JP2012078244A - Flaw detection device - Google Patents

Abstract

To enable temperature compensation of a detection signal at an early stage after start-up, and to make the configuration therefor relatively inexpensive.
A flaw detection apparatus includes a detection coil for generating an eddy current on the surface of an inspection object, an oscillator for supplying an alternating current to the detection coil, and a bridge circuit for measuring the impedance of the detection coil. And an electric component that generates heat, and configured to detect a flaw on the surface of the object to be inspected based on a change in impedance measured by a bridge circuit. The flaw detection apparatus 1 circulates at least an oscillator, a bridge circuit, and an electric component that generates heat inside the housing 6, isolates the inside of the housing 6 from the outside, and stirs the air inside the housing 6. A fan 31 was provided.
[Selection] Figure 4

Description

  The present invention relates to a flaw detection apparatus used for detecting a flaw on a surface of an object to be inspected by using an eddy current flowing through a detection coil.

  Conventionally, as this type of technology, for example, a gap detection device using a bridge circuit described in Patent Document 1 below is known. This apparatus includes a detection coil, an oscillation circuit that generates a signal, a detection rectification circuit that detects a detection signal from an output signal from the coil, and a linearizer that linearizes the detection signal. The device also includes a coil temperature detection circuit that detects the coil temperature, a low temperature range correction circuit that corrects the coil detection signal when the coil temperature is low, and a coil detection signal when the coil temperature is high. And a high temperature range correction circuit for correcting. By configuring the apparatus as described above, a detection signal in which the temperature is compensated for a wide range of temperatures can be obtained with a simple configuration.

JP 2001-183106 A

  However, in the detection device described in Patent Document 1, if the temperature of each electrical resistance of the bridge circuit is not uniform, the measurement accuracy may be deteriorated. However, there is no particular mention or suggestion regarding this in Patent Document 1. In addition, coil temperature compensation requires the addition of a circuit, which tends to increase the cost of the device.

  Here, with respect to the conventional flaw detection apparatus, the behavior of the internal temperature of the housing containing the electric circuit such as the bridge circuit, the external temperature of the housing, and the variation of the measured value with respect to the number of measurements is shown in FIG. As is apparent from this graph, when the number of measurements is “1 to 120 (times)”, the internal temperature changes from “27.5 (° C.)” to around “40 (° C.)” and The difference also varies between “2-12 (° C.)”. The variation in the measured value during this period is also large. On the other hand, after the number of measurements is “120 (times)”, the change in the difference between the internal temperature and the external temperature is small as the internal temperature changes between “40 to 42 (° C.)”. Therefore, accurate measurement cannot be performed for a while after the operation of the flaw detection apparatus is started. As shown in FIG. 7, the temperature inside the casing is less than “45 (° C.)”, so that it does not originally reach “80 to 90 (° C.)” at which the bridge circuit breaks down.

  The present invention has been made in view of the above circumstances, and the object thereof is to enable temperature compensation of the detection signal early after startup, and to make the configuration therefor relatively inexpensive. The object is to provide a flaw detector.

  In order to achieve the above object, an invention according to claim 1 includes a detection coil for generating an eddy current on the surface of an object to be inspected, an oscillator for supplying an alternating current to the detection coil, and a detection coil. In a flaw detection apparatus that includes a bridge circuit for measuring impedance and an electric component that generates heat, and detects a flaw on the surface of an object to be inspected based on a change in impedance measured by the bridge circuit, at least an oscillator, a bridge circuit, and The purpose of the present invention is to provide an air agitating means for accommodating a heat generating electrical component inside the housing, blocking the inside of the housing from the outside, and stirring the air inside the housing.

  According to the configuration of the above invention, by starting this flaw detection apparatus, the heat generated from the electrical components is stirred together with the air by the air stirring means inside the casing, and the inside of the casing is warmed up early. Along with this, the oscillator and the bridge circuit inside the casing are also warmed early.

  In order to achieve the above object, according to a second aspect of the present invention, in the first aspect of the present invention, the air stirring means is preferably an electric fan.

  In order to achieve the above object, the invention according to claim 3 is the invention according to claim 1 or 2, in which the internal temperature detecting means for detecting the temperature inside the casing, the outside of the casing, External temperature detection means for detecting temperature, operation determination means for determining whether or not the bridge circuit can normally operate based on the detected internal and external temperatures, and display means for displaying the determined result The purpose of this is to further provide.

