JP2013105964A - Method for manufacturing columnar bond magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a columnar bond magnet excellent in magnetic characteristics.SOLUTION: In a method for manufacturing a columnar bond magnet to be obtained by performing extrusion molding of a bond magnet composition consisting of anisotropic magnetic powder and resin, it has processes of: forming a magnetic field for orientation in which a magnetic field line goes along the axis direction in a space inside a columnar magnet axially oriented in the axis direction by arranging the columnar magnet in a metal mold 2 for extrusion molding as a magnet 5 for orientation; orienting the magnetic powder in the axis direction and performing extrusion molding of a bond magnet composition by making the bond magnet composition passing through in the magnetic field for orientation; preparing a magnetizer with at least a pair of air-core coils which are constituted by winding thin metallic wire for a plurality of times, respectively, in forward and backward directions; and performing magnetization processing of the bond magnet composition whose extrusion molding is performed by the magnetizer, and the magnetic field line which radially goes in and out of the radial direction of the columnar bond magnet is formed by the processes.

Description

  The present invention relates to a method of manufacturing a cylindrical bonded magnet in which N poles and S poles are alternately magnetized in the axial direction and a radial magnetic force is generated from one pole in the radial direction.

  A cylindrical magnet having a multipole magnetized alternately with N and S poles in the axial direction is used in various fields. For example, a foreign matter removing device that removes iron powder or the like from product powder, a stator of a linear motor, or a magnetic necklace.

JP 2003-303714 A JP 2008-182873 A Japanese Patent Laid-Open No. 2005-73466 JP 2004-320827 A Japanese Patent No. 3421799 JP-A-8-130862 Japanese Patent Laid-Open No. 2003-068527 JP 2008-173405 A JP 2009-22341 A Japanese Patent No. 2008-173405

  Prior art documents described below are broadly divided into Patent Documents 1 to 3, in which a plurality of sintered magnets are assembled into a columnar magnet. Patent Documents 4 to 5 are bonded magnets and columnar magnets. Is configured.

  In Patent Documents 1 to 3, a plurality of sintered magnets are arranged so that the same poles face each other, and a cylindrical magnet is assembled while being repelled. Thereby, a magnet in which N poles and S poles are alternately multipolar magnetized in the axial direction of the cylindrical magnet can be manufactured. In the manufacturing methods according to these patent documents, since the cylindrical magnet is composed of a sintered magnet, the magnetic force of the manufactured cylindrical magnet becomes strong. However, an assembling work for arranging a plurality of sintered magnets is indispensable, and the assembling work is performed while repelling the plurality of sintered magnets, so that the assembling work requires a lot of time and labor. It will be. Further, since the sintered magnet has a lower mechanical strength than the bonded magnet, the sintered magnet may be cracked or chipped during assembly work or use.

  Patent Documents 4 to 6 attempt to solve the above-described problems of sintered magnets by forming a cylindrical magnet with bonded magnets.

  In the production methods described in Patent Documents 4 and 5, the magnetic powder is oriented in a desired pattern by injection molding or compression molding, so that the N pole and S in the axial direction of the cylindrical bonded magnet are formed in one molding step. A magnet molded product in which the poles are alternately magnetized in multiple poles can be obtained. However, since injection molding and compression molding are both batch-type, there is a limit to the length of the magnet molded product in consideration of ease of molding. In particular, when molding a flexible bonded magnet that employs rubber as a binder resin for magnetic powder, the longer the length of the molded product is, the more the ejection force when the molded product is taken out of the mold is absorbed by the molded product itself, and the ejection failure is reduced. It tends to happen. That is, it becomes difficult to remove from the mold after molding.

  In Patent Document 6, a long bonded magnet made of isotropic magnetic powder is magnetized to produce a bonded magnet in which N poles and S poles are alternately magnetized in the axial direction. However, since it is a bonded magnet using an isotropic magnetic powder as the magnetic powder, its magnetic properties are lower than when an anisotropic magnetic powder is used.

