Rare earth permanent magnets and methods for manufacturing the same, and electrical equipment

Abstract

To provide a rare-earth permanent magnet with excellent demagnetizing properties. [Solution] The rare-earth permanent magnet has a rectangular parallelepiped structure, where the height direction H is the direction of easy magnetization, and the coercivity Hcj decreases in the width direction along W from the surface toward the center. Let H1 be the coercivity at any point on the surface, and H1' be the coercivity at the central point along the W direction corresponding to that point, such that H1 - H1' > 80 kA / m.

Description

[Technical Field]

[0001] This invention relates to a rare-earth permanent magnet, a method for manufacturing the same, and an electric machine containing the rare-earth permanent magnet. [Background technology]

[0002] R2Fe 14 R-Fe-B rare-earth sintered magnets, with B as the main phase, are high-performance permanent magnets and are mainly used in voice coil motors for hard disk drivers, piggyback motors for hybrid vehicles, and various home appliances.

[0003] The demagnetism resistance of an electrical device refers to its ability to be affected by external magnetic fields during its operation. Generally speaking, the stronger the demagnetism resistance of an electrical device, the greater its stability and reliability. The strength of an electrical device's demagnetism resistance is closely related to the materials used. For example, in the case of permanent magnet electrical devices, the coercivity of the permanent magnetic material is an important factor affecting its demagnetism resistance.

[0004] Generally speaking, in actual motor operation, the corner regions of the magnets are most susceptible to demagnetization. One study found that by diffusing heavy rare earth elements only in the corner regions of the magnets to increase coercivity, the amount of heavy rare earth elements used could be reduced, improving the performance-to-value ratio of the product. However, the overall coercivity of the resulting magnets was relatively low, and further improvements in demagnetization resistance are needed.

[0005] CN113506665A discloses a method for improving the coercivity of bonded neodymium iron boron magnets by efficient diffusion, which includes coating the edges of bonded neodymium iron boron magnets with a grain boundary diffuser containing heavy rare earth elements, light rare earth elements, or no rare earth elements, and then performing heat treatment. The coercivity of the magnets obtained by this method still needs to be improved.

[0006] CN117497276A discloses a selectable region R-T-Ga-B rare earth permanent magnet based on grain boundary diffusion and a manufacturing method thereof. This manufacturing method includes coating a diffusion source on a selected region from the diffusion surface of the substrate of a bonded neodymium iron boron magnet, coating the diffusion source on the corner region of the diffusion surface, not coating the diffusion source on the non-corner region, where the diffusion source is a mixed dry powder of heavy rare earth and metal Ga, and then performing a diffusion process to obtain a selectable region R-T-Ga-B rare earth permanent magnet based on grain boundary diffusion.

[0007] CN115602402A discloses a kind of rare earth permanent magnet and a manufacturing method thereof. This rare earth permanent magnet includes a P1 surface on the outer surface and a P2 surface on the adhering surface facing the P1 surface. The coercive force of the central part a1 of the P1 surface is set to H a1 and the coercive force of the central part a2 of the adhering surface P2 is set to H a2 satisfying H a1 >H a2 Taking a2 as the origin, a rectangular coordinate system is set up. The length direction of the P2 surface is defined as the X-axis, and the width direction of the P2 surface is defined as the Y-axis. The coercive force of the position b1 at (0, -Y) on the edge of the P1 surface is set to H b1 the coercive force of the position c1 at (X, -Y) on the edge of the P1 surface is set to H c1 the coercive force of the position d1 at (X, 0) on the edge of the P1 surface is set to H d1 satisfying the value of Y < the value of X, TIFF2026116773000002.tif5170 This rare earth permanent magnet needs to be realized by coating two or more times, and the manufacturing method is rather complicated. Moreover, the coercive force of the obtained rare earth permanent magnet still needs to be improved.

Summary of the Invention

[0009] On the one hand, the present invention provides a rare earth permanent magnet having a rectangular parallelepiped structure. This rectangular parallelepiped structure has a length, a width, and a height. The height direction is defined as the H direction, and the H direction is the direction in which the rare earth permanent magnet is easily magnetized. The width direction is defined as the W direction, This rectangular parallelepiped structure has two mutually parallel surfaces A1 and An composed of the length and the height. There are some cross-sections Ai parallel to the surface A1 between the surface A1 and the surface An. Among them, the cross-section located on the central axis of the rectangular parallelepiped structure is denoted as Aj. Along the W direction, from the surface A1 towards the cross-section Aj, the coercive force H cj decreases. Along the W direction, from the surface An towards the cross-section Aj, the coercive force H cj decreases, The coercive force of a point D1 on the surface A1 is denoted as H1. Draw an extension line along the W direction from the point D1. The extension line intersects the cross-section Aj at a point E1. If the coercive force of the point E1 is denoted as H1’, then H1 - H1’ > 80 kA / m. The coercive force of a point Dn on the surface An is denoted as Hn. Draw an extension line along the W direction from the point Dn. The extension line intersects the cross-section Aj at a point En. If the coercive force of the point En is denoted as Hn’, then Hn - Hn’ > 80 kA / m.

[0010] In the rare earth permanent magnet according to the present invention, preferably, the content of rare earth RE in the rare earth permanent magnet is 28 - 34 wt%. RE is light rare earth elements and heavy rare earth elements. The light rare earth elements essentially contain Nd, and the heavy rare earth elements are one or more selected from Dy, Tb, Gd, Ho, and Y.

[0011] In the rare earth permanent magnet according to the present invention, preferably, the light rare earth elements are one or more selected from Pr, Nd, La, and Ce, and essentially contain Nd. The heavy rare earth elements are Dy and Tb.

[0012] In the rare earth permanent magnet according to the present invention, preferably, in the W direction, the relationship between the coercive force y at a certain point of the rare earth permanent magnet and the position x of this point approximately satisfies the parabola y = ax2 + bx + c, where a > 0, b < 0, and c > 0.

[0013] On the other hand, the present invention includes the following steps: 1) Provide an initial sintered bonded neodymium iron boron magnet having a rectangular parallelepiped structure, denote the height direction of the initial sintered bonded neodymium iron boron magnet as the H0 direction, the width direction as the W0 direction, align the H0 direction with the H direction of the formed rare earth permanent magnet, and align the W0 direction with the W direction of the formed rare earth permanent magnet. 2) Coat the two opposing surfaces of the initial sintered bonded neodymium iron boron magnet with a heavy rare earth coating containing Dy along the direction perpendicular to the H0 direction to obtain Magnet A. 3) Coat the two opposing side surfaces of Magnet A with a heavy rare earth coating containing Tb along the direction perpendicular to the W0 direction to obtain Magnet B. 4) Heat-treat Magnet B to obtain the rare earth permanent magnet. The present invention provides a method for manufacturing the above rare earth permanent magnet, which includes the above steps.

