JP2015207687A - Permanent magnet, and method for manufacturing permanent magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permanent magnet which enables the decrease in the amount of Dy or Tb used, and enables the appropriate increase in the coercive force of a permanent magnet even if the permanent magnet is a large-sized one; and a method for manufacturing such a permanent magnet.SOLUTION: A method for manufacturing a permanent magnet 1 comprises the steps of: pulverizing a magnet raw material into magnet powder; mixing the resultant magnet powder with a binder, thereby producing a compound 12; molding the compound 12 in a sheet-like form into a green sheet 14; thereafter, forming shaped parts 31-33 from the green sheet 14; making a combination of the shaped parts 31-33; and sintering the combination of the shaped parts collectively. Thus, the permanent magnet 1 including a combination of the shaped parts 31-33 is manufactured in a form according to a coercive force that the finished permanent magnet is required to have.

Description

  The present invention relates to a permanent magnet and a method for manufacturing the permanent magnet.

In recent years, permanent magnet motors used in hybrid cars, hard disk drives, and the like have been required to be smaller, lighter, higher in output, and more efficient. Further, in order to realize a reduction in size and weight, an increase in output, and an increase in efficiency in the permanent magnet motor, further improvement in magnetic characteristics is required for the permanent magnet embedded in the permanent magnet motor. Permanent magnets include ferrite magnets, Sm—Co magnets, Nd—Fe—B magnets, Sm ₂ Fe ₁₇ N _x magnets, etc. Nd—Fe—B magnets with particularly high residual magnetic flux density. Used as a permanent magnet for a permanent magnet motor.

  However, Nd-based magnets such as Nd—Fe—B have a problem that the heat-resistant temperature is low. Therefore, when an Nd magnet is used for a permanent magnet motor, the residual magnetic flux density of the magnet gradually decreases when the motor is continuously driven. In addition, irreversible demagnetization has also occurred. Therefore, when an Nd magnet is used for a permanent magnet motor, Dy (dysprosium), Tb (terbium), etc. (hereinafter referred to as Dy) having high magnetic anisotropy are used to improve the heat resistance of the Nd magnet. Is added to further improve the coercive force of the magnet.

  Here, as a method for adding Dy and the like, conventionally, powders corresponding to the main phase and the grain boundary phase are separately manufactured, mixed (dry blended), and sintered using vapor deposition or sputtering. There is a grain boundary diffusion method in which Dy or the like is deposited on the surface of the magnet and then diffused into the sintered magnet by heat treatment (for example, JP-A-2005-11973).

JP 2005-111973 (page 7-9)

  However, the two-alloy method has a drawback in that since two alloys are blended and pressed to produce a magnet, Dy and the like diffuse into the grains and cannot be unevenly distributed at the grain boundaries. On the other hand, the grain boundary diffusion method can concentrate Dy and the like at a very high concentration in the vicinity of the grain boundary part and the grain boundary part in the sintered body main phase grains, compared with the case of the two alloy method. Although it is possible to obtain an ideal texture form, the distance that can be diffused is short (about 2 mm), so a large magnet has a drawback that the diffusion distance such as Dy cannot be extended to the internal grain boundary phase. Therefore, for example, there is a problem that an appropriate coercive force cannot be improved with respect to a large permanent magnet used in an electric rotating machine for an elevator or a wind power generator.

  Moreover, since Dy etc. are rare metals and the production origin is also limited, it is desirable to suppress the usage-amount of Dy etc. as much as possible. Further, when a large amount of Dy or the like is added, there is a problem that the residual magnetic flux density indicating the strength of the magnet decreases while the coercive force increases. Therefore, a technique for improving the coercive force of a magnet without reducing the residual magnetic flux density by efficiently distributing a small amount of Dy or the like at grain boundaries has been desired.

  The present invention has been made to solve the above-described problems of the prior art, and is configured to improve only the coercive force of a necessary portion rather than the entire permanent magnet, thereby reducing the amount of Dy and Tb used. An object of the present invention is to provide a permanent magnet and a method for manufacturing the permanent magnet that can appropriately improve the coercive force of the permanent magnet even if it is a large permanent magnet.

  In order to achieve the above object, the permanent magnet according to claim 1 of the present application combines a plurality of molded bodies having different coercive force values after magnetization and simultaneously sinters the plurality of combined molded bodies. And a plurality of the molded bodies after sintering are combined with each other.

  A permanent magnet according to claim 2 is the permanent magnet according to claim 1, wherein the plurality of molded bodies are combined in a manner according to a coercive force required for the manufactured permanent magnet. It is characterized by.

  Moreover, the permanent magnet according to claim 3 is the permanent magnet according to claim 2, wherein the plurality of molded bodies have a high coercive force after magnetization in a position where a high coercive force is required. It is characterized by being combined so that the body is located.

  A permanent magnet according to a fourth aspect is the permanent magnet according to any one of the first to third aspects, wherein the plurality of molded bodies are joined together by an adhesive, a plasticizer, and thermocompression bonding. It is characterized by being combined.

  Moreover, the permanent magnet which concerns on Claim 5 is a permanent magnet in any one of Claim 1 thru | or 4, Comprising: As for the said some molded object, content of Dy or Tb changes with molded objects. Features.

  A permanent magnet according to claim 6 is the permanent magnet according to any one of claims 1 to 5, wherein the molding is performed by molding a mixture in which pulverized magnet powder and a binder are mixed. It is characterized by forming a body.

  The method for manufacturing a permanent magnet according to claim 7 includes a step of pulverizing a magnet raw material into magnet powder, a step of forming a plurality of compacts by molding the pulverized magnet powder, and a plurality of the moldings. A step of obtaining a combined body in which a plurality of the molded bodies are combined by combining the bodies, a step of sintering the plurality of the molded bodies at a time by holding the combined body at a firing temperature, and sintering. And a step of magnetizing the combined body later, wherein the plurality of molded bodies have different coercive force values after the magnetization depending on the molded body.

  Moreover, the manufacturing method of the permanent magnet which concerns on Claim 8 is a manufacturing method of the permanent magnet of Claim 7, Comprising: In the process of obtaining the said coupling | bonding, the coercive force requested | required with respect to the permanent magnet after manufacture A plurality of the molded bodies are combined in a manner corresponding to the above.

  Further, a method for manufacturing a permanent magnet according to claim 9 is the method for manufacturing a permanent magnet according to claim 8, wherein in the step of obtaining the combined body, a position where a high coercive force is required, after magnetization. It combines so that the said molded object which has a high coercive force may be located.

  Moreover, the manufacturing method of the permanent magnet which concerns on Claim 10 is a manufacturing method of the permanent magnet in any one of Claim 7 thru | or 9, Comprising: In the process of obtaining the said coupling body, an adhesive, a plasticizer, A plurality of the molded bodies are combined by bonding to each other by thermocompression bonding.

  A method for producing a permanent magnet according to an eleventh aspect is the method for producing a permanent magnet according to any one of the seventh to tenth aspects, wherein the plurality of molded bodies have a Dy or Tb content. It differs depending on the molded product.

  Furthermore, the manufacturing method of the permanent magnet which concerns on Claim 12 is a manufacturing method of the permanent magnet in any one of Claim 7 thru | or 11, Comprising: In the process of forming the said molded object, the said pulverized magnet The molded body is formed by molding a mixture in which powder and a binder are mixed.

