WO2025057757A1 - Motor - Google Patents

Abstract

The present invention provides a novel motor in which a decrease in efficiency can be suppressed.　This motor (30) is provided with a rare earth magnet (10). The rare earth magnet (10) has a plurality of magnets (11) and an insulating layer (13) present between the plurality of magnets (11). The insulating layer (13) contains an inorganic crystal as a main component.

Description

motor

This disclosure relates to a motor. This application is based on Japanese Patent Application No. 2023-146628 filed on September 11, 2023, and Japanese Patent Application No. 2023-146627 filed on September 11, 2023, and claims the benefit of priority thereto, the entire contents of which are incorporated herein by reference.

Patent Document 1 discloses a rotor equipped with a permanent magnet. Patent Document 2 also discloses a rotor equipped with a permanent magnet. In either case, the permanent magnet is a block-shaped magnet that is not divided.
Patent Document 3 discloses an IPM rotor equipped with a magnet, in which an example of the magnet is composed of a plurality of segmented magnets that are divided in the axial direction.

JP 2022-155164 A JP 2022-155204 A JP 2018-161001 A

In recent years, there are various demands for motors. For example, there is a demand for suppressing a decrease in motor efficiency by using magnets that can reduce eddy current loss that occurs inside the motor in high-temperature environments such as 150° C.
The present disclosure has been made in consideration of the above-mentioned circumstances, and has an object to provide a novel motor capable of suppressing a decrease in efficiency. The present disclosure can be realized in the following form.

A motor having a laminated magnet,
The magnet stack has a plurality of magnets and an insulating layer between the magnets,
A motor, wherein the insulating layer is mainly composed of inorganic crystals.

This disclosure provides a new motor that can suppress efficiency decline.

FIG. 1 is a perspective view showing a schematic diagram of an example of a rare earth magnet according to a first embodiment. FIG. 2 is a top view of a rare earth magnet. 3 is a cross-sectional view taken along line AA in FIG. 2. FIG. 2 is a diagram for explaining a method for measuring the average orientation degree of magnets. FIG. 2 is a cross-sectional view of another example 1 of a rare earth magnet. FIG. 6 is an enlarged view showing a part of FIG. 5 . FIG. 13 is a perspective view showing another example of a rare earth magnet according to the present invention; FIG. 11 is a diagram for explaining a method for measuring the average orientation degree of magnets in another example 2. FIG. 2 is a diagram illustrating each part for measuring an average degree of orientation. FIG. 2 is a cross-sectional view illustrating a schematic view of a part of a motor. FIG. FIG. 11 is a perspective view illustrating an example of a magnet stack according to a second embodiment. FIG. 2 is a top view of a laminated magnet. This is a cross-sectional view of line AA in Figure 13. FIG. 2 is a cross-sectional view of another example 1 of a laminated magnet. FIG. 2 is a diagram for explaining a method for measuring the average orientation degree of magnets. FIG. 13 is a diagram for explaining a method for measuring the average degree of orientation of magnets in Example 2. FIG. 2 is a diagram illustrating each part for measuring an average degree of orientation. FIG. 2 is a cross-sectional view illustrating a schematic view of a part of a motor. FIG. 11A and 11B are diagrams showing the simulation results of sample A and an image of the distribution of magnetic flux density. 13A and 13B are diagrams showing the simulation results of sample B and an image of the distribution of magnetic flux density. 13A and 13B are diagrams showing the simulation results of sample C and an image of the distribution of magnetic flux density.

The present disclosure also aims to provide a new motor with improved performance by using magnets that can reduce eddy current losses generated inside and concentrate magnetic flux.

Here, a preferred example of the present disclosure is given.
[1]
A motor having a laminated magnet,
The magnet stack has a plurality of magnets and an insulating layer between the magnets,
A motor, wherein the insulating layer is mainly composed of inorganic crystals.
[2]
The magnet stack is formed by stacking the magnets and the insulating layer in a first direction,
the magnet contains a rare earth element and has a curved shape that is convex in a second direction when viewed from the first direction,
The motor described in [1], wherein the average orientation degree of each portion of a 1 mm width centered on the normal line at multiple points from one end to the other end on the curve on the convex side in the second direction on the outer periphery of the magnet when viewed from the first direction is 90% or more.
[3]
The motor according to [1] or [2], which is used at a maximum rotation speed of 7,500 rpm or more.

First Embodiment
The first embodiment of the present disclosure will be described in detail below. In the first embodiment, a description using "-" for a numerical range includes both the lower limit and the upper limit unless otherwise specified. For example, the description "10-20" includes both the lower limit "10" and the upper limit "20". That is, "10-20" has the same meaning as "10 or more and 20 or less". In this specification, the upper limit and the lower limit of each numerical range can be arbitrarily combined. Hereinafter, the Z-axis direction in each figure is the direction in which the multiple magnets 11 are arranged. One 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).

1. Motor 30
The motor 30 includes a rare earth magnet 10 (laminated magnet). The rare earth magnet 10 has a plurality of magnets 11 and insulating layers 13 present between the plurality of magnets 11. The insulating layers 13 are mainly composed of inorganic crystals.

The rare earth magnet 10 disclosed herein has low eddy current loss generated inside and is resistant to change, 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, compared to insulating layers made of resin or the like, the insulating layer 13 of the rare earth magnet 10 is less susceptible to changes in insulating performance due to the influence of humidity, temperature, and deterioration over time, which can suppress performance degradation of the motor 30.

Below, an example of a motor 30 equipped with a rare earth magnet 10 will be described with reference to Figures 10 and 11. The motor 30 includes a stator 31 and a rotor 33 arranged inside the stator 31. A rare earth magnet 10 is arranged in the rotor 33, and a winding (not shown) is arranged in the stator 31. The motor 30 in Figure 10 is an inner rotor type with magnets arranged on the inside (rotating shaft side) and windings arranged on the outside. The motor is not limited to the inner rotor type. For example, the motor may be an outer rotor type with windings arranged on the inside (rotating shaft side) and magnets arranged on the outside.

The rotor 33 comprises a rotating shaft 34, a rotating core 35, and a plurality of rare earth 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 rare earth magnet 10 is inserted into each magnet hole 39.

The motor 30 is preferably used at a maximum rotation speed of 7500 rpm or more. The upper limit of the maximum rotation speed is not particularly limited. The maximum rotation speed is, for example, 50,000 rpm or less. "Used at a maximum rotation speed of 7500 rpm or more" means that the motor can be used at a rotation speed of 7500 rpm or more under certain conditions, and is not limited to a configuration that is always used at a rotation speed of 7500 rpm or more. For example, the motor 30 can be variable speed controlled using an inverter. When variable speed control is performed using an inverter, there is a concern that eddy current loss will increase if the inverter's PWM (Pulse Width Modulation) carrier frequency becomes high. The motor 30 disclosed herein is expected to reduce eddy current loss even at high rotation speeds of 7500 rpm or more by using rare earth magnets 10.

The motor disclosed herein is not limited to an IPM (Interior Permanent Magnet) motor in the case of a permanent magnet synchronous motor, but may be an SPM (Surface Permanent Magnet) motor. In addition to a permanent magnet synchronous motor, the motor may be a permanent magnet DC motor, a linear synchronous motor, a voice coil motor, a vibration motor, etc.

As illustrated in Figures 1 to 3, the rare earth magnet 10 comprises a plurality of magnets 11 and an insulating layer 13 present between the magnets 11.

(1) Magnet 11
(1.1) Composition of magnet 11 Magnet 11 is a permanent magnet containing a rare earth element. From the viewpoint of having good magnetic properties, magnet 11 is preferably a rare earth sintered magnet.

The composition of 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 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 magnet 11 is, for example, 27 mass% or more, and may be 28 mass% or more, or 28.5 mass% or more. The total amount of rare earth elements in 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 contained in the raw materials of magnet 11 and insulating layer 13.

An example of magnet 11 is a magnet containing a rare earth element (R), a transition metal element (T), and boron (B). Such magnets are also called R-T-B magnets.

The rare earth element may be, for example, 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 that the rare earth element contains one or more of Nd, Pr, Dy, and Tb, and it is more preferable that Nd is contained as the main component. Note that Nd as the main component means that the content (mass%) of Nd 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 magnet 11, and more preferably 0.5% by mass or more and 1.5% by mass or less.

The transition metal element may be, for example, 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 content (mass%) of Fe is the highest among the transition metal elements.
The content of the transition metal element is preferably 60% by mass or more, and more preferably 65% by mass or more, of the entire magnet 11. There is no particular upper limit to the content of the transition metal element, and it can be, for example, 73% by mass or less of the entire magnet 11. In addition, when Fe and Co are contained, a part of the Fe may be substituted with Co. For example, when the sum of Fe and Co is 100% by mass, the content of Co can be more than 0% by mass and 1% by mass or less.

The magnet 11 may contain elements other than the above elements (hereinafter also referred to as other elements). Examples of other elements include one or more elements selected from the group consisting of 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% by mass or more and 3% by mass or less of the entire magnet 11 .

From the viewpoint of improving the coercive force, it is more preferable that the magnet 11 has a region in which the concentration of the heavy rare earth element decreases from at least a part of the surface of the magnet 11 toward the inside of the magnet 11. In FIG. 6, the decrease in the concentration of the heavy rare earth element is represented by the shade of the hatching. Parts with a high concentration of the heavy rare earth element are shown with a dark shade, while parts with a low concentration are shown with a light shade. A configuration having a region in which the concentration of the heavy rare earth element decreases can contribute to reducing the amount of the heavy rare earth element added while maintaining magnetic properties. The heavy rare earth element may 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 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 magnet 11 and then heat treating it. Details will be described later.

