JP5677832B2 - Field unit, bond magnet constituting the same, and method of manufacturing field unit - Google Patents

Description

The present invention relates to a field unit using a bonded magnet having planar multipolar anisotropy, and more particularly to a field unit for an actuator, a bonded magnet constituting the field unit, and a method of manufacturing the field unit.

  Many devices are known in which a magnetic field is generated in a gap formed between two permanent magnets and a motion function is exhibited in the gap by the interaction between magnetism and electricity. Familiar examples include speakers and microphones. Most motors have the same mechanism. For example, in a head drive mechanism of a hard disk drive (HDD), such an interaction between magnetism and electricity is used in an actuator called a VCM (voice coil motor) of the HDD.

  As an example, FIG. 11A is a side view of a VCM constituting the head drive mechanism of the HDD, FIG. 11B is a horizontal sectional view taken along the line AA of FIG. 11A, and FIG. Each is shown in FIG. As shown in these drawings, in the HDD head drive mechanism, a magnetic gap MG formed between two plate-like permanent magnet thin plates 111 spaced apart from each other is perpendicular to the permanent magnet thin plate. A magnetic field is generated in the direction. In addition, the permanent magnet thin plate 111 is attached to a material having a high magnetic permeability called a yoke plate 112 so that a closed magnetic path is formed except for the magnetic gap MG. The upper and lower yoke plates 112 are supported by a support 113 made of a high magnetic permeability material for forming the magnetic air gap MG.

  Further, an arm 117 is inserted into the magnetic gap MG as shown in FIG. A coil 114 is provided at one end of the arm 117. The coil 114 is wound so that the direction of the current is perpendicular to the magnetic field of the magnetic gap MG, and thrust is generated according to Bio-Savart's law or Fleming's law. The coil 114 is attached to a carriage at one end of the arm 117. On the other hand, a magnetic head 116 is provided at the other end of the arm 117. Further, a pivot 115 is provided as a support member near the center of the arm 117 in the longitudinal direction, and the arm 117 is rotated about this point.

  The performance of the HDD greatly depends on the movement of the magnetic head 116, that is, the movement of the arm 117. In order for the arm 117 to rotate quickly, it is necessary to increase the thrust. In order to increase the thrust, it is necessary to increase the current flowing through the coil 114 or to increase the magnetic field of the magnetic gap MG. Although it is possible to narrow the magnetic gap MG in order to increase the magnetic field, in that case, the size of the coil inserted into the magnetic gap MG is limited, and the current that can be passed is also limited. On the other hand, the thrust can be increased by increasing the current flowing through the coil while leaving the magnetic gap MG unchanged. However, simply increasing the current is not practical because of the problem of increased power consumption and heat generation of the HDD.

  After all, in order to increase the thrust, the general theory is that the performance of the permanent magnet must be improved to increase the magnetic flux density of the gap. A high-performance magnet is typically a sintered NdFeB magnet, and it can be said that a sintered NdFeB magnet is employed in most HDD VCMs. The performance of the permanent magnet is represented by a number represented by BHmax. In the 1980s when sintered NdFeB magnets were developed, BHmax was about 30 MGOe. After that, although the performance improved to about 50MGOe in the 90s, the progress has been slow since 2000, and there is no situation where significant performance improvement can be expected at the present time. Furthermore, it is difficult for the latest high-performance materials other than sintered NdFeB magnets to appear recently.

  Further, it is certain that sintered NdFeB magnets will be used in large quantities in the field of power equipment including electric vehicles in the future. From the viewpoint of balanced consumption of rare earth elements, the advent of VCM for HDD using materials other than sintered NdFeB magnets is strongly demanded. In particular, at the present time when the supply shortage of rare earth elements has become apparent due to resource nationalism, it is urgent to develop a magnet that can be used practically without relying on sintered NdFeB magnets from the viewpoint of stable supply of raw materials.

  On the other hand, an attempt has been made to increase the magnetic field in the gap not only by simply improving the magnet performance of the material but also by reviewing the orientation and arrangement of the permanent magnets. Patent Documents 1 and 2 are known as such examples.

