Low-frequency broadband underwater sound sensing unit

Abstract

The invention relates to a low-frequency broadband underwater sound sensing unit which comprises an electrode plate, piezoelectric films are arranged on the upper surface and the lower surface of the electrode plate respectively, carbon fiber plates are arranged on the outer sides of the piezoelectric films respectively, and the surfaces of the sides, attached to the piezoelectric films, of the carbon fiber plates are plated with conductive layers. The piezoelectric film is polarized in the thickness direction, conducting layers are plated on the surfaces of the two sides of the piezoelectric film respectively, and blank areas are correspondingly reserved between the surfaces of the two sides of the piezoelectric film. According to the invention, the anti-interference performance of the underwater sound sensing unit can be improved, high flatness of receiving sensitivity response in a broadband is realized, the weight of the underwater sound sensing unit is reduced, and the sound transmission performance of the underwater sound sensing unit is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of underwater acoustic transducers and relates to a low-frequency, broadband underwater acoustic sensing unit. Background Art

[0002] Piezoelectric film is a polymer sensing material with good ductility and can be easily made into piezoelectric sensing elements of various shapes. The characteristic impedance of the piezoelectric film is close to that of water, and its thickness resonance frequency can be very high, so it can be made into a highly sensitive broadband hydrophone.

[0003] Planar underwater acoustic sensor units generally adopt a design that combines piezoelectric film with a rigid backing. The rigid backing can improve the sensitivity of the unit and expand the working frequency band. However, since the characteristic impedance of the rigid backing is significantly different from that of water, the sound transmission performance of the planar underwater acoustic sensor unit is restricted. Specifically, the current low-frequency broadband underwater acoustic sensor unit adopts a structural design that combines piezoelectric film with a metal backing. Due to the large specific gravity of the metal plate, the underwater acoustic sensor unit with a metal backing is heavier under the same volume. In addition, since the characteristic impedance of the metal plate is significantly different from that of water, the working frequency band of the underwater acoustic sensor unit is limited. As the frequency of the sound wave increases, the more sound energy is reflected at the interface, which means that the risk of being discovered in underwater acoustic confrontation is higher. In addition, the design of a piezoelectric film attached to the surface of the metal backing will cause a resonant mode of the metal backing within a wide frequency band. Since the piezoelectric film on the surface is not subject to any constraints on the outer surface, it is greatly affected by the resonance, so the sensitivity of the unit within the frequency band fluctuates greatly. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a low-frequency broadband underwater acoustic sensing unit to improve the anti-interference ability of the underwater acoustic sensing unit, achieve high flatness of the receiving sensitivity response within a wide frequency band, and at the same time reduce the weight of the underwater acoustic sensing unit and improve its sound transmission performance.

[0005] The technical solution of the present invention is to provide a low-frequency broadband underwater sound sensing unit, including an electrode sheet, wherein piezoelectric films are respectively arranged on the upper and lower surfaces of the electrode sheet, and carbon fiber plates are respectively arranged on the outer sides of the piezoelectric films, wherein: The surface of the carbon fiber plate and the piezoelectric film on one side thereof is plated with a conductive layer; The piezoelectric film is polarized along the thickness direction, and the surfaces of both sides of the piezoelectric film are respectively plated with conductive layers, and a blank area is correspondingly left in the middle of the surfaces of both sides of the piezoelectric film. The conductive layer is not provided on the blank area, and the blank area divides the conductive layer on each side of the piezoelectric film into two independent areas; The edges of the electrode sheets are insulated and wrapped; The carbon fiber plates on both sides are provided with through holes, through which the metal conductive column penetrates from the through hole of the carbon fiber plate on one side, then penetrates the electrode sheet and the piezoelectric film, and passes out from the through hole of the carbon fiber plate on the other side, so as to realize the common ground connection of the upper and lower electrodes; The electrode sheet, piezoelectric film and carbon fiber plate are tightly connected through high-temperature vulcanization of epoxy glue.

[0006] At present, underwater sound sensing units adopt a structural design of metal backing and piezoelectric film. Since the characteristic impedance of metal is much greater than that of water, sound waves produce more reflections at the interface between water and the unit, increasing the exposure risk in underwater acoustic confrontation. Moreover, the large specific gravity of metal restricts the lightweight of the unit.

