JPH01248077A - Method and apparatus for measuring magnetic characteristic of magnetic body - Google Patents

Abstract

PURPOSE:To measure an accurate magnetic characteristic by certainly bringing a magnetic body to a saturated magnetized state by applying a large magnetic field to the magnetic body, by superposing the pulse magnetic field obtained by the pulse current supplied to a coil on the DC magnetic field obtained by the DC current supplied to the coil in a saturation magnetizing process for bringing the magnetic body to the saturated magnetized state. CONSTITUTION:A magnetic characteristic measuring apparatus 7 is used in the measurement of a magnetic characteristic and a pair of pole pieces 2 are arranged in a mutually opposed state so as to be moved toward and away from each other and magnetic field coils 3 are wound around the outer peripheries of the pieces 2. A Hall element 4 for measuring a magnetic field, a B-coil 5 for measuring magnetization and a magnetic body 6 are arranged between the poles 2 and a pulse magnetic field is applied to the magnetic body 6 by the pulse coils 8 wound around the outer peripheries of the pieces 2. The pulse magnetic field obtained by the pulse current allowed to flow to the coils 8 is superposed on the DC magnetic field obtained by the DC current flowing to the coils 3 to intensify the saturation magnetization of the magnetic body 6 and, after the pulse magnetic field is removed, the DC magnetic field is continuously changed to accurately measure a magnetic characteristic.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for measuring the magnetic properties of magnetic materials used as materials for permanent magnets, especially magnetic materials that exhibit extremely high remanence or coercive force, such as rare earth alloys. , relates to a magnetic property measuring device suitable for use in measuring magnetic properties.

[Prior Art] Permanent magnets are manufactured from raw material powder obtained by pulverizing a magnetic material, and the process includes a magnetic field press in which the raw powder is compressed while applying a magnetic field to form a green compact, It is roughly divided into a sintering process in which the body is sintered to form a sintered magnetic body, and a magnetization process in which the sintered magnetic body is magnetized to become a permanent magnet.

The strength of the permanent magnet manufactured as described above is greatly influenced not only by the strength of the magnetic field applied during magnetization treatment but also by the processing conditions during magnetic field pressing and sintering. For this reason, in manufacturing permanent magnets, it is essential to measure the magnetic properties of the magnetic material obtained by sintering in order to provide permanent magnets of constant quality.

Conventionally, the magnetic properties of a magnetic material have been measured by determining residual magnetism, coercive force, or magnetic energy product from the hysterin loop of the magnetic material.

In other words, as shown in Figure 2, the horizontal axis represents the strength of the magnetic field H applied to the magnetic material, and the vertical axis represents the magnetization strength of the magnetic material, or in the case of the figure, the magnetic flux density B. After the body is saturated magnetized from the origin 0 position in the 10 direction until it reaches the saturation magnetic flux density Bs, the magnetic field is reduced, and a magnetic field in the opposite direction is applied in the -T ■ direction (hereinafter, this process is Record the changes in the magnetic flux density B of the magnetic material during the demagnetization process (referred to as the demagnetization process), and calculate the magnetic flux density when the magnetic field H returns to 0, that is, the residual magnetism Br, and the magnetic flux density B of the magnetic material when it becomes O. The strength of the magnetic field when it becomes, that is, the coercive force II
c, and the point P where the area of the rectangle drawn by the perpendicular line drawn to the vertical and horizontal axes and the vertical and horizontal axes is maximum among arbitrary points on the demagnetization curve in the second quadrant recorded in the above-mentioned demagnetization process. The area of the rectangle given by or the maximum magnetic energy product (BH
) max, respectively, and these residual magnetism I3r, coercive force ■ (C or magnetic energy product (B
H) Magnetic materials with large max are considered to be excellent materials.

Incidentally, the measurement of the magnetic properties described above is performed using a magnetic property measuring device as shown in FIG. 3, and will be briefly explained below with reference to FIG. 3.

FIG. 3 (As shown in this figure, magnetic property measuring devices (hereinafter abbreviated as measuring devices)! are placed facing each other and close to each other.
It is composed of a pair of pole pieces 2 that are separably provided, a magnetic field coil 3 that is wound around the outer periphery of these pole pieces 2, and a Hall element 4 and a B coil 5 that are provided between the pole pieces 2. There is. The magnetic field coil 3
is for applying a magnetic field to the magnetic body 6 held between the facing surfaces 2a of the pole piece 2, and a direct current is used as the magnetizing current for exciting the pole piece 2.

