the aluminum alloy outer shell; and for the projection of the aluminum alloy receiving surface on a plane perpendicular to the central axis, the outer edge of the projection is in a circular shape or a positive n-polygon shape, wherein n is a positive integer greater than or equal to 6.

2. The flextensional acoustic pressure hydrophone of claim 1, wherein said 8 piezoceramic rings are of the same size and are placed in alignment; each piece of piezoelectric ceramic ring is polarized along the thickness direction, and the polarization directions of two adjacent pieces of piezoelectric ceramic rings are opposite.

3. The flextensional acoustic pressure hydrophone of claim 1, wherein a plane passing through said central axis intersects said aluminum alloy receiving surface on one side of said central axis to form a trumpet-shaped cross-section, and wherein the height of a cross-sectional area closer to said central axis is less than the height of a cross-sectional area farther from said central axis.

4. The flextensional acoustic pressure hydrophone of claim 1 wherein said transition bodies are located at the top and bottom of said piezoelectric crystal stack and are made of aluminum alloy.

5. The flextensional acoustic pressure hydrophone of claim 1 wherein the aluminum alloy receiving face comprises a plurality of aluminum alloy receiving face sub-assemblies sealed to one another with polyurethane acoustically transparent rubber.

6. The flextensional acoustic pressure hydrophone of claim 1, wherein for a projection of the aluminum alloy receiving face onto a plane perpendicular to the central axis, when the outer edge of the projection is a regular n-sided polygon, the aluminum alloy housing is composed of n aluminum alloy shell strips, each aluminum alloy shell strip corresponds to one aluminum alloy mass block and one aluminum alloy mass plate, and the aluminum alloy mass block and the aluminum alloy mass plate constitute an aluminum alloy receiving face subassembly corresponding to the aluminum alloy shell strip.

7. The flextensional acoustic pressure hydrophone of claim 1, wherein the 8 piezoelectric ceramic rings are specifically 8 PZT-4 piezoelectric rings, and the top and bottom surfaces of each piezoelectric ceramic ring are coated with epoxy glue and have electrode plates inserted; and a PZT-4 gasket is respectively arranged at the top and the bottom of the piezoelectric crystal stack and is connected with the piezoelectric crystal stack, and no electrode is additionally arranged, so that the piezoelectric crystal stack is prevented from being conductive with the upper aluminum alloy cover plate and the lower aluminum alloy cover plate, and the thickness of any PZT-4 gasket is smaller than that of any PZT-4 piezoelectric ring.

8. The flextensional acoustic pressure hydrophone of claim 1, wherein the upper aluminum alloy cover plate, the lower aluminum alloy cover plate and the piezoelectric crystal stack are connected by the pre-stressed bolt, and a polytetrafluoroethylene adhesive tape is filled between the pre-stressed bolt and the inner wall of the ring of the piezoelectric crystal stack; preferably, the teflon tape is wound on the prestressed bolt.

9. The flextensional acoustic pressure hydrophone of claim 1, wherein an upper stainless steel end cap is further provided above said upper aluminum alloy cover plate, and a lower stainless steel end cap is further provided below said lower aluminum alloy cover plate.

10. The flextensional acoustic pressure hydrophone of claim 9 wherein the exterior of said aluminum alloy receiving face is sealed with polyurethane sound-transparent rubber; the connecting parts of the aluminum alloy receiving surface, the upper stainless steel end cover and the lower stainless steel end cover are also sealed by polyurethane sound-transmitting rubber.

Technical Field

The invention belongs to the field of underwater acoustic equipment, and particularly relates to a low-frequency flextensional sound pressure hydrophone which can be suitable for the frequency range of 20Hz to 4kHz, and particularly relates to a cylindrical high-sensitivity sound pressure hydrophone without directivity in the horizontal direction.

Background

Sound waves are a good carrier of information and energy in water that people know. The underwater acoustic transducer is used as an underwater energy conversion device and plays an indispensable role in underwater detection and underwater acoustic related research. Among these, transducers that receive sound waves and convert them into electrical signals are called hydrophones. The current requirements for acoustic pressure hydrophones begin to trend toward continuous wave, low frequency, high sensitivity, and nondirectional. The array is manufactured, and the target positioning is realized by using the underwater acoustic signal processing technology.

