Ultrasonic sensor

Abstract

To provide an ultrasonic sensor that can be used stably in high-temperature environments. [Solution] The ultrasonic sensor comprises a metal substrate, a piezoelectric element provided on the surface of the metal substrate, an upper electrode provided on the surface of the piezoelectric element, a cable electrically connected to the upper electrode, a mica foil covering the piezoelectric element and the upper electrode from the surface side, and a cover that sandwiches the piezoelectric element, the upper electrode, and the mica foil between itself and the metal substrate and is fixed to the metal substrate. With this configuration, the heat resistance of the ultrasonic sensor can be significantly improved.

Description

Technical Field

[0001] The present disclosure relates to an ultrasonic sensor.

Background Art

[0002] In various plants, a large number of pipes, containers, etc. are provided. When a fluid at a high temperature (for example, 60°C to 600°C) flows through or is stored in such pipes, containers, etc. (hereinafter referred to as "pipes, etc."), wall thickness reduction and cracks may occur in the pipes, etc. due to aging deterioration. Such wall thickness reduction and cracks are likely to occur in curved portions such as curved pipes and elbow pipes where the flow of the internal fluid changes, and in narrow portions of the pipes, etc. Therefore, ultrasonic flaw detection inspection using an ultrasonic sensor is performed.

[0003] As this type of ultrasonic sensor, the one described in Patent Document 1 below is known. The device according to Patent Document 1 below mainly includes a metal substrate, a piezoelectric element, an upper electrode, and a silicon cover that integrally wraps these from the surroundings.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the configuration where the whole is covered with a silicon cover as described above, since the heat-resistant temperature of silicon is relatively low, there is a problem that it cannot withstand the high heat radiated from the pipe.

[0006] The present disclosure has been made to solve the above problems, and an object thereof is to provide an ultrasonic sensor that can be stably used in a high-temperature environment.

Means for Solving the Problems

[0007] To solve the above problems, the present disclosure comprises a metal substrate, a piezoelectric element provided on the surface of the metal substrate, an upper electrode provided on the surface of the piezoelectric element, a cable electrically connected to the upper electrode, a mica foil covering the piezoelectric element and the upper electrode from the surface side, and a cover fixed to the metal substrate, sandwiching the piezoelectric element, the upper electrode, and the mica foil between the metal substrate and the cover, and having heat resistance and insulation properties in a high-temperature environment of at least 500°C.

[0008] The ultrasonic sensor according to this disclosure comprises a metal substrate, a piezoelectric element provided on the surface of the metal substrate, an upper electrode provided on the surface of the piezoelectric element, a cable electrically connected to the upper electrode, a mica foil covering the piezoelectric element and the upper electrode from the surface side, and a metal cover that sandwiches the piezoelectric element, the upper electrode, and the mica foil between itself and the metal substrate and is fixed to the metal substrate, wherein the metal cover is fixed to the metal substrate by a plurality of spot welds provided therein. [Effects of the Invention]

[0009] This disclosure provides an ultrasonic sensor that can be used stably in high-temperature environments. [Brief explanation of the drawing]

[0010] [Figure 1] This is an exploded perspective view showing the configuration of an ultrasonic sensor according to the first embodiment of this disclosure. [Figure 2] This is an exploded perspective view showing the configuration of an ultrasonic sensor according to a second embodiment of this disclosure. [Figure 3] This is a plan view showing the configuration of an ultrasonic sensor according to the second embodiment of this disclosure. [Figure 4] This is a plan view showing a modified example of an ultrasonic sensor according to the first / second embodiment of this disclosure. [Figure 5] This is an exploded perspective view showing the configuration of an ultrasonic sensor according to the third embodiment of this disclosure. [Figure 6]This is an exploded perspective view showing the configuration of an ultrasonic sensor according to the fourth embodiment of this disclosure. [Modes for carrying out the invention]

[0011] <First Embodiment> (Configuration of ultrasonic sensor 1) Hereinafter, an ultrasonic sensor 1 according to the first embodiment of this disclosure will be described with reference to Figure 1. This ultrasonic sensor 1 is attached to the outer circumference of a pipe through which a high-temperature fluid flows and is used to detect thinning or cracks in the pipe.