[0007] The sensor unit of the present invention adopts a design in which a piezoelectric film is attached to the surface of a carbon fiber plate backing. The carbon fiber backing is equivalent to a shield, which improves the anti-interference ability of the unit. Since one side of the traditional piezoelectric film is a free surface, the vibration caused by the characteristic mode of the metal backing of the sensor unit in a wide frequency band will cause large fluctuations in the sensitivity response. Therefore, the present invention innovatively adopts a sandwich film design for the sensor unit, and the surface of the piezoelectric film is a constrained surface, so that the sensitivity response of the unit is flatter. At the same time, the backing plate is made of carbon fiber material, which improves the sound transmission performance of the underwater sound sensing unit without sacrificing the structural strength of the unit.

[0008] Preferably, the electrode sheet, the piezoelectric film and the carbon fiber plate are tightly connected by high-temperature vulcanization of epoxy glue.

[0009] Preferably, the blank area is arranged along the width or length direction of the piezoelectric film and is located in the middle of the piezoelectric film.

[0010] Preferably, the through hole is arranged in the middle of the carbon fiber plate, and the metal conductive column passes through the blank area of ​​the piezoelectric film.

[0011] Preferably, the width of the blank area is 2 mm.

[0012] Preferably, the piezoelectric film is a P(VDF-TrFE) or PVDF piezoelectric film.

[0013] Preferably, the blank area of ​​the electrode sheet corresponding to the piezoelectric film is also provided with an insulating strip to prevent the positive and negative electrodes of the unit from being conductive.

[0014] Preferably, the metal conductive column is a screw.

[0015] Preferably, the electrode sheet adopts an integrated design to simplify the structural form of the unit, effectively avoid the overlap of the left and right electrodes during the unit manufacturing process, and improve the yield rate of the unit manufacturing.

[0016] Compared with the prior art, the present invention has the following advantages: (1) The underwater sound sensing unit has a high sensitivity by using a piezoelectric copolymer film sensor element with high piezoelectric properties; (2) The underwater sound sensing unit is lightweight by using carbon fiber material as the backing, and the acoustic impedance of carbon fiber is close to that of water, which improves the sound transmission performance of the unit; (3) The bonding connection between carbon fiber and piezoelectric polymer film adopts a sandwich design. Under the action of epoxy glue, the vibration mode of the unit within a wide frequency band is suppressed, thereby improving the flatness of the unit's sensitivity response; (4) The upper and lower carbon fiber plates are connected to the same ground, which is equivalent to shielding, thereby improving the unit's anti-interference ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structural layering of the present invention.

[0018] Figure 2 It is a schematic diagram for comparing the sensitivity of the present invention and the metal backing unit. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to the accompanying drawings: A low-frequency broadband underwater acoustic sensing unit, such as Figure 1 As shown, it includes two layers of carbon fiber plates 1, two layers of piezoelectric films 2 and an electrode sheet 3. Two layers of piezoelectric films 2 are sandwiched between the two layers of carbon fiber plates 1, and another layer of electrode sheet 3 is placed between the two layers of piezoelectric films 2. The surface of the carbon fiber plate 1 and the piezoelectric film 2 is plated with a conductive layer; the backing plate of the present invention is a carbon fiber plate, which can improve the sound transmission performance of the underwater sound sensing unit without sacrificing the structural strength of the unit; The piezoelectric film 2 is polarized along the thickness direction, and the surfaces of both sides of the piezoelectric film 2 are respectively plated with conductive layers, and in order to prevent conduction between the positive and negative electrodes, a blank area 21 is correspondingly left in the middle of the surfaces of both sides of the piezoelectric film 2, and no conductive layer is provided on the blank area 21. The blank area 21 divides the conductive layer on the same side surface of the piezoelectric film 2 into two independent areas; in this embodiment, the blank area 21 is arranged along the width direction of the piezoelectric film 2 and is located in the middle of the piezoelectric film 2, and the blank area 21 is in a strip shape with a width of 2 mm; The electrode sheet 3 is provided with an insulating edging around its edges; The carbon fiber plates 1 on both sides are provided with corresponding through holes 11, which are located in the middle of the carbon fiber plates 1. The metal conductive column penetrates through the through hole of the carbon fiber plate 1 on one side, then penetrates the electrode sheet 3 and the piezoelectric film 2, and passes out from the through hole of the carbon fiber plate 1 on the other side, so as to realize the common ground connection of the upper and lower electrodes; this connection method improves the anti-interference performance of the unit and improves the reliability of the unit structure; The electrode sheet 3, the piezoelectric film 2 and the carbon fiber plate 1 are tightly connected by high-temperature vulcanization of epoxy glue. This structure is simple, the carbon fiber plate 1, the piezoelectric film 2 and the electrode sheet 3 have a large contact area with each other, the bonding strength is large, and the reliability is high.

