Piezoelectric ultrasonic transducer

Abstract

The invention discloses a piezoelectric ultrasonic transducer which comprises a piezoelectric element and an acoustic impedance matching layer. The piezoelectric element is composed of a cylindrical piezoelectric ceramic, at least one wafer piezoelectric ceramic and at least two wafer metal layers, the diameter of the wafer piezoelectric ceramic is larger than that of the cylindrical piezoelectric ceramic, and the metal layers serving as electrodes are connected with the wires. When the transducer is used as a transmitting end, the piezoelectric element can convert excitation electric signals into ultrasonic waves, and the ultrasonic waves are output outwards through the acoustic impedance matching layer; when serving as a receiving end, the piezoelectric element can convert ultrasonic signals into electric signals and output the electric signals through the wire. According to the piezoelectric type ultrasonic transducer, the structure of the piezoelectric element is improved, the transmitting voltage response level and the receiving sensitivity of the transducer are improved under the condition that the size is not increased, and the piezoelectric type ultrasonic transducer with high transmitting and receiving performance is achieved.

Description

Technical Field

[0001] The present invention relates to a transducer, and more particularly to a piezoelectric ultrasonic transducer. Background Art

[0002] Ultrasonic detection technology has advantages such as good penetrability, non-contact measurement, and little influence by the environment, and is of great significance in the fields of non-destructive testing, medical diagnosis, ranging, and tissue characterization. Ultrasonic transducers are classified into piezoelectric, electrodynamic, electromagnetic, magnetostrictive, etc. according to different working principles. Among them, piezoelectric transducers have become the type of ultrasonic transducers with the largest market scale and the widest application due to their high electro-acoustic efficiency, simple structure, and low manufacturing cost.

[0003] With the continuous expansion of application scenarios and the continuous development of detection technology, higher and higher requirements are put forward for the performance of ultrasonic transducers. The performance of piezoelectric ultrasonic transducers is mainly determined by the material, size, and structure of piezoelectric elements. Due to application and integration requirements, the size of piezoelectric elements is subject to increasingly stringent restrictions. Therefore, there is an urgent need for a new piezoelectric element structure that can improve the output and reception performance of transducers without increasing the volume of the transducer, so as to realize a high-performance piezoelectric ultrasonic transducer. Summary of the Invention

[0004] Object of the Invention: Aiming at the prior art, a piezoelectric ultrasonic transducer is proposed to improve the transmitted sound pressure and reception sensitivity without increasing the size.

[0005] Technical Solution: A piezoelectric ultrasonic transducer includes an acoustic impedance matching layer and a piezoelectric element; the acoustic impedance matching layer is arranged at the front end of the piezoelectric element; the piezoelectric element includes a first metal layer, a first disc-shaped piezoelectric ceramic, a second metal layer, a cylindrical piezoelectric ceramic, and a third metal layer that are coaxially arranged in sequence; the diameter of the first disc-shaped piezoelectric ceramic is larger than the diameter of the cylindrical piezoelectric ceramic; the second metal layer and the third metal layer serve as electrodes of the piezoelectric element and are respectively connected to wires.

[0006] Further, the piezoelectric element further includes a second disc-shaped piezoelectric ceramic and a fourth metal layer that are coaxially arranged in sequence after the second metal layer.

[0007] Further, the acoustic impedance matching layer and the piezoelectric element are located inside a housing, and the top surface of the piezoelectric element and the bottom surface of the acoustic impedance matching layer are bonded with glue; a waterproof layer is provided on the top of the acoustic impedance matching layer, and a sealing layer for sealing the transducer cavity is provided at the bottom of the housing.

[0008] Further, the side surfaces of the acoustic impedance matching layer and the piezoelectric element are directly pasted to the inner wall of the housing, or pasted to the inner wall of a sleeve and then placed inside the housing.