[0014] In the manufacturing method according to the present invention, preferably, the initial sintered bonded neodymium iron boron magnet has R2Fe 14 as the main phase.

[0015] In the manufacturing method according to the present invention, preferably, in step (1), the initial sintered bonded neodymium iron boron magnet further contains another element M, and the other element M is a variety selected from Cu, Co, Ga, Ti, Zr, Mo, and Nb.

[0016] In the manufacturing method according to the present invention, preferably, in step (2), the weight increase amount of Dy is 0.4 to 1.5 wt%.

[0017] In the manufacturing method according to the present invention, preferably, in step (3), the weight increase amount of Tb is 0.05 to 0.5 wt%.

[0018] The present invention further provides an electric machine including the above-mentioned rare earth permanent magnet, and the rare earth permanent magnet is arranged in any of the following ways: (1) The 2N rare earth permanent magnets are uniformly arranged in the circumferential direction along the rotation direction of the electric machine, the rare earth permanent magnets are located at a regular N-sided polygon, and the angle between two adjacent rare earth permanent magnets is the same. Here, N is a positive integer of 3 or more. (2) The 2M rare earth permanent magnets are divided into M groups and uniformly arranged in the circumferential direction along the rotation direction of the electric machine. The connecting line between the far ends of the end faces of each group of rare earth permanent magnets is located at a regular M-sided polygon. In each group of rare earth permanent magnets, the angle between two rare earth permanent magnets is the same and they are arranged in a V shape. Here, M is a positive integer of 8 or more. (3) The 3P rare earth permanent magnets are divided into P groups and uniformly arranged in the circumferential direction along the rotation direction of the electric machine. In each group of rare earth permanent magnets, an isosceles triangle is formed between three rare earth permanent magnets, and the rare earth permanent magnet serving as the base of the isosceles triangle is located at a regular P-sided polygon. Here, P is a positive integer of 8 or more. (4) The 4Q rare earth permanent magnets are divided into Q groups and uniformly arranged in the circumferential direction along the rotation direction of the electric machine. In each group of rare earth permanent magnets, two parallel V shapes are formed between four rare earth permanent magnets. In each group of rare earth permanent magnets, the connecting line between the far ends of the end faces of the two rare earth permanent magnets forming the V shape is located at a regular Q-sided polygon. Here, Q is a positive integer of 6 or more.

[0019] The rare earth permanent magnet of the present invention has good demagnetization resistance and is suitable for permanent magnet electric machines with 4 poles or more. By the manufacturing method of the present invention, a rare earth permanent magnet having a specific coercive force distribution and good demagnetization resistance can be obtained. The reproducibility of the process of the present invention is good.

Brief Description of the Drawings

[0020] [Figure 1] Schematic diagram of a kind of electric machine formed when using the rare earth permanent magnet of the present invention. [Figure 2] Schematic diagram of a kind of electric machine formed when using the rare earth permanent magnet of the present invention. [Figure 3] A schematic diagram showing how a test piece of the rare-earth permanent magnet of the present invention is cut out in Manufacturing Example 1. [Figure 4] A schematic diagram showing how test pieces of the rare-earth permanent magnet of the present invention are cut along the W and H directions in Manufacturing Example 1. [Figure 5] Plotted curves of coercivity for 15 test pieces (A1-A15) of one edge obtained by cutting along the W direction of the rare earth permanent magnet obtained by Manufacturing Example 1. [Modes for carrying out the invention]

[0021] The present invention will be further described below with reference to specific examples, but the scope of the present invention is not limited thereto.

[0022] The term "coercivity" as used in this invention, also known as intrinsic coercivity, refers to the magnetic field strength at which the magnetization strength decreases monotonically from the saturation magnetization state of a magnet to zero and then increases again, following the saturation hysteresis curve until it reaches zero. Its units are oorsted (Oe) or amperes per meter (A / m). 1 Oe = 79.6 A / m.

[0023] The term "residual magnetic flux density" as used in this invention refers to the numerical value of the magnetic flux density corresponding to the case where the magnetic field strength is zero in the saturation hysteresis curve, and its unit is tesla (T) or gauss (Gs).

[0024] In this invention, the term "inert gas" includes helium, neon, argon, krypton, and xenon. "Inert atmosphere" refers to an atmosphere consisting of an inert gas that does not affect the performance of the magnet.

[0025] <Rare Earth Permanent Magnets> The rare-earth permanent magnet of the present invention is mounted in a radial magnetic current conductor and is suitable for at least four-pole permanent magnet motors. A four-pole motor is a motor in which the magnetic poles of the motor are in two pairs.

[0026] In the present invention, the rare earth permanent magnet has a rectangular parallelepiped structure, which has length, width and height, the height direction is defined as the H direction, the H direction is the direction in which the rare earth permanent magnet is easily magnetized, and the width direction is defined as the W direction.

[0027] This rectangular prism structure has two mutually parallel surfaces A1 and An, which are composed of length and height, and some cross section Ai parallel to surface A1 between surface A1 and surface An, of which the cross section located on the central axis of the rectangular prism structure is denoted as Aj.

[0028] Along the W direction, from surface A1 toward cross-section Aj, coercive force H cj The coercivity H decreases along the W direction, from surface An towards cross-section Aj. cj It will decrease.

[0029] If the coercivity at a point D1 on surface A1 is denoted as H1, and an extension line is drawn from point D1 along the W direction, this extension line intersects cross section Aj at point E1, and the coercivity at point E1 is denoted as H1', ​​then H1 - H1' > 80 kA / m.

[0030] If the coercivity at a point Dn on surface An is denoted as Hn, and an extension line is drawn from point Dn along the W direction, this extension line intersects the cross section Aj at point En, and the coercivity at point En is denoted as Hn', then Hn - Hn' > 80 kA / m. Electrical devices formed from such rare-earth permanent magnets have superior demagnetizing properties.

[0031] According to one embodiment of the present invention, points D1, E1, and Dn are located on the same straight line in the W direction, and point E1 coincides with point En.

