Laminated iron core, method for manufacturing said laminated iron core, and rotary electric machine using said laminated iron core

Abstract

Provided are a laminated iron core and a method for manufacturing the same, which make it possible to separate an electrically insulating material from a soft magnetic plate with less environmental load than prior art while using, as the electrically insulating material, an oxide-based material with which desired heat resistance can be ensured. This laminated iron core is characterized in that a plurality of soft magnetic plates are laminated via an electrically insulating layer, and the electrically insulating layer is a layer in which used as a matrix is a lead-free glass composition having a softening point at a temperature lower than an A1 transformation point of the soft magnetic plates.

Description

Laminated iron core, manufacturing method of laminated iron core, and rotating electric machine using laminated iron core

[0001] The present invention relates to a technology for iron cores using soft magnetic materials, and more particularly to a laminated iron core formed by laminating a plurality of soft magnetic plates, a manufacturing method for such a laminated iron core, and a rotating electric machine using such a laminated iron core.

[0002] From the viewpoint of protecting the global environment, the application fields of electric machinery and devices that use iron cores (e.g., rotating electric machines and transformers) have been expanding in recent years, and as a result, there has been a growing demand for higher output, higher efficiency, and smaller size for these electric machinery and devices. The iron cores for rotating electric machines and transformers are widely made of laminated iron cores, which are made by laminating multiple sheets of soft magnetic material (e.g., 0.01 to 3 mm thick), such as pure iron sheets or electromagnetic steel sheets. Various technological developments are being conducted to achieve higher output, higher efficiency, and smaller size.

[0003] Taking rotating electrical machines as an example, increasing the saturation magnetic flux density Bs of soft magnetic materials is important for achieving high output, while suppressing losses in soft magnetic materials (iron loss Pi) is important for achieving high efficiency. Research is being conducted into controlling the composition and microstructure of soft magnetic materials in order to increase the Bs of the iron core. Pi is the sum of hysteresis loss and eddy current loss, and a small coercive force Hc is desirable for reducing hysteresis loss, while increasing electrical resistance and thinning the plate are effective for reducing eddy current loss. Miniaturization is being considered by striking a good balance between high output and high efficiency.

[0004] In order to properly utilize the thinning of soft magnetic materials, it is important to ensure electrical insulation / interlayer insulation between the soft magnetic plates that make up the laminated core. Methods for ensuring electrical insulation / interlayer insulation can be broadly divided into two methods: one in which soft magnetic plates are laminated and bonded together using a resin-based adhesive, and one in which oxide-based insulating materials are formed on the surfaces of the soft magnetic plates and then laminated.

[0005] The method of laminating and bonding soft magnetic plates together using a resin-based adhesive allows the entire laminated core to be fixed together while ensuring electrical insulation and interlayer insulation, so the resulting laminated core has the advantage of being compact and resistant to mechanical vibration. On the other hand, when heat resistance is required for the laminated core, the disadvantage is that the heat resistance of the entire core is limited by the heat resistance of the resin-based adhesive used.

[0006] For example, the following technology has been proposed for soft magnetic plates having an oxide-based insulating material formed on the surface thereof. Patent Document 1 (WO 2018 / 079845 A1) teaches a grain-oriented electrical steel sheet comprising a steel sheet and an insulating coating formed on the surface of the steel sheet, wherein the insulating coating contains a metal phosphate and colloidal silica, with 20 to 150 parts by mass of the colloidal silica per 100 parts by mass of the metal phosphate, and further contains 0.5 to 7 parts by mass of one or more fine particles selected from silicon carbide, silicon nitride, aluminum nitride, boron nitride, sialon, and cordierite per 100 parts by mass of the metal phosphate, the average particle size of the fine particles being 0.3 to 7.0 μm, the crystallinity of the metal phosphate being 2 to 40%, and the insulating coating being chromium-free.

[0007] Patent Document 2 (WO 2019 / 181945 A1) teaches a grain-oriented electrical steel sheet comprising: a silicon steel sheet having a predetermined chemical composition; a glass coating disposed on the surface of the silicon steel sheet; and an insulating coating disposed on the surface of the glass coating, wherein the glass coating contains a manganese-containing oxide.

[0008] Patent Document 1 states that it is possible to provide a grain-oriented electrical steel sheet that has good adhesion and corrosion resistance despite not containing chromium, and that has an insulating coating that can impart significantly higher tensile strength to the steel sheet than conventional coatings, and that has good magnetic properties. Patent Document 2 also states that it is possible to provide a grain-oriented electrical steel sheet that has excellent coating adhesion without impairing magnetic properties, and a method for manufacturing the same.

[0009] International Publication No. 2018 / 079845 International Publication No. 2019 / 181945

[0010] Meanwhile, the Sustainable Development Goals were adopted at the United Nations Summit in 2015, and in the area of ​​industrial products, a circular economy (CE) economic system is now required to replace the traditional economic system premised on mass production, mass consumption, and mass disposal. The circular economy is premised on the recovery and reuse of resources from the raw material procurement and product design and manufacturing stages. In other words, raw material procurement and product design and manufacturing must be carried out in a way that makes it easy to recover and reuse resources.

[0011] From the perspective of a circular economy, there is a growing demand for resource recovery and reuse (and for design and manufacturing that facilitate this) in electrical machinery and devices that use iron cores. For example, in the case of laminated iron cores, it is considered to disassemble used products to remove each soft magnetic plate, and then reassemble them to manufacture a new laminated iron core. In this case, when disassembling the laminated iron core to remove each soft magnetic plate, it is necessary to completely remove the electrical insulation layer. It is also desirable that the electrical insulation material itself can be reused.

