JP2017207483A - Workpiece abnormality inspection device and workpiece abnormality inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for inspecting an abnormality of a workpiece which can inspect a workpiece for an abnormality rapidly.SOLUTION: An abnormality inspection device 1 includes: a sensor 10 for inducing an eddy current in the inside of a workpiece 2 by an exciting current and obtaining an output voltage; an operation unit 32 for operating an output value on a frequency-by-frequency basis by conducting a frequency analysis on the waveform of an output voltage of the sensor 10 obtained for an actual workpiece 2A as an inspection target when the actual workpiece 2A and the sensor 10 have been relatively moved; a storage unit 34 for storing a threshold value on a frequency-by-frequency basis corresponding to the output value; and a determination unit 35 for determining an abnormality of the actual workpiece 2A when the output value for each frequency has become larger than the threshold value of the corresponding frequency stored in the storage unit 34.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an abnormality inspection apparatus and an abnormality inspection method for inspecting whether a workpiece is abnormal.

  In Patent Document 1, an excitation current having a frequency higher than a predetermined frequency is applied to a ground workpiece by a coil to generate an eddy current, and the presence or absence of grinding burn (abnormality) is determined from the obtained eddy current signal. An apparatus is described. Further, Patent Document 2 discloses that a transparent workpiece obtained by generating an eddy current by applying an excitation current having a frequency lower than a predetermined frequency and an excitation current having a frequency higher than a predetermined frequency to a ground workpiece by a sensor. An apparatus for detecting the presence / absence of a work-affected layer (abnormality) from magnetic susceptibility is described.

JP2013-224916A JP 2011-106932 A

  The apparatus described in Patent Document 1 uses high-frequency excitation currents, but these excitation currents react not only to grinding burn of the workpiece but also to variations in heat treatment applied to the workpiece. Need to be distinguished, and it becomes difficult to determine whether there is grinding burn. On the other hand, since the apparatus described in Patent Document 2 uses a low-frequency excitation current and a high-frequency excitation current, it can easily distinguish between grinding burn and heat treatment variation, and can detect the presence or absence of a work-affected layer. It becomes easy. However, when applying a low-frequency excitation current to the workpiece with the sensor, it is necessary to relatively move the sensor and the workpiece at a low speed, and there is a limit to speeding up the detection of the presence or absence of a work-affected layer.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a workpiece abnormality inspection apparatus and a workpiece abnormality inspection method capable of inspecting a workpiece abnormality at high speed.

  The abnormality inspection apparatus according to the present invention includes a sensor that induces an eddy current in a workpiece by an excitation current to obtain an output voltage, and the actual workpiece when the actual workpiece to be inspected and the sensor are relatively moved. A calculation unit that calculates an output value for each frequency by frequency analysis of the waveform of the output voltage of the sensor obtained for an object, a storage unit that stores a threshold value for each frequency corresponding to the output value, and the output for each frequency And a determination unit that determines that the actual workpiece has an abnormality when a value exceeds the threshold value of the corresponding frequency stored in the storage unit.

  The sensor output voltage includes reactions due to variations in the base material and reactions due to abnormality. If the output value for each frequency is calculated by frequency analysis of the output voltage waveform of the sensor, reactions and abnormalities due to variations in the base material are detected. The reaction by can be separated. That is, it has been found that a reaction due to abnormality appears when an output value of a frequency equal to or higher than a predetermined frequency exceeds a threshold value. Therefore, the abnormality inspection apparatus can inspect the presence or absence of abnormality of the workpiece at high speed by using the high-frequency excitation current.

  In the abnormality inspection method of the present invention, an acquisition step of inducing an eddy current in a workpiece by an excitation current to obtain an output voltage, and a waveform of the output voltage obtained for the actual workpiece to be inspected for each frequency by frequency analysis. And a determination step of determining that the actual workpiece has an abnormality when the output value for each frequency exceeds a threshold value for each frequency corresponding to the output value. . Thereby, the effect similar to the effect obtained with the above-mentioned abnormality inspection apparatus is acquired.

It is a top view of the abnormality inspection apparatus of the workpiece of embodiment of this invention. It is a side view which sees through and shows the inside of the magnetic sensor of the abnormality inspection apparatus of a workpiece. It is a flowchart for demonstrating the threshold value setting process of an abnormality inspection apparatus. It is a figure which shows the waveform of the induced electromotive force of the sensor head for every rotation phase angle of a some reference | standard workpiece. It is a figure which shows the waveform of the amplitude level for every frequency of a some reference | standard workpiece. It is a flowchart for demonstrating the abnormality inspection process of an abnormality inspection apparatus. It is a figure for demonstrating the abnormality inspection process of FIG. 6 in a real workpiece. It is a figure which shows the waveform of the induced electromotive force of the sensor head for every rotation phase angle of the actual workpiece by the process of FIG. It is a figure which shows the waveform of the amplitude level for every frequency of the actual workpiece by the process of FIG. It is a flowchart for demonstrating the abnormality inspection process of another example of an abnormality inspection apparatus. It is a figure for demonstrating the abnormality inspection process of FIG. 10 in a real workpiece. It is a figure which shows the waveform of the induced electromotive force of the sensor head for every rotation phase angle of the actual workpiece by the process of FIG. It is a figure which shows the waveform of the amplitude level for every frequency of the actual workpiece by the process of FIG. It is a figure for demonstrating the 1st modification of the abnormality inspection process of FIG. 10 in a real workpiece. It is a figure for demonstrating the 2nd modification of the abnormality test process of FIG. 10 in a real workpiece.

