JP4320710B2 - Polar anisotropic ring magnet and molding die - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention requires multistage molding.AbsentPolar anisotropic ring magnetAnd moldAbout.
[0002]
[Prior art]
  Radial anisotropic ring magnets and polar anisotropic ring magnets are often used in rotating machines such as servo motors. Radial of the same dimensions when using a polar anisotropic ring magnetanisotropyA high surface magnetic flux density can be obtained compared to a ring magnet, and a small and higher performance motor can be provided. For example, Japanese Patent Publication No. 8-28293 discloses polar anisotropy.ringThere is a description of magnets.
  In a motor using a permanent magnet, cogging is likely to occur because the magnetic resistance between the stator and the rotor changes depending on the rotation angle. In particularPolar anisotropic ringWhen the number of magnetic poles of the magnet is as small as 4 to 8, the cogging torque is significant. Since this cogging torque is proportional to the square of the magnetic flux density, in order to reduce the cogging torque, it is necessary to smooth the circumferential magnetic flux waveform of the gap portion. When a radial anisotropic ring magnet is used, a technique for suppressing cogging by using skew magnetization at the time of magnetization is common.
  However, a polar anisotropic ring magnet with a high surface magnetic flux density is radial.anisotropyUnlike a ring magnet, the magnetizable direction is determined from the orientation of molding. Since the orientation is performed while compression molding, variations between the magnetic poles of the molded body are likely to occur, and adjustment by magnetization cannot be performed. Therefore, measures to suppress cogging are necessary.
  For example, in Japanese Patent Publication No. 8-28293Number of magnetic polesA polar anisotropic ring magnet having P of 4 to 8 is described, and each magnetic pole portion is uniformly inclined by 5 ° or more with respect to the axis.Polar anisotropic ringmagnetButDescriptionHas been. However, thisPolar anisotropic ringWhen the magnet is actually manufactured, since the magnetic pole part is inclined with respect to the axis, when the magnetic powder is oriented in the mold while compressing and molding, the shape of the magnetic pole part when oriented in the initial stage is compressed.DeformedThere is a problem that the orientation is partially disturbed by the magnetic attraction force with the magnetic pole and the orientation is disturbed. In addition, there is a drawback in that the spacing between the magnetic poles and the skew angle vary due to variations in shrinkage during sintering, and as a result, it is difficult to keep the cogging torque of the motor constant.
  Multiple polar anisotropy as a countermeasureringThere is an example of using a magnet and laminating magnetic poles in the axial direction. JP-A-8-340652GazetteThere is a description of a servo motor that is divided into a plurality of polar anisotropic ring magnets in the axial direction and magnetized after shifting the magnetic poles, and apparently skewed, but for reducing the cogging torque There is no description about the control of the shift angle, and eachPolar anisotropic ringIt takes time to fix the magnet. Polar anisotropic ring magnetofThe manufacturing cost is low, but assembly cost to the rotor is required separately.
  Japanese Patent Laid-Open No. 11-8960ThenIn order to control the shift angle, the shift angle is controlled by using a magnetic pole shift jig in which the magnetic center of the magnetic field generation unit is shifted by an angle at which the cogging torque has an opposite phase between a plurality of jigs. With this method, when pulling out from the jigPolar anisotropic ringIt is necessary to take fixing means such as adhesion so that the magnet does not rotate, and productivity is poor.
[0003]
[Problems to be solved by the invention]
  Therefore, the problem of the present invention is,Magnetic poleofLess variation in spacingWithOf cogging torqueSmall variationWithout multistage moldingInObtained polar anisotropic ring magnetAnd moldIs to provide.
[0004]
[Means for Solving the Problems]
  The polar anisotropic ring magnet of the present invention is a one-stage molded polar anisotropic ring magnet, the ring magnet having a plurality of magnetic poles along the axial direction, and each magnetic pole of the ring magnet. In addition, magnetic pole portions parallel to the axial direction are respectively provided at both ends in the axial direction, and further, a helical magnetic pole portion inclined with respect to the axial direction is provided between the parallel magnetic pole portions, and the helical magnetic pole portion The length in the axial direction is shorter than the length in the axial direction of the parallel magnetic pole portions.
  In the polar anisotropic ring magnet of the present invention, the inclination of the boundary line (neutral line) of adjacent magnetic poles in the parallel magnetic pole part with respect to the boundary line (neutral line) of adjacent magnetic poles in the helical magnetic pole part The angle α is 85 ° or less.
  Whether there are joints by multi-stage moldingThe polar anisotropic ring magnet of the present inventionAxiallyAlongIt can be determined by measuring the surface magnetic flux density. That is1 stepIf molding, since the supply density of magnetic powder is almost uniform when molding,Polar anisotropyThe density does not change at the body of the ring magnet. ThereforeOf the polar anisotropic ring magnetAlthough the surface magnetic flux density at the end portion falls, the surface magnetic flux density does not vary by 5% or more at the body portion. In multi-stage molding, the magnetic powder in the cavity is compressed in multiple times by the punch, so the density difference slightly changes between the part pressed by the punch and the part to which new magnetic powder is supplied, and the surface magnetic flux density at the barrel part It varies from 5% or more, more than 8%. Therefore, by measuring this surface magnetic flux density,1 stepDifferences in molding can be determined.
[0005]
  The molding die of the present invention is a die for molding a one-stage molded body of a polar anisotropic ring magnet,
  A die having a hollow portion penetrating in the axial direction, a plurality of grooves formed on an inner peripheral surface of the die facing the hollow portion, a magnetic field generating coil embedded in the groove, and an inner periphery of the die A spacer disposed to cover the surface and the groove, a core disposed in the hollow portion of the die and extending along the axial direction of the die, and formed between the spacer and the core. A cavity,
  A polar anisotropic orientation magnetic flux corresponding to one magnetic pole of the polar anisotropic orientation magnetic flux generated in the cavity at the time of molding is generated for each coil of the magnetic field generating coil, and The winding portion along the axial direction of the die includes a winding portion parallel to the axial direction of the die and a winding portion inclined between the axial direction of the die formed between the parallel winding portions. It is characterized by the following.
