JP6451262B2 - Magnet characteristic measuring method and magnet characteristic measuring apparatus - Google Patents

Description

  The present invention relates to a magnet characteristic measuring method and a magnet characteristic measuring apparatus for measuring the magnetic characteristic of a magnet, and more particularly to a magnet characteristic measuring method and a magnet characteristic measuring apparatus for measuring a magnetic characteristic of a magnet using a Helmholtz coil.

  In recent years, the demand for higher performance of magnets has become more severe, and the demand for higher coercivity is particularly strong. Furthermore, there is a case where the magnetic property distribution inside the magnet is also a problem. For example, high-performance permanent magnets obtained by diffusing Dy are used in various devices such as various motors. A high-performance magnet formed by diffusing Dy has a non-uniform distribution of elements inside the magnet, and therefore has a different coercive force for each part. When this magnet is used in a motor or the like, it is desirable to know the magnetic property distribution inside the magnet in order to properly design the motor. This characteristic distribution is generally obtained by cutting out a magnet sample for each part and evaluating the characteristics. For this reason, it is required to measure magnetic characteristics with high accuracy for a micro magnet having a high coercive force.

  A closed magnetic circuit type B-H tracer is generally used as a magnet characteristic measuring device. This device is a device in which a magnet is sandwiched between pole pieces of an electromagnet, the magnetization is detected by a detection coil installed on the outer periphery of the magnet, and the magnetic characteristics of the magnet are measured. In this apparatus, a detection coil is installed between pole pieces. In order to measure a minute magnet, it is necessary to install a detection coil in a minute space, and since a sufficient detection signal cannot be obtained with the minute detection coil, it is not suitable for the measurement of a minute magnet. In addition, accurate measurement cannot be performed in a high magnetic field exceeding the magnetic saturation of the pole piece, and there is a limit to the measurement of a high coercivity magnet.

  In addition, there is an open magnetic circuit type magnet characteristic measuring device. In order to measure a demagnetization curve of a magnet having a minute size of about 1 mm square, a VSM (Vibrating Sample Magnetometer), a magnetic balance, or the like is generally used. In the case of VSM, means such as using a superconducting coil is required for measurement of a high coercive force magnet. Moreover, in order to measure the magnet with high accuracy, it is necessary to accurately place the magnet at the center of the detection coil.

  Furthermore, a pulse excitation type B-H tracer that applies a pulsed magnetic field to a magnet, detects magnetization and magnetic field with a detection coil, and measures the magnetic characteristics of the magnet has been put to practical use as an open magnetic path type magnet characteristic measuring device. Therefore, it is useful for measuring the coercivity of a high coercivity magnet (for example, Patent Document 1).

JP 2007-180372 A

  The VSM and pulse excitation type B-H tracer installs an excitation coil and a detection coil around a magnet to be measured, detects the magnetization and magnetic field of the magnet, and measures the magnetic characteristics of the magnet. However, the VSM and pulse excitation type B-H tracer is an open magnetic circuit type, so if the installation position of the magnet deviates from the center of the detection coil or the size of the magnet changes, the measurement results will be affected. It is necessary to arrange it accurately in the apparatus.

  Therefore, it is conceivable to use a Helmholtz coil as the magnetization detection coil. In this case, the same signal is detected in principle if the magnet remains inside the Helmholtz coil even if the size and position of the magnet change. Therefore, the displacement of the magnet installation position and the change in size are less affected by the measurement result of the magnetic characteristics, and the measurement accuracy can be improved.

  However, in the measurement of the pulse excitation type B-H tracer, the resonance of the coil due to the surge voltage of the excitation power supply occurs, and when the number of turns of the Helmholtz coil is increased, the stray capacitance increases in a complicated manner. There is a problem in that the resonance frequency is distributed on the frequency axis, and the resonance frequency component due to the resonance cannot be removed from the magnetization detection voltage waveform.

  As a technique for removing the resonance frequency component, a technique using a low-pass filter is conceivable, but a phase difference is generated between the detection voltage waveform of the magnetization detection coil and the detection voltage waveform of the magnetic field detection coil (hereinafter referred to as the H coil). Therefore, there is a problem that the output signals of the magnetic field and the magnetization cannot be synchronized.

