Manufacturing method of laminated core

Abstract

To provide a highly productive manufacturing method of a laminated core.SOLUTION: In a method of obtaining a core veneer by punching an electromagnetic steel strip having an insulating film and laminating the core veneer to manufacture a laminated core, at the same time as the punching process, the core veneer is temporarily bonded by applying pressure, and the core veneer after the temporary bonding and after the punching process is heated to perform the main bonding.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a laminated core. [Background technology]

[0002] Laminated cores used in motors (rotating electric machines) are manufactured by punching electromagnetic steel sheets into a predetermined shape and then laminating them in a metal die. In recent years, thinner electromagnetic steel sheets have been used in motor products to reduce iron loss in these products. However, thinner electromagnetic steel sheets present issues that did not arise in conventional manufacturing methods for laminated cores. For example, the number of punching steps increases. This is because when the thickness of the electromagnetic steel sheets is reduced to half of the conventional thickness, the number of punching steps doubles.

[0003] Patent Document 1 describes a method for producing a metal sheet laminate, in which a metal sheet is obtained by punching, and a predetermined number of the metal sheets are stacked and bonded to produce a metal sheet laminate. In Patent Document 1, stacking and bonding are performed after punching, so productivity cannot be sufficiently improved. In order to improve productivity and ensure the same level of productivity as before, there is a method of punching out a plurality of electromagnetic steel sheets bonded by caulking, welding, adhesive, etc. However, this method merely increases the number of steps and does not sufficiently improve productivity.

[0004] Furthermore, when joining electromagnetic steel sheets by adhesive bonding, the adhesive hardens and generates stress strain in the steel sheets, which acts to increase the iron loss of the electromagnetic steel sheets. As mentioned above, thinning the electromagnetic steel sheets is an effective way to reduce core iron loss. However, as the stiffness of the steel sheets decreases with thinning, the adverse effects of stress strain also increase, so there is a need to reduce these adverse effects. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-334648 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above-mentioned circumstances, and has an object to provide a method for manufacturing a laminated core which reduces the adverse effects of stress-strain associated with heat treatment and bonding, and has excellent productivity, in a method for bonding electromagnetic steel sheets by heat treating the core in the process of manufacturing a laminated core from electromagnetic steel sheets. [Means for solving the problem]

[0007] The gist of the present invention is as follows. (1) A method for manufacturing a laminated core according to one aspect of the present invention is a method for manufacturing a laminated core by punching an electromagnetic steel strip having an insulating coating to obtain a core plate, and laminating the core plate to manufacture a laminated core, At the same time as the punching process, the core veneer is Pressure of 3.0 to 10.0 MPa Apply pressure to temporarily bond the pieces together. The core veneer after the temporary bonding and the punching process is Transport to a heating device, The permanent adhesion is achieved by heating. (2) In the method for producing a laminated core according to the above (1), the surface temperature of the core veneer may be 15 to 50° C. during the punching process and the temporary bonding. ( 3 )(1) above Or (2) In the method for producing a laminated core described in the above, the insulating coating may have adhesive properties. ( 4 ) Above (1)~( 3 The method for producing a laminated core according to any one of claims 1 to 4, wherein the peel strength of the core veneer after the punching process and the temporary bonding and before the main bonding is 5 N / cm 2 It may be more than that. ( 5 ) Above (1)~( 4 In the method for producing a laminated core described in any one of the above items (1) to (5), the core veneers may be heated to a temperature range of 180 to 250° C. in the main bonding. Effect of the Invention

[0008] According to the above aspects of the present invention, a method for manufacturing a laminated core with excellent productivity can be provided. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a rotating electrical machine including a laminated core. [Diagram 2] FIG. [Diagram 3] 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. 2 is a plan view of a material forming the laminated core. [Diagram 5] 5 is a cross-sectional view of FIG. 4 taken along line B-B. [Figure 6] FIG. 6 is an enlarged view of part C in FIG. 5. [Figure 7] FIG. 2 is a side view of a manufacturing apparatus used to manufacture the laminated core. [Figure 8] FIG. 2 is a flow diagram of a method for manufacturing a laminated core according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a method for manufacturing a laminated core according to one embodiment of the present invention will be described with reference to the drawings. First, a laminated core manufactured by the method for manufacturing a laminated core according to this embodiment, a rotating electric machine including this laminated core, and a material for forming this laminated core will be described. Note that in this embodiment, an electric motor, specifically an AC electric motor, more specifically a synchronous electric motor, and even more specifically a permanent magnet field type electric motor will be used as an example of the rotating electric machine. This type of electric motor is preferably used in, for example, electric vehicles.