  The molding die of the present invention is characterized in that an axial length of the inclined winding portion is shorter than an axial length of the parallel winding portions.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
  The advantages of the present invention will now be described in detail with reference to FIGS. 2 and 7,Sign1 is mold, 2b, 2c, 2dIs a coil for obtaining an orientation magnetic field, 3 is an upper punch, 4 is a lower punchTheCavity surrounded by upper punch 3, lower punch 4 and mold 110Inside molding material 5aFilled. Also in the figureSign of6 is a magnetic pole and a magnetic pole by orientation during moldingBoundary withIndicateNeutral lineIt is. In the case of obtaining a spirally oriented polar anisotropic ring magnet, if the magnetic pole portion is oriented so as to be substantially uniformly inclined with respect to the axis as shown in the prior art and FIG. In a)), the molding material 5a is oriented along the orientation magnetic field. In the stage after molding (FIG. 7B) in which the molding material 5a is compressed by the upper punch 3 and the lower punch 4 (FIG. 7B), Is a neutral line 6 at a different angleaTherefore, the distance between the magnetic poles tends to vary due to this strain. Even if an orientation magnetic field is applied after the molding material is compressed to the final shape of the molded product, the molding material is not oriented. Conversely, if compression molding is attempted by taking into account the distortion of the magnetic pole portion due to molding compression, it is necessary to strictly control the amount of molding material placed in the mold cavity, which is substantially difficult in industrial production.
[0007]
  In the polar anisotropy ring magnet of the present invention, as shown in FIG.directionSo as to have a parallel magnetic pole part (hereinafter referred to as a parallel magnetic pole part) A and C.2bIs provided in the mold. As a result, as shown in FIG. 2, even if the molding material is compressed by compression molding, the width and direction of the neutral lines in the magnetic pole portions A and C are not substantially changed, and only the density is improved. The number of spirally oriented magnetic pole portions is small compared to the prior art, and a polar anisotropic ring magnet with reduced magnetic pole variation can be manufactured.
[0008]
  If the parallel magnetic pole portions are joined together without leaving a distance, cracks due to shrinkage during sintering are likely to occur. In order to suppress this, it is preferable to provide a certain width of the magnetic pole portion that is spirally oriented. Of course, if the parallel magnetic pole portion and the helical magnetic pole portion are arranged so that the magnetic pole portions are continuous, cracks due to the shrinkage rate during sintering can be further reduced. In this case, the orientation coil may be wound in a mold so as to overlap the neutral line 6a shown in FIG. 1, and can be configured by one coil with one magnetic pole passing from the end to the end of the polar anisotropic ring magnet. It is.
[0009]
  By the above manufacturing method, the magnetic pole position and the reverse position (neutral line) as shown in FIG.Axial at both endsParallel toandA polar anisotropic ring magnet running obliquely in the circumferential direction is obtained. During molding, the cavity is arranged so that the magnetic powder in the helical orientation position does not move relative to the mold.InsideBy pressing the magnetic powder of the same distance from both ends for the same distance, the orientation disorder is very small, and it has a certain deviation angle.One-stage moldingPolar anisotropyringmagnetMolded bodyCan be obtained.
[0010]
  Axial direction of intermediate part B in FIG.lengthHowever, if it is too short, cracks due to shrinkage during sintering cannot be suppressed. It is necessary to select appropriately according to the molding material, the degree of orientation and the like. For example, R-T-B systemA polar anisotropic ring (R is at least one rare earth element including Y)In the magnetInclination of the boundary line (neutral line) of the adjacent magnetic pole in the spiral magnetic pole part with respect to the boundary line (neutral line) of the adjacent magnetic pole in the parallel magnetic pole partThe angle α is preferably 85 ° or less. A preferable inclination angle is 80 ° or less, and more preferably 70 ° or less. Axial directionlengthIs preferably 0.3 mm or more.
  In addition, in a ferrite magnet that is relatively easily sintered and cracked, the inclination angle α is preferably 60 ° or less. A preferable inclination angle is 55 ° or less, and more preferably 45 ° or less. Axial directionlengthIs preferably 0.5 mm or more.
  Compared with multi-stage molding, the number of moldings per unit time for one molding machine is greatly improved, and variations in the magnetic pole part can be suppressed as compared with multi-stage moldings.
[0011]
  However,BondedIf it is a magnet,CureEven if the process is performed, cracks due to the shrinkage rate hardly occur. Therefore, the neutral line as shown in FIG.6bIt is possible to obtain a polar anisotropic ring magnet having It is also possible to suppress shrinkage cracking by applying an orientation magnetic field to a low level. Thereby, a polar anisotropic ring magnet having a small cogging torque can be obtained.
[0012]
  The present inventionPolar anisotropy ring magnetIs produced, for example, by the following steps.
(1)Sintered magnet: Raw material powder production-powder supply-Molding in polar anisotropic magnetic field-Sintering (heat treatment, processing and surface treatment are added if necessary)
(2)Bonded magnet
(Compression molding): Raw material compound production-powder supply-Molding in polar anisotropic magnetic field-Curing (processing and surface treatment are added if necessary)
(Injection molding): Raw material compound production-In polar anisotropy fieldInjectionMolding-Cooling (processing and surface treatment are added if necessary)
[0013]
  1 shows geometrically the polar anisotropic ring magnet of the present invention. Figure 1ShowlikePolar anisotropyAlign the center axis of the ring magnet with the z-axis of the r-θ-z cylindrical coordinate system;Polar anisotropic ringOne end of the magnet is brought into contact with the z = 0 plane,Polar anisotropyWhen the ring magnet is virtually divided into three perpendicular to the z axis and named A, B, C from the smaller z, the θ component of the magnetic pole part of A is substantially constant θa in the z axis direction, and the opposite end C The θ component of the corresponding magnetic pole portion is substantially constant θc in the z-axis direction, and the magnetization difficult direction of the intermediate portion (helical magnetic pole portion) B continuously changes from θa to θc. It is. Further, the absolute value | θc−θa | (shift angle) of the θ component of the magnetic pole portions of A and B is 5% or more and 50% or less of the average inter-pole angle of A and B.
