Apparatus and method for manufacturing laminated core

Abstract

A manufacturing apparatus 100 comprises: a punch 12; a punching die 14 disposed under the punch 12; a first holding part 16 disposed under the punching die 14; a second holding part 18 disposed under the first holding part 16 and composed of a member different from the first holding part 16; and a heating part 20 disposed around the second holding part 18 under the first holding part 16. A plurality of core sheets 1a are punched from a steel strip 1 by the punch 12 and the punching die 14, the plurality of core sheets 1a are pressed downward by the punch 12 while the outer peripheral parts of the plurality of punched core sheets 1a are pressed from the side by the first holding part 16, and the plurality of core sheets 1a being pressed downward by the punch 12 are heated by the heating part 20 while being held inside the second holding part 18.

Description

Manufacturing device and manufacturing method for laminated core

[0001] The present invention relates to an apparatus and method for manufacturing a laminated core.

[0002] Conventionally, laminated cores having a configuration in which a plurality of electromagnetic steel sheets are laminated have been used as cores for rotating electrical machines, etc. One known method for manufacturing laminated cores is to punch core sheets of a predetermined shape from a steel strip to which an adhesive has been applied, and then bond the resulting core sheets together to manufacture the laminated core.

[0003] For example, in the manufacturing method of a laminated core disclosed in Patent Document 1, core sheets punched out of a strip-shaped steel sheet by an outline punching punch are forced into an outline punching die. The core sheets forced into the outline punching die are stacked on top of the previously punched core sheets, and are then sequentially forced into a squeeze ring below the outline punching die. The core sheets forced into the squeeze ring are pressed against the inner circumferential surface of the squeeze ring while moving, thereby adhering to one another. At this time, the adhesive between each core sheet is hardened by the heat of a heater, and a laminated core is formed in which a predetermined number of core sheets are fixed together.

[0004] JP 2009-297758 A

[0005] The method disclosed in Patent Document 1 allows for the continuous punching of the thin core plates using a punching die and the continuous application of pressure and heat to the multiple thin core plates in a squeeze ring, thereby enabling efficient production of laminated cores.

[0006] However, as a result of research by the inventors, it was found that when multiple iron core thin plates are pressurized and heated simultaneously as described above, compressive residual stress occurs in the resulting laminated iron core, which can increase iron loss.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a laminated core manufacturing apparatus and method that can suppress the occurrence of iron loss.

[0008] A manufacturing apparatus according to one embodiment of the present invention is an apparatus for manufacturing a laminated core by punching multiple core sheets from a steel strip having an adhesive layer on its surface and bonding the resulting multiple core sheets to each other, and comprises: a punch; a punching die arranged below the punch; a first holding section arranged below the punching die; a second holding section arranged below the first holding section and made of a separate member from the first holding section; and a heating section arranged below the first holding section and around the second holding section, characterized in that the apparatus punches multiple core sheets from the steel strip with the punch and the punching die; presses the outer peripheries of the punched multiple core sheets from the sides with the first holding section while pressing the multiple core sheets downward with the punch; and heats the multiple core sheets pressed downward by the punch while holding them in the second holding section with the heating section.

[0009] Furthermore, a manufacturing method according to one embodiment of the present invention is a manufacturing apparatus comprising a punch, a punching die arranged below the punch, a first holding section arranged below the punching die, a second holding section arranged below the first holding section and made of a separate member from the first holding section, and a heating section arranged below the first holding section and around the second holding section, characterized in that the punch and the punching die are used to punch out multiple core sheets from a steel strip having an adhesive layer on its surface, the punch presses the outer peripheries of the punched core sheets from the sides while the first holding section presses the multiple core sheets downward, and the multiple core sheets pressed downward by the punch are heated by the heating section while being held in the second holding section.

[0010] The adhesive layer may be a thermosetting adhesive layer.

[0011] The first holding portion and the second holding portion may be connected via a connecting portion.

[0012] The first holding portion may have a vertical length of 5 mm or more.

[0013] The punch may press the core sheets with a pressure of 2.0 MPa or less.

