Electromagnetic ultrasonic sensor

Abstract

This invention provides an electromagnetic ultrasonic sensor, comprising a magnet assembly, a hollow coil, and a housing. The magnet assembly includes a first magnet and a second magnet, the second magnet being coaxially aligned with and sleeved on the first magnet, with the magnetic fields of the first and second magnets in opposite directions. The hollow coil is disposed below the magnet assembly and coaxially aligned with it, the inner diameter of the hollow coil being smaller than the outer diameter of the first magnet, and the outer diameter being larger than the inner diameter of the second magnet. The housing is sleeved on the magnet assembly and the hollow coil, and the housing has a connector electrically connected to the hollow coil. The sensor provided by this invention has a coil spanning two magnetic poles, significantly enhancing the intensity of longitudinal waves.

Description

Technical Field

[0001] This invention relates to the field of industrial testing technology, and in particular to an electromagnetic ultrasonic sensor. Background Technology

[0002] Bolts are commonly used fasteners for connecting various mechanical parts. When using torque tightening, the axial force (or preload) control accuracy is typically within ±20% to 30%, making precise control of the tightening process difficult. Furthermore, the different tightening sequences of multiple fasteners and bolt flanges can cause significant changes in bolt axial force after tightening. For equipment already in operation, effective measurement of bolt tightening axial force is also challenging. These factors lead to considerable uncertainty and unmeasurability in bolt tightening, jeopardizing safe equipment operation.

[0003] The ultrasonic bolt axial force measurement method uses an ultrasonic sensor to excite ultrasonic waves in the bolt, and indirectly measures the bolt axial force by measuring the time it takes for the ultrasonic waves to travel through the bolt.

[0004] Electromagnetic ultrasound is a technology that eliminates the need for ultrasonic coupling agents, enabling convenient ultrasonic excitation and reception, and offers significant advantages in bolt axial force measurement. Electromagnetic ultrasonic methods for bolt axial force measurement are divided into single-wavelength and dual-wavelength methods.

[0005] The basic principle of the single-wave method is to utilize the linear relationship between the time offlight (TOF) of sound waves (either transverse or longitudinal waves) in the bolt and the bolt axial force. The axial force is indirectly characterized by pre-calibrating the linear relationship between TOF and axial force and by measuring the TOF. Since TOF is insensitive to axial force, the TOF variation caused by bolt length tolerances is much greater than the influence of axial force on TOF. Therefore, the initial state of each bolt needs to be determined before axial force measurement.

[0006] The dual-wave method simultaneously generates transverse and longitudinal waves within the bolt. It integrates information from both waves, overcoming the limitations of the single-wave method. Utilizing the different sensitivities of longitudinal and transverse wave velocities to axial force, the dual-wave method eliminates the bolt length variable in the calculation formula through comparison and subtraction. With a single calibration, the axial force of the bolt in its in-service state can be measured without needing to measure its initial state.

[0007] Electromagnetic ultrasound technology can easily generate strong transverse wave signals in ferromagnetic conductors, but it is difficult to generate longitudinal waves. Currently used electromagnetic ultrasound probes with cylindrical magnets and helical coils produce relatively small longitudinal wave signals, making it difficult to accurately measure axial force. Existing technologies incorporate a magnetic circuit closure at the end of the magnet furthest from the coil to enhance the magnetic field; however, this closure is ineffective and increases the sensor's height, affecting the height limitations during use. Summary of the Invention

[0008] The purpose of this invention is to provide an electromagnetic ultrasonic sensor that can simultaneously excite transverse waves and strong longitudinal waves, thus solving the problem of difficulty in exciting strong longitudinal waves in the prior art.

[0009] To achieve one of the above-mentioned objectives, one embodiment of the present invention provides an electromagnetic ultrasonic sensor and a magnet assembly, including a first magnet and a second magnet, wherein the second magnet is coaxially arranged with the first magnet and sleeved outside the first magnet, and the magnetic field directions of the first magnet and the second magnet are opposite.

[0010] A hollow coil is disposed below the magnet assembly and coaxially arranged with the magnet assembly. The inner diameter of the hollow coil is smaller than the outer diameter of the first magnet, and the outer diameter is larger than the inner diameter of the second magnet.

[0011] The outer casing is fitted over the magnet assembly and the hollow coil. The outer casing is provided with a plug-in interface, which is electrically connected to the hollow coil.

[0012] As a further improvement of one embodiment of the present invention, the ratio of the inner diameter to the outer diameter of the hollow coil is 0.1 to 0.99.