Further, the Hall element 4 is used to measure the strength of the magnetic field applied from the pole piece 2 to the magnetic body 6. The B coil 5 is used to measure changes in the magnetic flux density of the magnetic body 6 itself. That is, B
The coil 5 is used while being wound around the outer periphery of the magnetic body 6, and is configured to replace changes in magnetic flux passing through the magnetic body 6 with changes in induced current and output the same.

Measurement of magnetic properties using the measuring device I having the above configuration is performed as follows.

First, the magnetic body 6 is set between the facing surfaces 2a of the pole piece 2 after winding the B coil 5 around its outer periphery, and is once saturated magnetized by a magnetic field obtained by supplying a direct current to the magnetic field coil 3.

Next, by decreasing the value of the DC current supplied to the magnetic field coil 3 from the current value at the time of saturation magnetization mentioned above and further increasing it in the opposite direction, the strength of the magnetic field applied to the magnetic body 6 is adjusted to saturation. The magnetic flux of the magnetized magnetic body 6 is changed to decrease.

Then, the Hall element 4 generates a current according to the change in the strength of the magnetic field applied to the magnetic body 6, and the B coil 5 wound around the outer circumference of the magnetic body 6 generates a current according to the strength of the magnetic field generated by the magnetic field coil 3. An induced current is output by adding the change in the magnetic flux of the magnetic body 6 itself to the change in the magnetic flux corresponding to the change, so from the change in this induced current, the strength of the magnetic field obtained from the Hall element 4 described above can be determined. By subtracting the change value of the current according to the change in , the change in the magnetic flux of the magnetic body 6 itself can be obtained, and from the above, a demagnetization curve as shown in FIG. 2 is obtained, and the remanence Br and coercive force Hc Or the maximum magnetic energy product (B
H) max is calculated.

[Problems to be Solved by the Invention] By the way, the conventional measuring device l described above uses direct current as a magnetizing current to be supplied to the magnetic field coil 3 in order to continuously change the strength of the magnetic field applied to the magnetic body 6. Does it use electric current?
This has the disadvantage that the types of magnetic material 6 that can be measured are limited.

That is, the above-mentioned measuring device uses a so-called DC magnetic field, in which DC current is supplied to the magnetic field coil 3 to excite the pole piece 2! In this case, the strength of the obtained magnetic field is limited by the saturation magnetic flux density of pole piece 2. For example, when pole piece 2
Even if the WJ product of the facing surface 2a is made as small as possible and the magnetic flux density is increased, the limit of the magnetic flux density is approximately 20,000 Gauss.

The value of this saturation magnetic flux density is less than 20,000 Gauss for conventionally widely used metal magnets and ferrite magnets, so it could be measured without any problems, but recently it has become widely used. 4,000 for rare earth magnets such as neodymium, iron, and boron magnets.
Because an extremely high saturation magnetic flux field of 0 Gauss is required, when measuring these rare earth alloy magnetic materials, the starting point of the demagnetization curve shifts significantly downward, as shown by the broken line in Figure 2, making it impossible to obtain an accurate demagnetization curve. was not obtained.

For this reason, attempts have been made to make the magnetic field coil 3 into an air-core state to generate a stronger magnetic field that is not limited by the pole piece 2, but problems such as heat generation of the magnetic field coil 3 arise, and the neodymium/iron - It was not possible to achieve saturation magnetization of magnetic materials such as poron. One way to simply obtain a strong magnetic field is to supply a pulsed current to a coil to obtain a strong magnetic field, but the magnetic field obtained by this pulsed current changes too quickly, causing the magnetic material 6 to The drawback was that it was not possible to record changes in magnetic field strength during the demagnetization process, so it could not be used to measure magnetic properties.

This invention was made against this background, and therefore it is possible to reliably saturate a magnetic material such as a rare earth alloy, which becomes an extremely strong permanent magnet, and measure its magnetic properties accurately. The purpose of the present invention is to provide a method for measuring magnetic properties and a measuring device suitable for this measurement.

[Means for Solving the Problems] In order to solve the above problems, the method for measuring magnetic properties of the present invention applies a direct current magnetic field obtained by supplying a direct current to a coil.
A pulsed magnetic field obtained by supplying a pulsed current to the coil is superimposed to saturate the magnetic material. During the saturation magnetization process, while the supply of the pulsed current is stopped, the DC current is
This method includes a demagnetization process in which a magnetic field is generated to reduce the magnetization of the saturated magnetic material, and the change in magnetization of the magnetic material at this time is measured.