[0014]
  In order to reduce cogging, the axial direction of the spiral magnetic polelengthButTotal axial length of polar anisotropic ring magnet1-30% or less ofThat's right.
[0015]
  FIG. 2 is a schematic sectional view of a mold used in the present invention (however,Molded bodyShows the orientation of the side surface). After the magnetic powder is supplied into the cylindrical mold 1, the upper punch 3 and the lower punch 4 are arranged at predetermined positions. Thereafter, N and S poles are periodically generated in the circumferential direction on the side surface of the mold in contact with the outer peripheral surface of the magnetic powder. The north and south poles have a parallel magnetic pole portion and a helical magnetic pole portion whose inclination is substantially 0 ° with respect to the axial direction. The coil 2b is a neutral wire between the poles6aIt is placed in the mold so that it is wound around the top.. Polar anisotropyThe oriented magnetic powder is axially moved by the upper punch 3 and the lower punch 4.compressionThis completes the molding process. At that time, the parallel magnetic polesAxial directionConstant lengthWhenUpper punch 3 and lower punch 4From bothLike pushing the punchMove. To facilitate subsequent handlingCompressedlaterDemagnetize.
[0016]
  Polar anisotropyForming in a magnetic field to impartIn FIG. 3, the magnetic flux between the magnetic poles is as shown in FIG.In cavity 10Flow in an arc,Particles with magnetic anisotropyTheArrange along arcMake. Polar anisotropyringmagnetMoldingThen, the direction that is easily magnetized is determined by the orientation.Yes. After sinteringMagnetizationdo itWhen the surface magnetic flux density is measured in the circumferential direction, periodic peaks of the magnetic flux density are observed. Neutral line6aCan be defined as a line connecting the positions where the magnetic poles switch. This line uses a magnet viewerto seeI can do things. In addition, by measuring the attractive force with magnetized micro magnets, using X-rays and the Kerr effect,After sinteringNeutral lines can be measured even before magnetization.
  8 polesveryanisotropyR-T-B systemSinteringringFIG. 4 shows the result of measuring the neutral line of the magnet and expanding it to the θ-z coordinate. The end faces of two line segments parallel to the z axis are not parallel to the z axisline segmentIt is connected with. Such a neutral lineMagnetismThere are a number equal to the number of poles. Three regions with different θ by drawing two straight lines that pass through the bending point and are parallel to the θ axis(A, B, C)Can be divided into
  In the region A, θm = θa + 2πm ÷ n (n isMagnetismNumber of poles, m is1To n)
  In the region C, θm = θc + 2πm ÷ n (n isMagnetismNumber of poles, m is1To n)
Can be expressed as The region of the helical magnetic pole portion B is an intermediate transition state between the parallel magnetic pole portions A and C.
  θa and θc are inevitable in productionVariationCan be included. TypicalVariationThe value of is within 3% of the angle between the poles, and further within 2%. In the region B, the neutral line continuously changes so as to connect θa and θc. For mold production, it is desirable that the magnetic poles bend with a smooth change according to the thickness of the winding.
  The length of the spiral magnetic pole portion B in the axial direction is preferably 1% or more and 40% or less of the entire length. If the helical magnetic pole B is less than 1%, the magnetization direction changes too rapidly,Of polar anisotropic ring magnets in the sintering processEasy magnetization direction and difficult magnetization directionofDifference in shrinkage rate, sinteringas well asHeat treatmentrearDue to the difference in thermal expansion coefficient between the easy magnetization direction and the hard magnetization direction during the cooling, thermal stress is generated and cracks are likely to occur. If the helical magnetic pole portion B exceeds 40%, the rate of disturbing orientation increases due to the effect of the inclined magnetic pole, so the cogging torque is increased.VariationCheap.
  Of the helical magnetic pole BAxial directionThe length H can be simply defined as follows. magnetViewerusing, Against the boundary line (neutral line) of adjacent magnetic polesHelical magnetic pole BBorderline of adjacent poles at (Neutral line)ofLeanOblique angleFind α.Polar anisotropic ringThe diameter of the magnet is D,MagnetismIf the number of poles is n, the pole width w is
  w = πD ÷ n
And H is represented by the following equation.
  H = w / tan α = πD / n / tan α
  By the above method, the spiral magnetic pole part BAxial directionYou can know the length.
  The absolute value of the angle difference (θc-θa) between the neutral lines at both endsTheThe reason why the average inter-pole angle is set to 5% or more and 50% or less is that if the angle is less than 5%, there is almost no cogging reduction effect. Above 50%motorThe torque becomes 80% or less, and cannot be put to practical use. The cogging torque waveform when the motor is rotated slowly is the rotorMagnetismNumber of poles n and statorMagnetismOften, it has the same number of valleys as the least common multiple M of poles p. Therefore, the desired neutral line angle difference | θc−θa | ≦ 2π / M.
[0017]
  When the product is magnetized, it can be divided into two parts: pre-magnetization that generates a weak magnetic field and main magnetization that generates a strong magnetic field.Polar anisotropic ringThe magnet can be rotated and fully magnetized by this magnetization. Set on the magnetized yoke based on the alignment mark,Polar anisotropic ringIf a magnetized yoke that incorporates a magnet and is spontaneously arranged in the easy magnetization direction is used, there is no problem even if preliminary magnetization is omitted.
[0018]
  Next, the present inventionPolar anisotropyThe reason for limiting the configuration and numerical values of the ring magnet will be described. Hereinafter, “%” simply means “mass%”.
