Rotor and rotor manufacturing method

Abstract

To provide a high strength bonded magnet rotor and a manufacturing method thereof.SOLUTION: A rotor 100 includes a cylindrical shaft 1 and a cylindrical bonded magnet layer 2 arranged on the outer peripheral surface of the shaft 1 and having magnetic powder and a first resin, and the bonded magnet layer 2 includes a coating layer 21 on its outer periphery that has a second resin.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to rotors and methods of manufacturing rotors. [Background technology]

[0002] Magnets include cast magnets, which have been used for a long time, sintered magnets made by sintering magnetic powder, and bonded magnets made by molding magnetic powder with a resin binder. Of these, bonded magnets have inferior magnetic properties to cast magnets and sintered magnets, but have high dimensional accuracy and a high degree of freedom in shape. One example of such bonded magnets is used as a magnet for electric motors, specifically, as a magnet for the rotor of an electric motor. When using a bonded magnet as a magnet for the rotor of an electric motor, the bonded magnet is required to have not only magnetic properties but also strength that can withstand the high speed rotation of the rotor.

[0003] Patent Document 1 discloses a method for manufacturing a shaft-integrated bonded magnet as an example of a rotor manufacturing method. In this shaft-integrated bonded magnet, a cylindrical bonded magnet is integrally provided on the circumferential surface of a cylindrical shaft. The shaft-integrated bonded magnet is formed by compressing a mixture of magnetic powder with a bimodal particle size distribution, resin, and the shaft to integrate a molded body that will become a bonded magnet with the shaft. The molded body integrated with the shaft is impregnated with an impregnation resin with a viscosity of 100 to 600 mPa·s. The impregnation resin is hardened after impregnation into the molded body. The impregnation of the impregnation resin into the molded body is performed in a pressurized atmosphere after reducing the pressure. In this shaft-integrated bonded magnet, it is said that the strength of the bonded magnet and the bonded strength between the bonded magnet and the shaft can be increased by impregnating the molded body integrated with the shaft with resin.

[0004] Patent Document 2 discloses a method for producing a bonded magnet and the bonded magnet itself. This method for producing a bonded magnet includes a first compression step in which a magnetic powder with an average particle size of 10 μm or less is compressed while being magnetically oriented to obtain a first compact, a second compression step in which the first compact is brought into contact with a thermosetting resin with a viscosity of 200 mPa s or less and then compressed to obtain a second compact, and a heat treatment step in which the second compact is heat treated. It is said that the bonded magnet produced by this method for producing a bonded magnet has improved magnetic properties due to the high filling rate and orientation rate of the magnetic powder. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-202369 A [Patent Document 2] JP 2020-109840 A Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, when a bonded magnet is used as a magnet for the rotor of an electric motor, the bonded magnet is required to have not only magnetic properties but also strength that can withstand the high speed rotation of the rotor. However, with the manufacturing method of the shaft-integrated bonded magnet disclosed in Patent Document 1, there are cases where the bonded magnet of the rotor does not have sufficient strength. For example, when it is desired to use an impregnation resin suitable for improving magnetic properties, there are cases where the impregnation resin cannot be sufficiently impregnated, or even if it is impregnated once, the impregnated state cannot be maintained until it is hardened. For this reason, it is desired to provide a rotor with high bonded magnet strength and a manufacturing method thereof.

[0007] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a rotor having a high strength bonded magnet and a manufacturing method thereof. [Means for solving the problem]

[0008] In order to achieve the above object, the manufacturing method of a bonded magnet and the bonded magnet according to the present disclosure are as follows.

[0009] [1] The rotor according to the present disclosure comprises: A cylindrical shaft; a cylindrical bonded magnet layer disposed on an outer circumferential surface of the shaft and including a magnetic powder and a first resin; The bonded magnet layer has a coating layer containing a second resin on the outer periphery.

[0010] The rotor has a bonded magnet layer having high strength.

[0011] [2] In the rotor described in [1] above, The coating layer may be formed in a cylindrical shape and have a thickness of 100 μm or more and 200 μm or less.

[0012] In the rotor described above, the content of magnetic powder in the bonded magnet layer is not reduced too much, and the strength of the bonded magnet layer can be increased.

[0013] [3] In the rotor described in [1] or [2] above, The second resin may be the first resin.

[0014] In the rotor described above, the resin in the vicinity of the magnetic powder and the resin in the coating layer may be integrated together, further increasing the strength of the bonded magnet and its coating layer.

[0015] [4] A method for manufacturing a rotor according to the present disclosure includes: a molding step of forming a cylindrical compression-molded layer on an outer circumferential surface of a cylindrical shaft using a magnetic powder mixture, which is a mixture of a magnetic powder and a first thermosetting composition; an impregnation step of immersing the compression molded layer in a liquid second thermosetting composition in an immersion container; and a curing step of heating the compression molded layer while immersed in the second thermosetting composition in the immersion vessel.

[0016] According to the above manufacturing method, the rotor described above can be realized.

[0017] [5] In the method for manufacturing a rotor according to the above [4], The molding step is performed by inserting the shaft into a cylindrical molding die having an inner diameter larger than a diameter of the shaft, filling the magnetic powder mixture into the cylindrical molding die and around the shaft, and compressing the filled layer of the magnetic powder mixture along the axial direction of the molding die; The impregnation step may be performed by inserting the compression molded layer together with the shaft into the immersion container having an inner diameter larger than the inner diameter of the molding die, and filling the space between the compression molded layer and the immersion container with the thermosetting composition.

[0018] The above manufacturing method allows the coating layer to have an appropriate thickness, which may further increase the strength of the bonded magnet and its coating layer.

[0019] [6] In the method for manufacturing a rotor according to the above [4] or [5], The inner diameter of the immersion container may be greater than the inner diameter of the molding die by 200 μm or more and 400 μm or less.

[0020] By using the above-mentioned production method, the thickness of the coating layer can be set to 100 μm or more and 200 μm or less.

[0021] [7] In the method for manufacturing a rotor according to any one of the above items [4] to [6], The molding pressure in the molding process is 1t / cm 2 More than 5t / cm 2 It may be the following:

[0022] The above manufacturing method may increase the strength of the bonded magnet layer.

[0023] [8] In the method for manufacturing a rotor according to any one of the above items [4] to [7], The second thermosetting composition may be the first thermosetting composition.

[0024] The above manufacturing method may result in the resin in the vicinity of the magnetic powder and the resin in the coating layer becoming integrated, further increasing the strength of the bonded magnet and its coating layer. [Brief description of the drawings]

[0025] [Figure 1] FIG. 2 is a side view of the rotor according to the embodiment. [Diagram 2] 1 is a view of a rotor according to an embodiment of the present invention as viewed in the axial direction. [Diagram 3] FIG. 4 is an explanatory diagram of a mold unit and a molding process. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] A rotor and a method for manufacturing a rotor according to an embodiment of the present disclosure will be described with reference to the drawings. First, an overview of a rotor and a method for manufacturing a rotor according to an embodiment of the present disclosure will be described.

[0027] FIG. 1 shows a side view of a rotor 100 according to this embodiment.

[0028] As shown in FIG. 1, rotor 100 comprises a cylindrical shaft 1, and a cylindrical bonded magnet layer 2 arranged on the outer peripheral surface of shaft 1 and containing magnetic powder and a first resin, and bonded magnet layer 2 has a coating layer 21 on its outer periphery containing a second resin.

[0029] This rotor 100 has a bonded magnet layer 2 which is a bonded magnet and has high strength.

[0030] The manufacturing method of the rotor according to this embodiment includes a molding step of forming a cylindrical compression-molded layer on the outer peripheral surface of a cylindrical shaft 1 using a magnetic powder mixture, which is a mixture of magnetic powder and a first thermosetting composition, an impregnation step of immersing the compression-molded layer in a liquid second thermosetting composition in an immersion container, and a curing step of heating the compression-molded layer while immersed in the second thermosetting composition in the immersion container.

[0031] The rotor 100 can be realized by this rotor manufacturing method.

[0032] The rotor 100 and a method for manufacturing the same will now be described in detail.

[0033] As described above, the rotor 100 includes the shaft 1 and the bonded magnet layer 2 having the coating layer 21 .