[0020] In this embodiment, the electrode sheet 3 adopts an integrated design to simplify the structural form of the unit, effectively avoid the overlap of the left and right electrodes during the unit manufacturing process, and improve the yield rate of the unit manufacturing. The metal conductive column adopts a screw, which runs through the unit as a common ground to achieve conduction between the upper and lower electrodes. At the same time, the carbon fiber plate as a backing is equivalent to a shield, which improves the anti-interference ability of the unit.

[0021] In addition, the surface of the carbon fiber plate 1 and the piezoelectric film 2 is plated with a conductive layer, which simplifies the structure of the unit and improves the reliability and yield rate of the unit. Moreover, the sensitive element uses a piezoelectric film with high voltage electrical performance. In this embodiment, the piezoelectric film 3 is a PVDF piezoelectric film, which improves the sensitivity response of the unit; the piezoelectric film 3 adopts a thickness direction polarization method and is sandwiched between two carbon fiber plates 1. This structure effectively suppresses the bending mode of the piezoelectric film and improves the flatness of the sensitivity response of the underwater sound sensing unit.

[0022] As an alternative, the piezoelectric film 2 may also be a P (VDF-TrFE) piezoelectric film.

[0023] As an implementation mode, the blank area of ​​the electrode sheet 3 corresponding to the piezoelectric film 2 is also provided with an insulating strip 31 to prevent the positive and negative electrodes of the unit from being conductive.

[0024] The present invention can improve the anti-interference performance of the underwater acoustic sensor unit, achieve high flatness of the receiving sensitivity response in a wide frequency band, and at the same time reduce the weight of the underwater acoustic sensor unit and improve its sound transmission performance. Figure 2 , which is a schematic diagram comparing the sensitivity of the underwater acoustic sensing unit of the present invention and the traditional metal backing unit.

[0025] The above is only an explanation of the preferred embodiments of the present invention, which should not be construed as a limitation on the claims. Any equivalent process changes made using the present invention specification are included in the patent protection scope of the present invention.

Claims

1. A low-frequency broadband underwater acoustic sensing unit, characterized in that: It includes an electrode sheet, and a piezoelectric film is provided on the upper and lower surfaces of the electrode sheet, and a carbon fiber plate is provided on the outer side of the piezoelectric film, wherein: A conductive layer is plated on the surface of the carbon fiber plate on the side where the piezoelectric film is attached; The piezoelectric film is polarized along the thickness direction, and the surfaces of both sides of the piezoelectric film are respectively plated with conductive layers, and a blank area is correspondingly left in the middle of the surfaces of both sides of the piezoelectric film. The conductive layer is not provided on the blank area, and the blank area divides the conductive layer on each side of the piezoelectric film into two independent areas; The edges of the electrode sheets are insulated and wrapped; The carbon fiber plates on both sides are provided with through holes, through which the metal conductive column penetrates from the through hole of the carbon fiber plate on one side, then penetrates the electrode sheet and the piezoelectric film, and passes out from the through hole of the carbon fiber plate on the other side, so as to realize the common ground connection of the upper and lower electrodes; The electrode sheet, piezoelectric film and carbon fiber plate are tightly connected by vulcanization.

2. The low-frequency broadband underwater acoustic sensing unit according to claim 1, characterized in that: The electrode sheet, piezoelectric film and carbon fiber plate are tightly connected by epoxy vulcanization.

3. The low-frequency broadband underwater acoustic sensing unit according to claim 1, characterized in that: The blank area is arranged along the width or length direction of the piezoelectric film and is located in the middle of the piezoelectric film.

4. The low-frequency broadband underwater acoustic sensing unit according to claim 3, characterized in that: The through hole is arranged in the middle of the carbon fiber plate, and the metal conductive column passes through the blank area of ​​the piezoelectric film.

5. The low-frequency broadband underwater acoustic sensing unit according to claim 3, characterized in that: The width of the blank area is 2 mm.

6. The low-frequency broadband underwater acoustic sensing unit according to claim 1, characterized in that: The piezoelectric film is a P (VDF-TrFE) or PVDF piezoelectric film.

7. The low-frequency broadband underwater acoustic sensing unit according to claim 1, characterized in that: The blank area of ​​the electrode sheet corresponding to the piezoelectric film is also provided with an insulating strip.

8. The low-frequency broadband underwater acoustic sensing unit according to claim 1, characterized in that: The metal conductive post is a screw.

9. The low-frequency broadband underwater acoustic sensing unit according to claim 1, characterized in that: The electrode sheet adopts an integrated design.

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