Piston type piezoelectric composite plate, underwater acoustic transducer and preparation method

Abstract

A piston-type piezoelectric composite plate, an underwater acoustic transducer and a preparation method. The piston-type piezoelectric composite plate is configured as a cylinder, and the piston-type piezoelectric composite plate is spliced ​​by an inner composite plate and an outer composite plate; the inner composite plate is configured as a cylinder that is concentric and equal in height to the piston-type piezoelectric composite plate, and the outer composite plate is configured as a circular cylinder that is concentric and equal in height to the inner composite plate, and the outer composite plate is sleeved on the outer side of the inner composite plate; the inner composite plate and the outer composite plate are both made of 1‑3 type piezoelectric composite materials, and the piezoelectric array density of the inner composite plate is higher than that of the outer composite plate. The underwater acoustic transducer formed by the present invention achieves a larger bandwidth and lower side lobes compared to existing similar products.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater detection, and specifically relates to a piston-type piezoelectric composite plate of an underwater acoustic transducer, an underwater acoustic transducer comprising the piston-type piezoelectric composite plate, and a method for preparing the underwater acoustic transducer. Background Art

[0002] Sonar is a technology that uses the propagation and reflection characteristics of sound waves in water to navigate and measure distance through electroacoustic conversion and information processing. The underwater acoustic transducer is a key device in the sonar system as a system device and medium for information transmission: when transmitting a signal, the system generates an electrical signal of a certain frequency band to excite the transducer to vibrate, generating sound waves to radiate into the medium; when receiving a signal, the transducer receives the sound wave signal in the medium and converts it into an electrical signal, and then the system processes the signal. In practice, in order to achieve a larger communication bandwidth and higher detection accuracy, the underwater acoustic transducer is required to have both broadband and low sidelobe characteristics. One method of expanding the bandwidth in the prior art is to increase the loss of piezoelectric materials: the mechanical quality factor of the transducer is Qm, the mechanical resonance frequency is f0, and the frequency bandwidth of the transducer is △f (-3dB). The relationship between the three is: Qm = f0 / △f, the lower the Qm value, the larger the bandwidth △f. Therefore, by adding high molecular polymers to the piezoelectric material to increase the loss of the piezoelectric material, the Qm value can be reduced and the bandwidth can be increased. However, when the Qm value is low, the sensitivity of the transducer is correspondingly reduced. One method of reducing side lobes in the prior art is to control the phase and amplitude of each array element of the transducer array through the circuit part, and achieve low side lobes through weighted means, but this method will increase the power and complexity of the electronic part, and reduce the reliability and stability of the system. (Tong Hui, Zhou Yiming, Wang Jialin, etc., Research on high-frequency broadband transducers, Acoustic Technology, 2013, 32(06): 524-527) discloses a method of increasing the bandwidth by making the transducer generate multiple vibration modes within the working frequency band and coupling the multiple vibration modes within the frequency range. (Zhang Bin, Zhou Bowen, Tong Hui, etc. Research on a low-sidelobe circular piston high-frequency transducer, Acoustic Technology, 2021, 40(03): 435-438) discloses a scheme of removing piezoelectric particles in a circular ring area of ​​a certain width with the center of the circular piston as the center, and reducing the side lobes by designing a ring-removing structure. At present, how to further optimize the structure of the underwater acoustic transducer based on the above scheme is still in the process of continuous exploration and research. Summary of the invention

[0003] The first object of the present invention is to provide a piston-type piezoelectric composite plate, which, when used in an underwater acoustic transducer, can achieve a larger bandwidth and lower side lobes compared to existing similar products.

[0004] The second object of the present invention is to provide an underwater acoustic transducer comprising the above-mentioned piston-type piezoelectric composite plate.

[0005] The third object of the present invention is to provide a method for producing the above-mentioned underwater acoustic transducer.

[0006] The first scheme provided by the present invention is a piston-type piezoelectric composite plate, which is configured as a cylinder, and the piston-type piezoelectric composite plate is spliced ​​by an inner composite plate and an outer composite plate; the inner composite plate is configured as a cylinder concentric with the piston-type piezoelectric composite plate and of the same height, the outer composite plate is configured as a circular cylinder concentric with the inner composite plate and of the same height, and the outer composite plate is sleeved on the outer side of the inner composite plate; the inner composite plate and the outer composite plate are both made of 1-3 type piezoelectric composite materials, and the piezoelectric array density of the inner composite plate is higher than the piezoelectric array density of the outer composite plate.

