JP2023050016A - Mold for compression molding, method for producing sintered magnet, sintered magnet, rotor, and method for producing rotor - Google Patents

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

The present invention provides 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 The present invention relates to a method for manufacturing the rotor.

Rare earth sintered magnets and ferrite sintered magnets are widely used in various applications including rotating machines such as motors and generators.

As the rare earth sintered magnet, an R-T-B system sintered magnet (R is at least one rare earth element and always contains at least one of Nd and Pr. T is at least one transition metal element and iron (Fe ). B means boron.), Sm-Co-based sintered magnets (part of Sm (samarium) may be replaced with other rare earth elements), etc. are known (Patent Document 1 ), and as ferrite sintered magnets, sintered magnets such as hexagonal system M-type (magnetoplumbite type) Sr ferrite and Ba ferrite are known (Patent Document 2).

These sintered magnets are obtained by forming a magnetic powder into a predetermined shape and sintering it. In addition, dry molding methods (for example, Patent Document 3 (Japanese Unexamined Patent Publication No. 2004-296849)) and wet molding methods (for example, Patent Document 4 (Patent No. 3833861)) are known as the molding method. In the dry compaction method, a compact is produced by press-molding dried magnetic powder while applying a magnetic field, and the obtained compact is sintered. In the wet compaction method, a slurry containing magnetic powder is pressure-molded while removing a liquid component in an applied magnetic field to produce a green body, and the green body obtained is sintered.

For example, a ferrite sintered magnet can be produced by: (a) a step of mixing raw materials such as compounds such as Fe, Sr, Ba, Ca, La, and Co; (c) a step of coarsely pulverizing the calcined body, adding a compound such as a sintering aid, and subjecting the mixture to wet fine pulverization; (d) a step of compacting the resulting slurry of fine calcined body particles in a magnetic field to obtain a molded body; (e) a step of sintering the molded body; and (f) a step of processing the obtained sintered body into a shape according to the purpose of use.

An example of a compression molding die for producing a sintered magnet is shown in FIGS. 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 . For example, as shown in FIG. 7(b), the cavity 54 has a trapezoidal shape when viewed in the pressurizing direction. The lower punch 52 and the upper punch 53 are configured to be able to move up and down independently of each other. Compression molding is performed by lowering the punch 53 . At this time, by performing compression molding while applying a magnetic field to the magnetic powder or slurry in the cavity 54, an anisotropic magnet in which the magnetic powder is oriented in a certain direction can be obtained.

A sintered magnet 100 manufactured using this compression molding die 50 has a trapezoidal columnar planar shape (FIG. 8(a)) as shown in a three-sided view in FIG. As shown, it can be used to form a rotor 200 of a rotary machine by arranging a plurality of them in a cylindrical rotor core 201 made of magnetic metal and embedding them in the circumferential direction. At this time, the sintered magnet 100 can be easily removed from the cylindrical rotor core 201 by filling the gap between the trapezoidal columnar sintered magnet 100 and the embedding hole 202 formed in the cylindrical rotor core 201 with an adhesive made of resin or the like. avoid However, in general, there is a draft taper in the direction of ejection of the molded product in mold molding, and if the tapered part is fixed to the rotor core as it is without processing after sintering, there is a concern that the taper will be pulled out in the widening direction. There is

In order to prevent this, it is conceivable to apply resin to the trapezoidal surface continuously from the tapered portion and fix it (molding the magnet with resin). In order to improve the output, there is a demand to reduce the clearance between the trapezoidal surface of the magnet and the opposing stator, and it is not preferable to increase the clearance by covering with resin.

Retable 2014/027638 JP 2011-216857 A Japanese Patent Application Laid-Open No. 2004-296849 Patent No. 3833861

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for efficiently manufacturing a sintered magnet that does not easily come off from the rotor core in a rotor having a sintered magnet embedded in the rotor core, a compression molding die for the method, and the method. It is another object of the present invention to provide a sintered magnet that is capable of being manufactured by a method for manufacturing a rotor and a rotor using the sintered magnet.

