Electromagnetic ultrasonic transducer probe of HalbacH permanent magnet assembly

Abstract

The invention provides an electromagnetic ultrasonic transducer probe of a HalbacH permanent magnet assembly. The electromagnetic ultrasonic transducer probe comprises a shell, a magnet set, a coil assembly and a driving mechanism. The magnet group is accommodated in the shell, is formed by arranging a plurality of magnets according to preset polarities and is used for providing a bias magnetic field, and the coil assembly is arranged outside the shell, is positioned on one side close to the test piece and is used for exciting ultrasonic waves in the bias magnetic field and receiving ultrasonic signals reflected from the test piece after pulse current is introduced; a fixing frame is arranged on the periphery of the magnet set and used for installing and fixing the magnet set, a movable interval is formed between the fixing frame and the inner wall of the shell and located on the side, away from the test piece, of the magnet set, and the driving mechanism is installed on the shell, connected with the fixing frame and used for driving the magnet set to be away from or close to the coil assembly in the direction perpendicular to the test piece. And the distances between the magnet group and the coil assembly are different. The bias magnetic field intensity acting on the test piece is adjusted by adjusting the position of the magnetic assembly.

Description

Technical Field

[0001] This invention relates to the technical field of electromagnetic ultrasonic transducers, and particularly to an electromagnetic ultrasonic transducer probe of a HalbacH permanent magnet assembly. Background Technology

[0002] Electromagnetic ultrasonic testing technology is a non-contact, non-destructive testing method that does not require coupling agents and is widely used in industrial online inspection. This technology uses a permanent magnet inside the probe to provide a bias magnetic field, which is then used by a coil to excite ultrasonic waves. It offers advantages such as flexible wave modes and no need for surface preparation of the test specimen. The testing process typically eliminates the need for pre-treatment of the specimen surface, such as grinding or applying coupling agents, thus improving testing efficiency and avoiding potential surface damage caused by contact testing.

[0003] However, the permanent magnet assemblies of existing probes are generally fixed. In practical applications, especially for test pieces with uneven surfaces, the lift-off distance changes due to surface undulations, vibrations, and other errors. This directly causes the attenuation of the effective bias magnetic field strength, which in turn weakens the excited ultrasonic signal, affecting the stability, reliability, and accuracy of the detection. Summary of the Invention

[0004] The purpose of this invention is to provide an electromagnetic ultrasonic transducer probe for a HalbacH permanent magnet assembly. The technical problem to be solved is to provide an electromagnetic ultrasonic transducer probe that can adjust the distance between the magnet assembly and the excitation coil.

[0005] To achieve the above objectives, the solution of the present invention is: an electromagnetic ultrasonic transducer probe of a HalbacH permanent magnet assembly, comprising a housing, a magnet assembly, a coil assembly, and a drive mechanism; The magnet assembly is housed inside the housing and consists of several magnets arranged according to a preset polarity to provide a bias magnetic field. The coil assembly is located outside the housing, close to the test piece, and is used to generate ultrasonic waves in the bias magnetic field after a pulse current is applied, as well as to receive ultrasonic signals reflected from the test piece. A fixing frame is provided on the outer periphery of the magnet assembly. The fixing frame is used to install and fix the magnet assembly. There is an movable gap between the fixing frame and the inner wall of the housing. This movable gap is located on the side of the magnet assembly away from the test piece. The drive mechanism is installed on the housing and connected to the fixing frame. It is used to drive the magnet assembly away from or towards the coil assembly in a direction perpendicular to the test piece, so that the distance between the magnet assembly and the coil assembly is different.

[0006] Furthermore, the magnet assembly includes a first magnet assembly and a second magnet assembly, which are arranged adjacent to each other. The first magnet assembly consists of a number of first magnets, and the second magnet assembly consists of a number of second magnets. The number and position of the first magnets correspond one-to-one with the number and position of the second magnets, and the magnetization direction is the same.

[0007] Furthermore, the first magnet has a square structure, and the second magnet has a trapezoidal structure. The first magnet is located on the top side of the second magnet, and the second magnet expands outward from the bottom end of the first magnet to form a trapezoidal structure, or shrinks inward from the bottom end of the first magnet to form a trapezoidal structure. The adjacent magnets are in close contact with each other.

[0008] Furthermore, there are 5 first magnets, and the magnetization directions of the 5 first magnets from left to right are vertically downward, horizontally to the left, vertically upward, horizontally to the right, and vertically downward. There are also 5 second magnets, and the magnetization directions of the 5 second magnets from left to right are vertically downward, horizontally to the left, vertically upward, horizontally to the right, and vertically downward.

