Ultrasound sensor

Abstract

An ultrasonic sensor includes a piezoelectric body, an acoustic impedance matching layer, a stress balancing layer, and a damping body, the stress balancing layer is in contact with the piezoelectric body, the stress balancing layer has a hardness greater than that of the damping body, and the stress balancing layer has an acoustic impedance less than 5 MRayl.

Description

Technical Field

[0001] This invention relates to an ultrasonic sensor, and more particularly to an ultrasonic sensor comprising a stress balancing layer. Background Technology

[0002] Ultrasonic transducers can be used for short-range object detection. They calculate the distance between the ultrasonic sensor and the object by measuring the time-of-flight (ToF) of the emitted ultrasonic waves after they collide with and reflect back from the object. For ultrasonic detection, the type and properties of the object being detected are not significantly limited; solids, liquids, or powders of various surface colors, transparency, and hardness can all be detected using ultrasonic sensors. Therefore, ultrasonic sensors are now widely used in parking sensors, level sensors, multiple sheet detection, and flow meters.

[0003] The main component of an ultrasonic sensor is piezoelectric ceramics, such as ceramics made of lead zirconate titanate (PZT), which are coated with conductive layers on both sides. During operation, applying a high-frequency alternating current signal causes the piezoelectric ceramic to vibrate at a high frequency. This high-frequency vibration is a sound wave; if the frequency of this sound wave falls within the ultrasonic range, it is ultrasonic vibration. To allow the generated ultrasonic waves to be transmitted from the piezoelectric ceramic to the air, an acoustic impedance matching layer is placed between the piezoelectric ceramic and the air, matching their acoustic impedance and thus effectively transmitting the ultrasonic waves into the air. The commonly used matching layer material in the industry is a composite material made of polymer resin and hollow glass spheres, achieving low acoustic impedance characteristics while also possessing good weather resistance and reliability. However, the vibrations generated by piezoelectric ceramics are transmitted simultaneously towards both the front end (emitting end) and the back end. If the ultrasound waves emitted towards the back cannot be eliminated, there will be significant reverberation when using this ultrasonic sensor. This reverberation can cause signal recognition failure. Therefore, a damping layer becomes an essential component in ultrasonic sensors. It is placed around the piezoelectric ceramic and / or acoustic impedance matching layer to quickly eliminate the residual vibrations of the piezoelectric ceramic. The damping layer commonly used in the industry is a composite material made of polymer resin mixed with metal or ceramic particles. Its acoustic impedance is similar to that of the piezoelectric ceramic, thus absorbing more of the back-transmitted ultrasound waves and reducing the residual vibrations of the ultrasonic sensor. Summary of the Invention

[0004] To provide the reader with a basic understanding of the invention, the following paragraphs offer a brief description of the invention. This summary is not an exhaustive overview of the invention, nor is it intended to represent all key or essential elements of the invention or to limit its scope. Its purpose is merely to present some concepts in a simplified form before proceeding with the detailed description of the invention to be discussed below.

[0005] The purpose of this invention is to propose a novel ultrasonic sensor, characterized by the addition of a stress-balancing layer between the piezoelectric ceramic and the damping material. This layer mitigates thermal stress on the piezoelectric ceramic caused by the difference in thermal expansion coefficients under high and low temperature environments, preventing cracking of the piezoelectric ceramic. Secondly, the material of this stress-balancing layer differs from commonly used high-density, high-acoustic-impedance damping material; it has a relatively low density and acoustic impedance, thus reducing ultrasonic wave transmission from the back of the piezoelectric ceramic and improving the overall sensor's emission sensitivity. This ultrasonic sensor with a stress-balancing layer structure enhances reliability and provides flexibility in the configuration of damping materials.

