Bond magnet manufacturing method

Abstract

To provide a bond magnet manufacturing method that can improve the density of a compact and the degree of orientation of magnetic powder in the compact.SOLUTION: In a bond magnet manufacturing method, after a crushing process (S6) in which a first compact 41 is crushed to form granulated powder 14, a second compression molding process (S10) (second compact formation process) is performed in which a second slurry 22 (second mixture) containing the granulated powder 14 is compressed and molded to form a second compact 42 while a magnetic field B for orienting a magnetic powder 11 is applied to the second slurry 22.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a bonded magnet. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been known a method for producing a bonded magnet by compression molding a mixture containing a magnetic powder and a resin binder (see, for example, Patent Document 1).

[0003] The above-mentioned Patent Document 1 discloses a method for manufacturing a resin-bonded magnet (bonded magnet) by mixing a magnetic powder with a resin binder to form a slurry (mixture), and then compression-molding the slurry while applying a magnetic field to the slurry to orient the magnetic powder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-142032 A Summary of the Invention [Problem to be solved by the invention]

[0005] Here, in the conventional manufacturing method of bonded magnets as described in the above Patent Document 1, the particles of the magnetic powder contained in the mixture that is compression molded while a magnetic field for orienting the magnetic powder is applied have a relatively small particle size, so that the specific surface area (surface area per unit volume) is large and the rotational torque caused by the application of the magnetic field is relatively small. The compression force when the mixture containing the magnetic powder is compression molded is transmitted between the particles of the magnetic powder, so if the specific surface area of ​​the magnetic powder is relatively large, the contact area between the particles of the magnetic powder is relatively large when the mixture containing the magnetic powder is compression molded. Therefore, when the mixture containing the magnetic powder is compression molded, the friction loss (heat loss due to friction) generated between the particles of the magnetic powder is relatively large, and the compression force is not easily transmitted between the particles of the magnetic powder to the extent that the friction loss is large. In this case, the density of the molded body after compression molding is not easily increased. Also, if the rotational torque caused by the application of a magnetic field to each particle of the magnetic powder is relatively small, the magnetic powder is not easily oriented when a magnetic field for orienting the magnetic powder is applied to the mixture containing the magnetic powder. In this case, the degree of orientation of the magnetic powder in the compact after compression molding tends to be low. For this reason, a manufacturing method for a bonded magnet that can improve the density of the compact and the degree of orientation of the magnetic powder in the compact is desired.

[0006] This invention has been made to solve the problems described above, and one object of the invention is to provide a method for manufacturing a bonded magnet that can improve the density of the compact after compression molding and the degree of orientation of the magnetic powder in the compact after compression molding. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, a manufacturing method of a bonded magnet in one aspect of the present invention includes a first compact formation step in which a first mixture containing a magnetic powder and a resin binder is compression-molded to form a first compact while applying a magnetic field to the first mixture for orienting the magnetic powder, a crushing step after the first compact formation step in which the first compact is crushed to form a granulated powder containing a plurality of particles of magnetic powder, and a second compact formation step in which the second mixture containing the granulated powder and a resin binder is compression-molded to form a second compact while applying a magnetic field to the second mixture for orienting the magnetic powder.

[0008] In one aspect of the present invention, the method for producing a bonded magnet includes, as described above, a crushing step in which the first compact is crushed to form a granulated powder containing a plurality of particles of magnetic powder, followed by a second compact forming step in which the second mixture containing the granulated powder and a resin binder is compressed and molded to form a second compact while applying a magnetic field to orient the magnetic powder to the second mixture. As a result, the granulated powder contained in the second mixture that is compression molded while applying a magnetic field to orient the magnetic powder is granulated into particles containing a plurality of particles of magnetic powder, and therefore has a larger particle size than each particle of the magnetic powder, and therefore has a smaller specific surface area than each particle of the magnetic powder, and a larger rotational torque due to the application of a magnetic field. Furthermore, the compression force when the second mixture containing the granulated powder is compressed and molded is transmitted between the granulated powder particles, and therefore, due to the relatively small specific surface area of ​​the granulated powder, the contact area between the granulated powder particles becomes relatively small when the second mixture containing the granulated powder is compressed and molded. Therefore, when the second mixture containing the granulated powder is compression molded, the friction loss between the granulated powder particles is relatively small, and the compression force is easily transmitted between the granulated powder particles because of the small friction loss. In this case, the density of the second molded body after compression molding is likely to be high. In addition, since the rotation torque caused by the application of a magnetic field to the granulated powder is relatively large, the magnetic powder is easily oriented when a magnetic field for orienting the magnetic powder is applied to the second mixture containing the granulated powder. In this case, the degree of orientation (degree of orientation) of the magnetic powder in the second molded body after compression molding is likely to be high. As a result, the density of the molded body and the degree of orientation of the magnetic powder in the molded body can be improved. This can improve the magnetic properties of the bonded magnet.

[0009] In the method for manufacturing a bonded magnet according to the above aspect, the second compact formation step is preferably a step of forming a second compact by compression molding a second mixture containing granulated powder, non-granulated powder that has not been granulated and has a smaller particle size than the granulated powder, and a resin binder, while applying a magnetic field to orient the magnetic powder to the second mixture.

[0010] With this configuration, in the second compact formation process, the second mixture can be compression molded in a state where the gaps between the granulated powder particles are filled with non-granulated powder that is not granulated and has a smaller particle size than the granulated powder. As a result, the density of the second compact can be improved compared to when the second mixture does not contain non-granulated powder that is not granulated and has a smaller particle size than the granulated powder. This can further improve the magnetic properties of the bonded magnet.

