JP2009031257A - Apparatus and method for detecting state of metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid reductions in detection accuracy due to mutual interference and shorten a response period when the state of metal is to be highly accurately detected through the use of a first oscillation circuit (a first detection coil) and a second oscillation circuit (a second detection coil). <P>SOLUTION: An apparatus for detecting the state of a metal is provided with the first oscillation circuit 2 for generating a phase shift in oscillation waves according to an inductance change of the first detection coil L1 and the second oscillation circuit 3 for generating a phase shift in oscillation waves according to an inductance change of the second detection coil L2. When the state of metal is to be detected on the basis of the phase shifts of oscillation waves outputted from both oscillation circuits 2 and 3, the first oscillation circuit 2 and the second oscillation circuit 3 are alternately driven in order to avoid mutual interference. At the time of the termination of the driving of the first oscillation circuit 2 and at the time of the termination of the driving of the second oscillation circuit 3, the difference between the newest measured time (phase shift) on the first oscillation circuit 2 and the newest measured time (phase shift) on the second oscillation circuit 3 is determined and outputted. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a metal state detection device and a metal state detection method for detecting a metal state, and in particular, a metal state detection device and a metal state detection method suitable for detecting a state of metal stress, fatigue, damage, defect, material, and the like. About.

  There are known a metal state detection device and a metal state detection method for detecting a metal state based on a magnetic property change (such as a magnetic permeability change) of the metal. For example, a magnetostrictive torque sensor that detects torque (torsional stress) of a rotating shaft by utilizing the inverse effect of magnetostriction has already been put into practical use in a torque assist system of an electrically assisted bicycle.

A conventional magnetostrictive torque sensor imparts magnetic anisotropy of + 45 ° and −45 ° to two outer peripheral regions of a rotating shaft, and arranges a pair of detection coils facing each outer peripheral region. The differential voltage generated between the two detection coils is output. That is, when torque is applied to the rotating shaft, the permeability of each outer peripheral region changes inversely due to the inverse effect of magnetostriction, so that a differential voltage is generated between the detection coils, and an output proportional to the torque is obtained (for example, (See Patent Documents 1 and 2).
JP 7-83769 A Japanese Patent Laid-Open No. 11-37863

  However, in the conventional metal state detection device, a slight differential voltage generated between the detection coils is detected using a bridge circuit or the like, and this differential voltage is amplified by the amplifier circuit. It was easy and high-precision detection was difficult.