[0012] As shown in Figure 1, the ultrasonic sensor 1 comprises a metal substrate 10, a piezoelectric element 20, an upper electrode 30, a cable 40, a plurality of mica foils 70, and a mica cover 80.

[0013] The metal substrate 10, piezoelectric element 20, upper electrode 30, mica foil 70, and mica cover 80 are stacked in this order from bottom to top. In the following description, the side where the mica cover 80 is located, as viewed from the metal substrate 10 side, will be referred to as the "front side," and the opposite side will be referred to as the "back side."

[0014] (Metal substrate 10) The metal substrate 10 is formed of a thin metal film and has a rectangular shape when viewed from above. More specifically, the metal substrate 10 is rectangular or square. The metal substrate 10 constitutes one of a pair of metal electrodes (the lower electrode) and is formed of, for example, a thin sheet of SUS (Stainless Steel), a thin sheet of platinum, a thin sheet of gold, or a thin sheet of Inconel® with a thickness of 20 μm to 50 μm.

[0015] (Piezoelectric element 20) The piezoelectric body 20 is a thin-film piezoelectric element that transmits and receives ultrasonic waves, and is formed by applying a solution containing piezoelectric ceramic powder to a part of the surface of the metal substrate 10 and performing heat treatment. As the piezoelectric body 20, for example, a lead zirconate titanate film (PZT film) with a thickness of 80 μm to 100 μm can be used. The piezoelectric body 20 has a circular shape with an outer diameter dimension smaller than that of the metal substrate 10 in a plan view. The piezoelectric body 20 is provided in a region including the central part of the metal substrate 10.

[0016] (Upper electrode 30) The upper electrode 30 is formed by, for example, metal paste, vapor deposition, plating, metal foil, etc., and for example, a silver (Ag) paste with a thickness of 5 μm to 20 μm can be used. The upper electrode 30 is formed by, for example, applying a metal paste to a part of the surface of the piezoelectric body 20 and then firing it. Alternatively, it is formed by pressing a metal wool such as gold onto a part of the surface of the piezoelectric body 20. Also, the upper electrode 30 has a circular shape with a smaller diameter than that of the piezoelectric body 20 in a plan view.

[0017] (Cable 40) The cable 40 is a coaxial cable, and its inner conductor is electrically connected to the upper electrode 30. The outer conductor is electrically connected to the metal substrate 10. The other end of the cable 40 is connected to an analysis device and a power supply device (not shown), etc.

[0018] (Mica foil 70) On the surface side of the upper electrode 30, a plurality of mica foils 70 are laminated. The mica foil 70 is in the form of a thin film formed of insulating mica. The mica foil 70 is provided to complement the insulation between the upper electrode 30 and the outside of a mica cover 80 described later and the heat resistance against ambient heat. Each mica foil 70 has an area large enough to cover the upper electrode 30 and the piezoelectric body 20 from the surface side. As an example, the mica foil 70 is rectangular. Further, among the plurality of mica foils 70, the mica foil 70 positioned closer to the piezoelectric body 20 side (that is, the back surface side) has a larger area when viewed from the surface side. This is to reduce the protruding heights of the upper electrode 30 and the piezoelectric body 20 located on the back surface side thereof when the mica foils 70 are laminated.

[0019] (Mica cover 80) The mica cover 80 (cover) is laminated on the further surface side of the above-described mica foil 70. The mica cover 80 is in the form of a thin film mainly composed of mica, similar to the mica foil 70, and an adhesive is pre-coated on its back surface. The mica cover 80 is rectangular, similar to the metal substrate 10, and its area is also equivalent to that of the metal substrate 10. The back surface of the mica cover 80 and the surface of the metal substrate 10 are adhesively fixed by the adhesive. Thereby, the piezoelectric body 20, the upper electrode 30, and the tip of the cable 40 are sandwiched between the mica cover 80 and the metal substrate 10.

