JP2023133745A - AE sensor structure - Google Patents

Abstract

To provide an AE sensor that can prevent an adhesive or a sensor part from being damaged even under an environment with a significant change of temperatures while maintaining a sensor performance.SOLUTION: An AE sensor structure 10 includes: a sensor part 1 made of a piezoelectric crystal; a supporting board 2 to which the sensor part 1 is fixed; a case 3 to which the supporting board 2 is attached, the case being fixed to the outside; an adhesive part 4 for fixing the supporting board 2 and the case 3, the adhesive part 4 having a thick part 5 for holding an adhesion function and a thin part 6 for propagation of an AE wave. The adhesive part 4 has a cross section in the shape of a substantially protruding shape and has the thin part 6 on the outside and the thick part 5 on the inside.SELECTED DRAWING: Figure 1

Description

The present invention relates to an AE sensor structure, and particularly to a technique that can expand the applicable temperature range of a resonant AE sensor.

BACKGROUND ART As a means for detecting failures in equipment, structures, etc., there is a method of monitoring elastic waves (AE waves) generated from them to detect abnormalities, and an AE sensor is an example of a sensor for detecting AE waves. As shown in FIG. 6, the AE sensor 910 mainly includes a sensor section 91 that detects elastic waves, an exterior component 93 that is fixed to the outside, and an adhesive 94 that fixes the sensor section 91 and the exterior component 93. Note that the sensor section 91 is made of a piezoelectric element, and the exterior component 93 is made of ceramic, metal, or the like. Further, since the adhesive 94 integrates the sensor section 91 and the exterior component 94, it is desirable that the adhesive be hard.

Conventionally, many patent applications have been filed regarding AE sensors. For example, Patent Document 1 listed below describes a sensor mounting method for a non-magnetic measurement object for which a magnetic holder cannot be used. In other words, it is a method that uses a plate-like member that assists in attaching a holding member to the object to be measured, in which the sensor is housed so that it can protrude, when measuring using a sensor, and a hole that penetrates in the thickness direction and can protrude and come into contact with the object to be measured is used. Disclosed is a plate-like member which has magnetism in the direction of attraction to the holding member.

JP2006-250559A “Sensor mounting auxiliary member and sensor mounting method”

Conventionally, there are some points that require improvement regarding the mounting and fixing of the AE sensor. For example, if the piezoelectric element that makes up the sensor section is made of LN (lithium niobate) or LT (lithium tantalate), and the exterior parts are made of ceramics, temperature changes will occur due to differences in their thermal expansion coefficients. The problem is that when used in a large environment, the adhesive that bonds and fixes the sensor part and exterior parts, and the relatively fragile sensor part, are damaged, deteriorating the function as a sensor.

As a countermeasure, it is possible to use a soft adhesive or thicken the adhesive to alleviate the influence of the difference in thermal expansion coefficient between the sensor section and the exterior component. However, in these methods, the integration of the sensor section and the exterior parts is impaired, the propagation of AE waves to the sensor section is buffered, and the sensor performance deteriorates. There is a need for technology that can maintain sensor performance and prevent damage to adhesives and sensor parts even in environments with large temperature changes.

Therefore, the problem to be solved by the present invention is to solve the problem of the conventional technology by providing a method that can prevent damage to the adhesive and sensor part while maintaining sensor performance even in an environment with large temperature changes. An object of the present invention is to provide an AE sensor that is less affected by In other words, the objective is to provide an AE sensor that can expand the applicable temperature range.

As a result of studying the above-mentioned problem, the inventor of the present application came up with the idea of newly installing a support base for fixing the sensor section. In other words, a sensor section made of a piezoelectric crystal, a support base for fixing the sensor section, a case to which the support base to which the sensor section is fixed are attached and fixed to the outside, and a case for fixing the sensor section to the support base and the support base to the case. The aim is to create an AE sensor made of adhesive. Furthermore, the cross-sectional shape of the support base was made into a U-shape, the U-shaped recess was fixed to the case with adhesive, and the sensor element was attached to the opposite side, and the inside of the recess was filled with adhesive. It was discovered that the problem could be solved by creating a structure, and based on this, the present invention was completed. That is, the invention claimed or at least disclosed in this application as a means for solving the above problems is as follows.