In view of the above circumstances, the metal state detection device of the present invention created for the purpose of solving these problems is a metal state detection device that detects the state of a metal, and according to a change in the state of the metal. The first detection coil and the second detection coil that are arranged so that the inductance changes, and autonomously oscillate at a predetermined reference frequency, and cause a phase shift in the oscillation wave according to the inductance change of the first detection coil Output from the first oscillation circuit, the second oscillation circuit that autonomously oscillates at a predetermined reference frequency and causes a phase shift in the oscillation wave according to the inductance change of the second detection coil, and the first oscillation circuit An oscillation wave count process is performed to count a plurality of oscillation waves and determine whether or not the count number has reached a predetermined number N, and based on the time measurement required for the oscillation wave count process. A first phase deviation detecting means for detecting a phase deviation of the accumulated oscillation wave and a plurality of oscillation waves output from the second oscillation circuit, and whether or not the count number reaches a predetermined number N A second phase shift detecting means for detecting a phase shift of the accumulated oscillation wave based on a time measurement required for the oscillation wave count process, and a measurement related to the first oscillation circuit Difference detection means for obtaining and outputting the difference between the time and the measurement time relating to the second oscillation circuit, and the first oscillation circuit and the second oscillation circuit are driven alternately to detect the difference in order to avoid mutual interference The means obtains a difference between the latest measurement time for the first oscillation circuit and the latest measurement time for the second oscillation circuit at the end of driving the first oscillation circuit and at the end of driving of the second oscillation circuit, respectively. It is characterized by outputting.
According to such a metal state detection device, the state of the metal can be detected with high accuracy. That is, in the oscillation wave output from the oscillation circuit as described above, the metal state (permeability change, etc.) appears clearly as a phase shift, and the phase shift in the oscillation wave is the same as the number of oscillation waves. Since it is accumulated, it is possible to detect a phase shift that changes according to the state of the metal with high accuracy. Further, since the phase shift of the oscillation wave is measured as the time required for the oscillation wave counting process, high-resolution measurement can be performed using an inexpensive digital circuit. In other words, the resolution of the metal state detection in the present invention is determined by the counter speed for time measurement and does not depend on the reference frequency of the oscillation circuit. Therefore, the high-resolution metal is optimized while optimizing the reference frequency of the oscillation circuit according to the detection target. State detection can be performed. Further, since the difference between the measurement time (phase shift) related to the first oscillation circuit and the measurement time (phase shift) related to the second oscillation circuit is detected, the temperature error and the displacement error can be easily eliminated. Further, since the first oscillation circuit and the second oscillation circuit are driven alternately, it is possible to avoid a decrease in detection accuracy due to mutual interference. Moreover, since the detection area of the first detection coil and the detection area of the second detection coil can be arbitrarily set without considering mutual interference, it is easy to optimize the detection area according to the use conditions. Also, at the end of driving the first oscillation circuit and at the end of driving the second oscillation circuit, obtain and output the difference between the latest measurement time for the first oscillation circuit and the latest measurement time for the second oscillation circuit, respectively. As a result, the response cycle is shortened and good responsiveness can be obtained. That is, instead of obtaining the difference at the time when the driving of the first oscillation circuit and the second oscillation circuit is completed, the difference is obtained every time the driving of each oscillation circuit is completed. It can be shortened to 2.
Also, the metal state detection method of the present invention is a metal state detection method for detecting a metal state, wherein the first detection coil and the second detection coil are arranged so that the inductance changes according to the change in the metal state. And a first oscillation circuit that oscillates autonomously at a predetermined reference frequency and causes a phase shift in the oscillation wave according to the inductance change of the first detection coil, and oscillates autonomously at a predetermined reference frequency, A second oscillation circuit that causes a phase shift in the oscillation wave in accordance with an inductance change of the second detection coil, and counts a plurality of oscillation waves output from the first oscillation circuit, and the count number is a predetermined number N Oscillating wave count processing is performed to determine whether or not the oscillation frequency has reached the second oscillation circuit based on the time measurement required for the oscillating wave counting processing. Counts a plurality of oscillation waves output from the output, performs an oscillation wave count process to determine whether or not the count number has reached a predetermined number N, and accumulates based on the time measurement required for the oscillation wave count process In detecting the phase shift of the generated oscillation wave and obtaining and outputting the difference between the measurement time of the first oscillation circuit and the measurement time of the second oscillation circuit, the first oscillation circuit and the second oscillation circuit are connected to each other. In order to avoid interference, drive alternately, at the end of driving the first oscillation circuit and at the end of driving the second oscillation circuit, respectively, the latest measurement time for the first oscillation circuit and the latest for the second oscillation circuit, respectively. It is characterized in that a difference from the measurement time is obtained and output.
According to such a metal state detection method, the metal state can be detected with high accuracy. That is, in the oscillation wave output from the oscillation circuit as described above, the metal state (permeability change, etc.) appears clearly as a phase shift, and the phase shift in the oscillation wave is the same as the number of oscillation waves. Since it is accumulated, it is possible to detect a phase shift that changes according to the state of the metal with high accuracy. Further, since the phase shift of the oscillation wave is measured as the time required for the oscillation wave counting process, high-resolution measurement can be performed using an inexpensive digital circuit. In other words, the resolution of the metal state detection in the present invention is determined by the counter speed for time measurement and does not depend on the reference frequency of the oscillation circuit. Therefore, the high-resolution metal is optimized while optimizing the reference frequency of the oscillation circuit according to the detection target. State detection can be performed. Further, since the difference between the measurement time (phase shift) related to the first oscillation circuit and the measurement time (phase shift) related to the second oscillation circuit is detected, the temperature error and the displacement error can be easily eliminated. Further, since the first oscillation circuit and the second oscillation circuit are driven alternately, it is possible to avoid a decrease in detection accuracy due to mutual interference. In addition, since the detection area of the first detection coil and the detection area of the second detection coil can be arbitrarily set without considering mutual interference, it is easy to optimize the detection area according to use conditions. Also, at the end of driving the first oscillation circuit and at the end of driving the second oscillation circuit, obtain and output the difference between the latest measurement time for the first oscillation circuit and the latest measurement time for the second oscillation circuit, respectively. As a result, the response cycle is shortened and good responsiveness can be obtained. That is, instead of obtaining the difference at the time when the driving of the first oscillation circuit and the second oscillation circuit is completed, the difference is obtained every time the driving of each oscillation circuit is completed. It can be shortened to 2.

