Preform, preform method, and method for manufacturing compression-bonded magnet

Abstract

The present invention provides a preform having a novel form in which a reduction in magnetic characteristics of a bonded magnet is suppressed, and which is capable of ensuring shape retention and workability. The present invention is a preform having: an outer shell section in which a part of a powdery or granular magnet material comprising a mixture or kneaded product of magnet particles and a thermosetting resin is bonded; and an inner shell section comprising the remainder of the magnet material located inside the outer shell section. The housing part is, for example, a part in which the thermosetting resin is bonded in an uncured state. The inner wrapping part is composed of a powdery or granular magnet raw material. Such a preform is obtained, for example, through a preform step in which a magnet raw material is subjected to warm pressure molding. The pre-forming step is performed, for example, by setting a pre-forming temperature (Tp), which is the temperature of the inner wall surface of a pre-forming die filled with a magnet material, to ts < = Tp < = ts + 20 DEG C (ts: the softening point of the thermosetting resin).

Description

Technical Field

[0001] The present invention relates to a preform and the like for producing a compressed bonded magnet. Background Art

[0002] In order to achieve energy saving, permanent magnets are often used in electromagnetic devices (motors, etc.). Permanent magnets include sintered magnets made by sintering magnet powder and bonded magnets made by bonding magnet powder with resin. Bonded magnets have greater freedom of shape and better formability than sintered magnets.

[0003] Bonded magnets mainly include injection bonded magnets obtained by injecting a molten mixture of magnet powder and thermoplastic resin into a cavity for molding, and compressed bonded magnets obtained by heating and compressing a mixture or kneaded product of magnet powder and thermosetting resin (referred to as "magnet raw material") in a cavity. Generally, the proportion of magnet powder in compressed bonded magnets is larger than that in injected bonded magnets, and the magnetic properties are higher. In addition, since thermosetting resin is used, heat resistance and the like are also excellent.

[0004] However, when manufacturing compressed bonded magnets, if the powdered or granular magnet raw materials are directly filled into a high-temperature cavity, sometimes the softening and melting of the magnet raw materials (especially the resin) filled first may cause a decrease in filling properties and inhomogeneity in the cavity (uneven distribution of magnet particles and thermosetting resin). Therefore, a preform (pre-compression molded body) formed by low-pressure molding of the powdered or granular magnet raw materials is put into the cavity for heating and compression molding (called "formal molding"). For example, there are related records in the following patent documents.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-256684 Summary of the invention

[0008] Problems to be solved by the invention

[0009] In Patent Document 1, the temperature of the film is set at 0.1 to 0.2 t / cm at room temperature (non-heated state). 2 The pre-compression molded body obtained by pressurizing the resin composition for bonded magnet (about 10-20MPa) is sent to a high-temperature chamber arranged in a non-contact manner directly below it to manufacture a compressed bonded magnet. The pre-compression molded body (preformed body) formed by low-pressure molding at room temperature is easy to disintegrate and difficult to transport. Therefore, in Patent Document 1, the pre-molding mold and the main molding mold are arranged close to each other up and down to deal with it.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a preform or the like having a new form having shape retention properties that enables conveyance or the like.

[0011] Methods used to solve problems

[0012] The inventors of the present invention have conducted intensive research to solve the above problems and have conceived a preform with a core-shell structure, and have successfully obtained a preform with desired shape retention by warm forming a magnet raw material. The results have been developed to complete the present invention described below.

[0013] Preform

[0014] (1) The present invention is a preform comprising: an outer shell portion formed by bonding a portion of a powdered or granular magnet raw material consisting of a mixture or kneaded product of magnet particles and a thermosetting resin; and an inner package portion formed by the remaining portion of the magnet raw material located within the outer shell portion.

[0015] (2) The preform of the present invention is not a compressed powder of a homogeneous magnet raw material, but a core-shell structure having an outer shell portion and an inner shell portion. The outer shell portion (shell portion) is formed by bonding (linking, combining, etc.) a portion of the magnet raw material, and bears the strength required for the shape retention and handling of the preform. The inner shell portion (core portion) does not require such strength, and bears a low-density state suitable for manufacturing compressed bonded magnets. According to the preform of the present invention, it is possible to ensure both its operability and the magnetic properties of the bonded magnet at a high level.