[0009] A piezoelectric ultrasonic transducer includes an acoustic impedance matching layer and a piezoelectric element; the acoustic impedance matching layer is disposed at the front end of the piezoelectric element; the piezoelectric element includes a fifth metal layer, a second piezoelectric ceramic, and a sixth metal layer that are coaxially and sequentially arranged; wherein, the second piezoelectric ceramic is a T-shaped integral structure composed of a coaxial disc portion and a cylinder portion; or, the second piezoelectric ceramic is an I-shaped integral structure composed of two coaxial disc portions and a cylinder portion; the fifth metal layer and the sixth metal layer serve as electrodes of the piezoelectric element and are respectively connected to wires.

[0010] Further, the acoustic impedance matching layer and the piezoelectric element are located inside a housing, and the top surface of the piezoelectric element and the bottom surface of the acoustic impedance matching layer are bonded with glue; a waterproof layer is provided on the top of the acoustic impedance matching layer, and a sealing layer for sealing the transducer cavity is provided on the bottom of the housing.

[0011] Further, the side surfaces of the acoustic impedance matching layer and the piezoelectric element are directly pasted to the inner wall of the housing, or pasted to the inner wall of a sleeve and then placed inside the housing.

[0012] Beneficial effects: Through the inverse piezoelectric effect, applying an alternating excitation signal across the piezoelectric element can cause the piezoelectric element to generate mechanical vibrations, thereby exciting ultrasonic waves of corresponding frequencies; similarly, when ultrasonic waves act on the piezoelectric element, an electric signal of the same frequency can be generated across the piezoelectric element through the direct piezoelectric effect, realizing the reception of ultrasonic signals. The piezoelectric ultrasonic transducer has advantages such as high electro-acoustic efficiency, simple structure, and low manufacturing cost, but its transmitting and receiving performance is often restricted by the size of the piezoelectric element.

[0013] The piezoelectric ultrasonic transducer of the present invention has a cylindrical shape and is composed of a piezoelectric element, an acoustic impedance matching layer, a wire, a housing, and a sealing layer. By coaxially adding a disc piezoelectric ceramic and a metal layer with a larger diameter above the upper electrode of the traditional cylindrical piezoelectric ceramic element, the transmitting and receiving performance of the piezoelectric ultrasonic transducer can be effectively enhanced. And a disc piezoelectric ceramic for impedance adjustment and a metal layer are sequentially added below the lower electrode of the cylindrical piezoelectric ceramic element. Further, the added disc piezoelectric ceramic and the cylindrical piezoelectric ceramic are integrally prepared and formed into a T-shaped integral structure or an I-shaped integral structure, and then metal layers are prepared on its upper and lower surfaces as electrodes, so that while simplifying the process flow, it still has better performance than the traditional cylindrical piezoelectric element structure. That is, using a piezoelectric element with an optimized structure to replace the traditional cylindrical piezoelectric element realizes a higher energy conversion efficiency and can significantly improve the transmitting and receiving performance of the ultrasonic transducer without increasing the volume of the transducer.

[0014] Compared with ultrasonic transducers based on other working principles, the present invention has higher electro-acoustic efficiency and lower manufacturing cost. The structure of the present invention can function both as an ultrasonic transmitting end and as an ultrasonic receiving end, and has wide applicability to various application scenarios. The structure of the present invention adopts an air-coupled acoustic impedance matching layer to achieve a gradient impedance change from the piezoelectric element to air, significantly reducing the transmission loss of ultrasonic signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a perspective structural schematic diagram of a piezoelectric ultrasonic transducer of the present invention; Figure 2 is a sectional view taken along line A-A' of the first embodiment of the present invention (along arrow B); Figure 3 is a sectional view taken along line A-A' of the second embodiment of the present invention (along arrow B); Figure 4 is a sectional view taken along line A-A' of the third embodiment of the present invention (along arrow B); Figure 5 is a sectional view taken along line A-A' of the fourth embodiment of the present invention (along arrow B). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] The perspective structural schematic diagrams of the piezoelectric ultrasonic transducers of Embodiment 1 to Embodiment 4 of the present invention are all as Figure 1 shown, and the corresponding sectional views taken along line A-A' of Embodiment 1 to Embodiment 4 are respectively as Figures 2 to 5 shown. Embodiment