[0013] As a further improvement of one embodiment of the present invention, the outer diameter of the hollow coil is not greater than the outer diameter of the second magnet.

[0014] As a further improvement of one embodiment of the present invention, the first magnet is a solid cylinder or a hollow cylinder along the length of the first magnet.

[0015] As a further improvement of one embodiment of the present invention, when the shape of the first magnet is a hollow cylinder along the length direction of the first magnet, the inner diameter of the hollow coil is greater than or equal to the inner diameter of the first magnet.

[0016] As a further improvement of one embodiment of the present invention, the magnet assembly is composed of permanent magnets or electromagnets.

[0017] As a further improvement of one embodiment of the present invention, it also includes a magnetic shielding component disposed between the magnet assembly and the hollow coil.

[0018] As a further improvement of one embodiment of the present invention, the magnetic shielding element is 1 to 6 layers of copper foil or magnetic sheet.

[0019] As a further improvement of one embodiment of the present invention, it also includes a wear-resistant sheet disposed below the hollow coil.

[0020] As a further improvement of one embodiment of the present invention, the insertion interface is disposed on the side wall of the housing along the length direction of the magnet assembly.

[0021] One or more technical solutions provided by this invention have at least the following technical effects or advantages:

[0022] The electromagnetic ultrasonic sensor provided by this invention uses a hollow coil, with the outer diameter of the hollow coil being larger than the inner diameter of the second magnet and the inner diameter being smaller than the outer diameter of the first magnet. That is, the hollow coil spans the magnetic poles of the first and second magnets. Thus, the hollow coil can generate longitudinal waves not only in conjunction with the first magnet but also in conjunction with the second magnet. The longitudinal waves generated by the sensor under this structure are stronger, which can effectively solve the problem of weak longitudinal wave excitation in the prior art. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the electromagnetic ultrasonic sensor in an embodiment of the present invention.

[0024] Figure 2 yes Figure 1 A top view of a medium-sized electromagnetic ultrasonic sensor.

[0025] Figure 3 yes Figure 2 Schematic diagram of cross section along line AA.

[0026] Figure 4 yes Figure 3 A schematic diagram showing the addition of a second coil.

[0027] Figure 5 It is the distribution of magnetic field intensity on the surface of the specimen without a closed-loop magnetic circuit.

[0028] Figure 6 It is the distribution of magnetic field intensity on the surface of a specimen with a closed-loop magnetic circuit.

[0029] Figure 7 This is an intensity diagram of the longitudinal and transverse waves excited by the electromagnetic ultrasonic sensor in this embodiment.

[0030] 1. Outer shell; 11. Housing; 12. Cover; 13. Socket; 14. Connector; 2. Magnet assembly; 21. First permanent magnet; 22. Second permanent magnet; 3. Hollow coil; 4. Second coil; 5. Magnetic shield; 6. Wear-resistant sheet. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The terms used in this document, such as “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” indicating spatial relative positions, are used for illustrative purposes to describe the relationship of one unit or feature relative to another unit or feature as shown in the accompanying drawings. The terms “spatial relative positions” may be intended to include different orientations of the equipment in use or operation other than those shown in the figures.

[0033] For example, if the device in the figure is flipped, a unit described as being "below" or "under" other units or features will be "above" other units or features. Therefore, the exemplary term "below" can encompass both above and below orientations. The device may be oriented in other ways (rotated 90 degrees or otherwise) and the spatially related descriptive terms used herein will be interpreted accordingly.

[0034] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0035] Furthermore, it should be understood that although the terms first, second, etc., may be used herein to describe various elements or structures, the objects described should not be limited by these terms. These terms are only used to distinguish these objects from one another. For example, a first may be referred to as a second magnet, and similarly, a second magnet may be referred to as a first magnet, without departing from the scope of protection of this application.

[0036] This invention provides an electromagnetic ultrasonic sensor, such as... Figures 1-4As shown, it includes: a shell 1, a magnet assembly 2, and a hollow coil 3. The magnet assembly 2 includes a first magnet and a second magnet, the second magnet being coaxially arranged with the first magnet and sleeved outside the first magnet, and the magnetic fields of the first magnet and the second magnet having opposite directions; the hollow coil 3 is disposed below the magnet assembly 2 and coaxially arranged with the magnet assembly 2, the inner diameter of the hollow coil 3 being smaller than the outer diameter of the first magnet, and the outer diameter being larger than the inner diameter of the second magnet; the shell 1 is sleeved outside the magnet assembly 2 and the hollow coil 3, and the shell 1 is provided with a plug-in interface 13, which is electrically connected to the hollow coil 3.