[0007] Preferably, the number of the outer composite plates is configured to be at least 2, and the piezoelectric array density of the radially outer composite plate on the piston type piezoelectric composite plate is lower than the piezoelectric array density of the radially inner outer composite plate on the piston type piezoelectric composite plate.

[0008] Preferably, the number of the outer composite panels is configured to be no more than five.

[0009] Preferably, the number of the outer composite plates is configured as 2, the volume percentage of the piezoelectric array on the inner composite plate is 60%-90%, the volume percentage of the piezoelectric array on the radially inner outer composite plate of the piston-type piezoelectric composite plate is 30%-70%, and the volume percentage of the piezoelectric array on the radially outer outer composite plate of the piston-type piezoelectric composite plate is 20%-40%.

[0010] The second solution provided by the present invention is an underwater acoustic transducer, which includes:

[0011] The above-mentioned piston-type piezoelectric composite plate;

[0012] A negative electrode layer, the negative electrode layer being configured to be coated on the upper surface of the piston-type piezoelectric composite plate;

[0013] A positive electrode layer, the positive electrode layer being configured to cover the lower surface of the piston-type piezoelectric composite plate;

[0014] a backing configured to cover a lower surface of the positive electrode layer;

[0015] a matching layer, the matching layer being configured to cover an upper surface of the negative electrode layer;

[0016] A lower shell, the lower shell being configured to be bonded and fixed to a side of the backing facing away from the positive electrode layer;

[0017] An upper shell, wherein the upper shell is configured to cooperate with the lower shell to form a packaging body, and is used to package the piston-type piezoelectric composite plate, the positive electrode layer, the negative electrode layer, the backing and the matching layer inside the packaging body;

[0018] A positive electrode lead, wherein one end of the positive electrode lead is configured to extend into the package body and be fixedly connected to the positive electrode layer;

[0019] A negative electrode lead is configured such that one end of the negative electrode lead extends into the package and is fixedly connected to the negative electrode layer.

[0020] Preferably, the upper shell is formed of a waterproof and sound-permeable layer.

[0021] Preferably, the matching layer includes at least two sub-matching layers, and the at least two sub-matching layers are stacked sequentially along a vertical direction.

[0022] Preferably, the number of the sub-matching layers is 2 or 3.

[0023] The third solution provided by the present invention is a method for preparing an underwater acoustic transducer, comprising the following steps:

[0024] Step 001: Cut and obtain the inner composite plate and the outer composite plate respectively;

[0025] Step 002: splicing the inner composite plate and the outer composite plate into a piston-type piezoelectric composite plate, and aligning the inner composite plate and the outer composite plate along a consistent cutting direction;

[0026] Step 003: pouring epoxy resin into the gaps on the surface of the piston-type piezoelectric composite plate, and performing a vacuum treatment on the piston-type piezoelectric composite plate to remove bubbles;

[0027] Step 004: grinding the thickness of the piston-type piezoelectric composite plate;

[0028] Step 005: uniformly coating the upper surface of the piston-type piezoelectric composite plate with a negative electrode layer and welding a negative electrode lead on the negative electrode layer, and uniformly coating the lower surface of the piston-type piezoelectric composite plate with a positive electrode layer and welding a positive electrode lead on the positive electrode layer;

[0029] Step 006: bonding a matching layer to the upper surface of the negative electrode layer, and bonding a backing to the lower surface of the positive electrode layer;

[0030] Step 007: Grind the thickness of the matching layer until the multi-resonance peak coupling and bandwidth expansion are met;

[0031] Step 008: Assemble the lower shell on the backing to form an assembly;

[0032] Step 009: Place the assembly in a potting mold and pour a waterproof and sound-permeable layer as the upper shell to complete the packaging.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] First, based on the solution of 1-3 type piezoelectric composite materials, the present invention reduces the density of piezoelectric arrays in the outer ring and further combines the solution of vibration mode coupling, so that the underwater acoustic transducer achieves a larger bandwidth and lower side lobes than existing similar products. In addition, the technical solution of the present invention has a simple structure and is easy to prepare. It can be mass-produced and widely used in multiple application scenarios such as underwater target detection, underwater acoustic communication, marine surveying, and underwater acoustic navigation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic cross-sectional structure diagram of the underwater acoustic transducer in Example 1;

