Piezoelectric ultrasonic transducer for ultrasonic flow meter and method for manufacturing the same

Abstract

The application discloses a piezoelectric ultrasonic transducer for an ultrasonic flowmeter and a preparation method thereof, and relates to the technical field of transducers, and comprises a piezoelectric sensitive element and a packaging layer. The piezoelectric sensitive element comprises a first electrode sheet, a piezoelectric crystal, a second electrode sheet and a matching layer which are sequentially connected. The piezoelectric crystal is electrically connected with the first electrode sheet at one end and electrically connected with the second electrode sheet at the other end. A plurality of longitudinal and transverse interlaced slits are arranged in the piezoelectric crystal. Each slit is open at one end close to the second electrode sheet and does not penetrate to the first electrode sheet. Each slit penetrates the piezoelectric crystal in a direction perpendicular to the polarization direction of the piezoelectric crystal. The circumferential side wall of the piezoelectric crystal is sealed by a sealing film. The first electrode sheet is electrically connected with a first lead wire, and the second electrode sheet is electrically connected with a second lead wire. The piezoelectric sensitive element is wrapped by the packaging layer except the matching layer. The application can improve the measurement accuracy of the ultrasonic flowmeter.

Description

Technical Field

[0001] This invention relates to the field of transducer technology, and in particular to a piezoelectric ultrasonic transducer for ultrasonic flowmeters and its preparation method. Background Technology

[0002] Currently, the core sensing element of ultrasonic transducers used in ultrasonic flow meters is made of a single pure piezoelectric crystal wafer. Due to the limitations of its geometry and size, the transducer has a large lateral coupling effect when radiating sound waves through thickness resonance. This causes the transducer to dissipate some energy in lateral vibration during operation, thereby reducing its ability to radiate sound waves longitudinally. It also results in a large directional angle of the transducer, thus reducing the measurement accuracy of the ultrasonic flow meter. Summary of the Invention

[0003] The purpose of this invention is to provide a piezoelectric ultrasonic transducer for ultrasonic flow meters and its preparation method, so as to solve the problems existing in the prior art and improve the measurement accuracy of ultrasonic flow meters.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] This invention provides a piezoelectric ultrasonic transducer for an ultrasonic flow meter, comprising a piezoelectric sensitive element and an encapsulation layer. The piezoelectric sensitive element includes a first electrode plate, a piezoelectric crystal, a second electrode plate, and a matching layer connected in sequence. One end of the piezoelectric crystal is electrically connected to the first electrode plate, and the other end is electrically connected to the second electrode plate. The piezoelectric crystal has a plurality of crisscrossing slits, each slit opening at one end near the second electrode plate and not penetrating to the first electrode plate. Each slit penetrates the piezoelectric crystal in a direction perpendicular to its polarization direction. The circumferential sidewalls of the piezoelectric crystal are sealed with a sealing film. The first electrode plate is electrically connected to a first wire, and the second electrode plate is electrically connected to a second wire. The matching layer is made of an ultrasonically permeable composite material.

[0006] The piezoelectric sensitive element, except for the matching layer, is encapsulated by the encapsulation layer, and the first wire and the second wire extend out from the encapsulation layer.

[0007] Preferably, the material of the encapsulation layer is an elastic resin adhesive.

[0008] Preferably, the gap includes a first transverse gap, a second transverse gap, a first longitudinal gap, and a second longitudinal gap, wherein the first transverse gap and the second transverse gap are alternately distributed, and the first longitudinal gap and the second longitudinal gap are alternately distributed.

[0009] Preferably, the length of the first transverse slit along the polarization direction of the piezoelectric crystal is greater than the length of the second transverse slit along the polarization direction of the piezoelectric crystal; the length of the first longitudinal slit along the polarization direction of the piezoelectric crystal is greater than the length of the second longitudinal slit along the polarization direction of the piezoelectric crystal.

[0010] Preferably, the portions of the first and second conductors located outside the potting mold are wrapped with shielded signal wires.

[0011] The present invention also provides a method for preparing the above-mentioned piezoelectric ultrasonic transducer for ultrasonic flowmeter, comprising the following steps:

[0012] S1: Prepare a piezoelectric crystal. With the polarization direction of the piezoelectric crystal as the thickness direction, cut a number of first transverse slits and a number of first longitudinal slits on the positive electrode surface of the piezoelectric crystal toward the negative electrode surface, and ensure that the depth of the first transverse slits and the first longitudinal slits are equal and both less than the thickness of the piezoelectric crystal.