[0037] Preferably, the magnet assembly 2 is composed of permanent magnets or electromagnets. In this embodiment, a permanent magnet is used as an example, that is, both the first magnet and the second magnet are permanent magnets, and are therefore referred to as the first permanent magnet 21 and the second permanent magnet 22.

[0038] The electromagnetic ultrasonic sensor provided in this embodiment of the invention uses a hollow coil 3 as its coil. The inner diameter of the hollow coil 3 is smaller than the outer diameter of the first permanent magnet 21, and the outer diameter is larger than the inner diameter of the second permanent magnet 22. That is, the hollow coil 3 spans two magnetic poles. The hollow coil 3 can not only cooperate with the first permanent magnet 21 to generate longitudinal waves, but also cooperate with the second permanent magnet 22 to generate longitudinal waves. Under this structure, the longitudinal waves generated by the sensor are stronger, which can effectively solve the problem of weak longitudinal wave excitation in the prior art.

[0039] Furthermore, the use of a hollow coil 3 can greatly reduce the reverse magnetization force generated in the central region of the coil, thereby increasing the positive resultant force and enhancing the longitudinal wave signal. The inner diameter of the second permanent magnet 22 matches the outer diameter of the first permanent magnet 21, which can ensure a strong longitudinal wave excitation while reducing the size of the electromagnetic ultrasonic sensor.

[0040] Furthermore, the outer diameter of the hollow coil 3 is not greater than the outer diameter of the second permanent magnet 22, which can prevent the part of the hollow coil 3 within the range of the second permanent magnet 22 and the part outside the range of the second permanent magnet 22 from forming force sources in opposite directions, resulting in a phase difference. When the sound wave propagates or is reflected in the specimen, it is easy to cause waveform bifurcation and distortion.

[0041] Furthermore, the ratio of the inner diameter to the outer diameter of the hollow coil 3 is 0.1 to 0.99. When the ratio of the inner diameter to the outer diameter of the hollow coil 3 is 0.1 to 0.99, the hollow coil 3, in conjunction with the magnet assembly 2, can significantly improve the ability to excite longitudinal waves.

[0042] Furthermore, the electromagnetic ultrasonic sensor also includes a coil, such as Figure 4 As shown, this is the second coil 4, which is also a hollow structure. The second coil 4 is located below the magnet assembly 2. Figure 4In this configuration, the second coil 4 is positioned below the hollow coil 3, but the vertical relationship between the second coil 4 and the hollow coil 3 is not restricted; the second coil 4 can also be positioned above the hollow coil 3.

[0043] Preferably, the outer diameter of the second coil 4 is not greater than the outer diameter of the first permanent magnet 21. This avoids the second coil 4 forming a force source with opposite directions, which would lead to a phase difference and cause waveform bifurcation and distortion when the sound wave propagates or is reflected in the specimen. The hollow coil 3 and the second coil 4 are connected to different excitation sources through the connector 13, so as to simultaneously excite strong, unbifurated, and undistorted transverse and longitudinal waves, thereby achieving better and more accurate measurement of the bolt axial force.

[0044] Furthermore, the first permanent magnet 21 is either a solid cylinder or a hollow cylinder along its length. When the first permanent magnet 21 is a solid cylinder, the inner diameter of the hollow coil 3 is affected by the material and diameter of the bolt being measured. When the first permanent magnet 21 is a hollow cylinder along its length, the inner diameter of the hollow coil 3 is greater than or equal to the inner diameter of the first permanent magnet 21. This avoids the hollow coil 3 being connected to force sources in opposite directions, which would lead to a phase difference and cause waveform bifurcation and distortion when the sound wave propagates or is reflected in the specimen.

[0045] Preferably, the difference between the outer diameter of the first permanent magnet 21 and the inner diameter of the second permanent magnet 22 does not exceed 1 mm. The difference between the outer diameter of the first permanent magnet 21 and the inner diameter of the second permanent magnet 22 does not need to be particularly limited, as long as the second permanent magnet 22 can fit the first permanent magnet 21. However, ensuring that the difference between the inner diameter of the second permanent magnet 22 and the outer diameter of the first permanent magnet 21 does not exceed 1 mm can avoid errors that prevent the first permanent magnet 21 and the second permanent magnet 22 from being able to combine.

