Single-crystal longitudinal transducer based on surface shear mode

Abstract

The invention relates to a single crystal longitudinal transducer based on a surface shear mode, which comprises a front cover plate, a rear cover plate and a piezoelectric element, the piezoelectric element is rectangular and is vertically arranged, the lower end of the piezoelectric element is abutted against the front cover plate through an insulating spacer, and the upper end of the piezoelectric element is abutted against the rear cover plate through an insulating spacer. The upper end of the piezoelectric element abuts against the rear cover plate through an insulating spacer. The piezoelectric element is made of a piezoelectric single crystal material polarized in a [011] c direction, and the cutting direction of the piezoelectric element is a d36 direction with the highest piezoelectric coefficient; the length direction of the piezoelectric element is consistent with the d36 direction. A traditional piezoelectric ceramic material is replaced by a relaxor ferroelectric single crystal material to serve as a driving material of the transducer, and the characteristics of high surface shear mode piezoelectric coefficient, high compliance coefficient and large electromechanical coupling coefficient of the relaxor ferroelectric single crystal material are fully exerted, so that the transducer has the characteristics of small size, high response and wide working frequency band.

Description

Technical Field The invention relates to the technical field of underwater acoustic transducers, and in particular to a single crystal longitudinal transducer based on a surface shear mode. Background Art Sound waves are the only carrier that can transmit information and energy over long distances in water. The main functions of sonar equipment are to detect, identify, locate, track and communicate underwater targets. As the main component of sonar equipment, the importance of transducers is self-evident. With the rapid development of sonar technology, the demand for transmitting transducers is concentrated in the directions of low frequency, small size, broadband, and array.

[0003] The transmitting transducer generally works at the fundamental frequency of the structural vibration mode. The resonant frequency of the transducer is directly related to its size. The larger the size of the structure, the lower the resonant frequency. Among the many types of transducers, although the longitudinal transducer is not suitable for low-frequency operation, it has the advantages of simple structure, mature manufacturing process, small size, stable performance, high power-to-weight ratio, compact structure and easy array formation, etc., and is still one of the first choices for medium-frequency sonar equipment. Research on longitudinal transducers mainly focuses on widening the frequency band, and common methods include longitudinal-bending coupling, dual excitation, dual front cover, and other multi-mode coupling methods. Although the above methods broaden the frequency band of the transducer, they all increase the length of the transducer or reduce the transducer's emission voltage response or other performance. The transducer's operating bandwidth, size, response, and other performance are the result of comprehensive design. Summary of the invention In view of this, the present invention provides a single crystal longitudinal transducer based on surface shear mode, which utilizes relaxor ferroelectric single crystal material to replace traditional piezoelectric ceramic material as the driving material of the transducer, and gives full play to the characteristics of relaxor ferroelectric single crystal material in surface shear mode, such as high piezoelectric coefficient, high compliance coefficient and large electromechanical coupling coefficient, so that the transducer has the characteristics of small size, high response and wide working frequency band. The technical solution adopted by the present invention is: A single crystal longitudinal transducer based on a surface shear mode comprises a front cover plate, a rear cover plate and a piezoelectric element, wherein the piezoelectric element is rectangular and vertically arranged, wherein the lower end of the piezoelectric element is in contact with the front cover plate via an insulating gasket, and the upper end of the piezoelectric element is in contact with the rear cover plate via an insulating gasket; The piezoelectric element adopts

