EP0240420B1 - Verfahren zur Herstellung eines stranggepressten Kunststoffmagnetstabes fortlaufender Länge und mit mehrpoliger Umfangsmagnetisierung - Google Patents

Verfahren zur Herstellung eines stranggepressten Kunststoffmagnetstabes fortlaufender Länge und mit mehrpoliger Umfangsmagnetisierung Download PDF

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Publication number
EP0240420B1
EP0240420B1 EP19870400682 EP87400682A EP0240420B1 EP 0240420 B1 EP0240420 B1 EP 0240420B1 EP 19870400682 EP19870400682 EP 19870400682 EP 87400682 A EP87400682 A EP 87400682A EP 0240420 B1 EP0240420 B1 EP 0240420B1
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EP
European Patent Office
Prior art keywords
circumferentially
multipolar
magnet
plastic magnet
magnetic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP19870400682
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English (en)
French (fr)
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EP0240420A1 (de
Inventor
Tawara Yoshio
Abe Tokuji
Uesaka Kenichi
Hirose Naoyuki
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shin Etsu Chemical Co Ltd
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Shin Etsu Chemical Co Ltd
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Publication date
Application filed by Shin Etsu Chemical Co Ltd filed Critical Shin Etsu Chemical Co Ltd
Publication of EP0240420A1 publication Critical patent/EP0240420A1/de
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Publication of EP0240420B1 publication Critical patent/EP0240420B1/de
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
    • H01F41/0273—Imparting anisotropy
    • H01F41/028—Radial anisotropy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/02—Permanent magnets [PM]
    • H01F7/0205—Magnetic circuits with PM in general
    • H01F7/021—Construction of PM

Definitions

  • the present invention relates to a method for manufacturing a continuous-length extruded bar of plastic magnet with circumferentially multipolar magnetization by extrusion molding.
  • Multipolar tubular permanent magnets can be manufactured by several different methods of magnetization of a bar material of a plastic magnet extruded without magnetization or extrusion molding through a multipolar magnetizer so that the extruded bar material of the plastic magnet is already magnetized.
  • the methods include:
  • the magnetic force of these three types of the permanent magnets is, as a general trend, in the decreasing order of circumferentially anisotropic magnets, radially anisotropic magnets and isotropic magnets. It is of course that control of a servo motor is easier when the inertia thereof is smaller and a smaller servomotor is preferable to larger ones assuming that the output force is the same. Accordingly, preferable multipolar tubular permanent magnets are of the type of the circumferentilally anisotropic magnets capable of generating a larger torque than the other types in order to design smaller and lighter motors.
  • One of the conventional methods for the manufacture of a circumferentially anisotropic magnet is to fill the space between a core and a metal mold having a coil of a multipolar magnetizer with a powder of a magnetic material which is compression-molded by means of a pair of upper and lower punches while the magnet particles are magnetized by energizing the coil of the magnetizer.
  • a method is disclosed in Japanese Patent Kokai 60-89717 by utilizing the techniques of injection molding.
  • the scope of the present invention consists in manufacturing a continuous-length extruded bar of a plastic magnet having a high degree of orientation and multipolar circumferential anisotropy by mounting a multipolar, circumferentially anisotropic magnetizing member on the discharge port of an extruder machine and cutting the thus extruded continuous-length bar in a desired product length.
  • the present invention provides a method for manufacturing a continuous-length extruded bar of a plastic magnet with circumferentially multipolar magnetization which comprises extruding a plastic magnet composition out of the discharge port of an extruder machine having a multipolar, circumferentially anisotropic magnetizing member which is constructed of a plural number of radially oriented sector-like magnetic pole plates formed of a magnetic material of a saturation magnetization of at least 10 kG (1,0 T) and a plural number of radially oriented sector-like permanent magnets, each pair of adjacent two thereof sandwiching one of the magnetic pole plates therebetween with the poles of the respective permanent magnets having the same polarity facing to each other, coaxially mounted thereon.
  • FIGURES 1a and 1b are for the illustration of a multipolar tubular magnets magnetized either circumferential or radial direction, respectively.
  • the present invention particularly relates to the former type of multipolar tubular magnet made of a plastic magnet composition.
  • Figures 2a and 2b are for the illustration of a molding die assembly used in the conventional compression molding method for the preparation of a circumferentially anisotropic multipolar tubular magnet.
  • the space formed between the core 3 and the metal mold 10 having a plural number of magnetizing coils 9 as a multipolar magnetizer is filled with a powder of the magnetic material, e.g. a plastic magnet composition, 8 which is compression-molded by means of the upper and lower punches 11, 11 while the powder is under magnetization by energizing the coils 9.
  • a powder of the magnetic material e.g. a plastic magnet composition, 8 which is compression-molded by means of the upper and lower punches 11, 11 while the powder is under magnetization by energizing the coils 9.
  • the method of the present invention is described in detail with reference to the other figures of the accompanying drawing.
  • the method of the invention is practiced by using an extruder machine, which is provided with a sizing die having a multipolar, circumferentially anisotropic orientating magnetizing member mounted on the discharge port.
  • This sizing die includes the circumferentially anisotropic multipolar orientating magnetizing member constructed, as is shown in FIGURE 3, by the assembly of a plural number of the sector-like permanent magnets 1 and a plural number of the magnetic pole plates 2 to surround the extruded material out of the discharge port of the extruder machine in such a magner that each pair of two adjacent pole plates 2 sandwiches one of the permanent magnets 1 therebetween or vice versa.
  • the orientating magnetizing member is mounted firmly on the holder frame 4 to form a sizing die 7.
  • the magnetic material 8 such as a plastic magnet composition
  • the extruded bar material is subjected to anisotropic multipolar magnetization as it goes through the opening of the sizing die 7.
  • FIGURE 3 illustrates an 8-polar member having eight permanent magnets 1 and eight pole plates 2, the number of the magnets is of course not limited thereto.
  • the magnetic pole plates 2 should be mate of a material of high saturation magnetization of, preferably, at least 10 kG (1 T) or, more preferably, at least 15 kG (1,5 T) such as iron and alloys of iron and cobalt.
  • a pole plate 2 is sandwiched by two sector-like permanent magnets 1 having the same polarity in the radial direction. Namely, the N-poles or S-poles of the two adjacent permanent magnets 1 face to each other with the pole plate 2 intervening therebetween and the magnets 1 and pole plates 2 are adhesively bonded together.
  • the direction of magnetic orientation in the permanent magnets 1 should preferably be parallel to the base of the equilateral triangle formed by the two adjacent magnetic pole plates or perpendicular to the magnetic pole plates adjacent to each other by sandwiching the same.
  • Each of the permanent magnets 1 should be so powerful that at least 15 kG (1,5 T) of the magnetic flix is obtained at the circumferential surface of the extruded material at the magnetic poles.
  • the permanent magnet should also have a coercive force of a least 6 KOe (477,6 kA m ) and residual density of magnetic flux of at least 6 kG (0,6 T) with the coefficient of temperature dependency of the coercive force and magnetic flux of each 0.1%/°C or smaller.