Moreover, the magnet 11 preferably has, for example, a main phase of Nd ₂ Fe ₁₄ B and a rare earth rich phase having a higher rare earth element content than the main phase. The 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 magnet 11 can be identified as the component with the greatest peak intensity by performing XRD (X-ray diffraction) analysis on magnet 11. That is, when the peak intensity of Nd ₂ Fe ₁₄ B is the greatest, it can be determined that magnet 11 has a main phase of Nd ₂ Fe ₁₄ B.

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

The average degree of orientation of the magnet 11 is determined, for example, as follows.
When the magnet 11 is a rectangular parallelepiped (rectangular prism) as shown in Figs. 1 and 4, for example, it is cut out to a size corresponding to the measuring device and measured. For example, in the rectangular bottom surface of the magnet 11 in Fig. 4, the average orientation degree is obtained as the average orientation degree of each part of 1 mm width centered on the normal line Nn at multiple points Pn from one end to the other end on the long side. The number of multiple points Pn is not particularly limited. In Fig. 4, five points P1-P5 and normal lines N1-N5 at each point P1-P5 are shown. When the size of the 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 pulse type high magnetic field measuring device (magnetic field: 4T) can be used as the measuring device. When the cut-out part 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 part.

When magnet 11 has a convex curved shape, for example as shown in Figures 7 and 8, the average orientation is determined as the average orientation degree of each portion of a 1 mm width centered on normal Nn at multiple points Pn from one end to the other end on the curve C1 on the convex side of the outer periphery of magnet 11 as viewed from the first direction (Z-axis direction). The number of multiple points Pn is not particularly limited. When the size of 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. Note that when magnet 11 has a convex curved shape, the radius of curvature of curve C1 is not limited to being constant and may vary.

8 and 9, a method for calculating the average degree of orientation when magnet 11 has a convex curved shape will be specifically described below. On the outer periphery of magnet 11 as viewed from the Z-axis direction, the curve on the convex side is designated as curve C1, and the line tracing the side opposite curve C1 is designated as opposite line C2.
First, a number of points Pn are identified as shown in Fig. 8. In this embodiment, five points P1-P5 are identified. In the magnet 11, points P1 and P5 at both ends are taken at a position within 5 mm from one end (e.g., the left end) of the curve C1 on the convex side, and a position within 5 mm from the other end (e.g., the right end). A number of points (points P2-P4 in this embodiment) are taken in order from one end at positions that divide the distance between points P1 and P5 at both ends of the curve C1 at equal intervals (positions that divide the distance into four in this embodiment). Note that point P3 in this embodiment is located in the middle of the curve C1.

On the curve C1, identify the normal lines N1-N5 at each of the points P1-P5. Cut out a 1 mm wide portion 12 centered on the normal line Nn from the magnet 11. Each portion 12 is, for example, in the shape of a roughly rectangular prism, as shown in FIG. 9. Note that in reality, the top and bottom surfaces in FIG. 9 are curved surfaces. The degree of orientation of each portion 12 is measured, for example, with a pulsed high magnetic field measuring device (magnetic field: 4T). If the cut-out portion does not fit into the measuring device, cut out a sample from the center of the cut-out portion to a size that can fit into the measuring device. The average value of the degrees of orientation of each portion 12 is calculated as the average degree of orientation.

The average degree of orientation of magnet 11 can be controlled, for example, by appropriately designing the magnetic field applied in the orientation process described below. For example, even if magnet 11 has a convex curved shape, the above-mentioned 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 magnet 11 in the orientation process described below.

(1.3) Shape of the magnet 11 The shape of the magnet 11 is not particularly limited. For example, the magnet 11 is preferably plate-shaped. The plate-shaped magnet 11 has a smaller distance from the surface to the deepest part than a block-shaped magnet with a larger thickness. Therefore, the plate-shaped magnet 11 is suitable because it is easy to diffuse the heavy rare earth element to the inside when the heavy rare earth element is diffused at grain boundaries. The plate-shaped magnet 11 can be preferably used as a laminated magnet in which multiple magnets 11 and insulating layers 13 are laminated. In the rare earth magnet 10 of FIG. 1, multiple magnets 11 are laminated with the thickness direction of the plate-shaped magnet 11 as the lamination direction. In this laminated magnet, the magnets 11 and the insulating layers 13 are laminated alternately. In the laminated magnet, each magnet 11 may also be referred to as a magnet body. Note that the magnet 11 in FIG. 1 and FIG. 2 has a rectangular shape when viewed from above (Z-axis direction). Magnet 11 may have a shape other than rectangular when viewed from above, and may, for example, as shown in Figures 7 and 8, have a curved shape (such as a so-called arc shape) that is convex in one direction when viewed from above (the positive direction in the X-axis direction in Figure 8, the upward direction in Figure 8).

(1.4) Thickness of magnet 11 The thickness of magnet 11 is preferably 0.5 mm or more and 4.0 mm or less, more preferably 1.2 mm or more and 2.5 mm or less. If the thickness of magnet 11 is 0.5 mm or more, it is easy to form magnet 11 while ensuring the average degree of orientation. If the thickness of magnet 11 is 4.0 mm or less, it is easy to diffuse the heavy rare earth element to the inside. Also, if the thickness is 4.0 mm or less, the eddy current loss inside rare earth magnet 10 can be suitably reduced. The dimensions of the plate-shaped magnet 11 in the direction perpendicular to the thickness are not particularly limited. For example, 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.

(2) Insulating layer 13
(2.1) Composition of insulating layer 13 The insulating layer 13 is mainly composed of inorganic crystals. The inorganic crystals are preferably non-magnetic crystalline particles. Incidentally, "mainly composed of inorganic crystals" means that the content of inorganic crystals in the insulating layer 13 is 50% by mass or more. Incidentally, the content of inorganic crystals in the insulating 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 layer 13 can be analyzed by the following method: The presence of inorganic crystals is determined by micro X-ray analysis or XRD analysis, and the content of inorganic crystals is calculated in combination with composition analysis by EPMA (Electron Probe Micro Analyser).

From the viewpoint of reducing eddy current loss, it is preferable _that the insulating layer 13 contains one or _more inorganic crystals selected from _the group consisting _{of CaF2, BaF2, SrF2, MgF2, Al2O3 , ZrO2 , Dy2O3 , Tb2O3 , Nd2O3} , _TbF3 , _DyF3 , LiF, _SiO2 , _{BN , ZrB2} , _Si3N4 , _TiB2 , _Pr2O3 , and _SiC .
From the viewpoint of reducing eddy current loss, the insulating layer 13 preferably contains at least a fluoride of Group 2A of the periodic table as an inorganic crystal. More preferably, the insulating layer 13 contains at least one or more fluorides of Group 2A of the periodic table selected from the group consisting of CaF ₂ , BaF ₂ , SrF ₂ , and MgF ₂ as the fluoride of Group 2A of the periodic table. Of these, the insulating layer 13 particularly preferably contains CaF ₂ .

When the entire inorganic crystal is taken as 100 mass%, the insulating layer 13 preferably contains 80 mass% or more of the fluoride of Group 2A of the periodic table as the inorganic crystal, more preferably 90 mass% or more, and even more preferably 95 mass% or more. There is no particular upper limit to the content of the above-mentioned fluoride of Group 2A of the periodic table, and it may be, for example, 100 mass%.

When insulating layer 13 is mainly composed of Group 2A fluoride of the periodic table, it is preferable that the raw material for insulating layer 13 contains a compound of a heavy rare earth element as described above in addition to the Group 2A fluoride of the periodic table. If the raw material for insulating layer 13 contains a compound of a heavy rare earth element as described above, the heavy rare earth element can be favorably diffused into magnet 11. The heavy rare earth element contained in the raw material for insulating layer 13 diffuses into magnet 11 after heat treatment. For this reason, insulating layer 13 of the obtained rare earth magnet 10 contains almost no heavy rare earth element.
There is no particular limitation on the mass ratio of the fluoride of Group 2A of the periodic table to the compound of the heavy rare earth element in the raw material of the insulating layer 13. The mass ratio of the fluoride of Group 2A of the periodic table to the compound of the heavy rare earth element in the raw material of the insulating layer 13 can be, for example, 20:80 to 40:60.

(2.2) State and Arrangement of Insulating Layer 13 It is sufficient that insulating layer 13 is present at least between magnets 11, 11.
The insulating layer 13 is disposed, for example, as follows.
The insulating layer 13 may be arranged so as to cover the entire surface of the magnet 11 (see FIG. 5). In the example of FIG. 5, both the upper and lower main surfaces 11A and both side surfaces 11B of each magnet 11 are covered with the insulating layer 13, and the insulating layer 13 is arranged so as to cover the entire surface of the magnet 11.
The insulating layer 13 may be arranged in a form that covers a part of the surface of the magnet 11 (see FIG. 3). In the example of FIG. 3, the side surface 11B of each magnet 11 is not covered with the insulating layer 13, and the insulating layer 13 is arranged in a form that covers a part of the surface of the magnet 11. In the example of FIG. 3, the main surface 11A of the topmost magnet 11 is covered with the insulating layer 13 on one side (lower side), but the main surface 11A of the other side (upper side) is not covered with the insulating layer 13, and the insulating layer 13 is arranged in a form that covers a part of the surface of the magnet 11. Similarly, in the example of FIG. 3, the main surface 11A of the bottommost magnet 11 is covered with the insulating layer 13 on one side (upper side), but the main surface 11A of the other side (lower side) is not covered with the insulating layer 13, and the insulating layer 13 is arranged in a form that covers a part of the surface of the magnet 11. Furthermore, the insulating layer 13 may be disposed between multiple magnets 11 so as to extend from one side 11B of the magnets 11 (e.g., the left side in Figs. 3 and 4) to the other side 11B (e.g., the right side in Figs. 3 and 5) (see Figs. 3 and 5), or may be disposed so as to partially cut off the magnets 11. In other words, as long as the rare earth magnet 10 has portions where the magnets 11 are insulated from each other by the insulating layer 13, the magnets 11 may have portions where the magnets 11 are partially connected to each other.