[011] c Directionally polarized piezoelectric single crystal material, the cutting direction is the d with the highest piezoelectric coefficient 36 direction; The length direction of the piezoelectric element is 36 The direction is consistent. Preferably, the piezoelectric single crystal material is PMN-PT or PZN-PT. Preferably, prestressed bolts are also included which pass through the front cover plate and the rear cover plate in sequence, so that the front cover plate and the rear cover plate clamp the piezoelectric element from the front and rear sides respectively. Preferably, there are multiple piezoelectric elements, and the multiple piezoelectric elements are evenly arranged around the prestressed bolt. Preferably, it further comprises an annular potting body, wherein the plurality of piezoelectric elements are embedded in the potting body, the potting body is located between the front cover plate and the rear cover plate, and the potting body is formed by potting with polyurethane material. Preferably, the number of the piezoelectric elements is four, and the projections of the four piezoelectric elements in the vertical direction are square. Preferably, the number of the piezoelectric elements is six, and the projections of the six piezoelectric elements in the vertical direction form six projection contours. The lines connecting the center points of the six projection contours and the midpoints of the projection contours are auxiliary lines, and the angle α between the auxiliary lines and the corresponding projection contours is 30°-80°, so that the six piezoelectric elements partially overlap in sequence in the circumferential direction. Preferably, it further comprises a sealed shell, in which the transducer assembly consisting of the front cover plate, the rear cover plate and the piezoelectric element is arranged, and the sealed shell is filled with polyurethane material. Preferably, the front cover is made of aluminum alloy or magnesium alloy, and is in a trumpet shape, and its radial dimension gradually increases from the back to the front; The rear cover plate is made of copper, 45# steel or tungsten alloy. Beneficial effects of the present invention: Compared with the mainstream functional material piezoelectric ceramics (d 33 About 400pC / N), the present invention uses piezoelectric single crystal material as the driving material of the transducer, especially

[011] c Directionally polarized single crystals, zxt-45° cut single crystals have larger d 36 (up to 2500-2800pC / N), which is 6-8 times that of traditional piezoelectric ceramic materials, which is beneficial to improve the emission voltage response of the transducer; at the same time, it also has a high electromechanical coupling coefficient (77% to 83%) and compliance coefficient (1.2×10 -10 m 2 / N), which is beneficial to the miniaturization design and large bandwidth of the transducer. Along the d of the piezoelectric single crystal material 36 direction, the piezoelectric element is obtained by plane shearing, and the piezoelectric element is rectangular, and the length direction of the piezoelectric element is the same as d 36 The directions are consistent, so when high voltage is applied to the piezoelectric element, there will be no change in material properties. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of the structure of the transducer; Figure 2 is a schematic diagram of a piezoelectric sheet; Figure 3 It is a schematic diagram of the maximum displacement direction of single crystal vibration in the surface shear mode; Figure 4 This is a schematic diagram of a single crystal in surface shear mode without the upper and lower corners; Figure 5 It is a schematic diagram of a single crystal in surface shear mode without the left and right corners (piezoelectric unit); Figure 6 It is a schematic diagram of the impure vibration mode of a single crystal in the surface shear mode; Figure 7 It is a schematic diagram of the structure of the potting body; Figure 8 is a schematic diagram of a transducer disposed in a sealed housing; Fig. 9 This is a schematic diagram of another arrangement of piezoelectric elements. In the figure: 1. piezoelectric element; 2. front cover; 3. rear cover; 4. prestressed bolts; 5. insulating gasket; 6. potting body. DETAILED DESCRIPTION The present invention is described below based on embodiments, but the present invention is not limited to these embodiments. In the following detailed description of the present invention, some specific details are described in detail. In order to avoid confusing the essence of the present invention, known methods, processes, procedures, and components are not described in detail. In addition, persons of ordinary skill in the art will appreciate that the drawings provided herein are for illustration purposes and are not necessarily drawn to scale. Unless the context clearly requires otherwise, throughout the specification and claims, the words "include", "comprising" and similar words should be interpreted in an inclusive sense rather than an exclusive or exhaustive sense; that is, in the sense of "including but not limited to". In the description of the present invention, it should be understood that the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more. See also Figure 1-Figure 9The present invention provides a single crystal longitudinal transducer based on the surface shear mode, comprising a front cover plate 2, a rear cover plate 3 and a piezoelectric element 1, wherein the piezoelectric element 1 is rectangular and vertically arranged, and the lower end of the piezoelectric element 1 is in contact with the front cover plate 2 through an insulating gasket 5, and the upper end of the piezoelectric element 1 is in contact with the rear cover plate 3 through an insulating gasket 5; The piezoelectric element 1 adopts