[0006] One embodiment of the present invention provides an ultrasonic sensor comprising a piezoelectric element having a first surface and a second surface opposite to each other, separated by a first surface and a side surface connecting the first surface and the second surface; an acoustic impedance matching layer having a third surface and a fourth surface opposite to each other, separated by a third surface, and the third surface being in contact with the second surface of the piezoelectric element; a stress balancing layer having a fifth surface and a sixth surface opposite to each other, separated by a stress balancing layer, the sixth surface being in contact with the first surface of the piezoelectric element; the hardness of the stress balancing layer being greater than the hardness of the damping body, and the acoustic impedance of the stress balancing layer being less than 5 MRayl; and a damping body covering the stress balancing layer and / or the piezoelectric element and / or the acoustic impedance matching layer.

[0007] Another embodiment of the present invention provides an ultrasonic sensor in which the stress balancing layer has a through hole penetrating the fifth and sixth surfaces of the stress balancing layer.

[0008] Another embodiment of the present invention provides an ultrasonic sensor in which the outer edge of the sixth surface of the stress balance layer can extend forward to connect with the side surface of the piezoelectric body.

[0009] Another embodiment of the present invention provides an ultrasonic sensor having a barrel-shaped carrier housing a piezoelectric element, an acoustic impedance matching layer, a stress balancing layer, and a shock absorber.

[0010] Another embodiment of the present invention provides an ultrasonic sensor having a tubular support housing a piezoelectric element, an acoustic impedance matching layer, a stress balancing layer, and a shock absorber.

[0011] These and other objects of the present invention will become clearer to the reader after reading the detailed description of the preferred embodiments, which are illustrated in various figures and drawings below. Attached Figure Description

[0012] This specification includes accompanying drawings, which form part of the document, to provide the reader with a further understanding of embodiments of the invention. These drawings depict some embodiments of the invention and, together with the description herein, illustrate its principles. In these drawings:

[0013] Figure 1 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 1 of the present invention is shown;

[0014] Figure 2 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 2 of the present invention is shown;

[0015] Figure 3 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 3 of the present invention is shown;

[0016] Figure 4 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 4 of the present invention is shown;

[0017] Figure 5 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 5 of the present invention is shown;

[0018] Figure 6 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment Six of the present invention is shown;

[0019] Figure 7 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 7 of the present invention is shown;

[0020] Figure 8 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 8 of the present invention is shown;

[0021] Figure 9 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 9 of the present invention is shown;

[0022] Figure 10 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 10 of the present invention is shown.

[0023] The reference numerals in the attached figures are explained as follows:

[0024] 1, 2, 3, 4, 5, 6, 7, 8, 9, 10: Ultrasonic sensors

[0025] 10: Piezoelectric material

[0026] 10A: First surface

[0027] 10B: Second Surface

[0028] 10C: Side surface

[0029] 10D: Side surface

[0030] 20: Acoustic impedance matching layer

[0031] 20A: Third Surface

[0032] 20B: Fourth Surface

[0033] 30: Stress balancing layer

[0034] 30A: Fifth Surface

[0035] 30B: Sixth Surface

[0036] 32: Through hole

[0037] 40: Shock absorber

[0038] 50: Barrel-shaped support body

[0039] 50A: Seventh Surface

[0040] 50B: Eighth Surface

[0041] 51: Bottom of the bucket

[0042] 52: Barrel body

[0043] 60: Tubular support body

[0044] 61: Inner surface

[0045] 62: Outer surface

[0046] 63: First Opening

[0047] 64: Second opening

[0048] 70: Support body

[0049] 70A: Third Surface

[0050] 70B: Fourth Surface Detailed Implementation

[0051] In the following detailed description of the invention, element reference numerals are indicated as part of the accompanying illustrations and are described in a manner specific to which the embodiments may be practiced. Such embodiments are described in sufficient detail to enable those skilled in the art to implement them. For clarity, the dimensions of some elements may be exaggerated in the illustrations. The reader should understand that other embodiments may be utilized in the invention, or structural, logical, and electrical changes may be made without departing from the described embodiments. Therefore, the following detailed description should not be considered limiting; rather, the embodiments included therein are defined by the appended claims.

[0052] Please refer to Figure 1 , Figure 1 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 1 of the present invention is shown. Figure 1 As shown, the ultrasonic sensor 1 in this embodiment includes a piezoelectric element 10, an acoustic impedance matching layer 20, a stress balancing layer 30, and a damping element 40. The piezoelectric element 10 is located between the acoustic impedance matching layer 20 and the stress balancing layer 30, while the damping element 40 covers the stress balancing layer 30, and / or covers the piezoelectric element 10, and / or covers the acoustic impedance matching layer 20.