The insulating layer 13 is preferably provided so as to be in direct contact with the magnet 11. The insulating layer 13 may also be an insulating bonding layer that bonds (adheres) the magnets 11, 11 located on both sides. From the viewpoint of bonding the magnets 11, 11 with sufficient strength, the insulating layer 13 preferably has an area in which components derived from the insulating layer 13 and components derived from the magnet 11 are mixed in the arrangement direction (Z-axis direction) of the multiple magnets 11. Such a rare earth magnet 10 can be suitably formed by hot pressing. The conditions for hot pressing will be described later.

The insulating layer 13 may be provided along the orientation direction of the magnetic field of each 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). As shown in FIG. 10, when the rare earth magnet 10 is used as a motor magnet, etc., from the viewpoint of efficiently reducing eddy current loss, it is preferable that the insulating layer 13 is provided along the orientation direction of the magnet 11 (the X-axis direction in FIG. 10). With this configuration, the insulating layer 13 is arranged approximately parallel to the direction in which the magnetic flux generated in the stator 31 passes through the rare earth magnet 10 (the X-axis direction in FIG. 10), so that eddy current loss can be effectively reduced.

(2.3) Thickness of Insulating Layer 13 The thickness T of the insulating layer 13 is not particularly limited. From the viewpoint of ensuring sufficient insulation, the thickness T of the insulating 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 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 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 layer 13 is measured, for example, by observing the cross section of the rare earth magnet 10 with a SEM (scanning electron microscope) and determining the distance between the magnets 11 located on either side of the insulating layer 13 (see FIG. 6).

2. Manufacturing Method of Rare Earth Magnet 10 There are no particular limitations on the manufacturing method of rare earth magnet 10. An example of a manufacturing method for rare earth magnet 10, which is a laminated magnet in which magnets 11 and insulating layers 13 are alternately laminated, is shown below.

(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.

(2) Hydrogen Crushing Step 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 hour to 5 hours), thereby embrittling the grain boundaries (rare earth rich phase) of the SC alloy.

(3) Coarse pulverization step, first lubricant addition step The SC alloy powder that has been subjected to the hydrogen crushing step is coarsely pulverized (coarse pulverization 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.).

(4) Fine pulverization step, second lubricant addition step The SC alloy powder after the coarse pulverization step is finely pulverized to a predetermined average particle size D50 (fine pulverization step). The average particle size D50 can be, for example, 2.0 μm to 3.5 μm. At this time, in order to improve the fluidity of the finely pulverized powder, a lubricant may be added to the finely pulverized SC alloy powder (second lubricant addition step). This step may be performed, for example, in an inert atmosphere (nitrogen atmosphere, argon atmosphere, etc.).

(5) Powder filling process, orientation process, molding process The powder of the SC alloy after the pulverization process is filled into a mold. This process may be performed, for example, under an inert atmosphere (nitrogen atmosphere, argon atmosphere, etc.). The mold has a plurality of molding spaces of a predetermined thickness. Each molding space is partitioned, for example, by a plurality of partition plates. A magnetic field is applied in a predetermined direction to the mold after the powder is filled to align the orientation of the SC alloy powder. Then, the powder of the SC alloy filled in the mold is pressed to form a molded body of the SC alloy. In this way, a molded body of the SC alloy having a predetermined degree of orientation (for example, an average degree of orientation of 90% or more) and a predetermined thickness (for example, a thickness of 1.2 mm or more and 2.5 mm or less) can be obtained without performing a cutting process.

(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 to 1200°C) for a predetermined time (e.g., 2 hours to 5 hours) (first sintering step). This sintering is preferably performed in a vacuum. Prior to this sintering, heating at a temperature lower than the sintering temperature may be performed for dehydrogenation.

(7) Insulation Layer Coating Step The raw material of the insulation layer 13 is coated on the surface of the fired compact. The raw material of the insulation layer 13 may be, for example, a mixture of raw material powder of an inorganic crystal component, a compound powder containing a heavy rare earth element, and a solvent. The raw material of the insulation 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 magnet 11. The raw material of the insulation layer 13 may be coated on the entire surface of the compact, that is, on both main surfaces and side surfaces when the compact is in the form of a plate.

(8) Laminate Temporarily Fixing Process A predetermined number of molded bodies coated with an insulating layer are stacked and temporarily fixed. Hereinafter, the temporarily fixed laminate of molded bodies is also referred to as a laminate. According to this method, it is possible to manufacture plate-shaped magnets 11 without the need for a cutting process or the like to cut out plate-shaped magnets from a large magnet.

(9) Hot Pressing Process The temporarily fixed laminate is placed in a hot press mold, and uniaxial hot pressing is performed. This process may be performed, for example, in a vacuum atmosphere (for example, 10 ⁻³ Pa to 10 ⁻⁴ Pa) or in an inert atmosphere (for example, a nitrogen atmosphere, an argon atmosphere, etc.). The temperature of the hot press may be, for example, 700° C. to 1100° C. The pressing time of the hot press may be, for example, 1 second to 1 hour. The pressure of the hot press 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 pressure of the hot press is not particularly limited, and is, for example, 100 MPa or less. The heat treatment time of the hot press may be, for example, 10 minutes to 20 hours.
Through the above series of steps, rare earth magnet 10 is manufactured, which includes magnets 11 and insulating layers 13. Rare earth magnet 10 is formed by bonding a plurality of magnets 11 together with insulating layers 13, forming an integrated unit.

The hot pressing process allows the heavy rare earth elements (Tb, Dy, etc.) contained in the raw material of the applied insulating layer 13 to diffuse into the magnet 11. The hot pressing process also allows the rare earth components (Nd components) in the magnet 11 (e.g., Nd ₂ Fe ₁₄ B) to flow out to the surface of the magnet 11, forming a surface layer of a rare earth-rich phase (Nd-rich phase) near the interface with the insulating layer 13 (e.g., a layer containing CaF ₂ ) in the magnet 11. This hot pressing process also allows the insulating layer 13 to be sufficiently thin, and the thickness of the insulating layer 13 to be made uniform.

The rare earth magnet 10 obtained in the above manner can be regarded as a rare earth magnet manufactured by hot pressing (hot uniaxial pressing) a laminate in which the raw material of the insulating layer 13 is sandwiched between at least a pair of magnets 11, 11 (sintered bodies of SC alloy) so that pressure is applied in a direction that crushes the raw material of the insulating layer 13.
Furthermore, rare earth magnet 10 can be understood as a rare earth magnet manufactured by arranging a first magnet 11 (sintered body of SC alloy), the raw material of insulating layer 13, and a second magnet 11 (sintered body of SC alloy) in that order to form a laminate, and heating the laminate while applying pressure to both sides of first magnet 11 and second magnet 11.
The raw material of the insulating layer 13 may contain inorganic crystals. The raw material of the insulating layer 13 may further contain a component containing a heavy rare earth element. For example, the raw material of the insulating 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.

3. Functions and Effects of the Present Embodiment Since the motor 30 of the present embodiment includes the rare earth magnet 10, it is possible to suppress the decrease in efficiency caused by eddy current loss. The reason for this is presumed to be as follows. Note that the present disclosure is not limited to this presumed reason.
Since the insulating layer 13 of the rare earth magnet 10 of this embodiment is mainly composed of inorganic crystals, the eddy current loss is unlikely to change in a high temperature environment.
Since the insulating layer 13, which is mainly composed of inorganic crystals, has almost no change in resistance value in the range from room temperature (e.g., 25°C) to 150°C, it is presumed that it will be possible to reduce eddy current loss over a wide temperature range.
Furthermore, since insulating layer 13, which is primarily composed of inorganic crystals, has a thermal expansion coefficient close to that of magnet 11, it is believed that insulating layer 13 is less likely to be altered by thermal cycling. It is preferable that the difference in thermal expansion coefficient between insulating layer 13 and magnet 11 is ±3.0×10 ^-5 /K or less. For this reason as well, it is presumed that the durability (heat resistance) of rare earth magnet 10 of this embodiment is improved.

When used at a maximum rotation speed of 7,500 rpm or more, the effect of suppressing efficiency reduction caused by eddy current loss is particularly effective. In motors equipped with conventional magnets, in the high frequency range of operating frequencies of 5 kHz or more, the magnets can heat up due to eddy current loss generated inside the magnets, causing a significant decrease in motor efficiency. On the other hand, in motor 30 equipped with rare earth magnet 10, even in the high frequency range of operating frequencies of 5 kHz or more, eddy current loss generated inside rare earth magnet 10 can be reduced, making it less likely to cause a significant decrease in motor efficiency.
[Example]

The following provides a more detailed explanation of this disclosure using examples.

1. Preparation of Laminated Magnets as Rare Earth Magnets In Experimental Examples 1A to 5A, 1B, and 2B, "laminated magnets" equivalent to "rare earth magnet 10" were prepared.

<Experimental Example 1A to Experimental Example 5A>
(1) SC alloy preparation process The main raw materials of Nd/Pr alloy, alloy containing Co, Al, Cu, Ga, Zr, and metal element were mixed to prepare a strip cast alloy (SC alloy) (for example, composition: Nd ₂ Fe ₁₄ B) under an argon atmosphere. The SC alloy was a plate-shaped powder, and the dimensions of the main surface were 10 mm × 10 mm to 20 mm × 20 mm.