[0018] As Figure 2 shown, a piezoelectric ultrasonic transducer includes a housing 2, an acoustic impedance matching layer 1, a piezoelectric element, and a sealing layer 5 located inside the housing 2. The acoustic impedance matching layer 1 is disposed at the front end of the piezoelectric element, the sealing layer 5 is disposed behind the piezoelectric element, and a transducer cavity is formed between the acoustic impedance matching layer 1 and the sealing layer 5.

[0019] The piezoelectric element includes a first metal layer 301, a first circular piezoelectric ceramic 302, a second metal layer 303, a cylindrical piezoelectric ceramic 304, and a third metal layer 305 that are coaxially and sequentially disposed along the A-A' axis. The first metal layer 301, the first circular piezoelectric ceramic 302, the second metal layer 303, and the third metal layer 305 have the same diameter, which is larger than the diameter of the cylindrical piezoelectric ceramic 304. The second metal layer 303 and the third metal layer 305 serve as electrodes of the piezoelectric element and are respectively welded and connected to a wire 4. The sealing layer 5 not only seals the transducer cavity but also fixes the wire 4.

[0020] A waterproof layer 6 is provided on the top of the acoustic impedance matching layer 1. The waterproof layer 6 is in the structure of a round cover. The top surface of the acoustic impedance matching layer 1 and the top of the waterproof layer 6 are bonded by glue. A sleeve 7 for enhancing the waterproof effect is provided between the side surface of the waterproof layer 6 and the acoustic impedance matching layer 1. The height of the sleeve 7 extends downward from the top surface of the acoustic impedance matching layer 1 to the top surface of the sealing layer 5. The top surface of the piezoelectric element and the bottom surface of the acoustic impedance matching layer 1 are bonded by glue; both the side surface of the acoustic impedance matching layer 1 and the first disc-shaped piezoelectric ceramic 302 are bonded to the inner side surface of the sleeve 7. The shell 2, the waterproof layer 6, and the sleeve 7 are all bonded by waterproof glue.

[0021] Among them, the material of the shell 2 can be POM, etc., and it can be prepared by 3D printing or mold opening technology. The material of the acoustic impedance matching layer 1 can be polyurethane, etc., and it can be prepared by cutting or mold opening technology. The sealing layer 5 can use silicone rubber, etc.

[0022] In Embodiment 1, a disc-shaped piezoelectric ceramic with a larger diameter and a metal layer are coaxially added above the upper electrode of the traditional cylindrical piezoelectric ceramic element, which can effectively enhance the transmitting and receiving performance of the piezoelectric ultrasonic transducer. Compared with the traditional cylindrical piezoelectric element, the piezoelectric element improves the output and receiving performance of the ultrasonic transducer without increasing the volume of the transducer. The piezoelectric ultrasonic transducer of Embodiment 1 and the ultrasonic transducer of the traditional cylindrical piezoelectric ceramic element (hereinafter referred to as the traditional structure) are experimentally measured. The experimental conditions and methods are as follows: As shown in the following figure, the piezoelectric ultrasonic transducer as the transmitting end and the piezoelectric ultrasonic transducer as the receiving end are placed facing each other at an interval of ten centimeters using a fixture. An excitation signal with an amplitude of 10V and a frequency of about 200kHz is input to the transmitting end through a signal generator, and the receiving end observes the peak-to-peak value of the output signal through an oscilloscope. The excitation signal frequency is finely adjusted around 200kHz to make the output signal reach the maximum. The experimental results are shown in the following table: Receiving end Transmitting end Frequency corresponding to the maximum output (kHz) Peak-to-peak value of the maximum output (mV) Traditional structure Traditional structure 193 98 Structure of Embodiment 1 Traditional structure 201.89 126 Traditional structure Structure of Embodiment 1 192.35 149 Embodiment

