CN105047811A - Stack piezoelectric transducer based on piezoelectric material layers with different thicknesses - Google Patents

Abstract

The present invention relates to a stacked piezoelectric transducer based on piezoelectric material layers of different thicknesses. The piezoelectric material layer preferably adopts piezoelectric composite materials, such as 1-3 type piezoelectric composite materials, or piezoelectric ceramics, Traditional piezoelectric materials such as piezoelectric single crystals. In the stacked piezoelectric material vibrator of the present invention, since the thicknesses of the piezoelectric material layers are different, the resonant frequencies of the piezoelectric material layers are different, so that the stacked piezoelectric material vibrators have multiple modes, that is, multiple resonant frequencies. By rationally designing the thickness of each piezoelectric material layer, the resonant frequency of each piezoelectric material layer in the piezoelectric vibrator is close to and coupled with each other, and works simultaneously in a wide frequency range, so that the combined frequency response does not produce discontinuities and overshoots. Deep valleys will form complex multi-mode vibrations in this frequency band, which can effectively expand the working bandwidth of the transducer and realize high-frequency and wide-band transmission and reception of sound waves.

Description

Stacked piezoelectric transducers based on piezoelectric material layers of different thicknesses

technical field

The invention belongs to the technical field of underwater acoustic detection, and in particular relates to a piezoelectric vibrator formed by stacking piezoelectric materials with different thicknesses, which is applied to a transducer to transmit and receive underwater acoustic signals to realize underwater detection.

Background technique

The underwater acoustic transducer is a device that converts sound energy and electrical energy into each other. Its status is similar to that of an antenna in radio equipment, and it is a key device for transmitting and receiving sound waves underwater. Underwater detection, identification, communication, as well as marine environment monitoring and the development of marine resources are inseparable from underwater acoustic transducers. Transducers can be divided into transmitting type, receiving type and dual-purpose type. Transducers that convert electrical signals into underwater acoustic signals and radiate sound waves into water are called transmitting transducers. The transmitting transducers require relatively large output sound power and relatively high electroacoustic conversion efficiency. The transducer used to receive acoustic signals in water and convert them into electrical signals is a receiving transducer, also often called a hydrophone. The receiving transducer requires broadband and high sensitivity. It can not only convert the acoustic signal into an electrical signal, but also convert the electrical signal into an acoustic signal. Transducers used to receive or transmit acoustic signals are called transceiver transducers.

The piezoelectric vibrator is the core component of the transducer, and the performance of the vibrator determines the working performance of the transducer. Therefore, in order to manufacture a high-performance underwater acoustic transducer, the performance of the piezoelectric vibrator must first be improved. Among the materials for making piezoelectric vibrators, piezoelectric composite materials are widely used because of their advantages such as small acoustic impedance, wide bandwidth, and high mechanical quality factor. Piezoelectric composite material is a multi-phase material made of piezoelectric materials, polymers, metals, etc. through a composite process. Each phase in the composite material can communicate with itself in 0, 1, 2, or 3 dimensions. The current composite materials include 1-3 type, 3-1 type, 3-2 type, 3-3 type, 0-3 type, 2-2 type composite material, and crescent and cap-shaped metal-piezoelectric ceramic wafers, among which Type 1-3 piezoelectric composites are the most widely used. The existing 1-3 composite piezoelectric transducers mainly include the following types:

1. Type 1-3 piezoelectric composite material transducer

Type 1-3 Piezoelectric Composite Transducers (Chen Junbo, Wang Yuebing, Zhong Linjian, Comparative Analysis of the Performance of Type 1-3 Piezoelectric Composite Materials and Common PZT Transducers, Acoustics and Electronics Engineering, 2007, vol.87(3) :25-27) The 1-3 type piezoelectric composite material was prepared by cutting-fill method, and two pieces of the same size 1-3 type piezoelectric composite material and PZT ceramic sheet were used to make piston-type transducers. The piezoelectric element of the transducer is a disc with a thickness of 9mm and a diameter of 42.7mm, which is fixed with a decoupling material and installed in a metal shell, and the radiation surface is potted with polyurethane. After measurement, the admittance curves of the two transducers in air and water, and the curves of sending voltage response, receiving sensitivity and directivity in water are obtained. Through comparative analysis, it is concluded that the transceiving performance of the 1-3 type piezoelectric composite transducer is significantly improved compared with the ordinary PZT piezoelectric transducer. Since the transverse coupling of the 1-3 type transducer is small, it presents a single thickness resonance and the bandwidth becomes wider.

