JPS62133705A - Manufacture and device of multipolar anisotropic cylindrical magnet - Google Patents

Abstract

PURPOSE:To simply manufacture a multipolar anisotropic cylindrical magnet by providing a specific shape yoke, a permanent magnet and a magnetizing coil adjacently around a formed cavity and by pouring a ferromagnetic powder kneaded material in the cavity for anisotropic formation. CONSTITUTION:Between ring type yokes 40, 43 which have a L-shape section, a ring type permanent magnet 46 is provided and a ring body 6 is formed by providing a cylindrical magnetizing coil 47 contained in a coil bobbin 48 in parallel inside the magnet 46. A notch is provided inside of the yokes 40, 43 in the radial direction, projections 41a, 41b... and 44a, 44b... and recessions 42a, 42b... and 45a, 45b... are located alternately along the circumferential direction and the projection of one yoke and the recession of the other yoke engage with a gap. A ferromagnetic powder kneaded material is poured in the cavity formed between the inside surface of the ring body 6 and a core for anisotropic formation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for manufacturing a multipolar anisotropic cylindrical magnet by molding a kneaded material mainly composed of ferromagnetic powder in a magnetic field.

[Prior Art] In recent years, magnet rolls for copying machines, rotors for motors, and the like have been required to have an increasing number of magnetic poles.

In particular, the rotor of a stepping motor is required to have an extremely large number of magnetic poles in order to accurately control the step angle.

Such multipolar anisotropic cylindrical magnets can be produced either by (a) press-molding a wet slurry of ferromagnetic powder, a binder, and a solvent in a magnetic field, and magnetizing it after sintering; It is produced by injecting a kneaded mixture of and into a mold cavity, applying a magnetic field during melting to make it anisotropic, and then magnetizing it. The latter method is attracting increasing attention because it does not require sintering and rarely requires machining after forming.

Various proposals have been made regarding methods of manufacturing cylindrical magnets having anisotropy. For example, JP-A-57-170501
No. No. 1 is a magnetic powder/resin kneading composition that is extruded into a mold consisting of a non-magnetic material region and a magnetic material region and formed into a roll or pipe shape. It discloses that a magnetic field is applied from the outside using an electromagnet or the like to generate lines of magnetic flux, and the axis of easy magnetization of magnetic particles blended in a molten resin is aligned in the direction of the lines of magnetic flux. In this case, the structure is such that the electromagnet is installed radially outward of the magnetic body (yoke) that comes into contact with the magnetized location of the magnet roll, so as the number of magnetized poles increases, the number of electromagnets also increases, and the structure of the mold changes. becomes extremely complex. Therefore, the number of magnetized poles cannot actually be increased too much.

JP-A-56-69805 discloses a method for manufacturing anisotropic plastic magnets by injecting a mixture of a polymer compound and ferromagnetic powder into a mold cavity in which a plurality of permanent magnets are embedded. There is. However, as the number of magnetic poles increases, the spacing between the permanent magnets for magnetic field alignment becomes narrower, and the alignment force rapidly weakens due to leakage of magnetic flux.

Japanese Patent Publication No. 54-8C1 discloses a magnetizing device in which an excitation coil is wound around a large number of magnetic yokes, and a permanent magnet is provided between each magnetic yoke to prevent leakage of magnetic flux from the excitation coils. . Although this structure increases the magnetizing magnetic field inside the cavity, the structure is complicated because an excitation coil is wound around each magnetic yoke, and in practice it is difficult to increase the number of yokes. Can not.

JP-A-56-114309 discloses a mold in which a pair of electromagnets are provided on both sides of the axis of a cylindrical cavity.

A mixture of ferromagnetic powder and synthetic resin is injected into the cavity. Opposite magnetic fluxes of the same polarity are generated by the electromagnets and collide at the center of the cavity to become magnetic fluxes in the radial direction of the cavity. This makes the ferromagnetic powder mixture radially anisotropic. The compact is then magnetized to have a large number of magnetic poles. However, in this method, multipolar anisotropy is not performed during molding.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to overcome the above-mentioned drawbacks of the prior art and to provide a method and apparatus for manufacturing multipolar anisotropic cylindrical magnets having predetermined magnetic properties using relatively simple equipment.

[Means for Solving the Problems] The method for manufacturing a multipolar anisotropic cylindrical magnet of the present invention includes a pair of yokes in which convex portions and concave portions are arranged alternately around a cylindrical cavity of a mold. A cylindrical permanent magnet and a magnetizing coil are interposed between the yokes so that N and S poles are arranged alternately on the surface of the cylindrical cavity. The method is characterized in that a multipolar static magnetic field having poles is formed, a kneaded material mainly composed of ferromagnetic powder is injected into the cylindrical cavity, and anisotropic molding is performed for a predetermined period of time.

