JP2011019401A - Method of manufacturing permanent magnet segment for permanent magnet rotating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnet that is free from decrease in residual magnetic flux density of a permanent magnet suitable for a permanent magnet rotating machine and, has high-coercive force.SOLUTION: In the permanent magnet rotating machine, a rotor with a plurality of permanent magnet segments attached to a side of a rotor core, and a stator with a winding wound around a stator core having a plurality of slots, are arranged via a void. An edge of the permanent magnet is thinner than a central part. The permanent magnet is a sintered magnet composed of an R-Fe-B composition. While powder, which is selected from an oxide of R, a fluoride of R, an acid fluoride of R(wherein, R, R, R, and Rare rare-earth elements), exists on a surface of the magnet, heat treatment is applied to the magnet and the powder at a sintering temperature of the magnet or below in a vacuum or in inert gas. The coercive force at the edge of the permanent magnet is higher than that at the central part in the method of manufacturing the permanent magnet segment for the permanent magnet rotating machine.

Description

  The present invention relates to a method of manufacturing a permanent magnet segment for a permanent magnet rotating machine made of an R-Fe-B permanent magnet having an increased coercive force while suppressing a reduction in residual magnetic flux density of a sintered magnet body, and in particular, cogging. The present invention relates to a method for manufacturing a permanent magnet segment for a permanent magnet rotating machine, which is composed of a magnet having a thin magnet end for the purpose of torque reduction and is optimal for an FA motor, an electric power steering motor, or the like.

  Nd-Fe-B permanent magnets are increasingly used because of their excellent magnetic properties. In recent years, in the field of rotating machines such as motors and generators, permanent magnet rotating machines using Nd-Fe-B based permanent magnets have been developed as devices become lighter, shorter, more powerful, and save energy. The permanent magnet in the rotating machine is exposed to a high temperature due to the heat generated by the winding and the iron core, and is in a state where it is very easily demagnetized by the demagnetizing field from the winding. For this reason, there is a demand for Nd—Fe—B sintered magnets that have a coercive force that is an index of heat resistance and demagnetization resistance at a certain level or higher and that has as high a residual magnetic flux density as an index of the magnitude of magnetic force.

The increase in the residual magnetic flux density of the Nd—Fe—B based sintered magnet has been achieved by increasing the volume fraction of the Nd ₂ Fe ₁₄ B compound and improving the degree of crystal orientation, and various processes have been improved so far. Regarding the increase in coercive force, among the various approaches such as refinement of crystal grains, use of a composition alloy with an increased Nd amount, or addition of an effective element, the most common method at present is A composition alloy in which a part of Nd is substituted with Dy or Tb is used. By substituting Nd of the Nd ₂ Fe ₁₄ B compound with these elements, the anisotropic magnetic field of the compound increases and the coercive force also increases. On the other hand, substitution with Dy or Tb reduces the saturation magnetic polarization of the compound. Therefore, as long as the coercive force is increased by the above method, a decrease in residual magnetic flux density is inevitable.

In the Nd-Fe-B magnet, the coercive force is the magnitude of the external magnetic field generated by the nucleus of the reverse magnetic domain at the crystal grain interface. The structure of the crystal grain interface strongly influences the nucleation of the reverse magnetic domain, and the disorder of the crystal structure in the vicinity of the interface causes the disorder of the magnetic structure and promotes the generation of the reverse magnetic domain. In general, it is considered that a magnetic structure from a crystal interface to a depth of about 5 nm contributes to an increase in coercive force (Non-Patent Document 1: K.-D. Durst and H. Kronmuller, “ THE COERCIVE FIELD OF SINTERED AND MELT-SPUN NdFeB MAGNETS ", Journal of Magnetics and Magnetic Materials 68 (1987) 63-75). The present inventors concentrated a small amount of Dy and Tb only in the vicinity of the crystal grain interface, and increased the anisotropy magnetic field only in the vicinity of the interface, thereby increasing the coercive force while suppressing the decrease in the residual magnetic flux density. (Patent Document 1: Japanese Patent Publication No. 5-31807). Furthermore, a manufacturing method has been established in which an Nd ₂ Fe ₁₄ B compound composition alloy and an alloy rich in Dy or Tb are separately manufactured and then mixed and sintered (Patent Document 2: JP-A-5-21218). In this method, an alloy rich in Dy or Tb becomes a liquid phase during sintering and is distributed so as to surround the Nd ₂ Fe ₁₄ B compound. As a result, Nd and Dy or Tb are replaced only near the grain boundary of the compound, and the coercive force can be effectively increased while suppressing a decrease in the residual magnetic flux density.

However, in the above method, since two kinds of alloy fine powders are mixed and sintered at a high temperature of 1,000 to 1,100 ° C., Dy or Tb is not only the interface of Nd ₂ Fe ₁₄ B crystal grains but also the inside. Easy to diffuse. From the observation of the structure of the actually obtained magnet, it is diffused from the interface to a depth of about 1 to 2 μm at the grain boundary surface layer portion, and when the diffused region is converted into a volume fraction, it becomes 60% or more. Further, the longer the diffusion distance into the crystal grain, the lower the concentration of Dy or Tb in the vicinity of the interface. Although it is effective to lower the sintering temperature in order to suppress excessive diffusion into the crystal grains as much as possible, this cannot be a practical method because it simultaneously inhibits densification by sintering. The method of sintering at a low temperature while applying stress by hot pressing or the like has a problem that the densification is possible but the productivity is extremely lowered.