[0034] The shaft 1 is a rotating shaft of the rotor 100, and is a base that holds the bonded magnet layer 2. The shaft 1 is formed in a cylindrical shape centered on the axis G. One end of the shaft 1 may be formed with a groove 11a that serves as a bearing when the rotor 100 is incorporated into a motor. The groove 11a may be a groove formed along the circumferential direction of the shaft 1. The groove 11a may be formed at a position on the shaft 1 that is closer to the end side than the central portion. Hereinafter, the end of the shaft 1 on the side where the groove 11a is formed is referred to as the first end 11, and the other end side is referred to as the second end 12. The direction along the axis G is referred to as the axial direction.

[0035] The shaft 1 may be made of, for example, iron, an iron-based alloy such as silicon steel or stainless steel, an aluminum alloy, or a resin. The shaft 1 may also be made of a composite material of resin and a metal powder or an alloy powder.

[0036] 1 and 2, the bonded magnet layer 2 is a layer having a magnet layer 20 and a covering layer 21 formed as an outer layer of the magnet layer 20. The bonded magnet layer 2 is formed on the outer peripheral surface of the cylinder of the shaft 1. The bonded magnet layer 2 is also formed in a cylindrical shape that covers the outer peripheral surface of the cylinder of the shaft 1. Note that FIG. 2 is a view of the rotor 100 viewed along the axis G from the second end 12 side.

[0037] 1, the bonded magnet layer 2 is disposed in the central portion in the axial direction of the shaft 1 in a range not overlapping with the groove portion 11a. The bonded magnet layer 2 is shorter than the shaft 1 in the axial direction of the shaft 1. In this embodiment, there are portions of the shaft 1 on the first end portion 11 side and the second end portion 12 side that are not covered with the bonded magnet layer 2.

[0038] As shown in Figures 1 and 2, the magnet layer 20 is a layer containing magnetic powder and a first resin. The magnet layer 20 is formed on the cylindrical outer circumferential surface of the shaft 1. The magnet layer 20 is formed in a cylindrical shape covering the cylindrical outer circumferential surface of the shaft 1. The magnet layer 20 is a layer of bonded magnet in the bonded magnet layer 2. The magnetic powder and the first resin will be described later.

[0039] The coating layer 21 is a layer containing the second resin. By having the coating layer 21 on the bonded magnet layer 2, the strength of the bonded magnet layer 2 is increased. The coating layer 21 is a layer on the outer periphery of the bonded magnet layer 2, and is formed on the cylindrical outer periphery of the magnet layer 20. The coating layer 21 may be formed in a cylindrical shape that covers the cylindrical outer periphery of the magnet layer 20. The second resin may be the same resin as the first resin. This may cause the resin in the vicinity of the magnetic powder and the resin of the coating layer 21 to be integrated together, further increasing the strength of the bonded magnet layer 2 and the coating layer 21. The second resin will be described later.

[0040] The coating layer 21 should have a thickness that does not reduce the magnetic powder content of the bonded magnet layer 2 too much relatively, and that increases the strength of the bonded magnet layer 2. The coating layer 21 may have a thickness of 100 μm or more and 200 μm or less. If the coating layer 21 is in this thickness range, the magnetic powder content of the bonded magnet layer 2 is not reduced too much, and the strength of the bonded magnet layer can be increased.

[0041] As described above, the method for manufacturing the rotor according to this embodiment includes the molding step, the impregnation step, and the curing step.

[0042] The molding step is a step of compressing and molding a magnetic powder mixture layer 31, which is a mixture of a magnetic powder and a first thermosetting composition, in a die unit 4 as shown in Fig. 3, and forming a compression molded layer 32 on the outer circumferential surface of a shaft 1 as shown in Fig. 4 to manufacture an integrally molded product 200. The compression molded layer 32 is a molded body serving as a precursor of a bonded magnet. Fig. 3 is an explanatory diagram of the die unit 4 and the compression molding performed by it. Fig. 4 is a side view of the integrally molded product 200.

[0043] As shown in FIG. 3, the die unit 4 includes, for example, a cylindrical molding die 41, a cylindrical lower punch 42 (lower punch), a columnar spacer 43 inserted into the cylinder of the lower punch 42, and a cylindrical upper punch 44 (upper punch). The die unit 4 may be made of iron or an iron alloy. A columnar space is formed inside the cylinder of the molding die 41, the lower punch 42, and the upper punch 44. The space inside the cylinder of the molding die 41 is a cavity for molding the compression molded layer 32. Hereinafter, the space inside the cylinder of the molding die 41 will be simply referred to as the inner space.

[0044] The mold unit 4 and the molding procedure for the integrally molded product 200 (see FIG. 4) using the mold unit 4 in the molding process will be described below.

[0045] In the mold unit 4, the compression molded layer 32 is molded with the shaft 1 inserted in the inner space of the molding die 41. The inner diameter d1 of the inner space of the molding die 41 is larger than the diameter of the shaft 1. In the following description, with the shaft 1 inserted in the inner space of the molding die 41, the side where the second end 12 of the shaft 1 is arranged is defined as the bottom, and the side where the first end 11 is arranged is defined as the top.

[0046] A lower punch 42 is inserted into the lower end of the inner space of the molding die 41. The outer diameter of the lower punch 42 is slightly smaller than the inner diameter d1 of the inner space of the molding die 41, but is approximately the same as the inner diameter d1.

[0047] A spacer 43 is inserted into the space inside the tube at the lower end of the lower punch 42. The inner diameter of the lower end of the lower punch 42 is slightly larger than the outer diameter of the spacer 43, but is approximately the same. The axial length of the spacer 43 is shorter than the axial length of the lower punch 42. The outer diameter of the spacer 43 is slightly smaller than the outer diameter of the shaft 1. When the spacer 43 is inserted into the space inside the tube at the lower end of the lower punch 42, a space surrounded by the inner circumferential surface of the tube of the lower punch 42 and the upper surface of the spacer 43 is defined at the upper end of the lower punch 42. The inner diameter of the upper end of the lower punch 42 is slightly larger than the outer diameter of the shaft 1, but is approximately the same. By fitting the second end 12 of the shaft 1 into this space surrounded by the inner circumferential surface of the tube of the lower punch 42 and the upper surface of the spacer 43, the shaft 1 can be fixed (positioned) in a state where it is inserted into the inner space of the molding die 41.

[0048] With shaft 1 fixed in the inner space of molding die 41, axis G overlaps with the axis of the inner space of molding die 41. As a result, the space formed between the inner surface of molding die 41 and the outer surface of shaft 1 has a cylindrical shape, and its axis overlaps with axis G.

[0049] After the shaft 1 is fixed in the inner space of the molding die 41 as described above, a predetermined amount of magnetic powder is poured between the shaft 1 and the inner wall of the molding die 41 to form a magnetic powder layer. Then, this magnetic powder layer is impregnated with a predetermined amount of a liquid first thermosetting composition to form the magnetic powder layer into the magnetic powder mixture layer 31. In other words, the magnetic powder mixture layer 31 is a filled layer of the magnetic powder mixture filled inside the cylindrical molding die 41 and around the shaft 1.

[0050] In this embodiment, the term "impregnation" refers to allowing a liquid material to permeate between particles or into the interior of a molded body.

[0051] In the present embodiment, the term "thermosetting" refers to a property of being cured by heating in a curing step described later, more than before heating. Hereinafter, the curing of a thermosetting composition by heating more than before heating may be simply referred to as "thermosetting".

[0052] The first thermosetting composition can be supplied to the magnetic powder layer by dropping, etc. The first thermosetting composition is thermally cured in the curing step described below to become the first resin of the bonded magnet layer 2. The first thermosetting composition will be described later.

[0053] Thereafter, the upper punch 44 is inserted into the inner space of the molding die 41, pressing down on the top surface of the magnetic powder mixture layer 31. In this state, the first end 11 of the shaft 1 is inserted into the space inside the cylinder of the upper punch 44. The inner diameter of the portion of the upper punch 44 where the first end 11 is inserted is slightly larger than, but approximately the same as, the outer diameter of the shaft 1. The outer diameter of the upper punch 44 is also slightly smaller than, but approximately the same as, the inner diameter d1 of the inner space of the molding die 41.