(1. Configuration of workpiece inspection system)
A configuration of a workpiece abnormality inspection apparatus according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the abnormality inspection apparatus 1 is mainly configured by a magnetic sensor 10 (corresponding to a “sensor” of the present invention), a rotation support unit 20, and a control device 30.

  This anomaly inspection apparatus 1 uses a magnetic nondestructive inspection using eddy current magnetism to detect abnormalities in the workpiece 2 processed by the machine tool 3 (deteriorated layers such as grinding burn, scratches such as cracks and nests). ) Inspect based on the signal according to. That is, the abnormality inspection apparatus 1 induces an eddy current by applying a magnetic field to the workpiece 2 by a primary coil and causing an exciting current to flow. Then, the primary coil to which the magnetic field is applied and the workpiece 2 are relatively moved, and the induced electromotive force (corresponding to the “output voltage” of the present invention) that changes due to this movement is detected by the secondary coil.

  Here, generally, when there is an abnormality in the workpiece 2, the induced electromotive force decreases. However, the induced electromotive force also decreases due to variations in the base material not subjected to surface heat treatment. As will be described later in detail, the inventor can analyze the abnormality of the workpiece 2 and the variation in the base material by analyzing the frequency of the induced electromotive force and obtaining the amplitude level (corresponding to the “output value” of the present invention). I found it. The abnormality inspection apparatus 1 inspects the abnormality of the workpiece 2 based on the amplitude level obtained by frequency analysis of the detected induced electromotive force.

  Here, the workpiece 2 is a magnetic material in the present embodiment, and will be described with respect to a cylindrical or columnar one that has been carburized and quenched. When the workpiece 2 is a carburized material, there is a large variation in residual strain, so that it is difficult to detect a work-affected layer with a conventional abnormality inspection apparatus. The layer can be easily detected. Further, the machine tool 3 is a grinding machine in this embodiment, and grinds the outer peripheral surface of a cylindrical or columnar workpiece 2. And the abnormality inspection apparatus 1 of this embodiment is demonstrated as what inspects the presence or absence of abnormality in the outer peripheral surface of the workpiece 2. FIG.

  The magnetic sensor 10 includes a sensor body 11, a sensor head 12, a measuring device 13, a touch sensor 14, and a sensor feed mechanism 15. The sensor body 11 is supplied with an excitation current set to a frequency higher than a predetermined frequency from a supply unit 31 of the control device 30 described later. The sensor body 11 supplies the excitation current to the sensor head 12 so that the sensor head 12 applies a magnetic field to the workpiece 2.

  The sensor head 12 applies a magnetic field to the workpiece 2 by the supplied excitation current and induces an eddy current in the workpiece 2. Thereby, the sensor head 12 detects the induced electromotive force which changes with the alteration state of the workpiece 2 as a signal in the penetration depth according to the frequency of the exciting current, respectively. When the sensor head 12 is stopped at a certain position, the sensor head 12 detects in the range of the length d in the direction of the rotation axis of the workpiece 2.

  The measuring device 13 receives a signal detected by the sensor head 12 from the sensor body 11 via a signal line. Then, the measuring device 13 outputs the value of the output signal as a detection value of the magnetic sensor 10 to the control device 30 described later. The touch sensor 14 is a contact-type sensor provided at the base end portion of the sensor head 12 inside the sensor body 11. The touch sensor 14 includes a spring 14a that urges the sensor head 12 to the workpiece 2 with a predetermined urging force (pressing force).

  The sensor head 12 is always in contact with the workpiece 2 by the spring 14a. The touch sensor 14 detects whether the sensor head 12 is in contact with or not in contact with the workpiece 1 based on the expansion / contraction state of the spring 14a. The touch sensor 14 outputs the detected contact information of the tip of the sensor head 12 to the control device 30.

  The sensor feed mechanism 15 is provided in the rear part (opposite side of the workpiece 2) of the sensor body 11, and holds the sensor body 11 so as to be movable in the axial direction of the workpiece 2. The sensor feed mechanism 15 is constituted by, for example, a ball screw and a servo motor or a hydraulic mechanism. The sensor feed mechanism 15 is a moving unit that moves the sensor body 11 relative to the workpiece 2 so as to vary the distance between the workpiece 2 and the sensor body 11.

  The sensor feed mechanism 15 detects a movement direction position (a radial direction position in the workpiece 2) of the holding unit that holds the sensor body 11 from a servo motor (not shown). The position sensor 15 a outputs the detected position information of the sensor body 11 to the control device 30. Thereby, the control device 30 detects the separation distance (clearance) of the sensor head 12 from the inspection surface based on the contact information of the sensor head 12 by the touch sensor 14 and the position information of the sensor main body 11 by the sensor feed mechanism 15.