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

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

(4) Fine pulverization step, second lubricant addition step The SC alloy powder after the addition of 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 to 3.5 μm.
A lubricant was added to the finely pulverized SC alloy powder. Methyl laurate was used as the lubricant. The mixing ratio of the lubricant to the amount of the SC alloy was 0.05% by mass to 0.1% by mass.

(5) Powder filling step, orientation step, molding step The powder of the SC alloy after the fine 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 later step. In the samples of Experimental Examples 1A to 5A and Experimental Examples 1B and 2B, each magnet was a rectangular parallelepiped with a thickness of 2 mm x 5 mm x 16 mm.
After the powder was packed 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 packed into the mold was compressed to form an SC alloy compact. The compression molding conditions were: pressure: 5 MPa-20 MPa, packing density: 3.0 g/cm3-4.0 ^g / ^cm3 , relative density: 40%-52%.

(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 (material to be fired) was prepared. For dehydrogenation, the material to be fired (with partition plates) was heated at 500°C for 3-4 hours in an Ar atmosphere. After that, the material to be fired (with partition plates) was held at 930°C-1050°C for 3 hours and fired in a vacuum atmosphere.

(7) Insulating Layer Coating Step After the first firing step, the partition plate was removed from the fired object, and the raw material for the insulating layer was coated on six surfaces of the magnet before lamination. The raw material for the insulating layer was a mixture of the main component compound powders listed in Table 1, the _TbF3 compound powder, and a solvent. The ratio of the _TbF3 compound powder in the raw material for the insulating layer was 10% by mass to 20% by mass. The coating thickness of the raw material for the insulating layer was 12 μm or more and 14 μm or less. The raw material for the insulating layer was coated in the air by a spray method.

(8) Laminate Temporary Fixing Process 25 magnets coated with an insulating layer were stacked in air and temporarily fixed. The number of stacked magnets 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 large magnet.

(9) Hot Pressing Process The temporarily fixed laminate was placed in a hot press mold and subjected to uniaxial hot pressing. This process was performed in a vacuum atmosphere (e.g., 10 ⁻³ Pa-10 ⁻⁴ Pa) or in an inert atmosphere (nitrogen atmosphere, argon atmosphere). The hot pressing temperature was 700°C-1100°C, the hot pressing pressure time was 1 second-1 hour, the hot pressing pressure was 3 MPa or more and 100 MPa or less, and the hot pressing heat treatment time was 10 minutes-20 hours. As described above, samples of laminated magnets of each of Experimental Examples 1A to 5A were produced.

<Experimental Example 1B>
In Experimental Example 1B, instead of the above-mentioned (7) insulating layer coating step and (9) hot pressing step, an insulating layer coating step and a pressing step, which will be described later, were performed. The steps other than the insulating layer coating step and the pressing step, which will be described later, were the same as the above-mentioned (1)-(6) and (8) steps of Experimental Examples 1A to 5A to produce a laminated magnet sample of Experimental Example 1B.

In the insulating layer coating process of Experimental Example 1B, a mixture of _TbF3 compound powder and a solvent was first coated. Next, the surface was heat-treated until the coating film was removed. After that, the resin with the main component shown in Table 1 was coated.

In the pressing process of Experimental Example 1B, the temporarily fixed laminate was placed in a press mold and pressed with uniaxial pressure. This process was carried out in an air atmosphere. The pressing temperature was 25°C, the pressing time was longer than the time required for the resin to harden, and the pressing pressure was 3 MPa.

<Experimental Example 2B>
In Experimental Example 2B, instead of a laminated magnet, a single magnet with a thickness of 50 mm was used. The planar shape of the magnet was a rectangle of 5 mm x 16 mm, similar to Experimental Examples 1A to 5A. Except for the magnet thickness being 50 mm, the same (1) SC alloy preparation step, (2) hydrogen crushing step, (3) coarse pulverization step, first lubricant addition step, (4) fine pulverization step, second lubricant addition step, (5) powder filling step, orientation step, and molding step were performed as in Experimental Examples 1A to 5A. The obtained compact was in the shape of a block with no partition plate between them.
For the mold disassembly step and first firing step of Experimental Example 2B, the outer frame was removed from the mold to prepare a molded body (object to be fired). Then, heating and firing were performed for dehydrogenation under the same conditions as those for the above (6) mold disassembly step and first firing step. After the first firing step, the raw material for the insulating layer was applied to six surfaces of the magnet of Experimental Example 2B. The raw material for the insulating layer and the thickness of the applied raw material for the insulating layer were the same as those of Experimental Examples 1A to 5A. The magnet to which the raw material for the insulating layer was applied was placed in a hot press mold, and uniaxial hot pressing was performed as in Experimental Examples 1A to 5A.

2. Characteristics of Experimental Examples 1A to 5A, 1B, and 2B Table 1 shows the characteristics of the magnets and insulating layers of Experimental Examples 1A to 5A, 1B, and 2B.
The "Type" column of "Magnet" indicates the type of magnet. "Neodymium magnet" refers to a magnet with Nd ₂ Fe ₁₄ B as the main phase.
The column "Insulating layer" indicates the compound that is contained in the insulating layer in the largest amount (mass %). The components of the insulating layer were identified by EPMA and XRD for inorganic substances and by NMR and IR analysis for organic substances.
The "number of divisions" column indicates the number of divisions of the laminated magnet, i.e., the number of layers of the magnet. Since Experimental Example 2B is a rare earth magnet that is not divided, the number of divisions is set to "0."

3. Performance Evaluation (1) Method for Evaluating Magnet Temperature Each of the magnets of Experimental Examples 1A to 5A, 1B, and 2B was attached to a motor and tested by driving it for 0.5 hours at a maximum torque of 500 Nm and a maximum rotation speed of 10,000 rpm. Immediately after the test, the surface of the magnets of each of Experimental Examples 1A to 5A, 1B, and 2B was observed with a laser and the surface temperature (°C) was measured.

(2) Method for evaluating magnet temperature after 200 hours of operation Each motor subjected to "(1) Method for evaluating magnet temperature" was further tested by operating it for 200 hours at a maximum torque of 500 Nm and a maximum rotation speed of 10,000 rpm. Immediately after the test, the surface of the magnet of each of Experimental Examples 1A to 5A, 1B, and 2B was observed with a laser to measure the surface temperature (°C). The surface temperature after 0.5 hours of operation was set as 100%, and the rate of change (%) of the surface temperature of the laminated magnet of Experimental Example 1A to 5A, and 1B was calculated. A small rate of change (%) is an indicator that temperature rise is suppressed and thermal degradation is less likely to occur.
Rate of change (%) = (T ₂₀₀ - _{T 0.5} )/T _0.5 × 100
T _0.5 : Surface temperature after driving for 0.5 hours (° C.)
_T200 : Surface temperature after 200 hours of operation (°C)

The evaluation was as follows:
Magnet temperature (change after 200 hours)
"A": rate of change 10% or less; "B": rate of change greater than 10%

(3) Method of Efficiency Region Evaluation A graph of rotation speed-torque characteristics was obtained for the motors equipped with the magnets of each of Experimental Examples 1A to 5A, 1B, and 2B, with the horizontal axis representing rotation speed (rpm) and the vertical axis representing torque (Nm). Motor efficiency is expressed as the ratio of the output (W) from the motor to the input power (W) input to the motor. Motor efficiency (%) can be calculated using the following formula:
Motor efficiency (%) = (output (W) / input power (W)) x 100
Output (W)=2π×rotation speed (s ⁻¹ )×torque (N·m)
1 (rpm) = 1/60 (s ⁻¹ )

In the graph of the rotation speed-torque characteristics of the motor described above, the area of the high efficiency region where the motor efficiency was 90% or more was calculated. The area A2 of the high efficiency region of the motor of Experimental Example 2B was set as 100%, and the rate of change (%) of the area As of the high efficiency region of the motors of Experimental Examples 1A to 5A and Experimental Example 1B was calculated. A large rate of change (%) is an indicator that the area of the high efficiency region is large and the decrease in motor efficiency is suppressed.
Rate of change (%) = (As-A2)/A2 x 100
A2: Area of the high efficiency region of the motor of Experimental Example 2B As: Area of the high efficiency region of the motors of Experimental Examples 1A to 5A and Experimental Example 1B

The evaluation was as follows:
Efficiency region "A": rate of change 5% or more "B": rate of change less than 5%

4. Evaluation Results The evaluation results are shown in Table 1.
Experimental Examples 1A to 5A satisfy the following requirements (a) and (b). In contrast, Experimental Example 1B does not satisfy the following requirement (b). Experimental Example 1B does not satisfy the following requirements (a) and (b).
Requirement (a): The rare earth magnet has a plurality of magnets and an insulating layer present between the plurality of magnets.
Requirement (b): The insulating layer is composed mainly of inorganic crystals.

In Experimental Examples 1A to 5A, the magnet temperature after 200 hours of operation was rated "A". In Experimental Examples 1A to 5A, the efficiency range was rated "A". In contrast, in Experimental Example 1B, the magnet temperature after 200 hours of operation was rated "B", and the efficiency range was rated "B". It was suggested that Experimental Examples 1A to 5A can reduce eddy current loss that occurs inside the magnet in a high-temperature environment, and suppress efficiency decline. Such a motor is considered to be useful as a high-speed motor used in a high rotation speed range (for example, rotation speed of 7,500 rpm or more).