[0009] Furthermore, several first magnets are arranged in an alternating pattern of large and small, and several second magnets are arranged in an alternating pattern of large and small, and the arrangement is consistent with the arrangement of the first magnets.

[0010] Furthermore, the drive mechanism is a lead screw and nut mechanism, including a lead screw, a threaded hole that is longitudinally threaded through the housing and screwed to the lead screw, one end of the lead screw being rotatably connected to the fixed frame through a bearing, and the other end of the lead screw passing upward through the threaded hole and extending out of the housing.

[0011] Furthermore, the coil assembly includes an excitation coil, a first base plate, a receiving coil, and a second base plate, arranged sequentially from top to bottom. A third base plate is provided on the bottom side of the housing, and the excitation coil is located below the third base plate, between the third base plate and the first base plate. The ends of the first base plate, the second base plate, and the third base plate extend out of the excitation coil and the receiving coil, respectively, and are fixedly connected by bolts. The first base plate and the second base plate are made of insulating material, while the third base plate and the housing are made of non-magnetic material.

[0012] Furthermore, the excitation coil has a planar racetrack coil structure, and the receiving coil has a planar racetrack coil structure.

[0013] Furthermore, it also includes a lift-off sensor for detecting the lift-off distance between the probe and the surface of the test piece, and the drive mechanism is configured to drive the magnet assembly to displacement based on the detection signal from the lift-off sensor.

[0014] The present invention also provides a method for lifting an electromagnetic ultrasonic transducer probe using the above-described HalbacH permanent magnet assembly, comprising the following steps; S1, obtain the current lift-off distance between the probe and the test piece; S2, Determine whether the current lift-off distance exceeds the preset lift-off range; S3, When the distance is exceeded, the target position of the magnet group corresponding to the current lift-off distance is determined according to the preset correspondence between the lift-off distance and the position of the magnet group, and the magnet group is driven to move to the target position. The correspondence is configured such that the bias magnetic field strength acting on the surface of the test piece is kept stable by adjusting the magnet group to the corresponding target position under different lift-off distances.

[0015] The beneficial effects of the present invention after adopting the above solution are as follows: By installing a driving mechanism on the housing and connecting the driving mechanism to the fixing frame of the fixed magnet assembly, the magnet assembly is driven to move away from or closer to the coil assembly in a direction perpendicular to the test piece, so that the distance between the magnet assembly and the coil assembly is different. When the surface height of the test piece is uneven or the distance between the test piece surface and the probe changes, the axial position of the magnet assembly inside the probe is actively adjusted, and the distance between the magnet assembly and the coil is reduced, thereby enhancing the effective bias magnetic field strength reaching the surface of the test piece to compensate for the magnetic field attenuation caused by the increase in air gap. Conversely, by increasing the distance between the magnet assembly and the coil, the effective bias magnetic field strength reaching the surface of the test piece is weakened to avoid the magnetic field being too strong, so that the magnetic field strength acting on the surface of the test piece is kept within a stable range, thereby ensuring the consistency and reliability of ultrasonic excitation and reception, and improving the reliability of detection and measurement accuracy. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention with the outer cover removed.

[0017] Figure 2 This is a schematic diagram of the magnet assembly of the present invention.

[0018] Figure 3 This is an exploded structural diagram of the present invention with the outer cover removed.

[0019] Figure 4 This is a schematic diagram of the excitation coil structure of the present invention.

[0020] Figure 5 This is a three-dimensional structural diagram of the present invention.

[0021] Figure 6 This is a simulation diagram of the bias magnetic field generated by the magnet assembly of the present invention.

[0022] Label Explanation: 1-Housing, 2-Magnet assembly, 3-Coil assembly, 4-Drive mechanism, 5-Fixing frame, 6-Excitation coil, 7-First base plate, 8-Receiving coil, 9-Second base plate, 10-Third base plate, 11-Threaded hole, 12-Lifting sensor, 13-Bottom shell, 14-Outer cover, 21-First magnet assembly, 22-Second magnet assembly, 210-First magnet, 220-Second magnet, 41-Lead screw. Detailed Implementation

[0023] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] like Figures 1-6 As shown, the present invention provides an electromagnetic ultrasonic transducer probe for a HalbacH permanent magnet assembly, comprising a housing 1, a magnet assembly 2, a coil assembly 3, and a drive mechanism 4. The magnet assembly 2 is housed within the housing 1 and consists of several magnets arranged according to a preset polarity to provide a bias magnetic field. The coil assembly 3 is disposed outside the housing 1, located near the test piece, and is used to excite ultrasonic waves after a pulse current is applied. The coil assembly 3 includes an excitation coil 6 and a receiving coil 8, which are arranged sequentially from top to bottom below the magnet assembly 2. The excitation coil 6 is used to excite ultrasonic waves in the bias magnetic field, and the receiving coil 8 is used to receive ultrasonic signals reflected from the test piece.