[0011] In the above-mentioned configuration in which the second compact formation step involves compression-molding the second mixture containing granulated powder, non-granulated powder, and a resin binder while applying a magnetic field to the second mixture to form the second compact, the method preferably further includes a classification step, after the crushing step and before the second compact formation step, of sifting the crushed powder obtained by crushing the first compact in the crushing step by particle size, and the second compact formation step is a step in which the second mixture containing the granulated powder, the non-granulated powder produced in the classification step, and a resin binder is compressed and molded to form the second compact while applying a magnetic field to the second mixture to orient the magnetic powder.

[0012] With this configuration, the crushed powder having a desired particle size can be easily sifted out from the crushed powder obtained by crushing the first compact in the crushing step to obtain the granulated powder to be used in the second compact forming step. In addition, the non-granulated powder generated in the classification step can be used as the non-granulated powder to be included in the second mixture in the second compact forming step, so that the yield of the magnetic powder can be effectively reduced.

[0013] In the manufacturing method of a bonded magnet according to the above aspect, preferably, the first compact formation step is a step of compression molding a first mixture containing a thermosetting resin as a resin binder to form a first compact, and the second compact formation step is a step of compression molding a second mixture containing a thermosetting resin as a resin binder to form a second compact, and further includes a first heat curing step of heating the first compact to heat-cure the thermosetting resin after the first compact formation step and before the crushing step, and a second heat curing step of heating the second compact to heat-cure the thermosetting resin after the second compact formation step.

[0014] With this configuration, in the first heat curing step, the thermosetting resin contained in the first compact is heat cured, which makes it easier to maintain the state in which the particles of the magnetic powder contained in the first compact are bonded together, and therefore, when the first compact is crushed in the crushing step, it is possible to prevent granulated powder from being formed and all of the crushed powder from becoming non-granulated powder. In addition, after the second compact formation step, the thermosetting resin contained in the second compact is heat cured, which makes it easier to maintain the state in which the granulated powder contained in the second compact is bonded together, and therefore, a compact having mechanical strength appropriate for a bonded magnet can be easily formed.

[0015] In the above-mentioned configuration in which the first molded body formation process is a process of compression molding a first mixture containing a thermosetting resin to form a first molded body and the second molded body formation process is a process of compression molding a second mixture containing a thermosetting resin to form a second molded body, preferably, the amount of thermosetting resin contained in the first mixture in the first molded body formation process is less than the amount of thermosetting resin contained in the second mixture in the second molded body formation process.

[0016] With this configuration, the amount of thermosetting resin that is thermally cured in the first thermal curing step can be made relatively small. This makes it possible to easily prevent the particles of the magnetic powder contained in the first compact from being excessively bonded to each other, since the amount of thermosetting resin that fills the gaps between the particles of the magnetic powder in the first compact is relatively small. As a result, it is possible to easily prevent the first compact from being difficult to crush in the crushing step, and to easily prevent the granulated powder from being sufficiently formed.

[0017] In the aforementioned method for producing a bonded magnet according to the first aspect, the pressure under which the first mixture is compression molded in the first compact forming step is preferably lower than the pressure under which the second mixture is compression molded in the second compact forming step.

[0018] With this configuration, the pressure when the first mixture is compression molded in the first compact forming step can be made relatively small. This makes it easy to prevent the multiple particles of the magnetic powder contained in the first compact from being excessively maintained in a bonded state. As a result, it is easy to prevent the first compact from being difficult to crush in the crushing step, and to prevent the granulated powder from being sufficiently formed.

[0019] In the above-mentioned configuration including the first heat-curing process and the second heat-curing process, the temperature at which heating is performed on the first molded body to heat-cure the thermosetting resin in the first heat-curing process is preferably lower than the temperature at which heating is performed on the second molded body to heat-cure the thermosetting resin in the second heat-curing process.

[0020] With this configuration, the temperature at which the thermosetting resin is thermally cured in the first thermal curing step can be made relatively low. This makes it easy to prevent the thermosetting resin contained in the first compact from being excessively cured, and therefore makes it easy to prevent the multiple particles of the magnetic powder contained in the first compact from being excessively likely to remain bonded to each other. As a result, it is easy to prevent the first compact from being difficult to crush in the crushing step, and to prevent the granulated powder from being sufficiently formed.

[0021] In the above-mentioned configuration including the first heat-curing process and the second heat-curing process, the time for which the first molded body is heated to heat-cure the thermosetting resin in the first heat-curing process is preferably equal to or less than the time for which the second molded body is heated to heat-cure the thermosetting resin in the second heat-curing process.

[0022] With this configuration, the time for thermally curing the thermosetting resin in the first thermal curing step can be relatively short. This makes it easy to prevent the thermosetting resin contained in the first compact from being excessively cured, and therefore makes it easy to prevent the multiple particles of the magnetic powder contained in the first compact from being excessively maintained in a bonded state. As a result, it is easy to prevent the first compact from being difficult to crush in the crushing step, and to prevent the granulated powder from being sufficiently formed. [Brief description of the drawings]