[0012] Laminated cores, in which soft magnetic plates are laminated and bonded together using a resin-based adhesive, require dissolution treatment using an organic solvent or thermal decomposition treatment using heat to remove the electrical insulation layer. This means that the separation process places a heavy burden on the environment and makes it difficult to reuse the electrical insulation material itself.

[0013] The electrical steel sheets taught in Patent Documents 1 and 2 and the laminated cores using them may be reusable because the insulating coating is made of an oxide-based material. However, because high-temperature heat treatment (e.g., 800°C or higher) is performed to form the insulating coating, it is likely that an equivalent or higher-temperature heat treatment is required to remove the electrical insulation layer, and the environmental impact of the separation process cannot be said to be small. Furthermore, if an attempt is made to separate the electrical insulation layer from the electrical steel sheets taught in Patent Documents 1 and 2, the high heat treatment temperature may result in a decrease / deterioration of the magnetic properties of the electrical steel sheet. In other words, the electrical steel sheets taught in Patent Documents 1 and 2 may not have been designed with circular economy in mind.

[0014] The present invention was made to address the above-mentioned issues while taking into consideration the circular economy. Therefore, a primary object of the present invention is to provide a laminated core and a manufacturing method thereof that use an oxide-based material that can ensure the desired heat resistance as an electrical insulating material, while enabling separation of the electrical insulating material and the soft magnetic plate with less environmental impact than conventional methods. A secondary object of the present invention is to provide a rotating electric machine that takes the circular economy into consideration by utilizing the laminated core.

[0015] (I) One aspect of the present invention provides a laminated core in which a plurality of soft magnetic plates are stacked with an electrical insulating layer interposed therebetween, characterized in that the electrical insulating layer is a layer having a matrix of a lead-free glass composition having a softening point lower than the A1 transformation point of the soft magnetic plates.

[0016] The present invention allows the following improvements and modifications to be freely combined in the laminated core (I) according to the present invention: (i) The lead-free glass composition, when expressed as nominal components in terms of oxides, contains 15 mol% to 35 mol% of V2O5 (vanadium oxide) and 5 mol% to 30 mol% of P2O5 (phosphorus oxide), the sum of the V2O5 and the P2O5 being 40 mol% to 65 mol%, and contains 35 mol% to 60 mol% in total of two or more selected from the group consisting of BaO (barium oxide), Sb2O3 (antimony oxide), WO3 (tungsten oxide), ZnO (zinc oxide), K2O (potassium oxide), Fe2O3 (iron oxide), TeO2 (tellurium oxide), Ag2O (silver oxide), and Li2O (lithium oxide), with the remainder being unavoidable impurities. (ii) The electrical insulation layer contains spherical spacer particles at 50 volume percent or less, and the spacer particles are one or more of the group consisting of SiO2 (silicon oxide), ZrO2 (zirconium oxide), Al2O3 (aluminum oxide), Nb2O5 (niobium oxide), ZrSiO4 (zirconium silicate), Zr2(WO4)(PO4)2 (zirconium tungstate phosphate), 2MgO·2Al2O3·5SiO2 (cordierite), 3Al2O3·2SiO2 (mullite), LiAlSiO4 (eucryptite), SiO2-Na2O-CaO-based glass (soda glass), and SiO2-B2O3-Na2O-Al2O3-based glass (borosilicate glass). (iii) The spacer particles have a D90 of 10 μm or less. (iv) The softening point of the lead-free glass composition is 500°C or less.

[0017] (II) Another aspect of the present invention provides a method for manufacturing the above-mentioned laminated core, comprising: a soft magnetic plate preparation step of preparing the soft magnetic plate; a glass paste preparation step of preparing a glass paste that will be the basis for the electrical insulating layer; a soft magnetic composite precursor formation step of forming a soft magnetic composite precursor by applying the glass paste to at least one main surface of the soft magnetic plate; a laminated core precursor formation step of laminating a plurality of the soft magnetic composite precursors to form a laminated core precursor; and a laminated core formation step of heat-treating the laminated core precursor to form the electrical insulating layer and joining the soft magnetic plates together via the electrical insulating layer to form the laminated core.

[0018] The present invention allows the following improvements and modifications to be freely combined in the laminated core manufacturing method (II) according to the present invention: (v) the glass paste preparation step includes a spacer particle mixing step of mixing spacer particles into the glass paste so as to uniformly disperse them; and (vi) the soft magnetic composite precursor formation step includes a spacer particle embedding and arranging step of embedding and arranging spacer particles in the glass paste-coated surface of the soft magnetic composite precursor so as to uniformly distribute them.

[0019] (III) Yet another aspect of the present invention provides a method for manufacturing the above-mentioned laminated core, comprising: a soft magnetic plate preparation step of preparing the soft magnetic plate; a glass-containing sheet preparation step of preparing a glass-containing sheet that will become the basis for the electrical insulating layer; a laminated core precursor formation step of alternately stacking the glass-containing sheet and the soft magnetic plate to form a laminated core precursor; and a laminated core formation step of heat-treating the laminated core precursor to form the electrical insulating layer and joining the soft magnetic plates together via the electrical insulating layer to form the laminated core.

[0020] The present invention allows the following improvements and modifications to be freely combined in the manufacturing method (III) of the laminated iron core according to the present invention: (v) the glass-containing sheet preparation step includes a spacer particle mixing step of mixing spacer particles so that the spacer particles are uniformly dispersed before forming the glass-containing sheet; and (vi) the glass-containing sheet preparation step includes a spacer particle embedding and arranging step of embedding and arranging spacer particles so that the spacer particles are uniformly distributed on the surface of the glass-containing sheet after forming the glass-containing sheet.

[0021] (IV) Yet another aspect of the present invention provides a rotating electric machine having an iron core, characterized in that the iron core is the laminated iron core according to the present invention.

