JP2013050390A - Magnetic characteristic measurement sensor, and magnetic characteristic measurement method using the same sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a measurement error when measuring a magnetic characteristic of a permanent magnet.SOLUTION: In a magnetic characteristic measurement sensor (1) for measuring the magnetic characteristic of the permanent magnet, a B coil (4) for measuring a magnetic flux density of the permanent magnet, and an H coil (5) for measuring an intensity of the magnetic field of the permanent magnet and/or an M coil (6) for measuring a magnetization intensity of the permanent magnet are wound coaxially around the periphery of the permanent magnet. The number of turns of the H coil (5) is the same as that of the B coil (4). A product of the cross sectional area and the number of the turns of the M coil (6) is the same as that of the B coil (4). The intensity of the magnetic field and the magnetization intensity of the permanent magnet are measured with the H coil (5) and/or the M coil (6), and the B coil (4).

Description

  The present invention relates to a magnetic property measuring sensor for measuring magnetic properties of a permanent magnet and a magnetic property measuring method using the sensor.

  Permanent magnets are evaluated for magnetic properties using magnetic flux density, magnetic field strength, and magnetization as parameters. And as a method of measuring the magnetic characteristic of a permanent magnet, it is standardized as a “permanent magnet test method” in Japanese Industrial Standards (see Non-Patent Document 1).

  According to the “permanent magnet test method” defined in the Japanese Industrial Standard, a closed magnetic circuit is constituted by a permanent magnet and an electromagnet to be measured, and the B coil and magnetic polarization for measuring the magnetic flux density are measured. The magnetic characteristics of the permanent magnet are measured using the J coil to be used and the H sensor for measuring the magnetic field strength.

  Here, the magnetic flux density of the permanent magnet is measured by winding a B coil around the permanent magnet and integrating the induced voltage of the B coil. The magnetization (magnetic polarization) of the permanent magnet is such that the J coil is wound around the permanent magnet and the B coil not wound around the permanent magnet is electrically connected to the J coil so as to cancel each other. The B coil is used as the air gap compensation coil, and the measurement is performed by integrating the induced voltage of the J coil. The magnetic field strength is measured by arranging an H sensor such as a flat search coil, a magnetic potentiometer, or a hall probe near the side of the permanent magnet.

Japanese Industrial Standard JIS C2501 “Permanent Magnet Test Method”

  However, the “permanent magnet test method” defined in the above Japanese Industrial Standards does not necessarily have a sufficiently small measurement error in the measurement of the magnetic field strength and magnetization of the permanent magnet. It was difficult to accurately evaluate the characteristics.

  Therefore, in the present invention according to claim 1, in the magnetic characteristic measuring sensor for measuring the magnetic characteristics of the permanent magnet, the B coil for measuring the magnetic flux density of the permanent magnet and the magnetic field strength of the permanent magnet are used. The H coil and / or the M coil used for measuring the magnetization of the permanent magnet were coaxially wound around the permanent magnet.

  Further, in the present invention according to claim 2, in the present invention according to claim 1, the number of turns of the H coil is the same as that of the B coil.

  In the present invention according to claim 3, in the present invention according to claim 1, the M coil has the same product of the cross-sectional area and the number of turns as the B coil.

  According to a fourth aspect of the present invention, in the magnetic property measuring method for measuring the magnetic property of the permanent magnet using the magnetic property measuring sensor, the magnetic property measuring sensor is a B coil for measuring the magnetic flux density of the permanent magnet. And an H coil used for measuring the magnetic field strength of the permanent magnet and / or an M coil used for measuring the magnetization of the permanent magnet are wound coaxially around the permanent magnet, and the H coil and / or M coil and the It was decided to measure the magnetic field strength and / or magnetization of the permanent magnet with the B coil.

  In the present invention, in the magnetic property measuring sensor for measuring the magnetic property of the permanent magnet, the B coil for measuring the magnetic flux density of the permanent magnet, the H coil used for measuring the magnetic field strength of the permanent magnet, and / or The M coil used for measuring the magnetization of the permanent magnet is coaxially wound around the permanent magnet to reduce the measurement error of the magnetic field strength and magnetization of the permanent magnet when measuring the magnetic characteristics of the permanent magnet. The magnetic characteristics of the permanent magnet can be evaluated more accurately than before.

1 is a front sectional view showing a magnetic property measuring sensor according to the present invention. FIG.

  Hereinafter, a specific configuration of a magnetic characteristic measurement sensor and a magnetic characteristic measurement method using the same according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the magnetic characteristic measuring sensor 1 has a B coil 4, an H coil 5, and an M coil 6 wound around a holder 3 through which a test piece 2 of a permanent magnet formed in a cylindrical shape having a predetermined length is inserted. It is turning. Here, the B coil 4 is a coil for measuring the magnetic flux density of the test piece 2, and the H coil 5 is a coil for measuring the magnetic field strength of the test piece 2 together with the B coil 4. The coil 6 is a coil for use with the B coil 4 to measure the magnetization of the test piece 2.

