JPH069471Y2 - Multipolar anisotropic cylindrical plastic magnet mold - Google Patents

Description

[Detailed Description of the Invention] <Industrial field of application> The present invention relates to a mold for molding a so-called multipolar anisotropic plastic magnet in which ferromagnetic powder is orientated anisotropically using plastic as a binder. is there.

<Prior Art> Plumbide type ferrite powder, samarium / cobalt alloy magnet powder, or a mixture of rare earth / iron / boron alloy magnet powder and synthetic resin or a kneaded material is molded into a predetermined shape by a mold (injection). Molding, extrusion molding, roll molding, or compression molding), so-called plastic magnets are used as gaskets for refrigerator doors, as well as rotors and magnet rolls for various stepping motors.
It is being adopted in many fields and types. In particular, in recent years, there is a strong demand for higher performance, that is, higher magnetic characteristics. In addition to the conventional isotropic and radial magnetic anisotropy technologies, we have moved to a more anisotropic orientation technology that achieves even higher magnetic characteristics. And research and development are done. Part of the magnetic powder is also shifting from ferrite to higher performance rare earth alloy magnets.

Known polar anisotropic orientation techniques include a method of incorporating a permanent magnet into a mold or an electromagnet method as a magnetic field generation source for orientation, and many products have already been put on the market under various contrivances.

In addition, with the aim of further improving performance, JP-A-59-220911
In the publication, a permanent magnet embedding / electromagnet (pulse current) method is proposed. In this method, a permanent magnet is used as a coil yoke for applying a pulse wave-shaped magnetic field.

However, in this method, since the magnetic permeability of the permanent magnet is low, the generated magnetic field is a magnetic field generated by the current itself, and is generally lower than when a soft magnetic yoke having a high magnetic permeability is used. Therefore, it is necessary to flow a high current, which naturally becomes a short-time pulse current. That is, the orientation of the ferromagnetic powder, that is, the strong magnetic field that induces rotation in the binder, is sufficient for a very short time, that is,
It was difficult to achieve the orientation. Therefore, it is necessary to prepare a plurality of power supplies and continuously perform discharging.

<Problems to be Solved by the Invention> The object of the present invention relates to the improvement of the method of Japanese Patent Laid-Open No. 59-220911 mentioned above, and a multi-pole anisotropic cylindrical plastic magnet capable of generating a stronger magnetic field. It is to propose a molding die.

<Means for Solving the Problems> In the present invention, a large number of permanent magnets are alternately arranged around a cavity for molding a multi-pole anisotropic plastic magnet with their magnetic poles N and S facing toward the center of the cavity through a non-magnetic mold material. In a mold arranged so that a soft magnetic material is connected to the back of the permanent magnet, and a coil for magnetic field generation is wound around each permanent magnet-soft magnetic material connection body. It is a mold for molding a cylindrical plastic magnet.

<Operation> The present invention is one in which a soft magnetic material portion having a high magnetic permeability is connected to one end of a permanent magnet embedded in a mold as described above.
The soft magnetic material generates a stronger magnetic field in a predetermined direction due to the high current flowing through the coil, so that the ferromagnetic powder in the compound being filled in the cavity and being molded is more anisotropically oriented. It can be achieved at a high level. Therefore, at this time, the applied current can be set to be slightly lower than that in the case of JP-A-59-220911, so that the time during which the current is flowing can be lengthened. In this way, the degree of orientation in the ferromagnetic material in the compound can be further increased.

In addition, subsequently, if a current that is even lower and that can be energized for a long time is passed, a combined magnetic field of the magnetic field corresponding to the current and the magnetic field of the permanent magnet can be continuously applied, so that the orientation degree is It is further improved. Further, in the present invention, since the permanent magnet can be exposed as a part of the outer peripheral surface of the cavity, there is an advantage that the magnetic field can be increased correspondingly.