[0046] Furthermore, the outer casing 1 is formed with a shell 11 and a cover 12. The shell 11 has an opening at the top and a detection port at the bottom, that is, the upper opening and the bottom detection port are arranged opposite to each other. The cover 12 covers the opening at the upper end of the shell 11. The aforementioned plug interface 13 is provided on the side wall of the outer casing 1 along the length direction of the magnet assembly 2. A plug is fixed at the plug interface 13. The hollow coil 3 is electrically connected to the plug through the plug interface 13.

[0047] Furthermore, the electromagnetic ultrasonic sensor also includes a magnetic shielding component 5 and a wear-resistant sheet 6. The magnetic shielding component 5 is disposed between the magnet assembly 2 and the coil, and can isolate most of the magnetic field generated by the coil under alternating current, thereby reducing the influence of the magnetic field generated by the coil under alternating current on the static magnetic field generated by the magnet assembly 2. Preferably, in the height direction of the magnet assembly 2, the projection of the coil is on the magnetic shielding component 5, which can minimize the influence of the magnetic field generated by the coil on the static magnetic field generated by the magnet assembly 2. Preferably, the magnetic shielding component 5 can be 1 to 6 layers of copper foil or magnetic conductive sheet.

[0048] The wear-resistant plate 6 is located below the coil to prevent the bolts from wearing down the coil during repeated testing, thus protecting the coil. The wear-resistant plate 6 is a ceramic or plastic sheet with low conductivity and low magnetic permeability. Two layers of wear-resistant plate 6 can be installed. When the wear-resistant plate 6 near the detection port wears out and needs replacement, it can be directly removed from the detection port, extending the time between wear-resistant plate replacements and reducing the number of replacements.

[0049] During installation, the wear-resistant sheet 6, hollow coil 3 and / or second coil 4, magnetic shield 5, and magnet assembly 2 are sequentially placed into the housing 11 through the opening at the top of the housing 11, and then the cover 12 is placed over the opening at the top of the housing 11. During measurement, the connector 13 located on the side wall of the housing 11 offers less restriction on the height of the measurement application compared to the connector 13 conventionally located on the top of the housing 1. The connector 13 is electrically connected inward to the hollow coil 3 and outward to the wires on the host machine that provide the excitation source for the hollow coil 3.

[0050] Furthermore, the hollow coil 3 can be wound with enameled wire or processed using PCB technology, wherein the PCB can be a flexible PCB or a conventional PCB.

[0051] To further optimize the implementation effect of the present invention, this embodiment uses both a scheme without a closed magnetic circuit (the scheme of the present invention) and a scheme with a closed magnetic circuit for experiments, and obtains the following results. Figure 5 , 6 The magnetic field strength distribution diagram on the surface of the specimen is shown. It can be seen from the figure that the presence or absence of a closed magnetic circuit has almost no effect on the magnetic field strength.

[0052] In addition, this embodiment also conducts simulation experiments on the sensor provided in this embodiment, and obtains the following results: Figure 7 The intensity diagrams of longitudinal and transverse waves are shown in Table 1, with specific reference values ​​and measured values.

[0053] Table 1

[0054]

[0055] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0056] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electromagnetic ultrasonic sensor, characterized in that, include: A magnet assembly includes a first magnet and a second magnet. The second magnet is coaxially arranged with the first magnet and sleeved outside the first magnet. The magnetic field directions of the first magnet and the second magnet are opposite. The first magnet is a hollow cylinder along its length. A hollow coil is disposed below the magnet assembly and coaxially arranged with the magnet assembly. The inner diameter of the hollow coil is smaller than the outer diameter of the first magnet and greater than or equal to the inner diameter of the first magnet. The outer diameter of the hollow coil is greater than the inner diameter of the second magnet. The outer casing is fitted over the magnet assembly and the hollow coil. The outer casing is provided with a plug-in interface, which is electrically connected to the hollow coil.

2. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, The ratio of the inner diameter to the outer diameter of the hollow coil is 0.1 to 0.

99.

3. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, The outer diameter of the hollow coil is not greater than the outer diameter of the second magnet.

4. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, The magnet assembly is composed of permanent magnets or electromagnets.

5. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, It also includes a magnetic shielding component disposed between the magnet assembly and the hollow coil.

6. The electromagnetic ultrasonic sensor according to claim 5, characterized in that, The magnetic shielding component consists of 1 to 6 layers of copper foil or magnetic sheets.

7. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, It also includes a wear-resistant sheet, which is disposed below the hollow coil.

8. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, The insertion interface is located on the side wall of the housing along the length of the magnet assembly.

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