  The holder 3 includes a cylindrical inner holder 7 through which the test piece 2 is inserted, and a cylindrical outer holder 8 attached to the outer periphery of the inner holder 7.

  The inner holder 7 is formed with a hollow portion 9 having an inner diameter in consideration of the dimensional tolerance of the diameter of the test piece 2 in order to allow the test piece 2 to be inserted, and a coil groove 10 is formed on the outer peripheral portion in the circumferential direction. Yes. A B coil 4 is wound around the coil groove 10, and an H coil 5 is wound around the outer periphery of the B coil 4 via an insulating sheet 11. Accordingly, the H coil 5 is arranged coaxially with the B coil 4 and concentrically with respect to the test piece 2 around the test piece 2. Further, the H coil 5 has the same number of turns as the B coil 4.

  The outer holder 8 is formed with a hollow portion 12 so that the inner holder 7 can be inserted therethrough, and a coil groove 13 is formed on the outer peripheral portion in the circumferential direction. An M coil 6 is wound around the coil groove 13, and an outer periphery of the M coil 6 is covered with an insulating sheet 14. The M coil 6 is configured such that the product of the number of turns and the cross-sectional area is the same as that of the B coil 4. In the outer holder 8, the coil groove 13 is positioned on the outer peripheral portion of the coil groove 10 of the inner holder 7, so that the M coil 6 has the B coil 4 and the B coil 4 and the test piece 2 around the test piece 2. It is arranged coaxially with the H coil 5 and concentrically.

  In the magnetic property measuring sensor 1, the test piece 2 and the coils 4, 5, 6 are arranged close to each other, and the coils 4, 5, 6 and the holder 3 are prevented from being deformed by heat, etc. The accuracy can be further improved. Therefore, in the magnetic property measuring sensor 1, the insulating sheet is made of a ceramic material that can ensure strength even when the holder 3 (inner holder 7 and outer holder 8) is thin and has excellent heat resistance, and is thin and has heat resistance. The H coil 5 is wound around the B coil 4 via 11.

  The magnetic characteristic measurement sensor 1 is configured as described above, and the magnetic characteristic of the test piece 2 can be measured using the magnetic characteristic measurement sensor 1.

  In order to measure the magnetic properties, the magnetic property measuring sensor 1 is attached to the substantially central portion of the test piece 2 in the extending direction, and the measurement object and the test piece are similar to the “permanent magnet test method” defined by the Japanese Industrial Standards. 2 and an electromagnet constitute a closed magnetic circuit, and the magnetic flux density, magnetization, and magnetic field strength of the test piece 2 are measured.

  When measuring the magnetic flux density, it can be measured by integrating the induced voltage of the B coil 4 wound around the test piece 2.

  When measuring the magnetization, the B coil 4 and the M coil 6 wound coaxially around the test piece 2 are used, and the M coil 6 is used as a gap compensation coil as described below. It can be measured.

First, the magnetic flux densities B _B and B _M obtained by each of the B coil 4 and the M coil 6 are expressed by Equation 1, where the magnetic field strength is H, the magnetization is M, and the magnetic permeability is μ ₀ .

When Expression 1 is expressed by magnetic fluxes φ _B and φ _M obtained by the B coil 4 and the M coil 6, the cross-sectional areas of the B coil 4, the M coil 6 and the test piece 2 are respectively represented by S _B , S _M and S _S. Then, it can be transformed into Equation 2.

The voltage e _BM measured when the B coil 4 and the M coil 6 are connected in series is expressed by Equation 3 when the number of turns of the B coil 4 and the M coil 6 is N _B and N _M , respectively. When the above expression 2 is substituted into the expression 3 and developed, the voltage e _BM can be transformed into the expression 4.

Here, since the product of the number of turns and the cross-sectional area of the B coil 4 and the M coil 6 is the same (N _B S _B = N _M S _M ), the expression 4 can be expressed as the expression 5.

Therefore, the magnetization can be obtained by using Equation 6 by integrating and transforming Equation 5, and integrating the voltage e _BM measured over time when the B coil 4 and the M coil 6 are connected in series. It can be measured from the value integrated by the circuit.

Here, the magnetization can also be measured by using Equation 7 from the voltage e measured when the air gap compensation coils that are not wound around the test piece 2 are connected to the B coil 4 so as to electrically cancel each other. .

  However, when actual measurement was performed on a test piece 2 made of nickel, cobalt, and iron with a diameter of 10 mm and a length of 20 mm and a purity of 99.99%, the relative error from the theoretical value was calculated. In contrast, the values of 1.3%, 2.74%, and 1.52% for each test piece 2 were 16.1%, 17.2%, and 14.7% for each test piece 2 when Equation 7 was used.

  From this, it was shown that the measurement error can be reduced by measuring using the B coil 4 and M coil 6 coaxially wound around the test piece 2 like the magnetic characteristic measuring sensor 1. .