2. Type 1-3 piezoelectric composite broadband underwater acoustic transducer

1-3 type piezoelectric composite broadband underwater acoustic transducer (Zhang Kai, Lan Yu, Li Qi, Research on 1-3 type piezoelectric composite broadband underwater acoustic transducer, Acta Acoustica Sinica, 2011, Vol.36(6) , 631-637) used thickness vibration modal theory, transverse modal theory and finite element method to study 1-3 piezoelectric composite transducers, and used ANSYS software to establish the finite element model of the transducer, and then carried out structural After optimization, a 1-3 type piezoelectric composite broadband transducer using the thickness vibration mode and the first-order transverse mode mode was finally fabricated. Its operating bandwidth is 190-390kHz. The results show that the bandwidth of type 1-3 piezoelectric composite transducers can be extended by using the thickness vibration mode and the first-order transverse mode.

3. Single crystal composite broadband transducer

In the literature (S.Cochran, M.Parker, and P.Marin-Franch, Ultrabroadbandsinglecrystalcompositetransducersforunderwaterultrasound, IEEEUltrasonicsSymposium, 2005, 231-234), the British scholar S.Cochran et al. used PMN-PT single crystal to make composite materials, and in the composite materials A matching layer is added to make a single crystal composite material broadband transducer. The -3dB relative bandwidth of the fabricated single crystal composite transducer is 125%, which is close to 135% of theoretical calculation. The single crystal composite transducer has a nearly four-fold increase in bandwidth compared to conventional ceramic composite transducers.

To sum up, in the method of expanding the bandwidth of the transducer, the first method of injecting polymer in the traditional piezoelectric material can expand the bandwidth, but its ability to expand the bandwidth is limited; the second method can also increase the bandwidth by using the coupling of thickness vibration and transverse vibration. Large bandwidth, but the size of the vibrator is not easy to control, making it more difficult. The third is to add a matching layer on the piezoelectric composite material, and the bandwidth can be significantly increased, but the performance of the matching layer will change with time, making the performance of the transducer unstable.

Contents of the invention

The object of the present invention is to solve the above problems and provide a piezoelectric transducer made of piezoelectric materials with different thicknesses stacked to expand the bandwidth of the high-frequency transducer.

To achieve the above object, the present invention adopts the following technical solutions:

A piezoelectric transducer includes stacked piezoelectric material layers with different thicknesses, and the resonant frequencies of the piezoelectric material layers are close to each other and coupled.

Further, the piezoelectric material used in the piezoelectric material layer is preferably a piezoelectric composite material, and may also be traditional piezoelectric materials such as piezoelectric ceramics and piezoelectric single crystals.

Further, the piezoelectric composite material is a 1-3 type piezoelectric composite material, a 2-2 type composite material, a 0-3 type composite material, etc. In the piezoelectric composite material, the piezoelectric phase material is piezoelectric ceramic or Piezoelectric single crystal, the polymer phase material is epoxy resin, polyurethane, silicone rubber, etc.

Further, the upper and lower surfaces of the piezoelectric material layer are covered with electrode layers, and the materials of the electrodes are gold, silver, conductive glue and the like.

Further, the stacked piezoelectric material layers with different thicknesses are formed by bonding two or more piezoelectric material layers with different thicknesses.

Further, the stacked piezoelectric material layers with different thicknesses are formed by stacking planar piezoelectric materials, or by stacking curved (such as arc-shaped) piezoelectric materials.

Further, the thickness t of the piezoelectric material layer is 2-10 mm, and the thickness difference Δt of each piezoelectric material layer is 0-1 mm.

In the stacked piezoelectric material vibrator of the present invention, since the thickness of each piezoelectric material layer is different, the resonant frequency of each piezoelectric material layer is different, so that the stacked piezoelectric material vibrator has multiple modes (multiple resonant frequencies). By rationally designing the thickness of each piezoelectric material layer, the resonant frequency of each piezoelectric material layer in the piezoelectric vibrator is close to and coupled with each other, and works simultaneously in a wide frequency range, so that the combined frequency response does not produce discontinuity and overshoot. Deep valleys will form complex multi-mode vibrations in this frequency band, which can effectively expand the working bandwidth of the transducer and realize high-frequency and wide-band transmission and reception of sound waves.

