阅读说明：本技术 一种增强涡流传感器线圈灵敏度的方法 (Method for enhancing sensitivity of eddy current sensor coil ) 是由 田中山 王现中 杨昌群 牛道东 李育特 于 2021-09-09 设计创作，主要内容包括：本发明是一种增强涡流传感器线圈灵敏度的方法。当电涡流探头的线圈中通入高频交流电时,线圈周围产生磁场,线圈产生的磁场与环形磁铁产生的磁场发生耦合,产生新的耦合强磁场；涡流传感器的线圈在耦合一个环形磁铁后对引起磁场改变的扰动更加敏感,用以增强灵敏度。本发明有利于在线圈外部产生更强的磁场,进而提高检测的灵敏度。本发明设计的环形磁铁及线圈耦合方式是通过一种特殊的磁铁排列方式将磁铁一侧的磁场叠加在另一侧,这样可以用最少量的磁铁产生最强的单侧磁场。(The invention relates to a method for enhancing the sensitivity of an eddy current sensor coil. When high-frequency alternating current is introduced into a coil of the eddy current probe, a magnetic field is generated around the coil, and the magnetic field generated by the coil is coupled with the magnetic field generated by the annular magnet to generate a new coupled strong magnetic field; the coil of the eddy current sensor is more sensitive to disturbances that cause changes in the magnetic field after coupling a ring magnet to enhance sensitivity. The invention is beneficial to generating stronger magnetic field outside the coil, thereby improving the detection sensitivity. The ring magnet and coil coupling of the present invention is designed to superimpose the magnetic field on one side of the magnet on the other side by a special magnet arrangement that produces the strongest single-sided magnetic field with the least amount of magnet.)

1. A method of enhancing the sensitivity of an eddy current sensor coil, comprising: the method specifically comprises the following steps: when high-frequency alternating current is introduced into a coil of the eddy current probe, a magnetic field is generated around the coil, and the magnetic field generated by the coil is coupled with the magnetic field generated by the annular magnet to generate a new coupled strong magnetic field; the coil of the eddy current sensor is more sensitive to disturbances that cause changes in the magnetic field after coupling a ring magnet to enhance sensitivity.

2. The method of enhancing eddy current sensor coil sensitivity as recited in claim 1, wherein: the annular magnet is divided into 16 parts with different polarization directions, and has 4 different polarization directions, and the polarization directions of the magnetic blocks in a sector area of 90 degrees are respectively leftward polarization, upward polarization, rightward polarization and downward polarization; every 90 degrees is an arrangement period to form a ring-shaped magnet which is specially arranged; the magnetic flux density of the side, close to the coil, of the annular magnet is far larger than that of the side, far away from the coil, so that the magnetic impedance changes more obviously when the metal surface is close to the coil, and the magnetic impedance of the part, far away from the coil, of the annular magnet does not change.

3. A method of enhancing the sensitivity of an eddy current sensor coil as set forth in claim 2, wherein: the center of the ring magnet is provided with a wire, and a tap of the coil is connected with an external circuit through the center of the ring magnet.

4. A method of enhancing the sensitivity of an eddy current sensor coil as set forth in claim 3, wherein: the material of the ring magnet is N50.

5. The method of claim 4, wherein the coil sensitivity of the eddy current sensor is enhanced by: the outer radius of the ring magnet is 5mm, the inner radius is 3mm, and the thickness of the ring magnet is 3 mm.

Technical Field

The invention relates to the technical field of nondestructive testing of eddy current sensors, in particular to a method for enhancing the sensitivity of an eddy current sensor coil.

Background

Eddy current sensors have found wide application in the field of non-destructive inspection, and some surface defects such as cracks, crevices, etc. can be characterized by changes in the induced current in the eddy current sensor's induction coil. For some eddy current sensors such as giant magnetoresistance eddy current sensors, pick-up coil sensors, etc., the coil is a special rectangular coil. Compared with a flat coil, the rectangular coil has the characteristic of being sensitive to the directional change and the frequency change, so that the rectangular coil is widely applied to nondestructive testing of the eddy current sensor. Due to the particularity of the rectangular coil structure, the eddy current induced by the coil is only determined by the winding at the bottom, and the winding at the other part has small effect on the induced eddy current, so that the rectangular coil has poor coupling effect, low generated current density and large influence on the sensitivity of the eddy current sensor. If the coupling effect of the rectangular coil is increased, the sensitivity of the eddy current sensor is greatly enhanced, and then the surface crack and other defect characteristics of the to-be-detected defect piece can be detected more conveniently.