[0022] According to the present invention, it is possible to provide a laminated core and a manufacturing method thereof that uses an oxide-based material that can ensure the desired heat resistance as an electrical insulating material, while enabling separation of the electrical insulating material and the soft magnetic plate with less environmental impact than conventional methods. Furthermore, by using this laminated core, it is possible to provide a rotating electric machine that takes circular economy into consideration.

[0023] Problems, configurations, and effects other than those described above will become clear from the description of the embodiments below.

[0024] Fig. 1 is a cross-sectional schematic diagram showing an example of the structure of a laminated iron core according to the present invention. Fig. 2 is an example of a chart obtained during the temperature rise process of differential thermal analysis of a lead-free glass composition used in the present invention. Fig. 3 is a schematic flow diagram showing an example of a method for manufacturing a laminated iron core according to the present invention. Fig. 4 is a schematic flow diagram showing another example of a method for manufacturing a laminated iron core according to the present invention. Fig. 5 is a perspective schematic diagram showing an example of a stator of a rotating electric machine. Fig. 6 is an enlarged cross-sectional schematic diagram of a slot region of the stator.

[0025] [Basic Concept of the Present Invention] When designing and manufacturing a new laminated core, the inventors aimed to facilitate separation of the soft magnetic plate and the electrical insulating material during disassembly (in other words, to reduce the environmental impact of the separation process) and to make the electrical insulating material reusable, taking into consideration the circular economy. As the electrical insulating material, they focused on oxide-based glass compositions from the perspective of enabling reuse while maintaining the desired heat resistance. Furthermore, from the perspective of facilitating separation of the soft magnetic plate and the electrical insulating material and suppressing changes in the magnetic properties of the soft magnetic plate, they considered using a glass composition with a low softening point Ts as the electrical insulating material.

[0026] On the other hand, the laminated cores and rotating electrical machines targeted by the present invention are types of electrical equipment and are therefore subject to the RoHS Directive (a European Union directive restricting the use of certain hazardous substances in electrical and electronic equipment, which came into effect on July 1, 2006). Glass compositions containing PbO (lead oxide) as a major component were once widely used as glass compositions with low Ts. However, because Pb is designated as a prohibited substance under the RoHS Directive, these glass compositions are incompatible with the RoHS Directive. Therefore, in the present invention, a glass composition that does not contain Pb (lead-free glass composition) was used.

[0027] As a result of extensive research, it was discovered that by using a specific lead-free glass composition as an electrical insulating material, which has a chemical composition consisting mainly of V2O5 (the component with the highest content) and also contains P2O5, and which has a Ts temperature lower than the A1 transformation point of the soft magnetic plate, it is possible to separate the soft magnetic plate and the electrical insulating material at a lower temperature than conventional methods, thereby reducing the environmental impact of the separation process of the laminated core, suppressing changes in the magnetic properties of the soft magnetic plate, and enabling the electrical insulating material to be recycled. The present invention was completed based on this finding.

[0028] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the specific embodiments described, and can be appropriately combined with or improved on known techniques without departing from the technical concept of the invention.

[0029] [Laminated Core of the Present Invention] Fig. 1 is a cross-sectional schematic diagram showing an example of the structure of a laminated core of the present invention. As shown in Fig. 1, a laminated core 10 of the present invention is formed by laminating multiple soft magnetic plates 1 with an electrical insulating layer 2 having a lead-free glass composition as a matrix therebetween. Although not an essential component, spherical spacer particles 3 may be mixed into the electrical insulating layer 2 for the purpose of defining the thickness of the electrical insulating layer 2 (the spacing between the soft magnetic plates 1).

[0030] The soft magnetic plate 1 used in the present invention is not particularly limited as long as it can be used as a laminated core for an electromechanical device, and conventional materials can be used as appropriate. For example, pure iron sheets, Fe (iron)-Si based electromagnetic steel sheets, Fe-Co (cobalt) based alloy sheets, Fe-N (nitrogen) based alloy sheets, Fe-NC (carbon) based alloy sheets, Fe-based amorphous alloy sheets, Fe-based nanocrystalline alloy sheets, etc. can be used.

[0031] The electrical insulating layer 2 is a layer having a lead-free glass composition as a matrix. The lead-free glass composition used in the present invention will be described.

[0032] 2 is an example of a chart (DTA curve) obtained during the temperature rise process of differential thermal analysis (DTA) for the lead-free glass composition used in the present invention. As shown in FIG. 2, the onset temperature of the first endothermic peak is taken as the glass transition point Tg (viscosity = 10 13.3 The peak temperature of the first endothermic peak is the sag point Td (viscosity = 10 11.0 The peak temperature of the second endothermic peak is the softening point Ts (viscosity = 10 7.65 The peak temperature of the first exothermic peak is defined as the crystallization peak temperature Tcp. Each temperature is determined by the tangent method.

[0033] The lower the characteristic temperatures Tg, Td, and Ts of a glass composition, the more easily it softens and flows at low temperatures, allowing the electrical insulating layer 2 to be formed and separated and recovered at low temperatures. From the viewpoints of workability and temperature controllability, it is desirable to form and separate and recover the electrical insulating layer 2 at a temperature that is approximately 20 to 50°C higher than Ts. On the other hand, if the glass composition crystallizes, the softening and flow properties are significantly impaired and the adhesion of the electrical insulating layer 2 is also greatly reduced, so it is necessary to form it at a temperature below Tcp.

[0034] For these reasons, the lead-free glass composition constituting the matrix of the electrical insulating layer 2 preferably has a characteristic temperature such that the temperature difference between Ts and Tcp is approximately 20 to 50°C or more. Furthermore, it is preferable to use a lead-free glass composition having a Ts that is 20°C or more lower than the A1 transformation point of the soft magnetic plate 1, and it is more preferable to use a lead-free glass composition having a Ts that is 50°C or more lower. Specifically, the glass composition used in the present invention preferably has a Ts of 700°C or less, more preferably 600°C or less, and even more preferably 500°C or less.