[0016] Preforming method

[0017] The present invention can also be understood as a method for producing a preform. For example, the present invention can be a preform method comprising a preform step of hot-pressing a magnet raw material composed of a mixture or kneaded product of magnet particles and a thermosetting resin.

[0018] 《Manufacturing method of compressed bonded magnet》

[0019] The present invention can also be understood as a method for producing a compressed bonded magnet. For example, the present invention can be a method for producing a compressed bonded magnet, which includes a main forming step of heating and compressing a preform.

[0020] 《Compressed bonded magnets / magnetic components》

[0021] The present invention can also be understood as a compressed bonded magnet, a magnetic component (electromagnetic component) in which the compressed bonded magnet is integrally formed with a cavity of a housing, etc. Hereinafter, in this specification, the compressed bonded magnet is appropriately referred to as simply a "bonded magnet."

[0022] "other"

[0023] Unless otherwise specified, the so-called "x to y" in this specification includes a lower limit x and an upper limit y. Any numerical value included in the various numerical values ​​or numerical ranges recorded in this specification can be used as a new lower limit or upper limit to set a new range such as "a to b". In addition, unless otherwise specified, the so-called "x to y μm" in this specification refers to x μm to y μm. The same applies to other unit systems (kA / m, kOe, etc.). BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a scatter diagram showing the relationship between the molding conditions of the preform and its apparent density.

[0025] Figure 2A These are photographs showing the appearance and failure mode of the warm-formed preform.

[0026] Figure 2B The photographs show the appearance and failure mode of the preform formed at room temperature.

[0027] Figure 3 These are photographs obtained by observing the outer surfaces of the preform formed at warm temperature and the preform formed at room temperature using a microscope.

[0028] Figure 4 It is a scatter diagram showing the influence of the apparent density and relative density of the preform on the orientation ratio of the bonded magnet. DETAILED DESCRIPTION

[0029] One or more constituent elements arbitrarily selected from the matters described in this specification may be added to the above-mentioned constitution of the present invention. The constituent elements related to the manufacturing method may also become constituent elements related to the article. Whether any embodiment is optimal depends on the object, required performance, etc.

[0030] Magnet Raw Materials

[0031] The magnet raw material is composed of a mixture or kneaded product of magnet particles (powder) and thermosetting resin (powder), and is in powder or granular form. The mixture can be a powder obtained by mixing a thermosetting resin and magnet particles at room temperature, or it can be a granular form obtained by mixing a thermosetting resin and magnet particles while heating. The kneaded product is a granular form obtained by kneading magnet particles and a thermosetting resin (especially heating and kneading). The granular magnet raw material is composed of composition particles (referred to as "composite") with a thermosetting resin roughly uniformly attached to the surface of the magnet particles. Compared with the mixed composite, the thermosetting resin attached to the surface of the magnet particles of the kneaded composite is more likely to become dense. It should be noted that the thermosetting resin used to make the composite may not be in a solid state (granular form, etc.).

[0032] Thermosetting resin and magnetic particles are heated, for example, at a warm temperature (for example, 40 to 120° C., or 80 to 100° C.) By mixing and kneading the thermosetting resin in a fluid state (softened or molten state), the magnetic particles can be prevented from breaking.

[0033] Magnetic Particles

[0034] The magnetic particles may be a single type or two or more types. The two or more types of magnetic particles are obtained by mixing powders different in at least one of alloy composition, particle size (particle size distribution), properties (anisotropy / isotropy), etc.

[0035] The magnetic particles may be, for example, a mixed powder of a coarse powder and a fine powder having different average particle sizes. The average particle size of the coarse powder is, for example, 40 to 200 μm, and further 80 to 160 μm. The average particle size of the fine powder is, for example, 1 to 10 μm, and further 2 to 6 μm. The average particle size is determined, for example, by measuring (using the Fraunhofer method) using a laser diffraction particle size distribution measuring device (HELOS manufactured by Nippon Laser Co., Ltd.).