First, the development of acoustic stealth technology makes underwater object detection more difficult. The novel quiet submarine utilizes the anechoic tiles to be paved on the surface of the submarine in a large area, and when the frequency is higher than 3kHz, the target intensity is reduced by about 10 dB. Therefore, it is desirable for an acoustic pressure hydrophone to have high sensitivity and non-directivity in the low frequency band below 3 kHz.

Secondly, the low frequency sound wave is more favorable for underwater long-distance propagation. The acoustic transmission loss of spherical waves in seawater is:

TL＝20log r+αr

r is the acoustic propagation distance, in units: km

α is the absorption coefficient of seawater in dB/km

Where the first term, 20log r, is the spherical wave expansion loss, the second term, α r, is the absorption loss, α decreasing with decreasing acoustic frequency.

The existing acoustic hydrophone usually adopts a cylindrical, spherical and composite rod-shaped structure, and although the sensitivity can meet the application requirements, the receiving sensitivity still has a space for improvement, so that the structure of the existing acoustic hydrophone also has a space for improvement.

Disclosure of Invention

In view of the above defects or improvement requirements of the prior art, an object of the present invention is to provide a flextensional acoustic pressure hydrophone, wherein the flextensional structure is applied to the construction of an acoustic pressure hydrophone and the reception of acoustic waves by improving the structure of each component in the hydrophone, the arrangement mode, the material, and the like, so as to obtain a cylindrical or near-cylindrical flextensional acoustic pressure hydrophone, which is a two-dimensional omni-directional acoustic pressure hydrophone and can be applied to the frequency range of 20Hz to 4 kHz. And moreover, the ANSYS 18.0 finite element simulation is utilized to analyze the low-frequency-band receiving sensitivity of the sound pressure hydrophone, so that the sound pressure hydrophone has higher receiving sensitivity in a low frequency band.

In order to achieve the above object, according to the present invention, there is provided a flextensional acoustic pressure hydrophone, which is characterized by comprising a piezoelectric crystal stack formed by coaxially stacking 8 piezoelectric ceramic rings, and a prestressed bolt located at the central axis of the 8 piezoelectric ceramic rings; an upper aluminum alloy cover plate and a lower aluminum alloy cover plate are respectively arranged above and below the piezoelectric crystal stack, and both the upper aluminum alloy cover plate and the lower aluminum alloy cover plate are connected with the piezoelectric crystal stack through transition bodies; the outer part of the side face of the piezoelectric crystal stack is also provided with an aluminum alloy shell which correspondingly forms the other side face; the aluminum alloy shell is connected with the upper aluminum alloy cover plate and the lower aluminum alloy cover plate to surround and form a surrounding space, the piezoelectric crystal stack is positioned in the surrounding space, and for a cross-sectional shape formed by the intersection of a plane passing through the central axis and the aluminum alloy shell positioned on one side of the central axis, the cross-sectional shape is in an arch shape, the projection length of the arch shape on the central axis is larger than the projection length of the arch shape on the direction vertical to the central axis, so that a concave-barrel type flextensional transducer structure is formed by utilizing the arch-shaped aluminum alloy shell;

in addition, an aluminum alloy receiving surface corresponding to the aluminum alloy outer shell is arranged outside the aluminum alloy outer shell; and for the projection of the aluminum alloy receiving surface on a plane perpendicular to the central axis, the outer edge of the projection is in a circular shape or a positive n-polygon shape, wherein n is a positive integer greater than or equal to 6.

As a further preferred aspect of the present invention, the 8 piezoelectric ceramic rings have the same size and are aligned; each piece of piezoelectric ceramic ring is polarized along the thickness direction, and the polarization directions of two adjacent pieces of piezoelectric ceramic rings are opposite.

In a further preferred embodiment of the present invention, a cross-sectional shape of a plane passing through the central axis and intersecting the aluminum alloy receiving surface on the side of the central axis is formed in a trumpet shape, and a height of a cross-sectional area near the central axis is smaller than a height of a cross-sectional area away from the central axis.

As a further preferred embodiment of the present invention, the transition bodies are located at the top and the bottom of the piezoelectric crystal stack, and the material is aluminum alloy.

As a further preferred aspect of the present invention, the aluminum alloy receiving face comprises a plurality of aluminum alloy receiving face subassemblies, and these aluminum alloy receiving face subassemblies are sealed with polyurethane sound-transmitting rubber.

