WO2024181326A1 - 界磁子の製造方法 - Google Patents

界磁子の製造方法 Download PDF

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Publication number
WO2024181326A1
WO2024181326A1 PCT/JP2024/006682 JP2024006682W WO2024181326A1 WO 2024181326 A1 WO2024181326 A1 WO 2024181326A1 JP 2024006682 W JP2024006682 W JP 2024006682W WO 2024181326 A1 WO2024181326 A1 WO 2024181326A1
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Prior art keywords
magnet
molding
field element
temperature
manufacturing
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PCT/JP2024/006682
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English (en)
French (fr)
Japanese (ja)
Inventor
勇輝 柘植
匡 藤巻
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Aichi Steel Corp
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Aichi Steel Corp
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Priority to JP2025503853A priority Critical patent/JPWO2024181326A1/ja
Publication of WO2024181326A1 publication Critical patent/WO2024181326A1/ja
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/22—Rotating parts of the magnetic circuit
    • H02K1/27—Rotor cores with permanent magnets
    • H02K1/2706—Inner rotors
    • H02K1/272—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis
    • H02K1/274—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets
    • H02K1/2753—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets the rotor consisting of magnets or groups of magnets arranged with alternating polarity
    • H02K1/276—Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K15/00—Processes or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
    • H02K15/02—Processes or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies
    • H02K15/03—Processes or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies having permanent magnets

Definitions

  • the present invention relates to a method for manufacturing a field element.
  • the permanent magnets that are the magnetic field source of the field element are either sintered magnets made by sintering magnetic powder or bonded magnets made by binding magnetic powder with a binder resin. Bonded magnets have a greater degree of freedom in shape than sintered magnets, are easier to integrate with the field element's housing (core), and are more manufacturable.
  • Bonded magnets come in two types: injection bonded magnets, which are made by injection molding a molten mixture of magnetic powder and thermoplastic resin into a cavity (magnet hole) in a housing, and compression bonded magnets, which are made by compressing a mixture or kneaded product of magnetic powder and thermosetting resin in the cavity. Compression bonded magnets that use thermosetting resin have better heat resistance and mechanical strength than injection bonded magnets.
  • the following patent documents contain information related to compression bonded magnets that serve as a field magnet source.
  • Patent Document 1 proposes a compression-bonded magnet made by high-pressure molding of a magnet raw material (compound) with a small amount of resin and a large amount of magnet powder in a heated alignment magnetic field. Specifically, the compression-bonded magnet is molded under the following conditions: magnet amount: 97.5-98.5 mass% (resin amount: 1.5-2.5 mass%), molding pressure: 392-882 MPa, molding temperature: 150°C, alignment magnetic field: 2 MA/m.
  • Patent Document 2 proposes a compression-bonded magnet made by molding a magnet raw material with a large amount of resin and a small amount of magnet powder at low pressure in a heated alignment magnetic field, in contrast to Patent Document 1.
  • the compression-bonded magnet is molded under the following conditions: magnet amount: 90-95.7% by mass (resin amount: 4.3-10% by mass), molding pressure: 8-70 MPa, molding temperature: 150°C, alignment magnetic field: 955 kA/m.
  • a curing process (a process to harden the thermosetting resin) is performed by heating at 150°C for 30 minutes in an air atmosphere.
  • an anisotropic ferrite bonded magnet is produced by separately carrying out molding in a non-magnetic field, orientation in a magnetic field, and heat curing on a mixture of magnetic powder (80% by mass) and resin (20% by mass).
  • a UV-curable resin is used as part of the resin, and the bonded magnet is not produced integrally with the housing.
  • the present invention was made in consideration of these circumstances, and aims to provide a new manufacturing method, etc., different from conventional methods, for a field element in which a compressed bonded magnet is integrated into a housing.