Japanese Patent No. 3865351 Special table 2010-515282

  In Patent Document 1, in order to increase the thrust (torque) of the arm of the VCM for HDD, a plurality of magnetic poles are formed in a flat portion in a magnet arranged above and below the gap, and adjacent to the planar magnetic poles. There is a description that at least two magnetic poles have polar anisotropy. However, this technique merely replaces the magnet at the site where sintered NdFeB was used with a polar anisotropic magnet. Although it is possible to increase the magnetic flux density by devising the orientation to be extremely anisotropic compared to the dipole orientation, the effect cannot be expected if the magnet shape and unit structure are substantially the same. This is because, in many cases, polar anisotropic orientation is difficult to achieve complete orientation compared to bipolar orientation and the like, and tends to be about 10% lower from the viewpoint of BHmax.

  Patent document 2 describes a measure for obtaining a strong and uniform parallel magnetic field, although it is not a matter of HDD VCM. That is, it has a substantially cylindrical magnet that defines a gap and has an upper end and a lower end, and there are face plates (yoke plates) on the upper and lower sides, and the relative permeability of this face plate must be 10,000 or more. It is written. In this technique, the thickness of the cylindrical magnet in the vertical direction forms a gap.

  However, in the HDD VCM, the arm extends with a face protruding from the gap, and thus a complete cylindrical magnet cannot be employed. In addition, in an actual HDD VCM, the size of parts is limited, and therefore an extremely thick cylindrical magnet or an extremely thick yoke plate cannot be used. Further, since the HDD unit is restricted by strict computer standards, it is not allowed that only the VCM becomes extremely large.

The present invention has been made in view of such a background. The main object of the present invention is a practical unit that does not use a sintered NdFeB magnet as a field unit that can be used for an HDD VCM or the like, has the same size as the current HDD VCM system, and is practical. An object of the present invention is to provide a field field unit , a bond magnet constituting the field field unit, and a method of manufacturing the field unit .

Means for Solving the Problems and Effects of the Invention

In order to achieve the above object, according to the field unit according to the first aspect of the present invention, a first bonded magnet in which a compound made of a magnetic material and a resin is formed in a substantially plate shape, and the first bonded magnet And a second bonded magnet in which a compound made of a magnetic material and a resin is formed in a substantially plate shape, the first bonded magnet and the second bonded magnet, has a flat portion in which a plurality of magnetic poles are formed with polar anisotropy respectively, and at least one of the first bond magnet and the second bonded magnet, projecting from a portion of said flat portion A protrusion for connecting to the other bond magnet, the protrusion has a magnetic pole, and the first bond magnet and the second bond magnet are connected to the first bond magnet; wherein as one flat portion second bond Magnetic gap between the second flat portion of the stone is formed, and can be different magnetic poles are coupled to face each other.

Thus, unlike the conventional configuration in which a plate-like permanent magnet is bonded to a magnetically permeable yoke plate, the present invention includes not only two yoke plates that constitute the conventional field unit, but also a support column that connects them. By forming with the same bonded magnet, a closed magnetic circuit can be constructed, and the magnetic flux density in the magnetic gap can be increased. As a result, even if the magnetic force of the bonded magnet is weak, a sufficient magnetic force can be exhibited as a field unit for the actuator. In addition, the present invention has an advantage that the magnetic unit can be divided into a first bond magnet and a second bond magnet so that the closed magnetic gap can be opened and each part can be easily molded with a mold or the like.

Moreover, according to the field unit which concerns on a 2nd side surface, a substantially circular arc-shaped magnetic force line can be formed in those inside by the said 1st bond magnet, said 2nd bond magnet, and the said protrusion part.

  Thereby, the closed magnetic circuit in the field unit can be configured without difficulty, and the magnetic flux density of the magnetic air gap obtained by the magnetic circuit can be improved.

Furthermore, according to the field unit according to the third aspect, the first bond magnet and the second bond magnet can be formed in a substantially point-symmetric shape with respect to the center of the magnetic gap.

Thereby, since the components of the same shape can be used for the first bond magnet and the second bond magnet, it is possible to reduce the manufacturing cost of molding by the mold.

Furthermore, according to the field unit according to the fourth aspect, the first bond magnet or the second bond magnet may have a fitting structure in which the protruding portion is fitted.

Thereby, when joining a 1st bond magnet and a 2nd bond magnet, the advantage which can be connected by magnetic force, without performing adhesion | attachment etc. is acquired.

  Furthermore, according to the field unit according to the fifth aspect, the fitting structure can be formed in the recessed portion or the stepped portion.

Thereby, when joining a 1st bond magnet and a 2nd bond magnet by magnetic force, both joining positions are specified and the advantage which can be comprised as a stable-shaped field unit is acquired.

Furthermore, according to the field unit according to the sixth aspect, the protrusion is formed in a prismatic shape having substantially the same width as the width of the first bond magnet or the second bond magnet, and the protrusion The side surfaces of the first bonded magnet and the second bonded magnet can be formed to be substantially flush with the side surfaces of the first bonded magnet and the second bonded magnet.

  As a result, the outer shape of the field unit can be formed in a rectangular shape or a block shape, and an excessive leakage flux of the magnetic circuit can be reduced to exhibit a high magnetic flux density.

Furthermore, according to the field unit according to the seventh aspect, the first bond magnet and the second bond magnet can be formed into a single molded body.

  As a result, the magnetic flux leakage at the first flat portion and / or the boundary portion between the second flat portion and the protruding portion is further reduced, and the bonding between the protruding portion and the flat portion is not required, and the structure is simplified. Magnetic flux density can be greatly improved.

  Furthermore, according to the field unit according to the eighth aspect, the magnetic material can be composed of an anisotropic SmFeN-based magnetic material.

Thereby, even if the magnetic force of the bond magnet is weak, a sufficient magnetic force can be exhibited as a field unit for the actuator.

Furthermore, according to the field unit which concerns on a 9th side surface, it can be set as the single body of the 1st bond magnet or the 2nd bond magnet which comprises one of the said field units.

Furthermore, according to the field unit according to the tenth aspect, the field unit manufacturing method includes the step of forming the flat portion and the protrusion on a mold for forming the first bond magnet and the second bond magnet. Arranging an orientation magnet for orienting a magnetic material constituting the part, injecting a compound made of a magnetic material and a resin into the mold, the first bonded magnet and the first A step of forming a two- bond magnet and a step of connecting the first bond magnet and the second bond magnet by their magnetic force to form a magnetic gap may be included.

Thus, unlike the conventional configuration in which a plate-like permanent magnet is bonded to a magnetically permeable yoke plate, the present invention is not limited to the two yoke plates in the conventional field unit, but also the struts connecting them are the same bonded magnet. By forming, a closed magnetic circuit can be configured, and the magnetic flux density in the magnetic gap can be increased. As a result, even if the magnetic force of the bonded magnet is weak, a sufficient magnetic force can be exhibited as a field unit for the actuator.

It is a perspective view which shows the field unit which concerns on Embodiment 1 of this invention. It is a disassembled perspective view of the field unit of FIG. It is a front view of the field unit of FIG. It is a schematic diagram which shows the magnetic force line of a field unit. 6 is a front view showing a field unit according to Embodiment 2. FIG. 6 is a front view showing a field unit according to Embodiment 3. FIG. FIG. 10 is a front view showing a field unit according to Embodiment 4. It is a top view which shows the state which inserted the arm of VCM in the field unit of FIG. It is a schematic cross section which shows an example of the metal mold | die which carries out the injection molding of the 1st bonded magnet of FIG. It is a schematic cross section which shows the other example of the metal mold | die which carries out the injection molding of the 1st bonded magnet of FIG. It is the horizontal sectional view in the (a) side view and (b) AA line which show the conventional VCM. It is a top view which shows the arm of the conventional VCM. It is a schematic diagram which shows a Halbach magnet. It is a schematic cross section which shows the metal mold | die which shape | molds the molded object which concerns on a comparative example.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, the form shown below exemplifies the field unit for actuator and the manufacturing method thereof for embodying the technical idea of the present invention, and the present invention describes the field unit for actuator and the manufacturing method thereof as follows. It is not limited to.

  Further, the present specification by no means specifies the members shown in the claims to the members of the embodiments. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments are not intended to limit the scope of the present invention only to the description unless otherwise specified. It's just an example. Note that the size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation. Further, in the following description, the same name and reference sign indicate the same or the same members, and detailed description will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured such that a plurality of elements are constituted by the same member and the plurality of elements are shared by one member, and conversely, the function of one member is constituted by a plurality of members. It can also be realized by sharing. In addition, the contents described in some examples and embodiments may be used in other examples and embodiments.

  FIG. 1 is a perspective view of a field unit 100 according to an embodiment of the present invention, FIG. 2 is an exploded perspective view thereof, and FIG. 3 is a front view of FIG. A field unit 100 shown in these drawings is a field unit of an HDD VCM having an outer shape that is a box-shaped rectangle. The field unit 100 has a magnetic gap MG opened at the center. The magnetic gap MG is a gap opened in a slit shape, and the magnetic body is polar-oriented so that different magnetic poles are exposed on the opposed surfaces.

Further, the present invention is not a configuration in which the end portions of two yoke plates to which permanent magnets are attached are fixed to each other by a support column, but the present invention is a bond in which the yoke plate and the support column in a conventional field unit are integrally configured. It is a magnet. Specifically, it is formed continuously without the boundary between the conventional yoke plate and the column. Furthermore, the yoke plate and the column are not made of a ferromagnetic material such as soft iron with high magnetic permeability, but are composed of bonded magnets. In other words, according to the present invention, the yoke plate itself in the conventional field unit is used as a bonded magnet, and a part of the yoke plate is further projected to replace the support column.

  Furthermore, the permeance is improved by reducing the leakage flux to the outside and orienting the magnetic material so that the magnetic flux is concentrated in the magnetic gap MG. With this configuration, even if it is an SmFeN-based magnet whose BHmax is inferior to that of a sintered NdFeB magnet, a magnetic force equivalent to that of a field unit using the sintered NdFeB magnet can be exhibited. That is, a field unit that can be used for VCM or the like can be realized without using expensive rare earth Nd. As a result, it is possible to exhibit a sufficient magnetic force as a field unit for an actuator, such as being able to construct a practical VCM while using an inexpensive and easily available SmFeN-based magnet using Sm as a permanent magnet.

The field unit in the conventional VCM has a three-piece structure of a flat magnet, a yoke plate, and a support. As a result of diligent research, we created a strong permanent magnet such as a sintered NdFeB magnet by creating the field unit itself with a single material bonded magnet and adopting a pole-oriented structure over the entire field unit. Even if it is not used, a field unit having a sufficiently large magnetic flux density that can be used for a VCM or the like has been realized. That is, the permanent magnet, the yoke plate, and the column portion in the VCM are formed of a single material bonded magnet. Here, as what constitutes a yoke plate with a single magnet, a so-called Halbach arrangement as shown in FIG. 13 or a Halbach magnet is known. However, in applications such as HDD VCM, a field unit must be housed in a limited size, and a manufacturing method capable of mass production at an appropriate cost is also required. From this point of view, the Halbach method of combining magnets in a mosaic manner requires a high level of skill in the assembly of magnets, and thus has a problem in application to the assembly of industrial products.

In contrast, in the field unit according to the present embodiment, as described above, the yoke plate and the support in the conventional field unit are integrally formed of the same material, and the entire field unit is a bonded magnet. Furthermore, by forming the first bonded magnet and the second bonded magnet divided at the magnetic gap MG portion, it is possible to form by injection molding and succeeded in providing a field unit suitable for mass production. .
(Magnetic gap MG)

  The magnetic gap MG is opened in a rectangular shape as shown in FIGS. The magnetic air gap MG is configured such that the first main surface 14 and the second main surface 24 face each other along the longitudinal direction. FIG. 4 shows a magnetic field line pattern of the field unit. Thus, in the magnetic air gap MG sandwiched between the first main surface 14 and the second main surface 24, the plurality of magnetic poles are flat so that the anisotropic magnetic poles face each other on the two main surfaces facing each other. It is expressed in the form. In this example, two main poles, an N pole and an S pole, are provided on each main surface, and a substantially uniform magnetic flux density is realized in almost the entire main surface. However, it may be configured such that four or more magnetic poles are exposed on the main surface.

The fact that the entire field unit has a polar orientation structure also means that a C-type field unit that includes a gap portion sandwiched between the first main surface 14 and the second main surface 24 is configured. That is, as shown in FIG. 4, the first main surface 14 that faces the gap portion, the first protrusion 12 and the second protrusion 22, and the second main portion on the opposite side from the first protrusion 12 and the second protrusion 22. Virtual field lines extend to the surface 24. Thus, by forming the magnetic field lines in an arc shape inside the field unit, the magnetic poles exposed from the magnetic circuit can be limited to the magnetic gap MG, and leakage of the magnetic field lines to the outside can be reduced, and the magnetic flux density obtained by the magnetic circuit Can be increased. On the other hand, the N pole and S pole adjacent to the gap portion are also connected by virtual lines of magnetic force inside the molded body. In addition, the lines of magnetic force are continuous at the part other than the gap.
(Divided structure)

  In addition, the field unit is made easier by being divided and configured rather than integrally formed. In particular, at the time of injection molding using a mold, it is not easy to create a strong mold magnet that can be arranged in a magnetic gap portion that is a closed space. Therefore, the magnetic gap is formed by joining the divided members together so that a desired magnetic pole appears on the first main surface 14 and the second main surface 24. Can be molded.

In the example of FIGS. 1 to 3, the first bonded magnet 10 and the second bonded magnet 20 are divided. The first bond magnet 10 includes a first flat portion 11 and a first protrusion 12, and the second bond magnet 20 includes a second flat portion 21 and a second protrusion 22. Further, the first flat portion 11 includes the first main surface 14, and the second flat portion 21 includes the second main surface 24. For this reason, a magnetic gap MG is formed between the first main surface 14 and the second main surface 24 by combining the first bond magnet 10 and the second bond magnet 20. In other words, since the magnetic unit MG is divided into the first bond magnet 10 and the second bond magnet 20 at the magnetic gap MG portion, the closed magnetic gap MG can be opened, so that each part is molded with a mold or the like. Easy to do.

In this example, the first bond magnet 10 and the second bond magnet 20 are members having the same shape. Thereby, a field unit can be constituted by combining parts molded with the same mold, and the manufacturing cost can be reduced and the manufacturing efficiency can be improved. In particular, the first main surface 14 and the second main surface 24 have a configuration in which only a pair of N and S poles are exposed, so that when the one is inverted, the N and S poles are It can be easily configured to face each other.

The first bond magnet and the second bond magnet are connected by fitting the protrusions. For this reason, these 1st bond magnets and 2nd bond magnets are provided with the fitting structure for receiving any one protrusion part. As a fitting structure, it can be set as a stepped step part or a recessed part.

In the example shown in FIG. 2 and the like, the first bonded magnet 10 has a protruding portion formed in a prismatic shape having substantially the same width as the first flat portion 11 and the second flat portion 21, and the side surface of the protruding portion is the first flat. It is formed in substantially the same plane as the end face of the portion 11. By doing in this way, a magnetic circuit is made continuous and the excess leakage magnetic flux of a magnetic circuit is reduced, As a result, a strong magnetic flux density can be exhibited.

Moreover, in the example of FIG. 2, the external shape of the 1st bond magnet 10 is comprised in step shape. That is, the first projecting portion 12 is projected from one end (left side in FIG. 2) of the first flat portion 11, while the other end is a first stepped portion 13 that is recessed in a stepped shape. The stepped portion is a portion for receiving the second protruding portion 22 of the second bonded magnet 20, and as shown in FIG. As shown, the side surfaces of the first bond magnet 10 and the second bond magnet 20 are in the same plane, and the joint portions are integrated. In other words, the tip end portion of the second protrusion 22 is integrated with the edge of the first flat portion 11 and partially forms part of the first flat portion 11. The shapes and dimensions of the second projecting portion 22 and the first stepped portion 13 are set so that the outer surfaces are flush with each other when they are joined.

Similarly, the first protruding portion 12 of the first bonded magnet 10 is also joined to the second stepped portion 23 of the second bonded magnet 20. In particular, the first bond magnet 10 and the second bond magnet 20 have the same shape and are joined in a posture rotated point-symmetrically, whereby the field unit 100 whose outer shape is a block shape can be configured. Thus, the 1st bonded magnet 10 and the 2nd bonded magnet 20 can be joined using the 1st protrusion part 12 and the 2nd level | step-difference part 23 and the 2nd protrusion part 22 and the 1st level | step-difference part 13 for positioning.

The first bond magnet 10 and the second bond magnet 20 may be combined with a fixing structure such as adhesion or screwing. However, the structure of the closed circuit described above is sufficient even when they are joined by magnetic force. We can show joining power.
(Modification)

In the above example, the first bond magnet and the second bond magnet are configured by members having the same shape. However, the present invention is not limited to this configuration, and it is needless to say that the first bond magnet and the second bond magnet can be configured in different shapes. That is, as shown in FIG. 4, any configuration can be used as long as it is a combination of shapes in which the magnetic gap MG is formed at the center. For example, in the field unit 200 according to Embodiment 2 shown in FIG. 5, the first bond magnet 10B is a flat plate, and a convex portion 15 is provided at the center, and the center of the second bond magnet 20B is a concave portion 25. To form. The first bond magnet 10B and the second bond magnet 20B can be joined by inserting the convex portion 15 into the concave portion 25. With this configuration, there is an advantage that positioning can be performed more accurately by the insertion structure of the convex portion 15 into the concave portion 25.

