CN118131241A - Ultrasonic sensor - Google Patents

Ultrasonic sensor Download PDF

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Publication number
CN118131241A
CN118131241A CN202410290560.9A CN202410290560A CN118131241A CN 118131241 A CN118131241 A CN 118131241A CN 202410290560 A CN202410290560 A CN 202410290560A CN 118131241 A CN118131241 A CN 118131241A
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CN
China
Prior art keywords
matching layer
layer
piezoelectric ceramic
plastic shell
ultrasonic sensor
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CN202410290560.9A
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Chinese (zh)
Inventor
申桃
曹淼
旷东升
阴伏星
李佳
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Chengdu Huitong West Electronic Co ltd
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Chengdu Huitong West Electronic Co ltd
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Priority to CN202410290560.9A priority Critical patent/CN118131241A/en
Publication of CN118131241A publication Critical patent/CN118131241A/en
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Abstract

The invention relates to the technical field of ultrasonic sensors, in particular to an ultrasonic sensor, which comprises a plastic shell (3), a piezoelectric ceramic piece (4) and a matching layer (1), wherein the piezoelectric ceramic piece (4) is connected with the matching layer (1), the plastic shell (3) is connected with the matching layer (1), and the piezoelectric ceramic piece (4), the plastic shell (3) and the matching layer (1) are connected into a whole in the curing and forming process of the matching layer (1). In the ultrasonic sensor, the plastic shell, the piezoelectric ceramic plate and the matching layer are connected and formed at one time to form a whole, so that the assembly process is reduced, the cost is saved, the consistency is better, and the actual product performance is closer to the theoretical design parameter.

Description

Ultrasonic sensor
The application is a divisional application of a patent application with the application number 2022116079874 of 2022, 12 months and 14 days, and the name of an ultrasonic sensor.
Technical Field
The invention relates to the technical field of ultrasonic sensors, in particular to an ultrasonic sensor.
Background
In the material identification module of intelligent household electrical appliances, ultrasonic sensor is used to detect the distance more to realize automatic identification and intelligent work. For example, the intelligent sweeping robot recognizes an obstacle through an ultrasonic sensor to perform route planning. Ultrasonic sensors for material identification which are popular in the market at present are not of a large variety, some ultrasonic sensors are relatively low in cost, and matching layer materials are directly filled between a piezoelectric ceramic plate and a plastic shell in a matching layer forming mode, so that the ceramic plate is inclined, and an echo test value deviation is caused as a result. Some of the piezoelectric ceramic plates are manufactured by adopting an integrated forming mode, and then the piezoelectric ceramic plates are bonded to the matching layer, so that the inclination of the ceramic plates is reduced, but the assembly process is relatively complex, the assembly efficiency is low, the product consistency is poor, and the deviation between the performance of the product and the theoretical design value is large.
Patent "a sensor" (CN 113390969 a) discloses a sensor comprising a housing having a mounting hole, a matching layer embedded on the inner wall of the mounting hole, and a piezoelectric ceramic sheet mounted on the matching layer; the matching layer is provided with a groove, and the piezoelectric ceramic piece is arranged on the bottom wall of the groove. The invention can increase the sensitivity, reduce the residual vibration and improve the performance of the sensor. The sensor explicitly mentions that the matching layer is integrally formed through an injection molding process, and the piezoelectric ceramic plate is stuck on the bottom wall of the U-shaped matching layer through the adhesive, and the left end and the right end of the piezoelectric ceramic plate are connected with the side wall of the groove through the adhesive. In addition, as the negative welding spots are arranged on the negative electrode of the piezoelectric ceramic plate, in order to ensure that the piezoelectric ceramic plate is tightly adhered to the bottom wall of the matching layer, welding spot grooves are reserved on the bottom wall of the matching layer, and after the piezoelectric ceramic plate is adhered to the bottom wall of the U-shaped matching layer, the negative welding spots are adhered in the welding spot grooves through the adhesive.
The above scheme has the following problems: although the matching layer is of an integrally formed U-shaped structure, and in order to adapt to the fact that the lower surface of the piezoelectric ceramic piece is provided with a convex welding spot, a welding spot groove for accommodating the welding spot is formed in the bottom wall of the U-shaped structure, in the scheme, the piezoelectric ceramic piece still needs to be adhered to the matching layer by glue, then the plastic shell is adhered to the matching layer, the adhesion process is manual assembly, errors still easily occur in glue adhesion and manual assembly, for example, when the piezoelectric ceramic piece is adhered to the bottom wall of the U-shaped matching layer by the adhesive, the thickness of the glue is difficult to be kept consistent, and the consistency of products is poor; for example, although the bottom of the U-shaped structure of the matching layer is used for placing the piezoelectric ceramic chip, the piezoelectric ceramic chip and the U-shaped bottom surface cannot be guaranteed to be parallel when being attached, so that the gravity center of the piezoelectric ceramic chip is unbalanced, the concentricity is affected, the piezoelectric ceramic chip can emit ultrasonic signals unevenly, and the performance is affected. In addition, after matching layer and piezoceramics chip paste, glue is placed between piezoceramics chip and the matching layer, and the structure after matching layer and piezoceramics chip assemble relates to three materials, and three materials expansion coefficient is different, can cause the vibration signal that piezoceramics chip sent to transmit in different materials can have great deviation with theoretical design value, and three materials expansion coefficient is different moreover, can also cause the product after the equipment to be under vibration effect, life is influenced.