[0036] The mass ratio of the coarse powder to the total of the coarse powder and the fine powder (or the whole magnet powder) is, for example, 60 to 90 mass%, and further 65 to 80 mass%. In other words, the mass ratio of the fine powder to the total is, for example, 10 to 40 mass%, and further 20 to 35 mass%. In addition, the ratio of the magnet particles to the magnet raw material (the total of the magnet particles and the resin (including additives)) is, for example, 88 to 98 mass%, 91 to 95 mass%, and further 92 to 94 mass%.

[0037] As magnetic particles, there are, for example, rare earth magnetic particles. Rare earth magnetic particles include NdFeB system with Nd, Fe and B as basic components, SmFeN system with Sm, Fe and N as basic components, SmCo system with Sm and Co as basic components, etc. As an example, magnetic particles can be mixed particles of coarse particles composed of NdFeB system anisotropic magnetic particles and fine particles composed of SmFeN system anisotropic magnetic particles or SmCo system anisotropic magnetic particles. It should be noted that the magnetic particles can contain rare earth isotropic magnetic particles and ferrite particles.

[0038] 《Thermosetting resin》

[0039] Thermosetting resin becomes a binder for holding the magnet particles. Thermosetting resins include epoxy resins, phenolic resins, melamine resins, urea resins, unsaturated polyester resins, and the like. Representative epoxy resins, for example, are composed of a mixture of a main agent (prepolymer) and a curing agent, and are cured by cross-linking networking based on epoxy groups. As the main agent of the epoxy resin, for example, phenolic type, bisphenol A type, bisphenol F type, biphenyl type, naphthalene type, aliphatic type, glycidylamine type, etc. can be used. As the curing agent of the epoxy resin, for example, amines, phenols, and acid anhydrides can be used. At least one of the main agent and the curing agent can be two or more resins. It should be noted that a single-liquid epoxy resin can be used that can adjust the thermal curing period by curing treatment (thermal curing process).

[0040] Thermosetting resin can be a resin composition containing additives such as a curing accelerator and a release agent. In this specification, such a resin composition is also referred to as "thermosetting resin". It should be noted that the magnetic particles can be magnetic particles coated with a surfactant corresponding to the thermosetting resin. In this specification, the magnetic particles that have been subjected to such surface treatment are also referred to as "magnet particles". In addition, as a surfactant corresponding to the epoxy resin, for example, there are titanate coupling agents and silane coupling agents.

[0041] Preform

[0042] (1) The preform has an outer shell and an inner shell. The outer shell is formed by bonding a portion of the magnet material (especially thermosetting resin). The inner shell is formed by the remaining portion of the magnet material located inside the outer shell.

[0043] The outer shell may be a state in which the particles of the magnet raw material (mixed magnet particles and thermosetting resin particles, or composites) are only pressed together (compressed powder state). It is further preferred that at least a portion of the outer surface of the outer shell has a connecting portion formed by integrating the thermosetting resin constituting the magnet raw material throughout its multiple particles (multiple thermosetting resin particles or multiple composite particles). The connecting portion is, for example, formed by resolidifying between adjacent particles of the magnet raw material after the thermosetting resin contacts the inner wall surface of the heated forming mold and softens or melts. Of course, the outer edge of the connecting portion integrated with the thermosetting resin is expanded (enlarged) than the outer edge of the thermosetting resin constituting the magnet raw material particles. The connecting portion may be a structure in which the softened thermosetting resin wets and expands to cover the entire outer surface of the outer shell in a layered or film-like manner, or it may be a structure dispersed in the outer surface of the outer shell in an island shape. It should be noted that, not limited to the inner package, the thermosetting resin located in the outer shell may also be in a substantially uncured state without undergoing a curing reaction (cross-linking reaction) almost.

[0044] The magnet material of the inner package can be in the form of compressed powder, powder, granules, or a mixture of these. The closer the magnet material of the inner package is to the state before preforming, the better the magnetic properties of the bonded magnet can be.

[0045] For the preform, for example, the ratio of the apparent density (ρ) to the true density (ρ0), i.e., the relative density (ρ / ρ0), is 48-72%, 50-70%, 55-65%. The true density is obtained from the density and mix ratio of the magnet particles and thermosetting resin constituting the magnet raw material. The apparent density is obtained by dividing the mass of the preform by its apparent volume (e.g., the volume calculated from the outer dimensions).

