Wet compaction die, method for manufacturing sintered magnet, sintered magnet, rotor, and method for manufacturing rotor

Abstract

To provide a method for efficiently manufacturing a sintered magnet that does not easily fall out of a rotor core in a rotor having a sintered magnet embedded in a rotor core, a mold for compression molding for that purpose, a sintered magnet obtained by the method, a rotor using the sintered magnet, and a method of manufacturing the rotor.SOLUTION: A mold for compression molding includes a die and upper and lower punches for compression molding a magnetic powder filled in the cavity of the die, and a plurality of ridges or grooves parallel to the pressing direction on a surface forming the cavity of the die.SELECTED DRAWING: Figure 1(a)

Description

[Technical Field]

[0001] The present invention relates to a compression molding die, a method for manufacturing a sintered magnet using the compression molding die, a sintered magnet manufactured using the compression molding die, a rotor using the sintered magnet, and a method for manufacturing the rotor. [Background technology]

[0002] BACKGROUND ART Sintered rare earth magnets and sintered ferrite magnets are widely used in a variety of applications, including rotating machines such as motors and generators.

[0003] Known examples of rare earth sintered magnets include RTB sintered magnets (R is at least one rare earth element and always includes at least one of Nd and Pr. T is at least one transition metal element and always includes iron (Fe). B represents boron), Sm—Co sintered magnets (Sm (samarium) may be partially substituted with other rare earth elements) (Patent Document 1), and known examples of ferrite sintered magnets include hexagonal M-type (magnetoplumbite) Sr ferrite, Ba ferrite, and other sintered magnets (Patent Document 2).

[0004] These sintered magnets are obtained by molding magnetic powder into a predetermined shape and sintering it. Known molding methods include dry molding (e.g., Patent Document 3 (JP 2004-296849 A)) and wet molding (e.g., Patent Document 4 (JP Patent No. 3833861 A)). In the dry molding method, dried magnetic powder is pressure-molded in an applied magnetic field to produce a molded body, and the resulting molded body is then sintered. In the wet molding method, a slurry containing magnetic powder is pressure-molded in an applied magnetic field while removing the liquid component to produce a molded body, and the resulting molded body is then sintered.

[0005] For example, a ferrite sintered magnet can be manufactured by the following steps: (a) mixing raw materials such as compounds of Fe, Sr, Ba, Ca, La, Co, etc.; (b) calcining the mixture to cause a ferritization reaction and obtain a calcined body; (c) roughly pulverizing the calcined body, adding compounds such as sintering aids, and wet-pulverizing the resulting calcined body; (d) molding a slurry of the resulting calcined fine particles in a magnetic field to obtain a molded body; (e) sintering the molded body; and (f) processing the resulting sintered body into a shape appropriate for its intended use.

[0006] An example of a compression molding die for producing a sintered magnet is shown in Figures 7(a) and 7(b). The compression molding die 50 has a die 51, a lower punch 52, and an upper punch 53, and the space surrounded by these constitutes a cavity 54. As shown in Figure 7(b), the cavity 54 is trapezoidal when viewed in the direction of pressure application. The lower punch 52 and the upper punch 53 are configured to be able to move up and down independently. With the upper punch 53 removed upward, a predetermined amount of magnetic powder or a slurry containing magnetic powder is filled into the cavity 54, and the upper punch 53 is then lowered to perform compression molding. By applying a magnetic field to the magnetic powder or slurry in the cavity 54 during compression molding, an anisotropic magnet can be produced in which the magnetic powder is oriented in a specific direction.

[0007] As shown in the three-view diagram of FIG. 8, the sintered magnets 100 manufactured using this compression molding die 50 have a trapezoidal columnar shape in plan view (FIG. 8(a)). For example, as shown in FIG. 9, they can be used to form a rotor 200 for a rotating machine by arranging a plurality of magnets 100 in a row in the circumferential direction and embedding them in a cylindrical rotor core 201 made of a magnetic metal. At this time, an adhesive such as a resin is filled into the gaps between the trapezoidal columnar sintered magnets 100 and embedding holes 202 formed in the cylindrical rotor core 201 to prevent the sintered magnets 100 from easily slipping out of the cylindrical rotor core 201. However, in general, die molding has a draft taper in the direction in which the molded product is removed, and if this tapered portion is fixed to the rotor core as is without processing after sintering, there is a concern that the sintered magnets may slip out in the direction in which the taper widens.

