JPH0626169B2 - Method and apparatus for forming rare earth magnet in magnetic field - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and apparatus for forming a rare earth magnet having high performance magnetic properties in a magnetic field.

Magnets such as SmCo ₅ , Cu-added Sm ₂ Co ₁₇ , and Nd-Fe-B systems have been used in a wide range of fields because they have higher performance than conventional ferrite and alnico magnets. In applying the rare earth magnets to various uses, there are many demands not only for magnets having a single anisotropy direction but also for magnets having a special distribution. It is necessary to meet such special orientation demands in order to exert the high performance of rare earth magnets in various applications. For example, of the special magnetization distribution, a ring-shaped magnet whose anisotropy direction is a so-called radial distribution exhibits excellent performance when applied to stepping motors, linear actuators, magnetic couplings, etc. Is expected.

(Prior Art) However, a magnet having a special magnetization distribution such as a radial distribution is difficult in terms of a manufacturing method, and its practical use is limited.

Conventionally, in order to improve such a point, if a rare earth magnet material powder is magnetized with a magnetizing magnetic field in an arbitrary direction and then molded with an orientation magnetic field applied, a high orientation degree is obtained with a low orientation magnetic field. A molding method in a magnetic field based on the idea that it can be obtained has been proposed (JP-A-56-30706). The method of manufacturing a ring-shaped rare earth magnet oriented in the radial direction, which is specifically molded in a magnetic field by this method, defines the upper and lower punches, the center rod that defines the center hole of the ring magnet, and the outer surface of the ring magnet. A magnetizing air core coil and an orientation coil are attached to the molding machine, and a magnetic field of 5 KOe or more is generated by the magnetizing coil and magnetized by the magnetic flux flowing in one direction up and down, and then in the radial direction. It has a function of compressing the material powder between the upper and lower punches while applying a weak orientation magnetic field.

(Problems to be Solved by the Invention) However, in the above-mentioned device, a powder having a particularly high coercive force, for example, a non-nuclear type Cu-added 2-17 series rare earth cobalt series magnet for a plastic magnet is used after the aging protection. In the case of the powder used in a state where the magnetic force ( _I Hc) is 5 times or more that in the magnetic field orientation in a normal sintered magnet, extremely insufficient results are obtained.

The inventors of the present invention have diligently studied the radial orientation of the magnet powder having such a high _I Hc, and as a result, the magnetizing magnetic flux is applied to the _I Hc of the material in the magnetizing method such that the magnetizing magnetic flux flows in the cylindrical powder axial direction. On the other hand, it was found that the magnetization intensity due to the magnetization was not sufficient, which resulted in insufficient orientation.

(Means for Solving Problems) As a result of research on a magnetizing magnetic field applying method for solving the above-mentioned problems, the present inventors have found that pulse-like radial repulsion is applied to the magnetizing magnetic field applying magnetic field generating coils facing the same pole. It was found that a sufficient magnetizing magnetic field and thus the degree of orientation can be obtained only when a magnetic field is generated, which led to the present invention.

That is, by arranging magnetizing and magnetizing applying pulse magnetic field generating coils facing each other at the same pole above and below the die, it is possible to magnetize a powder aggregate having a high coercive force. Therefore, the arrangement of the pulsed magnetic field generating coil for applying magnetization according to the present invention is completely different from the arrangement in which the conventional magnetizing coil surrounds the die.

In the method of the present invention embodying this finding, molding, orientation, heat treatment, the powder as a material of the rare earth magnet is subjected to an appropriate treatment such as bonding, to maintain the shape as an aggregate having an appropriate unit, For example, when a magnetic field generated by a magnetizing magnetic field applying pulse magnetic field generating coil of the same polarity is applied to such an aggregate having an annular or disc shape, when the magnetic field repels inside the aggregate and leaks out of the aggregate, An extremely large magnetic field is generated in the aggregate. When such a homopolar facing magnetizing coil is arranged on the cylindrical axis of the assembly, the repulsive magnetic field due to the homopolar facing flows in the radial direction with respect to the assembly.

In the method of the present invention, when the molding is carried out while applying the repulsive magnetic field of the same polarity opposite to each other in the radial direction, the radially oriented magnet is obtained in the magnetizing step. For this reason, this method requires a high-power magnetizing coil for magnetization, but it is not necessary to perform the alignment step separately from the magnetization.

In addition, according to the method of the present invention, if the assembly is molded in an orientation magnetic field after being magnetized, a radial orientation magnet can be manufactured in a weak orientation magnetic field. In this method, the aggregate may be molded after being taken out from the container or the mold, or the aggregate may be continuously molded in the mold.