[0046] (2) The preformed body is obtained, for example, by subjecting the magnet raw material to warm pressure forming (preforming process). The preforming process can be carried out, for example, by setting the temperature of the inner wall surface of the preforming mold filled with the magnet raw material, i.e., the preforming temperature (Tp), to ts≤Tp≤ts+20°C, or further to ts+5°C≤Tp≤ts+15°C (ts: softening point of thermosetting resin).

[0047] The softening point is measured by the ring and ball method (ASTM D36) or the cup and ball method (ASTM D3461). In both methods, a weight is placed on the material filled in a cylindrical container and heated, and the temperature at which the amount of material softened by the weight reaches a specified value is taken as the softening point.

[0048] The softening point (ts) of the present invention may be a softening point described in a product catalog, etc., in addition to an actually measured value. In addition, when the thermosetting resin is a resin composition composed of two or more resins, the softening point (ts) may be a softening point calculated according to the mixing law from the mixing ratio of each resin (e.g., a main agent and a curing agent) and each known softening point.

[0049] Furthermore, in the case where the thermosetting resin is composed of two or more resins, the intermediate temperature of the softening points of each resin can be used as the preforming temperature (Tp). For example, in the case where the thermosetting resin contains at least a first resin having a first softening point (ts1) and a second resin having a second softening point (ts2) higher than the first softening point, the temperature of the inner wall surface of the preforming mold filled with the magnet raw material, that is, the preforming temperature (Tp) can be set to ts1≤Tp≤ts2 to perform the preforming process. In the case where the thermosetting resin is composed of three or more resins with different softening points, the selection of the first softening point (first resin) and the second softening point (second resin) is arbitrary.

[0050] If the thermosetting resin is composed of a plurality of resins and among their softening points, the first softening point (ts1) is the smallest and the second softening point (ts2) is the largest, the preforming temperature (Tp) may be set to be higher than the first softening point and lower than the second softening point (ts1 < Tp < ts2). In other words, the preforming temperature (Tp) may be set to be an intermediate temperature between the smallest softening point (tsm1) and the largest softening point (tsm2) (tsm1 < Tp < tsm2).

[0051] If the pre-molding temperature is near the softening point of the thermosetting resin, the molding pressure and molding time of the pre-molding process can be easily adjusted. If the pre-molding temperature is too low or too high relative to the softening point, it is difficult to form the desired outer shell and inner package.

[0052] In the preforming process, the forming pressure can be set to, for example, 0.1 to 100 MPa, 0.5 to 50 MPa, or even 1 to 10 MPa. If the forming pressure is too low, the forming of the preform itself is difficult. Excessive forming pressure causes the magnet particles to break, the density of the preform to increase, etc.

[0053] In the preforming step, it is sufficient to perform the forming time for, for example, about 1 second to about 20 seconds, and further about 1 second to about 5 seconds. By shortening the forming time, a preform having a desired outer shell and inner package can be efficiently obtained.

[0054] (3) The preform can be in a form that can be filled, loaded, or introduced into the cavity of the bonded magnet. The preform can be a one-piece object similar to the bonded magnet, or it can be a divided object that is finer than the bonded magnet. The shape of the preform can be based on the shape of the cavity in the formal forming process. Usually, a different forming mold can be used in the preform process than in the formal forming process.

[0055] 《Formal Forming Body / Formal Forming Process》

[0056] (1) A fully formed body as a bonded magnet is obtained by heating and compressing a preform in a cavity (full forming step). When the magnet raw material contains anisotropic magnet particles (especially rare earth anisotropic magnet particles), the full forming step can be performed by applying an oriented magnetic field to the cavity in which the preform is placed.