[0008] One way to prevent this is to apply resin from the tapered section to the trapezoidal surface and secure it in place (resin molding the magnet), but in order to improve torque and output when the rotor is incorporated into a motor, there is a desire to reduce the clearance between the trapezoidal surface of the magnet and the opposing stator, and increasing the clearance by covering it with resin is not desirable. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Re-tabled publication 2014 / 027638 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-216857 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-296849 [Patent Document 4] Patent No. 3833861 Summary of the Invention [Problem to be solved by the invention]

[0010] Therefore, an object of the present invention is to provide a method for efficiently manufacturing a sintered magnet that does not easily fall out of a rotor core, in a rotor in which the sintered magnet is embedded, a compression molding die for this method, a sintered magnet obtained by this method, and a rotor using the sintered magnet and a method for manufacturing a rotor. [Means for solving the problem]

[0011] As a result of extensive research in light of the above-mentioned object, the present inventors discovered that when a molded body obtained by compression molding of magnetic powder or slurry is sintered in the manufacturing process of a sintered magnet, the degree of shrinkage during sintering varies along the compression direction during molding, and the density of the sintered magnet is not constant. Therefore, by sintering a molded body with multiple parallel grooves in the compression direction, the parallel grooves no longer become parallel after sintering, and by manufacturing a rotor by embedding the sintered magnet in the rotor core of a rotating machine and fixing it with an adhesive, a rotor from which the magnet does not easily fall out can be obtained, and thus arrived at the present invention.

[0012] That is, the compression molding mold of the present invention is A compression molding die having a die, and an upper punch and a lower punch for compression molding magnetic powder filled in a cavity of the die, The die has a surface that forms the cavity and is characterized by having a plurality of protrusions or grooves that are parallel to the pressing direction.

[0013] The compression molding die is preferably a wet molding die.

[0014] The method of the present invention for producing a sintered magnet includes the steps of filling a magnetic powder into a compression molding die having a die and an upper punch and a lower punch for compression molding the magnetic powder filled in the cavity of the die, and pressing the filled magnetic powder with the upper punch and the lower punch to form a compact; a step of sintering the compact to produce a sintered body, The die has a surface that forms the cavity and is characterized by having a plurality of protrusions or grooves that are parallel to the pressing direction.

[0015] The sintered magnet is preferably a rare earth sintered magnet or a ferrite sintered magnet.

[0016] The sintered magnet of the present invention is characterized in that it has a plurality of grooves or ridges on at least one surface, and the plurality of grooves or ridges are not parallel within the surface.

[0017] The sintered magnet is preferably a rare earth sintered magnet or a ferrite sintered magnet.

[0018] The rotor of the present invention using the sintered magnet is a rotor core, an embedding hole provided in the rotor core, and the sintered magnet embedded in the embedding hole; The sintered magnet is fixed with an adhesive that fills the gap between the embedding hole and the surface having the plurality of grooves or protrusions.

[0019] The method of the present invention for manufacturing the rotor comprises: The sintered magnet is embedded in an embedding hole provided in the rotor core, and adhesive is poured between the embedding hole and the surface of the sintered magnet having the multiple grooves or protrusions, thereby fixing the sintered magnet to the embedding hole. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a rotor in which sintered magnets do not easily fall out, in an efficient manner. [Brief explanation of the drawings]

[0021] [Figure 1(a)] FIG. 1 is a partial cross-sectional view schematically showing an example of a compression molding die of the present invention used to mold a sintered magnet. [Figure 1(b)] FIG. 2 is a cross-sectional view taken along the line AA in FIG. [Figure 2] FIG. 2 is a cross-sectional view schematically showing another example of the compression molding die of the present invention used for molding a sintered magnet. [Figure 3] 1A to 1C are a plan view, a front view, and a side view showing an example of a molded product molded using a mold for compression molding of the present invention. [Figure 4] FIG. 2 is a plan view showing another example of a molded body molded by the compression molding die of the present invention. [Figure 5] 4A, 4B, and 4C are a plan view, a front view, and a side view, respectively, showing an example of a sintered body obtained by sintering the compact shown in FIG. [Figure 6(a)]1 is a schematic diagram showing a rotor of the present invention. [Figure 6(b)] FIG. 6(b) is a partially enlarged view of FIG. [Figure 7(a)] FIG. 1 is a partial cross-sectional view schematically showing an example of a conventional compression molding die used to mold a sintered magnet. [Figure 7(b)] FIG. 7B is a cross-sectional view taken along line BB in FIG. [Figure 8] 1A to 1C are a plan view, a front view, and a side view showing an example of a sintered magnet manufactured using a conventional compression molding die. [Figure 9] FIG. 2 is a schematic diagram showing a rotor of a rotating machine. DETAILED DESCRIPTION OF THE INVENTION

