Laminated magnet and motor

Abstract

To reduce an eddy current loss generated inside while suppressing a decrease in degree of orientation (decrease in residual magnetic flux density Br).SOLUTION: A laminated magnet 10 includes a plurality of plate magnets 11 laminated via an insulation bonding layer 13 containing inorganic crystals 14. Two plate magnets 11, 11 adjacent each other are set in a mutual non-contact state by being divided by the insulation bonding layer 13. Each of the plate magnets 11 contains a rare earth element. A difference between the maximum value and the minimum value of a thickness T of the insulation bonding layer 13 is 10 μm or less.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to laminated magnets and motors. [Background technology]

[0002] Patent Document 1 discloses a rare earth magnet having a resistive layer formed on the surface of a magnet body, and also shows a laminated magnet in which a plurality of rare earth magnets are stacked and molded with resin. Furthermore, various magnets have been proposed with the aim of reducing eddy current loss (for example, Patent Documents 2-4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-174962 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-219911 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-157903 [Patent Document 4] Japanese Patent Application Laid-Open No. 2003-164083 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there have been various demands for laminated magnets. For example, there is a demand for new laminated magnets that can reduce eddy current loss generated inside while suppressing a decrease in the degree of orientation (a decrease in remanence Br) within the general composition range of magnets. The present disclosure has been made in consideration of the above circumstances, and aims to reduce eddy current loss generated inside a magnet while suppressing a decrease in the degree of orientation (a decrease in remanence Br) within the general composition range of a magnet. The present disclosure can be realized in the following forms. [Means for solving the problem]

[0005] [1] A laminated magnet in which a plurality of plate magnets are stacked via an insulating bonding layer containing inorganic crystals, The two adjacent plate magnets are separated by the insulating bonding layer, and are therefore not in contact with each other; the plate magnet contains a rare earth element; A laminated magnet, wherein the difference between the maximum and minimum thicknesses of the insulating bonding layers is 10 μm or less. [Effects of the Invention]

[0006] According to the present disclosure, within the general composition range of a magnet, it is possible to reduce the eddy current loss generated inside while suppressing a decrease in the degree of orientation (variation in residual magnetic flux density Br). [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view schematically illustrating an example of a laminated magnet. [Figure 2] FIG. 2 is a top view of a laminated magnet. [Figure 3] FIG. 3 is a cross-sectional view of the magnet laminate of FIG. 2 cut along an imaginary plane. [Figure 4] FIG. 2 is an enlarged view showing the vicinity of the interface between the plate magnet and the insulating bonding layer. [Figure 5] FIG. 10 is a perspective view schematically showing another example 2 of the magnet laminate. [Figure 6] FIG. 10 is a top view of another example 2 of the laminated magnet. [Figure 7] FIG. 7 is a cross-sectional view of the magnet laminate of FIG. 6 cut along an imaginary plane. [Figure 8] FIG. 4 is a cross-sectional view showing the thickness of an insulating bonding layer. [Figure 9] FIG. 4 is a cross-sectional view showing the thickness of an insulating bonding layer. [Figure 10] 1 is a cross-sectional view illustrating an insulating bonding layer, the thickness of which is to be measured; [Figure 11] FIG. 2 is a cross-sectional view schematically illustrating a part of a motor. [Figure 12] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] Here, a preferred example of the present disclosure will be described. [2] The magnet laminate according to [1], wherein the inorganic crystal is at least one selected from the group consisting of fluorides of Group 2A of the periodic table and light rare earth oxides. [3] The plate magnet is Nd2Fe 14 B is the main phase, The thickness of the plate magnet is 0.5 mm or more and 4.0 mm or less, When an imaginary line passing through the center of gravity of the laminated magnet and extending in the lamination direction is taken, and a cross section of the laminated magnet cut so as to have the largest cross-sectional area is observed on an imaginary plane including the imaginary line, The laminated magnet according to [1] or [2], wherein a Nd-rich phase having a higher Nd content than the main phase is present in a range from the interface between the plate magnet and the insulating bonding layer to a depth of 10 μm on the plate magnet side. [4] A motor having the laminated magnet according to any one of [1] to [3]. The present disclosure will be described in detail below. In this specification, when a numerical range is indicated using "-", it is assumed that both the lower and upper limits are included unless otherwise specified. For example, the expression "10-20" includes both the lower limit "10" and the upper limit "20". In other words, "10-20" has the same meaning as "10 or more and 20 or less". Furthermore, in this specification, the upper and lower limits of each numerical range can be arbitrarily combined. Hereinafter, the Z-axis direction in each figure is the arrangement direction (stacking direction) of the multiple plate magnets 11. The direction perpendicular to the Z-axis direction is the X-axis direction (also referred to as the horizontal direction), and the direction perpendicular to the Z-axis direction and the X-axis direction is the Y-axis direction (also referred to as the vertical direction). It should be noted that all of the drawings are conceptual diagrams for explaining the disclosed contents and do not accurately depict actual dimensions.

[0009] 1.Laminated magnet 10 The laminated magnet 10 is formed by stacking a plurality of plate magnets 11 via insulating bonding layers 13 containing inorganic crystals. Two adjacent plate magnets 11 are separated by the insulating bonding layers 13 and are therefore not in contact with each other.

[0010] (1) Plate magnet 11 The plate magnet 11 contains a rare earth element, and when the entire plate magnet 11 is taken as 100 mass %, The total amount of rare earth elements is 28.50 mass% or more and 31.75 mass% or less, The Co (cobalt) content is 0.80 mass% or more and 1.00 mass% or less, The Cu (copper) content is 0.02 mass% or more and 0.18 mass% or less, The content of Al (aluminum) is 0.12 mass% or more and 0.28 mass% or less. The total content of Ga (gallium) is 0.15 mass% or more and 0.25 mass% or less, The content of B (boron) is 0.92% by mass or more and 1.02% by mass or less, The balance preferably consists of Fe (iron) and unavoidable impurities. The difference between the maximum and minimum values ​​of the thickness T of the insulating bonding layer 13 is 10 μm or less.