[1] A sensor unit made of a piezoelectric crystal, a support base to which the sensor unit is fixed, a case to which the support base is attached and the case itself is fixed to the outside, and a case that fixes the support base and the case. An AE sensor structure comprising an adhesive part.
[2] A sensor unit made of a piezoelectric crystal, a support base to which the sensor unit is fixed, a case to which the support base is attached and the case itself is fixed to the outside, and a case that fixes the support base and the case. The AE sensor structure according to [1], characterized in that the adhesive part consists of a thick part for retaining the adhesive function and a thin part for propagating AE waves. .
[3] The AE sensor structure according to [2], wherein the adhesive portion has a substantially convex cross-sectional shape, and the thin wall portion is located on the outside and the thick wall portion is located on the inside.
[4] The support stand has a substantially U-shaped cross section, and is arranged with its open end facing toward the case side with the adhesive portion in between. AE sensor structure described in ].
[5] The support stand has a substantially H-shaped cross section, and is arranged with one open end thereof facing toward the case side with the adhesive portion sandwiched therebetween; [3] AE sensor structure described in ].
[6] The surface of the support base facing the adhesive portion is flat, the case is provided with a recess, and the support base is placed in a position opposite to the recess with the adhesive portion sandwiched therebetween. The AE sensor structure according to [3], characterized in that:

[7] The support base has a cross-sectional shape having one or more recesses, and is arranged with the open end of the recess facing toward the case side with the adhesive portion in between. , the AE sensor structure described in [2].
[8] The AE sensor structure according to [7], wherein the shape of the recessed portion is triangular, rectangular, or arcuate.
[9] [2], [3], [4], [5], [6], [2], [2], [3], [4], [5], [6], [2], wherein the thickness of the thickest part of the thick part is five times or more that of the thin part. 7], the AE sensor structure according to any one of [8].
[10] Any of [2], [3], [4], [5], [6], [7], [8], and [9], wherein the support base is made of metal. AE sensor structure described in Crab.
[11] [2], [3], [4], wherein the coefficient of thermal expansion of the support base is within ±30% of the coefficient of thermal expansion of the sensor section, more preferably within ±10%. , [5], [6], [7], [8], [9], and [10].

Since the AE sensor structure of the present invention is configured as described above, it is possible to maintain sensor performance and prevent damage to the adhesive and sensor part even when used in an environment with large temperature changes. be able to. That is, according to the present invention, it is possible to provide an AE sensor that is less affected by temperature changes and an AE sensor that can expand the applicable temperature range.

1 is a sectional view showing the basic configuration of an AE sensor structure of the present invention. FIG. 7 is a sectional view showing another configuration example (H type) of the AE sensor structure of the present invention. FIG. 7 is a sectional view showing another configuration example (concave case type) of the AE sensor structure of the present invention. FIG. 7 is a cross-sectional view showing another configuration example (multi-concave type) of the support base of the AE sensor structure of the present invention. FIG. 7 is a cross-sectional view showing another configuration example (triangular type, arc type) of the support base of the AE sensor structure of the present invention. FIG. 2 is a cross-sectional view showing a fixing method in a conventional AE sensor.

Hereinafter, the present invention will be explained in detail with reference to the drawings.
FIG. 1 is a sectional view showing the basic configuration of the AE sensor structure of the present invention. As shown in the figure, the present AE sensor structure 10 includes a sensor part 1 made of a piezoelectric crystal, a support base 2 to which the sensor part 1 is fixed, and a case 3 to which the support base 2 is attached and which is fixed to the outside. , and an adhesive part 4 for fixing the support base 2 and the case 3. Furthermore, the adhesive part 4 can be configured to include a thick part 5 for maintaining the adhesive function and a thin part 6 for propagating AE waves.

With this configuration, in the present AE sensor structure 10, the sensor section 1 does not come into direct contact with the adhesive section 4 for fixing the case 3, but through the support stand 2, and the sensor section 1 and the sensor section 1, which have different coefficients of thermal expansion, Inconveniences caused by the case 3 being directly adjacent to the case 3 with the adhesive in between can be alleviated.