Further, the magnetic property measuring device used in the above method includes: a magnetic field generating means for applying a magnetic field to a magnetic body; a magnetic field measuring means for measuring the strength of the magnetic field applied to the magnetic body; A magnetic property measuring device comprising a magnetization measuring means for measuring the magnetization strength of a magnetized magnetic body, the magnetic field generating means comprising a direct current coil supplied with a direct current and a pulsed current supplied with the magnetic field generating means. It is characterized by comprising a pulse coil.

In the above-mentioned magnetic property measuring device, the magnetic field generating means may be replaced with a DC coil and a pulse current coil, and may be a magnetic field coil provided to be able to superimpose a DC current and a pulse current.

[Operation] With the above configuration, a strong pulsed magnetic field is instantaneously obtained by the pulsed current supplied to the coil during the saturation magnetization process, and the magnetic material is easily separated by the pulsed magnetic field superimposed on the DC magnetic field caused by the DC current. It is saturated magnetized.

During the demagnetization process, the pulsed magnetic field is removed and only the DC magnetic field is applied, making it possible to continuously change the magnetic field strength and obtain an accurate demagnetization curve for the magnetic material.

[Embodiment] Hereinafter, embodiments of the present invention will be described in order of the apparatus and the measuring method with reference to FIG. In addition, the same reference numerals are attached to the same components in the measuring device as in the conventional magnetic property measuring device described above, and the explanation thereof will be simplified.

As shown in FIG. 1, the measuring device 7 of this embodiment is the conventional measuring device described above! (See Figure 3), magnetic material 6
As a magnetic field generating means for applying a magnetic field to the magnetic field, a pair of pole pieces 2 are provided facing each other and can be moved close to each other and separated from each other, and a magnetic field coil (direct current coil) 3 wound around the outer circumference of these pole pieces 2 is used. In addition, the pole piece 2 serves as a magnetic field measuring means for measuring the magnetic field applied to the magnetic body 6 and a magnetization measuring means for measuring the magnetization of the magnetic body 6.
This uses a Hall element 4 and a B coil 5 provided between the pole piece 2 and a pulse coil 8 on the outer periphery of the pole piece 2 as means for applying a magnetic field to the magnetic body 6.
It is provided adjacent to the magnetic field coil 3.

The pulse coil 8 is supplied with a pulse current in contrast to the direct current supplied to the magnetic field coil 3, and the duration thereof is just an example! ~10m5e
c, and the peak current value is 10,000 to 1,500.
It is about 0A.

The measurement of the magnetic properties of the magnetic body 6 using the measuring device 7 having the above configuration is performed in the following manner.

First, similarly to the conventional measuring device 1, the magnetic body 6 is set between the opposing surfaces 2a of the pole piece 2 after the B coil 5 is wound around its outer periphery. Next, a DC current is supplied to the magnetic field coil 3 to excite the pole piece 2 and the magnetic body 6 is saturated magnetized. At this time, the current value of the DC current supplied to the magnetic field coil 3 is increased, A pulse current is supplied to the pulse coil 8.

After the magnetic body 6 has been saturated magnetized as described above, the supply of pulse current to the pulse coil 8 is stopped, and the current value of the DC current supplied to the magnetic field coil 3 is decreased as in the conventional case. Furthermore, by raising the magnetic body 6 in the opposite direction, the strength of the magnetic field applied to the magnetic body 6 is changed so as to reduce the magnetic flux of the magnetic body 6 that has been magnetized to saturation. Then, the magnetic flux density of the magnetic body 6 is continuously reduced, and the changes in the magnetic field and the magnetic flux density at this time are measured by the Hall element 4 and the B coil 5 in the same way as the conventional measuring device 1 described above. , the demagnetization curve shown in Figure 2 is obtained and the remanence Br, coercive force Hc, or maximum magnetic energy product (BH) ma
x is required.

In the above measurement method, in the saturation magnetization process of saturating the magnetic body 6, a pulse obtained by a pulse current supplied to the pulse coil 8 is added to the DC magnetic field obtained by supplying a DC current to the magnetic field coil 3. Although a magnetic field is superimposed, since the pulse current has an extremely high instantaneous current value as described above, the magnetic field generated from the pulse coil becomes extremely strong. Therefore, even the magnetic body 6 with a large saturation magnetic flux density Bs, which cannot be saturated magnetized only by a DC magnetic field, is easily saturated magnetized.

