JP3007492B2 - Inner closed magnetic circuit type anisotropic magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner surface closed magnetic circuit type anisotropic magnet, and more particularly, to an improvement in a surface magnetic field on a working surface after magnetization. The present invention can be universally applied to applications that require a strong surface magnetic field or a long magnetic field line length, and the application is not particularly limited. It is suitable for use as a fixed display magnet such as a sheet or an adsorption display panel, as well as a health appliance.

[0002]

2. Description of the Related Art Conventionally, rare earth or ferrite based sintered magnets or synthetic resin magnets have been used as adsorption and fixing magnets, and the orientation direction of magnetic powder is shown in FIG. 1 (a). Therefore, the quality of the magnetic properties depends on the type of the raw material used and the content of the magnetic powder. To improve this point, Japanese Patent Publication No. 63-59243 proposes an anisotropic permanent magnet in which the magnetic properties are improved by modifying the orientation direction of the magnetic powder. In this magnet, as shown in FIG. 2A, the direction of the axis of easy magnetization is focused and oriented from the non-working surface (all surfaces other than the working surface) to the working surface. If
The magnetic flux density per unit area (or the magnetic flux density per unit line segment) can be made larger than before. However, although the above-mentioned focused orientation type magnet has a large surface magnetic field as compared with an isotropic magnet, it is not always sufficient when considering its application to a signal generation magnet or the like.

Conventionally, as a magnet for signal generation, a magnetic powder particle in which the easy axis of magnetization is oriented isotropically or in the thickness direction has been used. Although the thickness-oriented magnet still has a larger surface magnetic field than the isotropic magnet, it was still not enough. As a countermeasure against the above-mentioned problem, it has been generally practiced to change the magnet material to one having good magnetic properties, but there have been the following problems. (1) Increasing costs. (2) Magnetization is difficult due to the large intrinsic coercivity of the material.

[0004]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems, in which a large surface magnetic field peak value can be obtained without using an expensive material and without causing a disadvantage that the specific coercive force is increased. The aim is to propose an anisotropic magnet obtained.

[0005]

First, the details of the invention will be described. Now, the inventors compared the conventional magnet having the magnetic powder orientation (hereinafter referred to as axial orientation) along the plate thickness direction shown in FIG. 1A with a change from the non-active surface shown in FIG. In order to elucidate the reason why the magnet oriented in the direction of focusing (hereinafter referred to as the focusing orientation) is superior in magnetic properties, the inventors have conducted intensive studies. I came to think that it might be in the lines of magnetic force radiated on Thus, when the lines of magnetic force that are radiated unnecessarily at the time of adsorption are eliminated and the radiation of the magnetic flux is limited to the working surface, an unexpected result was obtained with respect to the improvement of the magnetic characteristics. The present invention is based on the above findings.

That is, the gist of the present invention is as follows. 1. A permanent magnet having one or two or more magnetic powder particle orientation regions on a plane or curved working surface, wherein the easy axis of the magnetic powder particles in the orientation region extends from the peripheral edge of the region to the inside of the magnet. And the inner surface closed magnetic path type anisotropic magnet is oriented so as to be focused again at the center of the region. 2. 2. The inner closed magnetic path type anisotropic magnet according to the above item 1, wherein the magnet shape is a flat plate shape. 3. 3. The inner closed magnetic path type anisotropic magnet according to the above item 2, wherein the upper surface or the lower surface of the plate-shaped magnet is used as a working surface, and the whole working surface becomes a single orientation region. 4. One or both sides of the upper and lower surfaces of the plate-shaped magnet are used as the working surface,
3. The internal closed magnetic circuit type anisotropic magnet according to the above item 2, having a plurality of orientation regions on the working surface. 5. 2. The inner surface closed magnetic circuit type anisotropic magnet according to the above item 1, wherein the magnet has an annular shape. 6. 6. The inner closed magnetic circuit type anisotropic magnet according to the above item 5, wherein the upper surface or the lower surface of the toroidal magnet is used as a working surface, and a plurality of orientation regions are provided on the working surface. 7. 6. The inner closed magnetic circuit type anisotropic magnet according to the above item 5, wherein the inner circumferential surface or the outer circumferential surface of the annular magnet is used as a working surface, and a plurality of orientation regions are provided on the working surface. 8. 2. The inner closed magnetic path type anisotropic magnet according to the above item 1, wherein the magnet has a spherical shape, the entire surface of the sphere is a working surface, and a plurality of orientation regions are provided on the outer working surface.

