JP5499916B2 - Eddy current inspection apparatus and eddy current inspection method - Google Patents

Description

  The present invention relates to an eddy current type inspection apparatus and inspection method.

  The eddy current type inspection apparatus induces eddy currents on the surface of a subject using a magnetic sensor, and inspects the physical characteristics of the subject in a nondestructive manner based on changes in the eddy current. Such an eddy current type inspection apparatus is applied to, for example, a flaw detection test apparatus that detects a flaw generated on the surface layer of a subject from the physical characteristics of the subject.

  Patent Documents 1 and 2 disclose an eddy current type inspection method for detecting a work-affected layer from the physical characteristics of a workpiece to be examined. When grinding or cutting is performed, the temperature of the processed part of the workpiece tends to be high. Therefore, depending on the processing conditions, a work-affected layer (generally referred to as “grinding burn” or “cutting burn”) may occur on the surface of the workpiece. This work-affected layer may become a factor that reduces the mechanical strength of the workpiece depending on the state of deterioration. Therefore, according to the inspection methods of Patent Documents 1 and 2, it is possible to detect the presence / absence of a work-affected layer and the state of deterioration of a workpiece.

  Incidentally, the sensitivity of the magnetic sensor may fluctuate due to deterioration over time. Such deterioration of the magnetic sensor can be considered, for example, when the tip of the magnetic sensor is worn when the inspection is performed with the magnetic sensor in contact with the subject. Further, even if the magnetic sensor is the same type and is not used, the initial sensitivity may differ due to individual differences. Such fluctuations and differences in the sensitivity of the magnetic sensor may be dealt with by performing an appropriate gain adjustment based on detection values in a plurality of master works, as described in Patent Document 1, for example.

JP-A-10-206395 JP 2000-180415 A

Here, when a work-affected layer occurs in a workpiece, it is considered that the influence on the mechanical strength varies depending on the degree of the state of change such as the depth and range of the work-affected layer. Therefore, it is desirable to detect the presence / absence of a work-affected layer and the state of deterioration in a workpiece with higher accuracy. For this reason, the work-affected layer detection device accurately grasps the state of deterioration of the workpiece even when the sensitivity of the magnetic sensor fluctuates and reliably detects the work-affected layer in a minute range. Therefore, it is necessary to adjust the gain appropriately. The same applies to various inspection apparatuses to which the eddy current type inspection apparatus is applied. However, the method of acquiring the sensitivity described in Patent Document 1 requires labor and time for acquiring the sensitivity because it inspects a plurality of master works, and is unsuitable for fine adjustment according to the sensitivity fluctuation. .
The present invention has been made in view of the above problems, and an eddy current inspection apparatus and an eddy current inspection capable of detecting the physical characteristics of a subject with high accuracy by accurately acquiring the sensitivity of a sensor. It aims to provide a method.

(Eddy current inspection device)
In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that an eddy current is induced in a subject by an exciting current and a detection value corresponding to a change in the eddy current is output, and a predetermined frequency. Supply means for supplying the exciting current set to the sensor, moving means for moving the sensor relative to the subject so that the distance between the subject and the sensor fluctuates, Sensitivity acquisition means for acquiring the sensitivity of the sensor based on the plurality of detection values output by the sensor at a plurality of different detection positions, and the supply means is set to a plurality of different frequencies An excitation current is supplied to the sensor, and the sensor outputs each detection value corresponding to each set frequency at a plurality of detection positions, and the sensitivity acquisition means includes a plurality of the sensitivity acquisition means. Each detection value at the output position is acquired, and calculated by a change amount of each detection value according to a reference frequency among the frequencies and a change amount of each detection value according to another frequency. a Rukoto to obtain the sensitivity of the sensor based on a rate of change that.
In order to solve the above-described problem, the invention according to claim 2 is characterized in that an eddy current is induced in the subject by an excitation current and a detection value corresponding to a change in the eddy current is output, and a predetermined frequency. Supply means for supplying the exciting current set to the sensor, moving means for moving the sensor relative to the subject so that the distance between the subject and the sensor fluctuates, Sensitivity acquisition means for acquiring the sensitivity of the sensor based on the plurality of detection values output by the sensor at a plurality of different detection positions, and the supply means is set to a plurality of different frequencies An excitation current is supplied to the sensor, and the sensor outputs each detection value corresponding to each set frequency at a plurality of detection positions, and the sensitivity acquisition means includes a plurality of the sensitivity acquisition means. Each of the detection values at the output position is acquired, and a plurality of the detection values detected at the plurality of detection positions using a reference frequency among the frequencies and a plurality of the detection positions using other frequencies Calculating an approximate straight line indicating a relationship with the plurality of detected values detected in step, and acquiring the sensitivity of the sensor based on the rate of change indicated by the slope of the approximate straight line.
A feature of the invention according to claim 3 is the wear amount determination for determining the amount of wear at the tip of the sensor in contact with the subject based on the sensitivity of the sensor acquired by the sensitivity acquisition means. And further comprising means.

The above-mentioned problem is solved. A feature of the invention according to claim 4 is that the sensor is configured to induce an eddy current inside the detection body by an excitation current and output a detection value corresponding to a change in the eddy current, and to be set to a predetermined frequency. Supply means for supplying the excitation current to the sensor; movement means for moving the sensor relative to the subject so that the distance between the subject and the sensor varies; and a plurality of different distances Sensitivity acquisition means for acquiring the sensitivity of the sensor based on the plurality of detection values output by the sensor at a detection position, and contact with the subject based on the sensitivity of the sensor acquired by the sensitivity acquisition means Wear amount determining means for determining the wear amount of the tip portion of the sensor.
The invention according to claim 5 is characterized in that, in claim 4 , the supply means supplies the excitation current set to a plurality of different frequencies to the sensor, and the sensor is set at a plurality of the detection positions. The detected values corresponding to the respective frequencies are output, and the sensitivity acquisition means acquires the sensitivity of the sensor based on the detected values at a plurality of the detection positions.

According to a sixth aspect of the present invention, in the fourth aspect , the supply means supplies the excitation current set to a single frequency to the sensor, and the sensor is set at a plurality of the detection positions. The detection values corresponding to the detected frequencies are respectively output, and the sensitivity acquisition means acquires the sensitivity of the sensor based on a rate of change of the detection values with respect to the distance at a plurality of detection positions.

Feature of the invention according to claim 7, in any one of claims 1 to 6, based on the sensitivity with a preset reference sensitivity of the sensor obtained by the sensitivity acquiring means, the sensitivity of the sensor It is further provided with the correction | amendment means to correct | amend.

  According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the sensor outputs a detection value corresponding to a work-affected layer, scratches, and quenching of the workpiece that is the subject. That is.

(Eddy current inspection method)
In order to solve the above-described problem, a feature of the invention according to claim 9 is that a sensor that induces an eddy current in the subject by an excitation current and outputs a detection value corresponding to a change in the eddy current, and a predetermined frequency Supplying the excitation current set to the sensor, a moving step of moving the sensor relative to the subject so that a distance between the subject and the sensor fluctuates, A sensitivity acquisition step of acquiring the sensitivity of the sensor based on the plurality of detection values output by the sensor at a plurality of different detection positions, and the supply step is set to a plurality of different frequencies An excitation current is supplied to the sensor, and the sensor outputs each detection value according to each set frequency at a plurality of detection positions, and the sensitivity acquisition step includes a plurality of the sensitivity acquisition steps. The detection values at the output position are acquired, and the change amounts of the plurality of detection values detected at the plurality of detection positions using a reference frequency that is a reference among the frequencies, and a plurality of variations using other frequencies. a Rukoto to obtain the sensitivity of the sensor and variation in the detected plurality of said detection value, based on the rate of change calculated by the said detection position.