  Patent Document 7 relates to a sheet-like bonded magnet, unlike the cylindrical bonded magnet as described above. In the orientation method and the magnetization method disclosed in this patent document, when a sheet-like bonded magnet is produced by extrusion, a magnetic field parallel to the extrusion direction is generated by an electromagnet, and the magnetic powder is oriented in-plane in the extrusion direction. ing. Thereafter, the magnetic lines of force are extracted to the outside by performing a magnetizing process so as to repel in-plane with a permanent magnet. In the case of this manufacturing method, it is necessary to always pass an electric current through the electromagnet during the extrusion molding, which requires a huge electricity bill. In addition, when this sheet-like bonded magnet is cut out and rounded into a cylindrical shape to produce a cylindrical magnet, not only is it time-consuming, but the longer the length, the greater the problem in terms of processing accuracy. Become.

  Patent Documents 8 to 10 relate to a magnetic necklace formed by bending a flexible long cylindrical bonded magnet and having a joint at its end. The magnetic necklace disclosed in these patent documents, for example, as described in FIG. 2 of the patent document 10 (FIG. 13 in this specification), is a magnet portion 22 made of a flexible long cylindrical bond magnet. And a covering portion 21 that covers the magnet portion 22, and the magnetic force pattern is expressed by the point c that is the N pole in the radial direction and the point e that is a position rotated 180 ° therefrom. A pole is generated. In the case of such an arrangement of magnetic poles, there is a magnetic force at point d, which is a position rotated 90 ° from point c that is the N pole, and point f, which is a position rotated 270 ° from point c that is the N pole. Almost no. Therefore, even if the magnetic necklace is in contact with the human skin at the positions of the d point and the f point, there is a problem that the magnetic treatment effect cannot be obtained.

  Therefore, the present invention has been made in view of such circumstances, and uses N-pole in the axial direction and S in the axial direction by utilizing extrusion molding which is excellent in magnetic characteristics and productivity and has no processing restrictions in the length direction. An object of the present invention is to provide a method for producing a cylindrical bonded magnet having poles alternately magnetized in multiple poles.

  In order to achieve the above object, a method for producing a cylindrical bonded magnet according to the present invention is the production of a cylindrical bonded magnet obtained by extrusion molding a bonded magnet composition comprising anisotropic magnetic powder and resin. In the method, a cylindrical magnet axially oriented in the axial direction is arranged in an extrusion mold as an orientation magnet, whereby a magnetic field for orientation in which magnetic lines of force extend in the axial direction in the space inside the cylindrical magnet. Forming the magnetic powder in the axial direction by passing the bonded magnet composition through the orientation magnetic field, extruding the bonded magnet composition, and forming a fine metal wire. A step of preparing a magnetizing device provided with at least a pair of air-core coils each wound in the reverse direction a plurality of times, and applying the extruded bonded magnet composition in the magnetizing device. A step of processing, has, by these steps, and forming the magnetic field lines in and out radially in a radial direction of the cylindrical bonded magnet.

  It is preferable that the extrusion mold in contact with the orientation magnet is made of nonmagnetic steel. The magnetic powder is preferably an anisotropic Sm—Fe—N based magnetic powder. The resin is preferably silicone rubber.

  Moreover, this invention is a manufacturing method of the magnetic necklace using the said manufacturing method. Furthermore, the present invention is a magnetic necklace manufactured by the above manufacturing method.

  The present invention is a method of manufacturing a cylindrical bonded magnet in which N poles and S poles are alternately magnetized in the axial direction and radial magnetic force is generated from one pole in the radial direction. By the extrusion molding, the method for producing a cylindrical bonded magnet according to the present invention is excellent in magnetic properties and productivity, and can eliminate the restriction on processing in the length direction. In particular, when the magnetic necklace is configured with the cylindrical bond magnet according to the present invention, since the radial magnetic lines of force appear in the radial direction of the cylindrical bond magnet, the user wears the magnetic necklace in any direction. However, the lines of magnetic force can be effectively applied to the body.