[0032] The difference between H1 and H1' is greater than 80 kA / m, preferably greater than 100 kA / m, and more preferably 145 kA / m or more. The difference between Hn and Hn' is greater than 80 kA / m, preferably greater than 100 kA / m, and more preferably 145 kA / m or more. Electrical devices formed from such rare-earth permanent magnets exhibit superior demagnetization resistance.

[0033] In this invention, along the W direction, from surface A1 toward cross section Aj, coercivity H cj The coercivity H gradually decreases along the W direction, from the surface An towards the cross-section Aj. cj The coercivity gradually decreases. Specifically, in the W direction, the coercivity of the rare-earth permanent magnet gradually decreases from both ends towards the center, with the maximum coercivity at both ends (A1 or An) being greater than 2016 kA / m, preferably 2019 kA / m or more, and the minimum coercivity at the center (Aj) being greater than 1700 kA / m, preferably 1730 kA / m or more.

[0034] In this invention, the length of the rare-earth permanent magnet is greater than its width.

[0035] In the present invention, the rare earth permanent magnet may be a single-piece magnet or a joined magnet. According to one specific embodiment of the present invention, the rare earth permanent magnet is a single-piece magnet and not a joined magnet.

[0036] In the W direction, the relationship between the coercivity y of a point on a rare-earth permanent magnet and the position x of that point is a parabola y = ax. 2 The equation +bx+c is almost satisfied, where a>0, b<0, and c>0. A point on the surface A1 (or surface A2) of the rare earth permanent magnet is the origin of the plane orthogonal coordinate system, the W direction is the x-axis, the H direction is the y-axis, and the range of x is 0.1 to 20, preferably 0.2 to 19.

[0037] In some embodiments, a is 2 to 5, b is -88 to -38, and c is 2000 to 2070. In some specific embodiments, a is 3 to 5, b is -82 to -50, and c is 2060 to 2070. In some other specific embodiments, a is 2 to 4, b is -65 to -38, b is preferably -65 to -40, c is 2015 to 2030, and c is preferably 2020 to 2030.

[0038] According to one embodiment of the present invention, a = 2.3, b = -40.3, and c = 2029.0. According to another embodiment of the present invention, a = 3.6, b = -64.0, and c = 2020.8.

[0039] In this invention, in the W direction, the residual magnetic flux density of the rare-earth permanent magnet tends to gradually increase from both ends towards the center.

[0040] The rare earth permanent magnet of the present invention contains light rare earth elements and heavy rare earth elements. The light rare earth elements must contain Nd, and the heavy rare earth elements are one or more selected from Dy, Tb, Gd, Ho, and Y. According to one embodiment of the present invention, the light rare earth elements are one or more selected from Pr, Nd, La, and Ce, and must contain Nd, and the heavy rare earth elements are Dy and Tb.

[0041] In the present invention, based on the total weight of the rare earth permanent magnet, the content of rare earth element RE is 28 to 34 wt%, preferably 29 to 34 wt%, and more preferably 31 to 34 wt%.

[0042] According to one embodiment of the present invention, the length of the rare-earth permanent magnet is 30 to 45 mm, the width is 10 to 20 mm, and the height is less than 10 mm.

[0043] The present invention finds that such rare-earth permanent magnets possess high residual magnetic flux density and high coercivity, have good demagnetization resistance, and are suitable for permanent magnet electric devices with four or more poles.

[0044] <Manufacturing method> The present invention further provides a method for manufacturing the above-mentioned rare-earth permanent magnet. This manufacturing method includes the following steps: (1) providing an initial sintered bonded neodymium-iron-boron magnet, (2) obtaining magnet A, (3) obtaining magnet B, and (4) heat treatment. This is advantageous for obtaining the above-mentioned rare-earth permanent magnet.

[0045] The details are explained below.

[0046] This provides an initial sintered bonded neodymium iron boron magnet. R2Fe 14 The present invention provides an initial sintered bonded neodymium iron boron magnet with B as the main phase. The initial sintered bonded neodymium iron boron magnet has a rectangular parallelepiped structure and has length, width, and height.

[0047] The height direction of the initial sintered bonded neodymium iron boron magnet is indicated by the H0 direction, and the width direction is indicated by the W0 direction. The H0 direction is aligned with the H direction of the formed rare earth permanent magnet, and the W0 direction is aligned with the W direction of the formed rare earth permanent magnet.

[0048] In the initial sintered bonded neodymium iron boron magnet, R is a rare earth element and includes Nd and Pr. Based on the total weight of the sintered bonded neodymium iron boron magnet, the sintered bonded neodymium iron boron magnet contains the following components: PrNd is 28-32 wt%, B is 0.85-0.99 wt%, Dy is 0.01-2 wt%, Cu is 0.01-0.27 wt%, Co is 0.01-1.95 wt%, Ga is 0.01-0.5 wt%, Q is 0.01-0.25 wt%, and Fe is the remainder. Here, Q is at least one selected from Ti, Zr, Mo, and Nb. Here, the weight ratio of Pr to Nd is 1:3-1:4. In a preferred embodiment, the sintered bonded neodymium iron boron magnet consists of the above components.

[0049] Based on the total weight of the initial sintered bonded neodymium iron boron magnet, the PrNd content is preferably 29.0 to 31 wt%, more preferably 29.5 to 30.5 wt%. The B content is preferably 0.87 to 0.97 wt%, even more preferably 0.89 to 0.96 wt%. The Dy content is preferably 0.1 to 1.9 wt%, even more preferably 0.4 to 1.6 wt%. The Cu content is preferably 0.05 to 0.26 wt%, even more preferably 0.10 to 0.21 wt%. The Co content is preferably 0.1 to 1.7 wt%, even more preferably 0.5 to 1.5 wt%, and even more preferably 1.0 to 1.25 wt%. The Ga content is preferably 0.1 to 0.44 wt%, more preferably 0.15 to 0.36 wt%, for example 0.18 wt%, 0.21 wt%, and 0.34 wt%. The Q content is preferably 0.05 to 0.21 wt%, more preferably 0.10 to 0.19 wt%, and even more preferably 0.15 to 0.18 wt%. Q is preferably Ti.

[0050] Manufacturing of magnet A Magnet A is obtained by coating two opposing surfaces of an initial sintered bonded neodymium iron boron magnet with a heavy rare earth coating containing Dy, along a direction perpendicular to the H0 direction. In the initial sintered bonded neodymium iron boron magnet having a rectangular parallelepiped structure, these two opposing surfaces are length × width surfaces. This is advantageous for obtaining a rare earth permanent magnet with a specific coercivity distribution.