  The polar anisotropic ring magnet of the present invention is, for example, R₂T₁₄Sintered magnet having a main phase of B intermetallic compound (R is at least one of rare earth elements including Y and T is Fe or Fe and Co)It is.A composition consisting of R: 27 to 34%, B: 0.5 to 2%, and the balance T (T is Fe or Fe and Co) is selected with the total of R, T and B as main components being 100%. The
  Polar anisotropyWhen the mass of the ring magnet is 100%, the inevitable impurities are 0.6% or less, preferably 0.3% or less, more preferably less than 0.2% oxygen, 0.3% or less, preferably 0.00. 1% or less of carbon, 0.08% or less of nitrogen, 0.02% or less of hydrogen, 0.2% or less, preferably 0.05% or less, more preferably 0.02% or less of Ca is allowed. Is done.
  A combination of (Nd, Dy), (Pr, Dy) or (Nd, Pr, Dy) as R is highly practical. The R amount is preferably 27 to 34%. A part of Dy may be replaced with Tb. When the R amount is less than 27%, the intrinsic coercive force iHc is significantly reduced, and when it exceeds 34%, the residual magnetic flux density Br and the maximum energy product (BH) max are greatly reduced.
  The B content is preferably 0.5 to 2%, more preferably 0.8 to 1.2%. If the amount of B is less than 0.5%, iHc that can withstand practical use cannot be obtained, and if it exceeds 2%, Br and (BH) max greatly decrease. It is known that a part of B can be replaced by C, and is applicable to the present invention.
  In order to improve surface magnetic flux density and corrosion resistance, it is preferable to contain an appropriate amount of at least one element selected from the group of Nb, Al, Co, Ga and Cu.
  The Nb content is preferably 0.1 to 2%. By containing Nb, a boride of Nb is generated during the sintering process, and abnormal grain growth of crystal grains can be suppressed. If the Nb content is less than 0.1%, the effect of addition is not observed, and if it exceeds 2%, the amount of Nb borides produced increases and the reduction of Br becomes remarkable.
  The Al content is preferably 0.02 to 2%. If the Al content is less than 0.02%, the effect of improving iHc and corrosion resistance cannot be obtained, and if it exceeds 2%, Br and (BH) max are significantly reduced.
  The Co content is preferably 0.3 to 5%. If the Co content is less than 0.3%, the effect of improving the Curie point and corrosion resistance cannot be obtained, and if it exceeds 5%, both Br and iHc are greatly reduced.
  The Ga content is preferably 0.01 to 0.5%. If the Ga content is less than 0.01%, the effect of improving iHc cannot be obtained, and if it exceeds 0.5%, the decrease in Br and (BH) max becomes remarkable.
  The Cu content is preferably 0.01 to 1%. If the Cu content is less than 0.01%, the effect of improving the corrosion resistance and iHc cannot be obtained, and if it exceeds 1%, the reduction of Br becomes remarkable.
  When both Cu and Co are contained in the specific amount range, an effect of widening the allowable temperature range of the secondary heat treatment is preferably obtained.
  The present inventionPolar anisotropy ring magnetIs R₂T₁₄In the case of a bonded magnet in which anisotropic magnetic powder having a main phase of B intermetallic compound (R is at least one kind of rare earth element including Y and T is Fe or Fe and Co) is bound by a binder, It is desirable to use magnetic powder having an average crystal grain size of 0.01 to 0.5 μm and imparted anisotropy by a method such as hot working or HDDR. As the binder, rubber, nylon, epoxy, PPS or other plastic materials, zinc, or a low melting point alloy, which are known materials, can be used.
  The present inventionPolar anisotropy ring magnetIs bonded with an anisotropic magnetic powder having a main phase of an R—T—N intermetallic compound (R is at least one rare earth element including Y, and T is Fe or Fe and Co). When it is a magnet, it is an intermetallic compound known as Sm-Fe-N, with an average of 1 to 10 μmInIt is desirable to use pulverized anisotropic fine powder. Additives and inevitable impurities that do not significantly degrade the magnetic properties are acceptable. As the binder, rubber, nylon, epoxy, PPS or other plastic materials, zinc, or a low melting point alloy, which are known materials, can be used.
[0019]
  If the polar anisotropic ring magnet of the present invention is made of a known ferrite magnet, it is preferable in terms of cost performance.
  In particular (A_1-xR ’_x) O · n [(Fe_1-yM_y)₂O₃] (Atomic ratio)
(However, A is Sr and / or Ba, R ′ is at least one of rare earth elements including Y and necessarily contains La, M is Co or Co and Zn, and x, y and n are respectively conditions:
    5.0 ≦ n ≦ 6.4
    0.01 ≦ x ≦ 0.4, and
    0.005 ≦ y ≦ 0.04
It is a number that satisfies When a polar anisotropic sintered ring magnet made of a high-performance ferrite magnet having a main component composition represented by) and having a magnetoplumbite type crystal structure is used, it is preferable because the rotating machine performance can be improved.
  In order to increase the saturation magnetization, the ratio of La to R ′ is preferably 50 atomic% or more, more preferably 70 atomic% or more, and particularly preferably 99 atomic% or more. Ideally, R ′ should be composed of La except for the unavoidable R ′ component. Therefore, it is practical to use an inexpensive Misch metal oxide containing 50 atomic% or more of La and the balance of at least one of Pr, Nd, and Ce and an inevitable R ′ component as the R ′ element feedstock. is there. In this case, R 'is composed of La, at least one of Nd, Pr and Ce and an unavoidable R' component.
  The molar ratio n needs to be 5.0 to 6.4, more preferably 5.5 to 6.3, and particularly preferably 5.7 to 6.2. When n exceeds 6.4, a different phase other than the magnetoplumbite phase (α-Fe₂O₃Etc.) iHc is greatly reduced, and when n is less than 5.0, Br is greatly reduced.
  x is preferably 0.01 to 0.4, more preferably 0.1 to 0.3, and particularly preferably 0.15 to 0.25. When x is less than 0.01, the effect of addition is not recognized, and when it exceeds 0.4, the surface magnetic flux density is greatly reduced.