[0054] In the molding step, with the shaft 1 inserted into a cylindrical molding die 41 having an inner diameter larger than the diameter of the shaft 1, the magnetic powder mixture is filled into the cylindrical molding die 41 and around the shaft 1 to form a magnetic powder mixture layer 31 as a filled layer of the magnetic powder mixture. Then, the magnetic powder mixture layer 31 is sandwiched between an upper punch 44 and a lower punch 42 along the axial direction and compressed to form a compression molded layer 32. As a result, the compression molded layer 32 is molded integrally with the shaft 1. A pusher 45 may be used to push the upper punch 44 during compression molding, if necessary.

[0055] In the molding process, the compression molded layer 32 is molded into a cylindrical shape whose outer circumferential surface follows the inner circumferential surface of the tube of the molding die 41. The axis of the cylinder of the compression molded layer 32 overlaps with the axis G. When the integrally molded product 200 (see FIG. 4) is removed from the molding die 41, the compression molded layer 32 expands due to spring back, and the outer diameter of the compression molded layer 32 becomes slightly larger than the inner diameter d1 of the molding die 41.

[0056] The molding pressure in the molding step (the pressure with which the magnetic powder mixture layer 31 is compressed by the upper punch 44 and the lower punch 42) is not particularly limited. In order to manufacture a more highly packed bonded magnet layer 2, the molding pressure is preferably 1 t / cm 2 More than 11t / cm 2 Less than 1t / cm 2 More than 5t / cm 2 Less than 2t / cm, more preferably 2 More than 5t / cm 2 By setting the molding pressure within this range, the strength of the bonded magnet layer 2 may be increased.

[0057] The molding pressure is 1t / cm 2 If the molding pressure is 11 t / cm or more, the filling rate in the molded body is sufficiently high. 2 If the molding pressure exceeds 2 t / cm, the density of the compression molded layer 32 becomes too high, which may result in poor impregnation with the second thermosetting composition described below. This may result in a decrease in the strength of the resulting bonded magnet layer 2. 2 More than 5t / cm 2If it is equal to or less than this, the strength of the bonded magnet layer 2 (see FIG. 1) after the hardening step described below tends to increase.

[0058] Compression in compression molding may be performed two or more times. For example, the mold may be compressed at a first pressure as a preliminary compression, and then a second pressure higher than the first pressure may be used for finishing compression to form a molded body.

[0059] The compression molding may be performed while magnetically orienting the magnetic powder. When magnetic orientation is performed during compression molding, the magnitude of the external magnetic field applied for magnetic orientation is not particularly limited, but is preferably 0.5 T or more, and more preferably 1 T or more. If it is less than 0.5 T, the magnet tends not to be sufficiently oriented. The upper limit is preferably 10 T or less. If it exceeds 10 T, the magnetic powder will be excessively magnetized, making it impossible to perform sufficient molding.

[0060] The magnetic powder is not particularly limited. An example of the magnetic powder that can be used in the method for producing a bonded magnet according to the present embodiment is a rare earth magnetic material such as SmFeN, NdFeB, or SmCo.

[0061] The SmFeN magnetic powder can be produced by the method disclosed in JP-A-11-189811, the NdFeB magnetic powder can be produced by the HDDR method disclosed in WO-A-2003 / 85147, and the SmCo magnetic powder can be produced by the method disclosed in JP-A-08-260083.

[0062] The particle shape of the magnetic powder is preferably close to spherical. For example, the aspect ratio of the magnetic powder shape is preferably 3 or less. When the magnetic powder particle shape is, for example, spherical with an aspect ratio of 3 or less, it becomes easy to realize a bonded magnet with a high filling rate of the magnetic powder.

[0063] In this embodiment, the aspect ratio of the magnetic powder can be determined by observing the magnetic powder with a SEM (scanning electron microscope), measuring the maximum diameter (long diameter) and the particle diameter (short diameter) in the direction perpendicular to the maximum diameter for any 50 particles, and calculating the average value of the ratio of the long diameter to the short diameter (long diameter / short diameter). The magnification ratio during SEM observation may be appropriately changed depending on the particle diameter. The magnification ratio may be, for example, 100 to 1000 times.

[0064] The particle size of the magnetic powder may be, for example, 3 μm or more and 300 μm or less in terms of the median diameter (50% particle size, so-called D50). In this embodiment, the particle size and particle size distribution of the magnetic powder can be determined as volume-based values ​​measured using a laser diffraction / scattering type particle size distribution measuring device (manufactured by Horiba, Ltd., model "LA960"). For measurement using the laser diffraction / scattering type particle size distribution measuring device, a suspension in which 1 g of the magnetic powder to be measured is dispersed in methyl ethyl ketone as a solvent may be used.

[0065] The magnetic powder may be treated with phosphoric acid, which forms a passivation film having PO bonds on the surface of the magnetic powder.

[0066] The phosphating is carried out by reacting the magnetic powder with a phosphating agent, which may be, for example, phosphates such as orthophosphoric acid, sodium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, zinc phosphate, calcium phosphate, etc., inorganic phosphoric acids such as hypophosphorous acid, hypophosphites, pyrophosphoric acid, polyphosphoric acid, etc., organic phosphoric acids, and salts thereof.

[0067] The magnetic powder may be mixed with a surface treatment agent, that is, the magnetic powder used in the molding step may be a surface-treated magnetic powder to which a predetermined amount of a surface treatment agent has been added.

[0068] The surface treatment agent may be an additive that protects the surface or modifies the surface properties, such as preventing oxidation of the magnetic powder, compact, or bonded magnet, or improving wettability in the impregnation process of the linked body, or an additive that functions as a so-called binder, improving the binding force between the particle surfaces of the magnetic powder in the compact. Examples of the surface treatment agent include alkyl silicates that perform silica treatment on the particle surfaces of the magnetic powder, silane coupling agents that perform silane treatment, and surfactants such as nonionic surfactants. The surface treatment agent is not limited to one type, and two or more types may be used in combination.

[0069] The surface treatment agent is preferably mixed in an amount of 5 parts by mass or less, and more preferably 1 to 3 parts by mass, per 100 parts by mass of the magnetic powder. This may increase the strength of the molded body or bonded magnet. It may also improve the handleability of the molded body.

[0070] The magnetic powder is preferably surface-treated with a coupling agent, preferably silane-treated, in order to improve the magnetic properties of the magnetic powder, improve wettability with the thermosetting composition in the impregnation step described below, and increase the mechanical strength of the bonded magnet. Note that the coupling agent has two or more different groups in the molecule, one of which has a group that reacts with inorganic materials and the other has a group that reacts with organic materials.

[0071] The coupling agent is not particularly limited, and examples of the coupling agent include a silane coupling agent having no alkyl or alkenyl group with a carbon number of 8 to 24, and a coupling agent having an alkyl or alkenyl group with a carbon number of 8 to 24.

[0072] Examples of coupling agents having an alkyl or alkenyl group having 8 to 24 carbon atoms include silane coupling agents, phosphate coupling agents, and hydrogen phosphite coupling agents. These coupling agents may be used alone or in combination of two or more.

[0073] Examples of silane coupling agents having an alkyl group or an alkenyl group having 8 to 24 carbon atoms include those represented by the following general formula: Specific examples include decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, octyltriethoxysilane, and the like, with octadecyltriethoxysilane and octyltriethoxysilane being particularly preferred. (R 1 ) x Si(OR 2 ) (4-x) (R 1 is C n H 2n+1 or C n H 2n-1 where n is an integer of 8 to 24; R 2 is C m H 2m+1 where m is an integer of 1 to 4, and x is an integer of 1 to 3. In addition, the group in the silane coupling agent that reacts with the organic material refers to, for example, a group in which a silicon atom is directly bonded to a carbon atom, and in the above formula, R 1 and the group that interacts with inorganic materials is OR 2 It is.

[0074] Examples of phosphate coupling agents having an alkyl or alkenyl group having 8 to 24 carbon atoms include those represented by the following general formula: Specific examples include didecyl acid phosphate, isodecyl acid phosphate, isotridecyl acid phosphate, lauryl acid phosphate, oleyl acid phosphate, stearyl acid phosphate, isostearyl acid phosphate, tetracosyl acid phosphate, etc., with oleyl acid phosphate being preferred among them. (R 1 O) x PO(OH) (3-x) (R 1 is C n H 2n+1 or C n H 2n-1 where n is an integer of 8 to 24, and x is an integer of 1 or 2. In addition, the group in the phosphate coupling agent that reacts with the organic material is R 1 O, and the group that interacts with inorganic materials is OH.