Disclosure of Invention
The invention aims at: the structure of the existing ultrasonic sensor is improved, the piezoelectric ceramic plate, the plastic shell and the matching layer are connected and formed at one time in the curing process of the matching layer, so that the assembly difficulty is simplified, the product performance is improved, and the consistency of the product is improved, and therefore the ultrasonic sensor is provided.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
The utility model provides an ultrasonic sensor, includes moulded case 3, piezoceramics piece 4 and matching layer 1, piezoceramics piece 4 with matching layer 1 connects, moulded case 3 with matching layer 1 connects, piezoceramics piece 4 moulded case 3 with matching layer 1 is in matching layer 1 solidification in-process connects into an integer.
The step of connecting the piezoelectric ceramic plate 4, the plastic shell 3 and the matching layer 1 into a whole in the curing and forming process of the matching layer 1 means that the plastic shell 3 and the piezoelectric ceramic plate 4 are placed at the position capable of being connected with the matching layer 1, a reserved space capable of being filled with a liquid matching layer material is reserved, the liquid matching layer material is injected into the reserved space, then the piezoelectric ceramic plate 4 is connected with the matching layer 1 in the curing and forming process of the liquid matching layer material into the matching layer, and the plastic shell 3 is connected with the matching layer 1, so that the plastic shell 3, the piezoelectric ceramic plate 4 and the matching layer 1 form a whole.
In the prior art, after a plastic shell, a piezoelectric ceramic plate and a matching layer are prepared as parts, the parts are assembled through glue adhesion, so that an ultrasonic sensor meeting the performance requirement is formed, so that how to design the shape structure of each part is critical to enable the parts to be closely adhered to realize theoretical design parameters. The method reduces the steps of pasting, reduces the assembly process, reduces the difficulty of the processing process, reduces the error generated by assembly, has good product consistency and high yield and reduces the cost.
As a preferred embodiment of the present invention, a part of the piezoelectric ceramic sheet 4 is embedded in the matching layer 1. The piezoelectric ceramic piece 4 imbeds the matching layer in the curing process of the matching layer 1, fix on the matching layer 1, the piezoelectric ceramic piece 4 part imbeds the matching layer 1, the matching layer wraps up the piezoelectric ceramic piece 4, combine more firmly, simultaneously, such embedding is not the complete embedding, but imbeds partial piezoelectric ceramic piece 4 in the matching layer 1 for the vibration signal of piezoelectric ceramic piece 4 can be transmitted through the lower surface and the side of laminating with the matching layer, satisfies ultrasonic sensor and follows the directionality demand that the moulded case terminal surface was transmitted.
As a preferred embodiment of the present invention, the piezoelectric ceramic sheet 4 has a lead terminal on one side embedded in the matching layer 1, the lead terminal being for electrical connection with the terminal wire 7.
Since the piezoelectric ceramic piece 4 is embedded in the matching layer 1 in the curing process of the matching layer, when the lead terminal is arranged on the embedding side of the piezoelectric ceramic piece 4, the matching layer is self-adaptively attached to the lead terminal, and a space for placing the lead terminal does not need to be reserved in the matching layer 1 in advance, and the number of the lead terminals and the shape of the lead terminal on the embedding side of the piezoelectric ceramic piece 4 do not need to be considered. The problems that the contact surfaces of the piezoelectric ceramic chip and the matching layer are not parallel, the center of gravity of the piezoelectric ceramic chip is unbalanced, and concentricity is affected are avoided, and the problems that the piezoelectric ceramic chip emits ultrasonic signals to the outside due to the fact that the contact surfaces of the piezoelectric ceramic chip and the matching layer are not parallel and the performance is affected due to the fact that the lead ends are arranged are also solved.
As a preferable scheme of the invention, the matching layer 1 is a groove, and the piezoelectric ceramic piece 4 is embedded into the bottom of the groove.
The design of the ultrasonic sensor needs to have directivity, namely, the transmission of vibration signals is blocked in the direction away from the end face of the plastic shell in the plastic shell, the vibration signals are concentrated and transmitted out from the end face of the plastic shell, the design of the grooves of the matching layer 1 and the design of the bottoms of the grooves embedded by the piezoelectric ceramic plates 4 are beneficial to filling damping materials of the damping layer into the space of the upper surfaces of the piezoelectric ceramic plates 4 in the grooves of the matching layer 1, the depth of the damping layer is also beneficial to controlling when the damping materials are filled, and the damping layer can be better attached to the upper surfaces of the piezoelectric ceramic plates 4.
As a preferred embodiment of the present invention, the mesa 301 on the inside wall of the plastic case 3 is connected to the matching layer 1. The plastic shell 3 is a container for containing all filling materials, and after the plastic shell 3 is fixedly connected with the matching layer 1 through the table top 301 on the inner side wall, the space in the plastic shell 3 is divided into areas by taking the matching layer 1 as a boundary, so that the filling of the materials and the assembly of components are conveniently carried out based on the area division in the subsequent process.