[0057] The forming pressure (compression force) is, for example, 5 to 500 MPa, 10 to 250 MPa, 20 to 100 MPa, and further 30 to 50 MPa. When the compression force is too large, deformation of the bonded magnet or the cavity, rupture of the magnet particles (especially particles obtained by hydrogen treatment (HDDR, d-HDDR) of the magnet alloy) and the like may occur. If the compression force is not too small, a bonded magnet showing high Br and high Hk can be obtained even by low-pressure forming (for example, less than 100 MPa). It should be noted that Hk represents the size of the reverse magnetic field at a magnetic flux density equivalent to 90% of Br (residual magnetic flux density), and becomes an indicator of the effective magnetic flux density relative to the reverse magnetic field or an indicator of the squareness of the magnetization curve (JH curve).

[0058] The molding temperature (heating temperature) is, for example, 120 to 200° C., and further 130 to 170° C. If the heating temperature is too low, the softening or melting of the thermosetting resin is insufficient, which may lead to the breakage of the magnet particles, the reduction of the orientation rate, etc. If the heating temperature is too high, the magnetic properties of the bonded magnet may be reduced due to the early solidification of the thermosetting resin and the oxidation degradation of the magnet particles.

[0059] The orientation magnetic field is usually applied in an orientation direction that intersects (and is orthogonal to) the compression direction of the preform (magnet raw material). The magnitude of the orientation magnetic field is, for example, 0.5 to 3 T, and further 1 to 2 T. The orientation magnetic field is the magnetic flux density on the inner circumference of the cavity that forms the bonded magnet. The magnetic source of the orientation magnetic field can be either an electromagnet or a (rare earth) permanent magnet.

[0060] (2) The bonded magnet may be in a state of a fully formed body, or in a state where the fully formed body has been subjected to a heat treatment (curing treatment) to cure the resin and then magnetized. The curing treatment is performed by heating the fully formed body at a temperature corresponding to the type of thermosetting resin. The heating temperature is, for example, 130 to 250°C, or further 150 to 230°C.

[0061] Magnetization can be performed, for example, by applying a magnetic field of about 2 T to about 6 T. It should be noted that the bonded magnet that is heat-compressed and molded in an orientation magnetic field does not need to be magnetized, but magnetization is preferably performed to improve the magnetic properties of the bonded magnet.

[0062] The bonded magnet can be taken out (discharged) from the cavity after the formal forming process, or it can be integrated with a housing having a cavity (groove, etc.) during the formal forming process. As a magnetic component formed by integrating the bonded magnet with the cavity of the housing, for example, there are magnetic field elements (rotors, stators) of electric motors (motor for vehicle drive, air conditioners, motors for household appliances, etc.). It should be noted that the electric motor can be a DC motor or an AC motor. In addition, the electric motor includes not only a motor but also a generator.

[0063] Example

[0064] The forming conditions are changed in various ways to produce a plurality of preforms (samples). In addition, the preforms are used to produce bonded magnets. Their appearance and properties are evaluated. Based on such specific examples, the present invention is described in detail below.

[0065] 《Sample Manufacturing》

[0066] (1) Magnetic powder and thermosetting resin

[0067] As magnet powders, commercially available NdFeB-based anisotropic magnet powder (MAGFINE / Br: 1.28T, iHc: 1313 kA / m, average particle size: 125 μm, manufactured by Aichi Steel, Ltd.) which is a coarse powder produced by hydrogen treatment (d-HDDR) and commercially available SmFeN-based anisotropic magnet powder (SmFeN alloy fine powder C / Br: 1.35T, iHc: 875 kA / m, average particle size: 3 μm, manufactured by Sumitomo Metal Mining, Ltd.) which is a fine powder were used.

[0068] As a thermosetting resin, an epoxy resin composed of a main agent (first resin) and a curing agent (second resin) shown in Table 1 is used. All of them are in powder form at room temperature. In addition, in this embodiment, a resin composition in which a curing accelerator and a release agent (the two are collectively referred to as "additives") shown in Table 1 are added to the epoxy resin is prepared. In this specification, a resin composition containing additives is also referred to as "epoxy resin".

[0069] The resin composition placed on the heating plate begins to deform (soften) when the surface temperature of the heating plate reaches about 60°C. This temperature is close to the softening point calculated from the softening point of the main agent (ts1) and the softening point of the curing agent (ts2) and their mixing ratio: 53°C×100+65°C×74.4) / (100+74.4)≈58.1°C (about 59°C).