[0014] The heating unit may include an infrared heating device.

[0015] According to the present invention, it is possible to suppress the occurrence of iron loss in the laminated core.

[0016] Fig. 1 is a schematic cross-sectional view showing a laminated core manufacturing apparatus according to one embodiment of the present invention. Fig. 2 is an enlarged cross-sectional view showing the vicinity of the surface of a steel strip. Fig. 3 is a diagram for explaining a laminated core manufacturing method according to one embodiment of the present invention. Fig. 4 is a diagram for explaining a laminated core manufacturing method according to one embodiment of the present invention. Fig. 5 is a diagram for explaining a laminated core manufacturing method according to one embodiment of the present invention. Fig. 6 is a diagram showing a modified example of the manufacturing apparatus. Fig. 7 is a diagram showing another modified example of the manufacturing apparatus. Fig. 8 is a diagram showing another modified example of the manufacturing apparatus.

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a laminated core manufacturing apparatus and method according to an embodiment of the present invention will be described with reference to the drawings.

[0018] FIG. 1 is a schematic cross-sectional view showing a laminated core manufacturing apparatus according to one embodiment of the present invention. The manufacturing apparatus 100 is an apparatus for manufacturing a laminated core 2 by punching multiple core sheets 1a from a steel strip 1 conveyed in a predetermined direction and bonding the resulting multiple core sheets 1a together. In this embodiment, the laminated core 2 has, for example, a cylindrical shape and is used as a stator core in a rotating electric machine. Note that the laminated core 2 may also be a laminated core used as a rotor core in a rotating electric machine. The laminated core 2 may also be a split core. The laminated core 2 may also be a core for a device other than a rotating electric machine.

[0019] Below, a brief description of the steel strip 1 will be given, followed by a detailed description of the manufacturing apparatus 100. Figure 2 is an enlarged cross-sectional view showing the vicinity of the surface of the steel strip 1.

[0020] As shown in Figure 2, the steel strip 1 comprises a base steel sheet 11a and an adhesive layer 11b. In this embodiment, a non-oriented electrical steel sheet is used as the base steel sheet 11a, but a directional electrical steel sheet may also be used as the base steel sheet 11a. In this specification, the term "electrical steel sheet" refers to the base material portion (base steel sheet) excluding the insulating coating, etc. The adhesive layer 11b is formed on the surface of the base steel sheet 11a. In this embodiment, the adhesive layer 11b is formed on both sides of the base steel sheet 11a, but the adhesive layer 11b may also be formed on only one surface of the base steel sheet 11a.

[0021] The base steel plate 11a has a chemical composition containing basic elements, optional elements as needed, and the balance being Fe and impurities. In this embodiment, the base steel plate 11a has a chemical composition containing, for example, in mass %, as basic elements, Si: 1.0 to 4.5%, Al: 0.1 to 1.5%, and Mn: 0.2 to 4.0%.

[0022] The adhesive layer 11b is formed so as to cover the entire surface of the base steel plate 11a. A thermosetting resin is used as the adhesive layer 11b. In this embodiment, the adhesive layer 11b has insulating properties in addition to adhesive properties. In this embodiment, the adhesive layer 11b is, for example, an insulating coating containing an epoxy resin and an epoxy resin curing agent.

[0023] The epoxy resin may be, for example, an epoxy resin having two or more epoxy groups per molecule. Examples of such epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, alicyclic epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, hydantoin epoxy resins, isocyanurate epoxy resins, acrylic acid-modified epoxy resins (epoxy acrylates), phosphorus-containing epoxy resins, and their halides (e.g., brominated epoxy resins) or hydrogenated versions. The epoxy resins may be used alone or in combination.

[0024] Examples of epoxy resin curing agents include aromatic polyamines, acid anhydrides, phenolic curing agents, dicyandiamide, boron trifluoride-amine complexes, and organic acid hydrazides. Examples of aromatic polyamines include metaphenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone. Examples of phenolic curing agents include phenol novolac resins, cresol novolac resins, bisphenol novolac resins, triazine-modified phenol novolac resins, and phenol resole resins. Phenol-based curing agents are preferred, and phenol resole resins are more preferred. One type of epoxy resin curing agent may be used alone, or two or more types may be used in combination.