As a preferable mode of the present invention, the width of the connection surface of the matching layer 1 and the mesa 301 in the radial direction of the plastic housing 3 is 1/2 to 4/5 of the width of the mesa 301 in the radial direction of the plastic housing 3. The matching layer 1 and the plastic shell 3 are connected only through the table top 301 on the inner side wall of the plastic shell 3, if the contact surface is small, no enough fixing area is reserved, and the connecting end between the matching layer 1 and the table top 301 is easily broken by vibration under the action of a vibration signal so as to be damaged. The width of the connection surface of the matching layer 1 and the mesa 301 in the radial direction of the plastic housing 3 is 1/2 to 4/5 of the width of the mesa 301 in the radial direction of the plastic housing 3, and this feature is defined because: a part of the mesa 301 is to be connected to the matching layer 1, and another part is to be used for filling the damping material, and the width of the connecting end between the matching layer 1 and the mesa 301 is that the wider the connecting surface is, the more firmly the connecting surface is, but the wider the connecting surface is, the thickness of the damping material on the mesa adjacent to the matching layer 1 is narrowed, and the thickness narrowing damping effect of the damping material is weakened. On the other hand, the wider the width of the mesa for filling the vibration-absorbing material is, the better the vibration-absorbing effect is, the wider the width of the mesa for filling the vibration-absorbing material is, the narrower the connecting surface between the matching layer 1 and the mesa 301 is, and the connecting end is easily broken. In order to achieve the purpose of considering the width of the connecting surface and the thickness of the filling material, a value range of 1/2-4/5 is set, namely, the width of the connecting surface of the matching layer 1 connected with the table 301 in the radial direction of the plastic shell 3 is 1/2-4/5 of the width of the table 301 in the radial direction of the plastic shell 3, the connecting surface occupies one half of the width of the table 301, and the vibration reduction material occupies one half of the width of the table 301; the connecting surface occupies the width of four fifths of the table top 301, and the vibration damping material occupies the width of one fifth of the table top 301, so that the arrangement in the range has the advantages that the connecting end between the matching layer 1 and the table top 301 is not easy to break, and the thickness of the vibration damping material meets the vibration damping requirement.
As the preferable scheme of the invention, the piezoelectric ceramic composite material further comprises a damping layer 5, a potting layer 6 and a terminal wire 7, wherein the damping layer 5 and the potting layer 6 are sequentially connected in a space, far away from the matching layer 1, in the plastic shell 3, one end of the terminal wire 7 is embedded into the potting layer 6, the piezoelectric ceramic sheet 4 is positioned between the damping layer 5 and the matching layer 1, one end of the piezoelectric ceramic sheet 4, which is embedded into the potting layer 6, of the terminal wire 7 is electrically connected, and the piezoelectric ceramic sheet 4 and the terminal wire 7 can be directly connected.
As the preferred scheme of the invention, the invention further comprises a PCB 21, the PCB 21 is positioned between the damping layer 5 and the encapsulating layer 6, the piezoelectric ceramic sheet 4 is electrically connected with the PCB 21, the terminal wire 7 is electrically connected with the PCB 21, in order to improve the convenience of assembly, the PCB 21 is added, after the terminal wire 7 is electrically connected with the PCB 21, the PCB 21 is used as a transfer component, the terminal wire 7 and the piezoelectric ceramic sheet 4 are electrically connected with the PCB 21, the welding is convenient, and the wire on the piezoelectric ceramic sheet 4 is not required to be directly welded with the terminal wire 7 (the welding process between wires has higher requirements and is not easy to weld firmly, but the PCB is provided with welding spots, the contact area of the welding spots is large, and the welding between wires and welding spots is easy to realize).
As a preferable scheme of the invention, a vibration reduction layer 2 is arranged in an annular groove formed among the table top 301, the plastic shell 3 and the matching layer 1.
As a preferable mode of the present invention, the vibration damping layer 2 is divided into a first vibration damping layer and a second vibration damping layer in the axial direction of the plastic case 3, the width of the first vibration damping layer in the radial direction of the plastic case 3 is smaller than the width of the second vibration damping layer in the radial direction of the plastic case 3, and the distance from the interface between the first vibration damping layer and the second vibration damping layer to the end face of the plastic case is greater than or equal to the distance from the upper end face of the piezoelectric ceramic piece 4 to the end face of the plastic case 3.
The thickness of the vibration reduction layer 2 is thicker, but after the thickness of the vibration reduction layer 2 is thickened, the width of the connecting surface reserved on the table top 301 for the matching layer 1 and the table top 301 is reduced, so that the width of the connecting surface between the matching layer 1 and the table top 301 is not broken, the thickness of the vibration reduction layer can be increased, further, the vibration reduction layer 2 is axially divided into a first vibration reduction layer and a second vibration reduction layer in the plastic shell 3, the first vibration reduction layer is narrow and is used for being connected with the table top 301, the second vibration reduction layer is wide and is used for increasing the vibration reduction effect, and the vibration reduction layer 2 presents an L shape in section. Considering that the vibration damping layer 2 dampens the piezoelectric ceramic plate 4 without damping the damping layer 5 on the piezoelectric ceramic plate 4, the distance from the interface between the first vibration damping layer and the second vibration damping layer to the molded case end face 302 is greater than or equal to the distance from the upper end face of the piezoelectric ceramic plate 4 to the molded case end face 302, that is, the interface between the first vibration damping layer and the second vibration damping layer is bounded by the interface between the piezoelectric ceramic plate 4 and the damping layer 5, so that the performance effect is optimal.
As a preferred embodiment of the present invention, the side of the vibration reduction layer 2 located on the end face 302 of the plastic shell is concave.
As a preferable scheme of the invention, the front end face of the matching layer 1 is 0.05mm-0.5mm higher than the plastic shell end face 302 of the plastic shell 3, so that the thickness of the matching layer can be conveniently polished according to the requirement to adjust the resonant frequency and impedance parameters of the product, and different requirements of the product are met.