[0011] Examples of rare earth elements include one or more selected from the group consisting of neodymium (Nd), praseodymium (Pr), terbium (Tb), dysprosium (Dy), samarium (Sm), yttrium (Y), scandium (Sc), lanthanum (La), cerium (Ce), europium (Eu), gadolinium (Gd), holmium (Ho), ytterbium (Yb), and lutetium (Lu). Among these, it is preferable to include one or more of Nd, Pr, Dy, and Tb as the rare earth element, and it is more preferable to include Nd as the main component. Note that "containing Nd as the main component" means that the content (mass %) of Nd is the highest among the rare earth elements.

[0012] The composition of the plate magnet 11 is NdFe 14It is preferable that the permanent magnet has a main phase of B. From the viewpoint of having good magnetic properties, the plate magnet 11 is preferably a rare earth sintered magnet. From the viewpoint of increasing the magnetic flux density, the total amount of rare earth elements is preferably 28.50% by mass or more and 31.75% by mass or less, more preferably 28.50% by mass or more and 30.90% by mass or less, and even more preferably 28.50% by mass or more and 30.10% by mass or less. The total amount of rare earth elements in plate magnet 11 can be measured by fluorescent X-ray analysis. The total amount of rare earth elements can be adjusted by changing the content of rare earth elements in the raw materials of plate magnet 11 and insulating bonding layer 13.

[0013] The Co (cobalt) content is preferably 0.80 mass % or more and 1.00 mass % or less, preferably 0.82 mass % or more and 0.98 mass % or less, and more preferably 0.84 mass % or more and 0.96 mass % or less. The Cu (copper) content is preferably 0.02 mass % or more and 0.18 mass % or less, preferably 0.04 mass % or more and 0.16 mass % or less, and more preferably 0.06 mass % or more and 0.14 mass % or less. The Al (aluminum) content is preferably 0.12 mass % or more and 0.28 mass % or less, preferably 0.14 mass % or more and 0.26 mass % or less, and more preferably 0.16 mass % or more and 0.24 mass % or less. The total content of Ga (gallium) is preferably 0.15 mass % or more and 0.25 mass % or less, preferably 0.17 mass % or more and 0.23 mass % or less, and more preferably 0.19 mass % or more and 0.21 mass % or less. The content of B (boron) is preferably 0.92 mass % or more and 1.02 mass % or less, preferably 0.94 mass % or more and 1.00 mass % or less, and more preferably 0.96 mass % or more and 0.98 mass % or less. The amounts of Co (cobalt), Cu (copper), Al (aluminum), Ga (gallium), and B (boron) can be measured by X-ray fluorescence analysis. The amounts of Co (cobalt), Cu (copper), Al (aluminum), Ga (gallium), and B (boron) can be adjusted by changing the content of each element in the raw materials of plate magnet 11 and insulating bonding layer 13.

[0014] The plate magnet 11 is made of Nd2Fe 14 It is preferable that B is the main phase. It is preferable that the plate magnet 11 has an Nd-rich phase that has a higher Nd content than the main phase. 14 B has a tetragonal crystal structure. The main phase of the plate magnet 11 can be identified as the component with the greatest peak intensity by XRD (X-ray diffraction) analysis of the plate magnet 11. 14 When the peak intensity of B is the largest, the plate magnet 11 is NdFe 14 It can be determined that the main phase is B.

[0015] The thickness of each plate magnet 11 is not particularly limited. The thickness of each plate magnet 11 is preferably 0.5 mm or more and 4.0 mm or less, and more preferably 1.2 mm or more and 2.5 mm or less. If the thickness of the plate magnet 11 is 0.5 mm or more, it is easy to form the plate magnet 11 while ensuring an average degree of orientation. If the thickness of the plate magnet 11 is 4.0 mm or less, it is easy to diffuse the heavy rare earth element to the interior. Furthermore, if the thickness is 4.0 mm or less, eddy current loss inside the magnet laminate 10 can be suitably reduced. The dimensions of the plate magnet 11 in the direction perpendicular to the thickness are not particularly limited. For example, the plate magnet 11 can be 0.5 mm or more and 4.0 mm or less in thickness, 4 mm or more and 10 mm or less in length, and 10 mm or more and 30 mm or less in width. The heavy rare earth element may be at least one selected from the group consisting of terbium (Tb), dysprosium (Dy), gadolinium (Gd), holmium (Ho), europium (Eu), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Of these, the heavy rare earth element is preferably at least one of Dy and Tb.

[0016] When a cross section of the magnet laminate 10 is observed along a virtual line L1 that passes through the center of gravity G1 of the magnet laminate 10 and extends in the stacking direction, and cut along a virtual plane VP that includes the virtual line L1 so that the cross-sectional area of ​​the magnet laminate 10 is maximized, it is preferable that a Nd-rich phase 17A with a higher Nd content than the main phase is present in the range from the interface I between the sheet magnet 11 and the insulating bonding layer 13 to a depth of 10 μm on the sheet magnet 11 side (see FIG. 4). Note that inorganic crystals 14 (e.g., fluoride particles of a metal of Group 2A of the periodic table) may be present in the range from the interface I between the sheet magnet 11 and the insulating bonding layer 13 to a depth of 10 μm on the sheet magnet 11 side.

[0017] A cross section of the magnet laminate 10 will be described in detail with reference to FIGS. 1 to 3. In the magnet laminate 10, an imaginary line L1 that passes through the center of gravity G1 in FIG. 1 and extends in the stacking direction extends in the Z-axis direction. An imaginary plane VP that cuts the magnet laminate 10 so that its cross-sectional area is maximized is a plane that includes the imaginary line L1, as shown in FIG. 2. In a cross section cut by the imaginary plane VP, multiple cut surfaces of the plate magnet 11 appear, as shown in FIG. 3. The cut surface of each plate magnet 11 forms a rectangular planar shape. In the magnet laminate 10 of FIGS. 5 to 7, the imaginary line L1 also extends in the Z-axis direction. The imaginary plane VP is a plane that includes the imaginary line L1. In a cross section cut along the imaginary plane VP, multiple cut surfaces of the plate magnet 11 appear, as shown in FIG. 7. Each cut surface of the plate magnet 11 forms a rectangular planar figure.