  The present invention has been made in view of such circumstances, and a resonant frequency component resulting from the use of a Helmholtz coil when measuring the magnetic characteristics of a magnet using a Helmholtz coil and a pulse excitation coil with an increased number of turns. It is an object of the present invention to provide a magnet characteristic measuring method and a magnet characteristic measuring apparatus that can measure the detected voltage waveform of magnetization and magnetic field without phase difference.

A magnet characteristic measuring method according to the present invention is a magnet characteristic measuring method for measuring a magnetic characteristic of a magnet using a magnetization detecting coil made of a Helmholtz coil, and measuring a detected voltage waveform of the magnet using the magnetization detecting coil. A step of centralizing and stabilizing the resonance frequency derived from the measurement system including the magnet on the frequency axis, and the resonance frequency component of the detection voltage waveform of the magnetization detection coil from the detection voltage waveform of the magnetization detection coil by moving average processing Removing a component derived from the magnetization of the magnet from the detected voltage waveform from which the resonance frequency component has been removed; integrating the extracted detected voltage waveform of the magnetization; and measuring coil of the magnetization detecting coil Converting to a magnetizing value of the magnet using an intrinsic coefficient and a value of the volume of the magnet.

  In the magnet characteristic measuring method of the present invention, the resonance frequency derived from the measurement system including the magnet is concentrated and stabilized on the frequency axis so that the resonance frequency component can be removed from the detection voltage waveform of the magnetization detection coil. be able to.

  The magnet characteristic measuring method according to the present invention includes a step of integrating the detected voltage waveform of the H coil and converting it to a value of the magnetic field of the magnet using a specific coefficient of the H coil, and the converted magnetization of the magnet And a step of creating a JH curve by synchronizing the value of the magnetic field and the value of the magnetic field of the magnet.

  In the magnet characteristic measuring method of the present invention, after the resonance frequency of the detected voltage waveform is intensively stabilized on the frequency axis, the resonance frequency component is removed by Fourier transform and moving average processing, whereby the Helmholtz coil is formed. The resulting resonance frequency component can be accurately removed from the detected voltage waveform, and the JH curve can be measured.

A magnet characteristic measuring apparatus according to the present invention is a magnet characteristic measuring apparatus for measuring the magnetic characteristics of a magnet, and two sets of Helmholtz that are provided in the vicinity of the magnet and are provided in the vicinity of the magnet, and exciting coils that excite the magnet. A magnetization detection coil composed of a coil, a capacitor connected in parallel with the magnetization detection coil, for centrally stabilizing the resonance frequency derived from the measurement system including the magnet on the frequency axis, and a detection voltage waveform of the magnetization detection coil Means for removing the resonance frequency component from the magnetic field, and magnetization measuring means for measuring the magnetization value of the magnet based on the detected voltage waveform of the magnetization detection coil after removing the resonance frequency component.

  In the magnet characteristic measuring apparatus of the present invention, after the resonance frequency derived from the measurement system including the magnet is concentrated and stabilized on the frequency axis by the capacitor connected to the Helmholtz coil as the magnetization detecting coil, the magnetization detection is performed. The resonance frequency component is removed from the detection voltage waveform of the coil, and the magnetization value of the magnet is measured based on the detection voltage waveform of the magnetization detection coil after the removal.

  In the magnet characteristic measuring apparatus according to the present invention, since a Helmholtz coil is used as the magnetization detection coil of the magnet, it can be measured accurately without being influenced by the size of the magnet or the deviation of the installation position. In addition, the resonant frequency component is concentrated and stabilized on the frequency axis with a capacitor connected in parallel to the magnetization detection coil, and then the resonant frequency component is removed to obtain highly accurate measurement results. Can do.

  The magnet characteristic measuring apparatus according to the present invention includes an H coil provided at a position distant from the magnet, and a magnetic field measuring means for measuring the value of the magnetic field applied to the magnet based on the detected voltage waveform of the H coil. And magnetic characteristic measuring means for measuring magnetic characteristics of the magnet based on the measurement results of the magnetization measuring means and the magnetic field measuring means.

  In the magnet characteristic measuring apparatus of the present invention, a JH curve is created based on the measurement results of the magnetization value and the magnetic field value of the magnet.

  According to the present invention, the resonance frequency component can be removed from the detected voltage waveform without causing a phase delay, and the magnetic characteristics of the magnet can be measured with high accuracy.