  Next, embodiments of the present invention will be described with reference to the drawings. However, the waveform shown in the drawing includes an actual detection waveform and a simulation waveform.

[First embodiment]
FIG. 1 is a block diagram showing a configuration of a metal state detection device (magnetostrictive torque sensor) according to the first embodiment of the present invention. The metal state detection device shown in this figure is a magnetostrictive torque sensor 1 that detects the torque of a rotating shaft S (or a stationary shaft) using the inverse effect of magnetostriction generated on the shaft surface, and includes a first detection coil L1, A second detection coil L2, a first oscillation circuit 2, a second oscillation circuit 3, and a detection circuit 4 are provided.

  The first detection coil L1 is arranged to detect a magnetic permeability change in the first direction (for example, + 45 ° direction) on the shaft surface, and detects the magnetic permeability change as a change in inductance. The second detection coil L2 is arranged to detect a change in permeability in the second direction (for example, −45 ° direction) on the shaft surface, and detects the change in permeability as a change in inductance.

  The detection coils L1 and L2 of this embodiment include a core formed of a high magnetic permeability material and a coil wound around the core in order to limit the detection region and the detection direction on the shaft surface. Has been. Specifically, a coil is wound around U-shaped cores 2a and 3a made of a high permeability material such as ferrite, permalloy, and amorphous, and both ends of U-shaped cores 2a and 3a are close to the shaft surface. By doing so, a closed magnetic circuit is formed with the shaft surface. Thereby, it is possible to form magnetic paths in the first direction and the second direction in a limited region of the shaft surface, and to detect a change in permeability in the magnetic path.

  The first oscillation circuit 2 is configured to autonomously oscillate at a predetermined reference frequency and to cause a phase shift in the oscillation wave in accordance with an inductance change of the first detection coil L1. Further, the second oscillation circuit 3 is configured to autonomously oscillate at a predetermined reference frequency and to cause a phase shift in the oscillation wave in accordance with an inductance change of the second detection coil L2. For example, if the detection coils L1 and L2 are arranged in the feedback circuit of the Schmitt oscillation circuit, it is possible to configure the oscillation circuits 2 and 3 in which a phase shift occurs in the oscillation wave according to the inductance change of the detection coils L1 and L2.

  The Schmitt oscillation circuit is an oscillation circuit that uses the hysteresis characteristics of the Schmitt inverter INV. The Schmitt inverter INV, the capacitor C connected to the input side of the Schmitt inverter INV, and the output of the Schmitt inverter INV are input to the Schmitt inverter INV. And a resistance element interposed in the feedback circuit.

In the Schmitt oscillation circuit in the initial state, since no charge is accumulated in the capacitor C, the voltage across the capacitor C is 0V. At this time, the Schmitt inverter INV has an output H level (5 V) because the input side voltage Vin is equal to or lower than _VL . When the output side voltage Vout of the Schmitt inverter INV is 5V, a current flows to the input side of the Schmitt inverter INV via the feedback circuit 2a, so that electric charges are gradually accumulated in the capacitor C, and the voltage at both ends thereof increases. When the input side voltage Vin of the Schmitt inverter INV reaches _VH , the output of the Schmitt inverter INV is switched to the L level (0 V). When the output side voltage Vout of the Schmitt inverter INV becomes 0V, the capacitor C is discharged, and the input side voltage Vin of the Schmitt inverter INV gradually decreases. When the input voltage Vin of the Schmitt inverter INV drops to _VL , the output of the Schmitt inverter INV is switched to the H level.

By repeating the above operation, a rectangular wave having a predetermined frequency is obtained from the output side of the Schmitt inverter INV. The Schmidt oscillation circuit of the oscillation frequency f (= 1 / T) is determined by the energy storage time period _{T H} discharge period _{T L,} the electric storage period _{T H} and the discharging period _{T L} is determined by the constants of the capacitor C and a resistor element. Therefore, if the detection coils L1 and L2 are arranged in the feedback circuit as resistance elements, it is possible to cause a phase shift in the oscillation wave of the Schmitt oscillation circuit according to the inductance change of the detection coils L1 and L2.

  Of course, the oscillation circuit of the present invention is not limited to the Schmitt oscillation circuit. If the oscillation circuit generates a phase shift in the oscillation wave according to the inductance change of the detection coils L1, L2, the CR oscillation circuit, LC An oscillation circuit, a crystal oscillation circuit, or the like may be used.