[0023] As Figure 3 shown, the difference from Embodiment 1 is only that the sleeve 7 and the waterproof layer 6 are not provided, and a second disc-shaped piezoelectric ceramic 306 and a fourth metal layer 307 are further provided after the piezoelectric element and the second metal layer 305. The side surfaces of the acoustic impedance matching layer 1, the first disc-shaped piezoelectric ceramic 302, and the second disc-shaped piezoelectric ceramic 306 are directly bonded to the inner side wall of the shell 2 by waterproof glue.

[0024] Compared with Embodiment 1, Embodiment 2 meets the impedance adjustment requirements in actual applications and plays a certain sound absorption role by adding a disc-shaped piezoelectric ceramic structure and a metal layer. Embodiment

[0025] As Figure 4As shown in the figure, a piezoelectric ultrasonic transducer includes a housing 2, an acoustic impedance matching layer 1, a piezoelectric element, and a sealing layer 5 located inside the housing 2. The acoustic impedance matching layer 1 is provided at the front end of the piezoelectric element, the sealing layer 5 is provided at the rear of the piezoelectric element, and a transducer cavity is formed between the acoustic impedance matching layer 1 and the sealing layer 5.

[0026] The piezoelectric element includes a fifth metal layer 308, a second piezoelectric ceramic 309, and a sixth metal layer 310 that are coaxially arranged along the A-A' axis in sequence. Among them, the second piezoelectric ceramic 309 is a T-shaped integral structure composed of a coaxial disc portion and a cylindrical portion. The fifth metal layer 308 and the sixth metal layer 310 serve as the electrodes of the piezoelectric element and are respectively welded to the wire 4. The sealing layer 5 not only seals the transducer cavity but also plays a role in fixing the wire 4.

[0027] The top surface of the piezoelectric element is bonded to the bottom surface of the acoustic impedance matching layer 1 with glue; the side surfaces of the acoustic impedance matching layer 1 and the second piezoelectric ceramic 309 are directly bonded to the inner side wall of the housing 2 with waterproof glue.

[0028] Among them, the material of the housing 2 can be POM, etc., and it can be prepared by 3D printing or mold opening technology. The material of the acoustic impedance matching layer 1 can be polyurethane, etc., and it can be prepared by cutting or mold opening technology. The sealing layer 5 can use silicone rubber, etc.

[0029] The same method as in Embodiment 1 was used to experimentally measure the structure of this embodiment and the ultrasonic transducer with a traditional cylindrical piezoelectric ceramic element (hereinafter referred to as the traditional structure), and the experimental results are shown in the following table: Receiving end Transmitting end Frequency corresponding to the maximum output (kHz) Peak-to-peak value of the maximum output (mV) Traditional structure Traditional structure 206.98 262 Structure of Embodiment 3 Traditional structure 204.45 308 Traditional structure Structure of Embodiment 3 201.63 291 Embodiment

[0030] As Figure 5 shown, the difference from Embodiment 3 is only that the second piezoelectric ceramic 309 is an I-shaped integral structure composed of two coaxial disc portions and a cylindrical portion.

[0031] Compared with Embodiment 1 and Embodiment 2, in Embodiment 3 and Embodiment 4, the piezoelectric material part of the piezoelectric element is integrally prepared and formed, which simplifies the preparation process flow of the piezoelectric element, and at the same time still has good transmitting and receiving performance.

