JPS5923448B2 - anisotropic magnet - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in anisotropic magnets.

Anisotropic magnets, which are made by finely pulverizing crystalline anisotropic materials such as ferrite and rare earth cobalt alloys into single-domain particles and press-molding them in a specific magnetic field, can be used in speakers, motors, attraction magnets, telephones, etc. Widely used for electrical equipment.

Conventionally, this type of magnet is made by filling a mold 1 with magnetic powder 2 and then applying it to a panner 4 while forming a magnetic field in the direction of the arrow by a coil 3, as shown in FIGS. 1 and 2. Then, press molding is performed to impart magnetic anisotropy to the molded body.

Thereafter, if necessary, the material is sintered to solidify it, and a magnetic field is applied again to magnetize it depending on the type of use. However, the magnet 5 made by such a conventional method has its magnetization direction parallel to one direction as shown by the arrows in FIGS. 3 and 4. For example, the magnet 5 in FIG. When used for the field of a motor with a pole or larger size, it is necessary to remove a specified length from both J ends of the J-cut line cut along the line A-A in the figure, or to cut it as appropriate even if the direction of magnetization is slightly tilted. Ta.

In order to improve this problem, attempts have been made to make ferrite magnets (oxide magnets) by dividing a cylinder into two or more arcuate columns, magnetizing them, and then piecing them together (Japanese Patent Application Laid-Open No. 1983-1999). No. 22295). With these improvements, it has become possible to obtain a ferrite magnet that has a magnetic field radially radially from the center.
On the other hand, economic losses have arisen due to unbalanced magnetic properties or an increase in the number of processes due to the fact that separately magnetized materials are joined together using adhesives or frameworks. The inventor discovered that ferrite magnets and rare earth cobalt magnets have different radial magnetization patterns in the radial direction due to the different properties of the starting raw material powder95, and discovered that the characteristics of rare earth cobalt magnets can be effectively utilized. Ta.

In other words, in the case of a ferrite magnet, the shape of the powder particles in the layer 11 before molding is approximately square plate-like, and this shape almost determines the direction of easy magnetization, and the distance between this direction of easy magnetization and the pressing direction during powder molding is It is difficult to magnetize regularly radially in the radial direction with integrally molded products due to the regular relationship between the Due to the difference, sintering distortion occurs during sintering, which tends to cause cracks and chips, making it difficult to obtain a normal product.

On the other hand, in rare earth cobalt magnets, the shape of the powder particles before molding is approximately spherical. Based on this knowledge, the inventor recalled that it would be preferable to integrate rare earth cobalt magnets rather than to divide them, and completed the present invention. In rare earth cobalt magnets, since the powder particles are approximately spherical, a predetermined magnetization direction can be easily obtained even if the powder particles are integrally molded and then magnetized. The present invention has been made in view of the above points, and it is an object of the present invention to provide an anisotropic magnet made of rare earth cobalt powder that is integrally molded and has a through hole in the shaft part, which is particularly suitable for use in the field of a motor. The purpose is to

The magnet of the present invention is, for example, an annular magnet having anisotropy in the radial direction from the shaft portion produced by a press device as shown in FIG. For example, it can be magnetized in the direction of the arrow.

In FIG. 5, a powdered magnetic material 11 such as samarium cobalt that has been crushed to the state of single-domain particles is placed in a mold 12 and a through hole 13 is provided in the shaft portion, as described in the conventional example described above.
Press molding is performed using a punch 15 having a yoke 14 passed through the through hole 13.

During press molding, a magnetic field in the direction of the arrow is formed by coils 16 and 17 that are wound separately above and below the mold 12. Since this magnetic field is applied in the radial direction from the shaft of the cylindrical magnet, a magnet having anisotropy in this direction is obtained.

In order to form such a magnetic field well, Eil16,17
The casing 18 surrounding the bunch shaft and the yoke 14 of the bunch shaft
The mold 12 is made of a magnetic material such as iron, and the bunch 15 and the spacers 19 and 20 around which each coil is wound are made of a material with relatively low magnetic permeability, preferably a non-magnetic material such as copper. This is desirable.

The annular magnet 21 of the present invention made as described above has anisotropy in the radial direction from its shaft, so as shown in FIG. It is possible to alternately form magnetized portions Y in the direction outward from the portion, and this can be used as is for the rotor of a step motor.

The method of magnetizing the magnet shown in FIG. 6 may be achieved by using a magnetizing yoke in which S poles and N poles are alternately directed inward from all sides. In addition, if all the magnets are magnetized in the direction of the shaft or in the opposite direction, a motor field magnet 22 as shown in FIG.
3, it is magnetized with a uniform distribution in the radial direction, so it is possible to form a larger magnetic field with the same volume.

Figure 8 shows the distribution of the magnetic field strength H with respect to the motor rotation angle θ seen from the motor axis when the magnet shown in Figure 7 is used as the field of the motor. b' is a conventional magnet, and it can be seen that the former has a significantly more uniform distribution of magnetic field strength than the latter.

In addition, although the pressurizing chamber of the mold for manufacturing the magnet of the present invention is described as being cylindrical in FIG. The surface can be of any shape, such as a square or a triangle.

[Brief explanation of drawings]

Figures 1 and 2 are vertical cross-sectional views of a press machine for explaining a conventional magnet molding method, Figures 3 and 4 are perspective views of magnets made by these machines, and Figure 5 is a press machine according to the present invention. FIG. 6 is a longitudinal cross-sectional view of a press apparatus for manufacturing magnets, FIG. 6 is an annular magnet made by this, FIG. 7 is an end view of the divided magnet of the present invention and a conventional magnet, and FIG. It is a graph comparing the magnetic fields formed by these. FIG. 9 is a graph showing a comparison of the surface magnetic flux densities of the magnet of the present invention and the segmented ferrite magnet. 12...Mold, 14...Yoke, 15...Punch, 16, 17...Coil, X...Towards the shaft part A portion magnetized in the Y direction, a portion magnetized in a direction outward from the shaft.

Claims (1)

[Claims] 1. Consisting of a rare earth cobalt powder integrally molded with a through hole in the shank and a magnetization direction along the radial direction from the shank, and anisotropy in the radial direction from the shank. An anisotropic magnet characterized by a flattened structure. 2. An anisotropic magnet according to claim 1, characterized by having a portion magnetized in a direction toward the shaft portion and a portion magnetized in a direction outward from the shaft portion.