Hereinafter, the present invention will be described specifically. The magnet according to the present invention has a working surface composed of a flat surface or a curved surface. Therefore, the attraction action by the magnet can be performed on an arbitrary surface, and application to a rotor of a precision motor or the like is also possible. Also, an orientation region of the magnetic powder particles is formed on the working surface of the magnet. The number of magnets may be one or several when the magnets are used for simple adsorption or the like. However, for example, when the magnets are applied to a length measuring device or the like, they need to be arranged in a large number at regular intervals.

The most important feature of the present invention resides in the orientation of the axis of easy magnetization of the magnetic powder particles in the magnetic powder orientation region. That is, in the present invention, the axis of easy magnetization of the magnetic powder particles is as shown in FIG.
In the case of a flat (disk) -shaped magnet, as shown by the broken line, the magnet is oriented along a series of lines passing from the peripheral edge of the magnetic powder orientation region to the inside of the magnet and again toward the center of the region, and as a result, In the above area, in a section perpendicular to the working surface,
It looks as if the easy magnetization axes are arranged along the annual ring pattern. As a result of the easy axis of magnetization being arranged as described above, in the above-mentioned orientation region, the distribution of the lines of magnetic force after magnetization also matches the easy axis of magnetization and presents an annual ring-shaped pattern. Completely gone.

As a result, the surface magnetic field pattern on the working surface of the magnet of the present invention is as shown in FIG.
Compared to the conventional axially oriented magnet and the focused oriented magnet shown in FIG. 2B and FIG. 2B, a sharper mountain shape is drawn, so that a higher surface magnetic field than before and a deep magnetic flux line can be obtained. You get the length.

As described above, as an example of a magnet having a flat plate shape, FIG.
The disk-shaped magnets having the magnetic powder orientation as shown in FIG. 4A have been mainly described. However, as shown in FIG. 4B, the magnets are oriented so as to converge from the outermost periphery and the center to the intermediate band. Further, a magnet having a rectangular shape (FIG. 4C) is also advantageously adapted. Further, a magnet having a disk shape or a strip shape as shown in FIGS. 5 (a) and 5 (b), in which a plurality of orientation regions are arranged on a single working surface along a fixed pitch or a geometric pattern, Although not shown in the drawings, the magnet of the present invention includes a magnet in which both surfaces are set as working surfaces and a plurality of orientation regions are provided on each surface.

The present invention can be applied not only to the above-mentioned flat magnets but also to magnets of various shapes. Hereinafter, a magnet having a typical shape will be described. -Annular magnet Here, the annular magnet means mainly a cylindrical or ring-shaped magnet. FIG. 6 is a perspective view showing the radiation state of the magnetic field lines when a magnet having the upper surface of the toroidal magnet as the working surface and magnets in which magnetic particles are regularly arranged on the working surface is magnetized.
FIGS. 7A and 7B show AA and BB in FIG.
FIGS. 8A and 8B show the orientation direction of the easy axis of the magnetic particles in the cross section, and FIGS. 8A and 8B show the surface magnetic field patterns at that time. As is clear from FIG. 8, even in this case, there is almost no radiation of the magnetic field lines from surfaces other than the working surface. In addition, since the surface magnetic field pattern has a clean mountain shape and exhibits a peak effect, it is needless to say that a deep magnetic field line reaching length can be obtained, and control accuracy can be improved particularly when used for signal generation. . Further, in this magnet, the polarities of the peak poles in the magnetic field generating operation region can be made the same, and the surface magnetic field peak value can be further improved by making the same polarity.