According to the permanent magnet of the first aspect having the above-described configuration, it is possible to improve only the coercive force of a necessary portion, not the entire permanent magnet, by combining a plurality of molded bodies. Therefore, the state in which the permanent magnet retains the function as a magnet (that is, a state in which a demagnetizing field is generated by passing a current through the stator, or a coercive force higher than a reverse magnetic field can be maintained even if the temperature rises due to an eddy current). Thus, it is possible to prevent the residual magnetic flux density from being reduced. In particular, the effect becomes large in a large-sized permanent magnet used for a rotary electric machine of an elevator or a wind power generator.
Further, since the permanent magnet finally becomes a unitary combined body, when the permanent magnet is arranged in the rotor of the rotating electrical machine, the rotor is different from the case where the permanent magnets having different coercive forces are arranged side by side. Assembling accuracy can be improved. As a result, it is possible to prevent displacement of the permanent magnet from the design position, and to realize high output, high efficiency, and low torque ripple of the rotating electrical machine.
Moreover, since it manufactures by collectively sintering in the state which combined the some molded object, compared with the case where a several molded object is combined after sintering, the highly accurate process after sintering becomes unnecessary. That is, if the molded body is combined after being sintered, the molded body is contracted or deformed with the sintering, so that it is necessary to combine them after correcting them. If sintering is performed after combining a plurality of molded bodies, those steps are not required, and an increase in manufacturing cost can be suppressed.

  In addition, according to the permanent magnet of the second aspect, since it is configured to improve only the coercive force of a necessary portion according to the application, the residual magnetic flux density can be reduced as a whole while providing the necessary coercive force. It becomes possible to prevent.

  In addition, according to the permanent magnet of claim 3, since the molded body having a high coercive force is positioned after magnetization, the position where a high coercive force is required is combined. The coercive force can be increased to a required value at a necessary location. On the other hand, it is possible to prevent the residual magnetic flux density from being reduced by giving priority to the residual magnetic flux density over the coercive force at a location where a high coercive force is not required in the permanent magnet.

  Moreover, according to the permanent magnet of claim 4, since the plurality of molded bodies are combined by bonding with an adhesive, a plasticizer, and thermocompression bonding, the molded bodies before sintering can be appropriately bonded to each other. It becomes.

  Further, according to the permanent magnet of claim 5, since the content of Dy or Tb varies depending on the molded body, the target to which Dy or Tb is added (or added in large quantities) can be limited to only the necessary molded body, It is possible to reduce the amount of Dy and Tb used. In particular, when Dy or Tb is added by the grain boundary diffusion method, the size of the compact to be added becomes small, so that Dy and Tb can be appropriately diffused into the magnet. As a result, the coercive force of the permanent magnet can be appropriately improved even with a large permanent magnet.

  Moreover, according to the permanent magnet of claim 6, since the molded body is formed by molding a mixture of magnet powder and binder, the molded body is compared with the case of using conventional compacting or the like. Appropriate bonding between them becomes possible. Moreover, compared with the case where compacting etc. are used, a magnet particle does not rotate after orientation and it becomes possible to improve the degree of orientation. In addition, when magnetic field orientation is performed on a mixture of magnet powder and binder, the number of current turns can be used, so that a large magnetic field strength can be ensured when performing magnetic field orientation, and a long time can be obtained with a static magnetic field. Therefore, a high degree of orientation with little variation can be realized. Furthermore, the realization of high orientation with little variation leads to a reduction in variation in shrinkage due to sintering. That is, the uniformity of the product shape after sintering can be ensured. As a result, the burden on external processing after sintering is reduced.

In addition, according to the method for manufacturing a permanent magnet according to claim 7, it is possible to improve only the coercive force of a necessary portion, not the entire permanent magnet, by combining a plurality of molded bodies. . Therefore, the state in which the permanent magnet retains the function as a magnet (that is, a state in which a demagnetizing field is generated by passing a current through the stator, or a coercive force higher than a reverse magnetic field can be maintained even if the temperature is increased by eddy current). Thus, it is possible to prevent the residual magnetic flux density from being reduced. In particular, the effect becomes large in a large-sized permanent magnet used for a rotary electric machine of an elevator or a wind power generator.
Further, since the permanent magnet finally becomes a unitary combined body, when the permanent magnet is arranged in the rotor of the rotating electrical machine, the rotor is different from the case where the permanent magnets having different coercive forces are arranged side by side. Assembling accuracy can be improved. As a result, it is possible to prevent displacement of the permanent magnet from the design position, and to realize high output, high efficiency, and low torque ripple of the rotating electrical machine.
Moreover, since it manufactures by collectively sintering in the state which combined the some molded object, compared with the case where a several molded object is combined after sintering, the highly accurate process after sintering becomes unnecessary. That is, if the molded body is combined after being sintered, the molded body is contracted or deformed with the sintering, so that it is necessary to combine them after correcting them. If sintering is performed after combining a plurality of molded bodies, those steps are not required, and an increase in manufacturing cost can be suppressed.

  Further, according to the method for manufacturing a permanent magnet according to claim 8, since it is configured so as to improve only the coercive force of a necessary portion according to the use, the residual magnetic flux density as a whole magnet is provided with the necessary coercive force. Can be prevented.

  In addition, according to the method for manufacturing a permanent magnet according to claim 9, since the molded body having a high coercive force is positioned so that a position where a high coercive force is required is positioned after magnetization, it is high in the permanent magnet. About the location where a coercive force is required, a coercive force can be raised to the required value. On the other hand, it is possible to prevent the residual magnetic flux density from being reduced by giving priority to the residual magnetic flux density over the coercive force at a location where a high coercive force is not required in the permanent magnet.

  Further, according to the method for producing a permanent magnet according to claim 10, since the plurality of molded bodies are combined by bonding with an adhesive, a plasticizer, and thermocompression bonding, the molded bodies before sintering are appropriately bonded to each other. It becomes possible.

  In addition, according to the method of manufacturing a permanent magnet according to claim 11, since the content of Dy or Tb varies depending on the molded body, only the molded body that needs Dy or Tb added (or added in large quantities) is required. It can be limited, and the amount of Dy and Tb used can be reduced. In particular, when Dy or Tb is added by the grain boundary diffusion method, the size of the compact to be added becomes small, so that Dy and Tb can be appropriately diffused into the magnet. As a result, the coercive force of the permanent magnet can be appropriately improved even with a large permanent magnet.

  Furthermore, according to the method for manufacturing a permanent magnet according to claim 12, since a molded body is formed by molding a mixture of magnet powder and binder, compared with the case of using conventional compacting or the like. Thus, it becomes possible to appropriately join the molded bodies. Moreover, compared with the case where compacting etc. are used, a magnet particle does not rotate after orientation and it becomes possible to improve the degree of orientation. In addition, when magnetic field orientation is performed on a mixture of magnet powder and binder, the number of current turns can be used, so that a large magnetic field strength can be ensured when performing magnetic field orientation, and a long time can be obtained with a static magnetic field. Therefore, a high degree of orientation with little variation can be realized. Furthermore, the realization of high orientation with little variation leads to a reduction in variation in shrinkage due to sintering. That is, the uniformity of the product shape after sintering can be ensured. As a result, the burden on external processing after sintering is reduced.

1 is an overall view showing a permanent magnet according to the present invention. It is the figure which showed the rotor of the SPM motor by which the permanent magnet is arrange | positioned. It is the figure which showed the detailed structure of the permanent magnet. It is the figure which showed the example which used the permanent magnet for the IPM motor. It is explanatory drawing which showed the manufacturing process of the permanent magnet which concerns on this invention. It is explanatory drawing which showed the formation process of the green sheet especially among the manufacturing processes of the permanent magnet which concerns on this invention. It is the figure explaining the temperature rising aspect of the calcining process among the manufacturing processes of the permanent magnet which concerns on this invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment embodying a permanent magnet and a method for manufacturing a permanent magnet according to the present invention will be described in detail with reference to the drawings.