  Ideally, a relationship of y = x / (2.0n) needs to be established between y and x for charge compensation. However, when y is x / (2.6n) or more, x / If it is (1.6n) or less, a ferrite magnet having a square shape with a high Br and a high demagnetization curve can be obtained. When y deviates from x / (2.0n), Fe²⁺May be included, but there is no problem. In a typical example, the preferred range for y is 0.04 or less, especially 0.005 to 0.03. Also, an R′-excess major component composition of 5.7 ≦ n ≦ 6.2, 0.2 ≦ x ≦ 0.3 and 1.0 <x / 2ny ≦ 1.3 is selected, and the CaO content is When the content is 0.5 to 1.5% and the content of SiO 2 is 0.25 to 0.55%, the square shape of the demagnetization curve can be remarkably increased as compared with the conventional case.
  SiO as an additive to control sinterability to obtain a dense ferrite sintered magnet₂And CaO (CaCO₃It is practically important to contain a predetermined amount of).
  SiO₂Is an additive that suppresses crystal grain growth during sintering, and the total mass of the ferrite magnet is 100%.₂The content is preferably 0.05 to 0.55%, more preferably 0.25 to 0.55%. SiO₂If the content is less than 0.05%, crystal grain growth proceeds excessively during sintering and the coercive force is greatly reduced. It becomes insufficient and Br greatly decreases.
  CaO is an additive that promotes crystal grain growth, and the total mass of the ferrite magnet is 100 mass%, and the CaO content is preferably 0.35 to 1.5%, more preferably 0.4 to 1.5%, 0.5 to 1.5% is particularly preferable. When the CaO content exceeds 1.5%, the crystal grain growth proceeds excessively during sintering, and the coercive force is greatly reduced. When the CaO content is less than 0.35%, the crystal grain growth is excessively suppressed. Improvement is insufficient and Br is greatly reduced.
  In the case where the present invention is a bonded magnet in which anisotropic magnetic powder having a known ferrite as a main phase is bonded with a binder, it is preferable in terms of cost performance.
[0020]
  Of the present inventionPolar anisotropyThe sintered ring magnet is formed by, for example, a pressing machine equipped with the molding die 1 (for symmetric octupole anisotropic orientation) shown in FIG. In FIG. 3, the solid line is the AA cross section in FIG. 2B, and the broken line is the coil position in the BB cross section. In the molding die 1, 7 is a die made of a ferromagnetic material, and 8 is a core having a circular cross section made of a nonmagnetic material arranged concentrically in the annular space of the die 7. A plurality of grooves 12 are formed on the cylindrical inner surface of the die 7, and a magnetic field generating coil 2 b is embedded in each groove 12. The magnetic field generating coil 2b has a bent portion for forming a helical magnetic pole portion in the middle. A nonmagnetic spacer 9 having a circular cross section similar to the core 8 is provided on the inner peripheral surface of the die 7 so as to cover the groove 12. A cavity 10 is between the spacer 9 and the core 8. When a current is applied to each coil 2b, a magnetic flux indicated by an arrow is generated in the cavity 10 and N, S, N, S,...ofA magnetic pole is formed.
  Next, the molding die 1 of FIG.Polar anisotropyAn example of a method for forming a sintered ring magnet shaped body will be described. First, in a state where the upper punch 3 in FIG. 2 is pulled up, a predetermined amount of raw material powder or slurry is filled into the cavity by a supply means such as a vibration feeder. Next, a pulse current is applied to the coil 2b to keep the fine powder or slurry for the sintered magnet oriented, and the upper punch 3 is lowered as it is, with the lower punch 4 centering on the helical magnetic pole portion.SymmetryLower to the position. Thereafter, the lower punch 4 and the upper punch 3 are pressed in the cavity direction at the same speed and pressure to obtain a polar anisotropic ring magnet compact. In addition, when the upper punch 3 is pressed, the die is lowered at half the speed of the upper punch 3 so that the left and right in the axial direction are the same as described above.SymmetryIt is possible to obtain a parallel magnetic pole portion having a sufficient length.
  The applied polar anisotropic orientation magnetic field strength is preferably as high as possible, but is usually 0.4 to 2.0 MA / m (5 to 25 kOe). When the orientation magnetic field strength is less than 0.4 MA / m, the orientation becomes insufficient, and it is difficult to ensure a high orientation magnetic field strength of more than 2.0 MA / m for industrial production. In order to suppress cracking and obtain a predetermined degree of orientation, the compression molding pressure is 49 to 392 MPa (500 to 4000 kg / cm in the case of a molded body for an RTB-based sintered magnet.²), And 29 to 39 MPa (300 to 400 kg / cm) in the case of a ferrite magnet shaped body²) Is preferred.
[0021]
  If the molding machine is a servo press using a servo motor, a mechanical press using a cam, or a hydraulic press with a numerically controlled hydraulic cylinder, the lower punch is reversed against the movement of the upper punch. By moving the die in the direction or moving the die in the same direction as the movement of the upper punch, a place where the raw material in the mold does not move in the vertical direction (hereinafter referred to as a neutral line) can be set.
  The present inventor minimizes the vertical movement of the raw material at the position of the mold for forming the spirally oriented portion by controlling the center of the spirally oriented portion of the mold to coincide with the neutral line.What you can doAnd the effectiveness was confirmed by conducting experiments.
[0022]
  Furthermore, sintered magnets andBond magnetIn the manufacture of spiral by combining underfill operationMagnetic poleParallel magnetic poles A and C separated byHelical magnetic poleB'sAxial directionWe also found that the length can be changed. Underfill operation is the upper punch after filling the material into the cavitysoThis is a method of feeding the raw material powder into the mold by moving the relative position of the die and the lower punch before pressurization. By underfillAxial directionIntermediate position B with different lengthPolar anisotropic ringmagnetofYou can bring it to a non-central position. This means that adjustment with emphasis on total torque or cogging torque can be performed using the same mold.
  Also, the axial dimensions with the same shift angle differ depending on the use of underfill.Polar anisotropic ringMagnets can be made.