Next, FIGS. 9 (a) and 9 (b) show an annular magnet in which the outer peripheral surface and the inner peripheral surface are used as working surfaces and the magnetic powder particles are regularly arranged on the working surfaces. Illustrate. Here, the annular magnet and the disk-shaped magnet as shown in FIGS. 6 and 5A are used as health pendants, and the annular magnet as shown in FIG. 9A is used as a signal generating magnet. An annular magnet as shown in FIG. 9 (b) is particularly advantageous as a health bracelet. In the above example, the cross-sectional shape of the magnet is described as an annular magnet having a rectangular cross-section, but the cross-sectional shape of the magnet is not limited to this case.
(A), (b) and (c) may be semicircular or triangular in which the upper and lower surfaces are respectively arc-shaped.

Spherical magnet As shown in FIG. 11 (a), a spherical surface is used as an active surface, and magnetic particles are oriented at a constant pitch along a meridian and / or a latitude line on the active surface. . In this spherical magnet, as shown in FIG. 11 (b), it is possible to provide a projection on the surface of the sphere, and to form an orientation region of the magnetic powder at the projection. Such spherical magnets are particularly suitable for use in applications such as health magnets.

Although the magnet having the typical shape has been described above, the magnet shape is not limited to this case.
A rectangular parallelepiped as shown in (a), (b), (c) and (d), a polygonal truncated pyramid such as a truncated triangular pyramid or a quadrangular pyramid, or a hemisphere, or a triangular prism or an elliptical prism may be used. The point is that the axis of easy magnetization of the magnetic powder particles may be oriented so that it passes through the inside of the magnet from the periphery in the orientation region of the working surface and converges to the central region of the working surface.

[0015]

The present invention is applicable to both synthetic resin magnets and sintered magnets. For example, as the magnetic powder in the synthetic resin magnet and the sintered magnet, any of conventionally known magnetic powders such as ferrite-based magnetic powder, alnico-based magnetic powder, and rare earth-based magnetic powder such as samarium-cobalt-based magnetic powder and neodymium-iron-boron-based magnet can be used. The average grain size is preferably about 1.5 μm for ferrites and about 5 to 50 μm for others.

As the synthetic resin, any conventionally known synthetic resin can be used, and typical examples thereof are as follows. Polyamide-based synthetic resins such as polyamide-6 and polyamide-12. Homo- or copolymerized vinyl synthetic resins such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polymethyl methacrylate, polystyrene, polyethylene, and polypropylene. Synthetic resins such as polyurethane, silicone, polycarbonate, PBT, PET, polyetheretherketone, PPS, chlorinated polyethylene, and Hypalon. Rubbers such as propylene, neoprene, styrene butadiene and acrylonitrile butadiene. Epoxy resin. Phenolic synthetic resin. Further, the mixing ratio of the magnetic powder and the synthetic resin as the binder depends on the application, but generally, the magnetic powder is 40 to 40% by volume percentage.
It is desirable to be about 70 vol%. In addition, it goes without saying that an appropriate amount of conventionally used plasticizers, antioxidants, surface treatment agents, and the like can be used according to the purpose.

In the present invention, the surface magnetic field is improved by controlling the orientation direction of the magnetic powder in the magnet. FIG. 13 shows the orientation of the magnetic powder according to the present invention.
This is illustrated by taking a disk-shaped magnet as an example. In the figure, number 1 is a cavity provided in a magnetic field orientation molding die, 2 is a main pole, 3 is a counter electrode,
4 is a yoke. In this example, the case where a permanent magnet is used as the main pole 2 and the counter electrode 3 has been described, but the present invention is not necessarily limited to this, and an electromagnet may be used. Now, after a synthetic resin magnet in which, for example, a magnetic powder and a synthetic resin are mixed at a predetermined ratio is inserted into the cavity 1,
When the magnetic pole is installed at a predetermined position, the axis of easy magnetization of the magnetic powder particles is oriented along the magnetic force lines 5 indicated by arrows in the figure. Here, the lines of magnetic force are emitted only on the working surface, and there is almost no leakage of magnetic flux from other surfaces.

FIG. 14 schematically shows a typical example of a magnetic field orientation molding machine having an injection mold suitable for producing a plurality of the above disk-shaped magnets at one time. In this example, the case where the magnetic circuit is formed by the permanent magnet has been described, but the electromagnet can be used instead of the permanent magnet as described above.