  On the other hand, after processing the sintered magnet to a small size, Dy and Tb are deposited on the magnet surface by sputtering, and the magnet is heat-treated at a temperature lower than the sintering temperature to diffuse Dy and Tb only at the grain boundary part. A method for increasing the coercive force has been reported (Non-Patent Document 2: K. T. Park, K. Hiraga and M. Sagawa, "Effect of Metal-Coating and Conscientious Heat Treatment on Co-Circency of T Sintered Magnets ", Proceedings of the Sixteen International Works on Rare-Earth Magnets and Ther Application , Sendai, p. 257 (2000), Non-Patent Document 3: Kenichi Machida, Naoshi Kawamata, Toshiharu Suzuki, Masahiro Ito, Takashi Horikawa, “Granular boundary modification and magnetic properties of Nd—Fe—B based sintered magnet”, (Powder Metallurgy Association Abstracts, 2004 Spring Meeting, p. 202). In this method, since Dy and Tb can be concentrated more efficiently at the grain boundary, the coercive force can be increased with almost no decrease in the residual magnetic flux density. Moreover, since the amount of Dy and Tb supplied increases as the specific surface area of the magnet increases, that is, the magnet body decreases, this method is applicable only to small or thin magnets. However, there has been a problem that the productivity is poor when depositing a metal film by sputtering or the like.

  For example, a radial air gap type permanent magnet rotating machine as shown in FIG. 1 is used for the AC servo motor. The permanent magnet rotating machine includes a rotor 3 having a magnet (permanent magnet segment) 2 attached to the surface of a rotor core (rotor core) 1, and a stator core having a plurality of slots arranged via gaps (gap). (Stator core) 11 and a stator 13 composed of a coil 12 wound around a tooth. In the case of the permanent magnet rotating machine shown in FIG. 1, the number of poles of the permanent magnet is 6, the number of teeth is 9, and the arrow in the permanent magnet indicates the direction of magnetization of the permanent magnet. Permanent magnets are oriented in a parallel magnetic field, and the easy magnetization direction is parallel to the center line of the magnet. In addition, the coil is wound around the teeth with concentrated winding, and a U-phase V-phase W-phase three-phase Y-connection is made. The black circle mark of the coil means that the coil winding direction is in front, and the x mark means that the coil winding direction is in the back.

  The torque of an AC servo motor or the like that requires high-accuracy torque control must have a small pulsation. Therefore, when the permanent magnet rotates, the cogging torque (torque in a state where no current flows through the coil) or the coil due to the change in the magnetic flux distribution of the air gap is determined based on the positional relationship between the stator slot and the permanent magnet. It is not preferable that torque ripple occurs when driven by passing an electric current. Torque ripple causes noise as well as poor controllability. As a method of reducing the cogging torque, the end shape of the permanent magnet as shown in FIG. 1 is made thinner than the center portion. According to this method, the magnetic flux distribution at the end of the permanent magnet, which is the switching portion of the magnetic pole where the change of the magnetic flux distribution is large, becomes smooth, and the cogging torque can be reduced.

  When a current is passed through the coil, it is magnetized in the direction of the arrow written on the stator core portion, causing the rotor to rotate counterclockwise. At this time, the field behind the rotation direction of the permanent magnet segment (the portion surrounded by a circle in FIG. 1) is in a situation where it is easy to demagnetize because the field is in the opposite direction to the magnetization of the permanent magnet. Demagnetization not only lowers the drive torque, but also raises the problem of increasing the cogging torque due to partial magnetic field inhomogeneity.

  In particular, the thickness of the end portion of the eccentric permanent magnet is very thin and is easily demagnetized. Here, the reason why demagnetization is easy when the magnet thickness is thin will be described. The magnitude of demagnetization is determined by the magnitude of the coercive force and the demagnetizing field at the operating temperature of the permanent magnet. The smaller the coercivity and the larger the demagnetizing field, the easier it is to demagnetize. The demagnetizing field is the sum of the self-demagnetizing field generated by the magnetization of the permanent magnet and the reverse magnetic field from the outside, and the self-demagnetizing field is larger as the magnetization direction thickness of the permanent magnet is thinner.

  For this reason, there is a method of using a permanent magnet with a low coercive force but a high residual magnetic flux density for a portion that is not demagnetized, and a composite magnet integrally molded with a permanent magnet with a low residual magnetic flux density but a high coercive force that is easily demagnetized. (Patent Document 3: Japanese Patent Application Laid-Open No. 61-139252). However, in this method, since the reduction of the residual magnetic flux density of the permanent magnet with increased coercive force is inevitable, the output of the motor is reduced.

Japanese Patent Publication No. 5-31807 JP-A-5-21218 JP-A-61-139252

K. -D. Durst and H.M. Kronmuller, “THE COERCIVE FIELD OF SINTERED AND MELT-SPUN NdFeB MAGNETS”, Journal of Magnetics and Magnetic Materials 68 (1987) 63-75. K. T. T. et al. Park, K.M. Hiraga and M.M. Sagawa, "Effect of Metal-Coating and Consecutive Heat Treatment on Coercivity of Thin Nd-Fe-B Sintered Magnets", Proceedings of the Sixteen International Workshop on Rare-Earth Magnets and Their Applications, Sendai, p. 257 (2000) Kenichi Machida, Naoshi Kawamata, Toshiharu Suzuki, Masahiro Ito, Takashi Horikawa, “Granular boundary modification and magnetic properties of Nd—Fe—B based sintered magnets”, Proceedings of the Powder and Powder Metallurgy Association, Spring Meeting of 2004, p. 202

  The present invention has been made in view of the above-described conventional problems, and has a large coercive force without lowering the residual magnetic flux density of a permanent magnet suitable for a permanent magnet rotating machine, and particularly a large coercive force at the end of the permanent magnet. An object of the present invention is to provide a method for producing a permanent magnet segment for a permanent magnet rotating machine composed of a Fe-B sintered magnet (R is one or more elements selected from rare earth elements including Y and Sc). To do.

The inventors of the present invention have compared R ¹ -Fe-B sintered magnets represented by Nd—Fe—B based sintered magnets with respect to R ² oxides, R ³ fluorides, and R ⁴ oxyfluorides. A state in which a powder containing one or more selected from the above (wherein R ^{1 to} R ⁴ are one or more selected from rare earth elements including Y and Sc, respectively) is present on the magnet surface It was found that R ² , R ^3, or R ⁴ contained in the powder was absorbed by the magnet body by heating at 1, and the coercive force could be increased while significantly suppressing the decrease in residual magnetic flux density. In this case, in particular, when R ³ fluoride or R ⁴ oxyfluoride is used, R ³ or R ⁴ is absorbed into the magnet body together with fluorine with high efficiency, the residual magnetic flux density is high, and the coercive force is large. It has been found that a magnet can be obtained.

