JP2005260189A - Circular rare earth permanent magnet and method of forming the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circular rare earth permanent magnet in the shape which can be formed under high pressure using magnetic powder of SmCo system, NdFeB system, and the like to obtain high magnetic property, and the method of forming the same. <P>SOLUTION: In a circular rare earth permanent magnet 1 having an inner periphery surface 3 and an outer periphery surface 2, the outer periphery surface 2 has a circular surface 2a on the center portion and a surface 2b which is positioned on both sides of the circular surface 2a and is different from the circular surface 2a in curvature. The surface 2b and the end portion of the outer periphery surface are positioned on the circumference extended with curvature radius of the circular surface 2a on the center portion or the inner side of this circumference. Further, the end portion of the outer periphery surface 2 is a flat surface 2c in parallel in outline with a tangent of the midpoint of the outer periphery. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an arc-shaped rare earth permanent magnet used for a motor or an actuator, and particularly used when a small size and a high output are required, and a molding method thereof.

  Conventionally, as a magnet used for a small motor or the like, there are many resin-bonded permanent magnets obtained by mixing a magnetic powder (magnet powder) made of ferrite or rare earth and a resin. When such a resin-bonded permanent magnet is used for a motor or the like, a mixture of magnetic powder and resin is formed into an arc shape and then heat-treated, and in some cases, a surface-treated one is used as a stator (stator). Adhere to the inside of a case such as a motor using an adhesive. The molding used here is compression molding, injection molding, extrusion molding or the like, and a molding method is selected according to the purpose.

  As motors are further reduced in size and performance, arc-shaped permanent magnets used are required to be thinner. In particular, compression molding is preferred for improving the properties of the resin-bonded magnet, but when the thickness is 1.5 mm or less, compression molding becomes very difficult.

  When the arc-shaped resin-bonded permanent magnet molded body is sufficiently thick, as shown in FIG. 5, there is a method (vertical pressing) in which compression molding is performed in a direction perpendicular to the surface having an arc-shaped cross section. Used. However, in the molding method of FIG. 5, when the thickness is reduced, the mixture of magnetic powder and resin cannot be filled in the molding die.

  Therefore, as shown in FIG. 6, the following Patent Document 1 proposes forming in a direction perpendicular to the compression molding direction of FIG. 5 (that is, the thickness direction).

Japanese Patent Laid-Open No. 9-327813

In this case, problems such as cracks and cracks occur as mentioned in Patent Document 1, and in order to solve this problem, in Patent Document 1, the amount of elastic recovery in the compression direction of the powder compact is suppressed to 30% or less. Thus, a powder compression molding method of a magnetic material having a cross-sectional arc shape for removing the load is presented. Moreover, as a metal mold | die in the case of performing such compression molding, as disclosed in the following Patent Document 2, it is possible to form a thin arc by defining the punch bending force and the average radius of curvature. There is what I did.

JP 2002-80904 A

As described above, as the motor and the like are miniaturized, the thickness of the permanent magnet is reduced and higher characteristics are required. In order to cope with this, in the case of a resin-bonded permanent magnet made of a resin and a magnetic powder, a method using high-quality powder as the magnetic powder and a method for improving the ratio of the magnetic powder in the whole are taken. As the high-performance magnetic powder, SmCo-based or NdFeB-based magnetic powder is used in place of the conventionally used ferrite powder. Further, in order to increase the ratio of the magnetic powder to the whole, compression molding is performed at a very high pressure, specifically, 784 to 980 MPa (8 to 10 tf / cm ² ) or more. In this case, it is difficult to cope with the method disclosed in Patent Document 2 described above.

  Therefore, in view of the above points, the present invention has an object to provide an arc-shaped rare earth permanent magnet having a shape that can be molded under high pressure and a molding method thereof in order to obtain high magnetic characteristics.

  Other objects and novel features of the present invention will be clarified in embodiments described later.

In order to achieve the above object, the invention of claim 1 of the present application provides an arc-shaped rare earth permanent magnet having an inner peripheral surface and an outer peripheral surface.
The outer peripheral surface has a circular arc surface in the central portion and surfaces having different curvatures from the circular arc surfaces located on both sides thereof, and the outer peripheral surface end portion is a circle extended by the radius of curvature of the circular arc surface in the central portion. It is characterized by being located on the circumference or inside the circumference.

  An arc-shaped rare earth permanent magnet according to a second aspect of the present invention is characterized in that, in the first aspect, the end of the outer peripheral surface is a plane (2c) substantially parallel to a tangent to the intermediate point of the outer peripheral surface. Yes.

  An arc-shaped rare earth permanent magnet according to a third aspect of the present invention is the arc-shaped rare earth permanent magnet according to the first or second aspect, wherein the inner peripheral surface has an arc surface of one curvature, and the inner peripheral surface end is the inner peripheral surface intermediate point. It is characterized by being a plane substantially parallel to the tangent line.

  An arc-shaped rare earth permanent magnet according to a fourth aspect of the present invention is characterized in that, in the first, second or third aspect, the thickness between the inner peripheral surface and the outer peripheral surface is 1.5 mm or less.

  The arc-shaped rare earth permanent magnet according to the invention of claim 5 is characterized in that, in claim 1, 2, 3 or 4, the length is larger than the width in the circumferential direction.

In the method of forming an arc-shaped rare earth permanent magnet according to the invention of claim 6 of the present application, the concave end surface has a circular arc surface at the center and surfaces having different curvatures from the circular arc surfaces located on both sides thereof. The concave end is a first punch located on or inside the circumference extended by the radius of curvature of the arc surface of the central portion,
A rare-earth magnet powder is compression-molded using a second punch having a circular arc surface with one curvature at the tip convex surface.

  The method for forming an arc-shaped rare earth permanent magnet according to the invention of claim 7 is the method according to claim 6, wherein the end of the tip convex surface of the second punch is a plane substantially parallel to the tangent to the midpoint of the tip convex surface. It is characterized by becoming.

The arc-shaped rare earth permanent magnet molding method according to the invention of claim 8 is characterized in that, in claim 6 or 7, the compression molding pressure is 784 MPa (8 tf / cm ² ) or more.

  According to the present invention, the outer peripheral surface of the arc-shaped rare earth permanent magnet has a central arc surface and surfaces having different curvatures from the arc surfaces located on both sides of the arc-shaped rare earth permanent magnet. Since the shape is located on the extension line of the radius of curvature of the arc surface of the portion or on the inner side of the extension line, compression molding can be performed with a high pressure, and the magnetic characteristics can be improved. In addition, it can be easily incorporated into a case such as a motor.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an arc-shaped rare earth permanent magnet and a molding method thereof will be described below with reference to the drawings as the best mode for carrying out the present invention.

  An embodiment of an arc-shaped rare earth permanent magnet and a molding method thereof according to the present invention will be described with reference to FIGS. First, the shape of the arc-shaped rare earth permanent magnet will be described with reference to FIGS. 1 and 2. The arc-shaped rare earth permanent magnet 1 has a thickness (thickness T) between the outer peripheral surface 2 and the inner peripheral surface 3 of 1.5 mm or less. 2 has a length L greater than the width W in the circumferential direction.

  Most of the outer peripheral surface 2 and the inner peripheral surface 3 including the central portion are an arc surface 2a and an arc surface 3a having a curvature along the shape of the motor or the like used. For example, when the radius of curvature R1 of the arc surface 3a is 3.0 mm, the radius of curvature R2 of the arc surface 2a is 3.6 mm, and the thickness T is 0.6 mm, the arc surfaces 2a and 3a are concentric arc surfaces. Moreover, the shape with circular arc surface which is not concentric like thickness T 0.8mm may be sufficient.

  The end of the inner peripheral surface 3 is a plane 3b that is substantially parallel to the tangent line of the inner peripheral surface intermediate point (in other words, a plane that is substantially perpendicular to the normal line of the inner peripheral surface intermediate point).

  On both sides of the arc surface 2a of the outer peripheral surface 2, there are located surfaces 2b (a plane or curved surface cut inward so that the wall thickness is thin) having a curvature different from that of the arc surface 2a, and are located at the end. The surface 2c is a plane that is substantially parallel to the tangent line of the outer peripheral surface intermediate point (in other words, a plane that is substantially perpendicular to the normal line of the outer peripheral surface intermediate point). However, since the case of a motor or the like to be incorporated is usually cylindrical as shown in FIG. 3, the surface 2b, the surface 2c, and the outer peripheral edge 2d cover most of the outer peripheral surface 2 as shown in FIG. It is set so as to be positioned on or inside the circumference P extended by the radius of curvature of the arc surface 2a that is formed (usually matching the radius of curvature of the case such as a motor). Further, as shown in FIG. 1, the angle α occupied by the arc surface 2a as viewed from the center point of the arc surface 2a at the center of the outer peripheral surface is preferably 60 ° or more, and more preferably 70 ° or more. In the illustrated example, the angle α is 76 °. When the angle α is less than 60 °, the magnetic force contributing to the motor may be reduced. In addition, the stability and adhesive strength at the time of bonding to the motor case are insufficient.