Since the thick part 5 and the thin part 6 are formed, the thick part 5 of the adhesive part 4 maintains the adhesive function of fixing the support base 2 and the case 3. The AE wave propagation function is ensured by the section 6, thereby ensuring the AE detection function of the sensor section 1 fixed on the support base 2. As a result, the present AE sensor structure 10 maintains sensor performance even when used in an environment with large temperature changes, and has an adhesive part 4 that adheres and fixes the sensor part 1 and exterior parts, and a relatively fragile sensor. It is possible to prevent the portion 1 from being damaged and deteriorating its function as a sensor.

As mentioned above, when the piezoelectric element constituting the sensor section is LN or LT, and the exterior parts are made of ceramics, there will be a difference in their respective thermal expansion coefficients, and therefore stress will occur due to temperature changes. . By absorbing the stress with the support base, the effect of stress on the sensor side is reduced. However, if the adhesive is not thick enough, the difference in thermal expansion coefficient between the support base and the case may cause the difference between the support base and the case. The adhesive that secures the case will be damaged.

In the AE sensor structure 10 of the present invention, as shown in the figure, for example, the support base 3 is formed into a U-shape and filled with adhesive, so that the adhesive part 4 has different thicknesses, such as a thick part 5 and a thin part 6. This structure ensures the adhesive function in the thick portion 5. If the thickness of the adhesive is made uniform, the adhesive will act as a buffer material and the function of propagating externally generated AE waves to the sensor will be weakened. However, in the present invention, since the thin portion 6 performs the AE wave propagation function, the attenuation of the AE waves can be minimized.

As shown in FIG. 1, the adhesive portion 4 of the present AE sensor structure 10 has a substantially convex cross-sectional shape, and has a thin wall portion 6 on the outside and a thick wall portion 5 on the inside. I can do it. That is, the adhesive part 4 has a structure in which the central part is filled with adhesive thickly and the peripheral part is filled with thinner adhesive.In other words, the thick part 5 is included in the area of the adhesive part 4 that contacts the case 3. This is the structure that will be used. In this configuration, the adhesion function is maintained at the center, while the AE wave propagation function is maintained at the periphery. Note that the stress due to the difference in coefficient of thermal expansion between the support base 2 and the thin wall portion 6 in the peripheral portion can be alleviated at the center of the support base 2, so that the influence can be minimized.

Examples of piezoelectric crystals constituting the sensor section 1 of the present invention include lithium niobate (LN, lithium niobate), lithium tantalate (LT, lithium tantalate), potassium niobate (KN), crystal, and PZT. Examples include.

As the adhesive for constructing the adhesive part 4, a conventionally known resin adhesive or the like can be used as appropriate. In addition to the adhesive part 4 between the support stand 2 and the case 3, the support stand 2 and the sensor part 1 are also glued, but whether these adhesives are the same or different, there is no difference between them. However, it is desirable that the adhesive used particularly on the case 3 side has a higher hardness after solidification.

As shown in FIG. 1, the support stand 2 of the present AE sensor structure 10 has a substantially U-shaped cross section, and is arranged with its open end facing toward the case 3 with the adhesive part 4 in between. (U-shaped). As will be described later, the shape of the support is not limited to this, but the shape shown in this figure is the simplest and is advantageous in manufacturing. As mentioned above, the stress due to the coefficient of thermal expansion of the bond between the convex portions at both ends of the U-shape of the support base 2 and the case 3 can be alleviated by the U-shape concave portion of the support base 2, so the effect is minimal. be held down by

FIG. 2 is a sectional view showing another configuration example (H type) of the AE sensor structure of the present invention. As shown in the figure, the present AE sensor 210 has a support base 22 having a substantially H-shaped cross section, and is arranged with one open end thereof facing toward the case 23 with the adhesive portion 24 in between. It can be done. That is, in the approximately H-shaped cross section of the overturned recess 27C on the case 23 side, the recess 27C is filled with adhesive to form a thick wall portion 25, and thin wall portions 24 are formed at both ends thereof.