[0013] S2: A plurality of second transverse slits and a plurality of second longitudinal slits are cut from the positive electrode surface of the piezoelectric crystal toward the negative electrode surface. The depth of the second transverse slits and the depth of the second longitudinal slits are equal and both are less than the thickness of the first transverse slits. The first transverse slits and the second transverse slits are staggered, and the first longitudinal slits and the second longitudinal slits are staggered.

[0014] S3: A first electrode sheet is coated on the negative electrode surface of the piezoelectric crystal. The first electrode sheet is made of silver paste electrode layer. The circumferential sidewall of the piezoelectric crystal is sealed with a sealing film. Then, a second electrode sheet is electrically connected to the positive electrode surface of the piezoelectric crystal.

[0015] S4: An ultrasonic acoustic composite material is attached as a matching layer on the side of the second electrode sheet away from the piezoelectric crystal, thus obtaining the piezoelectric sensitive element;

[0016] S5: Connect one end of the first wire to the first electrode plate, and connect one end of the second wire to the second electrode plate;

[0017] S6: Prepare a potting mold with a placement hole and a perforation. The placement hole is a blind hole. The diameter of the perforation is smaller than the diameter of the placement hole. The depth of the placement hole is greater than the sum of the thicknesses of the first electrode sheet, the piezoelectric crystal, the second electrode sheet, and the matching layer. The diameter of the placement hole is greater than the diameter of the piezoelectric crystal. The bottom of the perforation is connected to the bottom of the placement hole. The opening of the perforation is located at the end of the potting mold away from the opening of the placement hole.

[0018] S7: Apply a release agent to the wall and bottom of the placement hole, place the piezoelectric sensitive element in the placement hole, so that the matching layer abuts against the bottom of the placement hole, and seal the gap between the matching layer and the wall of the placement hole with silicone rubber;

[0019] S8: After the silicone rubber dries and cures, inject elastic resin into the placement hole until the placement hole is full; after the elastic resin dries and cures, the piezoelectric ultrasonic transducer for the ultrasonic flow meter is formed.

[0020] S9: The ultrasonic flow meter is ejected from the potting mold using a piezoelectric ultrasonic transducer.

[0021] Preferably, in step S8, the first wire and the second wire should extend out of the potting mold.

[0022] Preferably, it also includes an ejection device, which includes a top column and a base, one end of the top column being fixedly connected to the center of the base;

[0023] In step S9, the top post is inserted into the perforation and brought into close contact with the matching layer to push the piezoelectric ultrasonic transducer for the ultrasonic flow meter out toward the opening of the placement hole.

[0024] The present invention achieves the following technical effects compared to the prior art:

[0025] The piezoelectric ultrasonic transducer for ultrasonic flowmeters and its preparation method of the present invention can effectively provide the longitudinal radiation sound wave capability of the piezoelectric ultrasonic transducer, improve the directivity of the transducer, and thus improve the measurement accuracy of the ultrasonic flowmeter.

[0026] Specifically, the piezoelectric crystal of the ultrasonic transducer for the ultrasonic flowmeter of the present invention has several crisscrossing gaps, that is, multiple small oscillators are formed on the piezoelectric crystal. The aspect ratio of the small oscillators is significantly greater than that of the piezoelectric crystal. When performing thickness resonance, the lateral coupling effect can be greatly reduced, the longitudinal radiation of sound waves of the sensitive element can be improved, and the directivity of the transducer can be improved, which is beneficial to improving the measurement accuracy of the whole meter. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1This is a schematic diagram of the structure of the piezoelectric ultrasonic transducer for the ultrasonic flow meter of the present invention when it has not been ejected from the potting mold.