[Configuration of permanent magnet]
First, the configuration of the permanent magnet 1 according to the present invention will be described. FIG. 1 is an overall view showing a permanent magnet 1 according to the present invention. As shown in FIG. 1, a permanent magnet 1 according to the present invention is a permanent magnet having a saddle shape (segment type). As shown in FIG. 2, a plurality of surface magnet type generators (or motors) are arranged on the surface of the rotor 2 to constitute a surface magnet type generator (or motor). FIG. 2 is a view showing the rotor 2 of the SPM motor in which the permanent magnet 1 is arranged. In the following embodiment, an example in which the permanent magnet 1 has a saddle shape will be described. However, the shape of the permanent magnet 1 can be appropriately changed depending on the shape of the rotor 2 to be arranged, the number of arrangements, and the like. For example, it may be a fan shape, a bow shape, or a rectangular parallelepiped shape. In addition to the surface magnet type generator (or motor), the present invention can also be applied to an embedded magnet type generator (or motor) such as an IPM motor.

  The permanent magnet 1 according to the present invention is made of an Nd—Fe—B based magnet. In addition, content of each component shall be Nd: 27-40 wt%, B: 0.8-2 wt%, Fe (electrolytic iron): 60-70 wt%. In order to improve magnetic properties, other elements such as Dy, Tb, Co, Cu, Al, Si, Ga, Nb, V, Pr, Mo, Zr, Ta, Ti, W, Ag, Bi, Zn, and Mg are added. May contain a small amount. Further, as will be described later, the permanent magnet 1 is composed of a combined body in which a plurality of molded bodies having different components (especially Dy or Tb) are combined, so that the content of the components varies depending on the location in the permanent magnet 1. .

  Further, the number of permanent magnets 1 arranged with respect to the rotor 2 is a number corresponding to the number of poles formed around the rotor 2. For example, when the number of poles is set to twelve, twelve permanent magnets as shown in FIG. 1 are arranged at equal intervals with respect to the rotor 2.

  Further, the permanent magnet 1 is formed by a molded body (green molded body) obtained by molding a mixture obtained by mixing magnet powder and a binder as described later. In addition, the mixture is not directly formed into a final product shape (for example, the saddle shape shown in FIG. 1), but once formed into a shape other than the final product shape (for example, a sheet shape, a block shape, etc.), and then punched, It is good also as a structure which makes it a final product shape by performing a cutting process, a deformation process, etc. In particular, if the mixture is once formed into a sheet shape and then processed into a final product shape, productivity can be improved by producing in a continuous process, and molding accuracy can also be improved. When making a mixture into a sheet shape, it is set as the thin film-like sheet member provided with thickness of 0.05 mm-10 mm (for example, 1 mm), for example. Even in the case of a sheet shape, a large permanent magnet 1 can be manufactured if a plurality of sheets are laminated.

  In addition, the permanent magnet 1 according to the present invention is composed of a combined body in which a plurality of molded bodies having different component contents are combined. Here, the magnetic performance of the permanent magnet 1 is defined by, for example, a combination of a coercive force (Hcj) and a residual magnetic flux density (Br). In general, rare earth permanent magnets such as Nd—Fe—B are added with Dy or Tb in order to increase the coercive force. As a result, even if a demagnetizing field is generated by passing an electric current through the stator or a high temperature state (for example, 200 ° C.) is caused by the generation of eddy current, the coercive force higher than the reverse magnetic field can be maintained. However, when Dy or Tb is added, the coercive force increases, but there is a problem that the residual magnetic flux density decreases. Further, when the size of the permanent magnet 1 is particularly large, there is a problem that Dy and Tb do not diffuse into the magnet when Dy or Tb is added by the grain boundary diffusion method.

  Therefore, in the present invention, the permanent magnet 1 is composed of a combined body in which a plurality of molded bodies having different component contents are combined, and in particular, by changing the content of Dy or Tb for each molded body, the permanent magnet 1 is provided after magnetization. The coercive force and the residual magnetic flux density are configured to change for each molded body. That is, the permanent magnet 1 is composed of a plurality of regions having different coercive force and residual magnetic flux density. Moreover, a some molded object is combined in the aspect according to the coercive force requested | required with respect to the permanent magnet 1 after manufacture. More specifically, it is combined so that a molded body having a high coercive force after the magnetization is positioned at a position where a high coercive force is required.

  Here, when the saddle-shaped permanent magnet 1 shown in FIG. 1 drives the SPM motor arranged around the rotor 2, the magnetic flux density is not changed uniformly with respect to the permanent magnet 1. However, there is a possibility that a large change in magnetic flux density will occur at a specific location, causing demagnetization. Specifically, as shown in FIG. 3, at both ends of the permanent magnet 1 along the rotor circumferential direction, the permanent magnet 1 is easily affected by a demagnetizing field generated when a current is passed through the stator, and a strong eddy current is generated. There is a high risk. Accordingly, there is a high possibility that a large change in magnetic flux density will occur, and a high coercive force is required to prevent demagnetization. On the other hand, the influence of the demagnetizing field is small in other places, and it is predicted that strong eddy currents are less likely to occur, and the necessity for increasing the coercive force is small.

  Therefore, the permanent magnet 1 is combined so that a molded body having a high coercive force is located near both ends of the permanent magnet 1 after magnetization. As a result, as shown in FIG. 3, the permanent magnet 1 combined with the compact, sintered and magnetized, has a low coercive force but a high residual magnetic flux density, and a high residual magnetic flux density. The low region 4 is configured. As a result, the permanent magnet 1 can maintain a coercive force equal to or higher than the reverse magnetic field even when the permanent magnet 1 has a function as a magnet (that is, even when a demagnetizing field is generated by passing a current through the stator or the temperature is increased by an eddy current). In the state), it is possible to prevent the residual magnetic flux density from being reduced.

  As a method for improving the coercive force in the region 4, Dy or Tb is unevenly arranged at the grain boundary of the magnet. And as a method of unevenly arranging Dy or Tb at the grain boundaries of the magnet, for example, the grain boundary diffusion method in which Dy or Tb is attached to the surface of the molded body and diffused by heat treatment, or the main phase and grains A two-alloy method is used in which powders corresponding to the boundary phase are separately produced and mixed (dry blended). Here, especially when adding Dy or Tb by the grain boundary diffusion method, by attaching Dy, Tb or the like to the surface of a small-sized molded body before being combined with the product shape, the entire region 4 is added. It is possible to diffuse Dy or Tb uniformly. Further, the amount of Dy and Tb used can be reduced and the manufacturing cost can be reduced. On the other hand, conventional large permanent magnets do not extend the diffusion distance of Dy and Tb to the grain boundary phase inside the magnet, and the amount of Dy and Tb used increases.

  Moreover, although the case where the permanent magnet 1 is used for the SPM motor has been described in the above example, the position where a high coercive force is required differs depending on the application of the permanent magnet 1, and the shape of the molded body to be combined varies accordingly. For example, when the permanent magnet 1 is used in an IPM motor, the rectangular parallelepiped permanent magnet 1 is accommodated in the slot 6 so as to have a reverse C shape along the axial direction of the rotor, as shown in FIG. A particularly large change in magnetic flux density occurs at the corner near the center of the paired permanent magnet 1. Therefore, the permanent magnets 1 are combined so that a molded body having a high coercive force is located near the corner of the permanent magnet 1 especially after magnetization. As a result, as shown in FIG. 4, the permanent magnet 1, which is formed by combining the compacts and sintered and magnetized, has a low coercive force but a high residual magnetic flux density, and a high residual magnetic flux density. The low region 8 is constituted. As a result, the permanent magnet 1 can maintain a coercive force equal to or higher than the reverse magnetic field even when the permanent magnet 1 has a function as a magnet (that is, even when a demagnetizing field is generated by passing a current through the stator or the temperature is increased by an eddy current). In the state), it is possible to prevent the residual magnetic flux density from being reduced and to appropriately diffuse Dy and Tb to the inside of the magnet by the grain boundary diffusion method.

（但し、Ｒ１及びＲ２は、水素原子、低級アルキル基、フェニル基又はビニル基を表す） On the other hand, in the case of producing the permanent magnet 1 in the present invention, resin, long chain hydrocarbon, fatty acid ester, a mixture thereof or the like is used as the binder mixed with the magnet powder.
Furthermore, when a resin is used for the binder, it is preferable to use a polymer that does not contain an oxygen atom in the structure and has a depolymerization property. In addition, as will be described later, in order to reuse the residue of the mixture generated when the mixture of the magnet powder and the binder is formed into a desired shape (for example, a saddle shape), and in a state where the mixture is heated and softened, the magnetic field A thermoplastic resin is used for orientation. Specifically, the polymer which consists of 1 type, or 2 or more types of polymers or copolymers chosen from the monomer shown by the following general formula (1) corresponds.

(However, R1 and R2 represent a hydrogen atom, a lower alkyl group, a phenyl group or a vinyl group.)

Examples of the polymer satisfying the above conditions include polyisobutylene (PIB), which is a polymer of isobutylene, polyisoprene (isoprene rubber, IR), which is a polymer of isoprene, and polybutadiene (butadiene) that is a polymer of 1,3-butadiene. Rubber, BR), polystyrene as a polymer of styrene, styrene-isoprene block copolymer (SIS) as a copolymer of styrene and isoprene, butyl rubber (IIR) as a copolymer of isobutylene and isoprene, styrene and butadiene A styrene-butadiene block copolymer (SBS) which is a copolymer of 2-methyl-1-pentene, a 2-methyl-1-pentene polymer which is a polymer of 2-methyl-1-pentene, and a polymer of 2-methyl-1-butene. A 2-methyl-1-butene polymer, a polymer of α-methylstyrene. That there is α- methyl styrene polymer resin. In addition, it is desirable to add a low molecular weight polyisobutylene to the α-methylstyrene polymer resin in order to give flexibility. The resin used for the binder may include a small amount of a polymer or copolymer of a monomer containing an oxygen atom (for example, polybutyl methacrylate, polymethyl methacrylate, etc.). Furthermore, a monomer that does not correspond to the general formula (1) may be partially copolymerized. Even in that case, it is possible to achieve the object of the present invention.
As the resin used for the binder, it is desirable to use a thermoplastic resin that softens at 250 ° C. or lower, more specifically a thermoplastic resin having a glass transition point or a melting point of 250 ° C. or lower in order to appropriately perform magnetic field orientation. .

  On the other hand, when a long-chain hydrocarbon is used as the binder, it is preferable to use a long-chain saturated hydrocarbon (long-chain alkane) that is solid at room temperature and liquid at room temperature or higher. Specifically, it is preferable to use a long-chain saturated hydrocarbon having 18 or more carbon atoms. Then, when the mixture of the magnetic powder and the binder is magnetically oriented as described later, the magnetic field orientation is performed in a state where the mixture is heated and softened at a temperature equal to or higher than the glass transition point or the melting point of the long-chain hydrocarbon.

  Similarly, when a fatty acid ester is used as the binder, it is preferable to use methyl stearate, methyl docosanoate or the like that is solid at room temperature and liquid at room temperature or higher. And, as will be described later, when the magnetic powder and binder mixture is magnetically oriented, the magnetic field orientation is performed in a state where the mixture is heated and softened above the melting point of the fatty acid ester.

  By using a binder that satisfies the above conditions as a binder to be mixed with the magnet powder, the amount of carbon and oxygen contained in the magnet can be reduced. Specifically, the amount of carbon remaining in the magnet after sintering is 2000 ppm or less, more preferably 1000 ppm or less. Further, the amount of oxygen remaining in the magnet after sintering is set to 5000 ppm or less, more preferably 2000 ppm or less.

  Further, the amount of the binder added is an amount that appropriately fills the gaps between the magnet particles in order to improve the thickness accuracy of the molded body when molding the slurry or the heated and melted compound. For example, the ratio of the binder to the total amount of the magnet powder and the binder is 1 wt% to 40 wt%, more preferably 2 wt% to 30 wt%, and still more preferably 3 wt% to 20 wt%.

[Permanent magnet manufacturing method]
Next, a method for manufacturing the permanent magnet 1 according to the present invention will be described with reference to FIG. FIG. 5 is an explanatory view showing a manufacturing process of the permanent magnet 1 according to the present embodiment.

  First, an ingot made of a predetermined fraction of Nd—Fe—B (for example, Nd: 32.7 wt%, Fe (electrolytic iron): 65.96 wt%, B: 1.34 wt%) is manufactured. Thereafter, the ingot is roughly pulverized to a size of about 200 μm by a stamp mill or a crusher. Alternatively, the ingot is melted, flakes are produced by strip casting, and coarsely pulverized by hydrogen crushing. Thereby, coarsely pulverized magnet powder 10 is obtained.

  Next, the coarsely pulverized magnet powder 10 is finely pulverized by a wet method using a bead mill 11 or a dry method using a jet mill. For example, in fine pulverization using a wet method using a bead mill 11, the coarsely pulverized magnet powder 10 is finely pulverized in a solvent to a predetermined particle size (for example, 0.1 μm to 5.0 μm) and the magnet powder is dispersed in the solvent. . Thereafter, the magnet powder contained in the solvent after the wet pulverization is dried by vacuum drying or the like, and the dried magnet powder is taken out. Moreover, there is no restriction | limiting in particular in the kind of solvent used for grinding | pulverization, Alcohols, such as isopropyl alcohol, ethanol, methanol, Esters, such as ethyl acetate, Lower hydrocarbons, such as pentane and hexane, Aromatics, such as benzene, toluene, xylene , Ketones, mixtures thereof and the like. In addition, Preferably, the solvent which does not contain an oxygen atom in a solvent is used.

  On the other hand, in fine pulverization using a dry method using a jet mill, coarsely pulverized magnet powder is (a) in an atmosphere composed of an inert gas such as nitrogen gas, Ar gas, and He gas having substantially 0% oxygen content. Or (b) Finely pulverizing by a jet mill in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, and He gas with an oxygen content of 0.0001 to 0.5%, A fine powder having an average particle diameter of 0.7 μm to 5.0 μm. The oxygen concentration of substantially 0% is not limited to the case where the oxygen concentration is completely 0%, but may contain oxygen in such an amount that a very small amount of oxide film is formed on the surface of the fine powder. Means good.

  Next, the magnet powder finely pulverized by the bead mill 11 or the like is molded into a desired shape. The magnet powder is molded by molding a mixture of magnet powder and binder. In the following examples, a magnetic field is applied by applying a magnetic field in a state where the mixture is once formed in a shape other than the product shape, and then the product shape (for example, as shown in FIG. 1) is performed by punching, cutting, deformation, or the like.蒲 鉾). In particular, in the following examples, the mixture is once formed into a sheet-shaped green molded body (hereinafter referred to as a green sheet) to obtain a product shape. In addition, when the mixture is formed into a sheet shape, for example, hot melt coating that forms a sheet shape after heating a compound in which a magnet powder and a binder are mixed, or a slurry containing a magnet powder, a binder, and an organic solvent. There is molding by slurry coating or the like to form a sheet by coating the substrate on a substrate.