[0018] FIG. 4 is an enlarged schematic view of region R0 of the magnet laminate 10 in FIG. 3. The main surface 11A (upper bottom surface 11A1 described later) of the plate magnet 11 constitutes an interface I between the plate magnet 11 and the insulating bonding layer 13. The interface I between the plate magnet 11 and the insulating bonding layer 13 can be identified by image analysis using, for example, an EPMA. The Nd-rich phase 17A is composed of NdFe 14 The Nd-rich phase 17A has a higher Nd content than the B main phase (e.g., main phase particles 19). The Nd-rich phase 17A is, for example, layered on the surface of the sheet magnet 11. Note that at least a portion of the inorganic crystals 14 may be included in the layered Nd-rich phase 17A. In this case, the sheet magnet 11 can also be said to have a surface layer 17 of the Nd-rich phase 17A that includes the inorganic crystals 14. The presence of the Nd-rich phase 17A and inorganic crystals 14 in the range from the interface I between the plate magnet 11 and the insulating bonding layer 13 to a depth of 10 μm on the plate magnet 11 side can be expected to have the following effects. That is, with this configuration, insulation between the plate magnets 11 can be preferably ensured compared to when only the Nd-rich phase 17A is present. Therefore, the eddy current loss of the magnet laminate 10 can be preferably reduced. The presence of the Nd-rich phase 17A and the inorganic crystals 14 can be confirmed, for example, by subjecting a cross section of the magnet laminate 10 to micro X-ray analysis or XRD analysis in combination with composition analysis by EPMA. Furthermore, the requirements regarding the interface I between the plate magnet 11 and the insulating bonding layer 13 need only be met in at least one of multiple 50 μm x 50 μm square fields of view when observing the cross-sectional structure of the laminated magnet 10.

[0019] Generally, the lower the total amount of rare earth elements in sheet magnet 11, the less likely Nd-rich phase 17A is present near interface I between sheet magnet 11 and insulating bonding layer 13. The reason for this is presumed to be as follows: the lower the total amount of rare earth elements in sheet magnet 11, the less likely Nd-rich components derived from the main phase to flow to the surface of sheet magnet 11. The present inventors have newly discovered that even in laminated magnet 10 using sheet magnet 11 with a low total amount of rare earth elements (31.75 mass% or less), Nd-rich phase 17A can be present near interface I by hot pressing. Furthermore, they have developed a technology for using inorganic crystals 14 as the raw material for insulating bonding layer 13 to cause Nd-rich phase 17A and inorganic crystals 14 to be present near interface I. The method for making the Nd-rich phase 17A and the inorganic crystal 14 exist near the interface I by hot pressing will be explained later.

[0020] The thickness of the surface layer 17 of the Nd-rich phase 17A is not particularly limited. From the viewpoint of reducing eddy current loss, the thickness of the surface layer 17 is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 25 μm or more. The upper limit of the thickness of the surface layer 17 is not particularly limited, and is usually 40 μm or less. The thickness of the surface layer 17 can be measured, for example, by subjecting a cross section of the magnet laminate 10 to micro X-ray analysis or XRD analysis in combination with composition analysis by EPMA.

[0021] (2) Insulating bonding layer 13 The insulating bonding layer 13 is not particularly limited as long as it contains inorganic crystals 14. The insulating bonding layer 13 preferably contains inorganic crystals 14 as a main component. Incidentally, containing inorganic crystals 14 as a main component means that the content of inorganic crystals 14 in the insulating bonding layer 13 is 50 mass % or more. The content of inorganic crystals 14 in the insulating bonding layer 13 is preferably 80 mass % or more, more preferably 90 mass % or more, and may be 100 mass %. The composition of insulating bonding layer 13 can be analyzed by the following method: The presence of inorganic crystals 14 is determined by micro X-ray analysis or XRD analysis, and the content of inorganic crystals 14 is calculated in combination with composition analysis by EPMA (Electron Probe Micro Analyser).

[0022] From the viewpoint of reducing eddy current loss, the inorganic crystal 14 is preferably one or more selected from the group consisting of Group 2A fluorides of the periodic table and light rare earth oxides. The Group 2A fluorides are preferably one or more selected from the group consisting of CaF2, BaF2, SrF2, and MgF2. Among these, it is particularly preferable to include CaF2. The light rare earth oxide is preferably one or more selected from the group consisting of Nd2O3, Sm2O3, Pr2O3, and La2O3. When the entire inorganic crystal 14 is taken as 100 mass %, the insulating bonding layer 13 preferably contains 80 mass % or more, more preferably 90 mass % or more, and even more preferably 95 mass % or more of the fluoride of Group 2A of the periodic table as the inorganic crystal 14. The upper limit of the content of the fluoride of Group 2A of the periodic table is not particularly limited and may be, for example, 100 mass %.

[0023] When insulating bonding layer 13 is primarily composed of a Group 2A fluoride of the periodic table, the raw material for insulating bonding layer 13 preferably contains a compound of the above-mentioned heavy rare earth element in addition to the Group 2A fluoride of the periodic table. If the raw material for insulating bonding layer 13 contains a compound of the above-mentioned heavy rare earth element, the heavy rare earth element can be favorably diffused into plate magnet 11. Note that the heavy rare earth element contained in the raw material for insulating bonding layer 13 diffuses into plate magnet 11 after heat treatment. Therefore, insulating bonding layer 13 of the obtained magnet laminate 10 contains almost no heavy rare earth element. There is no particular limitation on the mass ratio of the Group 2A fluoride of the periodic table to the compound of the heavy rare earth element in the raw materials of insulating bonding layer 13. The mass ratio of the Group 2A fluoride of the periodic table to the compound of the heavy rare earth element in the raw materials of insulating bonding layer 13 can be, for example, 20:80 to 40:60.