The apparatus according to the present invention is an apparatus for holding the above-mentioned powder as a ring-shaped aggregate by using a mold, and manufacturing a radial anisotropic rare earth magnet using a magnetizing magnetic field applying coil and an orienting coil. The gist of this is that the mill having a through hole, the upper punch and the lower punch that can be fitted into the through hole, the pulse magnetic field generating coil for applying a magnetizing magnetic field above and below the mill, and the magnetic field of the center rod and the orientation coil. It is characterized in that it is provided with a magnetic field coil for applying an orienting magnetic field which is arranged at a position on the yoke which is magnetically connected to the magnetic field or a coil for applying a magnetic field.

(Working) Especially when magnetizing in a ring-shaped oriented magnet manufacturing mold,
Since the ferromagnetic mold member existing around the above-mentioned powder aggregate is often higher in magnetic permeability than the powder, the magnetic flux of magnetization easily flows through the mold member. However, according to the method of the present invention, since magnetic fields of the same polarity are repelled by each other, even if there is a ferromagnetic mold member, the magnetic flux deflected by the repulsion strongly magnetizes the powder. Of course, the method of the present invention is useful even if the ferromagnetic mold member does not exist around the powder aggregate, and the repulsive magnetic field magnetizes the powder more strongly. Therefore, it can be said that the method of the present invention is highly useful in order to effectively magnetize a magnet material which has been improved in performance in recent years and thus to enhance the degree of orientation.

(Example) Hereinafter, the Example of this invention is described according to drawing.

FIG. 1 and FIG. 2 show a schematic configuration of a device for molding a rare earth cobalt magnet in a magnetic field. In this figure, a cylindrical through hole 2 is formed in the center of the die 1, and the through hole 2
The upper punch 3 is arranged so as to be vertically movable so as to be fitted into the through hole 2, and the lower punch 4 is arranged so as to be vertically moved so as to be fitted into the through hole 2 from below. A center rod 5 is inserted in the center of the upper punch 3 and a center rod 6 is provided in the center of the lower punch 4 so as to be vertically movable. Here, the upper punch 3 and the lower punch 4 are non-magnetic materials, and are the die 1, the center rod 5, and the center rod 6.
The outer yoke 10 is composed of a magnetic material having a saturation magnetic flux density Bs ≧ 10 KG. In the vicinity of the die 1, magnetic field generating coils 7A and 7B having the same poles and facing each other and having the same poles are arranged so as to face each other with the same poles through an outer yoke 10, and in the vicinity of the upper punch 3 and the lower punch 4 as well. In the vicinity of the upper and lower surfaces of the die 1, magnetizing magnetic field applying pulse magnetic field generating coils 8A and 8B facing each other are arranged.

The magnetic field generated by the orientation magnetic field applying coils 7A and 7B is applied in the radial direction to the material powder 9 filled in the die 1 as shown by the arrow in FIG. Since 6 and the outer yoke 10 are made of a magnetic material, it is possible to efficiently generate a magnetic field in the radial direction. However, the absolute value of the orientation magnetic field that is usually obtained is low.

In the above structure, the radial orientation rare earth magnet of the present invention is molded in a magnetic field as follows. First, the material powder 9 is put into the through hole 2 of the die 1 with the lower punch 4 fitted in the die 1 and the center rod 6 protruding.

Then, the upper punch is moved to the vicinity of the upper surface of the die 1, and a pulse current is applied to the magnetizing magnetic field applying coils 8A and 8B facing each other of the same pole. Using the obtained pulsed radial magnetic field, a strong magnetizing magnetic field of at least ₁ Hc of the powder pair is applied to pre-magnetize the material powder 9. In this case, air core coil 8A, 8B
It is easy to generate a large magnetic field using the one-way generated magnetic field generating means having a different polarity. However, in this case, when the die 1, the magnetic body 5 and the center rod 6 are present, most of the magnetic flux flows in the ferromagnetic body, so that only a very weak magnetizing magnetic field of 2 to 3 KOe is generated in the through hole 2. However, homopolar air core coil 8
Although A and 8B generate only a small magnetic field, they generate a repulsive radial magnetic field, so that the mortar 1, the center rod 5, and the center rod 6 are instantaneously magnetized in the radial direction, and the cavities between the center rod 6 and the mortar are generated. , A large magnetizing magnetic field is generated.

After magnetizing the material powder 9, the magnetizing magnetic field applying coils 8A, 8B
To the orientation magnetic field applying coils 7A and 7B by applying a relatively weak radial orientation magnetic field of ₁ Hc or less of the material and lowering the upper punch 3 to compress the material powder 9 Mold. As a result, a ring-shaped molded body is obtained in which the direction of anisotropy is the radial direction.