[0025] Although detailed description is omitted, another insulating coating may be formed between the base steel sheet 11a and the adhesive layer 11b. Examples of materials that can be used to form the insulating coating include (1) inorganic compounds, (2) organic resins, and (3) mixtures of inorganic compounds and organic resins. Examples of inorganic compounds include (1) composites of dichromate and boric acid, (2) composites of phosphate and colloidal silica, (3) phosphates, (4) Zr compounds, and (5) Ti compounds. Examples of organic resins include epoxy resins, acrylic resins, acrylic-styrene resins, polyester resins, silicone resins, and fluororesins.

[0026] (Configuration of the manufacturing apparatus) Next, the manufacturing apparatus 100 will be described in detail. As shown in Figure 1, the manufacturing apparatus 100 according to this embodiment includes a base section 10, a punch 12, a punching die 14, a first holding section 16, a second holding section 18, and a heating section 20. Although not shown, in the manufacturing apparatus 100, a predetermined punching process (such as forming a slot) is also performed on the steel strip 1 by another punch and die upstream of the punch 12 and punching die 14 in the conveying direction of the steel strip 1.

[0027] The punch 12 is arranged above the base portion 10 and is movable back and forth in the vertical direction. The punching die 14 is arranged below the punch 12. The punching die 14 has a cylindrical shape corresponding to the outer shape of the laminated core 2. In this embodiment, the opening edge 14a on the upper end side of the punching die 14 functions as a cutting blade. In this embodiment, the opening edge 14a has a circular shape. In this embodiment, the punch 12 and the punching die 14 repeatedly perform outer shape punching processing on the steel strip 1 being transported in a predetermined direction, and multiple core sheets 1a are punched out of the steel strip 1.

[0028] 1, an imaginary line A extending in the vertical direction through the center of the opening edge 14a of the punching die 14 is shown by a dashed line. In the following, the radial direction means a direction perpendicular to the imaginary line A. In addition, in the following, the circumferential direction means the circumferential direction of an imaginary circle centered at the center of the opening edge 14a when viewed from above.

[0029] The first holding portion 16 is disposed below the punching die 14. In this embodiment, the first holding portion 16 is fixed to the base portion 10 using an attachment member (not shown). In this embodiment, the first holding portion 16 includes a plurality of holding members 16a and a plurality of pressing devices 16b.

[0030] The plurality of holding members 16a are arranged in a line in the circumferential direction. Each holding member 16a is provided so as to be movable in the radial direction. A pressing device 16b is provided for each holding member 16a. The pressing device 16b is a device that moves the holding members 16a in the radial direction. In this embodiment, the pressing device 16b includes, for example, a hydraulic device, and moves the pressing device 16b in the radial direction by hydraulic pressure.

[0031] The first holding unit 16 may be configured to apply pressure from the side (radially outward) to the multiple core sheets 1a punched by the punch 12 and the punching die 14. Therefore, for example, one of the multiple holding members 16a may be fixed so as not to move in the radial direction. In this case, the pressing device 16b does not need to be connected to the fixed holding member 16a. The configuration of the first holding unit is not limited to the above example, and the first holding unit can be configured using various known squeeze ring configurations.

[0032] The second retaining portion 18 is disposed below the first retaining portion 16. The second retaining portion 18 is formed of a separate member from the first retaining portion 16. In this embodiment, the second retaining portion 18 is provided coaxially with the first retaining portion 16. In this embodiment, the second retaining portion 18 has a plurality of retaining members 18a that are provided to be movable in the radial direction. Although not shown, a biasing device is provided for each retaining member 18a. In this embodiment, the biasing device includes, for example, an elastic member such as a spring, and biases the retaining members 18a radially inward (toward the imaginary line A). Note that the configuration of the second retaining portion is not limited to the above example, and the second retaining portion can be configured using the configuration of various known squeeze rings.