5. Effects of the Examples Experimental Examples 1A to 5A were able to suppress the decrease in efficiency.

The present invention is not limited to the embodiments detailed above, and various modifications and variations are possible within the scope of the claims of the present invention.

<<Second embodiment>>
The second embodiment of the present disclosure will be described in detail below. In the second embodiment, a description using "-" for a numerical range includes both the lower limit and the upper limit unless otherwise specified. For example, the description "10-20" includes both the lower limit "10" and the upper limit "20". That is, "10-20" has the same meaning as "10 or more and 20 or less". In this specification, the upper limit and the lower limit of each numerical range can be arbitrarily combined. Hereinafter, the Z-axis direction in each figure is the stacking direction (first direction) of the laminated magnet 110. One direction perpendicular to the Z-axis direction is 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 the Y-axis direction.

1. Motor 130
The motor 130 includes a magnet stack 110. The magnet stack 110 includes a plurality of magnets 111 and an insulating layer 113 stacked in a first direction. The magnet 111 includes a rare earth element. The magnet 111 has a curved shape that is convex in a second direction when viewed from the first direction, and the average orientation degree of each portion having a width of 1 mm centered on a normal line at a plurality of points from one end to the other end on the curve on the convex side in the second direction on the outer periphery of the magnet 111 when viewed from the first direction is 90% or more. The insulating layer 113 is mainly composed of inorganic crystals.

The laminated magnet 110 disclosed herein has low eddy current loss generated inside and can concentrate magnetic flux, which can contribute to one or more of the following effects: downsizing of the motor, suppression of heat generation, improved heat resistance, and improved heat dissipation.

The motor 130 of the present disclosure is preferably a rotary motor. An example of a motor 130 equipped with a laminated magnet 110 will be described below with reference to Figs. 19 and 20. The motor 130 is equipped with a stator 131 and a rotor 133 arranged inside the stator 131. The laminated magnet 110 is arranged on the rotor 133, and a winding (not shown) is arranged on the stator 131. The motor 130 in Fig. 19 is an inner rotor type in which the magnet is arranged on the inside (rotating shaft side) and the winding is 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 winding is arranged on the inside (rotating shaft side) and the magnet is arranged on the outside.

The rotor 133 includes a rotating shaft 134, a rotating core 135, and a plurality of laminated magnets 110. The rotating core 135 is formed by laminating electromagnetic steel sheets. A shaft hole 137 is formed in the center of the rotating core 135. The rotating shaft 134 is inserted into the shaft hole 137. A plurality of magnet holes 139 are formed in the rotating core 135 at intervals in the circumferential direction. A laminated magnet 110 is inserted into each magnet hole 139. Each laminated magnet 110 is arranged with the convex side of the convex curved shape facing the rotating shaft 134. The arrangement of the laminated magnets 110 is not limited to the arrangement in FIG. 20. For example, two magnets may be arranged side by side in an arc, as in the rotor of sample C shown in the lower part of FIG. 23.

The motor 130 is preferably used at a maximum rotation speed of 7500 rpm or more. The upper limit of the maximum rotation speed is not particularly limited. The maximum rotation speed is, for example, 50,000 rpm or less. "Used at a maximum rotation speed of 7500 rpm or more" means that the motor can be used at a rotation speed of 7500 rpm or more under certain conditions, and is not limited to a configuration that is always used at a rotation speed of 7500 rpm or more. For example, the motor 130 can be variable speed controlled using an inverter. When variable speed control is performed using an inverter, there is a concern that eddy current loss will increase if the inverter's PWM (Pulse Width Modulation) carrier frequency becomes high. The motor 130 of the present disclosure is expected to reduce eddy current loss even at high rotation speeds of 7500 rpm or more by using the laminated magnet 110.

The motor disclosed herein is not limited to an IPM (Interior Permanent Magnet) motor in the case of a permanent magnet synchronous motor, but may be an SPM (Surface Permanent Magnet) motor. In addition to a permanent magnet synchronous motor, the motor may be a permanent magnet DC motor, a voice coil motor, a vibration motor, etc.

As illustrated in Figures 12 to 14, the laminated magnet 110 has multiple magnets 111 and insulating layers 113 stacked in a first direction.

(1) Magnet 111
The composition of magnet 111 is similar to that explained in the section "(1.1) Composition of magnet 11" in the first embodiment, and the explanation in this section applies as is.

The average degree of orientation of magnets 111 and the method for measuring it will be explained later. Note that in Figures 13 and 14, the white arrows indicate the orientation direction. Multiple magnets 111 can be used, for example, lined up in a direction perpendicular to the orientation direction, as shown in Figure 14.

The shape of the magnet 111 is not particularly limited. For example, the magnet 111 is preferably plate-shaped. The plate-shaped magnet 111 has a smaller distance from the surface to the deepest part than a block-shaped magnet that is thicker. Therefore, the plate-shaped magnet 111 is suitable because it is easy to diffuse the heavy rare earth element to the inside when the heavy rare earth element is diffused at grain boundaries. The plate-shaped magnet 111 can be preferably used as a laminated magnet in which multiple magnets 111 and insulating layers 113 are stacked. In the laminated magnet 110 of FIG. 12, multiple magnets 111 are stacked with the thickness direction of the plate-shaped magnet 111 as the stacking direction. In this laminated magnet 110, the magnets 111 and insulating layers 113 are stacked alternately. In the laminated magnet, each magnet 111 may also be referred to as a magnet body. The shape of the magnet 111 when viewed from the first direction (Z-axis direction) will be described later.

The thickness of the magnet 111 is the same as that explained in the section "(1.4) Thickness of the magnet 11" in the first embodiment, and the description in this section applies as is.

(2) Insulating layer 113
The composition of the insulating layer 113 is similar to that explained in the section "(2.1) Composition of the insulating layer 113" in the first embodiment, and the explanation in this section applies as is.

The insulating layer 113 needs to be present at least between the magnets 111, 111.
The insulating layer 113 is disposed, for example, as follows.
The insulating layer 113 may be arranged so as to cover the entire surface of the magnet 111 (see FIG. 15). In the example of FIG. 15, both upper and lower main surfaces 11A and both side surfaces 11B of each magnet 111 are covered with the insulating layer 113, and the insulating layer 113 is arranged so as to cover the entire surface of the magnet 111.
The insulating layer 113 may be arranged in a form that covers a part of the surface of the magnet 111 (see FIG. 14). In the example of FIG. 14, the side surface 11B of each of the magnets 111 is not covered with the insulating layer 113, and the insulating layer 113 is arranged in a form that covers a part of the surface of the magnet 111. In the example of FIG. 14, the main surface 11A of the topmost magnet 111 on one side (lower side) is covered with the insulating layer 113, but the main surface 11A of the other side (upper side) is not covered with the insulating layer 113, and the insulating layer 113 is arranged in a form that covers a part of the surface of the magnet 111. Similarly, in the example of FIG. 14, the main surface 11A of the bottommost magnet 111 on one side (upper side) is covered with the insulating layer 113, but the main surface 11A of the other side (lower side) is not covered with the insulating layer 113, and the insulating layer 113 is arranged in a form that covers a part of the surface of the magnet 111.

The insulating layer 113 is preferably provided so as to be in direct contact with the magnet 111. The insulating layer 113 may also be an insulating bonding layer that bonds (adheres) the magnets 111, 111 located on both sides. From the viewpoint of bonding the magnets 111, 111 with sufficient strength, the insulating layer 113 preferably has an area in which components derived from the insulating layer 113 and components derived from the magnet 111 are mixed in the arrangement direction (Z-axis direction) of the multiple magnets 111. Such a laminated magnet 110 can be suitably formed by hot pressing. The conditions for hot pressing will be described later.

The insulating layer 113 may be provided along the orientation direction of the magnetic field of each magnet 111 (e.g., the X-axis direction in FIG. 14, the direction of the white arrow in FIG. 14), or along a direction intersecting the orientation direction (e.g., the X-axis direction in FIG. 14) (e.g., the Z-axis direction in FIG. 14). As shown in FIG. 19, when the laminated magnet 110 is used as a motor magnet, etc., from the viewpoint of efficiently reducing eddy current loss, it is preferable that the insulating layer 113 is provided along the orientation direction of the magnet 111 (the X-axis direction in FIG. 19). With this configuration, the insulating layer 113 is arranged approximately parallel to the direction in which the magnetic flux generated in the stator 131 passes through the laminated magnet 110 (the X-axis direction in FIG. 19), so that eddy current loss can be effectively reduced.

The thickness of the insulating layer 113 is the same as that explained in the section "(2.3) Thickness of the insulating layer 13" in the first embodiment, and the description in this section applies as is.

(3) Configuration of magnet stack 110 From the viewpoint of reducing eddy current loss, it is preferable that 10 or more magnets 111 are used per 50 mm dimension of the magnet stack 110 in the first direction, preferably 20 or more magnets are used, and preferably 25 or more magnets are used. There is no particular upper limit on the number of magnets, and it may be, for example, 35 or less.

(4) Shape of magnet 111 when viewed from a first direction When viewed from a first direction, magnet 111 has a curved shape that is convex toward a second direction. In this embodiment, the first direction corresponds to the Z-axis direction. The second direction corresponds to the X-axis direction.

The shape of magnet 111 is not particularly limited as long as it is a curved shape that is convex in the second direction. From the viewpoint of concentrating magnetic flux, magnet 111 is preferably arc-shaped. In this disclosure, an arc-shaped shape is defined as a shape in which the curve C1 on the convex side of the outer periphery of the magnet when viewed from the first direction is approximately arc-shaped, and the line opposing curve C1 (opposing line C2 described below) is also approximately arc-shaped. In other words, the arc-shaped shape includes two approximately arc-shaped curves that extend parallel to each other in the contour line of the outer periphery of the magnet when viewed from the first direction. Magnet 111 may be a convex curved shape other than an arc-shaped shape.