As a result of intensive studies in view of the above object, the inventors of the present invention found that, in the manufacturing process of a sintered magnet, when a compact obtained by compression molding magnetic powder or slurry is sintered, along the compression direction during molding, Since the degree of shrinkage during sintering changes and the density of the sintered magnet is not constant, by sintering a molded body provided with a plurality of parallel grooves in the compression direction, the parallel grooves are formed after sintering. By embedding the sintered magnet in the rotor core of a rotating machine and fixing it with an adhesive to manufacture a rotor, a rotor in which the magnet does not easily fall out can be obtained, and arrived at the present invention. .

That is, the compression molding die 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,
A surface of the die forming the cavity has a plurality of ridges or grooves parallel to the pressing direction.

Preferably, the compression mold is a wet mold.

The method of the present invention for producing a sintered magnet comprises: 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; A step of pressing the filled 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 compact,
A surface of the die forming the cavity has a plurality of ridges or grooves parallel to the pressing direction.

The sintered magnet is preferably a rare earth sintered magnet or a ferrite sintered magnet.

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.

The sintered magnet is preferably a rare earth sintered magnet or a ferrite sintered magnet.

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 a space between the embedding hole and the surface having the plurality of grooves or ridges.

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, an adhesive is poured between the embedding hole and the surface of the sintered magnet having the plurality of grooves or the ridges, and the sintering is performed. A magnet is fixed in the embedding hole.

ADVANTAGE OF THE INVENTION According to this invention, the rotor from which a sintered magnet does not fall out easily can be provided by an efficient method.

1 is a partial cross-sectional view schematically showing an example of a compression molding die of the present invention used for molding a sintered magnet; FIG. FIG. 1(a) is a cross-sectional view taken along line A-A of FIG. 1(a). FIG. 4 is a cross-sectional view schematically showing another example of the compression molding die of the present invention used for molding a sintered magnet. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is (a) a plan view, (b) a front view, and (c) a side view showing an example of a compact molded by the compression molding die of the present invention; FIG. 4 is a plan view showing another example of a compact molded by the compression molding die of the present invention; 4(a) is a plan view, (b) is a front view, and (c) is a side view showing an example of a sintered body obtained by sintering the molded body shown in FIG. 3. FIG. It is a schematic diagram which shows the rotor of this invention. FIG. 7 is a partially enlarged view of FIG. 6(a); 1 is a partial cross-sectional view schematically showing an example of a conventional compression molding die used for molding a sintered magnet; FIG. FIG. 7(a) is a cross-sectional view taken along line B-B of FIG. 7(a). FIG. 2(a) is a plan view, (b) is a front view, and (c) is a side view showing an example of a sintered magnet manufactured using a conventional compression molding die. It is a schematic diagram which shows the rotor of a rotary machine.

[1] Compression Mold An example of the compression mold of the present invention for producing a sintered magnet is shown in FIGS. 1(a) and 1(b). A compression molding die 10 has a die 11, a lower punch 12, and an upper punch 13, and a space surrounded by these constitutes a cavity . The lower punch 12 and the upper punch 13 are configured so that they can move up and down independently. With the upper punch 13 removed upward, the cavity 14 is filled with a predetermined amount of magnetic powder (or slurry containing the magnetic powder). (When slurry containing magnetic powder is used, the slurry may be filled from the slurry injection hole provided in the die 11 with the cavity closed by the upper punch 13), and the upper punch 13 is lowered (or the lower punch 12 ) to press 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 move downward or upward in conjunction with the die 11 . The shape of the upper punch 13 is not limited to a shape that allows it to move up and down within the cavity, and may have a shape that covers the top of the die 11 so as to cover the cavity 13 . By compressing the magnetic powder or slurry in the cavity 14 while applying a magnetic field, an anisotropic magnet in which the magnetic powder is oriented in a certain direction can be obtained.

For example, as shown in FIG. 1(b), the cavity 14 has a trapezoidal shape when viewed in the pressure direction, and a plurality of ridges are provided parallel to the pressure direction on surfaces 14a and 14b corresponding to the two legs of the trapezoid. It has part 15. The shape of the cavity 14 when viewed in the pressurizing direction is not limited to a trapezoid, and may be arc-shaped, square, rectangular, polygonal, or the like, depending on the intended use of the sintered magnet to be finally manufactured. Further, the shape of the cavity when viewed from the direction orthogonal to the pressurizing direction is not limited to the rectangular shape illustrated in FIG. 1(a), and may be an arc shape or the like.

The plurality of ridges 15 provided on the surfaces 14a and 14b must be formed parallel to the pressing direction. If it is not provided parallel to the pressurizing direction, it will be impossible to take out the compact after compression molding from the die 11 . Instead of the plurality of ridges 15, as shown in FIG. 2, the surfaces 14a and 14b may be provided with a plurality of grooves 16 parallel to the pressing direction. Also, the ridges 15 and the grooves 16 may be mixed. In either case, the ridges 15 and/or the grooves 16 are formed parallel to the pressing direction.

The number of ridges 15 and/or grooves 16 depends on the size of the sintered magnet to be produced, but preferably 2 to 10 are provided on one surface. The width of the ridges 15 and/or grooves 16 is preferably 1 to 3 mm. A range of W to 0.1×W is preferred. Also, the depth of the ridges 15 and/or the grooves 16 is preferably smaller than the width.

The surfaces on which the ridges 15 and/or the grooves 16 are provided are not limited to the surfaces 14a and 14b corresponding to the two legs of the trapezoid, and at least one of the surfaces parallel to the pressurizing direction of the cavity 14. Good to have. Either one of the surfaces 14a and 14b may be used, or either one of the surfaces 14c and 14d corresponding to the upper and lower bases of the trapezoid may be used. Even if the cavity 14 does not have a trapezoidal shape when viewed in the pressurizing direction, the ridges 15 and/or the grooves 16 may be provided on at least one surface. It is not necessary to provide ridges 15 and/or grooves 16 on all faces, but preferably on a pair of opposite sides, such as faces 14a and 14b corresponding to the two legs of the trapezoid.

As will be described later, the sintered magnet manufactured using this compression molding die 10 has grooves and/or ridges corresponding to the ridges 15 and/or grooves 16 provided in the cavity 14, respectively. In particular, when a plurality of sintered magnets are embedded in a rotor core made of magnetic metal or the like in the circumferential direction and embedded in the rotor, the sintered magnets adjacent to each other in the circumferential direction (rotational direction of the rotor) The ridges 15 and/or grooves 16 are preferably provided on the corresponding surfaces of the cavity 14 so that the grooves and/or ridges are formed on the opposing surfaces.

In addition, when a ridge is formed on the molded body and sintered body (sintered magnet), defects such as cracks and chips are likely to occur in the ridged part during handling, so the molded body and sintered body (sintered magnet) It is preferable to form a groove in the That is, it is preferable to provide the protrusion 15 in the cavity 14 of the compression molding die 10 .

[2] Method for producing a sintered magnet The method of the present invention for producing a sintered magnet of the present invention (described later) comprises a die, an upper punch and a lower punch for compression-molding the magnetic powder filled in the cavity of the die. A step of filling a compression molding die having a punch with a magnetic powder, pressing the filled magnetic powder with the upper punch and the lower punch to form a compact, and sintering the compact. Having a step of making a body,
A surface of the die forming the cavity has a plurality of ridges or grooves parallel to the pressing direction.

The compact 20 molded using the compression molding die 10 shown in FIGS. 1(a) and 1(b) has a planar shape (FIG. 3(a)) as shown in the three-view diagram of FIG. It has a trapezoidal columnar shape, and has a plurality of grooves 21 parallel to the pressure direction during molding on surfaces 20a and 20b corresponding to the two legs of the trapezoid. When molding is performed using the compression molding die 10' having the cavity 14 shown in FIG. 2, as shown in the plan view of FIG. A compact 20' having a plurality of ridges 22 parallel to the pressing direction is obtained.

The sintered body 30 obtained by sintering the molded body 20 has a trapezoidal columnar planar shape (FIG. 5(a)), as shown in a three-sided view in FIG. 5, corresponding to the two legs of the trapezoid. The surfaces 30a and 30b have a plurality of grooves 31 that are not parallel to each other. 1(a) and 1(b) using the compression molding die 10 shown in FIGS. 1(a) and 1(b). Since it is molded by pressurizing the slurry, one end 20-1 side (upper punch 13 side) and the other end 20-2 side (lower punch 12 side) in the pressurizing direction, The densities of the magnetic powders are slightly different. Especially when wet molding is performed, pressure molding is usually performed while liquid components in the slurry are drained from the drainage holes provided in the upper punch 13. The difference in density between the punch 13 side) and the other end 20-2 side (lower punch 12 side) becomes more pronounced. In this way, the compact 20 having a magnetic powder density difference between one end 20-1 side (upper punch 13 side) and the other end 20-2 side (lower punch 12 side) was sintered. In this case, the shrinkage rate due to sintering is different between the one end 20-1 side and the other end 20-2 side, and usually the other end 20-2 side (lower punch 12 side) with lower density is higher than the one end 20-1 side (upper punch 13 side). , the grooves 31 are not parallel in the sintered body 30 .