[0029] Figure 2 This is a schematic diagram of the structure of the piezoelectric ultrasonic transducer for the ultrasonic flow meter of the present invention;

[0030] Figure 3 This is an exploded view of the piezoelectric ultrasonic transducer for the ultrasonic flow meter of the present invention;

[0031] Figure 4 This is a schematic diagram of the piezoelectric crystal in the piezoelectric ultrasonic transducer for the ultrasonic flow meter of the present invention;

[0032] Figure 5 This is a schematic diagram of the potting mold in the piezoelectric ultrasonic transducer for the ultrasonic flow meter of the present invention;

[0033] Figure 6 for Figure 5 BB cross-sectional diagram;

[0034] The components include: 1. potting mold; 2. encapsulation layer; 3. piezoelectric crystal; 301. first transverse slit; 302. second transverse slit; 303. first longitudinal slit; 304. second longitudinal slit; 4. first electrode sheet; 5. second electrode sheet; 6. matching layer; 7. top post; 8. base; 9. sealing film; 10. nickel-plated tab; 11. second conductor; 12. first conductor; and 13. shielded signal line. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The purpose of this invention is to provide a piezoelectric ultrasonic transducer for ultrasonic flow meters and its preparation method, so as to solve the problems existing in the prior art and improve the measurement accuracy of ultrasonic flow meters.

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] like Figures 1-6As shown, this embodiment provides a piezoelectric ultrasonic transducer for an ultrasonic flow meter, including a piezoelectric sensitive element. The piezoelectric sensitive element includes a first electrode plate 4, a piezoelectric crystal 3, a second electrode plate 5, and a matching layer 6 connected in sequence. The distribution direction of the first electrode plate 4, the piezoelectric crystal 3, the second electrode plate 5, and the matching layer 6 is the same as the polarization direction of the piezoelectric crystal 3. One end of the piezoelectric crystal 3 is electrically connected to the first electrode plate 4, and the other end is electrically connected to the second electrode plate 5. The piezoelectric crystal 3 is provided with a plurality of crisscrossing slits. All slits open at one end near the second electrode plate 5 and do not penetrate to the first electrode plate 4. All slits penetrate the piezoelectric crystal 3 in a direction perpendicular to the polarization direction of the piezoelectric crystal 3.

[0039] The first electrode plate 4 is electrically connected to the first wire 12, the second electrode plate 5 is electrically connected to the second wire 11, the circumferential sidewall of the piezoelectric crystal 3 is sealed with a sealing film 9, and the material of the matching layer 6 is an ultrasonic sound-transmitting composite material.

[0040] Except for the matching layer 6, the piezoelectric sensing element is encapsulated by the encapsulation layer 2, and both the first wire 12 and the second wire 11 extend out from the encapsulation layer 2. The encapsulation layer 2 is made of elastic resin.

[0041] The gaps in the piezoelectric crystal 3 include a first transverse gap 301, a second transverse gap 302, a first longitudinal gap 303, and a second longitudinal gap 304. The first transverse gap 301 and the second transverse gap 302 are alternately distributed, and the first longitudinal gap 303 and the second longitudinal gap 304 are alternately distributed. The length of the first transverse gap 301 along the polarization direction of the piezoelectric crystal 3 is greater than the length of the second transverse gap 302 along the polarization direction of the piezoelectric crystal 3; the length of the first longitudinal gap 303 along the polarization direction of the piezoelectric crystal 3 is greater than the length of the second longitudinal gap 304 along the polarization direction of the piezoelectric crystal 3.

[0042] In this embodiment, the material of the second electrode sheet 5 is stainless steel. The second electrode sheet 5 is cylindrical. The piezoelectric crystal 3 extends into the second electrode sheet 5, and the end of the piezoelectric crystal 3 away from the first electrode sheet 4 is bonded to the bottom surface of the second electrode sheet 5 with conductive adhesive. Nickel-plated tabs 10 are provided on the circumferential sidewall of the second electrode sheet 5, and the second wire 11 is electrically connected to the nickel-plated tabs 10.

[0043] It should be noted that the portions of the first conductor 12 and the second conductor 11 located outside the potting mold 1 are wrapped with shielded signal wire 13.

[0044] In this embodiment, the piezoelectric crystal 3 of the piezoelectric ultrasonic transducer for the ultrasonic flowmeter has several crisscrossing gaps, that is, multiple small oscillators are formed on the piezoelectric crystal 3. The aspect ratio of the small oscillators is significantly greater than that of the piezoelectric crystal. When performing thickness resonance, the lateral coupling effect can be greatly reduced, the longitudinal radiation sound wave capability of the sensitive element can be improved, and the directivity of the transducer can be improved, which is beneficial to improving the measurement accuracy of the whole meter.

