Laminated magnet and motor

Abstract

The present invention provides a novel laminated magnet which can be efficiently provided with heat resistance without excessively using a heavy rare earth element.　In the laminated magnet (10), three or more plate magnets (11) containing a rare earth element are used. In the laminated magnet (10), a plate magnet (11) and an insulating junction layer (13) are alternately laminated. Regarding a specific intermediate magnet (112A) that is any of intermediate magnets (112) obtained by excluding an uppermost magnet (111) positioned at the uppermost position and a lowermost magnet (113) positioned at the lowermost position from among the plate magnets (11), a first diffusion depth α µm measured by a measurement method (1) and a second diffusion depth β µm measured by a measurement method (2) satisfy 0.35 ≤ β / α ≤ 0.50. When the amount of the heavy rare earth element in a first region (R1) satisfying conditions (3)-(6) is defined as γ mass% and the amount of the heavy rare earth element in a second region (R2) satisfying conditions (7) and (8) is defined as δ mass%, γ / δ ≥ 5.0 is satisfied.

Description

Laminated magnet and motor

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

[0002] Patent Document 1 discloses a method for producing a rare earth permanent magnet. This method involves heat treating a sintered magnet body and powder containing a rare earth fluoride present on the surface of the sintered magnet body at a temperature below the sintering temperature of the sintered magnet body, thereby absorbing the rare earth element contained in the powder into the sintered magnet body. Furthermore, laminated magnets using multiple rare earth magnets have also been proposed (see, for example, Patent Documents 2 and 3).

[0003] JP 2008-147634 A JP 2007-266200 A JP 2020-41022 A

[0004] In recent years, there have been various demands for laminated magnets. For example, there is a demand for novel laminated magnets that can efficiently impart heat resistance without using excessive heavy rare earth elements. The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide novel laminated magnets that can efficiently impart heat resistance without using excessive heavy rare earth elements. The present disclosure can be realized in the following forms.

[0005] [1] A laminated magnet comprising three or more plate magnets each having an upper bottom surface, a lower bottom surface, and a side surface, and each containing a rare earth element, wherein the plate magnets and insulating bonding layers are alternately stacked, wherein a specific intermediate magnet is any of the intermediate magnets among the plate magnets, excluding the top magnet located at the top and the bottom magnet located at the bottom, wherein when an imaginary line passing through the center of gravity of the laminated magnet and extending in the stacking direction is taken, and a cross section of the laminated magnet cut so as to have the smallest cross-sectional area is observed on an imaginary plane including the imaginary line, the first diffusion depth αμm measured by the following measurement method (1) and the second diffusion depth βμm measured by the following measurement method (2) satisfy 0.35≦β / α≦0.50, and when the amount of heavy rare earth element in a first region that satisfies the following conditions (3) to (6) is γ% by mass, and the amount of the heavy rare earth element in a second region that satisfies the following conditions (7) to (8) is δ% by mass, the laminated magnet satisfies γ / δ≧5.0. Measurement method (1): A line analysis is performed on a line passing through the center of gravity of the planar figure of the specific intermediate magnet that appears in the cross section and extending in the stacking direction, from the top and bottom surfaces to the center of gravity of the planar figure, to obtain a first profile of the intensity of the heavy rare earth element, normalized so that the maximum intensity along that line is 1. The distance between the position of the top and bottom surfaces and the position where the intensity of the heavy rare earth element first reaches 0.7 is defined as a first diffusion depth α μm. Measurement method (2): A line analysis is performed on a line passing through the center of gravity of the planar figure of the specific intermediate magnet that appears in the cross section and extending in a direction perpendicular to the stacking direction, from the side surface to the center of gravity of the planar figure, to obtain a second profile of the intensity of the heavy rare earth element, normalized so that the maximum intensity along that line is 1. The distance between the position of the side surface and the position where the intensity of the heavy rare earth element first reaches 0.7 is defined as a second diffusion depth β μm. Condition (3): The first region is located on the specific intermediate magnet side from the interface between the specific intermediate magnet and the insulating bonding layer. Condition (4): The first region is a rectangle that is 10 μm in the stacking direction and 50 μm in the direction perpendicular to the stacking direction. Condition (5): If a line is drawn that passes through the center of gravity of the planar figure of the specific intermediate magnet that appears in the cross section and extends in the stacking direction, the center of the rectangle lies on the line. Condition (6): The rectangle is in contact with the insulating bonding layer.Condition (7): The second region is a rectangle having a size of 10 μm in the stacking direction and a size of 50 μm in the direction perpendicular to the stacking direction. Condition (8): The center of the rectangle is located at the center of gravity of the planar shape of the specific intermediate magnet that appears in the cross section.

[0006] According to the present disclosure, it is possible to provide a novel laminated magnet that can efficiently impart heat resistance without using an excessive amount of heavy rare earth elements.

[0007] 10 is a cross-sectional view of the laminated magnet of FIG. 10 cut along an imaginary plane. FIG. 11 is an enlarged view showing a portion of FIG. 3 . FIG. 12 is a diagram for explaining a method for measuring the first diffusion depth and the second diffusion depth in a plate magnet. FIG. 13 is a diagram for explaining the first region and the second region in a specific intermediate magnet. FIG. 14 is a diagram for explaining the first region in a specific intermediate magnet. FIG. 15 is an enlarged view showing the vicinity of the interface between the plate magnet and the insulating bonding layer. FIG. 16 is a diagram for explaining a method for measuring the average degree of orientation of a magnet. FIG. 17 is a cross-sectional view of the laminated magnet of FIG. 10 cut along an imaginary plane. FIG. 18 is a diagram for explaining a method for measuring the average degree of orientation of a plate magnet in other example 1. FIG. 19 ...20 is a diagram for explaining a method for measuring the average degree of orientation of a plate magnet in other example 1. FIG. 21 is a cross-sectional view of a motor. FIG. 22 is a plan view of a rotor.

[0008] Here, desirable examples of the present disclosure are described. [2] The magnet laminate according to [1], wherein the corners of the upper base surface and the side surface, or the corners of the lower base surface and the side surface, of the specific intermediate magnet are the regions where the amount of the heavy rare earth element is greatest. [3] The magnet laminate according to [1] or [2], wherein a metal element of Group 2A of the Periodic Table 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 specific intermediate magnet side. [4] The magnet laminate according to any one of [1] to [3], wherein fluoride particles of a metal element are in contact with a phase containing the heavy rare earth element and two or more metal components. [5] The magnet laminate according to [4], wherein the average particle diameter of the fluoride particles is 2.0 μm or more and 8.0 μm or less. [6] A motor having the magnet laminate according to any one of [1] to [5].

[0009] 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 limit and the upper limit are included unless otherwise specified. For example, the expression "10-20" includes both the lower limit of "10" and the upper limit of "20". In other words, "10-20" has the same meaning as "10 or more and 20 or less". In this specification, the upper and lower limit values ​​of each numerical range can be arbitrarily combined. Hereinafter, the Z-axis direction in each figure is the stacking direction (first direction) of the magnet laminate 10. One direction perpendicular to the Z-axis direction is referred to as the X-axis direction (also referred to as the second direction), and the direction perpendicular to the Z-axis direction and the X-axis direction is referred to as the Y-axis direction.