Further, in the field unit 300 according to Embodiment 3 shown in FIG. 6, the first bond magnet 10C is formed in a flat plate shape, the second bond magnet 20C is formed in a U shape, and these are combined to form a magnetic gap at the center. Can be configured. In this configuration, since the first bonded magnet 10C can be a flat plate, an advantage that the manufacturing can be simplified is obtained. On the other hand, since the positioning mechanism for joining the first bonded magnet 10C and the second bonded magnet 20C is not provided, alignment is difficult compared to other configurations.

In addition, in the field unit 400 according to the fourth embodiment shown in FIG. 7, the first bonded magnet 10D and the second bonded magnet 20D are formed in the same shape, and are formed in the respective U-shaped sections with a U-shaped cross section. By joining the protruding portions 16 and 26 to each other, a field unit 400 having a magnetic gap opened at the center is configured. In this configuration, as in the first embodiment, the same mold can be used, but positioning is not as easy as in the third embodiment.
(VCM for HDD)

  FIG. 8 shows an example in which an HDD VCM is configured by inserting an arm into the magnetic gap MG as an example of a swing type actuator. A flat movable coil 4 is disposed at one end of the arm 7 and a magnetic head 6 is disposed at the other end. The arm 7 is configured to be rotatable or swingable via a shaft 5 that is a fulcrum so that the movable coil 4 is positioned in the magnetic gap MG.

When a current is passed through the moving coil 4 of this VCM, a driving force around the shaft 5 acts on the moving coil 4 according to Fleming's left-hand rule, and the arm 7 is turned or swung to the other end of the arm 7. The provided magnetic head 6 can be positioned on a predetermined recording track on the magnetic disk. The swing direction is switched by appropriately reversing the direction of the energization current to the movable coil 4. Moreover, it can use as an actuator which can be used also for uses other than HDD by arrange | positioning another functional member instead of a magnetic head.
(Field unit manufacturing method)

The 1st bonded magnet and the 2nd bonded magnet which comprise the above field unit can be manufactured with an injection molding method. The injection molding method is a method in which a compound in which a thermoplastic resin and a magnetic material powder are mainly mixed is once melted and then injected into a mold for molding. Thereby, an integrated and pole-oriented field unit can be manufactured industrially. It is also possible to obtain a sintered body by degreasing and sintering the injection-molded molded body. However, in this case, since the thin part and the thick part are integrated, and the crystal has a directivity, many cracks are generated at the time of manufacture, and the dimensional accuracy is inferior. In addition, as a manufacturing method of the same material and an integrated bonded magnet, a method of mixing and charging magnet powder and an appropriate resin (for example, a thermosetting resin or a thermoplastic resin) into a mold, and press molding can be considered. In order to realize the above complex polar orientation structure, it is considered that the method of pressing with a mold is not suitable. The reason is that, in order to obtain a polar orientation structure, the direction of the particles needs to be freely changed in the mold, and in the case of press molding, the rotation of the particles is difficult.

  An anisotropic material is adopted as the magnetic material. An anisotropic material is a material from which a predetermined magnetic performance is obtained by anisotropy. Since the anisotropic material has magnetic anisotropy in each particle, the direction of the crystal is changed in the anisotropic direction, that is, in the direction of magnetism. On the other hand, the isotropic material has a simpler magnet manufacturing process, and the merit of obtaining a polar anisotropic structure by adjusting magnetization is well known without going through an anisotropic process. However, the BHmax of isotropic injection-molded permanent magnets industrially available at present is 9 to 10 MGOe. This level of BHmax could not provide an effective magnetic flux density for the gap. On the other hand, anisotropic injection molding materials are commercially available up to 18 MGOe, which is suitable for achieving the object of the present invention. Among them, the most suitable material is an SmFeN-based anisotropic material. Among the SmFeN particles, in the case of having a substantially spherical particle, there is an advantage that when the anisotropy is imparted, the particle freely rotates to obtain the desired orientation pattern.