  • the present invention is a manufacturing method comprising a molding step of compressing a magnet raw material containing anisotropic magnet particles and a thermosetting resin in a heated orienting magnetic field within a cavity of a housing made of a soft magnetic material to obtain a shape-retaining body, and a hardening step of obtaining a hardened body by hardening the thermosetting resin of the shape-retaining body, wherein the thermosetting resin is contained in an amount of 4 to 10 mass% of the entire magnet raw material, and the molding step is performed at a molding temperature (Tf: ts + 5 ⁇ Tf ⁇ ts + 30°C) that is 5 to 30°C higher than the softening point (ts) of the thermosetting resin, and the field element in which a bonded magnet made of the hardened body is enclosed in the housing is obtained.
  • Tf molding temperature
  • thermosetting resin also simply called “resin”
  • resin has a sufficiently low viscosity
  • the molding time cycle time of the molding process required from filling (putting) the magnet raw material into the cavity to removing the molded body from the cavity was previously significantly long.
  • the molding temperature in the present invention is set in the warm range, which is slightly higher than the softening point of the thermosetting resin. Even in this warm range, the magnetic particles were able to change their position sufficiently along the aligning magnetic field. One reason for this is thought to be the large amount of resin in the magnetic raw material.
  • a curing process separated from the molding process makes it possible to process multiple (many) shape-retaining bodies together (batch processing) or to process them in parallel on multiple lines.
  • the manufacturing method of the present invention can shorten the cycle time or takt time required for manufacturing the field element compared to conventional methods, improving productivity while maintaining the magnetic properties of the field element.
  • the present invention is not limited to a manufacturing method, but can also be understood as a field element obtained by the above-mentioned manufacturing method.
  • the field element includes a housing made of a soft magnetic material, and a bonded magnet is contained in a cavity provided in the housing.
  • the cavity has, for example, a closed ring-shaped cross section intersecting (or even perpendicular to) the pressure direction of the magnet raw material.
  • Such a cavity is not limited to a through-hole cylindrical shape, but may be a cylindrical shape with a bottom.
  • the cross-sectional shape of the cavity may be constant or change in the pressure direction.
  • an opening of the cavity an inlet for the magnet raw material
  • the field element is, for example, the rotor or stator of an electric motor.
  • the housing is, for example, a rotor core or stator core.
  • the cavity is a slot (a magnet hole that contains (embeds) a bonded magnet) provided in the rotor core or stator core.
  • a typical example of a field element is an interior permanent magnet (IPM) rotor.
  • the rotor may be either an inner rotor or an outer rotor.
  • the electric motor includes a generator.
  • the electric motor may be either a DC motor or an AC motor.
  • the present invention is not limited to a field element, and may be understood as an electromagnetic device (e.g., an electric motor) equipped with a field element.
  • x to y in this specification includes a lower limit value x and an upper limit value y. Any numerical value included in the various numerical values or numerical ranges described in this specification may be used as a new lower limit or upper limit value to create a new range such as "a to b".
  • x to y MPa in this specification means x MPa to y MPa. The same applies to other unit systems (mWb, etc.).
  • FIG. 1 is a photograph showing the appearance of a prototype IPM rotor (an example of a field element). 1 shows a schematic overview of an orientation heat curing device. The curing process using the device is shown diagrammatically.
  • One or more components selected arbitrarily from the items described in this specification may be added to the above-mentioned configuration of the present invention.
  • the components may relate to the manufacturing method or to the product. Which embodiment is best depends on the target, required performance, etc.
  • the magnet raw material is molded in a heated and oriented magnetic field within the cavity of the housing to form a shape-retaining body.
  • the heating temperature (molding temperature: Tf) of the magnet raw material placed in the cavity is higher than the softening point (ts) of the thermosetting resin (also simply called “resin”) by, for example, 5 to 30°C, 10 to 20°C (ts + 5 ⁇ Tf ⁇ ts + 30°C, ts + 10 ⁇ Tf ⁇ ts + 20°C).
  • the molding temperature is too low, the resin will become highly viscous, which can reduce the orientation of the magnetic particles (variability in the position of the magnetic particles). If the molding temperature is too high, it will take a long time for the oriented magnetic particles to maintain their position stably (to become a shape-retaining body that can be removed).