[0033] The heating unit 20 is disposed below the first holding unit 16 and around the second holding unit 18. In this embodiment, the heating unit 20 includes a plurality of heating devices 20a. For example, an infrared heating device is used as the heating device 20a. In this embodiment, a heating device 20a is provided for each holding member 18a. The configuration of the heating unit 20 is not limited to the above example, and various heating devices capable of heating the second holding unit 18 (holding member 18a) or the core sheet 1a held by the second holding unit 18 can be used as the heating unit. For example, a high-frequency induction heating device arranged to surround the second holding unit 18 may be used as the heating unit.

[0034] (Manufacturing Method of Laminated Core) Next, a description will be given of a manufacturing method of the laminated core 2 using the above-described manufacturing apparatus 100. In this embodiment, a steel strip 1 is fed in a predetermined direction from a coil (hoop material) (not shown) by a feed mechanism (roller, etc.) (not shown), while a plurality of core sheets 1a are punched out of the steel strip 1 by a punch 12 and a punching die 14 (opening edge 14a).

[0035] As shown in Figure 3, the punched core sheets 1a are stacked in order inside the punching die 14. Note that although the outer periphery of the core sheet 1a punched from the steel strip 1 comes into contact with the inner peripheral surface of the punching die 14, in this embodiment, the punching die 14 does not apply a large amount of pressure to the core sheet 1a. Therefore, the core sheet 1a punched from the steel strip 1 by the punch 12 and the punching die 14 (opening edge 14a) moves downward inside the punching die 14 without being held by the inner peripheral surface of the punching die 14.

[0036] 4, as more core sheets 1a are punched out from the steel strip 1, a plurality of core sheets 1a are successively pushed into the first holding section 16. In this embodiment, each time a new core sheet 1a is punched out by the punch 12 and the punching die 14, one core sheet 1a is pushed from the punching die 14 into the first holding section 16.

[0037] As described above, the first holding portion 16 is configured to be able to apply pressure to the core sheets 1a from the sides (radially outward). In this embodiment, the multiple core sheets 1a are maintained in a state where they are pressed from the sides within the first holding portion 16. Therefore, the pressure generated between vertically adjacent core sheets 1a when the punch 12 presses the multiple core sheets 1a downward can be maintained within the first holding portion 16. As a result, the multiple core sheets 1a are pressed in the vertical direction, and vertically adjacent base steel plates 11a within the first holding portion 16 are pressure-bonded via the adhesive layer 11b. In this embodiment, a pressure greater than the pressure generated between vertically adjacent core sheets 1a due to the weight of the multiple core sheets 1a itself can be generated and maintained between vertically adjacent core sheets 1a within the first holding portion 16. Vertically adjacent core sheets 1a pressed in the first holding unit 16 are fixed together with a weaker adhesive force than the core sheets 1a after being heated and pressed in the second holding unit 18 (described later). In other words, vertically adjacent core sheets 1a are bonded (temporarily bonded) together in the first holding unit 16. The pressure applied by the punch 12 to the core sheets 1a is preferably set to 2.0 MPa or less, and more preferably close to the pressure required to punch the core sheets 1a (punching pressure: e.g., approximately 0.1 MPa). The pressure may be set to, for example, 1.8 MPa or less, or 1.0 MPa or less. It may also be set to 0.1 MPa or more. The pressure applied by the first holding unit 16 (in this embodiment, the holding member 16a) to the outer periphery of the core sheet 1a is set to, for example, a magnitude sufficient to prevent the core sheet 1a from falling. In this embodiment, the pressure is set so that the static friction force generated between the core sheet 1a and the first holding portion 16 is greater than the weight of the core sheet 1a.

[0038] As described above, no large pressure is applied to the core sheets 1a from the inner peripheral surface of the punching die 14. Therefore, even if pressure is generated between adjacent core sheets 1a in the vertical direction within the punching die 14 as a result of the punch 12 pressing the multiple core sheets 1a downward, this state is not maintained. Therefore, the multiple core sheets 1a are not pressure-bonded to each other within the punching die 14.