[011] c Directionally polarized piezoelectric single crystal material, the cutting direction is the d with the highest piezoelectric coefficient 36 direction; The length direction (up and down direction) of the piezoelectric element 1 is 36 The same direction ( Figure 2 The white part in the figure is the final piezoelectric element 1, and its length direction is d 36 direction). Preferably, the piezoelectric single crystal material is PMN-PT or PZN-PT. The piezoelectric element 1 of the present invention is made of a piezoelectric single crystal material, which is specifically formed by plane shearing the piezoelectric single crystal material, polarizing the piezoelectric single crystal material in the

[011] direction, and then forming a sheet-shaped piezoelectric sheet by cutting, and then forming a rectangular piezoelectric element 1 by cutting, and making the length direction of the piezoelectric element 1 and d 36 The direction is consistent. like Figure 3 As shown, the diagonal direction of the piezoelectric element 1 is d 36 direction, the vibration is mainly in d 36 The angular position of the direction results in a smaller contact area during transmission. like Figure 4 As shown, the up and down direction is d 36 Although the contact area is increased in the direction, it has a certain size in width, which is not conducive to the miniaturization of the transducer. like Figure 5 As shown, the contact area between the single crystal and the insulating gasket 5 can be increased, and at the same time, the vibration mode of the single crystal must be pure. The vibration form of the single crystal with an impure mode is as follows Figure 6 shown. Preferably, prestressed bolts 4 are also included that pass through the front cover plate 2 and the rear cover plate 3 in sequence, so that the front cover plate 2 and the rear cover plate 3 clamp the piezoelectric element 1 from the front and rear sides respectively. Preferably, there are multiple piezoelectric elements 1 , and the multiple piezoelectric elements 1 are evenly arranged around the prestressed bolt 4 . Arranging a plurality of piezoelectric elements 1 in the circumferential direction increases the number of piezoelectric elements 1 and also increases the energy level of the transducer, so that it can be used underwater. Preferably, it further comprises an annular potting body 6, wherein the plurality of piezoelectric elements 1 are embedded in the potting body 6, the potting body 6 is located between the front cover plate 2 and the rear cover plate 3, and the potting body 6 is formed by potting with polyurethane material. Preferably, the number of the piezoelectric elements 1 is four, and the projections of the four piezoelectric elements 1 in the vertical direction are square. Preferably, the number of the piezoelectric elements 1 is six, and the projections of the six piezoelectric elements 1 in the vertical direction form six projection contours. The lines connecting the center points of the six projection contours and the midpoints of the projection contours are auxiliary lines, and the angle α between the auxiliary lines and the corresponding projection contours is 30°-80°, so that the six piezoelectric elements 1 partially overlap in sequence in the circumferential direction. Preferably, it further comprises a sealed shell, in which the transducer assembly consisting of the front cover plate 2, the rear cover plate 3 and the piezoelectric element 1 is arranged, and the sealed shell is filled with polyurethane material. Preferably, the front cover plate 2 is made of aluminum alloy or magnesium alloy, and is in a trumpet shape, and its radial dimension gradually increases from the back to the front; The rear cover plate 3 is made of copper, 45# steel or tungsten alloy. The functional material selected for the transducer of the present invention is

