Ultrasonic Sensor

Abstract

An ultrasonic sensor capable of being stably used in a high-temperature environment is provided. [Solution] The ultrasonic sensor includes a metal substrate, a piezoelectric body provided on the surface of the metal substrate, an upper electrode provided on the surface of the piezoelectric body, a cable electrically connected to the upper electrode, mica foil covering the piezoelectric body and the upper electrode from the surface side, and a cover that sandwiches the piezoelectric body, the upper electrode, and the mica foil between the metal substrate and the cover 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 ultrasonic sensors. [Background technology]

[0002] Various plants are equipped with many pipes, containers, etc. When high-temperature (e.g., 60°C to 600°C) fluid flows or is stored in such pipes, containers, etc. (hereinafter referred to as "pipes, etc."), thinning and cracks may occur in the pipes, etc. due to aging. Such thinning and cracks are likely to occur in curved parts such as curved pipes and elbow pipes, where the flow of the internal fluid changes, and in narrow parts of pipes, etc. For this reason, ultrasonic flaw detection inspections are performed using ultrasonic sensors.

[0003] A known ultrasonic sensor of this type is described in the following Patent Document 1. The device according to the following Patent Document 1 mainly comprises a metal substrate, a piezoelectric element, an upper electrode, and a silicon cover that encases these elements from all sides. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6432097 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-described configuration in which the entire device is covered with a silicone cover has a problem in that the heat resistance temperature of silicone is relatively low and therefore the device cannot withstand the high heat radiated from the piping.

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

[0007] In order to solve the above problems, the present disclosure provides a metal substrate, a piezoelectric body provided on the surface of the metal substrate, an upper electrode provided on the surface of the piezoelectric body, a cable electrically connected to the upper electrode, mica foil covering the piezoelectric body and the upper electrode from the surface side, and a cover that sandwiches the piezoelectric body, the upper electrode, and the mica foil between the metal substrate and is fixed to the metal substrate, the cover having heat resistance and insulation properties in a high-temperature environment of at least 500°C. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide an ultrasonic sensor that can be used stably in a high-temperature environment. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is an exploded perspective view showing a configuration of an ultrasonic sensor according to a first embodiment of the present disclosure. [Diagram 2] FIG. 11 is an exploded perspective view showing a configuration of an ultrasonic sensor according to a second embodiment of the present disclosure. [Diagram 3] FIG. 11 is a plan view showing a configuration of an ultrasonic sensor according to a second embodiment of the present disclosure. [Figure 4] 10A and 10B are plan views showing modified examples of ultrasonic sensors according to the first and second embodiments of the present disclosure. [Diagram 5] FIG. 11 is an exploded perspective view showing a configuration of an ultrasonic sensor according to a third embodiment of the present disclosure. [Figure 6] FIG. 11 is an exploded perspective view showing a configuration of an ultrasonic sensor according to a fourth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] First Embodiment (Configuration of ultrasonic sensor 1) Hereinafter, an ultrasonic sensor 1 according to a first embodiment of the present disclosure will be described with reference to Fig. 1. The ultrasonic sensor 1 is attached to the outer periphery 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 FIG. 1, the ultrasonic sensor 1 includes a metal substrate 10, a piezoelectric body 20, an upper electrode 30, a cable 40, a plurality of mica foils 70, and a mica cover 80.

[0013] The metal substrate 10, the piezoelectric body 20, the upper electrode 30, the mica foil 70, and the mica cover 80 are layered in this order from below. In the following description, the side on which the mica cover 80 is located as viewed from the metal substrate 10 side is referred to as the "front side," and the opposite side is referred to as the "rear side."

[0014] (Metal substrate 10) The metal substrate 10 is formed of a thin metal film and has a rectangular shape in a plan view. More specifically, the metal substrate 10 has a rectangular or square shape. The metal substrate 10 constitutes one of a pair of metal electrodes (lower electrode), and is formed of, for example, a SUS (Stainless Steel) thin plate, a platinum thin plate, a gold thin plate, or an Inconel (registered trademark) thin plate having a thickness of 20 μm to 50 μm.

[0015] (Piezoelectric body 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 part of the surface of the metal substrate 10 and heat treating it. For example, a lead zirconate titanate film (PZT film) of 80 μm to 100 μm can be used as the piezoelectric body 20. The piezoelectric body 20 has a circular shape with an outer diameter smaller than that of the metal substrate 10 in a plan view. The piezoelectric body 20 is provided in an area including the center of the metal substrate 10.