[0023]
  In the case of a molded body for an RTB-based sintered magnet, the molded body density: 3.7 to 4.6 Mg / m³In the case of a molded body for sintered ferrite magnets, the molded body density: 2.6 to 3.2 Mg / m³Adjusted to degree. In the case of an R-T-B bonded magnet or an R-T-N bonded magnet, the compression molding is 5.5 to 6.5 Mg / m.³To the extent, 4.0 to 5.7 Mg / m for injection molding³Adjusted to degree. 2.6 to 3.6 Mg / m for ferrite bonded magnet injection molding³Adjusted to degree.
  Next, the resulting compression molded body remains in a pressurized stateFor magnetic field generationThe coil is demagnetized by applying a pulse current in the opposite direction to the above. In bonded magnets, demagnetization and powder removal are important because adhesion of magnetic particles affects reliability such as corrosion resistance and contamination.
[0024]
  Of the present inventionPolar anisotropyThe dimensions of the sintered ring magnet are not particularly limited, but the axial length (L) and outer diameter dimension (Do) are L = 5 to 100 mm, preferably L = 8 to 50 mm and Do = 3 to 200 mm, respectively. The practicality of Do = 7 to 50 mm is high. It is practically difficult to impart polar anisotropy to those with Do <3 mm.Polar anisotropySintered ring magnets do not meet the needs of miniaturization. And if L <5mmTraditionalThere is no significant difference from a one-stage molded product, and L> 100 mm does not meet the needs for miniaturization.
  Of the present inventionPolar anisotropyThe number of magnetic poles of the sintered ring magnet is not particularly limited, but it is highly practical to form 4 to 100 poles, preferably 4 to 24 poles at equal intervals or different intervals in the circumferential direction of the outer diameter surface or inner diameter surface. The variation in cogging torque can be within 2.5%.
[0025]
【Example】
  Hereinafter, the present invention will be described in detail by way of examples.ofThe present invention is not limited to the examples.
Example 1
  Nd: 30.5 mass%, Dy: 1.5 mass%, Ga: 0.1 mass%, B: 1.0 mass%, Fe: 64.8 mass% The alloy coarse powder having the main component composition in an inert gas atmosphere Finely pulverized by a jet mill to obtain a fine powder for sintered magnet having an average particle size of 4.5 μm (FSSS). When the bulk density of this fine powder for sintered magnet was measured, 1.7 Mg / m³Met. Next, by using the molding die shown in FIG. 2 capable of spiral magnetic pole portion orientation shown in FIG. 1 and the servo press capable of numerically controlling the movement of the upper ram and the die, the upper punch is first pulled up into the cavity. A predetermined amount of the fine powder was filled. 8 moldsveryPolar anisotropy shift angle 11°It is. The underfill operation was performed so that the center of the filled raw material coincided with the bent portion of the mold. The upper punch was lowered while the polar anisotropic magnetic field was intermittently applied three times to the cavity at a pulse current of 5.0 kA turn per magnetic pole. At this time, compression molding was performed while lowering the die at half the speed of the upper punch, and the lower punch was substantially pressurized in the cavity direction. Thereafter, demagnetization was performed, and the density of the obtained molded body was 4.2 Mg / m.³Met.
  Next, the molded body was about 0.07 Pa (5 × 10 5^-4In Torr) vacuum at 1100 ° C. for 2 hours and cooled to room temperature. Next, a second heat treatment was performed at 550 ° C. for 2 hours in an Ar atmosphere, and the mixture was cooled to room temperature. Next, the end surface and the outer peripheral surface are processed (the inner diameter surface is not processed), and a thermosetting resin (epoxy resin) is coated by electrodeposition, and the outer diameter is 14 mm, the inner diameter is 9 mm, and the axial length is 15 mm. An anisotropic ring magnet was obtained. Next, the magnetic flux was magnetized under the condition that the total magnetic flux amount was saturated along the polar anisotropy application direction, and the surface magnetic flux density was measured in the circumferential direction.
  The measurement location was measured at five locations in 2.5 mm steps from the axial end face. Shift angle 11 between the top 2 and bottom 2°The data corresponding to was obtained. The waveform shape is shown in FIG. In the parallel magnetic pole part (A) in FIG. 4, the waveform shape of a substantially sine wave is the same at two locations, and the lower parallel magnetic pole part (C) is 11 in comparison with the waveform shape of (A).°Except for different phases, a substantially equivalent waveform shape was obtained. In addition, the data of the spiral magnetic pole part B was between the two. In addition, the spiral magnetic pole BAxial directionThe length is 3.0mmPolar anisotropic ring magnetoverallAxial directionIt was 20% of the length. When the variation of the cogging torque of this polar anisotropic ring magnet was measured, it was a very small value of 2%. Cogging torque variation is measured by measuring the variation in torque for each cogging when a polar anisotropic ring magnet is assembled with a rotor core and placed in a stator corresponding to the rotor, and then rotated once, and this is measured as 20 samples. The average value is obtained for each sample.
  Moreover, as shown in FIG. 6, the symmetrical octupole anisotropic ring magnet obtained as shown in FIG.shaftFixed on top,RotorWhen 5 was configured and incorporated in a predetermined rotating machine, useful rotating machine performance was obtained.
[0026]
(Comparative Example 1)
  Of the helical magnetic poleAxial directionThe study was conducted with almost no length. Apparently multiple polar anisotropiesringShifting magnet angle 11°Manufactured as fixed with (helical magnetic pole partAxial directionA molded article of a polar anisotropic ring magnet having a length of about 0.1 mm was obtained. The molded body is 1100℃When the material was sintered for 2 hours, cracking occurred from the spiral magnetic pole part, causing sintering cracks, and it could not be used.
[0027]
(Comparative Example 2)
  Of the helical magnetic poleAxial directionLength of each parallel magnetic poleAxial length ofIt was considered longer than that. Parallel magnetic poleAxial direction4mm in length each other,Axial direction of helical magnetic poleThe length was 7 mm. Otherwise, a polar anisotropic ring magnet was manufactured in the same manner as in Example 1. When the variation in cogging torque of this polar anisotropic ring magnet (N = 50) was measured, it was a large value of about 10%. This polar anisotropic ring magnet was made the same as in Example 1.shaftFixed on top,Rotor5 can be incorporated into a specified rotating machine, but if there is a variation in cogging torque, there will be a difference in the performance of each rotating machine. I understood that it would come off.
