CN115728757A

CN115728757A - Ultrasonic sensor

Info

Publication number: CN115728757A
Application number: CN202111095552.1A
Authority: CN
Inventors: 陈隆; 吴玮仁; 杨松儒; 苏益廷
Original assignee: Unictron Technologies Corp
Current assignee: Unictron Technologies Corp
Priority date: 2021-09-01
Filing date: 2021-09-17
Publication date: 2023-03-03
Also published as: TWI772167B; TW202312666A

Abstract

An ultrasonic sensor comprises a piezoelectric body, an acoustic resistance matching layer, a stress balancing layer and a shock absorber, wherein the stress balancing layer is connected with the piezoelectric body, the hardness of the stress balancing layer is greater than that of the shock absorber, and the acoustic resistance of the stress balancing layer is less than 5MRayl.

Description

Ultrasonic sensor

Technical Field

The present invention relates to an ultrasonic sensor, and more particularly, to an ultrasonic sensor including a stress balance layer.

Background

Ultrasonic transducers (ultrasonic transducers) are used for short-distance object detection, and the distance between an ultrasonic transducer and an object to be detected can be calculated by the time of flight (ToF) of the ultrasonic waves reflected by the ultrasonic waves after the ultrasonic waves collide with the object. For ultrasonic detection, the type and properties of the object to be detected are not limited too much, including various surface colors, transparency, hardness of solid, liquid, or powder, etc., which can be detected by the ultrasonic sensor. Therefore, the ultrasonic sensor is widely used in the fields of car backing radar (backing sensor), level sensor (level sensor), multiple sheet detection (multiple sheet detection), and flow meter (flow meter).

The main component of the ultrasonic sensor is piezoelectric ceramics (PZT), such as ceramics made of lead zirconate titanate (PZT) material, and both surfaces of the PZT are coated with conductive layers. In operation, the piezoelectric ceramic is vibrated at a high frequency, which is a sound wave, if the frequency of the sound wave falls within the ultrasonic range, the piezoelectric ceramic is vibrated at the high frequency. In order to transmit the generated ultrasonic wave from the piezoelectric ceramic to the air, an acoustic resistance matching layer is arranged between the piezoelectric ceramic and the air, so that the acoustic resistances of the piezoelectric ceramic and the air are matched, and the ultrasonic wave can be effectively transmitted to the air. The matching layer material commonly used in the industry is a composite material formed by mixing polymer resin and hollow glass spheres, so as to achieve a lower sound resistance characteristic and have better weather resistance and reliability. However, the vibration generated by the piezoelectric ceramic is transmitted towards the front end (emitting end) and the back surface simultaneously, and if the ultrasonic wave emitted towards the back surface cannot be eliminated, when the ultrasonic sensor is used, the ultrasonic sensor has larger reverberation, and the reverberation can cause the signal discrimination to be invalid, so that the damping layer (damping layer) becomes a necessary part in the ultrasonic sensor and is arranged around the piezoelectric ceramic and/or the acoustic impedance matching layer, so that the residual wave of the vibration of the piezoelectric ceramic can be eliminated quickly. The vibration absorber for ultrasonic sensor is a composite material of polymer resin and metal or ceramic particles, and has an acoustic impedance similar to that of piezoelectric ceramic to absorb more ultrasonic waves transmitted back to the outside, so as to reduce the aftershock of the ultrasonic sensor.

Disclosure of Invention

The following paragraphs present a brief description of the invention in order to give the reader a basic understanding of the invention. This summary is not an extensive overview of the disclosure and is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention, but is intended to merely present some concepts of the invention in a simplified form as a prelude to the more detailed description that is discussed later.

The present invention is directed to a novel ultrasonic sensor, which is characterized in that a stress balance layer is added between a piezoelectric ceramic and a vibration absorber to improve the thermal stress generated by an acoustic resistance matching layer on the piezoelectric ceramic due to the difference of thermal expansion coefficients of the piezoelectric ceramic and the acoustic resistance matching layer under high and low temperature environments, thereby causing the piezoelectric ceramic to crack. Secondly, the material of the stress balance layer is different from the common high-density and high-acoustic-impedance shock absorber material in the industry, the density is relatively small, and the acoustic impedance is relatively low, so that the transmission of ultrasonic waves from the back of the piezoelectric ceramic can be reduced, and the emission sensitivity of the whole sensor is improved. The ultrasonic sensor with the stress balance layer structure can improve the reliability of the ultrasonic sensor and also provides the flexibility of the configuration of the damping material of the ultrasonic sensor.