It is a fragmentary figure which shows the structure of the magnet characteristic measuring apparatus which concerns on this invention. It is a schematic diagram which shows the structure of each coil in the magnet characteristic measuring apparatus which concerns on this invention. It is a figure which shows the circuit structure of the magnetization measurement part of the magnet characteristic measuring apparatus which concerns on this invention. It is a block diagram which shows the structure of the signal processing part of the magnet characteristic measuring apparatus which concerns on this invention. It is a flowchart which shows the operation | movement procedure of the magnet characteristic measuring method which concerns on this invention. It is a graph which shows the measurement result of the detection voltage waveform of the magnetization detection coil which consists of a Helmholtz coil at the time of providing the capacitor | condenser which concerns on this invention, and the result of having carried out the fast Fourier transform of the detection voltage waveform. It is a graph which shows the measurement result of the detection voltage waveform of the magnetization detection coil which consists of a Helmholtz coil when not providing a capacitor | condenser, and the result of having carried out the fast Fourier transform of the detection voltage waveform. It is a graph showing the detection voltage waveform of the magnetization detection coil before and behind a moving average process. Graph showing detection voltage waveform after removing resonance frequency component of magnetization detection coil when magnet is installed and when magnet is not installed (blank measurement), and magnetization detection coil after removing (subtracting) the influence of blank waveform It is a graph showing a detection voltage waveform of. It is a graph showing the detection voltage waveform of H coil. It is a graph showing the value (J waveform) of the magnetization of the converted magnet, the value (H waveform) of the magnetic field of the converted magnet, and a JH curve. It is a graph showing the JH curve (full loop) obtained by performing an offset process and inversion synthetic | combination process, and the JH curve (full loop) before and behind performing a self-demagnetizing field correction.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.

  FIG. 1 is a partial view showing the configuration of a magnet characteristic measuring apparatus according to the present invention, FIG. 2 is a schematic diagram showing the configuration of each coil in the magnet characteristic measuring apparatus according to the present invention, and FIG. 3 is a magnet characteristic measuring apparatus according to the present invention. It is a figure which shows the circuit structure of the magnetization measurement part. FIG. 1 shows a state where a magnet to be measured is installed.

  As shown in FIG. 1, a magnet 1 to be measured is fixed in the apparatus with a holder 2 that is long in the vertical direction. The magnet 1 has a rectangular parallelepiped shape of 1 mm square, for example. A magnet to be measured by the holder 2 can be installed near the center of the magnetization detection coil. As the magnetization detection coil, a primary Helmholtz coil 3 and a secondary Helmholtz coil 4 outside thereof are provided.

  The primary Helmholtz coil 3 is composed of a pair of circular coils having the same radius and having a common axis. The distance between the pair of circular coils is equal to the radius of each circular coil, and the magnet 1 is installed near the center of the pair of circular coils. The If the position of the magnet 1 remains inside the Helmholtz coil, the same signal is detected in principle.

  As an example, the primary Helmholtz coil 3 has a one-side dimension of 16 mm outer diameter × 8 mm inner diameter × 4 mm height, a distance between coil centers of 6 mm, and a winding specification of 700 turns of copper wire having a diameter of 0.14 mm. It is. The secondary Helmholtz coil 4 is also composed of a pair of circular coils having the same radius, the distance between the pair of circular coils is equal to the radius of each circular coil, and the coil center coincides with the primary Helmholtz coil. The secondary Helmholtz coil 4 is a copper wire having a one-side dimension of 31.5 mm outer diameter × 22.5 mm inner diameter × 4.5 mm height, a coil center distance of 13.5 mm, and a winding specification of 0.3 mm in diameter. Is 145 turns.

  An H coil 5 is provided on the outer side in the vertical direction of the primary Helmholtz coil 3 and the secondary Helmholtz coil 4. The H coil 5 has, for example, a copper wire 7-turn coil with dimensions of outer diameter 20.5 mm × inner diameter 16.5 mm × height 2 mm and winding specifications 0.3 mm in diameter. The upper and lower coil spacing is 40 mm. The center axis and center of the H coil 5 preferably coincide with the center axis and center of the primary Helmholtz coil 3 and the secondary Helmholtz coil 4.