[0023] [Figure 1] FIG. 2 is a diagram showing a manufacturing flow of a bonded magnet according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram for explaining a first slurry formation step in the manufacturing flow of the bonded magnet according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram for explaining a first orientation step in the manufacturing flow of the bonded magnet according to one embodiment of the present invention. [Figure 4] FIG. 2 is a diagram for explaining a first compression molding step in the manufacturing flow of the bonded magnet according to one embodiment of the present invention. [Diagram 5] FIG. 2 is a diagram for explaining a first heat curing step in the manufacturing flow of the bonded magnet according to one embodiment of the present invention. [Figure 6] FIG. 2 is a diagram for explaining a crushing step in the manufacturing flow of a bonded magnet according to one embodiment of the present invention. [Figure 7] FIG. 2 is a diagram for explaining a classification step in the manufacturing flow of a bonded magnet according to an embodiment of the present invention. [Figure 8]FIG. 2 is a schematic diagram showing granulated powder in a manufacturing flow of a bonded magnet according to an embodiment of the present invention. [Figure 9] FIG. 4 is a diagram for explaining a second slurry formation step in the production flow of the bonded magnet according to one embodiment of the present invention. [Figure 10] FIG. 4 is a diagram for explaining a second orientation step in the manufacturing flow of the bonded magnet according to one embodiment of the present invention. [Figure 11] FIG. 4 is a diagram for explaining a second compression molding step in the manufacturing flow of the bonded magnet according to one embodiment of the present invention. [Figure 12] FIG. 4 is a diagram for explaining a second heat curing step in the manufacturing flow of the bonded magnet according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0025] A method for manufacturing a bonded magnet according to one embodiment of the present invention will be described with reference to Figures 1 to 12. The bonded magnet is used, for example, as a permanent magnet that is inserted and fixed inside the rotor of a rotating electrical machine (magnet insertion hole).

[0026] (First slurry formation process) As shown in FIG. 1, in step S1, a first slurry formation step is performed. As shown in FIG. 2, the first slurry formation step (S1) is a step of mixing a magnetic powder 11, a thermosetting resin 12, and a solvent 13 to form a first slurry 21. The magnetic powder 11 is, for example, a Sm-Fe-N magnetic powder, a Ne-Fe-B magnetic powder, or the like. The thermosetting resin 12 is, for example, an epoxy resin, a phenolic resin, a silicone resin, or the like. The first slurry 21 may be mixed with a material (for example, a molding aid) other than the magnetic powder 11, the thermosetting resin 12, and the solvent 13. The thermosetting resin 12 and the first slurry 21 are examples of the "resin binder" and the "first mixture" in the claims, respectively.

[0027] (First orientation process) As shown in FIG. 1, in step S2, a first orientation step is performed. As shown in FIG. 3, the first orientation step (S2) is a step of applying a magnetic field B for orienting the magnetic powder 11 to a first slurry 21 containing the magnetic powder 11 (see FIG. 2) to orient the magnetic powder 11. Specifically, the first slurry 21 is filled into a cavity 31a formed in a main body 31 of a die 30 for compression molding. Then, an upper punch 32 of the die 30 is disposed above the cavity 31a so as to close the cavity 31a. Then, in a state in which the first slurry 21 is sealed by the main body 31 and the upper punch 32 of the die 30, a static magnetic field B1 and a pulse magnetic field B2 for orienting the magnetic powder 11 are applied to the first slurry 21. The static magnetic field B1 is applied continuously. In addition, the pulse magnetic field B2 is applied instantaneously. The pulse magnetic field B2 may be applied once or multiple times.

[0028] (First compression molding process) As shown in FIG. 1, in step S3, a first compression molding step is performed. As shown in FIG. 4, the first compression molding step (S3) is a step of forming a first compact 41 by compression molding a first slurry 21 (see FIG. 3) containing a magnetic powder 11 (see FIG. 2) and a thermosetting resin 12 (see FIG. 2) while applying a magnetic field B for orienting the magnetic powder 11 to the first slurry 21. Specifically, in a state in which the first slurry 21 is sealed by a mold 30 and an upper punch 32, and in a state in which a magnetic field B (static magnetic field B1 and pulse magnetic field B2) for orienting the magnetic powder 11 is applied to the first slurry 21, the upper punch 32 descends toward the cavity 31a while applying pressure to the first slurry 21. When the upper punch 32 descends to a predetermined height, the magnetic powder 11 contained in the first slurry 21 is oriented, and the first compact 41 is formed by compression molding the first slurry 21. As described above, the first slurry 21 contains the solvent 13 (see FIG. 2). That is, the first compression molding step (S3) is a step of performing wet compression molding. The first compression molding step (S3) is an example of the "first compact forming step" in the claims.

[0029] The first compression molding step (S3) is a step of forming a first compact 41 while removing the solvent 13 from the first slurry 21 (see FIG. 3). Specifically, a plurality of flow paths 33a for removing the solvent are formed in the lower punch 33 disposed below the cavity 31a. Each of the plurality of flow paths 33a is connected to a suction pump 34 at the lower part of the lower punch 33. A filtration filter 35 is disposed between the cavity 31a and the lower punch 33. Then, while the first slurry 21 is being compression molded, suction is performed by the suction pump 34. The solvent 13 exuded by the compression molding of the first slurry 21 is sucked by the suction pump 34 through the filtration filter 35 and the plurality of flow paths 33a.

[0030] The amount of the thermosetting resin 12 contained in the first slurry 21 (see FIG. 3) in the first compression molding step (S3) is less than the amount of the thermosetting resin 12 contained in the second slurry 22 (see FIG. 11) in the second compression molding step (S10) (see FIG. 11) described later. Specifically, the amount of the thermosetting resin 12 contained in the first slurry 21 in the first compression molding step (S3) is 0.2 wt% or more and 2 wt% or less, and the amount of the thermosetting resin 12 contained in the second slurry 22 in the second compression molding step (S10) is 3 wt% or more and 7 wt% or less. Preferably, the amount of the thermosetting resin 12 contained in the first slurry 21 in the first compression molding step (S3) is 0.5 wt% or more and 1 wt% or less, and the amount of the thermosetting resin 12 contained in the second slurry 22 in the second compression molding step (S10) is 5 wt% or more and 6 wt% or less.