One embodiment of the present invention provides an ultrasonic sensor including a piezoelectric body having a first surface and a second surface opposite to each other with the piezoelectric body interposed therebetween, and a side surface connecting the first surface and the second surface. And the acoustic impedance matching layer is provided with a third surface and a fourth surface which are opposite to each other by separating the acoustic impedance matching layer, and the third surface is connected with the second surface of the piezoelectric body. And a stress balance layer having a fifth surface and a sixth surface facing each other with the stress balance layer interposed therebetween, the sixth surface being in contact with the first surface of the piezoelectric body. The hardness of the stress balance layer is greater than that of the damper, and the acoustic resistance of the stress balance layer is less than 5MRayl. And the shock absorption body is used for coating the stress balance layer, and/or the piezoelectric body, and/or the acoustic resistance matching layer.

Another embodiment of the present invention provides an ultrasonic sensor, wherein the stress balance layer has a through hole penetrating through the fifth surface and the sixth surface of the stress balance layer.

Another embodiment of the present invention provides an ultrasonic sensor, wherein an outer edge of the sixth surface of the stress balance layer extends forward to cover and connect with a side surface of the piezoelectric body.

Another embodiment of the present invention provides an ultrasonic sensor having a barrel-shaped supporting body for accommodating a piezoelectric body, an acoustic impedance matching layer, a stress balancing layer and a vibration absorbing body.

In another embodiment of the present invention, an ultrasonic sensor is provided, which has a tubular supporting body for accommodating a piezoelectric body, an acoustic impedance matching layer, a stress balancing layer and a vibration absorbing body.

These and other objects of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description of the preferred embodiment illustrated in the various figures and drawings.

Drawings

The accompanying drawings are included to provide a further understanding of embodiments of the invention, and are incorporated in and constitute a part of this specification. The drawings depict some embodiments of the invention and, together with the description, serve to explain its principles. In these figures:

FIG. 1 is a schematic cross-sectional view of an ultrasonic sensor according to an embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view of an ultrasonic sensor according to a second embodiment of the present invention;

FIG. 3 is a schematic cross-sectional view of an ultrasonic sensor according to a third embodiment of the present invention;

FIG. 4 is a schematic cross-sectional view of an ultrasonic sensor according to a fourth embodiment of the present invention;

FIG. 5 is a schematic cross-sectional view of an ultrasonic sensor according to a fifth embodiment of the invention;

FIG. 6 is a schematic cross-sectional view of an ultrasonic sensor according to a sixth embodiment of the invention;

FIG. 7 is a schematic cross-sectional view of an ultrasonic sensor according to a seventh embodiment of the invention;

FIG. 8 is a schematic cross-sectional view of an ultrasonic sensor according to an eighth embodiment of the invention;

FIG. 9 is a schematic cross-sectional view of an ultrasonic sensor according to a ninth embodiment of the invention;

fig. 10 is a schematic cross-sectional view of an ultrasonic sensor according to a tenth embodiment of the invention.

Wherein the reference numerals are as follows:

1. 2, 3, 4, 5, 6, 7, 8, 9, 10 ultrasonic sensor

10 piezoelectric body

10A first surface

10B second surface

10C side surface

10D lateral surface

20 acoustic impedance matching layer

20A third surface

20B fourth surface

30 stress balance layer

30A fifth surface

30B sixth surface

32 through hole

40 damping body

50-barrel-shaped carrier

50A seventh surface

50B eighth surface

51, barrel bottom

52, a barrel body

60 tubular supporting body

61 inner surface

62 outer surface

63 first opening

64 second opening

70 supporting body

70A third surface

70B fourth surface

Detailed Description

In the following detailed description of the present invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments in which the embodiments may be practiced. Such embodiments will be described in sufficient detail to enable those skilled in the art to practice them. The size of some of the elements in the figures may be exaggerated for clarity. It is to be understood that other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the described embodiments. The following detailed description is, therefore, not to be taken in a limiting sense, and the embodiments included therein are defined by the appended claims.