  A method of forming the arc-shaped rare earth permanent magnet having the above shape will be described with reference to FIG. As shown in this figure, the mold 10 includes a mortar 11, an upper punch 12, and a lower punch 13. The upper punch 12 is fitted to the mortar 11 from above, and the lower punch 13 is fitted to the mortar 11 from below. . The constituent members of the mold 10 are preferably a cemented carbide, an ultrafine particle cemented carbide, or the like from the viewpoint of hardness and wear.

  The lower punch 13 has a concave surface 20 at the center of the arcuate surface 20a and a surface 20b having a different curvature from the arcuate surface 20a located on both sides thereof (a flat surface cut inwardly so that the thickness of the molded body is reduced or The end of the concave end surface 20 is a flat surface 20c substantially parallel to the tangent to the midpoint of the concave end surface. Further, the surfaces 20b and 20c are configured to be located on the circumference extended by the radius of curvature of the arcuate surface 20a at the center or on the inner side (upper side) of the circumference (the outer circumference surface 2 and the circumference P in FIG. 3). The same as the relationship).

  Further, the upper punch 12 has a convex surface 30 having a circular arc surface 30a having one curvature, and a flat surface 30b in which the end of the convex surface 30 of the upper punch 12 is substantially parallel to a tangent to the middle point of the convex surface of the distal end. It has become.

The arc-shaped rare earth permanent magnet body is molded by filling a molding space S composed of the mortar 11, the upper punch 12 and the lower punch 13 in the mold 10 with a mixture of resin and magnetic powder. The upper punch 12 and the lower punch 13 are compression-molded in the vertical direction in the direction of the arc surface. In a magnet body formed by mixing resin and magnetic powder and compression molding, the magnetic powder preferably occupies 95% or more (weight ratio) in order to obtain high magnetic properties. The magnetic powder is preferably SmCo-based or NdFeB-based rare earth magnetic powder, and the average particle size must be in the range of 10 to 100 μm and the maximum particle size in the range of 150 μm or less. When the particle diameter is larger than this, it is difficult to form a thin permanent magnet body. On the other hand, the resin used is a thermosetting resin, for example, an epoxy resin or a phenol resin is preferable. The compression molding pressure is set to 784 MPa (8 tf / cm ² ) or more, preferably 980 MPa (10 tf / cm ² ) or more, so that the ratio of the magnetic powder in the resin-bonded permanent magnet is increased.

  When molding the magnet body shape, when filling the mold 10 with a mixture of resin and magnetic powder, filling is performed along the longitudinal direction (L direction in FIG. 2). A permanent magnet filled in a direction perpendicular to the longitudinal direction is likely to have density variations in the motor rotation direction when incorporated in a motor or the like. That is, the permanent magnet has a variation in magnetic characteristics in the rotation direction, causing a problem in motor characteristics. Further, when the mold 10 is filled with the above mixture and is taken out from the mold 10 after compression molding, it is easier to take out in the longitudinal direction because the shape of the lower punch 13 is a circular arc surface, which is suitable for continuous molding.

  In general, after compression molding of a resin-bonded permanent magnet body, a resin heat curing process is performed, and a surface treatment for rust prevention is performed, followed by a magnetization process.

  According to this embodiment, the following effects can be obtained.

(1) In an arc-shaped resin-bonded rare earth permanent magnet having an outer peripheral surface 2 and an inner peripheral surface 3, the outer peripheral surface 2 has different curvatures from the central arc surface 2a and the arc surfaces 2a located on both sides thereof. And the end of the outer peripheral surface is positioned on or inside the circumference P of FIG. 3 extended by the radius of curvature of the arcuate surface 2a at the center. Since the surface 2c located at the end of the outer peripheral surface 2 is a plane substantially parallel to the tangent to the intermediate point of the outer peripheral surface, the lower punch 13 has a sharp angle. (The surface 20c substantially perpendicular to the compression direction is formed at the end of the lower punch tip surface).

(2) Since the inner peripheral surface 3 has a circular arc surface 3a having one curvature and the inner peripheral surface end 3b is a plane substantially parallel to the tangent to the intermediate point of the inner peripheral surface, the upper punch 12 is sharp. A portion having an angle disappears (a surface substantially perpendicular to the compression direction is formed at the end of the top end surface of the upper punch).

(3) From the above (1) and (2), the upper and lower punches 12 and 13 have no sharp angled portions (the surfaces 30b and 20c that are substantially perpendicular to the compression direction are formed at the ends of the upper and lower punch tips. Therefore, compression molding at a high pressure (784 MPa (8 tf / cm ² ) or more, preferably 980 MPa (10 tf / cm ² ) or more) is possible. Thus, an arc-shaped resin-bonded permanent magnet having a wall thickness T of 1.5 mm or less and a length L (longitudinal direction) larger than the circumferential width W as shown in FIG. 2 can be compression molded.

  When the thickness T of the magnet body to be molded is 1.5 mm or less, when the length L is larger than the width W, the conventional compression molding method shown in FIG. 5 fills the molding die with a mixture of magnetic powder and resin. In addition, since the punch stroke is long, problems such as heat generation also occur, and the obtained magnet body has a very large density variation. When the length L is equal to or less than the width W, it can be dealt with by the method of the prior art.

  The molding method according to the present invention will be specifically described below with reference to examples.

Magnetic powder: NdFeB magnet powder, average particle size 50 μm
Resin: Epoxy resin Mixing ratio: Magnet powder: Resin = 97: 3 (% by weight)
Molding size: Thickness = 1.0mm, width 5.0mm, height (length) 20mm
Molding pressure: 10 t / cm ²
Number of moldings: 10 (the following values are average values of 10)

Thickness dimension Width dimension Density
Molding method of this example 1.02 mm 5.01 mm 5.82
Vertical push (conventional method) 1.02mm 4.83mm Drum shape with non-uniform density
Measurement impossible

  Although the embodiments and examples of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited thereto and various modifications and changes can be made within the scope of the claims. Will

1 is a front view showing an outer shape of an arc-shaped rare earth permanent magnet according to an embodiment of the present invention. It is the same top view. It is a front view explaining the shape of the outer peripheral surface of the said arc-shaped rare earth permanent magnet. FIG. 3 is a partial cross-sectional view of a mold for explaining a method of forming an arc-shaped rare earth permanent magnet according to an embodiment of the present invention. It is explanatory drawing which shows the conventional shaping | molding method (vertical pressing). It is explanatory drawing which shows another shaping | molding method pressurized from the direction orthogonal to FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rare earth permanent magnet 2 Outer peripheral surface 2a, 3a, 20a, 30a Circular arc surface 2b, 2c, 20b Surface 3b, 20c, 30b Plane 2d Edge 3 Inner peripheral surface 10 Mold 11 Die 12 Upper punch 13 Lower punch 20 Tip concave surface L Length P Circumference S Molding space T Thickness W Width

Claims (8)

In an arc-shaped rare earth permanent magnet having an inner peripheral surface and an outer peripheral surface,
The outer peripheral surface has a circular arc surface (2a) at the center and a surface (2b) having a different curvature from the circular arc surface (2a) located on both sides of the circular arc surface (2a). An arc-shaped rare earth permanent magnet having an end located on a circumference (P) extended by a radius of curvature of the arcuate surface (2a) at the center or on the inside of the circumference.   The arc-shaped rare earth permanent magnet according to claim 1, wherein an end of the outer peripheral surface is a flat surface (2c) substantially parallel to a tangent to the intermediate point of the outer peripheral surface.   The inner peripheral surface has an arc surface (3a) having one curvature, and an end portion of the inner peripheral surface is a plane (3b) substantially parallel to a tangent to the intermediate point of the inner peripheral surface. The arc-shaped rare earth permanent magnet described.   The arc-shaped rare earth permanent magnet according to claim 1, 2 or 3, wherein a thickness (T) between the inner peripheral surface and the outer peripheral surface is 1.5 mm or less.   The arc-shaped rare earth permanent magnet according to claim 1, 2, 3, or 4, wherein the length (L) is larger than the width (W) in the circumferential direction. The tip concave surface (20) has a circular arc surface (20a) in the central portion and surfaces (20b) having different curvatures from the circular arc surfaces located on both sides thereof, and the tip concave surface end portion is an arc of the central portion. A first punch located on or inside the circumference (P) extended by the radius of curvature of the surface;
A method of forming an arc-shaped rare earth permanent magnet, comprising compression-molding rare earth magnet powder using a second punch having an arcuate surface (30a) having a curved surface (30a) having a tip convex surface (30).   The method of forming an arc-shaped rare earth permanent magnet according to claim 6, wherein an end of the convex surface (30) of the second punch is a flat surface (30b) substantially parallel to a tangent to the intermediate point of the convex surface.   The method for forming an arc-shaped rare earth permanent magnet according to claim 6 or 7, wherein the compression molding pressure is 784 MPa or more.

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