The means for obtaining the polar orientation structure is achieved by appropriately applying an appropriate magnetic field from the outside of the mold during injection molding. An orientation permanent magnet may be disposed adjacent to the mold internal cavity, or a magnetic field may be applied by an energizing coil from outside the mold.
(Injection mold)

FIG. 9 shows a schematic structure of an example of an injection mold that constitutes the field unit of FIG. A permanent magnet 31 for performing orientation is charged in the mold 30. The compound injected from the gate 33 is filled in the cavity portion 34. Further, magnetic field lines are emitted from the N pole toward the S pole, and in FIG. 9, the magnetic field 35 generated by the permanent magnet 31 and generated in the cavity portion 34 is indicated by a dotted line. In the manufacture of the field unit using this mold, only half of the molded body constituting the field unit (one of the first bond magnet or the second bond magnet) can be manufactured by one injection molding. Since there is no limitation on the size of the orientation permanent magnet charged in the mold, a sufficient orientation magnetic field can be obtained. One field unit is configured by combining a first bonded magnet and a second bonded magnet, which are two molded bodies. Moreover, an adhesive agent etc. can be made unnecessary when combining compacts. Since the N pole and the S pole appear on the joint surface, they can be joined by magnetic force just by bringing them closer to each other, and a field unit having the correct polarity can be configured.

  Further, another example of the injection mold is shown in FIG. In this figure, a mold 40 has a cavity portion 44 so as to surround a permanent magnet 41 for orientation, and a molded body is obtained by injecting a compound made of a magnetic material and a resin. According to this mold, there is an advantage that two molded bodies, that is, one field unit can be formed by one molding. On the other hand, this method limits the size of the magnet for orientation. That is, it is not easy to secure a sufficient magnetic force as a permanent magnet having a size constituting the magnetic gap.

  An injection mold shown in FIG. 9 was prepared. An orientation permanent magnet 31 is embedded in the mold 30. The permanent magnet for orientation of the present embodiment uses four sintered NdFeB magnets according to the magnetic poles. As a compound, A12 material (product name) of SmFeN material manufactured by Nichia Chemical was used. The BHmax of this compound is 12.5 MGOe. The barrel temperature during injection molding is 240 ° C, and the nozzle temperature is 250 ° C. The mold temperature was set to 90 ° C. Two identical molded bodies were made and combined into one field unit. The dimensions of the field unit were a width of 57 mm, a height of 9.7 mm, a depth of 18 mm, a gap width of 37 mm, and a gap thickness of 1.4 mm. The magnetic flux density of the magnetic gap MG was a maximum of 4500 gauss. As described above, a magnetic flux density that can be sufficiently used as a field unit for VCM was obtained.

Comparative Example 1

  The protruding portion of the molded body obtained in Example 1 was cut into a flat plate having a thickness of 4.15 mm. A field unit having exactly the same dimensions as the above-described field unit was obtained by sandwiching a permendule material having a thickness of 1.4 mm. In this case, the maximum magnetic flux density of the magnetic gap was 4000 gauss. The permendurous material is a soft magnetic material having the highest saturation magnetic flux density and permeability, and the highest performance that can be expected. By replacing the protrusion in Example 1 with another material, the magnetic flux density was lower than that in Example 1.

Comparative Example 2

  The protruding portion of the molded body obtained in Example 1 was cut into a flat plate having a thickness of 4.15 mm. A 1.4 mm-thick Teflon (registered trademark) material was sandwiched therebetween to obtain a field unit having exactly the same dimensions as the field unit. In this case, the magnetic flux density of the magnetic gap was a maximum of 3800 gauss. A Teflon (registered trademark) material was used as a representative non-magnetic material. By replacing the protrusion in Example 1 with another material, the magnetic flux density was lower than that in Example 1.

Comparative Example 3

  A molded body having the same shape as that of the example but not subjected to polar orientation was prepared. As shown in FIG. 14, the anisotropic direction was obtained by applying a magnetic field in the longitudinal direction of the cavity portion 54 using an external magnetic field coil 55 arranged outside the mold. In this case, since the magnetic pole does not appear correctly on the surface, it is necessary to magnetize so that a predetermined pole appears after molding. The magnetic air gap obtained in Comparative Example 3 had a magnetic flux density of 2800 gauss.