That is, the present invention provides the following method for producing a permanent magnet segment for a permanent magnet rotating machine.
Claim 1:
A permanent magnet rotating machine in which a rotor in which a plurality of permanent magnet segments are attached to a side surface of a rotor core and a stator in which a winding is wound around a stator core having a plurality of slots are arranged with a gap therebetween. Both end portions in the width direction are thinner than the central portion, and the permanent magnet segment is made of a fired R ¹ —Fe—B composition (R ¹ is one or more selected from rare earth elements including Y and Sc). A method for producing a permanent magnet segment for a permanent magnet rotating machine, which is a magnetized body, comprising one or more selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride (R ² , R ³ , and R ⁴ are each one or two or more elements selected from rare earth elements including Y and Sc), and the magnet body and the powder The body of the magnet body By performing heat treatment in vacuum or inert gas at a temperature lower than the sintering temperature, the coercive force at both ends in the width direction is higher than the central part, and the difference HcJ between the central part and the end part is 30 kAm ⁻¹ or more. A method for producing a permanent magnet segment for a permanent magnet rotating machine, wherein an eccentric sintered magnet body is obtained.
Claim 2:
The manufacturing method of the permanent magnet segment of Claim 1 which obtains the eccentric sintered magnet body whose difference HcJ of the coercive force of a center part and an edge part is 30-500kAm < ^-1 >.
Claim 3:
The method of manufacturing a permanent magnet segment according to claim 1 or 2, wherein the magnet body to be heat-treated has a shape having a maximum portion dimension of 100 mm or less and a minimum dimension in the direction of magnetic anisotropy of 10 mm or less.
Claim 4:
4. The method of manufacturing a permanent magnet segment according to claim 1, wherein the magnet body has a C-shaped or D-shaped cross section.
Claim 5:
A permanent magnet segment is obtained by performing heat treatment in such a manner that a powder selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride is partially present on the surfaces of both ends in the width direction of the magnet. The method of manufacturing a permanent magnet segment according to any one of claims 1 to 4, wherein
Claim 6:
The abundance of the powder containing one or more selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride with respect to the surface of the magnet body is within a distance of 1 mm from the surface of the magnet body. The method for manufacturing a permanent magnet segment according to any one of claims 1 to 5, wherein an average occupancy is 10% by volume or more in a space surrounding the magnet body.
Claim 7:
Oxide of R ^2, fluoride of R ^3, any one of claims 1 to 6 average particle size of the powder containing one or more kinds selected from an acid fluoride of R ⁴ is 100μm or less The manufacturing method of the permanent magnet segment of description.
Claim 8:
A powder containing one or more selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride was dispersed in water or an organic solvent, and the magnet body was immersed in the resulting slurry. The method for producing a permanent magnet segment according to any one of claims 1 to 7, wherein the powder is allowed to exist on the surface of the magnet body by subsequent drying.

  The present invention provides a permanent magnet rotating machine suitable for a permanent magnet rotating machine, having no reduction in the residual magnetic flux density of the permanent magnet, having a large coercive force, particularly a large coercive force at the end of the permanent magnet, and being difficult to demagnetize even at high temperatures. can do.

It is sectional drawing explaining an example of the surface magnet structure type motor of 6 poles and 9 slots. (A)-(c) is sectional drawing explaining the magnet shape of this invention, respectively. It is a perspective view explaining the magnet shape of the Example and comparative example of this invention. It is sectional drawing explaining an example of the magnet body which apply | coated to the surface the powder containing 1 type, or 2 or more types chosen from R oxide, R fluoride, and R oxyfluoride. It is sectional drawing explaining the other example of the magnet body which apply | coated the powder containing the 1 type (s) or 2 or more types chosen from R oxide, R fluoride, and R oxyfluoride to the magnet end part surface.

Hereinafter, the present invention will be described in more detail.
The present invention relates to a method of manufacturing a permanent magnet segment for a permanent magnet rotating machine using a magnet having a large coercive force of a permanent magnet suitable for a permanent magnet rotating machine, particularly a magnet having a large coercive force at the end of the permanent magnet.

The rare earth permanent magnet segment used in the present invention is a columnar sintered magnet body having an R ¹ —Fe—B series composition (R ¹ is one or more selected from rare earth elements including Y and Sc), One or two types selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride, which are processed into the shape of an eccentric magnet whose thickness at both ends is thinner than the central portion in the width direction. In the state where the powder containing the above (R ² , R ³ , R ⁴ is one or more elements selected from rare earth elements including Y and Sc, respectively) is present on the surface of the magnet body, It is obtained by subjecting the body and powder to heat treatment in a vacuum or an inert gas at a temperature not higher than the sintering temperature of the magnet, and the coercive force at the end of the permanent magnet segment is higher than that at the center.

  Here, the R—Fe—B based sintered magnet body can be obtained by roughly pulverizing, finely pulverizing, forming, and sintering the mother alloy according to a conventional method.

In the present invention, R and R ¹ are both selected from rare earth elements including Y and Sc. R is mainly used for the obtained magnet body, and R ¹ is mainly used for the starting material. .