[0039] As described above, the core sheet 1a is provided with a thermosetting adhesive layer 11b. In this embodiment, the temperature of the first holding section 16 is adjusted so that the adhesive layer 11b does not soften, at least at the upper end of the first holding section 16. For example, the temperature of the first holding section 16 is adjusted so that the adhesive layer 11b between a pair of vertically adjacent base steel sheets 11a is prevented from softening before the pair of base steel sheets 11a are pressure-bonded to each other within the first holding section 16. More specifically, the first holding section 16 may hold the multiple core sheets 1a at a temperature below the softening temperature of the adhesive layer 11b. When the multiple core sheets 1a are held in the first holding section 16 at a temperature below the softening temperature of the adhesive layer 11b, the compressive residual stress generated in the resulting laminated core can be reduced and an increase in iron loss can be suppressed, even when the multiple core sheets 1a are simultaneously pressurized and heated. The holding temperature of the multiple core sheets 1a in the first holding unit 16 can be, for example, 10°C or more lower than the softening temperature of the adhesive layer 11b, or may be 30°C or more lower than the softening temperature of the adhesive layer 11b. The lower limit of the holding temperature in the first holding unit 16 is not particularly limited, but may be, for example, 0°C or higher, or about room temperature (20°C) or higher, or 40°C or higher. The holding temperature of the multiple core sheets 1a in the first holding unit 16 (the temperature of the adhesive layer 11b) can be measured by embedding a thermocouple thermometer or a radiation thermometer in the first holding unit 16. In this embodiment, based on the holding temperature (the temperature of the adhesive layer 11b) measured as described above, the output of the heating unit 20 is controlled so that the temperature of the core sheets 1a (adhesive layer 11b) in the first holding unit 16 is kept below the softening temperature. In addition, the vertical length of the first holding unit 16 may be adjusted, or a heat insulating section may be provided at the boundary between the first holding unit 16 and the second holding unit 18. Furthermore, a heating test of the heating unit 20 may be performed in advance to simulate the temperature rise behavior of the adhesive layer 11b due to heating by the heating unit 20. Then, the output of the heating unit 20 may be controlled based on the temperature rise behavior of the adhesive layer 11b obtained by the simulation.Although the temperature within the first holding section 16 may rise due to the influence of the temperature within the second holding section connected to the first holding section 16, the above-described method can control the temperature within the first holding section 16 to be below the softening temperature of the adhesive layer 11b. In this embodiment, the holding temperature within the first holding section 16 is only required to be below the softening temperature of the adhesive layer 11b. The effects of this embodiment are not affected by the presence or absence of a heating section within the first holding section 16 or the intentional heating of the core sheet 1a. On the other hand, from the perspective of further reducing the compressive residual stress generated in the core sheet 1a, it is preferable that the first holding section 16 suppresses heating of multiple core sheets 1a. For example, to simplify the device and further reduce the compressive residual stress generated in the core sheet 1a, it is preferable not to provide a heating section 20 within the first holding section 16. For this reason, in this embodiment, the heating section 20 is positioned below the lower end of the first holding section 16.

[0040] In order to prevent the temperature of the upper end of the first holding portion 16 from rising due to heating by the heating unit 20, the vertical length of the first holding portion 16 (more specifically, the length of the portion that contacts the core sheet 1a; in this embodiment, the length of the holding member 16a) is preferably 5 mm or more, and more preferably 10 mm or more. In this case, the core sheets 1a can be more appropriately pressed together in the first holding portion 16 before the adhesive layer 11b softens. There is no particular limit to the upper limit of the vertical length of the first holding portion 16, but it may be, for example, 160 mm or less, or may be 20 mm or less.

[0041] 5, as more core sheets 1a are punched out from the steel strip 1, the multiple core sheets 1a are sequentially pushed into the second holding section 18. In this embodiment, each time a new core sheet 1a is punched out by the punch 12 and the punching die 14, one core sheet 1a is pushed from the first holding section 16 into the second holding section 18.