[0020] The portion formed by the metal substrate 10, the piezoelectric body 20, the upper electrode 30, the mica foil 70, and the mica cover 80 configured as described above is in the form of a thin film with a thickness of about 1 mm, so the whole has flexibility and elasticity. That is, this ultrasonic sensor 1 can be deformed following the outer surface of a pipe having a curved surface shape or the like. Note that the area of the ultrasonic sensor 1 is, for example, 400 mm 2 or so.

[0021] (Function and effect) According to the above configuration, the back side of the ultrasonic sensor 1 is formed from a metal substrate 10, and the front side is formed from a mica cover 80. In other words, no resin is used in the exposed parts. Therefore, the ultrasonic sensor 1 will not be damaged even in high-temperature environments of at least 500°C and can be used stably. Consequently, ultrasonic flaw detection can be performed even when high-temperature fluid is flowing through the piping to be inspected, i.e., when the plant is in operation. This makes it possible to minimize the possibility of affecting the plant's operating rate and operational efficiency.

[0022] Here, on the metal substrate 10, the area of ​​the piezoelectric element 20 and the upper electrode 30 is relatively small. If they were simply covered with a mica cover 80, a portion of the surface would be raised. However, in the above configuration, multiple mica foils 70 are laminated, and the area of ​​the mica foil 70 on the piezoelectric element 20 side is larger. This absorbs the protruding height and minimizes the height difference with the surrounding area. As a result, the flatness of the surface of the ultrasonic sensor 1 can be improved. Therefore, it becomes possible to further improve the adhesion between the ultrasonic sensor 1 and the object to be inspected, thereby further improving the accuracy and efficiency of inspection.

[0023] <Second Embodiment> Next, the ultrasonic sensor 101 according to the second embodiment of this disclosure will be described with reference to Figures 2 and 3. Note that components similar to those in the first embodiment are denoted by the same reference numerals, and detailed descriptions are omitted.

[0024] As shown in Figure 2, in this embodiment, a metal cover 180 is used instead of the mica cover 80 described above. The metal cover 180 is a thin plate made of SUS or a nickel-based alloy. The thickness of the metal cover 180 is, for example, 5 μm to 30 μm. More preferably, the thickness is 15 μm to 30 μm. When considering heat resistance, the most preferable thickness is 30 μm.

[0025] As shown in Figure 3, the metal substrate 10 and the metal cover 180 are joined by spot welds 181 provided at each of the four corners. In other words, the metal substrate 10 and the metal cover 180 are not joined at the edges other than these corners and are in a free state. To put it another way, multiple spot welds 181 are provided at intervals along the outer edge of the metal cover 180.

[0026] (Effects and Benefits) According to the above configuration, the back side of the ultrasonic sensor 1 is formed from a metal substrate 10, and the front side is formed from a metal cover 180. In other words, no resin is used in the exposed parts. Therefore, the ultrasonic sensor 1 will not be damaged even in high-temperature environments of at least 500°C and can be used stably. Consequently, ultrasonic flaw detection can be performed even when high-temperature fluid is flowing through the piping to be inspected, i.e., when the plant is in operation. This makes it possible to minimize the possibility of affecting the plant's operating rate and operational efficiency.

[0027] With the above configuration, by setting the thickness of the metal cover 180 to the minimum thickness that ensures heat resistance, the overall thickness of the ultrasonic sensor 1 can be made as thin as possible. This makes it easier to bend and conform to the outer surface of pipes and other objects with small radii of curvature. Therefore, the usable range of the ultrasonic sensor 1 is expanded, improving inspection efficiency and minimizing costs.