Hereinafter, green sheet forming using hot melt coating will be described.
First, a powdery mixture (compound) 12 composed of magnet powder and binder is prepared by mixing a binder with magnet powder finely pulverized by a bead mill 11 or the like. Here, as the binder, a resin, a long-chain hydrocarbon, a fatty acid ester, a mixture thereof, or the like is used as described above. For example, when a resin is used, a thermoplastic resin made of a depolymerizable polymer that does not contain an oxygen atom in the structure is used. On the other hand, when a long-chain hydrocarbon is used, the resin is solid at room temperature or above room temperature. It is preferable to use a long-chain saturated hydrocarbon (long-chain alkane) that is liquid. Moreover, when using fatty acid ester, it is preferable to use methyl stearate, methyl docosanoate, or the like. In addition, as described above, the amount of the binder is such that the ratio of the binder to the total amount of the magnet powder and the binder in the compound 12 after the addition is 1 wt% to 40 wt%, more preferably 2 wt% to 30 wt%, still more preferably 3 wt%. % To 20 wt%.

  In addition, an additive for promoting orientation may be added to the compound 12 in order to improve the degree of orientation in a magnetic field orientation step performed later. As the additive for promoting the orientation, for example, a hydrocarbon-based additive is used, and it is particularly preferable to use an additive having polarity (specifically, an acid dissociation constant pKa of less than 41). Moreover, the addition amount of the additive depends on the particle diameter of the magnet powder, and it is necessary to increase the addition amount as the particle diameter of the magnet powder is smaller. The specific addition amount is 0.1 part to 10 parts, more preferably 1 part to 8 parts, with respect to the magnet powder. The additive added to the magnet powder adheres to the surface of the magnet particles and has a role of assisting the rotation of the magnet particles in the magnetic field orientation process described later. As a result, orientation is easily performed when a magnetic field is applied, and the easy magnetization axis directions of the magnet particles can be aligned in the same direction (that is, the degree of orientation can be increased). In particular, when a binder is added to the magnet powder, since the binder is present on the particle surface, the frictional force at the time of orientation is increased and the orientation of the particles is lowered, so that the effect of adding the additive is further increased.

  The binder is added in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, or He gas. The mixing of the magnet powder and the binder is performed, for example, by putting the magnet powder and the binder into a stirrer and stirring with the stirrer. In addition, heating and stirring may be performed to promote kneading properties. The mixing of the magnet powder and the binder is preferably performed in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, or He gas. In particular, when the magnet powder is pulverized by a wet method, the binder is added to the solvent without kneading the magnet powder from the solvent used for pulverization, and then the solvent is volatilized. It is good also as a structure to obtain.

  Subsequently, a green sheet is created by forming the compound 12 into a sheet shape. In particular, in hot melt coating, the compound 12 is heated to melt the compound 12 to form a fluid, and then the coating is applied on the support substrate 13 such as a separator. Then, the long sheet-like green sheet 14 is formed on the support base material 13 by heat dissipation and solidifying. The temperature at which the compound 12 is heated and melted varies depending on the type and amount of the binder used, but is 50 to 300 ° C. However, the temperature needs to be higher than the melting point of the binder to be used. When slurry coating is used, magnet powder and binder (additional additives may be added) are dispersed in a large amount of solvent, and the slurry is coated on a support substrate 13 such as a separator. Work. Thereafter, the long sheet-like green sheet 14 is formed on the support substrate 13 by drying and volatilizing the solvent.

  Here, as the coating method of the melted compound 12, it is preferable to use a method having excellent layer thickness controllability such as a slot die method and a calendar roll method. In particular, in order to achieve high thickness accuracy, a die method or comma coating method that is particularly excellent in layer thickness controllability (that is, a method capable of applying a high-accuracy thickness layer on the surface of a substrate). It is desirable to use For example, in the slot die method, coating is performed by extruding a heated compound 12 in a fluid state by a gear pump and inserting the compound 12 into a die. In the calendar roll method, a certain amount of the compound 12 is charged into the gap between the two heated rolls, and the compound 12 melted by the heat of the roll is applied onto the support base 13 while rotating the roll. Moreover, as the support base material 13, for example, a silicone-treated polyester film is used. Furthermore, it is preferable to sufficiently defoam the film so that bubbles do not remain in the spreading layer by using an antifoaming agent or performing heating vacuum defoaming. In addition, the green sheet is formed on the support substrate 13 by molding the compound 12 melted by extrusion molding or injection molding into a sheet shape and extruding the support substrate 13 instead of coating on the support substrate 13. 14 may be formed.

  In the process of forming the green sheet 14 by the slot die method, the sheet thickness of the green sheet 14 after coating is measured, and the gap D between the die 15 and the support base 13 is feedback-controlled based on the measured value. desirable. Further, the fluctuation of the amount of the fluid compound 12 supplied to the die 15 is reduced as much as possible (for example, suppressed to fluctuation of ± 0.1% or less), and the fluctuation of the coating speed is reduced as much as possible (for example, ± 0. It is desirable to suppress the fluctuation to 1% or less. Thereby, it is possible to further improve the thickness accuracy of the green sheet 14. The thickness accuracy of the formed green sheet 14 is within ± 10%, more preferably within ± 3%, and even more preferably within ± 1% with respect to the design value (for example, 1 mm). In the other calendar roll method, it is possible to control the transfer film thickness of the compound 12 onto the support base 13 by similarly controlling the calendar conditions based on the actually measured values.

  The set thickness of the green sheet 14 is desirably set in the range of 0.05 mm to 20 mm. When the thickness is less than 0.05 mm, the productivity must be reduced because multiple layers must be stacked.

  Next, the magnetic field orientation of the green sheet 14 formed on the support base material 13 by the hot melt coating described above is performed. Specifically, the green sheet 14 is first softened by heating the green sheet 14 that is continuously conveyed together with the support base material 13. Specifically, the green sheet 14 is softened until the viscosity becomes 1 to 1500 Pa · s, more preferably 1 to 500 Pa · s. Thereby, the magnetic field orientation can be appropriately performed.

  In addition, although the temperature and time at the time of heating the green sheet 14 change with kinds and quantity of a binder to be used, they are 100-250 degreeC and 0.1 to 60 minutes, for example. However, in order to soften the green sheet 14, it is necessary to set the temperature to be equal to or higher than the glass transition point or melting point of the binder used. As a heating method for heating the green sheet 14, for example, there are a heating method using a hot plate and a heating method using a heat medium (silicone oil) as a heat source. Next, magnetic field orientation is performed by applying a magnetic field to the in-plane direction and the length direction of the green sheet 14 softened by heating. The strength of the applied magnetic field is 5000 [Oe] to 150,000 [Oe], preferably 10,000 [Oe] to 120,000 [Oe]. As a result, the C axis (easy magnetization axis) of the magnet crystal included in the green sheet 14 is oriented in one direction. Note that the magnetic field may be applied in the in-plane direction and the width direction of the green sheet 14. Moreover, it is good also as a structure which orientates a magnetic field simultaneously with respect to the several green sheet 14. FIG.

  Furthermore, when applying a magnetic field to the green sheet 14, a configuration in which a magnetic field is applied at the same time as the heating process may be performed, or a magnetic field may be applied after the heating process and before the green sheet solidifies. It is good also as performing the process to perform. Moreover, it is good also as a structure which magnetic field orientates before the green sheet 14 apply | coated by hot-melt application solidifies. In that case, the heating step is not necessary.