  The detection circuit 4 is configured using, for example, a microcomputer (one-chip microcomputer) including a CPU, a ROM, a RAM, an I / O, and the like, and performs a torque detection process to be described later according to a program written in the ROM. Note that the detection circuit 4 may be configured by a plurality of microcomputers, or may be configured by one or a plurality of ICs.

  The detection circuit 4 counts a plurality of oscillation waves output from the first oscillation circuit 2, performs an oscillation wave count process for determining whether or not the count number has reached a predetermined number N, and performs the oscillation wave count process. The first direction permeability detecting means (first phase deviation detecting means) for detecting the change in permeability in the first direction and the plurality of oscillation waves output from the second oscillation circuit 3 are counted based on the time required for Then, an oscillation wave count process for determining whether or not the count number has reached a predetermined number N is performed, and a second change in the permeability in the second direction is detected based on the time required for the oscillation wave count process. Directional permeability detecting means (second phase shift detecting means) and torque detecting means (difference detecting means) for detecting the torque of the rotating shaft S based on the difference between the magnetic permeability in the first direction and the magnetic permeability in the second direction. ).

  In this way, the torque detection accuracy of the magnetostrictive torque sensor 1 can be improved. That is, in the oscillating wave output from the first oscillating circuit 2 and the second oscillating circuit 3 configured as described above, the change in the magnetic permeability of the shaft surface clearly appears as a phase shift, Since the phase shift is accumulated by the number of oscillation waves, it is possible to detect the change in permeability in the first direction and the second direction with high accuracy, and to detect the torque of the rotating shaft S with high accuracy from the difference. Become. Also, the number of oscillation waves output from the oscillation circuits 2 and 3 is counted, and an oscillation wave count process is performed to determine whether or not the count number has reached a predetermined number N, which is necessary for the oscillation wave count process. Since the phase shift (permeability change) of the oscillation wave accumulated based on time is measured, the phase shift component of the oscillation wave can be measured with high accuracy using an inexpensive digital circuit. Moreover, since the resolution is determined by the counter speed for time measurement and does not depend on the reference frequency of the oscillation circuits 2 and 3, high-resolution stress can be achieved while optimizing the reference frequency of the oscillation circuits 2 and 3 according to the detection target. Detection can be performed.

  The first oscillation circuit 2 and the second oscillation circuit 3 are driven alternately to avoid mutual interference. In this way, it is possible to avoid a decrease in detection accuracy due to mutual interference. In addition, since the detection area of the first detection coil L1 and the detection area of the second detection coil L2 can be arbitrarily set without considering mutual interference, it is easy to optimize the detection area according to use conditions. It becomes.

  Further, when the first oscillation circuit 2 and the second oscillation circuit 3 are alternately driven, the detection circuit 4 has the first oscillation circuit at the end of the driving of the first oscillation circuit 2 and at the end of the driving of the second oscillation circuit 3, respectively. The difference between the latest measurement time according to 2 and the latest measurement time according to the second oscillation circuit 3 is obtained and output. In this way, the response cycle is shortened and good responsiveness can be obtained. That is, the difference is not obtained when the driving of the first oscillation circuit 2 and the second oscillation circuit 3 is completed, but is obtained every time the driving of the oscillation circuits 2 and 3 is completed. The period can be shortened to about ½.

  The first detection coil L1 and the second detection coil L2 preferably form a closed magnetic path with the shaft surface in order to limit the detection region and the detection direction on the shaft surface. That is, in the magnetostrictive torque sensor 1 of the present invention, the phase shift of the oscillating wave corresponding to the torque is accumulated and detected by the number of oscillating waves, so that an error component included in the phase shift of the oscillating wave is also accumulated. However, by limiting the detection region and detection direction on the shaft surface, the SN ratio can be increased, so that accumulated error components can be suppressed and detection accuracy can be improved. Further, since the detection direction can be limited on the detection coils L1 and L2 side, it is not necessary to process a striped pattern with grooves, slits, thin films, or the like on the shaft surface. As a result, the torque detection according to the present invention can be applied even to the rotating shaft S in which these processes are not allowed.

  The shaft surface of the rotating shaft S for detecting torque by the magnetostrictive torque sensor 1 is preferably a magnetostrictive film 5 formed by plating. For example, a magnetostrictive film 5 made of a nickel alloy is plated over the entire circumference of a part or the entire region of the rotating shaft S. In this way, not only can the torque be detected with high accuracy based on the inverse effect of magnetostriction in the magnetostrictive film 5 in accordance with the torque, but also hysteresis in torque detection can be suppressed. Moreover, in the magnetostrictive torque sensor 1 of the present invention, sufficient detection accuracy can be obtained even with the magnetostrictive film 5 formed by the plating method. Compared to the case of forming a magnetostrictive film, not only can the cost be reduced significantly, but also high-accuracy torque detection can be performed for existing members (including resin) that have been plated with nickel.