[0051] In the present invention, the method for applying the heavy rare earth coating containing Dy is not particularly limited, and methods known in the art can be employed. In some embodiments, the method for applying the heavy rare earth coating containing Dy to two opposing surfaces of an initial sintered bonded neodymium iron boron magnet along a direction perpendicular to the H0 direction is selected from spraying, screen printing, and magnetron sputtering.

[0052] According to one embodiment of the present invention, a heavy rare earth coating containing Dy can be applied by employing a spray method, and spray equipment can be used during the spraying process.

[0053] According to one embodiment of the present invention, a heavy rare earth coating containing Dy is formed by spraying a material containing Dy. The material containing Dy can be formed by mixing a substance containing Dy (e.g., dysprosium hydride, dysprosium powder) with an organic solvent to form a Dy mixture. The mass concentration of the Dy mixture may be 25 to 50 wt%, preferably 25 to 45 wt%, and more preferably 25 to 35 wt%. The organic solvent can be selected from those known in the art, for example, one selected from acetone, ethanol, isopropanol, and petroleum ether, for example, ethanol, preferably anhydrous ethanol. In this way, Dy can be coated more accurately, the adhesion rate is high, and the reproducibility is good.

[0054] According to one embodiment of the present invention, when spraying, the initial sintered bonded neodymium iron boron magnet is preheated beforehand, and the preheating temperature may be 120 to 240°C, preferably 150 to 200°C, and more preferably 180 to 200°C. A material containing Dy is sprayed onto one surface of the initial sintered bonded neodymium iron boron magnet along a direction perpendicular to the H0 direction, thereby coating this surface with a heavy rare earth coating containing Dy. The weight increase of Dy on one side is controlled to be 0.2 to 1 wt%, preferably 0.25 to 0.8 wt%, and more preferably 0.3 to 0.55 wt%. The weight increase of Dy on one side = (weight of the initial sintered bonded neodymium iron boron magnet coated with a heavy rare earth coating containing Dy on one side - weight of the initial sintered bonded neodymium iron boron magnet) / weight of the initial sintered bonded neodymium iron boron magnet × 100%.

[0055] After spraying one surface, the magnet is flipped over, and a material containing Dy is sprayed onto the other surface of the initial sintered bonded neodymium iron boron magnet in a direction perpendicular to the H0 direction to form magnet A. The weight increase of Dy on one side is controlled to be 0.2 to 1 wt%, preferably 0.25 to 0.8 wt%, and more preferably 0.3 to 0.55 wt%.

[0056] During spraying, the total weight increase of Dy is controlled to be 0.4 to 1.5 wt%, preferably 0.5 to 1.2 wt%, and more preferably 0.6 to 1.0 wt%. The total weight increase of Dy = (weight of magnet A - weight of initial sintered bonded neodymium iron boron magnet) / weight of initial sintered bonded neodymium iron boron magnet × 100%.

[0057] Magnet B Magnet B is obtained by coating two opposing sides of magnet A with a heavy rare earth coating containing Tb, along a direction perpendicular to the W0 direction. In magnet A, which has a rectangular parallelepiped structure, these two opposing sides are surfaces with length × height (or thickness). This is advantageous for obtaining a rare earth permanent magnet with a specific coercivity.

[0058] In the present invention, the method of coating two opposing sides of magnet A with a heavy rare earth coating containing Tb along a direction perpendicular to the W0 direction is not particularly limited, and a method known in the art can be employed, for example, one selected from spraying, screen printing, or magnetron sputtering.

[0059] According to one embodiment of the present invention, a Tb-containing material is sprayed to form a Tb-containing heavy rare earth coating. The Tb-containing material can be formed by mixing a Tb-containing substance (e.g., terbium powder) with an organic solvent to form a Tb mixture, the mass concentration of which may be 25 to 50 wt%, preferably 25 to 40 wt%, and more preferably 25 to 30 wt%. The organic solvent can be selected from those known in the art, for example, one selected from acetone, ethanol, isopropanol, and petroleum ether, preferably ethanol. This allows for accurate coating of Tb, high adhesion, and good reproducibility.

[0060] According to one embodiment of the present invention, before spraying, magnet A is preheated, and the preheating temperature may be 120 to 240°C, preferably 150 to 200°C, and more preferably 180 to 200°C. A material containing Tb is sprayed onto one side of magnet A along a direction perpendicular to the W0 direction, thereby coating this side with a heavy rare earth coating containing Tb. The weight increase of Tb on one side is controlled to be 0.02 to 0.2 wt%, preferably 0.03 to 0.15 wt%, and more preferably 0.05 to 0.1 wt%. The weight increase of Tb on one side = (weight of magnet A coated with heavy rare earth coating containing Tb on one side - weight of magnet A) / weight of magnet A × 100%.

[0061] After spraying one surface, the magnet is turned over, and the material containing Tb is sprayed onto the other side of magnet A in a direction perpendicular to the W0 direction to form magnet B. The weight increase of Tb on one side is controlled to be 0.02 to 0.2 wt%, preferably 0.03 to 0.15 wt%, and more preferably 0.05 to 0.1 wt%.

[0062] During spraying, the weight increase of the total controlled Tb is 0.05 to 0.5 wt%, preferably 0.1 to 0.5 wt%, and more preferably 0.15 to 0.35 wt%. The weight increase of the total Tb = (weight of magnet B - weight of magnet A) / weight of magnet A × 100%.

[0063] heat treatment The rare earth permanent magnet is obtained by heat-treating magnet B.

[0064] In the present invention, the heat treatment can be carried out under vacuum conditions, where the vacuum level is 0.1 Pa or less, preferably 0.01 Pa or less, and more preferably 0.001 Pa or less.

[0065] A rare-earth permanent magnet can be obtained by heat-treating magnet B at multiple gradient temperatures. Preferably, after heat treatment at the first, second, third, and fourth temperatures, it is cooled, and then heat-treated again at the fifth temperature, cooled, and a rare-earth permanent magnet is obtained.

[0066] Magnet B is heated to a first temperature and heat-treated at this first temperature for 1 to 1.5 hours. The first temperature is 100 to 140°C, preferably 100 to 130°C, and more preferably 100 to 120°C. Next, it is heated to a second temperature and heat-treated at this second temperature for 1 to 1.5 hours. The second temperature may be 180 to 250°C, preferably 200 to 230°C, and more preferably 200 to 220°C. Then, it is heated again to a third temperature and heat-treated at this third temperature for 1 to 1.5 hours. The third temperature may be 450 to 550°C, preferably 500 to 550°C, and more preferably 500 to 530°C. Next, it is heated again to a fourth temperature and heat-treated at this fourth temperature for 8 to 24 hours. The fourth temperature may be 860-950°C, preferably 880-920°C, and more preferably 900-920°C. The heat treatment time at the fourth temperature is preferably 10-11 hours.