[0011] (Rotary Electric Machine 10) 1, the rotating electric machine 10 includes a stator 20, a rotor 30, a case 50, and a rotating shaft 60. The stator 20 and the rotor 30 are housed in the case 50. The stator 20 is fixed within the case 50. In this embodiment, an inner rotor type rotating electric machine 10 is used in which the rotor 30 is located radially inside the stator 20. However, an outer rotor type rotating electric machine 10 in which the rotor 30 is located outside the stator 20 may also be used. Also, in this embodiment, the rotating electric machine 10 is a three-phase AC motor with 12 poles and 18 slots. However, the number of poles, the number of slots, the number of phases, etc. can be changed as appropriate. The rotating electric machine 10 can rotate at a rotation speed of 1000 rpm by applying an excitation current with an effective value of 10 A and a frequency of 100 Hz to each phase, for example.

[0012] The stator 20 includes a stator adhesive laminated core (hereinafter, stator core) 21 and a winding (not shown). The stator core 21 includes an annular core back portion 22 and a plurality of teeth portions 23. Hereinafter, the direction of the central axis O of the stator core 21 (or the core back portion 22) will be referred to as the axial direction, the radial direction of the stator core 21 (or the core back portion 22) (the direction perpendicular to the central axis O) will be referred to as the radial direction, and the circumferential direction of the stator core 21 (or the core back portion 22) (the direction going around the central axis O) will be referred to as the circumferential direction.

[0013] The core back portion 22 is formed in an annular shape when viewed in a plan view of the stator 20 in the axial direction. The multiple teeth portions 23 protrude radially inward from the inner circumference of the core back portion 22 (toward the central axis O of the core back portion 22 along the radial direction). The multiple teeth portions 23 are arranged at equal angular intervals in the circumferential direction. In this embodiment, 18 teeth portions 23 are provided at central angle intervals of 20 degrees centered on the central axis O. The multiple teeth portions 23 are formed to have the same shape and size as one another. Therefore, the multiple teeth portions 23 have the same thickness dimension as one another. The winding is wound around the teeth portion 23. The winding may be a concentrated winding or a distributed winding.

[0014] The rotor 30 is disposed radially inside the stator 20 (the stator core 21). The rotor 30 includes a rotor core 31 and a plurality of permanent magnets 32. The rotor core 31 is formed in an annular (circular) shape and is disposed coaxially with the stator 20. The rotating shaft 60 is disposed within the rotor core 31. The rotating shaft 60 is fixed to the rotor core 31. The multiple permanent magnets 32 are fixed to the rotor core 31. In this embodiment, a pair of the permanent magnets 32 forms one magnetic pole. The multiple pairs of permanent magnets 32 are arranged at equal angular intervals in the circumferential direction. In this embodiment, 12 pairs (24 in total) of permanent magnets 32 are provided at central angle intervals of 30 degrees around the central axis O.

[0015] In this embodiment, an embedded magnet type motor is used as the permanent magnet field type motor. A rotor core 31 is formed with a plurality of through holes 33 that pass through the rotor core 31 in the axial direction. The plurality of through holes 33 are provided corresponding to the arrangement of the plurality of permanent magnets 32. Each permanent magnet 32 ​​is fixed to the rotor core 31 while being arranged in the corresponding through hole 33. Each permanent magnet 32 ​​can be fixed to the rotor core 31 by, for example, bonding the outer surface of the permanent magnet 32 ​​to the inner surface of the through hole 33 with an adhesive. Note that a surface magnet type motor may be used as the permanent magnet field type motor instead of the embedded magnet type.

[0016] Both the stator core 21 and the rotor core 31 are laminated cores. For example, the stator core 21 is formed by laminating a plurality of core plates 40 in a lamination direction, as shown in FIG. The lamination thickness (total length along the central axis O) of each of the stator core 21 and the rotor core 31 is, for example, 50.0 mm. The outer diameter of the stator core 21 is, for example, 250.0 mm. The inner diameter of the stator core 21 is, for example, 165.0 mm. The outer diameter of the rotor core 31 is, for example, 163.0 mm. The inner diameter of the rotor core 31 is, for example, 30.0 mm. However, these values ​​are merely examples, and the lamination thickness, outer diameter, and inner diameter of the stator core 21 and the lamination thickness, outer diameter, and inner diameter of the rotor core 31 are not limited to these values. Here, the inner diameter of the stator core 21 is based on the tip end of the teeth portion 23 of the stator core 21. In other words, the inner diameter of the stator core 21 is the diameter of an imaginary circle inscribed in the tip end of all the teeth portion 23.

[0017] Each of the core plates 40 forming the stator core 21 and the rotor core 31 is formed, for example, by punching a blank 1 as shown in Fig. 4 to Fig. 6. The blank 1 is a steel plate (electromagnetic steel plate) that serves as the base material of the core plate 40. Examples of the blank 1 include a strip-shaped steel plate and a cut plate. Although we are still in the middle of explaining the laminated core, the following will explain this material 1. In this specification, the strip-shaped steel plate that is the base material of the core veneer 40 may be referred to as material 1 or electromagnetic steel strip 1. The steel plate that is punched into the shape used for the laminated core by the material 1 or electromagnetic steel strip 1 may be referred to as core veneer 40.