[0036] Figure 2 Schematic diagram of the three-dimensional structure of the underwater acoustic transducer in Example 1, in which the watertight cable, the lower shell and the upper shell are omitted;

[0037] Figure 3 It is a structural schematic diagram of the piston-type piezoelectric composite plate of Example 1;

[0038] Figure 4 Schematic diagram of the preparation process of the underwater acoustic transducer in Example 1;

[0039] Figure 5 The water conductivity diagram of the piston-type piezoelectric composite plate in Example 1;

[0040] Figure 6 is the directivity diagram of the underwater acoustic transducer in Example 1;

[0041] Figure 7 The water conductivity diagram of the piston-type piezoelectric composite plate after being coated with a single matching layer in Example 1;

[0042] Figure 8 is a schematic diagram of the cross-sectional structure of the underwater acoustic transducer in Example 2;

[0043] Fig. 9 is the underwater conductance diagram of the underwater acoustic transducer in Example 2;

[0044] Fig.10 is a schematic cross-sectional structure diagram of the underwater acoustic transducer in Example 3;

[0045] Fig.11 This is the underwater conductivity diagram of the underwater acoustic transducer in Example 3.

[0046] In the figure, the component names corresponding to the reference numerals are as follows:

[0047] 1. Piston piezoelectric composite plate; 21. Inner composite plate; 22. Outer composite plate; 31. Piezoelectric array; 32. High polymer; 41. Negative electrode layer; 42. Positive electrode layer; 5. Backing; 6. Matching layer; 61: First sub-matching layer; 62: Second sub-matching layer; 63: Third sub-matching layer; 7. Upper shell; 81. Negative electrode lead; 82. Positive electrode lead; 83. Watertight cable; 9. Lower shell. DETAILED DESCRIPTION

[0048] The following is an explanation of the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the orientation or position relationship indicated by the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0049] It should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0050] First, the applicant explains the creation process of this application:

[0051] In the current practical application of underwater acoustic transducers, transducers with low side lobes and broadband have more application scenarios, which can improve the communication bandwidth and detection accuracy of the sonar system. In response to this demand, the inventor first proposed a structure in which the piezoelectric circular piston removes the piezoelectric particles in the circular ring area of ​​a certain width in the middle, and reduces the side lobes by designing the ring-removing structure. But later, the inventor found that although the first side lobe can be reduced in the above scheme, some other side lobes will be increased accordingly. And the more the first side lobe is reduced, the more the other side lobes are increased. Therefore, the effect of the above scheme on reducing the side lobes is limited, and the distal side lobes of the transducer will be increased, which weakens the ability of the scheme to reduce the side lobes and has great limitations. On the basis of the above scheme, after many theoretical demonstrations and experimental adjustments, the inventor found that the 1-3 type piezoelectric composite circular piston is divided into several rings from the inside to the outside, and the distribution density of the piezoelectric particles on each ring is arranged in the order of "inner dense-outer comb", which can further reduce the first side lobe of the transducer, and no longer produce the problem of corresponding increase in the distal side lobe. At the same time, different particle distribution densities on each ring will produce different resonant frequencies. Therefore, it is necessary to select a certain particle distribution density to achieve mutual coupling vibration between different resonant frequencies to effectively expand the bandwidth. It is also possible to achieve coupling by setting corresponding coating matching layers to generate different resonant peaks.

[0052] Example 1, please refer to the attached Figure 1-3 :

[0053] An underwater acoustic transducer, comprising:

[0054] The piston-type piezoelectric composite plate 1 is cylindrical in shape as a whole, and is composed of a cylindrical inner composite plate 21 and two annular outer composite plates 22 which are concentrically arranged at equal heights and distributed in sequence along the radial direction and are spliced ​​in sequence from the inside to the outside. Among them, the inner composite plate 21 and the outer composite plate 22 are both made of 1-3 type piezoelectric composite materials. Among them, the volume percentage of the piezoelectric array on the inner composite plate 21 is 60%-90%, the volume percentage of the piezoelectric array on the outer composite plate 22 located on the radial inner side of the piston-type piezoelectric composite plate 1 is 30%-70%, and the volume percentage of the piezoelectric array on the outer composite plate 22 located on the radial outer side of the piston-type piezoelectric composite plate 1 is 20%-40%. Among them, the 1-3 type piezoelectric composite material has the advantages of increasing piezoelectric loss and controllable and adjustable particle density distribution, and can reduce the low side lobe of the transducer and generate multi-resonance frequency coupling to expand the bandwidth by preferably having different piezoelectric particle distribution densities.