Referring to fig. 1, fig. 1 is a schematic cross-sectional view of an ultrasonic sensor according to an embodiment of the invention. As shown in fig. 1, the ultrasonic sensor 1 of the present embodiment includes a piezoelectric body 10, an acoustic impedance matching layer 20, a stress balance layer 30, and a vibration absorber 40. The piezoelectric body 10 is located between the acoustic resistance matching layer 20 and the stress balance layer 30, and the damping body 40 covers the stress balance layer 30, and/or covers the piezoelectric body 10, and/or covers the acoustic resistance matching layer 20.

More specifically, the piezoelectric body 10 of the present embodiment has a first surface 10A, a second surface 10B opposite to the first surface 10A with the piezoelectric body 10 interposed therebetween, and

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 opposite to the third surface 20A with the acoustic impedance matching layer 20 therebetween, and the third surface 20A of the acoustic impedance matching layer 20 is in contact with the second surface 10B of the piezoelectric body 10. The stress balance layer 30 has a fifth surface 30A and a sixth surface 30B opposite to the fifth surface 30A with the stress balance layer 30 therebetween, wherein the sixth surface 30B of the stress balance layer 30 is in contact with the first surface 10A of the piezoelectric body 10. The damper 40 is connected to the fifth surface 30A of the stress balance layer 30 and covers the side wall of the stress balance layer 30, and in this embodiment, the damper 40 also covers the side wall of the piezoelectric body 10 and the side wall partially covering the acoustic impedance matching layer 20. It should be noted that the covering range of the shock absorbing body 40 may be adjusted according to actual requirements, that is, in other embodiments of the present invention, the shock absorbing body 40 may cover more/or less layers of surface or side wall, and the present invention is not limited thereto.

In the present embodiment, the material of the piezoelectric body 10 includes a piezoelectric ceramic, for example, barium titanate (BaTiO) ₃ ) Lead titanate (PbTiO) ₃ ) And lead zirconate titanate (Pb (ZrTi) O ₃ PZT), etc., but are not limited thereto. The material of the acoustic impedance matching layer 20 comprises an organic polymer material or a composite material formed by mixing the organic polymer material and hollow powder or solid powder, for example, organic polymeric materials include epoxy resins (epoxy), vinyl ester resins (vinyl ester resins),UV curable adhesive (UV adhesive), polyurethane (polyurethane), acrylic resin (acrylic resin), or cyanate ester resin (cyanate ester resin), but not limited thereto. The material of the stress balance layer 30 includes an organic polymer material or a composite material formed by mixing an organic polymer material with hollow powder or solid powder, for example, the organic polymer material includes epoxy resin (epoxy), vinyl ester resin (vinyl ester resin), ultraviolet curable adhesive (UV adhesive), polyurethane (polyurethane), acrylic resin (acrylic resin), or cyanate ester resin (cyanate ester resin), but is not limited thereto. The material of the shock absorbing body 40 includes an organic polymer material or a composite material formed by mixing an organic polymer material with metal or ceramic particles, and the organic polymer material includes, but is not limited to, epoxy resin (epoxy), polyurethane (polyurethane), or silicone.

In this embodiment, the piezoelectric body 10 functions to generate ultrasonic waves by vibrating at a high frequency, because of the acoustic resistance (about 35mrayl,35 × 10) of the piezoelectric body 10 ⁶ Kilogram per square meter second) and the acoustic resistance of air (about 4 x 10) ^-4 MRayl), the difference between the two is 5 steps, so it is necessary to dispose the acoustic resistance matching layer 20 between the piezoelectric body 10 and the air, so that the acoustic resistances of the piezoelectric body 10 and the air are matched, and the ultrasonic wave can be effectively transmitted to the air. The damper 40 is provided to reduce the noise generated when the ultrasonic sensor is used. The piezoelectric body 10, the acoustic impedance matching layer 20 and the vibration absorbing body 40 are common elements of the conventional ultrasonic sensor, and the detailed principles and materials thereof belong to the prior art in the field, and are not described herein.

