CN101321411B - Cylindrical stack wafer underwater transducer - Google Patents

Abstract

The invention provides an underwater acoustic transducer, which comprises a stack of piezoelectric ceramic wafers and metal cover plates at the upper and lower ends thereof. The stack of piezoelectric ceramic wafers is cylindrical and is formed by stacking a plurality of circular piezoelectric ceramic wafers. , the polarization direction of the piezoelectric ceramic wafer is along the thickness direction; every 2 to 8 piezoelectric ceramic wafers form a group, and the wafer stack contains 1 or more groups of wafers, and each group is separated by a rubber sheet; adjacent wafers Between, and between the chip and the rubber sheet, there is a metal sheet, and the electrode lead is welded on the metal sheet; the piezoelectric ceramic chip stack and the upper and lower metal cover plates are also separated by a rubber sheet. The cylindrical stacked chip transducer of the present invention not only maintains the characteristics of high density and high sensitivity of the emitted acoustic energy of the traditional stacked chip transducer by rationally designing the diameter of the piezoelectric stacked chip, but also can change the piezoelectric stacked chip transducer The thickness of the chip stack or the number of groups are adjusted to adjust the axial directivity opening angle of the transducer.

Description

Cylindrical stacked chip hydroacoustic transducer

technical field

The invention belongs to the technical field of underwater acoustic detection, and in particular relates to an underwater acoustic transducer which uses the piezoelectric effect of piezoelectric ceramics to emit underwater acoustic signals to realize underwater detection, and can be widely used in underwater communication, detection, target positioning, and tracking etc., are important components used by sonar.

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. A transducer that can convert an acoustic signal into an electrical signal, and an electrical signal into an acoustic signal, is called a transceiver transducer for receiving or emitting an acoustic signal.

At present, the most widely used transducer in the field of underwater acoustics is a piezoelectric ceramic transducer that uses the piezoelectric effect for energy conversion. Its working principle is based on the piezoelectric principle of ceramics. When the alternating pressure of the sound wave acts on the piezoelectric ceramic When the ceramic is applied, the ceramic will deform, and then generate alternating charges on its surface and output an alternating voltage. The magnitude of the voltage is proportional to the sound pressure, and the strength of the sound wave can be measured by detecting the output voltage. The receiving transducer uses the positive piezoelectric effect of ceramics to receive acoustic signals and converts them into electrical signals to detect sound waves; the transmitting transducer uses the inverse piezoelectric effect of ceramics to convert the applied electrical signals into underwater acoustic signals to Radiate sound waves.

Currently commonly used underwater acoustic transducers include stacked wafer (ceramic sheet) transducers, cylindrical transducers and spherical transducers. The stacked chip transducer uses the thickness of the chip stack to vibrate, and receives or radiates the acoustic signal with the load end face of the chip stack. This stacked chip vibrator can obtain a large sound energy density with a small weight and volume, and has high sensitivity, but the beam The directivity opening angle is limited by the radiating surface. Cylindrical and spherical transducers use the radial vibration of the circular tube and spherical shell to receive or radiate sound waves on a cylindrical or spherical surface. Cylindrical transducers have horizontal omnidirectional beam directivity, and spherical transducers have spatial omnidirectional beam directivity, but the sensitivity of this type of transducer is not as high as stacked chips. The above-mentioned transducers mainly include the following types:

(1) Composite rod piezoelectric transducer

Composite rod piezoelectric transducers are also known as sandwich piezoelectric transducers or horn-shaped piezoelectric transducers (T.Inoue, T.Nada, T.Tsuchiya, T.Nakanishi, T.Miyama, M.Konno, "Tonpilz piezoelectricers with acousticmatching plates for underwater color image transmission", IEEE Trans.Ultrason.Ferroelect., Freq.Contr., Vol.40, pp.121-129, 1993; Qingshan Yao Bjorno.L. "Broad band tonpilzunderwaterducousers based on multimode optimization IEEE VFFC.Vol 44 5 1997P 1060-1066; Inoue T.Nada.T."Tonpilz Piezoelectric transducer with acoustic matching plates for underwater color image IEEE VFFC Vol.40.2, 1993P) It is a commonly used high-power stacked chip transmitting transducer, and it also has high sensitivity for receiving. The schematic diagram of the vibrator structure of the composite rod piezoelectric transducer is shown in Figure 1. It consists of a plurality of identical piezoelectric ceramic rings that are stacked in series mechanically and in parallel on the circuit to form a piezoelectric vibrator. When an alternating voltage is applied to the vibrator, the vibrator will produce axial stretching vibration (longitudinal vibration mode). Since the front cover 21 is lighter than the rear cover 22, the vibrator will push the front cover 21 to vibrate, thereby radiating sound waves outward. The prestressing screw 11 is used to fix the front cover 21, the chip stack 41 and the rear cover 22, and apply a certain prestress on the chip stack at the same time, so that there is good vibration transmission between the chips and between the vibrator and the front and rear cover plates. The metal section plate 12 fixes the vibrator on the casing or the bracket.