[0016] (Top electrode 30) The upper electrode 30 is formed by metal paste, deposition, plating, metal foil, etc., and for example, a silver (Ag) paste 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, the upper electrode 30 is formed by pressing a metal wool such as gold onto a part of the surface of the piezoelectric body 20. The upper electrode 30 has a circular shape with a smaller diameter than 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, a power supply device, etc., not shown.

[0018] (Mica foil 70) A plurality of mica foils 70 are laminated on the front surface side of the upper electrode 30. The mica foils 70 are in the form of a thin film formed of insulating mica. The mica foils 70 are provided to complement the insulation between the upper electrode 30 and the outside of the mica cover 80 described later, and the heat resistance against the surrounding heat. Each mica foil 70 has an area sufficient to cover the upper electrode 30 and the piezoelectric body 20 from the front surface side. As an example, the mica foils 70 are rectangular. Furthermore, among the plurality of mica foils 70, the mica foils 70 located on the piezoelectric body 20 side (i.e., the back surface side) have a larger area as viewed from the front surface side. This is to make the protruding height of the upper electrode 30 and the piezoelectric body 20 located on the back surface side smaller when the mica foils 70 are laminated.

[0019] (Mica Cover 80) The mica cover 80 (cover) is laminated on the front side of the mica foil 70. The mica cover 80 is a thin film mainly composed of mica, like the mica foil 70, and has an adhesive applied to its back side in advance. The mica cover 80 is rectangular like the metal substrate 10, and has the same area as the metal substrate 10. The back side of the mica cover 80 and the front side of the metal substrate 10 are bonded and fixed by the adhesive. As a result, 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, piezoelectric body 20, upper electrode 30, mica foil 70, and mica cover 80 constructed as described above is a thin film having a thickness of about 1 mm, so that the entire portion has flexibility and elasticity. In other words, this ultrasonic sensor 1 is capable of deforming to conform to the outer surface of a curved pipe, etc. The area of ​​the ultrasonic sensor 1 is, for example, 400 mm 2 That's about it.

[0021] (Action and effect) According to the above configuration, the back side of the ultrasonic sensor 1 is formed of the metal substrate 10, and the front side is formed of the mica cover 80. That is, no resin is used in the exposed parts. Therefore, even in a high-temperature environment of at least 500°C, the ultrasonic sensor 1 is not damaged and can be used stably. Therefore, ultrasonic inspection can be performed even when a high-temperature fluid is flowing through the pipe to be inspected, that is, when the plant is operating. This makes it possible to minimize the possibility of affecting the plant's availability and operational efficiency.

[0022] Here, since the areas of the piezoelectric body 20 and the upper electrode 30 are relatively small on the metal substrate 10, if these are covered with a mica cover 80 or the like, a part of the surface side will be raised. However, in the above configuration, a plurality of mica foils 70 are laminated, and the area of ​​the mica foil 70 closer to the piezoelectric body 20 is larger. This makes it possible to absorb the protruding height and reduce the difference in height with the surroundings. As a result, the flatness of the surface of the ultrasonic sensor 1 can be increased. Therefore, it is possible to further increase the adhesion between the ultrasonic sensor 1 and the object to be inspected, and it is possible to further improve the accuracy and efficiency of the inspection.

[0023] Second Embodiment Next, an ultrasonic sensor 101 according to a second embodiment of the present disclosure will be described with reference to Fig. 2 and Fig. 3. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0024] As shown in Fig. 2, in this embodiment, a metal cover 180 is used instead of the above-mentioned mica cover 80. The metal cover 180 is in the form of 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 heat resistance is taken into consideration, the thickness is most preferably 30 µm.

[0025] 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 sides other than the corners, and are in a free state. In other words, a plurality of spot welds 181 are provided at intervals along the edge of the outer periphery of the metal cover 180.

[0026] (Action and effect) According to the above configuration, the back side of the ultrasonic sensor 1 is formed of the metal substrate 10, and the front side is formed of the metal cover 180. That is, no resin is used in the exposed parts. Therefore, even in a high-temperature environment of at least 500°C, the ultrasonic sensor 1 is not damaged and can be used stably. Therefore, ultrasonic flaw detection inspection can be performed even when a high-temperature fluid is flowing through the pipe to be inspected, that is, when the plant is operating. This makes it possible to minimize the possibility of affecting the plant's availability and operational efficiency.