[0010] 1. Magnet Laminate 10 As shown in FIGS. 1 to 3 , the magnet laminate 10 uses three or more sheet magnets 11 containing rare earth elements. Each sheet magnet 11 has an upper bottom surface 11A1, a lower bottom surface 11A2, and a side surface 11B. The magnet laminate 10 is formed by alternating stacking of sheet magnets 11 and insulating bonding layers 13. When a virtual 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 is observed on a virtual plane VP that includes the virtual line L1, cutting the magnet laminate 10 so that its cross-sectional area is minimized, the first diffusion depth α μm measured by measurement method (1) and the second diffusion depth β μm measured by measurement method (2) satisfy the following relationship: 0.35≦β / α≦0.50. When the amount of heavy rare earth element in the first region R1 satisfying conditions (3) to (6) is γ% by mass, and the amount of heavy rare earth element in the second region R2 satisfying conditions (7) to (8) is δ% by mass, the following relationship is satisfied: γ / δ≧5.0. Measurement method (1): A line analysis is performed on a line L2 that passes through the center of gravity G2 of the planar figure of the specific intermediate magnet 112A appearing in the cross section and extends in the stacking direction, from the upper base surface 11A1 to the center of gravity G2 of the planar figure, and a first profile of the intensity of the heavy rare earth element is obtained, normalized so that the maximum intensity along that line is 1. The distance between the position of the upper base surface 11A1 and the position where the intensity of the heavy rare earth element first reaches 0.7 is defined as the first diffusion depth αμm. Measurement method (2): A line analysis is performed on a line L3 that passes through the center of gravity G2 of the planar figure of the specific intermediate magnet 112A that appears in the cross section and extends in a direction perpendicular to the stacking direction, from the side surface 11B to the center of gravity G2 of the planar figure, and a second profile of the intensity of the heavy rare earth element is obtained, normalized so that the maximum intensity along that line is 1. The distance between the position of the side surface 11B and the position where the intensity of the heavy rare earth element first becomes 0.7 is defined as the second diffusion depth β μm. Condition (3): The first region is located on the specific intermediate magnet side from the interface between the specific intermediate magnet and the insulating bonding layer. Condition (4): The first region is a rectangle that is 10 μm in the stacking direction and 50 μm in the direction perpendicular to the stacking direction.Condition (5): When a line is drawn that passes through the center of gravity of the planar figure of the specific intermediate magnet that appears in the cross section and extends in the stacking direction, the center of the rectangle lies on the line. Condition (6): The rectangle is in contact with the insulating bonding layer. Condition (7): The second region is a rectangle that is 10 μm in the stacking direction and 50 μm in a direction perpendicular to the stacking direction. Condition (8): The center of the rectangle is located at the center of gravity of the planar figure of the specific intermediate magnet that appears in the cross section.

[0011] (1) Plate Magnet 11 The plate magnet 11 is a permanent magnet containing a rare earth element. From the viewpoint of having good magnetic properties, the plate magnet 11 is preferably a rare earth sintered magnet.

[0012] The composition of the plate magnet 11 is not particularly limited as long as it contains rare earth elements. From the viewpoint of increasing the magnetic flux density, the total amount of rare earth elements in the plate magnet 11 is preferably 31.0 mass% or less, and preferably 29.5 mass% or less. The lower limit of the total amount of rare earth elements in the plate magnet 11 may be, for example, 27 mass% or more, 28 mass% or more, or 28.5 mass% or more. The total amount of rare earth elements in the plate magnet 11 can be measured by X-ray fluorescence analysis. The total amount of rare earth elements can be adjusted by changing the content of rare earth elements in the raw materials of the plate magnet 11 and the insulating bonding layer 13.

[0013] The plate magnet 11 may be, for example, a magnet containing a rare earth element (R), a transition metal element (T), and boron (B). Such a magnet is also called an RTB-based magnet.

[0014] 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, rare earth elements preferably include one or more of Nd, Pr, Dy, and Tb, and more preferably include Nd as the primary component. Note that "primarily Nd" means that the Nd content (mass%) is the highest among the rare earth elements. The B content is preferably 0.1% by mass or more and 3% by mass or less of the entire plate magnet 11, and more preferably 0.5% by mass or more and 1.5% by mass or less.

[0015] Examples of transition metal elements include one or more selected from the group consisting of iron (Fe), cobalt (Co), and nickel (Ni). Among these, from the viewpoint of magnetic properties, it is preferable to include one or more of Fe and Co as the transition metal element, and it is more preferable to include Fe as the main component. Incidentally, "Fe as the main component" means that the Fe content (mass %) is the highest among the transition metal elements. The content of the transition metal element is preferably 60 mass % or more of the entire plate magnet 11, more preferably 65 mass % or more. The upper limit of the transition metal element is not particularly limited, and can be, for example, 73 mass % or less of the entire plate magnet 11. Furthermore, when Fe and Co are included, a portion of the Fe may be substituted with Co. For example, when the total of Fe and Co is 100 mass %, the Co content can be greater than 0 mass % and less than 1 mass %.

[0016] Plate magnet 11 may contain elements other than those listed above (hereinafter also referred to as "other elements"). Examples of other elements include aluminum (Al), copper (Cu), zinc (Zn), indium (In), silicon (Si), phosphorus (P), sulfur (S), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), gallium (Ga), germanium (Ge), zirconium (Zr), niobium (Nb), molybdenum (Mo), palladium (Pd), silver (Ag), cadmium (Cd), tin (Sn), antimony (Sb), hafnium (Hf), tantalum (Ta), and tungsten (W). The content of other elements is preferably 0% to 3% by mass of the entire plate magnet 11.

[0017] From the viewpoint of improving coercivity, it is more preferable that the plate magnet 11 have a region in which the concentration of the heavy rare earth element decreases from at least a portion of the surface of the plate magnet 11 toward the interior of the plate magnet 11. In FIG. 4, the decrease in concentration of the heavy rare earth element is represented by the shade of the shading. Areas with high concentrations of the heavy rare earth element are shown with dark shading, while areas with low concentrations are shown with light shading. A configuration having a region in which the concentration of the heavy rare earth element decreases can contribute to reducing the amount of heavy rare earth element added while maintaining magnetic properties. The heavy rare earth element can be one or more selected from the group consisting of terbium (Tb), dysprosium (Dy), gadolinium (Gd), holmium (Ho), europium (Eu), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Among these, the heavy rare earth element is preferably one or more of Dy and Tb. The region in plate magnet 11 where the concentration of the heavy rare earth element is reduced can be formed, for example, by applying a material containing the heavy rare earth element to the surface of plate magnet 11 and then heat treating it. Details will be described later.

[0018] The plate magnet 11 is, for example, Nd ２ Fe １４It is preferable that the plate magnet 11 has a main phase of B and a rare earth-rich phase having a higher rare earth element content than the main phase. The plate magnet 11 may further have a boron-rich phase having a higher boron content than the main phase. The main phase usually has a tetragonal crystal structure. For example, the above-mentioned Nd ２ Fe １４ B has a tetragonal crystal structure. The main phase of the plate magnet 11 can be identified as the component with the largest peak intensity by XRD (X-ray diffraction) analysis of the plate magnet 11. ２ Fe １４ When the peak intensity of B is the largest, the plate magnet 11 is Nd ２ Fe １４ It can be determined that the main phase is B.

[0019] The average degree of orientation of the plate magnets 11 is preferably 90% or more, and more preferably 95% or more. The higher the average degree of orientation of the plate magnets 11, the better, but it is usually 99.5% or less. In Figures 2 and 3, the white arrows indicate the orientation direction. Multiple plate magnets 11 can be used, for example, lined up in a direction perpendicular to the orientation direction, as shown in Figure 3.

[0020] The average orientation of the plate magnet 11 can be determined, for example, as follows. If the plate magnet 11 is rectangular (rectangular prism-shaped), as shown in Figures 1 and 9, it is cut out to a size compatible with the measuring device and measured. For example, on the rectangular bottom surface of the plate magnet 11 in Figure 9, the average orientation is determined as the average orientation of each 1 mm-wide section centered on the normal Nn at multiple points Pn from one end of the long side to the other. The number of multiple points Pn is not particularly limited. Figure 9 shows five points P1-P5 and normals N1-N5 at each point P1-P5. If the size of the plate magnet 11 is sufficiently small, the number of multiple points Pn may be two, but five or more is preferable. The number of multiple points Pn is usually 10 or less. For example, a pulsed high magnetic field measuring device (magnetic field: 4 T) can be used as the measuring device. If the cut-out portion does not fit into the measuring device, a sample of a size that can fit into the measuring device is cut out from the center of the cut-out portion.

[0021] When the plate magnet 11 has a convex curved shape, as shown in Figures 10 and 13, the average orientation is calculated as the average degree of orientation of each 1 mm wide portion centered on the normal Nn at multiple points Pn from one end to the other on the curve C1 on the convex side of the outer periphery of the plate magnet 11 when viewed from the first direction (Z-axis direction). The number of points Pn is not particularly limited. When the size of the plate magnet 11 is sufficiently small, the number of points Pn may be two, but five or more is preferable. The number of points Pn is usually 10 or less. Note that when the plate magnet 11 has a convex curved shape, the radius of curvature of the curve C1 is not limited to a constant value and may vary.