  The rotation support unit 20 includes drive wheels 21 and an adjustment wheel 22 and supports the workpiece 2 to be rotatable. The drive wheel 21 contacts the peripheral surface of the workpiece 2 and rotates the workpiece 2 by being driven to rotate by a motor (not shown). Moreover, the drive wheel 21 has an encoder 21a that detects the rotational position of the motor.

  The encoder 21 a outputs the detected rotational position information of the motor to the control device 30. Thereby, the control apparatus 30 detects the circumferential direction phase with respect to the workpiece 2 of the sensor head 12 based on the shape information including the diameter and circumference of the workpiece 2 and the rotational position information of the motor, which are initial information. The adjustment wheel 22 supports the workpiece 2 together with the drive wheels 21 and is driven to rotate by a frictional force with the peripheral surface of the workpiece 2.

  The control device 30 includes a supply unit 31, a calculation unit 32, a reference calculation unit 33, a storage unit 34, and a determination unit 35. The supply unit 31 is connected to the sensor body 11 via the measuring device 13 and supplies only the excitation current set to a high frequency to the sensor body 11. The arithmetic unit 32 calculates the waveform of the induced electromotive force of the sensor head 12 obtained for the actual workpiece 2A when the workpiece 2 to be inspected (hereinafter referred to as the actual workpiece 2A) and the sensor body 11 are relatively moved. The amplitude level for each frequency is calculated by frequency analysis.

  The reference calculation unit 33 performs a process of obtaining an amplitude level threshold value for determining whether or not the workpiece 2 to be inspected is abnormal. That is, the reference calculation unit 33 performs the induction of the sensor head 12 obtained for the reference workpiece 2B when the workpiece 2 having no abnormality (hereinafter referred to as the reference workpiece 2B) and the sensor body 11 are relatively moved. The amplitude level for each frequency is calculated by frequency analysis of the power waveform. Then, this processing is performed on the plurality of reference workpieces 2B, and the maximum value among the obtained amplitude levels for the plurality of frequencies is calculated as a threshold (shown in FIG. 5).

  The storage unit 34 stores the threshold value of the amplitude level for each frequency obtained by the reference calculation unit 33. The determination unit 35 determines that there is an abnormality if the frequency level is equal to or higher than the frequency F1 (shown in FIGS. 5 and 8) among the amplitude levels for each frequency obtained by the calculation unit 32 and exceeds the threshold value read from the storage unit 34. The determination unit 35 is less than the frequency F1 (shown in FIGS. 5 and 8) of the amplitude level for each frequency obtained by the calculation unit 32 and exceeds the threshold value read from the storage unit 34. Judged to be large.

(2. Overview of inspection of workpiece abnormalities)
As described above, the inspection of the abnormality of the actual workpiece 2A is performed by frequency-analyzing the waveform of the induced electromotive force detected by the sensor head 12 to obtain the amplitude level for each frequency, and the obtained amplitude level and the frequency obtained in advance. This is performed by comparing with the threshold of the amplitude level. The waveform of the induced electromotive force detected by the sensor head 12 includes a reaction due to variations in the base material and a reaction due to an abnormality such as grinding burn. If the amplitude level for each frequency is calculated by frequency analysis of the power waveform, the response due to the variation in the base material and the response due to the abnormality can be separated.

  That is, the reaction due to the variation of the base material appears when the amplitude level of the frequency less than the frequency F1 exceeds the threshold, and the reaction due to the abnormality appears when the amplitude level of the frequency equal to or higher than the frequency F1 exceeds the threshold. I found out. Here, the frequency F1 is set between 0.5 Hz and 1 Hz. In particular, in this example, the frequency F1 is 1 Hz. In addition, since the frequency range in which abnormality due to processing such as dispersion of the base material and grinding / burning varies depending on the base material used, processing conditions, and the like, the frequency F1 for distinguishing between the two is obtained from an inspection of a plurality of normal products in advance. Good.

(3. Threshold setting method)
A threshold setting process performed by the control device 30 of the abnormality inspection apparatus 1 having the above-described configuration will be described with reference to FIG. The control device 30 rotates the reference workpiece 2B at a rotation speed of 6 rpm (step S1 in FIG. 3), and supplies an excitation current set to a frequency of 250 kHz to the sensor body 11 (step S2 in FIG. 3). Note that the rotation speed of the reference workpiece 2B is not limited to the above value, and the frequency of the excitation current is not limited to the above value as long as the frequency is higher than 100 kHz.

  The control device 30 measures the induced electromotive force of the sensor head 12 for each rotational phase of the reference workpiece 2B (step S3 in FIG. 3). FIG. 4 shows waveforms of the induced electromotive force of the sensor head 12 for each rotation phase of the 30 reference workpieces 2B. For example, in the induced electromotive force waveform indicated by the one-dot chain line in FIG. 4, the portions B1, B2, and B3 where the value of the induced electromotive force is reduced indicate reactions due to variations in the base material.