[0053] More specifically, in this embodiment, the piezoelectric element 10 has a first surface 10A and a second surface 10B separated from the first surface 10A by the piezoelectric element 10, and also has side surfaces 10C and 10D connecting the first surface 10A and the second surface 10B. The acoustic impedance matching layer 20 has a third surface 20A and a fourth surface 20B separated from the third surface 20A by the acoustic impedance matching layer 20, and the third surface 20A of the acoustic impedance matching layer 20 is in contact with the second surface 10B of the piezoelectric element 10. The stress balancing layer 30 has a fifth surface 30A and a sixth surface 30B separated from the fifth surface 30A by the stress balancing layer 30, wherein the sixth surface 30B of the stress balancing layer 30 is in contact with the first surface 10A of the piezoelectric element 10. Furthermore, the damper 40 is in contact with the fifth surface 30A of the stress balancing layer 30 and covers the sidewalls of the stress balancing layer 30. In addition, in this embodiment, the damper 40 also covers the sidewalls of the piezoelectric element 10 and partially covers the sidewalls of the acoustic impedance matching layer 20. However, it is worth noting that the coverage area of ​​the damper 40 may be adjusted according to actual needs. That is, in other embodiments of the present invention, the damper 40 may cover more or fewer layers of surfaces or sidewalls, and the present invention is not limited thereto.

[0054] In this embodiment, the piezoelectric element 10 is made of piezoelectric ceramics, such as barium titanate (BaTiO3), lead titanate (PbTiO3), and lead zirconate titanate (Pb(ZrTi)O3, PZT), but is not limited to these. The acoustic impedance matching layer 20 is made of organic polymer materials or composite materials made of organic polymer materials mixed with hollow or solid powders. For example, organic polymer materials include epoxy resin, vinyl ester resin, UV-curable adhesive (UV adhesive), polyurethane, acrylic resin, or cyanate ester resin, but are not limited to these. The stress balancing layer 30 is made of organic polymer materials or composite materials composed of organic polymer materials mixed with hollow or solid powders. Examples of organic polymer materials include epoxy resin, vinyl ester resin, UV-curable adhesive, polyurethane, acrylic resin, or cyanate ester resin, but are not limited to these. The damping body 40 is made of organic polymer materials or composite materials composed of organic polymer materials mixed with metal or ceramic particles. These organic polymer materials include epoxy resin, polyurethane, or silicone, but are not limited to these.

[0055] In this embodiment, the piezoelectric element 10 functions to generate ultrasound through high-frequency vibration. This is because the acoustic impedance of the piezoelectric element 10 is approximately 35 MTayl, 35*10. 6 (approximately kg / m²·s) and air resistance (approximately 4*10) -4 The acoustic impedance difference between the piezoelectric element 10 and the air is five orders of magnitude. Therefore, an acoustic impedance matching layer 20 is needed between the piezoelectric element 10 and the air to match the acoustic impedance of the piezoelectric element 10 and the air, thereby effectively transmitting the ultrasound waves into the air. Additionally, the purpose of the damper 40 is to reduce the reverberation generated when using the ultrasound sensor. The piezoelectric element 10, acoustic impedance matching layer 20, and damper 40 are all common components of existing ultrasound sensors. Their detailed principles and materials are prior art and will not be elaborated upon here.