  • the upper limit of the molding temperature may be less than 120°C, 110°C or less, or 100°C or less.
  • the lower limit of the molding temperature may be, for example, the softening point of the resin (or more), so long as the desired aligning magnetic field molding can be achieved.
  • Softening points, melting points, etc. are physical properties determined for each resin.
  • known values such as nominal values or catalog values can be used. If these are unknown, actual measured values obtained using a typical method can be used.
  • the softening point is measured using the ring and ball method (ASTM D36) or the cup and ball method (ASTM D3461). Specifically, a cylindrical container is filled with material, a weight is placed on top of it, and the material is heated. The softening point is determined by the temperature at which the weight pushes out a specified amount of the softened material.
  • a thermosetting resin is a composition
  • its overall softening point may be calculated from the known softening points of the constituent resins according to the rule of composition.
  • the molding temperature is specified, for example, as the wall temperature of the cavity.
  • the molding temperature may also be substituted with the temperature of the entire housing or the temperature of the molding mold surrounding the housing (its inner wall temperature).
  • the entire housing is heated (preheated) to a desired set temperature before the magnet raw material is filled into the cavity.
  • the set temperature may be used as the molding temperature.
  • the "molding temperature” in this specification refers to the highest temperature (point) reached by the magnet raw material (or resin) inside the cavity. Contents regarding the molding temperature also apply to the curing (treatment) temperature as appropriate.
  • the molding pressure may be high, but may also be low, for example, 5 to 50 MPa or 10 to 40 MPa. By reducing the compressive force, cracking of the magnet particles and deformation of the housing that constitutes the cavity can be suppressed.
  • the compressive force may be constant or may change during molding.
  • the magnitude of the aligning magnetic field applied in the molding process is, for example, 159 kA/m to 1274 kA/m, 318 kA/m to 955 kA/m, or 477 kA/m to 796 kA/m. This magnitude is the magnitude of the magnetic field applied to the inner peripheral surface of the cavity in which the bonded magnet is molded.
  • the direction of the aligning magnetic field is, for example, a direction that intersects (or is perpendicular to) the compression direction of the magnet raw material.
  • the magnetomotive source of the aligning magnetic field may be an electromagnet or a (rare earth) permanent magnet. These contents also apply to the aligning magnetic field applied in the hardening process as appropriate.
  • the molding time depends on the amount of magnet raw material, the shape of the cavity, the molding temperature, etc., and is, for example, 1 to 30 seconds, 3 to 20 seconds, or 5 to 12 seconds. Note that the molding time in this specification is the time during which the magnet raw material heated in the aligning magnetic field is net pressurized.
  • Shape-retaining body may be in a state in which the orientation of the oriented magnetic particles is almost maintained. This makes it possible for the shape-retaining body contained (contained) in the cavity of the housing to be removed from the molding die (orientation mold) together with the housing.
  • the resin does not need to be in a solidified (coagulated or hardened) state. Even if the resin is in a softened state, the oriented magnetic particles in the shape-retaining body surrounded by a housing made of a soft magnetic material can form a magnetic circuit with the housing, and the orientation can be maintained by magnetic force.
  • the hardening process when moving from the molding process to the hardening process, it is not essential to remove the shape-retaining body contained in the cavity together with its casing from the orientation mold (by knocking it out, etc.).
  • the hardening process may be performed as an extension of the molding process, or the casing containing the shape-retaining body may be moved to the hardening process together with the mold.
  • the hardening process is performed collectively on multiple (many) shape-retaining bodies obtained after the molding process, the field element can be manufactured efficiently not only in terms of time but also in terms of equipment, etc.
  • shape-retaining body enclosed in the housing is also simply referred to as the "shape-retaining body.”
  • hardened body enclosed in the housing is also simply referred to as the “hardened body”
  • bonded magnet enclosed in the housing is also simply referred to as the "bonded magnet.”