[0035] Furthermore, since it is undesirable for the electrical insulating layer 2 to soften and flow during operation of an electrical machine device using the laminated iron core 10 of the present invention, it is preferable that the Ts of the lead-free glass composition be higher than the operating temperature of the electrical machine device (e.g., 150°C).

[0036] In the present invention, when an Fe-based amorphous alloy plate or an Fe-based nanocrystalline alloy plate is used as the soft magnetic plate 1, the A1 transformation point is to be read as the second crystallization temperature (the temperature at which all of the amorphous phases are crystallized and the nanocrystalline alloy phases begin to combine and coarsen).

[0037] The lead-free glass composition used in the present invention, when expressed as nominal oxide components, contains 15 to 35 mol% V2O5 and 5 to 30 mol% P2O5, the sum of V2O5 and P2O5 being 40 to 65 mol%, and contains 35 to 60 mol% of two or more selected from the group consisting of BaO, Sb2O3, WO3, ZnO, KO, Fe2O3, TeO2, Ag2O, and Li2O, with the balance being unavoidable impurities. Note that "lead-free" in this invention means that the glass composition may contain the aforementioned substances prohibited by the RoHS Directive within the specified range.

[0038] In the lead-free glass composition used in the present invention, V2O5 is a component that contributes to lowering the glass softening flow temperature. P2O5 is a component that can form the glass skeleton and also contributes to suppressing crystallization of glass. BaO, Sb2O3, WO3, ZnO, K2O, and Fe2O3 are components that contribute to improving the moisture resistance and water resistance of glass and suppressing crystallization. TeO2 and Ag2O, like V2O5, are components that contribute to lowering the glass softening flow temperature. Li2O is a vitrifying component that contributes to improving adhesion and adhesion.

[0039] By controlling the above components and their contents, a lead-free glass composition having a desired characteristic temperature can be obtained.

[0040] In the present invention, the lead-free glass composition used has a softening point Ts that is lower than the A1 transformation point of the soft magnetic plate 1, and therefore the heating temperature during the formation and separation and recovery of the electrical insulating layer 2 can be lower than conventional, thereby reducing the environmental load and suppressing the deterioration / deterioration of the magnetic properties of the soft magnetic plate 1. In addition, the separated electrical insulating material can be reused.

[0041] As mentioned above, spacer particles 3 may be mixed into the electrical insulating layer 2 to define the thickness (the spacing between layers of the soft magnetic plate 1). Naturally, mixing spacer particles 3 is not essential. Oxide particles are preferred as spacer particles 3 due to their compatibility with oxide glass. Examples of suitable spacer particles include SiO2, ZrO2, Al2O3, Nb2O5, ZrSiO4, Zr2(WO4)(PO4)2, 2MgO·2Al2O3·5SiO2, 3Al2O3·2SiO2, LiAlSiO4, SiO2-Na2O-CaO-based glass, and SiO2-B2O3-Na2O-Al2O3-based glass. The spacer particles 3 are preferably spherical (e.g., with a minor axis / major axis ratio of 0.8 or greater).

[0042] The particle size of the spacer particles 3 may be set to a thickness of the electrical insulating layer 2 (the lamination spacing of the soft magnetic plates 1) that is desirable when designing the laminated core 10. For example, D90 (the particle size of 90% by volume of the cumulative particle distribution) is preferably 0.1 μm to 10 μm, and more preferably 0.5 μm to 5 μm. When spacer particles 3 are mixed, their mixing ratio of the electrical insulating layer 2 is preferably 50% by volume or less, more preferably 20% by volume or less, and even more preferably 5% by volume or less.

[0043] The average linear expansion coefficient of the spacer particles 3 is smaller than that of the lead-free glass composition described above, which is smaller than that of the soft magnetic plate 1. Therefore, when the electrical insulating layer 2 is formed by mixing the spacer particles 3 into the lead-free glass composition, there is a secondary advantage that the average linear expansion coefficient of the electrical insulating layer 2 can be controlled to be smaller, and there is also a secondary advantage that the viscosity during softening and flowing can be controlled.

[0044] Furthermore, if the average linear expansion coefficient of the electrical insulating layer 2 is controlled to be smaller than that of the soft magnetic plate 1, during the formation of the electrical insulating layer 2 (softening and flowing → hardening), the difference in the average linear expansion coefficients between the electrical insulating layer 2 and the soft magnetic plate 1 causes compressive stress to be applied to the electrical insulating layer 2 and tensile stress to be applied to the soft magnetic plate 1. The compressive stress on the electrical insulating layer 2 suppresses the occurrence of cracks in the electrical insulating layer 2, and the tensile stress on the soft magnetic plate 1 has the secondary advantage of contributing to improved magnetic properties (particularly, reduced iron loss Pi).

[0045] [Method for manufacturing laminated iron core] Fig. 3 is a schematic flow diagram showing an example of a method for manufacturing a laminated iron core according to the present invention. As shown in Fig. 3, first, a soft magnetic plate preparation step S1 for preparing a soft magnetic plate 1 and a glass paste preparation step S2 for preparing a glass paste that will be the source of the electrical insulation layer 2 are performed. The order of steps S1 and S2 does not matter.

[0046] Next, a soft magnetic composite precursor forming step S3 is performed in which the glass paste prepared in step S2 is applied to at least one main surface of the soft magnetic plate 1 prepared in step S1 to form a soft magnetic composite precursor.