  The control device 30 obtains an amplitude level for each frequency by performing fast Fourier transform (FFT) on the measured electromotive force of the sensor head 12 (step S4 in FIG. 3). Then, it is determined whether or not the above-described series of processing has been completed for the predetermined number of reference workpieces 2B (step S5 in FIG. 3), and it is determined that the processing of the predetermined number of reference workpieces 2B has not been completed. When it does, it returns to step S1 and repeats the above-mentioned processing.

  On the other hand, when it is determined that the processing of the predetermined number of reference workpieces 2B has been completed, the maximum value of the obtained amplitude level for each frequency is set as a threshold (step S6 in FIG. 3). FIG. 5 shows the amplitude level for each frequency of 30 reference workpieces 2B obtained by fast Fourier transform of the induced electromotive force obtained in FIG. 4, and the maximum value of the amplitude level for each frequency obtained by the thick solid line shown in FIG. That is, it is set as a threshold value. The waveform of the amplitude level shown in FIG. 5 becomes a waveform shifted to the high frequency side when the number of rotations of the workpiece 2 at the rotation support unit 20 is increased, and thus the threshold value can be set similarly.

(4. Abnormality inspection process)
An abnormality inspection process for the cylindrical actual workpiece 2A by the control device 30 of the abnormality inspection apparatus 1 having the above-described configuration will be described with reference to FIG. As shown in FIG. 7, the abnormality inspection process is performed by rotating the actual workpiece 2A once around the rotation axis every time the sensor head 12 is moved at a constant first pitch P1 in the rotation axis direction of the actual workpiece 2A. The frequency of the detected induced electromotive force waveform is analyzed to determine the amplitude level for each frequency. The first pitch P1 is set to a pitch equal to or less than the detection length d in the rotational axis direction of the actual workpiece 2A in the sensor head 12, in this example, the same pitch as the detection length d. Thereby, the entire peripheral surface of the actual workpiece 2A can be inspected.

  The control device 30 moves and positions the sensor head 12 to the inspection start point of the actual workpiece 2A, that is, the peripheral edge on the one end face side (step S11 in FIG. 6). Then, the actual workpiece 2A is rotated at a rotational speed of 6 rpm similarly to the reference workpiece 2B (step S12 in FIG. 6), and an excitation current set at a frequency of 250 kHz is supplied to the sensor body 11 (step in FIG. 6). S13). And the induced electromotive force of the sensor head 12 for every rotation phase in the surrounding surface of the actual workpiece 2A is measured (step S14 in FIG. 6).

  FIG. 8 shows a waveform of the induced electromotive force of the sensor head 12 for each rotation phase on the peripheral surface including the abnormal portion E of the actual workpiece 2A shown in FIG. In the induced electromotive force waveform indicated by the one-dot chain line in FIG. 7, the portions B11, B12, and B13 where the value of the induced electromotive force is reduced indicate reactions due to variations in the base material, and the value of the induced electromotive force is reduced. The portions A11, A12, A13, and A14 that are present indicate a reaction due to an abnormality (the portion A11 in which the value of the induced electromotive force decreases is a reaction due to the abnormality portion E illustrated in FIG. 7). In this way, the induced electromotive force waveform includes a response due to variations in the base material and a response due to abnormality, so it is difficult to distinguish between a response due to variations in the base material and a response due to abnormality only with the induced electromotive force waveform. It is.

  The control device 30 obtains an amplitude level for each frequency by performing a fast Fourier transform (FFT) on the measured electromotive force of the sensor head 12 (step S15 in FIG. 6). FIG. 8 shows the amplitude level for each frequency of the actual workpiece 2A obtained by fast Fourier transform of the induced electromotive force obtained in FIG. And the control apparatus 30 compares an amplitude level and a threshold value in the frequency area | region of 1 Hz or more.

  The control device 30 determines whether or not the amplitude level exceeds the threshold value (step S16 in FIG. 6), and determines that the actual workpiece 2A whose amplitude level exceeds the threshold value is abnormal (step S17 in FIG. 6). ), It is determined that there is no abnormality in the actual workpiece 2A whose amplitude level does not exceed the threshold (step S18 in FIG. 6). In FIG. 8, since there is a portion A in which the amplitude level exceeds the threshold between about 1 kHz and about 5 kHz, it is determined that the actual workpiece 2A has a machining abnormality. In the actual workpiece 2A, there is a portion B where the amplitude level is less than 1 Hz and the threshold level exceeds the threshold value, which makes it possible to determine that the variation of the base material is large.

  The control device 30 determines whether or not the abnormality determination is completed when the sensor head 12 reaches the inspection end point of the actual workpiece 2A, that is, the peripheral edge on the other end surface side (step S19 in FIG. 6). If the sensor head 12 does not reach the peripheral edge on the other end surface side of the actual workpiece 2A, the sensor head 12 is moved by the first pitch toward the other end surface side of the actual workpiece 2A and positioned (step S20 in FIG. 6). . And it returns to step S12 and repeats the above-mentioned process. On the other hand, when the control device 30 determines in step S19 that the sensor head 12 has reached the periphery on the other end surface side of the actual workpiece 2A and the abnormality determination has been completed, all the processes are terminated.