[0027] According to the above configuration, the thickness of the metal cover 180 is set to the minimum thickness that ensures heat resistance, thereby making the overall thickness of the ultrasonic sensor 1 as thin as possible. This makes it easier for the ultrasonic sensor 1 to bend and follow the outer surface of a pipe or the like with a small radius of curvature. This expands the usable range of the ultrasonic sensor 1, improving the efficiency of inspection 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 the corners. This increases the allowable amount of deflection compared to, for example, welding the entire edge on the outer periphery of the metal cover 180. This allows the entire ultrasonic sensor 1 to bend and follow the outer surface of a pipe or the like with a small radius of curvature more flexibly. This makes it possible to expand the range of objects to be inspected, making it possible to achieve efficient and smooth inspection.

[0029] <Modifications of the First and Second Embodiments> As a modified example of each of the above-mentioned embodiments, the configuration shown in FIG. 4 can be adopted. In the example shown in the figure, the mica cover 80 (metal cover 180) and the metal substrate 10 are circular in plan view. This configuration can also provide the same effects as those described above. When the metal cover 180 is used, it is desirable to join the metal cover 180 and the metal substrate 10 by spot welds 181 arranged at intervals along the outer peripheral edge, as in the second embodiment.

[0030] <Third embodiment> Next, an ultrasonic sensor 201 according to a third embodiment of the present disclosure will be described with reference to Fig. 5. Note that the same components as those in the above-described embodiments are given the same reference numerals, and detailed description thereof will be omitted.

[0031] As shown in Fig. 5, in this embodiment, a mesh material made of metal fibers is used as the metal cover 280. As this mesh material, for example, a standard product of about 200 mesh to 800 mesh is preferably used. More preferably, this value is 300 mesh to 600 mesh. Most preferably, this value is 400 mesh to 500 mesh. Even within the same mesh, the lower the void ratio, the more preferable it is.

[0032] In this embodiment, the metal substrate 10 and the metal cover 280 are also joined by spot welds 181 provided at the four corners. In other words, the metal substrate 10 and the metal cover 280 are not joined at the sides other than the corners, and are in a free state.

[0033] (Action and effect) According to the above configuration, by forming the metal cover 280 from a mesh material, the flexibility of the ultrasonic sensor 1 as a whole can be further increased. This makes it easier for the ultrasonic sensor 1 to bend and follow the outer surface of a pipe or the like with a small radius of curvature. It also makes it possible to reduce the overall weight. This expands the range in which the ultrasonic sensor 1 can be used, improves the efficiency of inspection, and minimizes costs.

[0034] <Fourth embodiment> Next, an ultrasonic sensor 301 according to a fourth embodiment of the present disclosure will be described with reference to Fig. 6. Note that the same components as those in the above-described embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0035] As shown in Fig. 6, in this embodiment, the means for joining the mesh material as the metal cover 280 and the metal substrate 10 is different from that of the third embodiment. 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 a heat-resistant fiber with a ceramic adhesive. As the heat-resistant fiber, aromatic polyamide (aramid), polyimide, polybenzimidazole, novoloid, flame-retardant cotton, etc. are preferably used.

[0036] (Action and effect) According to the above configuration, for example, when the metal cover 180 is made of a mesh material, the adhesive layer 390 can be interposed between the mesh material and the metal substrate 10 to improve the bonding strength significantly compared to welding or the like. This improves the durability of the ultrasonic sensor 1 as a whole. In addition, in the case of welding, the molten pool flows out through the gaps in the mesh, which makes processing difficult. However, according to the above configuration, such difficulties in the assembly work can be overcome. This makes it possible to manufacture the ultrasonic sensor 301 more easily and efficiently.

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

[0038] For example, in each of the above-described embodiments, an example has been described in which the reinforcing plate 50 is used to support the cable 40. However, depending on the strength of the cable 40, etc., this reinforcing plate 50 may be omitted.

