A low-frequency broadband underwater acoustic sensing unit

Abstract

The present invention relates to a low-frequency, broadband underwater acoustic sensing unit comprising an electrode sheet, piezoelectric films disposed on the upper and lower surfaces, respectively, and carbon fiber plates disposed on the outer sides of the piezoelectric films. The carbon fiber plates are plated with a conductive layer on the side where they adhere to the piezoelectric films. The piezoelectric films are polarized along their thickness, and the conductive layers are plated on both sides of the piezoelectric films, with a corresponding blank area left between the two surfaces of the piezoelectric films. This invention improves the anti-interference capabilities of the underwater acoustic sensing unit, achieving high flatness of the receiving sensitivity response across a wide frequency band, while also reducing the weight of the underwater acoustic sensing unit and improving its acoustic transparency.

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 highly sensitive broadband hydrophones.

[0003] Planar underwater acoustic sensor units generally use a design that combines a piezoelectric film with a rigid backing. The rigid backing can improve the unit's sensitivity and expand the operating frequency band. However, the characteristic impedance of the rigid backing is significantly different from that of water, which restricts the acoustic transparency of the planar underwater acoustic sensor unit. Specifically, current low-frequency, broadband underwater acoustic sensor units use a structural design that combines a piezoelectric film with a metal backing. Due to the higher specific gravity of the metal plate, underwater acoustic sensor units with metal backing are heavier for the same volume. In addition, the significant difference in the characteristic impedance of the metal plate and water limits the operating frequency band of the underwater acoustic sensor unit. As the frequency of the sound wave increases, more sound energy is reflected at the interface, which means a higher risk of being detected during underwater acoustic countermeasures. Furthermore, when a piezoelectric film is attached to the surface of the metal backing, the metal backing will exhibit resonant modes within a wide frequency band. Since the piezoelectric film on the surface is not constrained by any external surface, it is greatly affected by the resonance, resulting in large fluctuations in the sensitivity of the unit within the frequency band. 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 the upper and lower surfaces of the electrode sheet are respectively provided with a piezoelectric film, and the outer sides of the piezoelectric film are respectively provided with a carbon fiber plate, wherein:

[0006] The surface of the carbon fiber plate and the piezoelectric film on the side where they are bonded is coated with a conductive layer;

[0007] The piezoelectric film is polarized along the thickness direction. Conductive layers are plated on both sides of the piezoelectric film. A blank area is left between the two sides of the piezoelectric film. No conductive layer is provided on the blank area. The blank area divides the conductive layer on each side of the piezoelectric film into two independent areas.

[0008] The edges of the electrode sheets are insulated and wrapped;

[0009] There are corresponding through holes on the carbon fiber plates on both sides. The metal conductive column penetrates through the through hole of the carbon fiber plate on one side, then passes through the electrode sheet and the piezoelectric film, and exits from the through hole of the carbon fiber plate on the other side to achieve common ground connection of the upper and lower electrodes;

[0010] The electrode sheet, piezoelectric film and carbon fiber plate are tightly connected through high-temperature vulcanization of epoxy glue.

[0011] Currently, underwater acoustic sensing units use a structural design in which a metal backing is bonded to a 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 risk of exposure in underwater acoustic confrontation. Moreover, the high specific gravity of metal restricts the lightweighting of the unit.

[0012] The sensor unit of the present invention utilizes a piezoelectric film attached to the surface of a carbon fiber backing. The carbon fiber backing acts as a shield, enhancing the unit's anti-interference capabilities. Because conventional piezoelectric films have one free surface, the vibrations caused by the characteristic modes of the metal backing within a wide frequency band can cause significant fluctuations in the sensitivity response. Therefore, the present invention innovatively utilizes a sandwich design for the sensor unit, where the piezoelectric film surfaces serve as constrained surfaces, resulting in a flatter sensitivity response. Furthermore, the carbon fiber backing plate enhances the acoustic transparency of the underwater acoustic sensing unit without sacrificing its structural strength.

[0013] Preferably, the electrode sheet, the piezoelectric film and the carbon fiber plate are tightly connected by high-temperature vulcanization of epoxy glue.