As a preferred embodiment of the present invention, the matching layer 1 is connected to the mesa 301 through a boss 405, and the diameter of the boss 405 is smaller and larger. The design scheme is considered in that on one hand, based on the consideration of a die, the diameter of the boss 405 is small, and the boss is large, so that the die is convenient to clean, easy to demould and difficult to deposit ash; on the other hand, the diameter of the boss 405 is smaller and larger at the bottom, and the side wall of the lower end face of the matching layer has no stress concentration in the working process of the sensor, so that the side wall of the matching layer has higher strength.
As a preferred embodiment of the present invention, the angle between the oblique side and the bottom side in the cross section of the boss 405 is in the range of 40 DEG.ltoreq.a.ltoreq.60 deg.
In conclusion, by adopting the technical scheme, the invention has the beneficial effects that:
Because of structural improvement, the piezoelectric ceramic chip, the plastic shell and the matching layer in the ultrasonic sensor are connected and formed at one time in the curing process of the matching layer, so that the assembly process is reduced, the error generated by assembly is reduced, the plastic shell, the piezoelectric ceramic chip and the matching layer which are main components of the ultrasonic sensor can be tightly combined, and the piezoelectric ceramic chip is not required to be adhered to the matching layer by using glue, because the adhesive glue is reduced, the ultrasonic wave only penetrates through the matching layer instead of penetrating through the glue layers and the matching layers which are made of different materials in the transmission process, and the sensitivity is higher. In addition, as the steps of pasting are reduced, the difficulty in the processing process is reduced, the consistency of products is good, the yield is high, and the cost is reduced.
Drawings
FIG. 1 is a cross-sectional view of an ultrasonic sensor molded case, a piezoelectric ceramic sheet, and a matching layer of embodiment 1 after one-time connection molding;
FIG. 2 is a cross-sectional view of a molded case of an ultrasonic sensor according to embodiment 1 of the present invention;
FIG. 3 is a second cross-sectional view of the ultrasonic sensor of embodiment 1 after the plastic housing, the piezoelectric ceramic plate and the matching layer are connected and molded at one time;
FIG. 4 is a cross-sectional view showing the whole structure of an ultrasonic sensor according to embodiment 1 of the present invention;
FIG. 5 is a cross-sectional view of an ultrasonic sensor with a PCB in embodiment 2 of the present invention;
FIG. 6 is a diagram of a complete matching layer of an ultrasonic sensor according to embodiment 3 of the present invention;
FIG. 7 is a pattern of a broken matching layer of an ultrasonic sensor according to embodiment 3 of the present invention;
FIG. 8 is a graph showing echo sensitivity of the correlation ultrasonic sensor in example 3 of the present invention;
fig. 9 is a schematic structural diagram of a boss designed as a right-angle side for connecting the lower end surface of the matching layer with the mesa in embodiment 4 of the present invention;
FIG. 10 is a diagram showing the structure of a boss for connecting the lower end surface of the matching layer with the mesa in embodiment 4;
FIG. 11 is a force simulation diagram of a boss for connecting the lower end surface of the matching layer with the table top in embodiment 4 of the present invention;
fig. 12 is a simulation diagram of inclined plane stress analysis of a boss designed to connect the lower end surface of the matching layer with the mesa in embodiment 4 of the present invention.
Reference numerals: 1-matching layer, 2-vibration reduction material (vibration reduction layer), 201-first vibration reduction layer, 202-second vibration reduction layer, 3-plastic shell, 301-mesa, 302-plastic shell end face, 303-second cylindrical through hole, 304-first cylindrical through hole, 4-piezoelectric ceramic piece, 401-upper lead end, 402-lower lead end, 403-matching layer front end face, 404-matching layer rear end face, 405-boss, 5-damping material (damping layer), 6-potting material (potting layer), 7-terminal wire, 20-adhesive, 21-PCB board.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings.
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Example 1
The utility model provides an ultrasonic sensor, includes moulded case 3, piezoceramics piece 4 and matching layer 1, piezoceramics piece 4 with matching layer 1 connects, moulded case 3 with matching layer 1 connects, piezoceramics piece 4 moulded case 3 with matching layer 1 is in the one-time connection shaping of matching layer 1 solidification in-process. The cross-sectional view of fig. 1 can intuitively show the shape after molding, and the matching layer 1 is attached to the table board 301 and the inner wall inside the plastic shell 3 after being cured, so that the matching layer 1 can be well connected with the plastic shell 3. The matching layer 1 is also connected with a piezoelectric ceramic piece 4, and the connection relation among the plastic shell 3, the piezoelectric ceramic piece 4 and the matching layer 1 as shown in fig. 1 is as follows: the piezoelectric ceramic piece 4, the plastic shell 3 and the matching layer 1 are connected into a whole in the solidification forming process of the matching layer 1, specifically, the plastic shell 3 and the piezoelectric ceramic piece 4 are placed at a position which can be connected with the matching layer, a reserved space which can be filled with liquid matching layer materials is reserved, the liquid matching layer materials are injected into the reserved space, then the piezoelectric ceramic piece 4 is connected with the matching layer 1 in the solidification forming process of the liquid matching layer materials into the matching layer, the plastic shell 3 is connected with the matching layer 1, the plastic shell 3, the piezoelectric ceramic piece 4 and the matching layer 1 form a whole, and the piezoelectric ceramic piece is connected and formed at one time in the process that the matching layer is changed from liquid into solid.