[0024] The thickness T of the insulating bonding layer 13 is not particularly limited. From the viewpoint of ensuring sufficient insulation, the thickness T of the insulating bonding layer 13 is preferably 5 μm or more, more preferably 9 μm or more, and even more preferably 12 μm or more. From the viewpoint of ensuring magnetic properties, the thickness T of the insulating bonding layer 13 is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 18 μm or less. From these viewpoints, the thickness T of the insulating bonding layer 13 is preferably 5 μm or more and 30 μm or less, more preferably 9 μm or more and 25 μm or less, and even more preferably 12 μm or more and 18 μm or less. The thickness T of the insulating bonding layer 13 is measured, for example, by observing the cross section of the magnet laminate 10 with a scanning electron microscope (SEM) and measuring the distance between the plate magnets 11 located on both sides of the insulating bonding layer 13 (see FIG. 8). Specifically, as described above, an imaginary line L1 is taken that passes through the center of gravity G1 of the magnet laminate 10 and extends in the stacking direction, and a cross section of the magnet laminate 10 cut so as to have the largest cross-sectional area is observed on an imaginary plane VP that includes the imaginary line L1.

[0025] In the present disclosure, from the viewpoint of suppressing a decrease in the degree of orientation (a decrease in the residual magnetic flux density Br) while reducing eddy current loss generated inside, the difference between the maximum and minimum values ​​of the thickness T of the insulating bonding layer 13 is 10 μm or less, preferably 8 μm or less, more preferably 4 μm or less, and most preferably 0 μm. Fig. 8 schematically shows the concept when the difference between the maximum and minimum values ​​is small, and Fig. 9 schematically shows the concept when the difference between the maximum and minimum values ​​is large. The maximum and minimum values ​​of the thickness T of the insulating bonding layer 13 can be determined by measuring the thickness T at 2 μm intervals from one end of the insulating bonding layer 13 to the other end when it is sandwiched between the plate magnets 11 in an SEM cross section. In addition, when the magnet laminate 10 has multiple insulating bonding layers 13, the difference between the maximum and minimum thicknesses T of the insulating bonding layers 13 is determined as follows. First, the maximum and minimum thicknesses are determined for each insulating bonding layer 13, and the difference is calculated. The largest of the differences thus determined is defined as the "difference between the maximum and minimum thicknesses of the insulating bonding layers 13" in this disclosure. In this disclosure, the difference between the maximum and minimum thicknesses T determined in this manner is 10 μm or less, and therefore the difference between the maximum and minimum thicknesses T of all insulating bonding layers 13 is also 10 μm or less.

[0026] The insulating bonding layer 13 is a layer that bonds the multiple plate magnets 11, 11 together in a stacked state. The insulating bonding layer 13 keeps two adjacent plate magnets 11, 11 from contacting each other. Therefore, even if layers with the same composition as the insulating bonding layer 13 are formed on the top, bottom, and side surfaces of the magnet stack 10, these layers do not keep the plate magnets 11, 11 from contacting each other, and therefore are not treated as "insulating bonding layers 13" for measuring the thickness T in this disclosure. For example, in Figure 10, the layers indicated by cross-hatching have the same composition as the insulating bonding layer 13, but are not treated as "insulating bonding layers 13" for measuring the thickness T.

[0027] The insulating bonding layer 13 is provided so as to be in direct contact with the plate magnet 11. The insulating bonding layer 13 also bonds (adheses) the plate magnets 11, 11 located on both sides. Such a laminated magnet 10 can be suitably formed by hot pressing.

[0028] The difference between the maximum and minimum values ​​of the thickness T of the insulating bonding layer 13 being 10 μm or less is one indicator that the plate magnets 11 are arranged approximately parallel. With a configuration in which the difference between the maximum and minimum values ​​is 10 μm or less, the orientation direction of the plate magnets 11 can be aligned, and the magnetic flux density of the magnet stack 10 can be improved. The difference between the maximum and minimum values ​​of the thickness T of the insulating bonding layer 13 can be reduced by reducing the unevenness in the thickness of the raw material applied when forming the insulating bonding layer 13. The unevenness in the thickness of the applied raw material can be reduced by controlling the amount and number of times the raw material is applied. This difference can also be reduced by increasing the temperature and / or pressing pressure in the hot press. It can also be adjusted by changing the pressing speed.

[0029] The insulating bonding layers 13 may be provided along the orientation direction of the magnetic field of each plate magnet 11 (for example, the direction of the white arrow in FIG. 3), or along a direction intersecting the orientation direction (for example, the Z-axis direction in FIG. 3). Note that, as shown in FIG. 11, when the magnet stack 10 is used as a motor magnet or the like, the insulating bonding layers 13 are preferably provided along the orientation direction of the plate magnets 11 (the X-axis direction in FIG. 11) from the perspective of efficiently reducing eddy current loss. With this configuration, the insulating bonding layers 13 are arranged approximately parallel to the direction in which the magnetic flux generated in the stator 31 passes through the magnet stack 10 (the X-axis direction in FIG. 11), thereby effectively reducing eddy current loss.

[0030] (3) Configuration of the magnet stack 10 From the viewpoint of reducing eddy current loss, it is preferable that 10 or more plate magnets 11 are used per 50 mm of dimension of the magnet stack 10 in the stacking direction, preferably 20 or more, and preferably 25 or more. There is no particular upper limit on the number of magnets, and it may be, for example, 42 or less.

[0031] 2. Manufacturing method of laminated magnet 10 There are no particular limitations on the method for manufacturing the magnet laminate 10. An example of a method for manufacturing the magnet laminate 10, in which plate magnets 11 and insulating bonding layers 13 are alternately stacked, will be described below.

[0032] (1)SC alloy preparation process A raw alloy (strip cast alloy (SC alloy)) containing rare earth elements, transition metal elements, boron, and the like is prepared.