[0045] This embodiment also provides a method for preparing the above-mentioned piezoelectric ultrasonic transducer for ultrasonic flowmeter, including the following steps:

[0046] S1: Prepare a piezoelectric crystal 3. With the polarization direction of the piezoelectric crystal 3 as the thickness direction, cut a number of first transverse slits 301 and a number of first longitudinal slits 303 on the positive electrode surface of the piezoelectric crystal 3 facing the negative electrode surface, and ensure that the depth of the first transverse slits 301 and the first longitudinal slits 303 are equal and both less than the thickness of the piezoelectric crystal 3.

[0047] S2: A number of second transverse slits 302 and a number of second longitudinal slits 304 are cut from the positive electrode surface of the piezoelectric crystal 3 toward the negative electrode surface. The depth of the second transverse slits 302 and the depth of the second longitudinal slits 304 are equal and both are less than the thickness of the first transverse slit 301. The first transverse slits 301 and the second transverse slits 302 are staggered, and the first longitudinal slits 303 and the second longitudinal slits 304 are staggered.

[0048] S3: A first electrode sheet 4 is coated on the negative electrode surface of the piezoelectric crystal 3. The first electrode sheet 4 is made of silver paste electrode layer. The circumferential sidewall of the piezoelectric crystal 3 is sealed with a sealing film 9. Then, the second electrode sheet 5 is electrically connected to the positive electrode surface of the piezoelectric crystal 3.

[0049] S4: An ultrasonic sound-transmitting composite material is pasted on the side of the second electrode sheet 5 away from the piezoelectric crystal 3 as a matching layer 6, thus obtaining the piezoelectric sensitive element.

[0050] S5: Connect one end of the first wire 12 to the first electrode plate 4, and connect one end of the second wire 11 to the second electrode plate 5.

[0051] S6: Prepare a potting mold 1 with placement holes and perforations. The placement holes are blind holes. The diameter of the perforations is smaller than the diameter of the placement holes. The depth of the placement holes is greater than the sum of the thicknesses of the first electrode sheet 4, the piezoelectric crystal 3, the second electrode sheet 5, and the matching layer 6. The diameter of the placement holes is greater than the diameter of the piezoelectric crystal 3. The bottom of the perforations is connected to the bottom of the placement holes. The opening of the perforations is located at the end of the potting mold 1 away from the opening of the placement holes.

[0052] S7: Apply release agent to the wall and bottom of the placement hole, place the piezoelectric sensitive element in the placement hole, so that the matching layer 6 abuts against the bottom of the placement hole, and seal the gap between the matching layer and the wall of the placement hole with silicone rubber.

[0053] S8: After the silicone rubber dries and cures, inject elastic resin into the placement hole, ensuring that the first wire 12 and the second wire 11 extend out of the potting mold 1 until the placement hole is filled; after the elastic resin dries and cures, a piezoelectric ultrasonic transducer for ultrasonic flowmeter is formed.

[0054] S9: Eject the ultrasonic flow meter from the potting mold using a piezoelectric ultrasonic transducer.

[0055] It should be noted that this embodiment also includes an ejection device, which includes a top column and a base, with one end of the top column fixedly connected to the center of the base;

[0056] In step S9, the top post is inserted into the perforation and makes close contact with the matching layer to push out the piezoelectric ultrasonic transducer of the ultrasonic flow meter toward the orifice where the hole is placed.