Next, a description will be given of a mold magnetic circuit suitable for use in manufacturing an annular magnet having an upper surface as a working surface. Fig. 15
Denotes a single-pole magnetomotive force generator, in which reference numeral 6 denotes a permanent magnet serving as a main body of the magnetomotive force, and 7 denotes a non-magnetic material. The magnetomotive force generating portion faces the magnet working surface side of the annular cavity. By arranging them at appropriate intervals, a magnet having a desired magnetic powder orientation can be obtained. FIG. 16 shows a multi-pole magnetomotive force generating device. In this device, a ferromagnetic yoke 4 'is disposed so as to face the entire surface of the cavity 1 on which the magnet acts, and the ferromagnetic yoke 4' is provided in the ferromagnetic yoke 4 '. Desired number of permanent magnets 6
Are buried and arranged at appropriate intervals.

The feature of the above-described mold magnetic circuit is that a magnetomotive force generator is intermittently arranged on the working surface side of the mold cavity,
This portion where the magnetomotive force is generated is covered with a ferromagnetic material.
As described above, it is advantageous to install the magnetism generating portion so that the magnetism-side magnets have the same polarity. In other words, by adopting the above-described homopolar arrangement, the lines of magnetic force exit from the product cavity side of the magnetomotive force generating section in the independent magnetic powder particle orientation regions, and curve inside the cavity around this magnetic pole surface. It enters the ferromagnetic material surrounding the magnet and returns to the opposite pole of the magnetomotive force generating part through the ferromagnetic material. In the present invention,
This curved line of magnetic force is used as an orientation magnetic field. When the magnetic field is oriented in this way, there is almost no radiation of the line of magnetic force from a surface other than the working surface. In the above-described mold magnetic circuit, the magnetomotive force generating body may be an electromagnet or a strong permanent magnet, but is preferably made of a permanent magnet in that the mold can be simplified.

As the molding method, any conventionally known method can be used and is not particularly limited, but injection molding, compression molding, RIM molding and the like are particularly advantageously applicable. Here, the product obtained by compacting can be completed as a sintered magnet by sintering, and can be directly provided as a plastic magnet without sintering by selecting a binder in advance. Heretofore, the number of magnetic poles of the ring magnet for signal generation has been limited to an even number due to manufacturing restrictions, but in the present invention, it can be set to either an odd number or an even number.

[0022]

Embodiment 1 Using a mold in which the magnetic circuits shown in FIGS. 17 (a) and (b) and FIGS. 18 (a) and (b) were set, the diameter was 30 mm, respectively.
A disc-shaped or square magnet having a height of 10 mm was formed by a magnetic field orientation injection molding method or a magnetic field orientation compression molding method under the following conditions.

[Table 1] Raw materials ・ Magnetic powder particles Magnetic powder A: Ferrite magnetic powder (Magnetoplumbite-based strontium-based ferrite with an average particle diameter of 1.5 μm B: Samarium-cobalt magnetic powder (Sm ₂ Co _17- based: average particle diameter of 10 μm) ・ Synthetic resin: Polyamide 12 ・ Plasticizer: TTS (isopropyl triisostearoyl titanate)

[0023]

[Table 2] Formulation • Formulation A (Plamag formulation) Magnetic powder: 64 vol% Polyamide 12: 35 vol% TTS: 1 vol% • Formulation B (sintering formulation) Magnetic powder: 50 wt% Water: 50 wt%

[0024]

[Table 3] Molding conditions • Injection molding conditions (magnetic coil orientation injection molding machine with built-in coil) Pellet compound used: Compound A Injection cylinder temperature: 280 ° C Mold temperature: 100 ° C Injection pressure: 1500 kg / cm ² Excitation time: 20 seconds Cooling time: 25 seconds Injection cycle: 40 seconds-Compression molding conditions Raw materials: Formulation B Drainage method: Chamber method Excitation method: Vertical magnetic field Molding temperature: 25 ° C Firing temperature: 1250 ° C

Table 4 shows the results obtained by examining the surface magnetic field (peak value) of the thus obtained disk magnet and square magnet after magnetization and the number of linear magnetic fluxes when attracted to an iron plate. Here, the number of linear magnetic fluxes corresponds to the total area of the magnetic flux distribution as illustrated in FIG.