  Next, the heating process and the magnetic field orientation process of the green sheet 14 will be described in more detail with reference to FIG. FIG. 6 is a schematic diagram showing a heating process and a magnetic field orientation process of the green sheet 14. In the example shown in FIG. 6, an example in which the magnetic field orientation process is performed simultaneously with the heating process will be described.

  As shown in FIG. 6, heating and magnetic field orientation on the green sheet 14 coated by the slot die method described above are performed on the long green sheet 14 in a state of being continuously conveyed by a roll. That is, an apparatus for performing heating and magnetic field orientation is disposed on the downstream side of the coating apparatus (die or the like), and is performed by a process continuous with the above-described coating process.

Specifically, the solenoid 25 is disposed on the downstream side of the die 15 and the coating roll 22 so that the transported support base material 13 and the green sheet 14 pass through the solenoid 25. Further, the hot plates 26 are arranged in a pair above and below the green sheet 14 in the solenoid 25. The green sheet 14 is heated by a pair of upper and lower hot plates 26 and an electric current is passed through the solenoid 25, so that the in-plane direction of the long green sheet 14 (that is, the sheet surface of the green sheet 14). A magnetic field in the longitudinal direction). Thereby, the continuously conveyed green sheet 14 is softened by heating, and a magnetic field is applied to the in-plane direction and the length direction (in the direction of arrow 27 in FIG. 6) of the softened green sheet 14. On the other hand, it becomes possible to orient a uniform magnetic field appropriately. In particular, the surface of the green sheet 14 can be prevented from standing upright by setting the direction in which the magnetic field is applied to the in-plane direction.
Moreover, it is preferable that the heat dissipation and solidification of the green sheet 14 performed after the magnetic field orientation is performed in a transported state. Thereby, the manufacturing process can be made more efficient.

  When the magnetic field orientation is performed in the in-plane direction and the width direction of the green sheet 14, a pair of magnetic field coils are arranged on the left and right sides of the green sheet 14 that is conveyed instead of the solenoid 25. And it becomes possible to generate a magnetic field in the in-plane direction and the width direction of the long sheet-like green sheet 14 by passing a current through each magnetic field coil.

  Further, the magnetic field orientation can be set to a direction perpendicular to the surface of the green sheet 14. When the magnetic field orientation is performed in a direction perpendicular to the surface of the green sheet 14, for example, the magnetic field application device using a pole piece or the like is used. In the case where the magnetic field orientation direction is a direction perpendicular to the surface of the green sheet 14, it is preferable that the film is laminated on the surface on the opposite side of the green sheet 14 where the support base material 13 is laminated. Accordingly, it is possible to prevent the surface of the green sheet 14 from standing upside down.

  Further, instead of the heating method using the hot plate 26 described above, a heating method using a heat medium (silicone oil) as a heat source may be used.

  Here, when the green sheet 14 is formed from a liquid material having high fluidity such as slurry by a general slot die method or doctor blade method without using hot melt molding, a magnetic field gradient is generated. When the green sheet 14 is carried in, the magnetic powder contained in the green sheet 14 is attracted toward the stronger magnetic field, so that the slurry forming the green sheet 14 is closer to the liquid, that is, the thickness of the green sheet 14 is uneven. May occur. On the other hand, when the compound 12 is molded into the green sheet 14 by hot melt molding as in the present invention, the viscosity near room temperature reaches several tens of thousands to several hundred thousand Pa · s, and the magnetism when passing through the magnetic field gradient is reached. There is no powder slippage. Furthermore, the viscosity of the binder is lowered by being transported and heated in a uniform magnetic field, and uniform C-axis orientation is possible only by the rotational torque in the uniform magnetic field.

  Further, when the green sheet 14 is molded by a liquid material having high fluidity such as a slurry containing an organic solvent by a general slot die method or doctor blade method without using hot melt molding, the thickness exceeds 1 mm. When an attempt is made to produce a sheet, foaming due to vaporization of the organic solvent contained in the slurry or the like at the time of drying becomes a problem. Further, if the drying time is prolonged to suppress foaming, the magnet powder is settled, and accordingly, the density distribution of the magnet powder is biased with respect to the direction of gravity, which causes warping after firing. Therefore, in the molding from the slurry, the upper limit value of the thickness is substantially regulated, so it is necessary to mold the green sheet with a thickness of 1 mm or less and then laminate it. However, in such a case, the entanglement between the binders becomes poor, and delamination occurs in the subsequent binder removal step (calcination process), which causes a decrease in C-axis (easy magnetization axis) orientation, that is, residual magnetic flux density ( Br) decreases. On the other hand, when the compound 12 is molded into the green sheet 14 by hot melt molding as in the present invention, since it does not contain an organic solvent, even when a sheet having a thickness exceeding 1 mm is prepared, Concerns are resolved. And since the binder is in a sufficiently entangled state, there is no possibility of delamination in the debinding process.

  When applying a magnetic field to a plurality of green sheets 14 at the same time, for example, a plurality of (for example, six) green sheets 14 are continuously conveyed, and the stacked green sheets 14 pass through the solenoid 25. Configure to pass. As a result, productivity can be improved.

  And after performing the magnetic field orientation of the green sheet 14 by the method shown in FIG. 6, the green sheet 14 is punched or deformed to form a molded body having a desired shape. In addition, you may comprise so that magnetic field orientation may be performed with respect to the molded object after performing punching and a deformation | transformation instead of the green sheet 14. FIG. In the magnetic field orientation and molding, the magnetic field orientation and shaping are performed so as to realize the direction of the easy axis required for the final product (for example, radial orientation, polar anisotropic orientation, etc.).

  In the molding of the molded body, when one permanent magnet is manufactured, a plurality (three in the example shown in FIG. 5) of molded bodies 31 to 33 are molded as shown in FIG. In addition, each molded object 31-33 is comprised so that it may become a final product shape (for example, saddle shape shown in FIG. 1) by combining. In addition, the molded bodies 32 and 33 that are positioned at both ends of the saddle shape that requires a high coercive force when combined have a coercive force that is obtained after magnetization by adding Dy or Tb at the center. It is configured to be higher than the molded body 31 to be performed. On the contrary, the molded body 31 is higher than the molded bodies 32 and 33 with respect to the residual magnetic flux density. In addition, Dy or Tb is added by a grain boundary diffusion method in which Dy or Tb is attached to the surfaces of the molded bodies 32 and 33 and diffused therein by heat treatment, or powders corresponding to the main phase and the grain boundary phase are separately provided. The two-alloy method for manufacturing and mixing (dry blending) is used. In the case of using the 2-alloy method, it is necessary to separately manufacture a green sheet for forming the formed body 31 and a green sheet for forming the formed bodies 32 and 33.

  Further, as described above, the addition of Dy or Tb to the compacts 31 to 33 may be added only to the compacts 32 and 33 without being added to the compact 31, and the amount to be added may be changed. It may be configured. That is, you may comprise so that more Dy or Tb may be added with respect to the molded objects 32 and 33 rather than the molded object 31. FIG.

  Subsequently, the molded bodies 31 to 33 manufactured by the above process are joined and combined with each other by an adhesive, a plasticizer, thermocompression bonding, or the like, thereby forming an integrated molded body (hereinafter referred to as a combined body 34) that becomes a final product shape. ). For example, after apply | coating the mixture of PIB and toluene to the joint surface of the molded bodies 31-33, the molded bodies 31-33 are joined by heating and pressurizing. In addition, in the manufacturing method which concerns on this invention, since the green body shaping | molding which added the binder to the magnet powder is used, compared with the case where general compacting is used, it becomes possible to join the molded bodies appropriately. Moreover, it is good also as a structure which does not perform the joining process of the molded objects 31-33 before sintering. Even in that case, for example, the adjacent molded bodies 31 to 33 can be joined to each other in the sintering process, and the integral permanent magnet 1 can be manufactured.