[0018] (Material 1) The material 1 is handled in a state where it is wound around a coil 1A, for example. In this embodiment, a non-oriented electromagnetic steel sheet is used as the material 1. As the non-oriented electromagnetic steel sheet, a non-oriented electromagnetic steel strip according to JIS C 2552:2014 can be used. However, as the material 1, a directional electromagnetic steel sheet may be used instead of the non-oriented electromagnetic steel sheet. As the directional electromagnetic steel sheet in this case, a directional electromagnetic steel strip according to JIS C 2553:2019 can be used. In addition, a non-oriented thin electromagnetic steel strip and a directional thin electromagnetic steel strip according to JIS C 2558:2015 can be used.

[0019] The upper and lower limits of the average plate thickness t0 of the raw material 1 are set, for example, as follows, taking into consideration the case where the raw material 1 is used as the core veneer 40. The thinner the material 1, the higher the manufacturing cost of the material 1. Therefore, taking the manufacturing cost into consideration, the lower limit of the average plate thickness t0 of the material 1 is 0.10 mm, preferably 0.15 mm, and more preferably 0.18 mm. On the other hand, if the material 1 is too thick, the manufacturing cost is favorable, but when the material 1 is used as the core veneer 40, the eddy current loss increases and the core iron loss deteriorates. Therefore, in consideration of the core iron loss and the manufacturing cost, the upper limit of the average sheet thickness t0 of the material 1 is 0.65 mm, preferably 0.35 mm, and more preferably 0.30 mm. An example of the average sheet thickness t0 of the raw material 1 that satisfies the above range is 0.20 mm.

[0020] The average thickness t0 of the raw material 1 includes not only the thickness of the base steel plate 2 described later, but also the thickness of the insulating coating 3. The average thickness t0 of the raw material 1 is measured, for example, by the following measurement method. For example, when the raw material 1 is wound in the shape of a coil 1A, at least a part of the raw material 1 is wound out in a flat plate shape. In the raw material 1 that has been wound out in a flat plate shape, a predetermined position in the longitudinal direction of the raw material 1 (for example, a position away from an edge in the longitudinal direction of the raw material 1 by a length of 10% of the total length of the raw material 1) is selected. At this selected position, the raw material 1 is divided into five regions along its width direction. The thickness of the raw material 1 is measured at four locations that are the boundaries between these five regions. The average value of the thicknesses at the four locations can be set as the average thickness t0 of the raw material 1.

[0021] The upper and lower limits of the average thickness t0 of the material 1 can naturally be adopted as the upper and lower limits of the average thickness t0 of the core veneer 40. The average thickness t0 of the core veneer 40 can be measured, for example, by the following measurement method. For example, the lamination thickness of the laminated core is measured at four locations equally spaced apart in the circumferential direction (i.e., at 90° intervals around the central axis O). Each of the measured lamination thicknesses at the four locations is divided by the number of laminated core veneers 40 to calculate the thickness per sheet. The average value of the thicknesses at the four locations can be regarded as the average thickness t0 of the core veneer 40.

[0022] 5 and 6, the material 1 includes a base steel plate 2 and an insulating coating 3. The material 1 is formed by covering both sides of a strip-shaped base steel plate 2 with the insulating coating 3. In this embodiment, most of the material 1 is formed of the base steel plate 2, and the insulating coating 3 that is thinner than the base steel plate 2 is formed on the surface of the base steel plate 2.

[0023] The chemical composition of the base steel plate 2 is shown below in mass %, and contains 2.5% to 4.5% by mass of Si. By setting the chemical composition within this range, the yield strength of the material 1 (core veneer 40) can be set to, for example, 380 to 540 MPa.

[0024] Silicon: 2.5% to 4.5% Al: 0.001% to 3.0% Mn: 0.05% to 5.0% Remainder: Fe and impurities

[0025] When the material 1 is used as the core veneer 40, the insulating coating 3 exerts insulating properties between the core veneer panels 40 adjacent to each other in the stacking direction. In this embodiment, the insulating coating 3 has an adhesive property and bonds the core veneer panels 40 adjacent to each other in the stacking direction. The insulating coating 3 may have a single layer structure or a multi-layer structure. More specifically, for example, the insulating coating 3 may have a single layer structure that combines insulating properties and adhesive properties, or may have a multi-layer structure including a base insulating coating with excellent insulating properties and a top insulating coating with excellent adhesive properties.