Below, the magnet 111 in Figures 16 and 17 will be specifically explained, with the curve on the convex side of the outer periphery of the magnet 111 when viewed from the Z-axis direction being curve C1, and the line tracing the side opposite to curve C1 being opposite line C2.
The magnet 111 in Fig. 16 is an arc-shaped magnet. The curve C1 is an arc of a perfect circle. The radius of curvature of the curve C1 is constant. The counter line C2 is an arc of a perfect circle that is concentric with the curve C1. In Fig. 16, the centers of curvature of the curve C1 and the counter line C2 are indicated by point O. The counter line C2 is a curve (a parallel curve to the curve C1) that is a constant distance from each point on the curve C1 in the normal direction.
The magnet 111 in Fig. 17 is an example of a convex curved shape other than a circular arc shape. This magnet 111 is approximately U-shaped. The curve C1 is a curve with a changing radius of curvature. Specifically, the curve C1 has a straight portion and a portion that is bent from the straight portion. When the radius of curvature of the curve C1 changes, it is preferable that the radius of curvature changes continuously. The counter line C2 is a curve (a parallel curve to the curve C1) that is at a certain distance from each point on the curve C1 in the normal direction.

The radius of curvature of the curve C1 is not particularly limited. Hereinafter, the smallest radius of curvature among the radii of curvature of the points on the curve C1 will be referred to as the minimum radius of curvature. When the curve C1 is an arc of a perfect circle, the minimum radius of curvature is the same as the radius of the perfect circle.
The minimum radius of curvature of the curve C1 is preferably 10 mm or more, more preferably 20 mm or more, and even more preferably 30 mm or more. From the viewpoint of favorably concentrating the magnetic flux density, the minimum radius of curvature of the curve C1 is preferably 100 mm or less, more preferably 75 mm or less, and even more preferably 50 mm or less. From these viewpoints, the minimum radius of curvature of the curve C1 is preferably 10 mm or more and 100 mm or less, more preferably 20 mm or more and 75 mm or less, and even more preferably 30 mm or more and 50 mm or less. When the curve C1 is an arc of a perfect circle, the central angle of the curve C1 is preferably 120° or more and 180° or less, and more preferably 150° or less.

(5) Average Orientation of Magnet 111 Magnet 111 has an average orientation of 90% or more in each 1 mm wide portion 112 centered on normal Nn at multiple points Pn from one end to the other end on curve C1 on the convex side in the second direction on the outer periphery of magnet 111 when viewed from the first direction. The average orientation can be, for example, 92% or more, 94% or more, 95% or more, or 96% or more. The higher the average orientation of magnet 111, the better, but it is usually 99.5% or less.

A method for measuring the average degree of orientation of magnet 111 will be described below with reference to FIGS.
The average orientation of the magnet 111 is determined as the average orientation of each portion of 1 mm width centered on the normal Nn at multiple points Pn from one end to the other end on the curve C1 on the convex side of the outer periphery of the magnet 111 as viewed from the first direction (Z-axis direction). The number of multiple points Pn is not particularly limited. When the size of the magnet 111 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.

First, as shown in FIG. 16, a number of points Pn are identified. In this embodiment, five points P1-P5 are identified. In the magnet 111, points P1 and P5 at both ends are taken within 5 mm from one end (e.g. the left end) and within 5 mm from the other end (e.g. the right end) of the curve C1 on the convex side. A number of points (points P2-P4 in this embodiment) are taken in order from one end at positions that divide the distance between points P1 and P5 at both ends of the curve C1 into equal intervals (positions that divide the distance into four in this embodiment). Note that point P3 in this embodiment is located in the middle of the curve C1.

On the curve C1, identify the normal lines N1-N5 at each of the points P1-P5. Cut out portions 112 of 1 mm width centered on the normal line Nn from the magnet 111. Each portion 112 is, for example, in the shape of a roughly rectangular prism, as shown in FIG. 18. Note that in reality, the top and bottom surfaces of FIG. 18 are curved surfaces. The degree of orientation of each portion 112 is measured, for example, with a pulsed high magnetic field measuring device (magnetic field: 4T). If the cut-out portion does not fit into the measuring device, cut out a sample of a size that can fit into the measuring device from the center of the cut-out portion. The average value of the degrees of orientation of each portion 112 is calculated as the average degree of orientation.

The average orientation of magnet 111 in Figure 17 can also be calculated using the same measurement method as above.

In addition, the magnet 111 can achieve the above average orientation degree of 90% or more by applying a magnetic field that spreads in the normal direction of the curve C1 of the magnet 111 in the orientation process described below.

2. Manufacturing Method of the Magnet Laminate 110 There is no particular limitation on the manufacturing method of the magnet laminate 110. An example of a manufacturing method of the magnet laminate 110 in which magnets 111 and insulating layers 113 are alternately stacked is shown below.

In the manufacturing method of the laminated magnet 110, the (1) SC alloy preparation step, (2) hydrogen crushing step, (3) coarse crushing step, first lubricant addition step, (4) fine crushing step, and second lubricant addition step are the same as the explanation of the (1) SC alloy preparation step, (2) hydrogen crushing step, (3) coarse crushing step, first lubricant addition step, (4) fine crushing step, and second lubricant addition step in "2. Manufacturing method of rare earth magnet 10" in the first embodiment, and this description applies as is.

(5) Powder filling process, orientation process, molding process The powder of the SC alloy after the pulverization process is filled into a mold. This process may be performed, for example, under an inert atmosphere (nitrogen atmosphere, argon atmosphere, etc.). The mold has a plurality of molding spaces of a predetermined thickness. Each molding space is partitioned, for example, by a plurality of partition plates. A magnetic field is applied in a predetermined direction to the mold after the powder is filled to align the orientation of the SC alloy powder. For example, when the magnet 111 has an arc shape as shown in FIG. 16, a radial magnetic field (a magnetic field in which magnetic lines spread radially) is applied. Then, the powder of the SC alloy filled in the mold is pressed to mold the compact of the SC alloy. In this way, it is possible to obtain a compact of the SC alloy having a predetermined degree of orientation (for example, an average degree of orientation of 90% or more) and a predetermined thickness (for example, a thickness of 1.2 mm or more and 2.5 mm or less) without performing a cutting process. The shape of the compact can be made as desired by changing the shape of the mold in which the SC alloy powder is filled after the pulverization process. In addition, the average degree of orientation of the compact can be increased by using an orientation coil that matches the shape of the compact.

In the manufacturing method of the magnet laminate 110, the (6) mold disassembly process, the first sintering process, (7) insulating layer application process, (8) laminate temporary fixing process, and (9) hot pressing process are the same as the (6) mold disassembly process, the first sintering process, (7) insulating layer application process, (8) laminate temporary fixing process, and (9) hot pressing process in "2. Manufacturing method of rare earth magnet 10" in the first embodiment, and this description applies as is.

The laminated magnet 110 obtained in the above manner can be regarded as a laminated magnet manufactured by hot pressing (hot uniaxial pressing) a laminate having the raw material of the insulating layer 113 sandwiched between at least a pair of magnets 111, 111 (sintered bodies of SC alloy) so that pressure is applied in a direction in which the raw material of the insulating layer 113 is crushed.
In addition, the laminated magnet 110 can be understood as a laminated magnet manufactured by arranging a first magnet 111 (sintered body of SC alloy), the raw material of the insulating layer 113, and a second magnet 111 (sintered body of SC alloy) in this order to form a laminate, and heating the laminate while applying pressure to both sides of the first magnet 111 and the second magnet 111.
The raw material of the insulating layer 113 may further contain a component containing a heavy rare earth element. For example, the raw material of the insulating layer 113 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.

3. Actions and Effects of the Present Embodiment Since the motor 130 of the present embodiment includes the magnet stack 110, it is possible to improve performance in terms of suppressing thermal degradation, suppressing efficiency decline, reducing magnet temperature, etc. The reason for this is presumed to be as follows. Note that the present disclosure is not limited to this presumed reason.
In the magnet stack 110 of this embodiment, the magnets 111 and the insulating layer 113 are stacked, so that eddy current loss can be reduced. On the other hand, when the magnets 111 having a convex curved shape are used for the magnet stack 110 as in this embodiment, it is difficult to increase the average orientation measured as described above. For example, the high-pressure magnetic field press method is generally said to be an effective method for increasing the orientation of magnets. However, the high-pressure magnetic field press method is limited to the manufacture of coarse block magnets because of restrictions on the dimensions and shapes of the molds used for molding. Therefore, the high-pressure magnetic field press method is not suitable for the manufacture of thin magnets used for magnet stacks. In addition, for example, it has been considered to manufacture a magnet with a convex curved shape by first aligning a rectangular magnet in a first direction in parallel and then bending the magnet to be convex in a second direction. However, bending the magnet reduces the orientation of the magnet, and it is difficult to ensure a sufficient average orientation when the magnet is bent. The inventors of the present application conducted extensive research to improve the average degree of orientation of the magnets 111 described above, and developed the novel laminated magnet 110 of the present disclosure.