  Next, the phase shift accumulation action of the oscillation wave in the present invention will be described with reference to FIGS.

  FIG. 2 is an explanatory diagram showing the phase shift accumulation action of the oscillation wave (enlarged detection waveform start end), and FIG. 3 is an explanatory view showing the phase shift accumulation action of the oscillation wave (enlargement of the detection waveform end section). The waveforms shown in these figures are the output waveforms of the oscillation circuits 2 and 3 in one detection process. The number of oscillation waves output from the oscillation circuits 2 and 3 is counted, and the count number is set to a predetermined number N. Oscillation wave count processing is performed to determine whether or not the oscillation wave has been reached, and when measuring the phase deviation of the accumulated oscillation wave based on the time required for the oscillation wave count processing, the oscillation wave count in the oscillation wave count processing is counted. The waveform when the number N is 100 is shown. The upper waveform indicates a case where no torque is applied to the rotation axis S, and the lower waveform indicates a case where torque is applied to the rotation axis S. As is clear from these figures, since the phase shift is not accumulated so much at the beginning of the detected waveform, that is, at the stage where the number N of oscillation waves in the oscillation wave count processing is small, the difference is not clear ( It can be seen that when the count number N increases, the phase shift of the oscillation wave is accumulated and the difference becomes clear, so that the phase shift can be easily measured (see FIG. 3). Since the phase shift of the oscillation wave increases in proportion to the torque acting on the rotation axis S, the torque acting on the rotation axis S can be measured with high accuracy based on the phase shift of the oscillation wave. Become. Further, since the phase shift of the oscillation wave output from each oscillation circuit 2 and 3 appears in a contradictory direction based on the inverse effect of magnetostriction, it is only possible to detect the torque amount and torque polarity of the rotating shaft S based on the difference. Therefore, it is possible to obtain a detection value in which the temperature error and the displacement error are offset.

  Next, a specific detection processing procedure of the detection circuit 4 will be described with reference to FIGS.

  In the torque detection process shown in FIG. 4, first, after initial setting (S11: including initial value setting of the oscillation wave count number N), the count number change process (S12) is performed to determine the previous detection direction. (S13). Here, when it is determined that the previous detection direction is the second direction (or none), the first direction permeability detection process (S14: first phase shift detection means) is executed, and the previous detection direction is the first direction. If it is determined that the direction is one direction, a second direction permeability detection process (S15: second phase shift detection means) is executed. Thereafter, the latest first direction permeability detection value (measurement time according to the first oscillation circuit 2) obtained in the permeability detection process (S14, S15) and the latest second direction permeability detection value (second oscillation circuit). 3 is calculated (S16: difference detection means), and the calculated difference is converted into a predetermined detection signal format and output (S17), thereby completing one torque detection process. .

  In the count number changing process shown in FIG. 5, first, the input of the count number change signal is determined (S21). If the determination result is YES, the oscillation wave count number N included in the count number change signal is read (S22). In accordance with this, the oscillation wave count number N is changed (S23).

  In the first direction magnetic permeability detection process shown in FIG. 6, after the drive of the first oscillation circuit 2 is started (S31), the counter clear process (S32), the oscillation wave count process (S33, S34), and the time measurement process (S35) is executed, and then the driving of the first oscillation circuit 2 is stopped (S36). The counter clear process is a process for clearing the oscillation wave counter and the time measurement counter (S32). The oscillation wave counting process is a process for counting the number of oscillation waves output from the first oscillation circuit 2 (S33) and determining whether the count number has reached a predetermined number N (S34). . The time measurement process is a process of reading a time measurement counter value (first-direction magnetic permeability detection value) when the count number of oscillation waves reaches N (S35).

  In the second direction magnetic permeability detection process shown in FIG. 7, after the driving of the second oscillation circuit 3 is started (S41), the counter clear process (S42), the oscillation wave count process (S43, S44), and the time measurement process (S45) is executed, and then the driving of the second oscillation circuit 3 is stopped (S46). The counter clear process is a process for clearing the oscillation wave counter and the time measurement counter (S42). The oscillation wave counting process is a process for counting the number of oscillation waves output from the second oscillation circuit 3 (S43) and determining whether or not the count number has reached a predetermined number N (S44). . The time measurement process is a process of reading a time measurement counter value (second-direction magnetic permeability detection value) when the count number of oscillation waves reaches N (S45).