  According to the configuration of the above invention, in addition to the operation of the invention described in claim 1 or 2, is the operation determining means capable of normal operation of the bridge circuit based on the internal and external temperatures detected inside and outside the housing? It is determined whether or not, and the determination result is displayed on the display means. Therefore, the operator can compare the detection result of the flaw detection apparatus with the display result of the display means.

  According to the first or second aspect of the invention, the temperature of the detection signal can be compensated at an early stage after startup, and the configuration for that purpose can be made relatively inexpensive.

  According to the invention described in claim 3, in addition to the effect of the invention described in claim 1 or 2, it is possible to accurately detect a flaw on the object to be inspected by a normal flaw detection apparatus, and the reliability of the detection result. Can be secured.

1 is a schematic configuration diagram illustrating a flaw detection apparatus according to an embodiment. FIG. 3 is a block circuit diagram showing an electrical configuration of the flaw detection apparatus according to the embodiment. The block diagram which shows the plane arrangement | positioning of the electrical structure inside a housing | casing concerning the embodiment. The block diagram which concerns on the same embodiment and shows the block diagram of FIG. 3 in detail. The flowchart which shows the control program for apparatus inspection concerning the embodiment. The graph which shows the change of the measured value with respect to the number of measurements concerning the embodiment. The graph which shows the behavior of the dispersion | variation in the internal temperature of a housing | casing, the external temperature of a housing | casing, and a measured value with respect to the number of measurements regarding a prior art example.

  DETAILED DESCRIPTION Hereinafter, an embodiment of a flaw detection apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration diagram of a flaw detection apparatus 1 according to this embodiment. FIG. 2 is a block circuit diagram showing the electrical configuration of the flaw detector 1.

  As shown in FIGS. 1 and 2, the flaw detection apparatus 1 supplies a detection coil 11 for generating an eddy current on the surface of a metal workpiece 2 that is an object to be inspected, and an alternating current to the detection coil 11. The oscillator 12 and a bridge circuit 13 for measuring the impedance of the detection coil 11 are provided. Further, the flaw detection apparatus 1 includes an amplifier circuit 14 for amplifying the output signal of the bridge circuit 13, a synchronous detection circuit 15 for facilitating determination by phase discrimination of the output signal of the amplifier circuit 14, and a synchronous detection circuit 15 A filter circuit 16 for improving the detection performance by noise-cutting the output signal, and a software processing circuit 17 for outputting a pass / fail judgment signal by performing processing such as amplitude / phase judgment on the signal that has passed through the filter circuit 16 And a display 18.

  The bridge circuit 13 exchanges signals with the detection coil 11. A signal is output from the synchronous detection circuit 15 to the display 18. Data is output from the filter circuit 16 to the outside. The software processing circuit 17 outputs determination output to the outside. The flaw detection apparatus 1 detects the flaw 3 on the surface of the workpiece 2 based on the change in impedance measured by the bridge circuit 13.

  As shown in FIGS. 1 and 2, the flaw detection apparatus 1 includes a housing that houses an oscillator 12, a bridge circuit 13, an amplifier circuit 14, a synchronous detection circuit 15, a filter circuit 16, a software processing circuit 17, a display 18 and the like. A body 6 is provided. The inside of the housing 6 is blocked from the outside. FIG. 3 is a block diagram showing a planar arrangement of the electrical configuration inside the housing 6. FIG. 4 is a more detailed block diagram of FIG.

  As shown in FIG. 3, a display unit 21, a measurement unit 22, a calculation unit 23, an input / output unit 24, and a power supply unit 25 are arranged in the housing 6 as an electrical configuration. The display unit 21 is arranged over the entire front side width of the housing 6. On the rear side of the display unit 21, a measurement unit 22 and a calculation unit 23 are arranged side by side. An input / output unit 24 is disposed on the rear side of the measurement unit 22. A power supply unit 25 is disposed on the rear side of the calculation unit 23. The input / output unit 24 and the power supply unit 25 are arranged side by side.

  As shown in FIG. 4, a sensor substrate including an oscillator 12, a bridge circuit 13, an amplifier circuit 14, and the like is disposed in the measurement unit 22. The calculation unit 23 includes a plurality of calculation units 23A, 23B, and 23C. A CPU and an A / D board are arranged in each of the arithmetic units 23A to 23C. The power supply unit 25 includes a rectifying unit 26 arranged on the right half thereof. The sensor board, the calculation unit 23, and the power supply unit 25 correspond to the heat-generating electrical component of the present invention.