However, the conventional ultrasonic sensor has a drawback that the acoustic resistance matching layer is only located on a single surface of the piezoelectric body, and thus the conventional ultrasonic sensor is prone to crack due to a large difference between the thermal expansion coefficient of the piezoelectric body and the thermal expansion coefficient of the acoustic resistance matching layer in a temperature cycle test. More specifically, a typical ultrasonic sensor is usually subjected to a temperature cycling test (e.g., cycling test at about-40 ℃ to +85 ℃) before being shipped from a factory to test the reliability of the ultrasonic sensor under the environmental temperature change. The applicant found that in the conventional ultrasonic sensor (i.e. the ultrasonic sensor including only the piezoelectric body, the acoustic resistance matching layer and the shock absorber), because the acoustic resistance matching layer is only located on one side of the surface of the piezoelectric body, and the difference between the thermal expansion coefficients of the piezoelectric body and the acoustic resistance matching layer is large (generally, the thermal expansion coefficient of the piezoelectric body is about 5PPM, and the thermal expansion coefficient of the acoustic resistance matching layer is about 50PPM, and the difference between the two is about 10 times), during the temperature cycle test, the one side surface of the piezoelectric body, i.e. the surface adjacent to the acoustic resistance matching layer, is susceptible to a relatively significant compression/tension force, and thus the piezoelectric body is cracked.

The reason why the piezoelectric body is cracked is mainly that the acoustic resistance matching layer is only arranged on one surface of the piezoelectric body, and the other surface of the piezoelectric body is directly connected with the shock absorber, so that when thermal expansion and cold contraction occur, the piezoelectric body is obviously stressed from one surface (namely the acoustic resistance matching layer), and further the cracking condition is generated. Therefore, the present embodiment is characterized in that the stress balance layer 30 is additionally provided on the other surface of the piezoelectric body 10 (i.e., the opposite surface with respect to the acoustic resistance matching layer 20). In some embodiments, the material of the stress balance layer 30 may be the same as that of the acoustic resistance matching layer 20, and the stress balance layer 30 and the acoustic resistance matching layer 20 are respectively disposed on two sides of the piezoelectric body 10, so that when performing a temperature cycling test, the stress borne by the piezoelectric body 10 will be evenly dispersed to the two sides, thereby achieving an effect of bilateral stress balance, and preventing the piezoelectric body 10 from bearing the stress from a single side to generate a fracture condition.

It should be noted that the stress balance layer 30 and the shock absorbing body 40 belong to different layers, and both of them preferably comprise different materials, and since the material and purpose of the shock absorbing body 40 are different from those of the stress balance layer 30, the invention preferably does not use all or a part of the shock absorbing body 40 instead of the stress balance layer 30. In the present embodiment, the hardness of the stress balance layer 30 is greater than that of the damper 40, and the acoustic resistance of the stress balance layer 30 is less than 5MRayl. The stress balance layer 30 is added between the piezoelectric body 10 and the damping body 40 in the present invention, so that the reliability and durability of the ultrasonic sensor can be effectively improved compared with the prior art (i.e. the structure without the stress balance layer). According to the practical test results of the applicant, the conventional ultrasonic sensor may be cracked after about 10 temperature cycling tests, but after the stress balance layer 30 is added, the ultrasonic sensor 1 may not be cracked after more than 50 temperature cycling tests, so that the reliability of the ultrasonic sensor is greatly improved.

In addition, the ultrasonic sensor of the present invention has the advantage of improving reliability, and can also adjust parameters of the stress balance layer 30, such as adjusting the thickness or the material, to reduce the efficiency of transmitting the ultrasonic waves generated by the piezoelectric body 10 from the back surface, thereby improving the front emission performance of the ultrasonic sensor 1.

The following description will mainly describe the differences of the embodiments of the ultrasonic sensor of the present invention, and for simplicity, the following description will not repeat the description of the same parts. In addition, the same elements in the embodiments of the present invention are denoted by the same reference numerals to facilitate the comparison between the embodiments.