[0025] Key points combined Figure 1 As shown, the coil assembly 3 also includes a first base plate 7 and a second base plate 9. The first base plate 7 is the base plate of the excitation coil 6 and is located on the bottom side of the excitation coil 6. The second base plate 9 is the base plate of the receiving coil 8 and is located on the bottom side of the receiving coil 8. The first base plate 7 and the second base plate 9 are made of insulating material. A third base plate 10 is provided on the bottom side of the housing 1. The third base plate 10 is located between the magnet assembly 2 and the excitation coil 6. The excitation coil 6 is located below the third base plate 10 and between the third base plate 10 and the first base plate 7. The two ends of the first base plate 7, the second base plate 9, and the third base plate 10 extend to the outside of the excitation coil 6 and the receiving coil 8, respectively, and are fixedly connected by bolts. The third base plate 10 and the housing 1 are made of non-magnetic material, specifically, aluminum.

[0026] Key points combined Figure 4 As shown, the excitation coil 6 has a planar racetrack coil structure, and the receiving coil 8 has a planar racetrack coil structure.

[0027] Key points combined Figure 1 As shown, a fixing frame 5 is provided on the outer periphery of the magnet assembly 2. The fixing frame 5 is used to install and fix the magnet assembly 2. There is an movable gap D between the fixing frame 5 and the inner wall of the housing 1. The movable gap D is located on the side of the magnet assembly 2 away from the test piece. The drive mechanism 4 is installed on the housing 1 and connected to the fixing frame 5. It is used to drive the magnet assembly 2 away from or towards the coil assembly 3 in a direction perpendicular to the test piece, so that the distance between the magnet assembly 2 and the coil assembly 3 is different. The fixing frame 5 has an inverted U-shaped structure. Its inner contour is consistent with the outer contour of the magnet assembly 2 so as to fit on the outer periphery of the magnet assembly 2 and fix the magnet assembly 2. Specifically, the fixing frame 5 is made of iron.

[0028] Key points combined Figure 2As shown, the magnet group 2 includes a first magnet group 21 and a second magnet group 22. The first magnet group 21 and the second magnet group 22 are arranged adjacent to each other. The first magnet group 21 is composed of a number of first magnets 210, and the second magnet group 22 is composed of a number of second magnets 220. The number and position of the first magnets 210 correspond one-to-one with the number and position of the second magnets 220, and the magnetization direction is the same.

[0029] In this specific embodiment, the first magnet 210 has a square structure, and the second magnet 220 has a trapezoidal structure. The first magnet 210 is located on the top side of the second magnet 220. The second magnet 220 expands outward from the bottom end of the first magnet 210 to form a trapezoidal structure, or shrinks inward from the bottom end of the first magnet to form a trapezoidal structure. Adjacent magnets are in close contact with each other. There are five first magnets 210, and their magnetization directions from left to right are vertically downward, horizontally to the left, vertically upward, horizontally to the right, and vertically downward. There are also five second magnets 220, and their magnetization directions from left to right are vertically downward, horizontally to the left, vertically upward, horizontally to the right, and vertically downward. Preferably, several first magnets 210 are arranged in an alternating pattern of large and small sizes, and several second magnets 220 are arranged in an alternating pattern of large and small sizes, and the arrangement is consistent with the arrangement of the first magnets 210, which can enhance the magnetic field strength. Figure 6 As shown, the magnetic field strength below the magnet group 2 has a concentrating effect, which increases the magnetic field strength on one side of the magnet group 2 and weakens the magnetic field on the other side.

[0030] Key points combined Figure 5 As shown, the drive mechanism 4 is a lead screw and nut mechanism, including a lead screw 41. A threaded hole 11 is longitudinally passed through the housing 1 and screwed to the lead screw 41. One end of the lead screw 41 is rotatably connected to the fixed frame 5 through a bearing. The other end of the lead screw 41 passes upward through the threaded hole 11 and extends out of the housing 1 to be connected to the drive motor, or can be driven manually.

