WO1991016717A1 - Method of manufacturing high energy rare earth alloy magnets - Google Patents
Method of manufacturing high energy rare earth alloy magnets Download PDFInfo
- Publication number
- WO1991016717A1 WO1991016717A1 PCT/US1991/002679 US9102679W WO9116717A1 WO 1991016717 A1 WO1991016717 A1 WO 1991016717A1 US 9102679 W US9102679 W US 9102679W WO 9116717 A1 WO9116717 A1 WO 9116717A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- rare earth
- earth alloy
- high energy
- mixture
- mold
- Prior art date
Links
- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 14
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 14
- 239000000956 alloy Substances 0.000 title claims description 11
- 229910045601 alloy Inorganic materials 0.000 title claims description 8
- 238000004519 manufacturing process Methods 0.000 title description 3
- 239000000696 magnetic material Substances 0.000 claims abstract description 12
- 238000001746 injection moulding Methods 0.000 claims abstract description 11
- 238000000034 method Methods 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 9
- 230000005291 magnetic effect Effects 0.000 claims description 8
- 239000004033 plastic Substances 0.000 claims description 7
- 229920003023 plastic Polymers 0.000 claims description 7
- 229910001172 neodymium magnet Inorganic materials 0.000 claims description 6
- 239000006247 magnetic powder Substances 0.000 claims description 5
- 239000000843 powder Substances 0.000 claims description 3
- 229920001169 thermoplastic Polymers 0.000 claims description 3
- 239000004416 thermosoftening plastic Substances 0.000 claims description 3
- 239000011230 binding agent Substances 0.000 claims description 2
- 229920002647 polyamide Polymers 0.000 claims description 2
- 230000005415 magnetization Effects 0.000 abstract description 6
- 238000000465 moulding Methods 0.000 abstract description 4
- 238000002347 injection Methods 0.000 description 7
- 239000007924 injection Substances 0.000 description 7
- 229910001004 magnetic alloy Inorganic materials 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- JHWNWJKBPDFINM-UHFFFAOYSA-N Laurolactam Chemical compound O=C1CCCCCCCCCCCN1 JHWNWJKBPDFINM-UHFFFAOYSA-N 0.000 description 1
- 239000004677 Nylon Substances 0.000 description 1
- 229920000299 Nylon 12 Polymers 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229920006351 engineering plastic Polymers 0.000 description 1
- 230000005294 ferromagnetic effect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229920001778 nylon Polymers 0.000 description 1
- 229920005596 polymer binder Polymers 0.000 description 1
- 239000002491 polymer binding agent Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
Classifications
-
- 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
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0578—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together bonded together
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F13/00—Apparatus or processes for magnetising or demagnetising
- H01F13/003—Methods and devices for magnetising permanent magnets
Definitions
- This invention relates to methods of making plastic bonded permanent magnets and more particularly to methods of injection molding such plastic bonded magnets employing isotrophic high energy rare earth alloy magnetic materials.
- High energy rare earth alloy magnetic materials require high magnetizing field strength to magnetize the materials to saturation.
- rapid solidified NdFeB magnetic material typically requires fields on the order of 3183 KA/m or more to substantially fully saturate the magnetic materials. See published European patent application 0 125 752 A2 published 21.11.84.
- the present inventors have discovered that under the elevated temperatures and pressures experienced in the injection molding environment, a surprising reduction in the coercivity of high energy rare earth magnetic materials occurs, and it is therefore possible to fully saturate a permanent magnetic material that ordinarily requires fields in acess of 3183 KA/m at room temperature and pressure with fields of only 7.9 KA/m or less.
- a plastic bonded permanent magnet is formed by injection molding a mixture of high energy rare earth alloy magnetic material (preferably rapid solidified NdFeB) requiring magnetization fields on the order of 3183 KA/m or greater at room temperature and pressure, and thermoplastic powder in a mold having means for providing magnetizing fields of 7.9 KA/m or less, and at a sufficiently elevated temperature and pressure to allow the field to fully magnetize the injection molded magnet, whereby high energy bonded magnets are provided without the need for further magnetization of the finished product.
- high energy rare earth alloy magnetic material preferably rapid solidified NdFeB
- Figure 1 is a schematic perspective view of a permanent magnetic roller made according to the method of the present invention
- Figure 2 is a cross sectional view of an injection mold useful in practicing the method of the present invention
- Figure 3 is a partial cross sectional view of the injection port of the mold shown in Figure 2.
- a bonded plastic cylindrical magnet 10 produced according to the present invention is shown.
- the magnet has longitudinal alternating N and S poles, and is of the type found in rotating motors and employed as toner transport rollers in electrographic apparatus.
- the roller 10 comprises a mixture of rare earth alloy permanent magnetic powder, preferably rapid solidified NdFeB, in a plastic binder such as nylon.
- the magnetic alloy material has a coercivity at room temperature and pressure of 3183 KA/m or greater.
- the magnet is formed in injection molding apparatus having means for molding the material in the presence of a magnetic field of 7.9 KA/m or less, preferably about 477 KA/m, and at an elevated temperature and pressure to fully magnetize the magnetic alloy material.
- Figure 2 is a cross section of a mold useful in practicing the present invention.
- the mold comprises a mold body 12 supporting a plurality of soft iron pole pieces 14.
- the pole pieces 14 are in the shape of rectangular blades that fit into slots in the mold body 12.
- the mold parts along the line 16.
- a tube 18 that forms a cylindrical mold cavity.
- the tube may be nonmagnetic material such as stainless steel or aluminum.
- the pole pieces 14 are in contact with the outside of the tube 18.
- the pole pieces 14 are wrapped with high temperature insulated wire coils 20, and sufficient current is supplied to the coils during the molding operation to generate a magnetic field at the pole tips of less than 7.9 KA/m, preferably about 477 KA/m.
- Figure 3 is a vertical cross section of the molding apparatus shown in Figure 2 at one end thereof. Current is maintained in the coils 20 while the mold fills, and then is terminated. After a short cooling time, the tube 18 is removed from the mold and the magnet 10 is forced from the tube 18. It has been found that the finished magnets can be produced in this manner with no need for further processing or post magnetization.
- the magnet forming method of the present invention is useful in forming high energy injection molded magnets, and is advantageous in that fully magnetized rare earth magnets are formed in a single injection step with low magnetizing field, without the need for subsequent magnetization steps.
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Manufacturing Cores, Coils, And Magnets (AREA)
- Hard Magnetic Materials (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
Abstract
High energy rare earth magnets are formed by injection molding and magnetizing (14, 20) in the mold (12) at a temperature sufficient to substantially reduce the coercivity of the magnetic material, whereby high energy fully magnetized rare earth magnets are formed in a single molding step without the need for post magnetization.
Description
METHOD OF MANUFACTURING HIGH ENERGY RARE EARTH ALLOY MAGNETS
Field of the Invention This invention relates to methods of making plastic bonded permanent magnets and more particularly to methods of injection molding such plastic bonded magnets employing isotrophic high energy rare earth alloy magnetic materials. Background of the Invention
High energy rare earth alloy magnetic materials require high magnetizing field strength to magnetize the materials to saturation. For example, rapid solidified NdFeB magnetic material typically requires fields on the order of 3183 KA/m or more to substantially fully saturate the magnetic materials. See published European patent application 0 125 752 A2 published 21.11.84.
It is known to form permanent magnets by injection molding a mixture of ferromagnetic powder and polymer binder to form a body of magnetic material, and to magnetize the magnetic material in the mold by employing electromagnets within the mold. See for example U.S. patent no. 4,678,616 issued July 7, 1987 to Kawashima.
The high magnetic fields required to fully saturate the high energy rare earth magnetic alloy materials are difficult to achieve in an injection mold, particularly for small parts, where the pole pieces are relatively small, and there is little room for large magnetizing coils. Summary of the Invention
It is the object of the present invention to provide a method of making permanent magnets by injection molding while magnetizing in the mold, that overcomes the difficulty noted above.