[0033] (2) Hydrocracking process In a hydrogen atmosphere, the SC alloy is allowed to absorb hydrogen at a predetermined temperature (for example, 200°C) for a predetermined time (for example, 1 hour to 5 hours), thereby embrittling the grain boundaries (Nd-rich phase) of the SC alloy.

[0034] (3) Coarse grinding step, first lubricant addition step The SC alloy powder that has undergone the hydrogen cracking process is coarsely crushed (coarse crushing process). At this time, a lubricant may be added to the SC alloy powder (first lubricant addition process). This process may be carried out, for example, in an inert atmosphere (nitrogen atmosphere, argon atmosphere, etc.).

[0035] (4) Fine pulverization process, second lubricant addition process The SC alloy powder after the coarse pulverization step is then pulverized to a predetermined average particle size D50 (fine pulverization step). The average particle size D50 can be, for example, 2.0 μm-3.5 μm. At this time, to improve the flowability of the pulverized powder, a lubricant may be added to the pulverized SC alloy powder (second lubricant addition step). This step is preferably carried out in an inert atmosphere (such as a nitrogen atmosphere or an argon atmosphere).

[0036] (5) Powder filling process, orientation process, molding process The SC alloy powder after the pulverization process is filled into a mold. This process is preferably carried out in an inert atmosphere (such as a nitrogen atmosphere or an argon atmosphere). The mold has multiple molding spaces of a predetermined thickness. Each molding space is separated, for example, by multiple partition plates. A magnetic field is applied in a predetermined direction to the mold after the powder has been filled to align the orientation of the SC alloy powder. The SC alloy powder filled into the mold is then compressed to form an SC alloy compact. In this way, an SC alloy compact with a predetermined degree of orientation (for example, an average orientation of 90% or more) and a predetermined thickness (for example, a thickness of 0.5 mm to 4.0 mm) can be obtained without a cutting process.

[0037] (6) Mold removal process, first firing process The compact is removed from the mold (molding removal step). The compact is then fired at a predetermined firing temperature (e.g., 900°C-1200°C) for a predetermined time (e.g., 2 hours-5 hours) (first firing step). This firing is preferably carried out in a vacuum. Prior to this firing, heating at a temperature lower than the firing temperature may be carried out for dehydrogenation.

[0038] (7) Insulating bonding layer coating process The raw material for the insulating bonding layer 13 is applied to the surface of the sintered compact. The raw material for the insulating bonding layer 13 can be, for example, a mixture of raw material powder of inorganic crystal components, compound powder containing a heavy rare earth element, and a solvent. The raw material for the insulating bonding layer 13 may be applied to at least one main surface of the compact, or may be applied to both main surfaces. The main surface of the compact is the surface corresponding to the main surface 11A of the plate magnet 11. The raw material for the insulating bonding layer 13 may be applied to the entire surface of the compact, i.e., both main surfaces and side surfaces if the compact is plate-shaped.

[0039] (8) Laminate temporary fixing process A predetermined number of compacts coated with the raw material of the insulating bonding layer 13 are stacked and temporarily fixed. Hereinafter, the stack of temporarily fixed compacts will also be referred to as a laminate. This method makes it possible to manufacture plate magnet 11 without the need for a cutting process or other process to cut out plate-shaped magnets from a larger magnet.

[0040] (9) Hot pressing process The temporarily fixed laminate is placed in a hot press mold and subjected to uniaxial hot pressing. This process is carried out, for example, under a vacuum atmosphere (for example, 10 -3 Pa-10 -4 The hot pressing may be carried out under a pressure of 1000 psi (1000 Pa) or in an inert atmosphere (such as a nitrogen atmosphere or an argon atmosphere). The hot pressing temperature may be, for example, 700°C to 1100°C. The hot pressing time may be, for example, 1 second to 1 hour. The hot pressing pressure is preferably 3 MPa or more, more preferably 5 MPa or more, and even more preferably 8 MPa or more. The upper limit of the hot pressing pressure is not particularly limited, and is, for example, 100 MPa or less. The heat treatment time for the hot pressing may be, for example, 10 minutes to 20 hours. Through the above series of steps, a magnet stack 10 is manufactured, which includes plate magnets 11 and insulating bonding layers 13. The magnet stack 10 is formed by bonding a plurality of plate magnets 11 together with the insulating bonding layers 13, forming an integrated unit.

[0041] The hot pressing process allows the heavy rare earth elements (Tb, Dy, etc.) contained in the raw material of the applied insulating bonding layer 13 to diffuse into the inside of the plate magnet 11. The hot pressing process also allows the plate magnet 11 (for example, NdFe 14 The rare earth component (Nd component) in B) flows out to the surface of plate magnet 11, and Nd-rich surface layer 17 can be formed near interface I with insulating bonding layer 13 (e.g., a layer containing CaF2) in plate magnet 11. Furthermore, this hot pressing process can sufficiently thin insulating bonding layer 13, and can also make the thickness of insulating bonding layer 13 uniform.

[0042] The laminated magnet 10 obtained in the above manner can be regarded as a laminated magnet manufactured by hot pressing (hot uniaxial pressing) a laminate in which the raw material of the insulating bonding layer 13 is sandwiched between at least a pair of plate magnets 11, 11 (sintered bodies of SC alloy), so that pressure is applied in a direction that crushes the raw material of the insulating bonding layer 13. Furthermore, the laminated magnet 10 can be understood as a laminated magnet manufactured by arranging a first plate magnet 11 (sintered body of SC alloy), the raw material of the insulating bonding layer 13, and a second plate magnet 11 (sintered body of SC alloy) in this order to form a laminate, and then heating the laminate while applying pressure to the first plate magnet 11 and the second plate magnet 11 from both sides. The raw material of insulating bonding layer 13 preferably contains inorganic crystal 14. The raw material of insulating bonding layer 13 may further contain a component containing a heavy rare earth element. For example, the raw material of insulating bonding layer 13 preferably contains 20% by mass to 40% by mass of CaF2 and 60% by mass to 80% by mass of TbF3, where the total of CaF2 and TbF3 is 100% by mass.

