Electromagnetic ultrasonic sensor

Abstract

The utility model discloses an electromagnetic ultrasonic sensor relates to industrial bolt detection equipment technical field. Electromagnetic ultrasonic sensor includes sensing assembly and shell, sensing assembly includes coaxial line setting's first magnet, the second magnet of setting in first magnet outside, the coil of being located first magnet with second magnet below, the shell has the first shell department of setting in sensing assembly outside, is connected in second shell department and protrudes downwards in first shell department, wherein, the inner wall surface structure of second shell department is the arc surface of can provide radial constraint, and defines the positioning space of open bottom, second shell department is provided with with the positioning space intercommunication to allow the bolt of being measured along the radial of shell enters the clamping port of positioning space. Through adopting the technology that the utility model provides, reduced to the demand of bolt upper axial space, makes electromagnetic ultrasonic sensor still can efficiently carry out detection operation in the narrow space.

Description

Technical Field

[0001] This utility model relates to the technical field of industrial bolt testing equipment, and specifically to an electromagnetic ultrasonic sensor. Background Technology

[0002] In the non-destructive testing of bolt preload, electromagnetic ultrasonic technology, with its non-contact advantage of requiring no coupling agent, is widely used in various fields such as power and petrochemicals. Its basic principle is to use an electromagnetic ultrasonic sensor to excite ultrasonic waves in the bolt, and then measure the bolt preload by measuring the propagation time of the ultrasonic waves within the bolt. However, in practical applications, to ensure stable signal excitation and reception, the bottom end face of the electromagnetic ultrasonic sensor must still be vertically aligned and tightly fitted to the center of the end face of the bolt being tested (usually the top surface of the bolt head).

[0003] This structure means that the electromagnetic ultrasonic sensor must occupy a certain axial space above the bolt. However, in many operating conditions, the installation space above the bolt is extremely limited. For example, in the testing and use of wind turbine generators, the turbine blades are connected to the hub via bolt sets. These bolts often feature a countersunk design, resulting in extremely limited axial space above the bolt end face. Traditional electromagnetic ultrasonic sensors are difficult to fit into such confined axial spaces, or even if placed within them, it is difficult to adjust them to a state of good fit with the bolt end face. Utility Model Content

[0004] This invention provides an electromagnetic ultrasonic sensor to solve the problem that the limited axial space of the bolt being tested makes it difficult to detect it.

[0005] To solve the above-mentioned technical problems, the present invention provides an electromagnetic ultrasonic sensor for detecting bolts. The electromagnetic ultrasonic sensor includes a sensing component and a housing; the sensing component includes a first magnet arranged coaxially, a second magnet sleeved outside the first magnet, and a coil located below the first and second magnets; the housing has a first housing portion sleeved outside the sensing component and a second housing portion connected to the first housing portion and protruding downwards; wherein the inner wall surface of the second housing portion is constructed as an arc surface that provides radial constraint and defines a positioning space with an open bottom, and the second housing portion has a locking interface communicating with the positioning space to allow the bolt to be tested to enter the positioning space radially along the housing.

[0006] By adopting the above technical solution, this utility model uses a first magnet, a second magnet, and a coil arranged on the same axis to ensure that ultrasonic waves with excellent mode directivity can be excited on the surface of the bolt to be tested, thereby ensuring the transduction efficiency and signal-to-noise ratio of the electromagnetic ultrasonic sensor.

[0007] The electromagnetic ultrasonic sensor, via a snap-fit ​​interface in the second housing and an open positioning space at the bottom, can radially snap onto the bolt. This allows the inner wall surface (arc-shaped surface) of the second housing to directly engage with the outer circumference of the bolt, providing stable radial constraint on the bolt head. This effectively prevents sensor wobbling and displacement during testing, ensuring consistency in the relative geometry between the sensing component and the bolt. Furthermore, this passive, radially snap-fit ​​positioning mechanism, compared to traditional methods requiring complex alignment from the bolt top, fundamentally reduces the need for axial space above the bolt, fully utilizing the more ample radial space. This enables the electromagnetic ultrasonic sensor to perform efficient testing even in confined spaces.

[0008] According to another specific embodiment of the present invention, the second outer shell is arc-shaped, and the inner wall surface is coaxially arranged with the sensing component, wherein the arc of the inner wall surface is 90° to 180°.

[0009] According to another specific embodiment of the present invention, the length of the second outer shell portion protruding downward from the bottom surface of the sensing component is no more than 12mm.