  According to the first aspect of the present invention, the sensitivity acquisition means of the eddy current inspection apparatus is configured to acquire the sensitivity of the sensor based on a plurality of detection values output by the sensor at a plurality of detection positions at different distances. . The sensor of this eddy current type inspection apparatus is a magnetic sensor that induces an eddy current in the subject by an excitation current supplied from a supply means and outputs a detection value corresponding to a change in the eddy current. Here, the eddy current inspection apparatus moves the sensor to a predetermined distance (including the contact state) with respect to the subject by the moving means, and inspects the physical characteristics of the subject based on the detection value output from the sensor. Yes. Thus, the presence / absence and state of a work-affected layer or a flaw in the subject and the quenching state of the subject are detected.

  A sensor using magnetism in such an eddy current inspection apparatus outputs different detection values depending on the clearance (distance between the subject and the sensor) when the moving means approaches or separates from the subject. The sensor also outputs a detection value that varies depending on the frequency set for the supplied excitation current. This is because, for example, the balance of the bridge circuit in the eddy current inspection apparatus is balanced so that the detection value when the sensor is separated from the surface layer of the subject by a predetermined distance becomes a predetermined value. And the behavior of the change of the detection value output according to the frequency of a clearance or an exciting current changes with sensor sensitivities. That is, the sensitivity acquisition means can acquire the sensitivity of the sensor based on a plurality of detection values output at a plurality of detection positions that differ depending on the excitation current set to a predetermined frequency.

  As described above, the sensitivity acquisition means of the eddy current inspection apparatus of the present invention acquires the sensitivity of the sensor based on a plurality of detection values output by the sensor at different clearances. In the inspection using the eddy current, the sensor approaches and separates from the subject by the moving means. For this reason, the eddy current inspection apparatus can use the detection value output when the sensor moves, so that it is not necessary to replace the subject with a master work or the like in order to obtain sensitivity. Therefore, the eddy current type inspection apparatus can acquire the sensitivity of the sensor with a simpler configuration than the conventional one. In addition, since the sensitivity of the sensor can be acquired every time the sensor approaches or moves away from the subject, it is possible to appropriately adjust the gain in accordance with the change in sensitivity in response to the deterioration of the sensor.

The sensitivity acquisition unit acquires the sensitivity of the sensor based on the detection values at the plurality of detection positions. In addition, the sensor is configured to be supplied with excitation currents set at a plurality of different frequencies by a supply unit and to output detection values corresponding to the respective frequencies at a plurality of detection positions. As described above, the sensor in the eddy current inspection apparatus is supplied with excitation currents having a plurality of different frequencies simultaneously or a plurality of times by changing the frequency setting. Here, the penetration depth becomes shallower as the excitation current frequency is set higher, and the penetration depth becomes deeper as it is set lower. Therefore, in general, in the examination using eddy current, the frequency of the excitation current is appropriately set depending on the examination target region in the subject.

  For each detection value corresponding to each frequency output by the above configuration, the behavior of changes in the plurality of detection values on the high frequency side with respect to the plurality of detection values on the low frequency side among the plurality of frequencies is the sensitivity of the sensor. It depends on. That is, the sensitivity acquisition means can more accurately acquire the sensitivity of the sensor based on the detection values output at a plurality of detection positions that differ depending on the excitation current set at a plurality of frequencies. In addition, a sensor capable of setting a plurality of frequencies for the excitation current can simultaneously output detection values corresponding to the frequencies. On the other hand, a sensor capable of setting only a single frequency for the excitation current first outputs detection values corresponding to the frequencies at a plurality of detection positions. And after changing a frequency, the detection value according to the frequency is each output in a some detection position. Even in such a configuration, an effect similar to that in the case where an excitation current with a plurality of frequencies set is supplied.

Moreover, the sensitivity acquisition means is configured to acquire the sensitivity of the sensor based on the ratio of the change in each detected value according to another frequency with respect to each detected value according to the reference frequency as a reference among the frequencies. As described above, the behavior of changes in the plurality of detection values on the high frequency side with respect to the plurality of detection values on the low frequency side among the plurality of frequencies varies depending on the sensitivity of the sensor. Therefore, for example, the lowest frequency among the plurality of frequencies is set as the reference frequency. And how each detection value according to the other frequency except the reference frequency changes is obtained for each detection value according to the reference frequency. Based on the calculated change rate of each detected value, the sensitivity acquisition means can acquire the sensitivity of the sensor with higher accuracy. The rate of change may be obtained from an inclination of the straight line calculated by a least square method or the like based on each detection value in a preset predetermined section. In addition, it is possible to obtain the slope of a straight line passing through the detection values at both ends of the predetermined section or the slope of a tangent line at a point on a curve calculated from a plurality of detection values.
According to the third and fourth aspects of the invention, the apparatus further includes a wear amount determination unit that determines the wear amount of the tip of the sensor that contacts the subject based on the sensitivity of the sensor acquired by the sensitivity acquisition unit. As described above, the variation in the sensitivity of the sensor is considered to be caused by wear of the tip portion that contacts the subject in the examination. And when the amount of wear at the tip increases, it is necessary to replace the sensor or the tip of the sensor in order to perform an appropriate inspection. Therefore, by adopting the above configuration, it is possible to determine how much the tip of the sensor in the inspection is worn and to obtain a replacement time for the sensor or the like. Thereby, as a eddy current type inspection device, an appropriate inspection state can be maintained.

According to the invention of claim 6 , the sensitivity acquisition means acquires the sensitivity of the sensor based on the distances and detection values at a plurality of detection positions. Further, the sensor is configured to be supplied with an excitation current set to a single frequency by the supply means and to output detection values corresponding to the set frequencies at a plurality of detection positions. For the multiple detection values output according to the frequency of the excitation current supplied by the sensor, the behavior of the change in the detection value at the detection position on the separation side with respect to the detection value at the detection position on the proximity side of the subject depends on the sensitivity of the sensor. Different. That is, the sensitivity acquisition unit can acquire the sensitivity of the sensor more accurately based on the distances at the plurality of detection positions and the detection values output at the detection positions.

Further, the sensitivity acquisition means is configured to acquire the sensitivity of the sensor based on the rate of change of the detection value with respect to the distance at a plurality of detection positions. As described above, the behavior of the change in the detection value on the far side with respect to the detection value on the near side of the subject varies depending on the sensitivity of the sensor. Therefore, for example, how the plurality of detection values change with respect to the clearance is obtained. The rate of change may be obtained from an inclination of the straight line calculated by a least square method or the like based on a plurality of detection values in a predetermined section set in advance. In addition, it is possible to obtain the slope of a straight line passing through the detection values at both ends of the predetermined section or the slope of a tangent line at a point on a curve calculated from a plurality of detection values. Based on the rate of change calculated in this way, the sensitivity acquisition means can acquire the sensitivity of the sensor with higher accuracy.

According to the invention which concerns on Claim 7 , it is set as the structure further equipped with the correction means which correct | amends the sensitivity of a sensor based on the sensitivity of the sensor acquired by the sensitivity acquisition means, and the preset reference sensitivity. Here, for example, when the tip of the sensor wears due to aging degradation of the sensor and the sensitivity of the sensor fluctuates, the detection value may change accordingly, and erroneous detection may occur. Therefore, a correction amount for adjusting to an appropriate sensitivity is calculated based on the sensitivity of the sensor acquired by the sensitivity acquisition means and the reference sensitivity. Thereby, since the correction means can perform appropriate gain adjustment, the physical characteristics of the subject can be inspected with higher accuracy, so that erroneous detection in various inspections can be prevented.

  Here, in order to inspect the physical characteristics of the subject with high accuracy from the detection value output from the sensor, it is necessary to increase the sensitivity of the sensor to some extent. However, as the sensitivity increases, electrical noise increases. Become. Therefore, based on the physical characteristics including the material characteristics of the subject to be inspected and the characteristics of the sensor, the gain is adjusted to a sensitivity that enables proper testing using eddy currents. Sensitivity ".