  • the hardening process is performed by (heat) hardening the thermosetting resin in the shape-retaining body to make the shape-retaining body into a hardened body. This results in a field element in which a bonded magnet made of a hardened body is integrally contained in a housing.
  • the hardening process is performed, for example, by heating the entire housing that integrally contains the shape-retaining body.
  • thermosetting resin progresses mainly according to the thermal history (temperature x time). It is advisable to carry out the hardening process with a heat pattern that roughly maintains the orientation of the magnetic particles imparted in the molding process.
  • the hardening process may involve gradually or continuously increasing the temperature of the shape-retaining body or housing (referred to as the "hardening process temperature” or simply the “hardening temperature”) until it reaches a maximum temperature.
  • the hardening process temperature may be gradually changed from below the molding temperature to above the molding temperature.
  • An aligning magnetic field may be applied during the curing process. This allows the orientation of the magnetic particles to be actively maintained during the curing process.
  • the aligning magnetic field may be applied to the housing in the same direction as in the molding process during the curing process. As long as the orientation of the magnetic particles is maintained, the strength of the aligning magnetic field may be the same as or different from that in the molding process.
  • the aligning magnetic field applied in the curing process may be a magnetizing magnetic field. The magnetizing magnetic field is usually stronger than the aligning magnetic field applied in the molding process.
  • the maximum curing temperature is, for example, 1 to 50°C, or 3 to 30°C higher than the molding temperature.
  • the upper limit is, for example, 180°C or less, 150°C or less, 130°C or less, 115°C or less, or 100°C or less.
  • the curing time (the processing time for the entire curing process) depends on the curing temperature, but is, for example, 0.03 to 5 hours, 0.1 to 4 hours, or 0.5 to 3 hours.
  • At least a part (time) of the curing process may be heated with the opening of the cavity closed (orientation heating process). This prevents the softened and molten thermosetting resin from leaking from the cavity and prevents the magnetic particles from expanding when an orientation magnetic field is applied.
  • the form of the member (lid) that closes the opening may be adjusted depending on the form (shape, size, number, etc.) of the cavity opening. For example, if the cavity is cylindrical with a bottom, only the opening on one side needs to be closed with a lid. Also, multiple openings may be closed all at once.
  • Thermosetting resin generally has a viscosity that decreases when heated, and then increases again as it hardens. Leakage of the thermosetting resin and expansion of the magnetic particles are likely to occur when the viscosity of the thermosetting resin is low near the start of heating (initial stage). For this reason, the orientation heating process should be performed at least at the beginning of the hardening process (almost simultaneously with the start). Once the hardening of the thermosetting resin has progressed, the blocked opening may be opened even during the hardening process.
  • the magnet raw material includes anisotropic magnet particles and a thermosetting resin.
  • the magnet raw material may be a mixed powder, a compound obtained by granulating the mixed powder, or a preform obtained by solidifying the mixed powder or compound into a desired shape.
  • the magnet particles are contained, for example, in an amount of 90-96 mass%, 91-95 mass%, or 92-94 mass% of the total magnet raw material (bonded magnet) (total of magnet powder, resin, etc.). In terms of volumetric percentage, the magnet particles may be contained, for example, in an amount of 60-80 volume%, 65-75 volume%, or 68-73 volume% of the total. If there are too few magnet particles, the magnetic properties of the field element (bonded magnet) will decrease, and if there are too many magnet particles, the orientation of the field element will decrease.
  • the magnet particles may be of a single type or of multiple types.
  • the magnet particles may include isotropic magnet particles in addition to anisotropic magnet particles.
  • the magnet particles are, for example, mixed particles (mixed powder) containing coarse particles (coarse powder) and fine particles (fine powder) with different average particle sizes.
  • the average particle size of the coarse particles is, for example, 40 to 200 ⁇ m or 80 to 160 ⁇ m.
  • the average particle size of the fine particles is, for example, 1 to 10 ⁇ m or 2 to 6 ⁇ m.
  • the average particle size referred to in this specification is determined by measuring the particle group (powder) with a laser diffraction particle size distribution measuring device (HELOS, manufactured by Nippon Laser).