[0022] Below, a method for calculating the average degree of orientation when the plate magnet 11 has a convex curved shape will be described in detail with reference to Figures 13 and 14. When viewed from the Z-axis direction, the curve on the convex side of the outer periphery of the plate magnet 11 is designated as curve C1, and the line tracing the edge opposite curve C1 is designated as opposing line C2. First, as shown in Figure 13, multiple points Pn are identified. In this embodiment, five points P1-P5 are identified. On the plate magnet 11, points P1 and P5 at both ends of the convex curve C1 are located within 5 mm of one end (e.g., the left end) and within 5 mm of the other end (e.g., the right end). Multiple points (points P2-P4 in this embodiment) are located at equal intervals (four equal positions in this embodiment) between points P1 and P5 at both ends of the curve C1, starting from one end. In this embodiment, point P3 is located in the middle of the curve C1.

[0023] On the curve C1, the normal lines N1-N5 at each point P1-P5 are identified. 1 mm wide portions 12 are cut out from the plate magnet 11, centered on the normal line Nn. Each portion 12 is, for example, approximately rectangular prism-shaped, as shown in FIG. 14. In reality, the top and bottom surfaces of FIG. 14 are curved surfaces. The degree of orientation of each portion 12 is measured, for example, using a pulsed high magnetic field measuring device (magnetic field: 4 T). If the cut-out portion does not fit into the measuring device, a sample of a size that can fit into the measuring device is cut out from the center of the cut-out portion. The average value of the degrees of orientation of each portion 12 is calculated as the average degree of orientation.

[0024] The average degree of orientation of plate magnet 11 can be controlled, for example, by appropriately designing the magnetic field to be applied in the orientation process described below. For example, even if plate magnet 11 has a convex curved shape, the average degree of orientation of 90% or more can be achieved by applying a magnetic field that spreads in the normal direction of curve C1 of plate magnet 11 in the orientation process described below.

[0025] The plate magnet 11 has a shorter distance from the surface to the deepest part than a block-shaped magnet with a larger thickness. Therefore, the plate magnet 11 is suitable because it allows heavy rare earth elements to diffuse easily into the interior when diffusing through grain boundaries. The plate magnet 11 can be suitably used as a laminated magnet in which multiple plate magnets 11 and insulating bonding layers 13 are stacked. The laminated magnet 10 of FIG. 1 has multiple plate magnets 11 stacked with the thickness direction of the plate magnets 11 as the stacking direction. In this laminated magnet, the plate magnets 11 and insulating bonding layers 13 are stacked alternately. In a laminated magnet, each plate magnet 11 is sometimes referred to as a magnet body. Note that the plate magnet 11 in FIGS. 1 and 2 has a rectangular shape when viewed from above (Z-axis direction). The plate magnet 11 may have a shape other than rectangular when viewed from above, and may have a curved shape (such as a circular arc) that is convex in one direction when viewed from above (the positive direction in the X-axis direction in FIG. 11, or the upward direction in FIG. 11), as shown in Figures 10 and 11.

[0026] The thickness of the 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.

[0027] (2) Insulating Bonding Layer 13 The insulating bonding layer 13 is not particularly limited. The insulating bonding layer 13 preferably contains inorganic crystals as a main component. Incidentally, "containing inorganic crystals as a main component" means that the content of inorganic crystals in the insulating bonding layer 13 is 50% by mass or more. The content of inorganic crystals in the insulating bonding layer 13 is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass. The composition of the insulating bonding layer 13 can be analyzed by the following method. The presence of inorganic crystals is determined by X-ray microanalysis or XRD analysis, and the content of inorganic crystals is calculated in combination with composition analysis by EPMA (Electron Probe Micro Analyser).

[0028] The insulating bonding layer 13 is made of inorganic crystals such as CaF ２ , BaF ２ , SrF ２ , MgF ２ , Al ２ O ３ , ZrO ２ , Dy ２ O ３ , Tb ２ O ３ , Nd ２ O ３ , TbF ３ , DyF ３ , LiF, SiO ２ , BN, ZrB ２ , Si ３ N ４ , TiB ２ , Pr ２ O ３ From the viewpoint of reducing eddy current loss, the insulating bonding layer 13 preferably contains at least a fluoride of Group 2A of the periodic table as an inorganic crystal. The insulating bonding layer 13 preferably contains CaF as the fluoride of Group 2A of the periodic table. ２ , BaF ２ , SrF ２ , and MgF ２ It is more preferable that the insulating bonding layer 13 contains at least one selected from the group consisting of CaF ２It is particularly preferable that the insulating bonding layer 13 contains 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more of a fluoride of Group 2A of the periodic table as an inorganic crystal, when the entire inorganic crystal is taken as 100% by mass. 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% by mass.

[0029] When the insulating bonding layer 13 is primarily composed of a Group 2A fluoride, the raw material for the insulating bonding layer 13 preferably contains the above-mentioned heavy rare earth element compound in addition to the Group 2A fluoride. If the raw material for the insulating bonding layer 13 contains the above-mentioned heavy rare earth element compound, the heavy rare earth element can be favorably diffused into the plate magnet 11. The heavy rare earth element contained in the raw material for the insulating bonding layer 13 diffuses into the plate magnet 11 after heat treatment. Therefore, the insulating bonding layer 13 of the resulting magnet laminate 10 contains almost no heavy rare earth element. The mass ratio of the Group 2A fluoride to the heavy rare earth element compound in the raw material for the insulating bonding layer 13 is not particularly limited. The mass ratio of the Group 2A fluoride to the heavy rare earth element compound in the raw material for the insulating bonding layer 13 can be, for example, 20:80-40:60.

[0030] The insulating bonding layer 13 may be arranged, for example, as follows: The insulating bonding layer 13 may be arranged to cover the entire surface of the plate magnet 11 (see FIG. 3). In the example of FIG. 3, both the upper and lower main surfaces 11A and both side surfaces 11B of each plate magnet 11 are covered with the insulating bonding layer 13, and the insulating bonding layer 13 is arranged to cover the entire surface of the plate magnet 11. The insulating bonding layer 13 may be arranged to cover only a portion of the surface of the plate magnet 11.

[0031] 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. The conditions for hot pressing will be explained later.

[0032] The insulating bonding layers 13 may be provided along the orientation direction of the magnetic field of each plate magnet 11 (e.g., the X-axis direction in FIG. 3 , the direction of the white arrow in FIG. 3 ), or along a direction intersecting the orientation direction (e.g., the X-axis direction in FIG. 3 ) (e.g., the Z-axis direction in FIG. 3 ). Note that, as shown in FIG. 15 , 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. 15 ) from the perspective of efficiently reducing eddy current loss. With this configuration, the insulating bonding layers 13 are disposed 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. 15 ), thereby effectively reducing eddy current loss.

[0033] 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. 4 ).

[0034] (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 first 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.

[0035] (4) Requirements for the diffusion depth β / α of heavy rare earth elements When the laminated magnet 10 is observed in cross section by taking an imaginary line L1 that passes through the center of gravity G1 of the laminated magnet 10 and extends in the stacking direction, and cutting the laminated magnet 10 so that its cross-sectional area is smallest on an imaginary plane that includes the imaginary line L1, the first diffusion depth α μm measured by the following measurement method (1) and the second diffusion depth β μm measured by the following measurement method (2) satisfy 0.35≦β / α≦0.50 for a specific intermediate magnet 112A that is any of the intermediate magnets 112 among the plate magnet 11, excluding the uppermost magnet 111 located at the top and the lowermost magnet 113 located at the bottom. Measurement method (1): A line analysis is performed on a line L2 that passes through the center of gravity G2 of the planar figure of the specific intermediate magnet 112A that appears in the cross section and extends in the stacking direction, from the upper bottom surface 11A1 to the center of gravity G2 of the planar figure, to obtain a first profile of the intensity of the heavy rare earth element normalized so that the maximum intensity along that line is 1. The distance between the position of the upper bottom surface 11A1 and the position where the intensity of the heavy rare earth element first reaches 0.7 is defined as the first diffusion depth α μm. Measurement method (2): A line analysis is performed on a line L3 that passes through the center of gravity G2 of the planar figure of the specific intermediate magnet 112A that appears in the cross section and extends in a direction perpendicular to the stacking direction, from the side surface 11B to the center of gravity G2 of the planar figure, to obtain a second profile of the intensity of the heavy rare earth element normalized so that the maximum intensity along that line is 1. The distance between the position of the side surface 11B and the position where the intensity of the heavy rare earth element first reaches 0.7 is defined as the second diffusion depth β μm.