  • a coercive force of the permanent magnet smaller than 6 KOe (447,6 kA m ) means greater demagnetization thereof while a larger permanent magnet must be used when the density of the residual magnetic flux is smaller than 6 kG (0,6 T) resulting in an increase in the magnetic leakage along the magnetic circuit in each case.
  • the coefficient of temperature dependency should be as small as possible because a magnetic material having a larger temperature dependency is subject to greater thermal demagnetization in the process of molding.
  • Recommendable permanent magnet materials for the permanent magnets 1 in view of the above mentioned requirements include those of a rare earth-based magnet alloy or, in particular, samarium-cobalt magnet alloy though not particularly limitative thereto.
  • the material of the magnetic pole plates 2 should have a saturation magnetization of at least 10 kG (1 T) or, preferably, at least 18 kG (1,8 T).
  • the saturation magnetization of the material of the magnetic pole plates 2 is smaller than 10 kG (1,0 T), the magnetic leakage from the magnetic pole plates is increased so that the magnetic orientation in the extruded bar material may eventually be incomplete.
  • the magnetic material molded according to the invention is a plastic magnet composition compounded of a fine powder of a permanent magnet such as rare earth-based magnets, ferrites and the like and a thermoplastic polymer as the matrix together with optional additives.
  • the magnet powder should have an average particle diameter in the range from 0.5 to 100 ⁇ m or, preferably, from 1 to 40 ⁇ m.
  • thermoplas-ticity Various kinds of polymers having thermoplas-ticity can be used as the matrix including polyethylenes, polypropylenes, polystyrenes, polyvinyl chlorides, acrylic resins, polyamides, polyphenylene sulfides, polyphenylene oxides, polyacetales, polyethylene terephthalates, polybutylene terephthalates, polycarbonates, polyester elastomers, polyurethane elastomers and the like.
  • the plastic magnet composition should be compounded in such a proportion of 35 to 70% by volume or, preferably, 40 to 65% by volume of the magnet powder and 70 to 25% by volume or, preferably, 60 to 35% by volume of the thermoplastic polymer.
  • the accompanying drawing and the Examples given below are directed to a manufacturing process of an extruded bar material having a circular or annular cross section, it is of course that the above described inventive method is applicable to the manufacturing process of any tubular bar materials having different cross sections such as tubes having a polygonal cross section.
  • the present invention provides a very efficient method for manufacturing a continuous-length extruded bar of plastic magnet with circumferentially multipolar magnetization so that the inventive method is industrially very valuable.
  • the method of the present invention is described in more detail by way of Examples.
  • a plastic magnet composition was prepared by uniformly milling a mixture composed of 91% by weight or 58% by volume of a powdered rare earth-based permanent magnet (R-30, a product by Shin-Etsu Chemical Co.) having an average particle diameter of about 3.5 ⁇ m and 9% by weight or 42% by volume of a plasticized polyvinyl chloride resin compound (MF-200, a product by the same company, supra).
  • the plastic magnet composition was shaped into a continuous-length tubular bar by extrusion molding using a 25 mm diameter extruder machine.
  • the sizing die of the extruder machine was equipped with a multipolar, circumferentially anisotropic orientating magnetizing member as illustrated in FIGURES 4a and 4b.
  • the orientating magnetizing member was constructed of 24 pieces of permanent magnets 1 made of the same R-30 rare earth magnet and 24 magnetic pole plates 2 made of pure iron having saturation magnetization of 21 kG (2,1 T) each in a sector-like form with a central angle of 7.5° and alternately arranged around the center axis as is illustrated in FIGURE 4a.
  • the sizing die had dimensions of 18 mm of outer diameter, 16 mm of inner diameter and 50 mm of length as is shown in FIGURE 4b and the temperature thereof was controlled not to exceed 50°C.
  • the extruder machine was run at 150°C with the screw rotated at a velocity of 60 rpm.
  • a piece of plastic magnet with circumferentially multipolar magnetization was taken from the thus prepared continuous-length extruded bar material by cutting in a plane perpendicular to the axis and the distribution of magnetic open flux around the circumference was measured by using a gaussmeter to give the results shown in FIGURE 5 indicating that the tubular plastic maggnet with circumferentially multipolar maggnetization had a very high open flux of almost 2 kG (0,2 T).
  • the same plastic magnet composition as used in the above described experiment was extrusion-molded into a continuous-length tube of the same dimensions as above without mounting the circumferentially orientating magnetizing member on the discharge port of the extruder maching.
  • the thus obtained plastic magnet bar was subjected to circumferential multipolar magnetization using a 24-polar magnetization yoke having an inner diameter of 18.1 mm by energizing each magnetizing coil with discharge of a capacitor of 600 ⁇ F capacity charged at 2000 volts.
  • the thus prepared multipolar circumferentially magnetized plastic magnet was subjected to the measurement of the magnetic open flux around the circumference in the same manner as above to find that the maximum value of the peaks in a chart similar to FIGURE 5 was about 1 kG (0,1 T).
  • a plastic magnet composition was prepared by uniformly Kneading, in a kneader at 220°C, 45% by volume of a polyester elastomer having a hardness of 60 according to JIS K 6301 and 55% by volume of a powder of the same rare earth-based magnetic alloy as used in Example 1 having an average particle diameter of about 3.5 ⁇ m.
  • This plastic magnet composition was extrusion-molded into a continuous-length tubular form of the same dimensions as in Example 1 with the die of which the temperature was controlled not to exceed 50 °C.
  • the same circumferentially orientating magnetizing member as in Example 1 was mounted on the discharge port of the extruder machine which was run at 250°C.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Manufacturing Cores, Coils, And Magnets (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)