  Further, the remaining part of the green sheet 14 generated by the step of forming the molded bodies 31 to 33 can be reused as the melted compound 12 by heating to the melting point or higher of the binder. As a result, the reused remaining portion is reproduced as a part of the green sheet 14. Therefore, even when it is molded into a complicated shape, the yield is not reduced.

  Subsequently, a non-oxidizing atmosphere (particularly hydrogen atmosphere or hydrogen and inert in the present invention) in which the bonded body 34 is pressurized to atmospheric pressure, or a pressure higher or lower than atmospheric pressure (for example, 1.0 Pa or 1.0 MPa). The calcination treatment is performed by maintaining the binder decomposition temperature for several hours to several tens of hours (for example, 5 hours) in a mixed gas atmosphere). The calcining process may be performed on the molded bodies 31 to 33 before being bonded to the bonded body 34. In the case of performing in a hydrogen atmosphere, for example, the supply amount of hydrogen during calcination is 5 L / min. By performing the calcination treatment, an organic compound such as a binder can be decomposed into a monomer by a depolymerization reaction or the like and scattered to be removed. That is, so-called decarbonization that reduces the amount of carbon in the bonded body 34 is performed. The calcining treatment is performed under the condition that the carbon content in the bonded body 34 is 2000 ppm or less, more preferably 1000 ppm or less. As a result, the entire bonded body 34 can be densely sintered by the subsequent sintering process, and the residual magnetic flux density and coercive force are not reduced. Moreover, when performing the pressurization conditions at the time of performing the calcining process mentioned above by the pressure higher than atmospheric pressure, it is desirable to set it as 15 Mpa or less. In addition, if the pressurizing condition is a pressure higher than atmospheric pressure, more specifically 0.2 MPa or more, the effect of reducing the carbon amount can be expected.

  The binder decomposition temperature is determined based on the analysis results of the binder decomposition product and decomposition residue. Specifically, a temperature range is selected in which decomposition products of the binder are collected, decomposition products other than the monomers are not generated, and products due to side reactions of the remaining binder components are not detected even in the analysis of the residues. Although it varies depending on the type of the binder, it is set to 200 ° C to 900 ° C, more preferably 400 ° C to 600 ° C (for example, 450 ° C).

  In the calcining process, it is preferable to reduce the rate of temperature rise compared to the case of performing general magnet sintering. Specifically, the temperature rising rate is set to 2 ° C./min or less (for example, 1.5 ° C./min). Therefore, when performing the calcining treatment, as shown in FIG. 7, the temperature is increased at a predetermined temperature increase rate of 2 ° C./min or less, and after reaching a preset temperature (binder decomposition temperature), The calcination treatment is performed by holding at the set temperature for several hours to several tens of hours. By reducing the rate of temperature increase in the calcination treatment as described above, the carbon in the bonded body 34 is not removed rapidly but is removed stepwise, so that the density of the sintered permanent magnet is increased ( That is, it is possible to reduce the air gap in the permanent magnet. And if a temperature increase rate shall be 2 degrees C / min or less, the density of the permanent magnet after sintering can be made 95% or more, and a high magnet characteristic can be anticipated.

Further, the dehydrogenation process may be performed by holding the bonded body 34 calcined by the calcining process in a vacuum atmosphere. Dehydrogenation process, a calcination process NdH 3 in conjugate 34 produced by _(activity Univ), NdH 3 _(activity Univ) → NdH 2 by gradually changed to _(activity small) The activity of the conjugate 34 activated by the calcination treatment is reduced. Thereby, even when the bonded body 34 calcined by the calcining process is subsequently moved to the atmosphere, Nd is prevented from being combined with oxygen, and the residual magnetic flux density and coercive force are reduced. There is no. Moreover, the effect of returning the structure of the magnet crystals from NdH ₂ etc. to _Nd 2 _{Fe 14} B structure can be expected.

  Then, the sintering process which sinters the conjugate | bonded body 34 calcined by the calcining process is performed. Thereby, the molded bodies 31 to 33 are sintered together, and a sintered body having a state in which the plurality of molded bodies 31 to 33 after sintering are combined is manufactured. As a method of sintering the bonded body 34, pressureless sintering in a vacuum, uniaxial pressure sintering for sintering in a uniaxially pressurized state, and sintering in a state of being biaxially pressurized. There are two-axis pressure sintering, isotropic pressure sintering for sintering in an isotropically pressurized state, and the like. For example, uniaxial pressure sintering is used in which the bonded body 34 is sintered in a state where the bonded body 34 is pressed in a direction crossing the bonding surfaces of the molded bodies 31 to 33. Examples of pressure sintering include hot press sintering, hot isostatic pressing (HIP) sintering, ultra-high pressure synthetic sintering, gas pressure sintering, and discharge plasma (SPS) sintering. . However, it is preferable to use SPS sintering that can be uniaxially pressurized and sintered by current sintering. In addition, when sintering by SPS sintering, a pressurization value shall be 0.01MPa-100MPa, it shall be raised to 940 degreeC by 10 degreeC / min in a vacuum atmosphere of several Pa or less, and it shall hold | maintain for 5 minutes after that. Is preferred. Then, it is cooled and heat-treated again at 300 ° C. to 1000 ° C. for 2 hours.

  Thereafter, the sintered body is magnetized along the C axis. As a result, the permanent magnet 1 can be manufactured. For magnetizing the permanent magnet 1, for example, a magnetizing coil, a magnetizing yoke, a condenser magnetizing power supply device or the like is used. The permanent magnet 1 may be magnetized after being arranged on the rotor of the rotating electrical machine.

  When the permanent magnet 1 manufactured by the above manufacturing method is installed in the rotor 2 as shown in FIG. 3, the permanent magnet 1 has a high coercive force in the regions 4 located at both ends along the circumferential direction of the rotor. . In the region 3 near the center, the coercive force is lower than that in the region 4, but the residual magnetic flux density is high. Therefore, it is possible to manufacture the permanent magnet 1 that has a high coercive force at a location where a high coercive force is required and also prevents a decrease in the residual magnetic flux density.