[0031] The pressure at which the first slurry 21 (see FIG. 3) is compressed and molded in the first compression molding step (S3) is lower than the pressure at which the second slurry 22 (see FIG. 11) is compressed and molded in the second compression molding step (S10) (see FIG. 11) described later. Specifically, the pressure at which the first slurry 21 is compressed and molded in the first compression molding step (S3) is 0.3 ton / cm. 2 More than 2 ton / cm 2The pressure for compressing and molding the second slurry 22 in the second compression molding step (S10) is 2 ton / cm or less. 2 Larger than 10 ton / cm 2 Preferably, the pressure for compressing and molding the first slurry 21 in the first compression molding step (S3) is 0.5 ton / cm or less. 2 More than 1 ton / cm 2 The pressure for compressing and molding the second slurry 22 in the second compression molding step (S10) is 2 ton / cm or less. 2 and 3 ton / cm 2 The following is the result.

[0032] (1st demagnetization process) As shown in Fig. 1, a first demagnetization step is performed in step S4. The first demagnetization step (S4) is a step of demagnetizing the magnetic powder 11 contained in the first compact 41 (see Fig. 4) by alternately applying magnetic fields B in opposite directions to the first compact 41 (see Fig. 4) containing the magnetic powder 11 (see Fig. 2) while gradually decreasing the strength of the magnetic fields B.

[0033] (1st heat curing process) As shown in Fig. 1, in step S5, a first thermal curing step is performed. As shown in Fig. 5, the first thermal curing step (S5) is a step of heating the first molded body 41 to thermally cure the thermosetting resin 12 (see Fig. 2). Specifically, the first molded body 41 is placed in a heating furnace 51. Then, in the heating furnace 51, the thermosetting resin 12 is heated so that the thermosetting resin 12 is thermally cured. In the first thermal curing step (S5), the heating for thermally curing the thermosetting resin 12 in the first molded body 41 is performed at a temperature of about 120°C or higher for a time of 30 minutes or longer. Due to the thermal curing of the thermosetting resin 12 contained in the first compact 41 in the first thermal curing step (S5), the bonded state of the multiple particles 11a (see FIG. 8) of the magnetic powder 11 (see FIG. 2) contained in the first compact 41 is more likely to be maintained between the crushing step (S6) (see FIG. 1) described later and just before the second compression molding step (S10) (see FIG. 1) described later is performed, and the shape of the granulated powder 14 (see FIG. 7) formed in the crushing step (S6) and the orientation state of the multiple particles 11a contained in the granulated powder 14 are more likely to be maintained.

[0034] (Crushing process) As shown in FIG. 1, a crushing step is performed in step S6. As shown in FIG. 6, the crushing step (S6) is a step of crushing the first compact 41 to form a granulated powder 14 (see FIG. 8) containing a plurality of particles 11a (see FIG. 8) of the magnetic powder 11 (see FIG. 2). Specifically, the first compact 41 is crushed by a crushing device 52. The crushing device 52 is, for example, a crushing machine, a jaw crusher, a pin mill, or other pulverizer. The crushed first compact 41 becomes crushed powder 15. As shown in FIG. 7, the crushed powder 15 contains the granulated powder 14. As shown in FIG. 8, the granulated powder 14 is formed by bonding a plurality of particles 11a of the magnetic powder 11 via a thermosetting resin 12, forming a mass.

[0035] As shown in Fig. 7, in the crushing step (S6), crushing is performed so that the distribution of particle sizes contained in the crushed powder 15 is relatively wide. Specifically, the type of crusher 52 (see Fig. 6) is selected or the settings of the crusher 52 are adjusted so that the distribution of particle sizes contained in the crushed powder 15 is relatively wide. As a result, the crushed powder 15 itself generated in the crushing step (S6) contains non-granulated powder 16 (see Fig. 7) having various particle sizes, which will be described later.

[0036] (Classification process) As shown in Fig. 1, a classification step is performed in step S7. As shown in Fig. 7, the classification step (S7) is a step of sifting, by particle size, the crushed powder 15 (see Fig. 6) obtained by crushing the first compact 41 (see Fig. 6) in the crushing step (S6). Specifically, the crushed powder 15 is classified by a classifier 53 into granulated powder 14 and non-granulated powder 16 that is not granulated, has a smaller particle size than the granulated powder 14, and has various particle sizes.

[0037] (Second slurry formation process) As shown in FIG. 1, in step S8, a second slurry formation step is performed. As shown in FIG. 9, the second slurry formation step (S8) is a step of mixing the crushed powder 15 including the granulated powder 14 (see FIG. 8), the thermosetting resin 12, and the solvent 13 to form a second slurry 22. The second slurry 22 may be mixed with a material other than the crushed powder 15, the thermosetting resin 12, and the solvent 13 (for example, a molding aid). The thermosetting resin 12 in the second slurry formation step (S8) may be the same type of thermosetting resin as the thermosetting resin 12 in the first slurry formation step (S1), or may be a different type of thermosetting resin from the thermosetting resin 12 in the first slurry formation step (S1). The solvent 13 in the second slurry formation step (S8) may be the same type of solvent as the solvent 13 in the first slurry formation step (S1), or may be a different type of solvent from the solvent 13 in the first slurry formation step (S1). The second slurry 22 is an example of the "second mixture" in the claims.

[0038] (Second Orientation Process) As shown in FIG. 1, in step S9, the second orientation step is performed. As shown in FIG. 10, the second orientation step (S9) is a step of applying a magnetic field B for orienting the magnetic powder 11 to a second slurry 22 containing the magnetic powder 11 (see FIG. 2) to orient the magnetic powder 11. Specifically, the second slurry 22 is filled into a cavity 31a formed in a die 30 for compression molding. Then, an upper punch 32 of the die 30 is placed above the cavity 31a so as to close the cavity 31a. Then, in a state in which the second slurry 22 is sealed by the die 30 and the upper punch 32, a static magnetic field B1 and a pulse magnetic field B2 for orienting the magnetic powder 11 are applied to the second slurry 22. The static magnetic field B1 is applied continuously. In addition, the pulse magnetic field B2 is applied instantaneously. The pulse magnetic field B2 may be applied once or multiple times.

[0039] (Second compression molding process) As shown in FIG. 1, in step S10, a second compression molding process is performed. As shown in FIG. 11, the second compression molding process (S10) is a process in which the second slurry 22 containing the granulated powder 14 (see FIG. 8) and the thermosetting resin 12 (see FIG. 9) is compression molded to form a second molded body 42 while applying a magnetic field B to the second slurry 22 for orienting the magnetic powder 11 (see FIG. 2). Specifically, in a state in which the second slurry 22 is sealed by the mold 30 and the upper punch 32, and in a state in which the magnetic field B (static magnetic field B1 and pulse magnetic field B2) for orienting the magnetic powder 11 is applied to the second slurry 22, the upper punch 32 descends toward the cavity 31a while applying pressure to the second slurry 22. When the upper punch 32 descends to a predetermined height, the magnetic powder 11 contained in the second slurry 22 is oriented, and the second molded body 42 is formed by compression molding the second slurry 22. As described above, the second slurry 22 contains the solvent 13 (see FIG. 9). That is, the second compression molding step (S10) is a step of performing wet compression molding. The second compression molding step (S10) is an example of a "second compact forming step" in the claims.

[0040] As described above, the second slurry 22 contains the pulverized powder 15 (see FIG. 9), and the pulverized powder 15 contains the granulated powder 14 (see FIG. 7) and the non-granulated powder 16 (see FIG. 7). That is, the second compression molding step (S10) is a step of forming a second compact 42 by compression molding the second slurry 22, which contains the granulated powder 14, the non-granulated powder 16 generated in the classification step (S7), and the thermosetting resin 12, while applying a magnetic field B for orienting the magnetic powder 11 to the second slurry 22.

[0041] The amount of non-granulated powder 16 (see FIG. 7) among the crushed powder 15 mixed with the second slurry 22 in the second compression molding step (S10) is adjusted to an amount according to the particle size of the granulated powder 14 (see FIG. 7) among the crushed powder 15 (see FIG. 9) mixed with the second slurry 22 (see FIG. 10) in the second compression molding step (S10). Specifically, the first compact 41 is crushed so that the particle size of the granulated powder 14 among the crushed powder 15 mixed with the second slurry 22 in the second compression molding step (S10) is 3 mm or less, and the amount of non-granulated powder 16 among the crushed powder 15 mixed with the second slurry 22 in the second compression molding step (S10) is adjusted so that the proportion of the non-granulated powder 16 in the crushed powder 15 is 50% or less. Preferably, the first compact 41 is crushed so that the particle size of the granulated powder 14 in the crushed powder 15 to be mixed with the second slurry 22 in the second compression molding step (S10) is 2 mm or less, and the amount of non-granulated powder 16 in the crushed powder 15 to be mixed with the second slurry 22 in the second compression molding step (S10) is adjusted so that its proportion in the crushed powder 15 is 20% or less.

[0042] (Second demagnetization process) As shown in Fig. 1, a second demagnetization step is performed in step S11. The second demagnetization step (S4) is a step of demagnetizing the magnetic powder 11 contained in the second compact 42 by alternately applying magnetic fields B in mutually opposite directions and gradually decreasing the strength to the second compact 42 containing the magnetic powder 11 (see Fig. 2).

[0043] (Second heat curing process) As shown in FIG. 1, in step S12, a second heat curing step is performed. As shown in FIG. 12, the second heat curing step (S12) is a step of performing heating for heat curing the thermosetting resin 12 (see FIG. 9) on the second molded body 42. In the second heat curing step (S12), the heating for heat curing the thermosetting resin 12 on the second molded body 42 is performed at a temperature of about 120° C. or more for a time of 30 minutes or more. That is, the temperature and time for heating for heat curing the thermosetting resin 12 on the first molded body 41 in the first heat curing step (S5) are the same as the temperature and time for heating for heat curing the thermosetting resin 12 on the second molded body 42 in the second heat curing step (S12).

[0044] (Effects of the embodiment) In this embodiment, the following effects can be obtained.

[0045] In this embodiment, as described above, after the crushing step (S6) of crushing the first compact 41 to form the granulated powder 14 granulated into particles containing a plurality of particles 11a of the magnetic powder 11, a second compression molding step (S10) (second compact formation step) is performed in which the second slurry 22 (second mixture) containing the granulated powder 14 and the thermosetting resin 12 (resin binder) is compressed and molded to form the second compact 42 while applying a magnetic field B for orienting the magnetic powder 11 to the second slurry 22. As a result, the granulated powder 14 contained in the second slurry 22 compressed and molded while applying the magnetic field B for orienting the magnetic powder 11 is granulated into particles containing a plurality of particles 11a of the magnetic powder 11, and therefore has a larger particle size than each particle 11a of the magnetic powder 11, and therefore has a smaller specific surface area than each particle 11a of the magnetic powder 11, and a larger rotational torque due to the application of the magnetic field B. The compression force when the second slurry 22 containing the granulated powder 14 is compressed and molded is transmitted between the granulated powders 14. Therefore, since the specific surface area of ​​the granulated powder 14 is relatively small, the contact area between the granulated powders 14 is relatively small when the second slurry 22 containing the granulated powder 14 is compressed and molded. Therefore, the friction loss generated between the granulated powders 14 is relatively small when the second slurry 22 containing the granulated powder 14 is compressed and molded, and the compression force is easily transmitted between the granulated powders 14 because the friction loss is small. In this case, the density of the second molded body 42 after compression molding is likely to be high. In addition, since the rotation torque caused by the application of the magnetic field B of the granulated powder 14 is relatively large, the magnetic powder 11 is easily oriented when the magnetic field B for orienting the magnetic powder 11 is applied to the second slurry 22 containing the granulated powder 14. In this case, the degree of orientation (degree of orientation) of the magnetic powder 11 in the second molded body 42 after compression molding is likely to be high. As a result, it is possible to improve the density of the compact and the degree of orientation of the magnetic powder 11 in the compact, thereby improving the magnetic properties of the bonded magnet.

[0046] In the present embodiment, as described above, the second compression molding step (S10) (second compact formation step) is a step of forming a second compact 42 by compression molding the second slurry 22 (second mixture) containing the granulated powder 14, the non-granulated powder 16 that is not granulated and has a smaller particle size than the granulated powder 14, and the thermosetting resin 12 (resin binder) while applying a magnetic field B for orienting the magnetic powder 11 to the second slurry 22. As a result, in the second compression molding step (S10), the second slurry 22 can be compression molded in a state in which the gaps between the granulated powders 14 are filled with the non-granulated powder 16 that is not granulated and has a smaller particle size than the granulated powder 14. As a result, the density of the second compact 42 can be further improved compared to a case in which the non-granulated powder 16 that is not granulated and has a smaller particle size than the granulated powder 14 is not included in the second slurry 22. As a result, the magnetic properties of the bonded magnet can be further improved.

[0047] In this embodiment, as described above, after the crushing step (S6) and before the second compression molding step (S10) (second compact formation step), a classification step (S7) is performed in which the crushed powder 15 obtained by crushing the first compact 41 in the crushing step (S6) is sifted according to particle size. The second compression molding step (S10) is a step in which the second slurry 22 (second mixture) containing the granulated powder 14, the non-granulated powder 16 generated in the classification step (S7), and the thermosetting resin 12 (resin binder) is compression molded to form the second compact 42 while applying a magnetic field B for orienting the magnetic powder 11 to the second slurry 22. As a result, the classification step (S7) makes it possible to easily sift out the crushed powder 15 obtained by crushing the first compact 41 in the crushing step (S6) to obtain the crushed powder 15 having a desired particle size as the granulated powder 14 to be used in the second compression molding step (S10). In addition, since the non-granulated powder 16 produced in the classification process (S7) can be utilized as the non-granulated powder 16 to be contained in the second slurry 22 in the second compression molding process (S10), the yield of the magnetic powder 11 can be effectively reduced.

[0048] In the present embodiment, as described above, the first compression molding step (S3) (first compact formation step) is a step of compression molding a first slurry 21 (first mixture) containing a thermosetting resin 12 as a resin binder to form a first compact 41. The second compression molding step (S10) (second compact formation step) is a step of compression molding a second slurry 22 (second mixture) containing a thermosetting resin 12 as a resin binder to form a second compact 42. After the first compression molding step (S3) and before the crushing step (S6), a first heat curing step (S5) is performed in which the first compact 41 is heated to heat-cure the thermosetting resin 12. After the second compression molding step (S10), a second heat curing step (S12) is performed in which the second compact 42 is heated to heat-cure the thermosetting resin 12. As a result, in the first heat curing step (S5), the thermosetting resin 12 contained in the first compact 41 is heat cured, which makes it easier to maintain the state in which the particles 11a of the magnetic powder 11 contained in the first compact 41 are bonded together, and therefore, when the first compact 41 is crushed in the crushing step (S6), it is possible to prevent granulated powder 14 from being formed and all of the crushed powder 15 from becoming non-granulated powder 16. In addition, after the second compression molding step (S10), the thermosetting resin 12 contained in the second compact 42 is heat cured, which makes it easier to maintain the state in which the granulated powder 14 contained in the second compact 42 is bonded together, and therefore, a compact having a mechanical strength appropriate for a bonded magnet can be easily formed.

[0049] In addition, in this embodiment, as described above, the amount of thermosetting resin 12 contained in the first slurry 21 (first mixture) in the first compression molding step (S3) (first compact formation step) is less than the amount of thermosetting resin 12 contained in the second slurry 22 (second mixture) in the second compression molding step (S10) (second compact formation step). This allows the amount of thermosetting resin 12 to be thermally cured in the first thermal curing step (S5) to be relatively small. This allows the amount of thermosetting resin 12 filling the gaps between the multiple particles 11a of the magnetic powder 11 in the first compact 41 to be relatively small, making it easy to prevent the multiple particles 11a of the magnetic powder 11 contained in the first compact 41 from being excessively maintained in a bonded state. As a result, it is easy to prevent the first compact 41 from being difficult to crush in the crushing step (S6) and the granulated powder 14 from being insufficiently formed.

[0050] In addition, in this embodiment, as described above, the pressure for compressing and molding the first slurry 21 (first mixture) in the first compression molding step (S3) (first compact formation step) is lower than the pressure for compressing and molding the second slurry 22 (second mixture) in the second compression molding step (S10) (second compact formation step). This makes it possible to easily prevent the particles 11a of the magnetic powder 11 contained in the first compact 41 from being excessively likely to remain bonded to each other. As a result, it is possible to easily prevent the first compact 41 from being difficult to disintegrate in the disintegration step (S6) and the granulated powder 14 from being sufficiently formed.