[0010] According to another specific embodiment of the present invention, the inner diameter of the second outer shell portion is not greater than the inner diameter of the first outer shell portion, and the outer diameter of the second outer shell portion is greater than or equal to the outer diameter of the first outer shell portion.

[0011] According to another specific embodiment of the present invention, the inner diameter of the second outer shell portion is smaller than the inner diameter of the first outer shell portion, so as to form an annular step that protrudes radially on the inner side of the connection between the first outer shell portion and the second outer shell portion.

[0012] According to another specific embodiment of the present invention, the sensing component further includes an inner shell covering the first magnet, the second magnet and the coil, and the first outer shell is detachably sleeved on the inner shell.

[0013] According to another specific embodiment of the present invention, the top surface of the first outer shell is constructed as a centrally open annular structure, and the annular structure is attached to the top surface of the inner shell.

[0014] According to another specific embodiment of the present invention, the inner shell is formed with a plug interface that is electrically connected to the coil, and the first outer shell is provided with a mounting groove that corresponds to the position of the plug interface and communicates with the card interface; the electromagnetic ultrasonic sensor further includes a plug-in component that passes through the mounting groove and is connected to the plug interface.

[0015] According to another specific embodiment of the present invention, the radial length of the connector is 35mm to 60mm.

[0016] According to another specific embodiment of the present invention, the connector includes a gland plugged into the inner shell, a spring connected to the side of the gland away from the inner shell, and a cable passing through the gland, the spring and electrically connected to the coil. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a three-dimensional structural schematic diagram of an embodiment of the electromagnetic ultrasonic sensor provided in this application; Figure 2 yes Figure 1 A diagram from another perspective; Figure 3 yes Figure 1 Another perspective illustration; Figure 4 yes Figure 3 A schematic diagram of a cross-section along section AA; Figure 5 yes Figure 4 A magnified view of part B in the middle section; Figure 6 This is a three-dimensional structural schematic diagram of an embodiment of the housing provided in this application; Figure 7 yes Figure 6 A diagram from another perspective.

[0018] Explanation of reference numerals in the attached figures: 1. Sensing component; 10. First magnet; 11. Second magnet; 12. Coil; 13. Wear-resistant sheet; 14. Magnetic shield; 15. Inner shell; 150. Socket; 2. Outer shell; 20. First outer shell section; 200. Circular ring structure; 201. Mounting groove; 21. Second outer shell section; 210. Inner wall surface; 211. Positioning space; 212. Snap-on interface; 213. Circular step; 3. Connector; 30. Gland connector; 31. Spring; 32. Cable. Detailed Implementation

[0019] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. Although the description of this utility model will be presented in conjunction with preferred embodiments, this does not mean that the features of this utility model are limited to this embodiment. On the contrary, the purpose of describing the utility model in conjunction with the embodiments is to cover other options or modifications that may be derived based on the claims of this utility model. To provide a deep understanding of this utility model, many specific details will be included in the following description. This utility model may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this utility model, some specific details will be omitted in the description. It should be noted that, without conflict, the embodiments and features in the embodiments of this utility model can be combined with each other.

[0020] In the description of this embodiment, it should be noted that the terms "upper", "lower", "inner", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the utility model product is usually placed in during use. They are only for the convenience of describing the utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the utility model.

[0021] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] The terms "first," "second," etc., are used only for distinguishing descriptions and should not be interpreted as indicating or implying relative importance. For example, "first magnet" and "second magnet" are only used to distinguish two different magnet components, without any distinction of primary or secondary importance, sequence, or other significance.

[0023] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.

[0024] This application provides an electromagnetic ultrasonic sensor for detecting bolts, particularly suitable for non-destructive measurement of bolt axial stress (axial force).

[0025] It should be noted that in the application scenario addressed in this application, the bolts being tested are generally standard parts. That is, the bolt typically includes a head and a stud that connects to the head and is embedded (or screwed) inside the installed equipment (or component).

[0026] Please see Figures 1 to 7The electromagnetic ultrasonic sensor has a sensing component 1 for exciting and receiving electromagnetic ultrasonic waves and a housing 2 for housing the sensing component 1.

[0027] The sensing component 1 includes a first magnet 10 arranged coaxially, a second magnet 11 sleeved outside the first magnet 10, and a coil 12 located below the first magnet 10 and the second magnet 11. This arrangement ensures that the coil 12, the first magnet 10, and the second magnet 11 always maintain a coaxial relationship.