FIG. 1 is a schematic view of an extruder according to the production method of the present invention. 2 is a cross-sectional view taken along the line AA of the mold part of FIG. FIG. 3 is a schematic diagram of the distribution of magnetic lines of force emitted from the magnet for orientation according to the manufacturing method of the present invention. FIG. 4 is a schematic diagram showing the orientation direction of the magnetic powder in the bonded magnet after extrusion. FIG. 5 is a schematic view of a coil constituting the magnetizing device. FIG. 6 is a schematic diagram showing the magnetization direction and magnetic field lines of the magnetic powder in the bonded magnet after the magnetization process. FIG. 7 is a schematic diagram showing the lines of magnetic force in the BB cross section of FIG. FIG. 8 shows the result of measuring the surface magnetic flux density in the axial direction of the columnar bonded magnet of Example 1. FIG. 9 shows the result of measuring the surface magnetic flux density in the axial direction of the cylindrical bonded magnet of Comparative Example 1. FIG. 10 shows the result of measuring the surface magnetic flux density in the axial direction of the cylindrical bonded magnet of Comparative Example 2. FIG. 11 shows the result of measuring the surface magnetic flux density for one round in the circumferential direction from the point on the surface of the cylindrical bonded magnet corresponding to the point a in FIG. FIG. 12 shows the result of measuring the surface magnetic flux density for one round in the circumferential direction from the point on the surface of the cylindrical bonded magnet corresponding to the point b in FIG. FIG. 13 shows a cross-sectional view of a conventional magnetic necklace.

  In order to solve the above-mentioned problems, the present inventors have intensively studied and, as a result, have completed the present invention.

  The present invention provides a method for producing a cylindrical bonded magnet obtained by extruding a bonded magnet composition comprising an anisotropic magnetic material and a resin, at least at one point after being oriented in the longitudinal direction during extrusion molding. A method for producing a cylindrical bonded magnet, wherein radial magnetic lines of force are generated in a radial direction by magnetizing the same poles so as to face each other.

  That is, the method for manufacturing a cylindrical bonded magnet according to the present invention includes at least the following steps.

  (1) A cylindrical magnet that is axially oriented in the axial direction is arranged in an extrusion mold as an orientation magnet, whereby a magnetic field for orientation in which magnetic lines of force extend in the axial direction in the space inside the cylindrical magnet. Forming.

  (2) A step of orienting the magnetic powder in the axial direction by passing the bonded magnet composition through the orientation magnetic field formed in the previous step, and extruding the bonded magnet composition.

  (3) A step of preparing a magnetizing device including at least a pair of air-core coils formed by winding a thin metal wire in a forward direction and a reverse direction a plurality of times.

(4) A step of magnetizing the extruded bonded magnet composition with the magnetizing apparatus.
The present invention forms magnetic lines of force entering and exiting radially in the radial direction of the cylindrical bonded magnet by these steps.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of an extruder according to the production method of the present invention.

  First, a cylindrical bonded magnet is produced by an extruder shown in FIG. The raw material is a bonded magnet composition obtained by mixing anisotropic magnetic powder and a resin, and preferably has a pellet shape. Examples of the anisotropic magnetic powder include ferrite, Sm—Co, Nd—Fe—B, and Sm—Fe—N. The magnetic material may be a single type or a mixture of two or more types. In order to increase the magnetic force, it is preferable to use Sm—Fe—N magnetic powder rather than ferrite magnetic powder. The residual magnetic flux density Br of the magnetic powder is about 0.4 T for the ferrite-based magnetic powder, and 1.3 T, which is about three times that of the Sm—Fe—N-based magnetic powder. Since many Sm—Co-based and Nd—Fe—B-based magnetic powders have a large particle size, the variation in magnetic force is particularly large when the molded product is small. The magnetic powder has a particle diameter of 50 to 100 μm for Sm—Co and Nd—Fe—B magnetic powders, and about 3 μm of Sm—Fe—N magnetic powder, which is 1/10 or less. Therefore, the Sm—Fe—N based magnetic powder can reduce the variation in magnetic force even when the molded product is smaller.

  If necessary, the magnetic material may be subjected to an oxidation resistance treatment or a coupling treatment. In the present invention, the resin used as the binder of the magnetic powder is not particularly limited, but a thermoplastic resin, a thermosetting resin, and rubber can be used.