[0051] In addition, in this embodiment, as described above, the temperature at which the first compact 41 is heated to thermally cure the thermosetting resin 12 in the first thermal curing step (S5) is the same as the temperature at which the second compact 42 is heated to thermally cure the thermosetting resin 12 in the second thermal curing step (S12). This allows the temperature at which the thermosetting resin 12 is thermally cured in the first thermal curing step (S5) to be relatively low. This allows the thermosetting resin 12 contained in the first compact 41 to be easily prevented from being excessively cured, and therefore allows the multiple particles 11a of the magnetic powder 11 contained in the first compact 41 to be easily prevented from being excessively maintained in a state in which they are bonded to each other. As a result, it is possible to easily prevent the first compact 41 from being difficult to disintegrate in the disintegration step (S6) and the granulated powder 14 from being sufficiently formed.

[0052] In addition, in this embodiment, as described above, the time for which the first compact 41 is heated to thermally cure the thermosetting resin 12 in the first heat curing step (S5) is the same as the time for which the second compact 42 is heated to thermally cure the thermosetting resin 12 in the second heat curing step (S12). This allows the time for thermally curing the thermosetting resin 12 in the first heat curing step (S5) to be relatively short. This allows the thermosetting resin 12 contained in the first compact 41 to be easily prevented from being excessively cured, and therefore allows the multiple particles 11a of the magnetic powder 11 contained in the first compact 41 to be easily prevented from being excessively maintained in a state in which they are bonded to each other. As a result, it is possible to easily prevent the first compact 41 from being difficult to disintegrate in the disintegration step (S6) and the granulated powder 14 from being sufficiently formed.

[0053] [Variations] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the description of the embodiments above, and further includes all modifications (variations) within the meaning and scope of the claims.

[0054] For example, in the above embodiment, the temperature and time for which the first molded body 41 is heated to thermally cure the thermosetting resin 12 in the first heat curing step (S5) are the same as the temperature and time for which the second molded body 42 is heated to thermally cure the thermosetting resin 12 in the second heat curing step (S12), respectively, but the present invention is not limited to this. In the present invention, the time for which the first molded body is heated to thermally cure the thermosetting resin in the first heat curing step may be shorter than the time for which the second molded body is heated to thermally cure the thermosetting resin in the second heat curing step. This allows the time for thermally curing the thermosetting resin in the first heat curing step to be relatively short. In addition, the temperature for which the first molded body is heated to thermally cure the thermosetting resin in the first heat curing step may be lower than the temperature for which the second molded body is heated to thermally cure the thermosetting resin in the second heat curing step. This allows the temperature for thermally curing the thermosetting resin in the first heat curing step to be relatively low. As a result, the thermosetting resin contained in the first compact can be easily prevented from being excessively hardened, and the magnetic powder particles contained in the first compact can be easily prevented from being excessively maintained in a bonded state. As a result, the first compact can be easily prevented from being difficult to crush in the crushing step, and the granulated powder can be easily prevented from being sufficiently formed.

[0055] In the above embodiment, the pressure for compression molding the first slurry 21 (first mixture) in the first compression molding step (S3) (first compact formation step) is lower than the pressure for compression molding the second slurry 22 (second mixture) in the second compression molding step (S10) (second compact formation step), but the present invention is not limited to this. In the present invention, the pressure for compression molding the first mixture in the first compact formation step may be the same as the pressure for compression molding the second mixture in the second compact formation step.

[0056] In the above embodiment, the amount of thermosetting resin 12 contained in the first slurry 21 (first mixture) in the first compression molding step (S3) (first compact formation step) is smaller than the amount of thermosetting resin 12 contained in the second slurry 22 (second mixture) in the second compression molding step (S10) (second compact formation step), but the present invention is not limited to this. In the present invention, the amount of thermosetting resin contained in the first mixture in the first compact formation step may be the same as the amount of thermosetting resin contained in the second mixture in the second compact formation step.

[0057] In the above embodiment, the first compression molding step (S3) (first compact formation step) is a step of compression molding a first slurry 21 (first mixture) containing a thermosetting resin 12 as a resin binder to form a first compact 41, and a first heat curing step (S5) is performed after the first compression molding step (S3) and before the crushing step (S6) to heat the first compact 41 to heat the thermosetting resin 12, but the present invention is not limited to this. In the present invention, the first heat curing step of heating the first compact to heat the thermosetting resin may not be performed after the first compact formation step and before the crushing step. In that case, the first compact formation step may be a step of compression molding a first mixture that does not contain a thermosetting resin as a resin binder (containing a resin binder other than a thermosetting resin) to form a first compact.

[0058] In the above embodiment, the second compression molding step (S10) (second compact formation step) is a step of compression molding a second slurry 22 (second mixture) containing a thermosetting resin 12 as a resin binder to form a second compact 42, and after the second compression molding step (S10), a second heat curing step (S12) is performed to heat the second compact 42 to heat-cure the thermosetting resin 12. However, the present invention is not limited to this. In the present invention, the second heat curing step of heating the second compact to heat-cure the thermosetting resin may not be performed after the second compact formation step. In that case, the second compact formation step may be a step of compression molding a second mixture not containing a thermosetting resin as a resin binder to form a second compact.

[0059] In the above embodiment, the second compression molding step (S10) (second compact formation step) is a step of forming the second compact 42 by compression molding the second slurry 22 (second mixture) containing the granulated powder 14, the non-granulated powder 16 generated in the classification step (S7), and the thermosetting resin 12 (resin binder) while applying a magnetic field B for orienting the magnetic powder 11 to the second slurry 22 (second mixture), but the present invention is not limited to this. In the present invention, the second compact formation step may be a step of forming the second compact by compression molding the second mixture containing the granulated powder, non-granulated powder other than the non-granulated powder generated in the classification step, and the resin binder while applying a magnetic field for orienting the magnetic powder to the second mixture.

