AE sensor structure

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

[Technical Field]

[0001] The present invention relates to an AE sensor structure, and more particularly to a technique capable of expanding the applicable temperature range of a resonance type AE sensor. [Background technology]

[0002] One method for detecting faults in equipment and structures is to monitor the elastic waves (AE waves) generated by them to detect abnormalities, and an AE sensor is used to detect AE waves. As shown in Figure 6, an AE sensor 910 is primarily composed of a sensor unit 91 that detects elastic waves, an exterior component 93 that is fixed to the outside, and an adhesive 94 that fixes the sensor unit 91 to the exterior component 93. The sensor unit 91 is made of a piezoelectric element, and the exterior component 93 is made of ceramic or metal. A hard adhesive is desirable because it integrates the sensor unit 91 and the exterior component 94.

[0003] Many patent applications have been filed for AE sensors. For example, Patent Document 1, listed below, describes a sensor mounting method for non-magnetic objects that cannot be measured using a magnetic holder. That is, the method uses a plate-like member that assists in mounting a holding member that stores the sensor so that it can protrude during measurement using the sensor to the object. The plate-like member is disclosed as having a hole that penetrates through the thickness and protrudes so that it can come into contact with the object, and has magnetism in the direction of attraction to the holding member. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-250559 A "Sensor mounting auxiliary member and sensor mounting method" Summary of the Invention [Problem to be solved by the invention]

[0005] There are still some areas that need improvement in the mounting and fixing of AE sensors. For example, if the piezoelectric element that makes up the sensor is made of LN (lithium niobate) or LT (lithium tantalate) and the exterior part is made of ceramic, there is a difference in the thermal expansion coefficients of the two, so if the sensor is used in an environment with large temperature changes, the adhesive that bonds and fixes the sensor part to the exterior part, as well as the relatively fragile sensor part, can be damaged, resulting in a deterioration in the sensor's functionality.

[0006] One possible solution to this problem is to use a softer adhesive or thicken the adhesive to mitigate the impact of the difference in thermal expansion coefficient between the sensor unit and the exterior component. However, these methods compromise the integration of the sensor unit and the exterior component, buffering the propagation of AE waves to the sensor unit and degrading sensor performance. There is a need for technology that can prevent damage to the adhesive and sensor unit while maintaining sensor performance, even in environments with large temperature changes.

[0007] In light of the problems with the conventional technology, the problem that the present invention aims to solve is to provide an AE sensor that is less affected by temperature changes and can prevent damage to the adhesive or sensor unit while maintaining sensor performance even in environments with large temperature changes. In other words, to provide an AE sensor that can expand the applicable temperature range. [Means for solving the problem]

[0008] After studying the above-mentioned problems, the inventors of the present application came up with the idea of creating a new support base for fixing the sensor unit. Specifically, the AE sensor is composed of a sensor unit made of a piezoelectric crystal, a support base for fixing the sensor unit, a case for attaching the support base with the sensor unit fixed thereto and fixing it to the outside, and an adhesive for fixing the sensor unit to the support base and the support base to the case. Furthermore, the inventors discovered that this problem can be solved by making the cross section of the support base U-shaped, fixing the U-shaped recess to the case with adhesive, and attaching the sensor element to the opposite surface, with the recess filled with adhesive. Based on this, the present invention was completed. Specifically, the invention claimed in this application, or at least the invention disclosed therein, as a means for solving the above-mentioned problems is as follows:

[0009] [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 which is fixed to the outside, and an adhesive part that fixes the support base and the case. The adhesive part is composed of a thick part for maintaining the adhesive function and a thin part for AE wave propagation. 1. An AE sensor structure comprising: 〔2〕 The adhesive portion has a cross-sectional shape that is approximately convex, and the thin portion is located on the outside and the thick portion is located on the inside. 1 10. The AE sensor structure according to claim 9. [ 3 The support base has a substantially U-shaped cross section, and is disposed with its open end facing the case side across the adhesive portion. 2 10. The AE sensor structure according to claim 9. [ 4 The support base has a substantially H-shaped cross section, and is disposed with one open end facing the case with the adhesive portion sandwiched therebetween. 2 10. The AE sensor structure according to claim 9. [ 5 The surface of the support base facing the adhesive portion is flat, a recess is provided in the case, and the support base is disposed in a position facing the recess with the adhesive portion interposed therebetween. 2 10. The AE sensor structure according to claim 9.