Furthermore, the apparatus for manufacturing a multipolar anisotropic cylindrical magnet of the present invention includes (
a) a cylindrical cavity for magnet molding; and (b) a pair of yokes arranged around the cylindrical cavity and having convex portions and concave portions arranged alternately, the concave portion of one yoke having a convex portion of the other yoke. and (Q) interposed between the yokes. It is characterized by comprising a cylindrical permanent magnet and a magnetizing coil that form a multipolar static magnetic field having alternating north and south poles on the surface of the cylindrical cavity.

[Function] In the present invention, a pair of yokes having convex portions and concave portions arranged alternately around an annular molding space are arranged such that the concave portion of one yoke engages with the convex portion of the other yoke through a gap. has been done. Between the yokes above. Therefore, when the protrusion of one yoke is magnetized to the north pole, the protrusion of the other yoke is magnetized to the south pole. Furthermore, by energizing the magnetizing coil, the magnetization of these protrusions becomes stronger. In this way, north and south poles can be formed alternately on the surface of the molding space.

[Example] Embodiments of the present invention will be described with reference to the accompanying drawings.

FIGS. 1 and 2 show an example of an apparatus for manufacturing the multipolar anisotropic cylindrical magnet of the present invention.

The device 1 has a fixed mold 2, a movable mold 4, and an annular body 6.

A core 8 having an axis coincident with the central axis of the annular body 6 is provided in the movable mold 4 . A cylindrical space formed by the fixed mold 2, the movable mold 4, the annular body 6, and the central core 8 is a magnet molding cavity 10. The outer periphery of the annular body 6 is surrounded by a backup member 7 made of a non-magnetic material.

A plate 12 and a lower plate 14 are provided on the second side of the fixed mold 2, and a nozzle port 16 is provided on the plate 12 on the fixed mold.
is formed. A sprue 18 below the nozzle opening 16 passes through the upper plate 12 and the lower plate 14 and is connected to a runner 20 formed on the lower surface of the fixed lower plate 14.

The runners 20 communicate with vertical runners 22 formed at corresponding positions on the fixed mold 2. Runner 22 is gate 2
4 to the cylindrical cavity 10.

The movable mold 4 is fixed to the second part of the movable mold fixed plate 26.

Furthermore, the movable fixed plate 26 is fixed to a lower plate 32 via a spacer block 30.

The movable mold 4 has a vertical hole opening into a cylindrical cavity 10, through which a projecting pin 34 is vertically movable.

The ejection pin 34 is fixed to an ejection pin fixing upper plate member 36, and a rod 38 connected to the center of the lower surface of the lower plate member 37 fixed to the upper plate member 36 is inserted into the center hole 5 of the lower plate 32.
0 and is connected to the piston (not shown) of the cylinder.

3 and 4 show the structure of the annular body 6 in detail. The annular body 6 has a ring-shaped yoke 40 having an L-shaped cross-section and a ring-shaped yoke 43 having an L-shaped cross-section, which are bifurcated at a predetermined interval, and a ring-shaped permanent magnet 46 is disposed between the two yokes. Attach the coil bobbin 4 to the inside of the permanent magnet 46.
Cylindrical magnetizing coils 47 housed in 8 are arranged in parallel. A non-magnetic sleeve 49 is provided on the inner peripheral surface of the annular body 6. Further, all of the above yokes are made of soft magnetic material.

The above-mentioned yoke 40 has a notch in the radial direction on the inner circumferential side, and has convex portions 41a, 41b, 41c, . . . and concave portions 42.
a, 42b, 42c, . . . are arranged alternately at predetermined intervals in the circumferential direction. Similarly, the yoke 43 is also cut in the radial direction on the inner peripheral side to form convex portions 44a, 44.
b, 44C1... and recesses 45a, 45b, 45c
, . . . are arranged alternately at predetermined intervals in the circumferential direction. Further, the yokes 40 and 43 are combined such that the convex portion of one engages with the concave portion of the other through a gap.