  FIG. 8 shows the response periods of the comparative example (A) and the present example (B). That is, when the first oscillation circuit 2 and the second oscillation circuit 3 are alternately driven, the latest oscillation circuit 2 related to the first oscillation circuit 2 is respectively obtained when the first oscillation circuit 2 is driven and when the second oscillation circuit 3 is driven. The response period of the present embodiment, which calculates and outputs the difference between the measurement time and the latest measurement time related to the second oscillation circuit 3, is the difference when the driving of the first oscillation circuit 2 and the second oscillation circuit 3 is completed. It can be seen that the response cycle of the comparative example obtained and output is shortened to about ½. Note that when the difference processing is started when the driving of one oscillation circuit is stopped, the other oscillation circuit is started to perform the difference processing and the phase shift detection processing related to the other oscillation circuit in parallel. . In this way, the response cycle can be further shortened.

  According to the present embodiment configured as described above, the magnetostrictive torque sensor 1 detects the torque of the rotating shaft S by utilizing the inverse effect of magnetostriction generated on the shaft surface, and is transparent in the first direction on the shaft surface. A first detection coil L1 that is arranged to detect a change in magnetic permeability and detects the change in permeability as a change in inductance, and is arranged to detect a change in permeability in the second direction on the shaft surface. A second detection coil L2 that detects the change of the first detection circuit, a first oscillation circuit 2 that oscillates autonomously at a predetermined reference frequency, and causes a phase shift in the oscillation wave in accordance with an inductance change of the first detection coil L1, A second oscillation circuit 3 that autonomously oscillates at a predetermined reference frequency and generates a phase shift in the oscillation wave in accordance with a change in inductance of the second detection coil L2, and a first oscillation circuit A plurality of oscillation waves output from 2 are counted, and an oscillation wave count process is performed to determine whether or not the count number has reached a predetermined number N. Based on the time required for the oscillation wave count process, Detecting a change in permeability in one direction, counting a plurality of oscillation waves output from the second oscillation circuit 3, and performing an oscillation wave count process for determining whether or not the count number has reached a predetermined number N; Based on the time required for the oscillation wave counting process, a change in the magnetic permeability in the second direction is detected, and based on the difference between the magnetic permeability in the first direction and the magnetic permeability in the second direction, the torque of the rotating shaft S is calculated. Since the detection circuit 4 for detection is provided, torque detection accuracy can be improved.

  That is, in the oscillating wave output from the first oscillating circuit 2 and the second oscillating circuit 3 configured as described above, the change in the magnetic permeability of the shaft surface clearly appears as a phase shift, Since the phase shift is accumulated by the number of oscillation waves, it is possible to detect the change in permeability in the first direction and the second direction with high accuracy, and to detect the torque of the rotating shaft S with high accuracy from the difference. Become. Also, the number of oscillation waves output from the oscillation circuits 2 and 3 is counted, and an oscillation wave count process is performed to determine whether or not the count number has reached a predetermined number N, which is necessary for the oscillation wave count process. Since the phase shift (permeability change) of the oscillation wave accumulated based on time is measured, the phase shift component of the oscillation wave can be measured with high accuracy using an inexpensive digital circuit. Moreover, since the resolution is determined by the counter speed for time measurement and does not depend on the reference frequency of the oscillation circuits 2 and 3, high-resolution stress can be achieved while optimizing the reference frequency of the oscillation circuits 2 and 3 according to the detection target. Detection can be performed.

  Further, since the first oscillation circuit 2 and the second oscillation circuit 3 are driven alternately in order to avoid mutual interference, it is possible to avoid a decrease in detection accuracy due to mutual interference. In addition, since the detection area of the first detection coil L1 and the detection area of the second detection coil L2 can be arbitrarily set without considering mutual interference, it is easy to optimize the detection area according to use conditions. It becomes.

  Further, when the first oscillation circuit 2 and the second oscillation circuit 3 are alternately driven, the detection circuit 4 has the first oscillation circuit at the end of the driving of the first oscillation circuit 2 and at the end of the driving of the second oscillation circuit 3, respectively. Since the difference between the latest measurement time according to 2 and the latest measurement time according to the second oscillation circuit 3 is obtained and output, the response cycle is shortened and good responsiveness is obtained. That is, the difference is not obtained when the driving of the first oscillation circuit 2 and the second oscillation circuit 3 is completed, but is obtained every time the driving of the oscillation circuits 2 and 3 is completed. The period can be shortened to about ½.