[0042] The core sheet 1a pressed into the second holding section 18 is held from the side (radially outward) by the second holding section 18 (plurality of holding members 18a), heated by the heating section 20, and pressed by the punch 12. In this embodiment, the heating section 20 heats the core sheets 1a, softening and hardening the adhesive layer 11b of each core sheet 1a within the second holding section 18. This fixes the core sheets 1a to one another within the second holding section 18. The core sheets 1a are pressed into the second holding section 18 one by one from the bottom and heated in order of their insertion into the second holding section 18. Therefore, the stacked core sheets 1a are heated sequentially from the bottom to the top, gradually heating from the bottom. In this embodiment, the heating section 20 heats the second holding section 18 so that the temperature of the adhesive layer 11b within the second holding section 18 rises to a temperature above the softening temperature. In this embodiment, the lateral pressure applied from the second holding portion 18 to the laminated core 2 is set to a magnitude sufficient to prevent the laminated core 2 from falling. In this embodiment, the pressure is set so that the static friction force generated between the laminated core 2 and the second holding portion 18 is greater than the weight of the laminated core 2. The heating temperature in the second holding portion 18 may be equal to or higher than the softening temperature of the adhesive layer 11b. For example, the heating temperature may be 10°C or higher than the softening temperature of the adhesive layer 11b, or 40°C or higher than the softening temperature of the adhesive layer 11b. The upper limit of the heating temperature in the second holding portion 18 is not particularly limited, but may be, for example, 200°C or lower. In addition, when the adhesive forming the adhesive layer 11b is a thermosetting resin, the heating unit 20 heats the multiple core sheets 1a held by the second holding portion 18 to a temperature equal to or higher than the hardening temperature of the adhesive layer 11b.

[0043] When an infrared heating device is used as the heating unit 20, the temperature of each core sheet 1a can be gradually increased from the outer periphery toward the center. This allows the adhesive layer 11b of each core sheet 1a to be gradually hardened from the outer periphery toward the center. In this case, it is possible to prevent the adhesive from leaking out from between adjacent base steel plates 11a in the second holding unit 18. From this perspective, it is preferable to use an infrared heating device as the heating unit 20. In this embodiment, for example, an infrared heating device that emits near-infrared rays with a wavelength of 750 to 1000 nm is used.

[0044] Finally, as shown in FIG. 1 , the multiple core sheets 1a fixed together within the second holding unit 18 are ejected from the second holding unit 18 as the laminated core 2. In this manner, the laminated core 2 is manufactured. In this embodiment, the thickness of the core sheets 1a (steel strips 1) is, for example, 0.1 mm to 0.5 mm, and the mass of the laminated core 2 is, for example, 0.1 kg to 6.0 kg. When manufacturing a larger laminated core 2, for example, a laminated core 2 with a mass exceeding 6.0 kg, it may be difficult to hold the laminated core 2 with only the force of the biasing device provided in the second holding unit 18. In such cases, it is preferable to support the laminated core 2 from below using a support device 26, as shown in FIG. 8 (described later).

[0045] Effect of this embodiment In the manufacturing apparatus 100 according to this embodiment, when the heating unit 20 heats the multiple core sheets 1a held in the second holding unit 18, the second holding unit 18 is also heated. The first holding unit 16 is provided above the second holding unit 18, and heat is transferred from the second holding unit 18 to the first holding unit 16, causing the temperature of the first holding unit 16 to also rise.

[0046] However, in the manufacturing apparatus 100 according to this embodiment, the first holding unit 16 and the second holding unit 18 are configured as separate members, which can suppress heat transfer from the second holding unit 18 to the first holding unit 16. This sufficiently prevents the first holding unit 16 (holding member 16a) from reaching or exceeding the softening temperature of the adhesive layer 11b. In other words, it is possible to prevent the adhesive layer 11b from softening before adjacent core sheets 1a in the vertical direction within the first holding unit 16 are pressed against each other. As a result, it is possible to reduce the compressive residual stress that occurs in the core sheets 1a due to the pressurization and heating of multiple core sheets 1a.