[0026] In this embodiment, the insulating coating 3 covers both sides of the base steel sheet 2 without any gaps over the entire surface. However, as long as the above-mentioned insulating performance and adhesive performance are ensured, some layers of the insulating coating 3 do not need to cover both sides of the base steel sheet 2 without any gaps. In other words, some layers of the insulating coating 3 may be provided intermittently on the surface of the base steel sheet 2. However, to ensure insulating performance, both sides of the base steel sheet 2 need to be covered with the insulating coating 3 so that the entire surface is not exposed. Specifically, when the insulating coating 3 does not have an underlying insulating coating with excellent insulating performance and has a single-layer configuration combining insulating performance and adhesive performance, the insulating coating 3 needs to be formed over the entire surface of the base steel sheet 2 without any gaps. In contrast, when the insulating coating 3 has a multi-layer structure including a base insulating coating with excellent insulating performance and a top insulating coating with excellent adhesion, it is possible to achieve both insulating performance and adhesion by forming both the base insulating coating and the top insulating coating without gaps over the entire surface of the base steel sheet 2, or by forming the base insulating coating without gaps over the entire surface of the base steel sheet and providing the top insulating coating intermittently.

[0027] The coating composition for forming the insulating undercoat is not particularly limited, and for example, a general treatment agent such as a chromate-containing treatment agent or a phosphate-containing treatment agent can be used.

[0028] The adhesive insulating coating is formed by applying a coating composition for electrical steel sheet, which will be described later, onto a base steel sheet. The adhesive insulating coating is, for example, a single-layer insulating coating having both insulating properties and adhesive properties, or a top insulating coating provided on a base insulating coating. The adhesive insulating coating is in an uncured or semi-cured state (B stage) before thermocompression bonding during laminated core production, and a curing reaction proceeds due to heating during thermocompression bonding, thereby developing adhesive properties.

[0029] The coating composition for the electrical steel sheet is not particularly limited, and may be, for example, a composition containing an epoxy resin and an epoxy resin curing agent. That is, an example of an insulating coating having adhesive properties is a film containing an epoxy resin and an epoxy resin curing agent.

[0030] As the epoxy resin, a general epoxy resin can be used, specifically, any epoxy resin having two or more epoxy groups in one molecule can be used without any particular limitation. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, alicyclic epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, hydantoin type epoxy resins, isocyanurate type epoxy resins, acrylic acid modified epoxy resins (epoxy acrylates), phosphorus-containing epoxy resins, and their halides (brominated epoxy resins, etc.) and hydrogenated products. As the epoxy resin, one type may be used alone, or two or more types may be used in combination.

[0031] The coating composition for electrical steel sheets may contain an acrylic resin. The acrylic resin is not particularly limited. Examples of monomers used for the acrylic resin include unsaturated carboxylic acids such as acrylic acid and methacrylic acid, and (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate. The (meth)acrylate means acrylate or methacrylate. The acrylic resin may be used alone or in combination of two or more.

[0032] The acrylic resin may have a structural unit derived from a monomer other than the acrylic monomer. Examples of the other monomer include ethylene, propylene, and styrene. The other monomer may be used alone or in combination of two or more.

[0033] When an acrylic resin is used, it may be used as an acrylic-modified epoxy resin obtained by grafting an acrylic resin onto an epoxy resin, or may be included as a monomer forming an acrylic resin in a coating composition for an electrical steel sheet.

[0034] As the epoxy resin curing agent, a latent heat-curing type can be used, and examples thereof include aromatic polyamines, acid anhydrides, phenol-based curing agents, dicyandiamide, boron trifluoride-amine complexes, and organic acid hydrazides. As the aromatic polyamines, examples thereof include metaphenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone. As the phenol-based curing agents, examples thereof include phenol novolac resins, cresol novolac resins, bisphenol novolac resins, triazine-modified phenol novolac resins, and phenol resol resins. Among them, as the epoxy resin curing agent, phenol-based curing agents are preferred, and phenol resol resins are more preferred. As the epoxy resin curing agent, one type may be used alone, or two or more types may be used in combination.

[0035] The content of the epoxy resin curing agent in the coating composition for electrical steel sheets is preferably 5 to 35 parts by mass, and more preferably 10 to 30 parts by mass, per 100 parts by mass of the epoxy resin.

[0036] The coating composition for electrical steel sheets may contain additives such as a curing accelerator (curing catalyst), an emulsifier, an antifoaming agent, etc. As the additives, only one type may be used, or two or more types may be used in combination.

[0037] The upper and lower limits of the average thickness t1 of the insulating coating 3 are set, for example, as follows, taking into consideration the case where the material 1 is used as a core veneer 40. When the material 1 is used as a core veneer 40, the average thickness t1 of the insulating coating 3 (thickness per one side of the core veneer 40 (material 1)) is adjusted so as to ensure the insulating performance and adhesive ability between the core veneers 40 that are stacked on top of each other.

[0038] In the case of the insulating coating 3 having a single layer configuration, the average thickness t1 of the insulating coating 3 (the thickness per one side of the core veneer 40 (material 1)) can be, for example, 1.5 μm or more and 8.0 μm or less. In the case of the insulating coating 3 having a multi-layer structure, the average thickness of the base insulating coating may be, for example, from 0.3 μm to 1.2 μm, and preferably from 0.7 μm to 0.9 μm. The average thickness of the top insulating coating may be, for example, from 1.5 μm to 8.0 μm. The average thickness t1 of the insulating coating 3 on the base material 1 can be measured in the same manner as the average plate thickness t0 of the base material 1, by measuring the thicknesses of the insulating coating 3 at multiple locations and averaging these thicknesses.

[0039] The upper and lower limits of the average thickness t1 of the insulating coating 3 in the material 1 can be naturally adopted as the upper and lower limits of the average thickness t1 of the insulating coating 3 in the core veneer 40. The average thickness t1 of the insulating coating 3 in the core veneer 40 can be measured, for example, by the following measurement method. For example, among the multiple core veneers 40 forming the laminated core, the core veneer 40 located at the outermost position in the lamination direction (the core veneer 40 whose surface is exposed in the lamination direction) is selected. On the surface of the selected core veneer 40, a predetermined position in the radial direction (for example, a position exactly halfway (center) between the inner peripheral edge and the outer peripheral edge of the core veneer 40) is selected. At the selected position, the thickness of the insulating coating 3 of the core veneer 40 is measured at four points equally spaced apart in the circumferential direction (i.e., at 90° intervals around the central axis O). The average value of the thicknesses measured at the four points can be regarded as the average thickness t1 of the insulating coating 3. The reason why the average thickness t1 of the insulating coating 3 is measured in the core veneer 40 located at the outermost position in the stacking direction is that the insulating coating 3 is fabricated so that the thickness of the insulating coating 3 hardly changes depending on the stacking position along the stacking direction of the core veneer 40.

[0040] The blank 1 as described above is punched to produce a core plate 40, and a laminated core (the stator core 21 or the rotor core 31) is produced from the core plate 40.

[0041] (Lamination method of laminated core) Returning to the description of the laminated core, a plurality of core plates 40 forming the stator core 21 are laminated with insulating coatings 3 interposed therebetween, as shown in FIG.

[0042] The core veneers 40 adjacent to each other in the stacking direction are bonded over their entire surfaces by the insulating coating 3. In other words, the surface of the core veneers 40 facing the stacking direction (hereinafter referred to as the first surface) is an adhesive region over its entire surface. However, the core veneers 40 adjacent to each other in the stacking direction do not have to be bonded over their entire surfaces. In other words, the first surface of the core veneers 40 may include both adhesive regions 41a and non-adhesive regions (not shown).

[0043] In this embodiment, the multiple core plates forming the rotor core 31 are fixed to each other by crimps 42 (dowels) shown in Fig. 1. However, the multiple core plates forming the rotor core 31 may also have a laminated structure fixed by an insulating coating 3, similar to the stator core 21. Furthermore, laminated cores such as the stator core 21 and the rotor core 31 may be formed by so-called rotational lamination.

[0044] (Manufacturing method of laminated core) A method for manufacturing a laminated core according to one embodiment of the present invention will be described below with reference to Figures 7 and 8. Figure 7 is a side view of a manufacturing apparatus used to manufacture the laminated core, and Figure 8 is a flow diagram of the manufacturing method for the laminated core according to this embodiment. In the following description of the manufacturing method, first, a manufacturing apparatus 100 for a laminated core (hereinafter, simply referred to as manufacturing apparatus 100) will be described.

[0045] In the manufacturing equipment 100, the raw material 1 is sent from the coil 1A (hoop) toward the upstream side in the conveying direction (the right side in FIG. 7), while being punched multiple times by dies arranged at each stage, gradually forming the shape of the core veneer 40. In the punching process by the die at the rearmost stage among the punching dies, the core veneers 40 are stacked, and at the same time as punching, the core veneers 40 are temporarily bonded by pressure. Next, the stacked core veneers 40 are transported to a heating device (not shown) and heated. As a result, the core veneers 40 adjacent in the stacking direction are bonded by the insulating coating 3 (i.e., the portion of the insulating coating 3 located in the bonding region 41a is allowed to exert its adhesive ability), and the main bonding is completed.

[0046] In FIG. 7, the manufacturing apparatus 100 includes a plurality of punching stations 110. The number of punching stations 110 may be two or more. Each punching station 110 includes a female die 111 disposed below the material 1 and a male die 112 disposed above the material 1. The plurality of punching stations 110 may be collectively referred to as a punching die. The manufacturing apparatus 100 may also include a mechanism for re-pressurizing the laminated core veneers 40.

[0047] The manufacturing method of a laminated core in this embodiment is a method of producing a laminated core by punching an electromagnetic steel strip having an insulating coating to obtain a core veneer, and stacking the core veneer to manufacture a laminated core. Simultaneously with the punching process, the core veneer is temporarily bonded by applying pressure to the core veneer, and the core veneer after the temporary bonding and after the punching process is heated to perform the final bonding. The details are explained below.