[0067] In this invention, cooling can be performed using an inert gas, preferably argon gas. Cooling can be performed to 50°C or below.

[0068] The material is then heated to a fifth temperature and heat-treated at this fifth temperature for 4 to 7 hours. The fifth temperature may be 450 to 550°C, preferably 490 to 530°C, and more preferably 500 to 530°C. The heat treatment time is preferably 5 to 6 hours. After the heat treatment at the fifth temperature is completed, it is cooled to below 50°C to obtain a rare-earth permanent magnet. This method is advantageous for obtaining a rare-earth permanent magnet with stable performance.

[0069] According to one embodiment of the present invention, magnet B is heated to a first temperature of 100-140°C and heat-treated at this first temperature for 1-1.5 hours. Next, it is heated to a second temperature of 180-250°C and heat-treated at this second temperature for 1-1.5 hours. Then, it is heated to a third temperature of 450-550°C and heat-treated at this third temperature for 1-1.5 hours. The heating is continued to increase to a fourth temperature of 850-950°C and heat-treated at this fourth temperature for 8-24 hours. Then, heating is stopped and the magnet is cooled to below 50°C using an inert gas. Finally, it is heated to a fifth temperature of 450-520°C and heat-treated at this fifth temperature for 4-7 hours, and heating is stopped. The magnet is then cooled to below 50°C using an inert gas to obtain a rare-earth permanent magnet. Thus, it is advantageous to obtain a rare-earth permanent magnet with stable performance.

[0070] <Electrical equipment> The present invention also provides an electric machine comprising one of the above-mentioned rare-earth permanent magnets, wherein the rare-earth permanent magnet is arranged in one of the following ways.

[0071] (1) The N rare-earth permanent magnets are uniformly arranged in a ring direction along the direction of rotation of the electric motor, the rare-earth permanent magnets are arranged in a regular N-gon, and the angle between any two adjacent rare-earth permanent magnets is the same, where N is a positive integer of 3 or more.

[0072] (2) The 2M rare earth permanent magnets are divided into M groups and uniformly arranged in a ring direction along the direction of rotation of the electric motor, and the connections between the farthest end faces of the rare earth permanent magnets in each group are arranged in a regular M-gon, and in each group of rare earth permanent magnets the angle between the two rare earth permanent magnets is the same and they are arranged in a V-shape, where M is a positive integer greater than or equal to 8.

[0073] (3) The 3P rare earth permanent magnets are divided into P groups and uniformly arranged in a ring direction along the direction of rotation of the electric motor. In each group of rare earth permanent magnets, an isosceles triangle is formed between the three rare earth permanent magnets, and the rare earth permanent magnet that forms the base of the isosceles triangle is located in a regular P-gon, where P is a positive integer greater than or equal to 8.

[0074] (4) The 4Q rare earth permanent magnets are divided into Q sets and uniformly arranged in a ring direction along the direction of rotation of the electric motor, and in each set of rare earth permanent magnets, two parallel V shapes are formed between the four rare earth permanent magnets, and the connection between the far apart end faces of the two rare earth permanent magnets forming the V shape in each set of rare earth permanent magnets is in a regular Q-gon, where Q is a positive integer greater than or equal to 6.

[0075] The electric motor has four or more poles. The electric motor has excellent resistance to demagnetism.

[0076] According to one embodiment of the present invention, eight of the rare earth permanent magnets are uniformly arranged in a ring direction along the rotation direction of the electric motor, the rare earth permanent magnets are arranged in a regular octagon, and the angle between two adjacent rare earth permanent magnets is the same. According to another embodiment of the present invention, sixteen rare earth permanent magnets are divided into eight sets and are uniformly arranged in a ring direction along the rotation direction of the electric motor. The connections between the far apart end faces of the rare earth permanent magnets in each set are arranged in a regular octagon, and in each set of rare earth permanent magnets, the angle between two rare earth permanent magnets is the same, and they are arranged in a V-shape.

[0077] <Testing Method> Magnetic properties are measured using a magnetic tester from Metis, Belgium, at room temperature.

[0078] <Ingredients Description> During spraying, the material containing Dy is a Dy mixture formed from dysprosium powder and anhydrous ethanol, with a mass concentration of Dy of 30 wt%. The material containing Tb is a Tb mixture formed from terbium powder and anhydrous ethanol, with a mass concentration of Tb of 30 wt%.

[0079] Manufacturing Example 1 - Rare Earth Permanent Magnet This embodiment provides a rare-earth permanent magnet to be mounted on a type of radial flux electromechanism.

[0080] A rare-earth permanent magnet has a rectangular parallelepiped structure, which has length, width, and height. The height direction is defined as the H direction, which is the direction in which the rare-earth permanent magnet is easily magnetized, and the width direction is defined as the W direction.

[0081] This rectangular prism structure has two mutually parallel surfaces A1 and An, which are composed of length and height, and some cross section Ai parallel to surface A1 between surface A1 and surface An, of which the cross section located on the central axis of the rectangular prism structure is denoted as Aj.

[0082] Along the W direction, from surface A1 toward cross section Aj, coercive force H cj The coercivity H decreases along the W direction, from surface An towards cross section Aj. cj The coercivity decreases. If the coercivity at a point D1 on surface A1 is denoted as H1, and an extension line is drawn from point D1 along the W direction, this extension line intersects cross section Aj at point E1, and the coercivity at point E1 is denoted as H1', ​​then H1-H1'>80kA / m. If the coercivity at a point Dn on surface An is denoted as Hn, and an extension line is drawn from point Dn along the W direction, this extension line intersects cross section Aj at point En, and the coercivity at point En is denoted as Hn', then Hn-Hn'>80kA / m, and D1, E1 and Dn are located on the same straight line in the W direction, and E1 coincides with En.

[0083] In the W direction, the relationship between the coercivity y of a point on a rare-earth permanent magnet and the position x of that point is a parabola y = ax. 2The equation +bx+c is nearly satisfied, where a>0, b<0, and c>0. A point on the surface A1 of the rare-earth permanent magnet is the origin of the Cartesian coordinate system, with the W direction being the x-axis and the x-value range being 0.1 to 20, and the H direction being the y-axis.