(5. Another example of abnormality inspection processing)
In the above-described abnormality inspection process, as shown in FIG. 11, when a uniform abnormality Ea occurs around the circumference of the actual workpiece 2 </ b> A, as shown in FIG. 7, the peripheral surface of the actual workpiece 2 </ b> A Since the difference between the amplitude levels for each frequency obtained by the actual workpiece 2A and the reference workpiece 2B does not appear even if the inspection is performed on the circumference, the abnormality cannot be detected.

  However, even if a uniform abnormality occurs over one circumference in the circumferential direction of the actual workpiece 2A, the abnormal state is often uneven in the rotation axis direction of the actual workpiece 2A. The abnormality can be detected by inspecting the peripheral surface of the actual workpiece 2A in a spiral shape. Therefore, as a result of performing the process of inspecting the circumferential surface of the actual workpiece 2A shown in FIG. 6 in a circumferential shape, no abnormality was detected in the actual workpiece 2A. Since such an abnormality may occur, the process of inspecting the peripheral surface of the actual workpiece 2A in a spiral manner is continued.

  The control device 30 moves and positions the sensor head 12 to the inspection start point of the actual workpiece 2A, that is, the peripheral edge on the one end surface side (step S21 in FIG. 10). Then, while moving the sensor head 12 relative to the rotation axis of the actual workpiece 2A along the peripheral surface of the actual workpiece 2A at the second pitch, the actual workpiece 2A is rotated at a rotational speed of 6 rpm in the same manner as the reference workpiece 2B. Rotate (step S22 in FIG. 10). The second pitch is set to a pitch larger than the detection length in the rotation axis direction of the actual workpiece 2A in the sensor head 12. Thereby, the surrounding surface of the actual workpiece 2A can be inspected spirally in a short time.

  The control device 30 supplies the excitation current set to the frequency of 250 kHz to the sensor body 11 (step S23 in FIG. 10), and measures the induced electromotive force of the sensor head 12 in the rotation axis direction on the peripheral surface of the actual workpiece 2A. (Step S24 in FIG. 10). Then, it is determined whether or not the sensor head 12 has reached the inspection end point of the actual workpiece 2A, that is, the periphery on the other end surface side (step S25 in FIG. 10). When it is determined that the sensor head 12 has not reached the periphery on the other end surface side of the actual workpiece 2A, the process returns to step S22 and the above-described processing is repeated.

  On the other hand, when it is determined in step S25 that the sensor head 12 has reached the periphery on the other end surface side of the actual workpiece 2A, the measured electromotive force of the sensor head 12 is subjected to fast Fourier transform (FFT) for each frequency. An amplitude level is obtained (step S26 in FIG. 10). Then, it is determined whether or not the amplitude level exceeds the threshold in the frequency region of 1 Hz or more (step S27 in FIG. 10), and the actual workpiece 2A having the amplitude level exceeding the threshold is determined to be abnormal (FIG. 10). Step S28), it is determined that the actual workpiece 2A whose amplitude level does not exceed the threshold value has no abnormality (Step S29 in FIG. 10), and all the processes are terminated.

  12 shows the induction of the sensor head 12 on the spiral on the circumferential surface of the actual workpiece 2A from the rotational axis direction position s on one end surface side to the rotational axis direction position e on the other end surface side of the actual workpiece 2A shown in FIG. The power waveform is shown. A portion C1 where the value of the induced electromotive force indicated by a one-dot chain line in FIG. FIG. 13 shows the amplitude level for each frequency of the actual workpiece 2A obtained by fast Fourier transform of the induced electromotive force obtained in FIG. In FIG. 13, since there is a portion C in which the amplitude level exceeds the threshold between about 1 kHz and about 5 kHz, it is determined that the actual workpiece 2 </ b> A has a machining abnormality.

  In the above-described abnormality inspection process, the case where the second pitch is set to a pitch larger than the detection length of the actual workpiece 2A in the rotation axis direction in the sensor head 12 has been described. However, as shown in FIG. 14, by setting the sensor head 12 to a detection pitch d equal to or less than the detection length d of the actual workpiece 2A in the rotational axis direction, in this example, the third pitch P3 equal to the detection length d is set. Since the entire circumferential surface can be inspected, the process of inspecting the circumferential surface of the actual workpiece 2A in a circumferential shape can be omitted.

  Moreover, in the above-described abnormality inspection process, the case where the peripheral surface of the actual workpiece 2A is inspected spirally has been described. However, as shown in FIG. 15, the process of inspecting the circumferential surface of the actual workpiece 2A in a circumferential shape is not more than the detection length d in the rotation axis direction of the actual workpiece 2A in the sensor head 12, which is the detection length d in this example. And every fourth pitch P4. And among the induced electromotive forces of the sensor head 12 obtained on the inspection peripheral surface S1 on the one end surface side of the actual workpiece 2A, the induced electromotive force at one point Q1 on the inspection peripheral surface S1 is selected.