[0048] (Temporary adhesion by applying pressure during punching) The blank 1 is inserted into a punching die and gradually punched into a desired shape. The desired shape is, for example, the shape of the core plate 40 having the shape of the stator core 21 or the rotor core 31.

[0049] Among the punching dies, the blank 1 is processed into the shape of the core veneer 40 by punching in the die at the rearmost stage, and is layered in the female die 111. At this time, pressure is applied to the core veneer 40 simultaneously with the punching process, and the core veneer 40 is temporarily bonded to the layered core veneer 40. That is, the punched core veneer 40 is temporarily bonded to the uppermost core veneer 40 layered in the female die 111 by the pressure applied during the punching process. By sequentially repeating the punching, pressure, and layering described above, a predetermined number of core veneers 40 are stacked. The core veneer 40 to be temporarily bonded has an insulating coating 3 on both sides. This insulating coating 3 is preferably formed so that the average thickness t1 falls within the above-mentioned range. As described above, this insulating coating 3 has insulating properties and adhesive properties.

[0050] In this embodiment, the term "temporarily bonded" means that the core veneers 40 are bonded by applying pressure without heating. After the temporary bonding, the laminated core is temporarily fixed. The temporarily bonded laminated core is then permanently bonded by heating, which will be described later.

[0051] As described above, in this embodiment, it is not necessary to heat the core veneer 40 during punching and temporary bonding. In order to heat the core veneer 40 during punching and temporary bonding, a heating device is required, and since heating takes time, productivity is significantly reduced. The surface temperature of the core veneer 40 during punching and temporary bonding may be room temperature, for example, 15 to 50°C. The surface temperature of the core veneer 40 is obtained by measuring the temperature of the central part in the width direction of the core veneer 40 during punching and temporary bonding using an infrared radiation thermometer, and calculating the average value of the temperatures.

[0052] The lower limit of the pressure during punching and temporary bonding is preferably 3.0 MPa. More preferably, it is 5.0 MPa or more. There is no particular need to limit the upper limit, but in consideration of the enlargement of the device and the prevention of deformation of the mold, it is preferably 30.0 MPa or less. More preferably, it is 20.0 MPa or less, and even more preferably, it is 10.0 MPa or less. By setting the pressure within this range, the core veneer 40 can be reliably temporarily bonded.

[0053] Whether or not the core veneer 40 is in a temporarily bonded state is determined by the following method. A test piece of a specified size is taken and subjected to a tensile test (shear tensile test in accordance with JIS K 6850:1999). The peel strength per unit area obtained by the tensile test is 5N / cm 2 If the strength is equal to or greater than this, it is determined that the core veneer 40 is temporarily bonded. There is no particular lower limit, and the purpose can be achieved as long as disturbance in the laminated state during and after removal from the mold can be avoided. A pressure of 10 N / cm is preferable. 2 More preferably, 15N / cm 2 The upper limit is not particularly limited, and in the present invention, when the strength is less than the full adhesive strength achieved by heating, it is judged to be in a temporary adhesive state. Within the range of less than the full adhesive strength, preferably 200 N / cm 2 Less than 150N / cm, more preferably 2 Less than 100N / cm, more preferably 100N / cm 2 Less than 50N / cm, more preferably 50N / cm 2 The temporary adhesive strength is naturally determined depending on the adhesive that can provide the required permanent adhesive strength, and on the balance with the above-mentioned pressure force, etc.

[0054] By temporarily bonding the core veneers 40 in the mold in this manner, it is possible to prevent the laminated core veneers 40 from being disturbed when and after they are removed from the mold. This also makes it easier to handle the laminated core veneers 40 thereafter, which contributes to improving productivity. Furthermore, the temporary bonding at this stage also contributes to suppressing the adverse effects of stress distortion in the process of subsequently heating and permanently bonding the laminated core veneers 40. This will be described later, including examples.

[0055] (real adhesion) The laminated and temporarily bonded core veneers 40 are transported to a heating device (not shown) and heated to a temperature range of, for example, 180 to 250°C for permanent bonding. This heating hardens the adhesive (insulating coating 3) to form a bonding region 41a. When transporting to the heating device, the laminated core veneers 40 may be transported while being held by clamping them from both sides in the stacking direction with a jig (not shown). The laminated core can be manufactured by the method described above.