[0036] 1 to 3, a cross section of the magnet laminate 10 will be specifically described. In the magnet laminate 10, an imaginary line L1 passing through the center of gravity G1 in FIG. 1 and extending in the stacking direction extends in the Z-axis direction. As shown in FIG. 2, an imaginary plane VP that cuts the magnet laminate 10 so that its cross-sectional area is smallest is the XZ plane including the imaginary line L1. Note that a cross section of the magnet laminate 10 cut along a plane that includes the imaginary line L1 and intersects with the X-axis direction has a larger cross-sectional area than a cross section cut along the XZ plane. As shown in FIG. 3, multiple cut surfaces of the plate magnet 11 appear in the cross section cut along the imaginary plane VP. The cut surfaces of each plate magnet 11 form a rectangular planar shape. In the magnet laminate 10 of FIGS. 10 to 12, the imaginary line L1 also extends in the Z-axis direction. The imaginary plane VP is an XZ plane including the imaginary line L1. As shown in FIG. 12, multiple cut surfaces of the plate magnet 11 appear in the cross section cut along the imaginary plane VP. Each cut surface of the plate magnet 11 forms a rectangular planar figure.

[0037] Referring to FIG. 5 , a method for measuring the first diffusion depth α μm and the second diffusion depth β μm will be described. The first diffusion depth α μm can be measured, for example, by analyzing the line L2 with an EPMA. In measurement method (1), a graph is obtained as a first profile, with the horizontal axis representing the distance from the upper base surface 11A1 and the vertical axis representing the detected intensity of the heavy rare earth element. The intensity of the heavy rare earth element is usually greatest near the upper base surface 11A1 and tends to decrease as the distance from the upper base surface 11A1 increases. When multiple heavy rare earth elements are detected by the line analysis in measurement method (1), the profile of the heavy rare earth element with the highest intensity in measurement method (1) is used as the first profile. The second diffusion depth β μm can be measured, for example, by analyzing the line L3 with an EPMA. In measurement method (2), a graph is obtained as a second profile, with the horizontal axis representing the distance from the side surface 11B and the vertical axis representing the detected intensity of the heavy rare earth element. The intensity of the heavy rare earth element usually has a maximum intensity near the side surface 11 B and tends to decrease as the distance from the side surface 11 B increases. When multiple types of heavy rare earth elements are detected by the line analysis of the measurement method (2), the profile of the heavy rare earth element with the highest intensity in the measurement method (1) is designated as the second profile.

[0038] A β / α value of 0.50 or less is an indicator that the diffusion depth of the heavy rare earth element from the upper bottom surface 11A1 is sufficiently greater than the diffusion depth of the heavy rare earth element from the side surface 11B. In the plate magnet 11, the distance from the upper bottom surface 11A1 to the deepest part is shorter than the distance from the side surface 11B to the deepest part. Therefore, by ensuring the diffusion depth of the heavy rare earth element from the upper bottom surface 11A1, a predetermined amount of heavy rare earth element can be sufficiently diffused toward the deepest part of the plate magnet 11. A β / α value of 0.35 or more is an indicator that a certain amount of heavy rare earth element is present between the upper bottom surface 11A1 and the lower bottom surface 11A2. Therefore, if the β / α value is 0.35 or more, the heat resistance of the plate magnet 11 can be sufficiently ensured.

[0039] The first diffusion depth α μm is not particularly limited. The first diffusion depth α μm is preferably 650 μm or more and 1000 μm or less, and more preferably 700 μm or more and 980 μm or less. The second diffusion depth β μm is not particularly limited. The second diffusion depth β μm is preferably 200 μm or more and 600 μm or less, and more preferably 250 μm or more and 500 μm or less. The requirement regarding the heavy rare earth element ratio β / α can be met by calculating the heavy rare earth element ratio β / α of multiple specific intermediate magnets 112A and finding that it is satisfied in at least one of the specific intermediate magnets 112A.

[0040] In the magnet stack 10, it is preferable that the upper bottom surface 11A1 of the specific intermediate magnet 112A is covered with an insulating bonding layer 13, and that the side surface 11B of the specific intermediate magnet 112A is also covered with an insulating bonding layer 13. With this configuration, heavy rare earth elements are diffused into the plate magnet 11 from the material of the insulating bonding layer 13 applied to the upper bottom surface 11A1 of the specific intermediate magnet 112A and the material of the insulating bonding layer 13 applied to the side surface 11B of the specific intermediate magnet 112A, making it possible to preferably achieve the above-mentioned β / α value.

[0041] The value of β / α can be controlled, for example, by adjusting the amount of material for the insulating bonding layer 13 applied on the upper surface 11A1 and the amount of material for the insulating bonding layer 13 applied on the side surface 11B. The greater the amount of material for the insulating bonding layer 13 applied on the upper surface 11A1, the greater the first diffusion depth α μm. The greater the amount of material for the insulating bonding layer 13 applied on the side surface 11B, the greater the second diffusion depth β μm. Furthermore, the value of β / α can be controlled, for example, by adjusting the hot pressing conditions. For example, increasing the pressure during hot pressing tends to increase the first diffusion depth α μm. On the other hand, decreasing the pressure during hot pressing tends to decrease the first diffusion depth α μm. Furthermore, for example, increasing the temperature during hot pressing tends to increase the first diffusion depth α μm. On the other hand, decreasing the temperature during hot pressing tends to decrease the first diffusion depth α μm. Furthermore, extending the pressure application time during hot pressing tends to increase the first diffusion depth α μm. On the other hand, by shortening the pressurizing time during hot pressing, the first diffusion depth α μm tends to become smaller.

[0042] (5) Requirements for the Ratio γ / δ of Heavy Rare Earth Elements When the amount of heavy rare earth elements in the first region R1 that satisfies the following conditions (3) to (6) is γ% by mass, and the amount of the heavy rare earth elements in the second region R2 that satisfies the following conditions (7) to (8) is δ% by mass, then γ / δ≧5.0 is satisfied. Condition (3): The first region R1 is located on the specific intermediate magnet 112A side of the interface I between the specific intermediate magnet 112A and the insulating bonding layer 13. Condition (4): The first region R1 is a rectangle that is 10 μm in the stacking direction and 50 μm in the direction perpendicular to the stacking direction. Condition (5): If a line L2 is drawn that passes through the center of gravity G2 of the planar shape of the specific intermediate magnet 112A that appears in the cross section and extends in the stacking direction, the center CT1 of the rectangle will be on the line L2. Condition (6): The rectangle is in contact with the insulating bonding layer 13. Condition (7): The second region R2 is a rectangle that is 10 μm in the stacking direction and 50 μm in the direction perpendicular to the stacking direction. Condition (8): The center CT2 of the rectangle is located at the center of gravity G2 of the planar figure of the specific intermediate magnet 112A that appears in the cross section.

[0043] A method for identifying the first region R1 will be described in detail with reference to Figures 6 and 7. The specific intermediate magnet 112A in Figure 6 has an upper bottom surface 11A1, a lower bottom surface 11A2, and a side surface 11B. As shown in Figure 7, an insulating bonding layer 13 is located above the upper bottom surface 11A1. That is, the upper bottom surface 11A1 of the specific intermediate magnet 112A forms the interface I between the specific intermediate magnet 112A and the insulating bonding layer 13. The interface I between the specific intermediate magnet 112A and the insulating bonding layer 13 can be identified, for example, by image analysis using an electron probe microanalyzer (EPMA). As shown in Figure 6, the center of gravity G2 of the planar figure of the specific intermediate magnet 112A is identified. Because the planar figure of the specific intermediate magnet 112A is rectangular, the center of gravity G2 of the planar figure of the specific intermediate magnet 112A can be identified as the intersection of the diagonals of the planar figure. A straight line L2 is drawn that passes through the center of gravity G2 and extends in the Z-axis direction. Of the rectangles with a center CT1 on the line L2 and a size of 10 μm in the Z-axis direction and 50 μm in the X-axis direction, the rectangle whose top edge is in contact with the insulating bonding layer 13 is identified as the first region R1 (see FIG. 7). Note that the actual interface I has irregularities as shown in FIG. 8, but the lowest point of the irregularities (the point closest to the center of the plate magnet) is used as the contact point, and a rectangle 10 μm in the stacking direction and 50 μm in the planar direction is identified as R1. Note that in the case where the lower bottom surface 11A2 of the specific intermediate magnet 112A forms the interface I between the specific intermediate magnet 112A and the insulating bonding layer 13, the rectangle whose bottom edge is in contact with the insulating bonding layer 13 may be identified as the first region R1.