  According to the eighth aspect of the present invention, the sensor is configured to output a detection value corresponding to a work-affected layer, a flaw, and quenching of a workpiece that is an object. In other words, the eddy current type inspection device is configured to be applied to a work-affected layer detection device for inspecting the presence or absence of a work-affected layer and its state of alteration on a workpiece, or a flaw detection test device for detecting a flaw generated on a workpiece. . For example, in order to improve the quality of a workpiece, it may be necessary to detect minute work-affected layers and scratches. In such a case, if the detection value fluctuates as the sensor sensitivity fluctuates, there is a risk of erroneous detection due to the relationship between the fluctuation range of the detection value and the threshold value set for detecting a minute damaged layer. is there.

  Thus, with the above configuration, for example, gain adjustment can be appropriately performed in accordance with fluctuations in sensor sensitivity. As a result, it is possible to detect an appropriate physical property of the subject in accordance with the sensitivity of the sensor, and thus it is possible to perform an eddy current type inspection with higher accuracy. Thus, in order to improve the quality of the workpiece, it is necessary to know in detail the minute work-affected layer and scratches on the workpiece or the quenching state of the workpiece. A machined layer detection apparatus to which the apparatus is applied is particularly useful.

  According to the invention of claim 9, the eddy current inspection method is configured to acquire the sensitivity of the sensor based on a plurality of detection values output by the sensor at a plurality of detection positions at different distances in the sensitivity acquisition step. Yes. The sensor of this eddy current type inspection method is a magnetic sensor that induces an eddy current inside a subject by an excitation current supplied from a supply step and outputs a detection value corresponding to a change in the eddy current. Here, in the eddy current type inspection method, the sensor is moved to a predetermined distance (including the contact state) with respect to the subject by the moving process, and the physical characteristics of the subject are inspected based on the detection value output from the sensor. Yes. As a result, the presence or absence and alteration state of the work-affected layer or scratches in the subject, the quenching state of the subject, and the like are detected.

With such a configuration, the eddy current inspection method can use the detection value output when the sensor moves, so that it is not necessary to replace the subject with a master work or the like in order to obtain sensitivity. Therefore, the eddy current inspection method can acquire the sensitivity of the sensor with a simpler configuration than the conventional one. In addition, since the sensitivity of the sensor can be acquired every time the sensor approaches or moves away from the subject, it is possible to appropriately adjust the gain in accordance with the change in sensitivity in response to the deterioration of the sensor.
Further, other characteristic portions of the eddy current inspection apparatus of the present invention can be similarly applied to the eddy current inspection method of the present invention. And the effect in this case also has the same effect as the effect as the eddy current inspection apparatus.

1st embodiment: It is the schematic which shows the external appearance of the process deterioration layer detection apparatus 1. FIG. It is a side view which sees through and shows the inside of the magnetic sensor 10 of the process deterioration layer detection apparatus 1. FIG. It is a circuit diagram which shows the bridge circuit of a magnetic sensor. It is a circuit diagram which shows the pseudo circuit of the workpiece 2 in which the eddy current was induced. It is a graph which shows the phase and detection value in a test | inspection of a process-affected layer. It is a graph which shows the relationship between a clearance and a detected value. It is a graph which shows the detected value of the other frequency with respect to the detected value of a reference frequency. It is a conceptual diagram which shows the change of the impedance with respect to clearance. It is a correspondence table of a change rate of a detected value and a coupling coefficient. It is a correspondence table of the material characteristic estimated from a coupling coefficient and impedance. 2nd embodiment: It is a side view which shows the process deterioration layer detection apparatus 101. FIG. It is a graph which shows the relationship between clearance and detection. 6 is a correspondence table between a change amount of a detected value and a coupling coefficient.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments embodying an eddy current inspection apparatus and an eddy current inspection method of the present invention will be described with reference to the drawings. In each embodiment, an example of a damaged layer detection device to which an eddy current inspection device and an eddy current inspection method are applied is illustrated.

<First embodiment>
(Configuration of Worked Deteriorated Layer Detection Device 1)
The processed deteriorated layer detection apparatus 1 of the present invention will be described with reference to FIGS. As shown in FIGS. 1 and 2, the work-affected layer detection device 1 includes a magnetic sensor 10 (corresponding to a “sensor” of the present invention), a rotation support unit 20, and a control device 30. The workpiece 2 is a workpiece made of a magnetic material and includes shapes such as a cylindrical shape, a column shape, a plate shape, and a free curved surface shape. The workpiece 2 is an object to be inspected by the processing-affected layer detection apparatus 1, and the presence / absence of the processing-affected layer and the state of deterioration are inspected on the inspection surface of the workpiece 2. In the present embodiment, the workpiece 2 will be described as a cylindrical member having a peripheral surface as an inspection surface. The machine tool 3 is a grinder that grinds the outer peripheral surface of a cylindrical or columnar workpiece 2. In addition, the machined layer detection apparatus and the machined layer detection method of the present invention can employ a cutting machine such as a lathe and a machining center in addition to a grinding machine as the machine tool 3.

  Further, the work-affected layer detection apparatus 1 outputs a signal corresponding to the work-affected layer of the subject (workpiece 2) by a magnetic nondestructive inspection using eddy current magnetism. Here, the inspection of the work-affected layer by the eddy current method will be described. In general, the eddy current type induces an eddy current by applying a magnetic field to a subject by a primary coil and flowing an excitation current. Then, the primary coil to which the magnetic field is applied and the subject are relatively moved, and the induced electromotive force of the eddy current that changes due to this movement is detected by the secondary coil. In the eddy current inspection, the detected induced electromotive force changes with the state of alteration of the work-affected layer. Is intended.

  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 with a first frequency on the low frequency side and a second frequency on the high frequency side 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. As a result, the sensor head 12 uses the induced electromotive force that changes in accordance with the alteration state of the workpiece 2 as a signal at each penetration depth corresponding to the frequency of the exciting current that sets the first frequency and the second frequency. Detected.

  As shown in FIG. 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 this 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). In this embodiment, the sensor head 12 is always in contact with the workpiece 2 by the spring 14a in the inspection for detecting the work-affected layer. The touch sensor 14 detects whether the sensor head 12 is in contact or non-contact with the workpiece 2 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 a mechanism that is provided at the rear portion (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 and the radial direction of the workpiece 2. The sensor feed mechanism 15 includes 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 sensor feed mechanism 15 outputs the detected position information of the sensor body 11 to the control device 30. Thus, 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 body 11 by the sensor feed mechanism 15. doing.

  As shown in FIG. 2, the rotation support unit 20 includes drive wheels 21 and an adjustment wheel 22, and supports the workpiece 2 in a rotatable manner. The drive wheel 21 is in contact with the peripheral surface of the workpiece 2 and is rotated by a motor (not shown) to rotate the workpiece 2. 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. As a result, the control device 30 detects the circumferential phase of the sensor head 12 with respect to the workpiece 2 based on the shape information including the diameter and circumference of the workpiece 2 as the initial information and the rotational position information of the motor. doing. 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 sensitivity acquisition unit 32, a correction unit 33, and a wear amount determination unit 34. The supply unit 31 is a supply unit of the magnetic sensor 10 that supplies the excitation current that sets the first frequency and the second frequency to the sensor body 11 of the magnetic sensor 10. The supply unit 31 is connected to the sensor main body 11 via the measuring device 13 and supplies the excitation current with the first frequency and the second frequency set to the sensor main body 11 at the same time. That is, the sensor body 11 is simultaneously supplied with excitation currents having a plurality of frequencies by the supply unit 31. Thereby, the magnetic sensor 10 is inspecting the presence or absence and the altered state of the work-affected layer at a plurality of penetration depths at the same time. The first frequency and the second frequency correspond to the “predetermined frequency” of the present invention.

  The sensitivity acquisition unit 32 is a sensitivity acquisition unit that acquires the sensitivity of the magnetic sensor 10 based on the detection value output by the magnetic sensor 10. Further, the sensitivity acquisition unit 32 calculates the clearance from the contact information of the sensor head 12 and the position information of the sensor body 11 input to the control device 30. And the position used as the said clearance is linked | related as a detection position where the detection value by the magnetic sensor 10 was detected. The correction unit 33 is a correction unit that corrects the sensitivity of the magnetic sensor 10 by adjusting the gain. The correction unit 33 is a correction amount for adjusting to an appropriate sensitivity based on the sensitivity of the magnetic sensor 10 acquired by the sensitivity acquisition unit 32 and the preset reference sensitivity stored in the control device 30. Is calculated. The correction unit 33 adjusts the gain of the magnetic sensor 10 based on the correction amount.