In the prior art, the plastic shell 3 (the cross section of the plastic shell is shown in fig. 2), the piezoelectric ceramic piece 4 and the matching layer 1 are usually prepared as parts, and then are assembled by glue adhesion, so that an ultrasonic sensor meeting the performance requirement is formed, so that how to design the shape and structure of each part to enable the parts to be closely adhered is critical to achieve theoretical design parameters, but the piezoelectric ceramic piece 4, the plastic shell 3 and the matching layer 1 of the ultrasonic sensor are connected and formed at one time in the curing process of the matching layer 1, the assembling process is reduced, errors generated in the assembling process are reduced, the plastic shell 3, the piezoelectric ceramic piece 4 and the matching layer 1 which are main components of the ultrasonic sensor can be closely combined, and the piezoelectric ceramic piece 4 is not required to be adhered to the matching layer 1 by using glue additionally, because the adhered glue is reduced, ultrasonic waves only need to penetrate through the matching layer instead of penetrating through glue layers and matching layers of different materials in transmission, and the sensitivity is higher. The steps of pasting are reduced, the difficulty in the processing process is reduced, the product consistency is good, the yield is high, and the cost is reduced.
As a preferred embodiment of the present invention, a part of the piezoelectric ceramic sheet 4 is embedded in the matching layer 1. As shown in fig. 1, the piezoelectric ceramic piece 4 is embedded into the matching layer 1 in the curing process of the matching layer 1, the piezoelectric ceramic piece 4 is fixed on the matching layer 1, and part of the piezoelectric ceramic piece 4 is embedded into the matching layer 1 instead of being completely embedded, so that vibration signals of the piezoelectric ceramic piece 4 can be transmitted through the matching layer 1 on the lower surface and the side surface, and the directivity requirement of the ultrasonic sensor transmitted from the molded end face 302 is met. In addition, the piezoelectric ceramic piece 4 is partially embedded into the matching layer 1, and the matching layer 1 wraps the piezoelectric ceramic piece 4 and is combined more firmly.
As a preferred embodiment of the present invention, the piezoelectric ceramic sheet 4 has a lead terminal embedded in one side of the matching layer 1, the lead terminal being for electrical connection with the terminal wire 7.
As shown in fig. 3, since the piezoelectric ceramic sheet 4 is embedded in the matching layer 1 during the curing process of the matching layer 1, when the lead terminals 401 are provided on the embedded side of the piezoelectric ceramic sheet 4, the matching layer 1 is adaptively attached to the lead terminals 401 without reserving the end point grooves for placing the lead terminals in the matching layer 1 in advance, and without considering the number of the lead terminals and the shape of the lead terminals on the embedded side of the piezoelectric ceramic sheet 4. The problem that the contact surfaces of the piezoelectric ceramic chip and the matching layer are not parallel due to the lead ends is avoided, so that the problems that the center of gravity of the piezoelectric ceramic chip is unbalanced and the concentricity is affected are avoided, and the problems that the piezoelectric ceramic chip emits ultrasonic signals to the outside due to the fact that the contact surfaces of the piezoelectric ceramic chip and the matching layer are not parallel due to the lead ends are also overcome, and the performance is affected are also solved.
As a preferable scheme of the invention, the matching layer 1 is a groove, and the piezoelectric ceramic piece 4 is embedded into the bottom of the groove.
The design is considered in that the piezoelectric ceramic piece 4 is embedded in the bottom of the groove, the structure that the piezoelectric ceramic piece 4 is wrapped by three faces of the matching layer 1 is easier to form, the piezoelectric ceramic piece 4 and the matching layer 1 are attached more tightly in the curing process of the matching layer 1, vibration signals can be transmitted out through the face, which is in contact with the matching layer 1, of the piezoelectric ceramic piece 4, and the directivity requirement of vibration signal transmission of the ultrasonic sensor is met. The space left in the groove of the matching layer 1 after the piezoelectric ceramic piece 4 is installed is used for filling the damping layer, and the filling of the damping layer under the groove structure is more convenient and easy to process. The depth of the damping layer is also beneficial to control when the damping material is filled, and the damping layer can be better attached to the surface of the piezoelectric ceramic plate (4).
The appearance of the matching layer 1 is a groove, the bottom of the groove forms a front end face 403, the side wall except the bottom of the groove forms a rear end face 404, the front end face 403 of the matching layer 1 is 0.05mm-0.5mm higher than the end face 302 of the plastic shell 3, the thickness of the matching layer is convenient to polish according to the requirement so as to adjust the resonant frequency and impedance parameters of the product, and different requirements of the product are met.
The rear end face 404 of the matching layer 1 is attached to the mesa 301 of the plastic housing interior 3, and the length ratio of the line segment AB to the line segment AC is 1/2 to 4/5 (i.e., the width of the connection surface of the matching layer 1 to the mesa 301 in the radial direction of the plastic housing 3 is 1/2 to 4/5 of the width of the mesa 301 in the radial direction of the plastic housing 3) as seen in fig. 4, wherein points a and B are two end points of the connection portion of the mesa 301 to the matching layer 1 in the plastic housing 3 in the longitudinal sectional view of the ultrasonic sensor, and point C is the connection point of the mesa 301 to the inner wall of the plastic housing 3. The reason for this is that the length ratio of the line segment AB to the line segment AC is greater than 1/2, so that the matching layer can have enough contact area on the table 301, and is not damaged; the length ratio of the line segment AB to the line segment AC is smaller than 4/5, so that a certain space is reserved between the matching layer and the plastic shell for filling the vibration reduction material, the side wall of the matching layer is prevented from being in hard contact with the plastic shell, and radial vibration of the matching layer is directly transmitted to the plastic shell, so that residual vibration is large. The above limitation is to ensure that the side wall of the matching layer has enough contact area with the surface of the molded case table, and the side wall of the matching layer cannot be broken under the action force when the table limits the matching layer.