[Second Embodiment]
Next, a metal state detection device (magnetostrictive torque sensor) according to a second embodiment of the present invention will be described with reference to FIGS. However, about the part which is common with 1st embodiment, the same code | symbol as 1st embodiment is attached | subjected and description of 1st embodiment is used.

  As shown in FIG. 9, the magnetostrictive torque sensor 11 according to the second embodiment is different from the first embodiment in that each oscillation circuit 2, 3 includes a plurality of detection coils L1, L2. More specifically, the first oscillation circuit 2 includes a plurality of (for example, four) first detection coils L1 connected in series (or parallel), and the second oscillation circuit 3 is in series (or parallel). A plurality of (for example, four) second detection coils L2 connected to the. In this way, by arranging a plurality of first detection coils L1 and second detection coils L2 on the shaft surface, temperature and material variations existing on the shaft surface, and further, the detection coils L1, L2 and the shaft surface Variation in the gap between the two can be averaged, so that a decrease in detection accuracy due to these error factors can be avoided.

  As shown in FIGS. 10 and 11, the plurality of first detection coils L <b> 1 and the plurality of second detection coils L <b> 2 are preferably arranged so as to be aligned on the same circumference of the rotation axis S. In this way, not only can the temperature and material variations existing in the circumferential direction of the shaft surface, and also the gap fluctuation between the detection coils L1, L2 and the shaft surface, etc. be averaged, It is possible to minimize the influence of the temperature gradient existing in the axial direction and to avoid a decrease in detection accuracy due to these error factors. The plurality of first detection coils L1 and the plurality of second detection coils L2 are held at predetermined positions by the annular bobbin B. The bobbin B may be an integral type or a divided type.

  When the plurality of first detection coils L1 and the plurality of second detection coils L2 are arranged on the same circumference of the rotation axis S, as shown in FIG. An arrangement configuration in which the detection areas of the two detection coils L2 are alternated can be employed. In this way, it is possible not only to suppress the occurrence of an error due to the deviation between the detection region of the first detection coil L1 and the detection region of the second detection coil L2, but also to eliminate this error based on the rotation of the rotating shaft S. be able to.

  Further, when the plurality of first detection coils L1 and the plurality of second detection coils L2 are arranged on the same circumference of the rotation axis S, as shown in FIG. 10, the detection region of the first detection coil L1 Further, the arrangement may be such that the detection area of the second detection coil L2 overlaps. For example, the height dimensions of the first detection coil L1 and the second detection coil L2 are made different from each other and arranged so as to intersect in plan view. By doing so, it is possible to prevent the occurrence of an error due to the deviation between the detection region of the first detection coil L1 and the detection region of the second detection coil L2.

[Third embodiment]
Next, a metal state detection device (tensile / compressive stress sensor) according to a third embodiment of the present invention will be described with reference to FIG. However, about the part which is common with 1st embodiment, the same code | symbol as 1st embodiment is attached | subjected and description of 1st embodiment is used.

  The tensile / compressive stress sensor 21 shown in FIG. 12 has substantially the same configuration as the magnetostrictive torque sensor 1 of the first embodiment, but the arrangement direction of the first detection coil L1 and the second detection coil L2 is the second embodiment. This is different from the magnetostrictive torque sensor 1 of FIG. More specifically, the tensile / compressive stress sensor 21 is a metal state detection device that detects the tensile stress and the compressive stress of the stationary shaft S using the inverse effect of magnetostriction generated on the shaft surface. L1 is disposed so as to detect an axial permeability change on the shaft surface, and the second detection coil L2 is disposed so as to detect a circumferential permeability change on the shaft surface. That is, since the magnetic permeability in the axial direction changes inversely according to the tensile stress and the compressive stress, the first detection coil L1 can detect the tensile stress and the compressive stress satisfactorily. Further, since the magnetic permeability in the circumferential direction hardly changes depending on the tensile stress and the compressive stress, the temperature change of the first detection coil 1 can be performed by detecting the temperature change by the second detection coil L2.

  Of course, the present invention is not limited to the above-described embodiment, and any magnetostrictive torque sensor or tensile / compressive stress sensor may be used as long as it is a metal state detection device or a metal state detection method for detecting a metal state. In addition, it can be applied to state detection of metal fatigue, damage, defect, material, and the like.