  Here, it is necessary to increase the sensitivity of the magnetic sensor 10 to some extent in order to detect the presence / absence of a work-affected layer and the state of deterioration from the detection value output from the magnetic sensor 10, but as the sensitivity increases, electrical noise increases. Will do. In view of this, gain adjustment is performed to a sensitivity at which the inspection for detecting the work-affected layer can be appropriately performed based on the physical characteristics including the material characteristics of the subject to be inspected and the characteristics of the magnetic sensor 10. In the present embodiment, the adjusted sensitivity of the magnetic sensor 10 is referred to as “reference sensitivity”.

  The wear amount determination unit 34 is a wear amount determination unit that determines the wear amount of the tip portion of the sensor head 12 in the magnetic sensor 10. The magnetic sensor 10 in the present embodiment is in a state where the sensor head 12 is in contact with the workpiece 2 in the inspection of the work-affected layer. Therefore, the tip of the sensor head 12 is worn due to friction with the workpiece 2 by repeated inspection. Further, when the sensor head 12 is worn, the distance between the coil embedded in the sensor head 12 and the workpiece 2 changes, so that the sensitivity of the sensor head 12 varies. Accordingly, the wear amount determination unit 34 determines how much the wear amount of the sensor head 12 is based on the sensitivity of the magnetic sensor 10 acquired by the sensitivity acquisition unit 32. Details of sensitivity acquisition, correction, and wear amount determination of the magnetic sensor 10 will be described later.

(Inspection by processing layer 1)
The inspection by the work-affected layer detection apparatus 1 will be described with reference to FIGS. The work-affected layer detection device 1 first supplies an excitation current set to the first frequency and the second frequency by the supply unit 31 to the magnetic sensor 10 as a supply process. Thereby, the magnetic sensor 10 is in a state in which a magnetic field can be applied to the subject. Next, as a moving process, the sensor main body 11 is caused to approach the workpiece 2 at a constant speed by the sensor feed mechanism 15 in the state where the excitation current is supplied to the magnetic sensor 10. The clearance, which is the distance between the workpiece 2 and the sensor head 12, gradually decreases, and the tip of the sensor head 12 comes into contact with the peripheral surface of the workpiece 2.

  At this time, the touch sensor 14 of the magnetic sensor 10 assumes that the workpiece 2 and the sensor head 12 are in contact with each other when the spring 14a arranged at the base end of the sensor head 12 starts to contract. The contact information is output to 30. Thereby, the control device 30 stops the approach of the sensor main body 11 to the workpiece 2 by the sensor feed mechanism 15.

  Here, as shown in FIG. 3, the magnetic sensor 10 includes a bridge circuit. In the magnetic sensor 10 according to the present embodiment, an excitation coil (primary coil) that applies a magnetic field to a subject and a detection coil (secondary coil) that detects an induced electromotive force are an integral excitation and detection coil. In addition to the excitation and detection coil, the magnetic sensor 10 forms a bridge circuit from a calibration coil and a plurality of variable resistors, and the impedances of the bridge circuit are indicated as Z1 to Z4.

  Next, the magnetic sensor 10 is supplied with an excitation current in a state where the tip of the sensor head 12 is in contact with a master work in which a work-affected layer is not generated. Then, the gain of the magnetic sensor 10 is adjusted by setting an amplification circuit in a state where the tip of the sensor head 12 is sufficiently separated from the subject and the master work. Further, by adjusting the resistance value of the variable resistor, the balance of the bridge circuit is balanced so that no current flows through the amplifier circuit. The detection value V output by such a bridge circuit has a correlation with each impedance Z1 to Z4, as shown in [Equation 1].

[Equation 1]
V = E {Z1 / (Z2 + Z1) -Z4 / (Z3 + Z4)}
V: Detected value E: Effective value of AC power supply Z1 to Z4: Impedance

  Further, the impedance Z1 of the excitation / detection coil can be calculated from [Z1 = V1 / I1] by regarding the subject to which a magnetic field is applied as a pseudo circuit, as shown in FIG. At this time, V1 is a voltage value and I1 is a current value. Thus, for example, if a work-affected layer is generated on the surface layer of the workpiece 2 to be inspected, the resistance R2 of the workpiece 2 is increased because the magnetic permeability at that portion is low, and the impedance of the excitation / detection coil is increased. Z1 varies. Then, the balance of the bridge circuit of the magnetic sensor 10 is lost, a current flows through the amplifier circuit, and a detected value is output.

  In such a pseudo circuit, the mutual induction coefficient M of each coil has a correlation with the inductances L0 and L2 of each coil as shown in [Equation 2]. The coupling coefficient K is a constant determined by the distance (clearance) between the subject and the sensor head 12. That is, since the coupling coefficient K has a correlation with the impedance Z1, it has a correlation with the detected value output by the fluctuation of the impedance Z1. Therefore, by obtaining the coupling coefficient K from a plurality of detection values, it is possible to obtain the degree of sensitivity of the magnetic sensor 10 that has output the detection values.

[Equation 2]
M = K√ (L0 ・ L2)
M: Mutual induction coefficient (mutual inductance)
K: Coupling coefficient L0: Inductance of sensor side coil L2: Inductance of workpiece side pseudo coil

  Subsequently, while the sensor head 12 is in contact with the workpiece 2, the workpiece 2 is rotated by the rotation support portion 20, and the sensor main body 11 is appropriately moved in the axial direction of the workpiece 2 by the sensor feed mechanism 15. . At this time, the rotational position information of the drive wheel 21 motor detected by the encoder 21 a of the rotation support unit 20 is output to the control device 30. Thereby, the detection value according to the presence / absence of the work-affected layer and the altered state at the penetration depth of the first frequency and the second frequency is output. Then, as shown in FIG. 5, the control device 30 acquires the inspection result of the work-affected layer in which grinding burn has occurred at a predetermined axial position. In the present embodiment, the control device 30 determines that a work-affected layer is generated in the phase of the workpiece 2 in which the threshold value T is preset and the detected value exceeds the threshold value T.

  When the work-affected layer detection apparatus 1 completes the inspection of the work-affected layer over the entire circumference of the workpiece 2 to be inspected, the sensor feed mechanism in a state in which an excitation current is supplied to the magnetic sensor 10 as a moving process. 15, the sensor body 11 is moved away from the workpiece 2 at a constant speed. Then, the urging force that urges the sensor head 12 against the workpiece 2 by the spring 14 a of the touch sensor 14 gradually decreases, and the tip of the sensor head 12 separates from the peripheral surface of the workpiece 2.

  At this time, the touch sensor 14 of the magnetic sensor 10 is controlled so that the workpiece 2 and the sensor head 12 are brought into a non-contact state when the spring 14a arranged at the base end portion of the sensor head 12 has been extended. The contact information is output to the device 30. Thus, the control device 30 stops the separation of the sensor body 11 from the workpiece 2 by the sensor feed mechanism 15 after the sensor body 11 has sufficiently separated from the workpiece 2. In this way, the work-affected layer detection device 1 inspects the presence / absence of the work-affected layer or the deteriorated state.

(Acquisition of sensitivity of magnetic sensor 10)
Acquisition of the sensitivity of the magnetic sensor 10 in the present embodiment will be described with reference to FIGS. First, in the process of moving the sensor main body 11 away from the workpiece 2 after detecting the work-affected layer, the work-affected layer detection device 1 detects a plurality of detections output at a plurality of detection positions with different clearances as a sensitivity acquisition process. Get the value. At each detection position, each detection value corresponding to the excitation current set to the first frequency and the second frequency is output.