In the annular body described above, the permanent magnet 46 causes a flow of magnetic flux as shown by the broken line in the figure. Further, when the magnetizing coil is energized in the direction shown in the figure, magnetic flux is generated in the direction shown by the broken line in the figure, and the magnetic flux due to the permanent magnet is enhanced. For example, if we pay attention to the old protrusions a, 44a, and 41b among the above-mentioned protrusions, the magnetic flux generated in the yoke 40 is transferred from the protrusions 41a and 41b to the yoke 4.
3 and also flows into the convex portion 44a. Therefore, the protrusions 41a and 41b are magnetized as north poles, while the protrusion 44a is magnetized as south poles. That is, all the convex parts of the yoke 40 are N poles,
All of the convex portions of the yoke 43 serve as S poles. In this case, the minimum distance between the convex portion 41 and the convex portion 44 is Ω1, and the convex portion 44 and the concave portion 4 are
2 is the minimum distance from 2, it is desirable to set Q1 to 0□ in order to increase the magnetic flux generated on the cavity surface. In this way, S, N, S
... Magnetic poles of opposite polarity appear alternately. A multipolar static magnetic field is formed on the surface of the cavity 10 by the alternating magnetic poles of the permanent magnet and the magnetized coil.

In a preferred embodiment of the present invention, a magnetic field strength of 30,000 e or more is required to achieve sufficient orientation. For this reason, the above-mentioned permanent magnet for generating magnetomotive force must have a high residual magnetic flux density in order to form an extremely large number of magnetic poles at small intervals on the magnet surface. For this reason samarium
Rare earth magnets such as cobalt magnets and neodymium/iron/boron magnets are preferred. These rare earth magnets have a residual magnetic flux density Br of 8,5000 or more, preferably 10,0OOG or more.
(for example, JP-A-55-50100, JP-A-5
8-142507).

The shape and dimensions of the permanent magnets constituting the magnetic circuit of the mold can be set as appropriate using analytical methods such as the finite element method, depending on the number of poles of the anisotropic cylindrical magnet to be manufactured and the required magnetic properties. can.

The apparatus of FIG. 1 is particularly suitable for injection molding of composite magnets. Such injection molding can be performed as follows.

The apparatus of FIG. 1 is particularly suitable for injection molding of composite magnets. Such injection molding can be performed as follows.

First, mix the magnetic powder and resin at about 50°C to about 350°C.
temperature and approx. 600 kg/cm” - approx. 1 + OO
It is injected from the nozzle port 16 at a pressure of 0 kg/cm 2 and is injected into the cylindrical cavity via the sprue 18 and the runners 20 and 22.

After cooling, the anisotropically formed composite magnet is removed from the core 8 by moving the movable mold 4 downward, pushing up the iron 38 with a cylinder piston (not shown), and raising the protruding pin 34, and then collected. can do. Subsequently, the ejecting pin 34 is returned to its original position and the movable mold 4 is raised until it comes into contact with the annular body 6, thereby restoring the cylindrical cavity 10 and performing the next molding cycle. The obtained composite magnet molded body is processed to have a predetermined outer diameter as required, and magnetized in the same direction as the anisotropic direction.

In the case of forming the above-mentioned composite magnet, the magnetic powder is ferrite powder such as Ba ferrite or Sr ferrite, alnico magnet powder, Fe-Cr-Go magnet powder, N d
-Fe-based magnet powder, rare earth cobalt magnet powder, etc. can be used. As resins, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer,
Thermoplastic resins such as polyethylene and polyamide can be used.

The blending ratio of magnetic powder and resin needs to be 60% by weight or more from the viewpoint of magnetic properties, but if it exceeds 90%, molding becomes difficult. In order to improve moldability, a small amount (several percent by weight) of a lubricant such as polyethylene or calcium stearate may be added. Further, in order to improve the wettability between the magnetic powder and the resin, the magnetic powder can be coated with an organic silicon compound, an organic titanate compound, or the like.

In addition to the injection molding of the composite magnet described above, the present invention is also applicable to extrusion molding thereof and wet molding of ferrite and the like.

Wet molding uses powder of magnetic material such as ferrite, approximately 50 to 70
About 0.01 to about 0.2% by weight of a binder such as polyvinyl alcohol or methyl cellulose and about 30 to about 50% by weight of a solvent such as water are mixed to form a slurry, and the slurry is poured into the mold of the present invention. In this case, multipolar anisotropy is performed in the static magnetic field described above.

The present invention will be explained in more detail using the following specific examples.

[Specific example] Ferrite particles (Sr0.6Fe
203) was added with 1.35 kg of nylon I-2 (Ube Industries layer 3014U), premixed using a Henschel mixer, premixed at a temperature of 235°C using a twin screw extruder, and hot cut to create pellets. .