Fig. 2 is a schematic cross-sectional view of an ultrasonic sensor according to a second embodiment of the invention. As shown in fig. 2, the ultrasonic sensor of the present embodiment is similar to the ultrasonic sensor described in the first embodiment (see fig. 1), and the main difference is that the stress balance layer 30 of the ultrasonic sensor 2 in the present embodiment further includes a plurality of through holes 32, wherein the through holes 32 are hollow holes penetrating through the fifth surface 30A and the sixth surface 30B of the stress balance layer 30. From its cross-sectional view, its shape includes, but is not limited to, circular, rectangular, triangular, irregular, or other shapes. In the present embodiment, the through holes 32 have the effect of reducing the overall density of the stress balance layer 30, so as to achieve the advantage of low acoustic resistance, thereby improving the sensitivity of the ultrasonic waves emitted from the front acoustic resistance matching layer. Except for the above features, the material characteristics or the structure of other elements of this embodiment are the same as those of the first embodiment, and are not repeated herein.

Fig. 3 is a schematic cross-sectional view of an ultrasonic sensor according to a third embodiment of the invention. As shown in fig. 3, the ultrasonic sensor of the present embodiment is similar to the ultrasonic sensor (see fig. 1) of the first embodiment, but the main difference is that the stress balance layer 30 in the ultrasonic sensor 3 of the present embodiment not only covers the first surface 10A of the piezoelectric body 10, but also partially extends to cover the side surfaces 10C and 10D of the piezoelectric body 10. That is, the outer edge of the sixth surface 30B of the stress balance layer 30 may extend forward to cover the side surfaces 10C and 10D of the piezoelectric body 10. This can protect the piezoelectric body 10 more effectively, and the side wall of the piezoelectric body 10 is less likely to be broken. Except for the above features, the material characteristics or the structure of other elements of this embodiment are the same as those of the first embodiment, and are not repeated herein.

Fig. 4 is a schematic cross-sectional view of an ultrasonic sensor according to a fourth embodiment of the invention. As shown in fig. 4, the ultrasonic sensor 4 of the present embodiment is similar to the ultrasonic sensor (see fig. 1) of the first embodiment, but the main difference is that the ultrasonic sensor 4 of the present embodiment further includes a barrel-shaped supporting body 50, wherein the piezoelectric body 10, the acoustic impedance matching layer 20, the stress balance layer 30 and the vibration absorbing body 40 are located in the barrel-shaped supporting body 50. More specifically, the barrel-shaped carrier 50 has a barrel bottom 51 and a barrel 52, and the barrel-shaped carrier 50 has a seventh surface 50A and an eighth surface 50B opposite to each other across the barrel bottom 51, wherein the piezoelectric body 10, the acoustic impedance matching layer 20, the stress balance layer 30 and the shock absorbing body 40 are disposed in the barrel-shaped carrier 50, and the seventh surface 50A of the barrel bottom 51 of the barrel-shaped carrier 50 is connected to the fourth surface 20B of the acoustic impedance matching layer 20. The barrel-shaped carrier 50 can serve as a housing for the ultrasonic sensor 4 to protect other internal components. The material of the barrel-shaped supporting body 50 may include, but is not limited to, metal, plastic, polymer, etc. Except for the above features, the material characteristics or the structure of other elements of this embodiment are the same as those of the first embodiment, and are not repeated herein.

Fig. 5 is a schematic cross-sectional view of an ultrasonic sensor according to a fifth embodiment of the invention. As shown in fig. 5, the ultrasonic sensor 5 of the present embodiment is similar to the ultrasonic sensor (see fig. 1) of the first embodiment, but the main difference is that the ultrasonic sensor 5 of the present embodiment further includes a tubular supporting body 60, wherein the piezoelectric body 10, the acoustic impedance matching layer 20, the stress balance layer 30 and the vibration absorbing body 40 are located in the tubular supporting body 60. In more detail, the tubular carrier 60 has an inner surface 61 and an outer surface 62 opposite to each other across the tubular carrier 60, and a first opening 63 and a second opening 64 opposite to each other, and the piezoelectric body 10 and the stress balance layer 30 are covered by the damping body 40, wherein the inner surface 61 of the tubular carrier 60 surrounds the damping body 40 and is connected to the damping body 40, and the fourth surface 20B of the acoustic resistance matching layer 20 is exposed from the first opening 63 of the tubular carrier 60. The tubular carrier 60 can also protect other internal components. In addition, the tubular supporting body 60 can easily control the emitting direction of the ultrasonic waves. Except for the above features, the material characteristics or the structure of other elements of this embodiment are the same as those of the first embodiment, and are not repeated herein.