  Here, the second frequency, which is a higher frequency than the first frequency, has a large amount of change in the detection value due to the increase in the clearance because the region to be examined is on the surface side of the subject. Thus, it has been found that the curve passing through the detection values on the high frequency side and the low frequency side varies depending on the set frequency, but also varies depending on the sensitivity of the magnetic sensor 10 in addition to the difference in frequency. Specifically, as shown in FIG. 6, when the sensitivity of the magnetic sensor 10 is high, the detected values on the high frequency side and the low frequency side have a large amount of change accompanying an increase in clearance. In particular, since the increment of the change amount on the low frequency side is large, the curves Ch1 and Ch2 corresponding to the respective detection values are also approached. On the other hand, when the sensitivity of the magnetic sensor 10 is low, the detected values on the high frequency side and the low frequency side have a small amount of change accompanying an increase in clearance. Therefore, the curves Cl1 and Cl2 by the respective detection values are separated from each other as compared with the case where the sensitivity is high.

  As described above, the behavior of changes in the detected values of the first frequency and the second frequency output at a plurality of different detection positions varies depending on the sensitivity of the magnetic sensor 10. Therefore, in the present embodiment, the sensitivity acquisition unit 32 uses the first frequency as the reference frequency, and the ratio of the change in the detection value according to another frequency (second frequency) with respect to the detection value according to the reference frequency (first frequency). α is calculated. More specifically, as shown in FIG. 7, the change is based on the change amount ΔVs of the detection values Vs1, Vs2 according to the reference frequency and the change amount ΔVe of the detection values Ve1, Ve2 according to other frequencies. The ratio α = ΔVe / ΔVs is calculated.

  Here, as described above, the impedance Z1 in the configuration of the work-affected layer detection device 1 varies depending on the distance between the workpiece 2 and the magnetic sensor 10. As shown in FIG. 8, the impedance Z1 includes a coil resistance component (real axis) and a reactance component (imaginary axis), and is correlated with a coupling coefficient K that is a constant determined by clearance and the like. The possible range of the coupling coefficient K is 0 or more and 1 or less. For example, when the coupling coefficient K is 1, the locus Lo1 of possible values of the impedance Z1 draws the outermost curve in FIG. When the coupling coefficient K is smaller than 1, the loci Lo2 and Lo3 of the values that the impedance Z1 can take draw a curved line that is reduced inward in FIG.

Here, when the distance between the peripheral surface of the workpiece 2 as the subject and the tip of the sensor head 12 is greatly separated, that is, when the clearance is sufficiently large, the coupling coefficient K becomes zero. On the other hand, as the clearance decreases, the coupling coefficient K increases from 0, and when the subject is in contact with the peripheral surface of the workpiece 2 as the subject and the tip of the sensor head 12 (clearance is reduced). In 0), the coupling coefficient K is maximized. The maximum value of the coupling coefficient K at the time of contact with the subject differs depending on the sensitivity of the sensor. Therefore, when placing the coupling coefficient at the time of the subject in contact with K _T, the sensor coupling coefficient K _T is small insensitive, (close to 1 or 1) sensor coupling coefficient K _T is large is determined that sensitive be able to. That is, the coupling coefficient K _T upon the subject contacting is said parameter indicating the sensitivity of the sensor.

  In FIG. 8, curves Cr1 and Cr2 intersecting the loci Lo1 to Lo3 of the impedance Z1 are curves determined by the frequency set for the excitation current and the material characteristics of the subject to be examined. This material characteristic is a characteristic such as the magnetic permeability and specific resistance of the specimen, and can be regarded as constant for each specimen as long as it is a part where the work-affected layer is not generated. Therefore, let θ be the material property of the subject. The intersections between the curves Cr1 and Cr2 corresponding to the first frequency and the second frequency and the loci Lo1 to Lo3 of the impedance Z1 are the values of the impedance Z1 when inspected by the excitation current set to the frequency.

Thus, since the coupling coefficient K and the detection value by the magnetic sensor 10 have a correlation, the ratio α of change in the detection value and the coupling coefficient K _T at the time of contact with the subject are determined by magnetic field analysis by experiments and the finite element method. And the relationship between the coupling coefficient _KT and the impedance Z1 when the subject is in contact with the material property θ of the subject can be acquired in advance. Therefore, in the present embodiment, as shown in FIGS. 9 and 10, a correspondence table showing the respective relationships is created in advance and the sensitivity of the magnetic sensor 10 is acquired based on the experiment and analysis described above.

In the sensitivity acquisition step, the sensitivity acquisition unit 32 of the control device 30 calculates a change rate α of each detection value according to another frequency (second frequency) with respect to each detection value according to the reference frequency (first frequency). (See FIG. 7). Then, a ratio α of the calculated changes, based on the correspondence table of FIG. 9, to derive the coupling coefficient K _T upon the subject contact. Thus, the coupling coefficient K _T upon the subject contacted derived, can the sensitivity of the magnetic sensor 10 which outputs the respective detection values corresponding to each frequency to obtain a degree in either.

Next, the detected value V corresponding to the reference frequency is substituted into [Equation 1] to calculate the impedance Z1. Then, the coupling coefficient K _T of the calculated impedance Z1 and the object upon contact, based on the correspondence table of FIG. 10, to derive the material characteristics theta. Here, the reference impedance Zstd is derived based on the preset reference coupling coefficient Kstd and the derived material characteristic θ and the correspondence table of FIG. The reference coupling coefficient Kstd is a value set as a reference value for the coupling coefficient, and is a coupling coefficient corresponding to the reference sensitivity. The reference impedance Zstd is an impedance corresponding to the reference sensitivity (or the reference coupling coefficient Kstd) in the derived material characteristic θ.

The derived reference impedance Zstd is substituted into [Equation 1] to calculate a reference output value Vstd. This reference output value Vstd is a detection value that should be output in the case of a subject that originally has the material characteristic θ. Therefore, the work-affected layer detection device 1 calculates a correction amount and performs gain adjustment so that the detection value V becomes equal to the reference output value Vstd as a correction step. Correcting unit 33 of the controller 30, the derived based on the sensitivity with a preset reference sensitivity of the magnetic sensor 10 that is obtained based on the coupling coefficient K _T upon the subject contact, correcting the sensitivity of the magnetic sensor 10 To do. In the present embodiment, the correction unit 33 corrects the sensitivity of the magnetic sensor 10 by adjusting the gain more specifically so that the detection values V and Vstd at the respective sensitivities become equal.

Further, as the wear amount determination step, the work-affected layer detection device 1 determines the amount of wear from the initial state of the tip of the sensor head 12 based on the variation of the detected value V output by the magnetic sensor 10 so far. . Wear amount determination unit 34 of the controller 30, based on the sensitivity with a preset reference sensitivity of the magnetic sensor 10 that is obtained based on the coupling coefficient K _T upon the subject contacted derived, sensors in the magnetic sensor 10 It is determined how much the tip 12 of the head 12 is worn. In the present embodiment, the wear amount determination unit 34 more specifically determines the wear amount based on the amount of change in the detection values V and Vstd at each sensitivity. Then, the control device 30 determines that it is time to replace the sensor or the sensor head 12 when the amount of wear exceeds a predetermined value, and appropriately performs display or the like so as to prompt the operator to replace it.

(Effects of the work-affected layer detection device 1)
According to the processed damaged layer detection apparatus 1 described above, the sensitivity acquisition unit 32 of the processed deteriorated layer detection apparatus 1 uses the magnetic sensor based on a plurality of detection values output by the magnetic sensor 10 at a plurality of detection positions at different distances. 10 sensitivities are acquired. In the inspection for detecting the work-affected layer, the magnetic sensor 10 approaches and separates from the workpiece 2 that is the subject by the sensor feed mechanism 15. For this reason, the work-affected layer detection apparatus 1 can use the detection value output when the magnetic sensor 10 moves, so that it is not necessary to replace the workpiece 2 with a master work or the like in order to obtain sensitivity. Therefore, the work-affected layer detection device 1 can acquire the sensitivity of the magnetic sensor 10 with a simpler configuration than the conventional one. In addition, since the sensitivity of the magnetic sensor 10 can be acquired every time the magnetic sensor 10 approaches or separates from the workpiece 2, the gain adjustment is performed in accordance with the sensitivity variation in response to deterioration of the magnetic sensor 10 or the like. It can be performed appropriately.