[0022] [1] Compression molding mold An example of a compression molding die of the present invention for producing a sintered magnet is shown in Figures 1(a) and 1(b). The compression molding die 10 includes a die 11, a lower punch 12, and an upper punch 13, and the space enclosed by these defines a cavity 14. The lower punch 12 and the upper punch 13 are configured to be able to move up and down independently. With the upper punch 13 removed upward, a predetermined amount of magnetic powder (or a slurry containing magnetic powder) is filled into the cavity 14 (if a slurry containing magnetic powder is used, the slurry may be filled through a slurry injection hole provided in the die 11 while the cavity is closed with the upper punch 13). The upper punch 13 is then lowered (or the lower punch 12 is raised) to compress the magnetic powder in the cavity 11 in the direction in which the upper punch 13 and the lower punch 12 face each other, thereby performing compression molding. At this time, the upper punch 13 and / or the lower punch 12 may be configured to lower or rise in conjunction with the die 11. The upper punch 13 is not limited to a shape that allows it to move up and down within the cavity, but may also be shaped to cover the top of the die 11 so as to act as a lid on the cavity 13. By compression molding the magnetic powder or slurry in the cavity 14 while applying a magnetic field, an anisotropic magnet can be produced in which the magnetic powder is oriented in a certain direction.

[0023] As shown in Fig. 1(b), for example, cavity 14 is trapezoidal when viewed in the pressure application direction, and has multiple protrusions 15 provided parallel to the pressure application direction on surfaces 14a, 14b corresponding to two legs of the trapezoid. The shape of cavity 14 when viewed in the pressure application direction is not limited to trapezoidal and may be arc-shaped, square, rectangular, polygonal, etc., depending on the intended use of the sintered magnet to be produced. Furthermore, the shape of the cavity when viewed in a direction perpendicular to the pressure application direction is not limited to rectangular as shown in Fig. 1(a) and may be arc-shaped, etc.

[0024] The multiple protrusions 15 provided on the surfaces 14a and 14b must be formed parallel to the pressure application direction. If they are not formed parallel to the pressure application direction, the compact after compression molding will not be able to be removed from the die 11. Instead of the multiple protrusions 15, multiple grooves 16 parallel to the pressure application direction may be provided on the surfaces 14a and 14b, as shown in FIG. 2. Also, the protrusions 15 and grooves 16 may be mixed. In either case, the protrusions 15 and / or grooves 16 are formed parallel to the pressure application direction.

[0025] The number of ridges 15 and / or grooves 16 varies depending on factors such as the size of the sintered magnet to be produced, but preferably 2 to 10 ridges 15 and / or grooves 16 are provided on one surface. The width of the ridges 15 and / or grooves 16 is preferably 1 to 3 mm, and, where W is the width of the surface on which they are provided (the length in the direction perpendicular to the pressure application direction), it is preferably in the range of 0.01 × W to 0.1 × W. The depth of the ridges 15 and / or grooves 16 is preferably smaller than the width.

[0026] The surfaces on which the protrusions 15 and / or grooves 16 are provided are not limited to the surfaces 14a and 14b corresponding to the two legs of the trapezoid, but may be at least one of the surfaces parallel to the pressurizing direction of the cavity 14. The surfaces may be either one of the surfaces 14a and 14b, or either one of the surfaces 14c and 14d corresponding to the upper and lower bases of the trapezoid. Even if the shape of the cavity 14 as viewed in the pressurizing direction is not trapezoidal, it is sufficient to provide the protrusions 15 and / or grooves 16 on at least one surface. It is not necessary to provide the protrusions 15 and / or grooves 16 on all surfaces; it is preferable to provide them on a pair of opposite sides, such as the surfaces 14a and 14b corresponding to the two legs of the trapezoid.