[0014] 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.

[0015] Preferably, the through hole is provided in the middle of the carbon fiber plate, and the metal conductive column passes through the blank area of the piezoelectric film.

[0016] Preferably, the width of the blank area is 2 mm.

[0017] Preferably, the piezoelectric film is a P(VDF-TrFE) or PVDF piezoelectric film.

[0018] 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.

[0019] Preferably, the metal conductive column is a screw.

[0020] 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.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) The underwater sound sensing unit has a high sensitivity due to the adoption of piezoelectric copolymer film sensing elements with high piezoelectric properties. (2) The use of carbon fiber material as a backing material makes the underwater sound sensing unit lightweight, and since the acoustic impedance of carbon fiber is close to that of water, the sound transmission performance of the unit is improved. (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 in 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

[0023] Figure 1 It is a schematic diagram of the structural layering of the present invention.

[0024] Figure 2 Schematic diagram comparing the sensitivity of the present invention and the metal backing unit. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings:

[0026] 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.

[0027] 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 made of carbon fiber material, which can improve the sound transmission performance of the underwater sound sensing unit without sacrificing the structural strength of the unit;

[0028] The piezoelectric film 2 is polarized along its thickness. Conductive layers are plated on both sides of the piezoelectric film 2. To prevent conduction between the positive and negative electrodes, a blank area 21 is left in the middle of each side of the piezoelectric film 2. No conductive layer is provided on the blank area 21. This blank area 21 divides the conductive layer on the same side of the piezoelectric film 2 into two separate areas. In this embodiment, the blank area 21 is provided along the width of the piezoelectric film 2 and is located in the middle of the piezoelectric film 2. The blank area 21 is strip-shaped and has a width of 2 mm.

[0029] The edges of the electrode sheet 3 are insulated and wrapped;

[0030] The carbon fiber plates 1 on both sides are provided with corresponding through holes 11. The through holes 11 are located in the middle of the carbon fiber plates 1. A metal conductive column is passed 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 exits 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.

[0031] 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 high, and the reliability is high.

[0032] In this embodiment, the electrode sheet 3 adopts an integrated design, simplifying the unit's structure and effectively preventing overlap of the left and right electrodes during unit manufacturing, thereby improving the unit's production yield. The metal conductive posts are screws, which serve as a common ground and penetrate the unit to achieve electrical continuity between the upper and lower electrodes. Furthermore, the carbon fiber backing acts as a shield, enhancing the unit's anti-interference capabilities.

[0033] In addition, the conductive layer coating on the surface of the carbon fiber plate 1 and the piezoelectric film 2 simplifies the unit's structure and improves its reliability and yield rate. Furthermore, the sensitive element uses a piezoelectric film with high piezoelectric properties. In this embodiment, the piezoelectric film 3 is a PVDF piezoelectric film, which improves the unit's sensitivity response. The piezoelectric film 3 is polarized in the thickness direction and sandwiched between the two carbon fiber plates 1. This structure effectively suppresses the piezoelectric film's bending mode, improving the flatness of the underwater acoustic sensing unit's sensitivity response.

[0034] As an alternative, the piezoelectric film 2 may also be a P(VDF-TrFE) piezoelectric film.

[0035] As an embodiment, 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.

[0036] 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.

[0037] The above description is only for the preferred embodiment of the present invention, which should not be understood as limiting the claims. Any equivalent process changes made using the present invention description are included in the patent protection scope of the present invention.

Claims

1. A low-frequency, broadband underwater acoustic sensing unit, characterized by: 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. The surface of the carbon fiber plate and the piezoelectric film on the side where they are bonded is coated with a conductive layer; The piezoelectric film is polarized along the thickness direction. Conductive layers are plated on both sides of the piezoelectric film. A blank area is left between the two sides of the piezoelectric film. No conductive layer is provided on the blank area. 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; There are corresponding through holes on the carbon fiber plates on both sides. The metal conductive column penetrates through the through hole of the carbon fiber plate on one side, then passes through the electrode sheet and the piezoelectric film, and exits from the through hole of the carbon fiber plate on the other side to achieve 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 glue 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 set 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 column 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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