  The sensitivity acquisition unit 32 of the control device 30 acquires the sensitivity of the magnetic sensor 10 based on the detection values at a plurality of detection positions. Further, the magnetic sensor 10 is configured to be supplied with excitation currents set at different frequencies by the supply unit 31 and to output detection values corresponding to the respective frequencies at a plurality of detection positions. And about each detection value according to each frequency output by this structure, the behavior of the change of the some detected value in the high frequency side with respect to the some detected value in the low frequency side among several frequencies is the magnetic sensor 10's. It depends on the sensitivity. That is, the sensitivity acquisition unit 32 can more accurately acquire the sensitivity of the magnetic sensor 10 based on the detection values output at a plurality of detection positions that differ depending on the excitation currents set at a plurality of frequencies.

  The sensitivity acquisition unit 32 of the control device 30 is configured based on the change rate α of each detected value according to another frequency (second frequency) with respect to each detected value according to the reference frequency (first frequency). It is configured to acquire sensitivity. The work-affected layer detection device 1 determines how each detection value according to other frequencies other than the reference frequency changes with respect to each detection value according to the reference frequency. Based on the calculated change rate α of each detected value, the sensitivity acquisition unit 32 can acquire the sensitivity of the magnetic sensor 10 with higher accuracy. Further, the change rate α may be obtained from an inclination of a straight line calculated by a least square method or the like based on detection values in a predetermined section set in advance. In addition, it is possible to obtain the slope of a straight line passing through the detection values at both ends of the predetermined section or the slope of a tangent line at a point on a curve calculated from a plurality of detection values.

  The work-affected layer detection device 1 is configured to further include a correction unit 33 that corrects the sensitivity of the magnetic sensor 10 based on the sensitivity of the magnetic sensor 10 acquired by the sensitivity acquisition unit 32 and a preset reference sensitivity. Here, for example, when the tip of the magnetic sensor 10 is worn due to aging degradation of the magnetic sensor 10 and the sensitivity of the magnetic sensor 10 changes, the detection value may change accordingly, and erroneous detection may occur. Therefore, a correction amount for adjusting to an appropriate sensitivity is calculated based on the sensitivity of the magnetic sensor 10 acquired by the sensitivity acquisition unit 32 and the reference sensitivity. Thereby, since the correction | amendment part 33 can perform appropriate gain adjustment, it can detect the alteration state of a process deterioration layer with higher precision, and can prevent the erroneous detection in the said test | inspection.

  The work-affected layer detection device 1 further includes a wear amount determination unit 34 that determines the wear amount of the tip of the magnetic sensor 10 that contacts the workpiece 2 based on the sensitivity of the magnetic sensor 10 acquired by the sensitivity acquisition unit 32. It is configured. As described above, the sensitivity fluctuation of the magnetic sensor 10 is considered to be caused by wear of the tip portion that contacts the workpiece 2 in the inspection. And when the amount of wear at the tip increases, it is necessary to replace the magnetic sensor 10 or the tip of the magnetic sensor 10 in order to perform an appropriate inspection. Therefore, with the above configuration, it is possible to determine how much the tip of the magnetic sensor 10 in the inspection is worn, and to obtain a replacement time for the magnetic sensor 10 and the like. Thereby, as a process deteriorated layer detection apparatus 1, an appropriate inspection state can be maintained.

  In the present embodiment, the work-affected layer detection device 1 is the one to which the eddy current inspection device of the present invention is applied, and the magnetic sensor 10 outputs a detection value corresponding to the work-affected layer of the workpiece 2 that is the subject. It is configured. Further, by maintaining an appropriate inspection state as described above, a highly accurate eddy current type inspection can be performed. As described above, the eddy current inspection apparatus of the present invention is applied when it is necessary to grasp in detail the presence or absence and the state of alteration of a minute work-affected layer of the workpiece 2 in order to improve the quality of the workpiece 2. A work-affected layer detection device or the like is particularly useful.

<Modification of First Embodiment>
In the present embodiment, the sensitivity acquisition unit 32 of the control device 30 uses the first frequency as a reference frequency, and detects a detection value corresponding to another frequency (second frequency) with respect to a detection value corresponding to the reference frequency (first frequency). The rate of change α was calculated. More specifically, the change rate α = ΔVe / ΔVs based on the change amount ΔVs of the detection values Vs1 and Vs2 according to the reference frequency and the change amount ΔVe of the detection values Ve1 and Ve2 according to other frequencies. Was calculated. On the other hand, it is good also considering a 2nd frequency as a reference frequency among a 1st frequency and a 2nd frequency.

  In addition, a section where detection values Vs1 and Vs2 corresponding to the reference frequency are set. This section may be appropriately set for the reason that sensitivity is easily affected by a difference in sensitivity between detection values corresponding to a plurality of frequencies. Furthermore, a large number of detection values may be acquired, an approximate straight line may be calculated by the method of least squares, and the slope thereof may be used as the change rate α. Similarly, with respect to a large number of detection values, an average in a predetermined section or a tangent line in a specific clearance may be calculated as the above approximate straight line, and the inclination thereof may be used as the change rate α. Even in such a configuration, the same effect can be obtained.

  In addition, in this embodiment, in order to simplify the description, the case of using two types of frequencies of the first and second frequencies has been described. On the other hand, the sensitivity of the magnetic sensor 10 may be acquired from detection values output at three or more frequencies. In such a case as well, the reference frequency may be set from among three or more types of frequencies, and the sensitivity may be selectively acquired from two types of frequencies as in the present embodiment. Even in such a configuration, the same effect can be obtained. Further, as described above, in this embodiment, the change rate α is calculated from the detection values output at a plurality of frequencies. However, the clearance at the time when the detection values are output may be added as position information. Good. Thereby, the behavior of the change of the detected value can be evaluated in a multifaceted manner, and the sensitivity of the magnetic sensor 10 can be acquired with higher accuracy.

<Second embodiment>
The configuration of the second embodiment will be described with reference to FIGS. Here, the work-affected layer detection apparatus 1 according to the first embodiment supplies the excitation currents set at different frequencies to the magnetic sensor 10 and acquires the sensitivity of the magnetic sensor 10. On the other hand, the work-affected layer detection apparatus 101 according to the second embodiment supplies an excitation current set to a single frequency to the magnetic sensor 10 and acquires the sensitivity of the magnetic sensor 10. Since other configurations are the same as those in the first embodiment, detailed description thereof is omitted. Only the differences will be described below.

(Configuration of Worked Deteriorated Layer Detection Device 101)
The process deteriorated layer detection apparatus 101 of this invention is demonstrated with reference to FIG. As shown in FIG. 11, the work-affected layer detection device 101 is mainly composed of a magnetic sensor 10 (corresponding to a “sensor” of the present invention), a rotation support unit 20, and a control device 130. In the present embodiment, the sensor body 11 of the magnetic sensor 10 is supplied with an excitation current having a third frequency set from the supply unit 131 of the control device 130. 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 each penetration depth according to the 3rd frequency set to the exciting current.

  The control device 130 includes a supply unit 131, a sensitivity acquisition unit 132, a correction unit 33, and a wear amount determination unit 34. The supply unit 131 sets a single frequency for the excitation current, whereas the supply unit 31 of the first embodiment sets a plurality of frequencies for the excitation current. That is, the supply unit 131 supplies the excitation current with the third frequency set to the sensor body 11 of the magnetic sensor 10. The third frequency corresponds to the “predetermined frequency” of the present invention.

  The sensitivity acquisition unit 132 acquires the sensitivity of the magnetic sensor 10 based on the detection value output by the magnetic sensor 10. Further, the sensitivity acquisition unit 132 is based on the contact information of the sensor head 12 input from the touch sensor 14 to the control device 130 and the position information of the sensor main body 11 input from the sensor feed mechanism 15 to the control device 130. Calculate clearance. And the position used as the said clearance is linked | related as a detection position where the detection value by the magnetic sensor 10 was detected.