As shown in fig. 4, the AD section is attached to the inner wall of the plastic shell, and the length of the line section AD is greater than or equal to 1mm, so as to further enhance the adhesion of the matching layer on the plastic shell, where the line section AD is a line section of the longitudinal section of the ultrasonic sensor, where the side wall of the matching layer 1 is not connected to the mesa 301.
In order to realize the function of the ultrasonic sensor, in addition to the plastic case 3, the piezoelectric ceramic sheet 4 and the matching layer 1, a vibration damping material 2, a damping material (damping layer) 5, a potting material (potting layer) 6 and a terminal wire 7 are included, and a sectional view of the complete structure of the ultrasonic sensor is shown in fig. 4.
As can be seen from fig. 1 to 3, in a further scheme, the plastic shell 3 is made of a polymer material, a cylindrical through hole is formed in the plastic shell 3, the cylindrical through hole is divided into a first cylindrical through hole 304 and a second cylindrical through hole 303, the cross-sectional diameter of the first cylindrical through hole 304 in the radial direction of the plastic shell is larger than that of the second cylindrical through hole 303 in the radial direction of the plastic shell, a table 301 on the inner side wall of the plastic shell 3 is formed in the plastic shell 3 due to the diameter difference between the first cylindrical through hole 304 and the second cylindrical through hole 303, the table 301 is fixedly connected with the matching layer 1, the first cylindrical through hole 304 is used for placing the piezoelectric ceramic sheet 4 and the matching layer 1, and the second cylindrical through hole 303 is used for filling the damping material 5 and the potting material 6.
Because of the design of the table top 301, the matching layer 1 of the internal fixed piezoelectric ceramic plate 4 can be fixed in the plastic shell 3, and the matching layer 1 is attached to the table top 301 inside the plastic shell 3 and the inner wall of the plastic shell 3 after being solidified, so that the matching layer 1 can be well connected with the plastic shell 3 and form a whole with the plastic shell 3, therefore, the piezoelectric ceramic plate 4, the matching layer 1 and the plastic shell 3 form a designed structure without being stuck by glue, components in the ultrasonic sensor are reduced, the assembly process is facilitated to be simplified, the cost is reduced, the consistency of products is improved, and the performance of the ultrasonic sensor is more close to a theoretical design value.
As a specific embodiment, the upper end surface and the lower end surface of the piezoelectric ceramic piece 4 are respectively provided with a lead terminal, which includes an upper lead terminal 401 and a lower lead terminal 402, and the lead terminals are used for electrically connecting with the terminal wire 7. Since the piezoelectric ceramic piece 4 is embedded in the matching layer 1 during the curing process of the matching layer 1, when the embedding side of the piezoelectric ceramic piece 4 is provided with the upper lead terminal 401, the matching layer 1 is adaptively attached to the upper lead terminal 401 without reserving a space for placing the upper lead terminal 401 in the matching layer 1 in advance, and without considering the number of the embedded side lead terminals of the piezoelectric ceramic piece 4 and the shape of the lead terminals. The problems that the contact surfaces of the piezoelectric ceramic chip and the matching layer are not parallel, the center of gravity of the piezoelectric ceramic chip is unbalanced, and concentricity is affected are avoided, and the problems that the piezoelectric ceramic chip emits ultrasonic signals to the outside due to the fact that the contact surfaces of the piezoelectric ceramic chip and the matching layer are not parallel and the performance is affected due to the fact that the lead ends are arranged are also solved.
In addition, in order to ensure the strength of the connection end of the matching layer and the plastic shell table surface, the diameter of the front end face 403 of the matching layer 1 is at least 1mm larger than the diameter of the piezoelectric ceramic plate 4, and the diameter of the front end face 403 of the matching layer 1 is at least 1mm larger than the diameter of the piezoelectric ceramic plate 4, so that the strength of the side wall of the matching layer can be ensured.
Further, an annular groove is formed between the matching layer 1 and the plastic shell 3 for filling the vibration reduction material 2. As a preferable mode of the present invention, the vibration damping layer 2 is divided into a first vibration damping layer and a second vibration damping layer in the axial direction of the plastic case 3, the width of the first vibration damping layer in the radial direction of the plastic case 3 is smaller than the width of the second vibration damping layer in the radial direction of the plastic case 3, and the distance from the interface between the first vibration damping layer and the second vibration damping layer to the plastic case end face 302 is greater than or equal to the distance from the lower end face of the piezoelectric ceramic piece 4 to the plastic case end face 302.
The thickness of the vibration damping layer is thicker, but after the thickness of the vibration damping layer is thickened, the width of the connecting surface reserved on the table top 301 for the matching layer and the table top is reduced, so that the width of the connecting surface between the matching layer and the table top is not broken, and the thickness of the vibration damping layer can be increased, therefore, the vibration damping layer 2 is divided into the first vibration damping layer 201 and the second vibration damping layer 202 in the axial direction of the plastic shell 3, the first vibration damping layer 201 is narrow and is used for being connected with the table top, the second vibration damping layer 202 is wide and is used for increasing the vibration damping effect, and the vibration damping layer presents an L shape in terms of section. Considering that the vibration damping layer dampens the piezoelectric ceramic 4 without damping the damping layer on the piezoelectric ceramic 4, the distance from the interface between the first vibration damping layer 201 and the second vibration damping layer 202 to the molded case end face 302 is greater than or equal to the distance from the upper end face of the piezoelectric ceramic 4 to the molded case end face 302, that is, the interface between the first vibration damping layer 201 and the second vibration damping layer 202 is bounded by the interface between the piezoelectric ceramic 4 and the damping layer, so that the performance effect is optimal.