[0056] However, existing ultrasonic sensors have a drawback: the acoustic impedance matching layer is only located on one side of the piezoelectric element. Therefore, they are prone to breakage under temperature cycling tests due to the significant difference in thermal expansion coefficients between the piezoelectric element and the acoustic impedance matching layer. More specifically, typical ultrasonic sensors usually undergo temperature cycling tests (e.g., cycling from approximately -40°C to +85°C) before leaving the factory to test their reliability under varying ambient temperatures. The applicant discovered that in existing ultrasonic sensors (i.e., ultrasonic sensors that only contain a piezoelectric element, an acoustic impedance matching layer, and a damping element), the acoustic impedance matching layer is only located on one side of the piezoelectric element. In addition, the thermal expansion coefficients of the piezoelectric element and the acoustic impedance matching layer are significantly different (generally, the thermal expansion coefficient of the piezoelectric element is about 5 PPM, while that of the acoustic impedance matching layer is about 50 PPM, a difference of nearly 10 times). Therefore, during temperature cycling tests, the one-sided surface of the piezoelectric element, that is, the surface adjacent to the acoustic impedance matching layer, is easily subjected to significant compressive / tensile forces, which can cause the piezoelectric element to break.

[0057] The reason for the piezoelectric material's breakage is mainly due to the acoustic impedance matching layer being only applied to one side of the piezoelectric material, while the other side is directly connected to the damping element. Therefore, when thermal expansion and contraction occur, the piezoelectric material experiences significant stress from only one side (i.e., the acoustic impedance matching layer), leading to breakage. Therefore, this embodiment is characterized by the additional provision of a stress balancing layer 30 on the other side of the piezoelectric material 10 (i.e., the surface opposite to the acoustic impedance matching layer 20). In some embodiments, the stress balancing layer 30 can be made of the same material as the acoustic impedance matching layer 20, and the stress balancing layer 30 and the acoustic impedance matching layer 20 are respectively applied to both sides of the piezoelectric material 10. Therefore, during temperature cycling tests, the stress borne by the piezoelectric material 10 will be evenly distributed to both sides, achieving a bilateral stress balance and preventing the piezoelectric material 10 from experiencing stress from only one side and thus breaking.

[0058] It is worth noting that in this invention, the stress balancing layer 30 and the damping body 40 are different layers, and preferably contain different materials. Since the material and purpose of the damping body 40 are different from those of the stress balancing layer 30, this invention preferably does not use all or part of the damping body 40 to replace the stress balancing layer 30. In this embodiment, the hardness of the stress balancing layer 30 is greater than that of the damping body 40, and the acoustic impedance of the stress balancing layer 30 is less than 5 MRayl. The addition of the stress balancing layer 30 between the piezoelectric body 10 and the damping body 40 in this invention effectively improves the reliability and durability of the ultrasonic sensor compared to existing technologies (i.e., structures without a stress balancing layer). According to the applicant's actual test results, existing ultrasonic sensors may experience piezoelectric body breakage after approximately 10 temperature cycle tests. However, with the addition of the stress balancing layer 30, the ultrasonic sensor 1 can remain intact after more than 50 temperature cycle tests, thus significantly improving the reliability of the ultrasonic sensor.

[0059] In addition to improving reliability, the ultrasonic sensor of the present invention can also adjust the parameters of the stress balancing layer 30, such as adjusting the thickness or material, to reduce the efficiency of the ultrasonic waves generated by the piezoelectric body 10 being transmitted from the back side, thereby improving the front emission performance of the ultrasonic sensor 1.

[0060] The following description will focus on different embodiments of the ultrasonic sensor of the present invention. For the sake of simplicity, the description will mainly focus on the differences between the embodiments, and will not repeat the same points. In addition, the same elements in the embodiments of the present invention are identified by the same reference numerals to facilitate comparison between the embodiments.

[0061] Figure 2 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 2 of the present invention is shown. Figure 2 As shown, the ultrasonic sensor in this embodiment is different from the ultrasonic sensor described in Embodiment 1 above (see...). Figure 1 Similar to the previous embodiment, the main difference lies in that the stress balancing layer 30 in the ultrasonic sensor 2 of this embodiment further includes multiple through holes 32, wherein the through holes 32 are hollow pore structures penetrating the fifth surface 30A and the sixth surface 30B of the stress balancing layer 30. From its cross-section, its shape includes, but is not limited to, circles, rectangles, triangles, irregular shapes, or other shapes. In this embodiment, the through holes 32 have the effect of reducing the overall density of the stress balancing layer 30, thereby achieving the advantage of low acoustic impedance and improving the sensitivity of ultrasonic waves emitted from the front acoustic impedance matching layer. Apart from the above features, the material properties or structures of other components in this embodiment are the same as those described in Embodiment 1 above, and will not be repeated here.