In addition to the above-mentioned barrel-shaped carrier or tubular carrier, in some embodiments, other shapes of carriers, such as a plate-shaped carrier, may be included. In still other embodiments, a plate-like carrier may be used in place of the acoustic impedance matching layer. Fig. 6 is a schematic cross-sectional view of an ultrasonic sensor according to a sixth embodiment of the invention. As shown in fig. 6. The ultrasonic sensor 6 of the present embodiment is similar to the ultrasonic sensor (see fig. 1) of the first embodiment, and includes a piezoelectric body 10, a stress balance layer 30, and a damping body 40. In this embodiment, however, the carrier 70 is used to replace the acoustical resistance matching layer 20 in the first embodiment. More specifically, the present embodiment includes: a piezoelectric body 10 having a first surface 10A and a second surface 10B facing each other with the piezoelectric body 10 interposed therebetween, and

side surfaces

10C and 10D connecting the first surface 10A and the second surface 10B; a carrier 70, wherein the carrier 70 has a third surface 70A and a fourth surface 70B opposite to each other across the carrier 70, and the third surface 70A is connected to the second surface 10B of the piezoelectric body 10; a stress balance layer 30, the stress balance layer 30 having a fifth surface 30A and a sixth surface 30B facing each other with the stress balance layer 30 interposed therebetween, the sixth surface 30B being in contact with the first surface 10A of the piezoelectric body 10, and the stress balance layer having an acoustic resistance of less than 5MRayl; and a shock absorbing body 40 covering the stress balance layer 30, and/or the piezoelectric body 10, and/or the carrier 70, wherein the hardness of the stress balance layer 30 is greater than that of the shock absorbing body 40. In this embodiment, the carrier 70 is used as the acoustic impedance matching layer in the first embodiment, so that a part of the device space can be saved and the manufacturing process can be simplified. The supporting body 70 may also be made of a material similar to the acoustic resistance matching layer, such as an organic polymer material or a composite material formed by mixing an organic polymer material with hollow powder or solid powder, where the organic polymer material includes epoxy resin (epoxy), vinyl ester resin (vinyl ester resin), ultraviolet curable adhesive (UV adhesive), polyurethane (polyurethane), acrylic resin (acrylic resin), or cyanate ester resin (cyanate ester resin), or a metal material such as aluminum, titanium, copper, or stainless steel, or a non-metal material such as glass, acryl, teflon (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polybutylene terephthalate (PBT), acrylonitrile-butadiene-styrene copolymer (ABS), polyphenylene Sulfide (PPs), liquid Crystal Polymer (LCP), or polyether ether ketone (PEEK), but not limited thereto. Except for the above features, the material characteristics or the structure of other elements of this embodiment are the same as those of the first embodiment, and are not repeated herein.

Fig. 7 is a schematic cross-sectional view of an ultrasonic sensor according to a seventh embodiment of the present invention, fig. 8 is a schematic cross-sectional view of an ultrasonic sensor according to an eighth embodiment of the present invention, and fig. 9 is a schematic cross-sectional view of an ultrasonic sensor according to a ninth embodiment of the present invention. In these embodiments, the concept of replacing the acoustic resistance matching layer with the bearer in the sixth embodiment can be applied. As shown in fig. 7, the ultrasonic sensor 7 of the seventh embodiment is similar to the ultrasonic sensor of the second embodiment (see fig. 2), except that the ultrasonic sensor 7 of the present embodiment does not include an acoustic impedance matching layer, but uses a carrier 70 instead of the acoustic impedance matching layer. The material and characteristics of the carrier 70 have been described in the above embodiments, and are not repeated herein. Except for the above features, the material characteristics or the structure of other elements of this embodiment are the same as those of the above embodiments, and are not repeated herein.