  Next, out of the induced electromotive force of the sensor head 12 obtained on the inspection peripheral surface S2 adjacent to the inspection peripheral surface S1, on the inspection peripheral surface S2 shifted by a predetermined phase angle θ with respect to one point Q1 on the inspection peripheral surface S1. The induced electromotive force at one point Q2 is selected. Thereafter, the induced electromotive force is similarly selected up to one point Qn of the inspection peripheral surface Sn on the other end surface side of the actual workpiece 2A. Then, by connecting the induced electromotive forces of all the selected points Q1-Qn in the order of selection, it can be obtained as data obtained by inspecting the peripheral surface of the actual workpiece 2A in a spiral shape.

(6. Others)
In the above-described embodiment, the maximum value among the amplitude levels for each of the plurality of frequencies is set as the threshold value. However, the average value (a) and the standard deviation (σ) of the amplitude levels for each of the plurality of frequencies are obtained. A threshold value may be set based on a range of 4σ. Further, although the threshold value of the amplitude level for each frequency obtained by the reference calculation unit 33 is stored in the storage unit 34, the threshold value for the amplitude level for each frequency obtained by the operator in advance outside the control device 30 is stored in the storage unit. 34 may be stored.

  Further, the workpiece 2 to which the abnormality inspection apparatus 1 can be applied is not limited to the carburized and quenched material, and a material that has been thoroughly quenched can also be applied. Moreover, it is not limited to a cylindrical shape or a columnar shape, but can be an arbitrary shape such as a flat plate shape. In addition to the cylindrical or columnar outer peripheral surface, the abnormality inspection target part of the workpiece 2 includes a cylindrical inner peripheral surface, a conical outer peripheral surface, a spherical outer peripheral surface, a flat surface, and It can also be a free-form surface. Further, as the machine tool 3, in addition to a grinding machine, a cutting machine such as a lathe and a machining center can be applied. And the machine tool 3 is good also as a structure provided with the function of the abnormality inspection apparatus 1. FIG.

(7. Effects of the embodiment)
The abnormality inspection apparatus 1 for the workpiece 2 according to the present embodiment is configured such that the sensor 10 that obtains an output voltage by inducing eddy current in the workpiece 2 by an excitation current, and the actual workpiece 2A to be inspected and the sensor 10 are relatively When moved, the calculation unit 32 that calculates an output value for each frequency by frequency analysis of the waveform of the output voltage of the sensor 10 obtained for the actual workpiece 2A, and a memory for storing a threshold value for each frequency corresponding to the output value And a determination unit 35 that determines that the actual workpiece 2A has an abnormality when the output value for each frequency exceeds the threshold value of the corresponding frequency stored in the storage unit 34.

  The output voltage of the sensor 10 includes a response due to a variation in the base material and a response due to an abnormality. When the output value for each frequency is calculated by analyzing the waveform of the output voltage of the sensor 10 and the response due to the variation in the base material. The reaction due to abnormality can be isolated. That is, it has been found that the reaction due to abnormality appears when the output value of the frequency equal to or higher than the frequency F1 exceeds the threshold value. Therefore, the abnormality inspection apparatus 1 can inspect for an abnormality of the workpiece 2 at high speed by using a high-frequency excitation current.

The storage unit 34 was obtained by performing frequency analysis on the waveform of the output voltage of the sensor 10 obtained for the reference workpiece 2B when the reference workpiece 2B having no abnormality and the sensor 10 are relatively moved. Since the threshold value for each frequency is stored, an accurate threshold value suitable for the workpiece 2 can be set.
In addition, the abnormality inspection apparatus 1 includes a reference calculation unit 33 that calculates a threshold value using a plurality of reference workpieces 2B, and the storage unit 34 stores the threshold value calculated by the reference calculation unit 2B. It can be done at high speed.

Moreover, since the threshold value for every frequency is calculated | required based on the maximum value among the several output values for every frequency obtained by the frequency analysis about the some reference | standard workpiece 2B, a threshold value can be set easily.
The threshold value for each frequency is obtained based on a and σ by obtaining an average value (a) and a standard deviation (σ) of a plurality of output values for each frequency obtained by frequency analysis for a plurality of reference workpieces 2B. Therefore, the accuracy of determining whether there is an abnormality can be improved.

In addition, when the output value exceeds the threshold value at a predetermined frequency or higher, the determination unit 35 determines that there is a work-affected layer or a flaw in the actual workpiece 2A, so it can be easily determined whether there is an abnormality.
In addition, when the output value exceeds the threshold value at a frequency lower than the predetermined frequency, the determination unit 35 determines that the variation in the base material that is not subjected to the surface heat treatment of the actual workpiece 2A is large. The reaction and the reaction due to abnormality can be separated.