Since the average orientation of the magnet stack 110 is 90% or more, the magnetic flux can be concentrated. Below, the magnetic flux distribution of Sample A, Sample B, and Sample C when the magnet is applied to a rotor is examined by computer simulation. Finite element method electromagnetic field analysis software JMAG (JSOL Corporation) was used to examine the magnetic flux distribution. The upper part of Fig. 21 to Fig. 23 is a graph showing the relationship between the angle of the rotor in the range of the central angle of 90° and the magnetic flux density. The magnets described below are used for each rotor. The horizontal axis represents the angle (°) with respect to the straight line OX shown in the rotor in the lower part. The vertical axis represents the magnetic flux density (W/m ² ). The lower part of Fig. 21 to Fig. 23 is an image diagram of the rotor and the distribution of the magnetic flux density (absolute value) by simulation. The arrows in each magnet roughly indicate the orientation direction of the magnet.

The magnet properties of Sample A, Sample B, and Sample C are as follows.
<Sample A>
Shape of magnet as viewed from first direction: rectangular Area of main surface of magnet: 96.8 mm ² (long side dimension 22 mm, short side dimension 4.4 mm)
Magnet orientation: Parallel orientation Average magnet orientation: 97%
- Arrangement: Two magnets are arranged in a V shape.
<Sample B>
Shape of the magnet as viewed from the first direction: Arc shape (corresponding to a convex curved shape)
Area of the main surface of the magnet: 96.8 ^mm2 (radius of curvature of the outer arc: 25.4 mm, radius of curvature of the inner arc: 21 mm, the outer arc and the inner arc are concentric, and both have a central angle of 54.3°)
Magnet orientation: Parallel orientation Average magnet orientation: 88%
- Arrangement: Two magnets are arranged in an arc shape.
<Sample C>
Shape of the magnet as viewed from the first direction: Arc shape (corresponding to a convex curved shape)
Area of the main surface of the magnet: 96.8 ^mm2 (radius of curvature of the outer arc: 25.4 mm, radius of curvature of the inner arc: 21 mm, the outer arc and the inner arc are concentric, and both have a central angle of 54.3°)
Magnet orientation: radial orientation Average magnet orientation: 95%
- Arrangement: Two magnets are arranged in an arc shape.

The maximum magnetic flux density of sample A was 0.5388 W/m ^2. The maximum magnetic flux density of sample B was 0.5521 W/m ^2. The maximum magnetic flux density of sample C was 0.5729 W/m ^2. Each magnetic flux density is rounded off to the fifth decimal place.

The properties of "magnet shape,""average degree of orientation," and "maximum magnetic flux density" for Sample A, Sample B, and Sample C are summarized in Table 2 below. Each item is evaluated according to the following criteria.
Satisfaction of shape requirements: If the magnet shape was a convex curved shape, it was rated as "satisfied", and if it was a shape other than a convex curved shape, it was rated as "not satisfied".
Satisfaction of orientation requirements: When the average orientation of the magnets measured by the above measurement method was 90% or more, it was rated as "satisfied", and when it was less than 90%, it was rated as "not satisfied".
As can be seen from Table 2, compared to sample A (average orientation 97%, V-shaped arrangement) which uses rectangular magnets, sample B (average orientation 88%, arc-shaped arrangement) and sample C (average orientation 95%, arc-shaped arrangement) which use convex curved magnets have high magnetic flux density despite their low average orientation. Furthermore, when comparing sample B (average orientation 88%, arc-shaped arrangement) and sample C (average orientation 95%, arc-shaped arrangement), both of which use convex curved magnets, sample C has a higher magnetic flux density than sample B.
From these results, it can be seen that in a convex curved magnet, the higher the average orientation, the more concentrated the magnetic flux density, and the higher the magnetic flux density can be. Therefore, it can be seen that a convex curved magnet with an average orientation of 90% or more will have a higher magnetic flux density than a magnet with an average orientation of less than 90%. Sample B, which uses a convex curved magnet, has a higher magnetic flux density than sample A, which uses a rectangular magnet, even though it has an average orientation of 88%, so it can be seen that when a magnet is convex curved and the average orientation is 90% or more, sufficient magnetic flux density can be achieved.

Furthermore, in the magnet laminate 110, the insulating layer 113 is mainly composed of inorganic crystals, so that the eddy current loss is unlikely to change. The reason for this is presumed to be as follows. Note that the present disclosure is not limited to this presumed reason.
Since the insulating layer 113, which is primarily composed of inorganic crystals, has almost no change in resistance value in the range from room temperature (e.g., 25°C) to 150°C, it is presumed that this will enable reduction in eddy current loss to be achieved over a wide temperature range.
Furthermore, since the insulating layer 113, which is mainly composed of inorganic crystals, has a thermal expansion coefficient close to that of the magnet 111, it is believed that the insulating layer 113 is less likely to be altered by thermal cycling. It is preferable that the difference in thermal expansion coefficient between the insulating layer 113 and the magnet 111 is ±3.0×10 ^-5 /K or less. For this reason as well, it is presumed that the durability (heat resistance) of the magnet stack 110 of this embodiment is improved.

In the magnet stack 110 of this embodiment, an insulating layer 113 is present between the magnets 111, 111. With this configuration, the insulating layer 113, which is mainly composed of inorganic crystals, can bond (adhere) the magnets 111, 111 with sufficient strength. In addition, since the insulating layer 113 is mainly composed of inorganic crystals, it can be made thinner while ensuring the bonding strength compared to a bonding layer made of resin or the like. Furthermore, if amorphous glass is used for the insulating layer, unlike this embodiment, there is a concern that the magnet will oxidize and the magnetic properties will be impaired. On the other hand, since the insulating layer 113 of this embodiment is mainly composed of inorganic crystals, the magnetic properties of the magnet 111 can be suitably secured.
[Example]

The following provides a more detailed explanation of this disclosure using examples.

1. Preparation of laminated magnets <Experimental Examples 1C to 5C>
(1) SC alloy preparation process The main raw materials of Nd/Pr alloy, alloy containing Co, Al, Cu, Ga, Zr, and metal element were mixed to prepare a strip cast alloy (SC alloy) (for example, composition: Nd ₂ Fe ₁₄ B) under an argon atmosphere. The SC alloy was a plate-shaped powder, and the dimensions of the main surface were 10 mm × 10 mm to 20 mm × 20 mm.

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

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

(4) Fine pulverization step, second lubricant addition step The SC alloy powder after the addition of 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 to 3.5 μm.
A lubricant was added to the finely pulverized SC alloy powder. Methyl laurate was used as the lubricant. The mixing ratio of the lubricant to the amount of the SC alloy was 0.05% by mass to 0.1% by mass.

(5) Powder filling step, orientation step, molding step The powder of the SC alloy 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 later step. In the samples of Experimental Example 1C to Experimental Example 5C, the thickness of each magnet was 2 mm. The planar shape of each magnet was an arc shape with a central angle of 180°, with the curve C1 having a radius of curvature of 15 mm, the opposing line C2 having a radius of curvature of 12 mm, and the curve C1 and the opposing line C2 being concentric.
After the powder was filled, a magnetic field (e.g., 5000 V) was applied to the mold in the planar direction of each compact (perpendicular to the thickness direction) to align the orientation of the SC alloy powder. At this time, a radial magnetic field (a magnetic field in which magnetic lines of force spread radially) was used. The SC alloy powder filled in the mold was compressed to form an SC alloy compact. The conditions for the compression molding were pressure: 5 MPa-20 MPa, packing density: 3.0 g/cm ³ -4.0 g/cm ³ , and relative density: 40%-52%.

(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 (material to be fired) was prepared. For dehydrogenation, the material to be fired (with partition plates) was heated at 500°C for 3-4 hours in an Ar atmosphere. After that, the material to be fired (with partition plates) was held at 930°C-1050°C for 3 hours and fired in a vacuum atmosphere.

(7) Insulating Layer Coating Step After the first firing step, the partition plate was removed from the fired object, and the raw material for the insulating layer was coated on six surfaces of the magnet before lamination. The raw material for the insulating layer was a mixture of the main component compound powders listed in Table 3, the compound powder of _TbF3 , and a solvent. The ratio of the compound powder of _TbF3 in the raw material for the insulating layer was 10% by mass to 20% by mass. The coating thickness of the raw material for the insulating layer was 12 μm or more and 14 μm or less. The raw material for the insulating layer was coated in the air by a spray method.

(8) Laminate Temporary Fixing Process 25 magnets coated with an insulating layer were stacked in air and temporarily fixed. The number of stacked magnets 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 large magnet.

(9) Hot Pressing Process The temporarily fixed laminate was placed in a hot press mold and subjected to uniaxial hot pressing. This process was performed in a vacuum atmosphere (e.g., 10 ⁻³ Pa-10 ⁻⁴ Pa) or in an inert atmosphere (nitrogen atmosphere, argon atmosphere). The hot pressing temperature was 700°C-1100°C, the hot pressing pressure time was 1 second-1 hour, the hot pressing pressure was 3 MPa or more and 100 MPa or less, and the hot pressing heat treatment time was 10 minutes-20 hours. As described above, laminated magnet samples of Experimental Examples 1C to 5C were produced.

<Experimental Example 1D>
In Experimental Example 1D, instead of the above-mentioned (7) insulating layer coating step and (9) hot pressing step, an insulating layer coating step and a pressing step, which will be described later, were performed. The steps other than the insulating layer coating step and the pressing step, which will be described later, were the same as the above-mentioned (1)-(6) and (8) steps of Experimental Examples 1C to 5C to produce a laminated magnet sample of Experimental Example 1D.

In the insulating layer coating process of the experimental example 1D, a mixture of _TbF3 compound powder and a solvent was first coated. Then, the substrate was heat-treated until the coating on the surface was completely removed. After that, an epoxy resin was coated.

In Experimental Example 1D, in the pressing process, the temporarily fixed laminate was placed in a press mold and pressed with uniaxial pressure. This process was carried out in an air atmosphere. The pressing temperature was 25°C, the pressing time was longer than the time required for the resin to harden, and the pressing pressure was 3 MPa.