As a further preferable mode of the present invention, when the outer edge of the projection is a regular n-polygon, the aluminum alloy housing is composed of n aluminum alloy strips, each aluminum alloy strip corresponds to one aluminum alloy mass block and one aluminum alloy mass plate, and the aluminum alloy mass block and the aluminum alloy mass plate constitute an aluminum alloy receiving surface subassembly corresponding to the aluminum alloy strip.

As a further preferred aspect of the present invention, the 8 piezoelectric ceramic rings are specifically 8 PZT-4 piezoelectric rings, and the top surface and the bottom surface of each piezoelectric ceramic ring are coated with epoxy glue and are inserted with electrode plates; and a PZT-4 gasket is respectively arranged at the top and the bottom of the piezoelectric crystal stack and is connected with the piezoelectric crystal stack, and no electrode is additionally arranged, so that the piezoelectric crystal stack is prevented from being conductive with the upper aluminum alloy cover plate and the lower aluminum alloy cover plate, and the thickness of any PZT-4 gasket is smaller than that of any PZT-4 piezoelectric ring.

As a further preferred aspect of the present invention, the upper aluminum alloy cover plate, the lower aluminum alloy cover plate and the piezoelectric crystal stack are connected by the pre-stressed bolt, and a polytetrafluoroethylene tape is filled between the pre-stressed bolt and the inner wall of the ring of the piezoelectric crystal stack; preferably, the teflon tape is wound on the prestressed bolt.

As a further preferred aspect of the present invention, an upper stainless steel end cap is further provided above the upper aluminum alloy cover plate, and a lower stainless steel end cap is further provided below the lower aluminum alloy cover plate.

As a further preferable aspect of the present invention, the outside of the aluminum alloy receiving surface is sealed with urethane sound-transmitting rubber; the connecting parts of the aluminum alloy receiving surface, the upper stainless steel end cover and the lower stainless steel end cover are also sealed by polyurethane sound-transmitting rubber.

Through the technical scheme, compared with the prior art, the cylindrical high-sensitivity low-frequency sound pressure hydrophone can be obtained correspondingly by forming the piezoelectric crystal stack by 8 piezoelectric ceramic wafers and forming the I-type flextensional transducer structure (a concave barrel type) by the upper aluminum alloy cover plate, the lower aluminum alloy cover plate and the side aluminum alloy shell. The invention adopts an arched aluminum alloy shell (namely, for a cross section shape formed by the intersection of a plane passing through the central axis of the piezoelectric crystal stack and the aluminum alloy shell positioned on one side of the central axis, the cross section shape is arched), and the arched aluminum alloy shell has the characteristics of long axial length and short axial length (namely, the projection length of the arched shape on the central axis is greater than the projection length of the arched shape on the direction vertical to the central axis), so that a concave barrel type flextensional transducer structure is formed by utilizing the arched aluminum alloy shell; the cylindrical or nearly cylindrical flextensional sound pressure hydrophone is obtained by constructing the flextensional structure and receiving sound waves, can be suitable for the frequency range of 20 Hz-4 kHz, and is a sound pressure hydrophone without directivity in the horizontal direction.

The 8 piezoelectric ceramic wafers are of circular ring structures, have the same size, are aligned and stacked together, and are provided with prestressed bolts in middle holes. The polarization directions of the four piezoelectric sheets 1, 3, 5 and 7 are consistent in the thickness direction from top to bottom, and the polarization directions of the four piezoelectric sheets 2, 4, 6 and 8 are consistent in the thickness direction and opposite to the polarization directions of the four piezoelectric sheets 1, 3, 5 and 7, and are electrically equivalent to parallel connection.

The receiving sensitivity of the sound pressure hydrophone in a low frequency band is analyzed by ANSYS finite element simulation, and the sound pressure hydrophone has higher receiving sensitivity in the low frequency band; the cylindrical or nearly cylindrical side surface of the invention is used as a receiving surface of a signal, and the invention can obtain omni-directivity (namely, non-directivity in the horizontal direction) in the horizontal plane. According to the invention, through finite element analysis, a receiving sensitivity curve of the cylindrical flextensional acoustic pressure hydrophone model can be obtained. The sound pressure hydrophone model has relatively flat receiving sensitivity response in a frequency band below 4kHz, fluctuation is less than 3dB, and receiving sensitivity is relatively high (about-180 dB). Ideally, the acoustic pressure hydrophone is non-directional in a plane perpendicular to the receiving surface.