The present inventors have discovered that under the elevated temperatures and pressures experienced in the injection molding environment, a surprising reduction in the coercivity of high energy rare earth magnetic materials occurs, and it is therefore possible to fully saturate a permanent magnetic material that ordinarily requires fields in acess of 3183 KA/m at room temperature and pressure with fields of only 7.9 KA/m or less. Thus, according to the present invention, a plastic bonded permanent magnet is formed by injection molding a mixture of high energy rare earth alloy magnetic material (preferably rapid solidified NdFeB) requiring magnetization fields on the order of 3183 KA/m or greater at room temperature and pressure, and thermoplastic powder in a mold having means for providing magnetizing fields of 7.9 KA/m or less, and at a sufficiently elevated temperature and pressure to allow the field to fully magnetize the injection molded magnet, whereby high energy bonded magnets are provided without the need for further magnetization of the finished product. Brief Descri ion of the Drawings
Figure 1 is a schematic perspective view of a permanent magnetic roller made according to the method of the present invention;
Figure 2 is a cross sectional view of an injection mold useful in practicing the method of the present invention; and Figure 3 is a partial cross sectional view of the injection port of the mold shown in Figure 2. Modes of Carrying Out the Invention
Referring to Figure 1, a bonded plastic cylindrical magnet 10 produced according to the present invention is shown. The magnet has longitudinal alternating N and S poles, and is of the
type found in rotating motors and employed as toner transport rollers in electrographic apparatus.
According to the present invention, the roller 10 comprises a mixture of rare earth alloy permanent magnetic powder, preferably rapid solidified NdFeB, in a plastic binder such as nylon. The magnetic alloy material has a coercivity at room temperature and pressure of 3183 KA/m or greater. According to the present invention, the magnet is formed in injection molding apparatus having means for molding the material in the presence of a magnetic field of 7.9 KA/m or less, preferably about 477 KA/m, and at an elevated temperature and pressure to fully magnetize the magnetic alloy material. Figure 2 is a cross section of a mold useful in practicing the present invention. The mold comprises a mold body 12 supporting a plurality of soft iron pole pieces 14. The pole pieces 14 are in the shape of rectangular blades that fit into slots in the mold body 12. The mold parts along the line 16. At the center of the mold body 12 is a tube 18 that forms a cylindrical mold cavity. The tube may be nonmagnetic material such as stainless steel or aluminum. The pole pieces 14 are in contact with the outside of the tube 18. The pole pieces 14 are wrapped with high temperature insulated wire coils 20, and sufficient current is supplied to the coils during the molding operation to generate a magnetic field at the pole tips of less than 7.9 KA/m, preferably about 477 KA/m.
The mixture of magnetic powder and plastic is heated in the injection molding machine and injected under pressure into the mold cavity through a heated barrel 22 shown in Figure 3. Figure 3 is a vertical cross section of the molding apparatus shown in Figure 2 at one end thereof.
Current is maintained in the coils 20 while the mold fills, and then is terminated. After a short cooling time, the tube 18 is removed from the mold and the magnet 10 is forced from the tube 18. It has been found that the finished magnets can be produced in this manner with no need for further processing or post magnetization. Working Example
A mixture of rapid solidified NdFeB magnetic powder (obtained from General Motors Corporation)
80-90% by weight and nylon 12, polyamid thermoplastic resin purchased from LNP Engineering Plastics Inc., Malvern, PA. was injection molded in apparatus as shown in Figures 2 and 3 at a barrel temperature of 280-290°C and a mold temperature of 90°C to produce a magnetic roller shown in Figure 1. A field of 477 KA/m was applied for 2 seconds while the mold was filled. The resulting magnetic roller exhibited a magnetic field at the surface of 5000 gauss indicating substantially complete magnetization, and a coercivity of 1114 KA/m. Industrial Applicability and Advantages
The magnet forming method of the present invention is useful in forming high energy injection molded magnets, and is advantageous in that fully magnetized rare earth magnets are formed in a single injection step with low magnetizing field, without the need for subsequent magnetization steps.
Claims
1. A method of forming a bonded plastic magnet comprising the steps of: a. providing a mixture of rare earth alloy magnetic powder requiring a magnetic field of
7.9 KA/m at room temperature and pressure of 3183 KA/m greater to substantially fully magnetize the magnetic powder, and a thermoplastic binder; and b. injection molding the mixture in an injection molding apparatus having means for providing a magnetizing field of less than 7.9 KA/m at a sufficiently elevated temperature and pressure effective to fully magnetize the rare earth alloy magnetic material.