[0055] A negative electrode layer 41, wherein the negative electrode layer 41 is configured to cover the upper surface of the piston-type piezoelectric composite plate 1;

[0056] A positive electrode layer 42, wherein the positive electrode layer 42 is configured to cover the lower surface of the piston-type piezoelectric composite plate 1;

[0057] A backing 5, wherein the backing 5 is configured to cover the lower surface of the positive electrode layer 42;

[0058] a matching layer 6, wherein the matching layer 6 is configured to cover the upper surface of the negative electrode layer 41;

[0059] A lower shell 9, wherein the lower shell 9 is configured to be bonded and fixed to the lower surface of the backing 5;

[0060] An upper shell 7, wherein the upper shell 7 is configured to cooperate with the lower shell 9 to form a packaging body that encapsulates the piston-type piezoelectric composite plate 1, the negative electrode layer 41, the positive electrode layer 42, the backing 5, and the matching layer;

[0061] A negative electrode lead 81, wherein one end of the negative electrode lead 81 is configured to extend into the lower shell 9 and be fixedly connected to the negative electrode layer 41;

[0062] The positive electrode lead 82 is configured such that one end of the lead extends into the lower shell 9 and is fixedly connected to the positive electrode layer 42 .

[0063] In this example: the piezoelectric array 31 adopts any one of piezoelectric ceramics or piezoelectric single crystals or a composite material of piezoelectric ceramics and piezoelectric single crystals. The polymer 32 in the 1-3 type piezoelectric composite material includes at least one of epoxy resin, silicone rubber, polycarbonate, oil nylon, glass, polyurethane, and rubber. It also includes at least one powder component of aluminum powder, tungsten powder, ceramic powder, and glass microbeads. The matching layer is a single-layer structure, and its layer thickness is about 1 / 4 of the wavelength of the sound wave. The other ends of the negative electrode lead 81 and the positive electrode lead 82 are respectively wrapped in a watertight cable 83 and extend out of the lower shell 9.

[0064] Please refer to Figure 4 , the preparation process of the above-mentioned underwater acoustic transducer is as follows:

[0065] Step 001: fix the piezoelectric material on a cutting plate, and use a precision cutting machine to perform transverse and longitudinal cutting according to the pre-designed particle size and slit width, to obtain an inner composite plate 21 and two outer composite plates 22;

[0066] Step 002: splicing the one inner composite plate 21 and the two outer composite plates 22 into a piston-type piezoelectric composite plate 1, and aligning the inner composite plate 21 and the two outer composite plates 22 along the cutting direction;

[0067] Step 003: preparing epoxy resin, and pouring the epoxy resin into the gap formed by cutting on the piston type piezoelectric composite plate 1, and then placing the piston type piezoelectric composite plate 1 into a vacuum box for vacuum treatment to remove bubbles;

[0068] Step 004: grinding the thickness of the piston type piezoelectric composite plate 1 using a precision grinder;

[0069] Step 005: uniformly coating the upper surface of the piston-type piezoelectric composite plate 1 with a negative electrode layer 41 and welding a positive electrode lead on the negative electrode layer 41, and uniformly coating the lower surface of the piston-type piezoelectric composite plate 1 with a positive electrode layer 42 and welding a positive electrode lead on the positive electrode layer 42;

[0070] Step 006: Prepare the matching layer material in proportion, and bond the matching layer to the upper surface of the negative electrode layer 41; bond the backing 5 to the lower surface of the positive electrode layer 42;

[0071] Step 007: grinding the thickness of the matching layer using a precision grinder; the thickness of the matching layer should be ground to meet the multi-resonance peak coupling and bandwidth expansion requirements;

[0072] Step 008: Assemble the 1-3 piezoelectric composite material with non-uniform density distribution with the lower shell 9 to form an assembly.

[0073] Step 009: Place the assembly in a potting mold and cast the upper shell 7 to form a package.