[0070] (2) Magnet raw materials

[0071] The mixture of magnet powder (coarse powder and fine powder) and thermosetting resin is mixed while heating in a kneading machine (appropriately referred to as "melt mixing") to prepare a granular composite (mixture / magnet raw material). The mixing ratio of the mixture is set to 65.2% by mass of coarse powder, 27.9% by mass of fine powder, and 6.9% by mass of thermosetting resin (including additives) in terms of mass ratio relative to the whole. The true density (ρ0) of the magnet raw material obtained from the true density and mixing ratio is 5.6 g / cm 3 .

[0072] In addition, if the volume ratio is calculated, the magnet powder (coarse powder and fine powder) and the thermosetting resin are 7:3. The volume ratio of the coarse powder and the fine powder is approximately the same as their mass ratio, which is 7:3.

[0073] During the kneading, the kneader was kept at 90°C and the kneader was rotated at a low speed (10 rpm) for 5 minutes (melt mixing step). At this time, the thermosetting resin was softened or melted. However, due to the low temperature and short time melt mixing, the thermosetting resin was almost not heat-cured.

[0074] (3) Pre-forming process

[0075] The compound is loaded into the cavity of the preform mold to produce a rectangular preform (upper and lower surfaces: □13.8mm). The inner wall temperature of the cavity (mold side wall temperature) is set to about 23°C (normal temperature), 60°C or 65°C (warm), 150°C (hot). These temperatures are measured by thermocouples buried near the inner wall of the mold. At each temperature, the molding pressure (0.15 to 500 MPa) is varied.

[0076] (4) Formal forming process

[0077] Each preform after warm forming is placed in the cavity of the formal forming mold and compression formed in a heated orientation magnetic field. At this time, the inner wall temperature of the cavity is set to 150°C, and the forming pressure (compression force) is set to 20MPa. In addition, the orientation direction is set to a direction (lateral) orthogonal to the compression direction (axial direction), and the orientation magnetic field (5~18kOe / 398~1432kA / m) is changed in various ways. In this way, a formal formed body of a rectangular parallelepiped (upper and lower surfaces: □14mm) is obtained.

[0078] As a comparative sample, a final molded body was prepared by directly placing a granular composite into a cavity of a final mold without using a preform and performing heating and compression molding in an aligning magnetic field in the same manner.

[0079] (5) Heat treatment process

[0080] The final molded body taken out of the cavity of the mold was heated in the air at 150°C for 30 minutes (curing treatment). In this way, a bonded magnet after the thermosetting resin was thermally cured was obtained. Each bonded magnet was further magnetized by applying a 6T magnetic field using an air-core coil (magnetization step).

[0081] Observation and Measurement

[0082] (1) Forming pressure and apparent density (ρ) of preform

[0083] The apparent density (ρ) of each preform with different molding temperatures and molding pressures is calculated. The apparent density is calculated by measuring the mass and dimensions of each preform and dividing the mass by the volume calculated from the dimensions. The relationship between them is summarized in Figure 1 middle.

[0084] (2) Appearance and failure mode of preform

[0085] For warm-formed preforms (ρ=3g / cm 3 ) and room temperature formed preforms (ρ = 3g / cm 3 ),exist Figure 2A and Figure 2B The appearance and the failure mode are shown in FIG. 2 (the two are collectively referred to as “FIG. 2”). The failure mode shows the state when the preform is lightly hit with a plastic hammer.

[0086] In addition, the outer surface of the preform was observed using an optical microscope. Figure 3 In addition, the boundary (outer edge) of the resin appearing on the surface (part) of each preform is shown by a solid line or a dotted line.

[0087] (3) Orientation rate of bonded magnets

[0088] The orientation ratio was calculated from the magnetic properties of the bonded magnet. The orientation ratio was compared with the orientation magnetic field in the main forming step and the apparent density of the preform (ρ[g / cm 3 ]) or relative density (%) are summarized in Figure 4 middle.

[0089] Here, the magnetic properties of the bonded magnet are obtained from the BH curve obtained by room temperature measurement using a DC BH tracer (TRF-5BH-25Auto manufactured by Toei Industries Co., Ltd.). The relative density (ρ / ρ0[%]) is obtained by dividing the apparent density (ρ) of the preform by the true density (ρ0) of the magnet raw material.