[0075] The silane coupling agent, phosphate coupling agent or hydrogen phosphite coupling agent having an alkyl group or alkenyl group having 8 to 24 carbon atoms may be used alone or in combination of two or more kinds.

[0076] The treatment with a coupling agent having an alkyl or alkenyl group having 8 to 24 carbon atoms can be carried out by mixing the above-mentioned coupling agent with the magnetic powder and heating it in air to form a coating of the coupling agent. Examples of moisture required for hydrolyzing the coupling agent include acidic aqueous solutions such as an aqueous acetic acid solution, sulfuric acid solution, and phosphoric acid solution, and basic aqueous solutions such as ammonia water, sodium hydroxide solution, and potassium hydroxide solution.

[0077] The amount of coupling agent having an alkyl or alkenyl group with a carbon number of 8 to 24 is preferably 0.01 to 1 part by mass, and more preferably 0.05 to 0.5 parts by mass, per 100 parts by mass of magnetic powder. If it is less than 0.01 part by mass, sufficient lubricity cannot be imparted to the magnetic powder, and if it is more than 1 part by mass, the mechanical strength of the obtained molded product is impaired.

[0078] Examples of silane coupling agents having no alkyl or alkenyl group and having a carbon number of 8 to 24 include γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethylenedisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, γ-chloropropylmethyldimethoxysilane, γ-mercaptopropyl Methyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, Examples of such silanes include γ-aminopropyltriethoxysilane, ureidopropyltriethoxysilane, γ-isocyanatepropyltriethoxysilane, bis(3-triethoxysilylpropyl)tetrasulfane, γ-isocyanatepropyltrimethoxysilane, vinylmethyldimethoxysilane, 1,3,5-N-tris(3-trimethoxysilylpropyl)isocyanurate, and N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propaneamine.Examples of silane coupling agents having a cyclic structure include coupling agents having an alicyclic structure such as a monocyclo ring or a bicyclo ring, or an aromatic ring as the cyclic structure. For example, coupling agents having a norbornene skeleton, which is a bicyclo ring, include 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltrimethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltriethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)trimethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)triethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)triethoxysilane, [2.2.1]hept-2-enyl)ethynyltrimethoxysilane, 2-(bicyclo[2.2.1]hept-2-enyl)ethynyltriethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)hexyltrimethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)hexyltriethoxysilane, and coupling agents having an aromatic ring skeleton include N-phenyl-3-aminopropyltrimethoxysilane, N-aminoethylaminomethylphenyl-3-ethyltrimethoxysilane, p-styryltrimethoxysilane, and m-allylphenylpropyltriethoxysilane. These silane coupling agents may be used alone or in combination of two or more. Among these, in terms of wettability and compatibility with the thermosetting composition, slipperiness of the magnetic powder particle surface, heat resistance, and the like, silane coupling agents having a cyclic structure are preferred, silane coupling agents having a norbornene skeleton are more preferred, and 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltrimethoxysilane and 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltriethoxysilane are even more preferred.

[0079] The treatment with a silane coupling agent having no alkyl or alkenyl group with a carbon number of 8 to 24 can be carried out by mixing the above-mentioned coupling agent with the magnetic powder and heating it in air to form a coating of the silane coupling agent. Examples of moisture required for hydrolyzing the coupling agent include acidic aqueous solutions such as an aqueous solution of acetic acid, sulfuric acid, or phosphoric acid, or basic aqueous solutions such as aqueous ammonia, sodium hydroxide, or potassium hydroxide.

[0080] The amount of the silane coupling agent having no alkyl or alkenyl group and having a carbon number of 8 to 24 is preferably 0.1 to 2 parts by mass, more preferably 0.2 to 1.2 parts by mass, per 100 parts by mass of the magnetic powder. If the amount is less than 0.1 part by mass, the effect of the coupling agent is small, and if the amount exceeds 2 parts by mass, the magnetic powder tends to aggregate and the magnetic properties tend to deteriorate.

[0081] The magnetic powder may be silica-treated with an alkyl silicate in order to protect the magnetic powder from oxidation during the molding process and during use of the resulting molded product. For example, the magnetic powder may be silica-treated prior to the treatment with the coupling agent. The alkyl silicate is represented by the following general formula, and methyl silicate or ethyl silicate is preferred. SinO (n-1) (OR) (2n+2) (R is an alkyl group, and n is an integer of 1 to 10.)

[0082] The silica treatment can be carried out by mixing the above-mentioned alkyl silicate with the magnetic powder and heating in air to form a silica coating. Examples of moisture required for hydrolyzing the silicate include acidic aqueous solutions such as an aqueous solution of acetic acid, sulfuric acid, and phosphoric acid, and basic aqueous solutions such as aqueous ammonia, aqueous sodium hydroxide, and aqueous potassium hydroxide. The amount of alkyl silicate mixed is preferably 1 part by mass or more and 4 parts by mass or less, more preferably 1.5 parts by mass or more and 2.5 parts by mass or less, per 100 parts by mass of the magnetic powder.

[0083] It is preferable that a surfactant such as a nonionic surfactant is added to the magnetic powder in order to improve wettability with the first thermosetting composition and the second thermosetting composition described below.

[0084] Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as laureth-4, laureth-7, laureth-9, laureth-21, laureth-23, ceteth-10, ceteth-20, steareth-2, steareth-20, steareth-21, steareth-25, beheneth-20, beheneth-30, oleth-2, and oleth-10. Other examples include polyoxyethylene fatty acid esters such as PEG-25 stearate, PEG-40 stearate, PEG-45 stearate, PEG-55 stearate, PEG-75 stearate, PEG-100 stearate, PEG-150 stearate, and PEG-150 distearate. Other examples include glycerin fatty acid esters such as glyceryl myristate, glyceryl stearate, glyceryl isostearate, glyceryl oleate, glyceryl dioleate, and glyceryl distearate. Other examples include polyglycerin fatty acid esters such as polyglyceryl-10 stearate, polyglyceryl-10 distearate, polyglyceryl-10 tristearate, polyglyceryl-10 pentastearate, polyglyceryl-10 oleate, polyglyceryl-10 isostearate, polyglyceryl-10 myristate, polyglyceryl-10 laurate, polyglyceryl-4 stearate, polyglyceryl-6 stearate, and polyglyceryl-2 stearate. Other examples include polyoxyethylene glycerin fatty acid esters such as PEG-6 glyceryl isostearate, PEG-20 glyceryl triisostearate, PEG-20 glyceryl tristearate, and PEG-7 glyceryl coconut oil fatty acid. Further examples include sorbitan fatty acid esters such as sorbitan laurate, sorbitan palmitate, sorbitan stearate, sorbitan isostearate, sorbitan oleate, sorbitan sesquistearate, sorbitan sesquiisostearate, sorbitan sesquioleate, sorbitan trioleate, sorbitan tristearate, sorbitan olivoyl fatty acid, and sorbitan coconut fatty acid.Further examples include polyoxyethylene sorbitan fatty acid esters such as POE(20) sorbitan laurate, POE(20) sorbitan stearate, POE(20) sorbitan oleate, and POE(20) sorbitan isostearate.

[0085] The first thermosetting composition is not particularly limited as long as it is thermosetting. The first thermosetting composition may contain a thermosetting monomer, a thermosetting prepolymer, a thermosetting polymer, or the like.

[0086] Examples of the thermosetting monomer include norbornene-based monomers, epoxy-based monomers, phenol-based monomers, acrylic-based monomers, and vinyl ester-based monomers. Examples of the norbornene-based monomers include tricyclo[5.2.1.0 2,6 ]Deca-3,8-diene (dicyclopentadiene), tricyclo[5.2.1.0 2,6 ]decane-3-ene, bicyclo[2.2.1]hepta-2,5-diene (2,5-norbornadiene), bicyclo[2.2.1]hept-2-ene (2-norbornene), bicyclo[3.2.1]oct-2-ene, 5-ethylidene-2-norbornene, bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride, 5-vinylbicyclo[2.2.1]hept-2-ene, tetracyclo[6.2.1.1 3,6 .0 2,7 ]dodec-4-ene, etc. Thermosetting prepolymers include epoxy resins, phenolic resins, melamine resins, guanamine resins, unsaturated polyesters, vinyl ester resins, diallyl phthalate resins, silicone resins, alkyd resins, furan resins, acrylic resins, urea resins, allyl carbonate resins, etc. Thermosetting polymers include polyurethane resins, polyimide resins, polyester resins, etc.