[0027] As will be described later, the sintered magnets manufactured using this compression molding die 10 are formed with grooves and / or protrusions corresponding to the protrusions 15 and / or grooves 16 provided in the cavity 14. Therefore, particularly when a plurality of sintered magnets are embedded in a rotor core made of magnetic metal or the like in a circumferential arrangement to be used as a rotor, it is preferable to provide the protrusions 15 and / or grooves 16 on the corresponding surfaces of the cavity 14 so that grooves and / or protrusions are formed on the surfaces facing each other of the sintered magnets adjacent to each other in the circumferential direction (the direction of rotation of the rotor).

[0028] Furthermore, if protrusions are formed on the compact and sintered body (sintered magnet), defects such as cracks and chips are likely to occur in the protrusions during handling, so it is preferable to form grooves in the compact and sintered body (sintered magnet).In other words, it is preferable to provide protrusions 15 in the cavity 14 of the compression molding die 10.

[0029] [2] Manufacturing method for sintered magnets A method of the present invention for producing a sintered magnet (described below) of the present invention includes the steps of filling a magnetic powder into a compression molding die having a die and an upper punch and a lower punch for compression molding the magnetic powder filled in the cavity of the die, pressing the filled magnetic powder with the upper punch and the lower punch to form a compact, and sintering the compact to produce a sintered body, The die has a surface that forms the cavity and is characterized by having a plurality of protrusions or grooves that are parallel to the pressing direction.

[0030] The molded article 20 molded using the compression molding die 10 shown in Figures 1(a) and 1(b) has a trapezoidal columnar shape in plan view (Figure 3(a)), as shown in the three-view diagram of Figure 3, and has a plurality of grooves 21 parallel to the pressure direction during molding on surfaces 20a, 20b corresponding to the two legs of the trapezoid. When molding is performed using a compression molding die 10' having a cavity 14 shown in Figure 2, a molded article 20' is obtained that has a plurality of protrusions 22 parallel to the pressure direction during molding on surfaces 20a, 20b corresponding to the two legs of the trapezoid, as shown in the plan view of Figure 4.

[0031] As shown in the three-view diagram of FIG. 5, the sintered body 30 obtained by sintering the compact 20 has a trapezoidal columnar planar shape (FIG. 5(a)), with multiple grooves 31 that are not parallel to each other on surfaces 30a, 30b corresponding to the two legs of the trapezoid. The compact 20 is formed by compressing the slurry in the direction in which the lower punch 12 and the upper punch 13 face each other (almost in the direction of gravity) using the compression molding die 10 shown in FIGS. 1(a) and 1(b). Therefore, the density of the magnetic powder differs slightly between one end 20-1 (the upper punch 13 side) in the compression direction and the other end 20-2 (the lower punch 12 side). In particular, when wet compacting is performed, pressure molding is usually performed while draining the liquid component of the slurry through drainage holes provided in the upper punch 13. This results in a more pronounced density difference between one end 20-1 (the upper punch 13 side) of the compact 20 and the other end 20-2 (the lower punch 12 side). In this way, when a molded body 20 having a difference in magnetic powder density between one end 20-1 side (upper punch 13 side) and the other end 20-2 side (lower punch 12 side) is sintered, the shrinkage rate due to sintering differs between one end 20-1 side and the other end 20-2 side, and the shrinkage rate of the other end 20-2 side (lower punch 12 side), which has a lower density, is usually higher than that of one end 20-1 side (upper punch 13 side).As a result, the multiple grooves 21 formed in the molded body 20 and parallel to the pressure direction become non-parallel grooves 31 in the sintered body 30, as shown in Figure 5(c).

[0032] The sintered body 30 having multiple grooves 31 that are not parallel to each other on the faces 30a, 30b (side faces) corresponding to the two legs of the trapezoid is processed as necessary to form a sintered magnet 35 having multiple grooves 31 that are not parallel to each other.

[0033] Furthermore, when a molded body 20' having multiple protrusions 22 parallel to the pressure direction molded using a compression molding die 10' (see Figure 2) having grooves 16 in the cavity 14 is sintered, a sintered body and sintered magnet are obtained having multiple protrusions that are not parallel to each other on the surfaces 30a, 30b corresponding to the two legs of the trapezoid.

