Magnetic flaw detection apparatus using an E-shaped magnetic sensor and high-pass filter
First Claim
1. A magnetic flaw detection apparatus comprising:
- a magnetizer for magnetizing a moving subject;
an E-shaped magnetic sensor including a core of a ferromagnetic substance, said core having an E-shape formed by a base portion and three projecting portions mounted on said base portion, said projecting portions constituting magnetic poles and being disposed facing said subject, said sensor further including a search coil wound on a center projecting portion of said three projecting portions for detecting magnetic flux generated due to a fault portion of said magnetized subject, said search coil providing an output signal when said magnetic flux is generated; and
a high-pass filter having a predetermined cutoff frequency, F, for processing an output signal from said E-shaped magnetic sensor, said cutoff frequency being determined on the basis of the distance between the centers of said projecting portions, a liftoff which is the distance between said subject and said E-shaped core, and the moving speed of said subject.
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Accused Products
Abstract
A magnetic sensor in which magnetic leakage flaw detection can be performed with high accuracy without so reducing liftoff, and a magnetic flaw detection method and apparatus to which the magnetic sensor is applied. The magnetic sensor 50 for detecting magnetic flux generated due to a defect portion of a magnetized subject to be inspected has an E-shaped core 51 having magnetic poles (51a, 51b and 51c) arranged in the neighborhood of a steel plate (13) to be inspected, and a search coil (52) wound on the center magnetic pole (51b) of the E-shaped core for detecting the magnetic flux. An external magnetic field floating in the circumference of the E-shaped magnetic sensor passes through the opposite side magnetic poles (51a and 51c) of the E-shaped core 51 but does not cross the center magnetic pole (51b) of the E-shaped core. Accordingly, no voltage due to the external magnetic field is induced in the search coil (52), so that only the magnetic flux caused by the defect portion is detected. Accordingly, the directivity with respect to the external magnetic field is improved so that the generation of a noise voltage due to the external magnetic field is suppressed and S/N at the time of flaw detection is improved.
85 Citations
14 Claims
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1. A magnetic flaw detection apparatus comprising:
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a magnetizer for magnetizing a moving subject; an E-shaped magnetic sensor including a core of a ferromagnetic substance, said core having an E-shape formed by a base portion and three projecting portions mounted on said base portion, said projecting portions constituting magnetic poles and being disposed facing said subject, said sensor further including a search coil wound on a center projecting portion of said three projecting portions for detecting magnetic flux generated due to a fault portion of said magnetized subject, said search coil providing an output signal when said magnetic flux is generated; and a high-pass filter having a predetermined cutoff frequency, F, for processing an output signal from said E-shaped magnetic sensor, said cutoff frequency being determined on the basis of the distance between the centers of said projecting portions, a liftoff which is the distance between said subject and said E-shaped core, and the moving speed of said subject. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification