JP2009281748A - Metal state detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid decline of detection accuracy caused by mutual interference, when detecting a metal state highly accurately by using the first oscillation circuit (the first detection coil) and the second oscillation circuit (the second detection coil). <P>SOLUTION: This device includes the first oscillation circuit 2 for generating a phase shift in an oscillation wave corresponding to an inductance change of the first detection coil L1, the second oscillation circuit 3 for generating a phase shift in an oscillation wave corresponding to an inductance change of the second detection coil L2, and a detection circuit 4 for detecting the metal state based on each phase shift of the oscillation waves output from both oscillation circuits 2, 3. When avoiding simultaneous oscillation from the first oscillation circuit 2 and the second oscillation circuit 3, each oscillation circuit 2, 3 is switched to an oscillation state and a non-oscillation state corresponding to signal input to each gate G (an AND gate, a Schmidt NAND gate or the like) carried by each oscillation circuit 2, 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a metal state detection device that detects a metal state, and more particularly, to a metal state detection device suitable for state detection of metal stress, fatigue, damage, defect, material, and the like.

  2. Description of the Related Art A metal state detection device that detects a metal state based on a change in magnetic characteristics (such as a change in magnetic permeability) of the metal is known. For example, a magnetostrictive torque sensor that detects torque (torsional stress) of a rotating shaft by utilizing the inverse effect of magnetostriction has 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 for detecting a metal state, 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 The first oscillation circuit and the second oscillation circuit include a detection circuit that detects a phase shift of the oscillation wave and a phase shift of the oscillation wave output from the second oscillation circuit and obtains a difference between the two. Each has a gate and can be switched between an oscillating state and a non-oscillating state according to the signal input to each gate, and the detection circuit inputs a contradictory signal to the gate of each oscillating circuit. Further, it is characterized in that the phase shift of the oscillation wave related to each oscillation circuit is detected alternately while avoiding simultaneous oscillation of both oscillation circuits. In this way, the state of the metal can be detected with high accuracy. That is, in the oscillating wave output from the oscillation circuit as described above, the metal state (permeability change, etc.) clearly appears as a phase shift (including frequency change and period change). Since the phase shift is not easily affected by noise, the metal state can be detected with high accuracy based on the phase shift of the oscillation wave. In addition, since the first oscillation circuit and the second oscillation circuit are prevented from simultaneous oscillation, it is possible to prevent mutual interference of magnetic fields generated from the respective detection coils, and to avoid a decrease in detection accuracy due to the alternate 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. In addition, since the first oscillation circuit and the second oscillation circuit are switched between the oscillation state and the non-oscillation state in accordance with the signal input to the gate, the switching can be performed at a higher speed than when switching at the power supply level. At the same time, it is possible to stably start oscillation, and as a result, it is possible to avoid a decrease in responsiveness due to alternate oscillation as much as possible.
The first oscillation circuit and the second oscillation circuit are both Schmitt oscillation circuits, and a Schmitt NAND gate constituting the Schmitt oscillation circuit is also used as the gate. In this way, the number of necessary gates can be reduced and the oscillation circuit can be configured simply.
The detection circuit counts a plurality of oscillation waves output from the first oscillation circuit, performs an oscillation wave count process for determining whether or not the count number has reached a predetermined number N, and outputs the oscillation wave count. Based on the time measurement required for the processing, the first phase shift detecting means for detecting the phase shift of the accumulated oscillation wave and the plurality of oscillation waves output from the second oscillation circuit are counted, and the count number is predetermined. Second phase shift detection means for performing an oscillation wave count process for determining whether or not the number N has been reached and detecting a phase shift of the accumulated oscillation wave based on a time measurement required for the oscillation wave count process; And a difference detecting means for obtaining a difference between a measurement time relating to the first oscillation circuit and a measurement time relating to the second oscillation circuit. In this way, detection accuracy can be further improved. That is, the phase shift in the oscillating wave is accumulated by the number of oscillating waves, and the accumulated phase shift is measured as time, so that highly accurate detection can be performed 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 circuit, it is possible to detect the metal state with high resolution while optimizing the reference frequency of the oscillation circuit according to the detection target. it can.

  Next, embodiments of the present invention will be described with reference to the drawings.

[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, it is configured by winding a coil around U-shaped cores 2a and 3a made of ferrite, and by bringing both ends of U-shaped cores 2a and 3a close to the shaft surface, A closed magnetic circuit is configured. 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 trigger circuit. For example, 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 connected to the Schmitt inverter INV. A feedback circuit for feeding back to the input side and a resistance element interposed in the feedback circuit are provided.