[0047] Here, as a result of detailed investigations, the inventors have found that when heating and pressurizing of multiple core sheets 1a at a temperature equal to or higher than the softening temperature of the adhesive layer 11b are started simultaneously, compressive residual stress (radially inward residual stress) is generated in the core sheets 1a. Specifically, when heating and pressurizing of the core sheets 1a are started simultaneously, softening of the adhesive layer 11b between a pair of vertically adjacent core sheets 1a progresses before the pair of core sheets 1a is pressed. In this case, compressive residual stress is likely to be generated in the base steel plate 11a due to the difference in thermal expansion between the adhesive layer 11b and the base steel plate 11a above or below it, and the contraction of the adhesive layer 11b.

[0048] On the other hand, it has been found that compressive residual stresses generated in the core sheets 1a due to pressure and heating can be reduced by first pressing adjacent core sheets 1a together while maintaining them at a temperature below the softening temperature of the adhesive layer 11b, and then heating and pressing the adjacent core sheets 1a together at a temperature above the softening temperature of the adhesive layer 11b. Furthermore, when multiple core sheets 1a pressed vertically are heated sequentially, starting from the bottom core sheet 1a, the adhesive layer 11b and the base steel sheets 11a above and below it expand and contract in a mutually conforming manner. In this case, compressive residual stresses in the base steel sheets 11a are further suppressed. Therefore, in the manufacturing apparatus 100 according to this embodiment, the first holding unit 16 and the second holding unit 18 are configured as separate members, as described above, to suppress heat transfer from the second holding unit 18 to the first holding unit 16 and thereby suppress temperature rise in the first holding unit 16. Furthermore, in the second holding unit 18, the core sheets 1a are heated and pressurized at a temperature equal to or higher than the softening temperature of the adhesive layer 11b, thereby bonding and fixing the core sheets 1a together. This prevents the adhesive layer 11b from softening before vertically adjacent core sheets 1a are pressed together in the first holding unit 16. As a result, the generation of compressive residual stress in each base steel sheet 11a in the first holding unit 16 can be suppressed, thereby reducing iron loss in the laminated core 2. Furthermore, in the manufacturing apparatus 100 according to this embodiment, the punching die 14, the first holding unit 16, and the second holding unit 18 are arranged successively in the vertical direction. In this configuration, the core sheets 1a pressed downward by the punch 12 are heated one by one from the bottom in the second holding unit 18 to a temperature equal to or higher than the softening temperature of the adhesive layer 11b. In the second holding portion 18, the multiple core sheets 1a are gradually heated from the bottom side to a temperature above the softening temperature of the adhesive layer 11b, thereby reducing the compressive residual stress generated in each base steel plate 11a and further reducing the iron loss of the laminated core 2.

[0049] Typically, to obtain a laminated core with an appropriate shape, it is necessary to apply a large pressure exceeding 2.0 MPa from the punch to the multiple core sheets to cure the adhesive layer. However, in this case, the frictional force between the adhesive layer and the base steel sheet increases, generating compressive residual stress in the base steel sheet, thereby increasing iron loss. In contrast, in this embodiment, the multiple core sheets 1a are heated while the outer peripheries of the multiple core sheets 1a are laterally held (pressurized in this embodiment) by the second holding unit 18. This allows the adhesive layer 11b between the multiple core sheets 1a (base steel sheets 11a) to cure without applying large pressure to the multiple core sheets 1a in the stacking direction. This prevents the frictional force between the adhesive layer 11b and the base steel sheet 11a from increasing, and sufficiently suppresses the generation of compressive residual stress in the base steel sheet 11a. As a result, even when the pressure applied by the punch 12 to the multiple core sheets 1a is low, at 2.0 MPa or less, the multiple core sheets 1a can be properly bonded to obtain a laminated core 2 with an appropriate shape.

[0050] (Modification) In the above-described embodiment, the first retaining portion 16 and the second retaining portion 18 are provided independently of each other. However, as shown in FIG. 6 , the first retaining portion 16 and the second retaining portion 18 may be connected to each other by a plurality of connecting portions 22. In this case, the first retaining portion 16 and the second retaining portion 18 can be interlocked, thereby simplifying the configuration of the first retaining portion 16 and the second retaining portion 18 (the configuration for pressing the retaining members 16 a and 18 a). Note that the connecting portions 22 may be recessed and protruding portions formed on the retaining members 16 a and 18 a. In this case, the retaining members 16 a and 18 a can be fixed together by, for example, crimping the recessed and protruding portions. The connecting portions 22 may also be fastening members such as bolts and nuts.