The pellets were put into an injection molding machine equipped with the mold shown in Figs.
Cavity 10 in a mold heated to 80°C with a pressure of
It was injected and then cooled and solidified. The dimensions inside the cavity were an inner diameter of 35+nl11, an outer diameter of 40 mm, and a length of 9.6 mm. The permanent magnet for generating magnetomotive force is a samarium cobalt magnet (manufactured by Hitachi Metals Co., Ltd. I (-30), and B r
10,800, BHe 8,0000 e, x
Hc was 9,000. The magnetizing coil is formed by winding the coil wire 300 times in the circumferential direction, and each coil wire is
．． A current of 5A was passed through it. The magnetic field strength on each pole at the surface of cavity 10 is approximately 3,0000e. In this example, since yokes each having 50 convex portions were used, the multipolar static magnetic field had 50 north poles and 50 south poles alternately on the surface of the cavity 10.

In this way, an anisotropic cylindrical composite magnet with 100 poles was obtained. This composite magnet was placed in a magnetizing device having a known coil type structure having 30 magnetic poles, and magnetized with a magnetic field of 8,000 e. When the surface magnetic flux density distribution of the obtained magnet was measured, the waveform shown in FIG. 5 was obtained. The average surface magnetic flux density was 760G.

On the other hand, in the case of a composite magnet obtained by radial anisotropy and magnetization as disclosed in JP-A-56-114309, the average surface magnetic flux density was only about 500G.

Although the present invention has been described based on examples, the present invention is not limited thereto, and various changes can be made without departing from the spirit of the present invention. For example, although the cavity 10 is completely cylindrical in the embodiment, it can also be an incomplete cylinder, such as a semi-cylindrical shape, depending on the use of the magnet. Therefore, the term "cylindrical" used in this specification is defined to include not only a complete cylinder but also an incomplete cylinder such as a semi-cylindrical shape. Further, in the embodiment, the multipolar static magnetic field is formed on the outer diameter surface of the cavity, but it can also be formed on the inner diameter surface of the cavity depending on the use of the magnet. Hence the term "cavity surface"
should be understood to include both the outer diameter surface and the inner diameter surface of the cavity.

[Effects of the Invention] As described above, the device of the present invention uses a yoke of a specific shape, a permanent magnet, and a magnetizing coil around the molding cavity so that north and south poles alternately appear on the surface of the molding cavity. Since they are arranged adjacent to each other, an extremely strong multipolar static magnetic field can be formed on the cavity surface. Furthermore, by using such a device, it has become possible to manufacture a multipolar anisotropic cylindrical magnet with 100 or more poles, which was previously impossible to achieve. Furthermore, by forming a magnetic circuit mainly composed of permanent magnets, the structure of the entire device can be made extremely simple.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an apparatus according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1, and FIG.
FIG. 4 is a partial perspective view of the annular body, and FIG. 5 is a graph showing the surface magnetic flux density distribution of the multipolar anisotropic cylindrical magnet obtained by the example of the present invention. It is. 2...Fixed type 4...Movable type 6...Annular body 8...Core 10...Cavity 40.43...Yoke 46...Permanent magnet l @ Fig. 2 3 Fig. Figure 4

Claims (1)

[Claims] 1. In a method for manufacturing a multipolar anisotropic cylindrical magnet by molding a kneaded material mainly composed of ferromagnetic powder in the presence of a magnetic field, A pair of yokes having convex portions and concave portions arranged alternately are installed so that the concave portion of one yoke engages with the convex portion of the other yoke with a gap between them, and a cylindrical permanent magnet and a cylindrical permanent magnet are placed between the yokes. A magnetizing coil is arranged on the surface of the cylindrical cavity to alternately form N poles and S poles.
A method characterized by forming a multipolar static magnetic field having poles, injecting the kneaded material into the cylindrical cavity, and performing anisotropic molding for a predetermined period of time. 2. The method according to claim 1, wherein the permanent magnet is a rare earth magnet having a Br of 8,500 G or more. 3. The method according to claim 1 or 2, wherein the kneaded material mainly contains ferromagnetic powder and resin. 4. In an apparatus for manufacturing a multipolar anisotropic cylindrical magnet, (a) a cylindrical cavity for forming the magnet; and (b) a pair of alternating convex portions and concave portions arranged around the cylindrical cavity. (c) a yoke in which a concave part of one yoke engages with a convex part of the other yoke through a gap; A device comprising: a cylindrical permanent magnet and a cylindrical magnetization coil that form a multipolar static magnetic field that alternately has . 5. The device according to claim 4, wherein the permanent magnet is a rare earth magnet having a Br of 8,500 G or more.