[0060] In the above embodiment, an example was shown in which the classification step (S7) of sieving the crushed powder 15 obtained by crushing the first compact 41 in the crushing step (S6) according to particle size was performed after the crushing step (S6) and before the second compression molding step (S10) (second compact formation step), but the present invention is not limited to this. In the present invention, the classification step of sieving the crushed powder obtained by crushing the first compact in the crushing step according to particle size may not be performed after the crushing step and before the second compact formation step. For example, if the crushed powder crushed in the crushing step has a suitable particle size distribution as the crushed powder to be mixed with the second mixture in the second compact formation step (the crushed powder crushed in the crushing step can be used as it is as the crushed powder to be mixed with the second mixture in the second compact formation step), there is no need to adjust the particle size of the crushed powder to be mixed with the second mixture, and therefore the classification step may not be performed.

[0061] In the above embodiment, the second compression molding step (S10) (second compact formation step) is a step of forming the second compact 42 by compression molding the second slurry 22 (second mixture) containing the granulated powder 14, the non-granulated powder 16 that is not granulated and has a smaller particle size than the granulated powder 14, and the thermosetting resin 12 (resin binder) while applying a magnetic field B for orienting the magnetic powder 11 to the second slurry 22, but the present invention is not limited to this. In the present invention, the second compact formation step may be a step of forming the second compact by compression molding the second mixture, which contains the granulated powder and the resin binder, does not contain the non-granulated powder that is not granulated and has a smaller particle size than the granulated powder, while applying a magnetic field for orienting the magnetic powder to the second mixture.

[0062] In the above embodiment, an example has been shown in which the first demagnetization step (S4) of demagnetizing the magnetic powder 11 contained in the first compact 41 is performed after the first compression molding step (S3) and before the first heat curing step (S5), but the present invention is not limited to this. In the present invention, the first demagnetization step of demagnetizing the magnetic powder contained in the first compact may be performed after the first heat curing step and before the crushing step, or the first demagnetization step of demagnetizing the magnetic powder contained in the compression molded body may not be performed.

[0063] In the above embodiment, the static magnetic field B1 and the pulse magnetic field B2 are applied as the magnetic field B for orienting the magnetic powder 11, but the present invention is not limited to this. In the present invention, only the static magnetic field may be applied as the magnetic field for orienting the magnetic powder.

[0064] In the above embodiment, the first compression molding step (S3) (first compact forming step) and the second compression molding step (S10) (second compact forming step) are steps of performing wet compression molding, but the present invention is not limited to this. In the present invention, the first compact forming step and the second compact forming step may be steps of performing dry compression molding. [Explanation of symbols]

[0065] Magnetic powder...11, (multiple) particles of magnetic powder...11a, thermosetting resin (resin binder)...12, granulated powder...14, crushed powder...15, non-granulated powder...16, first slurry (first mixture)...21, second slurry (second mixture)...22, first compact...41, second compact...42, magnetic field...B

Claims

1. a first compact formation step of forming a first compact by compression-molding a first mixture containing a magnetic powder and a resin binder while applying a magnetic field to the first mixture for orienting the magnetic powder; a crushing step of crushing the first compact to form a granulated powder containing a plurality of particles of the magnetic powder, which is performed after the first compact forming step; a second compact formation process for forming a second compact by compression molding a second mixture containing the granulated powder and the resin binder while applying a magnetic field to the second mixture to orient the magnetic powder after the crushing process.

2. 2. The method for manufacturing a bonded magnet according to claim 1, wherein the second compact formation process is a process of forming the second compact by compression molding the second mixture, which contains the granulated powder, non-granulated powder that is not granulated and has a smaller particle size than the granulated powder, and the resin binder, while applying a magnetic field to orient the magnetic powder to the second mixture.

3. The method further includes a classification step, which is performed after the crushing step and before the second compact forming step, of sieving the crushed powder obtained by crushing the first compact in the crushing step according to particle size.

3. The method for manufacturing a bonded magnet according to claim 2, wherein the second compact formation process is a process of forming the second compact by compression molding the second mixture, which contains the granulated powder, the non-granulated powder produced in the classification process, and the resin binder, while applying a magnetic field to the second mixture to orient the magnetic powder.

4. the first compact formation step is a step of forming the first compact by compression molding the first mixture containing a thermosetting resin as the resin binder, the second molded body forming step is a step of forming the second molded body by compression molding the second mixture containing the thermosetting resin as the resin binder, a first heat curing step of heating the first molded body for heat curing the thermosetting resin after the first molded body forming step and before the crushing step; 2. The method for producing a bonded magnet according to claim 1, further comprising a second heat curing step of heating the second compact to heat-cure the thermosetting resin after the second compact formation step.

5. 5. The method for manufacturing a bonded magnet according to claim 4, wherein the amount of the thermosetting resin contained in the first mixture in the first compact formation process is less than the amount of the thermosetting resin contained in the second mixture in the second compact formation process.

6. 2. The method for producing a bonded magnet according to claim 1, wherein a pressure for compression molding the first mixture in the first compact forming step is lower than a pressure for compression molding the second mixture in the second compact forming step.

7. 5. The method for manufacturing a bonded magnet as described in claim 4, wherein the temperature at which the first compact is heated to thermally harden the thermosetting resin in the first thermal hardening step is lower than the temperature at which the second compact is heated to thermally harden the thermosetting resin in the second thermal hardening step.

8. 5. The method for manufacturing a bonded magnet as described in claim 4, wherein the time during which the first compact is heated to thermally harden the thermosetting resin in the first thermal hardening step is equal to or less than the time during which the second compact is heated to thermally harden the thermosetting resin in the second thermal hardening step.

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