In order to increase the current density and improve the sensitivity of the eddy current sensor, many research organizations improve the performance of the eddy current probe by optimizing the probe structure and the like. The Yangzhou industrial occupational technology college provides a metal flaw detector based on eddy current sensing measurement (patent number: CN202022380248.9), and relates to a metal flaw detector based on eddy current sensing measurement. The method can measure the surface defects of the metal by a nondestructive testing method by utilizing the electromagnetic induction principle, but the coil coupling effect of the eddy current sensor is not substantially improved. The invention discloses an improved orthogonal electrical disturbance eddy current sensor (CN 201911369449.4), which is provided by Aidessen (Xiamen) electronic Limited company and discloses an improved orthogonal electrical disturbance eddy current sensor.A structure of a conventional orthogonal eddy current probe is improved, specifically, two orthogonally wound eddy current detection coils are respectively changed into two coaxial and parallel eddy current detection coils, the two coaxial and parallel eddy current detection coils are connected to an output detection circuit in a differential input mode, and during detection, only one group of eddy current detection coils vertical to the advancing direction in the sensor has a detection function through rapid switching of an electronic switch, namely, the detection function of one group of eddy current detection coils parallel to the advancing direction of the sensor is cancelled, so that the sensor has a function of detecting the hole-shaped defects. The method enables the eddy current sensor to have the function of detecting the hole-shaped defects by improving the structure of the probe, but the probe part is bulky, and the sensitivity of the coil is not improved.

Disclosure of Invention

The invention provides a method for enhancing the sensitivity of an eddy current sensor coil for improving the detection sensitivity of the eddy current sensor, and the invention provides the following technical scheme:

a method of enhancing eddy current sensor coil sensitivity, the method comprising: when high-frequency alternating current is introduced into a coil of the eddy current probe, a magnetic field is generated around the coil, and the magnetic field generated by the coil is coupled with the magnetic field generated by the annular magnet to generate a new coupled strong magnetic field; the coil of the eddy current sensor is more sensitive to disturbances that cause changes in the magnetic field after coupling a ring magnet to enhance sensitivity.

Preferably, the ring magnet is divided into 16 parts with different polarization directions, and has 4 different polarization directions, and the polarization directions of the magnetic blocks in the sector area of 90 degrees are respectively leftward polarization, upward polarization, rightward polarization and downward polarization; every 90 degrees is an arrangement period to form a ring-shaped magnet which is specially arranged; the magnetic flux density of the side, close to the coil, of the annular magnet is far larger than that of the side, far away from the coil, so that the magnetic impedance changes more obviously when the metal surface is close to the coil, and the magnetic impedance of the part, far away from the coil, of the annular magnet does not change.

Preferably, the ring magnet is wired at the center, and the coil tap is connected with an external circuit through the center of the ring magnet.

Preferably, the material of the ring magnet is N50.

Preferably, the outer radius of the ring magnet is 5mm, the inner radius is 3mm, and the thickness of the ring magnet is 3 mm.

The invention has the following beneficial effects:

the invention is beneficial to generating stronger magnetic field outside the coil, thereby improving the detection sensitivity. The ring magnet and coil coupling of the present invention is designed to superimpose the magnetic field on one side of the magnet on the other side by a special magnet arrangement that produces the strongest single-sided magnetic field with the least amount of magnet. For the eddy current probe, the diameter is about 10mm generally, and the coupling method can not cause the probe part to be bulky, thereby being more beneficial to the miniaturization design of the eddy current sensor probe.

Drawings

FIG. 1 is a schematic view of an eddy current sensor probe;

FIG. 2 is a schematic view of a coil and ring magnet coupling;

FIG. 3 is a schematic diagram showing the distribution of magnetic induction lines in the cross section of a ring magnet;

fig. 4 is a schematic view of the magnetic flux density distribution of the normal line of the surface of the ring magnet.

Detailed Description

The present invention will be described in detail with reference to specific examples.

The first embodiment is as follows:

referring to fig. 1 to 4, the present invention provides a method for enhancing coil sensitivity of an eddy current sensor, and aims at the defects of low coupling strength and low detection sensitivity of the current eddy current sensor for nondestructive detection. The invention is to strengthen the magnetic field near the coil by placing a special ring magnet above the coil. When the coil and the surface of the metal conductor are changed to cause the characteristic impedance of the coil to be changed, the current in the coil is also changed, and the changed distance between the coil and the surface of the metal conductor can be obtained by measuring the current change.