[0084] Next, we will introduce the manufacturing method for this rare-earth permanent magnet, which includes the following steps.

[0085] We provided an initial sintered bonded neodymium iron boron magnet with dimensions of 39 mm (length) x 17.8 mm (width) x 4 mm (height, i.e., orientation direction), and the surface of the magnet was polished. The composition of the initial sintered bonded neodymium iron boron magnet is shown in Table 1 below.

[0086] TIFF2026116773000003.tif25170 Note: The weight ratio of Pr to Nd is 1:3.

[0087] The height direction of the initial sintered bonded neodymium iron boron magnet is indicated by the H0 direction, and the width direction is indicated by the W0 direction. The H0 direction is aligned with the H direction of the formed rare earth permanent magnet, and the W0 direction is aligned with the W direction of the formed rare earth permanent magnet.

[0088] Magnet A was obtained by coating two opposing surfaces of an initial sintered bonded neodymium iron boron magnet with a heavy rare earth coating containing Dy, along a direction perpendicular to the H0 direction. Specifically, the process included the following steps: the initial sintered bonded neodymium iron boron magnet was placed in a spraying apparatus, one surface (39 mm × 17.8 mm surface) was facing upwards, preheated to 180°C, and then a heavy rare earth coating containing Dy was applied to this surface by spraying. The weight increase of Dy on one side was 0.325 wt%. The magnet was then flipped over. The other surface (the opposite surface of the 39 mm × 17.8 mm surface) was coated with a heavy rare earth coating containing Dy by spraying to obtain magnet A. The weight increase of Dy on one side was 0.325 wt%.

[0089] Magnet B was obtained by coating two opposing sides of magnet A with a heavy rare earth coating containing Tb, along a direction perpendicular to the W0 direction. Specifically, the following steps were taken: One side of magnet A (a 39mm x 4mm side) was placed facing upwards and preheated to 180°C. A heavy rare earth coating containing Tb was then applied to this side by spraying. The weight increase on one side of Tb was 0.075%. The magnet was then flipped over, and the other side (the opposite side of the 39mm x 4mm side) was coated with a heavy rare earth coating containing Tb by spraying to obtain magnet B. The weight increase on one side of Tb was 0.075%.

[0090] The rare earth permanent magnet was obtained by heat-treating magnet B. Specifically, the process included the following steps: magnet B was heated to a first temperature of 100°C and held at 100°C for 1 hour. Then, it was heated to a second temperature of 200°C and held at 200°C for 1 hour. Then, it was heated to a third temperature of 500°C and held at 500°C for 1 hour. The heating was continued to a fourth temperature of 920°C and held at 920°C for 12 hours. Heating was stopped and it was cooled to below 50°C using argon gas. Next, it was heated to a fifth temperature of 490°C and held at 490°C for 5 hours. Heating was stopped and it was cooled to below 50°C using argon gas to obtain the rare earth permanent magnet.

[0091] Referring to Figure 3, three samples measuring 17.8 mm × 4 mm × 1 mm were cut along the length and width of the rare-earth permanent magnet (length was 39 mm and width was 17.8 mm). The cutting positions were located at two end positions and one center position along the length of the magnet (length was 39 mm), namely position 1, position 2, and position 3.

[0092] Referring to Figure 4, a 17.8 mm × 4 mm × 1 mm sample was cut along the H direction (height was 4 mm) at the center line position and two edge positions, with test specimens measuring 1 mm × 1 mm × 1 mm. There were 15 test specimens per layer, and their numbers are shown in the table below. The room temperature performance of each test specimen was measured, and the details are shown in Table 2. Since positions 1 and 3 are symmetrical, only the performance of the test specimens cut from position 1 was measured. The coercivity formation curves of the test specimens A1 to A15 at position 1 are shown in Figure 5.

[0093] TIFF2026116773000004.tif182170

[0094] As can be seen from this, in the rare-earth permanent magnet of the present invention, in the W direction, the coercivity of the rare-earth permanent magnet tended to decrease from both ends toward the center. Furthermore, the difference between the coercivity H1 at a point D1 on the surface A1 of the rare-earth permanent magnet (for example, the coercivity of the A1 test piece was 2030 kA / m) and the coercivity H1' at point E1 where an extension line drawn from point D1 along the W direction intersects the cross section Aj (for example, the coercivity of the A8 test piece was 1843 kA / m) was greater than 80 kA / m, for example, 187 kA / m.

[0095] Similarly, the difference between the coercivity of specimen A15 (2019 kA / m) and specimen A8 (1843 kA / m) was greater than 80 kA / m, for example, 176 kA / m.

[0096] Similarly, the difference between the coercivity of specimen B1 (2013 kA / m) and specimen B8 (1738 kA / m) was greater than 80 kA / m, for example, 275 kA / m.

[0097] Similarly, the difference between the coercivity of specimen B15 (1988 kA / m) and specimen B8 (1738 kA / m) was greater than 80 kA / m, for example, 250 kA / m.

[0098] In the W direction, the relationship between the coercivity y of a point on a rare-earth permanent magnet and the position x of that point is a parabola y = ax. 2The equation +bx+c is nearly satisfied, where a>0, b<0, and c>0. A point on the surface A1 of the rare-earth permanent magnet is the origin of the plane orthogonal coordinate system, with the W direction being the x-axis and the x-value range being 0.1 to 20, and the H direction being the y-axis.

[0099] In the peripheral region (A1~A15), the parabola is, TIFF2026116773000005.tif5170

[0100] In the central region (B1-B15), the parabola is, TIFF2026116773000006.tif5170

[0101] Sampling was continued at position 2 in Figure 3, and referring to Figure 4, the test specimen at position 2 was sampled and measured using the sampling method at position 1. Sampling was performed from A1' to A15' (i.e., the same sampling positions as A1 to A15), and from B1'' to B15'' (i.e., the same sampling positions as B1 to B15). The measured coercivity is shown in Table 3.

[0102] TIFF2026116773000007.tif182170

[0103] As can be seen from this, in the rare-earth permanent magnet of the present invention, in the W direction, the coercivity of the rare-earth permanent magnet tended to decrease from both ends towards the center.

[0104] Furthermore, the difference between the coercivity H1 at a point D1 on the surface A1 of the rare-earth permanent magnet (for example, the coercivity of the A1' test specimen is 2035 kA / m) and the coercivity H1' at point E1 where an extension line drawn from point D1 along the W direction intersects the cross section Aj (for example, the coercivity of the A8' test specimen was 1848 kA / m) is greater than 80 kA / m, and may be, for example, 187 kA / m or more.