The invention adopts the structure of the class I flextensional transducer, and utilizes the lever action of the structural shell of the flextensional transducer to realize displacement amplification in the long axis direction, thereby realizing the improvement of the receiving sensitivity of the hydrophone. Furthermore, a horn-shaped receiving surface is added on the side surface of the hydrophone, displacement amplification is achieved in the short axis direction, and therefore receiving sensitivity of the hydrophone is improved.

The hydrophone has flat response in a receiving sensitivity curve of a low frequency band (20 Hz-4 kHz), and the sensitivity value reaches-180 dB. The side surface (cylindrical surface) is used as a receiving surface, and no directivity exists in the horizontal direction.

Drawings

FIG. 1 is a finite element model constructed in accordance with the present invention.

Fig. 2 is a receiving sensitivity curve of the acoustic pressure hydrophone of the present invention obtained by harmonic response analysis by finite element analysis using ANSYS 18.0.

FIG. 3 is a hydrophone mockup of the present invention.

FIG. 4 is a cross-sectional view of a hydrophone phantom of the invention.

FIG. 5 is a schematic diagram of the hydrophone of the present invention; wherein (a) in fig. 5 is a top view, and (b) in fig. 5 is a cross-sectional view; as can be seen from the figure, the hydrophone has an overall diameter of 140mm and an overall height of 134.9 mm.

Fig. 6 is a diagram of an assembled vibrator.

Fig. 7 is a physical diagram of the mounted shell bar and mass block on the basis of fig. 6.

Fig. 8 is a physical diagram of the installed mass plate on the basis of fig. 7.

Fig. 9 is a view showing the upper and lower stainless steel plates mounted on the base of fig. 8.

FIG. 10 is a pictorial view of a finished hydrophone; as can be seen from the figure, the diameter of the cylindrical hydrophone is 140 mm.

Fig. 11 is a graph of measured receive sensitivity of a hydrophone.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

In the present invention, a cylindrical or nearly cylindrical two-dimensional omni-directional acoustic pressure hydrophone, which takes a nearly cylindrical flextensional acoustic pressure hydrophone with n as 12 as an example, is constructed in a finite element analysis, as shown in fig. 1, and includes: 8 piezoelectric ceramic wafers, prestressed bolts, upper and lower transition bodies, upper and lower aluminum alloy cover plates, aluminum alloy shells on the side surfaces, aluminum alloy radiation surfaces corresponding to the aluminum alloy shells on the side surfaces, near water fields, far water fields and boundary water (the specific requirements of the near water fields, the far water fields and the boundary water can be directly referred to the prior technical documents, such as Moxiping, and the application of ANSYS software in a simulation analysis acoustic transducer [ J ] acoustic technology, 2007; 26(6): 1280-1290). The upper and lower transition bodies are positioned at the top and the bottom of the 8 piezoelectric ceramic rings and made of aluminum alloy (namely, the 8 stacked piezoelectric plates are integrally provided with one transition body respectively at the upper and the lower parts, and the transition bodies are made of aluminum alloy).

Accordingly, the design of the actual model includes: the piezoelectric ceramic crystal mass spectrometer comprises a piezoelectric ceramic crystal stack, a prestressed bolt, upper and lower stainless steel end covers, upper and lower aluminum alloy cover plates, 12 aluminum alloy shell strips arranged on the side surface, 12 aluminum alloy mass blocks corresponding to the shell strips and 12 mass plates (receiving surfaces), a polyurethane water-tight layer, an O-shaped sealing ring, a flange and a leading-out cable. On the side, the aluminum alloy mass blocks and the mass plates (receiving surfaces) correspond to the adjacent aluminum alloy shell strips inside one by one, and each mass block and the mass plate (receiving surface) are n (taking n equals 12 as an example, actually, a whole circle is approximate to a regular 12-sided shape), and the mass blocks and the mass plates are fastened by screws. Furthermore, the connection part of the upper aluminum alloy cover plate and the lower aluminum alloy cover plate and the piezoelectric sheet is provided with a through wire hole for a wire to pass through. Stainless steel end covers are arranged outside the upper aluminum alloy cover plate and the lower aluminum alloy cover plate; further, for example, an upper steel plate is connected with a flange for fixing the cable, and the cable is encapsulated by vulcanized rubber.

The following is a detailed description: