Sintered magnet, method for manufacturing sintered magnet, and mold

Abstract

A method for manufacturing sintered magnets using a mold is presented. This mold has a pair of second magnetic yokes, which allow adjustment of the magnetic flux of the magnetic field applied during pressing. Because local magnetic flux disturbances are regulated, the overall magnetic field orientation can approach the ideal magnetic field orientation along the magnetization direction, achieving uniform magnetic field distribution.

Description

Technical Field

[0001] This disclosure relates to sintered magnets, methods for manufacturing sintered magnets, and molds. Background Technology

[0002] Sintered magnets with a magnetization direction (i.e., uniaxial anisotropy) in a single axis have long been known. These sintered magnets are widely used in devices such as electric motors, generators, electromagnetic actuators, and electromagnetic sensors.

[0003] In recent years, as a measure to address global warming, the introduction of renewable energy has been promoted, one example being wind power generation. The higher the magnetic properties of the sintered magnets mounted on wind turbines, the higher the output; this magnetic property can be improved by highly oriented the sintered magnets.

[0004] Patent document 1 discloses a technique that improves the orientation of magnets by pressing magnetic powder filled in a mold while applying a high magnetic field.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 62-276812 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] The magnetic field distribution of the high magnetic field in the aforementioned prior art is determined by the size of the magnetic poles and the distance between the magnetic poles of the electromagnet coil used to generate the magnetic field. The magnetic flux lines generated between the electromagnet coils are more prone to deflection the further away from the center of the electromagnet coil. Therefore, especially when forming large sintered magnets mounted on wind turbines, it is difficult to achieve a uniform magnetic field distribution within the mold, which may result in localized areas of weakened magnetic field or deflected magnetic flux lines. In this case, the orientation degree of the sintered magnet obtained by firing the pressed magnetic powder will be reduced.

[0010] According to various aspects of this disclosure, it is possible to provide a sintered magnet that achieves uniform magnetic field distribution, a method for manufacturing the sintered magnet, and a mold.

[0011] Means for solving technical problems

[0012] One aspect of this disclosure is a method for manufacturing a sintered magnet using a mold, the mold comprising: a body having an opening for filling magnetic powder and extending in a first direction; and a yoke disposed around the opening of the body in a cross section orthogonal to the first direction. The manufacturing method includes: a step of pressing the magnetic powder filled in the opening in the first direction while applying a magnetic field in a second direction orthogonal to the first direction to form a compact; and a step of firing the compact to form a sintered magnet. In the cross section orthogonal to the first direction, the opening is rectangular, defined by two sides extending in the second direction and two sides extending upward in a third direction orthogonal to both the first and second directions. The yoke in the cross section orthogonal to the first direction has: a pair of first yoke portions sandwiching the opening in the second direction, and a pair of second yoke portions sandwiching the opening upward in the third direction.

[0013] A mold according to one aspect of this disclosure includes: a body having an opening for filling magnetic powder and extending in a first direction; and a magnetic yoke disposed around the opening of the body in a cross section orthogonal to the first direction, the mold being used to press the magnetic powder filled in the opening of the body in the first direction while applying a magnetic field in a second direction orthogonal to the first direction, the opening in the cross section orthogonal to the first direction being rectangular in shape defined by two sides extending in the second direction and two sides extending upward in a third direction orthogonal to both the first and second directions, the magnetic yoke having in the cross section orthogonal to the first direction: a pair of first magnetic yoke portions sandwiching the opening in the second direction, and a pair of second magnetic yoke portions sandwiching the opening upward in the third direction.

[0014] The inventors discovered that when magnetic powder filled in an opening is pressed in a first direction while a magnetic field along a second direction is applied, the magnetic field distribution may become uneven at the end in the third direction. In the above-described method for manufacturing a sintered magnet and the mold, the magnetic flux at the end in the third direction can be adjusted by a pair of second magnetic yokes, thereby achieving uniform magnetic field distribution. Attached Figure Description

[0015] Figure 1 This is a schematic perspective view of a mold representing one embodiment.

[0016] Figure 2 It means Figure 1 A schematic perspective view of the cylindrical part of the mold shown.

[0017] Figure 3 It means Figure 1 A schematic three-dimensional view of the magnetic yoke of the mold shown.

[0018] Figure 4 yes Figure 1The diagram shows a cross-sectional view of the mold along line IV-IV.

[0019] Figure 5 It means to use Figure 1 A flowchart illustrating the steps of a method for manufacturing sintered magnets using the mold shown.

[0020] Figure 6 It means Figure 5 The flowchart shows the pressing process.

[0021] Figure 7 This is a schematic three-dimensional diagram representing a sintered magnet.

[0022] Figure 8 This is a diagram showing the magnetic field orientation of the sintered magnet.

[0023] Figure 9 These are cross-sectional views showing different shapes of molds.

[0024] Figure 10 These are cross-sectional views showing different shapes of molds.

[0025] Figure 11 These are cross-sectional views showing different shapes of molds.

[0026] Figure 12 This is a table representing the simulation results of Example 1.

[0027] Figure 13 This is a table representing the simulation results of Example 1.

[0028] Figure 14 This is a table representing the simulation results of Example 1.

[0029] Figure 15 This is a table representing the simulation results of Example 1.

[0030] Figure 16 This is a table showing the simulation results of Example 2.

[0031] Figure 17 This is a table showing the simulation results of Example 2.

[0032] Figure 18 This is a table showing the simulation results of Example 2.

[0033] Figure 19 This is a table showing the simulation results of Example 2.

[0034] Figure 20 This is a table showing the simulation results of Example 2.

[0035] Figure 21 This is a table showing the simulation results of Example 2.

[0036] Figure 22 This is a table showing the simulation results of Example 2.

[0037] Figure 23 This is a table showing the simulation results of Example 2.

[0038] Figure 24 This is a table showing the simulation results of Example 2.

[0039] Figure 25 This is a table showing the simulation results of Example 2.

[0040] Figure 26 This is a table showing the simulation results of Example 3.

[0041] Figure 27 This is a table showing the simulation results of Example 3.

[0042] Figure 28 This is a table showing the simulation results of Example 3.

[0043] Figure 29 This is a table showing the simulation results of Example 3.

[0044] Figure 30 This is a table showing the simulation results of Example 3.

[0045] Figure 31 This is a table showing the simulation results of Example 3.

[0046] Figure 32 This is a table showing the simulation results of Example 3.

[0047] Figure 33 This is a table showing the simulation results of Example 3. Detailed Implementation

[0048] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, in the description of the drawings, the same or equivalent elements are labeled with the same reference numerals, and repeated descriptions are omitted.

[0049] First, refer to Figures 1-4 A mold 1 according to one embodiment will be described. Mold 1 includes a main body 10 and a magnetic yoke 20.

[0050] In this embodiment, the main body 10 includes a cylindrical portion 14 having an opening 12 and a surrounding portion 16.

[0051] like Figure 2As shown, the cylindrical portion 14 has a square cylindrical shape extending in one direction, and an opening 12 with a rectangular cross-section is formed inside it along its extending direction. In this embodiment, the opening 12 has a generally square cross-section (for example, 60mm × 60mm). The opening 12 can also have a generally rectangular cross-section (e.g., 120mm × 80mm, 60mm × 200mm, etc.). The cylindrical portion 14 can be made of, for example, a non-magnetic material, or it can be made of a hard alloy or carbon steel, which are soft magnetic materials. In the following description, the extending direction of the opening 12 and the extending direction of the cylindrical portion 14 will also be referred to as the first direction D1.

[0052] The surrounding portion 16 covers the outer periphery of the cylindrical portion 14, covering all four outer peripheral surfaces of the cylindrical portion 14. In this embodiment, the surrounding portion 16 has a generally rectangular cylindrical shape, with a top surface 10a and a bottom surface 10b facing each other in the first direction D1, and four side surfaces 10c to 10f. In the following description, the direction in which side surface 10c faces side surface 10d is referred to as the second direction D2, and the direction in which side surface 10e faces side surface 10f is referred to as the third direction D3. The second direction D2 is a direction orthogonal to the first direction D1, and the third direction D3 is a direction orthogonal to both the first direction D1 and the second direction D2. In this embodiment, the length of the surrounding portion 16 in the first direction D1 is designed to be shorter than the length of the cylindrical portion 14, and the cylindrical portion 14 protrudes upward from the top surface 10a of the surrounding portion 16. The surrounding portion 16 can be composed of multiple components or a single component. In this embodiment, the surrounding portion 16 is composed of four components that respectively constitute the four side surfaces 10c to 10f. The surrounding portion 16 can be made of, for example, a non-magnetic material (specifically stainless steel, etc.).

[0053] Magnetic yoke 20 Figure 4 As shown, in a cross-section orthogonal to the first direction D1, it is disposed around the opening 12 of the main body 10. Figure 3 As shown, in this embodiment, the magnetic yoke 20 includes four magnetic yoke portions 30A, 30B, 40A, and 40B. Each of the magnetic yoke portions 30A, 30B, 40A, and 40B has a flat plate shape that extends along the entire length of the surrounding portion 16 in the first direction D1 and is embedded in the surrounding portion 16.

[0054] The magnetic yokes 30A and 30B constitute a pair of first magnetic yokes, arranged opposite each other in the second direction D2. The first magnetic yokes 30A and 30B can be made of, for example, carbon steel, iron, or die steel (alloy tool steel). In this embodiment, the first magnetic yokes 30A and 30B have substantially the same cross-sectional dimensions and shape, having a rectangular cross-section with its long side parallel to the third direction D3. Figure 4As shown, a pair of first magnetic yokes 30A and 30B are separated by an opening 12 in a cross section orthogonal to the first direction D1, and are symmetrically arranged with respect to a reference line L1 (second reference line) extending in the second direction D2, passing through the center C of the opening 12. Specifically, in a cross section orthogonal to the first direction D1, the centers of each pair of first magnetic yokes 30A and 30B in a third direction D3 are located on the reference line L1. In this embodiment, the first magnetic yokes 30A and 30B are designed such that, in a cross section orthogonal to the first direction D1, their length in the third direction D3 is longer than the length of the side of the opening 12 extending in the third direction D3, and both ends in the third direction D3 extend from the opening 12. As described later in the method for manufacturing sintered magnets, when a magnetic field along the second direction D2 is applied to the mold 1, the first magnetic yokes 30A and 30B opposite each other in the direction of magnetic field application are magnetized, thereby enhancing the magnetic flux along the second direction D2.

[0055] The yoke portions 40A and 40B constitute a pair of second yoke portions, arranged opposite each other in the third direction D3. The second yoke portions 40A and 40B can be made of, for example, carbon steel, iron, or die steel (alloy tool steel), and can be made of the same or different materials as the first yoke portions 30A and 30B. In this embodiment, the yoke portions 40A and 40B have substantially the same cross-sectional dimensions and shape, having a rectangular cross-section with its long side parallel to the second direction D2. Figure 4 As shown, in a cross-section orthogonal to the first direction D1, a pair of second magnetic yokes 40A and 40B sandwich an opening 12 on a third direction D3, and are symmetrically arranged with respect to a reference line L2 (first reference line) extending in the third direction D3 through the center C of the opening 12. Specifically, in a cross-section orthogonal to the first direction D1, the centers of each pair of second magnetic yokes 40A and 40B on the second direction D2 are located on the reference line L2. The pair of second magnetic yokes 40A and 40B are also symmetrically arranged with respect to the reference line L1 in a cross-section orthogonal to the first direction D1. Specifically, in a cross-section orthogonal to the first direction D1, the pair of second magnetic yokes 40A and 40B are positioned opposite each other, sandwiching the reference line L1. In a cross-section orthogonal to the first direction D1, the area occupied by the second magnetic yokes 40A and 40B can be designed to be smaller than the area occupied by the first magnetic yokes 30A and 30B. As described later in the method for manufacturing sintered magnets, when a magnetic field along the second direction D2 is applied to the mold 1, the magnetic flux near the second yoke portions 40A and 40B is regulated.

[0056] In this embodiment, in the second direction D2, the ratio (G1 / W1) of the distance G1 between the first yoke portions 30A and 30B and the opening 12 to the length W1 of the opening 12 is 0.01 to 3, and for example, this ratio G1 / W1 is 0.24. Furthermore, in the third direction D3, the ratio (G2 / W2) of the distance G2 between the second yoke portions 40A and 40B and the opening 12 to the length W2 of the opening 12 is 0.05 to 3, and for example, it is 0.41.

[0057] Furthermore, in this embodiment, in the third direction D3, the ratio (T2 / W2) of the length T2 of the second yoke portions 40A and 40B to the length W2 of the opening portion 12 is 0.01 to 0.5, and for example, it is 0.17. Furthermore, in the second direction D2, the ratio (H2 / W1) of the length H2 of the second yoke portions 40A and 40B to the length W1 of the opening portion 12 is 0.01 to 0.8, and for example, it is 0.04.

[0058] Furthermore, in this embodiment, in the third direction D3, the ratio (T2 / H1) of the length T2 of the second yoke portions 40A and 40B to the length H1 of the first yoke portions 30A and 30B is 0.01 to 1, for example, 0.17. In addition, in the second direction D2, the ratio (H2 / T1) of the length H2 of the second yoke portions 40A and 40B to the length T1 of the first yoke portions 30A and 30B is 0.05 to 12, for example, 0.36.

[0059] Next, refer to Figure 5 , 6 The steps for forming a sintered magnet using the mold 1 described above are explained.

[0060] When forming sintered magnets, magnetic powder to be used as sintered magnets is first prepared. Magnetic powder can be obtained by known methods, such as by pulverizing the raw material alloy. The pulverization process can be carried out in two stages or in one stage. The pulverization method is not particularly limited. For example, it can be carried out using various pulverizers. For example, the pulverization process can be carried out in two stages: a coarse pulverization stage and a fine pulverization stage. The coarse pulverization stage can, for example, be hydrogen-absorbing pulverization. Hydrogen-absorbing pulverization can be carried out by releasing hydrogen based on the difference in hydrogen absorption between different phases after the main phase alloy absorbs hydrogen, thereby producing spontaneous disintegration. The process of releasing hydrogen based on the difference in hydrogen absorption between different phases is called dehydrogenation. The conditions for dehydrogenation are not particularly limited; for example, dehydrogenation can be carried out at 300–650°C, in an argon atmosphere, or in a vacuum. Furthermore, the fine pulverization stage can be carried out by adding lubricants such as oleamide, laurylamide, or zinc stearate as pulverization aids to the coarsely pulverized powder, and then performing fine pulverization using, for example, a jet mill or a wet atritor. There are no particular limitations on the particle size of the resulting micronized powder (raw material powder). For example, it is possible to perform micronization to obtain raw material powder with a particle size (D50) of 1 μm to 10 μm.

[0061] Then, the above magnetic powder is pressed into shape ( Figure 5 (Process S1). Rare-earth magnets can be obtained when the magnetic powder is a rare-earth magnet material, and ferrite magnets can be obtained when the magnetic powder is ferrite. As an example, the pressing process in process S1 is achieved through… Figure 6 Perform the steps shown. Figure 6 (a) indicates the situation where magnetic powder 50 is filled into the opening 12 of the mold 1. At this time, the lower opening of the opening 12 is closed by the lower punch 60. When the upper punch 70 descends, the upper opening of the opening 12 is closed, as shown in the image. Figure 6 As shown in (b), a magnetic field along the second direction D2 is applied to the mold 1, and the magnetic powder 50 is oriented along the direction of the magnetic field. Then, under the applied magnetic field, the upper punch 70 further descends, and the magnetic powder 50 filling the opening 12 is pressed between the upper punch 70 and the lower punch 60 in the first direction D1. Since the pressed first direction D1 is perpendicular to the second direction D2 of the applied magnetic field, this pressing molding is called right-angle magnetic field molding (transverse magnetic field compacting). The upper punch 70 and the lower punch 60 can be made of magnetic materials, such as hard alloys or carbon steel, which are soft magnetic materials. After the pressing molding is completed, the applied magnetic field is cut off, and demagnetization is performed by alternating magnetic field. As a result, as Figure 6 As shown in (c), a compact 51 can be formed with magnetic powder oriented in the second direction D2.

[0062] In the pressing process S1, pressure can be applied between 30 MPa and 300 MPa. The applied magnetic field can be between 950 kA / m and 1600 kA / m. The applied magnetic field is not limited to a static magnetic field; it can also be a pulsed magnetic field. Furthermore, a static magnetic field and a pulsed magnetic field can be used together.

[0063] Then, the compact 51 taken out of the mold 1 is fired under known firing conditions, thereby forming a sintered body oriented in the second direction D2. Figure 5 (Process S2). By magnetizing the sintered body along the second direction D2 using a known method, a sintered magnet 52 magnetized in the second direction D2 can be obtained. From the perspective of firing the compact 51, process S2 can be regarded as a firing process, and therefore will be described as a firing process in the following description. However, from the viewpoint that the compact 51 is sintered, it can also be regarded as a sintering process.

[0064] The sintering process S2 is a process of sintering the compact 51 under a vacuum or inert gas atmosphere to obtain a sintered body. The sintering temperature needs to be adjusted according to various conditions such as composition, grinding method, particle size, and particle size distribution. For example, the compact is heated to 1000°C or 1200°C for 1 to 10 hours under vacuum or in the presence of an inert gas, thereby performing sintering. This yields a high-density sintered body. Furthermore, the entire process, from hydrogen-absorbing grinding to sintering, can be carried out under a low-oxygen atmosphere with an oxygen concentration below 230 ppm.

[0065] The aging process involves heating the sintered body after the firing process in a vacuum or inert gas atmosphere at a temperature lower than the sintering temperature. There are no particular limitations on the temperature and time of the aging process; for example, it can be carried out at temperatures between 450°C and 900°C for 0.2 hours to 3 hours. Furthermore, this aging process can be omitted.

[0066] Furthermore, the aging process can be carried out in one stage or in two stages. In the case of two stages, for example, the first stage can be carried out at a temperature between 700°C and 900°C for 0.2 to 3 hours, and the second stage can be carried out at a temperature between 450°C and 700°C for 0.2 to 3 hours. Furthermore, the first and second stages can be carried out consecutively, or the first stage can be followed by cooling to near room temperature and then reheating for the second stage.

[0067] The obtained sintered body can be subjected to a diffusion treatment that allows heavy rare earth elements to diffuse from the outside of the sintered body to the inside. There are no particular limitations on the diffusion treatment method. For example, it can be a coating diffusion method in which powder or foil containing heavy rare earth elements is brought into close contact with the sintered body and heat-treated, or it can be a gas-phase diffusion method in which the sintered body is heat-treated in an atmosphere obtained by evaporating heavy rare earth elements.

[0068] like Figure 7 As shown, the sintered magnet 52 has a cuboid shape. Specifically, the sintered magnet 52 has a pair of main faces 52a facing each other in the pressing direction, i.e., the first direction D1, and four side faces 52b connecting the pair of main faces 52a. The sintered magnet 52 has a length w1 in the second direction D2 and a length w2 in the third direction D3. The size of the sintered magnet 52 (i.e., w1 × w2) is smaller than the size (W1 × W2) of the opening 12, which is caused by the thermal shrinkage of the compact 51 during firing. For example, the shrinkage rate (1-w1 / W1) in the second direction D2 is 20-40%, and the shrinkage rate (1-w2 / W2) in the third direction D3 is 5-32%. The shrinkage rate in the third direction D3 can be lower than the shrinkage rate in the second direction D2. For example, when the size of W1 in the opening 12 is 60 mm and the size of W2 is 60 mm, the size of W1 in the sintered magnet 52 can be 42 mm and the size of W2 can be 54 mm. With the opening 12 having a W1 dimension of 120 mm and a W2 dimension of 80 mm, the sintered magnet 52 can have a w1 dimension of 84 mm and a w2 dimension of 72 mm. Furthermore, the length (i.e., thickness) of the sintered magnet 52 in the first direction D1 can be appropriately selected according to the application.

[0069] The sintered magnet 52 is sometimes used directly at its sintered dimensions, and sometimes it is used after being appropriately cut according to its application. When used directly at its sintered dimensions, the surfaces of the sintered magnet 52 (i.e., the main surface 52a and the side surface 52b) are the original sintered surfaces (the so-called sintered surfaces). When used after cutting, at least a portion of the surface of the sintered magnet 52 becomes the cut surface. The surface of the sintered magnet 52 may be subjected to surface finishing processes such as grinding or coating as needed.

[0070] The inventors discovered that when the sintered magnet 52 is formed using right-angle magnetic field forming (transverse magnetic field forming), the orientation becomes locally disordered. This orientation disorder can be confirmed by the difference in orientation degree relative to the second direction D2 over the entire region of the sintered magnet 52 when viewed from the first direction D1. The orientation degree can be calculated using known calculation methods, for example, by using the Lotgering method of X-ray diffraction as a percentage value. Specifically, the Lotgering method is performed by mirror polishing the magnetic pole surface of the sintered magnet 52, followed by X-ray diffraction measurement of the mirror-polished surface. Then, the orientation degree is calculated based on the diffraction peaks obtained by the X-ray diffraction measurement. The orientation degree is calculated as a percentage of the quotient of the sum of the X-ray diffraction intensities I(00l) of the (00l) reflected component ΣI(00l) divided by the sum of the X-ray diffraction intensities I(hkl) of the (hkl) reflected component ΣI(hkl). Furthermore, when calculating orientation degree using the Lotgering method, the accuracy can be improved by performing vector correction on the X-ray diffraction intensity of each diffraction peak. That is, when calculating orientation degree using the Lotgering method, if only the component of complete (00l) reflection is accumulated, the calculated orientation degree may be a very small value. Therefore, by using vector correction, the component that can also be considered as (00l) reflection is accumulated, thus obtaining an orientation degree that more closely matches reality. In vector correction, diffraction peaks with X-ray orientations different from those of the (00l) plane are separated into the reflection component of the (00l) plane and the reflection component of the (hk0) plane, which is orthogonal to it. The separated reflection component of the (00l) plane is accumulated into the accumulated value ΣI(00l). For example, if the orientation of a certain crystal plane X is different from that of (00l), the diffraction peak corresponding to the orientation of that crystal plane X is multiplied by cosα based on the tilt angle α of that diffraction peak. The reflection component of the (00l) plane in the reflection component of crystal plane X is calculated using this multiplication. The reflection component of (00l) calculated based on the reflection component of crystal plane X is accumulated into the accumulated value ΣI(00l). The orientation difference is obtained by the difference between the orientation degree of the region with the maximum orientation degree and the region with the minimum orientation degree relative to the second direction D2.

[0071] exist Figure 8 In (a) to (c), the portion located on the third direction D3 during pressing is shown magnified from the first direction D1. Figure 8In (a) to (c), orientations (da, db, dc) at nine locations are shown. Orientation da has substantially 100% orientation and its direction is substantially consistent with the second direction D2. Orientation db has a relatively high but less than 100% orientation, and its direction deviates slightly from the second direction D2. Orientation dc has a lower orientation than orientation db, and its direction deviates further from the second direction D2 compared to orientation db. Therefore, in Figure 8 In (a) to (c), the region with orientation da has the highest orientation degree, and the region with orientation dc has the lowest orientation degree. In this case, regarding the difference in orientation degree, Figure 8 (a) and Figure 8 Method (b) has the same orientation difference (da-dc), in Figure 8 There is no orientation difference in method (c) (orientation difference = 0).

[0072] As a way in which the orientation of the sintered magnet 52 is locally disrupted, one could consider, for example... Figure 8 Like the orientations db and dc in (a), the orientation is near the end face on the third direction D3 in a direction away from the end face, or as... Figure 8 As in (b) db and dc, the magnetic powder 50 is oriented in a direction close to the end face near the third direction D3. This can be attributed to the fact that when the magnetic powder 50 filled in the opening 12 is pressed in the first direction D1 while a magnetic field along the second direction D2 is applied, the magnetic field distribution at the end in the third direction D3 becomes uneven. The magnetic field distribution is determined by the size of the magnetic poles and the distance between the poles of the pair of electromagnet coils used to generate the magnetic field, which are sandwiched between the mold 1 in the second direction D2. Both electromagnet coils are, for example, wound around a common center line that coincides with the reference line L1 when viewed from the first direction D1. In this case, the magnetic flux within the mold 1 formed by the pair of electromagnet coils is approximately parallel to the second direction D2 near the center line, but expands outwards (i.e., towards the third direction D3) with increasing curvature as it moves away from the center line. Therefore, near the end in the third direction D3 of the opening 12, the magnetic flux is inclined relative to the second direction D2, making the magnetic field distribution prone to becoming uneven.

[0073] The aforementioned mold 1 includes a pair of second magnetic yokes 40A and 40B, which allow adjustment of the magnetic flux of the magnetic field applied during pressing. That is, the second magnetic yokes 40A and 40B attract surrounding magnetic flux, thereby... Figure 8 (a) and Figure 8 The deviations in orientation, such as db and dc, caused by the local magnetic flux disturbance shown in (b) are corrected, resulting in an orientation close to... Figure 8The magnetic field is oriented in an ideal direction along the magnetization direction, as shown in (c). By homogenizing the magnetic field distribution, high magnetic properties of the sintered magnet 52 obtained from mold 1 can be achieved. After homogenizing the magnetic field distribution through the second yoke portions 30A and 30B, the yoke portions 30A and 30B are magnetized overall along the magnetization direction. Through the above structure, the magnetic field distribution is homogenized and enhanced, thereby achieving high magnetic properties of the sintered magnet 52 obtained from mold 1.

[0074] In the aforementioned mold 1, in the cross section orthogonal to the first direction D1, by extending the two ends of the first magnetic yoke portions 30A and 30B on the third direction D3 from the opening 12, the magnetic field orientation disorder at the ends or corners of the opening 12 is significantly suppressed. Near the two ends of the first magnetic yoke portions 30A and 30B on the third direction D3, the outward expansion of the magnetic flux tends to increase, but by extending the two ends from the opening 12, the outward expansion of the magnetic flux within the opening 12 can be suppressed, thereby achieving further homogenization of the magnetic field distribution.

[0075] Furthermore, in the aforementioned mold 1, in the second direction D2, the ratio (G1 / W1) of the distance G1 between the first yoke portions 30A and 30B and the opening 12 to the length W1 of the opening 12 is 3 or less. If the ratio of G1 / W1 exceeds 3, the magnetic flux within the opening 12 weakens due to the excessive distance between the first yoke portions 30A and 30B and the opening 12, resulting in a decrease in the overall orientation of the sintered magnet 52. However, if the ratio of G1 / W1 is 3 or less, the magnetic flux of the magnetic field applied during pressing is easily regulated, and further homogenization of the magnetic field distribution can be achieved, as the distance between the first yoke portions 30A and 30B and the opening 12 is not too far. When the ratio of G1 / W1 is less than 0.01, the surrounding portion 16 between the first yoke portions 30A and 30B and the opening 12 becomes thinner, making it difficult to ensure sufficient strength. Furthermore, in the aforementioned mold 1, the ratio (G2 / W2) of the distance G2 between the second yoke portions 40A and 40B and the opening 12 relative to the length W2 of the opening 12 in the third direction D3 is 3 or less. When the ratio of G2 / W2 exceeds 3, the length (thickness) of the surrounding portion 16 of the second yoke portions 40A and 40B in the third direction D3 becomes longer, leading to increased costs such as material costs, and the rectification effect becomes smaller compared to the manufacturing cost of mold 1. If the ratio of G2 / W2 is 3 or less, since the distance between the second yoke portions 40A and 40B and the opening 12 is not too far, the magnetic flux of the magnetic field applied during pressing is easily regulated, and further homogenization of the magnetic field distribution can be achieved. When the ratio of G2 / W2 is less than 0.05, since the surrounding portion 16 located between the second yoke portions 40A and 40B and the opening 12 becomes thinner, it is difficult to ensure sufficient strength.

[0076] In the aforementioned mold 1, the ratio (T2 / W2) of the length T2 of the second yoke portions 40A and 40B to the length W2 of the opening portion 12 in the third direction D3 is 0.01 or more. By sufficiently ensuring the length (thickness) of the second yoke portions 40A and 40B, the magnetic flux of the magnetic field applied during pressing is easily regulated, and further uniformity of the magnetic field distribution can be achieved. If the ratio T2 / W2 exceeds 0.5, as the length (thickness) of the second yoke portions 40A and 40B increases, the length (thickness) of the surrounding portion 16 holding the second yoke portions 40A and 40B in the third direction D3 also increases, leading to increased costs such as material costs. Compared with the manufacturing cost of mold 1, the rectification effect becomes smaller. Furthermore, in the aforementioned mold 1, in the second direction D2, the ratio (H2 / W1) of the length H2 of the second yoke portions 40A and 40B to the length W1 of the opening 12 is 0.01 or more. By sufficiently ensuring the lengths of the second yoke portions 40A and 40B, the magnetic flux of the magnetic field applied during pressing is easily organized, and further homogenization of the magnetic field distribution can be achieved. If the H2 / W1 ratio exceeds 0.8, the magnetic flux is concentrated in the second yoke portions 40A and 40B, the magnetic flux within the opening 12 weakens, and the overall orientation of the sintered magnet 52 decreases.

[0077] In the aforementioned mold 1, by ensuring that the ratio (T2 / H1) of the length T2 of the second yoke portions 40A and 40B to the length H1 of the first yoke portions 30A and 30B in the third direction D3 is 0.01 or more, the length (thickness) of the second yoke portions 40A and 40B is sufficiently ensured. This facilitates the regulation of the magnetic flux of the magnetic field applied during pressing and molding, thereby achieving further homogenization of the magnetic field distribution. If the ratio T2 / H1 exceeds 0.5, as the length (thickness) of the second yoke portions 40A and 40B increases, the length (thickness) of the surrounding portion 16 of the second yoke portions 40A and 40B in the third direction D3 also increases, leading to increased material costs and a smaller rectification effect compared to the manufacturing cost of mold 1. Furthermore, in the aforementioned mold 1, in the second direction D2, the ratio (H2 / T1) of the length H2 of the second yoke portions 40A and 40B to the length T1 of the first yoke portions 30A and 30B is 0.05 or more. By sufficiently ensuring the length of the second yoke portions 40A and 40B, the magnetic flux of the magnetic field applied during pressing is easily organized, and further homogenization of the magnetic field distribution can be achieved. If the ratio of H2 / T1 exceeds 12, the magnetic flux is concentrated in the second yoke portions 40A and 40B, and the magnetic flux in the opening 12 weakens, resulting in a decrease in the overall orientation of the sintered magnet 52. If the ratio of H2 / T1 is less than 12, the magnetic flux is easily concentrated in the opening 12. If the ratio of H2 / T1 is less than 8, the magnetic flux is even more easily concentrated in the opening 12, thereby improving the overall orientation of the sintered magnet 52.

[0078] In the above embodiments, each of the second magnetic yoke portions 40A and 40B is composed of a single magnetic yoke member, but they may also be composed of multiple magnetic yoke members. The relative positions of the multiple magnetic yoke members with respect to the opening 12 can be appropriately designed and modified.

[0079] For example, such as Figure 9 As shown, the second yoke portions 40A and 40B can each be composed of two yoke members 41 and 42 sandwiching the reference line L2. Even when composed of two yoke members 41 and 42, the pair of second yoke portions 40A and 40B are symmetrically arranged with respect to the reference line L2 in a cross section orthogonal to the first direction D1. Furthermore, the yoke member 41 constituting the second yoke portion 40A and the yoke member 41 constituting the second yoke portion 40B are arranged in opposite positions in the third direction D3, and the yoke member 42 constituting the second yoke portion 40A and the yoke member 42 constituting the second yoke portion 40B are also arranged in opposite positions in the third direction D3. More specifically, the centers of the yoke members 41 and 42 in the second direction D2 are located on the line L3 that divides the opening 12 into four equal parts in the second direction D2.

[0080] Magnetic yoke components 41 and 42 can also be as follows Figure 10 As shown, the magnetic flux is biased towards the reference line L2 with the center of the second direction D2 close to the reference line L2. In this case, the magnetic flux disturbance generated near the reference line L2 is rectified. The yoke components 41 and 42 can also be... Figure 11 As shown, the magnet deflects to the side opposite to the reference line L2, with its center in the second direction D2 away from the reference line L2. In this case, the magnetic flux disturbance generated at the corner of the sintered magnet 52 away from the reference line L2 is regulated. By preventing the two ends of the yoke members 41 and 42 in the second direction D2 from extending out of the opening 12, the magnetic flux disturbance of the magnetic field applied to the opening 12 can be efficiently regulated. Furthermore, by preventing the two ends of the yoke members 41 and 42 in the second direction D2 from extending out of the opening 12, the excessive outflow of magnetic flux toward the mold 1 (more specifically, the surrounding portion 16) in the second direction D2 can be suppressed, thus enhancing the magnetic field applied to the opening 12.

[0081] In the above embodiment, a pair of second yoke portions 40A and 40B are shown to be completely opposite each other in a cross section orthogonal to the first direction D1, along a third direction D3. However, as long as the opening 12 is sandwiched in the third direction D3, the second yoke portions 40A and 40B can also be partially opposite each other. Furthermore, in a cross section orthogonal to the first direction D1, the pair of second yoke portions 40A and 40B can also be arranged asymmetrically with respect to the reference line L2. The cross-sectional dimensions and shapes of the second yoke portions 40A and 40B can be different from each other, and the cross-sectional dimensions and shapes of the yoke members 41 and 42 constituting the second yoke portions 40A and 40B can also be different from each other.

[0082] This disclosure is not limited to the embodiments described above, and various modifications are possible. For example, the first magnetic yoke portions 30A and 30B and the second magnetic yoke portions 40A and 40B can be constructed separately or integrally. Furthermore, the magnetic yoke portions 30A, 30B, 40A, and 40B do not necessarily need to be embedded in the surrounding portion 16; for example, they can be mounted on the surface of the surrounding portion 16. The magnetic yoke portions 30A, 30B, 40A, and 40B may be shorter than the entire length of the surrounding portion 16 in the first direction D1. The pair of second magnetic yoke portions 40A and 40B may or may not clamp the opening 12 in the third direction D3. Furthermore, the opening 12 provided in the mold 1 may also be divided into multiple parts (e.g., bisected) by a partition wall extending in the second direction D2 or in the third direction D3 when viewed from the first direction D1.

[0083] (Example)

[0084] In order to confirm the effectiveness of the present invention, the inventors, etc., Figures 12-33 The orientation difference was measured by changing various set values. The set values ​​shown in the table (i.e., values ​​other than magnetic flux density difference, maximum angle difference, and orientation difference) were calculated using electromagnetic field analysis software (JMAG, manufactured by JSOL Co., Ltd.). The orientation difference is the actual measured value of the sintered body obtained through the above embodiment. On the other hand, the magnetic flux density difference and maximum angle difference are the values ​​when the magnetic field is applied ( Figure 6 (b) represents the simulated value calculated using the aforementioned electromagnetic field analysis software. Regarding the magnetic flux density difference, the difference in magnetic flux density between the location with the maximum and minimum magnetic flux density in the entire region of the magnetic powder was calculated. For the maximum angle difference, the angle of magnetic flux density in the entire region of the magnetic powder was calculated, which is the maximum value of the angle difference (i.e., angle deviation) tilted towards the third direction D3 with the second direction D2 as the reference.

[0085] (Example 1)

[0086] Example 1 adopted Figure 4The shape shown has the following set values, magnetic flux density difference, maximum angular difference, and orientation difference as follows: Figures 12-15 The table shows the specific settings, including: the length of the opening in the second direction (W1), the length of the opening in the third direction (W2), the length of the first yoke in the third direction (H1), the length of the second yoke in the second direction (H2), the length of the first yoke in the second direction (T1), the length of the second yoke in the third direction (T2), the distance between the first yoke and the opening in the second direction (G1), and the distance between the second yoke and the opening in the third direction (G2). In all embodiments of Example 1 (Examples 1-1 to Example 1-48), the orientation difference was less than 10%, confirming a high orientation degree. In the examples where the orientation difference is less than 5% (Examples 1-1 to 1-4, Examples 1-6 to 1-8, Examples 1-10 to 1-12, Examples 1-14 to 1-16, Examples 1-18 to 1-20, Examples 1-22 to 1-24, Examples 1-26 to 1-28, Examples 1-30 to 1-32, Examples 1-34 to 1-36, Examples 1-38 to 1-40, Examples 1-42 to 1-44, Examples 1-47 to 1-48), the G2 / W2 ratio is relatively high, confirming that the orientation degree will be higher in this case.

[0087] (Example 2)

[0088] Example 2 adopted Figure 9 The shape shown has the following set values, magnetic flux density difference, maximum angular difference, and orientation difference as follows: Figures 16-25 The table shows the specific settings, including: the length of the opening in the second direction (W1), the length of the opening in the third direction (W2), the length of the first yoke in the third direction (H1), the length of the second yoke in the second direction (H2), the length of the first yoke in the second direction (T1), the length of the second yoke in the third direction (T2), the distance between the first yoke and the opening in the second direction (G1), the distance between the second yoke and the opening in the third direction (G2), and the distance between the first yoke and the second yoke in the second direction (P1). In all embodiments of Example 2 (Examples 2-1 to 2-119), the orientation difference was less than 10%, confirming a high orientation degree. In embodiments with an orientation difference of less than 5% (Examples 2-1 to 2-46, Examples 2-48 to 2-73, Examples 2-75 to 2-119), it was confirmed that the orientation degree would be even higher.

[0089] (Example 3)

[0090] Example 3 adopted Figure 9 The shape shown has the following set values, magnetic flux density difference, maximum angular difference, and orientation difference as follows: Figures 26-33 The table shows the specific settings, including: the length of the opening in the second direction (W1), the length of the opening in the third direction (W2), the length of the first yoke in the third direction (H1), the length of the second yoke in the second direction (H2), the length of the first yoke in the second direction (T1), the length of the second yoke in the third direction (T2), the distance between the first yoke and the opening in the second direction (G1), the distance between the second yoke and the opening in the third direction (G2), and the distance between the first yoke and the second yoke in the second direction (P1). In all embodiments of Example 3 (Examples 3-1 to Example 3-108), the orientation difference was less than 10%, confirming a high orientation degree. In the examples where the orientation difference was less than 5% (Examples 3-1 to 3-14, Examples 3-16 to 3-25, Examples 3-28 to 3-49, Examples 3-52 to 3-61, Examples 3-64 to 3-74, Examples 3-76 to 3-85, Examples 3-88 to 3-97, Examples 3-101 to 3-108), it was confirmed that the orientation difference was higher.

Claims

1. A method for manufacturing a sintered magnet, wherein, A mold was used, the mold comprising: a body having an opening for filling magnetic powder and extending in a first direction; and a magnetic yoke disposed around the opening of the body in a cross-section orthogonal to the first direction. The manufacturing method includes: A process of forming a compact by pressing magnetic powder filled in the opening in the first direction while applying a magnetic field in the second direction, wherein the second direction is orthogonal to the first direction; and The process of firing the pressed blank to form a sintered magnet. In a cross-section orthogonal to the first direction, the opening is rectangular in shape, defined by two sides extending in the second direction and two sides extending upward in a third direction, wherein the third direction is orthogonal to both the first and second directions. The magnetic yoke has, in a cross section orthogonal to the first direction, a pair of first magnetic yoke portions clamping the opening in the second direction; and a pair of second magnetic yoke portions clamping the opening in the third direction.

2. The method for manufacturing a sintered magnet as described in claim 1, wherein, In a cross section orthogonal to the first direction, the pair of second magnetic yokes face each other on the third direction and are symmetrically arranged with respect to the first reference line, which passes through the center of the opening and extends on the third direction.

3. The method for manufacturing a sintered magnet as described in claim 1, wherein, In a cross section orthogonal to the first direction, the pair of first magnetic yokes are symmetrically arranged with respect to a second reference line, which passes through the center of the opening and extends in the second direction.

4. The method for manufacturing a sintered magnet as described in claim 1, wherein, In a cross section orthogonal to the first direction, the pair of second magnetic yokes are symmetrically arranged with respect to a second reference line, which passes through the center of the opening and extends in the second direction.

5. The method for manufacturing a sintered magnet as described in claim 2, wherein, In a cross section orthogonal to the first direction, the center of each of the pair of second magnetic yokes in the second direction is located on the first reference line.

6. The method for manufacturing a sintered magnet as described in claim 2, wherein, In a cross section orthogonal to the first direction, each of the pair of second magnetic yokes is composed of multiple magnetic yoke components.

7. The method for manufacturing a sintered magnet as described in claim 6, wherein, In a cross section orthogonal to the first direction, each of the pair of second magnetic yokes is composed of two magnetic yoke members that freely clamp the first reference line.

8. The method for manufacturing a sintered magnet as described in claim 7, wherein, In a cross section orthogonal to the first direction, each magnetic yoke component is biased toward the first reference line.

9. The method for manufacturing a sintered magnet as described in claim 7, wherein, In a cross section orthogonal to the first direction, each magnetic yoke component is biased toward the side opposite to the first reference line.

10. The method for manufacturing a sintered magnet according to any one of claims 1 to 9, wherein, In a cross section orthogonal to the first direction, the length of the first magnetic yoke portion in the third direction is longer than the length of the side of the opening portion extending in the third direction.

11. The method for manufacturing a sintered magnet according to any one of claims 1 to 10, wherein, In the second direction, the ratio of the distance between the first magnetic yoke and the opening to the length of the opening is 0.01 to 3 and less, and in the third direction, the ratio of the distance between the second magnetic yoke and the opening to the length of the opening is 0.05 to 3 and less.

12. The method for manufacturing a sintered magnet according to any one of claims 1 to 11, wherein, In the third direction, the length of the second yoke portion is 0.01 to 0.5 or less relative to the length of the opening portion, and in the second direction, the length of the second yoke portion is 0.01 to 0.8 or less relative to the length of the opening portion.

13. The method for manufacturing a sintered magnet according to any one of claims 1 to 12, wherein, In the third direction, the length of the second yoke portion is 0.01 to 1 less than the length of the first yoke portion, and in the second direction, the length of the second yoke portion is 0.05 to 12 less than the length of the first yoke portion.

14. A mold, in, Includes: a body having an opening for filling magnetic powder and extending in a first direction; A magnetic yoke, which is disposed around the opening of the main body in a section orthogonal to the first direction. The mold is used to press the magnetic powder filled in the opening of the main body in the first direction while applying a magnetic field in the second direction, wherein the second direction is orthogonal to the first direction. In a cross-section orthogonal to the first direction, the opening is rectangular in shape, defined by two sides extending in the second direction and two sides extending upwards in a third direction, wherein the third direction is orthogonal to both the first and second directions. The magnetic yoke has, in a cross section orthogonal to the first direction, a pair of first magnetic yoke portions clamping the opening in the second direction; and a pair of second magnetic yoke portions clamping the opening in the third direction.

15. The mold as described in claim 14, wherein, In a cross section orthogonal to the first direction, the pair of second magnetic yokes face each other on the third direction and are symmetrically arranged with respect to the first reference line, which passes through the center of the opening and extends on the third direction.

16. The mold as claimed in claim 14, wherein, In a cross section orthogonal to the first direction, the pair of first magnetic yokes are symmetrically arranged with respect to a second reference line, which passes through the center of the opening and extends in the second direction.

17. The mold as claimed in claim 14, wherein, In a cross section orthogonal to the first direction, the pair of second magnetic yokes are symmetrically arranged with respect to a second reference line, which passes through the center of the opening and extends in the second direction.

18. The mold as claimed in claim 15, wherein, In a cross section orthogonal to the first direction, the center of each of the pair of second magnetic yokes in the second direction is located on the first reference line.

19. The mold as claimed in claim 15, wherein, In a cross section orthogonal to the first direction, each of the pair of second magnetic yokes is composed of multiple magnetic yoke components.

20. The mold as claimed in claim 19, wherein, In a cross section orthogonal to the first direction, each of the pair of second magnetic yokes is composed of two magnetic yoke members that freely clamp the first reference line.

21. The mold as claimed in claim 20, wherein, In a cross section orthogonal to the first direction, each magnetic yoke component is biased toward the first reference line.

22. The mold as claimed in claim 20, wherein, In a cross section orthogonal to the first direction, each magnetic yoke component is biased toward the side opposite to the first reference line.

23. The mold as described in any one of claims 14 to 22, wherein, In a cross section orthogonal to the first direction, the length of the first magnetic yoke portion in the third direction is longer than the length of the side of the opening portion extending in the third direction.

24. A sintered magnet, wherein, It has a pair of main faces opposite each other in a first direction and oriented in a second direction orthogonal to the first direction. When viewed from the first direction, the difference in orientation degree between the part with the maximum orientation degree and the part with the minimum orientation degree relative to the second direction is less than 10%.

25. The sintered magnet of claim 24, wherein, The orientation difference is less than 5%.

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