[0044] A method for identifying the second region R2 will be described in detail with reference to Figure 6. As shown in Figure 6, the center of gravity G2 of the planar figure of the specific intermediate magnet 112A is identified. Because the planar figure of the specific intermediate magnet 112A is rectangular, the center of gravity G2 of the planar figure of the specific intermediate magnet 112A can be identified as the intersection of the diagonals of the planar figure. A rectangle measuring 10 μm in the Z-axis direction and 50 μm in the X-axis direction, with a center CT2 at the center of gravity G2, is identified as the second region R2.

[0045] The heavy rare earth element content γ and the heavy rare earth element content δ can be calculated, for example, by subjecting a cross section of the magnet laminate 10 to micro X-ray analysis or XRD analysis in combination with EPMA composition analysis. For example, 10 or more points in each region are measured using EPMA point analysis, and the average value is used as the heavy rare earth element content of that region. The heavy rare earth element content γ in the first region R1 is not particularly limited. The heavy rare earth element content γ is preferably 5.5 mass% or more and 7.5 mass% or less. The heavy rare earth element content δ in the second region R2 is not particularly limited. The heavy rare earth element content β is preferably 0.3 mass% or more and 1.5 mass% or less. Note that, when multiple specific intermediate magnets 112A are present, the requirement regarding the heavy rare earth element ratio γ / δ only needs to be satisfied in at least one of the specific intermediate magnets 112A.

[0046] The ratio γ / δ of the heavy rare earth elements can be controlled, for example, by adjusting the thickness of the plate magnet 11 and the hot pressing conditions. For example, increasing the thickness of the plate magnet 11 tends to increase the γ / δ value. On the other hand, decreasing the thickness of the plate magnet 11 tends to decrease the γ / δ value. For example, increasing the temperature during hot pressing while shortening the pressing time tends to increase the γ / δ value. On the other hand, decreasing the temperature during hot pressing while lengthening the pressing time tends to decrease the γ / δ value.

[0047] (6) Requirements for the Location Where the Amount of Heavy Rare Earth Element is Maximum In terms of improving heat resistance, it is preferable that the corner E1 between the upper base surface 11A1 and the side surface 11B, or the corner E2 between the lower base surface 11A2 and the side surface 11B, be the location where the amount of heavy rare earth element is maximum in the specific intermediate magnet 112A. As shown in Figure 5, the cross-sectional plan view of the specific intermediate magnet 112A has two corners E1 between the upper base surface 11A1 and the side surface 11B and two corners E2 between the lower base surface 11A2 and the side surface 11B, for a total of four corners E1, E1, E2, E2. The location where the amount of heavy rare earth element is maximum may be any of the four corners E1, E1, E2, E2.

[0048] The area with the largest amount of heavy rare earth element can be identified by EPMA line analysis. For example, line analysis is performed along two diagonals of the planar shape of the specific intermediate magnet 112A, from corner E1 of the specific intermediate magnet 112A to the corner E2 opposite corner E1. The largest amount of heavy rare earth element in the four corners E1, E2, and E2 is defined as the "amount of heavy rare earth element in corner E1 or E2." Line analysis is also performed along line L2 of the specific intermediate magnet 112A from the upper bottom surface 11A1 to the lower bottom surface 11A2. The larger of the amount of heavy rare earth element in the upper bottom surface 11A1 or the amount of heavy rare earth element in the lower bottom surface 11A2 is defined as the "amount of heavy rare earth element in the main surface 11A." Furthermore, line analysis is performed between both side surfaces 11B, 11B along line L3 of the specific intermediate magnet 112A. The larger of the amounts of heavy rare earth element on both side surfaces 11B is referred to as the "amount of heavy rare earth element on side surface 11B." If the amount of heavy rare earth element on corner E1 or corner E2 is greater than the amount of heavy rare earth element on main surface 11A and the amount of heavy rare earth element on side surface 11B, corner E1 or corner E2 can be determined to be the region where the amount of heavy rare earth element is greatest. Note that the amount of heavy rare earth element on main surface 11A and the amount of heavy rare earth element on side surface 11B may be greater or equal. To satisfy the requirement regarding the diffusion depth β / α of the heavy rare earth element, it is preferable that the amount of heavy rare earth element on main surface 11A is greater than the amount of heavy rare earth element on side surface 11B. Note that, if there are multiple specific intermediate magnets 112A described above, the requirement regarding the region where the amount of heavy rare earth element is greatest only needs to be satisfied in at least one of these specific intermediate magnets 112A.

[0049] The portion where the amount of the heavy rare earth element is greatest can be controlled, for example, by adjusting the amount of material of the insulating bonding layer 13 applied to the upper bottom surface 11A1 and the lower bottom surface 11A2 and the amount of material of the insulating bonding layer 13 applied to the side surface 11B.

[0050] (7) Requirements for Interface I Between Plate Magnet 11 and Insulating Bonding Layer 13 From the viewpoint of improving insulation, it is preferable that the magnet laminate 10 contains a Group 2A metal element in the periodic table in a 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 Group 2A metal element may be present as a component of a specific metal phase 17A (described later) in a 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. Furthermore, the Group 2A metal element may be present as fluoride particles 14 of the Group 2A metal element contained in the specific metal phase 17A, as shown in FIG. 8 .

[0051] Furthermore, from the viewpoint of improving bonding strength, the magnet laminate 10 preferably has fluoride particles of a metal element, such as fluoride particles 14 of a metal element of Group 2A of the periodic table, in contact with a phase 17A containing a heavy rare earth element and two or more metal components (hereinafter also referred to as the specific metal phase 17A). The fluoride particles of a metal element are not limited to fluoride particles 14 of a metal element of Group 2A of the periodic table, but may also be, for example, fluoride particles of a heavy rare earth element. From the viewpoint of further improving bonding strength, it is more preferable that the specific metal phase 17A is an alloy of a heavy rare earth element and two or more metal components. The specific metal phase 17A, for example, constitutes a surface layer 17 on the surface of the plate magnet 11. The thickness of the surface layer 17 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 surface layer 17 is not particularly limited and is usually 40 μm or less. The manner in which fluoride particles of a metal element contact specific metal phase 17A is not particularly limited. For example, fluoride particles 14 of a metal element of Group 2A of the periodic table may be contained within specific metal phase 17A, as shown in FIG. 8 . Alternatively, fluoride particles of a metal element exposed on the surface of insulating bonding layer 13 may contact specific metal phase 17A.

[0052] Fig. 8 is an enlarged schematic view of region R0 of the magnet stack 10 in Fig. 3. The upper bottom surface 11A1 of the plate magnet 11 forms 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.

[0053] The metal component is, for example, two or more selected from the group consisting of light rare earth elements and metals of Group 2A of the periodic table. Specifically, the metal component is preferably two or more selected from the group consisting of neodymium (Nd), praseodymium (Pr), lanthanum (La), samarium (Sm), calcium (Ca), barium (Ba), and strontium (Sr).

[0054] Examples of the phase 17A containing a heavy rare earth element and two or more metal components include phases containing the following combinations of components: A combination of Tb, Pr, and Nd A combination of Tb, La, and Nd A combination of Tb, Pr, La, and Nd A combination of Tb, Sm, Nd, and Ca A combination of Tb, Pr, Nd, and Ca A combination of Tb, Dy, Pr, Nd, and Ba A combination of Tb, La, Pr, Nd, and Sr A combination of Tb, La, Nd, and Ca

[0055] The heavy rare earth element is derived from, for example, a compound of a heavy rare earth element contained in the raw material of the insulating bonding layer 13. In addition, the metal component Nd is derived from, for example, Nd in the plate magnet 11. ２ Fe １４ The metal of Group 2A of the periodic table in the metal component is derived from, for example, a compound of Group 2A of the periodic table contained in the raw material of insulating bonding layer 13 .

[0056] Generally, the lower the total amount of rare earth elements in the sheet magnet 11, the less likely Nd and Pr derived from the sheet magnet 11 are to be present near the interface I between the sheet magnet 11 and the insulating bonding layer 13. The reason for this is presumed to be as follows. Specifically, the lower the total amount of rare earth elements in the sheet magnet 11, the less likely Nd-rich components and Pr-containing components derived from the main phase are to flow to the surface of the sheet magnet 11. The present inventors have newly discovered that even in a magnet stack 10 using a sheet magnet 11 with a low total amount of rare earth elements (e.g., 31.0 mass% or less), Nd and Pr can be present near the interface I by hot pressing. Furthermore, the presently disclosed technology has been developed to satisfy the requirements for the interface I between the sheet magnet 11 and the insulating bonding layer 13 by using fluoride particles 14 of a Group 2A metal element and fluoride particles of a heavy rare earth element as raw materials for the insulating bonding layer 13 and adjusting the hot pressing conditions. For example, by increasing the pressure during hot pressing and lengthening the pressing time, it is possible to preferably form a configuration in which fluoride particles of a metal element are in contact with a specific metal phase 17A containing a heavy rare earth element and two or more metal components.

