JP2007121050A - Flaw detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flaw detector dispensing with work for initial setup while performing flaw detection on an object under inspection with high accuracy and at a high speed. <P>SOLUTION: A cylindrical passage is formed by using a plurality of sensor parts to move the object under inspection relative to the sensor parts through the passage. Each of the sensor parts comprises a comparison coil, an excitation coil, and a detection coil, disposed on the same axis, any of which is a circular coil of the same diameter. Any of the sensor parts is structured so that the same axis lies in a plane parallel to the center axis of the passage and that the same axes of all the sensor parts are parallel to each other. By suitably changing their inclination, sensitivity to the direction of a flaw existing on a surface of the object is adjusted. By generating a differential signal with two sensor parts paired with each other, only a flaw signal can be taken out. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an apparatus for detecting a flaw existing on the surface of an object to be inspected using eddy currents, and in particular, by moving an inspected object whose surface layer is made of a conductive material with respect to a sensor unit of the flaw detection apparatus. The present invention relates to a flaw detection apparatus that detects the existence of a flaw.
In the present invention, the scratch refers to a scratch or an abnormal part present on the surface layer portion of the inspection object.

  In high-precision products and products that hold harmful substances inside, very fine scratches may cause failures or accidents. Therefore, a nondestructive flaw detection inspection is usually performed on such a product, and the product in which the scratch is found is removed to ensure the quality of the product and the safety.

  Nondestructive flaw detection inspections are carried out in various product fields, and various techniques have been developed and disclosed so far in order to detect flaws more reliably. As an example of such a technique, Patent Document 1 describes an information extraction method for automatically detecting flaws by using an eddy current signal. In this information extraction method, a flaw detection technique for drawing a Lissajous figure or the like based on an eddy current signal and recognizing the drawn figure is used.

  One of the products that are subjected to nondestructive testing is a dry cell. Various types of dry batteries are widely used socially, but the electrolyte held in the inside is often a highly corrosive substance. For example, alkaline manganese manganese batteries use potassium hydroxide electrolyte, but if for some reason the liquid leaks and the potassium hydroxide electrolyte adheres to the equipment that uses the batteries, the equipment will be damaged. There is a risk of giving or damaging the equipment. Therefore, flaw detection inspection plays a very important role for a manufacturer who manufactures and sells dry batteries.

  In order to reliably prevent failures caused by scratches existing on the surface of the dry cell, it is not sufficient to conduct a sampling inspection for only a part of the manufactured product. It goes without saying that it is desirable to perform flaw detection inspections one by one and ship only those that are confirmed to be intact. And since dry batteries are usually mass-produced, in order to inspect all products, it is preferable that the time required for inspection per product is as short as possible.

In order to solve the above problems, the inventor of the present application
A flaw detection device for detecting a flaw on an inspection object,
A coil to which a high-frequency voltage is applied;
A high-frequency control unit that performs control related to a high-frequency voltage applied to the coil;
A waveform generator for drawing a Lissajous waveform of each object to be inspected based on a voltage change of the coil that occurs when the object to be inspected passes through the inside of the coil;
A reference waveform setting unit for setting a predetermined Lissajous waveform as a reference waveform;
When the Lissajous waveform of the object to be inspected is drawn within a predetermined error from the reference waveform, it is determined that there is no damage, and when it is drawn outside the error, a wound determination unit that determines that there is a wound,
Invented a flaw detection apparatus characterized by comprising (Japanese Patent Application 2005-274602).
In addition, the present inventor does not perform a scratch determination based only on the Lissajous waveform in the above flaw detection apparatus, but also performs a scratch determination based on the length of the inspection object, the speed at which the inspection object passes through the coil, or the like. Disclosure.

  According to the flaw detection apparatus of the above invention, flaw detection on the same article can be continuously performed at high speed.

JP-A-8-292174

  In the flaw detection apparatus of the above invention, a Lissajous waveform of an inspection object that is known to be intact is set as a reference waveform, and whether another inspection object is intact or damaged is determined based on the reference waveform. To do. That is, there has been a problem that the accuracy of flaw detection is reduced unless the selection of an intact inspection object as a reference is performed appropriately. There is also a problem in that the flaw detection accuracy is lowered when it is attempted to increase the tolerance of the individual difference of the inspection object. Furthermore, when the inspection object has a finite length, the output signal is greatly disturbed (end signal) at the terminal of the inspection object, so that the flaw detection sensitivity is limited.

  Furthermore, not only the flaw detection apparatus of the invention described above, but generally in a through-coil type flaw detection apparatus, the bridge balance adjustment, phase adjustment, and sensitivity adjustment are performed with the inspection object placed in the sensor before the flaw detection test is started. It is necessary to perform a setup work such as this, but this is a work requiring labor.

The flaw detection apparatus according to the present invention, which has been made to solve the above problems,
An eddy current flaw detector for detecting a flaw in an inspection object based on a signal output from the sensor section when the inspection object passes in the vicinity of a sensor section provided on a cross-sectional circle of a cylindrical passage. There,
A plurality of sensor parts each having a comparison coil, an excitation coil, and a detection coil arranged on the same axis are circular coils having the same diameter. Is also configured such that the same axis is in a plane parallel to the central axis of the passage, and the same axes of all sensor parts are parallel to each other.
Two predetermined sensor units are differentially connected to each other.