  The excitation coil 6 is provided outside the magnetization detection coil (Helmholtz coil). The exciting coil 6 is a pulse exciting coil that excites a pulse magnetic field, for example. The exciting coil 6 has dimensions of an outer diameter of 116 mm, an inner diameter of 50 mm, and a height of 61 mm, and the winding specification is 66 turns of a hollow copper wire having an outer diameter of 5 mm and an inner diameter of 3 mm. In addition, a cooling water can be poured through a hollow copper wire, and the heat_generation | fever of a coil can be suppressed. When this exciting coil 6 is excited with a 3000 μF-3500 V capacitor discharge type excitation power source, a magnetic field of maximum 80 kOe (about 6366 kA / m) is generated, and the magnetization of the magnet 1 fully magnetized with this magnetic field is completely It has been confirmed that it can be reversed.

  The primary Helmholtz coil 3 and the secondary Helmholtz coil 4 are connected in opposite phases to form a magnetization detection coil. The number of turns × coil area of each of the primary Helmholtz coil 3 and the secondary Helmholtz coil 4 is the same as that of the magnet 1. Although the detection voltage when not installed (blank measurement) is set to be zero as much as possible, the residual component can be subjected to blank measurement and correction processing can be performed. A capacitor 7 is connected in parallel with the magnetization detection coil composed of the primary Helmholtz coil 3 and the secondary Helmholtz coil 4 (see FIG. 3). The capacity of the capacitor 7 is, for example, 0.01 μF.

  In this magnet characteristic measuring apparatus, a capacitor 7 is connected in parallel to a magnetization detection coil (Helmholtz coil), and resonance is intentionally caused at a specific frequency to centrally stabilize the resonance frequency of the detected voltage waveform. The resonance frequency component is removed. In this case, the resonance frequency component can be removed from the detected voltage waveform by data processing such as moving average, and only the signal component derived from the magnet 1 can be separated. This signal component has no phase lag with respect to the magnetic field signal component. The capacitance of the capacitor 7 may be determined experimentally by setting the resonance frequency to be intensively stabilized at a specific frequency and not causing a phase delay with respect to the magnetic field signal component.

  In the magnetization detection unit of the magnet characteristic measuring apparatus, as shown in FIG. 3, the primary Helmholtz coil 3, the secondary Helmholtz coil 4, the capacitor 7 and the H coil 5 constitute a detection circuit 10, and the excitation coil 6 and the capacitor An excitation circuit 20 is configured including C, DC power supply V, and the like.

  FIG. 4 is a block diagram showing the configuration of the signal processing unit of the magnet characteristic measuring apparatus according to the present invention. In FIG. 4, reference numeral 30 denotes a measurement unit configured by, for example, a CPU (Central Processing Unit), an MPU (Micro Processing Unit), and the like. The measurement unit 30 includes the detection circuit 10, the storage unit 31, and the temporary unit. A storage unit 32 is connected.

  The measurement unit 30 performs various processes as described later on the detection voltage waveform obtained from the detection circuit 10 to measure the magnetic characteristics of the magnet 1. The storage unit 31 can use an external storage device such as a hard disk or an SSD (Solid State Drive). The storage unit 31 stores a program for performing an operation process by the measurement unit 30, and stores a coefficient unique to the measurement coil of the magnetization detection coil (Helmholtz coil) to be used, a coefficient specific to the H coil 5, and the like. . The temporary storage unit 32 is preferably a volatile random access memory such as DRAM (Dynamic Random Access Memory) or SRAM (Static RAM). The temporary storage unit 32 can store various data in the operation process by the measurement unit 30, the permeance coefficient of the magnet 1 to be measured, and the like.

  Hereinafter, an example of the procedure of the magnet characteristic measuring method according to the present invention will be described with reference to the flowchart of FIG. In this measurement procedure, a process of measuring the blank waveform of the magnetization detection coil when the magnet 1 is not provided (steps S1 to S4), and a process of installing the magnet 1 and measuring the magnetic characteristics of the magnet 1 (steps S5 to S5). S11). In the drawing, the magnetization value (magnetization detection voltage waveform) of the magnet of the present invention is a J waveform, and the magnetic field value (magnetic detection voltage waveform) of the magnet is an H waveform.