Due to the use of multiple chip stacks, the vibration of the vibrator is the superposition of the vibration of each chip, so it can generate a larger energy density, that is, the sensitivity of this transducer is higher. And because the piezoelectric ceramic longitudinal vibration mode frequency is relatively high, and its emitter is horn-shaped, so this kind of transducer mainly works in the middle and high frequency range (tens of kHz to hundreds of kHz), and the beam of its emission directivity pattern The width (opening angle) is smaller.

(2) Ring transducer

Ring transducer (S.G.Schock, L.R.Leblanc, S.Panda "spatial and temporal pulse design considerations for a marine sediment classification sonar", IEEE J.Oceanic Eng., Vol.19 PP406-415, July 1994; Y.Qinqshan, L.Bjomo, "Broadband tonpilz underwater acoustic transducers based on multimode optimization", IEEE Frans Ulorason., Ferroelect., freq.Contr., Vol.44, P1060-1066, 1997.) The outer ring is used as the radiation surface, as shown in the figure As shown in 2, the thickness of the ring can be determined through calculation so that it can withstand the hydrostatic pressure of deep water. Some length oscillators are inserted into the ring in a "star" shape. Each length vibrator is composed of piezoelectric ceramic stack 42 and tail mass 23 . This kind of transducer can work in deep water due to its structural characteristics. And there are two main resonant frequencies that can be applied, one is the resonant frequency of the ring itself (breathing mode of the ring), a slightly lower vibration frequency; the other is the resonant frequency of each length vibrator (similar to the composite rod piezoelectric transducer energy device longitudinal vibration mode), slightly higher vibration frequency.

Considering the shortcomings of composite rod piezoelectric transducers and Janus transducers that are difficult to achieve low-frequency emission, the transducer uses longitudinal vibration mode ceramics to drive the outer ring to vibrate in bending mode, so that low-frequency emission can be achieved. However, this transducer has a shortcoming that the relative radiation area is too small, and the longitudinal vibration energy of the ceramic stack is not fully converted into the energy of low-frequency bending vibration, so the radiation capacity is not large enough.

(3) Barrel plate (Type I) flexural transducer

Barrel bending transducer (Jone D F. Flextensional Barrel-stave Projectors, in Transducers for Sonic and Ultrasonic, MeCollum M D. Hamonic B F. Wilson O.B.eds. Technomic Publishing co. Inc., Lancaster, 1993: 150-159 .) A plurality of arcuate curved beams (or other curves) bent from planes are installed on the mass blocks at both ends of the piezoelectric ceramic chip stack 43 with screws to form a piezoelectric vibrator. Among them, a typical structure is shown in FIG. 3 . By filling part of the cavity with closed-cell foam and using free immersion, it has the ability to work in 500m deep water. The stave flexural transducer converts the longitudinal vibration of the wafer stack into the bending vibration of the stave, and the working frequency is low. When the convex shell works in water, the resultant force of the hydrostatic pressure acting on it is the tension along the long axis direction, which offsets part of the applied precompressive stress. As the depth increases, this tension increases proportionally, and it is impossible to ensure safe stress during high-drive work, thereby limiting the working depth.

The concave flextensional transducer (Figure 4) is designed to address this problem. Its advantages are: the hydrostatic pressing force is the pressure along the long axis, which increases with the depth, so the assembly prestress to be applied is the smallest; when the shell vibrates in the radial direction at the fundamental frequency, all the shells vibrate in the same phase, which can More efficient radiation of sound power into the far field.

The disadvantage of this transducer is that the overall layout is slender. On the same maximum scale, the number of piezoelectric ceramics used as driving elements is relatively small, and the driving ability is relatively insufficient.