  A circulation fan 31 is disposed between the front side of the rectification unit 26 and the calculation unit 23. The arrangement of the circulation fan 31 in the height direction of the casing 6 is arranged near the upper surface of the casing 6 in order to effectively agitate the warm air in the casing 6 regardless of the arrangement of other parts. . The wind direction of the circulation fan 31 is directed to the calculation unit 23. The circulation fan 31 corresponds to air agitation means for agitating the air inside the housing 6 and is constituted by an electric fan. A temperature sensor substrate 32 is disposed on the front side of the left half of the power supply unit 25 and next to the circulation fan 31.

  Further, the flaw detection apparatus 1 includes a first internal temperature sensor 33 and a second internal temperature sensor 34 corresponding to internal temperature detection means for detecting the temperature inside the housing 6, and the temperature outside the housing 6. An external temperature sensor 35 as an external temperature detection means for detecting is further provided. The first internal temperature sensor 33 is disposed between the rectifying unit 26 and the circulation fan 31, and detects the temperature of that portion as the first internal temperature Ti1. The second internal temperature sensor 34 is disposed between the display 18 constituting the display unit 21 and the measurement unit 22, and detects the temperature of that portion as the second internal temperature Ti2. The external temperature sensor 35 is disposed outside the housing 6 and behind the power supply unit 25 and detects the external temperature To of the housing 6. Each temperature sensor 33 to 35 is connected to the temperature sensor substrate 32.

  The temperature sensor substrate 32 is connected to the calculation unit 23. The calculation unit 23 corresponds to an operation determination unit of the present invention for determining whether or not the bridge circuit 13 can normally operate based on the internal temperatures Ti1 and Ti2 and the external temperature To detected by the temperature sensors 33 to 35. To do. The calculation unit 23 displays the determined result on the display 18 as display means.

  Next, a control program for device inspection executed by the CPU of the calculation unit 23 will be described below with reference to the flowchart of FIG.

  When an instruction for apparatus inspection is given in step 100, the CPU reads the detection values of the temperature sensors 33 to 35 in order to inspect the flaw detection apparatus 1 in step 101. That is, the CPU determines the first internal temperature Ti1 detected by the first internal temperature sensor 33, the second internal temperature Ti2 detected by the second internal temperature sensor 34, and the external temperature To detected by the external temperature sensor 35. Read each detected value.

  Next, in step 102, the CPU calculates a difference between the read first internal temperature Ti1 and the external temperature To as an internal / external temperature difference TEio.

  Subsequently, in step 103, the CPU calculates the absolute value of the difference between the first internal temperature Ti1 and the second internal temperature Ti2 as the absolute value of the internal temperature difference TEii.

  Thereafter, in step 104, the CPU determines whether the internal / external temperature difference TEio is higher than “12 (° C.)” and lower than “16 (° C.)”. This range of “12 to 16 (° C.)” is a substantially constant difference that occurs between the external temperature To when the internal temperatures Ti1 and Ti2 of the housing 6 are stabilized. When this determination result is negative, the CPU returns the process to step 101. If the determination result is affirmative, the CPU proceeds to step 105.

  In step 105, the CPU determines whether or not the absolute value of the internal temperature difference TEii is lower than “2 (° C.)”. This range of “0 to 2 (° C.)” means that the internal temperatures Ti1 and Ti2 of the housing 6 are stable. When this determination result is negative, the CPU returns the process to step 101. If the determination result is affirmative, the CPU proceeds to step 106.

  In step 106, the CPU calculates a difference between the previous internal / external temperature difference TEioO and the current internal / external temperature difference TEio as an internal / external temperature difference variation ΔTEio.

  In step 107, the CPU determines whether or not the calculated internal / external temperature difference variation ΔTEio is equal to or less than “2 (° C.)”. That is, the CPU determines whether or not the fluctuation of the internal / external temperature difference TEio is small and the fluctuations of the internal temperatures Ti1 and Ti2 are small. When the determination result is affirmative, the calculated internal / external temperature difference TEio, the absolute value of the internal temperature difference TEii, and the value of the internal / external temperature difference variation ΔTEio are stored in the memory of the calculation unit 23. Thereafter, in step 109, the CPU performs normal display. That is, the CPU displays on the display 18 that the flaw detection apparatus 1 is normal.