[0057] In the description of this invention, it should be noted that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0058] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A piezoelectric ultrasonic transducer for use in an ultrasonic flow meter, characterized by: The device includes a piezoelectric sensing element and an encapsulation layer. The piezoelectric sensing element comprises a first electrode sheet, a piezoelectric crystal, a second electrode sheet, and a matching layer connected in sequence. One end of the piezoelectric crystal is electrically connected to the first electrode sheet, and the other end is electrically connected to the second electrode sheet. The piezoelectric crystal has a plurality of crisscrossing slits, each slit opening at one end near the second electrode sheet and not penetrating to the first electrode sheet. Each slit penetrates the piezoelectric crystal in a direction perpendicular to the polarization direction of the piezoelectric crystal. The circumferential sidewalls of the piezoelectric crystal are sealed with a sealing film. The first electrode sheet is electrically connected to a first wire, and the second electrode sheet is electrically connected to a second wire. The matching layer is made of an ultrasonically permeable composite material. The piezoelectric sensitive element, except for the matching layer, is encapsulated by the encapsulation layer, and the first wire and the second wire extend out from the encapsulation layer; the gap includes a first transverse gap, a second transverse gap, a first longitudinal gap and a second longitudinal gap, the first transverse gap and the second transverse gap are staggered, and the first longitudinal gap and the second longitudinal gap are staggered. The length of the first transverse slit along the polarization direction of the piezoelectric crystal is greater than the length of the second transverse slit along the polarization direction of the piezoelectric crystal; the length of the first longitudinal slit along the polarization direction of the piezoelectric crystal is greater than the length of the second longitudinal slit along the polarization direction of the piezoelectric crystal.

2. The piezoelectric ultrasonic transducer for ultrasonic flow meters of claim 1, wherein: The encapsulation layer is made of elastic resin adhesive.

3. A method of manufacturing a piezoelectric ultrasonic transducer for an ultrasonic flow meter as claimed in claim 1 or 2, characterized in that, Includes the following steps: S1: Prepare a piezoelectric crystal. With the polarization direction of the piezoelectric crystal as the thickness direction, cut a number of first transverse slits and a number of first longitudinal slits on the positive electrode surface of the piezoelectric crystal toward the negative electrode surface, and ensure that the depth of the first transverse slits and the first longitudinal slits are equal and both less than the thickness of the piezoelectric crystal. S2: A plurality of second transverse slits and a plurality of second longitudinal slits are cut from the positive electrode surface of the piezoelectric crystal toward the negative electrode surface. The depth of the second transverse slits and the depth of the second longitudinal slits are equal and both are less than the thickness of the first transverse slits. The first transverse slits and the second transverse slits are staggered, and the first longitudinal slits and the second longitudinal slits are staggered. S3: A first electrode sheet is coated on the negative electrode surface of the piezoelectric crystal. The first electrode sheet is made of silver paste electrode layer. The circumferential sidewall of the piezoelectric crystal is sealed with a sealing film. Then, a second electrode sheet is electrically connected to the positive electrode surface of the piezoelectric crystal. S4: An ultrasonic acoustic composite material is attached as a matching layer on the side of the second electrode sheet away from the piezoelectric crystal, thus obtaining the piezoelectric sensitive element; S5: Connect one end of the first wire to the first electrode plate, and connect one end of the second wire to the second electrode plate; S6: Prepare a potting mold with a placement hole and a perforation. The placement hole is a blind hole. The diameter of the perforation is smaller than the diameter of the placement hole. The depth of the placement hole is greater than the sum of the thicknesses of the first electrode sheet, the piezoelectric crystal, the second electrode sheet, and the matching layer. The diameter of the placement hole is greater than the diameter of the piezoelectric crystal. The bottom of the perforation is connected to the bottom of the placement hole. The opening of the perforation is located at the end of the potting mold away from the opening of the placement hole. S7: Apply a release agent to the wall and bottom of the placement hole, place the piezoelectric sensitive element in the placement hole, so that the matching layer abuts against the bottom of the placement hole, and seal the gap between the matching layer and the wall of the placement hole with silicone rubber; S8: After the silicone rubber dries and cures, inject elastic resin into the placement hole until the placement hole is full; after the elastic resin dries and cures, the piezoelectric ultrasonic transducer for the ultrasonic flow meter is formed. S9: The ultrasonic flow meter is ejected from the potting mold using a piezoelectric ultrasonic transducer.

4. The method of claim 3, wherein the piezoelectric ultrasonic transducer for ultrasonic flow meters is prepared by the steps of: In step S8, it should be ensured that the first wire and the second wire extend out of the potting mold.

5. The method for preparing a piezoelectric ultrasonic transducer for an ultrasonic flowmeter according to claim 3, characterized in that: It also includes an ejection device, which includes a top column and a base, with one end of the top column fixedly connected to the center of the base; In step S9, the top post is inserted into the perforation and brought into close contact with the matching layer to push the piezoelectric ultrasonic transducer for the ultrasonic flow meter out toward the opening of the placement hole.

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