The sintered body 30 having a plurality of grooves 31 that are not parallel to each other on the surfaces 30a and 30b (side surfaces) corresponding to the two legs of the trapezoid is processed as necessary to have a plurality of grooves 31 that are not parallel. Sintered magnet 35 is used.

In addition, when sintering a molded body 20' having a plurality of ridges 22 parallel to the pressurizing direction molded using a compression molding die 10' (see FIG. 2) having a groove 16 in the cavity 14, , a sintered compact and a sintered magnet having a plurality of non-parallel ridges on the surfaces 30a and 30b corresponding to the two legs of the trapezoid are obtained.

The sintered magnet that can be produced by the method of the present invention can be produced by forming magnetic powder (also referred to as magnetic powder) or a slurry obtained by dispersing magnetic powder in water or an organic solvent, and sintering the resulting compact. Although any magnet can be manufactured as long as it can be manufactured, rare earth sintered magnets or ferrite sintered magnets are particularly preferable. A method for producing a sintered magnet will be described in detail below.

(1) Molding Step Molding is performed by compression molding (dry molding, wet molding) using the compression molding die of the present invention. In the dry molding method, for example, a compact is formed by applying a magnetic field while press-molding dry magnetic powder. In the wet compaction method, for example, a compact is formed by removing a liquid component while press-molding a slurry containing a magnetic powder while applying a magnetic field.

In the case of compression molding, the magnetic powder or the slurry containing the magnetic powder is filled into the molding die of the present invention described above, and compression molding is performed. The compression molding pressure is 30 to 392 MPa (500 to 4,000 kg/cm ² ) for compacts for sintered RTB magnets, and 34 to 44 MPa (350 to 450 kg/cm ² ) for compacts for ferrite magnets. is preferable. In the case of RTB-based sintered magnet compacts, it is preferable to adjust the density of the compact to about 3.7 to 4.7 g/cm ³ . In the case of the ferrite magnet compact, it is preferable to adjust the density of the compact to about 2.6 to 3.2 g/cm ³ .

(2) Sintering step The molded body obtained in the molding step is sintered to obtain a sintered body.

(3) Other Steps When manufacturing a sintered magnet product, the sintered body is usually processed after the sintering step to obtain the desired magnet product. In the case of RTB sintered magnets, diffusion and heat treatment are normally performed between the sintering process and the working process, and surface treatment is performed after the working process.

[4] Sintered magnet The sintered magnet of the present invention is a sintered magnet having a plurality of grooves or ridges on at least one surface, wherein the plurality of grooves or ridges are not parallel within the surface. It is characterized by

The sintered magnet may be either a rare earth sintered magnet or a ferrite sintered magnet. The composition of each magnet will be described below.

(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 at least one of Nd, Dy and Pr. T is at least one transition metal, and preferably always contains Fe. A preferable composition is R: 24 to 34% by mass, B: 0.6 to 1.8% by mass, and the balance Fe. If R is less than 24% by mass, the residual magnetic flux density B _r coercive force H _cj decreases. If it exceeds 34%, the residual magnetic flux density B _r decreases. In addition, the area of the phase rich in rare earth elements inside the sintered body increases and the morphology becomes coarse, resulting in a decrease in corrosion resistance. If B: less than 0.6% by mass, the amount of B necessary for forming the R ₂ Fe ₁₄ B phase, which is the main phase, is insufficient, and the R ₂ Fe ₁₇ phase having soft magnetic properties is generated, resulting in a decrease in coercive force. . On the other hand, when the amount of B exceeds 1.8% by mass, the B-rich phase, which is a non-magnetic phase, increases and the residual magnetic flux density Br decreases. Fe may be partially substituted with Co, and may contain elements such as Al, Si, Cu, Ga, Nb, Mo, W, and Zr in an amount of about 3% by mass or less.