[0062] Figure 3A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 3 of the present invention is shown. Figure 3 As shown, the ultrasonic sensor in this embodiment is different from the ultrasonic sensor described in Embodiment 1 above (see...). Figure 1 Similar to the previous embodiment, the main difference lies in that, in this embodiment, the stress balancing layer 30 in the ultrasonic sensor 3 not only covers the first surface 10A of the piezoelectric body 10, but also partially extends to cover the sides 10C and 10D of the piezoelectric body 10. That is, the outer edge of the sixth surface 30B of the stress balancing layer 30 can extend forward to connect with the side surfaces 10C and 10D of the piezoelectric body 10. This more effectively protects the piezoelectric body 10 and makes its sidewalls less prone to breakage. Apart from the above features, the material properties or structures of other components in this embodiment are the same as those described in Embodiment 1 above, and will not be repeated here.

[0063] Figure 4 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 4 of the present invention is shown. Figure 4 As shown, the ultrasonic sensor 4 in this embodiment is similar to the ultrasonic sensor described in Embodiment 1 above (see [link]). Figure 1 Similar to the previous embodiment, the main difference lies in that, in this embodiment, the ultrasonic sensor 4 further includes a barrel-shaped support body 50, in which the piezoelectric element 10, acoustic impedance matching layer 20, stress balancing layer 30, and shock absorber 40 are located within the barrel-shaped support body 50. More specifically, the barrel-shaped support body 50 has a bottom 51 and a body 52, and has a seventh surface 50A and an eighth surface 50B facing each other across the bottom 51. The piezoelectric element 10, acoustic impedance matching layer 20, stress balancing layer 30, and shock absorber 40 are disposed within the barrel-shaped support body 50, and the seventh surface 50A of the bottom 51 of the barrel-shaped support body 50 is in contact with the fourth surface 20B of the acoustic impedance matching layer 20. The barrel-shaped support body 50 can serve as the outer shell of the ultrasonic sensor 4, protecting other internal components. The material of the barrel-shaped support body 50 can include metal, plastic, polymer materials, etc., but is not limited to these. Apart from the features mentioned above, the material properties or structures of other components in this embodiment are the same as those described in Embodiment 1 above, and will not be repeated here.

[0064] Figure 5 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 5 of the present invention is shown. Figure 5 As shown, the ultrasonic sensor 5 in this embodiment is different from the ultrasonic sensor described in Embodiment 1 above (see...). Figure 1Similar to the previous embodiment, the main difference lies in that the ultrasonic sensor 5 in this embodiment further includes a tubular support 60, in which the piezoelectric element 10, acoustic impedance matching layer 20, stress balancing layer 30, and shock absorber 40 are located within the tubular support 60. More specifically, the tubular support 60 has opposing inner surfaces 61 and outer surfaces 62, as well as opposing first openings 63 and second openings 64, and the shock absorber 40 covers the piezoelectric element 10 and stress balancing layer 30. The inner surface 61 of the tubular support 60 surrounds and is in contact with the shock absorber 40, and the fourth surface 20B of the acoustic impedance matching layer 20 is exposed from the first opening 63 of the tubular support 60. The tubular support 60 can also protect other internal components. In addition, the tubular support 60 makes it easier to control the ultrasonic wave emission direction. Apart from the above features, the material properties or structures of other components in this embodiment are the same as those described in Embodiment 1 above, and will not be repeated here.