[0074] Please refer to Figure 5-7 :

[0075] Figure 5 1 is the water conductivity diagram of the piezoelectric composite material 1-3 on the piston-type piezoelectric composite plate 1 in this example.

[0076] Number 1# represents the inner composite plate 21 described in this example, number 2# represents the outer composite plate 22 with a smaller outer diameter described in this example, number 3# represents the outer composite plate 22 with a larger outer diameter described in this example, and number 4# represents the spliced ​​piston-type piezoelectric composite plate 1 described in this example.

[0077] The one inner composite plate 21 and the two outer composite plates 22 generate different resonant frequencies respectively. The different resonant frequencies are coupled to vibrate. The water conductivity data thereof are shown in Table 1 below:

[0078] serial number Frequency (kHz) Conductivity(mS) -3dB bandwidth (kHz) 1# 309.6 7.0 24.3 2# 299.9 6.1 23.9 3# 291.4 5.9 23.7 4# 300.2 14.3 35.6 5# 299.9 24.5 23.9

[0079] Table 1

[0080] In the above table, the number 5# represents a circular piston array with the same area as the piston piezoelectric composite plate 1 and the same density of the piezoelectric array 31 as the outer composite plate 22 with a smaller outer diameter. By comparison, the bandwidth of the piston piezoelectric composite plate 1 used in this example is significantly larger than that of the circular piston array with the same area and uniform density of the piezoelectric array 31. Therefore, compared with the uniform array composite material, the bandwidth of the 1-3 piezoelectric composite material with non-uniform density distribution has been significantly expanded.

[0081] Figure 6 This is the directivity diagram of the underwater acoustic transducer in this example:

[0082] from Figure 6 It can be seen that the maximum sidelobe level of the 1-3 piezoelectric composite transducer under the non-uniform distribution density of the piezoelectric array 31 is -25.5dB, while the sidelobe level of the uniform piston array is -17.6dB, and the maximum sidelobe level is reduced by 7.9dB. Therefore, compared with the uniform array composite material, the maximum sidelobe level of the 1-3 piezoelectric composite material with non-uniform density distribution has been significantly reduced.

[0083] Figure 7 The conductivity curve in water of the 1-3 piezoelectric composite transducer with non-uniform density distribution after being coated with a single matching layer. Figure 7 It can be seen that after the matching layer is coated, the multi-resonance peaks are coupled. As shown in Table 2 below, it is a table of water conductivity data of 1-3 piezoelectric composite transducers with non-uniform distribution density (No. 1#) and uniform distribution density (No. 2#) after the matching layer is coated.

[0084] In Table 2, number 1# represents the piston-type piezoelectric composite plate 1 in this example, and number 2# represents a circular piston array having the same area as the piston-type piezoelectric composite plate 1 and the same density of piezoelectric arrays 31 as the outer composite plate 22 with a smaller outer diameter.

[0085] serial number Center frequency (kHz) -3dB bandwidth (kHz) 1# 302.1 137.8 2# 300.8 117.6

[0086] Table 2

[0087] It can be seen from Table 2 that compared with the uniform array composite material after coating the matching layer, the bandwidth of the 1-3 piezoelectric composite material with non-uniform density distribution after coating the matching layer has been significantly expanded.

[0088] Example 2, please refer to Figure 8-9 :

[0089] The difference between Example 2 and Example 1 is that the matching layer in this example specifically includes a first sub-matching layer 61 and a second sub-matching layer 62 which are sequentially stacked in the vertical direction. Fig. 9 The underwater conductivity diagram of the underwater acoustic transducer covered with two sub-matching layers in Example 2, Fig. 9 It can be seen that the three resonance peaks are coupled after being coated with two sub-matching layers.

[0090] As shown in Table 3 below: it is a table of the conductivity data of the 1-3 piezoelectric composite water acoustic transducer in water coated with two sub-matching layers (number B#) and one matching layer (number A#). By comparing the data in Table 3, the transducer coated with two sub-matching layers (number B#) has a bandwidth increased by 101.7kHz compared with the transducer coated with a single matching layer (number A#), so the transducer in this example has a larger bandwidth.