  For example, thermoplastic resin such as polypropylene, polyethylene, polyvinyl chloride, polyester, polyamide, polycarbonate, polyphenylene sulfide, acrylic resin, thermoplastic elastomer such as ester or polyamide, or epoxy resin, phenol resin, urea resin , Thermosetting resins such as melamine resin, unsaturated polyester resin, direal phthalate resin, polyurethane resin, or natural rubber, isoprene rubber, styrene butadiene rubber, butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, ethylene propylene rubber, Uses rubber materials such as urethane rubber, silicone rubber, acrylic rubber, chlorosulfonated polyethylene rubber, fluorine rubber, hydrogenated nitrile rubber, epichlorohydrin rubber, liquid rubber Rukoto can.

  Among these resins, if you want to obtain flexible molded products such as cylindrical bonded magnets for magnetic necklaces, select silicone rubber considering moldability, flexibility, and chemical stability to the human body. It is preferable.

  As shown schematically in FIG. 1, the bonded magnet composition charged into the extruder is first kneaded by a screw 9 in the main body 1 of the extruder. Next, the melted bonded magnet composition enters the mold part 2 of the extrusion molding machine, where it is molded into a columnar shape and is formed by the orientation magnet 5 disposed in the mold part 2. The magnetic field is oriented in the extrusion direction, that is, the longitudinal direction of the cylindrical bonded magnet.

  FIG. 2 is a cross-sectional view of the mold part 2 shown in FIG. As shown in FIG. 2, the flow path 8 is a space through which the bonded magnet composition passes and is a space in which the bonded magnet composition is formed into a columnar shape, and a molding die outside the flow path 8. The orienting magnets 5 arranged in the are separated by a partition wall 6.

  FIG. 3 is a schematic cross-sectional view showing the distribution of lines of magnetic force emitted from the magnet for orientation according to the manufacturing method of the present invention. As shown in FIG. 3, this orienting magnet 5 has a cylindrical shape, one bottom surface of which is an N pole, and the other bottom surface is an S pole, and the magnetic force lines coming out of the N pole return to the S pole. Such a magnetic field for orientation is formed. Here, if there is a magnetic field line passing through the outside of the orientation magnet 5 like the magnetic field line 10 in FIG. 3, the magnetic field line 11 passes through the inside of the cylindrical orientation magnet 5 and exits from the N pole. Some lines of magnetic force enter the poles. What is used for the orientation of the magnetic material contained in the bonded magnet composition is a magnetic field line 11 passing through the inside of the cylindrical orientation magnet 5. When the bonded magnet composition passes through the flow path 8, the magnetic powder is oriented in the extrusion direction, that is, the longitudinal direction of the columnar bonded magnet under the influence of the magnetic force lines 11.

  In order to strengthen the magnetic field lines 11 passing through the inside of the cylindrical orientation magnet 5, the spacer 3 disposed in contact with one bottom surface of the orientation magnet 5, and the holding member 4 disposed outside the orientation magnet The partition 6 and the fixed lid 7 disposed on the other bottom surface of the orientation magnet are preferably made of nonmagnetic steel. For the main body 1 of the extrusion molding machine, magnetic steel is usually used. Therefore, when the orientation magnet is brought close to the main body 1, the magnetic lines of force are taken away by the main body 1 of the extruder, and as a result, the magnetic lines 11 become weak. Therefore, by inserting the spacer 3, the magnetic field lines are not lost to the main body 1 of the extruder, and loss of the magnetic field lines can be avoided.

  If the holding member 4 for the magnet for orientation, the partition wall 6 and the fixing lid 7 for the magnet for orientation are made of magnetic steel, the magnetic lines of force 11 are similarly weakened. Therefore, these members are preferably made of nonmagnetic steel. . FIG. 4 is a cross-sectional view schematically showing the orientation direction of the magnetic powder in the cylindrical bonded magnet after extrusion molding. Inside the cylindrical bonded magnet molded article 12 obtained in this way, the magnetic powder is oriented along the axial direction as indicated by reference numeral 13 in FIG.

  The orientation magnet 5 is preferably a rare earth sintered magnet. For example, Sm—Co-based and Nd—Fe—B-based sintered magnets can be used. The magnetic force is preferably 25 MGOe or more.