The mother alloy contains R ¹ , Fe, and B. R ¹ is one or more selected from rare earth elements including Y and Sc, specifically, Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er , Yb, and Lu, preferably Nd, Pr, and Dy. These rare earth elements including Y and Sc are preferably 10 to 15 atomic%, particularly 12 to 15 atomic% of the whole alloy, more preferably 10% by atom of Nd and Pr or any ^{one of} them in R ^1. As mentioned above, it is suitable to contain especially 50 atomic% or more. B is preferably contained in an amount of 3 to 15 atomic%, particularly 4 to 8 atomic%. In addition, Al, Cu, Zn, In, Si, P, S, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta, One or two or more kinds selected from W may be contained in an amount of 0 to 11 atomic%, particularly 0.1 to 5 atomic%. The balance is inevitable impurities such as Fe and C, N, and O, but Fe is preferably contained in an amount of 50 atomic% or more, particularly 65 atomic% or more. Further, a part of Fe, for example, 0 to 40 atomic%, particularly 0 to 15 atomic% of Fe may be substituted with Co.

The mother alloy can be obtained by melting a raw metal or alloy in a vacuum or an inert gas, preferably in an Ar atmosphere, and then casting it in a flat mold or a book mold, or by strip casting. Also, an alloy close to the R ₂ Fe ₁₄ B compound composition that is the main phase of this alloy and an R-rich alloy that becomes a liquid phase aid at the sintering temperature are separately prepared, and are weighed and mixed after coarse pulverization. A two alloy method is also applicable to the present invention. In this case, an alloy close to the main phase composition can be obtained by, for example, strip casting. However, for alloys close to the main phase composition, α-Fe is likely to remain depending on the cooling rate during casting and the alloy composition, and it is homogeneous as necessary for the purpose of increasing the amount of R ₂ Fe ₁₄ B compound phase. The process is applied. The conditions are heat treatment at 700 to 1,200 ° C. for 1 hour or more in vacuum or Ar atmosphere. In addition to the above casting method, a so-called liquid quenching method or strip casting method can be applied to the R-rich alloy serving as the liquid phase aid.

Further, in the pulverization step described below, at least one of R ¹ carbide, nitride, oxide and hydroxide, or a mixture or composite thereof is mixed with the alloy powder in the range of 0.005 to 5% by mass. It is also possible to do.

  The alloy is generally coarsely pulverized to 0.05 to 3 mm, particularly 0.05 to 1.5 mm. Brown mill or hydrogen pulverization is used for the coarse pulverization process, and hydrogen pulverization is preferable in the case of an alloy produced by strip casting. The coarse powder is usually finely pulverized to 0.2 to 30 μm, particularly 0.5 to 20 μm, for example, by a jet mill using high-pressure nitrogen. The fine powder is formed by a compression molding machine in a magnetic field and put into a sintering furnace. Sintering is usually performed at 900 to 1,250 ° C, particularly 1,000 to 1,100 ° C in a vacuum or an inert gas atmosphere.

The sintered magnet body obtained here contains 60 to 99% by volume, particularly preferably 80 to 98% by volume of a tetragonal R ₂ Fe ₁₄ B compound as a main phase, and the balance is 0.5 to 20% by volume. It consists of R-rich phase, 0 to 10% by volume of B-rich phase and unavoidable impurities, or at least one of carbides, nitrides, oxides and hydroxides by addition, or a mixture or composite thereof.

  The manufacturing method of the permanent magnet can be obtained by molding and sintering the alloy powder in a magnetic field as described above, or a grindstone, a cutting blade, a wire so that the obtained sintered block fits the permanent magnet motor. It is obtained by grinding using a saw or the like and further grinding in a shape where both ends in the width direction are thinner than the center. The shape is particularly preferably a C-shaped or D-shaped magnet shape having an arc, and the widthwise end portions of the permanent magnet are made thin as shown in FIGS. 2 (a) to 2 (c) and FIG. Reduce cogging torque. The thickness Tc of the central portion of the permanent magnet and the thickness Te of the end portion are not particularly limited, but Te / Tc is preferably 0.8 or less, more preferably 0 in order to reduce the cogging torque. 0.1 to 0.5, more preferably 0.1 to 0.4.

The size of the powder is not particularly limited. In the present invention, the powder contains one or more selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride present on the magnet surface. The amount of R ² , R ^3, or R ⁴ absorbed by the magnet body increases as the specific surface area of the magnet body increases, that is, as the size decreases, so the dimension of the maximum portion of the above shape (L or W in FIG. 3). ) Is 100 mm or less, preferably 50 mm or less, particularly preferably 20 mm or less, and the minimum dimension in the direction of magnetic anisotropy (Te in FIG. 3) is 10 mm or less, preferably 5 mm or less, particularly preferably 2 mm or less. It is preferable. More preferably, the dimension in the direction of magnetic anisotropy is 1 mm or less.

  The lower limit of the dimension of the maximum part and the dimension in the direction of magnetic anisotropy is not particularly limited and is appropriately selected, but the dimension of the maximum part of the shape is 0.1 mm or more, and the magnetic anisotropy The dimension in the converted direction is 0.05 mm or more.

As shown in FIG. 4, powder 22 containing one or more selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride is provided on the surface of the ground magnet body 20. To exist. R ² , R ³ , and R ⁴ are one or more selected from rare earth elements including Y and Sc, and each of R ² , R ³ , and R ^{4 is} 10 atom% or more, more preferably 20 atom%. As described above, it is particularly preferable to contain 40 atomic% or more of Dy or Tb. In this case, the powder containing fluoride and / or oxyfluoride of R ⁴ of the R ^3, R ³ and / or R ⁴ to 10 atomic% or more Dy and / or Tb is included, and R ³ and It is preferable from the object of the present invention that the total concentration of Nd and Pr in R ⁴ is lower than the total concentration of Nd and Pr in R ¹ .

  In this case, FIG. 4 is the one in which the powder 22 is present and the following absorption treatment is performed on the entire surface of the magnet body 20, but as shown in FIG. 5, at least one, preferably both The following absorption treatment may be performed with the powder 22 partially present on the surface including the upper edge of the width direction end. In addition, after the powder 22 is present on the entire surface of the magnet body 20 and the absorption treatment is performed, the powder 22 is partially present at least at one end, preferably only at both ends, and the absorption treatment is performed again. May be.