[0091] serial number Center frequency (kHz) -3dB bandwidth (kHz) A# 302.1 137.8 B# 300.8 239.5

[0092] Table 3

[0093] Example 3, please refer to Figure 10-11 :

[0094] The difference between Example 3 and Example 2 is that the matching layer in this example specifically includes a first sub-matching layer 61 , a second sub-matching layer 62 and a third sub-matching layer 63 which are sequentially stacked along the vertical direction. Fig.11 is the underwater conductivity diagram of the underwater acoustic transducer in this example, from Fig.11 It can be seen that after being coated with three sub-matching layers, the four resonance peaks are coupled.

[0095] As shown in Table 4 below, it is the water conductivity data table of 1-3 piezoelectric composite underwater acoustic transducer coated with three layers of sub-matching layer (number C#), double layers of sub-matching layer (number B#), and single layer of matching layer (number A#). By comparing the data in Table 4, it can be seen that the transducer coated with three layers of sub-matching layer (number C#) has a bandwidth increased by 37.5kHz and 139.2kHz compared with the transducer coated with two layers of sub-matching layer (number B#) and the transducer coated with a single layer of matching layer (number A#). Therefore, the bandwidth of the transducer in this example has been further expanded.

[0096] serial number Center frequency (kHz) -3dB bandwidth (kHz) A# 302.1 137.8 B# 300.8 239.5 C# 302.8 277.0

[0097] Table 4

[0098] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they still fall within the protection scope of the present invention.

Claims

1. A piston-type piezoelectric composite plate, characterized in that: The piston-type piezoelectric composite plate is configured as a cylinder, and the piston-type piezoelectric composite plate is spliced ​​by an inner composite plate and an outer composite plate; the inner composite plate is configured as a cylinder concentric with the piston-type piezoelectric composite plate and of equal height, and the outer composite plate is configured as a circular cylinder concentric with the inner composite plate and of equal height, and the outer composite plate is sleeved on the outer side of the inner composite plate; the inner composite plate and the outer composite plate are both made of 1-3 type piezoelectric composite materials, and the piezoelectric array density of the inner composite plate is higher than the piezoelectric array density of the outer composite plate; The number of the outer composite plates is configured to be at least 2, and the piezoelectric array density of the outer composite plate located radially outward on the piston-type piezoelectric composite plate is lower than the piezoelectric array density of the outer composite plate located radially inward on the piston-type piezoelectric composite plate.

2. The piston-type piezoelectric composite plate according to claim 1, characterized in that: The number of the outer composite panels is configured to be no more than five.

3. The piston-type piezoelectric composite plate according to claim 1, characterized in that: The number of the outer composite plates is configured as 2, the volume percentage of the piezoelectric array on the inner composite plate is 60%-90%, the volume percentage of the piezoelectric array on the radially inner outer composite plate of the piston-type piezoelectric composite plate is 30%-70%, and the volume percentage of the piezoelectric array on the radially outer outer composite plate of the piston-type piezoelectric composite plate is 20%-40%.

4. An underwater acoustic transducer, characterized in that: A piston-type piezoelectric composite plate comprising any one of claims 1 to 3; Also includes: A negative electrode layer, the negative electrode layer being configured to be coated on the upper surface of the piston-type piezoelectric composite plate; A positive electrode layer, the positive electrode layer being configured to cover the lower surface of the piston-type piezoelectric composite plate; a backing configured to cover a lower surface of the positive electrode layer; a matching layer, the matching layer being configured to cover an upper surface of the negative electrode layer; A lower shell, the lower shell being configured to be bonded and fixed to a side of the backing facing away from the positive electrode layer; An upper shell, wherein the upper shell is configured to cooperate with the lower shell to form a packaging body, and is used to package the piston-type piezoelectric composite plate, the positive electrode layer, the negative electrode layer, the backing and the matching layer inside the packaging body; A positive electrode lead, wherein one end of the positive electrode lead is configured to extend into the package body and be fixedly connected to the positive electrode layer; A negative electrode lead is configured such that one end of the negative electrode lead extends into the package and is fixedly connected to the negative electrode layer.

5. The underwater acoustic transducer according to claim 4, characterized in that: The upper shell is formed by a waterproof and sound-permeable layer.

6. The underwater acoustic transducer according to claim 4, characterized in that: The matching layer includes at least two sub-matching layers, and the at least two sub-matching layers are stacked sequentially along a vertical direction.

7. The underwater acoustic transducer according to claim 6, characterized in that: The number of the sub-matching layers is 2 or 3.

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