[011] c The single crystal piece of the plane shear mode vibration with direction polarization is made of PMN-PT, PZN-PT or a ferroelectric single crystal doped with other elements. The vibration direction is selected to be the diagonal direction, and the shape is selected to be a rectangular strip along the vibration direction. The cross-sectional area is large enough to ensure the bonding area. The piezoelectric element 1 of the present invention is first fixed in the assembly method, first four piezoelectric single crystals are poured into one with epoxy or polyurethane material, and the relative position is fixed. When bonding, pay attention to the piezoelectric single crystal not to deflect, such as Figure 7 As shown, the leads of the piezoelectric element 1 are led out from both sides of the single crystal. Then the piezoelectric element 1 is glued to the insulating spacer 5 with epoxy resin. The piezoelectric element 1, the front cover plate 2, the rear cover plate 3, and the insulating gasket 5 of the present invention are stacked in sequence, bonded with epoxy resin glue, and placed in a fixture to ensure the overall verticality. The stacked transducer is placed in a prestressed device to add prestress and tightened with a prestressed bolt 4. Finally, the completed single crystal longitudinal transducer is placed in a sealed housing, the surface of the front cover 2 is potted with polyurethane material, and the rear is led out with a watertight cable. Figure 8 shown. It should be understood that the above-mentioned embodiments are merely illustrative and not restrictive. Without departing from the basic principles of the present invention, various obvious or equivalent modifications or substitutions that can be made by those skilled in the art to the above-mentioned details will all be included in the scope of the claims of the present invention.

Claims

1. A single crystal longitudinal transducer based on surface shear mode, characterized in that: It includes a front cover plate, a rear cover plate and a piezoelectric element, wherein the piezoelectric element is rectangular and vertically arranged, wherein the lower end of the piezoelectric element is in contact with the front cover plate via an insulating gasket, and the upper end of the piezoelectric element is in contact with the rear cover plate via an insulating gasket; The piezoelectric element is made of a piezoelectric single crystal material polarized in the [011]c direction, and the cutting direction is d 36 direction; The length direction of the piezoelectric element is 36 The direction is consistent.

2. The single crystal longitudinal transducer based on the surface shear mode according to claim 1, characterized in that: The piezoelectric single crystal material is PMN-PT or PZN-PT.

3. The single crystal longitudinal transducer based on the surface shear mode according to claim 2, characterized in that: It also includes prestressed bolts that pass through the front cover plate and the rear cover plate in sequence, so that the front cover plate and the rear cover plate clamp the piezoelectric element from the front and rear sides respectively.

4. The single crystal longitudinal transducer based on the surface shear mode according to claim 3, characterized in that: There are multiple piezoelectric elements, and the multiple piezoelectric elements are evenly arranged around the prestressed bolt.

5. The single crystal longitudinal transducer based on the surface shear mode according to claim 4, characterized in that: It also includes an annular potting body, in which a plurality of piezoelectric elements are embedded. The potting body is located between the front cover plate and the rear cover plate, and the potting body is formed by potting with a polyurethane material.

6. The single crystal longitudinal transducer based on the surface shear mode according to claim 4, characterized in that: The number of the piezoelectric elements is four, and the projections of the four piezoelectric elements in the vertical direction are square.

7. The single crystal longitudinal transducer based on surface shear mode according to claim 4, characterized in that: The number of the piezoelectric elements is six, and the projections of the six piezoelectric elements in the vertical direction form six projection contours. The lines connecting the center points of the six projection contours and the midpoints of the projection contours are auxiliary lines. The angle α between the auxiliary lines and the corresponding projection contours is 30°-80°, so that the six piezoelectric elements partially overlap in sequence in the circumferential direction.

8. The single crystal longitudinal transducer based on the surface shear mode according to any one of claims 1 to 7, characterized in that: It also includes a sealed shell, in which the energy conversion assembly composed of the front cover plate, the rear cover plate and the piezoelectric element is arranged, and the sealed shell is filled with polyurethane material.

9. The single crystal longitudinal transducer based on the surface shear mode according to claim 8, characterized in that: The front cover is made of aluminum alloy or magnesium alloy and is in a trumpet shape, and its radial dimension gradually increases from the back to the front; The rear cover plate is made of copper, 45# steel or tungsten alloy.

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