  On the other hand, if the determination result in step 107 is negative, the CPU performs an abnormal display in step 110. That is, the CPU displays on the display 18 that the flaw detection apparatus 1 is abnormal.

  According to the flaw detection apparatus 1 of this embodiment described above, the heat generated from various electrical components is stirred together with air by the circulation fan 31 inside the housing 6 by starting the apparatus 1. In particular, in this embodiment, the power supply unit 25 that generates a relatively large amount of heat is disposed in the housing 6, and the circulation fan 31 is disposed in front of the power supply unit 25. Therefore, the heat generated by the power supply unit 25 is effectively agitated and circulated through the housing 6, so that the interior of the housing 6 can be warmed up early. Along with this, circuits such as the oscillator 12 and the bridge circuit 13 inside the housing 6 are also warmed early. For this reason, the temperature of the detection signal can be compensated for early after the flaw detection apparatus 1 is activated. Moreover, the structure for that can also be made comparatively cheap.

  Further, according to the flaw detection apparatus 1 of this embodiment, whether or not the bridge circuit 13 can normally operate based on the internal temperatures Ti1, Ti2 and the external temperature To detected by the calculation unit 23 inside and outside the housing 6 is determined. The judgment result is displayed on the display 18. Therefore, the operator can compare the detection result of the flaw detection apparatus 1 with the display result of the display 18. For this reason, the normal flaw detection apparatus 1 can accurately detect the flaw 3 of the work 2 and the like. Thereby, the reliability of the detection result can be ensured.

  Here, the measurement result (diamond mark) by the flaw detection apparatus 1 of this embodiment is shown in FIG. 6 in comparison with the measurement result (black circle mark) of the conventional flaw detection apparatus. FIG. 6 is a graph showing changes in measured values with respect to the number of measurements. As is apparent from this graph, the measurement results of the flaw detection apparatus 1 are approximately “3130 (mv)” to “3140 (mv)” between the number of measurements from “1st” to “146”. It can be seen that the measured value becomes almost stable immediately after the flaw detection apparatus 1 is started only by fine fluctuation within the range of.

  On the other hand, in the conventional flaw detection apparatus, the measured value was “3200 (mv)” immediately after activation, but thereafter, the measured value was “3130 (mv) until the number of measurements was about“ 100 (times) ”. ) "Continues to fall close to, and then only slightly varies within the range of" 3130 (mv) "to" 3140 (mv) ". Therefore, in the conventional flaw detection apparatus, a stable measurement value cannot be obtained when the number of measurements is from “1 to 100 (times)”, and the measurement value cannot be used effectively after the flaw detection apparatus is activated. I understand.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the meaning of invention, it can implement as follows.

  For example, in the above-described embodiment, the power supply unit 25 is provided inside the housing 6 as an electric component that generates heat. However, when this power supply unit is separately provided outside the housing, various electric devices provided in the housing are provided. The circuit corresponds to an electrical component that generates heat.

  The present invention can be used for flaw detection on the surface of a metal product.

1 Flaw detector 2 Workpiece (inspected object)
3 Scratch 6 Case 11 Detection coil 12 Oscillator (Heat generating electrical component)
13 Bridge circuit (electric parts that generate heat)
18 Display (display means)
23 Calculation unit (operation judging means, heat generating electric parts)
25 Power supply (heated electrical parts)
31 Circulating fan (air stirring means)
32 Temperature sensor board (electric parts that generate heat)
33. First internal temperature sensor (internal temperature detection means)
34 Second internal temperature sensor (internal temperature detection means)
35 External temperature sensor (external temperature detection means)

Claims (3)

A detection coil for generating eddy currents on the surface of the object to be inspected;
An oscillator for supplying an alternating current to the detection coil;
A bridge circuit for measuring the impedance of the detection coil;
A flaw detection apparatus that detects flaws on the surface of the object to be inspected based on a change in impedance measured by the bridge circuit.
At least the oscillator, the bridge circuit, and the electric component that generates heat are accommodated in a housing, and the air inside the housing is shut off from the outside, and air agitating means for agitating the air inside the housing is provided. A flaw detection apparatus characterized by that.   The flaw detection apparatus according to claim 1, wherein the air agitating unit is an electric fan. Internal temperature detection means for detecting the temperature inside the housing;
An external temperature detecting means for detecting a temperature outside the housing;
Operation determining means for determining whether or not the bridge circuit is normally operable based on the detected internal and external temperatures;
The flaw detection apparatus according to claim 1, further comprising display means for displaying the determined result.

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