[0031] Key points combined Figure 6As shown, the device also includes a lift-off sensor 12, which can be an existing miniature eddy current sensor with high accuracy and fast response. Alternatively, a capacitive sensor can also be used. The lift-off sensor 12 is used to detect the distance between itself and the surface of the test piece. The drive mechanism 4 is configured to drive the magnet assembly 2 to move according to the detection signal of the lift-off sensor 12. Specifically, the probe also includes an outer cover 14 and a bottom shell 13. The outer cover 14 is fitted around the outer periphery of the housing 1, and the bottom shell 14 is located on the bottom side of the coil assembly 3 and is sealed on the bottom side of the outer cover 14. The lift-off sensor 12 is mounted on the bottom shell 13 and faces the test piece. The lift-off distance is the vertical distance between the bottom surface of the bottom shell 13 and the upper surface of the test piece. The device also includes a control unit (not shown in the figure). The control unit is electrically connected to the drive mechanism 4 and the lift-off sensor 12. The lift-off distance is the distance between the bottom surface of the bottom shell 13 and the test piece. The control unit is configured to perform the following operations. First, obtain the current lift distance detected by the lift sensor 12. ; Secondly, Working range with preset lift-off distance In comparison, among which, ; when If the lift-off is within the normal range, maintain the current position of magnet group 2; when > ,or < At that time, the control unit controls the drive mechanism 4 to move the magnet group 2 to the target position according to the preset lift-off distance and the correspondence between the magnet group 2 and the position of the magnet group 2. The preset lift-off distance and the correspondence between the magnet group 2 and the position of the magnet group 2 are the positions of the magnet group 2 that keep the effective bias magnetic field strength on the surface of the test piece basically stable under different lift-off distances.

[0032] The control unit can be a microcontroller (MCU) or a programmable logic controller (PLC). Processing data, executing algorithms, and driving execution through a microcontroller (MCU) is existing technology and will not be elaborated on in detail.

[0033] In this specific embodiment, the correspondence between different lift-off distances and the positions of magnet group 2 is different. The mapping relationship between the two can be established by a preset calibration method. The calibration method is as follows: first, a standard test piece is fixed to the probe, and different lift-off distances between the two are controlled. According to each lift-off distance, the magnet group 2 is controlled to move within a preset stroke range of the lift-off distance. When moving within the preset stroke range, the ultrasonic received signal characteristic values ​​corresponding to different positions are recorded, and then the preferred position of magnet group 2 that makes the signal characteristic values ​​optimal is determined. All lift-off distances and their corresponding preferred positions are summarized to form the mapping relationship between the lift-off distance and the target position of magnet group 2, and the mapping relationship is input into the control unit.

[0034] The present invention also provides a method for lifting an electromagnetic ultrasonic transducer probe using the above-mentioned HalbacH permanent magnet component, comprising the following steps; S1, obtain the current lift-off distance between the probe and the test piece; S2, Determine whether the current lift distance exceeds the preset lift range; S3, when the distance is exceeded, the target position of the magnet group 2 corresponding to the current lift-off distance is determined according to the correspondence between the preset lift-off distance and the position of the magnet group 2, and the magnet group 2 is driven to move to the target position. The correspondence is configured such that the bias magnetic field strength acting on the surface of the test piece is kept stable by adjusting the magnet group 2 to the corresponding target position under different lift-off distances.

Claims

1. An electromagnetic ultrasonic transducer probe for a HalbacH permanent magnet assembly, characterized in that: It includes a housing (1), a magnet assembly (2), a coil assembly (3), and a drive mechanism (4); The magnet assembly (2) is housed in the housing (1) and consists of several magnets arranged according to a preset polarity. It is used to provide a bias magnetic field. The coil assembly (3) is located outside the housing (1) and close to the test piece. It is used to generate ultrasonic waves in the bias magnetic field after a pulse current is applied, and to receive ultrasonic signals reflected from the test piece. A fixing frame (5) is provided on the outer periphery of the magnet assembly (2). The fixing frame (5) is used to install and fix the magnet assembly (2). There is an movable gap between the fixing frame (5) and the inner wall of the housing (1). The movable gap is located on the side of the magnet assembly (2) away from the test piece. The drive mechanism (4) is installed on the housing and connected to the fixing frame (5). It is used to drive the magnet assembly (2) away from or closer to the coil assembly (3) in a direction perpendicular to the test piece, so that the distance between the magnet assembly (2) and the coil assembly (3) is different.