[0010] [ 6 The support base has a cross-sectional shape with one or more recesses, and is disposed with the open ends of the recesses facing the case with the adhesive portion sandwiched therebetween. 1 10. The AE sensor structure according to claim 9. [ 7 The shape of the recess is either triangular, rectangular, or arcuate. 6 10. The AE sensor structure according to claim 9. [ 8 The thickness of the thickest part of the thick-walled portion is 5 times or more the thickness of the thin-walled portion. 〔1〕、〔2〕、〔3〕、〔4〕、〔5〕、〔6〕、〔7〕 10. The AE sensor structure according to claim 9, wherein [ 9 The support base is made of metal. 〔1〕、〔2〕、〔3〕、〔4〕、〔5〕、〔6〕、〔7〕、〔8〕 10. The AE sensor structure according to claim 9, wherein [ 10 The thermal expansion coefficient of the support base is within ±30% of the thermal expansion coefficient of the sensor unit, and more preferably within ±10%. 〔1〕、〔2〕、〔3〕、〔4〕、〔5〕、〔6〕、〔7〕、〔8〕〔9〕 10. The AE sensor structure according to claim 9, wherein [Effects of the Invention]

[0011] Because the AE sensor structure of the present invention is configured as described above, it is possible to prevent damage to the adhesive or sensor portion while maintaining sensor performance even when used in an environment with large temperature changes. In other words, the present invention can provide an AE sensor that is less affected by temperature changes and that can expand the applicable temperature range. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing the basic configuration of an AE sensor structure of the present invention. [Figure 2] FIG. 4 is a cross-sectional view showing another example (H-type) of the AE sensor structure of the present invention. [Figure 3] FIG. 4 is a cross-sectional view showing another example of the AE sensor structure of the present invention (recessed case type). [Figure 4] FIG. 10 is a cross-sectional view showing another example of the configuration (multiple recesses type) of the support base of the AE sensor structure of the present invention. [Figure 5] 4A and 4B are cross-sectional views showing other configuration examples (triangular and arc-shaped) of the support base of the AE sensor structure of the present invention. [Figure 6] FIG. 1 is a cross-sectional view showing a fixing method in a conventional AE sensor. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below with reference to the drawings. 1 is a cross-sectional view showing the basic configuration of the AE sensor structure of the present invention. As shown in the figure, the AE sensor structure 10 basically comprises a sensor unit 1 made of a piezoelectric crystal, a support base 2 to which the sensor unit 1 is fixed, a case 3 to which the support base 2 is attached and which is itself fixed to the outside, and an adhesive portion 4 that fixes the support base 2 to the case 3. Furthermore, the adhesive portion 4 can be configured to comprise a thick portion 5 for maintaining the adhesive function and a thin portion 6 for propagating the AE wave.

[0014] With this configuration, in the present AE sensor structure 10, the sensor part 1 does not come into direct contact with the adhesive part 4 used to fix the case 3, but rather comes into contact with the support base 2 via the adhesive, thereby mitigating problems that would occur if the sensor part 1 and the case 3, which have different thermal expansion coefficients, were directly adjacent to each other with the adhesive sandwiched between them.

[0015] Furthermore, by forming a configuration in which thick portions 5 and thin portions 6 are formed, the thick portions 5 of the adhesive portion 4 maintain the adhesive function of fixing the support base 2 and the case 3, while the thin portions 6 ensure the AE wave propagation function, thereby ensuring the AE detection function of the sensor portion 1 fixed on the support base 2. As a result, this AE sensor structure 10 can maintain sensor performance even when used in an environment with large temperature changes, and can prevent damage to the adhesive portion 4 that bonds and fixes the sensor portion 1 to the exterior component, or to the relatively fragile sensor portion 1, which would cause a deterioration in its function as a sensor.

[0016] As mentioned above, when the piezoelectric element that makes up the sensor is made of LN or LT and the exterior parts are made of ceramics, there will be a difference in the thermal expansion coefficients of the two, and therefore stress will occur due to temperature changes.The support base will absorb this stress, reducing its impact on the sensor, but if the adhesive is not thick enough, the difference in the thermal expansion coefficients of the support base and case will damage the adhesive that secures the support base and case.

[0017] In the AE sensor structure 10 of the present invention, as shown in the figure, the support base 3 is formed into a U-shape and filled with adhesive, thereby giving the adhesive portion 4 a structure with different thicknesses, consisting of a thick portion 5 and a thin portion 6, and thereby ensuring adhesive function in the thick portion 5. If the adhesive were made to be of uniform thickness, the adhesive would act as a buffer material, weakening its ability to propagate externally generated AE waves to the sensor. However, in the present invention, the thin portion 6 performs the AE wave propagation function, so AE wave attenuation can be minimized.

[0018] As shown in Figure 1, the adhesive portion 4 of this AE sensor structure 10 can be configured so that its cross section is approximately convex, with a thin portion 6 located on the outside and a thick portion 5 located on the inside. That is, the adhesive portion 4 is configured so that the adhesive is filled thickly in the center and thinner in the peripheral portions; in other words, the thick portion 5 is contained within the area of the adhesive portion 4 that contacts the case 3. In this configuration, the adhesive function is maintained in the center, while the AE wave propagation function is ensured in the peripheral portions. Note that stress due to differences in the thermal expansion coefficients between the support base 2 and the thin portion 6 in the peripheral portions can be alleviated in the center of the support base 2, minimizing the impact.