In the demagnetization process of demagnetizing the saturated magnetic body 6, the pulsed magnetic field whose magnetic field strength changes too quickly to obtain a continuous demagnetization curve is removed, so the magnetic field coil 3 An accurate demagnetization curve of the magnetic body 6 can be measured by continuously changing the current value of the supplied DC current.

As explained above, the magnetic property measuring device 7 of this embodiment uses the magnetic field coil 3 to which a direct current is supplied and the pulse coil 8 to which a pulse current is supplied as a magnetic field generating means for applying a magnetic field to the magnetic body 6. Because of this provision, an extremely strong magnetic field can be obtained in the saturation magnetization process of saturating the magnetic body 6, and restrictions on the types of magnetic bodies that can be measured are greatly relaxed.

In the measurement method of measuring the magnetic properties of the magnetic material 6 using the above-mentioned measuring device 7, the magnetic material 6 is reliably saturated magnetized by the pulsed magnetic field superimposed on the DC magnetic field, and the pulsed magnetic field is removed. The magnetic material is continuously demagnetized by the continuous change of the DC magnetic field in the magnetic state, making it possible to measure accurate magnetic properties.

In addition, in the measuring device 7 of this embodiment, the coil to which the pulse current is supplied is the pulse current coil 8 which is separate from the magnetic field coil 3, but the magnetic property measuring device of the present invention is not limited to this. None. That is, the same result can be obtained even if a pulse current is superimposed on the DC current supplied to the magnetic field coil 3 only during the saturation magnetization process.

[Effects of the Invention] As explained above, in the method for measuring magnetic properties of the present invention, in the saturation magnetization process of saturating the magnetic material, the coil is exposed to the DC magnetic field obtained by the DC current supplied to the coil. In order to superimpose the pulsed magnetic field obtained by the supplied pulsed current, an extremely large magnetic field is applied to the magnetic material, and even the magnetic material with a high saturation magnetic flux density is reliably saturated magnetized.

In the demagnetization process of demagnetizing the magnetic material, the pulsed magnetic field is removed and only the DC magnetic field is applied, so changes in the magnetization strength of the magnetic material can be accurately measured by continuous changes in the DC magnetic field.

In the magnetic property measuring device of the present invention, a direct current coil to which a direct current is supplied and a pulse coil to which a pulse current is supplied are provided as magnetic field generating means for applying a magnetic field to a magnetic material. An extremely large magnetic field is obtained during the magnetization saturation process, which greatly alleviates the restrictions on the types of magnetic materials that can be measured.Also, by superimposing the direct current and pulsed current on the magnetic field coil itself, A similar effect can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a magnetic property measuring device according to an embodiment of the present invention, Fig. 2 is a diagram showing an example of a hysteresis loop that is the basis for measuring the magnetic properties of a magnetic material, and Fig. 3 is a diagram showing a conventional magnetic property measuring device. FIG. 2 is a schematic diagram of a characteristic measuring device. 3...Magnetic field coil (DC coil), 4...
... Hall element (magnetic field measuring means), 5 ... B coil (magnetization measuring means), 6 ... Magnetic body, 7 ...
...Magnetic property measuring device, 8...Pulse coil.

Claims (3)

[Claims] (1) A saturation magnetization process in which a magnetic material is saturated magnetized by superimposing a pulsed magnetic field obtained by supplying a pulsed current to the coil on a DC magnetic field obtained by supplying a DC current to the coil, and A demagnetization process in which, with the supply stopped, the DC current is changed so as to generate a magnetic field that reduces the magnetization of the saturated magnetic material, and the change in magnetization of the magnetic material at this time is measured. A method for measuring the magnetic properties of magnetic materials. (2) a magnetic field generating means for applying a magnetic field to a magnetic body; and a magnetic field measuring means for measuring the strength of the magnetic field applied to the magnetic body;
A magnetic property measuring device comprising magnetization measuring means for measuring the magnetization strength of a magnetic body magnetized by the magnetic field applied by the magnetic field generating means, wherein the magnetic field generating means is supplied with a direct current. 1. A magnetic property measuring device comprising a direct current coil and a pulse coil to which a pulse current is supplied. (3) In the magnetic property measuring device according to claim 2, the magnetic field generating means is replaced by a magnetic field coil provided so that a direct current and a pulsed current can be superimposed, instead of a direct current coil and a pulsed current coil. Characteristic magnetic property measuring device.