[0087] The first thermosetting composition may contain a polymerization initiator and a curing agent. Examples of the initiator include Grubbs' catalyst (ruthenium carbene complex), dihalogen, and azo compounds. Examples of the curing agent include amine-based curing agents, acid anhydride-based curing agents, polyamide-based curing agents, imidazole-based curing agents, phenolic resin-based curing agents, polymercaptan resin-based curing agents, polysulfide resin-based curing agents, organic acid hydrazide-based curing agents, and isocyanate-based curing agents. Examples of the amine-based curing agents include diaminodiphenylsulfone, metaphenylenediamine, diaminodiphenylmethane, diethylenetriamine, and triethylenetetramine.

[0088] The viscosity of the first thermosetting composition may be, for example, 200 mPa·s or less. The viscosity of the first thermosetting composition is preferably 100 mPa·s or less, more preferably 50 mPa·s or less, even more preferably 15 mPa·s or less, and most preferably 10 mPa·s or less. If the viscosity of the first thermosetting composition is 200 mPa·s or less, the first thermosetting composition will more uniformly impregnate the magnetic powder, and the strength of the bonded magnet layer 2 (see FIG. 1) after the curing step described below will tend to be increased.

[0089] As shown in Fig. 5, the impregnation step is a step in which the compression molded layer 32 is immersed in a liquid second thermosetting composition in an immersion unit 5 to impregnate the compression molded layer 32 with the second thermosetting composition. Fig. 5 is an explanatory diagram of the immersion unit 5 and the compression molding performed by the immersion unit. The second thermosetting composition is thermally cured in a curing step described later to become the second resin of the bonded magnet layer 2.

[0090] As an example, as shown in FIG. 5, the immersion unit 5 includes a cylindrical immersion container 51, a cylindrical bottom cover 52, and a columnar spacer 53 inserted into the cylinder of the bottom cover 52. The immersion unit 5 may be made of iron, an iron alloy, or a synthetic resin such as a fluororesin. For example, if the bottom cover 52 is made of a fluororesin, the bonded magnet layer 2 may be easily released from the bottom cover 52, and the rotor may be easily removed from the immersion unit 5. A cylindrical space is formed inside the cylinder of the immersion container 51 and the bottom cover 52. The space inside the immersion container 51 is a tank that contains the compression molded layer 32 and the second thermosetting composition. Hereinafter, the space inside the immersion container 51 is simply referred to as the inner space.

[0091] The immersion unit 5 and the procedure for impregnating with the second thermosetting composition using the immersion unit 5 in the impregnation step will be described below.

[0092] In the immersion unit 5, the compression molded layer 32 is immersed in the second thermosetting composition with the shaft 1 inserted in the inner space of the immersion container 51. In the following description, with the shaft 1 inserted in the inner space of the immersion container 51, the side where the second end 12 of the shaft 1 is arranged is referred to as the bottom, and the side where the first end 11 is arranged is referred to as the top.

[0093] The inner diameter d2 of the inner space of the immersion container 51 is larger than the inner diameter d1 (see FIG. 3) of the molding die 41. This allows the immersion container 51 to accommodate the compression molded layer 32 expanded by springback. Also, the coating layer 21 (see FIG. 1) can be given an appropriate thickness, which may further increase the strength of the bonded magnet layer 2 and the coating layer 21. It is preferable that the inner diameter d2 is 200 μm or more and 400 μm or less larger than the inner diameter d1. This allows the thickness of the coating layer 21 to be 100 μm or more and 200 μm or less.

[0094] A bottom lid 52 is inserted into the bottom end of the inner space of the immersion container 51. The outer diameter of the bottom lid 52 is approximately the same as the inner diameter of the inner space of the immersion container 51.

[0095] A spacer 53 is inserted into the space inside the cylinder of the bottom lid 52. As a result, the lower end of the inner space of the immersion container 51 is sealed by the bottom lid 52 and the spacer 53, making it possible to hold the second thermosetting composition in a liquid state in the inner space of the immersion container 51.

[0096] The axial length of the spacer 53 is shorter than the axial length of the bottom cover 52. The inner diameter of the bottom cover 52 and the outer diameter of the spacer 53 are approximately the same. The outer diameter of the spacer 53 is the same as the outer diameter of the shaft 1. For example, if the lower end of the bottom cover 52 and the lower end of the spacer 53 are flush with each other, a space surrounded by the inner peripheral surface of the bottom cover 52 and the upper surface of the spacer 53 is defined at the upper end of the bottom cover 52. By fitting the second end 12 of the shaft 1 into this space, the integrally molded product 200 can be fixed (positioned) in the inner space of the immersion container 51.

[0097] When the integrally molded product 200 is fixed in the inner space of the immersion container 51, the axis G overlaps with the axis of the inner space of the immersion container 51. As a result, the space formed between the inner surface of the immersion container 51 and the outer surface of the compression molded layer 32 has a cylindrical shape with a thickness W (see, between the compression molded layer 32 and the inner wall of the immersion container 51), and the axis overlaps with the axis G.

[0098] In a state where the integrally molded product 200 is fixed in the inner space of the dipping container 51 , it is preferable that the compression molded layer 32 be in contact with the upper surface of the lower lid 52 .

[0099] As described above, the compression molded layer 32 together with the shaft 1 is inserted into the immersion container 51, and the integrally molded product 200 is fixed in the inner space of the immersion container 51. Then, a predetermined amount of liquid second thermosetting composition is poured between the compression molded layer 32 and the inner wall of the immersion container 51, and the compression molded layer 32 is immersed in the second thermosetting composition in a state where the second thermosetting composition is filled between the compression molded layer 32 and the inner surface of the immersion container 1. This allows the compression molded layer 32 to be sufficiently impregnated with the second thermosetting composition. In addition, the second thermosetting composition remaining between the compression molded layer 32 and the inner wall of the immersion container 51 is thermally cured in a curing process described later, thereby forming the coating layer 21 (see FIG. 2). In FIG. 6, the second thermosetting composition remaining between the compression molded layer 32 and the inner wall of the immersion container 51 is shown as a liquid layer 33. That is, the liquid layer 33 is thermally cured to become the coating layer 21 formed of the second resin. Figure 6 is an explanatory diagram showing an enlarged view of the vicinity of the upper end of the compression molded layer 32 when the compression molded layer 32 is immersed in the second thermosetting composition (liquid layer 33) in the immersion container 51 of the immersion unit 5.

[0100] When pouring the liquid second thermosetting composition between the compression molded layer 32 and the inner wall of the immersion container 51, it is preferable to make the liquid level of the second thermosetting composition flush with the upper surface of the compression molded layer 32, as shown in Fig. 6. This makes it possible to avoid the unintentional formation of a thick resin layer on the upper surface of the compression molded layer 32, i.e., the end surface of the bonded magnet layer 2 (see Fig. 1).

[0101] 5, by making the compression molded layer 32 contact the upper surface of the lower lid 52 as described above, it is possible to prevent the second thermosetting composition from flowing between the compression molded layer 32 and the lower lid 52 when the liquid second thermosetting composition is poured between the compression molded layer 32 and the inner wall of the immersion container 51. This makes it possible to prevent a thick resin layer from being unintentionally formed on the upper surface of the compression molded layer 32, i.e., the other end surface of the bonded magnet layer 2.

[0102] The viscosity of the second thermosetting composition is preferably 200 mPa·s or less. The viscosity of the second thermosetting composition is preferably 100 mPa·s or less, more preferably 50 mPa·s or less, even more preferably 15 mPa·s or less, and most preferably 10 mPa·s or less. If the viscosity of the second thermosetting composition is 200 mPa·s or less, impregnation in the impregnation step is performed appropriately, and the strength of the bonded magnet layer 2 (see FIG. 1) after the curing step described below is likely to be increased.

[0103] The second thermosetting composition is described in the same manner as the first thermosetting composition. The second thermosetting composition is not particularly limited as long as it is heat curable. The second thermosetting composition may contain a thermosetting monomer, a thermosetting prepolymer, a thermosetting polymer, or the like.

[0104] As described below, the second thermosetting composition is preferably the same thermosetting composition as the first thermosetting composition.

[0105] (hardening process) The curing process is a process in which the compression molded layer 32 (see FIG. 5) impregnated with the second thermosetting composition is heated (hereinafter, this may be referred to as heat treatment) to thermally cure the first thermosetting composition and the second thermosetting composition impregnated in the compression molded layer 32.

[0106] This curing step creates a resin bridge structure between the magnetic powder particles in the compression molded layer 32, which fixes the positional relationship between these particles, increasing the strength of the compression molded layer 32 and making it possible to obtain a high-strength bonded magnet layer 2. In other words, the compression molded layer 32 that has undergone the curing step is the bonded magnet layer 2 according to this embodiment.

[0107] Furthermore, this curing step thermally cures the second thermosetting composition between the compression molded layer 32 and the inner wall of the immersion container 51, forming a cylindrical coating layer 21 that covers the outer circumferential surface of the magnet layer 20. This increases the strength of the bonded magnet layer 2 (see FIG. 1).

[0108] As described above, the second thermosetting composition is preferably the same thermosetting composition as the first thermosetting composition. This allows the magnet layer 20 to be covered and protected by the covering layer 21, while a single resin bridge structure is formed across the magnet layer 20 and the covering layer 21, which may increase the strength of the bonded magnet layer 2 (see FIG. 1). In other words, the resin in the vicinity of the magnetic powder and the resin of the covering layer 21 may be integrated, further increasing the strength of the bonded magnet layer 2 and the covering layer 21.

[0109] The magnetic powder particles and the resin may be chemically bonded to each other, or may be bonded to each other by surface forces.

[0110] The heat treatment of the compression molded layer 32 may be performed in a state where the compression molded layer 32 is immersed in the second thermosetting composition in the immersion container 51. Specifically, the integrally molded product 200 together with the immersion unit 5 may be heated in a state where the compression molded layer 32 is immersed in the second thermosetting composition in the immersion container 51. This heating may be performed, for example, by placing the immersion unit 5 and the integrally molded product 200 in a heating device such as a heating furnace.

[0111] The heat treatment temperature during the heat treatment is not particularly limited, but is preferably 100° C. or higher and 150° C. or lower, and more preferably 110° C. or higher and 130° C. or lower. If the temperature is less than 100° C., the curing of the thermosetting composition may not proceed sufficiently, resulting in insufficient strength. If it is desired to further increase the strength, a higher strength may be achieved by performing a heat treatment (primary curing) at 100° C. or higher and 150° C. or lower, followed by a further heat treatment (secondary curing) at 150° C. or higher and 180° C. or lower.

[0112] The heat treatment time during the heat treatment is not particularly limited, but is preferably 1 minute or more and 120 minutes or less, and more preferably 3 minutes or more and 60 minutes or less. If it is less than 1 minute, the curing of the thermosetting composition may not proceed sufficiently, resulting in insufficient strength. If secondary curing is performed, the secondary curing time is preferably 1 minute or more and 120 minutes or less. If the secondary curing time exceeds 120 minutes, the oxidation of the thermosetting composition due to air proceeds, tending to result in insufficient strength.

[0113] The integrally molded product 200 that has undergone the above-described hardening process is the rotor 100 shown in Fig. 1. The bonded magnet obtained through the hardening process may be magnetized, for example, to strengthen the magnetic force.

[0114] In this manner, it is possible to provide a rotor having a high strength bonded magnet and a method for manufacturing the same. EXAMPLES

[0115] The bonded magnet and the manufacturing method of the bonded magnet according to this embodiment will be described below based on examples.

[0116] <Example 1> The rotor according to Example 1 was manufactured and evaluated in the following manner.

[0117] (Preparation of magnetic powder) In the mortar, as a magnetic filler, 2 Fe 14 B (True specific gravity: 7.6g / cm 3 A magnetic powder (product name: MF15P, manufactured by Aichi Steel Corporation) was prepared, which is a powder of a magnetic material having a particle size of 120 μm (hereinafter referred to as HDDR powder). The magnetic powder had an aspect ratio of 1.3. The magnification ratio during SEM observation when measuring the aspect ratio was 100 times. As a silane coupling agent, 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltrimethoxysilane (model: X-88-351, manufactured by Shin-Etsu Chemical Co., Ltd.) was prepared. As a non-ionic surfactant, fatty acid ester type sorbitan trioleate (manufactured by Kao Corporation, model: Rheodol SP-O30V) was prepared.

[0118] Then, 300g of the magnetic powder was placed in a stirring container (mortar), 3g of the silane coupling agent was added to the magnetic powder in the container, and the mixture was stirred with a pestle for 5 minutes. After the stirring was completed, the container was left open for 30 minutes and dried at room temperature. Then, 3g of the nonionic surfactant was added, and the mixture was stirred with a pestle for 5 minutes. After the stirring was completed, the container was left open for 30 minutes to obtain a magnetic powder after surface treatment.

[0119] (molding process) Next, the surface-treated magnetic powder was compression molded as follows to form a compression molded layer as a precursor of the bonded magnet on the outer circumferential surface of the shaft.

[0120] The die unit according to the above-mentioned configuration was used for compression molding. The inner diameter of the inner space of the molding die of the die unit is 9.91 mm, and the axial length is 100 mm. The shaft is cylindrical with a diameter of 6.02 mm and an axial length of 30 mm. The outer diameter of the lower punch is 9.887 mm, and the axial length is 30 mm. The inner diameter of the lower end of the lower punch (the part where the spacer is inserted) is 6.3 mm, and the inner diameter of the upper end (the part where the shaft is fixed) is 6.038 mm, and the axial length is 10 mm. The outer diameter of the spacer is 5.5 mm, and the axial length is 25 mm. The outer diameter of the upper punch is 9.887 mm, and the inner diameter of the part where the shaft is inserted is 6.038 mm, and the axial length is 30 mm. In this embodiment, a separate pusher was used to push the upper punch. The die unit used in this embodiment is made of an iron-based alloy.

[0121] First, a lower punch and a spacer were inserted into the molding die to fix the shaft, and then 4.0 g of the surface-treated magnetic powder was placed in the inner space of the molding die.

[0122] Then, 0.3 g of the liquid first thermosetting composition was dropped onto the magnetic powder layer to impregnate it, thereby forming a magnetic powder mixture layer. Note that as the liquid first thermosetting composition, a mixture of 100 parts by weight of dicyclopentadiene monomer (viscosity: 3 mPa s, density: 1.02 g / cc) and 0.3 parts by weight of dichloro[1,3-bis(2,6-isopropylphenyl)-2-imidazolidinylidene](2-isopropylphenylmethylene)ruthenium(III) as a reaction initiator was used.

[0123] Then, the upper punch is inserted into the inner space of the molding die to press down the upper surface of the magnetic powder mixture layer, and the pressure is increased by 3t / cm 2 The upper and lower punches were compressed at a molding pressure of 100 mm, and the compression molded layer was molded integrally with the shaft to obtain an integrally molded product. The integrally molded product was then removed from the mold. The axial length of the compression molded layer of the integrally molded product was 15 mm. The outer diameter of the compression molded layer was 10.06 mm. The reason why the outer diameter of the compression molded layer was larger than the inner diameter of the inner space of the mold is that so-called springback occurred, and the compression molded layer released from the mold expanded slightly. Note that due to this springback of the compression molded layer, it was impossible to fit the integrally molded product back into the mold. Here, the dimensions of the compression molded layer were measured using a three-dimensional shape measuring device (manufactured by Keyence Corporation, product name: One Shot 3D Measurement Macroscope).

[0124] (Impregnation process) The compression molded layer was then impregnated with a second thermosetting composition as follows.

[0125] The immersion unit according to the above-mentioned configuration was used for the impregnation. The inner diameter of the inner space of the immersion container of the immersion unit is 10.20 mm. The outer diameter of the bottom cover is 10.06 mm, and the axial length is 30 mm. The inner diameter of the bottom end of the bottom cover (where the spacer is inserted) is 6.3 mm, and the inner diameter of the top end (where the shaft is fixed) is 6.038 mm, and the axial length is 10 mm. The outer diameter of the spacer is 5.5 mm, and the axial length is 25 mm. The bottom cover of the immersion unit used in this embodiment is made of fluororesin, and the rest is made of iron-based alloy.

[0126] The second thermosetting composition used was the same as the first thermosetting composition.