With the flaw detection apparatus according to the present invention, the following excellent effects can be obtained.
・ Unlike the penetration coil that performs flaw detection using the entire circumference of the coil, the inspection object is flaw detected by only a part of the coil of the sensor section, so that the resolution of each sensor can be increased, and the flaw detection apparatus as a whole Improves flaw detection ability.
・ Since two specified sensor parts are differentially connected to each other and only the differential signals of both sensor parts are output, it is possible to extract only the scratch signal regardless of the individual difference or shape of the inspected object It is. Further, the flaw signal is not buried in the end signal generated at the end of the inspection object, and the flaw detection can be performed with high accuracy. Of course, flaw detection can be performed continuously at high speed.
・ Each sensor unit consists of a comparison coil, excitation coil, and detection coil, so initial setup such as bridge balance adjustment, phase adjustment, and sensitivity adjustment can be automatically adjusted without placing the inspection object in the sensor. it can. There is no need for the user to manually perform initial setup by placing the inspection object in the sensor as in the prior art.

  An embodiment of the flaw detection apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a flaw detection apparatus according to the present invention, and FIG. 2 is a diagram showing a configuration of a sensor unit.

  As shown in FIG. 1, the flaw detection apparatus of the present invention includes a plurality of sensor units 1. As shown in FIG. 2, the configuration of each sensor unit 1 includes a comparison coil, an excitation coil, and a detection coil arranged on the same axis. In this sensor configuration, a coil balance is established between the detection coil and the comparison coil.

  A plurality of sensor units 1 are arranged on a cross-sectional circle of a cylindrical passage through which the inspection object 10 passes. The “cylindrical passage” may be a virtual passage, and it is not always necessary that the passage is actually formed by some member.

  However, it is preferable to provide a passage cylinder through which the object to be inspected passes, and to arrange a plurality of sensor units 1 around the tube. With this configuration, the object to be inspected 10 can be prevented from tilting undesirably. Further, the internal shape of the passage cylinder is preferably a shape that substantially matches the external shape of the inspection object 10. As a result, the inspection object 10 can be controlled not only to pass through the vicinity of the sensor unit 1 while always maintaining a constant orientation, but also to control the passing position of the inspection object 10 to be equidistant from each sensor unit. It becomes possible.

  In the flaw detection apparatus of the present invention, in any sensor unit 1, the same axis of each coil is in a plane parallel to the central axis of the cylindrical passage, and the same axis of all the sensor units is parallel to each other. Placed in. FIG. 1A shows an example in which each sensor unit 1 is arranged so that the axis of the sensor unit 1 is parallel to the central axis of the passage, and FIG. 1B shows the axis of the sensor unit 1. Is an example in which each sensor unit 1 is arranged so as to be perpendicular (twisted) to the central axis of the passage. Of course, the sensor unit 1 may be arranged with an inclination different from those shown in these two examples.

When the inclination of the sensor unit 1 changes, the inclination of the coil in the sensor unit 1 changes. Then, the direction of the magnetic flux generated from the exciting coil changes, and the direction of the eddy current generated on the surface of the inspection object 10 also changes. Therefore, the sensitivity of the flaw detection changes depending on the shape of the flaw, that is, the flaw direction. When the sensor unit 1 is arranged as shown in FIG. 1A, the sensitivity to scratches parallel to the central axis of the passage is increased. When the sensor unit 1 is arranged with the inclination shown in FIG. 1B, the sensitivity to scratches perpendicular (twisted direction) to the central axis of the passage is increased.
Based on the above points, the inclination of the sensor unit 1 may be adjusted as appropriate according to the characteristics of the material constituting the surface of the inspection object 10, the purpose of flaw detection, and the like.

  A plurality of sensor units 1 are provided as a set of two predetermined sensor units 1 and are differentially connected to each other. Here, a certain sensor unit 1 may form a pair with two or more different sensor units. In general, it is preferable that the sensor portions to be paired are the sensor portions 1 facing each other with a cylindrical passage interposed therebetween, but the sensor portions are not particularly limited.

  FIG. 3 is a diagram showing a control configuration example when flaw detection is performed by the flaw detection apparatus according to the present invention. The control unit 2 is a device for controlling the flaw detection apparatus of the present invention. The control unit 2 includes a central processing unit (CPU) that performs various calculations, a storage unit including a hard disk and a memory for storing data, programs, and the like, a keyboard, a mouse, and a touch panel for a user to input various instructions. Including an input section. The control unit 2 may be connected to a display unit 6 for displaying various information including various waveforms. Various functions of the control unit 2 are realized by executing software in the CPU and also by various dedicated circuits.

  The control unit 2 includes a high frequency control unit 3. The high frequency control unit 3 adjusts the high frequency voltage applied to the excitation coil of the sensor unit.

  For each sensor unit 1, the waveform generation unit 4 subtracts the output of the comparison coil from the output of the detection coil (takes a bridge balance) to obtain an output signal, and the output signal and the other sensor units 1 of the pair A differential signal is generated by taking a differential with the output signal (more precisely, detecting a high frequency here).