2. The electromagnetic ultrasonic transducer probe of the HalbacH permanent magnet assembly as described in claim 1, characterized in that: The magnet group (2) includes a first magnet group (21) and a second magnet group (22). The first magnet group (21) and the second magnet group (22) are arranged adjacent to each other. The first magnet group (21) is composed of a number of first magnets (210), and the second magnet group (22) is composed of a number of second magnets (220). The number and position of the first magnets (210) correspond one-to-one with the number and position of the second magnets, and the magnetization direction is the same.

3. The electromagnetic ultrasonic transducer probe of the HalbacH permanent magnet assembly as described in claim 2, characterized in that: The first magnet (210) has a square structure, and the second magnet (220) has a trapezoidal structure. The first magnet (210) is located on the top side of the second magnet (220). The second magnet (220) is formed by expanding outward from the bottom end of the first magnet (210) into a trapezoidal structure, or by shrinking inward from the bottom end of the first magnet (210) into a trapezoidal structure. The adjacent magnets are in close contact with each other.

4. The electromagnetic ultrasonic transducer probe of the HalbacH permanent magnet assembly as described in claim 2, characterized in that: The number of first magnets (210) is 5, and the magnetization directions of the 5 first magnets (210) from left to right are vertically downward, horizontally to the left, vertically upward, horizontally to the right and vertically downward. The number of second magnets (220) is 5, and the magnetization directions of the 5 second magnets (220) from left to right are vertically downward, horizontally to the left, vertically upward, horizontally to the right and vertically downward.

5. The electromagnetic ultrasonic transducer probe of the HalbacH permanent magnet assembly as described in claim 2, characterized in that: The plurality of first magnets (210) are arranged in an alternating pattern of large and small, and the plurality of second magnets (220) are arranged in an alternating pattern of large and small, and the arrangement is consistent with the arrangement of the first magnets (210).

6. The electromagnetic ultrasonic transducer probe of the HalbacH permanent magnet assembly as described in claim 1, characterized in that: The drive mechanism (4) is a screw and nut mechanism, including a screw (41). A threaded hole (11) for screwing the screw (41) is longitudinally through the housing (1). One end of the screw (41) is rotatably connected to the fixed frame (5) through a bearing. The other end of the screw (41) passes through the threaded hole (11) upward and extends out of the housing (1).

7. The electromagnetic ultrasonic transducer probe of the HalbacH permanent magnet assembly as described in claim 1, characterized in that: The coil assembly (3) includes an excitation coil (6), a first base plate (7), a receiving coil (8), and a second base plate (9). The excitation coil (6), the first base plate (7), the receiving coil (8), and the second base plate (9) are arranged sequentially from top to bottom. A third base plate (10) is provided on the bottom side of the housing (1). The excitation coil (6) is located below the third base plate (10) and between the third base plate (10) and the first base plate (7). The first base plate (7), the second base plate (9), and the third base plate (10) extend to the outside of the excitation coil (6) and the receiving coil (8) respectively and are fixedly connected by bolts. The first base plate (7) and the second base plate (9) are made of insulating material, and the third base plate (10) and the housing (1) are made of non-magnetic material.

8. The electromagnetic ultrasonic transducer probe of the HalbacH permanent magnet assembly as described in claim 1, characterized in that: The excitation coil (6) has a planar runway coil structure, and the receiving coil (8) has a planar runway coil structure.

9. The electromagnetic ultrasonic transducer probe of the HalbacH permanent magnet assembly as described in claim 1, characterized in that: It also includes a lift-off sensor (12) for detecting the lift-off distance between the probe and the surface of the test piece, and the drive mechanism (4) is configured to drive the magnet assembly (2) to displacement based on the detection signal from the lift-off sensor (12).

10. A method for lifting an electromagnetic ultrasonic transducer probe using the HalbacH permanent magnet assembly as described in claim 1, comprising the following steps; S1, obtain the current lift-off distance between the probe and the test piece; S2, Determine whether the current lift-off distance exceeds the preset lift-off range; S3, when the distance exceeds the limit, the target position of the magnet group (2) corresponding to the current lift-off distance is determined according to the preset correspondence between the lift-off distance and the position of the magnet group (2), and the magnet group (2) is driven to move to the target position, wherein, The correspondence is configured such that, at different lift-off distances, the bias magnetic field strength acting on the surface of the test piece is kept stable by adjusting the magnet group (2) to the corresponding target position.

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