  In the present invention, since the resonance frequency component is removed by centrally stabilizing the resonance frequency derived from the measurement system including the magnet 1, the component due to the stray capacitance of the Helmholtz coil can be removed. Magnetic characteristics can be measured with high accuracy.

<Measurement processing of blank waveform of magnetization detection coil>
The exciting coil 6 is excited without installing a magnet, and the detection voltage waveform is measured by the measuring unit 30 (step S1). Here, the resonance frequency derived from the measurement system when measuring the detection voltage waveform using the magnetization detection coil is concentrated and stabilized. For this reason, the detection circuit 10 is provided with a capacitor 7 to concentrate and stabilize the resonance frequency derived from the measurement system on the frequency axis.

  The measurement unit 30 performs Fourier transform (for example, Fast Fourier Transform (FFT)) on the measured detected voltage waveform to identify the resonance frequency component (step S2).

  FIG. 6 is a graph showing the measurement result of the detection voltage waveform of the magnetization detection coil composed of the Helmholtz coil and the result of fast Fourier transform of the detection voltage waveform when the capacitor 7 according to the present invention is provided. FIG. 6 shows the result of measurement with no magnet 1 installed, the left side is the result of the detected voltage waveform, and the right side is the result of fast Fourier transform of the detected voltage waveform. According to the result of FIG. 6, the resonance frequency of the detection voltage waveform of the magnetization detection coil is concentrated and stabilized at 14 kHz (open arrow).

  FIG. 7 is a graph showing the measurement result of the detection voltage waveform of the magnetization detection coil formed of a Helmholtz coil and the result of fast Fourier transform of the detection voltage waveform when the capacitor 7 is not provided. FIG. 7 shows the results when the detection voltage waveform is measured under the same conditions as in FIG. 6 except that the capacitor 7 is not connected to the detection circuit 10. In the result of FIG. 7, the resonance frequency is distributed on the frequency axis (white arrow), and it cannot be separated only into the signal component derived from the blank except for the resonance frequency component of the detected voltage waveform.

The measuring unit 30 determines the number of moving average points that can remove the resonance frequency component from the analysis result of the fast Fourier transform and the time sampling interval (step S3). In the example of FIG. 6, the resonance frequency f: 1.4 × 10 ⁴ [Hz], the time sampling interval Δt: 0.2 × 10 ⁻⁶ [sec. ], The number of moving average points is 1 / (fΔt) ≈357 [points].

  The measurement unit 30 performs moving average processing with this number of points, thereby removing the resonance frequency component and determining the detected voltage waveform from which the resonance frequency component has been removed as the blank waveform of the magnetization detection coil (step S4).

  As described above, the detection voltage waveform (blank waveform) of the magnetization detection coil from which the resonance frequency component has been removed is acquired in a state where the magnet 1 is not installed (blank state).

<Measurement process of magnetic properties of magnet>
The magnet 1 to be measured is installed in the measuring apparatus shown in FIG. 1, the magnet 1 is pulse-excited by the excitation coil 6, and the detection voltage waveform of the magnetization detection coil and the detection voltage waveform of the H coil 5 are measured by the measurement unit 30 ( Step S5). Next, the measurement unit 30 removes the resonance frequency component from the detected voltage waveform by performing a moving average process on the measured voltage waveform of the magnetization detection coil with the number of moving average points determined in step S3. (Step S6). FIG. 8 is a graph showing the detected voltage waveforms of the magnetization detection coils before and after the moving average processing is performed with the moving average number of points 357 determined in step S3. In FIG. The original waveform is shown, and the solid line b shows the waveform after moving average processing. Resonance frequency components can be removed from the detection voltage waveform of the magnetization detection coil by centrally stabilizing the resonance frequency and performing a moving average process. Further, the measurement unit 30 subtracts the blank waveform of the magnetization detection coil determined in step S4 from the detection voltage waveform of the magnetization detection coil from which the resonance frequency component has been removed, and extracts only the signal component derived from the magnet 1. (Step S7).

  FIG. 9A is a graph showing the detected voltage waveform after removal of the resonance frequency component of the magnetization detection coil when the magnet 1 is installed and when the magnet 1 is not installed, and the solid line a and the broken line b each show the magnet 1 installed. The case where the magnet 1 is not installed is shown.