[0028] According to the above configuration, the metal cover 180 and the metal substrate 10 are joined by spot welds 181 provided at each corner. This increases the allowable amount of deflection compared to, for example, welding the entire outer edge of the metal cover 180. Therefore, the entire ultrasonic sensor 1 can bend and follow even the outer surface of pipes and other objects with a small radius of curvature more flexibly. This makes it possible to expand the range of objects that can be inspected, thereby improving the efficiency and smoothness of inspections.

[0029] <Modifications of the first and second embodiments> As a modified example of each of the embodiments described above, the configuration shown in Figure 4 can be adopted. In the example shown in the figure, the mica cover 80 (metal cover 180) and the metal substrate 10 have a circular shape in plan view. The same effects as described above can be obtained with this configuration as well. When using the metal cover 180, it is desirable that the metal cover 180 and the metal substrate 10 are joined by spot welds 181 arranged at intervals along the outer edge, similar to the method described in the second embodiment.

[0030] <Third Embodiment> Next, the ultrasonic sensor 201 according to the third embodiment of this disclosure will be described with reference to Figure 5. Note that components similar to those in the embodiments described above are denoted by the same reference numerals, and detailed descriptions are omitted.

[0031] As shown in Figure 5, in this embodiment, a mesh material made of metal fibers is used as the metal cover 280. As an example, standard mesh materials with a mesh count of approximately 200 to 800 are preferably used. More preferably, this range is 300 to 600 mesh. Most preferably, this range is 400 to 500 mesh. Furthermore, even within the same mesh count, a lower void ratio is preferable.

[0032] In this embodiment as well, the metal substrate 10 and the metal cover 280 are joined by spot welds 181 provided at each of the four corners. In other words, the edges other than these corners are not joined to the metal substrate 10 and the metal cover 280, and are in a free state.

[0033] (Effects and Benefits) According to the above configuration, forming the metal cover 280 from a mesh material further increases the overall flexibility of the ultrasonic sensor 1. This makes it easier to bend and conform to the outer surface of pipes and other structures with small radii of curvature. It also reduces the overall weight. Therefore, the usable range of the ultrasonic sensor 1 is expanded, improving inspection efficiency and minimizing costs.

[0034] <Fourth Embodiment> Next, the ultrasonic sensor 301 according to the fourth embodiment of this disclosure will be described with reference to Figure 6. Components similar to those in the embodiments described above are denoted by the same reference numerals, and detailed descriptions are omitted.

[0035] As shown in Figure 6, in this embodiment, the means of bonding the mesh material as the metal cover 280 to the metal substrate 10 differs from that of the third embodiment described above. Specifically, an adhesive layer 390 is interposed between the metal cover 280 and the mica foil 70. This adhesive layer 390 has an area equivalent to that of the metal substrate 10. The adhesive layer 390 is in the form of a film formed by impregnating heat-resistant fibers with a ceramic adhesive. Suitable heat-resistant fibers include aromatic polyamide (aramid), polyimide, polybenzimidazole, novoroid, and flame-retardant cotton.

[0036] (Effects and Benefits) According to the above configuration, for example, when the metal cover 180 is formed from a mesh material, the bonding strength between the mesh material and the metal substrate 10 can be significantly increased compared to welding by interposing the adhesive layer 390. Therefore, the overall durability of the ultrasonic sensor 1 can be improved. In the case of welding, the molten pool flows out through the gaps in the mesh, which presents difficulties in processing. However, according to the above configuration, such difficulties in assembly can be overcome. Therefore, it becomes possible to manufacture the ultrasonic sensor 301 more easily and efficiently.

[0037] (Other embodiments) Although embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include design changes and the like that do not depart from the gist of this disclosure.

[0038] For example, in each of the embodiments described above, an example was given in which a reinforcing plate 50 is used to support the cable 40. However, depending on the strength of the cable 40, it may be possible to omit this reinforcing plate 50.