(4) Cylindrical and spherical transducers

The spherical transducer and the cylindrical transducer are shown in Fig. 5a and Fig. 5b respectively, in which d refers to the displacement direction of the piezoelectric ceramic shell, and P refers to the polarization direction of the piezoelectric ceramic shell. This type of transducer uses the radial vibration of a spherical shell or a thin-walled circular tube to convert energy, receives or radiates sound waves in the radial direction, and has better beam directivity. The spherical shell structure can obtain omnidirectional beam directivity in space, and the cylindrical tube The structure can obtain horizontal omnidirectional beam directivity. However, since this type of transducer only receives or radiates acoustic signals through the vibration of a single-layer piezoelectric ceramic shell, obviously its vibration energy is far less than the energy generated by stacked wafers, that is, the sensitivity is not as high as that of stacked wafer transducers. This type of transducer generally works at a frequency of several kHz to 100kHz. If the frequency is too high (>100kHz), the diameter of the transducer is small, the process is difficult to process and the sensitivity is low. The frequency is too low (<1kHz), and the volume of the transducer is relatively large. Large, the required transmission power is large, and it is easy to break down and be damaged.

To sum up, there are two types of stacked chip transducers, one uses the longitudinal vibration mode of the piezoelectric ceramic chip to work, and the frequency is from several thousand to hundreds of kilohertz, and the other converts the longitudinal vibration mode of the chip to The bending vibration of the shell greatly reduces the working frequency of the transducer, which can generally be reduced to a few Hz to several thousand Hz. The beam directivity width (opening angle) of this type of transducer is limited by the radiation surface. Cylindrical and spherical transducers have simple structures, large beam directivity width (opening angle) (horizontal or spatial omnidirectional), but low sensitivity.

Contents of the invention

The purpose of the present invention is to make up for the shortcomings of the existing stacked chip transducers with small opening angles and cylindrical and spherical transducers with low sensitivity, and to provide an underwater acoustic transducer with high sensitivity and large opening angles.

The above-mentioned purpose is achieved through the following technical solutions:

An underwater acoustic transducer, including a piezoelectric ceramic wafer stack and metal cover plates at its upper and lower ends. The piezoelectric ceramic wafer stack is cylindrical and is formed by stacking multiple circular piezoelectric ceramic wafers. The polarization direction of the wafer is along the thickness direction; every 2 to 8 piezoelectric ceramic wafers form a group, and the wafer stack contains 1 or more groups of wafers, and each group is separated by a rubber sheet; between adjacent wafers, and A metal sheet is sandwiched between the wafer and the rubber sheet, and electrode leads are welded on the metal sheet; the piezoelectric ceramic chip stack and the metal cover are also separated by a rubber sheet.

The wafers of the above-mentioned piezoelectric wafer stack can be made of piezoelectric ceramic PZT. The polarization directions of two adjacent wafers in each group are opposite. The diameter of the wafers is generally 10-100 mm, and the thickness of each wafer is generally 0.5-5 mm.

The above-mentioned metal cover plate is made of heavy metal, and is mounted on the upper and lower ends of the piezoelectric ceramic chip stack, and is used to fix the piezoelectric ceramic chip stack and limit the vibration in its thickness direction. The cover plate is usually made of copper, and its surface size is equivalent to that of a piezoelectric ceramic wafer. It can be a circle or a polygon close to a circle, such as a regular hexagon, a regular octagon, etc., and its thickness is 2-10mm.

The above-mentioned metal flakes are discs made of easily weldable metals or alloys such as brass or zinc-platinum-copper, with the same diameter as the wafer and a thickness of 0.1-0.2 mm.

The above-mentioned rubber sheet is also a disc with the same diameter as the wafer, and its thickness is 1-2 mm.

Generally, epoxy resin is used for bonding between the metal sheet and the piezoelectric ceramic chip, between the metal sheet and the rubber sheet, and between the rubber sheet and the metal cover plate. Further, the above-mentioned wafers, thin metal sheets, rubber sheets and metal cover plates can have holes in the center, so that the stack of piezoelectric wafers, rubber sheets, and upper and lower metal cover plates can be fixed by screws passing through them.

Further, a base is installed at the bottom of the lower metal cover plate for the output of the lead wires of the electrodes of the piezoelectric wafer stack. The base can be a cylinder with a hole in the center made of metal aluminum, the upper surface of which is grooved along the diameter direction, and the electrode leads on both sides are led out from the center hole through the groove and connected to the cable. The base is bonded to the lower metal cover by epoxy resin.