  A conceptual diagram of processing in the waveform generation unit 4 is shown in FIG. Here, it is assumed that the sensor unit 1a and the sensor unit 1b installed on the opposite side of the sensor unit 1a across the cylindrical passage are differentially connected.

  An inspection object 10 whose surface layer is formed of a conductive material such as metal is passed through a cylindrical passage formed by a plurality of sensor units. When the inspection object 10 passes in the vicinity of the sensor unit 1, an eddy current is generated on the surface layer of the inspection object 10. Since the magnitude of the eddy current changes depending on the surface shape of the object to be inspected 10, if a flaw exists, the induced voltage of the detection coil and the comparison coil of each sensor unit 1 changes, and appears as a flaw signal in the output signal. .

  In the example of FIG. 4, since there is a scratch on the surface of the inspection object 10 on the sensor unit 1 a side, the output signal output from the sensor unit 1 a includes a scratch signal. Here, the scratch signal appears in two places because a time difference is generated between the detection coil and the comparison coil when the scratch on the inspection object 10 passes near the coil. Further, in the output signal, an end signal that is a waveform disturbance caused by both ends of the inspection object 10 appears. On the other hand, since there is no scratch on the sensor unit 1b side of the inspection object 10, the output signal output from the sensor unit 1b includes only the end signal.

  By taking a differential between the output signal of the sensor unit 1a and the output signal of the sensor unit 1b by the waveform generation unit 4, the end signal is canceled and a differential signal including only the flaw signal is generated.

  The scratch determination unit 5 included in the control unit 2 determines whether or not the output differential signal includes a scratch signal. The scratch determination may be configured such that, for example, the inspection object 10 is determined to be damaged when a signal equal to or higher than a predetermined threshold value is included. The flaw determination performed by the flaw determination unit 5 may be performed for each pair of differential signals of the sensor unit, or one flaw detection apparatus as a whole by further taking the differential signal of each pair of differential signals. An output signal may be obtained and performed based on the output signal.

  As described above, the determination result of the intact or injured determined by the scratch determining unit 5 is output from the scratch determining unit 5 as shown in FIG. The object to be inspected is separated.

  Note that the inspection object 10 may not pass the same distance from each sensor unit, and the output value of each sensor unit 1 may vary. In this case, the output signal of each sensor may be appropriately processed so that the final output value difference becomes zero.

As described above, according to the flaw detection apparatus according to the present invention, it is possible to perform flaw detection of an inspection object at a high speed and continuously with very high accuracy.
Note that the configuration given in the above embodiment is merely an example, and it goes without saying that various changes and improvements can be made within the spirit of the present invention.

  For example, as shown in FIG. 5, the configuration of the sensor unit 1 is compared with a detection sensor unit in which the excitation coil and the detection coil are arranged on the same axis, and a comparison in which the excitation coil and the comparison coil are arranged on the same axis. It is good also as a structure which consists of a sensor part. In this configuration, a coil balance is obtained between the detection sensor unit and the comparison sensor unit.

  Although only four sensor units are described in FIG. 5, in this sensor configuration, in the detection sensor unit and the comparison sensor unit that form a pair, the output of the comparison coil of the comparison sensor is output from the output of the detection coil of the detection sensor unit. To obtain an output signal, and obtain a differential signal by taking a differential of the output signals of different sets. Scratch determination can be performed based on this differential signal.

In addition, when the inspection object 10 has a cylindrical shape, the sensor portion can be formed as an insertion type in order to detect a flaw inside the cylinder, and flaw detection can be performed at the outer diameter portion of the sensor portion.

1 is a schematic view of a flaw detection apparatus according to the present invention. The coil structural example of a sensor part. The structural example including the control part of the flaw detection apparatus which concerns on this invention. The conceptual diagram of the process which produces | generates a differential signal in a waveform generation part. The other example of the coil structure of a sensor part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sensor part 2 ... Control part 3 ... High frequency control part 4 ... Waveform generation part 5 ... Scratch determination part 6 ... Display part 10 ... Inspected object

Claims (3)

An eddy current flaw detector for detecting a flaw in an inspection object based on a signal output from the sensor section when the inspection object passes in the vicinity of a sensor section provided on a cross-sectional circle of a cylindrical passage. There,
A plurality of sensor parts each having a comparison coil, an excitation coil, and a detection coil arranged on the same axis are circular coils having the same diameter. Is also configured such that the same axis is in a plane parallel to the central axis of the passage, and the same axes of all sensor parts are parallel to each other.
A flaw detection apparatus, wherein two predetermined sensor units are differentially connected to each other.   The plurality of sensor units are composed of a detection sensor unit in which an excitation coil and a detection coil are arranged on the same axis, and a comparison sensor unit in which the excitation coil and the comparison coil are arranged on the same axis. The flaw detection apparatus according to claim 1. The inspection object further includes a passage cylinder for passing through the inside,
The flaw detection apparatus according to claim 1, wherein the sensor unit is disposed around a part of the passage cylinder.

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