[0039] Furthermore, the dimensions of the ultrasonic sensor 1, such as its area and thickness, are examples only and can be changed as appropriate according to the design and specifications.

[0040] Furthermore, in each of the embodiments described above, the cases in which the planar shapes of the metal substrate 10 and the metal cover 180 are rectangular or circular have been explained. However, the planar shape is not limited to these, and may be a polygon such as a hexagon or octagon, or even an ellipse. In any case, the same effects and advantages as described above can be obtained.

[0041] Furthermore, various other materials can be used instead of the mica cover 80 described in the above embodiment. For example, any material that has heat resistance and insulation properties at least in a 500°C atmosphere, such as glass fiber, talc, or xansite, can be used.

[0042] In addition, the configurations of each of the embodiments described above can be combined with each other. For example, the adhesive layer 390 described in the fourth embodiment can be combined with the configuration described in the second embodiment.

[0043] <Note> The ultrasonic sensor 1 described in each embodiment is detected, for example, as follows.

[0044] (1) The ultrasonic sensor 1 according to the first embodiment comprises a metal substrate 10, a piezoelectric element 20 provided on the surface of the metal substrate 10, an upper electrode 30 provided on the surface of the piezoelectric element 20, a cable 40 electrically connected to the upper electrode 30, a mica foil 70 covering the piezoelectric element 20 and the upper electrode 30 from the surface side, and a cover 80 fixed to the metal substrate 10, which sandwiches the piezoelectric element 20, the upper electrode 30 and the mica foil 70 between itself and the metal substrate 10 and has heat resistance and insulating properties in a high-temperature environment of at least 500°C.

[0045] With the above configuration, the ultrasonic sensor 1 will not be damaged even in high-temperature environments and can be used stably.

[0046] (2) The ultrasonic sensor 1 according to the second embodiment is the ultrasonic sensor 1 according to (1), comprising: a metal substrate 10; a piezoelectric element 20 provided on the surface of the metal substrate 10; an upper electrode 30 provided on the surface of the piezoelectric element 20; a cable 40 electrically connected to the upper electrode 30; a mica foil 70 covering the piezoelectric element 20 and the upper electrode 30 from the surface side; and a metal cover 180 that sandwiches the piezoelectric element 20, the upper electrode 30 and the mica foil 70 between itself and the metal substrate 10 and is fixed to the metal substrate 10, wherein the metal cover 180 is fixed to the metal substrate 10 by a plurality of spot welds 181 provided on the metal substrate 10.

[0047] With the above configuration, the ultrasonic sensor 1 will not be damaged even in high-temperature environments and can be used stably.

[0048] (3) The ultrasonic sensor 1 according to the third embodiment is the ultrasonic sensor 1 of (2), wherein the metal cover 180 has a thickness of 5 μm or more and 30 μm or less.

[0049] With the above configuration, the ultrasonic sensor 1 can be easily bent and followed even on the outer surface of pipes and the like with a small radius of curvature.

[0050] (4) The ultrasonic sensor 1 according to the fourth embodiment is the ultrasonic sensor 1 of (2) or (3), wherein the metal cover 180 is a mesh material made of metal fibers.

[0051] With the above configuration, the ultrasonic sensor 1 can be easily bent and followed even on the outer surface of pipes and other structures with small radii of curvature. Furthermore, the overall weight can be reduced.

[0052] (5) The ultrasonic sensor 1 according to the fifth embodiment is an ultrasonic sensor 1 according to any one embodiment of (2) to (4), further comprising an adhesive layer 390 provided on the back side of the metal cover 180, which includes a heat-resistant adhesive that covers the mica foil 70, the piezoelectric element 20, and the metal substrate 10 to fix the metal cover 180 and the metal substrate 10.

[0053] The above configuration makes it possible to improve the overall durability of the ultrasonic sensor 1.

[0054] (6) The ultrasonic sensor 1 according to the sixth embodiment is an ultrasonic sensor 1 according to any one embodiment of (2) to (5), wherein the metal substrate 10 and the metal cover 180 are rectangular when viewed from the surface side, and the spot welds 181 are provided one at each corner of the rectangle.