[0065] In addition to the barrel-shaped or tubular support bodies described above, some embodiments may include support bodies of other shapes, such as plate-shaped support bodies. In other embodiments, plate-shaped support bodies may be used instead of acoustic impedance matching layers. Figure 6 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment Six of the present invention is shown. Figure 6 As shown. The ultrasonic sensor 6 in this embodiment is the same as the ultrasonic sensor described in Embodiment 1 above (see...). Figure 1Similarly, this embodiment also includes a piezoelectric element 10, a stress balancing layer 30, and a damping element 40. However, in this embodiment, a load-bearing element 70 replaces the acoustic impedance matching layer 20 in the first embodiment. More specifically, this embodiment includes: a piezoelectric body 10 having a first surface 10A and a second surface 10B facing each other across the piezoelectric body 10, and side surfaces 10C and 10D connecting the first surface 10A and the second surface 10B; a carrier 70 having a third surface 70A and a fourth surface 70B facing each other across the carrier 70, and the third surface 70A being in contact with the second surface 10B of the piezoelectric body 10; a stress balancing layer 30 having a fifth surface 30A and a sixth surface 30B facing each other across the stress balancing layer 30, the sixth surface 30B being in contact with the first surface 10A of the piezoelectric body 10, and the acoustic impedance of the stress balancing layer being less than 5MRayl; and a damping body 40 covering the stress balancing layer 30, and / or the piezoelectric body 10, and / or the carrier 70, and the hardness of the stress balancing layer 30 being greater than the hardness of the damping body 40. In this embodiment, the carrier 70 is used as the acoustic impedance matching layer in the original embodiment one, which can save some component space and simplify the manufacturing process. The carrier 70 can also be made of a similar material to the acoustic impedance matching layer, such as an organic polymer material or a composite material made of organic polymer materials mixed with hollow or solid powders. The organic polymer material includes epoxy resin, vinyl ester resin, UV-curable adhesive, polyurethane, acrylic resin, or cyanate ester resin, or metallic materials such as aluminum, titanium, copper, or stainless steel, or non-metallic materials such as glass, acrylic, Teflon (PTFE), polyvinyl difluoroethylene (PVDF), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polybutyl terephthalate (PBT), acrylonitrile-butadiene-styrene copolymer (ABS), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), or polyetheretherketone (PEEK), but is not limited to these. Apart from the features mentioned above, the material properties or structures of other components in this embodiment are the same as those described in Embodiment 1 above, and will not be repeated here.

[0066] Figure 7 A schematic cross-sectional view of the ultrasonic sensor according to Embodiment 7 of the present invention is shown. Figure 8 A schematic cross-sectional view of the ultrasonic sensor according to Embodiment 8 of the present invention is shown. Figure 9 A schematic cross-sectional view of an ultrasonic sensor according to Embodiment Nine of the present invention is shown. In these embodiments, the concept of replacing the acoustic impedance matching layer with a carrier, as described in Embodiment Six above, can be applied here. Figure 7As shown, the ultrasonic sensor 7 described in Embodiment 7 and the ultrasonic sensor described in Embodiment 2 (see Example 2) are similar in function to each other. Figure 2 Similar to the previous embodiment, the difference lies in that the ultrasonic sensor 7 in this embodiment does not include an acoustic impedance matching layer, but instead uses a carrier 70 to replace the acoustic impedance matching layer. The material and characteristics of the carrier 70 have been described in the above embodiments and will not be repeated here. Apart from the above features, the material characteristics or structures of other components in this embodiment are the same as those described in the above embodiments and will not be repeated here.

[0067] Similarly, as Figure 8 As shown, the ultrasonic sensor 8 described in Embodiment 8 and the ultrasonic sensor described in Embodiment 3 (see Example 3) are similar in function to each other. Figure 3 Similar to the previous embodiment, the difference lies in that the ultrasonic sensor 8 in this embodiment does not include an acoustic impedance matching layer, but instead uses a carrier 70 to replace the acoustic impedance matching layer. The material and characteristics of the carrier 70 have been described in the above embodiments and will not be repeated here. Apart from the above features, the material characteristics or structures of other components in this embodiment are the same as those described in the above embodiments and will not be repeated here.

[0068] Similarly, such as Figure 9 As shown, the ultrasonic sensor 9 described in Embodiment 9 and the ultrasonic sensor described in Embodiment 4 (see Example 4) Figure 4 Similar to the previous embodiment, the difference lies in that the ultrasonic sensor 9 in this embodiment does not include an acoustic impedance matching layer, but instead uses a barrel-shaped support 50 to replace the acoustic impedance matching layer. The material and characteristics of the barrel-shaped support 50 have been described in the above embodiments and will not be repeated here. Apart from the above features, the material characteristics or structures of other components in this embodiment are the same as those described in the above embodiments and will not be repeated here.