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

[0040] Furthermore, in each of the above embodiments, the planar shapes of the metal substrate 10, the metal cover 180, etc. are described as being rectangular or circular. However, the planar shape is not limited to these, and may be, for example, a polygonal shape such as a hexagon or octagon, or an elliptical shape. In any case, the same effects as those described above can be obtained.

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

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

[0043] <Additional Notes> The ultrasonic sensor 1 described in each embodiment can be understood, for example, as follows.

[0044] (1) The ultrasonic sensor 1 according to the first aspect includes a metal substrate 10, a piezoelectric body 20 provided on the surface of the metal substrate 10, an upper electrode 30 provided on the surface of the piezoelectric body 20, a cable 40 electrically connected to the upper electrode 30, a mica foil 70 covering the piezoelectric body 20 and the upper electrode 30 from the surface side, and a cover 80 sandwiching the piezoelectric body 20, the upper electrode 30, and the mica foil 70 between the metal substrate 10 and the cover 80 fixed to the metal substrate 10, and having heat resistance and insulation in a high-temperature environment of at least 500°C.

[0045] According to the above configuration, the ultrasonic sensor 1 is not damaged even in a high temperature environment and can be used stably.

[0046] (2) The ultrasonic sensor 1 according to the second aspect is the ultrasonic sensor 1 of (1), comprising a metal substrate 10, a piezoelectric body 20 provided on the surface of the metal substrate 10, an upper electrode 30 provided on the surface of the piezoelectric body 20, a cable 40 electrically connected to the upper electrode 30, a mica foil 70 covering the piezoelectric body 20 and the upper electrode 30 from the surface side, and a metal cover 180 sandwiching the piezoelectric body 20, the upper electrode 30, and the mica foil 70 between the metal substrate 10 and the metal cover 180 and fixed to the metal substrate 10, and the metal cover 180 is fixed to the metal substrate 10 by spot welds 181 provided at multiple locations.

[0047] According to the above configuration, the ultrasonic sensor 1 is not damaged even in a high temperature environment and can be used stably.

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

[0049] According to the above configuration, the ultrasonic sensor 1 can be easily curved and conformed to the outer surface of a pipe or the like having a small radius of curvature.

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

[0051] According to the above configuration, the ultrasonic sensor 1 can be easily curved and conformed to the outer surface of a pipe or the like having a small radius of curvature. In addition, the overall weight can be reduced.

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

[0053] According to the above configuration, the durability of the entire ultrasonic sensor 1 can be improved.

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

[0055] According to the above configuration, the entire ultrasonic sensor 1 can be more flexibly curved and conformed to the outer surface of a pipe or the like having a small radius of curvature.

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

[0057] According to the above configuration, the entire ultrasonic sensor 1 can be more flexibly curved and conformed to the outer surface of a pipe or the like having a small radius of curvature.

[0058] (8) The ultrasonic sensor 1 of the eighth aspect is an ultrasonic sensor 1 of any one of the aspects (1) to (7), in which the mica foil 70 is laminated in multiple layers, and the mica foil 70 closer to the piezoelectric body 20 has a larger area when viewed from the front side.

[0059] According to the above configuration, it is possible to further increase the contact between the ultrasonic sensor 1 and the object to be inspected, and it is possible to further improve the accuracy and efficiency of the inspection. [Explanation of symbols]

[0060] 1...ultrasonic sensor 10...metal substrate 20...piezoelectric body 30...upper electrode 40...cable 41...core wire 42...coating 50...reinforcing plate 51...reinforcing plate body 52...saddle 60...insulating tape 70...mica foil 80...mica cover 101...ultrasonic sensor 180...metal cover 181...spot weld 201...ultrasonic sensor 280...metal cover 301...ultrasonic sensor 390...adhesive layer

Claims

1. A metal substrate; a piezoelectric body provided on a surface of the metal substrate; an upper electrode provided on a surface of the piezoelectric body; a cable electrically connected to the upper electrode; a mica foil covering the piezoelectric body and the upper electrode from the front surface side; a cover that is fixed to the metal substrate and that sandwiches the piezoelectric body, the upper electrode, and the mica foil between the metal substrate and the cover, and that has heat resistance and insulation properties in a high-temperature environment of at least 500° C.; An ultrasonic sensor comprising:

2. 2. The ultrasonic sensor according to claim 1, wherein a plurality of the mica foils are laminated, and the mica foil closer to the piezoelectric body has a larger area when viewed from the front surface side.

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