Comparative Example 4

  Although the shape is exactly the same as in the examples, isotropic NdFeB was used as the magnetic material. Molding was performed by injection molding in the same manner as in the examples. BHmax as a material is 9 MGOe. In this case, the magnetic flux density of the magnetic gap was 2500 gauss.

Comparative Example 5

  A field unit actually used in an HDD as shown in FIG. 11 was prepared. The magnet used was sintered NdFeB and BHmax was 45 MGOe. The width of the unit was 36.2 mm, the height was 6.1 mm, the depth was 23.5 mm, and the gap thickness was 1.5 mm. The magnetic gap had a magnetic flux density of 5000 gauss. However, since a large number of members such as a column and a yoke plate are used, the assembly is not easier than the embodiment.

As described above, according to the present invention, it was confirmed that a molded body such as the first bond magnet and the second bond magnet constituting the field unit can be formed by injection, and a field unit having a sufficient magnetic force can be realized.

  The present invention can be suitably used as a VCM for a hard disk.

DESCRIPTION OF SYMBOLS 100, 200, 300, 400 ... Field unit 4 ... Moving coil 5 ... Shaft 6 ... Magnetic head 7 ... Arm 10, 10B, 10C, 10D ... First bonded magnet 11 ... First flat part 12, 16 ... First protrusion Part 13 ... First step part 14 ... First main surface 15 ... Convex parts 20, 20B, 20C, 20D ... Second bond magnet 21 ... Second flat part 22, 26 ... Second protrusion part 23 ... Second step part 24 ... second main surface 25 ... concave portions 30, 40, 50 ... molds 31, 41 ... permanent magnet 33 ... gates 34, 44, 54 ... cavity part 35 ... magnetic field 55 ... external magnetic field coil 111 ... permanent magnet thin plate 112 ... Yoke plate 113 ... post 114 ... coil 115 ... pivot 116 ... magnetic head 117 ... arm MG ... magnetic gap

Claims (10)

A first bonded magnet in which a compound made of a magnetic material and a resin is formed into a substantially plate shape ;
Wherein arranged in the first bond magnet and facing attitude, a second bonded magnet compound formed of a magnetic material and a resin is molded into a substantially plate shape,
A field unit comprising:
The first bond magnet and the second bonded magnet has a flat portion in which a plurality of magnetic poles having polar anisotropy formed respectively,
And at least one of said 1st bond magnet and said 2nd bond magnet has a projection part for projecting from a part of said flat part, and connecting with the other bond magnet,
The protrusion has a magnetic pole,
It said first bond magnet and the second bonded magnet, the magnetic gap between the second flat portion of the a first flat portion of the first bond magnet second bond magnet is formed, and different magnetic poles are A field unit characterized by being connected to face each other. The field unit according to claim 1,
A field unit, wherein the first bond magnet, the second bond magnet, and the protrusion have a substantially arc-shaped magnetic field line formed therein. The field unit according to claim 1 or 2,
The field unit, wherein the first bond magnet and the second bond magnet are formed in a substantially point-symmetric shape with respect to the center of the magnetic gap. The field unit according to any one of claims 1 to 3,
The first bond magnet or the second bond magnet has a fitting structure in which the protrusion is fitted. The field unit according to claim 4,
2. The field unit according to claim 1, wherein the fitting structure is formed in a recessed portion or a stepped portion. The field unit according to any one of claims 1 to 5,
The protrusion is formed in a prismatic shape having substantially the same width as the width of the first bond magnet or the second bond magnet,
The field unit, wherein a side surface of the projecting portion is formed to be substantially flush with a side surface of the first bond magnet or the second bond magnet. The field unit according to any one of claims 1 to 6,
The field unit, wherein the first bond magnet and the second bond magnet are formed into a single molded body. The field unit according to any one of claims 1 to 3,
The magnetic unit is an anisotropic SmFeN-based magnetic material. Constituting a field unit according to any one of 請 Motomeko 1 8, first the bonded magnet or the second bond magnet. A method of manufacturing a field unit according to any one of 請 Motomeko 1 8,
A step of arranging an orientation magnet for orienting the magnetic material constituting the flat portion and the protrusion in a mold for molding the first bond magnet and the second bond magnet;
Injecting a compound composed of a magnetic material and a resin into the mold;
Forming the first bonded magnet and the second bonded magnet;
Connecting the first bond magnet and the second bond magnet by their magnetic force to form a magnetic gap;
The manufacturing method of the field unit characterized by including.

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