[0028] Specifically, the first magnet 10 and the second magnet 11 are coaxially nested, forming a static magnetic field with concentrated direction and stable intensity in the bolt being tested. The coil 12, which is coaxially arranged with the first magnet 10 and the second magnet 11, is used to excite an alternating magnetic field to ensure the transduction efficiency and signal-to-noise ratio of the electromagnetic ultrasonic sensor.

[0029] Please see Figure 6 The outer shell 2 has a first outer shell portion 20 sleeved on the outside of the sensing component 1 and a second outer shell portion 21 connected to the first outer shell portion 20 and protruding downward.

[0030] For example, the first housing portion 20 and the second housing portion 21 may be an integral structure, such as being integrally formed by injection molding. Alternatively, the first housing portion 20 and the second housing portion 21 may also be a separate structure, such as the first housing portion 20 and the second housing portion 21 being made separately based on different working conditions or using different materials, and then assembled together by means of threaded connection, adhesive, etc.

[0031] To achieve accurate positioning during bolt inspection, the inner wall surface 210 of the second outer shell 21 is constructed as an arc surface that provides radial constraint. The inner wall surface 210 defines a positioning space 211 with an open bottom. The second outer shell 21 is provided with a card interface 212 that communicates with the positioning space 211 to allow the bolt to be tested to enter the positioning space 211 radially along the outer shell 2.

[0032] For ease of description below, the radial direction described in this application is clearly defined herein with reference to the accompanying drawings. Please refer to... Figure 3 The axis of sensing component 1 is defined as the reference axis. The radial direction (or radial direction) mentioned in this application specifically refers to the direction perpendicular to this axis and extending outward from it (e.g., ...). Figure 3 (As indicated by the middle arrow); the axial direction specifically refers to the direction parallel to the axis.

[0033] Accordingly, "the locking interface 212 that allows the bolt to be tested to enter the positioning space 211 radially along the outer shell 2" means that when the electromagnetic ultrasonic sensor is installed on the bolt to be tested, the direction of movement of the electromagnetic ultrasonic sensor relative to the bolt is along or substantially parallel to the radial direction of the outer shell 2, thereby achieving locking from the side of the bolt.

[0034] The bolt is radially engaged via the card interface 212, causing the inner wall surface 210 to mate with the outer peripheral surface of the bolt head and engage with the bolt head, thus applying radial constraint to the head. This effectively prevents the electromagnetic ultrasonic sensor from shaking during testing and ensures the consistency of the relative geometric relationship between the sensing component 1 and the bolt during the test.

[0035] Furthermore, the bottom open design of the positioning space 211 is used to ensure that the stud extending downward from the bolt head will not obstruct the electromagnetic ultrasonic sensor during the process of the electromagnetic ultrasonic sensor being snapped into the bolt.

[0036] The radial insertion bolt method used in this embodiment eliminates the need for complex alignment adjustments compared to the traditional method of directly fitting the bolt from the top. It also fully utilizes the radial space of the bolt, reducing the axial space requirement above the bolt and enabling the electromagnetic ultrasonic sensor to perform detection efficiently even in confined spaces.

[0037] Regarding the specific application scenario of this application, the inventors also noted that hexagon socket head cap screws are commonly used in the connection of wind turbine blades. When using electromagnetic ultrasonic sensors to detect the axial force of hexagon socket head cap screws, in addition to facing the limitation of extremely narrow axial space, the head structure of the hexagon socket head cap screws also introduces additional technical obstacles.

[0038] Specifically, the countersunk hole at the center of the head of the hexagon socket head cap screw results in an uneven and geometrically complex testing surface. Furthermore, hexagon socket head cap screws are typically made of magnetically conductive materials. This causes traditional electromagnetic ultrasonic sensors, which contain strong permanent magnets, to experience uneven magnetic attraction when near the testing surface of the hexagon socket head cap screw, making them prone to tilting or shifting. In space-constrained situations, this undoubtedly increases the difficulty of testing.

[0039] Based on this, this application designs the second outer casing 21 as an arc shape, and the inner wall surface 210 is coaxially arranged with the sensing component 1, so that the inner wall surface 210 forms an enclosing constraint on the bolt head along the bolt radial direction to counteract the offset tendency that may be caused by uneven magnetic attraction. This ensures that after the electromagnetic ultrasonic sensor is radially inserted into the bolt, it can force the bolt to be concentrically positioned with the sensing component 1.