[0057] The presence or absence of each of the above elements can be determined by combining X-ray microanalysis and EPMA composition analysis. Furthermore, the formation of an alloy between a heavy rare earth element and two or more metal components can be determined by detecting lattice strain, etc. The requirements for Group 2A metal elements in the Periodic Table can be met by observing the cross-sectional structure of magnet laminate 10 in multiple 50 μm × 50 μm square fields of view, and at least one of these fields of view must be satisfied.

[0058] (8) Requirements for the Average Particle Diameter of Fluoride Particles The average particle diameter of fluoride particles of metal elements, such as fluoride particles 14 of metal elements of Group 2A of the Periodic Table, is not particularly limited. The average particle diameter of the fluoride particles is preferably 2.0 μm or more and 8.0 μm or less, more preferably 2.2 μm or more and 6.0 μm or less, and even more preferably 2.5 μm or more and 4.0 μm or less. When the average particle diameter of the fluoride particles is within the above range, the insulation resistance is increased and eddy current loss can be reduced. Furthermore, when the average particle diameter of the fluoride particles is within the above range, the plate magnet 11 and the insulating bonding layer 13 are easily compatible with each other, and the adhesion strength between the plate magnet 11 and the insulating bonding layer 13 can be improved.

[0059] The average particle diameter of the fluoride particles can be determined, for example, by subjecting a cross section of the magnet laminate 10 to micro X-ray analysis or XRD analysis, performing image analysis using an EPMA, and calculating the equivalent-area circle diameter from the particle area of ​​the fluoride particles. Specifically, the average particle diameter is determined as follows: Focus is placed on multiple fluoride particles that can be observed without missing any particles within a predetermined observation field (e.g., 50 μm × 50 μm). The diameter (equivalent-area circle diameter) of an ideal circle (true circle) having an area equal to the area (projected area) of each particle image of the fluoride particles 14 is calculated as the particle diameter of each particle. The average particle diameter is then determined by arithmetically averaging the particle diameters of each particle.

[0060] The average particle size of the fluoride particles can be controlled by adjusting the average particle size of the fluoride particles of the metal element used as the raw material of insulating bonding layer 13 .

[0061] 2. Manufacturing Method of the Magnet Laminate 10 There are no particular limitations on the manufacturing method of the magnet laminate 10. An example of a manufacturing method of the magnet laminate 10 in which the plate magnets 11 and the insulating bonding layers 13 are alternately stacked is shown below.

[0062] (1) SC Alloy Preparation Step A raw alloy (strip cast alloy (SC alloy)) containing rare earth elements, transition metal elements, boron, and the like is prepared.

[0063] (2) Hydrogen decomposition process: In a hydrogen atmosphere, the SC alloy is allowed to absorb hydrogen at a predetermined temperature (e.g., 200°C) for a predetermined time (e.g., 1 to 5 hours), thereby embrittling the grain boundaries (Nd-rich phase) of the SC alloy.

[0064] (3) Coarse Crushing Step, First Lubricant Addition Step The SC alloy powder that has undergone the hydrogen cracking step is coarsely crushed (coarse crushing step). At this time, a lubricant may be added to the SC alloy powder (first lubricant addition step). This step may be performed, for example, in an inert atmosphere (nitrogen atmosphere, argon atmosphere, etc.).

[0065] (4) Fine Pulverization Step, Second Lubricant Addition Step The SC alloy powder obtained after the coarse pulverization step is 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, a lubricant may be added to the finely pulverized SC alloy powder to improve the flowability of the pulverized powder (second lubricant addition step). This step is preferably performed in an inert atmosphere (such as a nitrogen atmosphere or an argon atmosphere).

[0066] (5) Powder Filling Process, Orientation Process, and Molding Process The SC alloy powder after the pulverization process is filled into a mold. This process is preferably performed, for example, under 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 powder filling 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 having a predetermined degree of orientation (e.g., an average orientation of 90% or more) and a predetermined thickness (e.g., a thickness of 0.5 mm to 4.0 mm) can be obtained without a cutting process.

[0067] (6) Mold Breaking Step, First Firing Step The molded body is removed from the mold (mold breaking step). The molded body is sintered at a predetermined sintering temperature (e.g., 900°C-1200°C) for a predetermined time (e.g., 2 hours-5 hours) (first sintering step). This sintering is preferably carried out in a vacuum. Prior to this sintering, heating at a temperature lower than the sintering temperature may be carried out for dehydrogenation.

[0068] (7) Insulating Bonding Layer Coating Process The raw material for the insulating bonding layer 13 is coated on the surface of the fired compact. The raw material for the insulating bonding layer 13 can be, for example, a mixture of raw material powder of inorganic crystalline components, compound powder containing a heavy rare earth element, and a solvent. The raw material for the insulating bonding layer 13 may be coated on at least one main surface of the compact, or may be coated on 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 coated on the entire surface of the compact, i.e., on both main surfaces and side surfaces if the compact is plate-shaped.

[0069] (8) Laminate Temporarily 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 magnets 11 without the need for a cutting process or the like to cut out plate-shaped magnets from a larger magnet.

[0070] (9) Hot Pressing Step The temporarily fixed laminate is placed in a hot press mold and subjected to uniaxial hot pressing. This step is carried out, for example, under a vacuum atmosphere (for example, 10 －３ Pa-10 －４ The hot pressing may be performed 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-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. There is no particular upper limit to the hot pressing pressure, and it may be, 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 including a plate magnet 11 and an insulating bonding layer 13 is manufactured. The magnet stack 10 is formed by bonding a plurality of plate magnets 11 together via the insulating bonding layer 13, forming an integrated structure.

[0071] 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. In addition, the hot pressing process also allows the plate magnet 11 (e.g., Nd ２ Fe １４ B) flows out to the surface of the plate magnet 11 and forms an insulating bonding layer 13 (e.g., CaF ２ In addition, this hot pressing process can sufficiently thin the insulating bonding layer 13, and can also make the thickness of the insulating bonding layer 13 uniform.

[0072] The magnet laminate 10 obtained as described above can be understood as a magnet laminate 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), and applying pressure in a direction that crushes the raw material of the insulating bonding layer 13. Alternatively, the magnet laminate 10 can be understood as a magnet laminate 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 applying pressure to the first plate magnet 11 and the second plate magnet 11 from both sides while heating the laminate. The raw material of the insulating bonding layer 13 preferably contains inorganic crystals. The raw material of the insulating bonding layer 13 may further contain a component containing a heavy rare earth element. For example, the raw material of the insulating bonding layer 13 may be CaF ２ and TbF ３ When the total of CaF is taken as 100 mass % ２ It is preferable that the content of TbF is 20 mass % to 40 mass %. ３ It is preferable that the content is 60 mass % to 80 mass %.

[0073] 3. Uses of the Magnet Laminate 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, its insulating performance is less susceptible to changes due to the effects of 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.

[0074] An example of a motor 30 equipped with a magnet laminate 10 will be described below with reference to FIGS. 15 and 16 . 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. 15 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.

[0075] 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.

[0076] 4. Actions and Effects of the Present Embodiment The magnet laminate 10 of the present embodiment can be efficiently provided with heat resistance without using excessive heavy rare earth elements. The reason for this is presumed to be as follows. Note that the present disclosure is not limited to this presumption. The ideal heavy rare earth diffusion state in the plate magnet 11 is believed to be a state in which rare earths (e.g., Nd, Pr, etc.) are substituted with heavy rare earth elements (e.g., Tb, Dy, etc.) only on the surface of the main phase (magnet crystal grains) that constitutes the plate magnet 11. For example, Nd ２ Fe １４ In the main phase of B, (Nd, Tb)Fe １４Excessive substitution with B reduces the magnetic force. It is known that the effect of adding heavy rare earth elements to improve heat resistance cannot be expected beyond a certain amount of heavy rare earth elements. The magnet stack 10 of this embodiment satisfies both "(4) requirement regarding the diffusion depth β / α of the heavy rare earth elements" and "(5) requirement regarding the ratio γ / δ of the heavy rare earth elements." This allows for a configuration close to the ideal heavy rare earth diffusion state of the heavy rare earth elements while suppressing the total amount of heavy rare earth elements. Therefore, it is believed that heat resistance can be efficiently achieved without using excessive heavy rare earth elements. For example, not using excessive heavy rare earth elements can contribute to cost reduction and suppression of a decrease in magnetic force.