Claims (2)

1. Verfahren zur Herstellung eines extrudierten kunststoffmagnetstabes fortlaufender Länge mit einer in Umfangsrichtung verlaufenden multipolaren Magnetisierung bei dem man eine kunststoffmagnetzusammensetzung, die aus einem Pulver aus einem Permanentmagneten und einem thermoplastischen Polymer zusammengesetzt ist, aus der Austrittsöffnung einer Extrudiervorrichtung extrudiert, welche mit einem multipolaren, in Umfangsrichtung anisotrop orientierenden Magnetisierglied ausgestattet ist, das aufgebaut ist aus mehreren radial orientierten magnetischen Polplatten, die aus einem magnetischen Material mit einer Sättigungsmagnetisierung von mindestens 10 kg (1 T) gebildet sind, sowie aus mehreren radial orientierten Permanentmagneten, die koaxial an der Auslaßöffnung befestigt sind, wobei jedes Paar von zwei benachbarten Permanentmagneten eine der magnetischen Polplatten sandwichartig zwischen sich einschließt und wobei die Pole der entsprechenden Permanentmagneten mit der gleichen Polarität einander gegenüberliegen.
2. Verfahren nach Anspruch 1, bei dem die radial orientierten Permanentmagneten aus einer Permanentmagnetlegierung auf Basis der Seltenen Erden hergestellt werden.
EP19870400682 1986-03-29 1987-03-26 Verfahren zur Herstellung eines stranggepressten Kunststoffmagnetstabes fortlaufender Länge und mit mehrpoliger Umfangsmagnetisierung Expired EP0240420B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP61072234A JPH0624176B2 (ja) 1986-03-29 1986-03-29 極異方性長尺成形品の製造方法
JP72234/86 1986-03-29

Publications (2)

Publication Number Publication Date
EP0240420A1 EP0240420A1 (de) 1987-10-07
EP0240420B1 true EP0240420B1 (de) 1991-05-08

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EP19870400682 Expired EP0240420B1 (de) 1986-03-29 1987-03-26 Verfahren zur Herstellung eines stranggepressten Kunststoffmagnetstabes fortlaufender Länge und mit mehrpoliger Umfangsmagnetisierung

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EP (1) EP0240420B1 (de)
JP (1) JPH0624176B2 (de)
DE (1) DE3769823D1 (de)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1301602C (en) * 1987-11-18 1992-05-26 Vijay K. Chandhok Method and assembly for producing extruded permanent magnet articles
US6304162B1 (en) * 1999-06-22 2001-10-16 Toda Kogyo Corporation Anisotropic permanent magnet
GB2380309B (en) * 2001-08-20 2005-04-06 Richard Wolfe Magnetic device for reduction of electromagnetic interference (EMI) in audio circuitry
JP7030290B2 (ja) * 2018-04-27 2022-03-07 国立大学法人 新潟大学 異方性を有する樹脂成形体の製造方法

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3640657A (en) * 1967-11-21 1972-02-08 Robert L Rowe Apparatus for extruding cylindrical magnets
JPS59226367A (ja) * 1983-06-08 1984-12-19 Hitachi Metals Ltd 異方性マグネツトロ−ルの製造方法
JPS60182710A (ja) * 1984-02-29 1985-09-18 Yamauchi Rubber Ind Co Ltd 磁力サイジング方法および磁力サイジングダイ

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Publication number Publication date
DE3769823D1 (de) 1991-06-13
JPS62229817A (ja) 1987-10-08
EP0240420A1 (de) 1987-10-07
JPH0624176B2 (ja) 1994-03-30

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