  The detected voltage waveform when the magnet 1 is not installed is subtracted from the detected voltage waveform when the magnet 1 is installed. That is, the influence of the determined blank waveform is removed. FIG. 9B is a graph showing a detection voltage waveform of the magnetization detection coil after removing (subtracting) the influence of the blank waveform. In this way, a detection voltage waveform of the magnetization detection coil derived from the magnet 1 is obtained.

  The measurement unit 30 obtains the integral value of the detection voltage of the magnetization detection coil derived from the magnet 1 obtained in step S7, and uses the coefficient specific to the measurement coil of the magnetization detection coil and the volume of the magnet 1 to magnetize the magnet 1. (Step S8).

  In the Helmholtz coil, the relationship M = kΦ is established between the magnetic moment M and the total magnetic flux Φ interlinking the Helmholtz coil, where k is a coefficient specific to the measurement coil of the Helmholtz coil. When the magnetic moment M is divided by the volume V of the magnet to be measured, the magnetization J is obtained. Therefore, the magnetization J is obtained as J = M / V = kΦ / V. Thus, if the total amount of magnetic flux interlinking the Helmholtz coil, the coefficient specific to the measurement coil of the Helmholtz coil, and the volume of the magnet sample are known, the magnetization of the magnet can be measured.

As described above, since the integrated value of the detection voltage of the magnetization detection coil from which the blank waveform has been removed corresponds to the total amount of magnetic flux interlinking the coil, the integrated value of the detection voltage of the magnetization detection coil shown in FIG. By multiplying the coefficient specific to the measurement coil of the magnetization detection coil (the primary Helmholtz coil 3 and the secondary Helmholtz coil 4) and dividing by the volume of the magnet 1, it is converted into a magnetization value. The coefficient specific to the measurement coil of the magnetization detection coil is determined by the device configured. The coefficient specific to the measurement coil of the magnetization detection coil is adjusted so that the magnetization value obtained by measuring the magnet of the standard sample with the pulse BH tracer and the magnetization value obtained by the time integration value of the voltage change coincide. The coefficient specific to the measurement coil of the magnetization detection coil is 1.3093 × 10 ⁻⁵ [m] in the embodiment of FIG. 1, and the volume is 1.0 × 10 ⁻⁹ when the magnet 1 is a cube having a side of 1 mm. [M ³ ]. The converted magnetization value (magnetization detection voltage waveform: J waveform) is shown in FIG. 11A.

  The measurement unit 30 integrates the detected voltage waveform of the H coil 5 and converts it to the value of the magnetic field of the magnet 1 by using a specific coefficient of the H coil 5 (step S9). For the detection voltage waveform obtained from the H coil 5, the moving average process may not be performed. A search coil is used as the H coil 5.

FIG. 10 is a graph showing a detected voltage waveform of the H coil 5. The result of integration of the detected voltage of the H coil 5 shown in FIG. 10 is divided by a specific coefficient of the H coil 5 to be converted into a magnetic field value of the magnet 1. Here, the specific coefficient of the H coil 5 is 2.8968 × 10 ⁻³ [m ² ]. The intrinsic coefficient of the H coil 5 is adjusted so that the central magnetic field measured by the calibrated probe and the magnetic field obtained by the time integration value of the voltage change coincide. FIG. 11B shows the converted magnetic field value (magnetic field detection voltage waveform: H waveform).

  Using the J waveform that is the magnetization value (magnetization detection voltage waveform) of the magnet 1 and the H waveform that is the magnetic field value (magnetic field detection voltage waveform) of the magnet 1 obtained by the above conversion, J− An H curve is created (step S10). The created JH curve is shown in FIG. 11C.

  FIG. 12A is a graph showing a JH curve (full loop) obtained by performing offset processing and inversion synthesis processing on the JH curve shown in FIG. 11C. Furthermore, the self-demagnetizing field may be corrected with the permeance coefficient of the magnet 1 as necessary. FIG. 12B is a graph showing a JH curve (full loop) before and after performing self-demagnetizing field correction. In FIG. 12B, a broken line a indicates a JH curve before the self-demagnetizing field correction (JH curve shown in FIG. 12A), and a solid line b indicates the JH curve after the self-demagnetizing field correction.