[0043] 3. Uses of laminated magnet 10 The uses of the magnet laminate 10 are not particularly limited. The magnet laminate 10 is suitable as a magnet for motors. The magnet laminate 10 has low eddy current loss generated internally and is resistant to deterioration over time, which can contribute to one or more of the following effects: motor miniaturization, suppression of heat generation, improved heat resistance, and improved heat dissipation. Furthermore, when the insulating bonding layer 13 of the magnet laminate 10 is primarily composed of inorganic crystals 14, its insulating performance is less susceptible to changes due to humidity, temperature, and deterioration over time than insulating bonding layers made of resin or the like. Therefore, the magnet laminate 10 is useful in a variety of applications where resistance to changes in insulating performance is desired.

[0044] An example of a motor 30 equipped with a magnet laminate 10 will be described below with reference to FIGS. 11 and 12. The motor 30 includes a stator 31 and a rotor 33 arranged inside the stator 31. The magnet laminate 10 is arranged in the rotor 33, and a winding (not shown) is arranged in the stator 31. The motor 30 in FIG. 11 is an inner rotor type in which the magnets are arranged on the inside (rotating shaft side) and the windings are arranged on the outside. The motor is not limited to the inner rotor type. For example, the motor may be an outer rotor type in which the windings are arranged on the inside (rotating shaft side) and the magnets are arranged on the outside.

[0045] The rotor 33 includes a rotating shaft 34, a rotating core 35, and a plurality of laminated magnets 10. The rotating core 35 is formed by laminating electromagnetic steel sheets. A shaft hole 37 is formed in the center of the rotating core 35. The rotating shaft 34 is inserted into the shaft hole 37. A plurality of magnet holes 39 are formed in the rotating core 35 at intervals in the circumferential direction. A laminated magnet 10 is inserted into each magnet hole 39.

[0046] 4. Actions and Effects of the Present Embodiment The magnet laminate 10 of this embodiment can reduce eddy current loss generated inside while suppressing a decrease in the degree of orientation (a decrease in the residual magnetic flux density Br) within the general composition range of a magnet. When the inorganic crystal 14 contained in the insulating bonding layer 13 is one or more selected from the group consisting of fluorides of Group 2A of the periodic table and light rare earth oxides, the eddy current loss can be reduced after being held at a high temperature of 100°C or higher for 200 hours. If an Nd-rich phase 17A having a higher Nd content than the main phase is present in the range from the interface I between the plate magnet 11 and the insulating bonding layer 13 to a depth of 10 μm on the plate magnet 11 side, the stress difference between the plate magnet 11 and the insulating bonding layer 13 is alleviated, resulting in high durability in vibration impact tests (random wave vibration test ISO-16750-3). The presence of the Nd-rich phase 17A and fluoride particles of a metal of Group 2A of the periodic table between the plate magnets 11 makes it possible to improve the insulation between the plate magnets 11 and reduce eddy current loss. [Example]

[0047] The present disclosure will be described in more detail below with reference to examples. In Table 1 below, "LRE" represents the "amount of light rare earth elements," "HRE" represents the "amount of heavy rare earth elements," and "TRE" represents the "amount of total rare earth elements."

[0048] 1. Fabrication of laminated magnets <Examples 11-15> (1)SC alloy preparation process Nd / Pr alloy, alloy containing Co, Cu, Al, Ga, Zr, and metal single material are mixed to produce strip cast alloy (SC alloy) (for example, composition: NdFe 14 B) was prepared under an argon atmosphere. The SC alloy was a plate-shaped powder with the main surface dimensions of 10 mm × 10 mm to 20 mm × 20 mm.

[0049] (2) Hydrocracking process The SC alloy was allowed to absorb hydrogen in a hydrogen furnace (hydrogen atmosphere, 200°C, 2 hours), embrittling the grain boundaries (neodymium-rich phase) of the SC alloy.

[0050] (3) Coarse grinding step, first lubricant addition step A lubricant was added to the SC alloy powder that had undergone the hydrogen crushing process. Methyl caprylate was used as the lubricant. The lubricant was mixed at a ratio of 0.03% to 0.07% by mass relative to the amount of SC alloy. While adding the lubricant to the SC alloy powder, the powder was coarsely crushed using a stirrer in a nitrogen or argon atmosphere. The average particle size of the SC alloy after coarse crushing was 50 μm to 500 μm.

[0051] (4) Fine pulverization process, second lubricant addition process The SC alloy powder after adding the lubricant was finely pulverized in a nitrogen atmosphere using a jet mill. The average particle size D50 after fine pulverization was 2.0 μm-3.5 μm. A lubricant (methyl laurate) was added to the finely pulverized SC alloy powder at a mixing ratio of 0.05% to 0.1% by mass relative to the amount of SC alloy.

[0052] (5) Powder filling process, orientation process, molding process The SC alloy powder after the pulverization and second lubricant addition processes was filled into each molding space of a mold equipped with multiple partition plates in a nitrogen atmosphere. Each compact formed in each molding space corresponds to each plate magnet to be stacked in a subsequent process. In the samples of the examples and comparative examples, each plate magnet was 2 mm thick and had a rectangular shape with dimensions of 5 mm x 16 mm. After the powder was filled into the mold, a magnetic field (e.g., 5000 V) was applied in the planar direction of each compact (perpendicular to the thickness direction) to align the orientation of the SC alloy powder. The SC alloy powder filled into the mold was pressed to form an SC alloy compact. The pressure molding conditions were: pressure: 5 MPa - 20 MPa, packing density: 3.0 g / cm 3 -4.0g / cm 3 , relative density: 40%-52%.

[0053] (6) Mold removal process, first firing process The outer frame was removed from the mold, and a series of alternating compacts and partition plates (the object to be fired) was prepared. To dehydrogenate, the object to be fired (with the partition plates) was heated at 500°C for 3-4 hours in an Ar atmosphere. The object to be fired (with the partition plates) was then fired in a vacuum atmosphere at 930-1050°C for 3 hours.