[0032] In summary, the present invention provides a piezoelectric ultrasonic transducer. By introducing a wafer piezoelectric ceramic structure and a wafer metal layer, the piezoelectric element of the transducer is structurally optimized to improve the emission sound pressure level and reception sensitivity of the ultrasonic transducer. In Example 1, a wafer piezoelectric ceramic structure and a wafer metal layer are added above the upper electrode of the cylindrical piezoelectric structure. Compared with the existing structure, the amplitude of the output signal of the transducer under the same excitation is increased. On this basis, in Example 2, another wafer piezoelectric ceramic structure and a wafer metal layer are added below the lower electrode of the cylinder structure, With to meet the demand for impedance adjustment in practical applications. In Example 3 and Example 4, the piezoelectric ceramic material part of the piezoelectric element is integrally prepared, which reduces the manufacturing process while ensuring good transmitting and receiving performance, and reduces the production cost of the ultrasonic transducer. The present invention realizes a high-performance piezoelectric ultrasonic transducer without increasing the volume of the transducer.

[0033] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A piezoelectric ultrasonic transducer, characterized in that, It includes an acoustic impedance matching layer (1) and a piezoelectric element; the acoustic impedance matching layer (1) is arranged at the front end of the piezoelectric element; the piezoelectric element includes a first metal layer (301), a first disc-shaped piezoelectric ceramic (302), a second metal layer (303), a cylindrical piezoelectric ceramic (304), and a third metal layer (305) which are coaxially arranged in sequence; the diameter of the first disc-shaped piezoelectric ceramic (302) is larger than that of the cylindrical piezoelectric ceramic (304); the second metal layer (303) and the third metal layer (305) serve as electrodes of the piezoelectric element and are respectively connected to a wire (4).

2. The piezoelectric ultrasonic transducer according to claim 1, characterized in that, The piezoelectric element further includes a second disc-shaped piezoelectric ceramic (306) and a fourth metal layer (307) which are coaxially arranged in sequence after the second metal layer (305).

3. A piezoelectric ultrasonic transducer according to claim 1 or 2, characterized in that, The acoustic impedance matching layer (1) and the piezoelectric element are located inside a housing (2), and the top surface of the piezoelectric element and the bottom surface of the acoustic impedance matching layer (1) are bonded with glue; a waterproof layer (6) is provided on the top of the acoustic impedance matching layer (1), and a sealing layer (5) for sealing the transducer cavity is provided at the bottom of the housing (2).

4. The piezoelectric ultrasonic transducer according to claim 3, characterized in that, The side surfaces of the acoustic impedance matching layer (1) and the piezoelectric element are directly pasted to the inner wall of the housing (2), or are pasted to the inner wall of a sleeve (7) and then placed inside the housing (2).

5. A piezoelectric ultrasonic transducer, characterized in that, It includes an acoustic impedance matching layer (1) and a piezoelectric element; the acoustic impedance matching layer (1) is arranged at the front end of the piezoelectric element; the piezoelectric element includes a fifth metal layer (308), a second piezoelectric ceramic (309), and a sixth metal layer (310) which are coaxially arranged in sequence; wherein, the second piezoelectric ceramic (309) is a T-shaped integral structure composed of a coaxial disc part and a cylindrical part; or, the second piezoelectric ceramic (309) is an I-shaped integral structure composed of two coaxial disc parts and a cylindrical part; the fifth metal layer (308) and the sixth metal layer (310) serve as electrodes of the piezoelectric element and are respectively connected to a wire (4).

6. A piezoelectric ultrasonic transducer according to claim 5, characterized in that, The acoustic impedance matching layer (1) and the piezoelectric element are located inside a housing (2), and the top surface of the piezoelectric element and the bottom surface of the acoustic impedance matching layer (1) are bonded with glue; a waterproof layer is provided on the top of the acoustic impedance matching layer (1), and a sealing layer (5) for sealing the transducer cavity is provided at the bottom of the housing (2).

7. A piezoelectric ultrasonic transducer according to claim 6, characterized in that, The side surfaces of the acoustic impedance matching layer (1) and the piezoelectric element are directly pasted to the inner wall of the housing (2), or are pasted to the inner wall of a sleeve and then placed inside the housing (2).

Images