As described above, in the permanent magnet 1 and the method for manufacturing the permanent magnet 1 according to the present embodiment, the compound 12 is generated by pulverizing the magnet raw material into magnet powder and mixing the pulverized magnet powder and the binder. . And the green sheet 14 which shape | molded the produced | generated compound 12 in the sheet form is produced. Thereafter, a plurality of molded bodies 31 to 33 are molded from the molded green sheet 14 and sintered together in a state where the molded bodies 31 to 33 are combined, so that the required permanent magnet is manufactured. The permanent magnet 1 in which the plurality of molded bodies 31 to 33 are combined in a manner corresponding to the magnetic force is manufactured. As a result, it is possible to configure so as to improve only the coercive force of a necessary portion, not the entire permanent magnet, by combining a plurality of molded bodies. Therefore, the state in which the permanent magnet retains the function as a magnet (that is, a state in which a demagnetizing field is generated by passing a current through the stator, or a coercive force higher than a reverse magnetic field can be maintained even if the temperature is increased by eddy current). Thus, it is possible to prevent the residual magnetic flux density from being reduced. In particular, the effect becomes large in a large-sized permanent magnet used for a rotary electric machine of an elevator or a wind power generator.
Further, since the permanent magnet finally becomes a unitary combined body, when the permanent magnet is arranged in the rotor of the rotating electrical machine, the rotor is different from the case where the permanent magnets having different coercive forces are arranged side by side. Assembling accuracy can be improved. As a result, it is possible to prevent displacement of the permanent magnet from the design position, and to realize high output, high efficiency, and low torque ripple of the rotating electrical machine.
Moreover, since it manufactures by collectively sintering in the state which combined the some molded object, compared with the case where a several molded object is combined after sintering, the highly accurate process after sintering becomes unnecessary. That is, if the molded body is combined after being sintered, the molded body is contracted or deformed with the sintering, so that it is necessary to combine them after correcting them. If sintering is performed after combining a plurality of molded bodies, those steps are not required, and an increase in manufacturing cost can be suppressed.
In addition, the position where a high coercive force is required is combined so that a molded body having a high coercive force is positioned after magnetization. Can be raised. On the other hand, it is possible to prevent the residual magnetic flux density from being reduced by giving priority to the residual magnetic flux density over the coercive force at a location where a high coercive force is not required in the permanent magnet.
Moreover, since it combines by bonding a some molded object by an adhesive, a plasticizer, and thermocompression bonding, it becomes possible to join the molded object before sintering mutually appropriately.
In addition, since the content of Dy or Tb varies depending on the molded body, the target to which Dy or Tb is added (or added in large quantities) can be limited to only the necessary molded body, and the amount of Dy or Tb used can be reduced. It becomes. In particular, when Dy or Tb is added by the grain boundary diffusion method, the size of the compact to be added becomes small, so that Dy and Tb can be appropriately diffused into the magnet. As a result, the coercive force of the permanent magnet can be appropriately improved even with a large permanent magnet.
Furthermore, since a molded body is formed by molding a mixture in which magnet powder and a binder are mixed, it is possible to appropriately join the molded bodies as compared with the case where conventional compacting or the like is used. Moreover, compared with the case where compacting etc. are used, a magnet particle does not rotate after orientation and it becomes possible to improve the degree of orientation. In addition, when magnetic field orientation is performed on a mixture of magnet powder and binder, the number of current turns can be used, so that a large magnetic field strength can be ensured when performing magnetic field orientation, and a long time can be obtained with a static magnetic field. Therefore, a high degree of orientation with little variation can be realized. Furthermore, the realization of high orientation with little variation leads to a reduction in variation in shrinkage due to sintering. That is, the uniformity of the product shape after sintering can be ensured. As a result, the burden on external processing after sintering is reduced.

In addition, this invention is not limited to the said Example, Of course, various improvement and deformation | transformation are possible within the range which does not deviate from the summary of this invention.
For example, the pulverization conditions, kneading conditions, molding conditions, magnetic field orientation process, calcination conditions, sintering conditions, etc. of the magnet powder are not limited to the conditions described in the above examples. For example, in the above embodiment, the magnet raw material is pulverized by wet pulverization using a bead mill, but may be pulverized by dry pulverization using a jet mill. Moreover, as long as the atmosphere at the time of calcination is a non-oxidizing atmosphere, the atmosphere may be other than a hydrogen atmosphere (for example, a nitrogen atmosphere, a He atmosphere, or an Ar atmosphere). Moreover, you may abbreviate | omit a calcination process. In that case, decarbonization is performed during the sintering process.

  Moreover, in the said Example, in order to change the value of the coercive force for every some molded object 31-33, it is set as the structure which changes content of Dy or Tb for every molded object, but magnetic anisotropy is more than Nd. If it is a big element, it is good also as a structure which changes content of another element. For example, it is good also as a structure which changes content of Pr and Ho. Moreover, it is good also as a structure which changes content of the other element (For example, Al, Ti, V, Mo, Er, Cu) which can anticipate the improvement of a coercive force by adding. Furthermore, as a method for improving the coercive force, in addition to adding a metal, it is possible to make the crystal structure of the magnet a single domain structure.

  Moreover, in the said Example, although it is set as the structure which forms the final product shape by couple | bonding the three molded bodies 31-33, the number of the molded object used as coupling | bonding object is good also as 2 pieces or 4 pieces or more. .

  In the above embodiment, calcining is performed in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas after molding the magnet powder. However, the magnet powder before molding is calcined and calcined. It is good also as manufacturing a permanent magnet by shape | molding the magnetic powder which is a body into a molded object, and performing sintering after that. With such a configuration, since the powdered magnet particles are calcined, the surface area of the magnet to be calcined is increased compared to the case of calcining the molded magnet particles. can do. That is, the amount of carbon in the calcined body can be reduced more reliably. However, in order to thermally decompose the binder by calcining, it is desirable to perform calcining after molding.

  In the present invention, the Nd—Fe—B system magnet has been described as an example, but other magnets (for example, a samarium system cobalt magnet, an alnico magnet, a ferrite magnet, etc.) may be used. Further, in the present invention, the Nd component is larger than the stoichiometric composition in the present invention, but it may be stoichiometric.

DESCRIPTION OF SYMBOLS 1 Permanent magnet 2 Rotor 11 Bead mill 12 Compound 13 Support base material 14 Green sheet 15 Die 25 Solenoid 26 Hotplate 31-33 Molded body 34 Combined body

Claims (12)

It is manufactured by combining a plurality of molded bodies having different coercive force values after magnetization, and simultaneously sintering the plurality of combined molded bodies,
A permanent magnet comprising a plurality of sintered compacts bonded together.   2. The permanent magnet according to claim 1, wherein the plurality of molded bodies are combined in a manner corresponding to a coercive force required for a manufactured permanent magnet.   3. The permanent magnet according to claim 2, wherein the plurality of compacts are combined such that the compacts having a high coercive force after magnetization are located at positions where high coercive force is required. .   The permanent magnet according to any one of claims 1 to 3, wherein the plurality of molded bodies are combined by being bonded to each other by an adhesive, a plasticizer, and thermocompression bonding.   The permanent magnet according to any one of claims 1 to 4, wherein the plurality of compacts have different contents of Dy or Tb depending on the compacts.   6. The permanent magnet according to claim 1, wherein the molded body is formed by molding a mixture in which pulverized magnet powder and a binder are mixed. Crushing magnet raw material into magnet powder;
Forming a plurality of molded bodies by molding the pulverized magnet powder; and
By combining a plurality of the molded bodies to obtain a combined body in which the plurality of molded bodies are combined;
Holding the combined body at a firing temperature to sinter a plurality of the compacts together;
Magnetizing the combined body after sintering, and
The method for producing a permanent magnet, wherein the plurality of compacts have different coercive force values after magnetization.   The method for producing a permanent magnet according to claim 7, wherein, in the step of obtaining the combined body, the plurality of molded bodies are combined in a manner corresponding to a coercive force required for the permanent magnet after production.   9. The manufacturing of the permanent magnet according to claim 8, wherein in the step of obtaining the combined body, the molded body having a high coercive force is positioned so as to be positioned at a position where a high coercive force is required. Method.   10. The permanent magnet according to claim 7, wherein in the step of obtaining the bonded body, a plurality of the molded bodies are combined by bonding with an adhesive, a plasticizer, and thermocompression bonding. Production method.   The method for producing a permanent magnet according to any one of claims 7 to 10, wherein the plurality of compacts have different contents of Dy or Tb depending on the compacts.   The step of forming the formed body includes forming the formed body by forming a mixture in which the pulverized magnet powder and a binder are mixed. The manufacturing method of the permanent magnet of description.

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