  When the resin constituting the bonded magnet composition is a thermosetting resin or a rubber material, the molded product obtained by extrusion molding is preferably heated and cured as necessary. The heating temperature and heating time are determined by the type of resin and the filling rate of the magnetic powder.

  Next, a magnetizing process is performed by a magnetizing device. FIG. 5 is a schematic view of an air-core coil constituting the magnetizing device. As shown in FIG. 5, after winding the coil 14 in a certain direction, the coil 14 ′ is wound in the opposite direction, and a plurality of turns are repeated with this as a pair. When a magnetizing device is configured by connecting a power source to the coils 14 and 14 'and then a current is passed through the coil, magnetic lines 15 as shown by arrows in FIG. 5 are formed inside the coil. The tip of the arrow is the N pole, and the opposite is the S pole.

  FIG. 6 is a schematic diagram showing the orientation direction and magnetic lines of force of the magnetic powder inside the cylindrical bonded magnet after the magnetizing treatment. When a molded cylindrical bonded magnet is inserted inside the coil of the magnetizing apparatus and then a current is passed through the coil, the cylindrical bonded magnet is affected by the magnetic field lines as described above, and is shown in FIG. It is magnetized as Here, when the tip of the arrow in FIG. 6 is the N pole and the opposite is the S pole, the N poles and the S poles face each other. At the point where the north poles face each other, the magnetic lines of force 18 are emitted radially in the radial direction of the cylindrical bond magnet 16, and at the point where the south poles face each other, the magnetic lines of force enter radially in the radial direction of the cylindrical bond magnet 16. Go. The magnetic field lines are shown on the outer side of the cylindrical bond magnet in the broken line arrows in FIG. FIG. 7 shows a state in which the lines of magnetic force in the BB cross section of FIG. 6 are released. As shown in FIG. 7, it can be seen that radial magnetic force is released in a 360 ° direction.

  Examples according to the present invention will be described in detail below. Needless to say, the present invention is not limited to the following examples.

<Example 1>
Anisotropic Sm-Fe-N magnetic powder is surface treated with ethyl silicate and a silane coupling agent. 100 parts by weight of the surface-treated Sm—Fe—N magnetic material, 20 parts by weight of silicone rubber, 0.2 parts by weight of vulcanizing agent, and kneading with a lab plast mill are obtained as raw materials for extrusion.

  The orientation magnet used in this example has an outer diameter of Φ16 mm, an inner diameter of Φ4 mm, and a height of 20 mm, and is oriented in the height direction. The material is a commercially available NdFeB sintered magnet (35 MGOe). The partition wall 6 has an outer diameter of Φ4 mm × an inner diameter of Φ3 mm, and is made of SUS304 (nonmagnetic steel). The spacer 3, the orientation magnet holding member 4 and the orientation magnet fixing lid 7 were also made of SUS304 (nonmagnetic steel).

  The temperature of the screw part of the extruder is 40 ° C., the temperature of the mold part is 40 ° C., and the screw rotation speed is 10 rpm.

  The obtained molded product is a cylindrical bonded magnet oriented in the longitudinal direction with a diameter of 3 mm and a length of 10,000 mm. Further, the cylindrical bonded magnet was placed in an electric furnace at 150 ° C. for 1 hour to be cured.

  The magnetizing process is a magnetizing device comprising a double glass wound rectangular copper wire with a diameter of Φ2 mm, with a left winding and a right winding arranged alternately at a pitch of 10 mm, a total length of 250 mm, and a magnet insertion hole size of Φ4 mm. It went by. After inserting a cylindrical bonded magnet into this magnet insertion hole, a 4 kA pulse current was applied to perform a magnetization process. The magnetization process was performed 40 times every 250 mm.

  Next, the sample was cut every 500 mm, and a convex fastener was attached to one end and a concave fastener was attached to the other end to produce a magnetic necklace.