[0127] First, the integrally molded product 200 was fixed in the inner space of the impregnation container, and then 0.3 g of the liquid second thermosetting composition was poured between the compression molded layer and the inner wall of the impregnation container, so that the compression molded layer was immersed in the second thermosetting composition. When the liquid second thermosetting composition was poured between the compression molded layer and the inner wall of the impregnation container, the liquid level of the second thermosetting composition reached a height slightly higher than the upper surface of the compression molded layer.

[0128] (hardening process) Next, the compression molded layer was heat-treated to thermally cure the thermosetting composition, thereby obtaining the rotor according to this embodiment.

[0129] The heat treatment was carried out by placing the compression molded layer in an immersion container immersed in the second thermosetting composition in a heating furnace together with the immersion unit, and heating the immersion unit and the integrally molded product. The temperature in the furnace during the heat treatment was 120° C. The heat treatment time (time held in the furnace) was 15 minutes.

[0130] The outer diameter of the bonded magnet layer in the rotor after removal from the immersion container was 10.20 mm, the same as the inner diameter of the inner space of the immersion container. In other words, it is believed that no springback occurred after the immersion and hardening processes. The dimensions of the bonded magnet layer were measured using a three-dimensional shape measuring device (manufactured by Keyence Corporation, product name: One Shot 3D Measuring Macroscope).

[0131] (Strength evaluation) First, the strength of the bonded magnet layer in the rotor obtained as described above was strengthened. The strength was measured as the spin strength at high speed by performing a rotation test in which the rotor was rotated at high speed. Specifically, the strength was evaluated using a Maruwa Denki spin tester at a maximum rotation speed of 200,000 revolutions per minute in an environment of 25°C.

[0132] In the strength evaluation of this embodiment, if the bonded magnet layer was not destroyed when rotated at 200,000 revolutions per minute for 1 minute, it was rated A (best), if the bonded magnet layer was not destroyed when rotated at 150,000 revolutions per minute for 1 minute, it was rated B (good), if the bonded magnet layer was not destroyed when rotated at 100,000 revolutions per minute for 1 minute, it was rated C (fair), and if the strength was less than rating C, it was rated D (poor).

[0133] (Void evaluation) The degree of voids in the bonded magnet layer of the rotor was also evaluated. In this example, the voids were evaluated by observing the fracture surface of the bonded magnet layer with a scanning electron microscope (SEM). Specifically, the shaft was removed from the rotor to separate the bonded magnet layer, and the bonded magnet layer was broken by applying pressure to it. The fracture surface of the broken pieces was then observed with an SEM, and the diameter of the largest void among those observed was measured. The magnification rate during SEM observation was 100 times. The observation area was a rectangular area with a length and width of 500 μm each.

[0134] In the evaluation of the voids in this embodiment, a maximum void diameter of less than 10 μm was rated A (best), a maximum void diameter of 10 μm or more but less than 50 μm was rated B (good), a maximum void diameter of 50 μm or more but less than 100 μm was rated C (fair), and a maximum void diameter of 100 μm or more was rated D (poor).

[0135] (Coating layer thickness) The thickness of the coating layer of the bonded magnet layer of the rotor was also evaluated. The thickness of the coating layer was evaluated by SEM observation of the coating layer portion on the fracture surface of the bonded magnet layer. The magnification of the SEM observation was 100 times.

[0136] Table 1 lists information related to the above-mentioned manufacturing conditions and evaluation results for the rotor according to this embodiment.

[0137] [Table 1]

[0138] Table 1 shows information related to the manufacturing conditions of the rotor according to this embodiment, such as the type of magnetic powder, the type of surface treatment agent, the molding pressure, the type and amount of the first thermosetting composition, the inner diameter of the inner space of the molding die (inner diameter of the die in Table 1), the inner diameter of the inner space of the impregnation container (inner diameter of the container in Table 1), and the type and amount of the first thermosetting composition. In Table 1, DCP stands for dicyclopentadiene monomer.

[0139] Table 1 also shows information related to the evaluation of the rotor of this embodiment, including the evaluation results of the gaps in the bond resin layer (Gap Evaluation in Table 1), the outer diameter of the bond resin layer, the thickness of the coating layer of the bond resin layer, and the evaluation results of the rotation test (Strength in Table 1).

[0140] <Example 2> Example 2 differs from Example 1 in that the inner diameter of the inner space of the immersion container was 10.40 mm, and otherwise a rotor was manufactured in the same manner as Example 1. In this example, when the liquid second thermosetting composition was poured between the compression molded layer and the inner wall of the impregnation container in the impregnation step, the liquid level of the second thermosetting composition was at the same height as the upper surface of the compression molded layer.

[0141] For the rotor according to this embodiment, information on the manufacturing conditions and evaluation results is also listed in Table 1.

[0142] <Example 3> In Example 3, the molding pressure was 5t / cm 2 The rotor was manufactured in the same manner as in Example 1, except that the rotor was manufactured in the same manner as in Example 1. When the liquid second thermosetting composition was poured between the compression molded layer and the inner wall of the impregnation container, the liquid level of the second thermosetting composition reached a height slightly higher than the upper surface of the compression molded layer, and this height was higher than that in Example 1 when observed with the naked eye. The compression molded layer in Example 3 was less likely to be impregnated with the second thermosetting composition than the compression molded layer in Example 1.

[0143] For the rotor according to this embodiment, information on the manufacturing conditions and evaluation results is also listed in Table 1.

[0144] <Example 4> In Example 4, the molding pressure was 1t / cm 2 This example differed from Example 1 in that the rotor was manufactured in the same manner as Example 1, except that the rotor was manufactured in the same manner as Example 1. In this example, when the liquid second thermosetting composition was poured between the compression molded layer and the inner wall of the impregnation container in the impregnation step, the liquid level of the second thermosetting composition was at the same height as the upper surface of the compression molded layer.

[0145] In the rotor according to Example 4, a phenomenon occurred in which the bonded magnet layer peeled off from the shaft during the rotation test.

[0146] For the rotor according to this embodiment, information on the manufacturing conditions and evaluation results is also listed in Table 1.

[0147] <Comparative Example 1> Comparative Example 1 differs from Example 1 in that the one-piece molded product was not removed from the molding die after the molding process, and the molding die was repurposed as an immersion container to carry out the impregnation process; otherwise, the rotor was manufactured in the same manner as Example 1.

[0148] That is, in Comparative Example 1, after compression molding, the upper punch was pulled out from the inner space of the molding die, and the second thermosetting composition was poured into the inner space of the molding die, and the compression molded layer in the molding die was impregnated with the second thermosetting composition. The liquid level of the second thermosetting composition poured into the inner space of the molding die was higher than the upper surface of the compression molded layer. In addition, the heat treatment was performed by placing the integrally molded product together with the molding die in a heating furnace, and heating the molding die and the integrally molded product while the compression molded layer was still in the molding die.

[0149] In the rotor of Comparative Example 1, the outer diameter of the bonded magnet layer was 10.0 mm, and no spring back occurred.

[0150] For the rotor according to this comparative example, information on the manufacturing conditions and evaluation results is also listed in Table 1.

[0151] <Comparative Example 2> Comparative Example 2 differs from Example 1 in that the compression molded layer was impregnated with the second thermosetting composition without using an immersion container, but otherwise a rotor was produced in the same manner as in Example 1.

[0152] That is, in Comparative Example 2, the integrally molded product was removed from the mold after compression molding, and the second thermosetting composition was dropped onto the compression molded layer to impregnate the compression molded layer. The second thermosetting composition once impregnated into the compression molded layer seeped out and spilled out of the compression molded layer during the process of loading into the heating furnace for heat treatment. The second thermosetting composition is a mixed liquid mainly composed of dicyclopentadiene monomer with a very low viscosity of 3 mPa·s. Therefore, it is considered that the second thermosetting composition once impregnated into the compression molded layer could easily seep out of the compression molded layer.

[0153] For the rotor according to this comparative example, information on the manufacturing conditions and evaluation results is also listed in Table 1.

[0154] <Comparative Example 3> Comparative Example 3 differs from Example 1 in that the impregnation step was omitted and only the integrally molded product was placed in a heating furnace and heat-treated, but otherwise a rotor was manufactured in the same manner as Example 1.

[0155] For the rotor according to this comparative example, information on the manufacturing conditions and evaluation results is also listed in Table 1.