[0047] When the spacer particles 3 are mixed into the electrical insulating layer 2, it is desirable that the spacer particles 3 are uniformly distributed throughout the electrical insulating layer 2. There are no particular limitations on the process / method for mixing the spacer particles 3 into the electrical insulating layer 2, as long as the spacer particles 3 are ultimately uniformly distributed throughout the electrical insulating layer 2. For example, a method may be performed in which, as part of step S2, a spacer particle mixing elementary step is performed in which the spacer particles 3 are mixed so as to be uniformly dispersed in the glass paste, or a method may be performed in which, as part of step S3, a spacer particle embedding and arranging elementary step is performed in which the spacer particles 3 are embedded and arranged on the glass paste-coated surface of the soft magnetic composite precursor so as to be uniformly distributed.

[0048] Next, a laminated core precursor forming step S4 is performed in which a plurality of soft magnetic composite precursors are laminated to form a laminated core precursor.

[0049] Next, a laminated core formation step S5 is performed in which the laminated core precursor is heat treated to form an electrical insulating layer 2 and the soft magnetic plates 1 are joined together via the electrical insulating layer 2 to form the laminated core 10. Through these steps, the laminated core 10 according to the present invention is obtained.

[0050] Each step will be described in more detail.

[0051] Step S1 is a step of preparing a soft magnetic plate 1. This step is not particularly limited as long as the desired soft magnetic plate 1 can be prepared, and includes procuring a commercially available soft magnetic plate (e.g., an electromagnetic pure iron plate, an Fe-Si based electromagnetic steel plate, an Fe-Co based alloy plate, an Fe-N based alloy plate, an Fe-NC based alloy plate, an Fe-based amorphous alloy plate, an Fe-based nanocrystalline alloy plate, etc.).

[0052] Furthermore, as part of this process, a soft magnetic plate shaping process may be performed to process the soft magnetic plate 1 into a desired shape. There are no particular limitations on the method for shaping the soft magnetic plate 1, and conventional metal processing methods (e.g., punching) can be used as appropriate.

[0053] Step S2 is a step of preparing a glass paste that is the base of the electrical insulating layer 2. The glass paste is prepared by mixing a resin binder and a solvent with a glass frit made of powder of the aforementioned lead-free glass composition or a glass frit obtained by mixing spacer particles 3 with the glass powder.

[0054] When the spacer particles 3 are mixed with the glass frit as part of step S2, it is preferable to mix 50% to 98% by volume of the lead-free glass composition with 2% to 50% by volume of the spacer particles 3.

[0055] As a resin binder for the glass paste, for example, nitrocellulose can be preferably used. As a solvent for the glass paste, for example, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, methanol, ethanol, propanol, ethylene glycol, glycerin, dimethyl sulfoxide, tetrahydrofuran, butyl carbitol acetate, and α-terpineol can be preferably used. These solvents may be used alone or in combination. The mixing ratio of the resin binder and the solvent may be appropriately adjusted taking into account the workability when applying the glass paste.

[0056] Step S3 is a step of forming a soft magnetic composite precursor by applying the glass paste prepared in step S2 to at least one main surface of the soft magnetic plate 1 prepared in step S1. There are no particular limitations on the application method as long as the thickness of the applied glass paste film (e.g., on the order of μm) can be controlled, and for example, a doctor blade method or the like can be suitably used.

[0057] When spacer particles 3 are mixed / embedded in the glass paste coating film as part of step S3, it is preferable to mix 95% by volume or more of the lead-free glass composition with 5% by volume or less of the spacer particles 3, and it is more preferable to mix 99% by volume or more of the lead-free glass composition with 1% by volume or less of the spacer particles 3.

[0058] Step S4 is a step of forming a laminated iron core precursor by stacking multiple soft magnetic composite precursors prepared in step S3. There are no particular limitations on the method of stacking the soft magnetic composite precursors, and conventional stacking methods for laminated iron cores can be used as appropriate.

[0059] Step S5 is a step of heat treating the laminated core precursor prepared in step S4 to form an electrical insulating layer 2 and joining the soft magnetic plates 1 together via the electrical insulating layer 2 to form the laminated core 10. The heat treatment pattern may include, for example, a drying process in which the laminated core precursor is heated to and maintained at 120 to 200°C to dry out the moisture, binder components, and solvent components in the coating film, followed by a firing process in which the laminated core precursor is heated to and maintained at a temperature 20 to 50°C higher than the Ts of the lead-free glass composition used. The maximum temperature in the firing process is a temperature that is lower than the Tcp of the lead-free glass composition used and lower than the A1 transformation point of the soft magnetic plate 1 used.

[0060] The atmosphere for the heat treatment in step S5 is not particularly limited, and may be appropriately adjusted depending on the soft magnetic plate 1 and the electrical insulating material used. For example, it may be an oxygen-containing atmosphere such as air, or an inert atmosphere (an atmosphere substantially containing no oxygen) such as nitrogen gas or argon gas. The heat treatment method is also not particularly limited, and conventional heat treatment methods can be used as appropriate. For example, it may be radiant heat heating or high-frequency induction heating.

[0061] Furthermore, from the viewpoint of controlling the spacing between the soft magnetic plates 1 and the thickness of the electrical insulating layers 2 in the laminated core 10, it is preferable to apply pressure in the lamination direction during heat treatment (particularly during the firing process). However, excessive pressure may cause excessive outflow of the softened and fluidized electrical insulating material from the ends of the laminated core precursor (ends perpendicular to the lamination direction) or may cause undesired deformation of the laminated soft magnetic plates 1. Therefore, it is desirable to control the surface pressure within an appropriate range (for example, 5 kPa or more and 100 kPa or less).