(Equation 1) Is the value represented by

[0026]

[Table 4]

As is apparent from Table 4, each of the inner closed magnetic path type magnets obtained according to the present invention has a surface magnetic field on the working surface which is larger than that of the axially oriented magnet and the focused oriented magnet obtained according to the conventional method. Also, the magnetic flux density on the adsorption surface when adsorbed on the iron plate is remarkably improved. Therefore, the inner closed magnetic path anisotropic magnet of the present invention has an advantage that the attraction force is remarkably superior to the conventional magnet.

Example 2 An annular magnet having the shape and dimensions shown in FIG. 20 was produced under the following conditions using a mold having a magnetic circuit as shown in FIG. 16 described above. For comparison, magnets having the same dimensions were manufactured using the conventional mold shown in FIG.

[0029]

[Table 5] Magnetic circuit device ・ Magnetomotive force generation unit When the magnetic powder is ferrite, use a rare earth (Sm-Co) permanent magnet. When the magnetic powder is a rare earth type, an electromagnet method is used. The magnetic pole shape is 4mmφ × 20mm, and 22 poles are installed at the center of the product working surface at equal intervals. -Use ferromagnetic material SKD11. Shape is 60mmφ ×
52mmφ × 25mm, set up to wrap rare earth permanent magnets. -Other mold members SUS 304.

[0030]

[Table 6] Raw materials ・ Magnetic powder particles Magnetic powder A: Ferrite magnetic powder (Magnetoplumbite-based strontium-based ferrite with an average particle diameter of 1.5 μm B: Samarium-cobalt magnetic powder (Sm ₂ Co _17- based: average particle diameter of 20 μm) ・ Synthetic resin: Polyamide 12 ・ Plasticizer: TTS (isopropyl triisostearoyl titanate)

[0031]

[Table 7] Formulation ・ Formulation A (Plamag formulation) Magnetic powder: 66 vol% Polyamide 12: 33 vol% TTS: 1 vol% ・ Formulation B (sintering formulation) Magnetic powder: 40 wt% Water: 60 wt%

[0032]

[Table 8] Molding conditions • A: Injection molding conditions Injection cylinder temperature: 300 ° C Mold temperature: 100 ° C Injection pressure: 1800 kg / cm ² Cooling time: 15 seconds Injection cycle: 30 seconds • B: Compression molding conditions Drainage Method: Injection method Molding temperature: 20 ° C Firing temperature: 1250 ° C

Table 9 shows the results of examining the surface magnetic field (peak value) of the thus obtained annular magnet as it is or after magnetization. The magnetization condition is 1200
V, 1500 μF, and a yoke set to a magnetic circuit similar to that shown in FIG. 16 was used as a magnetized yoke.

[0034]

[Table 9]

As is clear from Table 9, the surface magnetic field peak value of each of the inner closed magnetic circuit type magnets obtained according to the present invention is remarkably improved as compared with the magnet obtained according to the conventional method.

[0036]

As described above, according to the present invention, the peak value of the surface magnetic field and the length of the line of magnetic force at the working surface of the magnet can be significantly improved. A surface magnetic field exceeding that of the magnet can be obtained.

[Brief description of the drawings]

FIG. 1A is a magnetic force diagram of a conventional axially oriented magnet. (B) is a diagram showing a surface magnetic field pattern on the working surface of the magnet.

FIG. 2A is a diagram illustrating a magnetic field line distribution of a conventional focused and oriented magnet. (B) is a diagram showing a surface magnetic field pattern on the working surface of the magnet.

FIG. 3 (a) is a diagram showing a magnetic field line distribution of a disk-shaped inner surface closed magnetic circuit type magnet according to the present invention. (B) is a diagram showing a surface magnetic field pattern on the working surface of the magnet.

FIG. 4 is a diagram showing an orientation state of an axis of easy magnetization of magnetic powder particles in a flat magnet according to the present invention.

FIG. 5 is a schematic view showing a case where a plurality of magnetic particle orientation regions are provided in a disk-shaped magnet and a strip-shaped magnet according to the present invention.

FIG. 6 is a perspective view showing a state of radiation of lines of magnetic force after the annular magnet according to the present invention is magnetized.