Description of drawings

Fig. 1 is a schematic structural diagram of a transducer in an embodiment.

Fig. 2 is a schematic structural view of the 1-3 type composite material in the embodiment.

Fig. 3 is a schematic diagram of the manufacturing process of type 1-3 piezoelectric composite materials in the embodiment.

Fig. 4 is a schematic diagram of stacking two pieces of piezoelectric composite materials with different thicknesses in the embodiment.

Fig. 5 is a schematic diagram of the side of the piezoelectric vibrator in the embodiment (two-layer structure).

Fig. 6 is a schematic diagram of resonance frequency coupling of piezoelectric composite materials with different thicknesses in the embodiment.

Fig. 7 is a schematic diagram of the resonant frequency and bandwidth performance of the two-piece stacked composite piezoelectric vibrator in the air in the embodiment.

Fig. 8 is a graph showing the transmission voltage response curve of the transducer made of the No. 1 piezoelectric vibrator in the embodiment.

Fig. 9 is a schematic diagram of stacking three sheets of composite materials with different thicknesses in the embodiment.

Fig. 10 is a schematic diagram of the side of the piezoelectric vibrator in the embodiment (three-layer structure).

Fig. 11 is a schematic diagram of the resonant frequency and bandwidth performance of the three-piece stacked composite piezoelectric vibrator in the air in the embodiment.

Fig. 12 is a graph of conductance curves of stacking two ceramic sheets with different thicknesses in the embodiment.

Fig. 13 is a graph of conductance curves of stacking two single wafers with different thicknesses in the embodiment.

Fig. 14 is a schematic diagram of the stack structure of arc-shaped piezoelectric materials with different thicknesses in the embodiment.

Explanation of symbols in the figure: 1. Piezoelectric phase; 2. Polymer phase; 3. Piezoelectric substrate; 4. Adhesive layer; 5. Electrode; t ₁ , t ₂ , is the thickness of the piezoelectric composite material.

Detailed ways

The present invention will be described in detail below through specific embodiments and accompanying drawings.

Example 1: Two sheets of composite materials with different thicknesses are stacked

FIG. 1 is a schematic structural diagram of a transducer stacked with two composite materials in this embodiment. As shown in the figure, the transducer includes two pieces of 1-3 piezoelectric composite materials with different thicknesses, that is, composite material 1 and composite material 2 in the figure; there is an adhesive layer between the two layers of composite materials, and the composite material The upper and lower surfaces are covered with electrodes, and cables are drawn from the electrodes; the upper part of the composite material 1 is provided with a sound-absorbing layer for absorbing excess sound waves and preventing sound wave reflection; the outermost part of the transducer is a waterproof sound-permeable layer (such as polyurethane) sealed.

FIG. 2 is a schematic structural view of the 1-3 type composite material for making the piezoelectric vibrator in this embodiment. As shown in the figure, the composite material includes a piezoelectric phase 1 , a polymer phase 2 and a piezoelectric substrate 3 .

Fig. 3 is a flow chart of making piezoelectric composite materials of type 1-3 in this embodiment. First cut the piezoelectric phase 1 along the x direction, then cut the piezoelectric phase 1 along the y direction, then pour the polymer phase 2, and finally make the electrode 5. The upper and lower surfaces of the composite material are covered with electrodes, which are polarized along the thickness direction, that is, the z direction. Electrodes can be made by sintering silver, sputtering gold (or silver) or brushing conductive glue.

Fig. 4 is a schematic diagram of stacking two piezoelectric composite materials with different thicknesses. The prepared two pieces of piezoelectric composite materials with different thicknesses are bonded through the bonding layer 4 to form a stacked piezoelectric vibrator. The polarization directions of the two pieces of composite materials are opposite and electrically connected in parallel. If the polarization directions of the two composite materials are the same, an insulating layer should be added between the two composite materials. The insulating layer can be made of insulating materials such as insulating glue and plastic, and the thickness of the insulating layer should be as small as possible. The adhesive layer is usually made of polyurethane, epoxy resin and silicon rubber, etc., and its thickness is between 0.2mm-0.5mm.