  The surface magnetic flux density was measured over 250 mm in the length direction of the cylindrical bonded magnet portion. The result is shown in FIG. As shown in FIG. 8, a surface magnetic flux density of about 150 mT was obtained. FIG. 11 shows the result of measuring the surface magnetic flux density for one round in the circumferential direction from the point on the surface of the cylindrical bond magnet corresponding to the point a in FIG. 8, which is the maximum surface magnetic flux density. FIG. 12 shows the result of measuring the surface magnetic flux density for one round in the circumferential direction from the point on the surface of the cylindrical bond magnet corresponding to the point b in FIG. . From these results, it can be seen that a radial magnetic force is emitted from one pole in almost 360 degrees.

<Comparative Example 1>
Example 1 except that the spacer 3, the orientation magnet holding member 4, and the orientation magnet fixing lid 7 constituting the extrusion machine used in Example 1 were made of SS400 (magnetic steel). A cylindrical bonded magnet was manufactured in the same manner. Similarly to Example 1, the surface magnetic flux density was measured, and the measurement result is shown in FIG.

<Comparative example 2>
A cylindrical bonded magnet was produced in the same manner as in Example 1 except that the orientation magnet was removed from the mold used in Example 1. Since the orientation magnet is removed from the mold, the magnetic powder is not oriented. Similarly to Example 1, the surface magnetic flux density was measured, and the measurement result is shown in FIG. Table 1 below summarizes the results of Example 1 and each comparative example.

  According to Table 1, the surface magnetic flux density is higher with the orientation magnet than without the orientation magnet, and the surface magnetic flux density is higher when the mold material is made of non-magnetic steel than when magnetic material is used. It turns out that it becomes high.

  The columnar bonded magnet of the present invention can be used in a foreign matter removing device that removes iron powder and the like from product powder, a linear motor stator, and a magnetic necklace.

  DESCRIPTION OF SYMBOLS 1 ... Main part of extrusion molding machine, 2 ... Mold part, 3 ... Spacer, 4 ... Magnet holding member for orientation, 5 ... Magnet for orientation, 6 ... Partition, 7・ ・ ・ Magnet fixing lid for orientation, 8 ... Flow path of bonded magnet composition, 9 ... Screw, 10 ... Magnetic field lines outside orientation magnet, 11 ... Magnetic field lines inside orientation magnet, 12 ... Cylinder-shaped bonded magnet molded product before magnetizing, 13 ... Orientation direction of magnetic powder, 14, 14 '... Coil, 15 ... Magnetic field lines by magnetizing coil, 16 ... After magnetizing Columnar bonded magnet molded product, 17 ... magnetizing direction, 18 ... magnetic field lines of cylindrical bonded magnet, 20 ... conventional magnetic necklace, 21 ... covering portion, 22 ... magnet portion.

Claims (6)

In the method for producing a cylindrical bonded magnet obtained by extruding a bonded magnet composition comprising an anisotropic magnetic powder and a resin,
A cylindrical magnet axially oriented in the axial direction is placed in an extrusion mold as an orientation magnet, thereby forming an orientation magnetic field having magnetic force lines along the axial direction in the space inside the cylindrical magnet. And a process of
Passing the bonded magnet composition through the magnetic field for orientation, orienting the magnetic powder in the axial direction, and extruding the bonded magnet composition;
Preparing a magnetizing device including at least a pair of air-core coils formed by winding a thin metal wire multiple times in forward and reverse directions;
And magnetizing the extruded bonded magnet composition with the magnetizing device, and these steps form magnetic lines of force that enter and exit radially in the radial direction of the cylindrical bonded magnet. A method of manufacturing a cylindrical bonded magnet.   The manufacturing method of the column-shaped bonded magnet of Claim 1 with which the extrusion die which contact | connects the said magnet for orientation is comprised with the nonmagnetic steel.   The method for producing a cylindrical bonded magnet according to claim 1, wherein the magnetic powder is an anisotropic Sm—Fe—N-based magnetic powder.   The method for producing a cylindrical bonded magnet according to any one of claims 1 to 3, wherein the resin is silicone rubber.   The manufacturing method of the magnetic necklace using the manufacturing method as described in any one of Claim 1 to 4.   The magnetic necklace manufactured by the manufacturing method as described in any one of Claim 1 to 5.

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