(Inspection by the work-affected layer detection device 101)
The inspection by the work-affected layer detection apparatus 101 will be described. The work-affected layer detection apparatus 101 first supplies the magnetic sensor 10 with an excitation current set to the third frequency by the supply unit 131 as a supply process. Thereby, the magnetic sensor 10 is in a state in which a magnetic field can be applied to the subject. Next, as a moving process, the sensor main body 11 is caused to approach the workpiece 2 at a constant speed by the sensor feed mechanism 15 in the state where the excitation current is supplied to the magnetic sensor 10. The clearance, which is the distance between the workpiece 2 and the sensor head 12, gradually decreases, and the tip of the sensor head 12 comes into contact with the peripheral surface of the workpiece 2.

  At this time, the touch sensor 14 of the magnetic sensor 10 assumes that the workpiece 2 and the sensor head 12 are in contact with each other when the spring 14a arranged at the base end of the sensor head 12 starts to contract. The contact information is output to 130. Thereby, the control apparatus 130 stops the approach to the workpiece 2 of the sensor main body 11 by the sensor feed mechanism 15. Subsequently, while the sensor head 12 is in contact with the workpiece 2, the workpiece 2 is rotated by the rotation support portion 20, and the sensor main body 11 is appropriately moved in the axial direction of the workpiece 2 by the sensor feed mechanism 15. . Thereby, the detection value according to the presence / absence of the work-affected layer and the state of change at the penetration depth of the third frequency is output.

  When the work-affected layer detection apparatus 101 completes the inspection of the work-affected layer over the entire circumference of the workpiece 2 to be inspected, the sensor feed mechanism in a state in which an excitation current is supplied to the magnetic sensor 10 as a moving process. 15, the sensor body 11 is moved away from the workpiece 2 at a constant speed. Then, the urging force that urges the sensor head 12 against the workpiece 2 by the spring 14 a of the touch sensor 14 gradually decreases, and the tip of the sensor head 12 separates from the peripheral surface of the workpiece 2.

  At this time, the touch sensor 14 of the magnetic sensor 10 is controlled so that the workpiece 2 and the sensor head 12 are brought into a non-contact state when the spring 14a arranged at the base end portion of the sensor head 12 has been extended. The contact information is output to the device 130. Thus, the control device 130 stops the separation of the sensor body 11 from the workpiece 2 by the sensor feed mechanism 15 after the sensor body 11 has sufficiently separated from the workpiece 2. In this manner, the work-affected layer detection apparatus 101 performs the inspection of the presence / absence of the work-affected layer or the deteriorated state.

(Acquisition of sensitivity of magnetic sensor 10)
Acquisition of the sensitivity of the magnetic sensor 10 in the present embodiment will be described with reference to FIGS. First, the work-affected layer detection apparatus 101 detects a plurality of detections output at a plurality of detection positions with different clearances in a moving step in which the sensor main body 11 is separated from the workpiece 2 after detecting a work-affected layer as a sensitivity acquisition step. Get the value. At each detection position, each detection value corresponding to the excitation current set at the third frequency is output.

  Here, as shown in FIG. 12, the detection value output by the magnetic sensor 10 increases as the clearance increases. The amount of change in the detected value differs depending on the set frequency, but it has been found that the detected value varies depending on the sensitivity of the magnetic sensor 10 in addition to the difference in frequency. Specifically, as shown in FIG. 12, when the sensitivity of the magnetic sensor 10 is high, the detected value has a large amount of change accompanying an increase in clearance. On the other hand, when the sensitivity of the magnetic sensor 10 is low, the detected value has a small amount of change accompanying an increase in clearance.

  As described above, the behavior of the change in the detection value of the third frequency output at a plurality of different detection positions varies depending on the sensitivity of the magnetic sensor 10. Therefore, in the present embodiment, the sensitivity acquisition unit 132 calculates the change rate β of the detection value with respect to the distance (clearance) at a plurality of detection positions. More specifically, as shown in FIGS. 11 and 12, predetermined clearances Xa and Xb (indicated as ΔXa and ΔXb in FIG. 11) and a detected value change amount ΔV in the clearances Xa and Xb, Based on this, the change ratio β = ΔV / (Xb−Xa) is calculated.

Here, as described above, the impedance Z <b> 1 in the configuration of the work-affected layer detection device 101 varies depending on the distance between the workpiece 2 and the magnetic sensor 10. Further, the coupling coefficient K and since there is a correlation between the value detected by the magnetic sensor 10, the experimental and the magnetic field analysis by the finite element method, the relationship between the coupling coefficient K _T at the rate of change of the detection value β and the specimen contacted The relationship between the coupling coefficient _KT and the impedance Z1 when the subject is in contact with the material property θ of the subject can be acquired in advance. Therefore, in the present embodiment, as shown in FIGS. 13 and 10, based on the above experiment and analysis, a correspondence table showing each relationship is created in advance, and the sensitivity of the magnetic sensor 10 is acquired. Also, Figure 13 and the corresponding table showing the relationship between the coupling coefficient K _T of time variation amount ΔV and the object contact detection values with respect to the amount of change in a predetermined clearance (Xb-Xa).

In the sensitivity acquisition step, the sensitivity acquisition unit 132 of the control device 130 changes the detection value ΔV according to the third frequency at the second detection position Xb with respect to the detection value according to the third frequency at the first detection position Xa. Is calculated (see FIG. 12). Then, the calculated change amount [Delta] V, based on the correspondence table of FIG. 13, to derive a coupling coefficient K _T upon the subject contact. Thus, the derived coupling coefficient K _T, it is possible to sensitivity of the magnetic sensor 10 that outputs a plurality of detection values corresponding to the third frequency to obtain a degree in either.

Next, the detected value V corresponding to the third frequency is substituted into [Equation 1] to calculate the impedance Z1. Then, the coupling coefficient K _T of the calculated impedance Z1 and the object upon contact, based on the correspondence table of FIG. 10, to derive the material characteristics theta. Here, the reference impedance Zstd is derived based on the preset reference coupling coefficient Kstd and the derived material characteristic θ and the correspondence table of FIG. Further, the derived reference impedance Zstd is substituted into [Equation 1] to calculate the reference output value Vstd. Then, the work-affected layer detection apparatus 101 performs a gain adjustment by calculating a correction amount so that the detection value V becomes equal to the reference output value Vstd as a correction step. Here, since the gain adjustment by the correction unit 33 of the control device 130 and the determination by the wear amount determination unit 34 are the same as those in the first embodiment, detailed description thereof is omitted.

(Effects of the processing damaged layer detection apparatus 101)
Even in such a configuration, the same effects as in the first embodiment can be obtained. Further, the sensitivity acquisition unit 132 of the control device 130 acquires the sensitivity of the magnetic sensor 10 based on the distance (clearance) and the detection values at the plurality of detection positions Xa and Xb. The magnetic sensor 10 is configured to be supplied with an excitation current set to a single third frequency by the supply unit 131 and to output detection values corresponding to the set frequencies at a plurality of detection positions. For a plurality of detection values output according to the third frequency of the excitation current supplied by the magnetic sensor 10, the behavior of the change in the detection value at the detection position on the separation side with respect to the detection value at the detection position on the proximity side to the workpiece 2 is Depending on the sensitivity of the magnetic sensor 10. That is, the sensitivity acquisition unit 32 can more accurately acquire the sensitivity of the magnetic sensor 10 based on the distances at the plurality of detection positions and the detection values output at the detection positions.

  Further, the control device 130 sensitivity acquisition unit 132 is configured to acquire the sensitivity of the magnetic sensor 10 based on the ratio β of the change in the detection value with respect to the distance at a plurality of detection positions. As described above, the behavior of the change in the detection value on the separation side with respect to the detection value on the proximity side of the workpiece 2 varies depending on the sensitivity of the magnetic sensor 10. Thus, with the above configuration, the sensitivity acquisition unit 32 can acquire the sensitivity of the magnetic sensor 10 with higher accuracy based on the change rate β.

