| 摘要 |
PROBLEM TO BE SOLVED: To accurately determine at all times whether or not flaws exist on a round bar-shaped inspected material independent of its eccentricity, if any. SOLUTION: This eddy current flaw detector is equipped with a plurality of reluctance sensors 3, an eccentricity detection sensor 5, and a determination circuit. The reluctance sensors 3 are circumferentially disposed apart from a peripheral surface of the round bar-shaped inspected material LM at an intermediate position between exciting coils 2A and 2B, and each output a detection signal corresponding to the intensity of magnetism circumferentially detected. The detection sensor 5 is used for detecting the eccentric direction of the inspected material LM and an eccentric position thereof in such direction. The determination circuit is used for storing, as a reference offset signal, a detection signal at each eccentric position in a relevant radial direction when the inspected material LM is made to forward/reverse eccentric state in a prescribed axial direction relative to the axis of the exciting coils 2A and 2B, selecting a reference offset signal corresponding to the detected eccentric position, changing the phase of the selected reference offset signal according to a directional difference between the detected eccentric direction and the prescribed radial direction thereby acquiring an offset signal, acquiring a determination signal by subtracting the offset signal from the detected signal, and determining whether or not flaws exist on the peripheral surface of the inspected material from the determination signal. COPYRIGHT: (C)2009,JPO&INPIT
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