  • the mass ratio (volume ratio is roughly the same) of the coarse particles to the total of the coarse particles and the fine particles (or to the entire magnet particles) is, for example, 60 to 90 mass%, or even 75 to 85 mass%.
  • the fine particles to that total are, for example, 10 to 40 mass%, or even 15 to 25 mass%.
  • the magnet particles are, for example, rare earth anisotropic magnet particles with high magnetic properties that have been hydrogen-treated.
  • Hydrogenation mainly involves a disproportionation reaction due to hydrogen absorption (also called the “Hydrogenation-Disproportionation” or “HD reaction”) and a recombination reaction due to desorption (also called the “Desorption-Recombination” or “DR reaction”).
  • the HD reaction and DR reaction are collectively called the “HDDR reaction.”
  • Hydrogen processing that produces the HDDR reaction is also called “HDDR (processing).”
  • HDDR in this specification also includes the improved d-HDDR (dynamic-Hydrogenation-Disproportionation-Desorption-Recombination).
  • d-HDDR dynamic-Hydrogenation-Disproportionation-Desorption-Recombination
  • d-HDDR is described in detail, for example, in International Publication WO2004/064085.
  • An example of a coarse particle is an NdFeB-based anisotropic magnet particle whose base components are Nd, Fe, and B.
  • An example of a fine particle is an SmFeN-based anisotropic magnet particle whose base components are Sm, Fe, and N, or an SmCo-based anisotropic magnet particle whose base components are Sm and Co.
  • anisotropic magnet particle whose base components are Sm and Co may contain unavoidable impurities or modifying elements that can improve magnetic properties, etc. The total amount of modifying elements is, for example, 10 atomic % or less, or even 7 atomic % or less, of the entire magnet particle.
  • the magnet particles may include rare earth isotropic magnet particles, ferrite magnet particles, etc.
  • the rare earth magnet particles may include elements (heavy rare earth elements such as Dy and Tb, Cu, Al, Co, Nb, etc.) that increase the coercive force, heat resistance, etc.
  • Thermosetting resin is a binder resin that binds or holds magnet particles.
  • the thermosetting resin is contained in an amount of, for example, 4 to 10 mass %, 5 to 9 mass %, or 6 to 8 mass % of the total magnet raw material.
  • Thermosetting resins include, for example, epoxy resin, phenolic resin, melamine resin, urea resin, and unsaturated polyester resin.
  • a typical epoxy resin is usually a mixture of a prepolymer and a hardener, and hardens by forming a crosslinked network with epoxy groups.
  • epoxy resin prepolymers that can be used include novolac type, bisphenol A type, bisphenol F type, biphenyl type, naphthalene type, aliphatic type, and glycidyl amine type.
  • Examples of epoxy resin hardeners that can be used include amine-based, phenol-based, and acid anhydride-based. Bonded magnets and field magnets can be efficiently manufactured using one-component epoxy resins.
  • Thermosetting resin may be a resin composition containing additives such as a curing accelerator and a release agent.
  • additives such as a curing accelerator and a release agent.
  • thermosetting resin such resin compositions are also referred to as "thermosetting resin” or simply "resin.”
  • the magnet particles may be coated with a surfactant suitable for the resin used. This can improve the positional variability of the magnet particles in the softened or molten resin, and the bonding between the magnet particles and the resin.
  • surfactants that can be used when using epoxy resin include titanate-based coupling agents and silane-based coupling agents.
  • magnet particles includes magnet particles that have been surface-treated in this way.
  • the bonded magnet may have a relative density of, for example, 90% or more, 95% or more, or even 98% or more. The upper limit is 99% or even 100%.
  • the relative density ( ⁇ / ⁇ 0 ) is the ratio (percentage) of the actual density ( ⁇ ) to the theoretical density ( ⁇ 0 ).
  • the theoretical density ( ⁇ 0 ) is determined from the true density and the blending amount of the magnetic particles and resin that make up the bonded magnet.
  • the actual density ( ⁇ ) is determined from the mass and volume obtained by measuring the molded (and cured) bonded magnet.
  • the volume may be determined by Archimedes' method or calculated from the shape (dimensions) of the molded body.
  • the bonded magnet may be magnetized (magnetizing magnetic field: 1989 to 3979 kA/m) after the curing process (after being integrated with the casing).
  • the housing is made of a soft magnetic material.
  • the soft magnetic material is, for example, an iron base material such as silicon steel, alloy steel, or pure iron. If the housing is, for example, a laminate of electromagnetic steel sheets with an insulating coating on at least one surface, iron loss (eddy current loss and hysteresis loss) can be reduced.
  • the housing may be a powder compact (powder core), a casting, or the like, depending on the application and specifications (strength, etc.) of the field element.
  • a field element integrally contains a bonded magnet made of hardened thermosetting resin, and usually has excellent magnetic properties as well as mechanical properties (strength, rigidity, etc.)
  • Such field elements are used in rotors (especially high-speed rotors) and stators of various electromagnetic devices, for example, electric motors (motors for driving vehicles, air conditioners, motors for home appliances, etc.).
  • Rotor core (casing) A rotor core was prepared by stacking and crimping 60 sheets of electromagnetic steel sheets (thickness: 0.5 mm) punched into the shape shown in Fig. 1 (outer diameter: ⁇ 93.6 mm ⁇ inner diameter: ⁇ 45 mm ⁇ height: 30 mm).
  • This rotor core is for 8 magnetic poles, and multiple slots (groove width: 3 mm) that are roughly arc-shaped (U-shaped) and open toward the outer diameter side are formed for each magnetic pole.
  • the slots are cylindrical with a constant closed annular cross section extending in the axial direction (up and down on the paper), and there is a narrow bridge at the outer peripheral end of the slot.
  • the slots have openings on both axial end faces.
  • the magnet raw material used was a compound made by melt-mixing magnet powder and thermosetting resin (binder resin). This compound was prepared as follows.
  • the magnet powders used were a commercially available NdFeB anisotropic magnet powder (Magfine, manufactured by Aichi Steel Corporation; Br: 1.28 T, iHc: 1313 kA/m, average particle size: 125 ⁇ m), which is a coarse powder produced by hydrogen treatment (d-HDDR), and a commercially available SmFeN anisotropic magnet powder (SmFeN alloy fine powder, manufactured by Sumitomo Metal Mining Co., Ltd.; C; Br: 1.35 T, iHc: 875 kA/m, average particle size: 3 ⁇ m), which is a fine powder.
  • NdFeB anisotropic magnet powder Magnetic Powder, manufactured by Aichi Steel Corporation; Br: 1.28 T, iHc: 1313 kA/m, average particle size: 125 ⁇ m
  • SmFeN anisotropic magnet powder SmFeN alloy fine powder, manufactured by Sumitomo Metal Mining Co., Ltd.
  • C Br: 1.35 T
  • thermosetting resin a resin composition prepared by blending a base resin, a curing agent, and a curing accelerator, as shown in Table 2, was used. All of the raw materials (agents) were in powder form at room temperature. This type of resin composition is called “epoxy resin” or simply “resin.”
  • the softening point of the resin was confirmed as follows: The resin composition placed on the hot plate began to deform (soften) when the surface temperature of the hot plate reached approximately 60°C. This temperature was close to the softening point calculated from the softening points of the base resin and hardener and their blending ratio: 53°C x 100 + 65°C x 74.4) / (100 + 74.4) ⁇ 58.1°C. Based on this experiment, the softening point of the resin used in this example was determined to be 60°C.
  • the softening points and melting points shown in Table 1 are nominal values listed in the manufacturer's catalog.
  • a mixture of magnet powder (coarse powder and fine powder) and resin was mixed (melted and mixed) while being heated in a kneader to prepare a granular compound (kneaded material/magnet raw material).