[0105] Similarly, the difference between the coercivity of specimen A15' (2026 kA / m) and specimen A8' (1848 kA / m) was greater than 80 kA / m, for example, 178 kA / m.

[0106] Similarly, the difference between the coercivity of specimen B1' (2009 kA / m) and specimen B8' (1741 kA / m) could be greater than 80 kA / m, for example, 268 kA / m.

[0107] Similarly, the difference between the coercivity of specimen B15' (1991 kA / m) and specimen B8' (1741 kA / m) was greater than 80 kA / m, for example, 250 kA / m.

[0108] In the W direction, the relationship between the coercivity y of a point on a rare-earth permanent magnet and the position x of that point is a parabola y = ax. 2 The equation +bx+c is nearly satisfied, where a>0, b<0, and c>0. A point on the surface A1 of the rare-earth permanent magnet is the origin of the plane orthogonal coordinate system, with the W direction being the x-axis and the x-value range being 0.1 to 20, and the H direction being the y-axis.

[0109] In the peripheral region (A1'~A15'), the parabola is, TIFF2026116773000008.tif5170

[0110] In the central region (B1'~B15'), the parabola is, TIFF2026116773000009.tif5170

[0111] Example 1 - Electrical Machine As shown in Figure 1, the eight rare-earth permanent magnets of Manufacturing Example 1 were uniformly arranged in a ring direction along the rotational direction of the electric motor. The rare-earth permanent magnets were arranged in a regular octagon, and the angle between any two adjacent rare-earth permanent magnets was the same.

[0112] Example 2 - Electrical Machine As shown in Figure 2, the 16 rare-earth permanent magnets of Manufacturing Example 1 were divided into 8 sets and uniformly arranged in a ring direction along the rotational direction of the magnet. The connections between the far apart end faces of the rare-earth permanent magnets in each set were positioned in a regular octagon. In each set of rare-earth permanent magnets, the angle between the two rare-earth permanent magnets was the same, and they were arranged in a V-shape.

[0113] Comparative Manufacturing Example 1 The difference from Manufacturing Example 1 was that the terbium Tb deposited along the direction perpendicular to the W0 direction was replaced with deposited dysprosium Dy. The details were as follows.

[0114] The orientation direction of the initial sintered bonded neodymium iron boron magnet is denoted by the H0 direction, and the width direction is denoted by the W0 direction. The H0 direction is aligned with the H direction of the formed rare earth permanent magnet, and the W0 direction is aligned with the W direction of the formed rare earth permanent magnet.

[0115] Magnet A was obtained by coating two opposing surfaces of an initial sintered bonded neodymium iron boron magnet with a heavy rare earth coating containing Dy, along a direction perpendicular to the H0 direction. Specifically, the process included the following steps: the initial sintered bonded neodymium iron boron magnet was placed in a spraying apparatus, one surface (39 mm × 17.8 mm surface) was facing upwards, preheated to 180°C, and then a heavy rare earth coating containing Dy was applied to this surface by spraying. The weight increase of Dy on one side was 0.325 wt%. The magnet was then flipped over. The other surface (the opposite surface of the 39 mm × 17.8 mm surface) was coated with a heavy rare earth coating containing Dy by spraying to obtain magnet A. The weight increase of Dy on one side was 0.325 wt%.

[0116] Magnet B'' was obtained by coating two opposing sides of magnet A with a heavy rare earth coating containing Dy, along a direction perpendicular to the W0 direction. Specifically, the following steps were taken: One side of magnet A (a 39mm x 4mm side) was placed facing upwards and preheated to 180°C. A heavy rare earth coating containing Dy was then applied to this side by spraying. The weight increase on one side due to Dy was 0.4%. The magnet was then flipped over, and the other side (the opposite side of the 39mm x 4mm side) was coated with a heavy rare earth coating containing Dy by spraying to obtain magnet B''. The weight increase on one side due to Dy was 0.4%.

[0117] A rare-earth permanent magnet was obtained by heat-treating magnet B''. Specifically, the process included the following steps: Magnet B'' was heated to a first temperature of 100°C and held at 100°C for 1 hour. Then, it was heated to a second temperature of 200°C and held at 200°C for 1 hour. Next, it was heated to a third temperature of 500°C and held at 500°C for 1 hour. The heating was continued to increase to a fourth temperature of 920°C and held at 920°C for 12 hours. Heating was stopped, and it was cooled to below 50°C using argon gas. Then, it was heated to a fifth temperature of 490°C and held at 490°C for 5 hours. Heating was stopped, and it was cooled to below 50°C using argon gas to obtain the rare-earth permanent magnet.

[0118] This rare-earth permanent magnet was sampled and measured with reference to Figures 3 and 4. Only position 1 was sampled, with sampling numbers A1'' to A15'' and B1'' to B15'', respectively. Only one end position 1 was analyzed. The results of the measurement and analysis are shown in Table 4.

[0119] TIFF2026116773000010.tif171170

[0120] In Table 4, in the W direction, the coercivity of the rare-earth permanent magnets did not gradually decrease from both ends towards the center. Moreover, the difference H1-H1' between the coercivity of A1'' (1785 kA / m) and the coercivity of A8'' (1781 kA / m) was less than 80 kA / m, and the difference Hn-Hn' between the coercivity of A15'' (1788 kA / m) and the coercivity of A8'' (1781 kA / m) was less than 80 kA / m. The difference between the coercivity of B1'' (1688 kA / m) and the coercivity of B8'' (1677 kA / m) was less than 80 kA / m. The difference between the coercivity of B15'' (1679 kA / m) and the coercivity of B8'' (1677 kA / m) was less than 80 kA / m.

[0121] The distribution of coercivity differed compared to the rare-earth permanent magnet of Manufacturing Example 1.

[0122] Comparative Example 1 - Electrical Machinery As shown in Figure 1, the eight rare-earth permanent magnets of Comparative Manufacturing Example 1 were uniformly arranged in a ring direction along the rotational direction of the electric motor. The rare-earth permanent magnets were arranged on a regular octagon, and the angle between two adjacent rare-earth permanent magnets was the same.

[0123] Comparative Example 2 - Electrical Machinery As shown in Figure 2, the 16 rare-earth permanent magnets of Comparative Manufacturing Example 1 were divided into 8 sets and uniformly arranged in a ring direction along the rotational direction of the electric motor. The connections between the far-off end faces of the rare-earth permanent magnets in each set were positioned in a regular octagon. In each set of rare-earth permanent magnets, the angle between the two rare-earth permanent magnets was the same, and they were arranged in a V-shape.