2. The method claimed in claim 1, wherein the rare earth alloy magnetic material is rapid solidified NdFeB.
3. The method claimed in claim-2, wherein the mixture is 80-90% by weight NdFeB powder and polyamid thermoplastic.
4. The method claimed in claim 3, wherein the injection molding is performed at a barrel temperature of 280-290 C and a mold temperature of 90°C.
5. The method according to any of claims
1-4 characterized in that a magneticaing field of about 477 KA/m is applied to said mixture.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US51337190A | 1990-04-23 | 1990-04-23 | |
| US513,371 | 1990-04-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1991016717A1 true WO1991016717A1 (en) | 1991-10-31 |
Family
ID=24042986
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/US1991/002679 WO1991016717A1 (en) | 1990-04-23 | 1991-04-19 | Method of manufacturing high energy rare earth alloy magnets |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0478751A1 (en) |
| JP (1) | JPH04506887A (en) |
| WO (1) | WO1991016717A1 (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6076110A (en) * | 1983-10-03 | 1985-04-30 | Sumitomo Special Metals Co Ltd | Assembling and magnetizing method for magnetic circuit |
| JPS61276303A (en) * | 1985-05-31 | 1986-12-06 | Seiko Epson Corp | Manufacturing method of rare earth permanent magnet |
| JPS63216309A (en) * | 1987-03-05 | 1988-09-08 | Seiko Epson Corp | Manufacturing method of cylindrical rare earth sintered magnet |
| EP0284033A1 (en) * | 1987-03-23 | 1988-09-28 | Tokin Corporation | A method for producing a rare earth metal-iron-boron anisotropic bonded magnet from rapidly-quenched rare earth metal-iron-boron alloy ribbon-like flakes |
| JPH0212801A (en) * | 1988-06-30 | 1990-01-17 | Hitachi Metals Ltd | Compound for bonding magnet and its manufacture |
-
1991
- 1991-04-19 WO PCT/US1991/002679 patent/WO1991016717A1/en not_active Application Discontinuation
- 1991-04-19 JP JP3508064A patent/JPH04506887A/en active Pending
- 1991-04-19 EP EP19910908294 patent/EP0478751A1/en not_active Withdrawn
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6076110A (en) * | 1983-10-03 | 1985-04-30 | Sumitomo Special Metals Co Ltd | Assembling and magnetizing method for magnetic circuit |
| JPS61276303A (en) * | 1985-05-31 | 1986-12-06 | Seiko Epson Corp | Manufacturing method of rare earth permanent magnet |
| JPS63216309A (en) * | 1987-03-05 | 1988-09-08 | Seiko Epson Corp | Manufacturing method of cylindrical rare earth sintered magnet |
| EP0284033A1 (en) * | 1987-03-23 | 1988-09-28 | Tokin Corporation | A method for producing a rare earth metal-iron-boron anisotropic bonded magnet from rapidly-quenched rare earth metal-iron-boron alloy ribbon-like flakes |
| JPH0212801A (en) * | 1988-06-30 | 1990-01-17 | Hitachi Metals Ltd | Compound for bonding magnet and its manufacture |
Non-Patent Citations (4)
| Title |
|---|
| PATENT ABSTRACTS OF JAPAN vol. 11, no. 130 (E-502)(2577) 23 April 1987, & JP-A-61 276303 (SEIKO EPSON CORP) 6 December 1986, see the whole document * |
| PATENT ABSTRACTS OF JAPAN vol. 13, no. 5 (E-701)(3353) 9 January 1989, & JP-A-63 216309 (SEIKO EPSON CORP) 8 September 1988, see the whole document * |
| PATENT ABSTRACTS OF JAPAN vol. 14, no. 154 (E-907)(4097) 23 March 1990, & JP-A-2 12801 (HITACHI METALS LTD) 17 January 1990, see the whole document * |
| PATENT ABSTRACTS OF JAPAN vol. 9, no. 216 (E-340)(1939) 3 September 1985, & JP-A-60 76110 (SUMITOMO) 30 April 1985, see the whole document * |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04506887A (en) | 1992-11-26 |
| EP0478751A1 (en) | 1992-04-08 |
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