JP6322911B2 - Method for producing non-cylindrical permanent magnet - Google Patents

Description

The present invention relates to a method for producing a plurality of non-cylindrical permanent magnets through extrusion.

  Rare earth element-iron group metal-boron permanent magnets with rectangular, arc-shaped, saddle-shaped, or crescent-shaped cross-sections that have been provided with magnetic anisotropy by hot (warm) plastic working are industrially And is used in the consumer sector. This permanent magnet is manufactured as follows, for example.

  A raw material containing a rare earth, an iron group metal and boron is melted, and the obtained melt of the magnet alloy is jetted onto a rotating roll such as copper to produce a flake-shaped ultra-quenched ribbon composed of nano-level crystal grains. The magnet alloy powder obtained by this ultra-quenching method is pulverized to a required particle size, and then cold pressed to obtain a green compact. Then, the green compact is hot or warm pressed to increase the density, and further subjected to hot or warm plastic processing to obtain a desired shape, thereby giving magnetic anisotropy. As a plastic working method for imparting this magnetic anisotropy, an extrusion process excellent in terms of material yield and yield rate is used. In addition, the magnet raw material after plastic working is put to practical use as a permanent magnet having magnetic anisotropy by being magnetized in a subsequent process.

  As a method for manufacturing a plurality of permanent magnets having radial anisotropy, for example, having an arc-shaped cross section by extrusion processing, for example, a manufacturing method disclosed in Patent Document 1 has been proposed. In this Patent Document 1, a mandrel with fins is inserted into a through-hole formed in a die, and a plurality of divisions matching the cross-sectional shape of the permanent magnet to be obtained are provided between the mandrel and an inner wall that defines the through-hole. With the holes defined, by pressing a columnar blank filled in the through-holes with a punch, the blanks are extruded from the respective divided holes and are made anisotropic in the radial direction (thickness direction). A magnet is manufactured.

JP 2001-15325 A

  In the manufacturing method disclosed in Patent Document 1, there is a possibility that the crystal orientation in the divided portions divided by the fins is not uniform when the columnar blank is extruded, and the magnetic properties of the divided portions in the obtained permanent magnet may be deteriorated. . In addition, since the blank is divided while being extruded, the stress at the divided portion becomes large, the divided portion of the obtained permanent magnet cracks, and the amount of grinding for removing the defective portion in the subsequent process increases. It is also pointed out that the yield is low.

That is, the present invention has been proposed in view of the above-mentioned problems inherent in the above-described conventional technology, and a non-cylindrical permanent magnet having excellent magnetic anisotropy has been proposed. It aims at providing the manufacturing method of the non-cylindrical permanent magnet which can be manufactured efficiently.

In order to overcome the above-mentioned problems and achieve the intended object, a method for manufacturing a non-cylindrical permanent magnet according to the invention of claim 1 comprises:
Prepare a pre-formed body pressed with magnet alloy containing rare earth, iron group metal and boron,
Said preform mandrel is loaded into the through hole of the inserted through extrusion die, to widen the center portion in the direction perpendicular to the extrusion direction of the preform causes scales the outline of the preform It performs extrusion molding the extruded tubular molded body with a pressing punch, a preform by extruding process, apart from the stress concentration portion extending in the extrusion direction in the circumferential direction form a plurality of,
By applying an external force to the obtained molded body in the radial direction, the molded body is divided at the stress concentration portion and divided into a plurality of permanent magnets ,
The gist of the extrusion processing is that the area reduction rate is 50 to 70%, and the processing rate in the expansion or reduction direction of the outer shape is 5 to 30% .

According to the first aspect of the present invention, since the plurality of permanent magnets are divided from the molded body formed by the extrusion process, the compression direction (crystal orientation direction) applied to the molded body at the time of the extrusion process is excellent throughout. A plurality of non-cylindrical permanent magnets having anisotropy and excellent magnetic characteristics can be produced without lowering the magnetic characteristics in the divided portions of the permanent magnets. Further, when extruding the preform, the inside and outside in the thickness direction orthogonal to the extrusion direction are deformed in the thickness direction to give distortion, so that the inside and outside in the thickness direction of the molded body are formed. Thus, a permanent magnet having excellent magnetic properties can be produced. Furthermore, since a large stress is not applied to the portion where the molded body is divided during the extrusion process, the split portion of the permanent magnet is not cracked, and the material yield can be improved. Furthermore, since the stress concentration portion for dividing the permanent magnet at the time of extrusion is formed, the manufacturing efficiency can be improved as compared with the case where the stress concentration portion is separately formed in the subsequent process.
In extrusion processing, the area reduction rate is 50 to 70% and the processing rate in the direction of enlargement or reduction of the outer shape is 5 to 30%, so it is easy to manufacture non-cylindrical permanent magnets with high magnetic properties. Can do.

The invention according to claim 2 is characterized in that the stress concentration portion is formed so that two circumferentially continuous surfaces form an angle on an inner surface or an outer surface of the molded body.
According to the invention which concerns on Claim 2 , the flatness of the partial cross section of a permanent magnet can improve, and it can make an external appearance favorable.

In the invention according to claim 3 , a protrusion projecting into a filling space defined between the inner surface of the through hole and the outer surface of the mandrel is provided on the inner surface of the through hole or the outer surface of the mandrel in the extrusion mold. The gist is that a groove as a stress concentration portion that is recessed in the thickness direction by the protrusion is formed on an inner surface or an outer surface of the molded body extruded from the filling space.
According to the invention which concerns on Claim 3 , the flatness of the partial cross section of a permanent magnet can be improved more.

The invention according to claim 4 is a molded body molded so that the radial thickness T _{1 of the} stress concentration portion is in the range of 15T ₀ <T ₁ <4 / 5T ₀ with respect to the maximum radial thickness T ₀ . The gist is that the stress concentration part is divided.
According to the invention which concerns on Claim 4 , the division | segmentation in a stress concentration part is easy, and it can suppress that orientation falls.

The gist of the invention according to claim 5 is that the molded body is clamped in the radial direction and divided at the stress concentration portion.
According to the invention which concerns on Claim 5 , a parting operation becomes easy.

According to the manufacturing method of the non-cylindrical permanent magnet according to the present invention may be manufactured with good non-cylindrical permanent magnet having excellent magnetic anisotropy efficiency.

It is the schematic which shows the extrusion die, press punch, and mandrel of the extrusion molding apparatus which manufactures the permanent magnet which concerns on an Example. In the extrusion molding apparatus of the form which manufactures the permanent cross-sectional magnet which concerns on Example 1, it is the schematic which looked at the state which inserted the mandrel in the through-hole of the extrusion die from the 1st through-hole side. It is explanatory drawing which shows the manufacturing process of the permanent magnet which concerns on Example 1, Comprising: (a) shows the molded object shape | molded with the extrusion molding apparatus, (b) shows the state which divides a molded object in a stress concentration part. (C) shows a state in which a plurality of permanent magnets are divided from the molded body. It is explanatory drawing which shows the manufacturing process of the cross-sectional crescent-shaped permanent magnet which concerns on Example 2, Comprising: (a) shows the state which isolate | separates the molded object shape | molded with the extrusion molding apparatus by a stress concentration part, (b) The state which the some permanent magnet was divided | segmented from the molded object is shown. It is explanatory drawing which shows the manufacturing process of the cross-sectional saddle-shaped permanent magnet which concerns on Example 3, Comprising: (a) shows the state which cut | disconnects the molded object shape | molded with the extrusion molding apparatus in a stress concentration part, (b) is The state which the some permanent magnet was divided | segmented from the molded object is shown. It is explanatory drawing which shows the extrusion die and mandrel of the extrusion molding apparatus which manufactures the cross-sectional arc-shaped permanent magnet which concerns on Example 4. FIG. It is explanatory drawing which shows the manufacturing process of the permanent magnet which concerns on Example 4, Comprising: (a) shows the state which divides | segments the molded object shape | molded with the extrusion molding apparatus in a stress concentration part, (b) is two or more from a molded object. This shows a state where the permanent magnet is divided. It is a figure which shows the measurement result of the magnetic orientation degree of the width direction in an experiment example, (a) shows the result of invention example 1, (b) shows the result of the comparative example 1. FIG. It is a table | surface which shows the measurement result of the magnetic orientation degree of the thickness direction in an experiment example.

Next, a method for manufacturing a non-cylindrical permanent magnet according to the present invention will be described below with reference to the accompanying drawings with a preferred embodiment.

  FIG. 1 shows a preferred embodiment of an extrusion molding apparatus used in a method for producing a permanent magnet. An extrusion molding apparatus 10 includes an extrusion mold 12 in which a through hole 11 is formed and one through hole 11. And a mandrel 16 having a smaller diameter than the through hole 11 inserted into the through hole 11 from the other opening. The through hole 11 of the extrusion die 12 is a first through hole 11a, a tapered hole 11b, and a second through hole 11c formed in series, and the first through hole 11a is larger than the second through hole 11c. The tapered hole 11b is formed so as to be narrowed with a uniform inclination from the first through hole 11a toward the second through hole 11c. Further, the mandrel 16 has an isomorphous portion 16a whose outer shape does not change in the extrusion direction, and is connected to one end of the isomorphous portion 16a so that the outer shape is narrowed with a uniform inclination as it is separated from the isomorphous portion 16a. And a taper portion 16b that changes. The mandrel 16 inserted into the through hole 11 is positioned so that the isomorphous portion 16a is located in the second through hole 11c and the tapered portion 16b is located in the tapered hole 11b. And between the inner surface (the inner wall of the extrusion die 12 that defines the second through hole 11 c) of the second through hole 11 c and the outer surface of the isomorphic portion 16 a in the mandrel 16 with the mandrel 16 inserted into the through hole 11. In addition, a filling space 20 communicating with the entire circumference of the mandrel 16 is defined. The filling space 20 is defined in a cylindrical shape in which a plurality of molding spaces 20a substantially matching the cross-sectional shape orthogonal to the extrusion direction of the permanent magnets 18, 32, 34, and 36 to be manufactured are connected to each other in the circumferential direction. The shape of the molding space 20a is changed by changing the shapes of the isomorphous portion 16a of the mandrel 16 and the second through hole 11c. Then, by the extrusion molding device 10, a cylindrical shape in which molding parts 18 a, 32 a, 34 a, 36 a having a cross-sectional shape of the permanent magnets 18, 32, 34, 36 to be obtained are connected to each other in a plurality of circumferential directions. The primary molded body (molded body) 22 is configured to be molded. In the preform, the direction perpendicular to the direction of extrusion by the extrusion molding apparatus 10 is referred to as the thickness direction, and along the inner surface of the through hole 11 of the extrusion die 12 in the manufactured permanent magnets 18, 32, 34, 36. The direction intersecting the extrusion direction is referred to as the width direction.

  As shown in FIG. 1, the preform molded by the extrusion die 12 of the embodiment in which the mandrel 16 is inserted into the through hole 11 has an outer shape centered in the thickness direction of the preform along the tapered hole 11c. It is distorted so as to be reduced while being compressed toward the part side, and the central part side in the thickness direction of the preform is distorted so as to be expanded while being compressed outward along the taper part 16b. The primary molded body 22 is molded. In this way, by imparting distortion to both the outer shape of the preform and the central portion in the thickness direction during extrusion, the deviation in the degree of magnetic orientation in the thickness direction (outer side, inner side) of the primary molded body 22 is reduced. Thus, high magnetic properties can be obtained. The degree of magnetic orientation is a value defined by residual magnetic flux density (Br) / saturation magnetic flux density (Js).

In the extrusion process using the extrusion molding apparatus 10, in the case of extruding a preform with a surface reduction ratio of 50 to 70%, the processing rate of the outer shape of the preform (hereinafter referred to as the outer shape processing rate) K is: It is preferable to set the range of 5% ≦ K ≦ 30% over the entire circumference in both cases where the outer shape of the preform is enlarged and reduced. If the outer shape processing rate K is less than 5%, the amount of distortion in the thickness direction of the preform will vary, so the residual magnetic flux density (Br) in the thickness direction (outside, inside) of the primary molded body 22 will vary. Therefore, the degree of magnetic orientation cannot be homogenized. On the other hand, when the outer shape processing rate K is greater than 30%, it becomes difficult to process and the manufacturing efficiency decreases. When the area reduction ratio is less than 50%, the amount of strain applied when extrusion from the preformed body to the primary molded body 22 is small, and a high residual magnetic flux density (Br) cannot be obtained. Further, if the area reduction ratio is greater than 70%, the load applied to the pressing punch 14 and the mandrel 16 during the extrusion process increases, and there is a risk that damage, seizure, or the like may occur. The area reduction ratio is the cross-sectional area in the cross section in the thickness direction orthogonal to the extrusion direction in the preform before processing, S ₀ , and the cross section in the thickness direction orthogonal to the extrusion direction in the primary molded body 22 after processing. Is a ratio defined by the formula {(S ₀ −S ₁ ) / S ₀ } × 100 (%), where S ₁ is the cross-sectional area of the preform and primary molded body 22 before and after processing. The reduction rate of the cross-sectional area is shown. In addition, the outer shape processing rate K means that the first through hole 11a extends from the center of the through hole 11 in the direction perpendicular to the extrusion direction in a cross section obtained by cutting the extrusion die 12 along the extrusion direction at the center of the through hole 11. When the length to the inner surface is L ₀ and the length from the center of the through hole 11 to the inner surface of the second through hole 11c is L ₁ , {(| L ₀ −L ₁ |) / L ₀ } × 100 (%) The ratio of expansion or contraction of the outer shape of the preform according to extrusion processing (see FIG. 1), and the outer surface of the preform from the center in the thickness direction before and after processing The change ratio of the length from the center of the primary molded body 22 to the outer surface of the primary molded body 22 is shown.

  The preform is produced by injecting molten metal obtained by melting a raw material containing rare earth, iron group metal and boron onto a rotating roll to produce a flake-shaped ultra-quenched ribbon. After being pulverized to a diameter, cold pressing is performed to form a green compact, and this green compact is preheated to a required temperature (hot or temperature during warm pressing) in an atmosphere of an inert gas (for example, Ar). And then densifying by hot or warm pressing. As the rare earth, Y or a lanthanoid can be employed, but Nd, Pr, Dy, Tb, or a mixture of two or more thereof can be suitably employed. Further, Fe, Co, and Ni can be employed as the iron group metal, but in particular, Fe, Co, or a mixture of both can be suitably employed. Ga may be added as necessary for the purpose of improving plastic workability (preventing cracking). Further, the preform formed by hot pressing or warm pressing to be densified is preheated to a temperature at which it is extruded by the extrusion molding apparatus 10 in an inert gas (for example, Ar) atmosphere. Hold. The preheating when forming the preform and the preheating before extruding the preform with the extrusion molding apparatus 10 are performed according to the processing conditions such as the difference in the type of magnet material and the processing schedule. It can be omitted.

  Here, as a general form of a motor in which a permanent magnet is used, there are a surface magnet type (SPM) motor in which a permanent magnet is attached to a rotor surface and a magnet embedded type (IPM) motor in which a permanent magnet is embedded in the rotor. The permanent magnets 32, 36, 34 having a crescent-shaped, arc-shaped and saddle-shaped cross section are preferably used for the surface magnet type motor, and the permanent magnets 18, 32, 36, 34 having a rectangular shape or a circular arc shape are used for the magnet-embedded motor. 36 is preferably employed. And in the said extrusion molding apparatus 10, the permanent magnets 18, 32, 34, 36 of the said various cross-sectional shape can be manufactured by changing each shape of the mandrel 16 and the through-hole 11. FIG. Therefore, the case where the permanent magnets 18, 32, 34, and 36 having different cross-sectional shapes are manufactured will be individually described below.

In the first embodiment, a case where a permanent magnet 18 having a rectangular cross section is manufactured will be described. In the first embodiment, as shown in FIG. 2, through-holes 11 (first through-hole 11a, tapered hole 11b, and second through-hole 11c) having a substantially rectangular opening are formed in the extrusion die 12. Has been. Further, the extrusion die 12 is formed with an inclined surface at a predetermined angle (45 ° in the first embodiment) at each corner of the through hole 11. The cross-sectional shape of the isomorphous portion 16a in the mandrel 16 is formed in a rectangular shape smaller than the second through hole 11c, and the entire circumference of the mandrel 16 is inserted in the state where the isomorphous portion 16a of the mandrel 16 is inserted into the second through hole 11c. A rectangular tube-shaped filling space 20 is defined as a whole. The filling space 20 includes a molding space 20a having a rectangular cross section defined outside the four surfaces of the mandrel 16 and communicating with each other at the corners. The mandrel 16 is inserted into the through hole 11 with each corner portion facing each inclined surface of the extrusion die 12. Further, the gap in the thickness direction between the isomorphous portion 16a and the inclined surface in the filling space 20 defined with the isomorphous portion 16a of the mandrel 16 inserted into the second through hole 11c is the second through hole 11c. And it is set smaller than the gap of the thickness direction of the part which the surfaces of the isomorphic part 16a oppose. Moreover, the opening dimension of the 1st through-hole 11a and the 2nd through-hole 11c in the through-hole 11 is set so that the external shape processing rate of the perimeter of a preforming body may become fixed at the time of an extrusion process. In addition, about an external shape processing rate, it is preferable to be settled in the range which is not restricted to what is constant over the perimeter of a preforming body , and is 5 to 30%. That is, when the outer shape processing rate is within this range, it is possible to suppress variations in the degree of magnetic orientation in the thickness direction of the permanent magnet 18 divided from the molded body .

  In the extrusion molding apparatus 10, the mandrel 16 is inserted into the through hole 11 from the other opening on the second through hole 11c side, and the preheated preheated from the one opening on the first through hole 11a side to the through hole 11 With the molded body loaded, the pressing punch 14 is inserted into the through hole 11 from one opening and pressed. As a result, the preform is extruded into the filling space 20 between the outer surface of the isomorphous portion 16a of the mandrel 16 and the inner surface of the second through hole 11c of the through hole 11, whereby the primary molded body shown in FIG. 22 is molded. The primary molded body 22 is magnetically anisotropic in the thickness direction orthogonal to the extrusion direction, which is the compression direction during extrusion. Further, when passing through the space defined by the tapered portion 16b of the mandrel 16 and the tapered portion 11b of the through hole 11, the preform is reduced so that the outer shape of the preform is narrowed inward, and the preform When the central portion in the thickness direction is expanded outward, the preform is distorted on the outer side and the inner side in the thickness direction, and the degree of magnetic orientation varies between the outer side and the inner side of the molded primary molded body 22. Becomes smaller. The primary molded body 22 molded by the extrusion molding apparatus 10 is extruded into the filling space 20 so that a plurality of molding sections 18a having a rectangular cross section are connected in the circumferential direction (four in the first embodiment). In the state which has the bottomed part 22a in the edge part of a shape part, it discharges | emits from the through-hole 11. FIG. Then, by cutting out the bottomed portion 22a from the primary molded body 22, a rectangular tube-shaped secondary molded body (molded body) 24 (see FIG. 3A) that opens before and after in the extrusion direction is obtained.

  As shown in FIG. 3A, the secondary molded body 24 is formed into a rectangular tube shape in which the inner side is formed in a rectangular cross section and the inclined surface 26 is formed in a portion corresponding to each outer corner. Is done. In other words, the angular corner connecting the two inner surfaces so as to form a corner functions as a stress concentration portion 28 where stress is concentrated when an external force is applied. That is, in Example 1, the stress concentration part 28 is formed inside the connection part of the shaping | molding parts 18a and 18a connected in the circumferential direction. Further, the thickness of the corner portion where the stress concentration portion 28 is formed in the secondary molded body 24 is thinner than other portions by forming the inclined surface 26 (the stress concentration portion 28 is weaker than other portions). ). Then, as shown in FIG. 3 (b), when the split jigs 30 and 30 are addressed to the pair of opposed inclined surfaces 26 and 26, the stress concentration portions 28 that face the jigs 30 and 30 close to each other. , 28, the secondary molded body 24 is divided starting from four stress concentration portions 28 extending over the entire length in the longitudinal direction (extrusion direction). ), The permanent magnet 18 having a rectangular cross section is obtained by appropriately processing the portion that has been divided into four and formed the inclined surface 26.

In Example 1, in the secondary molded body 24 obtained through the extrusion process, as shown in FIG. 3A, the upper limit of the thickness (radial thickness) T ₁ at the stress concentration portion 28 is 2 The maximum thickness T ₀ of the next molded body 24 is preferably set to T ₁ <4 / 5T _0, and more preferably set to T ₁ <3 / 5T ₀ . The lower limit of the thickness (radial thickness) T ₁ at the stress concentration portion 28, with respect to the maximum thickness T ₀ of the secondary molded body 24 is preferably set to _{T 1> 1 / 5T 0,} T 1 More preferably, it is set to> 2 / 5T ₀ . That is, if the thickness T ₁ at the stress concentration portion 28 is larger than the upper limit value (T ₁ <4 / 5T ₀ ), a large force is required when the secondary molded body 24 is divided at the stress concentration portion 28, resulting in a defect. There is a risk. On the other hand, if the thickness T ₁ at the stress concentration portion 28 is made smaller than the lower limit (T ₁ > 1/5 T ₀ ), the amount of plastic deformation when the stress concentration portion 28 is formed during extrusion is increased, and the orientation is increased. May decrease.

  As described above, in the method of manufacturing the permanent magnet 18 according to the first embodiment, the secondary molded body 24 after the extrusion process is divided by the stress concentration portion 28 to manufacture a plurality of permanent magnets 18. For this reason, a large stress is not applied to the divided portion during the extrusion process, and the yield is improved without requiring grinding of the defective portion in the subsequent process. In addition, a plurality of permanent magnets having excellent magnetic anisotropy in which crystal orientation directions are aligned at the divided portions of the permanent magnet 18 are compared with a method in which a preform is pressed against a fin and divided at the time of extrusion as in the prior art. The magnets 18 can be manufactured efficiently, and the magnetic characteristics of the permanent magnets 18 are uniform. Furthermore, when extruding the preform, the outer side and the inner side in the thickness direction are deformed in the thickness direction over the entire circumference so that distortion is applied, so that the permanent magnet obtained from the molded body 22 is obtained. As a result, there is no variation in the degree of magnetic orientation on the outer side and the inner side in the thickness direction, and an excellent permanent magnet 18 having no variation in magnetic characteristics in the thickness direction can be obtained. In addition, since the outer shape processing rate when extruding the preform is constant (or within 5 to 30%) over the entire circumference, the permanent magnet 18 extends over the entire width direction. Thus, there is no variation in the magnetic characteristics in the thickness direction. That is, the permanent magnet 18 having excellent magnetic properties can be manufactured with a high yield. Further, since the stress concentration portion 28 for dividing the secondary molded body 24 into a plurality of parts is formed at the same time during the extrusion process (at the time of forming the primary molded body 22), when the stress concentration portion 28 is separately formed in a subsequent process. Compared with this, the number of steps can be reduced and the production efficiency can be improved. Further, since the stress concentrating portion 28 is connected so that two surfaces forming the concentrating portion 28 form an angle, the stress concentrating portion 28 is formed when an external force is applied to the secondary molded body 24. As a starting point, the secondary molded body 24 is cleanly divided, and a section with high flatness is obtained. That is, the flatness of the sectional surface of the permanent magnet 18 divided from the secondary compact 24 is high, and the appearance of the permanent magnet 18 is good. The permanent magnet 18 divided from the secondary compact 24 is put to practical use as a permanent magnet having magnetic anisotropy by being magnetized in a subsequent process.

  In the first embodiment, the case where the permanent magnet 18 having a rectangular cross section is manufactured has been described. However, by changing the shape of the through hole 11 and the mandrel 16 of the extrusion die 12, the cross crescent shape shown in FIG. The permanent magnet 32 can be manufactured. The crescent-shaped permanent magnet 32 has the thickest central portion in the width direction, and the thickness decreases as the distance from the central portion increases. However, when extruding the preform, the outer shape processing rate is increased over the entire circumference. The opening shape and opening dimension of the first through hole 11a and the second through hole 11c in the through hole 11 are set so as to be constant. In addition, about an external shape processing rate, it is preferable to be settled in the range which is not restricted to what is constant over the perimeter of a preforming body, and is 5 to 30%. That is, when the outer shape processing rate is within this range, it is possible to suppress variations in the degree of magnetic orientation in the thickness direction of the permanent magnet 32 divided from the molded body.

  That is, when manufacturing the crescent-shaped permanent magnet 32, the mandrel 16 is inserted into the through hole 11, and the outer surface of the isomorphous portion 16 a in the mandrel 16 and the inner surface of the second through hole 11 c in the through hole 11 In the meantime, each shape of the mandrel 16 and the through-hole 11 is set so that the forming space 20a having a crescent-shaped cross section defines a cylindrical filling space 20 communicating with each other in the circumferential direction. Then, the columnar preform formed in the through-hole 11 is pressed and pressed by the pressing punch 14 so that the outside of the preform and the central portion in the thickness direction are distorted, and a plurality of molding parts 32a having a crescent-shaped cross section are formed around the circumference. A bottomed cylindrical primary molded body 22 having cylindrical portions connected in a direction is formed, and a bottomed portion 22a is cut from the primary molded body 22, whereby a substantially cylindrical secondary molded body 24 is formed. .

In Example 2, as shown in FIG. 4A, the secondary molded body 24 is formed such that the inner side is formed in a circular cross section, and the outer side is formed by alternately connecting arc-shaped peaks and V-shaped valleys. The V-shaped valley portion formed on the outer surface functions as the stress concentration portion 28. That is, in Example 2, the stress concentration part 28 is formed in the outer surface of the connection part of the shaping | molding parts 32a and 32a continuous in the circumferential direction. In Example 2, in the secondary molded body 24 obtained through the extrusion process, the upper limit value and the lower limit value of the thickness (radial thickness) T ₁ at the stress concentration portion 28 are the same as in Example 1. It is preferable to set the range of 1 / 5T ₀ <T ₁ <4 / 5T ₀ with respect to the maximum thickness T ₀ of the secondary molded body 24, and set the range 2 / 5T ₀ <T ₁ <3 / 5T _0. More preferably.

  In the second embodiment, as shown in FIG. 4A, the split jigs 30 and 30 are addressed to the opposing stress concentration portions 28 and 28 from the outside, and the jigs 30 and 30 are brought close to each other to be secondary. By pressing the compact 24 in the radial direction, the secondary compact 24 is divided starting from each stress concentration portion 28 extending over the entire length in the longitudinal direction (extrusion direction). As shown in FIG. 6, six cross-sectional crescent-shaped permanent magnets 32 are obtained. Also in the second embodiment, as in the first embodiment, the permanent magnet 32 having excellent magnetic characteristics can be manufactured with a high yield. In addition, the obtained crescent-shaped permanent magnet 32 has a uniform magnetic property and good appearance.

In the third embodiment, a case where a permanent magnet 34 having a bowl-shaped cross section shown in FIG. 5B is manufactured will be described. That is, when manufacturing the permanent magnet 34 having a bowl-shaped cross section, with the mandrel 16 inserted into the through hole 11, the outer surface of the isomorphous portion 16a in the mandrel 16 and the inner surface of the second through hole 11c in the through hole 11 In the meantime, each shape of the mandrel 16 and the through hole 11 is set so as to define a cylindrical filling space 20 in which the forming space 20a having a bowl-shaped cross section communicates with each other in the circumferential direction. Then, the columnar preform formed in the through-hole 11 is pressed and pressed by the press punch 14 so that the outer side of the preform and the central portion in the thickness direction are distorted, and a plurality of molding sections 34a having a bowl-shaped cross section are formed. A bottomed cylindrical primary molded body 22 having cylindrical portions connected in a direction is formed, and a bottomed portion 22a is cut from the primary molded body 22, whereby a substantially cylindrical secondary molded body 24 is formed. . Incidentally, the saddle-shaped permanent magnet 34 has the thickest central portion in the width direction and the thickness decreases as the distance from the central portion becomes similar to the crescent-shaped permanent magnet 32 of the second embodiment. When extruding the molded body, the opening shape and opening dimensions of the first through hole 11a and the second through hole 11c in the through hole 11 are set so that the outer shape processing rate is constant over the entire circumference. Also, the outer shape processing rate of the preform is not limited to a constant value over the entire circumference in the same manner as in Example 2, and is preferably within a range of 5 to 30%. That is, when the outer shape processing rate is within this range, it is possible to suppress variations in the degree of magnetic orientation in the thickness direction of the permanent magnet 34 divided from the molded body. In Example 3, in the secondary molded body 24 obtained through the extrusion process, the upper limit value and the lower limit value of the thickness (radial thickness) T ₁ at the stress concentration portion 28 are the same as in Example 1. It is preferable to set the range of 1 / 5T ₀ <T ₁ <4 / 5T ₀ with respect to the maximum thickness T ₀ of the secondary molded body 24, and set the range 2 / 5T ₀ <T ₁ <3 / 5T _0. More preferably.

  In Example 3, as shown in FIG. 5A, the secondary molded body 24 has an inner side formed in a rectangular cross section and an outer side formed in a circular cross section, and the secondary molded body 24 of Example 3 is formed. Then, as in the first embodiment, each inner corner portion functions as the stress concentration portion 28. Then, as shown in FIG. 5A, the split jigs 30 and 30 are addressed to the opposing stress concentration portions 28 and 28 from the outside, and the jigs 30 and 30 are brought close to each other to form the secondary molded body 24. 5 in the radial direction, the secondary molded body 24 is divided starting from each stress concentration portion 28 extending over the entire length in the longitudinal direction (extrusion direction), as shown in FIG. Thus, four permanent magnets 34 having a bowl-shaped cross section are obtained. In the third embodiment, as in the first embodiment, the permanent magnet 34 having excellent magnetic characteristics can be manufactured with a high yield. Further, the obtained permanent magnet 34 having a bowl-shaped cross section has uniform magnetic characteristics and good appearance.