[0019] Examples of piezoelectric crystals that form the sensor unit 1 of the present invention include lithium niobate (LN, lithium niobate), lithium tantalate (LT, lithium tantalate), potassium niobate (KN), quartz crystal, and PZT.

[0020] Any conventionally known resin adhesive or the like can be used as the adhesive for forming the adhesive portion 4. In addition to the adhesive portion 4 between the support base 2 and the case 3, the support base 2 and the sensor portion 1 are also bonded together, and these adhesives may be the same or different, but it is particularly desirable that the adhesive used on the case 3 side has a high hardness after solidification.

[0021] As shown in Figure 1, the support base 2 of this AE sensor structure 10 has a roughly U-shaped cross section, and can be configured with its open end facing the case 3, sandwiching the adhesive part 4 (U-shaped). As will be described later, the shape of the support base is not limited to this, but the one shown in this figure is the simplest and advantageous for manufacturing. As mentioned above, stress due to the thermal expansion coefficient of the adhesive part between the convex parts at both ends of the U-shape of the support base 2 and the case 3 can be alleviated by the concave parts of the U-shape of the support base 2, so the impact is minimized.

[0022] 2 is a cross-sectional view showing another example (H-type) of the AE sensor structure of the present invention. As shown in the figure, this AE sensor 210 can be configured such that the cross section of the support base 22 is approximately H-shaped, and one open end of the support base 22 is disposed facing the case 23 with the adhesive portion 24 sandwiched between them. That is, in the cross section of the approximately H-shape turned sideways, the recess 27C on the case 23 side is filled with adhesive to form the thick portion 25, and the thin portion 24 is formed on both ends of the recess 27C.

[0023] This configuration also maintains sensor performance and prevents damage to the adhesive and sensor portion in environments with large temperature changes, similar to the U-shaped configuration shown in Figure 1. Meanwhile, recess 27S on the sensor 21 side is the portion where sensor 21 is installed, and by sizing recess 27S to match the dimensions of sensor 21, sensor 21 can be stably fixed, and by reducing unevenness, the shape can be prevented from becoming too complicated.

[0024] 3 is a cross-sectional view showing another example (recessed case type) of the AE sensor structure of the present invention. As shown in the figure, this AE sensor structure 310 is characterized in that the surface of support base 32 facing adhesive portion 34 is flat, case 33 is provided with a recessed portion 38, and support base 32 is disposed in a position facing recessed portion 38 across adhesive portion 34. That is, unlike the examples shown in FIGS. 1 and 2, in this AE sensor structure 310, support base 32 is flat and has no particular irregularities, and the structural features lie in case 33.

[0025] That is, in this configuration, a recess 38 is formed in the case 33 as a portion for fixing the support base 32. The recess 38 formed in the case 33 is filled with adhesive to form a thick portion 35, and thin portions 34 are formed on both ends of the case 33 flush with the surface. The portion where the thick portion 35 is formed differs from the examples in Figures 1 and 2, but the adhesive portion is the same as in the examples in Figures 1 and 2, in that the thick portion and the thin portion form the adhesive portion.

[0026] As with the configurations described above, the configuration shown in this figure can maintain sensor performance in environments with large temperature changes and prevent damage to the adhesive and sensor unit. This configuration is particularly advantageous when it is preferable to change the structure of the case 33 rather than the structure of the support base 32 that contacts the sensor unit 31.

[0027] 4 is a cross-sectional view showing another example (multiple recesses) of the support base of the AE sensor structure of the present invention. As shown in (1) in the figure, support base 42 of this AE sensor structure has a cross-sectional shape with one or more recesses 47a, etc., and is characterized in that the open ends of the recesses 47a, etc. are arranged facing the case with an adhesive portion sandwiched between them. In the example of (1), there are two such recesses 47a, etc. (47a, 47b), but there may be three (57a, 57b, 57c), or four or more, as in support base 52 shown in (2) in the figure.

[0028] That is, recesses 47a, etc. on the case side of the support base 42, etc., are filled with adhesive to form thick sections, and thin sections are formed on both ends of the recesses. As with the above-mentioned configuration examples, this configuration maintains sensor performance in environments with large temperature changes and prevents damage to the adhesive and sensor unit. Furthermore, in a configuration in which multiple recesses 47a, etc. are provided on the support base 42, etc., as shown in this figure, it is possible to reduce the amount of adhesive used.

[0029] 5 is a cross-sectional view showing another example (triangular or arc-shaped) of the support base of the AE sensor structure of the present invention. As shown in the figure, the shape of the recess 67 of the support base 62 may be triangular ((1) in the figure), rectangular (see FIG. 4 above), or arc-shaped ((2) in FIG. 5). Although recesses of other shapes are within the scope of the present invention, the configurations shown in any of FIGS. 1 to 5 are advantageous in terms of manufacturing process and cost.

