JPH0738956U - Leakage magnetic detection sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a small leakage magnetic detection sensor capable of detecting leakage magnetic flux with high sensitivity. A leak magnetic detection sensor for detecting a magnetic field leaking from a surface of a magnetized material to be inspected or an internal defect, a coil sensor 11b having a coil 11a formed on a magnetically sensitive surface.
A ferromagnetic body 11c is arranged on the opposite side of the magnetic sensitive surface from the magnetic sensitive surface of the coil sensor 11b at a predetermined distance from the magnetic sensitive surface to attract the leakage magnetic flux to the ferromagnetic body 11c. Focus across.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a leakage magnetic detection sensor used in a leakage magnetic flux flaw detection method for detecting a magnetic flux leaking from or near the surface of a material to be inspected, which is a ferromagnetic material.

[0002]

[Prior art]

 The magnetic flux leakage flaw detection method is a method for detecting magnetic flux leaking from surface flaws when magnetizing the material to be inspected to detect flaws on the surface flaws, etc. There is a semiconductor magnetic sensor, or a coil sensor 2 in which two coils 1 in which a conductive wire is wound around ferrite or in which the conductive wire 1a is planarly wound as shown in FIG. 6 are arranged on the magnetically sensitive surface. The coil sensor 2 shown in FIG. 6 has a structure in which a magnetic field in a direction perpendicular to the magnetic sensing surface is detected and two coils 1 are used to obtain a differential output of a spatial magnetic field.

Among the leakage magnetic detection sensors, the semiconductor magnetic sensor has a high detection sensitivity, a small shape, and can measure a DC magnetic field. Therefore, the semiconductor magnetic sensor is widely used as a leakage magnetic detection sensor for a leakage magnetic flux flaw detection method. . In addition, the coil sensor has a simple structure and good environmental characteristics (heat resistance), so it is used as a leakage magnetic detection sensor for AC leakage flux flaw detection.

[0004]

[Problems to be solved by the device]

 However, both of the leaky magnetic field detection sensors described above have the following problems. First, since the semiconductor magnetic sensor has poor temperature characteristics and cannot be used at high temperatures, it must be housed in a sensor holder having a cooling function. Therefore, the sensor holder becomes complicated, large, and heavy, and there are problems in maintainability and the ability to follow the surface of the material to be inspected. Moreover, since the frequency characteristic is generally poor, it cannot be used as a leakage magnetic detection sensor for the magnetic flux flaw detection method to which the high frequency magnetization method is applied.

Next, since the coil sensor has a lower magnetic sensitivity than a magnetic diode or the like, there is a problem that the detection sensitivity is low when flaw detection of a minute defect is performed. Since the detection sensitivity of the coil sensor is proportional to the number of turns of the coil, it is possible to increase the number of turns to increase the sensitivity.However, increasing the number of turns of the coil increases the size and results in very small defects. It is not suitable for detecting a narrow magnetic flux leakage.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a leakage magnetic detection sensor that is small in size and capable of detecting leakage magnetic flux with high sensitivity.

[0007]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the magnetic leakage detection sensor of the present invention is a magnetic leakage detection sensor for detecting a magnetic field leaking from the surface of a magnetized material to be inspected or an internal defect. A ferromagnetic material is arranged on the side opposite to the magnetic sensitive surface at a predetermined distance.

[0008]

[Action]

 The leakage magnetic detection sensor of the present invention uses a ferromagnetic material having a magnetic permeability that is much larger than the magnetic permeability in the space on the opposite side of the magnetic sensing surface of the plane coil and with a certain distance from this magnetic sensing surface. Since the magnetic flux is arranged in the existing state, the leakage magnetic flux is attracted to the ferromagnetic material. Most of the attracted leakage magnetic flux crosses the magnetically sensitive surface 2a of the coil sensor 2 in a concentrated manner as shown in FIG. Note that FIG. 5B is a leakage magnetic flux distribution diagram in the case of the coil sensor 2 alone. In this case, since the leakage flux passes through the magnetic sensing surface 2a at a shallow angle, the vertical magnetic field component of the magnetic sensing surface 2a is The output of the detected leakage magnetic field is small. In FIG. 5, 3 is a ferromagnetic material, 4 is a material to be inspected, and 4a is a defect.

[0009]

[Embodiment] Hereinafter, a magnetic leakage detection sensor of the present invention will be described based on an embodiment shown in FIGS. FIG. 1 is an explanatory view of one embodiment of the leakage magnetic detection sensor of the present invention, FIGS. 2 (a) and 2 (b) are explanatory views of the shape of a ferromagnetic material constituting the leakage magnetic detection sensor of the present invention, and FIG. It is the schematic of the experimental apparatus which arrange | positioned the leak magnetic detection sensor of the invention.

In FIG. 1 to FIG. 3, reference numeral 11 is a leakage magnetic detection sensor of the present invention, and a coil 11a (width 2 mm, length 4 mm) made by aluminum vapor deposition is placed on the front surface (magnetic sensing surface) of a silicon wafer, for example. A rectangular parallelepiped-shaped (width 2 mm, length 4 mm, height 0.5 mm) ferromagnetic body 11c, for example, ferrite, having substantially the same size as the coil 11a is adhered to the back surface of the arranged coil sensor 11b, and the whole is bonded. It is a molded product. In addition, 12 in FIG. 1 shows an output terminal.

The material of the ferromagnetic body 11c is not limited to the ferrite shown in this embodiment, but may be an electromagnetic steel plate, amorphous, permalloy or the like. Further, the shape of the ferromagnetic body 11c is not limited to the rectangular parallelepiped as in the present embodiment, and may be an arch type as shown in FIG. 2A or a separated type as shown in FIG. 2B. Has the same effect. Furthermore, if the ferromagnetic material 11c is a ferromagnetic material such as ferrite with a coil directly formed on the surface by vapor deposition or plating, the distance between the ferromagnetic material and the coil can be made very small. Further higher sensitivity can be realized.

The magnetic leakage detection sensor 11 of the present invention has the above-mentioned configuration, and the results of experiments conducted to confirm the effects of the present invention will be described below. As shown in FIG. 3, the carbon steel pipe 13 has an axial depth of 0. Four notch-shaped defects (width 0.1 mm, length 20 mm) of 1 mm, 0.15 mm, 0.23 mm, and 0.33 mm, which were electric discharge machined, were magnetized by an AC electromagnet 14 laminated with electromagnetic steel sheets, and the present invention was devised. The artificial defect 13 a was detected by using the leak magnetic detection sensor 11 of. For comparison, the artificial defect 13a was detected under the same conditions even with the coil sensor alone.

As a result, when the leakage magnetic detection sensor 11 of the present invention is used [FIG. 4 (a)], the output sensitivity is 2 as compared with the conventional coil sensor alone [FIG. 4 (b)]. I was able to confirm that it doubled.

[0014]

[Effect of device]

 As described above, in the leak magnetic detection sensor of the present invention, a ferromagnetic material having a magnetic permeability much larger than the magnetic permeability in the space is provided on the opposite side of the magnetic sensitive surface of the plane coil to the magnetic sensitive surface. The magnetic fluxes are arranged at a predetermined interval, and the leaked magnetic flux is attracted to the ferromagnetic material and most of them cross the magnetic sensitive surface of the coil sensor in a concentrated manner. Therefore, the structure can be made small, the detection sensitivity of the leakage magnetic detection sensor is improved, and flaw detection of fine defects is possible.

[Brief description of drawings]

FIG. 1 is an explanatory view of an embodiment of a leak magnetic detection sensor of the present invention.

2 (a) and 2 (b) are explanatory views of the shape of a ferromagnetic material that constitutes the leak magnetic detection sensor of the present invention.

FIG. 3 is a schematic view of an experimental device in which the leak magnetic detection sensor of the present invention is arranged.

FIG. 4A is a diagram showing an artificial defect flaw detection waveform obtained by the leak magnetic field detection sensor of the present invention, and FIG. 4B is a diagram showing an artificial defect flaw detection waveform obtained by the conventional leak magnetism detection sensor.

5A is a diagram showing a leakage magnetic flux distribution by the leakage magnetic detection sensor of the present invention, and FIG. 5B is a diagram showing a leakage magnetic flux distribution by a conventional leakage magnetic detection sensor.

FIG. 6 is an explanatory diagram of a conventional coil sensor.

[Explanation of symbols]

 11 Leakage Magnetic Detection Sensor 11a Coil 11b Coil Sensor 11c Ferromagnetic Material

Claims (1)

[Scope of utility model registration request] 1. A leak magnetic detection sensor for detecting a magnetic field leaking from a surface of a magnetized material to be inspected or an internal defect, wherein a predetermined distance is provided between the flat coil and the magnetic sensing surface on the opposite side. A leak magnetic detection sensor characterized by arranging a ferromagnetic material.