The shape of the damping layer 1 is narrow at the top and wide at the bottom, also because it is determined by the mould during the shaping of the matching layer, which shape facilitates demoulding. The effect of the vibration reduction layer 2 for inhibiting residual vibration is achieved in two aspects, namely, the first vibration reduction layer 201 is used for blocking the side wall of the rear end face of the matching layer from being in hard contact with the plastic shell; the second is that the axial height of the vibration damping layer exceeds the lower end face of the piezoelectric ceramic plate 4.
As a preferred embodiment of the present invention, the side of the vibration reduction layer 2 located on the end face 302 of the plastic shell is concave. The concave structure is arranged in the vibration reduction layer 2, so that the emission sound pressure and the receiving sensitivity of the piezoelectric ceramic plate 4 are not influenced by forced clamping of the shell wall, the intensity of vibration emission signals and echo signals is enhanced, and the accuracy of short-distance measurement is improved when the ultrasonic sensor is used for high-frequency distance measurement.
Example 2
Embodiment 2 differs from embodiment 1 in that the ultrasonic sensor includes a PCB 21 in addition to a plastic case 3, a piezoelectric ceramic sheet 4, a matching layer 1, a vibration damping material 2, a damping material 5, a potting material 6, and a terminal wire 7, and a sectional view of the ultrasonic sensor with the PCB is shown in fig. 5. The PCB 21 has the function of better fixing the positive and negative leads and the terminal wires on the piezoelectric ceramic plate 4, and ensuring the stability and reliability of the electrical connection. The PCB 21 is fixed on the damping material 5 through the adhesive glue 20 and is positioned between the damping material 5 and the encapsulating material 6.
Example 3
An ultrasonic sensor is assembled by the following steps: firstly, the piezoelectric ceramic sheet 4 welded with the positive and negative leads is fixed on a chip positioning tool, and the chip positioning tool and the plastic shell 3 are fixed together. Filling the matching layer 1 in a matching layer forming tool, fixing the matching layer forming tool, a chip positioning tool and a plastic shell 3, and heating and curing to obtain the whole shown in fig. 2. The terminal wire 7 is connected with the piezoelectric ceramic plate 4, the positive end surface of the piezoelectric ceramic plate 4 is sequentially filled with damping material 5 and potting material 6, and finally vibration reduction material 2 is filled.
As shown in fig. 4, the rear end face of the matching layer 1 is well attached to the inner table 301 of the plastic housing 3, and the strength of the side wall of the matching layer 1 is sufficient, so that the matching layer 1, the plastic housing 3 and the piezoelectric ceramic plate 4 are well integrated. As shown in fig. 5, the sidewall strength of the matching layer 1 is insufficient, resulting in damage to the matching layer 1.
According to the sensor assembly step, a pair of sensors A and B are assembled, and the height of the front end face of the matching layer 1 of the corresponding sensor is 0.05mm-0.5mm higher than that of the plastic shell 3. The function signal generator is used as a driving source, the oscilloscope is used for receiving, the sensors A and B are used for correlation, square waves, 10Vpp and 9 waves are used for driving, the correlation distance is 5cm, the thickness of the matching layer 1 is polished in sequence, and different driving frequencies are adjusted, so that the receiving waveform shown in figure 8 is obtained. The specific results are shown in the following table:
Table 1 test data for correlation of sensors a and B
Fig. 8 is a schematic diagram of echo sensitivity received by the oscilloscope when the sensor AB is correlated. When the height of the end face of the matching layer is 0.5mm higher than that of the plastic shell 3, the resonant frequency of the sensors A and B is 270kHz, the driving frequency of the function signal generator is set to be 280kHz, and the echo sensitivity of AB correlation is 10.4mV; polishing the thickness of the matching layer by using sand paper, when the end face height of the matching layer is 0.3mm higher than that of the plastic shell 3, the resonance frequency of the sensors A and B is 280kHz, the driving frequency of the function signal generator is set to be 290kHz, and the echo sensitivity of AB correlation is 23.6mV; and (3) polishing the thickness of the matching layer by sand paper continuously, and when the end face height of the matching layer is 0.1mm higher than that of the plastic shell 3, setting the resonant frequency of the sensors A and B to be 290kHz, setting the driving frequency of the function signal generator to be 300kHz, so that the echo sensitivity of AB correlation is 30.4mV.
Since the front end surface of the matching layer 1 is 0.05mm-0.5mm higher than the plastic shell, the height matched with the resonance frequency can be polished out to improve the loop sensitivity.