[0030] 5, recesses 67 on the case side of support base 62 are filled with adhesive to form thick sections, and thin sections are formed on both ends of the thick sections. As with the above-mentioned configuration examples, this achieves the effect of maintaining sensor performance in an environment with large temperature changes and preventing damage to the adhesive and sensor section.

[0031] In each of the above-described configurations of the AE sensor structure 10 of the present invention, the thinner the thickness of the thin portion 6, the better, but it is better to make it thicker compared to the thinnest part of the support base 2, etc. For example, the thickness of the thickest part of the thick portion 5 can be set to be five times or more the thickness of the thin portion 6.

[0032] The thermal expansion coefficient of the sensor unit 1 and the like varies depending on the material and crystal orientation used for it, so the material for the support base 2 and the like is selected to have a thermal expansion coefficient as close as possible to that of the sensor unit 1 and the like. In each of the AE sensor structures 10 and the like described so far, the material for the support base 2 and the like can be made of metal, in particular. For example, if the material for the sensor unit 1 and the like is lithium niobate (XY plane), stainless steel (SUS), copper, or the like, with a thermal expansion coefficient of about 10 to 15 ppm / °C, is desirable.

[0033] Furthermore, in each of the configurations described above, the specifications of the AE sensor structure 10 of the present invention can be designed so that the thermal expansion coefficient of the support base 2, etc. is within ±30% of the thermal expansion coefficient of the sensor part 1, etc., and more preferably within ±10%. [Example]

[0034] 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 to these. ·Material conditions of the prototype AE sensor Sensor part (element): LN, thermal expansion coefficient 17 ppm / ℃ Support base: Stainless steel (SUS304) Thermal expansion coefficient 18 ppm / ℃ Adhesive: Epoxy resin Shape of the support base and adhesive part: U-shaped as shown in Figure 1 Thin part thickness: ~20um Thickness of the thick part: 0.2mm~0.22mm When this prototype was tested, it was confirmed that the desired effects of the present invention described above could be sufficiently obtained. [Industrial Applicability]

[0035] The AE sensor structure of the present invention can prevent damage to the adhesive or sensor unit while maintaining sensor performance even when used in environments with large temperature changes. Therefore, this invention has high industrial applicability in the fields of AE sensor manufacturing, use, and all related fields. [Explanation of symbols]

[0036] 1, 21, 31...Sensor section 2, 22, 32, 42, 52, 62, 72...Support stand 3, 23, 33…case 4, 24, 34...Adhesive section 5, 25, 35…thick part 6, 26, 36...thin section 10, 210, 310...AE sensor structure 27C...Concave portion on the case side of the support 27S...Recess on the sensor side of the support 38...recess in case 47a, 47b, 57a, 57b, 57c, 67, 77...recesses on the case side of the support base (The following symbols relate to prior art.) 91...Sensor section 93...Exterior parts 94...Adhesive 910...AE sensor

Claims

1. a sensor portion 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 which is fixed to the outside; and an adhesive portion that fixes the support base and the case, The AE sensor structure is characterized in that the adhesive portion comprises a thick portion for maintaining adhesive function and a thin portion for AE wave propagation.

2. 2. The AE sensor structure according to claim 1, wherein the adhesive portion has a cross section that is generally convex, with the thin portion located on the outside and the thick portion located on the inside.

3. 3. The AE sensor structure according to claim 2, wherein the support base has a substantially U-shaped cross section and is positioned with its open end facing the case, with the adhesive portion sandwiched between them.

4. 3. The AE sensor structure according to claim 2, wherein the support base has a substantially H-shaped cross section and is arranged with one open end facing the case, with the adhesive portion sandwiched between them.

5. 3. The AE sensor structure according to claim 2, wherein the surface of the support base facing the adhesive portion is flat, the case is provided with a recess, and the support base is positioned in a position facing the recess with the adhesive portion sandwiched between them.

6. 2. The AE sensor structure according to claim 1, wherein the support base has a cross-sectional shape with one or more recesses, and the open ends of the recesses are positioned facing the case with the adhesive portion sandwiched between them.

7. 7. The AE sensor structure according to claim 6, wherein the shape of the recess is either triangular, rectangular or arcuate.

8. 8. The AE sensor structure according to claim 1, wherein the thickness of the thickest part of said thick part is at least five times that of said thin part.

9. 9. The AE sensor structure according to claim 1, wherein the support base is made of metal.

10. 10. The AE sensor structure according to claim 1, wherein the thermal expansion coefficient of the support base is within ±30%, more preferably ±10%, of the thermal expansion coefficient of the sensor portion.

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