[0090] The orientation ratio was determined by dividing the residual magnetic flux density (Brx) when each orientation magnetic field (kOe) was applied by the residual magnetic flux density (Br0) when an orientation magnetic field of 20 kOe (1591 kA / m) was applied.

[0091] "evaluate"

[0092] (1) Apparent density of preform

[0093] Depend on Figure 1 It can be seen that the apparent density of the powdered composite (ρ: 2.4 g / cm 3 ) of the preform having a bulk density of .

[0094] (2) Preform shape retention

[0095] Depend on Figure 2A It can be seen that in the preform after warm forming, an outer shell (shell) is formed, and inside (inner package / core), the composite is in a granular form. Figure 2B It is found that the preform formed at room temperature has no outer shell (shell) and the whole is disintegrated into particles even when lightly hit.

[0096] Think of this difference as Figure 3 The figure shows the state of the thermosetting resin (the presence or absence of a connecting portion) caused by the vicinity of the outer surface of the preform.

[0097] (3) Orientation rate of bonded magnets

[0098] Depend on Figure 4 It can be seen that regardless of the size of the orientation magnetic field, the lower the apparent density of the preform, the greater the orientation ratio of the bonded magnet. 3 The orientation ratio of the bonded magnet of the preform is almost the same as the orientation ratio of the bonded magnet using the granular composite as it is.

[0099] As described above, it is clear that the preform having the outer shell portion and the inner shell portion can suppress the reduction in magnetic properties of the bonded magnet and ensure shape retention (and therefore handleability).

[0100]

Claims

1. A preform, comprising: An outer shell portion formed by bonding a portion of a powdered or granular magnet raw material consisting of a mixture or kneaded product of magnet particles and a thermosetting resin; and An inner package portion is formed by the remaining portion of the magnet material located within the outer shell portion.

2. The preform according to claim 1, wherein: The outer surface of the shell portion has a connecting portion formed by integrating the thermosetting resin between a plurality of particles at least in a portion thereof.

3. The preform according to claim 1 or 2, wherein: At least a portion of the inner package is in powder or granular form.

4. The preform according to any one of claims 1 to 3, wherein The magnet particles are contained in an amount of 88 to 98 mass % based on the entire magnet raw material.

5. The preform according to any one of claims 1 to 4, wherein The magnet particles include rare earth anisotropic magnet particles.

6. The preform according to any one of claims 1 to 5, wherein The ratio of the apparent density (ρ) to the true density (ρ0), that is, the relative density (ρ / ρ0) is 48 to 72%.

7. A preforming method comprising the step of subjecting a magnet raw material composed of a mixture or kneaded product of magnet particles and a thermosetting resin to warm pressure forming, The preform according to any one of claims 1 to 6 can be obtained.

8. The preforming method according to claim 7, wherein: The preforming step is performed by setting the temperature of the inner wall surface of the preforming mold filled with the magnet raw material, namely the preforming temperature (Tp), to the softening point (ts) of the thermosetting resin to the softening point + 20°C (ts≤Tp≤ts+20°C).

9. The preforming method according to claim 7, wherein: The thermosetting resin comprises at least a first resin having a first softening point (ts1) and a second resin having a second softening point (ts2) higher than the first softening point, The preforming step is performed by setting the temperature of the inner wall surface of the preforming mold filled with the magnet raw material, that is, the preforming temperature (Tp), to the first softening point to the second softening point (ts1≤Tp≤ts2).

10. The preforming method according to claim 9, wherein: Among the softening points of the resin constituting the thermosetting resin, the first softening point (ts1) is the smallest and the second softening point (ts2) is the largest, The preforming temperature (Tp) is higher than the first softening point and lower than the second softening point (ts1 < Tp < ts2). 11 . A method for producing a compressed bonded magnet, comprising a main molding step of heating and compression molding the preform according to claim 1 .

12. The method for manufacturing a compressed bonded magnet according to claim 11, wherein: The magnetic particles include anisotropic magnetic particles, The main forming step is performed by applying an alignment magnetic field to the cavity in which the preform is placed.

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