Fig. 5 is a schematic diagram of a side view of a piezoelectric vibrator stacked with two layers of composite materials, where t ₁ and t ₂ are the thicknesses of the two piezoelectric composite materials. The distribution range of the structural size of the piezoelectric composite material is preferably: the thickness t is 2 mm to 10 mm, and the thickness difference Δt of each composite material is 0 mm to 1 mm. The material of the piezoelectric phase of the composite material can be selected from piezoelectric ceramics, piezoelectric single crystal, etc., and the polymer phase can be selected from epoxy resin, polyurethane, etc.

Since the thickness of the two composite materials is not equal, the resonant frequency of each composite material is different, that is, there are multiple modes (multiple resonant frequencies) in the vibration system of the vibrator. Reasonably design the thickness of each composite material, through the polyurethane adhesive layer, make the resonance frequencies of the composite materials of the piezoelectric vibrator approach and couple each other (see Figure 6), and work simultaneously in a wide frequency range, so that its combined frequency response If discontinuity and deep valleys are not produced, complex multi-mode vibration will be formed in this frequency band, which can effectively expand the working bandwidth of the vibrator. The same goes for multiple films.

A specific example is provided below. In this example, two pieces of 1-3 piezoelectric composite materials with different thicknesses are used to make a piezoelectric vibrator, as shown in Figure 4, and the structural parameters of each part of the vibrator are shown in Table 1.

Table 1. Structural parameters of the components of the piezoelectric vibrator embodiment

Stack No. 1 and No. 2 composite materials in groups I to V in the table according to the structure shown in Figure 3, and use polyurethane to bond them in between, keeping the thickness of the adhesive layer at 0.2 mm to 0.5 mm, and wait for the polyurethane to cure Then the piezoelectric vibrator is made. Measure the resonant frequency and bandwidth of the vibrator with an impedance analyzer, and the results are shown in Table 2 and Figure 7.

Table 2. Measurement results of the piezoelectric vibrator embodiment

It can be seen from Table 2 and Figure 7 that within a certain range of thickness difference, the bandwidth of the stacked piezoelectric vibrator is much larger than that of the monolithic composite material. When the thickness difference between the two composite materials is too large, the conductance curves of each composite material will no longer be coupled at -3dB.

The No. 1 piezoelectric vibrator was packaged according to the structure shown in Figure 1, and the transducer was manufactured, and its transmission voltage response was tested in water, and the curve of transmission voltage response versus frequency was obtained as shown in Figure 8. It can be seen from the graph that its operating bandwidth is about 60KHz, which is significantly increased compared with the measured bandwidth in air. It shows that the structure of the present invention can remarkably increase the bandwidth of the vibrator, and has achieved progressive technical effects.

Example 2: Stacking of three composite materials with different thicknesses

FIG. 9 is a schematic diagram of the structure of a three-layer piezoelectric composite material stack vibrator with different thicknesses. The vibrator is formed by stacking three pieces of piezoelectric composite materials with different thicknesses through an adhesive layer. Among the three piezoelectric composite materials, the polarization directions of two adjacent piezoelectric composite materials are opposite. If the polarization directions of two adjacent piezoelectric composite materials are the same, an insulating layer should be added between the two piezoelectric composite materials. The insulating layer can be made of insulating materials such as insulating glue and plastic, and the thickness of the insulating layer should be as small as possible.

For the three-piece piezoelectric composite stack transducer, the structure is the same as that in Figure 1. The difference is that, compared with Figure 1, the three-piece piezoelectric composite stacked transducer will have one more piece of composite material, as shown in Figure 9, which is formed by bonding three pieces of composite material through an adhesive layer. In addition, in the present invention, more than three layers of composite materials can be stacked, and the n-layer composite material transducer is composed of n pieces of composite materials with different thicknesses, and so on.

Figure 10 is a cross-sectional view of a vibrator stacked with three layers of composite materials with different thicknesses. The size distribution range of the piezoelectric composite structure is consistent with the two-layer structure described above.

Fig. 11 is a diagram of the conductance curves of the piezoelectric vibrator and the composite material when the thickness of the three-layer composite material is 4.8mm, 4.6mm, and 5mm respectively. It can be seen from the figure that the operating bandwidth of the piezoelectric vibrator is much larger than the bandwidth of each composite material, indicating that the multi-layer stack structure can significantly increase the bandwidth of the vibrator.