[0124] For the electrical equipment of Example 1-2 and Comparative Example 1-2, the back electromotive force V0 was measured at room temperature, load tests were conducted at high temperatures of 120°C, 140°C, and 160°C, and then the back electromotive force V0 was measured again when the temperature returned to room temperature. t The following equation was used to calculate the corresponding damping rate α by measuring the voltage and employing the following formula. α = (V0 - V) t ) / V0×100% The calculation results are shown in Table 5.

[0125] TIFF2026116773000011.tif53170

[0126] As can be seen from the table, in the W direction, the coercivity of the rare earth permanent magnet tended to gradually decrease from both ends towards the center (i.e., along the W direction, from surface A1 towards cross section Aj, coercivity H cj The coercivity H decreases along the W direction, from surface An towards cross-section Aj. cj (The current decreased), and when H1-H1' was greater than 80 kA / m and Hn-Hn' was greater than 80 kA / m, the high-temperature attenuation of the current was small and the resistance to demagnetism was strong.

[0127] The present invention is not limited to the embodiments described above, and any modifications, improvements, substitutions, etc., that a person skilled in the art could conceive of, without departing from the spirit of the invention, are included within the scope of the present invention.

Claims

1. It has a rectangular parallelepiped structure, which has length, width, and height, with the height direction defined as the H direction, which is the direction in which rare-earth permanent magnets are easily magnetized, and the width direction defined as the W direction. The rectangular parallelepiped structure has two mutually parallel surfaces A1 and An, which are composed of length and height, and has some cross section Ai parallel to surface A1 between surface A1 and surface An, of which the cross section located at the central axis of the rectangular parallelepiped structure is denoted as Aj. Along the W direction, from surface A1 toward cross-section Aj, coercive force H cj The coercivity H decreases along the W direction, from surface An towards cross-section Aj. cj It decreased, If the coercivity at a point D1 on surface A1 is denoted as H1, and an extension line is drawn from point D1 along the W direction, this extension line intersects cross section Aj at point E1, and the coercivity at point E1 is denoted as H1', ​​then H1 - H1' > 80 kA / m. If the coercivity at a point Dn on surface An is denoted as Hn, and an extension line is drawn from point Dn along the W direction, this extension line intersects with cross section Aj at point En, and the coercivity at point En is denoted as Hn', then Hn - Hn' > 80 kA / m. A rare-earth permanent magnet characterized by the following features.

2. The content of rare earth elements RE in the aforementioned rare earth permanent magnet is 28-34 wt%, where RE consists of light rare earth elements and heavy rare earth elements, the light rare earth elements must contain Nd, and the heavy rare earth elements are one or more selected from Dy, Tb, Gd, Ho, and Y. The rare earth permanent magnet according to feature 1.

3. The light rare earth elements are one or more selected from Pr, Nd, La, and Ce, and must contain Nd; the heavy rare earth elements are Dy and Tb. The rare earth permanent magnet according to feature 2.

4. In the W direction, the relationship between the coercivity y of a point on a rare-earth permanent magnet and the position x of that point is a parabola y = ax. 2 The equation +bx+c is nearly satisfied, where a>0, b<0, and c>0. The rare earth permanent magnet according to feature 1.

5. The following steps, 1) Provides an initial sintered bonded neodymium iron boron magnet having a rectangular parallelepiped structure, wherein the height direction of the initial sintered bonded neodymium iron boron magnet is H 0 The directions are indicated by W. 0 Indicate direction, H 0 The direction is aligned with the H direction of the formed rare-earth permanent magnet, and W 0 The direction is aligned with the W direction of the formed rare-earth permanent magnet. 2) H 0 Magnet A is obtained by coating two opposing surfaces of an initial sintered bonded neodymium iron boron magnet with a heavy rare earth coating containing Dy, along a direction perpendicular to the direction. 3) W 0 Along the direction perpendicular to the [[0000009]] direction, a heavy rare earth coating containing Tb is coated on two opposite side surfaces of the magnet A respectively, and the magnet B is obtained. 4) The rare earth permanent magnet is obtained by heat-treating magnet B. A method for manufacturing a rare earth permanent magnet according to any one of claims 1 to 4, characterized by including the following:

6. The aforementioned initial sintered bonded neodymium iron boron magnet is R 2 Fe 14 B is the main phase The manufacturing method according to claim 5.

7. Step 1) further contains other elements M in the initial sintered bonded neodymium iron boron magnet, and the other elements M are selected from various types of Cu, Co, Ga, Ti, Zr, Mo, and Nb. The manufacturing method according to claim 6.

8. In step 2), the weight increase of Dy is 0.4–1.5 wt%. The manufacturing method according to claim 6.

9. In step 3), the weight increase of Tb is 0.05 to 0.5 wt%. The manufacturing method according to claim 6.

10. The rare-earth permanent magnets are arranged in one of the following ways: (1) The N rare-earth permanent magnets are uniformly arranged in a ring direction along the direction of rotation of the electric motor, the rare-earth permanent magnets are arranged in a regular N-gon, and the angle between two adjacent rare-earth permanent magnets is the same, where N is a positive integer of 3 or more. (2) The 2M rare-earth permanent magnets are divided into M groups and uniformly arranged in a ring direction along the direction of rotation of the electric motor, and the connections between the farthest end faces of the rare-earth permanent magnets in each group form a regular N-gon, and in each group of rare-earth permanent magnets the angle between the two rare-earth permanent magnets is the same, and they are arranged in a V-shape, where M is a positive integer greater than or equal to 8. (3) The 3P rare-earth permanent magnets are divided into P groups and uniformly arranged in a ring direction along the direction of rotation of the electric motor. In each group of rare-earth permanent magnets, an isosceles triangle is formed between the three rare-earth permanent magnets, and the rare-earth permanent magnets as the base of the isosceles triangle are located in a regular P-gon, where P is a positive integer greater than or equal to 8. (4) The 4Q rare-earth permanent magnets are divided into Q sets and uniformly arranged in a ring direction along the direction of rotation of the electric motor, and in each set of rare-earth permanent magnets, two parallel V shapes are formed between the four rare-earth permanent magnets, and in each set of rare-earth permanent magnets, the connection between the far apart end faces of the two rare-earth permanent magnets forming the V shape is located in a regular Q-gon, where Q is a positive integer greater than or equal to 6. An electric machine characterized by including a rare earth permanent magnet according to any one of claims 1 to 4.

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