[0040] For example, the curvature of the inner wall surface 210 is between 90° and 180°. The lower limit of this range of not less than 90° ensures that there is sufficient curved surface to contact the bolt head, so as to provide sufficient radial constraint force to effectively resist the displacement caused by magnetic attraction; the upper limit of not more than 180° also ensures that sufficient space is reserved for the locking interface 212, so that the electromagnetic ultrasonic sensor can smoothly enter and exit from the bolt side, which facilitates the electromagnetic ultrasonic sensor to quickly lock into and separate the bolt through the locking interface 212, thereby improving detection efficiency.

[0041] Preferably, the inner wall surface 210 is designed to be 180°. That is, the second outer shell portion 21 is completely open in the radial direction to form a semi-open clamp structure. Figure 3 As shown, it is a C-shaped arc. This design ensures sufficient space for the card interface 212 while also providing a strong and effective constraint on the bolts. Of course, depending on different testing conditions and bolt sizes, the arc-shaped inner wall 210 can also be selected with other suitable arc values ​​such as 120° or 150° to achieve the best balance between constraint strength and spatial adaptability.

[0042] To ensure the reliability of the constraint, the inner diameter of the second outer shell 21 matches the outer diameter of the bolt head to be measured. This is intended to enable the inner wall surface 210 to form a stable and reliable interference or small clearance fit with the outer cylindrical surface of the bolt head.

[0043] For example, based on the standard bolt specifications commonly used in wind turbine blades, the common nominal specifications for the outer diameter of the bolt head include 36mm, 39mm, 42mm, etc. Accordingly, the inner diameter of the second outer shell 21 is 36mm, 39mm, 42mm, etc., to accommodate bolts of different sizes.

[0044] Considering the actual situation on site where the head of the bolt protrudes 12-16mm (generally 3 to 4 threads) from the mounting plane after installation, in order to further ensure the applicability of the electromagnetic ultrasonic sensor in confined spaces, the length of the second outer shell 21 protruding downward from the bottom surface of the sensing component 1 is limited to no more than 12mm, so as to control the overall size of the electromagnetic ultrasonic sensor in the axial space.

[0045] In one specific embodiment, the first magnet 10 and the second magnet 11 are permanent magnets or electromagnets, and the magnetic field directions of the first magnet 10 and the second magnet 11 are opposite to each other, so as to form a static magnetic field below the gap between the first magnet 10 and the second magnet 11, which is conducive to exciting ultrasonic waves of a specific mode (such as transverse waves or longitudinal waves).

[0046] The following description will use a permanent magnet as an example.

[0047] For example, the first magnet 10 is configured to provide a first static magnetic field component along the axial direction of the electromagnetic ultrasonic sensor; the second magnet 11 is configured to provide a second static magnetic field component along the radial direction of the electromagnetic ultrasonic sensor; the eddy current field generated by the coil 12 is used to induce an alternating magnetic field in the bolt under test. This alternating magnetic field interacts simultaneously with both the first and second static magnetic field components to synchronously excite longitudinal waves (L-waves) and transverse waves (S-waves).

[0048] Specifically, such as Figure 4 As shown, the first magnet 10 is a solid cylindrical permanent magnet, and the second magnet 11 is a ring-shaped (hollow cylindrical) permanent magnet. The first magnet 10 and the second magnet 11 have the same axial height and are coaxially nested to ensure that the static magnetic field is symmetrically and uniformly distributed in the axial direction.

[0049] The coil 12 is a hollow coil, located below both the first magnet 10 and the second magnet 11. The inner diameter of the coil 12 is smaller than the outer diameter of the first magnet 10, while the outer diameter of the coil 12 is larger than the inner diameter of the second magnet 11. This design ensures that the coil 12 radially spans the annular gap between the first magnet 10 and the second magnet 11. This allows it to work with the first permanent magnet to excite longitudinal waves, and also with the second permanent magnet to enhance the excitation efficiency of the longitudinal waves, thereby improving the longitudinal wave excitation intensity during bolt inspection.

[0050] Continue to combine Figure 4 The sensing component 1 includes a wear-resistant sheet 13 located below the coil 12. The wear-resistant sheet 13 is disposed in close contact with the lower surface of the coil 12 to protect the coil 12 from mechanical wear. The wear-resistant sheet 13 may be a ceramic sheet or a plastic sheet with low conductivity and low magnetic permeability, and may be designed as one or two layers depending on the actual working conditions. This application does not limit this.