As shown in fig. 1, the probe of the eddy current sensor is a schematic diagram, and comprises a probe shell 1, a coil and ring magnet coupling part 2, a coil 2a, a ring magnet 2b and a probe thread 3, when high-frequency alternating current is introduced into the coil 2a of the eddy current probe, a magnetic field is generated around the coil, and the magnetic field generated by the coil is coupled with the magnetic field generated by the ring magnet 2b to generate a new coupling strong magnetic field. According to the Faraday's law of electromagnetic induction, when a metal object moves in a coupled strong magnetic field, an induced magnetic field opposite to the direction of the coupled strong magnetic field is generated while an induced current is generated due to the fact that the metal object cuts a magnetic induction line, and the induced magnetic field influences the effective impedance of the coil to cause the current in the coil to change. The eddy current sensor coil, coupled with a specially arranged ring magnet, is more sensitive to small disturbances that cause changes in the magnetic field, thereby greatly increasing sensitivity.

Fig. 2 is a schematic view showing a coupling portion of the coil and the ring magnet. The coil is arranged right below the ring-shaped magnet, and the ring-shaped magnet is specially arranged above the coil. The ring magnet is divided into 16 parts with different polarization directions, and it can be seen from the figure that the polarization directions of the magnetic blocks in the sector area of 90 degrees are respectively leftward polarization, upward polarization, rightward polarization and downward polarization. Every 90 deg. is an arrangement period, and the ring magnets are formed into a special arrangement as shown in fig. 2. The magnetic flux density of the ring magnet on the side close to the coil is much greater than the magnetic flux density on the side far from the coil, so that the magnetic impedance changes more significantly when the surface of the metal is close to the coil, and the magnetic impedance of the part far from the coil hardly changes.

The center of the ring magnet can be wired, and a tap of the coil can be connected with an external circuit through the center of the ring magnet, so that the utilization efficiency of the space of the probe is improved.

The magnetic field simulation is performed on the magnetic ring and the coil in the invention, and the magnetic induction line distribution diagram of the section part of the magnetic ring is obtained and is shown in fig. 3. It can be seen from the figure that the magnetic induction lines close to the coil part are dense, the magnetic induction lines far from the coil part are sparse, and the magnetic flux density below is greater than that above.

Taking a normal perpendicular to the ring surface of the ring magnet, the magnetic field intensity change on the analysis line is shown in fig. 4, and it can be seen from the figure that the magnetic flux density at the upper surface of the ring magnet decreases rapidly, the magnetic flux density slightly away from the upper surface is almost 0, while the magnetic flux density at the lower surface decreases slowly with increasing distance, and the magnetic flux density slightly away from the lower surface is much greater than the magnetic flux density slightly away from the upper surface.

The ring magnet is composed of 16 parts, 4 different polarization directions exist, each small part is easy to prepare, and the small parts can become a magnetic ring after being combined, so that compared with the traditional method of singly preparing the single polarization direction coupling magnet with a special shape, the single polarization direction coupling magnet has the advantages of manufacturing and cost.

The coupling method of the ring magnet and the coil is shown in fig. 2. Wherein the material of the ring magnet can be N50. The outer radius of the ring magnet is 5mm, the inner radius is 3mm, and the thickness of the ring magnet is 3 mm. The ring magnet is divided into 16 parts, 4 parts are arranged at every 90 degrees, and the polarization directions are respectively leftward polarization, upward polarization, rightward polarization and downward polarization. An eddy current sensor coil is arranged below the annular magnet. The ring magnet in the method of the invention enables the magnetic flux close to the coil part to be far larger than the magnetic flux far away from the coil part through a special composition mode.

The invention provides a method for enhancing the sensitivity of an eddy current sensor coil, which improves the coupling strength of the coil and a magnet on the premise of not increasing the size of a probe, and further improves the detection sensitivity of the sensor. The method can be used for designing the annular magnets with different sizes by combining the probes with different sizes, and is generally applicable to various eddy current sensor probes.

The above description is only a preferred embodiment of the method for enhancing the sensitivity of the coil of the eddy current sensor, and the protection scope of the method for enhancing the sensitivity of the coil of the eddy current sensor is not limited to the above embodiments, and any technical solutions belonging to the idea belong to the protection scope of the present invention. It should be noted that modifications and variations which do not depart from the gist of the invention will be those skilled in the art to which the invention pertains and which are intended to be within the scope of the invention.