[0069] Figure 10 A cross-sectional structural schematic diagram of an ultrasonic sensor according to Embodiment 10 of the present invention is shown. In this embodiment, the structure of the ultrasonic sensor 10 is similar to that of the ultrasonic sensor 4 described in Embodiment 4, but the difference is that in this embodiment, the acoustic impedance matching layer 20 is disposed on the outside of the barrel-shaped support 50, that is, the third surface 20A of the acoustic impedance matching layer 20 is connected to the eighth surface 50B of the barrel-shaped support 50. Apart from the above features, the material properties or structures of other components in this embodiment are the same as those described in the above embodiments, and will not be repeated here.

[0070] In summary, the purpose of this invention is to propose a novel ultrasonic sensor characterized by the addition of a stress-balancing layer between the piezoelectric ceramic and the damping material. This layer mitigates thermal stress on the piezoelectric ceramic caused by the difference in thermal expansion coefficients under high and low temperature environments, preventing cracking of the piezoelectric ceramic. Secondly, the material of this stress-balancing layer differs from commonly used high-density, high-acoustic-impedance damping material; it has a relatively low density and acoustic impedance, thus reducing ultrasonic wave transmission from the back of the piezoelectric ceramic and improving the overall sensor's emission sensitivity. This ultrasonic sensor with a stress-balancing layer structure enhances reliability and provides flexibility in the configuration of damping materials.

[0071] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made in accordance with the claims of the present invention shall fall within the protection scope of the present invention.

Claims

1. An ultrasonic sensor, characterized by, Include: A piezoelectric body has a first surface and a second surface opposite to each other separated by the piezoelectric body, and a side surface connecting the first surface and the second surface; An acoustic impedance matching layer has a third surface and a fourth surface that are opposite each other separated by the acoustic impedance matching layer, and the third surface is in contact with the second surface of the piezoelectric element; A stress balancing layer having a fifth surface and a sixth surface opposite each other, the sixth surface being in contact with a first surface of the piezoelectric element, and the acoustic impedance of the stress balancing layer being less than 5 MRayl; and A damping body, covering the stress balancing layer, and / or the piezoelectric element, and / or the acoustic impedance matching layer, wherein the hardness of the stress balancing layer is greater than the hardness of the damping body; The piezoelectric material comprises piezoelectric ceramic, and the stress balancing layer is used to receive and balance the thermal stress caused by the difference in thermal expansion coefficient between the acoustic impedance matching layer and the piezoelectric ceramic, so as to prevent the piezoelectric ceramic from breaking.

2. The ultrasonic sensor of claim 1, wherein, The stress balancing layer is made of organic polymer materials or a composite material made of organic polymer materials mixed with hollow or solid powders. The organic polymer materials include epoxy resin, vinyl ester resin, UV-curable adhesive, polyurethane, acrylic resin, or cyanate ester resin.

3. The ultrasonic sensor of claim 1, wherein, The stress balancing layer has through holes that penetrate the fifth and sixth surfaces of the stress balancing layer.

4. The ultrasonic sensor of claim 1, wherein, The outer edge of the sixth surface of the stress balancing layer can extend forward to connect with the side surface of the piezoelectric element.

5. The ultrasonic sensor of claim 1, wherein, It also includes a barrel-shaped support body having a barrel bottom and a barrel body, and the barrel-shaped support body having a seventh surface and an eighth surface opposite each other across the barrel bottom, wherein the piezoelectric element, the acoustic impedance matching layer, the stress balancing layer and the shock absorber are disposed in the barrel-shaped support body, and the seventh surface of the barrel bottom of the barrel-shaped support body is in contact with the fourth surface of the acoustic impedance matching layer.

6. The ultrasonic sensor of claim 1, wherein, It also includes a tubular support having opposing inner and outer surfaces and opposing first and second openings separated by the tubular support, and the damping body covering the piezoelectric body and the stress balancing layer, wherein the inner surface of the tubular support surrounds and is in contact with the damping body, and the fourth surface of the acoustic impedance matching layer is exposed from the first opening of the tubular support.