[0054] (7) Insulating bonding layer coating process After the first firing step, the partition plate was removed from the sintered object, and the raw material for the insulating bonding layer was applied to six surfaces of the magnet before lamination. The raw material for the insulating bonding layer was a mixture of the compound powder of the main components listed in Table 1, TbF3 compound powder, and a solvent. The proportion of TbF3 compound powder in the raw material for the insulating bonding layer was 10-20% by mass. The thickness of the insulating bonding layer was controlled by adjusting the thickness of the applied raw material for the insulating bonding layer. The raw material for the insulating bonding layer was applied in the air using a spray method.

[0055] (8) Laminate temporary fixing process Twenty-five magnets coated with an insulating adhesive layer were stacked in air and temporarily fixed. The number of layers was adjusted so that the dimension of the laminated magnet in the stacking direction was 50 mm. This method makes it possible to manufacture plate-shaped magnets without the need for a cutting process or other process to cut out plate-shaped magnets from a larger magnet.

[0056] (9) Hot pressing process The temporarily fixed laminate was placed in a hot press mold and subjected to uniaxial hot pressing. This process was carried out under a vacuum atmosphere (for example, 10 -3 Pa-10 -4 The reaction was carried out under 1000 kJ / cm 2 (Pa) or under an inert atmosphere (under a nitrogen atmosphere or an argon atmosphere). The specific conditions for the hot pressing step (9) in Examples 11 to 15 are as follows. Example 11 950°C-3MPa-20h Example 12 700°C-100 MPa-40 min Example 13 1100°C-3 MPa-10 min Example 14: 850°C, 50 MPa, 15 min Example 15 875°C-70 MPa-30 min As described above, samples of laminated magnets for each example were produced.

[0057] <Examples 1-10> In Example 1-10, pressure of less than 3 MPa was applied during the hot pressing step (9) above. For Examples 1-10, magnets were formed using the same steps (1)-(6) above, followed by applying a very thin layer of adhesive to the magnet surfaces, and then applying the raw material for the insulating bonding layer between adjacent magnets to bond the magnets together to produce laminated magnet samples. Note that when the above-mentioned (9) hot pressing step is performed, a surface layer is formed on the magnet, but in Examples 1-10, the pressure used in the hot pressing step was low, so no neodymium-rich layer was formed on the magnet.

[0058] <Comparative Example 1-3> In Comparative Examples 1-3, the insulating bonding layer coating step and the pressing step described below were performed instead of the insulating bonding layer coating step (7) and the hot pressing step (9). The steps other than the insulating bonding layer coating step and the pressing step described below were the same as the steps (1)-(6) and (8) above for Examples 11-15 to produce laminated magnet samples for each Comparative Example.

[0059] In Comparative Example 1-2, the resin shown in Table 1 was applied in the insulating bonding layer application step. In Comparative Example 3, alumina sol was applied in the insulating bonding layer application step.

[0060] In Comparative Example 1-2, in the pressing step, the temporarily bonded laminate was placed in a press mold and pressed uniaxially. This step was carried out in an atmospheric environment. The pressing temperature was 25°C, the pressing time was at least the time required for the resin to harden, and the pressing pressure was less than 3 MPa. In the pressing step of Comparative Example 3, the temporarily fixed laminate was placed in a press mold and pressed under uniaxial pressure under the following conditions. Comparative Example 3: 800°C, 1 MPa, 10 min

[0061] <Comparative Example 4> The magnet of Comparative Example 4 is not a laminated magnet. Therefore, Comparative Example 4 does not have an insulating bonding layer. Comparative Example 4 is not a laminated magnet, but a single block-shaped magnet. Specifically, in Comparative Example 4, the SC alloy powder after the fine pulverization step and the second lubricant addition step was filled into a molding die that was not provided with multiple partition plates. In Comparative Example 4, a block-shaped magnet was obtained without performing the (7) insulating layer application step and the (8) laminate temporary fixing step.

[0062] 2. Characteristics of Examples and Comparative Examples Tables 1 and 2 summarize the properties of the magnets and insulating bonding layers of each example and comparative example. The "Major Component" column of the "Insulating Bonding Layer" in Table 1 indicates the compound with the highest mass (% by weight) contained in the insulating bonding layer. Regarding the components of the insulating bonding layer, inorganic substances were identified using EPMA and XRD, and organic substances were identified using NMR and IR analysis. In both the examples and comparative examples, the content (mass %) of the major component was 65% or more when the entire insulating bonding layer was taken as 100 mass %. The amount (mass %) of inorganic crystals was calculated by determining the presence of inorganic crystals using micro X-ray analysis or XRD analysis and combining this with EPMA composition analysis. In the comparative examples, components other than inorganic crystals in the insulating bonding layer were considered to be the major components, and the content of the major component was calculated by subtracting the amount (mass %) of inorganic crystals from 100 (mass %). The "Thickness" column for "Insulating Bonding Layer" indicates the thickness of the insulating bonding layer. The thickness of the insulating bonding layer was measured by observing the cross section of the laminated magnet with a SEM (scanning electron microscope). Each sample of Examples 1-15 and Comparative Examples 1-3 contained multiple insulating bonding layers. In these cases, the difference between the maximum and minimum thicknesses of the insulating bonding layers was determined as follows: First, the maximum and minimum thicknesses of each insulating bonding layer were determined, and the difference was calculated. The largest of the differences thus determined was defined as the "difference between the maximum and minimum thicknesses of the insulating bonding layers" in this disclosure. For example, in the case of the sample of Example 1, there are multiple insulating bonding layers. First, the maximum and minimum thickness values ​​of each insulating bonding layer were determined, and the difference between them was calculated. Then, the insulating bonding layer with the largest difference was selected. Table 1 shows the maximum thickness (20 μm), minimum thickness (10 μm), and thickness difference (10 μm) of the insulating bonding layer selected in this way. In the sample of Example 1, the difference between the maximum and minimum thickness values ​​of the insulating bonding layer with the largest thickness difference is "10 μm," so the difference between the maximum and minimum thickness values ​​of all other insulating bonding layers is 10 μm or less.

