JPH09131025A - Method of magnetizing permanent magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To magnetize a permanent magnet even in the case that sufficient magnetizing field strength is hard to get, by performing magnetization after heating a permanent magnet until the tenacity of the permanent magnet falls under the magnetizing field intensity, and cooling it to room temperature, keeping it so that the permeance coefficient may be the straight part of a demagnetization curve. SOLUTION: A permanent magnet 3 is set between the pole pieces of a magnetizer, being caught with SS-41 ferromagnetic substances having heaters 100mm in diameter and 10mm in thickness. Next, an Nd-Fe-B magnet part is heated t0 140 deg.C by the heater, and a magnetizing field is applied to it to perform magnetization. The intensity of magnetizing field at this time is 8kOe. After magnetization of the magnet, the magnetizing field is removed, and an SS-41 ferromagnetic substance yoke is attached so that the SS-41 ferromagnetic substances catching the magnet may close the magnetic circuit. After attachment, the magnet and the SS-41 ferromagnetic substances are removed from a magnetizer while being set, and they are cooled to room temperature. As a result, even in case that enough magnetizing field intensity is hard to get, magnetization can be made.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a sufficient magnetizing magnetic field strength, such as a high coercive force type permanent magnet or a large-sized magnet, without using a large-scale facility for generating a high magnetic field. The present invention relates to a method of magnetizing a permanent magnet that can be magnetized even when it is difficult.

[0002]

2. Description of the Related Art In recent years, along with the market trend toward smaller and lighter electronic equipment and precision equipment, rare earth magnets have been used in many fields in permanent magnets instead of conventional alnico and ferrite magnets. . These rare earth magnets are magnetized by placing an unmagnetized field permanent magnet alone in a magnetizing coil or pole piece at room temperature and applying a pulsed magnetic field or a static magnetic field by a magnetizing power supply device or a permanent magnet for field magnetization. This is done by attaching a soft magnetic yoke to the magnet and then applying a pulsed magnetic field or a static magnetic field. Further, as described in JP-A-6-178507, a magnetizing method utilizing a decrease in coercive force of a rare earth magnet at high temperature is also adopted. This is a method in which the magnet is magnetized after it is installed in the yoke, and after it is installed, a large magnetizing magnetic field cannot be generated due to shape restrictions, so the permanent magnet is heated and kept so that it can be magnetized even in a low magnetic field. This is a method of magnetizing by lowering the magnetic force.

[0003]

However, in order to magnetize a high coercive force type permanent magnet or a large-sized magnet at room temperature, it is necessary to generate a high magnetic field in the permanent magnet, and it is necessary to apply a large current to the magnetizing coil. There is. Therefore, in order to magnetize the permanent magnet, it is indispensable to increase the capacity of the magnetizing power supply device and increase the size of the magnetizing equipment such as the magnetizing coil. Further, these large-scale and large-capacity magnetizing power supply devices are extremely dangerous in handling, as compared with normally used magnetizing power supply devices. In addition, passing a large current through the magnetizing coil leads to an increase in copper loss of the magnetizing coil, increasing heat generation of the magnetizing coil, and promoting deterioration of the magnetizing power supply device and the magnetizing coil. Become. Furthermore, generating a high magnetic field is extremely unstable and difficult to work due to the effects of eddy current and saturation of the magnetizing coil. Further, a magnetizing coil for generating a high magnetic field is required to have mechanical strength capable of withstanding the electromagnetic stress due to the electromagnetic stress caused by the instantaneous high magnetic field. In addition, when magnets are magnetized by incorporating them into the yoke, the permeance coefficient of the magnet itself (permeance coefficient is a coefficient that depends on the shape of the magnet. The demagnetizing field becomes larger than that of the magnet.) Therefore, if heated too high, it deviates from the linear part of the demagnetization curve of the magnet, and a large irreversible demagnetization is observed when returning to room temperature.

Therefore, according to the present invention, when it is difficult to obtain a sufficient magnetic field strength, such as a high coercive force permanent magnet or a large-sized magnet, without using a large-scale facility for generating a high magnetic field. However, it is an object of the present invention to provide a method of magnetizing a permanent magnet that can be magnetized.

[0005]

A method of magnetizing a permanent magnet according to the present invention for solving the above-mentioned problems is as follows.
It is a method of magnetizing a permanent magnet that is cooled to room temperature while heating it until the coercive force of the permanent magnet becomes equal to or less than the magnetizing magnetic field strength, and then cooling it to room temperature while keeping the permeance coefficient in the linear portion of the demagnetization curve. The permanent magnet is a method for magnetizing a permanent magnet, wherein the permanent magnet is an R—Fe—B system permanent magnet (R is one or more rare earth elements including Y).