With this configuration as well, it is possible to maintain the sensor performance in an environment with large temperature changes and to prevent damage to the adhesive and the sensor part, similar to the U-shape shown in FIG. On the other hand, the recess 27S on the sensor 21 side is the part where the sensor 21 is installed, and by making the recess 27S a size that matches the dimensions of the sensor 21, the sensor 21 can be stably fixed. Moreover, by reducing the unevenness, it is possible to suppress the complexity of the shape.

FIG. 3 is a sectional view showing another configuration example (concave case type) of the AE sensor structure of the present invention. As shown in the figure, in the present AE sensor structure 310, the surface of the support base 32 facing the adhesive part 34 is flat, the case 33 is provided with a recessed part 38, and the support base 32 is connected to the adhesive part 34. The characteristic configuration is that the recess 38 is disposed facing the recess 38 with the recess 38 interposed therebetween. That is, unlike the configuration examples shown in FIGS. 1 and 2, in the AE sensor structure 310 of this configuration, the support base 32 has a flat plate shape with no irregularities, and the case 33 has a structural feature.

In other words, the case 33 has a recess 38 formed therein as a part for fixing the support base 32. A recess 38 provided in the case 33 is filled with adhesive to form a thick wall portion 35, and a thin wall portion 34 is formed at both ends of the case 33 on the same plane. Although the portion where the thick portion 35 is formed differs from the examples shown in FIGS. 1 and 2, the point that the adhesive portion is formed by the thick portion and the thin portion is the same.

With the configuration shown in this figure, it is possible to maintain the sensor performance in an environment with large temperature changes and to prevent damage to the adhesive and the sensor section, as in the configuration examples described above. Further, this configuration is particularly advantageous when it is more desirable to change the structure of the case 33 than to change the structure of the support base 32 in contact with the sensor section 31.

FIG. 4 is a sectional view showing another configuration example (multi-concave type) of the support base of the AE sensor structure of the present invention. As shown in (1) in the figure, the support base 42 of the present AE sensor structure has a cross-sectional shape having one or more recesses 47a, etc., and the open ends of the recesses 47a, etc. are placed on the side of the case with the adhesive section in between. Its characteristic configuration is that it is placed in an orientation facing toward the In the example (1), there are two such recesses 47a (47a, 47b), but there may be three recesses (57a, 57b, 57c) as in the case of the support base 52 shown in (2) in the figure, or there may be four recesses (47a, 47b). It may be more than that.

That is, the recess 47a and the like on the case side of the support base 42 and the like are filled with adhesive to form a thick wall portion, and thin wall portions are formed at both ends thereof. As with each of the configuration examples described above, it is possible to maintain sensor performance in an environment with large temperature changes and to prevent damage to the adhesive and the sensor section. Furthermore, in the configuration in which a plurality of recesses 47a etc. are provided in the support base 42 etc. as shown in this figure, the cost of adhesive can be reduced.

FIG. 5 is a sectional view showing another configuration example (triangular type, arc type) of the support base of the AE sensor structure of the present invention. As shown in the figure, the shape of the recess 67 etc. of the support base 62 etc. can be triangular ((1) in the figure), rectangular (previous figure 4), or arcuate ((2) in FIG. 5). good. Although other shapes of the recess are within the scope of the present invention, the configuration shown in any one of FIGS. 1 to 5 is advantageous in terms of manufacturing process and cost.

In the example of FIG. 5 as well, the case-side recess 67 and the like in the support base 62 and the like are filled with adhesive to form a thick wall portion, and thin wall portions are formed at both ends thereof. As with each of the configuration examples described above, it is possible to maintain sensor performance in an environment with large temperature changes and to prevent damage to the adhesive and the sensor section.

In addition, in each of the configurations described above, in the AE sensor structure 10 of the present invention, etc., it is preferable that the thickness of the thin portion 6 etc. be as thin as possible; however, in comparison with the thinnest portion such as the support base 2, it is better to be thicker. For example, the thickness of the thickest portion of the thick portion 5 may be five times or more that of the thin portion 6.