It is a block diagram which shows the structure of the metal state detection apparatus (magnetostrictive torque sensor) which concerns on 1st embodiment of this invention. It is explanatory drawing which shows the phase shift accumulation effect | action (enlarged detection waveform start end part) of an oscillation wave. It is explanatory drawing which shows the phase shift accumulation effect | action (an enlarged detection waveform termination | terminus part) of an oscillation wave. It is a flowchart which shows the process sequence of the torque detection process in a detection circuit. It is a flowchart which shows the process sequence of the count number change process in a detection circuit. It is a flowchart which shows the process sequence of the 1st direction magnetic permeability detection process in a detection circuit. It is a flowchart which shows the process sequence of the 2nd direction magnetic permeability detection process in a detection circuit. (A) is a timing chart according to the comparative example, and (B) is a timing chart according to the embodiment. It is a block diagram which shows the structure of the metal state detection apparatus (magnetostrictive torque sensor) which concerns on 2nd embodiment of this invention. (A) is an expanded plan view showing a first arrangement example of detection coils, and (B) is a side view showing a first arrangement example of detection coils. (A) is a development top view showing the 2nd example of arrangement of a detection coil, and (B) is a side view showing the 2nd example of arrangement of a detection coil. It is a block diagram which shows the structure of the metal state detection apparatus (tensile / compressive stress sensor) which concerns on 3rd embodiment of this invention.

Explanation of symbols

1, 11 Magnetostrictive torque sensor 2 First oscillation circuit 3 Second oscillation circuit 4 Detection circuit L1 First detection coil L2 Second detection coil S Rotating shaft 21 Tension / compression stress sensor

Claims (2)

A metal state detection device for detecting a metal state,
A first detection coil and a second detection coil arranged such that the inductance changes in accordance with a change in the state of the metal;
A first oscillation circuit that oscillates autonomously at a predetermined reference frequency and causes a phase shift in an oscillation wave in accordance with an inductance change of the first detection coil;
A second oscillation circuit that oscillates autonomously at a predetermined reference frequency and causes a phase shift in the oscillation wave in accordance with an inductance change of the second detection coil;
Counting a plurality of oscillating waves output from the first oscillating circuit, performing an oscillating wave counting process for determining whether or not the counted number has reached a predetermined number N, and measuring the time required for the oscillating wave counting process First, a first phase shift detecting means for detecting a phase shift of the accumulated oscillation wave,
Counts a plurality of oscillation waves output from the second oscillation circuit, performs an oscillation wave count process for determining whether or not the count number has reached a predetermined number N, and measures the time required for the oscillation wave count process. First, a second phase shift detecting means for detecting a phase shift of the accumulated oscillation wave,
A difference detecting means for obtaining and outputting a difference between the measurement time according to the first oscillation circuit and the measurement time according to the second oscillation circuit;
The first oscillation circuit and the second oscillation circuit are driven alternately in order to avoid mutual interference,
The difference detection means calculates the difference between the latest measurement time related to the first oscillation circuit and the latest measurement time related to the second oscillation circuit at the end of driving of the first oscillation circuit and at the end of driving of the second oscillation circuit, respectively. A metal state detection device characterized by obtaining and outputting. A metal state detection method for detecting a metal state,
A first detection coil and a second detection coil arranged such that the inductance changes in accordance with a change in the state of the metal;
A first oscillation circuit that oscillates autonomously at a predetermined reference frequency and causes a phase shift in an oscillation wave in accordance with an inductance change of the first detection coil;
A second oscillation circuit that oscillates autonomously at a predetermined reference frequency and generates a phase shift in the oscillation wave in accordance with an inductance change of the second detection coil is used.
Counting a plurality of oscillating waves output from the first oscillating circuit, performing an oscillating wave counting process for determining whether or not the counted number has reached a predetermined number N, and measuring the time required for the oscillating wave counting process First, detect the phase shift of the accumulated oscillation wave,
Counts a plurality of oscillation waves output from the second oscillation circuit, performs an oscillation wave count process for determining whether or not the count number has reached a predetermined number N, and measures the time required for the oscillation wave count process. First, detect the phase shift of the accumulated oscillation wave,
In obtaining and outputting the difference between the measurement time related to the first oscillation circuit and the measurement time related to the second oscillation circuit,
In order to avoid mutual interference, the first oscillation circuit and the second oscillation circuit are driven alternately,
Obtain and output the difference between the latest measurement time for the first oscillation circuit and the latest measurement time for the second oscillation circuit at the end of driving the first oscillation circuit and at the end of driving the second oscillation circuit, respectively. A metal state detection method characterized by the above.

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