[0055] With the above configuration, the entire ultrasonic sensor 1 can be bent and conform to the outer surface of pipes and other structures with small radii of curvature even more flexibly.

[0056] (7) The ultrasonic sensor 1 according to the seventh embodiment is an ultrasonic sensor 1 according to any one embodiment of (2) to (6), wherein the metal substrate 10 and the metal cover 180 are circular when viewed from the surface side, and four spot welds 181 are provided at intervals along the outer edge of the circular surface.

[0057] With the above configuration, the entire ultrasonic sensor 1 can be bent and conform to the outer surface of pipes and other structures with small radii of curvature even more flexibly.

[0058] (8) The ultrasonic sensor 1 according to the eighth embodiment is an ultrasonic sensor 1 according to any one embodiment of (1) to (7), wherein the mica foil 70 is laminated in multiple layers, and the area of ​​the mica foil 70 on the piezoelectric element 20 side is larger when viewed from the surface side.

[0059] With the above configuration, it becomes possible to further improve the contact between the ultrasonic sensor 1 and the object being inspected, thereby further improving the accuracy and efficiency of the inspection. [Explanation of Symbols]

[0060] 1…Ultrasonic sensor 10…Metal substrate 20…Piezoelectric element 30…Upper electrode 40…Cable 41…Core wire 42…Coating 50…Reinforcement plate 51…Reinforcement plate body 52…Saddle 60…Insulating tape 70…Mica foil 80…Mica cover 101…Ultrasonic sensor 180…Metal cover 181…Spot welded part 201…Ultrasonic sensor 280…Metal cover 301…Ultrasonic sensor 390…Adhesive layer

Claims

1. A metal substrate and A piezoelectric element provided on the surface of the metal substrate, An upper electrode provided on the surface of the piezoelectric element, A cable electrically connected to the upper electrode, The piezoelectric element and the upper electrode are covered from the surface side by a mica foil, A cover is fixed to the metal substrate and sandwiches the piezoelectric element, the upper electrode, and the mica foil between them, and has heat resistance and insulating properties in a high-temperature environment of at least 500°C. An ultrasonic sensor equipped with [a specific feature].

2. A metal substrate and A piezoelectric element provided on the surface of the metal substrate, An upper electrode provided on the surface of the piezoelectric element, A cable electrically connected to the upper electrode, The piezoelectric element and the upper electrode are covered from the surface side by a mica foil, A metal cover is fixed to the metal substrate and sandwiches the piezoelectric element, the upper electrode, and the mica foil between the metal substrate and the metal substrate. Equipped with, The metal cover is fixed to the metal substrate by multiple spot welds, which are provided at various locations on the ultrasonic sensor.

3. The ultrasonic sensor according to claim 2, wherein the metal cover has a thickness of 5 μm or more and 30 μm or less.

4. The ultrasonic sensor according to claim 2 or 3, wherein the metal cover is made of a mesh material formed of metal fibers.

5. The ultrasonic sensor according to claim 4, further comprising an adhesive layer provided on the back side of the metal cover, which includes a heat-resistant adhesive that covers the mica foil, the piezoelectric element, and the metal substrate to fix the metal cover and the metal substrate together.

6. The ultrasonic sensor according to claim 2 or 3, wherein the metal substrate and the metal cover are rectangular when viewed from the surface side, and the spot welds are provided one at each corner of the rectangle.

7. The ultrasonic sensor according to claim 2 or 3, wherein the metal substrate and the metal cover are circular when viewed from the surface side, and four spot welds are provided at intervals along the outer edge of the circle.

8. The ultrasonic sensor according to any one of claims 1 to 3, wherein the mica foil is laminated in multiple layers, and the area of ​​the mica foil viewed from the surface side is larger as it is on the piezoelectric side.

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