  • the compounding ratios in terms of mass percentage relative to the entire mixture, were coarse powder: 65.2 mass%, fine powder: 27.9 mass%, and resin (including additives): 6.9 mass%.
  • the true density ( ⁇ 0 ) of the magnet raw material calculated from the true densities of each and the compounding ratio was 5.6 g/cm 3 .
  • the magnetic powder (coarse powder and fine powder) and resin are 7:3, and the mass ratio of the coarse powder and fine powder is almost the same, 7:3.
  • the kneading was carried out for 5 minutes by keeping the kneader at 90°C and rotating the kneader at a slow speed (10 rpm) (melt mixing process). At this point, the resin was in a softened or molten state.
  • the degree of thermosetting (hardening) of the resin that can progress during such a short melt mixing stage is at most 20-30%, so it has almost no effect on the orientation of the magnet powder or the density of the bonded magnet in subsequent processes (heated molding in a magnetic field) etc.
  • the orientation mold is equipped with a magnetomotive source (permanent magnet) that applies an orientation magnetic field inside the mold, and a heater that heats the inside of the mold.
  • a magnetomotive source permanent magnet
  • the temperature inside the mold is measured by a thermocouple installed near the inner wall surface, and the heater is controlled based on that temperature, so that the rotor core inside the mold can be maintained at the desired molding temperature.
  • the compound that had been filled into the cavity was compressed with a punch that conformed to the cavity shape.
  • the compression force was 20 MPa.
  • the aligning magnetic field (molding magnetic field) was 8 kOe (637 kA/m).
  • the aligning magnetic field was applied horizontally (perpendicular to the compression direction (axial direction)) from the alignment mold toward the outer circumferential surface of the rotor core. In both cases, the rotor core was preheated to the molding temperature before filling with the compound.
  • the net compression time (the time from the start of compression to the end of compression) of the magnet raw material heated in the aligning magnetic field is the molding time shown in Table 1.
  • the rotor core (encased in a shape-retaining body) was removed from the orientation mold and cured by heating in a furnace.
  • the removed rotor core was placed back into the orientation mold described above and cured while applying an orientation magnetic field (molding magnetic field: 8 kOe) in the same manner as in the molding process.
  • the curing process for sample 1 was carried out according to a heat pattern that gradually increased the curing temperature (70°C x 1 hour ⁇ 80°C x 0.5 hour ⁇ 90°C x 0.5 hour/curing process time: 2 hours in total). For sample 2, it was carried out at 90°C x 1 hour.
  • Sample C was not removed from the orientation mold, but instead was continuously cured while still in the state it was in during the molding process (compressed in the heated orientation magnetic field). In this way, rotors were obtained for each sample, containing bonded magnets whose resin had been sufficiently thermally hardened (cured) (see Figure 1). The rotors for each sample were then finally magnetized.
  • Measurement The magnetic properties (magnetic flux) of the rotors of each sample were measured. Specifically, the rotor was attached to a stator (armature), and the current value generated in the stator when the rotor was rotated at a predetermined speed was measured. The current value was converted into magnetic flux, and the results are shown in Table 1. Note that for sample 1 and sample 2, the rotors before the hardening process (as they were after the molding process) were also similarly measured to determine the magnetic flux.
  • the present invention can reduce the molding temperature, improving productivity, while producing a rotor (field element) with high magnetic properties.
  • the magnet particles can be sufficiently oriented in the pressurized magnetic field by heating the magnet raw material to a warm range slightly higher than the softening point of the resin, without having to heat it to a high temperature range.
  • the magnetic particles are in a magnetic circuit formed within a housing made of soft magnetic material, and so it is believed that the magnetic force of the magnetic particles allows them to maintain their oriented posture almost unchanged.
  • thermosetting temperature is changed stepwise or continuously from a temperature range lower than the molding temperature to a temperature range higher than the molding temperature, the posture of the oriented magnetic particles can be stably maintained even without applying an aligning magnetic field during the curing process. Even in curing processes in such a temperature range (warm range), the resin can be sufficiently thermoset if the processing time is set appropriately.