7A is a diagram showing the orientation direction of the axis of easy magnetization of the magnetic powder particles in the AA cross section in FIG. 6; (B)
FIG. 7 is a diagram showing the orientation direction of the easy axis of magnetization of the magnetic powder particles in the BB section of FIG. 6.

FIG. 8A is a diagram showing a surface magnetic field pattern in an AA section of FIG. 6; FIG. 7B is a diagram showing a surface magnetic field pattern in the BB section of FIG. 6.

FIG. 9A is a diagram showing an annular magnet having an outer peripheral surface as an action surface. (B) is a diagram showing an annular magnet having an inner peripheral surface as a working surface.

FIG. 10 is a view showing a preferred cross-sectional shape of an annular magnet.

FIG. 11 (a) is a schematic diagram of a spherical magnet according to the present invention. (B) is a schematic diagram of a spherical magnet with a projection.

FIG. 12 is a diagram showing a preferred shape of a magnet according to the present invention.

FIG. 13 is a schematic view of a molding die in which a magnetic circuit suitable for use in manufacturing the inner surface closed magnetic circuit type disk-shaped magnet according to the present invention is set.

FIG. 14 is a schematic diagram of a magnetic-field-oriented injection molding machine suitable for use in manufacturing an inner surface closed magnetic circuit type disk-shaped magnet according to the present invention.

FIG. 15 is an explanatory diagram of a single-pole magnetomotive force generator suitable for use in manufacturing an annular magnet.

FIG. 16 is an explanatory view of a multi-pole magnetomotive force generator suitable for use in manufacturing an annular magnet.

FIG. 17 is a schematic diagram of a molding die in which a suitable magnetic circuit is set for use in manufacturing the flat magnet according to the present invention.

FIG. 18A is a schematic view of a conventional mold for forming an axially oriented magnet. (B) is a schematic diagram of a molding die for a conventional focused and oriented magnet.

FIG. 19 is an explanatory diagram of a calculation procedure of a line magnetic flux number.

FIG. 20 is a diagram showing dimensions of an annular magnet produced in Example 2.

FIG. 21 is a schematic view of a conventional molding die for manufacturing an annular magnet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cavity 2 Main pole 3 Counter electrode 4, 4 'Yoke 5 Magnetic field line 6 Magnetomotive force generator 7 Non-magnetic material 8 Excitation coil

──────────────────────────────────────────────────の Continuing on the front page (72) Koichi Indai, 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. (72) Takahiro Kikuchi 1, Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation (58) Investigated field (Int. Cl. ⁷ , DB name) H01F 7/02

Claims (8)

(57) [Claims] 1. A permanent magnet having one or two or more magnetic particle particle orientation regions on a plane or curved working surface, wherein the easy axis of the magnetic powder particles in the orientation region is a peripheral portion of the region. An inner surface closed magnetic circuit type anisotropic magnet which is oriented so as to pass through the inside of the magnet from and through to the center of the region again. 2. The inner closed magnetic path type anisotropic magnet according to claim 1, wherein the shape of the magnet is a flat plate. 3. The anisotropic magnet according to claim 2, wherein an upper surface or a lower surface of the plate-shaped magnet is used as a working surface, and the entire working surface becomes a single orientation region. 4. The inner closed magnetic circuit type anisotropic magnet according to claim 2, wherein one or both of the upper and lower surfaces of the plate-like magnet is used as a working surface, and the working surface has a plurality of orientation regions. 5. The inner closed magnetic path type anisotropic magnet according to claim 1, wherein the magnet has an annular shape. 6. The anisotropic magnet according to claim 5, wherein the upper surface or the lower surface of the toroidal magnet is used as a working surface, and a plurality of orientation regions are provided on the working surface. 7. The internal closed magnetic circuit type anisotropic magnet according to claim 5, wherein an inner peripheral surface or an outer peripheral surface of the toroidal magnet is used as a working surface, and a plurality of orientation regions are provided on the working surface. 8. The inner closed magnetic path type anisotropic magnet according to claim 1, wherein the magnet has a spherical shape, the entire surface of the sphere is a working surface, and a plurality of orientation regions are provided on the outer working surface.