CN1044187A - 环形永磁体的成型方法及成型模具 - Google Patents

环形永磁体的成型方法及成型模具 Download PDF

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CN1044187A
CN1044187A CN 89109848 CN89109848A CN1044187A CN 1044187 A CN1044187 A CN 1044187A CN 89109848 CN89109848 CN 89109848 CN 89109848 A CN89109848 A CN 89109848A CN 1044187 A CN1044187 A CN 1044187A
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annular
permanent magnet
die cavity
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吉田和仁
清水俊夫
则武博
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Seikosha KK
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/58—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising fillers only, e.g. particles, powder, beads, flakes, spheres
    • B29C70/62—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising fillers only, e.g. particles, powder, beads, flakes, spheres the filler being oriented during moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/0013—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor using fillers dispersed in the moulding material, e.g. metal particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/26—Moulds
    • B29C45/2616—Moulds having annular mould cavities
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/88—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts characterised primarily by possessing specific properties, e.g. electrically conductive or locally reinforced
    • B29C70/882—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts characterised primarily by possessing specific properties, e.g. electrically conductive or locally reinforced partly or totally electrically conductive, e.g. for EMI shielding
    • 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
    • H01F41/0266—Moulding; Pressing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/26—Moulds
    • B29C45/27—Sprue channels ; Runner channels or runner nozzles
    • B29C45/2701—Details not specific to hot or cold runner channels
    • B29C45/2708—Gates
    • B29C2045/2714—Gates elongated, e.g. film-like, annular
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
    • B29K2995/0003—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds having particular electrical or magnetic properties, e.g. piezoelectric
    • B29K2995/0005—Conductive

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Composite Materials (AREA)
  • Power Engineering (AREA)
  • Dispersion Chemistry (AREA)
  • Manufacturing Cores, Coils, And Magnets (AREA)
  • Permanent Field Magnets Of Synchronous Machinery (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)

Abstract

一种环形永磁体的成型方法及成型模具。该成型方法包括将可塑磁性材料从环形门注入环形模腔的工艺步骤，环形门设置在模腔的一个端表面的内沿或外沿。该成型模具包括一个环形模腔和一个在模腔的一个端表面的内沿或外沿处的、与模腔连通的环形门。(图2)

Description

本发明涉及一种环形永磁体成形方法及成形模具。
当采用一种由可塑物和铁磁性颗粒例如铁氧体、钐-钴（Sm-Co）等组成的可塑性磁性材料成形永磁体时，就双极磁化而言，乞今已知的门结构有单门式，即具有与磁化方向垂直设置的一个门，和双门式，即具有分别设置在磁化方向的北极侧和南极侧的两个门（例如，专利公开号为149109/1987的专利申请中所公开的）。
图1是根据本发明的环形永磁体的剖面图;
图2是根据本发明的环形永磁体成形模具的剖面图;
图3是用本发明方法成形的环形永磁体内部结构的显微照片;
图4是该双极径向磁化的环形永磁体磁通密度分布曲线图;
图5是由已有技术使用单门成形的环形永磁体内部结构的显微照片;
图6是图5所示的双极径向磁化环形永磁体的磁通密度分布曲线图。
图中标号1是环形永磁体，标号2是环形模腔，标号6是环形门。
当采用可塑性磁性材料成形永磁体时，特别是对于径向磁化的环形磁体，园周上的磁通密度分布变化极大、这取决于门的位置或者多个门的位置。而且，无论磁体是各向同性，还是各向异性都存在这种现象。
诸如铁氧体、钐-钴（Sm-Co）等磁性颗粒具有形状各向异性，而且沿这类颗粒的晶体的C轴具有磁各向异性。铁氧体颗粒（图5中的a）、呈鳞状，并在厚度方向具有易磁化轴。因此，当注入可塑物时，其取向往往会受可塑物流动的影响。对于环形永磁体而言，安装在模腔中心的轴把可塑物流分为两股。图5是采用单门G1成形的各向同性磁体的剖面放大照片，照片是通过门拍摄的。照片显示了磁性颗粒的分布。在靠近门G1的一侧或左侧的外园周处，许多颗粒a的厚度方向位于磁体的径向。在靠近与门G1完全相反的一侧或右侧的外园周处，许多颗粒a的厚度方向位于磁体的厚度方向。我们看到，流动的可塑物以这种方式将颗粒呈现出来。因此，在门一侧的磁化是均匀的。然而，在相反一侧，要达到均匀磁化是很困难的。图6是各向同性磁体外园周上磁通密度的分布曲线图，该各向同性磁体是采用单门成形和双极径向磁化。如从图6可以看到的，与门G1相距180°的位置上的磁通密度分布，其均匀性比门位置上的磁通密度分布均匀性差。在这些位置上的磁通密度出现两个峰。在双极磁体中、磁通密度的不平衡出现在北极与南极之间。在两门式的情形下，与门相距90°的位置上的磁通密度分布正如所述的以同样方式出现紊乱。
某些种类的磁性颗粒在长度方向有一易磁化轴。对于这种磁性颗粒，无论是使用单门还是双门，要想模制一个在磁体整个外园周上磁性颗粒a都均匀分布的环形永磁体也都是困难的。当模制各向异性磁体时，磁场和可塑物的流动两者都会影响颗粒的取向，从而使模制条件的控制复杂化。
当磁通密度分布紊乱的磁体用在步进电机上时，转子会在无规律的位置上发生停顿，从而引起转子不均匀旋转。当这种磁体用于照相机时，则不能精确地实现自动聚焦和自动曝光的工作程序。
为此，本发明的目的是提供一种环形永磁体的成形方法及结构简单的成形模具，可使外园周上磁性颗粒的取向不存在异常点。而以前的方法会由于门的位置而出现这种异常点。按本发明可实现模腔内的可塑性磁性材料均匀取向和均匀磁化。
根据本发明的如下步骤实现上述目的。在一个与永磁体形状相符的环形模腔的一个端表面的内沿或外沿设置环形门，把可塑性磁性材料从环形门注入模腔。
从环形门注入模腔内的可塑磁性材料，沿模腔的内表面或外表面从顶部流入底部，同时，可塑磁性材料在整个表面上均匀地向外或向内流动，然后，沿外表面或内表面向上流动，添加在可塑磁性材料中的磁性颗粒由材料流运载。流入并充满模腔。由此，磁性颗粒在模腔内的整个表面上均匀地取向。
实施例
下面将参考附图说明本发明的一个实施例。
参见图1，采用注射模塑法成形的一个本发明的环形永磁体。在环形模腔2上表面内沿设置一个环形门6，添加有铁氧体磁性颗粒的可塑磁性材料从门6注入环形模腔2，由此模塑成磁体1。
图2显示了环形永磁体1的成形模具。该模具包括构成模腔外表面2a的模板3，另一块模板4构成环形模腔2的底表面2b，并起到一个注射套筒的作用，一个心柱5通过注射套筒的中心延伸，并构成模腔的内表面2c，一块模板7构成模腔的上表面2d，由此构成用于模塑永磁体1的环形模腔2。图2中的P·L·代表该模具的接合线。模板7上设置有浇口8。心柱5插入浇口8的前端部，由此构成环形门6，在本实施例中，浇口8的前端直径，即环形门6的外径做得比心柱5的直径大0.5毫米至0.6毫米。长度为0.1毫米至0.25毫米，厚度为30微米至50微米的磁性颗粒能够很容易地纵向通过门6。颗粒在心柱5的整个外园周上均匀地进入环形模腔2的内沿。
用该模具、按下述方法模塑成环形永磁体1。移动板7和3使模腔闭合、伸出心柱5。模腔2的底表面位置由模板4设定。然后，通过环形门6从浇口8将可塑性材料注入模腔2中。材料沿心柱5向下流动，同时在整个360度的方向上均匀地向外流动，并沿着模板3向上流动、从而充满模腔2。可塑磁性材料固化之后，除去模板7，打开模腔，于是，模腔2内的固化可塑物与浇口8内的固化物在门的位置处被分离。最后推出模板4、则注塑成图1所示的环形永磁体。
图3是一个采用本发明的制造方法成形的各向同性环形永磁体的剖面显微照片。如图3所示、许多磁性颗粒a以其厚度方向位于径向的方式均匀地分布。颗粒在整个表面上均匀地取向，无论它们是在门一侧、还是在与门相距180度的位置上。
图4是这种各向同性的、并且是双极径向磁化的环形永磁体的外园周上磁通密度的分布曲线。如图4所示，在以180度间隔磁化的北极和南极的周围，磁通密度的分布实质上是相同的。这里不存在图6中所示的不平衡，即门G1周围的磁通密度分布同距离门180度位置的磁通密度分布之间不存在不平衡。
如果环形门设置在环形模腔的一个端表面的外沿，则可塑磁性材料以同上述相同的方式在整个表面上均匀地流入模腔。因此，磁性颗粒在整个表面上均匀地取向。
本发明的永磁体制造方法和成形模具还可以用于在磁场下模塑制成各向异性磁体。当模塑制造这种各向异性磁体时，磁场加于模腔2上。与以前相比，磁场可以较弱。通过磁场和从环形门6注入的可塑磁性材料的均匀流动，使磁性颗粒沿磁场更流畅地取向。从而可以很容易地实现磁各向异性。
按这种方法模塑制成的环形永磁体不仅可以用作钟表电动机的转子，还可用作照相机的驱动电动机的转子。此外，本发明并不限于径向磁化的永磁体。本发明还可应用于磁流体轴承，悬浮式陀螺等使用的环形磁体。
正如已经说明的，当根据本发明成形环形永磁体时，在外园周上没有出现因门位置而引起的磁性颗粒取向异常点。这不同于采用现有技术成形的永磁体。因此，可以获得磁化方向不受门位置限制的各向同性磁体。当成形各向异性磁体时，模制条件不会被限制在窄的范围内。此外，弱磁场导致均匀磁化。
在按这种方法成形的本发明的环形永磁体中，磁性颗粒分布在整个外园周。磁体可以均匀磁化，并用作钟表或自动快门中使用的高质量转子。
由于本发明的环形永磁体成形模具的结构简单。因而，它适合于小尺寸环形永磁体的成形。并能充分满足微型化要求，而且不增加生产成本。

Claims (3)

1、一种环形永磁体的成形方法，包括将可塑磁性材料从环形门注入环形模腔的工艺步骤，环形门设置在模腔的一个端表面的内沿，或外沿。
2、按照权利要求1的环形永磁体的成形方法，成形的环形永磁体。
3、一种环形永磁体的成形模具，包括：
一个环形模腔;
一个在模腔的一个端表面的内沿或外沿处的、与模腔连通的环形门。
CN 89109848 1988-12-29 1989-12-29 环形永磁体的成型方法及成型模具 Pending CN1044187A (zh)

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JP331212/88 1988-12-29
JP33121288A JPH02178011A (ja) 1988-12-29 1988-12-29 ドーナツ型永久磁石の製造方法とこの方法によって製造したドーナツ型永久磁石およびドーナツ型永久磁石の成形金型

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CN101882505A (zh) * 2010-04-08 2010-11-10 广元瑞峰精工机械制造有限公司 一种细长结构精密模具的改进结构

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101447331B (zh) * 2002-10-08 2011-08-17 日立金属株式会社 烧结型R-Fe-B系永磁体的制造方法

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GB2226789B (en) 1992-04-29
HK22494A (en) 1994-03-25
DE3943328C2 (de) 1995-04-27
DE3943328A1 (de) 1990-07-05
FR2641228B1 (zh) 1995-02-24
JPH02178011A (ja) 1990-07-11
CH681183A5 (zh) 1993-01-29
GB2226789A (en) 1990-07-11
FR2641228A1 (fr) 1990-07-06

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