The higher the abundance ratio of the powder in the magnet surface space, the more R ² , R ^3, or R ⁴ is absorbed. Therefore, in order to achieve the effect of the present invention, the abundance ratio of the powder is 1 mm from the magnet surface. The average value in the space surrounding the inner magnet is preferably 10% by volume or more, and more preferably 40% by volume or more.

As a method for making the powder exist (powder processing method), for example, a fine powder containing one or more selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride is used as water or Examples include a method of dispersing in an organic solvent and immersing the magnet body in this slurry, followed by drying with hot air or vacuum, or natural drying. In addition, application by spraying is also possible. Whatever the specific method, it can be said that it can be processed very easily and in large quantities. The particle size of the fine powder affects the reactivity when the R ² , R ³ or R ⁴ component of the powder is absorbed by the magnet, and the smaller the particle, the greater the contact area involved in the reaction. In order to achieve the effect of the present invention, the average particle size of the existing powder is 100 μm or less, preferably 10 μm or less. The lower limit is not particularly limited, but is preferably 1 nm or more. The average particle diameter can be obtained as a mass average value D ₅₀ (that is, a particle diameter or a median diameter when the cumulative mass becomes 50%) using a particle size distribution measuring apparatus by a laser diffraction method, for example. .

Oxide of R ² in the present invention, fluoride of R ^3, and oxyfluoride of R ^4, preferably each _{^{R 2 2 O 3, R 3}} F 3, R 4 is a OF, other than this R ² O _n , R ³ F _n , R ⁴ O _m F _n (m, n are arbitrary positive numbers), or a part of R ² , R ³ , R ⁴ substituted or stabilized by a metal element, etc. , An oxide containing R ² and oxygen capable of achieving the effects of the present invention, a fluoride containing R ³ and fluorine, and an oxyfluoride containing R ⁴ , oxygen and fluorine.

In this case, the powder to be present on the magnet surface contains an oxide of R ² , a fluoride of R ^3, an oxyfluoride of R ⁴ , or a mixture thereof, in addition to R ⁵ (R ⁵ is Y and Sc). 1 type or 2 types or more selected from rare earth elements containing), carbides, nitrides, hydroxides, hydrides, or a mixture or composite thereof, and a fluoride of R ³ And / or when R ⁴ oxyfluoride is used, it may contain an oxide of R ⁵ . Furthermore, in order to promote the dispersibility of the powder and chemical / physical adsorption, fine powders such as boron, boron nitride, silicon, and carbon, and organic compounds such as stearic acid (fatty acid) can also be included. In order to achieve the effect of the present invention with high efficiency, the oxide of R ² , the fluoride of R ³ , the oxyfluoride of R ⁴ , or a mixture thereof is 10 mass% or more, preferably 20 More than mass% is contained. In particular, R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride as main components are 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass with respect to the whole powder. % Or more is recommended.

In a state where a powder composed of an oxide of R ² , a fluoride of R ^3, an oxyfluoride of R ⁴ , or a mixture thereof is present on the surface of the magnet, the magnet and the powder may be vacuum, argon (Ar), helium (He And the like (hereinafter, this treatment is referred to as absorption treatment). The absorption treatment temperature is lower than the sintering temperature of the magnet body. The reasons for limiting the treatment temperature are as follows.

That is, if the sintered magnet is processed at a temperature higher than the sintering temperature (referred to as T _S ° C), (1) the structure of the sintered magnet is altered and high magnetic properties cannot be obtained. The processing temperature cannot be maintained. (3) The diffused R diffuses not only into the crystal grain interface of the magnet but also into the interior, resulting in a decrease in residual magnetic flux density. Temperature or lower, preferably (T _S −10) ° C. or lower. In addition, although the minimum of temperature is selected suitably, it is 350 degreeC or more normally. Absorption treatment time is 1 minute to 100 hours. If it is less than 1 minute, the absorption treatment is not completed, and if it exceeds 100 hours, the structure of the sintered magnet is altered, and problems such as inevitable oxidation and evaporation of components adversely affect the magnetic properties. More preferably, it is 5 minutes to 8 hours, particularly 10 minutes to 6 hours.

By the absorption treatment as described above, R ² , R ³ or R ⁴ contained in the powder present on the magnet surface is concentrated in the rare earth-rich grain boundary phase component in the magnet, and this R ² , R ³ is concentrated. Alternatively, R ⁴ is substituted in the vicinity of the surface layer portion of the R ₂ Fe ₁₄ B main phase particle. In addition, when the powder contains R ³ fluoride or R ⁴ oxyfluoride, a part of the fluorine contained in the powder is absorbed in the magnet together with R ³ or R ^4. Significantly increases the supply from the R ³ or R ⁴ powder and the diffusion at the grain boundaries of the magnet.

The rare earth element contained in the oxide of R ² , the fluoride of R ^{3 and} the oxyfluoride of R ⁴ is one or more selected from the rare earth elements including Y and Sc. Since elements that have a particularly large effect of increasing crystal magnetic anisotropy are Dy and Tb, the rare earth elements contained in the powder preferably have a total ratio of Dy and Tb of 10 atomic% or more. is there. More preferably, it is 20 atomic% or more. Further, the total concentration of Nd and Pr in R ² , R ³ and R ⁴ is preferably lower than the total concentration of Nd and Pr in R ¹ .

  As a result of this absorption treatment, the coercive force of the R—Fe—B based sintered magnet is efficiently increased with little reduction in residual magnetic flux density.

  The absorption treatment is performed by, for example, putting a sintered magnet body into a slurry in which the powder is dispersed in water or an organic solvent, and performing a heat treatment with the powder adhered to the surface of the sintered magnet body. In this case, in the above-described absorption treatment, the magnets are covered with powder and the magnets are separated from each other, so that the magnets are not welded after the absorption treatment despite the heat treatment at a high temperature. Furthermore, since the powder does not adhere to the magnet after the heat treatment, it can be processed by putting a large amount of magnets in the heat treatment container, and the production method according to the present invention is excellent in productivity.