Similarly, as shown in fig. 8, the ultrasonic sensor 8 according to the eighth embodiment is similar to the ultrasonic sensor according to the third embodiment (see fig. 3), except that the ultrasonic sensor 8 does not include an acoustic impedance matching layer, but a carrier 70 is used instead of the acoustic impedance matching layer. The material and characteristics of the carrier 70 have been described in the above embodiments, and are not repeated herein. Except for the above features, the material characteristics or the structure of other elements of this embodiment are the same as those of the above embodiments, and are not repeated herein.

Similarly, as shown in fig. 9, the ultrasonic sensor 9 of the ninth embodiment is similar to the ultrasonic sensor of the fourth embodiment (see fig. 4), except that the ultrasonic sensor 9 of the present embodiment does not include an acoustic impedance matching layer, but replaces the acoustic impedance matching layer with a barrel-shaped carrier 50. The material and characteristics of the barrel-shaped carrier 50 have been described in the above embodiments, and are not repeated herein. Except for the above features, the material characteristics or the structure of other elements of this embodiment are the same as those of the above embodiments, and are not repeated herein.

Fig. 10 is a schematic cross-sectional view of an ultrasonic sensor according to a tenth embodiment of the invention. In this embodiment, the structure of the ultrasonic sensor 10 is similar to that of the ultrasonic sensor 4 described in the fourth embodiment, but the difference is that the acoustic impedance matching layer 20 is disposed outside the barrel-shaped carrier 50 in this embodiment, that is, the third surface 20A of the acoustic impedance matching layer 20 is connected to the eighth surface 50B of the barrel-shaped carrier 50. Except for the above features, the material characteristics or the structure of other elements of this embodiment are the same as those of the above embodiments, and are not repeated herein.

In view of the above, the present invention provides a novel ultrasonic sensor, which is characterized in that a stress balance layer is added between a piezoelectric ceramic and a shock absorber to improve the thermal stress generated by the acoustic resistance matching layer on the piezoelectric ceramic due to the difference of thermal expansion coefficients of the piezoelectric ceramic and the acoustic resistance matching layer under high and low temperature environments, thereby causing the piezoelectric ceramic to crack. Secondly, the material of the stress balance layer is different from the common high-density and high-acoustic-impedance shock absorber material in the industry, the density is relatively small, and the acoustic impedance is relatively low, so that the transmission of ultrasonic waves from the back of the piezoelectric ceramic can be reduced, and the emission sensitivity of the whole sensor is improved. The ultrasonic sensor with the stress balance layer structure can improve the reliability of the ultrasonic sensor and also provides the flexibility of the configuration of the damping material of the ultrasonic sensor.

The above description is only a preferred embodiment of the present invention, and all the equivalent changes and modifications made by the claims of the present invention should fall within the protection scope of the present invention.

Claims

1. An ultrasonic sensor, comprising:

a piezoelectric body having a first surface and a second surface opposed to each other with the piezoelectric body interposed therebetween, and a side surface connecting the first surface and the second surface;

the acoustic impedance matching layer is provided with a third surface and a fourth surface which are opposite to each other through the acoustic impedance matching layer, and the third surface is connected with the second surface of the piezoelectric body;

a stress balance layer having a fifth surface and a sixth surface facing each other with the stress balance layer interposed therebetween, the sixth surface being in contact with the first surface of the piezoelectric body, and the stress balance layer having an acoustic resistance of less than 5MRayl; and

and the shock absorber is used for coating the stress balance layer, and/or the piezoelectric body, and/or the acoustic resistance matching layer, wherein the hardness of the stress balance layer is greater than that of the shock absorber.

2. The ultrasonic sensor of claim 1, wherein the stress balance layer is made of an organic polymer material or a composite material formed by mixing an organic polymer material with hollow powder or solid powder, wherein the organic polymer material comprises 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 balance layer has a through hole penetrating through the fifth surface and the sixth surface of the stress balance layer.