The piezoelectric composite materials of different thicknesses described in the scheme of the present invention are not limited to 1-3 type piezoelectric composite materials, can be made of other composite materials (such as 2-2 type composite materials, 0-3 type composite materials, etc.) and piezoelectric ceramics , single crystal and other traditional piezoelectric materials instead. Fig. 12 is a graph of conductance curves of a stack of two ceramic sheets with a thickness of 5mm and 4.7mm respectively, and a piezoelectric vibrator formed by the ceramic sheets and their stacks. It can be seen from the figure that the bandwidth of the piezoelectric vibrator is about 40KHz, which is significantly increased compared with the bandwidth of monolithic ceramics. Fig. 13 is a graph of conductance curves of two single-chip stacks with a thickness of 5mm and 4.7mm respectively, and a piezoelectric vibrator formed by the single-chip and the stack. It can be seen from the figure that the bandwidth of the piezoelectric vibrator is also significantly increased compared with that of a monolithic single crystal.

The structure of the solution of the present invention is not limited to the planar piezoelectric material stack, but also includes arc-shaped piezoelectric material stack structures with different thicknesses, as shown in FIG. 14 .

The above embodiments are only used to illustrate the technical solution of the present invention and not to limit it. Those of ordinary skill in the art can modify or equivalently replace the technical solution of the present invention without departing from the spirit and scope of the present invention. The scope of protection should be determined by the claims.

Claims (10)

1. a PZT (piezoelectric transducer), is characterized in that, comprises the piezoelectric material layer with different-thickness stacked, and the resonance frequency of each piezoelectric material layer is close to each other and be coupled.

2. PZT (piezoelectric transducer) as claimed in claim 1, is characterized in that, the piezoelectric that described piezoelectric material layer adopts is piezo-electricity composite material, piezoelectric ceramic or piezoelectric monocrystal.

3. PZT (piezoelectric transducer) as claimed in claim 2, it is characterized in that, described piezo-electricity composite material is 1-3 type piezo-electricity composite material, 2-2 type composite material or 0-3 type composite material, piezoelectric phase in described piezo-electricity composite material is piezoelectric ceramic or piezoelectric monocrystal, and polymer is epoxy resin, polyurethane or silicon rubber mutually.

4. PZT (piezoelectric transducer) as claimed in claim 1, it is characterized in that, described stack have in the piezoelectric material layer of different-thickness, the polarised direction of two adjacent piezoelectric material layers is identical or different, between the piezoelectric material layer that different two of polarised direction are adjacent, add an insulating barrier.

5. PZT (piezoelectric transducer) as claimed in claim 1, is characterized in that, described in the piezoelectric material layer with different-thickness that stacks form by the piezoelectric material layer of two panels or multi-disc different-thickness is bonding, each piezoelectric material layer is plane stacked structure or curved surface stacked structure.

6. PZT (piezoelectric transducer) as claimed in claim 5, is characterized in that, adopt polyurethane, epoxy resin or silicon rubber to carry out described bonding, the thickness of adhesive linkage is 0.2mm ~ 0.5mm.

7. PZT (piezoelectric transducer) as claimed in claim 1, it is characterized in that, the upper and lower surface covering electrodes layer of described piezoelectric material layer, the material of described electrode layer is gold, silver or conducting resinl.

8. PZT (piezoelectric transducer) as claimed in claim 1, it is characterized in that, the thickness t of described piezoelectric material layer is 2 ~ 10mm, and the thickness difference Δ t of each piezoelectric material layer is 0 ~ 1mm.

9. the PZT (piezoelectric transducer) according to any one of claim 1 to 8, is characterized in that, also comprise the absorbent treatment adjacent with the described piezoelectric material layer with different-thickness stacked, and rubber seal is in outermost water-proof sound-transmitting layer.

10. prepare a method for composite material PZT (piezoelectric transducer), this composite material PZT (piezoelectric transducer) comprises the 1-3 type piezo-electricity composite material with different-thickness stacked, and the method comprises the steps:

1) cut piezoelectric phase in the x-direction, then cut this piezoelectric phase in the y-direction;

2) in the gap formed with the cutting of y direction in the x-direction, pour into polymer phase, form 1-3 type piezo-electricity composite material, at the upper and lower surface covering electrodes of 1-3 type piezo-electricity composite material;

3) the 1-3 type piezo-electricity composite material of different-thickness is undertaken bonding by tack coat, make the piezoelectric vibrator stacked, then cable is set and rubber seal formation composite material PZT (piezoelectric transducer).