<Modification of Second Embodiment>
In the present embodiment, the sensitivity acquisition unit 132 of the control device 130 calculates the change rate β of the detection value with respect to the distance (clearance) at a plurality of different detection positions. More specifically, the change ratio β = ΔV / (Xb−Xa) is calculated based on the predetermined clearances Xa and Xb and the detected value change ΔV in the clearances Xa and Xb.

  As described above, the sensitivity acquisition unit 132 sets the sections serving as the first and second detection positions Xa and Xb (clearances ΔXa and ΔXb). This section may be appropriately set for the reason that sensitivity is easily influenced by a difference in sensitivity among a plurality of detection values. Furthermore, a large number of detection values may be acquired, an approximate straight line may be calculated by the method of least squares, and the gradient may be used as the change rate β. Similarly, with respect to a large number of detection values, an average in a predetermined section or a tangent line in a specific clearance may be calculated as the above approximate straight line, and the inclination may be used as the change rate β. Even in such a configuration, the same effect can be obtained.

<Others>
In the first and second embodiments, in the sensitivity acquisition step of acquiring the sensitivity of the magnetic sensor 10, the plurality of detection values output in the moving step of separating the sensor body 11 from the workpiece 2 after detecting the work-affected layer are obtained. Based on this, the sensitivity of the magnetic sensor 10 is acquired. On the other hand, in the sensitivity acquisition step, the sensitivity of the magnetic sensor 10 is acquired based on a plurality of detection values output in the moving step of bringing the sensor body 11 closer to the workpiece 2 before detecting the work-affected layer. It may be a thing. Even in such a configuration, the same effect can be obtained. Moreover, it is good also considering the output several detected value in both the movement processes made to approach and separate said. As a result, it is possible to calculate the amount of change in sensitivity due to a single inspection for detecting the work-affected layer, and to determine the wear amount of the sensor head 12 and the like.

  Further, in the first and second embodiments, the processing deteriorated layer detection device to which the eddy current type inspection device and the eddy current type inspection method of the present invention are applied has been described as an example. In contrast, the eddy current inspection apparatus and eddy current inspection method of the present invention can be applied to various inspection apparatuses using eddy currents such as a flaw detection test apparatus. Even in such a configuration, the same effect can be obtained.

DESCRIPTION OF SYMBOLS 1,101: Processed layer detection apparatus, 2: Workpiece (subject), 3: Machine tool, 10: Magnetic sensor (sensor), 11: Sensor main body, 12: Sensor head, 13: Measuring apparatus, 14: Touch sensor, 14a: Spring 15: Sensor feed mechanism (moving means)
20: Rotation support part, 21: Drive wheel, 21a: Encoder, 22: Adjustment wheel 30, 130: Control device, 31, 131: Supply part (supply means)
32, 132: Sensitivity acquisition unit (sensitivity acquisition unit) 33: Correction unit (correction unit)
34: Wear amount determination unit (wear amount determination means)
T: threshold

Claims (9)

A sensor that induces an eddy current inside the detection body by an excitation current and outputs a detection value according to a change in the eddy current;
Supplying means for supplying the excitation current set to a predetermined frequency to the sensor;
Moving means for moving the sensor relative to the subject so that the distance between the subject and the sensor varies;
Sensitivity acquisition means for acquiring the sensitivity of the sensor based on the plurality of detection values output by the sensor at a plurality of detection positions with different distances;
Equipped with a,
The supply means supplies the excitation current set to a plurality of different frequencies to the sensor,
The sensor outputs each detection value corresponding to each set frequency at a plurality of detection positions, respectively.
The sensitivity acquisition means acquires the detection values at a plurality of the detection positions, and changes in the detection values detected at the plurality of detection positions using a reference frequency as a reference among the frequencies. , vortex characterized that you get the sensitivity of the sensor based on a rate of change that is calculated and the variation of the plurality of detection values detected in a plurality of the detection position by using other frequencies Current type inspection device. A sensor that induces an eddy current inside the detection body by an excitation current and outputs a detection value according to a change in the eddy current;
Supplying means for supplying the excitation current set to a predetermined frequency to the sensor;
Moving means for moving the sensor relative to the subject so that the distance between the subject and the sensor varies;
Sensitivity acquisition means for acquiring the sensitivity of the sensor based on the plurality of detection values output by the sensor at a plurality of detection positions with different distances;
Equipped with a,
The supply means supplies the excitation current set to a plurality of different frequencies to the sensor,
The sensor outputs each detection value corresponding to each set frequency at a plurality of detection positions, respectively.
The sensitivity acquisition means acquires the detection values at a plurality of the detection positions, and uses a plurality of detection values detected at the plurality of detection positions using a reference frequency as a reference among the frequencies, An approximate straight line indicating a relationship with a plurality of detected values detected at a plurality of detection positions using a frequency is calculated, and the sensitivity of the sensor is obtained based on a rate of change indicated by an inclination of the approximate straight line. An eddy current inspection apparatus characterized by the above. In claim 1 or 2,
An eddy current inspection apparatus, further comprising: a wear amount determination unit that determines a wear amount of a tip portion of the sensor that contacts the subject based on the sensitivity of the sensor acquired by the sensitivity acquisition unit. A sensor that induces an eddy current inside the detection body by an excitation current and outputs a detection value according to a change in the eddy current;
Supplying means for supplying the excitation current set to a predetermined frequency to the sensor;
Moving means for moving the sensor relative to the subject so that the distance between the subject and the sensor varies;
Sensitivity acquisition means for acquiring the sensitivity of the sensor based on the plurality of detection values output by the sensor at a plurality of detection positions with different distances;
Wear amount determination means for determining the wear amount of the tip of the sensor that contacts the subject based on the sensitivity of the sensor acquired by the sensitivity acquisition means;
An eddy current type inspection apparatus comprising: In claim 4 ,
The supply means supplies the excitation current set to a plurality of different frequencies to the sensor,
The sensor outputs each detection value corresponding to each set frequency at a plurality of detection positions, respectively.
The eddy current inspection apparatus, wherein the sensitivity acquisition means acquires the sensitivity of the sensor based on the detection values at a plurality of detection positions. In claim 4 ,
The supply means supplies the excitation current set to a single frequency to the sensor,
The sensor outputs the detection value according to a set frequency at each of the plurality of detection positions,
The sensitivity acquisition means acquires the sensitivity of the sensor based on a rate of change of the detection value with respect to the distance at a plurality of detection positions. In any one of Claims 1-6 ,
An eddy current inspection apparatus, further comprising a correction unit that corrects the sensitivity of the sensor based on the sensitivity of the sensor acquired by the sensitivity acquisition unit and a preset reference sensitivity. In any one of Claims 1-7,
The eddy current inspection apparatus according to claim 1, wherein the sensor outputs a detection value corresponding to a work-affected layer, a flaw, and quenching of the workpiece as the object. A sensor that induces an eddy current inside the subject by an excitation current and outputs a detection value according to a change in the eddy current;
A supply step of supplying the exciting current set to a predetermined frequency to the sensor;
A moving step of moving the sensor relative to the subject such that the distance between the subject and the sensor varies;
A sensitivity acquisition step of acquiring the sensitivity of the sensor based on the plurality of detection values output by the sensor at a plurality of detection positions at different distances;
Equipped with a,
The supply step supplies the excitation current set to a plurality of different frequencies to the sensor,
The sensor outputs each detection value corresponding to each set frequency at a plurality of detection positions, respectively.
The sensitivity acquisition step acquires the detection values at a plurality of detection positions, and uses a reference frequency as a reference among the frequencies to detect a plurality of change amounts of the detection values at the detection positions. , vortex characterized that you get the sensitivity of the sensor based on a rate of change that is calculated and the variation of the plurality of detection values detected in a plurality of the detection position by using other frequencies Current type inspection method.

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