[0028]
(Example 2)
  SrCO₃Powder (including Ba and Ca as impurities) and α-Fe₂O₃Powder, La₂O₃Powder and Co3O4 powder, after calcining (Sr_0.80La_0.20) O.5.95 [(_Fe0.983Co_0.017)₂O₃] After wet mixing so as to have the main component composition shown in FIG. The calcined product was dry-coared with a roller mill to obtain coarse powder. Subsequently, wet fine pulverization was performed with an attritor to obtain fine pulverized powder having an average particle size of 0.8 μm (FSSS), which was granulated by a known means. At the initial stage of fine pulverization, the mass ratio with respect to the coarse powder put into fine pulverization is La.₂O₃Only 0.6% by mass of powder was added. SrCO3 powder and CaCO as sintering aids at the initial stage of fine grinding₃Powder and SiO₂0.1 mass%, 1.0 mass%, and 0.3 mass% were added by the mass ratio with respect to the coarse powder thrown into the fine grinding | pulverization, respectively.
  When the bulk density of this ferrite magnet raw material was measured, it was 1.4 Mg / m.³Met. Next, in the state where the upper punch is first pulled up by a servo press equipped with the molding die of FIG. 2 and capable of numerically controlling the movement of the upper ram and the die.In the cavityWere filled with a predetermined amount of the fine powder. 8 moldsveryPolar anisotropy shift angle 11°It is. The underfill operation was performed so that the center of the filled raw material coincided with the bent portion of the mold. The upper punch was lowered while the polar anisotropic magnetic field was intermittently applied three times to the cavity with a pulse current of 0.4 MA / m (5 kOe). At this time, while lowering the die at half the speed of the upper punch, molding pressure: 44 MPa (450 kg / cm²), And the lower punch was substantially pressed in the cavity direction. Thereafter, demagnetization was performed, and the density of the obtained molded body was 3.2 Mg / m.³Met. Subsequently, sintering was performed at 1200 ° C. for 2 hours to obtain a sintered body having the following main component composition (La excess composition: La / Co = 1.2).
    (Sr_0.76La_0.24) O · 5.72 [(Fe_0.983Co_0.017)₂O₃]
  Next, the end surface and the outer peripheral surface of the sintered body were processed (the inner diameter surface was not processed) to obtain a symmetrical octupole anisotropic ring magnet having an outer diameter of 20 mm, an inner diameter of 14 mm, and an axial length of 30 mm. Next, the magnetic flux was magnetized under the condition that the total magnetic flux amount was saturated along the polar anisotropy application direction, and the surface magnetic flux density was measured in the circumferential direction.
  The measurement location was measured at five points in 5.0 mm steps from the axial end face. The upper two places and the lower two places are 11°The data corresponding to was obtained. In addition, the spiral magnetic pole BAxial directionThe length is 8.0mm,Polar anisotropic ring magnetoverallAxial directionIt was about 27% of the length. When the variation in cogging torque of this polar anisotropic ring magnet (N = 50) was measured, it was a very small value of 2%.
  Moreover, as shown in FIG. 6, the symmetrical octupole anisotropic ring magnet obtained as shown in FIG.shaftFixed on top,Rotor 5When it was configured and incorporated in a predetermined rotating machine, useful rotating machine performance was obtained.
[0029]
(Comparative Example 3)
  Of the helical magnetic poleAxial directionThe study was conducted by shortening the length. Spiral magnetic poleAxial directionA molded body of a polar anisotropic ring magnet having a length of 2.0 mm was obtained. The molded body is 1100℃When the material was sintered for 2 hours, cracking occurred from the spiral magnetic pole part, causing sintering cracks, and it could not be used.
[0030]
(Comparative Example 4)
  Of the helical magnetic poleAxial directionLength of each parallel magnetic poleAxial length ofIt was considered longer than that. Parallel magnetic poleAxial directionThe length is 8mm each other,Axial direction of helical magnetic poleThe length was 22 mm. Otherwise, a polar anisotropic ring magnet was manufactured in the same manner as in Example 1. When the variation of the cogging torque of this polar anisotropic ring magnet (N = 50) was measured, it was a large value of 9%. This polar anisotropic ring magnet was made the same as in Example 1.shaftFixed on top,Rotor5 can be incorporated into a specified rotating machine, but if there is a variation in cogging torque, there will be a difference in the performance of each rotating machine. I understood that it would come off.
[0031]
(Example 3)
  An alloy having the main component composition of Nd: 29.2 mass%, Ga: 0.8 mass%, B: 1.0 mass%, Co: 10.5 mass%, and the balance Fe is vacuum-melted and roll-cooled to obtain a cast alloy. Obtained. Roll cooling used the copper single roll method, and it produced so that plate | board thickness might be 300-500 micrometers. Cooling rate is about 5 × 10²Corresponds to ° C / sec. This alloy is subjected to homogenization heat treatment and then stored with hydrogen at room temperature.,It heated to 830 degreeC with the temperature increase rate of 10 degree-C / sec. After maintaining at this temperature for 2 hours, dehydrogenation treatment was performed for 1 hour. After completion of the dehydrogenation treatment, the inside of the furnace was replaced with an argon atmosphere and cooled. The alloy thus obtained was classified to 32-106 μm. This alloy coarse powder and epoxy resin were mixed to obtain a raw material.
  Next, using the molding die shown in FIG. 2 capable of helical magnetic pole portion orientation shown in FIG. 1, the cavity is first pulled up by a servo press capable of numerically controlling the movement of the upper ram and the die. Within a predetermined amount of saidmaterialFilled. Mold isOctupoleAn anisotropic type with a shift angle of 3 °. The underfill operation was performed so that the center of the filled raw material coincided with the bent portion of the mold. The upper punch was lowered while the polar anisotropic magnetic field was intermittently applied three times to the cavity at a pulse current of 5.0 kA turn per magnetic pole.