  Moreover, it is preferable to perform an aging treatment after the absorption treatment. The aging treatment is desirably less than the absorption treatment temperature, preferably 200 ° C. or more and 10 ° C. or less, more preferably 350 ° C. or more and 10 ° C. or less. The atmosphere is preferably in a vacuum or an inert gas such as Ar or He. The time for aging treatment is 1 minute to 10 hours, preferably 10 minutes to 5 hours, particularly 30 minutes to 2 hours.

In addition, at the time of grinding of the above-described sintered magnet body before the powder is present in the sintered magnet body, a water-based one is used as the coolant of the grinding machine, or the grinding surface is exposed to a high temperature during processing. In this case, an oxide film is likely to be formed on the surface to be ground, and this oxide film may hinder the absorption reaction of the R ² , R ³ or R ⁴ component from the powder to the magnet body. In such a case, an appropriate absorption treatment can be carried out by removing the oxide film by washing with one or more of alkali, acid or organic solvent, or by performing shot blasting.

  As alkali, potassium pyrophosphate, sodium pyrophosphate, potassium citrate, sodium citrate, potassium acetate, sodium acetate, potassium oxalate, sodium oxalate, etc., acids include hydrochloric acid, nitric acid, sulfuric acid, acetic acid, citric acid, As the organic solvent such as tartaric acid, acetone, methanol, ethanol, isopropyl alcohol and the like can be used. In this case, the alkali or acid can be used as an aqueous solution having an appropriate concentration that does not erode the magnet body.

  Furthermore, the surface layer of the sintered magnet body can be removed by shot blasting before the powder is present in the sintered magnet body.

  Further, the magnet subjected to the above-described absorption treatment or subsequent aging treatment can be washed with one or more of alkali, acid or organic solvent, or ground into a practical shape. Furthermore, plating or coating can be applied after such absorption treatment, aging treatment, washing or grinding.

  R-Fe-B sintered magnet with almost no reduction in residual magnetic flux density as a result of absorption treatment of Dy, Tb, etc., which are elements that are particularly effective in increasing the magnetocrystalline anisotropy from the surface of the sintered magnet body Since the coercive force is effectively increased, the amount of increase in the coercive force differs depending on the thickness of the sintered magnet body. That is, the coercive force of the end portion is more effectively enhanced in the sintered magnet body whose end portion shape is thinned.

  The permanent magnet material obtained as described above has a problem that it is easy to demagnetize because the end thickness is thin while the end thickness is suitable for low cogging torque. An increase in coercive force eliminates the problem of demagnetization, and it can be used for a permanent magnet rotating machine as a permanent magnet having a higher residual magnetic flux density, and a rotor in which a plurality of permanent magnet segments are attached to the side surface of the rotor core; It is possible to obtain a permanent magnet rotating machine in which a stator having a plurality of slots and a winding wound around a stator core are arranged with a gap. In this case, the permanent magnet rotating machine can be in a known manner except that the permanent magnet subjected to the above-described absorption treatment is used, and can be manufactured by a known method.

For example, a rotor including a rotor core yoke and a plurality of permanent magnets arranged on a side surface of the rotor core yoke at predetermined intervals so that polarities are alternately different in the circumferential direction of the rotor core yoke, and the rotation A stator core yoke arranged at a distance from the child, a salient pole magnetic pole opposed to the permanent magnet and arranged on the stator core yoke at equal intervals in the circumferential direction, and a three-phase connection concentratedly wound around the salient pole pole It can be obtained as a permanent magnet rotating machine including a stator including the armature winding that has been made.
The number of magnets used in the present invention is not particularly limited, but an even number of up to 100 magnets, preferably 4 to 36 magnets, are arranged so that the polarities are alternately different in the circumferential direction. ing.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to examples, but the content of the present invention is not limited thereto. In the following examples, the occupation ratio (existence ratio) of the magnet surface space by oxidation Dy or fluoride Dy was calculated from the increase in magnet mass after powder treatment and the true density of the powder substance.

[Examples 1-4 and Comparative Examples 1-3]
<Magnetic characteristics of examples and comparative examples>
Nd, Co, Al, Fe metal having a purity of 99% by mass or more and ferroboron are weighed in predetermined amounts and melted at high frequency in an Ar atmosphere, and this molten alloy is poured into a single copper roll in an Ar atmosphere by a so-called strip casting method. A thin plate-like alloy was used. The composition of the obtained alloy is 13.5 atomic% Nd, 1.0 atomic% Co, 0.5 atomic% Al, 5.8 atomic% B, and the balance Fe. Called. The alloy A was occluded with hydrogen and then heated to 500 ° C. while being evacuated to partially release hydrogen, so that a coarse powder of 30 mesh or less was obtained by so-called hydrogen pulverization. Further, Nd, Tb, Fe, Co, Al, Cu metal having a purity of 99% by mass or more and ferroboron were weighed in predetermined amounts, melted by high frequency in an Ar atmosphere, and then cast. The composition of the resulting alloy is Nd 20 atom%, Tb 10 atom%, Fe 24 atom%, B 6 atom%, Al 1 atom%, Cu 2 atom%, and Co remaining. Is referred to as Alloy B. Alloy B was coarsely pulverized to 30 mesh or less using a brown mill in a nitrogen atmosphere.