<Experimental Example 2D>
In Experimental Example 2D, instead of a laminated magnet, a single magnet with a thickness of 50 mm was used. The planar shape of the magnet was an arc shape with a central angle of 180°, with the curve C1 having a radius of curvature of 15 mm, the opposing line C2 having a radius of curvature of 12 mm, and the curve C1 and the opposing line C2 being concentric, similar to Experimental Examples 1C to 5C. Except for the thickness of the magnet being 50 mm, the (1) SC alloy preparation step, (2) hydrogen crushing step, (3) coarse crushing step, first lubricant addition step, (4) fine crushing step, second lubricant addition step, (5) powder filling step, orientation step, and molding step were performed similarly to Experimental Examples 1C to 5C. The obtained compact was a block shape with no partition plate interposed therebetween.
For the mold disassembly step and first firing step of Experimental Example 2D, the outer frame was removed from the mold to prepare a molded body (object to be fired). Then, heating and firing were performed for dehydrogenation under the same conditions as those for the above (6) mold disassembly step and first firing step. After the first firing step, the raw material for the insulating layer was applied to six surfaces of the magnet of Experimental Example 2D. The raw material for the insulating layer and the thickness of the applied raw material for the insulating layer were the same as those of Experimental Examples 1C to 5C. The magnet to which the raw material for the insulating layer was applied was placed in a hot press mold, and uniaxial hot pressing was performed as in Experimental Examples 1C to 5C.

<Experimental Example 3D>
For experimental example 3D, a sample of the laminated magnet of experimental example 3D was produced in the same manner as in the above steps (1)-(4) and (6)-(8), except that a parallel magnetic field was applied instead of a radial magnetic field in the above (5) powder filling step, orientation step, and molding step.

<Experimental Example 4D>
In Experimental Example 4D, the planar shape of the magnets was not an arc shape, but a rectangle of 5 mm x 16 mm. Each magnet was a rectangular parallelepiped of 2 mm thick x 5 mm x 16 mm. Other than the planar shape of the magnets being rectangular, the same (1) SC alloy preparation step, (2) hydrogen crushing step, (3) coarse crushing step, first lubricant addition step, (4) fine crushing step, and second lubricant addition step as in Experimental Examples 1C to 5C were performed.
In Experimental Example 4D, a sample of the laminated magnet of Experimental Example 4D was produced in the same manner as in the above steps (6)-(8), except that in the above (5) powder filling step, orientation step, and molding step, a parallel magnetic field along the short side direction of the rectangle was applied instead of a radial magnetic field.

2. Characteristics of Experimental Examples 1C to 5C and 1D to 4D Table 2 shows the characteristics of the magnets and insulating layers of Experimental Examples 1C to 5C and 1D to 4D.
The "Type" column of "Magnet" indicates the type of magnet. "Neodymium magnet" refers to a magnet whose main phase is Nd ₂ Fe ₁₄ B. The "Shape" column indicates the shape of the magnet when viewed from a first direction.
The column "Insulating layer" indicates the compound that is contained in the insulating layer in the largest amount (mass %). The components of the insulating layer were identified by EPMA and XRD for inorganic substances and by NMR and IR analysis for organic substances.
The "number of divisions" column indicates the number of divisions of the laminated magnet, i.e., the number of layers of the magnet. Since the magnet of Experimental Example 2D is not divided, the number of divisions is set to "0."
The column "Average orientation degree" indicates the average orientation degree measured by the method described in the embodiment.

3. Performance Evaluation (1) Method for Evaluating Magnet Temperature Each of the magnets of Experimental Examples 1C to 5C and Experimental Examples 1D to 4D was attached to a motor and tested by driving it for 0.5 hours at a maximum torque of 500 Nm and a maximum rotation speed of 10,000 rpm. Immediately after the test, the surface of the magnets of Experimental Examples 1C to 5C and Experimental Examples 1D to 4D was observed with a laser and the surface temperature (°C) was measured.

(2) Method for evaluating magnet temperature after 200 hours of operation Each motor subjected to "(1) Method for evaluating magnet temperature" was further tested by operating it for 200 hours at a maximum torque of 500 Nm and a maximum rotation speed of 10,000 rpm. Immediately after the test, the surface of the magnet of each of Experimental Examples 1C to 5C and Experimental Examples 1D to 4D was observed with a laser to measure the surface temperature (°C). The surface temperature after 0.5 hours of operation was set as 100%, and the rate of change (%) of the surface temperature of the laminated magnet of Experimental Examples 1C to 5C and Experimental Examples 1D, 3D, and 4D was calculated. A small rate of change (%) is an indicator that the temperature rise is suppressed and thermal degradation is less likely to occur.
Rate of change (%) = (T ₂₀₀ - _{T 0.5} )/T _0.5 × 100
T _0.5 : Surface temperature after driving for 0.5 hours (° C.)
_T200 : Surface temperature after 200 hours of operation (°C)

The evaluation was as follows:
Magnet temperature (change after 200 hours)
"A": rate of change 10% or less; "B": rate of change greater than 10%

(3) Method of Efficiency Region Evaluation A graph of rotation speed-torque characteristics was obtained for the motors equipped with the magnets of Experimental Examples 1C-5C and Experimental Examples 1D-4D, with the horizontal axis representing rotation speed (rpm) and the vertical axis representing torque (Nm). Motor efficiency is expressed as the ratio of the output (W) from the motor to the input power (W) input to the motor. Motor efficiency (%) can be calculated using the following formula:
Motor efficiency (%) = (output (W) / input power (W)) x 100
Output (W)=2π×rotation speed (s ⁻¹ )×torque (N·m)
1 (rpm) = 1/60 (s ⁻¹ )

In the graph of the motor rotation speed-torque characteristics described above, the area of the high efficiency region where the motor efficiency is 90% or more was calculated. The area A1 of the high efficiency region of the motor of Experimental Example 2D was set as 100%, and the rate of change (%) of the area As of the high efficiency region of the motor of each of Experimental Examples 1C to 5C and Experimental Examples 1D, 3D, and 4D was calculated. A large rate of change (%) is an indicator that the area of the high efficiency region is large and the decrease in motor efficiency is suppressed.
Rate of change (%) = (As-A1)/A1 x 100
A1: Area of the high efficiency region of the motor of Experimental Example 2D As: Area of the high efficiency region of the motors of Experimental Examples 1C to 5C and Experimental Examples 1D, 3D, and 4D

The evaluation was as follows:
Efficiency region "A": rate of change 5% or more "B": rate of change less than 5%

4. Evaluation Results The evaluation results are shown in Table 3.
Experimental Examples 1C to 5C satisfy the following requirements (a) to (d). In contrast, Experimental Example 1D does not satisfy the following requirement (d). Experimental Example 2D does not satisfy the following requirement (a). Experimental Example 3D does not satisfy the following requirement (c). Experimental Example 4D does not satisfy the following requirement (b).
Requirement (a): The laminated magnet has a plurality of magnets and insulating layers laminated in a first direction.
Requirement (b): The magnet contains a rare earth element and has a curved shape that is convex in a second direction when viewed from a first direction.
- Requirement (c): When viewed from the first direction, the average orientation of each portion of a 1 mm width centered on the normal line at multiple points from one end to the other end on the curve on the convex side in the second direction on the outer periphery of the magnet is 90% or more.
Requirement (d): The insulating layer is composed mainly of inorganic crystals.

　Experimental Examples 1C to 5C were rated "A" for magnet temperature after 200 hours of operation. Experimental Examples 1C to 5C were rated "A" for efficiency area. In contrast, Experimental Example 1D was rated "B" for magnet temperature after 200 hours of operation and "B" for efficiency area. Experimental Examples 2D and 3D were rated "B" for efficiency area. It was suggested that Experimental Examples 1C to 5C can reduce eddy current loss generated inside, and can suppress thermal degradation, suppress efficiency decline, and reduce magnet temperature by concentrating magnetic flux. Such motors are considered to be useful in high-speed motors used in high rotation speed ranges (e.g., rotation speeds of 7,500 rpm or more).

5. Effects of the Examples Experimental Examples 1C to 5C were able to improve any of the performances relating to suppression of thermal degradation, suppression of efficiency decline, and reduction in magnet temperature.

The present invention is not limited to the embodiments detailed above, and various modifications and variations are possible within the scope of the claims of the present invention.

<Explanation of symbols in the description of the first embodiment>
10: Rare earth magnet 11: Magnet 13: Insulating layer 30: Motor 31: Stator 33: Rotor 34: Rotating shaft 35: Rotating core 37: Shaft hole 39: Magnet hole <Explanation of symbols in the second embodiment>
Reference Signs List 110: laminated magnet 111: magnet 113: insulating layer 130: motor 131: stator 133: rotor 134: rotating shaft 135: rotating core 137: shaft hole 139: magnet hole

Claims (3)

A motor having a laminated magnet,
The magnet stack has a plurality of magnets and an insulating layer between the magnets,
A motor, wherein the insulating layer is mainly composed of inorganic crystals. The magnet stack is formed by stacking the magnets and the insulating layer in a first direction,
the magnet contains a rare earth element and has a curved shape that is convex in a second direction when viewed from the first direction,
2. The motor of claim 1, wherein the average orientation of each portion of a 1 mm width centered on a normal line at multiple points from one end to the other end on the curve on the convex side in the second direction on the outer periphery of the magnet when viewed from the first direction is 90% or more. The motor described in claim 1 or claim 2 is used at a maximum rotation speed of 7,500 rpm or more.

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