Example 4
As a preferable embodiment of the present invention, the matching layer 1 and the mesa 301 are connected by a boss 405, specifically, fig. 9 shows an example in which the boss connecting the lower end surface of the matching layer and the mesa is designed as a right-angle side, the boss 405 may also be designed in a state of small diameter and large diameter, and the boss 405 connecting the lower end surface of the matching layer and the mesa is designed as a slant structure as shown in fig. 10. The boss 405 of the matching layer is designed to be an inclined plane, on the one hand, based on the consideration of a die, the die is convenient to clean, easy to demould and difficult to deposit ash; on the other hand, the sensor is designed to be inclined, and in the working process of the sensor, the side wall of the lower end face of the matching layer is free from stress concentration, so that the side wall of the matching layer is higher in strength. The stress simulation diagram of the boss 405, which is used for connecting the lower end surface of the matching layer with the table top, is designed as a right-angle side by using simulation software analysis, as shown in fig. 11, and certain stress distribution exists on the side wall of the matching layer, wherein the numerical value is 1×10 4~2×104N/m2, so that the risk of damage to the side wall of the matching layer exists in the working engineering of the sensor; the boss 405 connecting the lower end surface of the matching layer with the table top is designed as an inclined plane stress analysis simulation diagram, as shown in fig. 12, and after the inclined plane is designed, the stress distribution of the side wall of the matching layer is very small, and the maximum value is 3000N/m 2.
Further, the angle a between the oblique side and the bottom side in the cross section of the boss 405 is preferably in the range of 40 ° to 60 °.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims (12)

1. An ultrasonic sensor comprises a plastic shell (3), a piezoelectric ceramic plate (4) and a matching layer (1), and is characterized in that,
The piezoelectric ceramic piece (4) is connected with the matching layer (1), the plastic shell (3) is connected with the matching layer (1), and the piezoelectric ceramic piece (4), the plastic shell (3) and the matching layer (1) are connected into a whole in the curing and forming process of the matching layer (1);
The piezoelectric ceramic piece (4), the plastic shell (3) and the matching layer (1) are connected into a whole in the curing and forming process of the matching layer (1), which specifically means that: placing a plastic shell (3) and a piezoelectric ceramic sheet (4) at a position which can be connected with a matching layer, reserving a reserved space for filling a liquid matching layer material, and injecting the liquid matching layer material into the reserved space, wherein the piezoelectric ceramic sheet (4) is connected with the matching layer (1) in the process of solidifying and forming the liquid matching layer material into the matching layer (1), the plastic shell (3) is connected with the matching layer (1), and the plastic shell (3), the piezoelectric ceramic sheet (4) and the matching layer (1) are connected and formed at one time;
the matching layer (1) is a groove, and the piezoelectric ceramic piece (4) is embedded into the bottom of the groove;
a table top (301) on the inner side wall of the plastic shell (3) is connected with the matching layer (1);
the matching layer (1) is adhered to the inner table top (301) of the plastic shell (3) and the inner wall of the plastic shell (3) after being solidified.
2. An ultrasonic sensor according to claim 1, characterized in that part of the piezoceramic wafer (4) is embedded in the matching layer (1).
3. An ultrasonic sensor according to claim 2, characterized in that the piezoelectric ceramic plate (4) is embedded in one side of the matching layer (1) with lead terminals for electrical connection with terminal wires (7).
4. An ultrasonic sensor according to claim 1, characterized in that the width of the connection surface of the matching layer (1) to the mesa (301) in the radial direction of the plastic housing (3) is 1/2-4/5 of the width of the mesa (301) in the radial direction of the plastic housing (3).
5. The ultrasonic sensor according to claim 4, further comprising a damping layer (5), a potting layer (6) and a terminal wire (7), wherein the damping layer (5) and the potting layer (6) are sequentially connected in a space, away from the matching layer (1), in the plastic housing (3), one end of the terminal wire (7) is embedded into the potting layer (6), the piezoelectric ceramic sheet (4) is located between the damping layer (5) and the matching layer (1), and the piezoelectric ceramic sheet (4) is electrically connected with one end, embedded into the potting layer (6), of the terminal wire (7).
6. An ultrasonic sensor according to claim 5, further comprising a PCB board (21), said PCB board (21) being located between said damping layer (5) and said potting layer (6), said piezoelectric ceramic sheet (4) being electrically connected to said PCB board (21), said terminal wires (7) being electrically connected to said PCB board (21).
7. An ultrasonic sensor according to claim 1, characterized in that an annular groove space is formed between the inner side wall of the table top (301), the plastic housing (3) and the outer side wall of the matching layer (1), and a vibration damping layer (2) is arranged in the annular groove space.
8. An ultrasonic sensor according to claim 7, wherein the vibration damping layer (2) is divided into a first vibration damping layer and a second vibration damping layer in the axial direction of the molded case (3), the width of the first vibration damping layer in the radial direction of the molded case (3) is smaller than the width of the second vibration damping layer in the radial direction of the molded case (3), and the distance from the interface between the first vibration damping layer and the second vibration damping layer to the molded case end face (302) is greater than or equal to the distance from the upper end face of the piezoelectric ceramic sheet (4) to the molded case end face (302).
9. An ultrasonic sensor according to claim 8, wherein the side of the vibration damping layer (2) at the end face (302) of the plastic housing is concave.
10. An ultrasonic sensor according to claim 9, characterized in that the front end face of the matching layer (1) is 0.05mm-0.5mm higher than the plastic case end face (302) of the plastic case (3).
11. An ultrasonic sensor according to claim 1 wherein said matching layer (1) is connected to said mesa (301) by a boss (405), said boss (405) having a smaller diameter at the top and a larger diameter at the bottom.
12. An ultrasonic transducer according to claim 11 wherein the angle between the oblique side and the bottom side in the cross-sectional view of the boss (405) is in the range 40 ° to 60 °.
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