The permanent magnet used in the present invention is preferably an alnico alloy magnet. The alloy has a high hardness and is suitable for forming a part of the die material. Moreover, since the residual magnetic flux density Br as a permanent magnet is high, the magnetic field induced by itself is considerably large.

In the present invention, a soft magnetic material having a high magnetic permeability such as S10C or S4C is preferably connected in a yoke shape to one end of a permanent magnet such as an alnico magnet. Then, the coil is arranged so as to wind the connection body of the permanent magnet and the soft magnetic body. When the number of turns of the coil is large, the generated magnetic field becomes strong, but on the other hand, considering the insulation and the durability of the mold in the limited space inside the mold, it is generally limited to several to 10 turns. .

Generally, the electric current is about 600 to 10,000 amperes. At this time, the maximum magnetic field is 90 due to the effect of the soft magnetic yoke.
The time is from 00 to 17,000 Oersted, and the magnetic field strength of 5000 Oersted or more is maintained for 3 to 5 msec.

It is desirable that after the high current is passed, a low current is continuously passed to secure a magnetic field corresponding to the current, and thus, it is possible to subsequently promote the orientation of the ferromagnetic material in the compound.

Further, when the permanent magnet used is an alnico magnet, it is easily demagnetized, but it is not demagnetized by the low current, and the magnetic flux generated by the permanent magnet also contributes, which is desirable.

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a horizontal sectional view of a mold of the present invention of a 4-pole arrangement type, FIG. 2 is a partial detailed view thereof, and FIG. 3 is a perspective view thereof. Permanent magnets 2 are arranged around the cavity 5 via a non-magnetic mold material 4 so that the magnetic poles N and S thereof alternate toward the center of the cavity. The soft magnetic yoke 1 is connected behind the permanent magnet 2. The permanent magnet-soft magnetic material connection body is surrounded by a coil 3. 6 is an outer frame of the mold, and in this example, the cavity 5
The outer periphery of is separated by the end of the permanent magnet 2 and the end of the non-magnetic die material.

Next, the following experiment was conducted in order to confirm the effect of the mold of the present invention.

Surface treated strontium ferrite by volume 67
% Of nylon 12 resin, a stabilizer and a lubricant are mixed into a mold according to the present invention and a pellet according to the present invention.
It was molded with the mold disclosed in Japanese Patent No. 911. Sm ₂ Co ₁₇ magnets were incorporated as permanent magnets, and S10C was used as the soft magnetic material yoke. A rotor with an outer diameter of 18 and a number of poles of 12 was prepared by injection molding at about 295 ° C. The applied current was 5000 A for the mold of the present invention and 6000 A for the conventional mold. As a result, the surface magnetic field of the rotor is
1630G, the conventional mold was 1510G.

<Effect of the Invention> As described above, when the mold according to the present invention is adopted, a high-strength magnetic field can be applied for a long time, and therefore a plastic magnet having high magnetic characteristics can be molded.

[Brief description of drawings]

FIG. 1 is a horizontal sectional view of a mold of the present invention, FIG. 2 is a partial detailed view of FIG. 1, and FIG. 3 is a perspective view thereof. 1 ... Yoke, 2 ... Permanent magnet, 3 ... Current coil, 4 ... Mold material (non-magnetic material), 5 ... Cavity, 6 ... Outer frame, 7 ... Direction of magnetic field lines.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Kashiro, 1st Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Headquarters (56) Bibliography 55-91118 (JP, U) 54-80 (JP, B2)

Claims (1)

[Scope of utility model registration request] 1. A mold in which a large number of permanent magnets are arranged around a cavity for forming a multi-pole anisotropic plastic magnet so that magnetic poles N and S are alternately arranged toward the center of the cavity through a non-magnetic mold material. In, a soft magnetic material is connected to the back of the permanent magnet, and a coil for generating a magnetic field is wound around each permanent magnet-soft magnetic material connection body. Type.