Further, the sensor 10 induces an eddy current in the workpiece 2 only by an excitation current set to a frequency higher than a predetermined frequency to obtain an output voltage, and therefore the sensor 10 and the workpiece 2 are relatively moved at a high speed. The presence or absence of abnormality can be detected at high speed.
Moreover, since the actual workpiece 2A is a workpiece that has been carburized and quenched, the abnormality inspection that is difficult with the conventional apparatus can be performed with the abnormality inspection apparatus of the present embodiment.
Further, the sensor 10 rotates relative to the workpiece 2 and induces an eddy current in the workpiece 2 by an exciting current to obtain an output voltage. Therefore, an abnormality of the cylindrical or columnar workpiece 2 can be easily inspected. it can.

  Further, the arithmetic unit 32 relatively rotates the actual workpiece 2A and the sensor 10 each time the actual workpiece 2A and the sensor 10 are relatively moved at the first pitch in the rotation axis direction of the actual workpiece 2A. The output value for each frequency is calculated by frequency analysis of the waveform of the output voltage of the sensor 10 obtained for 2A, and the actual workpiece 2A and the sensor 10 are moved relative to each other at the second pitch in the rotation axis direction of the actual workpiece 2A. The actual workpiece 2A and the sensor 10 are relatively rotated, and the output value for each frequency is calculated by frequency analysis of the waveform of the output voltage of the sensor 10 obtained for the actual workpiece 2A.

  By inspecting the circumferential surface of the actual workpiece 2A circumferentially, it is possible to detect abnormalities that partially occur on the circumferential surface of the actual workpiece 2A, and to make uniform abnormalities over the circumference of the actual workpiece 2A. Even if the above occurs, there are many cases where the abnormal state is uneven in the rotation axis direction of the actual workpiece 2A. Therefore, the circumferential direction of the actual workpiece 2A can be obtained by inspecting the peripheral surface of the actual workpiece 2A in a spiral shape. It is possible to detect a uniform abnormality that occurs over one round. Further, since the first pitch is the same as the detection length of the actual workpiece 2A in the rotation axis direction in the sensor 10, the entire circumferential surface of the actual workpiece 2A can be inspected, and the second pitch is the detection length of the sensor 10. Since it is the above pitch, the surrounding surface of the actual workpiece 2A can be inspected spirally in a short time.

  In addition, the calculation unit 32 relatively rotates the actual workpiece 2A and the sensor 10 while relatively moving the actual workpiece 2A and the sensor 10 in the rotation axis direction of the actual workpiece 2A at the third pitch, and thereby the actual workpiece 2A. Since the output value for each frequency is calculated by frequency analysis of the waveform of the output voltage of the sensor 10 obtained for the above, uniform abnormality that occurs over one round in the circumferential direction of the actual workpiece 2A can be detected. Moreover, since the third pitch is a pitch equal to or less than the detection length in the rotation axis direction of the actual workpiece 2A in the sensor 10, the entire circumferential surface of the actual workpiece 2A can be inspected.

In addition, the arithmetic unit 32 relatively rotates the actual workpiece 2A and the sensor 10 each time the actual workpiece 2A and the sensor are relatively moved at the fourth pitch in the rotation axis direction of the actual workpiece 2A, so The output voltage of the sensor 10 for the actual workpiece 2A at each phase angle obtained by shifting the predetermined phase angle by a certain angle for each relative movement is obtained, and the output value for each frequency is obtained by analyzing the waveform of the obtained output voltage by frequency analysis. Calculate. According to this, since the same data as the data obtained when the peripheral surface of the actual workpiece 2A is inspected in a spiral shape is obtained, it is possible to detect a uniform abnormality that occurs over the entire circumference of the actual workpiece 2A. Moreover, since the fourth pitch is a pitch equal to or less than the detection length of the actual workpiece 2A in the rotation axis direction in the sensor 10, the entire circumferential surface of the actual workpiece 2A can be inspected.
In addition, since the sensor 10 obtains an output voltage by inducing an eddy current in the workpiece 2 by the exciting current while the workpiece 2 is being processed, the occurrence of defects in the workpiece 2 can be suppressed.

  The abnormality inspection method for a workpiece according to the present embodiment includes an acquisition step of inducing an eddy current in the workpiece 2 by an excitation current to obtain an output voltage, and a waveform of the output voltage obtained for the actual workpiece 2A to be inspected. A calculation step of calculating an output value for each frequency by frequency analysis, and a determination step of determining that the actual workpiece 2A has an abnormality when the output value for each frequency exceeds a threshold value for each frequency corresponding to the output value; . Thereby, the effect similar to the effect obtained with the above-mentioned abnormality inspection apparatus 1 is acquired.