4. The ultrasonic sensor of claim 1, wherein the outer edge of the sixth surface of the stress balance layer is extended forward to cover and connect with the side surface of the piezoelectric body.

5. The ultrasonic sensor of claim 1, further comprising a barrel-shaped carrier having a barrel bottom and a barrel body, and the barrel-shaped carrier having a seventh surface and an eighth surface opposite to each other across the barrel bottom, wherein the piezoelectric body, the acoustic impedance matching layer, the stress balancing layer and the damping body are disposed in the barrel-shaped carrier, and the seventh surface of the barrel bottom of the barrel-shaped carrier is connected to the fourth surface of the acoustic impedance matching layer.

6. The ultrasonic sensor of claim 1, further comprising a tubular carrier having opposing inner and outer surfaces and opposing first and second openings across the tubular carrier, and the shock absorber covering the piezoelectric body and the stress-balancing layer, wherein the inner surface of the tubular carrier surrounds and interfaces with the shock absorber, and the fourth surface of the acoustic impedance matching layer is exposed from the first opening of the tubular carrier.

7. The ultrasonic sensor of claim 1, wherein the vibration absorber is made of an organic polymer material or a composite material formed by mixing an organic polymer material with metal or ceramic particles, and the organic polymer material comprises epoxy resin, polyurethane, or silicone.

8. The ultrasonic sensor of claim 1, wherein the acoustic impedance matching layer is made of an organic polymer material or a composite material formed by mixing an organic polymer material with hollow powder or solid powder, and the organic polymer material comprises epoxy resin, vinyl ester resin, uv-curable adhesive, polyurethane, acrylic resin, or cyanate ester resin.

9. An ultrasonic sensor, comprising:

a carrier having a third surface and a fourth surface opposite to each other with the carrier interposed therebetween, the third surface being in contact with the second surface of the piezoelectric body;

and the shock absorption body coats the stress balance layer and/or the piezoelectric body and/or the bearing body, and the hardness of the stress balance layer is greater than that of the shock absorption body.

10. The ultrasonic sensor of claim 9, wherein the stress balance layer is made of an organic polymer material or a composite material formed by mixing an organic polymer material with hollow powder or solid powder, wherein the organic polymer material comprises 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 balance layer has through holes penetrating through the fifth and sixth surfaces of the stress balance layer.

12. The ultrasonic sensor of claim 9, wherein the outer edge of the sixth surface of the stress balance layer is extended forward to cover and connect with the side surface of the piezoelectric body.

13. The ultrasonic sensor of claim 9, wherein the carrier further comprises a barrel-shaped carrier having a barrel bottom and a barrel body, and the barrel-shaped carrier has a third surface and a fourth surface opposite to each other across the barrel bottom, wherein the piezoelectric body, the stress balance layer and the vibration absorber are disposed in a barrel of the barrel-shaped carrier, and the third surface of the barrel bottom of the barrel-shaped carrier is connected to the second surface of the piezoelectric body.

14. The ultrasonic sensor of claim 9, wherein the material of the carrier comprises a metal material selected from the group consisting of: aluminum, titanium, copper, stainless steel, or a non-metallic material selected from the group consisting of: glass, acryl, teflon, polyvinylidene fluoride, polypropylene, polyethylene, polyvinyl chloride, polybutylene terephthalate, acrylonitrile-butadiene-styrene copolymer, polyphenylene sulfide, liquid crystal polymer, or polyetheretherketone.

15. The ultrasonic sensor of claim 9, wherein the vibration absorber is made of an organic polymer material or a composite material formed by mixing an organic polymer material with metal or ceramic particles, and the organic polymer material comprises epoxy resin, polyurethane, or silicone.

16. The ultrasonic sensor of claim 9, further comprising an acoustic impedance matching layer, wherein the acoustic impedance matching layer is connected to the fourth surface of the carrier.

17. The ultrasonic sensor of claim 16, wherein the material of the acoustic impedance matching layer comprises an organic polymer material or a composite material formed by mixing an organic polymer material with hollow powder or solid powder, and the organic polymer material comprises epoxy resin, vinyl ester resin, uv cured adhesive, polyurethane, acrylic resin, or cyanate ester resin.