[0051] The sensing component 1 also includes a magnetic shielding component 14 disposed below the first magnet 10 and the second magnet 11 to isolate most of the alternating electromagnetic field of the coil 12, thereby reducing the interference of the alternating magnetic field generated by the coil 12 on the static magnetic field generated by the first magnet 10 and the second magnet 11.

[0052] To optimize the signal quality and overall performance of sensing component 1, sensing component 1 may further include other auxiliary components. For example, sensing component 1 may also include an absorbing sheet disposed around the magnet to absorb stray sound waves and suppress noise, and wires connecting coil 12 to external excitation / receiving equipment. These auxiliary components are all designed to improve the overall performance of sensing component 1 in exciting and receiving longitudinal and transverse waves. The auxiliary components can be adapted according to actual detection needs and electromagnetic compatibility requirements, and will not be elaborated further here.

[0053] The sensing assembly 1 further includes an inner shell 15 covering the first magnet 10, the second magnet 11, and the coil 12, to tightly enclose and solidify the first magnet 10, the second magnet 11, the coil 12, and other auxiliary components into a single unit. This ensures the stability of the relative positions between the first magnet 10, the second magnet 11, and the coil 12, thereby guaranteeing the coaxial relationship between the first magnet 10, the second magnet 11, and the coil 12.

[0054] The first outer shell 20 is detachably fitted onto the inner shell 15, so that the inner shell 15 and the integrated sensing component 1 therein can be replaced as a whole according to actual working conditions.

[0055] For example, the top surface of the first outer shell portion 20 is configured as a centrally open annular structure 200, which fits against the upper top surface of the inner shell 15. This forms an annular contact surface between the top surface of the first outer shell portion 20 and the top surface of the inner shell 15, allowing for gradual pressing of the inner shell 15 and the first outer shell portion 20 together. Simultaneously, the centrally open area provides a natural venting channel for gas between the inner shell 15 and the first outer shell portion 20, enabling smoother and more precise installation of the first outer shell portion 20 and the inner shell 15.

[0056] In a specific application scenario, the central open area exposes the top surface of the inner shell 15. The central open area can also be marked with product model, specifications, etc., to facilitate quick identification by staff.

[0057] The inner diameter of the first outer shell portion 20 is adapted to the outer diameter of the inner shell 15, and the inner diameter of the second outer shell portion 21 is not greater than the inner diameter of the first outer shell portion 20, while the outer diameter of the second outer shell portion 21 is greater than or equal to the outer diameter of the first outer shell portion 20. This design achieves a precise and stable fit between the first outer shell portion 20 and the second outer shell portion 21.

[0058] More specifically, such as Figure 7 As shown, the inner diameter of the second outer shell portion 21 is smaller than the inner diameter of the first outer shell portion 20, so that an annular step 213 protrudes radially inside the connection between the first outer shell portion 20 and the second outer shell portion 21. This allows the inner shell 15 (along with the first magnet 10, the second magnet 11, etc. inside it) to be inserted into the first outer shell portion 20, and to rest downward against and sit on the annular step 213 formed by the second outer shell portion 21, thereby precisely defining the inner shell 15 in the axial direction.

[0059] In this application scenario, the bottom surface of the inner shell 15 serves as the detection contact surface, fitting snugly against the upper surface of the bolt head. This ensures efficient ultrasonic coupling while avoiding unnecessary gaps between the sensing component 1 and the bolt caused by the assembly of the outer shell 2.

[0060] Of course, in another application scenario, an isolation surface for contacting the bolt to be tested can also be formed between the first outer shell 20 and the second outer shell 21.

[0061] The inner shell 15 also has a plug-in interface 150 that is electrically connected to the coil 12. Correspondingly, the first outer shell portion 20 has a mounting groove 201 that corresponds to the position of the plug-in interface 150 and communicates with the card interface 212, so as to form a through channel from the outside of the electromagnetic ultrasonic sensor directly to the plug-in interface 150 of the inner shell 15.

[0062] The electromagnetic ultrasonic sensor is equipped with a connector 3 that passes through the mounting groove 201 and is connected to the connector 150. The connector 3 is plugged into and locked to the connector 150 to achieve electrical connection between the external cable 32 and the coil 12.

[0063] For example, the connector 150 is located on the side of the inner housing 15 to avoid additional axial space occupation caused by the cable 32 being led out from the top or bottom of the electromagnetic ultrasonic sensor.