  Further, the measurement error may be increased because the demagnetizing field is greatly influenced near the end of the test piece 2. Therefore, a test piece 2 having a diameter of 10 mm and a purity of 99.99% and a length of 4 mm, 10 mm, 20 mm, and 30 mm was actually measured by mounting the magnetic property measuring sensor 1 at the center in the distraction direction, and the relative value to the theoretical value. When the error was calculated, it was 26.7%, 7.6%, 1.1%, and 0.9% for each test piece 2.

  For this reason, when the magnetic property measuring sensor 1 is attached to the test piece 2, it is necessary to attach the magnetic property measuring sensor 1 as far as possible from the end of the test piece 2 so as to eliminate the influence of the demagnetizing field. It is desirable to attach the test piece 2 having a length of 20 mm or more to the central portion in the extending direction.

Since the magnetization can be accurately measured as described above, the magnetic field strength can be calculated from the relational expression shown in Expression 8 using the magnetic flux density and the magnetization.

  The magnetic field strength is measured by using the B coil 4 and the H coil 5 coaxially wound around the test piece 2 and using the H coil 5 as a gap compensation coil as will be described below. You can also.

First, the magnetic flux densities B _B and B _H obtained by the respective B coils 4 and H coils 5 are expressed by Equation 9 where the magnetic field strength is H, the magnetization is M, and the magnetic permeability is μ ₀ .

When Expression 9 is expressed by magnetic fluxes Φ _B and Φ _H obtained by the B coil 4 and the H coil 5, the cross-sectional areas of the B coil 4, the H coil 5 and the test piece 2 are respectively represented by S _B , S _H and S _S. Assuming that the numbers of turns of the B coil 4 and the H coil 5 are N _B and N _H , respectively, the equation 10 can be obtained.

The difference between the voltages e _H and e _B measured by the H coil 5 and the B coil 4 is expressed by Expression 11. When the above equation 10 is substituted into the equation 11 and developed, the difference between the voltages e _H and e _B can be transformed into the equation 12.

Here, since the B coil 4 and the H coil 5 have the same number of turns (N _B = N _H ), Expression 12 can be expressed as Expression 13.

Therefore, the magnetic field strength can be obtained by using Equation 14 by integrating and transforming Equation 13, and the difference between voltages e _H and e _B measured with time in H coil 5 and B coil 4 respectively. Can be measured from the value integrated by the integration circuit.

  As described above, in the present invention, in the magnetic property measuring sensor 1 for measuring the magnetic property of the test piece 2, the magnetic field strength is measured using the B coil 4 for measuring the magnetic flux density and the B coil 4. An H coil 5 for use with the B coil 4 and an M coil 6 for measuring magnetization are wound around the test piece 2 on the same axis.

  For this reason, in the present invention, when measuring the magnetic characteristics of the test piece 2, the measurement error of the magnetic field strength and the magnetization can be reduced, and the magnetic characteristics of the test piece 2 can be evaluated more accurately than before.

  In particular, in the present invention, the magnetic property measuring sensor 1 and the sensor 1 are used by arranging the H coil 5 or the M coil 6 and the B coil 4 coaxially and concentrically around the test piece 2. It is also possible to reduce the size of the measurement system.

  In the present invention, the number of turns of the H coil 5 is the same as the number of turns of the B coil 4, or the product of the sectional area and the number of turns of the M coil 6 is the same as the product of the sectional area and the number of turns of the B coil 4. Thus, the magnetic field strength and the magnetization can be easily measured by integrating the voltage measured over time with the integration circuit.

DESCRIPTION OF SYMBOLS 1 Magnetic characteristic measurement sensor 2 Test piece 3 Holder 4 B coil 5 H coil 6 M coil 7 Inner holder 8 Outer holder 9 Hollow part 10 Coil groove
11 Insulation sheet 12 Hollow part
13 Coil groove 14 Insulation sheet

Claims (4)

In a magnetic property measurement sensor for measuring the magnetic properties of a permanent magnet,
A B coil for measuring the magnetic flux density of the permanent magnet and an H coil used for measuring the magnetic field strength of the permanent magnet and / or an M coil used for measuring the magnetization of the permanent magnet are wound coaxially around the permanent magnet. Magnetic characteristic measurement sensor characterized by turning.   The magnetic property measuring sensor according to claim 1, wherein the H coil has the same number of turns as the B coil.   The magnetic property measuring sensor according to claim 1, wherein the M coil has the same cross-sectional area and number of turns as the B coil. In a magnetic property measurement method for measuring the magnetic properties of a permanent magnet using a magnetic property measurement sensor,
The magnetic characteristic measurement sensor includes a B coil for measuring the magnetic flux density of the permanent magnet, an H coil used for measuring the magnetic field strength of the permanent magnet, and / or an M coil used for measuring the magnetization of the permanent magnet. Wound around the same axis,
A magnetic characteristic measuring method, comprising: measuring magnetic field strength and / or magnetization of a permanent magnet with the H coil and / or M coil and the B coil.

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