[0034] The sintered magnet that can be produced by the method of the present invention can be any magnet that can be produced by a process of molding a magnetic powder (also called magnetic powder) or a slurry obtained by dispersing the magnetic powder in water or an organic solvent, and sintering the resulting molded body, but rare earth sintered magnets or ferrite sintered magnets are particularly preferred. The method of producing a sintered magnet is described in detail below.

[0035] (1) Molding process Molding is performed by compression molding (dry molding or wet molding) using the compression molding die of the present invention. In the dry molding method, for example, a molded body is formed by applying a magnetic field while pressure molding dried magnetic powder. In the wet molding method, for example, a molded body is formed by removing liquid components while pressure molding a slurry containing magnetic powder while applying a magnetic field.

[0036] In the case of compression molding, the magnetic powder or a slurry containing the magnetic powder is filled into the molding die of the present invention and compression molded. The compression molding pressure is 30 to 392 MPa (500 to 4,000 kg / cm) in the case of a green body for an RTB sintered magnet. 2 ) for ferrite magnet compacts, and 34 to 44 MPa (350 to 450 kg / cm 2 In the case of a compact for an RTB sintered magnet, the density of the compact is preferably 3.7 to 4.7 g / cm. 3 In the case of a compact for a ferrite magnet, the density of the compact is preferably adjusted to about 2.6 to 3.2 g / cm.3 It is preferable to adjust it to a certain extent.

[0037] (2) Sintering process The compact obtained in the compacting step is sintered to obtain a sintered body.

[0038] (3) Other processes When manufacturing sintered magnet products, the sintered body is usually processed after the sintering process to produce the desired magnet product. In the case of RTB sintered magnets, diffusion and heat treatment are usually carried out between the sintering and processing steps, and a surface treatment is then carried out after the processing step.

[0039] [4] Sintered magnets The sintered magnet of the present invention is a sintered magnet having a plurality of grooves or ridges on at least one surface, and is characterized in that the plurality of grooves or ridges are not parallel within the surface.

[0040] The sintered magnet may be either a rare earth sintered magnet or a ferrite sintered magnet. The composition of each magnet will be explained below.

[0041] (a) Rare earth sintered magnet The rare earth sintered magnet preferably consists essentially of RTB. R is at least one rare earth element including Y, and preferably always contains at least one of Nd, Dy, and Pr. T is at least one transition metal, and preferably always contains Fe. A preferred composition is R: 24-34 mass%, B: 0.6-1.8 mass%, and the remainder Fe. If R is less than 24 mass%, the residual magnetic flux density B r Coercive force H cj If it exceeds 34%, the residual magnetic flux density B r Furthermore, the area of ​​the rare earth-rich phase inside the sintered body increases, and the morphology becomes coarse, resulting in a decrease in corrosion resistance. When B is less than 0.6 mass%, the main phase R2Fe 14 The amount of B necessary to form the B phase is insufficient, resulting in R2Fe with soft magnetic properties. 17A phase is generated, and the coercivity decreases. On the other hand, if the B content exceeds 1.8 mass%, the non-magnetic B-rich phase increases, and the remanence Br decreases. The Fe may be partially substituted with Co, and may contain elements such as Al, Si, Cu, Ga, Nb, Mo, W, and Zr in amounts of up to 3 mass%.

[0042] (b) Sintered ferrite magnet The sintered ferrite magnet is preferably made of Sr ferrite, Ba ferrite, Sr-La-Co based ferrite, Ca-La-Co based ferrite, or the like, having a magnetoplumbite (M-type) structure.

[0043] [5] Rotor The sintered magnets 35 produced by processing the sintered body 30 shown in Fig. 5 as needed can be used to form a rotor 40 for a rotating machine by embedding a plurality of them in a circumferential arrangement in a cylindrical rotor core 41, as shown in Figs. 6(a) and 6(b). In this case, the trapezoidal cylindrical sintered magnets 35 are embedded in embedding holes 42 provided in the cylindrical rotor core 41, and an adhesive 43 made of resin or the like is filled into the gap between the sintered magnets 35 and the embedding holes 42 formed in the cylindrical rotor core 41.