Subsequently, 90% by mass of the alloy A powder and 10% by mass of the alloy B powder were weighed and mixed for 30 minutes in a nitrogen-substituted V blender. This mixed powder was finely pulverized to a mass median particle size of 4 μm by a jet mill using high-pressure nitrogen gas. The obtained mixed fine powder was molded at a pressure of about 1 ton / cm ² while being oriented in a magnetic field of 15 kOe under a nitrogen atmosphere. Next, this compact was put into a sintering furnace in an Ar atmosphere and sintered at 1,060 ° C. for 2 hours to produce a permanent magnet block of 71 mm × 45 mm × thickness 10 mm (magnetic anisotropy direction). . The permanent magnet block was ground to a D-shaped section as shown in FIG. The dimensions are L = 70 mm, W = 45 mm, Tc = 9 mm, Te = 3 mm (shape 1), L = 70 mm, W = 15 mm, Tc = 3 mm, Te = 1 mm (shape 2) (Tc and Te are magnetically different. Direction). The dimension of shape 1 is the same as that of shape 2 in the L direction, and the W and T directions are tripled. The ground magnet body was washed with an alkaline solution, and then washed with an acid and dried. A cleaning process with pure water is included before and after each cleaning.

  Next, dysprosium fluoride having an average powder particle size of 5 μm was mixed with ethanol at a mass fraction of 50%, and the magnet body was immersed for 1 minute while applying ultrasonic waves thereto. The magnet pulled up was immediately dried with hot air. The occupation ratio of the magnet surface space by dysprosium fluoride at this time was 45%. This was subjected to an absorption treatment at 900 ° C. for 1 hour in an Ar atmosphere, and further subjected to an aging treatment at 500 ° C. for 1 hour, followed by rapid cooling to obtain a magnet body. What performed this process with respect to the shape 1 is called the magnet body M1, and what performed this process with respect to the shape 2 is called the magnet body M2. For comparison, the shape 1 subjected only to heat treatment is referred to as a magnet body P1, and the shape 2 subjected to this treatment is referred to as a magnet body P2.

  To a magnet body having the same shape as M2 and P2, terbium fluoride having an average powder particle size of 5 μm was mixed with ethanol at a mass fraction of 50%, and the magnet body was immersed for 1 minute while applying ultrasonic waves thereto. The magnet pulled up was immediately dried with hot air. At this time, the occupation ratio of the magnet surface space by terbium fluoride was 45%. This was subjected to an absorption treatment at 900 ° C. for 1 hour in an Ar atmosphere, and further subjected to an aging treatment at 500 ° C. for 1 hour, followed by rapid cooling to obtain a magnet body. This is referred to as a magnet body M3.

  For the magnet body having the same shape as M2, M3, and P2, terbium fluoride having an average powder particle size of 5 μm is mixed with ethanol at a mass fraction of 50%, and ultrasonic waves are applied to this, and both ends of the magnet body are 4 mm. Each was soaked for 1 minute. The magnet pulled up was immediately dried with hot air. At this time, the occupation ratio of the magnet surface space by terbium fluoride was 45% in the immersed part at both ends of the magnet, and 0% in the central part without immersion. FIG. 5 shows a diagram illustrating a magnet body in which a powder containing one or more selected from R oxide, R fluoride, and R oxyfluoride of this example is applied to the surface of the magnet end. This was subjected to an absorption treatment at 900 ° C. for 1 hour in an Ar atmosphere, and further subjected to an aging treatment at 500 ° C. for 1 hour, followed by rapid cooling to obtain a magnet body. This is referred to as a magnet body M4.

Table 1 shows the magnetic characteristics of the magnet bodies M1, M2, M3, M4, P1, and P2. The permanent magnet according to the present invention has an increase in coercive force of 480 to 500 kAm ^{−1 at} the end and 300 to 450 kAm at the center with respect to the coercive force of the magnets (P1 and P2) not subjected to dysprosium absorption treatment. A coercivity increase of ^-1 was observed. The coercive force of the thicker shape 1 is smaller, and in particular, the difference in the central part is larger. Thus, when the thickness increases, the increase in coercive force becomes dull. Further, in the magnet (M3) subjected to the terbium absorption treatment, an increase in coercive force of 800 kAm ⁻¹ is recognized with respect to the coercive force of the magnet (P2) not subjected to the terbium absorption treatment. The decrease in residual magnetic flux density of the permanent magnet of the present invention was 5 mT.

For comparison, a permanent magnet was prepared using a composition alloy in which Nd part of alloy A was replaced with Dy, and the coercive force was increased by 500 kAm ⁻¹ . As a result, the residual magnetic flux density was reduced by 50 mT. This magnet body was designated as P3, and the magnetic characteristics are also shown in Table 1. The shape of P3 is shape 2.

  Dy and F were observed in the magnets by the reflected electron images of the magnet bodies M1 and M2 by SEM and EPMA. Since the magnet before processing does not contain Dy and F, the presence of Dy and F in the magnetic bodies M1 and M2 is due to the absorption processing of the present invention. The absorbed Dy is concentrated only in the vicinity of the crystal grain boundary. On the other hand, fluorine (F) is also present in the grain boundary part, and forms an oxyfluoride by being combined with an oxide that is an inevitable impurity contained in the magnet before the treatment. This Dy distribution makes it possible to increase the coercive force while minimizing the decrease in residual magnetic flux density.

<Motor characteristics of examples and comparative examples>
The motor characteristics when the magnets M1, M2, M3, and M4 of the present invention and the magnets P1, P2, and P3 of the comparative example are incorporated in a permanent magnet motor will be described. The permanent magnet motor is a surface magnet type motor shown in FIG. The rotor has a hexapole structure in which a permanent magnet is attached to the surface of a laminate of 0.5 mm electromagnetic steel plates. The outer diameter of the rotor using shape 1 magnets M1 and P1 (the outer diameter passing through the apex of the contour of the adjacent permanent magnet) is 90 mm and the length is 70 mm. The stator has a 9-slot structure in which 0.5 mm electromagnetic steel sheets are laminated. Each coil is wound with 15 turns of concentrated winding, and the coil has a U-phase, V-phase, and W-phase three-phase Y connection. ing. The gap between the rotor and the stator is 1 mm. The black circle mark of the coil shown in FIG. 1 means that the coil winding direction is in front, and the x mark means that the coil winding direction is in the back. When a current is passed through the coil, it is magnetized in the direction of the arrow written on the stator core portion, causing the rotor to rotate counterclockwise. At this time, the field behind the rotation direction of the permanent magnet segment (the portion surrounded by a circle in FIG. 1) is easily demagnetized because the field is in the opposite direction to the magnetization of the permanent magnet.