7. The ultrasonic sensor of claim 1, wherein, The material of the shock absorber includes organic polymer materials or composite materials made of organic polymer materials mixed with metal or ceramic particles. The organic polymer materials include epoxy resin, polyurethane, or silicone.

8. The ultrasonic sensor of claim 1, wherein, The acoustic impedance matching layer is made of organic polymer materials or a composite material made of organic polymer materials mixed with hollow or solid powders. The organic polymer materials include epoxy resin, vinyl ester resin, UV-curable adhesive, polyurethane, acrylic resin, or cyanate ester resin.

9. An ultrasonic sensor, characterized by Include: A piezoelectric body having a first surface and a second surface opposite to each other separated by the piezoelectric body, and a side surface connecting the first surface and the second surface; A carrier having a third surface and a fourth surface opposite each other, separated by the carrier, and the third surface being in contact with the second surface of the piezoelectric element; A stress balancing layer having a fifth surface and a sixth surface opposite each other separated by the stress balancing layer, the sixth surface being in contact with the first surface of the piezoelectric element, and the acoustic impedance of the stress balancing layer being less than 5 MRayl; as well as A damping body, covering the stress balancing layer and / or the piezoelectric element and / or the load-bearing body, wherein the hardness of the stress balancing layer is greater than the hardness of the damping body; The piezoelectric material comprises piezoelectric ceramic, and the stress balancing layer is used to receive and balance the thermal stress caused by the difference in thermal expansion coefficient between the carrier and the piezoelectric ceramic, so as to prevent the piezoelectric ceramic from breaking.

10. The ultrasonic sensor of claim 9, wherein, The stress balancing layer is made of organic polymer materials or a composite material made of organic polymer materials mixed with hollow or solid powders. The organic polymer materials include epoxy resin, vinyl ester resin, UV-curable adhesive, polyurethane, acrylic resin, or cyanate ester resin.

11. The ultrasonic sensor of claim 9, wherein, The stress balancing layer has through holes penetrating the fifth and sixth surfaces of the stress balancing layer.

12. The ultrasonic sensor of claim 9, wherein, The outer edge of the sixth surface of the stress balancing layer can extend forward to connect with the side surface of the piezoelectric element.

13. The ultrasonic sensor of claim 9, wherein, The carrier further includes a barrel-shaped carrier having a bottom and a body, and the barrel-shaped carrier having a third surface and a fourth surface opposite each other across the bottom, wherein the piezoelectric element, the stress balancing layer and the shock absorber are disposed inside the barrel of the barrel-shaped carrier, and the third surface of the bottom of the barrel-shaped carrier is in contact with the second surface of the piezoelectric element.

14. The ultrasonic sensor of claim 9, wherein, The carrier is made of metallic materials selected from the following groups or combinations thereof: aluminum, titanium, copper, stainless steel, or non-metallic materials selected from the following groups or combinations thereof: glass, acrylic, Teflon, polyvinyl fluoride, polypropylene, polyethylene, polyvinyl chloride, polybutyl terephthalate, acrylonitrile-butadiene-styrene copolymer, polyphenylene sulfide, liquid crystal polymer, or polyetheretherketone.

15. The ultrasonic sensor of claim 9, wherein, The material of the shock absorber includes organic polymer materials or composite materials made of organic polymer materials mixed with metal or ceramic particles. The organic polymer materials include epoxy resin, polyurethane, or silicone.

16. The ultrasonic sensor of claim 9, wherein, It also includes an acoustic impedance matching layer, and the acoustic impedance matching layer is in contact with the fourth surface of the carrier.

17. The ultrasonic sensor of claim 16, wherein, The acoustic impedance matching layer is made of organic polymer materials or a composite material made of organic polymer materials mixed with hollow or solid powders. The organic polymer materials include epoxy resin, vinyl ester resin, UV-curable adhesive, polyurethane, acrylic resin, or cyanate ester resin.

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