  • Apparatus D includes a base 1 attached to a lower ram (not shown) that moves up and down, a lid body 2 attached to an upper ram (not shown) that moves up and down, and an orientation mold 3.
  • the base 1 has a disk-shaped flange 11 with a flat upper surface and a cylindrical shaft 12 protruding from the center.
  • the cover 2 has a disk-shaped flange 21 with a flat underside.
  • the orientation mold 3 is substantially cylindrical, and the rotor core r can be fitted into its inner circumferential surface.
  • the orientation mold 3 has the same configuration as the orientation mold used in the molding process or hardening process of the first embodiment.
  • the base 1, lid 2 and orientation mold 3 are all equipped with heaters, and the entire assembly is maintained at a predetermined temperature (e.g., 150°C).
  • ⁇ Curing process> The molded body (before the curing step) obtained in the first embodiment was subjected to a curing step using the device D.
  • the procedure is shown in detail in Fig. 2B. Specifically, the procedure is as follows.
  • the lower ram is raised to move the top surface of the flange portion 11 close to the top surface of the orientation mold 3 (step S1).
  • the shaft hole of the rotor core r (simply referred to as "rotor core r") containing the molded body m is inserted onto the shaft portion 12, and the bottom surface of the rotor core r is set by abutting it against the top surface of the flange portion 11 (step S2).
  • step S3 the upper ram is lowered to press the lower surface of the flange 21 against the upper surface of the rotor core r.
  • both end surfaces of the rotor core r are clamped between the base 1 and the lid, and the openings of the slots that were on both end surfaces of the rotor core r are closed (step S3).
  • step S4 The upper and lower rams are then lowered to place the rotor core r in the orientation mold 3 (step S4), and the process waits until the resin hardens (step S5).
  • step S5 the entire periphery of the rotor core r is heated by the base 1, cover 2, and orientation mold 3, and the rotor core r is rapidly heated to a predetermined temperature.
  • the viscosity of the resin of the molded body m contained in the rotor core r drops rapidly, and the resin becomes almost molten.
  • the magnetic particles to which a magnetic field is applied from the orientation mold 3 are reliably oriented. Note that, since the opening of the rotor core r is closed after step S3, leakage of the molten resin from the rotor core r and expansion of the magnetic particles due to the orientation magnetic field are prevented.
  • the upper ram is raised to remove the lid 2 from the rotor core r (step S6).
  • the lower ram is then raised to move the rotor core r close to the top surface of the orientation mold 3 (step S7).
  • the rotor (rotor core r containing the bonded magnet (hardened body)) is then removed from the base 1 (step S8).
  • the timing for removing the cover 2 from the rotor core r in step S6 can be any time after the resin has hardened and there is no leakage of resin or expansion of magnet particles. In other words, there is no need to wait until the resin has completely hardened.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Manufacturing Cores, Coils, And Magnets (AREA)
PCT/JP2024/006682 2023-02-28 2024-02-26 界磁子の製造方法 Ceased WO2024181326A1 (ja)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11186027A (ja) * 1997-12-19 1999-07-09 Aichi Steel Works Ltd ラジアル配向した磁気異方性樹脂結合型磁石及びその製造方法
JP2018133983A (ja) * 2017-02-13 2018-08-23 株式会社三井ハイテック 固定子積層鉄心の製造方法及び固定子積層鉄心
JP2023005421A (ja) * 2021-06-29 2023-01-18 愛知製鋼株式会社 予成形体、予成形方法および圧縮ボンド磁石の製造方法

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11186027A (ja) * 1997-12-19 1999-07-09 Aichi Steel Works Ltd ラジアル配向した磁気異方性樹脂結合型磁石及びその製造方法
JP2018133983A (ja) * 2017-02-13 2018-08-23 株式会社三井ハイテック 固定子積層鉄心の製造方法及び固定子積層鉄心
JP2023005421A (ja) * 2021-06-29 2023-01-18 愛知製鋼株式会社 予成形体、予成形方法および圧縮ボンド磁石の製造方法

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