  Similarly, the outer diameter of the rotor using the magnets M2, M3, P2, and P3 having the shape 2 is 45 mm and the length is 70 mm. The gap between the rotor and the stator is 1 mm.

  In order to evaluate the degree of demagnetization, the difference in driving torque before and after the motor was exposed to temperatures of 100 ° C. and 120 ° C. was measured. First, the driving torque when rotating at room temperature with a three-phase current having an effective value of 50A per coil was measured, and then the motor was placed in an oven and rotated at the same current of 50A. When this was taken out of the oven, returned to room temperature, and rotated at 50 A, the driving torque was measured. Torque reduction rate due to demagnetization = (drive torque at room temperature after being put in oven−drive torque at room temperature before being put in oven) / (drive torque at room temperature before being put in oven).

Table 2 shows the values of the drive torque reduction rate due to demagnetization. In the motors using the magnets having a small coercive force in Comparative Examples 1 and 2, demagnetization was observed at 100 ° C., and even greater demagnetization was observed at 120 ° C. It turned out that it cannot be used in an environment of 100 ° C. On the other hand, the motors using the magnets whose coercive force is increased by the processing of the present invention in Examples 1 and 2 are not observed at 100 ° C., and can be used in an environment at 100 ° C. At 120 ° C., about 2% demagnetization is observed in both Examples 1 and 2. The amount of increase in coercive force by the treatment of the present invention is the same as that of the magnet M1 and the magnet M2 because the dysprosium is sufficiently absorbed because the end of the magnet is close to the magnet surface, and the center is the magnet M1. Therefore, dysprosium is not sufficiently absorbed, and there is a coercive force difference of 170 kAm ⁻¹ . Although there is a difference in the coercive force at the center of the magnet, the amount of torque reduction due to the demagnetization of the motor was similar. This is because the portion of the permanent magnet motor that is easily demagnetized is the magnet end, and the processing of the present invention can further increase the coercive force of the magnet end, so that the motor is difficult to demagnetize.

  Example 3 is a motor using a magnet in which terbium is absorbed to increase the coercive force, and no demagnetization is observed even at 120 ° C.

  Example 4 is a motor using a magnet in which the coercive force is increased by absorbing terbium at the end of the magnet in Example 1 as shown in FIG. 5, and there is no demagnetization at 100 ° C., and at 120 ° C. Slight demagnetization was observed. Since dysprosium and terbium are expensive elements, we want to reduce the amount used. Since the present invention can intensively absorb and absorb the coercive force, the amount of dysprosium and terbium used can be reduced.

  Comparative Example 3 is a permanent magnet having a coercive force equivalent to that of Example 2 using a composition alloy in which a part of Nd of alloy A is replaced with Dy, and the amount of torque reduction of the motor due to demagnetization is about the same. However, since the residual magnetic flux density is 3.3% smaller, the driving torque is smaller.

  Although the embodiment is a permanent magnet motor, the permanent magnet generator has the same structure, and the effect of the present invention is the same.

1 Rotor core (rotor core)
2 Magnet 3 Rotor 11 Stator core 12 Coil 13 Stator 20 Magnet body 22 Powder Tc Thickness of the permanent magnet central portion Te End thickness

Claims (8)

A permanent magnet rotating machine in which a rotor in which a plurality of permanent magnet segments are attached to a side surface of a rotor core and a stator in which a winding is wound around a stator core having a plurality of slots are arranged with a gap therebetween. Both end portions in the width direction are thinner than the central portion, and the permanent magnet segment is made of a fired R ¹ —Fe—B composition (R ¹ is one or more selected from rare earth elements including Y and Sc). A method for producing a permanent magnet segment for a permanent magnet rotating machine, which is a magnetized body, comprising one or more selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride (R ² , R ³ , and R ⁴ are each one or two or more elements selected from rare earth elements including Y and Sc), and the magnet body and the powder The body of the magnet body By performing heat treatment in vacuum or inert gas at a temperature lower than the sintering temperature, the coercive force at both ends in the width direction is higher than the central part, and the difference HcJ between the central part and the end part is 30 kAm ⁻¹ or more. A method for producing a permanent magnet segment for a permanent magnet rotating machine, wherein an eccentric sintered magnet body is obtained. The manufacturing method of the permanent magnet segment of Claim 1 which obtains the eccentric sintered magnet body whose difference HcJ of the coercive force of a center part and an edge part is 30-500kAm < ^-1 >.   The method of manufacturing a permanent magnet segment according to claim 1 or 2, wherein the magnet body to be heat-treated has a shape having a maximum portion dimension of 100 mm or less and a minimum dimension in the direction of magnetic anisotropy of 10 mm or less.   4. The method of manufacturing a permanent magnet segment according to claim 1, wherein the magnet body has a C-shaped or D-shaped cross section. A permanent magnet segment is obtained by performing heat treatment in such a manner that a powder selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride is partially present on the surfaces of both ends in the width direction of the magnet. The method of manufacturing a permanent magnet segment according to any one of claims 1 to 4, wherein The abundance of the powder containing one or more selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride with respect to the surface of the magnet body is within a distance of 1 mm from the surface of the magnet body. The method for manufacturing a permanent magnet segment according to any one of claims 1 to 5, wherein an average occupancy is 10% by volume or more in a space surrounding the magnet body. Oxide of R ^2, fluoride of R ^3, any one of claims 1 to 6 average particle size of the powder containing one or more kinds selected from an acid fluoride of R ⁴ is 100μm or less The manufacturing method of the permanent magnet segment of description. A powder containing one or more selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride was dispersed in water or an organic solvent, and the magnet body was immersed in the resulting slurry. The method for producing a permanent magnet segment according to any one of claims 1 to 7, wherein the powder is allowed to exist on the surface of the magnet body by subsequent drying.

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