[0056] In this embodiment, whether the core veneer 40 is in a permanently bonded state or not is determined by carrying out a shear tensile test in the same manner as in determining whether the core veneer 40 is temporarily bonded. 2 If the above conditions are met, it is determined that the core veneer 40 is in a fully bonded state. EXAMPLES

[0057] As an embodiment of the present invention, a coil of a non-oriented electromagnetic steel strip having a sheet thickness of 0.20 mm was prepared by forming an insulating coating on the surface and processing the strip to a predetermined slit width. The non-oriented electromagnetic steel strip used had, in mass %, 3.3% Si, 0.7% Al, 0.2% Mn, and the remainder Fe and impurities. The insulating coating was a single-layer insulating coating having insulating properties and adhesive properties. The average thickness of the insulating coating was 1.5 μm or more and 8.0 μm or less per side of the core veneer. The non-oriented electromagnetic steel strip was inserted into a punching die, punched into a predetermined core veneer shape, and pressurized simultaneously with the punching process in the most rear stage die, to temporarily bond the core veneer to the already laminated core veneer. This operation was repeated in synchronization to laminate the core veneer in a temporarily bonded state in the die. Note that the pressure during punching and temporary bonding was 3.0 to 10.0 MPa, and the surface temperature of the core veneer was 15 to 50°C. When the non-oriented electrical steel sheet after temporary bonding was subjected to a shear tensile test in accordance with JIS K 6850:1999, the peel strength per unit area was 5N / cm 2 That was all.

[0058] Next, the laminated core veneers were transported to a heating device and heated to 180 to 250°C for permanent bonding. When the non-oriented electrical steel sheets after permanent bonding were subjected to a shear tensile test in accordance with JIS K 6850:1999, the obtained peel strength per unit area was 250N / cm 2 That was all. The non-oriented electrical steel strip had an insulating coating with adhesive properties, so that the laminated core sheets were heated in the female die to obtain a fully bonded laminated core.

[0059] Next, a non-oriented electromagnetic steel strip having a thickness of 0.20 mm and containing, by mass%, 3.3% Si, 0.7% Al, and 0.2% Mn, with the remainder being Fe and impurities, and having an insulating coating on the surface was prepared. As the insulating coating, a chromic acid-containing treatment agent was used as a coating composition for forming a base insulating coating, and an insulating coating having insulating properties and adhesive properties was formed as a top insulating coating provided on the base insulating coating. The average thickness of the base insulating coating was 0.3 μm or more and 1.2 μm or less, and the average thickness of the top insulating coating was 1.5 μm or more and 8.0 μm or less. This non-oriented electromagnetic steel strip was cut into 25 mm x 200 mm, overlapped with an area of ​​25 mm x 25 mm, and pressed with various pressures shown in Table 1. At that time, in order to simulate punching, punching oil (Daphne New Punching Oil manufactured by Idemitsu Kosan Co., Ltd.) was dropped on the overlapping surfaces before pressing. Thereafter, the overlapping portion was subjected to a shear tensile test in the direction in which it was sheared at a test speed of 3 mm / min in accordance with JIS K 6850:1999, and the peel strength was measured. In addition, the non-oriented electromagnetic steel strip was punched using the device in Fig. 7 and temporarily bonded by changing the pressure as shown in Table 1. The laminated core veneers were dropped from a height of 5 cm on the desk surface, and if the core veneers maintained their temporarily bonded state, they were judged as good (OK), and if they did not maintain their temporarily bonded state, they were judged as poor (NG).

[0060] [Table 1]

[0061] In test numbers 1 and 2, where the applied pressure was small, temporary adhesion was not achieved. In test number 3, sufficient peel strength was not achieved, and the temporary adhesion could not be maintained when the laminated core veneer was dropped. In contrast, in test numbers 4 to 6, the applied pressure was within the appropriate range, so the peel strength was within the appropriate range and a good temporary adhesion state was achieved.

[0062] Furthermore, the non-oriented electromagnetic steel strip was punched into a stator shape using the device in Figure 7, and temporarily bonded by varying the pressure as shown in Table 2. The laminated core veneer removed from the die was carried into a heating device and heated at 200°C for 30 minutes for permanent bonding. In addition, as a comparative material, an electromagnetic steel sheet was manufactured in which only the top insulating coating was replaced with a coating that hardens at room temperature, and after temporary bonding by varying the pressure, it was removed from the die and held at room temperature for permanent bonding. The iron loss of the resulting laminated stator core was then evaluated.

[0063] The iron loss of the stator core is the energy loss generated in the stator core, and was evaluated as the energy loss in a rotating magnetic field by the method described in Japanese Patent No. 2740553. That is, search coils were placed at four different points in the circumferential direction of the core back, and the energy loss was obtained when magnetizing to obtain a magnetic flux density of 1.5 T as the average value of the four points. Then, this energy loss was divided by the weight of the stator core to convert it to a unit of W / kg, which was used as the iron loss of the stator core. The above energy loss was calculated from the difference in induced torque when the stator core was rotated at 300 rpm and the excitation current was applied to the excitation yoke located in the center of the stator core and when it was turned off. That is, the energy loss was calculated by utilizing the relationship that the product of the induced torque and the rotation speed is equal to the energy generated in the stator core. The results are shown in Table 2.

[0064] [Table 2]

[0065] Compared to test numbers 11 to 13, which used a smaller applied pressure, test numbers 14 to 16, which used a larger applied pressure, had lower iron loss. One of the reasons for this is thought to be that the collapse of the laminated shape during handling from temporary bonding to actual bonding was suppressed. Test numbers 11 to 13 were temporarily bonded under the same conditions as test numbers 1 to 3, and test numbers 14 to 16 were temporarily bonded under the same conditions as test numbers 4 to 6, respectively, and it is thought that the peel strength of test numbers 14 to 16 was sufficient to suppress the collapse of the laminated shape during handling.

[0066] Furthermore, although there was a large difference in the applied pressure between test numbers 17 and 18, no significant difference was observed in the iron loss. The electrical steel sheets used in test numbers 17 and 18 had a room temperature curing top insulating coating, and the temporary bonding function when applied pressure at room temperature was comparable to that of test numbers 11 to 16, which had a high temperature curing type. In other words, compared to test number 17, test number 18 is considered to have demonstrated the effect of suppressing the collapse of the laminated shape during the handling process from temporary bonding to actual bonding.

[0067] From this, it is considered that the iron loss reduction observed in test numbers 11 to 16 may be related to the suppression of the collapse of the laminated shape during the handling process from temporary bonding to real bonding, as well as the presence or absence of heating for real bonding. For example, it is considered that by performing moderate temporary bonding as in the present invention, the adverse effects of deformation of the core during heating can be effectively suppressed. In particular, when heating a bulk-shaped member in which steel plates are laminated, such as a core, it is considered that local temperature differences are likely to occur within the member, and inadvertent stress strain is likely to occur. It is considered that temporary bonding mitigates the occurrence of such stress strain and suppresses its adverse effects. Although the detailed mechanism is unknown, the manufacturing method of the present invention showed an effect that has hardly been considered in the temporary bonding in the past.

[0068] An embodiment of the present invention and examples have been described above. However, the technical scope of the present invention is not limited to the above embodiment and examples, and various modifications can be made without departing from the spirit of the present invention. For example, the shape of the stator core 21 is not limited to the form shown in the above embodiment. Specifically, the outer diameter and inner diameter dimensions of the stator core 21, the lamination thickness, the number of slots, the circumferential and radial dimensional ratios of the teeth portion 23, and the radial dimensional ratios of the teeth portion 23 and the core back portion 22 can be designed as desired according to the characteristics of the rotating electric machine. In the rotor 30 in the above embodiment, a pair of permanent magnets 32 form one magnetic pole, but the present invention is not limited to this embodiment. For example, one permanent magnet 32 ​​may form one magnetic pole, or three or more permanent magnets 32 may form one magnetic pole.

[0069] In the above embodiment, a permanent magnet field type motor has been used as an example of the rotating motor 10, but the structure of the rotating motor 10 is not limited to this, as exemplified below, and various known structures not exemplified below can also be adopted. In the above embodiment, a permanent magnet field type motor has been described as an example of the rotating electric machine 10, but the present invention is not limited to this. For example, the rotating electric machine 10 may be a reluctance type motor or an electromagnetic field type motor (wound field type motor). In the above embodiment, a synchronous motor is used as an example of an AC motor, but the present invention is not limited to this. For example, the rotating electric machine 10 may be an induction motor. In the above embodiment, an AC motor has been described as an example of the rotating electric machine 10, but the present invention is not limited to this. For example, the rotating electric machine 10 may be a DC motor. In the above embodiment, an electric motor has been taken as an example of the rotating electric machine 10, but the present invention is not limited to this. For example, the rotating electric machine 10 may be a generator. Also, the present invention may be applied to a transformer.

[0070] In addition, within the scope of the invention, the components in the above-described embodiments may be replaced with well-known components, and the above-described modified examples may be combined as appropriate. [Explanation of symbols]

[0071] 1. Material: electromagnetic steel strip 1A coil 2 Base steel plate 3. Insulation Coating 10 Rotating Electric Machine 21 Stator core 22 Core back section 23 Teeth 30 rotors 31 Rotor core 32 Permanent magnets 33 Through hole 40 core veneer 41a Adhesive area 50 cases

Claims

1. A method for manufacturing a laminated core by punching an electromagnetic steel strip having an insulating coating to obtain a core plate, and laminating the core plate, comprising the steps of: At the same time as the punching process, the core veneer is temporarily bonded by applying a pressure of 3.0 to 10.0 MPa. A method for manufacturing a laminated core, comprising the steps of: transporting the core veneer after the temporary bonding and the punching process to a heating device and heating the veneer to perform final bonding.

2. 2. The method for manufacturing a laminated core according to claim 1, wherein the surface temperature of said core veneers during said punching and said temporary bonding is 15 to 50°C.

3. 3. The method for manufacturing a laminated core according to claim 1, wherein the insulating coating has an adhesive property.

4. The peel strength of the core veneer after the punching process and the temporary bonding and before the main bonding is 5 N / cm ２ The method for producing a laminated core according to any one of claims 1 to 3, characterized in that

5. The method for manufacturing a laminated core according to any one of claims 1 to 4, characterized in that, in the main bonding, the core veneers are heated to a temperature range of 180 to 250°C.

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