After the cylindrical stacked wafer transducer of the present invention is assembled, it needs to be potted in a waterproof sound-permeable layer. The waterproof sound-permeable layer material of the underwater acoustic transducer is usually polyurethane sound-permeable rubber, which has the characteristics of high dielectric strength, high volume resistance, high tensile and shear strength, good wear resistance and high damping, and polyurethane is also It has good resistance to alcohol and aliphatic solvents. As the name implies, the main function of the waterproof and sound-permeable layer is waterproof and sound-permeable, so as to avoid damage to the device due to water ingress and short circuit inside the transducer. At the same time, the characteristic impedance of polyurethane matches water, and the sound attenuation coefficient is very low, which ensures good sound energy transmission between the transducer and the water medium.

The underwater acoustic transducer of the present invention is a cylindrical stacked wafer transducer. When adding an alternating voltage on the wafer stack, each wafer vibrates along the radial direction due to the piezoelectric effect of ceramics, and a plurality of stacked wafers Radial vibration forms a cylindrical sound radiation surface and radiates sound waves to the surroundings. Since the piezoelectric wafer stack adopts multiple ceramic stacks, the vibration of the vibrator is the superposition of the radial vibration of multiple wafers, which can generate a large energy density, thereby improving the sensitivity of the transducer. The horizontal directivity of the cylindrical radiation surface of the vibrator of the cylindrical stacked chip transducer is omnidirectional, and the beam width (opening angle) of the axial directivity can be adjusted by adjusting the number of groups of piezoelectric ceramic chip stacks.

In a word, the cylindrical stacked wafer transducer of the present invention not only maintains the characteristics of high emission density and high sensitivity of the traditional stacked wafer transducer by rationally designing the diameter of the piezoelectric stacked wafer, thereby making up for the existing cylindrical And the sensitivity of the spherical piezoelectric transducer is small. In addition, the axial directivity opening angle of the transducer can also be adjusted by changing the thickness of the piezoelectric chip stack or adjusting the number of groups.

Description of drawings

Fig. 1 is a structural schematic diagram of a vibrator of a composite rod piezoelectric transducer.

Fig. 2 is a schematic structural diagram of a ring transducer.

Fig. 3 is a structural schematic diagram of a convex stave flexural transducer.

Fig. 4 is a structural schematic diagram of a concave stave flexural transducer.

Figure 5a is a schematic diagram of a spherical transducer; Figure 5b is a schematic diagram of a cylindrical and spherical transducer.

Fig. 6 is a schematic structural view of the cylindrical stacked wafer transducer of the present invention.

Fig. 7 is a schematic diagram of the structure and connection of the piezoelectric wafer stack of the cylindrical stacked wafer transducer of the present invention.

Detailed ways

The cylindrical stacked wafer transducer of the present invention will be described in detail below with reference to the accompanying drawings and examples.

As shown in Figure 6, the cylindrical stacked wafer transducer of this example includes a piezoelectric wafer stack composed of piezoelectric ceramic wafers 4, upper and lower metal cover plates 2, prestressed screws 1, rubber sheet 3, base 6, waterproof Sound-permeable layer 9 and output cable 8 etc. In the piezoelectric chip stack, the piezoelectric ceramic chip 4 is made of a circular piezoelectric ceramic PZT with a hole in the center. The outer diameter of the chip is 23 mm, the inner diameter is 5 mm, and the thickness of each chip is 1 mm. Every four wafers constitute a group of piezoelectric wafers, and the polarization directions of adjacent wafers are opposite (see Figure 7). The piezoelectric chip stack is composed of 2 groups of piezoelectric chips. The piezoelectric chip groups are separated by circular rubber sheets 3 to eliminate the coupling between them. The piezoelectric chip stack and the upper and lower metal cover plates 2 are also separated by rubber Sheet 3 spaced apart. The inner and outer diameters of the rubber sheet 3 are the same as those of the wafer 4, and the thickness is 1-2mm. The shape of the upper and lower metal cover plates is the same as the wafer 4, made of copper, the thickness of the upper cover plate is 3mm, and the thickness of the lower cover plate is 5mm. A thin metal sheet 5 is clamped between the piezoelectric wafers 4 to weld the leads 7 . The inner and outer diameters of the thin metal sheet 5 are also the same as those of the wafer 4, and the thickness is 0.2 mm. . The base 6 is connected by two concentric circular columns. The outer diameter of the upper circular column is the same as that of the piezoelectric wafer, and the thickness is 3mm. A thin groove is opened on the upper surface along the diameter, and the outer diameter of the lower circular column is 5-5mm. 10mm, the thickness is 8mm, and the inner diameter of the base is 3-5mm.