[0063] [Table 1]

[0064] [Table 2]

[0065] 3.Performance evaluation (1) Eddy current loss (25°C, 1kHz) evaluation method After each sample was held at 100°C for 200 hours, the eddy current loss was measured at 25°C and 1 kHz. Specifically, each sample of the example and comparative example was sandwiched between the magnetic poles of a C-shaped core, and the loss at a frequency of 1 kHz and a magnetic flux density of 0.01 T was measured using a wattmeter.

[0066] Each sample was compared with a block-shaped magnet (Comparative Example 4) and evaluated as follows. Eddy current loss (25℃, 1kHz) "A"...Performance improved by more than 10% compared to the block (eddy current loss reduced). "B"...Performance improved by 5% to less than 10% compared to the block (eddy current loss reduced). "C"...Performance was equivalent to that of the block.

[0067] (2) Evaluation method for residual magnetic flux density Br Each sample (laminated magnet) was divided into three equal parts in the stacking direction, and measurement specimens measuring 2mm-7mm square were prepared from each of the three parts (upper, middle, and lower). The residual magnetic flux density (Br(T)) was measured using a pulsed BH tracer.

[0068] The evaluation was as follows: "A": The variation in the measurement values ​​for each of the measurement samples made from the three parts is less than 3%. "B": The variation in the measurement values ​​for each measurement sample made from the three parts is 3% or more and less than 5%. "C": The variation in the measurement values ​​for each of the measurement samples made from the three parts is 5% or more.

[0069] (3) Vibration and impact test The vibration and impact test was conducted in accordance with ISO-16750-3 (random wave vibration test) at a test temperature of 120°C.

[0070] The evaluation was as follows: "A": No peeling occurred even when tested for more than 30 hours. "B": No peeling occurred at 30 hours. "C": Peeled off in less than 30 hours.

[0071] 4. Evaluation Results The evaluation results are shown in Table 2. Examples 1-15 satisfy the following requirements (a)-(b). Requirement (a): A laminated magnet in which multiple plate magnets are stacked with an insulating bonding layer containing inorganic crystals interposed therebetween. Requirement (b): The difference between the maximum and minimum thicknesses of the insulating bonding layer is 10 μm or less.

[0072] In contrast, Comparative Example 1-4 does not satisfy the following requirements. Comparative Examples 1, 2, and 3 do not satisfy requirement (b). Comparative Example 4 does not satisfy requirement (a).

[0073] Examples 1-15 all fall within the general composition range for magnets. Examples 1-15 were evaluated for eddy current loss as "A" or "B." In other words, Examples 1-15 had reduced eddy current loss. In Example 1-15, the residual magnetic flux density Br was evaluated as “A” or “B.” Therefore, in Example 1-15, the variation in residual magnetic flux density Br was suppressed, and the decrease in the degree of orientation was suppressed. In contrast, the residual magnetic flux density Br of Comparative Example 1-4 was evaluated as “C.” Therefore, the residual magnetic flux density Br of Comparative Example 1-4 varied greatly, and the degree of orientation decreased significantly.

[0074] Among Examples 1 to 15, Examples 6 to 15, which further satisfied the following requirement (c), were evaluated as "A" for eddy current loss. This suggests that satisfying requirement (c) further suppresses eddy current loss. Requirement (c): The inorganic crystal is at least one selected from the group consisting of fluorides of Group 2A of the periodic table and light rare earth oxides.

[0075] Furthermore, among Examples 1-15, Examples 11-15, which further satisfied the following requirement (d), were evaluated as "A" in remanence Br and also as "A" in the vibration impact test. It was suggested that by satisfying requirement (d), the decrease in the degree of orientation was further suppressed, and vibration durability characteristics were high. Requirement (d): A Nd-rich phase containing more Nd than the main phase exists in the range from the interface between the plate magnet and the insulating bonding layer to a depth of 10 μm on the plate magnet side.

[0076] 5. Effects of the Example In this example, within the general composition range of a magnet, it was possible to reduce the eddy current loss generated inside while suppressing the decrease in the degree of orientation (variation in residual magnetic flux density Br).

[0077] The present invention is not limited to the above-described embodiments, and various modifications and variations are possible within the scope of the claims of the present invention. [Explanation of symbols]

[0078] 10...Laminated magnet 11...plate magnet 13...insulating bonding layer 14...inorganic crystals 17…Surface layer 17A...Nd-rich phase 19 …particle 30...Motor 31... Stator 33...Rotor 34...rotation axis 35...Rotating core 37... Shaft hole 39...Magnetic hole G1...center of gravity I...interface L1: Imaginary line R0…area T...Thickness VP...Virtual plane

Claims

1. A laminated magnet in which a plurality of plate magnets are stacked via an insulating bonding layer containing inorganic crystals, The two adjacent plate magnets are separated by the insulating bonding layer, and are therefore not in contact with each other; the plate magnet contains a rare earth element; A laminated magnet, wherein the difference between the maximum and minimum thicknesses of the insulating bonding layers is 10 μm or less.

2. 2. The magnet laminate according to claim 1, wherein the inorganic crystal is at least one selected from the group consisting of fluorides of Group 2A of the periodic table and light rare earth oxides.

3. The plate magnet is Nd ２ Fe １４ B is the main phase, The thickness of the plate magnet is 0.5 mm or more and 4.0 mm or less, When an imaginary line passing through the center of gravity of the laminated magnet and extending in the lamination direction is taken, and a cross section of the laminated magnet cut so as to have the largest cross-sectional area is observed on an imaginary plane including the imaginary line, 3. The laminated magnet according to claim 1, wherein a Nd-rich phase having a higher Nd content than the main phase is present in a range from the interface between the plate magnet and the insulating bonding layer to a depth of 10 μm on the plate magnet side.

4. A motor comprising the laminated magnet according to claim 1 or 2.

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