[0077] In the specific intermediate magnet 112A, if the corner E1 or corner E2 is the part where the amount of heavy rare earth element is greatest, this can further contribute to improving heat resistance.

[0078] Furthermore, when a metal element of Group 2A of the periodic table 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 insulation between the plate magnets 11 can be improved compared to when no metal element of Group 2A of the periodic table is present, and therefore a reduction in eddy current loss can be expected.

[0079] Furthermore, when the fluoride particles of the metal element are in contact with the phase 17A containing a heavy rare earth element and two or more metal components, the bonding strength between the plate magnet 11 and the insulating bonding layer 13 can be strengthened.

[0080] When the average particle size of the fluoride particles is 2.0 μm or more and 8.0 μm or less, the insulation between the plate magnets 11 can be suitably improved, and eddy current loss can be further reduced. The interface I between the plate magnet 11 and the insulating bonding layer 13 is well-fitted, and the adhesive strength between the plate magnet 11 and the insulating bonding layer 13 can be increased.

[0081] The present disclosure will be explained in more detail below with reference to examples.

[0082] 1. Preparation of Laminated Magnets in Examples 1-21 and Comparative Examples 1-5 (1) SC Alloy Preparation Step The main raw materials of an Nd / Pr alloy, an alloy containing Co, Al, Cu, Ga, and Zr, and a single metal were mixed to form a strip cast alloy (SC alloy) (for example, composition: Nd２ Fe １４ B) was prepared under an argon atmosphere. The SC alloy was a plate-shaped powder, with the dimensions of the main surface being 10 mm x 10 mm - 20 mm x 20 mm. The "Rare Earth Elements" column of "Plate Magnet" in Table 1 indicates the rare earth elements contained in the plate magnet.

[0083] (2) Hydrogen Crushing Step The SC alloy was allowed to absorb hydrogen in a hydrogen furnace (hydrogen atmosphere, 200°C, 2 hours) to embrittle the grain boundaries (neodymium-rich phases) of the SC alloy.

[0084] (3) Coarse grinding step, first lubricant addition step A lubricant was added to the SC alloy powder that had undergone the hydrogen crushing step. Methyl caprylate was used as the lubricant. The lubricant was mixed at a ratio of 0.03% by mass 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 ground using a stirrer in a nitrogen or argon atmosphere. The average particle size of the SC alloy after coarse grinding was 50 μm to 500 μm.

[0085] (4) Fine pulverization step, second lubricant addition step 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 was added to the SC alloy powder after fine pulverization. Methyl laurate was used as the lubricant. The mixing ratio of the lubricant to the amount of SC alloy was 0.05% by mass-0.1% by mass.

[0086] (5) Powder Filling Step, Orientation Step, and Compacting Step The SC alloy powder after the pulverization step and the second lubricant addition step was filled into each molding space of a mold provided with multiple partition plates in a nitrogen atmosphere. Each compact formed in each molding space corresponds to each magnet to be stacked in a subsequent step. In the samples of the Examples and Comparative Examples, each magnet had the thickness shown in Table 1 and was a rectangular parallelepiped with dimensions of 5 mm x 16 mm. A magnetic field (e.g., 5000 V) was applied to the mold after powder filling in the planar direction of each compact (direction perpendicular to the thickness direction) to align the orientation of the SC alloy powder. The SC alloy powder filled in the mold was compressed to form an SC alloy compact. The pressure molding conditions were pressure: 5 MPa-20 MPa, packing density: 3.0 g / cm.３ -4.0 g / cm ３ , relative density: 40%-52%.

[0087] (6) Mold Disassembly Process, First Firing Process The outer frame was removed from the mold, and a continuous arrangement of molded bodies and partition plates (the object to be fired) was prepared. For dehydrogenation, the object to be fired (with the partition plates) was heated at 500°C for 3-4 hours in an Ar atmosphere. Thereafter, the object to be fired (with the partition plates) was held at 930°C-1050°C for 3 hours and fired in a vacuum atmosphere.

[0088] (7) Insulating Bonding Layer Coating Step After the first firing step, the partition plate was removed from the fired object, and the raw material for the insulating bonding layer was coated on six surfaces of the magnet before lamination. The raw material for the insulating bonding layer was a mixture of compound powders 1-3 and a solvent as shown in Table 1. The compound powders 1-3 in the raw material for the insulating bonding layer (mass %) were as shown in Table 1 for compound ratios 1-3. The coating thickness of the raw material for the insulating bonding layer was 12 μm or more and 14 μm or less. The raw material for the insulating bonding layer was coated in the atmosphere using a spray method.

[0089] (8) Laminate Temporarily Fixing Process Eight to eighty magnets coated with an insulating bonding layer were stacked in air and temporarily fixed. The number of magnets stacked 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.

[0090] (9) Hot Pressing Process The temporarily fixed laminate was placed in a hot press mold and subjected to uniaxial hot pressing. The hot pressing conditions for each example and comparative example were as shown in Table 1. In Table 1, "vac" in "atmosphere" indicates vacuum conditions. The hot pressing time was 1 second to 1 hour, and the hot pressing heat treatment time was 10 minutes to 20 hours. In this way, laminated magnet samples were produced for each example and comparative example.

[0091]

[0092] 2. Characteristics of Examples and Comparative Examples Tables 1 and 2 summarize the characteristics of each Example and Comparative Example. The column "First diffusion depth: α" under "Diffusion depth of heavy rare earth element" indicates the first diffusion depth measured by the method described above in "(4) Requirement for diffusion depth β / α of heavy rare earth element." The column "Second diffusion depth: β" indicates the second diffusion depth measured by the method described above in "(4) Requirement for diffusion depth β / α of heavy rare earth element." The column "Depth ratio: β / α" indicates the value of β / α calculated by the method described above in "(4) Requirement for diffusion depth β / α of heavy rare earth element."

[0093] The column "First region: γ" in "Amount of heavy rare earth element" indicates the amount of heavy rare earth element in the first region measured by the method described above in "(5) Requirement regarding the ratio γ / δ of heavy rare earth element." The column "Second region: δ" indicates the amount of heavy rare earth element in the second region measured by the method described above in "(5) Requirement regarding the ratio γ / δ of heavy rare earth element." The column "Concentration ratio: γ / δ" indicates the value of γ / δ calculated by the method described above in "(5) Requirement regarding the ratio γ / δ of heavy rare earth element." The column "High concentration portion" in "Amount of heavy rare earth element" indicates the result of measurement by the method described above in "(6) Requirement regarding the portion with the highest amount of heavy rare earth element." "Corner portion" indicates that the amount of heavy rare earth element in the corner portion E1 or the corner portion E2 is greater than the amount of heavy rare earth element in the main surface 11A and the amount of heavy rare earth element in the side surface 11B. The term "main surface" means that the amount of heavy rare earth element in the main surface 11A is greater than the amount of heavy rare earth element in the corner E1 or E2 and the amount of heavy rare earth element in the side surface 11B. The term "side surface" means that the amount of heavy rare earth element in the side surface 11B is greater than the amount of heavy rare earth element in the corner E1 or E2 and the amount of heavy rare earth element in the main surface 11A.

[0094] The "Composition" column under "Interface" indicates elements detected 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, as explained above in "(7) Requirements for the interface between the plate magnet 11 and the insulating bonding layer 13." The "Presence of Group 2A metal elements" column indicates whether the requirement that Group 2A metal elements are present 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 is met. The "Bonding with specific metal phase" column indicates whether the requirement that fluoride particles of a metal element are in contact with a phase containing a heavy rare earth element and two or more metal components is met. The "Average particle size" indicates the average particle size of fluoride particles, measured using the method explained above in "(6) Requirements for the average particle size of fluoride particles."

[0095]

[0096] 3. Performance Evaluation (1) Strength To evaluate the strength of the examples and comparative examples, the three-point bending strength was measured in accordance with JIS R1601: 2008. High three-point bending strength is an indicator of high adhesive strength between the plate magnet and the insulating bonding layer.