Fig. 3 shows Sm25.5%, Cu8 as material powder 9 (Fig. 1).
%, Fe15%, Zr 1.5%, Co50% composition and ₁ Hc = 7KOe
With a coercive force of, outer diameter 27 mm, inner diameter 23 m
6 is a graph showing the relationship between the orientation magnetic field strength, orientation degree, residual magnetization (Br), and maximum energy product ((BH) _m ) when a radial orientation ring with m and a height of 12 mm is molded. In this figure, when curve A is radially oriented without applying a magnetizing magnetic field, curve B is a one-way pulse magnetic field of a magnetizing coil with opposite poles facing each other before molding in a magnetic field, and C is a repulsive radial pulse magnetic field. Shows the characteristics when the material powder 9 is magnetized and then molded in a magnetic field. However, the degree of orientation in the figure is represented by the orientation of 1 directional orientation magnetic field strength of 12 KOe. In this case, in A and B, only a degree of orientation of about 50 to 60% can be obtained. However, when the radial magnetizing magnetic field of C according to the present invention is used, the degree of orientation is about 90%, which is a very remarkable effect.

(Effects of the Invention) A radially oriented magnet can be obtained in which the method of the present invention is applied to a material powder having a high coercive force, which has been difficult to achieve high orientation.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing an embodiment of an apparatus for carrying out the method of the present invention, FIG. 2 is a plan view of the II-II line of FIG. The figure is a graph showing the relationship between the orientation magnetic field, (BH) _max , Br, and the degree of orientation. 1 ... Mortar, 2 ... Through hole, 3, 4 ... Punch, 5, 6 ... Middle rod, 7A, 7B ... Magnetic field generating coil for applying an orienting magnetic field in the radial direction with the same pole facing each other, 8A, 8B ... ... Pulse magnetic field generating coil for magnetizing magnetic field application facing the same pole, 9 ... Powder aggregate, 10 ... External yoke.

Claims (3)

[Claims] 1. A method of molding a rare earth magnet in a magnetic field, wherein a powder as a raw material of the rare earth magnet is produced by magnetizing magnetization applying pulse generating coils (8a, 8b) arranged on the upper and lower sides of a die (1) and facing each other with the same polarity. A pulse magnetic field applied in a radial direction is applied to the aggregate (9) to magnetize the powder aggregate with a magnetic field in the same direction as the orientation direction, and at the same time as the magnetization, a yoke that connects the die and the intermediate rod. A magnetic field generating coil (7) for applying a radially oriented magnetic field facing each other of the same pole
a, 7b) a radial orientation magnetic field is applied to the powder aggregate, and the powder aggregate is molded in a state in which the radial magnetic field is applied. 2. A method for molding a rare earth magnet in a magnetic field, wherein a powder for use as a raw material for the rare earth magnet is produced by magnetizing and magnetization applying pulse generating coils (8a, 8b) arranged on the upper and lower sides of a die (1) and facing each other. A pulsed magnetic field applied in a radial direction is applied to the aggregate (9), the powder aggregate is magnetized with a magnetic field in the same direction as the orientation direction, and the powder is placed on a yoke connecting the die and the intermediate rod. After the magnetic field generating coils (7a, 7b) for applying the radial orientation magnetic field of the same pole are magnetized, a radial orientation magnetic field is applied to the powder aggregate after the magnetization, and the powder aggregate is applied with the radial magnetic field applied. A method for molding a rare earth magnet in a magnetic field, which comprises molding a body. 3. A device for molding a rare earth magnet in a magnetic field, comprising a hollow cylindrical die (1) having a through hole (2), and a hollow cylindrical die which can be fitted in the through hole of the die and is vertically movable. An upper punch (3), a hollow cylindrical lower punch (4) that can be fitted in a through hole of the die and is arranged to be movable up and down, a middle rod (5) that penetrates to the lower end of the cylindrical portion of the upper punch, An aggregate (6) of a powder that penetrates the cylindrical portion of the lower punch and reaches the upper end of the die, and an aggregate of powder loaded in a hollow portion formed by the die and the lower punch in which the intermediate rod is incorporated ( 9), magnetizing magnetic field applying pulse magnetic field generating coils (8a, 8b) located above and below the mortar, facing each other with the same pole, a yoke (10) connecting the mortar and the intermediate rod, and a homopole arranged on the yoke. Equipped with magnetic field generating coils (7a, 7b) for applying an orienting magnetic field in the radiation direction facing each other A device for molding rare earth magnets in a magnetic field.