(b) Sintered ferrite magnet Sintered ferrite magnets are made of Sr ferrite, Ba ferrite, Sr-La-Co ferrite, Ca-La-Co ferrite, etc., which have a magnetoplumbite (M-type) structure. preferable.

[5] Rotor A sintered magnet 35 produced by processing the sintered body 30 shown in FIG. It can be used to form a rotor 40 of a rotating machine by embedding a plurality of them side by side in the circumferential direction. At this time, the trapezoidal columnar sintered magnet 35 is embedded in the embedding hole 42 provided in the cylindrical rotor core 41, and the gap between the sintered magnet 35 and the embedding hole 42 formed in the cylindrical rotor core 41 is filled with an adhesive made of resin or the like. Fill 43.

Here, since the sintered magnet 35 has a plurality of grooves 31 that are not parallel to each other on the side surface, the adhesion area between the adhesive 43 and the sintered magnet 35 is increased by filling the plurality of grooves 31 with the adhesive 43. In addition to the effect of increasing adhesion hardness, the direction in which the sintered magnet 35 is pulled out from the embedding hole 42 matches the direction of the plurality of grooves 31 provided on the side surface of the sintered magnet 35. (because the grooves 31 formed in the sintered magnet 35 are not parallel to each other), when a force acts on the sintered magnet 35 in the direction of pulling it out from the embedding hole 42, the plurality of grooves 31 that are not parallel to each other cause sintering. The movement of the magnets 35 is restricted, and as a result, once the adhesive 43 is cured, the sintered magnets 35 are firmly fixed in the embedding holes 42 of the cylindrical rotor core 41 and cannot easily come off.

The cylindrical rotor core 41 is preferably made of magnetic metal, resin material, or the like. Moreover, it is preferable to use a thermosetting resin as the resin used as the adhesive.

10,10'・・・Mold for compression molding
11... die
12・・・Lower punch
13・・・Upper punch
14 Cavity
14a, 14b... planes
14c, 14d... planes
15・・・Protrusions
16 Groove
20,20'・・・Molded body
20a, 20b... surface
20-1・・・One end
20-2 ... the other end
21 Groove
22 ridges
30 Sintered body
30a, 30b... planes
31 Groove
35 Sintered magnet
40 Rotor
41... Cylindrical rotor core
42 Buried hole
43 Adhesive
50・・・Mold for compression molding
51 Die
52 Lower punch
53 Upper punch
54 Cavity
100 Sintered magnet
200 Rotor
201・・・Cylindrical rotor core
202 Burying hole

Claims (8)

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,
A mold for compression molding, wherein a surface of the die forming the cavity has a plurality of ridges or grooves parallel to a pressing direction. In the compression mold according to claim 1,
A compression molding die, wherein the compression molding die is a wet molding die. A compression molding mold having a die and an upper punch and a lower punch for compression molding the magnetic powder filled in the cavity of the die is filled with the magnetic powder, and the filled magnetic powder is transferred to the upper punch and the lower punch. a step of pressing with a punch to form a compact;
and a method for producing a sintered magnet, comprising a step of sintering the molded body to produce a sintered body,
A method for producing a sintered magnet, wherein a surface of the die forming the cavity has a plurality of ridges or grooves parallel to a pressing direction. In the method for producing a sintered magnet according to claim 3,
A method for producing a sintered magnet, wherein the sintered magnet is a rare earth sintered magnet or a ferrite sintered magnet. A sintered magnet having a plurality of grooves or ridges on at least one surface,
A sintered magnet, wherein the plurality of grooves or ridges are not parallel in the plane. In the sintered magnet according to claim 5,
A sintered magnet, wherein the sintered magnet is a rare earth sintered magnet or a ferrite sintered magnet. A rotor using the sintered magnet according to claim 5 or 6,
a rotor core, an embedding hole provided in the rotor core, and the sintered magnet embedded in the embedding hole,
A rotor according to claim 1, wherein said sintered magnet is fixed with an adhesive that fills a space between said embedding hole and said surface having said plurality of grooves or ridges. A method of manufacturing a rotor according to claim 7, comprising:
The sintered magnet is embedded in an embedding hole provided in the rotor core, an adhesive is poured between the embedding hole and the surface of the sintered magnet having the plurality of grooves or the ridges, and the sintering is performed. A method of manufacturing a rotor, comprising fixing magnets in said embedding holes.

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