[0097] The evaluation was made as follows: "AA": bending strength greater than 50N; "A": bending strength greater than 40N and equal to or less than 50N; "B": bending strength greater than 20N and equal to or less than 40N; "C": bending strength equal to or less than 20N.

[0098] (2) Evaluation method for coercive force Coercive force (kA / m) was measured using a pulsed BH tracer. The measurement direction was perpendicular to the surface of the top magnet for laminated magnets. A high coercive force is an indicator of high heat resistance as a magnet.

[0099] The evaluation was made as follows: "A": 2150 kA / m or more and less than 2400 kA / m; "B": 2000 kA / m or more and less than 2150 kA / m; "C": less than 2000 kA / m

[0100] (3) Evaluation of Heat Generation Temperature A 5mm x 16mm x 50mm block magnet was prepared as a reference. The block magnet and the laminated magnets of each example and comparative example were attached to a motor, and a test was conducted in which the motor was driven at rotation speeds of 2000 rpm, 4000 rpm, 6000 rpm, and 8000 rpm. Immediately after the test, the surface temperatures of the block magnet and the laminated magnets of each example and comparative example were measured using a laser and Thermo Label (registered trademark). The difference (°C) was calculated by subtracting the surface temperature (°C) of the laminated magnets of each example and comparative example from the surface temperature (°C) of the block magnet, and the result was evaluated according to the following criteria. A lower difference (°C) is an indicator of an advantage in reducing eddy current loss.

[0101] The evaluation was made as follows: "A": difference value is less than -20°C; "B": difference value is between -20°C and -10°C; "C": difference value is -10°C or more.

[0102] 4. Evaluation Results The evaluation results are shown in Table 3.

[0103] Example 1-21 satisfies the following requirements (a) to (d). Requirement (a): The magnet is made up of three or more sheet magnets having an upper bottom surface, a lower bottom surface, and side surfaces, and containing a rare earth element. Requirement (b): The magnet is a laminate in which sheet magnets and insulating bonding layers are alternately stacked. Requirement (c): The first diffusion depth α μm measured by the above measurement method (1) and the second diffusion depth β μm measured by the above measurement method (2) satisfy the following relationship: 0.35≦β / α≦0.50. Requirement (d): When the amount of heavy rare earth element in the first region that satisfies the above conditions (3) to (6) is γ% by mass, and the amount of the heavy rare earth element in the second region that satisfies the above conditions (7) to (8) is δ% by mass, the magnet satisfies the following relationship: γ / δ≧5.0.

[0104] In contrast, Comparative Examples 1 to 5 do not satisfy the following requirements: Comparative Examples 1 and 5 do not satisfy requirements (c) and (d), and Comparative Examples 2 to 4 do not satisfy requirement (d).

[0105] In Example 1-21, the coercive force was evaluated as "A" or "B." In contrast, in Comparative Example 1-5, the coercive force was evaluated as "C." Example 1-21 suggests that heat resistance can be efficiently improved without using an excessive amount of heavy rare earth elements.

[0106] Furthermore, among Examples 1-21, Example 6-21, which further satisfied the following requirement (e), was rated "A" for coercivity. It was suggested that by satisfying requirement (e), heat resistance can be further improved. Requirement (e): In the specified intermediate magnet, the corners between the upper base surface and the side surface, or the corners between the lower base surface and the side surface, are the areas where the amount of heavy rare earth element is greatest.

[0107] Furthermore, among Examples 1-21, Examples 11-21, which further satisfied the following requirement (f), were evaluated as having a strength of "AA" or "A." It was suggested that by satisfying requirement (f), the adhesion strength between the plate magnet and the insulating bonding layer can be improved. Requirement (f): Fluoride particles of a metal element are in contact with a phase containing a heavy rare earth element and two or more metal components.

[0108] Furthermore, among Examples 1 to 21, Examples 17 to 21, which further satisfied the following requirement (g), were rated as "AA" in strength and "A" in heat generation temperature. It was suggested that by satisfying requirement (g), strength can be improved and eddy current loss can be reduced. Requirement (g): The average particle size of the fluoride particles is 2.0 μm or more and 8.0 μm or less.

[0109] 5. Effects of the Example In the present example, heat resistance could be efficiently imparted without using an excessive amount of heavy rare earth elements.

[0110] 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.

[0111] DESCRIPTION OF SYMBOLS 10...Laminated magnet 11...Plate magnet 11A1...Upper bottom surface 11A2...Lower bottom surface 11B...Side surface 13...Insulating bonding layer 14...Fluoride particles 17...Surface layer 17A...Specific metal phase 30...Motor 31...Stator 33...Rotor 34...Rotating shaft 35...Rotating core 37...Shaft hole 39...Magnet hole 111...Top magnet 112...Intermediate magnet 112A...Specific intermediate magnet 113...Bottom magnet E1, E2...Corner portion I...Interface

Claims

1. A laminated magnet comprising three or more plate magnets each having an upper bottom surface, a lower bottom surface, and a side surface, each containing a rare earth element, and in which the plate magnets and insulating bonding layers are alternately stacked, wherein for a specific intermediate magnet which is any of the intermediate magnets excluding the topmost magnet located at the top of the plate magnets and the bottommost magnet located at the bottom, when a virtual line is taken through the center of gravity of the laminated magnet and extending in the stacking direction, and a cross section of the laminated magnet is cut so that its cross-sectional area is smallest on a virtual plane including the virtual line, the first diffusion depth αμm measured by the following measurement method (1) and the second diffusion depth βμm measured by the following measurement method (2) satisfy 0.35≦β / α≦0.50, and when the amount of the heavy rare earth element in the first region which satisfies the following conditions (3) to (6) is γ% by mass, and the amount of the heavy rare earth element in the second region which satisfies the following conditions (7) to (8) is δ% by mass, the laminated magnet satisfies γ / δ≧5.

0. Measurement method (1): A line analysis is performed on a line that passes through the center of gravity of the plane figure of the specific intermediate magnet that appears in the cross section and extends in the stacking direction, from the top bottom surface to the center of gravity of the plane figure, to obtain a first profile of the intensity of the heavy rare earth element normalized so that the maximum intensity between the lines is 1. The distance between the position of the top bottom surface and the position where the intensity of the heavy rare earth element first becomes 0.7 is defined as a first diffusion depth α μm. Measurement method (2): A line analysis is performed on a line that passes through the center of gravity of the plane figure of the specific intermediate magnet that appears in the cross section and extends in a direction perpendicular to the stacking direction, from the side surface to the center of gravity of the plane figure, to obtain a second profile of the intensity of the heavy rare earth element normalized so that the maximum intensity between the lines is 1. The distance between the position of the side surface and the position where the intensity of the heavy rare earth element first becomes 0.7 is defined as a second diffusion depth β μm. Condition (3): The first region is present on the specific intermediate magnet side from the interface between the specific intermediate magnet and the insulating bonding layer. Condition (4): The first region is a rectangle that is 10 μm in the stacking direction and 50 μm in the direction perpendicular to the stacking direction. Condition (5): When a straight line is drawn that passes through the center of gravity of the planar figure of the specific intermediate magnet that appears in the cross section and extends in the stacking direction, the center of the rectangle is on the straight line. Condition (6): The rectangle is in contact with the insulating bonding layer.Condition (7): The second region is a rectangle having a size of 10 μm in the stacking direction and a size of 50 μm in a direction perpendicular to the stacking direction. Condition (8): The center of the rectangle is located at the center of gravity of the planar figure of the specific intermediate magnet that appears in the cross section.

2. The laminated magnet according to claim 1, wherein the specific intermediate magnet has a maximum amount of the heavy rare earth element at a corner between the upper base surface and the side surface, or at a corner between the lower base surface and the side surface.

3. A laminated magnet as described in claim 1 or 2, wherein a metal element of Group 2A of the Periodic Table is present in the range from the interface between the plate magnet and the insulating bonding layer to a depth of 10 μm on the specific intermediate magnet side.

4. A laminated magnet according to claim 1 or 2, wherein fluoride particles of a metal element are in contact with a phase containing the heavy rare earth element and two or more metal components.

5. The laminated magnet according to claim 4, wherein the average particle size of the fluoride particles is 2.0 μm or more and 8.0 μm or less.

6. A motor having the laminated magnet according to claim 1 or 2.

Images