  In the fourth embodiment, a case where a permanent magnet 36 having a circular arc cross section is manufactured will be described. That is, in the case of manufacturing the permanent magnet 36 having a circular arc cross section, the outer surface of the isomorphous portion 16a in the mandrel 16 and the inner surface of the second through hole 11c in the through hole 11 with the mandrel 16 inserted into the through hole 11 In the meantime, the shapes of the mandrel 16 and the through hole 11 are set so as to define a cylindrical filling space 20. Moreover, the opening dimension of the 1st through-hole 11a and the 2nd through-hole 11c in the through-hole 11 is set so that the external shape processing rate may become constant over the perimeter at the time of extrusion of a preforming body. In addition, about the external shape processing rate of a preforming body, it is preferable to be settled in the range of 5 to 30%, not only what becomes constant over a perimeter. That is, when the outer shape processing rate is within this range, it is possible to suppress variations in the degree of magnetic orientation in the thickness direction of the permanent magnet 36 divided from the molded body. Further, when the permanent magnet 36 having a circular arc cross section as in the fourth embodiment is manufactured, as shown in FIGS. 6A and 6B, the extrusion die 12 is formed so as to form the stress concentration portion 28 at the time of extrusion. A plurality of internal projections on the inner surface of the second through-hole 11c in the through-hole 11 at a position corresponding to the continuous end portion with the tapered portion 16b of the isomorphous portion 16a in the mandrel 16 inserted into the second through-hole 11c (Protrusions) 38 are provided apart from each other in the circumferential direction, and outer projections (projections) 40 corresponding to the inner projections 38 at the end portions of the mandrel 16 connected to the tapered portion 16b on the outer surface of the isomorphous portion 16a. Are provided. Then, the columnar preform formed in the through-hole 11 in which the mandrel 16 is inserted is pressed and pressed by the pressing punch 14 to the outer surface and the inner surface corresponding to the inner protrusion 38 and the outer protrusion 40. In the process, groove-like stress concentration portions 28 and 28 that are recessed in the thickness direction (radial direction) are formed. Then, the outside of the preform and the central portion in the thickness direction are distorted, and stress concentration portions 28 and 28 are formed over the entire length of the portion that becomes the secondary molded body 24 along the extrusion direction, and in the circumferential direction. A bottomed cylindrical primary molded body 22 having a cylindrical portion in which a plurality of molded portions 36a divided by adjacent stress concentration portions 28, 28 are connected in the circumferential direction is molded.

In Example 4, in the secondary molded body 24 obtained through the extrusion process shown in FIG. 7A, the upper limit value and lower limit value of the thickness (radial thickness) T ₁ at the stress concentration portion 28 are: Similarly to Example 1, it is preferable to set a range of 1 / 5T ₀ <T ₁ <4 / 5T ₀ with respect to the maximum thickness T ₀ of the secondary molded body 24. 2 / 5T ₀ <T ₁ <3 It is more preferable to set within the range of / 5T ₀ .

  Here, the inner protrusion 38 of the extrusion die 12 and the outer protrusion 40 of the mandrel 16 are connected to the tapered portion 16b of the isomorphous portion 16a when the mandrel 16 is inserted into the through hole 11, as described above. However, the inner protrusion 38 of the extrusion die 12 is connected to the tapered portion 16b of the isomorphous portion 16a of the mandrel 16 inserted into the through hole 11. The inner projections 38 and the corresponding outer projections 40 only need to be aligned in the thickness direction when viewed from the extrusion direction. Further, the groove-shaped stress concentration portion 28 formed by the inner protrusion 38 and the outer protrusion 40 has a sharp tip (bottom of the groove) when the molded portion 36a is divided by the stress concentration portion 28. Therefore, it is preferable that the shape of the inner protrusion 38 and the outer protrusion 40 is a triangular cross section and the inner angle on the protruding end side is an acute angle. In addition, the shape of the inner protrusion 38 and the outer protrusion 40 is not limited to a triangular cross-section, and may be other shapes such as a rectangular cross-section or an arc-shaped protruding end.

  As shown in FIG. 7A, the secondary molded body 24 of Example 4 is divided in the circumferential direction by stress concentration portions 28 and 28 formed so as to face the outer surface and the inner surface in the radial direction (thickness direction). In addition, it has a cylindrical shape in which a plurality of (four in Example 4) molding portions 36a are connected. That is, in the secondary molded body 24 of Example 4, the stress concentration portions 28 are formed on the outer surface and the inner surface of the connecting portions of the forming portions 36a and 36a that are connected in the circumferential direction. Then, as shown in FIG. 7A, the split jigs 30, 30 are addressed outside the stress concentration portions 28, 28 facing each other across the center of the secondary molded body 24. By pressing the secondary molded body 24 in the radial direction with 30 close, the secondary molded body 24 is divided at each stress concentration portion 28 extending over the entire length in the longitudinal direction (extrusion direction), As shown in FIG. 7B, four permanent magnets 36 having an arcuate cross section are obtained. In the fourth embodiment, as in the first embodiment, the permanent magnet 36 having excellent magnetic properties can be manufactured with a high yield. Further, the obtained permanent magnet 36 having an arc-shaped cross section has a uniform magnetic characteristic and a good appearance. Furthermore, in the fourth embodiment, the stress concentration portion 28 formed by the protrusions 38 and 40 is a substantially V-shaped groove, so that the plane of the sectional surface of the permanent magnet 36 divided by the stress concentration portion 28 is obtained. The degree is higher and the appearance of the permanent magnet 36 is better. When the stress concentration portion 28 is formed by the protrusions 38 and 40 formed on the extrusion die 12 and the mandrel 16, a protrusion is provided only on one of the extrusion die 12 and the mandrel 16, and the primary molded body 22 The form which forms the stress concentration part 28 in any one surface of an outer surface or an inner surface can be employ | adopted.

[Experimental example]
Nd: 29.5% by mass, Co: 5% by mass, B: 0.9% by mass, Ga: 0.6% by mass, a magnetic alloy consisting essentially of Fe is melted and rapidly cooled by a single roll method Thus, a magnetic ribbon having a thickness of 25 μm and an average crystal grain size of 0.1 μm or less was obtained. Further, the magnetic ribbon was pulverized to obtain a magnetic powder having a length of 300 μm or less. The magnetic powder was cold pressed at a surface pressure of about 3.0 ton and compacted, preheated to a temperature of 600 to 900 ° C. in an Ar atmosphere, and then heated to a temperature of 600 to 900 ° C. and a pressure of 200 MPa in an Ar atmosphere. Hot pressing was performed to manufacture a columnar preform. And the invention example 1 manufactured with the manufacturing method of this invention which shape | molds the crescent-shaped permanent magnet 32 from this preform, and the preform manufactured on the same conditions as above are finned to the through-hole of a metal mold | die. About the comparative example 1 manufactured with the manufacturing method disclosed by the said patent document 1 extruded from the some division hole defined by inserting the mandrel, it verified about the difference in a magnetic orientation degree.

  As conditions for extruding the preform, the temperature of the preform and the extrusion die 12 was 600 to 900 ° C., and a 50-ton hydraulic press was used as the processing machine. Further, before the preform was extruded, the preform was preheated to 600 to 900 ° C. It should be noted that, with the area reduction rate of the primary molded body with respect to the preformed body being constant at 55%, the profile processing rate K was 5% in Invention Example 1, and the profile processing rate was 0% in Comparative Example 1. For the specific measurement of the degree of magnetic orientation (magnetic characteristics) of each permanent magnet 32 of Invention Example 1 and Comparative Example 1, from the central part and both end parts in the width direction in the central part in the length direction (extrusion direction), A sample having a width × length of 7 mm × 7 mm was cut out, and both sides in the thickness direction of the sample were cut by 0.5 mm, and a magnetic measurement sample having a width × length × thickness of 7 mm × 7 mm × 6 mm was employed. Magnetic measurement samples were prepared by cutting out from a plurality of different positions in the length direction from the front end (tip) in the extrusion direction of the molded body obtained by extrusion. And what magnetized each magnetic measurement sample in the magnetic field of 3.2 MA / m was used. For each magnetic measurement sample that has reached saturation magnetization due to the magnetization, the degree of magnetic orientation is measured with a pulse excitation type-BH tracer, and the measurement result of Invention Example 1 is shown in FIG. The measurement result of 1 is shown in FIG.

(Measurement results of the degree of magnetic orientation in the width direction of the permanent magnet divided from the compact)
From the results shown in FIGS. 8 (a) and 8 (b), in Invention Example 1, the degree of magnetic orientation at the center and both ends in the width direction is improved as compared with Comparative Example 1 in which the magnet is divided during extrusion. It was also confirmed that the degree of magnetic orientation at the center and both ends in the width direction was substantially the same, and the magnetic characteristics were homogeneous in the width direction. In addition, the appearance of the permanent magnet 32 of Invention Example 1 was good, there were no cracks in the divided portions, and there were very few defective portions that required grinding. That is, according to the present invention, it is confirmed that a permanent magnet having high magnetic properties can be manufactured from a molded body formed by an extrusion process that is excellent in terms of productivity, material yield, yield rate, and manufacturing cost. It was done.

(Measurement results of the degree of magnetic orientation in the thickness direction of the permanent magnet divided from the compact)
By changing the outer shape processing rate K, the degree of magnetic orientation in the thickness direction of the crescent-shaped permanent magnet 32 extruded from the preform manufactured under the conditions described in the paragraph [0038], the outer shape ratio K is changed. The influence of the processing rate K was verified. The area reduction rate of the primary molded body 22 with respect to the preformed body is 55%. Inventive example 2 has the same outer shape processing rate K as that of inventive example 1 of experimental example 1, and in inventive example 3, the outer shape processing rate K is 10%, in Example 4, the outer shape processing rate K was 20%, and in Example 5, the outer shape processing rate K was 30%. Further, as Comparative Example 2, extrusion processing was performed from the same preform as described above with a reduction in surface area of 55% and an outer shape processing rate of 0%, that is, without deforming the outer shape of the preform, and in the circumferential direction by the stress concentration portion. A primary molded body in which a plurality of divided molded parts were formed was manufactured, and the degree of magnetic orientation was measured for the permanent magnets divided from the primary molded body. Various conditions other than the area reduction rate and the outer shape processing rate K when extruding the preform are as described above.

  About the specific measurement of the magnetic orientation degree (magnetic property) of each permanent magnet 32 of Invention Examples 2 to 5 and Comparative Example 2, the central portion in the thickness direction and the inner surface portion (primary compact 22 in the central portion in the width direction). ) And an outer surface portion (outside of the primary molded body 22), a sample having a width × length of 7 mm × 7 mm was cut out, and both sides in the thickness direction of the sample were cut by 0.5 mm each to obtain a width × length × A magnetic measurement sample having a thickness of 7 mm × 7 mm × 6 mm was employed. And what magnetized each magnetic measurement sample in the magnetic field of 3.2 MA / m was used. About each magnetic measurement sample which has reached saturation magnetization by the said magnetization, the magnetic orientation degree was measured with the pulse excitation type | mold -BH tracer, and the measurement result of invention example 2-5 and the comparative example 2 is shown in FIG.