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 detects the phase shift of the oscillation wave output from the first oscillation circuit 2 and the phase shift of the oscillation wave output from the second oscillation circuit 2, and obtains a difference between the two. In this way, the torque of the rotating shaft S can be detected with high accuracy. That is, in the oscillation wave output from the first oscillation circuit 2 and the second oscillation circuit 3 configured as described above, the permeability change of the shaft surface becomes a phase shift (including frequency change and period change). It appears clearly, and the phase shift in the oscillating wave is not easily affected by noise, so the torque of the rotating shaft S can be detected with high accuracy based on the phase shift of the oscillating wave.

  The detection circuit 4 of the present embodiment 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, Based on the time required for the oscillating wave counting process, a first direction permeability detecting means (first phase deviation detecting means) for detecting a change in permeability in the first direction, and a plurality of outputs outputted from the second oscillation circuit 3 An oscillating wave is counted, and an oscillating wave counting process is performed to determine whether or not the count number has reached a predetermined number N. Based on the time required for the oscillating wave counting process, the permeability change in the second direction is determined. Second direction magnetic permeability detecting means (second phase deviation detecting means) for detecting, and torque 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. (Difference detection means).

  In this way, the torque detection accuracy of the magnetostrictive torque sensor 1 can be further improved. That is, the detection circuit 4 of the present embodiment accumulates the phase deviation in the oscillation wave by the number of oscillation waves and measures the accumulated phase deviation as time, so that accurate torque detection can be performed using an inexpensive digital circuit. It can be performed. 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 torque 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 restricted from simultaneous oscillation in order to avoid mutual interference of magnetic fields generated from the detection coils L1 and L2. For example, after the oscillation driving of the first oscillation circuit 2 is stopped after the oscillation drive of the first oscillation circuit 2 is stopped after the oscillation wave count processing related to the first oscillation circuit 2 is executed in a state where the oscillation drive of the second oscillation circuit 3 is stopped, 3 is executed, and thereafter the difference in measurement time required for each oscillation wave count process is obtained. 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.

  The first oscillating circuit 2 and the second oscillating circuit 3 each have a gate, and can be switched between an oscillating state and a non-oscillating state in accordance with a signal input to each gate. For example, in this embodiment, an AND gate G having an A input connected to the upstream side and a Y output connected to the downstream side is provided at the upstream position of the Schmitt inverter INV, and the B input of the AND gate G is set to “ By setting “H (1)”, the oscillation circuits 2 and 3 are oscillated, and by setting the B input of the AND gate G to “L (0)”, the oscillation circuits 2 and 3 are not oscillated. State. Then, the detection circuit 4 inputs a contradictory signal to the AND gate G of each of the oscillation circuits 2 and 3, thereby avoiding simultaneous oscillation of both the oscillation circuits 2 and 3 and relating to each of the oscillation circuits 2 and 3. The phase shift of the oscillation wave is detected alternately.

  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 (torque detection means) 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), first direction transparent Magnetic permeability detection processing (S13: first direction magnetic permeability detection means) and second direction magnetic permeability detection processing (S14: second direction magnetic permeability detection means) are executed in order. Then, the difference between the first direction permeability detection value and the second direction permeability detection value obtained in the permeability detection process (S13, S14) is calculated (S15), and the calculated difference (torque detection value) is predetermined. Is converted into a detection signal format and output (S16), one torque detection process is completed.

  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 permeability detection process shown in FIG. 6, after the oscillation 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 The process (S35) is executed, and then the oscillation drive 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 permeability detection process shown in FIG. 7, after the oscillation drive 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 The process (S45) is executed, and then the oscillation drive 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).

  According to the present embodiment configured as described, the magnetostrictive torque sensor 1 detects the torque of the rotating shaft S, and the first detection is arranged such that the inductance changes according to the torque of the rotating shaft S. A first oscillation circuit 2 that autonomously oscillates at a predetermined reference frequency and causes a phase shift in an oscillation wave in accordance with a change in inductance of the first detection coil L1, a predetermined oscillation frequency; A second oscillation circuit 3 that oscillates autonomously at the reference frequency and generates a phase shift in the oscillation wave according to the inductance change of the second detection coil L2, and a phase shift of the oscillation wave output from the first oscillation circuit 2 And a detection circuit 4 that detects a phase shift of the oscillation wave output from the second oscillation circuit 3 and obtains a difference between the two, and the first oscillation circuit 2 and the second oscillation circuit 3 respectively have AND gates. The oscillation circuit and the non-oscillation state can be switched according to the signal input to each AND gate G. The detection circuit 4 is contrary to the AND gate G of each oscillation circuit 2 and 3. By inputting the signal, the phase shift of the oscillation wave related to each oscillation circuit 2 and 3 is detected alternately while avoiding simultaneous oscillation of both oscillation circuits 2 and 3, so the torque of the rotating shaft S can be accurately detected Can be detected.