[0062] Fig. 4 is a schematic flow diagram showing another example of a manufacturing method for a laminated iron core according to the present invention. As shown in Fig. 4, this manufacturing method is the same as the manufacturing method shown in Fig. 3 except that, instead of the glass paste preparation step S2, the soft magnetic composite precursor formation step S3, and the laminated iron core precursor formation step S4 shown in Fig. 3, a glass-containing sheet preparation step S6 is performed to prepare a glass-containing sheet that will become the base of the electrical insulating layer 2, and a laminated iron core precursor formation step S4' is performed to form a laminated iron core precursor by alternately stacking the glass-containing sheet and soft magnetic plates 1. Naturally, the order of steps S1 and S6 does not matter.

[0063] Step S6 and step S4' will now be described.

[0064] The glass-containing sheet prepared in step S6 is obtained by mixing a sheet-molding resin with glass frit made of powder of the aforementioned lead-free glass composition or glass frit obtained by mixing spacer particles 3 with the glass powder.

[0065] The mixing of the spacer particles is basically the same as above. For example, a method may be a method of performing a spacer particle mixing step as part of step S6, in which the spacer particles 3 are mixed so as to be uniformly dispersed before forming the glass-containing sheet, or a method may be a method of performing a spacer particle embedding and arranging step, in which the spacer particles 3 are embedded and arranged so as to be uniformly distributed on the surface of the glass-containing sheet after forming the glass-containing sheet.

[0066] Examples of resins that can be preferably used for sheet molding include acrylic resins, urethane resins, phenolic resins, imide resins, glyoxal resins, butadiene resins, methacrylic resins, fluorine resins, styrene resins, and ethylene resins. These resins may be used alone or in combination.

[0067] The mixing ratio of the sheet-forming resin in the glass-containing sheet is preferably 5% by volume or more and 70% by volume or less. By controlling the mixing ratio within this range, a highly flexible glass-containing sheet can be obtained.

[0068] As described above, step S4' is a step of forming a laminated core precursor by alternately stacking the soft magnetic plates 1 prepared in step S1 and the glass-containing sheets prepared in step S6. As part of step S4', spacer particles 3 may be embedded and arranged in the glass-containing sheets during the stacking process.

[0069] [Stator and Rotating Electric Machine Using Laminated Core of the Present Invention] Fig. 5A is a schematic perspective view showing an example of a stator for a rotating electric machine, and Fig. 5B is an enlarged schematic cross-sectional view of a slot region of the stator. Note that the cross-sectional view refers to a cross section perpendicular to the rotation axis direction (a cross section whose normal is parallel to the axial direction). In a rotating electric machine, a rotor (not shown) is disposed radially inside the stator shown in Figs. 5A and 5B.

[0070] 5A and 5B, the stator 20 has stator coils 21 wound in multiple stator slots 11 formed on the inner periphery of the laminated core 10. The stator slots 11 are spaces that are arranged at a predetermined circumferential pitch around the circumferential direction of the laminated core 10 and penetrate the laminated core 10 in the axial direction, with slits 12 opening in the innermost periphery and extending in the axial direction. The areas separated by adjacent stator slots 11 are called teeth 13 of the laminated core 10, and the parts of the inner periphery tip areas of the teeth 13 that define the slits 12 are called tooth claw portions 14.

[0071] The stator coil 21 is typically made up of a plurality of segment conductors 22. For example, in Figures 5A and 5B, the stator coil 21 is made up of three segment conductors 22 corresponding to the U, V, and W phases of a three-phase AC. Furthermore, in order to prevent partial discharge between the segment conductors 22 and the laminated core 10 and between the phases (U, V, and W), the outer periphery of each segment conductor 22 is typically covered with an electrical insulating material 23 (e.g., insulating paper or enamel coating).

[0072] The stator and rotating electric machine according to the present invention are respectively a stator and a rotating electric machine that utilize the laminated core 10 of the present invention. Compared to conventional laminated cores, the laminated core 10 of the present invention is designed and manufactured with circular economy in mind, which makes it easier to separate the soft magnetic plates from the electrical insulating material when disassembling the laminated core and also makes it possible to reuse the electrical insulating material. As a result, the stator and rotating electric machine of the present invention can reduce the environmental impact over the product life cycle compared to conventional products.

[0073] The present invention will be explained in more detail below with reference to various experiments, but the present invention is not limited to the configurations and structures described in these experiments.

[0074] [Experiment 1] (Preparation of lead-free glass compositions G-1 to G-3) Lead-free glass compositions G-1 to G-3 were prepared, each having the nominal composition shown in Table 1 below. The nominal compositions in the table are expressed as the molar ratio of each component converted to oxide. As starting materials, commercially available reagents of oxide powders shown in Table 1 (each with a purity of 99.9%) or commercially available reagents of carbonate powders of cations of the oxides shown in Table 1 (each with a purity of 99.9%) were used. As can be seen from the purity of the starting materials, the lead-free glass compositions used in the present invention contain a certain amount of unavoidable impurities.

[0075] First, the starting materials were weighed and mixed to prepare a mixed raw material powder to achieve the desired glass composition. The crucible containing the mixed raw material powder was placed in a glass melting furnace and heated to 700-800°C at a heating rate of 10°C / min to melt the mixed raw material powder. The mixture was then held for 1 hour while stirring with an alumina rod to homogenize the composition of the molten liquid in the crucible. The crucible was then removed from the glass melting furnace, and the molten liquid was poured into a mold preheated to 150°C to produce a bulk lead-free glass composition.

[0076] The cast bulk was then transferred to a stress relief furnace that had been preheated to a stress relief temperature, and held there for 1 hour to remove the strain, followed by cooling to room temperature at a rate of 1° C. / min. The bulk cooled to room temperature was pulverized using a stamp mill and a jet mill to prepare powders of lead-free glass compositions G-1 to G-3.

[0077]

[0078] (Measurement of characteristic temperatures of lead-free glass compositions G-1 to G-3) The characteristic temperatures of the prepared lead-free glass compositions G-1 to G-3 were measured using a differential thermal analyzer (Hitachi High-Tech Corporation, model: TG / DTA6200). The measurement conditions were as follows: α-alumina as the standard sample, nitrogen as the measurement atmosphere, and a heating rate of 5°C / min. Note that Figure 2 shown above is the DTA chart of G-1.