Since the coefficient of thermal expansion of the sensor part 1, etc. differs depending on the material used for it and its crystal orientation, the material of the support base 2, etc. should be selected accordingly, with a coefficient of thermal expansion as close to that of the sensor part 1, etc. as possible. . In each of the AE sensor structures 10 and the like described so far, the material of the support base 2 and the like can be particularly made of metal. For example, if the material of the sensor part 1 etc. is lithium niobate (XY plane), it is preferable to use stainless steel (SUS), copper, etc. with a thermal expansion coefficient of about 10 to 15 ppm/°C.

Furthermore, in each of the configurations described above, in the AE sensor structure 10 of the present invention, etc., the coefficient of thermal expansion of the support base 2, etc. is within ±30% of the coefficient of thermal expansion of the sensor portion 1, etc., and more preferably within ±10%. You can design the specifications accordingly.

The following are material conditions for each component in a prototype example of the AE sensor structure of the present invention, but the present invention is not limited thereto.
・Material conditions of prototype AE sensor Sensor part (element): LN Coefficient of thermal expansion 17 ppm/℃
Support stand: Stainless steel (SUS304) Thermal expansion coefficient 18ppm/℃
Adhesive: Epoxy resin Shape of support base and adhesive part: U-shape shown in Figure 1 Thickness of thin part: ~20um
Thickness of thick part: 0.2mm to 0.22mm
When this prototype was tested, it was confirmed that the above-mentioned effects intended by the present invention could be sufficiently obtained.

According to the AE sensor structure of the present invention, even when used in an environment with large temperature changes, it is possible to maintain sensor performance and prevent damage to the adhesive and the sensor section. Therefore, the present invention has high industrial applicability in the field of AE sensor manufacturing, use, and all related fields.

1, 21, 31...sensor part 2, 22, 32, 42, 52, 62, 72...support stand 3, 23, 33...case 4, 24, 34...adhesive part 5, 25, 35...thick part 6 , 26, 36...Thin wall portions 10, 210, 310...AE sensor structure 27C...Case side recess 27S in support body sensor side recess 38...Case recesses 47a, 47b, 57a, 57b, 57c, 67 , 77...Concavity on the case side of the support stand (the following symbols are related to the prior art)
91...Sensor part 93...Exterior component 94...Adhesive 910...AE sensor

Claims (11)

A sensor section made of piezoelectric crystal,
a support base to which the sensor unit is fixed;
a case to which the support base is attached and the case itself is fixed to the outside;
and an adhesive portion for fixing the support base and the case. 2. The AE sensor structure according to claim 1, wherein the adhesive part includes a thick part for maintaining an adhesive function and a thin part for propagating AE waves. 3. The AE sensor structure according to claim 2, wherein the adhesive part has a substantially convex cross-sectional shape, and the thin part is located on the outside and the thick part is located on the inside. 4. The support base has a substantially U-shaped cross-section, and is disposed with its open end facing toward the case with the adhesive portion sandwiched therebetween. AE sensor structure. 4. The support base has a substantially H-shaped cross section, and is disposed with one open end thereof facing toward the case side with the adhesive portion interposed therebetween. AE sensor structure. The surface of the support stand facing the adhesive part is flat, the case is provided with a recess, and the support stand is placed in a posture facing the recess with the adhesive part in between. The AE sensor structure according to claim 3, characterized in that: The support base has a cross-sectional shape having one or more recesses, and the open end of the recess is arranged with the open end facing toward the case side with the adhesive portion interposed therebetween. AE sensor structure according to 2. 8. The AE sensor structure according to claim 7, wherein the shape of the recess is any one of a triangle, a rectangle, and an arc shape. The AE sensor structure according to any one of claims 2, 3, 4, 5, 6, 7, and 8, wherein the thickness of the thickest portion of the thick portion is five times or more that of the thin portion. . The AE sensor structure according to any one of claims 2, 3, 4, 5, 6, 7, 8 and 9, wherein the support base is made of metal. Claims 2, 3, 4, 5, 6, 7, characterized in that the coefficient of thermal expansion of the support base is within ±30% of the coefficient of thermal expansion of the sensor section, more preferably within ±10%. AE sensor structure according to any one of 8, 9 and 10.