[0051] In the above-described embodiment, the second holding portion 18 is disposed directly below the first holding portion 16, but the first holding portion 16 and the second holding portion 18 may be connected via a heat insulating member 24 having a lower thermal conductivity than the holding member 18a (the portion of the second holding portion 18 that contacts the core sheet 1a). In this case, heat transfer from the second holding portion 18 to the first holding portion 16 can be sufficiently suppressed, and a temperature rise in the first holding portion 16 can be sufficiently prevented. In this embodiment, the heat insulating member 24 forms a connecting portion that connects the first holding portion 16 and the second holding portion 18.

[0052] In the above-described embodiment, the plurality of core sheets 1a are supported by applying pressure to the plurality of core sheets 1a from the sides in the first holding section 16 and the second holding section 18. However, as shown in Fig. 8, the plurality of core sheets 1a may be further supported from below by a support device 26. This allows the plurality of core sheets 1a to be supported more stably. The support device 26 is a device that supports the plurality of core sheets 1a from below by, for example, hydraulic pressure or the elastic force of an elastic member such as a spring.

[0053] According to the present invention, a laminated core with low iron loss can be manufactured.

[0054] REFERENCE SIGNS LIST 1 steel strip 2 laminated core 10 base portion 12 punch 14 punching die 16 first holding portion 18 second holding portion 20 heating portion 22 connecting portion 24 heat insulating member 26 supporting device

Claims

1. An apparatus for manufacturing a laminated core by punching out a plurality of core sheets from a steel strip having an adhesive layer on its surface and bonding the obtained plurality of core sheets to each other, comprising: punch, A punching die disposed below the punch; A first holding portion disposed below the punching die; A second holding portion disposed below the first holding portion and configured as a separate member from the first holding portion; and a heating section disposed around the second holding section below the first holding section; Equipped with punching a plurality of core sheets from the steel strip with the punch and the punching die; The punch presses the outer periphery of the punched core sheets from the side by the first holding part, while pressing the core sheets downward by the punch; A laminated core manufacturing apparatus, wherein the plurality of core sheets pressed downward by the punch are held in the second holding section and heated by the heating section.

2. The manufacturing apparatus according to claim 1 , wherein the adhesive layer is a thermosetting adhesive layer.

3. The manufacturing apparatus according to claim 1 , wherein the first holding unit and the second holding unit are connected via a connecting unit.

4. The manufacturing apparatus according to claim 1 or 2, wherein the first holding portion has a vertical length of 5 mm or more.

5. The manufacturing apparatus according to claim 1 , wherein the heating unit includes an infrared heating device.

6. A manufacturing apparatus including a punch, a punching die disposed below the punch, a first holding section disposed below the punching die, a second holding section disposed below the first holding section and made of a separate member from the first holding section, and a heating section disposed below the first holding section and around the second holding section, punching a plurality of core sheets from a steel strip having an adhesive layer on a surface thereof by the punch and the punching die; The punch presses the outer periphery of the punched core sheets from the side by the first holding part, while pressing the core sheets downward by the punch; A method for manufacturing a laminated core, comprising: heating the plurality of core sheets pressed downward by the punch by the heating section while holding them in the second holding section.

7. The manufacturing method according to claim 6 , wherein the adhesive layer is a thermosetting adhesive layer.

8. The manufacturing method according to claim 6 or 7, wherein the first holding portion and the second holding portion are connected via a connecting portion.

9. The manufacturing method according to claim 6 or 7, wherein the first holding portion has a vertical length of 5 mm or more.

10. The method according to claim 6 or 7, wherein the punch presses the core sheets with a pressure of 2.0 MPa or less.

11. The manufacturing method according to claim 6 or 7, wherein the heating unit includes an infrared heating device.