[0079] As a result of the characteristic temperature measurement, it was confirmed that G-1 to G-3 exhibited softening points Ts in the range of 380 to 490°C (i.e., Ts of 500°C or less), and that the crystallization peak temperatures Tcp were each 30°C or more higher than Ts.

[0080] [Experiment 2] (Preparation of glass pastes GP-1 to GP-4) For each of the powders G-1 to G-3 prepared in Experiment 1, a glass frit was prepared by mixing glass powder and spacer particles in a volume ratio of "glass powder:spacer particles = 95:5" so that the spacer particles were uniformly dispersed within the glass powder. Spherical SiO2 powder (D90 ≒ 5 μm) was used as the spacer particles.

[0081] Next, 100 parts by mass of glass frit was mixed with 10 parts by mass of nitrocellulose as a resin binder and 20 parts by mass of α-terpineol as a solvent to prepare glass pastes GP-1 to GP-3 that would serve as the base for the electrical insulating layers.

[0082] In addition, 100 parts by mass of the G-1 powder prepared in Experiment 1 was mixed with 10 parts by mass of nitrocellulose as a resin binder and 20 parts by mass of α-terpineol as a solvent to prepare glass paste GP-4 (glass paste without spacer particles mixed in), which is the base of the electrical insulation layer.

[0083] [Experiment 3] (Fabrication of simulated laminated cores LC-1 to LC-6) Commercially available Fe-3% by mass Si non-oriented electrical steel sheets (thickness: 0.27 mm) were prepared as soft magnetic sheets. One main surface of one soft magnetic sheet was coated with one of the glass pastes GP-1 to GP-3 prepared in Experiment 2, and another soft magnetic sheet was stacked on top of it with the coated surface facing inward to form simulated laminated core precursors LCP-1 to LCP-3.

[0084] The glass paste GP-4 prepared in Experiment 2 was applied to one main surface of one soft magnetic plate, and spacer particles were embedded in the applied surface to form a square lattice with 2 mm spacing. Another soft magnetic plate was then stacked on top of the soft magnetic plate with the applied surface facing inward to form the simulated laminated core precursor LCP-4. The mixing ratio of spacer particles to glass powder in LCP-4 was approximately 0.0003% by volume.

[0085] Next, each of the simulated laminated core precursors LCP-1 to LCP-4 was sandwiched between two silicon substrates, and a weight was placed on top of the simulated laminated core precursor to provide a surface pressure of 25 kPa. The resulting material was then placed in an electric furnace. The heat treatment process involved a drying process in which the material was heated to 170°C in air and held there for 30 minutes, followed by a firing process in which the material was heated to a temperature 20°C higher than the Ts of the lead-free glass composition used and held there for 30 minutes. This process resulted in the production of simulated laminated cores LC-1 to LC-4 according to the present invention.

[0086] A comparative sample, simulated laminated core LC-5, was separately prepared by laminating and bonding two soft magnetic plates together using a commercially available epoxy resin adhesive. A comparative sample, simulated laminated core LC-6 (a laminated core in which two soft magnetic plates were not glued together), was also prepared by applying a commercially available enamel paint to one main surface of one soft magnetic plate, allowing the paint to dry sufficiently, and then laminating another soft magnetic plate with the painted surface facing inward.

[0087] [Experiment 4] (Investigation of magnetic properties of simulated laminated cores LC-1 to LC-6) The magnetic properties of each sample were investigated using a vibrating sample magnetometer (BHV-525H, manufactured by Riken Denshi Co., Ltd.). The magnetization (unit: emu) of the sample was measured under conditions of a magnetic field of 1.6 MA / m and a temperature of 20°C, and the saturation magnetization Ms (unit: emu / g) was calculated from the sample mass.

[0088] As a result of the magnetic property investigation, the saturation magnetization Ms of the simulated laminated cores LC-1 to LC-6 was all approximately 203 emu / g, confirming that the electrical insulating material used in the present invention does not adversely affect Ms.

[0089] [Experiment 5] (Investigation of separation processing for simulated laminated cores LC-1 to LC-5) From the perspective of circular economy, the separability of laminated cores was investigated. Specifically, the simulated laminated cores LC-1 to LC-5 prepared in Experiment 4 were each suspended in an electric furnace, with a crucible placed underneath as a tray, and a separation heat treatment was performed. The temperature was raised in the air to the same temperature as in Experiment 3 (a temperature 20°C higher than the Ts of the lead-free glass composition used), held for 30 minutes, and then cooled to room temperature.

[0090] In the case of samples LC-1 to LC-4 according to the present invention, a mixture of lead-free glass composition and spacer particles (electrical insulating material) flowed down and solidified in the crucible after the separation heat treatment. The separation and recovery rate of the electrical insulating material was calculated from the mass changes of samples LC-1 to LC-4 and the crucible before and after the separation heat treatment, and it was confirmed that an extremely high separation and recovery rate of 99.9% could be achieved. Furthermore, because the heat treatment temperature was sufficiently lower than the A1 transformation point of the soft magnetic plate, it is believed that no significant changes would occur in the magnetic properties of the soft magnetic plate.

[0091] On the other hand, in the case of the comparative sample LC-5, the epoxy resin adhesive could not be completely thermally decomposed at a heating temperature of 500°C. Therefore, when the temperature was further increased to investigate the temperature at which the epoxy resin adhesive would be completely thermally decomposed, it was found that a heating temperature of around 800°C was necessary.

