JP2011109004A - Method of manufacturing magnetic anisotropic magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a magnetic anisotropic magnet in which the magnetic anisotropic magnet having orientation of a more superior easy magnetization direction. <P>SOLUTION: When the magnetic anisotropic magnet is manufactured which has an easy magnetization direction of magnet powder oriented at one point on a curved surface of a magnet surface to a direction of a straight line perpendicular to a tangential plane at the point, the magnetic powder is molded first in a magnetic field to form a flat plate molding having the easy magnetization direction of the magnet powder oriented to the direction of the straight line perpendicular to a molding plane comprising mutually parallel planes. Then planes of the flat plate molding are molded by a bending die to form a magnet molding. Lastly, the magnet molding is magnetized to manufacture the magnetic anisotropic magnet. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a magnetic anisotropic magnet, and more specifically, an easy magnetization direction is oriented at an arbitrary point on the curved surface of the magnet surface in a direction perpendicular to the tangential plane at that point. The present invention relates to a method for producing a magnetic anisotropic magnet suitable for use in a motor or the like.

  There are anisotropic sintered magnets as magnetic anisotropic magnets, and anisotropic sintered magnets include ferrite magnets such as Ba ferrite and Sr ferrite, and rare earths such as R-Co and R-Fe-B. Magnets (R is one or more selected from rare earth metals including Sc and Y) are widely used.

  These magnetic anisotropic magnets are obtained by aligning the easy magnetization directions of magnet powders composed of crystal grains carrying magnetism in a certain direction, so that the easy magnetization directions of the crystal grains are scattered. Compared to the isotropic magnet, the value of the residual magnetic flux density is large when magnetized in the easy magnetization direction, and therefore the maximum energy product can be increased. In addition, since it is a sintered magnet, the amount of nonmagnetic substance is small compared to a bonded magnet bonded with resin or the like, so that the value of residual magnetic flux density is increased and the maximum energy product can be increased. Therefore, anisotropic sintered magnets are widely used because they can obtain the largest maximum energy product among magnets using the same material.

  In order to align the easy magnetization direction of magnetic crystal grains in a certain direction, the magnetic anisotropic magnet pulverizes the material until each pulverized powder becomes a single crystal, and applies an external magnetic field to the pulverized powder. Thus, the easy axis of magnet powder is aligned in a direction parallel to the direction of the external magnetic field, and compression is performed by applying pressure. In the case of an anisotropic sintered magnet, the molded magnet powder is then sintered under predetermined conditions to produce an anisotropic sintered magnet. Depending on the material, heat treatment may be required after sintering.

  The magnetic field press used in the molding process includes a mold and a magnetic field generating means. Magnetic powder is supplied into the mold cavity, and an orientation magnetic field is applied by the magnetic field generator to align the easy magnetization direction of the magnet powder in one direction, and pressure is transmitted using a press to mold the magnetic powder in the cavity. To do. Molding is generally performed while applying a static magnetic field with an electromagnet or the like. In the direction of applying an orientation magnetic field to the magnet powder filled in the cavity, parallel magnetic field shaping in which a magnetic field is applied parallel to the direction of pressure application, and vertical magnetic field shaping in which a magnetic field is applied in a direction perpendicular to the direction of pressure application There is.

  Next, the shape of the magnet actually used for the motor and the motor will be described. As a motor for obtaining smooth torque without torque ripple, a surface magnet type motor in which a magnet having a tile-like cross section as shown in FIG. This motor uses a radially oriented magnet whose magnetization is directed in the thickness direction (radial direction) of the magnet as indicated by an arrow, and the stator winding has a rectangular wave that is relatively inexpensive. When current control is performed, a torque waveform with less pulsation can be obtained.

  As a method of manufacturing a radially oriented magnetic anisotropic magnet, a die that forms a cavity with a tile-like cross section, a punch that can be interlocked with the press to compress the inside of the cavity, and an outer arc and an inner arc of the cavity are aligned. And at least two magnetic cores provided in the die, and the magnetic core along the outer arc of the cavity has a shape extending from both ends of the outer arc and overhanging, and is used for magnetic powder molding for magnet powder There is one in which radial orientation can be obtained up to the end of the arc by using a mold (see, for example, Patent Document 1).

JP 2009-111418 A

  In this manufacturing method, the magnetic core along the outer arc of the cavity has a shape that extends from both ends of the outer arc and overhangs, so that the magnetic field in the tile-shaped cross section of the cavity portion that becomes weaker as it moves away from the center to both ends. The orientation is locally strengthened so that the magnetic field orientation in the tile-like cross section of the cavity portion can be made almost radial as a whole.

  However, the magnetic flux density of the entire facing surface of the magnetic core forming the outer arc and the inner arc of the cavity is not uniform, and the magnetic field between the facing surfaces is not uniform, so that the magnetic field in the roof section of the cavity is completely Only those that deviate from the radial orientation can be obtained.

  Of course, it may be possible to make the magnetic flux density of the entire opposing surface uniform by modifying the shape of the magnetic core by cut-and-try. It is difficult to do.

  Moreover, only the thing with limited magnetic anisotropy can be made with the manufacturing method mentioned above. For this reason, a three-dimensional magnet can only be produced by cutting a block having a certain direction of magnetic anisotropy, which is very expensive.

  Therefore, in view of the above-described conventional situation, the present invention provides a method for manufacturing a magnetic anisotropic magnet that can easily manufacture a three-dimensional magnetic anisotropic magnet having better orientation in the easy magnetization direction. The issue is to provide.

  Another object of the present invention is to provide a method for producing a magnetic anisotropic magnet capable of producing a complicated three-dimensional magnetic anisotropic magnet having orientation in the easy magnetization direction at low cost.

  The method of manufacturing a magnetic anisotropic magnet of the present invention, which has been made to solve the above problems, is such that the easy magnetization direction of the magnet powder is at one point on the curved surface of the magnet surface and in the direction of a straight line perpendicular to the tangential plane at that point. A method for producing an oriented magnetic anisotropy magnet, in which a magnet powder is molded in a parallel magnetic field, the easy magnetization direction of the magnet powder is oriented in the press direction, and the flat surfaces are formed by planes parallel to each other. Forming a three-dimensional magnet molded body by press-molding the flat surface of the flat plate molded body with a bending mold, and magnetizing the magnet molded body to produce a magnetic anisotropic magnet It is characterized by doing.

  Preferably, the molding of the magnet powder in the magnetic field is press molding in a horizontal magnetic field, and the molding process using the bending mold is a press molding process. The curved surface is a circular arc surface centered on one point or a part of a surface formed by moving a helix. When the magnet compact is magnetized, it is sintered in advance.

  According to the method for producing a magnetic anisotropic magnet of the present invention, when magnet powder is molded in a magnetic field, the easy magnetization direction of the magnet powder is oriented in the direction of a straight line perpendicular to the molding surface composed of planes parallel to each other. Therefore, in the molded flat plate molded body, the easy magnetization direction of the magnet powder is aligned and fixed perpendicular to the molding surface. Next, in the molding process of the flat molded body, the bending molds forming the magnet molded body bend the planes parallel to each other into a three-dimensional shape, and the flat molded bodies are parallel to each other by the molding process. Since the easy magnetization direction that was parallel between the flat surfaces is tilted in the bending direction, the easy magnetization direction in the resulting three-dimensional magnet molding is the normal direction of the surface curved surface of the magnet molding. That is, a three-dimensional magnet molded body in which the easy magnetization direction of the magnet powder is oriented at one point on the curved surface of the magnet surface in the direction of a straight line perpendicular to the tangent plane at that point is obtained.

  Therefore, it is possible to easily manufacture a three-dimensional magnetic anisotropy magnet having a better orientation in the easy magnetization direction than a conventional one in which a three-dimensional magnet molded body is formed in a magnetic field. A method of manufacturing a magnetic anisotropic magnet can be provided. Moreover, even if the three-dimensional shape is complicated, the magnetic anisotropic magnet can be manufactured at low cost.

It is a figure which shows simply the process of the manufacturing method of the magnetic anisotropic magnet of this invention. It is a fragmentary sectional view which shows an example of the magnetic field press molding machine used in the process 1 of FIG. 1 in a partial cross section. It is sectional drawing which shows an example of the metal mold | die used in the process 2 of FIG. It is a perspective view which shows a permanent magnet rotary machine. It is a longitudinal section showing a spiral type linear motor. It is a perspective view which shows a part of rotor of the motor of FIG. 5 and 6 show the detailed structure of the magnetic anisotropic magnet, wherein (a) is a plan view, (b) is a top view, (c) is a perspective view, (d) is a right side view, and (e). Is a bottom view, and (f) is a left side view. It is a figure which shows a magnetic anisotropic magnet and its magnetization direction.

  Embodiments of a method for producing a magnetic anisotropic magnet according to the present invention will be described below with reference to the drawings. FIG. 1 schematically shows steps of a method for manufacturing a magnetic anisotropic magnet according to an embodiment.

  The magnetic anisotropic magnet manufactured by the method of the embodiment is employed in a surface magnet type motor in which a magnet is attached to the surface of a rotor yoke, and is a point on a curved surface that is an arc surface of the magnet surface. The tile-shaped magnet has a cross section in which the easy magnetization direction of the magnet powder is oriented in the radial direction that is a straight line perpendicular to the tangential plane at that point.

  In manufacturing the magnetic anisotropic magnet, as shown in FIG. 1, first, in Step 1, the magnet powder 10 is press-molded in a parallel magnetic field, whereby the easy magnetization direction of the magnet powder is oriented in the press direction. Then, the flat plate molded body 20 is formed, the press surfaces of which are parallel to each other. Thereafter, in step 2, the flat surface of the flat plate-shaped body 10 is press-molded by a bending mold, thereby forming a magnet-shaped body 30 having a tile-like cross section. The magnet molded body 30 is finally magnetized in the easy magnetization direction of the magnet powder oriented in the radial direction in the magnet molding pair 30 by a magnetizing device (not shown) to produce a magnetic anisotropic magnet.

  How to make the magnet powder 10 when the magnetic anisotropic magnet is a rare earth magnet will be described below. First, a high-purity rare earth oxide is separated and purified from a rare earth ore and reduced in a molten salt electrolytic furnace to produce a rare earth metal. Next, a raw material obtained by weighing iron, cobalt, and other additive elements in addition to the rare earth metal is inserted into the crucible, and the raw material is melted by applying a high frequency to the crucible set in the vacuum melting furnace. After high temperature and homogeneous alloying, the molten metal is poured into a mold to produce an ingot. The ingot is pulverized through several steps, and finally becomes a fine powder having an average particle size of several microns. Each pulverization step is protected in an atmosphere of nitrogen or argon to prevent oxidation of fine powder.

  In press molding of the magnetic powder 10 in a parallel magnetic field, compression molding is performed while a magnetic field is applied in a direction parallel to the compression direction. For example, a magnetic field press molding machine 40 as shown in FIG. 2 is used. The magnet powder 10 is filled in the cavity 42 formed by the die 41 of the press molding machine, and the magnetic field generated by the magnetic field generating coil 43 through the die 41 made of a nonmagnetic material that passes the magnetic field is applied to the magnet powder 10 in the cavity 42. Added. The magnetic field moves so that each particle of the magnet powder 10 in the cavity 42 is aligned in the same direction as the magnetic field of the press molding machine 40 and the respective easy magnetization directions. In the press-molded flat plate molded body 20, the magnetization easy direction of the magnet powder 10 is aligned and fixed parallel to the press direction.

  The flat plate molded body 20 formed by press-molding the magnet powder 10 in a parallel magnetic field is formed of planes whose press surfaces are parallel to each other, and forms opposing walls of the cavity 42 that molds the plane parallel to the flat plate molded body 20. The opposing surfaces of the mold 41 are also parallel to each other. Therefore, the magnetic field generated by the magnetic field generating coil 43 uniformly forms a magnetic field between the opposing walls of the cavity 42 that forms the planes parallel to each other of the flat plate molded body 20 through the mold 42. As a result, the easy magnetization direction of the magnet powder 10 is oriented in the pressing direction, and the orientation is uniform between the planes of the flat plate body 20 parallel to each other.

  In the step 2 described above, the bending mold for forming the magnet molded body having a tile-like cross section by the press molding of the flat molded body 20 maintains the plate thickness of the flat molded body 20 and is parallel to the flat molded body 20. This is a mold 50 including a pair of split molds 51 and 52 for bending a plane into a three-dimensional shape having a tile-like cross section as shown in FIG. By the press forming process using the mold 50, the easy magnetization direction that is parallel between the parallel planes of the flat plate molded body 20 is tilted in the bending direction. In the press forming process using the mold 50, in order to bend the sheet into a three-dimensional shape while maintaining the plate thickness, it is necessary to perform a process in which the large-diameter arc side expands and the small-diameter arc side contracts.

  As a result, the easy magnetization direction in the magnet-shaped body 30 having a tile-shaped cross section is the normal direction of the curved surface of the magnet-shaped body 30. That is, a three-dimensional magnet molded body 30 is obtained in which the easy magnetization direction of the magnet powder is oriented at a point on the curved surface of the magnet surface in a direction perpendicular to the tangential plane at that point.

  When the magnetic anisotropic magnet to be manufactured is a sintered magnet, the magnet molded body 30 is then sintered and heat-treated in a vacuum sintering furnace to be a sintered magnet (not shown), and finally In particular, it is magnetized by a magnetizing device. The magnetic anisotropic magnet obtained by magnetization is magnetized in the easy magnetization direction of the magnet powder oriented in the magnet compact 30.

  In the case where the magnetic anisotropic magnet is a sintered magnet, the magnet compact 30 has a true density of about 50% in which only the volume occupied by the magnet powder 10 is a volume for density calculation. As it progresses, it hardens to a true density of 100%. At this time, each dimension of the sintered magnet is 70 to 80% of the magnet compact 30 and the volume is reduced to about half. Therefore, in the molding of the magnet molded body 30, molding is performed in consideration of the shrinkage due to the sintering and heat treatment.

  A surface magnet type motor to which a magnetic anisotropic magnet is applied is used for a control motor such as a servo motor because of its high efficiency and good controllability. For example, a radial air gap type permanent magnet rotating machine 60 as shown in FIG. 4 is used for the AC servo motor. The permanent magnet rotating machine 60 shown in FIG. 4 includes a rotor 64 in which a so-called C-shaped magnetic anisotropic magnet 63 having a tile-like cross section is attached to the surface of a rotor yoke 62, and a gap (gap) 65. A stator yoke having a plurality of slots arranged therebetween and a stator 68 including a coil 67 wound around a tooth 66. In the case of the permanent magnet rotating machine shown in FIG. 4, the number of poles of the magnetic anisotropic magnet is 6 and the number of teeth is 9, and the arrow in the magnetic anisotropic magnet indicates the direction of magnetization of the magnetic anisotropic magnet. ing. In addition, the coil is wound around the teeth with concentrated winding, and a U-phase V-phase W-phase three-phase Y-connection is made. U + of the coil means that the winding direction of the U-phase coil is in front, and U- means that the winding direction of the U-phase coil is in the back.

  Other motors to which magnetic anisotropy magnets are applied include a screw mechanism that converts rotational motion into translational motion and a power mechanism that uses electromagnetic force to achieve compact, light weight, high accuracy, and high thrust. For example, a spiral linear motor described in Japanese Patent No. 3712073 is conceivable.

  As shown in a longitudinal section in FIG. 5, this spiral linear motor includes a rotor 74 having a center shaft 72 and a spiral portion 73 protruding radially on the outer periphery of the center shaft, and the same pitch as the rotor 74. And a stator 75 having a hollow magnetic pole having a helical groove, the central axis 72 of the rotor 74 is within the hollow magnetic pole of the stator 75, and the axial side surface of the helical portion 73 of the rotor 74 and the stator. The spiral groove of 75 is opposed to the axial side surface so that it can rotate freely in the spiral groove of the hollow magnetic pole. Move. The rotor 74 includes a magnetic anisotropic magnet 76 on the spiral side surface of the spiral portion 73. The stator 75 is provided with slots on both sides of the spiral shape of the hollow magnetic pole, and two-phase windings that are shifted in phase by 90 degrees are wound around the slots in the axial direction. In the figure, reference numeral 77 denotes a linear rotary bearing that supports the rotary shaft 72 of the rotor 74, and 78 denotes a motor frame to which the stator 75 is attached.

  In the spiral type linear motor having this configuration, the spiral portion 73 of the rotor 74 formed in the same spiral shape is spirally rotated in the groove of the stator 75 formed in the spiral shape, similar to the screw mechanism. Directly moves in the axial direction. The torque and thrust of the spiral type linear motor are generated by electromagnetic force that intersects between the spiral side surfaces of the opposing magnetic poles of the rotor 74 and the stator 75, and can be controlled independently.

  In the spiral linear motor described above, the shape of the side surface in the axial direction of the spiral portion 73 is a very complicated three-dimensional shape as shown in FIG. That is, the axial side surface of the spiral portion 73 is a kind of a three-dimensional curve, and is formed by a surface formed by moving a helix, which is a curve that rises in a direction having a vertical component to the rotation surface while rotating. For this reason, a large number of magnetic anisotropic magnets 76 divided and attached to the axial side surface at predetermined angles also have a very complicated three-dimensional shape as shown in FIG. And has a complicated three-dimensional curved surface. 7A is a plan view of the magnetic anisotropic magnet 76 attached to the axial side surface of the spiral linear motor, FIG. 7B is a top view, FIG. 7C is a perspective view, and FIG. (E) is a bottom view and (f) is a left side view.

  However, when manufactured by the same manufacturing method as the magnetic anisotropic magnet having a cross-sectional tile shape, the magnetic anisotropic magnet 76 is one point on the curved surface of the three-dimensional shape of the surface and perpendicular to the tangential plane at that point. It is possible to inexpensively produce a magnet powder in which the direction of easy magnetization of the magnet powder is oriented.

  In the above-described embodiment, the dry method in which the magnet powder 10 is formed by pressing the magnet powder 10 in a horizontal magnetic field to form the compact has been described. However, the slurry containing the magnet powder is dehydrated. However, a wet method of compression molding may be employed. In addition to this, a magnet molded body (green body) is formed from a material obtained by kneading magnet powder and a resin binder through a flat molded body (green body), and only the binder component is removed from the magnet molded body (green body). Alternatively, a magnetic anisotropic sintered magnet may be manufactured by sintering the remaining magnet powder component. In this case, the resin-based binder is useful for improving the moldability when the flat molded body is press-molded into a three-dimensional magnet molded body.

  The method for producing a magnetic anisotropic magnet of the present invention can also be applied to the production of a bonded magnet obtained by kneading a thermoplastic resin and magnet powder that can ensure fluidity during injection molding. In this case, instead of press forming in a horizontal magnetic field, the flat plate molded body is formed by injection molding in a magnetic field in a linear direction perpendicular to the molding surface composed of planes parallel to each other in the magnet powder easy magnetization direction. Is done. When the flat molded body is molded into a three-dimensional magnet molded body, if the resin binder is softened to the extent that it does not flow, the molding process is performed without disturbing the orientation of the magnet powder. In this case, the resin-based binder helps to improve the moldability when the flat plate molded body is molded into a magnet molded body.

10 Magnet powder 20 Flat plate molded body 30 Magnet molded body

Claims (5)

A method for producing a magnetic anisotropic magnet in which the easy magnetization direction of magnet powder is oriented at a point on the curved surface of the magnet surface in a direction perpendicular to the tangential plane at that point,
Forming the magnetic powder in a magnetic field to form a flat molded body in which the easy magnetization directions of the magnetic powder are oriented in the direction of a straight line perpendicular to the molding surface composed of planes parallel to each other,
Forming the flat surface of the flat plate molded body by a bending mold to form a three-dimensional magnet molded body;
A method for producing a magnetic anisotropic magnet, comprising magnetizing the magnet compact to produce a magnetic anisotropic magnet. The magnetic anisotropic magnet according to claim 1, wherein the molding of the magnet powder in the magnetic field is press molding in a horizontal magnetic field, and the molding by the bending molding die is press molding. Manufacturing method. The method of manufacturing a magnetic anisotropic magnet according to claim 1, wherein the curved surface is an arc surface centered on one point. The method of manufacturing a magnetic anisotropic magnet according to claim 1, wherein the curved surface is a part of a surface formed by moving a helix. The method for producing a magnetic anisotropic magnet according to claim 1, wherein the magnet compact is sintered in advance when magnetized.

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