[0156] As shown in Table 1, the rotor according to the embodiment has a stronger bonded magnet layer than the comparative example in which the bonded magnet layer does not have a covering layer. It is believed that the strength of the bonded magnet layer is improved by the covering layer in the rotor according to the embodiment.

[0157] In addition, the rotor according to the embodiment has smaller voids in the bonded magnet layer than the comparative example, in which the bonded magnet layer does not have a coating layer. From this result, it is considered that the compression molded layer is impregnated with more thermosetting composition to fill the voids in the rotor according to the embodiment compared to the rotor according to the comparative example, and as a result, the bonded magnet layer contains more thermosetting resin. Therefore, it is considered that the strength of the bonded magnet layer is improved in the rotor according to the embodiment compared to the rotor according to the comparative example.

[0158] In Comparative Example 1, when the compression molded layer is impregnated with the second thermosetting composition, the second thermosetting composition is poured into the inner space of the molding die, and the compression molded layer is in a state where it is immersed in the liquid second thermosetting composition in the inner space of the molding die. Therefore, the method of impregnating the compression molded layer with the second thermosetting composition in Comparative Example 1 seems to be similar to that in Example 1 and the like.

[0159] However, in order to sufficiently impregnate the compression molding layer with the second thermosetting composition, air must flow out of the compression molding layer in place of the second thermosetting composition during impregnation. In this regard, in Comparative Example 1, the outer peripheral surface and bottom surface of the compression molding layer are sealed with a molding die, and the inner peripheral surface is sealed with a shaft. Therefore, the only path through which air can flow out of the compression molding layer is the upper surface. Therefore, in Comparative Example 1, the air does not flow out smoothly, and therefore, it is considered that in Comparative Example 1, the second thermosetting composition cannot sufficiently penetrate into the compression molding layer.

[0160] In addition, in Comparative Example 1, since there is no space between the molding die and the compression molded layer in the molding die into which the second thermosetting composition can flow, the only route through which the second thermosetting composition can permeate into the compression molded layer is the upper surface. For this reason, it is also considered that in Comparative Example 1, the second thermosetting composition could not sufficiently permeate into the compression molded layer.

[0161] For these reasons, it is believed that the rotor according to Comparative Example 1 contains less thermoset resin in its bonded magnet layer, resulting in a lower strength of the bonded magnet layer compared to the rotor according to the example.

[0162] As described above, the outer diameter of the bonded magnet layer was 10.0 mm and no springback occurred in the rotor of Comparative Example 1. It is believed that the cross-linked structure of the thermoset resin suppressed springback because the rotor of Comparative Example 1 was heat-treated while the compression-molded layer was still in the molding die.

[0163] In Comparative Example 2, the integrally molded product is removed from the mold after compression molding, and the second thermosetting composition is dropped onto the compression molded layer to impregnate the compression molded layer. Therefore, in Comparative Example 2, the upper surface, lower surface, and outer peripheral surface are secured as a path for air to flow out of the compression molded layer and as a path for the second thermosetting composition to permeate into the compression molded layer when the second thermosetting composition is impregnated into the compression molded layer, and the second thermosetting composition is easily permeated into the compression molded layer. However, at the same time, in Comparative Example 2, the second thermosetting composition impregnated into the compression molded layer also easily flows out. Therefore, in Comparative Example 2, the second thermosetting composition flows out of the compression molded layer after the second thermosetting composition is impregnated into the compression molded layer, and as a result, the rotor according to Comparative Example 2 has less thermoset resin contained in its bonded magnet layer, and it is considered that the strength of the bonded magnet layer is lower than that of the rotor according to the embodiment.

[0164] In contrast to these Comparative Examples 1 and 2, in the Examples, since there is a space between the compression molding layer and the immersion container into which the second thermosetting composition flows, the upper surface and the outer circumferential surface are secured as a path for air to flow out of the compression molding layer and as a path for the second thermosetting composition to permeate into the compression molding layer when the second thermosetting composition is impregnated into the compression molding layer, and the second thermosetting composition is easily permeated into the compression molding layer. In addition, in the Examples, the second thermosetting composition is filled between the compression molding layer and the inner surface of the immersion container, and the curing step is performed, so that the second thermosetting composition does not flow out of the compression molding layer after the second thermosetting composition is impregnated into the compression molding layer. As a result, the rotor according to the Examples is in a state in which the bond magnet layer contains a sufficient amount of thermoset resin, and the strength of the bond magnet layer is improved compared to the rotor according to the Comparative Example.

[0165] A comparison between Examples 1 and 2 shows that when the thickness of the coating layer is between 100 μm and 200 μm, the strength of the bonded magnet layer is sufficiently increased.

[0166] In comparing Examples 1 and 3, the molding pressure was 5t / cm 2 Even if the molding pressure is increased to 5t / cm (Example 3), the strength of the bonded magnet layer does not improve. 2 In addition, in the comparison between Examples 1 and 4, the molding pressure is 1t / cm 2 It can be seen that the above pressure is sufficient. In the rotor according to Example 4, the bonded magnet layer peeled off from the shaft during the rotation test, so in addition to the strength of the bonded magnet layer, a molding pressure of 2 t / cm was selected from the viewpoint of the adhesive strength between the bonded magnet layer and the shaft. 2 It is considered preferable that the above is the case.

[0167] In a comparison between Examples 1, 3 and 4, the voids become larger as the molding pressure increases. This is presumably because the higher the molding pressure, the more difficult it becomes for the second thermosetting composition to be impregnated into the compression molded layer in the impregnation step. From this perspective, too, the molding pressure is recommended to be 5 t / cm. 2 It can be seen that it is not necessary to set the value to be greater than

[0168] In this manner, a rotor and a method for manufacturing a rotor can be provided.

[0169] Note that the embodiments disclosed in this specification are merely examples, and the embodiments of the present disclosure are not limited thereto, and may be modified as appropriate within the scope of the purpose of the present disclosure. [Industrial Applicability]

[0170] The present disclosure is applicable to rotors and methods of manufacturing rotors. [Explanation of symbols]

[0171] 1: Shaft 11:First end 11a:Groove 12:Second end 20: Magnet layer 200: Integral molding 21: Covering layer 31:Magnetic powder mixture layer (filled layer) 32: Compression molding layer 33:Liquid layer 4: Mold unit 41: Molding tool 42: Lower pestle 43: Spacer 44: Upper pestle 45: Pusher 5: Immersion unit 51: Immersion container 52: Lower lid 53: Spacer d1: Inner diameter d2: Inner diameter

Claims

1. A cylindrical shaft; a cylindrical bonded magnet layer disposed on an outer circumferential surface of the shaft and including a magnetic powder and a first resin; The bonded magnet layer has a coating layer including a second resin on the outer periphery.

2. The rotor according to claim 1 , wherein the coating layer is formed in a cylindrical shape and has a thickness of 100 μm or more and 200 μm or less.

3. The rotor according to claim 1 or 2, wherein the second resin is the first resin.

4. a molding step of forming a cylindrical compression-molded layer on an outer circumferential surface of a cylindrical shaft using a magnetic powder mixture, which is a mixture of a magnetic powder and a first thermosetting composition; an impregnation step of immersing the compression molded layer in a liquid second thermosetting composition in an immersion container; and a curing step of heating the compression molded layer while immersed in the second thermosetting composition in the immersion container.

5. The molding step is performed by inserting the shaft into a cylindrical molding die having an inner diameter larger than a diameter of the shaft, filling the magnetic powder mixture into the cylindrical molding die and around the shaft, and compressing the filled layer of the magnetic powder mixture along the axial direction of the shaft, 5. The method for manufacturing a rotor according to claim 4, wherein the impregnation step is performed by inserting the compression molded layer together with the shaft into the immersion container having an inner diameter larger than an inner diameter of the molding die, and filling the space between the compression molded layer and the immersion container with the thermosetting composition.

6. The method for manufacturing a rotor according to claim 5 , wherein an inner diameter of the immersion container is greater than an inner diameter of the molding die by 200 μm to 400 μm.

7. The molding pressure in the molding step is 1 t / cm ２ More than 5t / cm ２ 7. A method for manufacturing a rotor according to claim 4, wherein:

8. The method for manufacturing a rotor according to claim 4 , wherein the second thermosetting composition is the first thermosetting composition.

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