According to the present invention, even when it is difficult to obtain a sufficient magnetic field strength such as a high coercive force type permanent magnet or a large-sized magnet without using a large-scale facility for generating a high magnetic field. The present invention relates to a method of magnetizing a permanent magnet that can be magnetized. That is, in general, when magnetizing a permanent magnet, it is necessary to apply a magnetizing magnetic field having a coercive force or more to the permanent magnet, but in order to magnetize a high coercive force type permanent magnet, the coercive force is large, so that a high magnetic field is generated. Therefore, large-scale equipment is required. Further, when magnetizing a large-sized magnet by sandwiching it between pole pieces, the gap between the pole pieces becomes large, and it becomes difficult to obtain a large magnetizing magnetic field strength, and thus large-scale equipment is required to generate a high magnetic field. Therefore, when magnetizing a high coercive force type permanent magnet or a large-sized magnet, the coercive force of the permanent magnet is lowered by heating the permanent magnet by utilizing the fact that the temperature coefficient of the coercive force in the permanent magnet is negative,
As a result, the magnetizing rate of the permanent magnet can be increased even with a normal magnetizing magnetic field strength without using a large-scale magnetic field generator. However, when the heated and magnetized permanent magnet is removed from the magnetizer while it is still hot, if the permeance coefficient deviates from the linear part of the demagnetization curve of the permanent magnet, demagnetization occurs due to the demagnetizing field of the magnetic pole of the magnet itself. The magnetic characteristics will deteriorate. Therefore, heating is performed until the coercive force of the permanent magnet becomes equal to or lower than the magnetizing magnetic field strength, and then the permanent magnet is magnetized by cooling it to room temperature while maintaining the permeance coefficient in the linear portion of the demagnetization curve. It is possible to obtain a permanent magnet having a high magnetic susceptibility and high magnetic properties.

Therefore, according to the present invention, the permanent magnet is heated and magnetized until the coercive force of the permanent magnet becomes equal to or less than the magnetizing magnetic field strength, and then the permeance coefficient is kept at room temperature with the linear portion of the demagnetization curve. A method of magnetizing a permanent magnet to be cooled, wherein the permanent magnet has a relatively large temperature coefficient of coercive force and is relatively large (R is one or more rare earth elements including Y). ) Is preferred.

The reasons for limitation of the present invention will be described below. In the present invention, the permanent magnet is heated until the coercive force of the permanent magnet becomes equal to or less than the magnetizing magnetic field strength of the magnetizer. The coercive force is sufficiently magnetized if the coercive force is larger than the magnetizing magnetic field strength. Because you can't. Also, after heating, magnetization is performed and the permanent magnet is cooled to room temperature while the permeance coefficient is in the straight line part of the demagnetization curve. This is because the permanent magnets are permanently demagnetized by the demagnetizing field of the magnetic poles of the permanent magnets themselves, and the magnetic characteristics are deteriorated. As a magnetized permanent magnet, the temperature coefficient of coercive force is negative and R-Fe- is larger than that of other magnet materials.
B-based permanent magnet (R is one or two rare earth elements including Y)
Or more) are preferred. Alternatively, after preheating, the magnetization may be performed using a magnetizer having a heating device.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

(Embodiment 1) FIG. 1 shows a schematic view of a magnetizer. This magnetizer has a pole piece 2 with a diameter of 1 at the tip cross section.
00 mm and a gap of 10 mm to generate a magnetizing field strength of 25 kOe. 40x7 using this magnetizer
0x30mm (magnetization direction: 30mm) Nd-Fe-B
System sintered magnet (Br = 12.5kG, iHc = 14.5k
Oe) was magnetized by the following procedure. First, as shown in FIG. 2, the permanent magnet 3 has a diameter of 100 mm and a thickness of 10 m.
scissors between SS-41 ferromagnets 4 with m heating device,
It was set between the pole pieces 2 of the magnetizer. Next, the Nd-Fe-B type | system | group magnet part was heated to 140 degreeC with the heating device, and the magnetizing magnetic field was applied and magnetized. The magnetizing magnetic field strength at this time was 8 kOe. After magnetizing the magnet, the magnetizing magnetic field is removed and the magnet is sandwiched as shown in FIG.
S-41 Ferromagnetic material SS-4 so that it closes like a magnetic circuit
1. A ferromagnetic yoke was attached. After mounting, the magnet and the SS-41 ferromagnetic material were removed from the magnetizer with the magnet and SS-41 ferromagnetic material assembled, and cooled to room temperature. After cooling, the SS-41 ferromagnetic material was removed from the magnet and the magnetic flux was measured to obtain a magnetic flux density of 7300G. FIG. 6 schematically shows changes in magnetic flux after heating and magnetization (a: room temperature → b: 140 ° C. → c: room temperature → d: when a ferromagnetic material is removed).