[0064] In one specific embodiment, to achieve the detachability of the housing 2 when connected to the connector 3, the mounting groove 201 includes a first mounting groove extending along the axial direction of the electromagnetic ultrasonic sensor and a second mounting groove communicating with the first mounting groove. The first mounting groove communicates with the card interface 212, and the second mounting groove corresponds to the connector 150 to form an L-shape (e.g., Figure 6 (as shown) or T-shaped channels.

[0065] The radial length of the connector 3 (the length protruding from the connector 150 in the direction away from the inner shell 15) is 35mm to 60mm. This length is significantly longer than that of conventional electrical connectors (the radial length of a typical electrical connector is usually only 15mm), thus ensuring that the connector 3 has sufficient operating leverage. That is, it has a sufficient radial extension for the operator to hold, thereby improving the convenience of operation in confined spaces and the insertion operation of the connector 3.

[0066] Preferably, the radial length of the connector 3 is 55 mm. This length ensures sufficient operating leverage while also providing enough space for the connector 3 to be installed in complex configurations such as those around wind turbine blade bolts.

[0067] like Figure 3 , Figure 4As shown, the connector 3 includes a gland 30 that plugs into the inner housing 15, a spring 31 connected to the side of the gland 30 away from the inner housing 15, and a cable 32 that passes through the gland 30 and the spring 31 and is electrically connected to the coil 12. Exemplarily, the gland 30 integrates conductive terminals and plugs into the connector 150. The spring 31 provides flexible restraint to the cable 32 inserted within it, effectively preventing wear caused by repeated bending of the cable 32.

[0068] Furthermore, the radial length of the connector 3 is defined as the sum of the lengths of the gland head 30 and the spring 31, specifically, the length from the mating end face of the gland head 30 and the inner shell 15 to the end of the spring 31 furthest from the gland head 30 ranges from 35mm to 60mm. By precisely defining this dimension, the electromagnetic ultrasonic sensor can achieve both applicability and ease of operation in confined spaces while ensuring the complete functionality of its core functions.

[0069] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of this utility model, and are not intended to limit the scope of protection of this utility model. All equivalent implementation methods or modifications made without departing from the spirit of this utility model should be included within the scope of protection of this utility model.

Claims

1. An electromagnetic ultrasonic sensor for detecting bolts, characterized in that, The electromagnetic ultrasonic sensor includes: The sensing component includes a first magnet arranged coaxially, a second magnet sleeved outside the first magnet, and a coil located below the first magnet and the second magnet; The housing has a first housing portion fitted over the sensing component and a second housing portion connected to the first housing portion and protruding downward; The inner wall of the second outer shell is constructed as an arc surface that provides radial constraint and defines a positioning space with an open bottom. The second outer shell is provided with a snap-fit ​​interface that communicates with the positioning space to allow the bolt to be tested to enter the positioning space radially along the outer shell.

2. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, The second outer casing is arc-shaped, and the inner wall surface is coaxially arranged with the sensing component, wherein the arc of the inner wall surface is 90° to 180°.

3. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, The length of the second housing portion protruding downward from the bottom surface of the sensing component is no more than 12 mm.

4. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, The inner diameter of the second outer shell portion is not greater than the inner diameter of the first outer shell portion, and the outer diameter of the second outer shell portion is greater than or equal to the outer diameter of the first outer shell portion.

5. The electromagnetic ultrasonic sensor according to claim 4, characterized in that, The inner diameter of the second outer shell portion is smaller than the inner diameter of the first outer shell portion, so as to form an annular step that protrudes radially inside the connection between the first outer shell portion and the second outer shell portion.

6. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, The sensing component further includes an inner shell covering the first magnet, the second magnet, and the coil, and the first outer shell is detachably fitted onto the inner shell.

7. The electromagnetic ultrasonic sensor according to claim 6, characterized in that, The top surface of the first outer shell is configured as a centrally open annular structure, which fits against the top surface of the inner shell.

8. The electromagnetic ultrasonic sensor according to claim 6, characterized in that, The inner shell has a plug interface that is electrically connected to the coil, and the first outer shell has a mounting groove that corresponds to the position of the plug interface and communicates with the card interface. The electromagnetic ultrasonic sensor also includes a connector that passes through the mounting slot and is connected to the connector interface.

9. The electromagnetic ultrasonic sensor according to claim 8, characterized in that, The radial length of the connector is 35 mm to 60 mm.

10. The electromagnetic ultrasonic sensor according to claim 8, characterized in that, The connector includes a gland that plugs into the inner housing, a spring connected to the side of the gland away from the inner housing, and a cable that passes through the gland, the spring, and is electrically connected to the coil.

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