[0092] The results of LC-5 confirmed that laminated cores bonded using a resin-based adhesive cannot recover electrical insulating materials during separation processing, and that the environmental impact is greater than that of the laminated core of the present invention. Furthermore, because the required heat treatment temperature is higher than the A1 transformation point of the soft magnetic plate, it can be said that the magnetic properties of the separated soft magnetic plate may be reduced / degraded.

[0093] [Experiment 6] (Investigation using other soft magnetic plates) As soft magnetic plates different from those described above, commercially available Fe-6.5% by mass Si non-oriented electrical steel plate, commercially available Fe-Co alloy plate (Fe-49% by mass Co-1% by mass V plate, Fe-20% by mass Co-1% by mass V plate), and commercially available Fe-based amorphous alloy plate (Fe-Si-B plate) were prepared, and simulated laminated cores according to the present invention were fabricated in the same manner as in Experiment 3. The obtained samples were subjected to the same investigations as in Experiments 4 and 5 above.

[0094] As a result, it was confirmed that the electrical insulating material used in the present invention does not adversely affect the Ms of other soft magnetic plates. It was also confirmed that the soft magnetic plate and the electrical insulating material can be separated by the separation heat treatment at the same temperature as in Experiment 3, and that the electrical insulating material can be recovered with a high recovery rate.

[0095] The above-described embodiments and experiments have been described to aid in understanding the present invention, and the present invention is not limited to the specific configurations described. For example, it is possible to replace part of the configuration of the embodiments with configurations that are within the technical common sense of those skilled in the art, and it is also possible to add configurations that are within the technical common sense of those skilled in the art to the configuration of the embodiments. In other words, it is possible to delete, replace, or add part of the configurations of the embodiments and experiments in this specification, as long as they do not deviate from the technical concept of the invention.

[0096] 1...soft magnetic plate, 2...electrical insulating layer, 3...spacer particles, 10...laminated core, 11...stator slot, 12...slit, 13...teeth, 14...teeth claw portion, 20...stator, 21...stator coil, 22...segment conductor, 23...electrical insulating material.

Claims

1. A laminated core in which a plurality of soft magnetic plates are stacked with an electrical insulating layer interposed therebetween, characterized in that the electrical insulating layer is a layer having a matrix of a lead-free glass composition having a softening point lower than the A1 transformation point of the soft magnetic plates.

2. A laminated iron core according to claim 1, wherein the lead-free glass composition, when expressed as nominal components in terms of oxides, contains 15 mol% to 35 mol% of V2O5 and 5 mol% to 30 mol% of P2O5, the sum of the V2O5 and the P2O5 being 40 mol% to 65 mol%, and the laminated iron core contains two or more elements selected from the group consisting of BaO, Sb2O3, WO3, ZnO, K2O, Fe2O3, TeO2, Ag2O, and Li2O in a total amount of 35 mol% to 60 mol%, and the remainder being unavoidable impurities.

3. A laminated core according to claim 2, wherein the electrical insulation layer contains spherical spacer particles in an amount of 50% by volume or less, and the spacer particles are one or more selected from the group consisting of SiO2, ZrO2, Al2O3, Nb2O5, ZrSiO4, Zr2(WO4)(PO4)2, 2MgO.2Al2O3.5SiO2, 3Al2O3.2SiO2, LiAlSiO4, SiO2-Na2O-CaO-based glass, and SiO2-B2O3-Na2O-Al2O3-based glass.

4. A laminated core according to claim 3, wherein the spacer particles have a D90 of 10 μm or less.

5. A laminated core according to any one of claims 1 to 4, wherein the softening point of the lead-free glass composition is 500°C or lower.

6. A rotating electric machine having an iron core, wherein the iron core is a laminated iron core as defined in claim 5.

7. A method for manufacturing a laminated core according to any one of claims 1 to 4, comprising: a soft magnetic plate preparation step of preparing the soft magnetic plate; a glass paste preparation step of preparing glass paste that is the basis for the electrical insulation layer; a soft magnetic composite precursor formation step of forming a soft magnetic composite precursor by applying the glass paste to at least one main surface of the soft magnetic plate; a laminated core precursor formation step of laminating a plurality of the soft magnetic composite precursors to form a laminated core precursor; and a laminated core formation step of heat treating the laminated core precursor to form the electrical insulation layer and joining the soft magnetic plates together via the electrical insulation layer to form the laminated core.

8. A method for manufacturing a laminated iron core according to claim 7, wherein the glass paste preparation step includes a spacer particle mixing step of mixing spacer particles into the glass paste so that they are uniformly dispersed.

9. A method for manufacturing a laminated iron core as described in claim 7, wherein the soft magnetic composite precursor formation process includes a spacer particle embedding and arranging process for embedding and arranging spacer particles so that they are uniformly distributed on the glass paste-coated surface of the soft magnetic composite precursor.

10. A method for manufacturing a laminated core according to any one of claims 1 to 4, comprising: a soft magnetic plate preparation step of preparing the soft magnetic plate; a glass-containing sheet preparation step of preparing a glass-containing sheet that will become the basis for the electrical insulating layer; a laminated core precursor formation step of alternately stacking the glass-containing sheet and the soft magnetic plate to form a laminated core precursor; and a laminated core formation step of heat-treating the laminated core precursor to form the electrical insulating layer and joining the soft magnetic plates together via the electrical insulating layer to form the laminated core.

11. A method for manufacturing a laminated iron core as described in claim 10, wherein the glass-containing sheet preparation process includes a spacer particle mixing process in which the spacer particles are mixed so that they are uniformly dispersed before forming the glass-containing sheet.

12. A method for manufacturing a laminated iron core as described in claim 10, wherein the glass-containing sheet preparation process includes a spacer particle embedding and arranging process for embedding and arranging spacer particles so that they are uniformly distributed on the surface of the glass-containing sheet after the glass-containing sheet is formed.

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