  Next, it is determined whether or not to measure the magnetic characteristics for the next time (repeating the same magnet 1 or changing to another magnet 1) (step S11). When the next magnetic property measurement is performed on the magnet 1 (S11: YES), the process of the measurement unit 30 is returned to step S5 and the measurement process is performed. On the other hand, when the next measurement is not performed (S11: NO), the process of the measurement unit 30 is terminated.

  As described above, if the magnetic characteristics of the magnet 1 are continuously measured, the number of moving average points determined in step S3 and the blank waveform determined in step S4 in the blank waveform measurement process are used again. The magnetic characteristics of 1 can be easily measured.

  In the present invention in which the Helmholtz coil is used as a magnetization detection coil, the resonance frequency component derived from the measurement system can be easily and reliably removed by digital processing by centrally stabilizing the resonance frequency derived from the measurement system. By using this, it is possible to accurately measure magnetic characteristics even with a small high coercive force magnet.

  Then, it is possible to measure the JH curve without phase delay as compared with the method of removing the resonance frequency component by the low-pass filter.

  In addition, although the example which analyzes a resonant frequency by a fast Fourier transform was shown, you may make it analyze a resonant frequency by giving other Fourier transforms, such as a discrete Fourier transform (DFT: Discrete Fourier Transform).

  The magnet used in the present invention is not limited to a high-performance permanent magnet formed by diffusing Dy. A permanent magnet formed by diffusing Dy, Tb, and Tb in addition to Dy may be used. Moreover, any of an Nd-Fe-B magnet, an Sm-Fe-N magnet, an Sm-Co magnet, and a ferrite magnet may be used, and any of a sintered magnet and a bonded magnet may be used.

  The magnet characteristic measuring apparatus according to the present invention is not limited to the pulse excitation type B-H tracer as described above, and is affected by stray capacitance generated by the use of the Helmholtz coil. The present invention can also be applied to other open magnetic circuit type magnetization measurements whose distribution is not stable.

  The disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 Magnet 2 Holder 3 Primary Helmholtz Coil 4 Secondary Helmholtz Coil 5 H Coil 6 Excitation Coil 7 Capacitor 10 Detection Circuit 20 Excitation Circuit 30 Measurement Unit 31 Storage Unit 32 Temporary Storage Unit

Claims (4)

In a magnet characteristic measurement method for measuring magnetic characteristics of a magnet using a magnetization detection coil comprising a Helmholtz coil,
When measuring the detection voltage waveform of the magnet using the magnetization detection coil, the step of centrally stabilizing the resonance frequency derived from the measurement system including the magnet on the frequency axis;
Removing the resonance frequency component of the detection voltage waveform of the magnetization detection coil from the detection voltage waveform of the magnetization detection coil by moving average processing ;
Extracting a component derived from the magnetization of the magnet from the detected voltage waveform from which the resonance frequency component has been removed;
Integrating the extracted detection voltage waveform of the magnetization and converting it to a magnetization value of the magnet using a coefficient specific to the measurement coil of the magnetization detection coil and a value of the volume of the magnet. A magnet characteristic measuring method. Integrating the detected voltage waveform of the H coil and converting it to the value of the magnetic field of the magnet using a unique coefficient of the H coil;
The magnet characteristic measuring method according to claim 1, further comprising: creating a JH curve by synchronizing the converted magnetization value of the magnet and the magnetic field value of the magnet. In a magnet characteristic measuring device that measures the magnetic characteristics of a magnet,
An exciting coil for exciting the magnet;
A magnetization detection coil comprising two sets of Helmholtz coils provided in the vicinity of the magnet and connected in opposite phases to each other;
A capacitor connected in parallel with the magnetization detection coil and for stabilizing the resonance frequency derived from the measurement system including the magnet on the frequency axis;
Means for removing a resonance frequency component from a detection voltage waveform of the magnetization detection coil;
A magnet characteristic measuring apparatus comprising: magnetism measuring means for measuring a magnetizing value of the magnet based on a detected voltage waveform of the magnetization detecting coil after removing a resonance frequency component. An H coil provided at a position away from the magnet;
Magnetic field measuring means for measuring the value of the magnetic field applied to the magnet based on the detected voltage waveform of the H coil;
The magnet characteristic measuring device according to claim 3, further comprising: a magnetic characteristic measuring unit that measures a magnetic characteristic of the magnet based on measurement results of the magnetization measuring unit and the magnetic field measuring unit.

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