[0044] Here, the sintered magnet 35 has a plurality of grooves 31 on its side surface that are not parallel to one another. When adhesive 43 is filled into these grooves 31, the adhesive area between the adhesive 43 and the sintered magnet 35 increases, thereby improving the hardness of the bond. In addition, since the direction in which the sintered magnet 35 is pulled out of the embedding hole 42 does not match the direction of the plurality of grooves 31 on the side surface of the sintered magnet 35 (because the grooves 31 formed in the sintered magnet 35 are not parallel to one another), when a force acts on the sintered magnet 35 in a direction that pulls it out of the embedding hole 42, the movement of the sintered magnet 35 is restricted by the plurality of grooves 31 that are not parallel to one another. As a result, once the adhesive 43 has hardened, the sintered magnet 35 is firmly fixed in the embedding hole 42 of the cylindrical rotor core 41 and will not easily come out.

[0045] The cylindrical rotor core 41 is preferably made of a magnetic metal, a resin material, etc. The resin used as the adhesive is preferably a thermosetting resin. [Explanation of symbols]

[0046] 10,10'···Compression molding mold 11 Die 12 Lower punch 13. Upper punch 14. Cavity 14a,14b...plane 14c,14d...plane 15...Protrusion section 16 Groove 20,20'...Molded body 20a,20b...plane 20-1...One end 20-2...other end 21 Groove 22... Protrusion section 30. Sintered body 30a,30b...plane 31 Groove 35. Sintered magnet 40... rotor 41 Cylindrical rotor core 42 Buried hole 43... Adhesive 50···Compression molding mold 51···Die 52 Lower punch 53 Upper punch 54. Cavity 100···Sintered magnet 200 rotor 201 Cylindrical rotor core 202 Buried hole

Claims

1. A wet molding die having a die, and an upper punch and a lower punch for compressing a slurry containing a magnetic powder filled in a cavity of the die into a columnar shape by applying pressure, A wet molding die characterized in that at least one of the faces of the die parallel to the pressure direction that form the cavity has a plurality of protrusions or grooves parallel to the pressure direction, and the shape of the cavity as viewed in the pressure direction is trapezoidal, arc-shaped, square, rectangular, or polygonal.

2. a step of filling a wet compacting mold having a die and an upper punch and a lower punch for compressing the slurry containing the magnetic powder filled in the cavity of the die into a columnar shape by pressing the slurry containing the magnetic powder, and compressing the filled slurry containing the magnetic powder with the upper punch and the lower punch to form a compact; and a step of sintering the compact to produce a sintered body. A method for producing a sintered magnet comprising: A method for producing a sintered magnet, characterized in that at least one of the faces of the die that are parallel to the pressure direction and form the cavity has a plurality of protrusions or grooves that are parallel to the pressure direction, and the shape of the cavity when viewed in the pressure direction is trapezoidal, arc-shaped, square, rectangular, or polygonal.

3. 3. The method for producing a sintered magnet according to claim 2, The method for producing a sintered magnet, wherein the sintered magnet is a rare earth sintered magnet or a ferrite sintered magnet.

4. A columnar wet-molded sintered magnet, which is a sintered body of a columnar wet-molded body having a density difference in the pressure-applied direction and a plurality of parallel grooves or protrusions extending in the pressure-applied direction on at least one surface thereof, the sintered magnet has, on at least one surface, a plurality of grooves or ridges corresponding to the plurality of grooves or ridges of the wet-formed body; the plurality of grooves or protrusions of the sintered magnet are not parallel within the plane; The sintered magnet has an outer circumferential shape, as viewed in the pressure direction, of a trapezoid, arc shape, square, rectangle, or polygon, and has the plurality of grooves or protrusions on surfaces corresponding to a pair of opposite sides of these shapes.

5. The sintered magnet according to claim 4, The sintered magnet is a rare earth sintered magnet or a ferrite sintered magnet.

6. A rotor using the sintered magnet according to claim 4 or 5, a rotor core, an embedding hole provided in the rotor core, and the sintered magnet embedded in the embedding hole; The rotor is characterized in that the sintered magnet is fixed with an adhesive that fills the gap between the embedding hole and the surface having the plurality of grooves or protrusions.

7. A method for manufacturing the rotor of claim 6, comprising the steps of: A method for manufacturing a rotor, characterized in that the sintered magnet is embedded in an embedding hole provided in the rotor core, and an adhesive is poured between the embedding hole and the surface of the sintered magnet having the multiple grooves or protrusions, thereby fixing the sintered magnet to the embedding hole.

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