  Heat the resulting molded body to cure the resin.Polar anisotropic bondA ring magnet was obtained. A thermosetting resin (epoxy resin) was coated by electrodeposition to obtain a symmetrical octupole anisotropic ring magnet having an outer diameter of 14 mm, an inner diameter of 10 mm, and an axial length of 15 mm as shown in FIG. Next, the magnetic flux was magnetized under the condition that the total magnetic flux amount was saturated along the polar anisotropy application direction, and the surface magnetic flux density was measured in the circumferential direction.
  The measurement location was measured at five locations in 2.5 mm steps from the axial end face. In FIG. 1, the waveform shape of a similar sine wave is similar at the two parallel magnetic pole portions (A), and the waveform shape of the parallel magnetic pole portion (C) is 11 compared with the waveform shape of (A).°An out-of-phase waveform shape was obtained. When the variation in cogging torque of this polar anisotropic ring magnet (N = 50) was measured, it was a very small value of 1.7%.
[0032]
(Reference Example 1)
  Polar anisotropy using the same raw materials as in Example 3BondedA ring magnet was manufactured.
  Figure 8ShowMolding was performed using the molding die shown in FIG. 7 capable of magnetic pole portion orientation. First, a predetermined amount of the raw material was filled in the cavity with the upper punch pulled up by a servo press capable of numerically controlling the movement of the upper ram and the die. 16 moldsveryIt was a polar anisotropic type with a shift angle of 3 °. The underfill operation was performed so that the center of the filled raw material coincided with the bent portion of the mold. The upper punch was lowered while the polar anisotropic magnetic field was intermittently applied three times to the cavity at a pulse current of 4.0 kA turn per magnetic pole. The obtained molded body is heat-treated to cure the resin.Polar anisotropic bondA ring magnet was obtained. A thermosetting resin (epoxy resin) was coated by electrodeposition to obtain a symmetrical 16-pole anisotropic ring magnet having an outer diameter of 14 mm, an inner diameter of 8 mm, and an axial length of 20 mm as shown in FIG. Next, the magnetic flux was magnetized under the condition that the total magnetic flux amount was saturated along the polar anisotropy application direction, and the surface magnetic flux density was measured in the circumferential direction.
  The measurement location was measured at four points in 4.0 mm steps from the axial end face. FIG. 8 shows that the parallel magnetic pole part (A) and the parallel magnetic pole part (C) are 3°Out-of-phase waveform shapes were obtained and the waveforms were substantially the same. This polar anisotropyBondedWhen the variation in cogging torque of the ring magnet (N = 50) was measured, it was a very small value of 2.2%.
[0033]
【The invention's effect】
  As described above, according to the present invention,Polar anisotropy ring magnet and molding die with little variation in magnetic pole spacing, less variation in cogging torque, and obtained without multi-stage moldingCould be provided.
[Brief description of the drawings]
FIG. 1 is a schematic view showing the appearance of a polar anisotropic ring magnet of the present invention.
FIG. 2 is a view showing an example of a mold structure used for forming a polar anisotropic ring magnet of the present invention.
FIG. 3 is a diagram showing an axial cross section of the mold structure of FIG. 2;
4 is a development view of a side surface of the polar anisotropic ring magnet of FIG. 1; FIG.
FIG. 5 is a surface magnetic flux waveform of the polar anisotropic ring magnet of FIG. 1;
FIG. 6Examples ofThis is a rotor using a polar anisotropic ring magnet.
[Fig. 7]Reference exampleIt is a figure which shows an example of the metal mold | die structure used for shaping | molding of a polar anisotropic ring magnet.
[Fig. 8]Reference exampleIt is a schematic diagram which shows the external appearance of a polar anisotropic ring magnet.
FIG. 9 is a view showing a mold structure used for forming a conventional polar anisotropic ring magnet.
[Explanation of symbols]
  1Mold2b, 2c, 2d  Coil, 3 upper punch, 4 lower punch,
  5Rotor,5a molding material,6a  Neutral line,6b Neutral line,
  7 dies, 8 cores, 9 spacers, 10 cavities, 12 grooves

Claims (4)

A polar anisotropic ring magnet formed in one stage , wherein the ring magnet has a plurality of magnetic poles along the axial direction, and each one magnetic pole of the ring magnet has an axial direction at each end of the axial direction. A parallel magnetic pole part, and a helical magnetic pole part inclined with respect to the axial direction between the parallel magnetic pole parts, and the axial length of the helical magnetic pole part is the parallel magnetic pole part Polar anisotropic ring magnet characterized by being shorter than the axial length of the part . In polar-anisotropic ring magnet according to claim 1, the boundary line of the adjacent magnetic poles in the spiral-shaped magnetic pole portions to (neutral line), the magnetic pole boundary line adjacent in parallel pole portion of the (neutral line) polar-anisotropic ring magnet inclination angle α of, characterized in der Rukoto 85 ° or less. A mold for forming a one-stage molded body of a polar anisotropic ring magnet,
A die having a hollow portion penetrating in the axial direction, a plurality of grooves formed on an inner peripheral surface of the die facing the hollow portion, a magnetic field generating coil embedded in the groove, and an inner periphery of the die A spacer disposed so as to cover the surface and the groove, a core disposed in a hollow portion of the die and extending along the axial direction of the die, and formed between the spacer and the core. A cavity,
A polar anisotropic orientation magnetic flux corresponding to one magnetic pole of the polar anisotropic orientation magnetic flux generated in the cavity at the time of molding is generated for each coil of the magnetic field generating coil, and The winding portion along the axial direction of the die includes a winding portion parallel to the axial direction of the die and a winding portion inclined between the axial direction of the die formed between the parallel winding portions. A molding die characterized by comprising: 4. The molding die according to claim 3, wherein an axial length of the inclined winding portion is shorter than an axial length of the parallel winding portion.

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