  From the results shown in FIG. 9, it is confirmed that the invention example 2 in which the outer shape processing rate K is 5% improves the magnetic orientation degree of the outer surface portion as compared with the comparative example 2 in which the outer shape processing rate K is 0%. It was. Moreover, it was confirmed from the measured value of the magnetic orientation degree of the invention examples 2-4 that the magnetic orientation degree of an outer surface part improves as the external shape processing rate K is enlarged. That is, it was confirmed that the degree of magnetic orientation was improved and the magnetic properties were improved by increasing the amount of strain (processing rate) applied to the material during extrusion. Further, in Invention Example 4 in which the outer shape processing rate K is 20% and in Invention Example 5 in which the outer shape processing rate K is 30%, the magnetic orientation degrees of the inner surface portion, the central portion, and the outer surface portion are substantially the same, and in the thickness direction. It was also confirmed to have homogeneous magnetic properties. According to the present invention, it has been confirmed that a permanent magnet which is homogeneous in the thickness direction and has high magnetic properties can be produced from a molded body formed by extrusion. That is, according to the manufacturing method of the present invention, after forming the cylindrical molded body by distorting both the outer shape of the preform and the central portion in the thickness direction during extrusion, the molded body is divided at the stress concentration portion. It was confirmed that a permanent magnet having uniform magnetic orientation in the width direction and thickness direction and excellent magnetic properties can be produced.

[Example of change]
The present invention is not limited to the configuration of the embodiment, and various modifications are possible. For example, the following configurations can be adopted.
(1) In the example, after extruding a primary molded body having a bottomed portion, the bottomed portion of the primary molded body was cut out to obtain a cylindrical secondary molded body. You may make it shape | mold the cylindrical secondary compact | molding | casting body which consists only of the cylindrical part with which the shaping | molding part corresponding to the shape permanent magnet was connected in the circumferential direction by extrusion.
(2) In Example 1, inclined surfaces are formed at the four corners of the secondary molded body. However, the inclined surfaces are not essential and may remain angular.
(3) In the embodiments, the case where the permanent magnet having a rectangular, crescent-shaped, bowl-shaped, or arc-shaped cross section is described is described. However, the shape of the permanent magnet is not limited to these shapes, and various other types are also described. The shape may also be Moreover, the number of the molding parts (parts corresponding to the permanent magnets) connected in the circumferential direction in the primary molded body molded by the extrusion process may be two or more, and is not limited to the number exemplified in each example.
(4) In Examples 1 to 3, protrusions are provided on the inner surface of the through hole and the outer surface of the mandrel in the extrusion die at positions corresponding to the stress concentration portions formed in the primary molded body as in Example 4. The grooves may be formed on the inner surface and / or the outer surface of the stress concentration portion. Further, instead of the protrusions for forming the stress concentration portion, it is possible to use ridges (projections) extending a predetermined length along the extrusion direction. The protrusions are not limited to those provided over the entire length of the extrusion mold and the mandrel, but may be provided only in a region where the mandrel is inserted into the through hole.
(5) In each example, when the molded body was divided at the stress concentration portion, the stress concentration portion opposed to the center of the molded body was clamped from the outside with a split jig. Other portions may be sandwiched and divided. However, it is easier to sever at each stress concentration part when the stress is concentrated at the stress concentration part.
(6) In each example, when extruding the primary molded body from the preform, it was narrowed down to reduce the outer shape and deformed so as to expand the central part in the thickness direction. You may make it give distortion to the outer side and inner side of a thickness direction by making it deform | transform so that the center part of the thickness direction may be expanded.
(7) The preform does not need to be solid, and may be a cylinder having a central through hole having a smaller diameter than the mandrel. When the preform is formed into a cylindrical shape, the mandrel taper portion is inserted into the central through hole when the preform is inserted into the through hole of the extrusion mold, so that the preform can be positioned.
(8) The preform can also be obtained by extruding (plastic working) a magnet alloy powder into a green compact by cold pressing, without passing through hot or warm pressing.

12 Extrusion mold, 11 Through hole, 14 Press punch, 16 Mandrel 18 Permanent magnet with rectangular cross section, 20 Filling space, 24 Secondary compact (molded compact)
28 Stress Concentration Section, 32 Crescent-shaped Permanent Magnet, 34 Cross-Section Permanent Magnet 36 Permanent Arc-shaped Permanent Magnet, 38 Inner Projection (Projection), 40 Outer Projection (Projection)
Maximum radial thickness of T ₀ compact, radial thickness of T ₁ stress concentration part

Claims (5)

Prepare a pre-formed body pressed with magnet alloy containing rare earth, iron group metal and boron,
It said preform mandrel (16) is loaded into the through-hole (11) of the insertion has been extrusion die (12), perpendicular to the extrusion direction of the preform causes scales the outline of the preform Extrusion is performed with a pressing punch (14) to form a cylindrical molded body (24) so that the central part in the direction of expansion is expanded, and stress that extends in the extrusion direction during the process of extruding the preform A plurality of concentrated portions (28) are formed spaced apart in the circumferential direction,
By applying an external force in the radial direction to the obtained molded body (24), the molded body (24) is divided by the stress concentration portion (28) to form a plurality of permanent magnets (18, 32, 34, 36). Like to split ,
The method for manufacturing a non-cylindrical permanent magnet, wherein the area reduction ratio is 50 to 70% in the extrusion process, and the process ratio in the direction of expansion or contraction of the outer shape is 5 to 30%. . The stress concentration portion (28), in the inner or outer surface of the molded body (24), two surfaces contiguous to the circumferential direction of the non-cylindrical permanent magnet of claim 1 Symbol placement is formed so as to form an angle Production method. Filling space (20) defined between the inner surface of the through hole (11) and the outer surface of the mandrel (16) on the inner surface of the through hole (11) or the outer surface of the mandrel (16) in the extrusion die (12). The protrusions (38, 40) protruding to the outer surface of the molded body (22) extruded from the filling space (20) are radially recessed by the protrusions (38, 40). The method for producing a non-cylindrical permanent magnet according to claim 1 or 2 , wherein a groove is formed as the stress concentration portion (28). Stress concentrator relative to the maximum thickness T ₀ of the radial and radial thickness T ₁ is _{1 / 5T 0 <T 1 <} 4 / 5T 0 in a range of as molded molded article (28) (24), The method for manufacturing a non-cylindrical permanent magnet according to any one of claims 1 to 3 , wherein the stress concentration portion (28) is divided. The method for producing a non-cylindrical permanent magnet according to any one of claims 1 to 4 , wherein the molded body (24) is clamped in a radial direction and divided by the stress concentration portion (28).

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