(Embodiment 2) With the magnetizer used in Embodiment 1, 4
Nd-F of 0x70x30mm (magnetization direction: 30mm)
e-B system sintered magnet (Br = 12.5kG, iHc = 1
4.5 kOe) was magnetized by the following procedure. First, as shown in FIG. 2, this magnet was sandwiched by a permender having a heating device having a diameter of 100 mm and a thickness of 10 mm, and set between pole pieces of a magnetizer. Next, the Nd-Fe-B type | system | group magnet part was heated to 140 degreeC with the heating device, and the magnetizing magnetic field was applied and magnetized. The magnetizing magnetic field strength at this time was 8.5 kOe. After magnetizing the magnet, the magnetizing magnetic field was removed, and an SS-41 yoke was attached so that the permenders sandwiching the magnet closed in a magnetic circuit as shown in FIG. After mounting, the magnet, the permendur and the SS-41 were removed from the magnetizer with the magnet assembled, and cooled to room temperature. After cooling, from magnet to permender and SS-4
1 was removed and the magnetic flux was measured to obtain a magnetic flux density of 7350G.

(Embodiment 3) Using the magnetizer shown in FIG.
Nd-F of 0x11x10mm (magnetization direction: 10mm)
e-B system sintered magnet (Br = 12.5kG, iHc = 1
4.5 kOe) was magnetized by the following procedure. Set this magnet between pole pieces as shown in Fig. 4,
Magnetization was performed by applying a magnetic field strength of Oe. After the magnetization, the demagnetization curve of the magnet was measured to obtain the demagnetization curve of FIG.

(Comparative Example 1) In the magnetizer used in Example 1, 4
Nd-F of 0x70x30mm (magnetization direction: 30mm)
e-B system sintered magnet (Br = 12.5kG, iHc = 1
4.5 kOe) was magnetized by the following procedure. First, as shown in FIG. 2, this magnet was sandwiched by a permender having a heating device having a diameter of 100 mm and a thickness of 10 mm, and set between pole pieces of a magnetizer. Next, the Nd-Fe-B type | system | group magnet part was heated to 140 degreeC with the heating device, and the magnetizing magnetic field was applied and magnetized. The magnetizing magnetic field strength at this time was 8.5 kOe. After magnetizing the magnet, it was removed from the pole piece while still hot and cooled to room temperature. After cooling, the yoke was removed and the magnetic flux was measured to obtain a magnetic flux density of 6500G. FIG. 6 schematically shows changes in magnetic flux after heating and magnetization (a ′: room temperature → b ′: 140 ° C. → c ′: room temperature demagnetization curve corresponding point → d ′: room temperature).

(Comparative Example 2) 40x using a magnetizer in FIG.
70x30 mm (magnetization direction: 30 mm) Nd-Fe-
B system sintered magnet (Br = 12.5 kG, iHc = 14.5
The kOe) was magnetized in the following procedure. This magnet is shown in Figure 4.
As shown in FIG. 5, the magnets were set between pole pieces and magnetized by applying a magnetizing magnetic field. The magnetizing magnetic field strength at this time was 8 kOe. After the magnetization, the magnetic flux is measured in the same manner as in Example 1 to obtain 530
A magnetic flux density of 0 G was obtained.

Comparative Example 3 Using the magnetizer shown in FIG.
Nd-F of 0x11x10mm (magnetization direction: 10mm)
e-B system sintered magnet (Br = 12.5kG, iHc = 1
4.5 kOe) was magnetized by the following procedure. Set this magnet between pole pieces as shown in Fig. 4,
Magnetization was performed by applying the magnetic field of e. After magnetization, the demagnetization curve of the magnet was measured to obtain the demagnetization curve of FIG. 5 (b).

[0016]

According to the present invention, sufficient magnetizing magnetic field strength can be obtained like a high coercive force type permanent magnet or a large-sized magnet without using large-scale equipment for generating a high magnetic field. It can be magnetized even when it is difficult, and its utility value is extremely high in industry.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a magnetizer.

[Fig. 2] Diagram of a permanent magnet sandwiched between ferromagnetic materials

[Fig. 3] A diagram in which a magnetic circuit is closed by a permanent magnet and a ferromagnetic material.

FIG. 4 shows a permanent magnet set on a pole piece.

FIG. 5 is a diagram showing a demagnetization curve.

FIG. 6 is a diagram showing changes in magnetic flux.

[Explanation of symbols]

1 magnetic field generating coil, 2 pole pieces, 3 permanent magnets, 4 ferromagnets, 5 permeance coefficient, 6 magnetic flux density obtained from magnets, 7 irreversible reduction.

Claims (2)

[Claims] 1. The permanent magnet is heated until the coercive force of the permanent magnet becomes equal to or less than the magnetizing magnetic field strength and then magnetized, and cooled to room temperature while the permeance coefficient is in the straight line portion of the demagnetization curve. A method for magnetizing a permanent magnet, characterized by: 2. The permanent magnet according to claim 1, wherein the permanent magnet is an R—Fe—B based permanent magnet (R is one or more rare earth elements including Y). Method.