  That is, in the oscillation wave output from the oscillation circuits 2 and 3 as described above, the permeability change of the rotation axis S clearly appears as a phase shift, and the phase shift in the oscillation wave is influenced by noise. Since it is difficult to receive, the torque of the rotating shaft S can be detected with high accuracy based on the phase shift of the oscillation wave. In addition, since the first oscillation circuit 2 and the second oscillation circuit 3 avoid simultaneous oscillation, the mutual interference of the magnetic fields generated from the detection coils L1 and L2 is prevented, and the decrease in detection accuracy due to the alternate interference is avoided. be able to. 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. Become. Further, since the first oscillation circuit 2 and the second oscillation circuit 3 are switched between an oscillation state and a non-oscillation state in response to a signal input to the AND gate G, switching can be performed faster than when switching at the power supply level. As a result, oscillation can be started stably, and as a result, it is possible to avoid as much as possible a decrease in response due to alternate oscillation.

The detection circuit 4 counts a plurality of oscillation waves output from the first oscillation circuit 2 and performs an oscillation wave count process for determining whether or not the count number has reached a predetermined number N. Based on the time measurement required for the counting process, the first direction permeability detecting means for detecting the phase shift of the accumulated oscillation wave and the plurality of oscillation waves output from the second oscillation circuit 3 are counted, and the count An oscillating wave count process for determining whether or not the number has reached a predetermined number N is performed, and based on the time measurement required for the oscillating wave count process, a second direction transparent signal for detecting a phase shift of the accumulated oscillating wave is detected. Since the magnetic field detection means and the torque detection means for obtaining the difference between the measurement time for the first oscillation circuit 2 and the measurement time for the second oscillation circuit 3 are provided, the detection accuracy can be further improved. That is, the phase shift in the oscillating wave is accumulated by the number of oscillating waves, and the accumulated phase shift is measured as time, so that highly accurate torque detection can be performed using an inexpensive digital circuit. In addition, 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, the high-resolution metal is optimized while optimizing the reference frequency of the oscillation circuits 2 and 3 according to the detection target. State detection can be performed.
[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 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.

  As shown in FIG. 8, the magnetostrictive torque sensor 11 according to the second embodiment is similar to the first embodiment in that the first oscillation circuit and the second oscillation circuit 3 are Schmitt oscillation circuits. Instead of using the Schmitt inverter INV as in the embodiment, the Schmitt oscillation circuit is configured by using the Schmitt NAND gate G, and the B input of the Schmitt NAND gate G is set to “H (1)”. The circuits 2 and 3 are set in an oscillating state, and the B input of the Schmitt NAND gate G is set to “L (0)”, whereby the oscillating circuits 2 and 3 are set in a non-oscillating state. That is, since each of the oscillation circuits 2 and 3 is switched between the oscillation state and the non-oscillation state by using the Schmitt NAND gate G constituting the Schmitt oscillation circuit, the number of necessary gates is reduced and the oscillation circuits 2 and 3 are simplified. Can be configured.

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

  As shown in FIG. 9, the magnetostrictive torque sensor 21 according to the third embodiment is different from the above-described 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.

  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. 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.

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

  The tensile / compressive stress sensor 31 shown in FIG. 12 has substantially the same configuration as the magnetostrictive torque sensor 11 of the second 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 11 of FIG. More specifically, the tensile / compressive stress sensor 31 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 metal state detection device that detects a metal state is not limited to a magnetostrictive torque sensor or a tensile / compressive stress sensor. It can also be applied to state detection such as damage, defect and material.

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 setting 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. 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. It is a block diagram which shows the structure of the metal state detection apparatus (magnetostrictive torque sensor) which concerns on 3rd 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 4th embodiment of this invention.

Explanation of symbols

1, 11, 21 Magnetostrictive torque sensor 2 First oscillation circuit 3 Second oscillation circuit 4 Detection circuit 31 Tensile / compression stress sensor G AND gate, Schmitt NAND gate INV Schmitt inverter L1 First detection coil L2 Second detection coil S Rotation axis

Claims (3)

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;
A detection circuit that detects a phase shift of the oscillation wave output from the first oscillation circuit and a phase shift of the oscillation wave output from the second oscillation circuit and obtains a difference between the two,
Each of the first oscillation circuit and the second oscillation circuit has a gate, and can switch between an oscillation state and a non-oscillation state according to a signal input to each gate.
The detection circuit is characterized by alternately detecting a phase shift of an oscillation wave related to each oscillation circuit while avoiding simultaneous oscillation of both oscillation circuits by inputting a contradictory signal to the gate of each oscillation circuit. Metal state detection device.   2. The metal state according to claim 1, wherein each of the first oscillation circuit and the second oscillation circuit is a Schmitt oscillation circuit, and a Schmitt NAND gate constituting the Schmitt oscillation circuit is also used as the gate. Detection device. The detection circuit includes:
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,
The metal state detection device according to claim 1, further comprising difference detection means for obtaining a difference between a measurement time relating to the first oscillation circuit and a measurement time relating to the second oscillation circuit.

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