When assembling the transducer, first use epoxy resin to bond the piezoelectric chip 4 to the metal sheet 5 one by one, and then bond each other. Every four pieces are a group of piezoelectric chips, and there are 2 groups in total. The rubber sheets 3 are pasted with epoxy resin to isolate them to form a stack of piezoelectric wafers. The piezoelectric chip stack and the metal cover plate 2 are also isolated with epoxy resin paste rubber sheet 3 . Then the metal cover plate 2, the piezoelectric chip stack and the rubber sheet 3 are fixedly connected with the prestressed screw 1. The wiring of the piezoelectric chip stack is shown in Figure 7, which is connected in parallel to ensure that the same phase voltage is applied to each chip at the same time to generate synchronous radial vibration. The lead wire 7 passes through the thin strip groove on the upper surface of the base 6, and is output from the inner hole of the base 6, and is connected to the cable, wherein one pole lead wire (the left lead wire in Fig. 7) is connected with the ground pole of the output cable 8, and the other pole lead wire ( The right lead wire in Fig. 8) is connected with the core wire of output cable 8. Bond the base 6 and the metal cover 2 below with epoxy resin. Finally, the above-mentioned assembly parts are put into a customized mold, and polyurethane rubber is poured to form a waterproof and sound-permeable layer 9, and finally the production of the transducer is completed.

The cylindrical stacked wafer transducer and its implementation method of the present invention described above through the embodiments are not intended to limit the present invention. Any person skilled in the art can do without departing from the spirit and essence of the present invention. Various changes and modifications, so the protection scope of the present invention is defined by the claims.

Claims (9)

1. underwater acoustic transducer comprises the piezoelectric ceramic wafer heap and the metal cover board at two ends up and down thereof, and the piezoelectric ceramic wafer heap is cylindrical, is stacked by the piezoelectric ceramic wafer of multi-disc circle to form, and the polarised direction of piezoelectric ceramic wafer is along thickness direction; Per 2～8 piezoelectric ceramic wafers are one group, and stack of wafers comprises 1 group or organize wafer more, separates with sheet rubber between every group; Between the adjacent wafer, and accompany sheet metal between wafer and the sheet rubber, welding electrode lead-in wire on the sheet metal; Piezoelectric ceramic wafer is piled and is also separated with sheet rubber between the metal cover board up and down; Described sheet rubber is the diameter disk identical with wafer; Described metal cover board is made with heavy metal; Described piezoelectric ceramic wafer, sheet metal, sheet rubber and metal cover board all have the hole at the center, by the screw that runs through wherein they are fixed.

2. underwater acoustic transducer as claimed in claim 1 is characterized in that: described piezoelectric ceramic wafer adopts piezoelectric ceramic PZT to make, and the polarised direction of every group of interior adjacent two wafer is opposite, and the diameter of wafer is 10～100mm, and the thickness of every wafer is 0.5～5mm.

3. underwater acoustic transducer as claimed in claim 1 is characterized in that: described metal cover board thickness is 2～10mm.

4. underwater acoustic transducer as claimed in claim 3 is characterized in that: described metal cover board is made of copper.

5. underwater acoustic transducer as claimed in claim 1 is characterized in that: described sheet metal is made of the metal or alloy that is easy to weld, and thickness is 0.1～0.2mm.

6. underwater acoustic transducer as claimed in claim 1 is characterized in that: described sheet rubber thickness is 1～2mm.

7. underwater acoustic transducer as claimed in claim 1 is characterized in that: between sheet metal and the piezoelectric ceramic wafer, between sheet metal and the sheet rubber and all glue together with epoxy resin between sheet rubber and the metal cover board.

8. underwater acoustic transducer as claimed in claim 1 is characterized in that: be equipped with one in the bottom of following metal cover board and be used for the base that output electrode goes between.

9. underwater acoustic transducer as claimed in claim 8 is characterized in that: the center with holes cylinder of described base for adopting metallic aluminium to make, and the surface is along the diametric(al) fluting thereon, and the contact conductor of both sides is drawn from centre bore by fluting.

Images