  DESCRIPTION OF SYMBOLS 1: Abnormality inspection apparatus, 2: Workpiece, 10: Magnetic sensor, 11: Sensor main body, 12: Sensor head, 20: Rotation support part, 30: Control apparatus, 31: Supply part, 32: Calculation part, 33: Reference | standard Calculation unit 34: Storage unit 35: Determination unit

Claims (18)

A sensor for obtaining an output voltage by inducing an eddy current inside the workpiece by an excitation current;
When the actual workpiece to be inspected and the sensor are relatively moved, a calculation unit that calculates an output value for each frequency by frequency analysis of the waveform of the output voltage of the sensor obtained for the actual workpiece;
A storage unit for storing a threshold value for each frequency corresponding to the output value;
A determination unit that determines that the actual workpiece has an abnormality when the output value for each frequency exceeds the threshold value of the corresponding frequency stored in the storage unit;
An abnormality inspection device for workpieces.   The storage unit performs frequency analysis on the waveform of the output voltage of the sensor obtained with respect to the reference workpiece when the reference workpiece having no abnormality and the sensor are moved relative to each other. The workpiece abnormality inspection apparatus according to claim 1, wherein the threshold value is stored. The abnormality inspection apparatus includes a reference calculation unit that calculates the threshold using a plurality of the reference workpieces,
The workpiece abnormality inspection apparatus according to claim 2, wherein the storage unit stores the threshold value calculated by the reference calculation unit.   The abnormality of the workpiece according to claim 2 or 3, wherein the threshold value for each frequency is obtained based on a maximum value among a plurality of output values for each frequency obtained by frequency analysis for the plurality of reference workpieces. Inspection device.   The threshold value for each frequency is obtained based on a and σ by obtaining an average value (a) and a standard deviation (σ) of a plurality of output values for each frequency obtained by frequency analysis for the plurality of reference workpieces. 4. The workpiece abnormality inspection apparatus according to claim 2, wherein the workpiece abnormality inspection apparatus is provided.   6. The determination unit according to claim 1, wherein when the output value exceeds the threshold value at a predetermined frequency or more, the determination unit determines that a work-affected layer or a flaw exists in the actual workpiece. Machine abnormality inspection equipment.   The said determination part determines that the dispersion | variation in the base material with which the surface heat treatment of the said actual workpiece is not performed is large when the said output value exceeds the said threshold value in less than the said predetermined frequency. Machine abnormality inspection equipment.   The workpiece according to any one of claims 1 to 7, wherein the sensor obtains an output voltage by inducing an eddy current in the workpiece only by the excitation current set to a frequency higher than a predetermined frequency. Abnormal inspection equipment.   The abnormal inspection apparatus for a workpiece according to any one of claims 1 to 8, wherein the actual workpiece is a workpiece that has been carburized and quenched.   The abnormal inspection of a workpiece according to any one of claims 1 to 9, wherein the sensor rotates relative to the workpiece and induces an eddy current in the workpiece by an excitation current to obtain an output voltage. apparatus.   The arithmetic unit relatively rotates the actual workpiece and the sensor each time the actual workpiece and the sensor are relatively moved at a first pitch in the rotation axis direction of the actual workpiece. An output value for each frequency is calculated by frequency analysis of the waveform of the output voltage of the obtained sensor, and the actual workpiece and the sensor are relatively moved at a second pitch in the rotation axis direction of the actual workpiece. The abnormality of the workpiece according to claim 10, wherein an output value for each frequency is calculated by frequency analysis of a waveform of the output voltage of the sensor obtained for the actual workpiece by relatively rotating an actual workpiece and the sensor. Inspection device.   The machine tool according to claim 11, wherein the first pitch is the same pitch as a detection length of the actual workpiece in the rotation axis direction of the sensor, and the second pitch is a pitch greater than or equal to a detection length of the sensor. Abnormality inspection equipment for things.   The arithmetic unit obtains the actual workpiece by rotating the actual workpiece and the sensor relative to each other while moving the actual workpiece and the sensor relative to each other at a third pitch in the rotation axis direction of the actual workpiece. The workpiece abnormality inspection apparatus according to claim 10, wherein an output value for each frequency is calculated by frequency analysis of a waveform of the output voltage of the sensor.   The workpiece abnormality inspection apparatus according to claim 13, wherein the third pitch is a pitch equal to or less than a detection length of the actual workpiece in the rotation axis direction of the sensor.   The arithmetic unit relatively rotates the actual workpiece and the sensor each time the actual workpiece and the sensor are relatively moved at a fourth pitch in the rotation axis direction of the actual workpiece, so that a predetermined one rotation is performed. The output voltage of the sensor for the actual workpiece at each phase angle obtained by shifting the phase angle by a fixed angle for each relative movement is obtained, and the waveform of the output voltage obtained is output by frequency analysis. The workpiece abnormality inspection apparatus according to claim 10, wherein   16. The workpiece abnormality inspection apparatus according to claim 15, wherein the fourth pitch is a pitch equal to or less than a detection length of the actual workpiece in the rotation axis direction of the sensor.   The workpiece according to any one of claims 1 to 15, wherein the sensor induces an eddy current in the workpiece by an exciting current during machining of the workpiece to obtain an output voltage. Abnormality inspection equipment for things. An acquisition step of obtaining an output voltage by inducing an eddy current inside the workpiece by an excitation current;
A calculation step of calculating an output value for each frequency by frequency analysis of the waveform of the output voltage obtained for the actual workpiece to be inspected;
A determination step of determining that the actual workpiece has an abnormality when the output value for each frequency exceeds a threshold value for each frequency corresponding to the output value;
An abnormality inspection method for a workpiece comprising: