Motor core and manufacturing method thereof

Abstract

The present invention relates to a motor core, and more particularly to a core with low iron loss and excellent flatness and squareness, and a manufacturing method thereof. According to one embodiment of the present invention, a method for manufacturing a block laminated core includes: a block core step of stacking and bonding magnetic steel sheets in a first direction to form a block core of a first length; a stacking step of rotating a plurality of the block cores in a second direction, i.e., a circumferential direction, by a first angle and stacking them to a second length in the first direction; and a welding step of welding two consecutive block cores among the plurality of block cores in the first direction at a third length that is less than twice the first length to form welds, wherein in the welding step, a plurality of imaginary lines extending in the first direction from portions of the welds formed on any one of the plurality of block cores are spaced apart by a predetermined distance, and the block laminated core manufactured in this manner includes the block laminated core.

Description

[Technical Field]

[0001] The present invention relates to a motor core, and to a core that generates low iron loss and has excellent flatness and squareness, and a manufacturing method thereof. [Background technology]

[0002] The need for energy conservation initiatives has become a major focus due to the imposition of carbon taxes worldwide. Eco-friendly policies have emphasized high efficiency in electrical equipment such as motors and generators, and efficiency regulations that began in Europe have led to legislation worldwide.

[0003] Electrical equipment such as motors consists of a stator and a rotor. Both the stator and rotor require excellent magnetic properties, and the rotor additionally requires high strength to withstand high-speed rotation. The core is made by stacking non-oriented electromagnetic steel sheets, which allow the magnetic field to flow well in all directions, into a single block in the stator and rotor.

[0004] The stator is made by laminating multiple electromagnetic steel sheets and then fastening them in various ways to secure the sheet-shaped electromagnetic steel sheets. After that, conductor windings are inserted into the core slots to supply electricity. The rotor is made by laminating multiple electromagnetic steel sheets and fixing them in place. A permanent magnet can be inserted into the rotor core, and a magnetic source can be provided by winding or die-casting conductor windings. However, it can also be made up of just the core itself without using any magnetic source.

[0005] Research into manufacturing electrical steel sheets with excellent magnetic properties to improve the efficiency of electrical equipment (Korean Patent Registration No. 10-2438474, Korean Patent Registration No. 10-2448799) has been widely reported. Despite advances in materials technology, the efficiency of electrical equipment remains difficult to achieve at the level required by the market. This is partly because material development is extremely difficult and many challenges remain to be overcome, and partly because the process of processing materials into core components can result in properties that are inferior to the raw materials. This is also because efficiency varies depending on the core structure and the method of assembling the equipment.

[0006] The main methods for stacking and fixing cores have been interlocking and welding (Korean Patent No. 10-0584116), but recently, methods for bonding magnetic steel sheets together have also been proposed (Korean Patent No. 10-2382699, Korean Patent No. 10-0950339). While these recent bonding methods are theoretically very superior, they do not provide a uniform adhesive force on the core surface and do not maintain a strong adhesive force over time, resulting in a very high core manufacturing defect rate and limiting their application. As a result, in industries where manufacturing yield is important, interlocking and welding are almost always used in core manufacturing.

[0007] Figure 1 shows an existing core that has been interlocked as a whole. In Figure 1, the magnetic steel sheet 100 of the existing core 1 has an interlocking portion 200 at once. Interlocking is a method of fastening by applying mechanical pressure to a certain portion and deforming it.

[0008] Even when using high-quality magnetic steel sheets, interlocking fastenings degrade the performance of electrical equipment due to processing and assembly during the core manufacturing process, making it difficult to achieve high efficiency. Interlocking applies mechanical shock and forces the magnetic steel sheets to bend, significantly worsening magnetic properties. Because almost no magnetic field flows through the magnetic steel sheets near the interlocking, the magnetic field flow is distorted. The magnetic field that cannot flow due to the interlocking seeks out other paths with less magnetic resistance, causing a bottleneck. The distorted magnetic field alters the frequency, resulting in the synthesis of high frequencies into the basic waveform. The magnetic field concentrated by the bottleneck phenomenon increases the operating magnetic flux density. When frequencies are synthesized or the magnetic flux density is high, the iron loss generated in the magnetic steel sheets increases dramatically, resulting in increased core loss.

[0009] 2 shows a welded core 2. Conventionally, as shown in FIG. 2, the entire outer circumferential surface of the magnetic steel sheet 100 is welded 300 to join the core 2.

[0010] When magnetic steel sheets are placed in a magnetic field, eddy currents are induced within the sheets, resulting in eddy current loss. One way to reduce this loss is to manufacture the sheets thinner and apply a highly insulating coating to the top and bottom of the sheets to create electrical insulation between them. However, welding, which is used in fastening, has the side effect of destroying the insulation between the sheets when applied to the sides of the core, artificially creating an electrical circuit through which current flows. This results in a rapid increase in eddy current loss and a deterioration in the core's no-load loss. The number of welds increases the number of interlayer insulation breakdowns in the magnetic steel sheets, increasing the amount of induced eddy currents, and the no-load loss rapidly worsens due to the current flow between the layers.

[0011] Therefore, there is a need for a core and a method for manufacturing the core that can solve the above problems. Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been made to solve the above problems, and has as its object to provide a core having excellent squareness and flatness and low iron loss. [Means for solving the problem]

[0013] In order to achieve the above object, the present invention provides a motor core formed as follows and a method for manufacturing the same.

[0014] A method for manufacturing a block laminated core according to an embodiment of the present invention includes: a block core forming step of stacking and bonding magnetic steel sheets in a first direction to form a block core of a first length; a stacking step of rotating a plurality of the block cores in a second direction, which is a circumferential direction of the block cores, by a first angle and stacking the plurality of block cores to a second length in the first direction; and a welding step of welding outer surfaces of two consecutive block cores among the plurality of block cores in the first direction at a third length that is shorter than twice the first length to form welds, wherein a plurality of the welds are formed and any two adjacent welds among the plurality of welds are spaced apart by a predetermined distance, thereby providing a core having excellent squareness and flatness, low iron loss, and low no-load loss.

[0015] In the block core step, the magnetic steel sheets may be interlockingly bonded.

[0016] In addition, the second length is an n-th multiple of the first length, and the first angle may comply with the following mathematical formula 1. Mathematical formula 1: θ1=360° / n Here, θ1 is the first angle (°) and n is a natural number.

[0017] The second length may be three to eight times the first length.

[0018] In the welding step, a plurality of the welded portions may be formed at the same position in the first direction and spaced apart from each other in the second direction.

[0019] The method may further include a heat treatment step, prior to the laminating step, in which heat treatment is performed to remove residual stress in the block core.

[0020] A block laminated core according to one embodiment of the present invention includes a block core in which magnetic steel sheets are stacked to a first length in a first direction and includes an interlocking joint; a block laminate in which a plurality of the block cores are stacked to a second length in the first direction; and a weld formed on an outer surface of the block laminate in the first direction with a third length that is less than twice the first length to connect two adjacent block cores among the plurality of block cores included in the block laminate. This allows for the provision of a core with excellent squareness and flatness, low iron loss, and low no-load loss.

[0021] In addition, a plurality of virtual first extension lines are formed connecting punched lines formed on the electromagnetic steel sheets forming the block cores to the centers of the block cores, and the first extension lines are formed at the same position in a second direction, which is a radial direction, within one block core, and an angle between the first extension lines formed on any two block cores arranged adjacent to each other in the first direction among the plurality of block cores may form a first angle.

[0022] The second length may be three to eight times the first length.

[0023] Furthermore, a plurality of the above-mentioned welds may be formed to join the same two block cores among the plurality of block cores, and a second angle, which is the smallest angle among the angles formed by the plurality of welds joining the same two block cores and any two of the third extension lines, which are extension lines connecting the centers of the block cores, may be 10 to 180 degrees.

[0024] The electrical steel sheet may be a non-oriented electrical steel sheet containing, by weight, Si: 0.25 to 4.8%, Al: 0.05 to 2.0%, Mn: 0.15 to 1.0%, C: 0.0015 to 0.0040%, N: 0.0005 to 0.0030%, S: 0.0005 to 0.003%, Mo: 0.0050 to 0.015%, Ti: 0.0005 to 0.0020%, Nb: 0.0005 to 0.0040%, V: 0.0005 to 0.0040%, the balance being Fe and unavoidable impurities. [Effects of the Invention]

[0025] With the above-described configuration, the present invention can provide a core that has excellent squareness and flatness, as well as low iron loss and no-load loss. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 10 is a perspective view showing a conventional core. [Figure 2] FIG. 10 is a perspective view showing yet another conventional core. [Figure 3] 1 is a flowchart illustrating a method for manufacturing a block laminated core according to an embodiment of the present invention. [Figure 4] 1 is a diagram showing a block core according to an embodiment of the present invention. [Figure 5] 3 is a view illustrating a lamination step in a manufacturing method of a block laminated core according to an embodiment of the present invention; [Figure 6] This is a diagram to explain the first angle of the stacking step in a manufacturing method of a block laminated core according to one embodiment of the present invention, and shows a first extension line connecting the punching line of the block cores stacked on one plane and the core center. [Figure 7] 1 is a schematic view of a block laminated core manufactured by a method for manufacturing a block laminated core according to an embodiment of the present invention, and is a view for explaining a welding step in the method for manufacturing a block laminated core. [Figure 8] 10 is a diagram illustrating a second angle in a block laminated core according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. However, the concept of the present invention is not limited to the examples shown, and a person skilled in the art who understands the concept of the present invention may easily propose other degenerate inventions or other embodiments within the concept of the present invention by adding, changing, or deleting other components within the same concept, which are also included within the concept of the present invention.

[0028] The core according to one embodiment of the present invention is formed using an electromagnetic steel sheet.

[0029] Typically, electrical steel sheets are provided in the form of rolls called mother coils with widths of 980 to 1200 mm. It is extremely difficult to precisely control the thickness of electrical steel sheets during the rolling process. Mother coils are typically thickest near the center and become thinner toward the edges. This thickness variation can reach within 5 to 10% of the total thickness. This can cause shape problems when forming cores. Because the core diameter ranges from tens to hundreds of mm, the mother coils provided by steel companies undergo a slitting process, where the entire width is custom-processed to within hundreds of mm to match the core diameter. After the slitting process, multiple electrical steel sheets are stacked together using a punching process to manufacture the core. During the punching process, punching lines are formed, allowing the punching position to be identified.

[0030] Generally, the thickness variations in cores cause problems, but in particular, in the case of drive motors in which the core diameter reaches several hundred mm and the stack height of the electromagnetic steel sheets exceeds 100 mm, it is extremely important to ensure the squareness and flatness of the core due to the thickness variations of the electromagnetic steel sheets depending on the position of the mother coil. An object of the present invention is to solve the above-mentioned problems by manufacturing cores using such general electromagnetic steel sheets.

[0031] The above-mentioned electrical steel sheet of the core according to one embodiment of the present invention may be a non-oriented electrical steel sheet containing, by weight, Si: 0.25 to 4.8%, Al: 0.05 to 2.0%, Mn: 0.15 to 1.0%, C: 0.0015 to 0.0040%, N: 0.0005 to 0.0030%, S: 0.0005 to 0.003%, Mo: 0.0050 to 0.015%, Ti: 0.0005 to 0.0020%, Nb: 0.0005 to 0.0040%, V: 0.0005 to 0.0040%, the balance being Fe and unavoidable impurities, but is not limited thereto and may be formed as an electrical steel sheet of other components.

[0032] Si: 0.25 to 4.8% Silicon (Si) increases the resistivity of the material, reducing iron loss, and increases strength through solid solution strengthening. If too little silicon is added, the effects of improving iron loss and strength may be insufficient. If too much silicon is added, the brittleness of the material increases, rolling productivity drops sharply, and problems may occur due to the formation of an oxide layer and oxides on the surface that are harmful to magnetic properties. Therefore, the silicon content can be 0.25 to 4.8%, and more preferably 3.2 to 3.6%.

[0033] Al: 0.05 to 2.0% Aluminum (Al) increases the resistivity of the material, reducing iron loss, and enhances strength through solid solution strengthening. If too little aluminum is added, fine nitrides are formed, or the oxide layer on the surface is not dense enough, making it difficult to achieve the desired magnetic improvement effect. If too much aluminum is added, excessive nitrides are formed, degrading magnetic properties and causing problems in all processes, including steelmaking and continuous casting, resulting in significant productivity declines. Therefore, the aluminum content can be 0.05 to 2.0%, more preferably 0.6 to 1.0%.

[0034] Mn: 0.15 to 1.0% Manganese (Mn) increases the resistivity of the material, improving iron loss, and plays a role in forming sulfides. If too little manganese is added, fine MnS is formed, causing magnetic deterioration. If too much manganese is added, fine MnS precipitates excessively, promoting the formation of a {111} texture that is unfavorable to magnetic properties, resulting in a rapid decrease in magnetic flux density. Therefore, manganese can be contained in an amount of 0.15 to 1.0%, and more preferably 0.30 to 0.75%.

[0035] C: 0.0015 to 0.0040% Carbon (C) causes magnetic aging and combines with other impurity elements to form carbides, which reduces magnetic properties, but it also plays a role in improving strength by preventing potential transfer. If too little carbon is added, the strength improvement effect may be insufficient. If too much carbon is added, the amount of fine carbides may increase, which may rapidly deteriorate magnetic properties. Therefore, the carbon content may be 0.0015 to 0.0040%, and more preferably 0.0020 to 0.0038%.

[0036] N: 0.0005 to 0.0030% Nitrogen (N) not only forms fine AlN precipitates inside the base material, but also combines with other impurities to form fine precipitates, which inhibit grain growth and worsen iron loss, but also improve strength. If too little nitrogen is added, strength may not be sufficiently improved. If too much nitrogen is added, fine nitrides may increase, causing a rapid deterioration in iron loss. Therefore, the nitrogen content can be 0.0005 to 0.0030%, and more preferably 0.0008 to 0.0018%.

[0037] S: 0.0005 to 0.003% Sulfur (S) forms fine precipitates of MnS and CuS, which deteriorate magnetic properties and hot workability, so it is preferable to keep the content low. However, adding a very small amount of sulfur may reduce magnetic flux density. Therefore, sulfur may be contained in an amount of 0.0005 to 0.003%, and more preferably 0.0010 to 0.0025%.

[0038] Mo: 0.0050 to 0.015% Molybdenum (Mo) segregates to grain boundaries during annealing, suppressing the development of {111} texture, which is detrimental to magnetic properties, and forms fine carbides during cooling, improving strength. If too little molybdenum is added, the effect may be insufficient. If too much molybdenum is added, it may promote carbide formation, deteriorating magnetic properties. Therefore, the molybdenum content can be 0.0050 to 0.015%, and more preferably 0.0060 to 0.0090%.

[0039] Ti:0.0005~0.0020%, Nb:0.0005~0.0040%, V:0.0005~0.0040% Titanium (Ti), niobium (Nb), and vanadium (V) have a strong tendency to form precipitates in steel. These elements form fine carbides, nitrides, or sulfides within the base material, inhibiting grain growth and domain wall motion, thereby degrading iron loss. Therefore, the upper limits of titanium, niobium, and vanadium must be appropriately adjusted. On the other hand, excessively low contents of these elements can significantly reduce the strength of the electrical steel sheet. Therefore, titanium, niobium, and vanadium can each be contained in an amount of 0.0005 to 0.0020%. More preferably, each can be contained in an amount of 0.0007 to 0.0018%.

[0040] The electrical steel sheet may contain the residual iron (Fe) and unavoidable impurities.

[0041] The commonly used non-oriented electrical steel sheet has a density of 7.51 g / cm 3The thickness may be 0.1 to 0.65 mm, but there is no limitation to the thickness and density.

[0042] The block laminated core and the method for manufacturing the block laminated core will be described below on the assumption that the block laminated core is formed from the above-mentioned electromagnetic steel sheets, but the block laminated core may also be formed from electromagnetic steel sheets having other components and characteristics.

[0043] FIG. 3 shows a flow chart of a method for manufacturing a block laminated core according to one embodiment of the present invention.

[0044] A method for manufacturing a block laminated core according to an embodiment of the present invention includes a block core step (S10), a lamination step (S30), and a welding step (S40), and may further include a heat treatment step (S20).

[0045] The block core step (S10) is a step of manufacturing a block core 10 (see FIG. 4) by stacking and interlocking magnetic steel sheets.

[0046] The stacking step (S30) is a step in which the block cores 10 are stacked to form a block stack 15 (see FIG. 5).

[0047] The welding step (S40) is a step of welding and connecting the plurality of block cores 10 along the outer periphery of the block stack 15 so that the stacked state in the stacking step (S30) is maintained.

[0048] According to an embodiment of the present invention, the method may further include a heat treatment step (S20) of performing heat treatment to remove residual stress of the block core before the lamination step (S30).

[0049] The heat treatment step (S20) may be a heat treatment step such as atmospheric heat treatment and high frequency heat treatment, and the specific method is not limited.

[0050] The core must be heated to a maximum temperature between 750℃ and 880℃, which is sufficient to remove residual stress generated during the punching process of the electrical steel sheet, and maintained at that temperature for a certain period of time. A reducing atmosphere is suitable, but the maximum temperature maintenance time may vary depending on the heat treatment method.

[0051] For example, in the heat treatment step (S20), a reducing atmosphere must be maintained by continuously supplying nitrogen or vacuum to a sealed heat treatment facility. Because heat treatment of a welded core can deform the weld and distort the core shape, it is advantageous to perform it before the welding step (S40). It can also be performed after the block core step (S10), i.e., on an interlocked block core. Heat treatment at an appropriate temperature is important because stress relief is not possible if the heat treatment temperature is low or the maximum temperature is maintained for a short time. However, if the temperature is too high or the maximum temperature is maintained for a long time, cracks may form in the coating layer on the surface of the electrical steel sheet, resulting in insulation degradation. The appropriate temperature may vary depending on the interlocking connection and the material and shape of the electrical steel sheet, and is therefore not limited to a specific temperature. By including the heat treatment step (S20) according to an embodiment of the present invention, a better core with reduced no-load loss can be manufactured.

[0052] Hereinafter, the first direction DR1 may refer to the direction in which the magnetic steel sheets 100 or the block core 10 described below are stacked, and the second direction DR2 may refer to the circumferential direction of the block core 10. And the third direction DR3 refers to the direction perpendicular to the first direction DR1.

[0053] FIG. 4 is a diagram illustrating a block core step in a method for manufacturing a block laminated core according to an embodiment of the present invention.

[0054] For example, the block core step (S10) is a step of stacking and bonding the magnetic steel sheets 100 in a first direction DR1 to form a block core 10 having a first length L1.

[0055] The first length L1 can be set as a preset length taking into consideration the fastening force for joining the electromagnetic steel sheets 100, the second length L2 (see FIG. 5), which is the length of the block stack 15 (see FIG. 5) described below, etc.

[0056] For example, punched magnetic steel sheets 100 may be laminated and then interlocked to form the block core 10. The shape of the interlocking is not limited.

[0057] The joints 11 formed on the block core 10 may be interlocking joints. Interlocking is a method of joining a plurality of magnetic steel sheets 100 by mechanically bending them into a partial shape.

[0058] Although a plurality of joints 11 can exist in one block core 10, if the number of joints 11 is small, the fastening strength will be insufficient, resulting in a defect in which the sheet-shaped electromagnetic steel plate 100 falls off.

[0059] If there are a large number of interlocking fastening joints 11, the magnetic properties of the electromagnetic steel sheets 100 will deteriorate and iron loss will increase, because the interlocking joint is a method of joining by mechanically bending the shape. Therefore, it is important to form an appropriate number of joints 11.

[0060] For example, it is advantageous that the number of interlocking bonded portions 11 included in the block core 10 is at least three, and this number may vary depending on the diameter and first length L1 of the block core 10.

[0061] If there are two or fewer joints 11, the fastening strength will be weak, which may cause defects such as the sheet-shaped electromagnetic steel sheet 100 easily falling off the core. Increasing the number of joints 11 improves the fastening strength, but worsens the iron loss.

[0062] Therefore, the block core 10 can be joined with four to eight joining portions 11 .

[0063] For comparison, when a core is manufactured by stacking electromagnetic steel sheets 100 at once, they are generally interlocked with a minimum of six or more joints 11 .

[0064] For example, in the block core step (S10), the interlocking process can be performed simultaneously with the punching process of the magnetic steel sheet in the mold, thereby shortening the manufacturing time. Since punching and interlocking can be performed simultaneously in the mold, the manufacturing time can be shortened.

[0065] By performing the block core step (S10), a motor core having excellent fastening strength and iron loss can be manufactured.

[0066] FIG. 5 is a diagram illustrating a stacking step in a method for manufacturing a block laminated core according to an embodiment of the present invention, and FIG. 6 is a diagram illustrating a plurality of first extension lines included in a block laminate in a stacked state according to an embodiment of the present invention on one plane.

[0067] The stacking step (S30) according to one embodiment of the present invention may be a step of rotating a plurality of the block cores 10a, 10b, 10c, and 10d at a first angle θ1 in a second direction DR2, which is the circumferential direction of the block cores 10a, 10b, 10c, and 10d, and stacking them in the first direction DR1 to a second length L2 to form a block stack 15.

[0068] For example, n number of block cores 10a, 10b, 10c, and 10d manufactured in the block core step (S10) may be stacked in the first direction DR1.

[0069] The second length L2, which is the length of the block stack 15 and the length of the core, is n times the first length L1. That is, since a plurality of block cores 10a, 10b, 10c, and 10d are stacked and each block core 10a, 10b, 10c, and 10d is formed with the first length L1, the second length L2 can be calculated by multiplying the first direction DR1 by n times the number of stacked block cores 10a, 10b, 10c, and 10d.

[0070] When stacked, the block cores can be rotated by a first angle θ1 in the second direction DR2. If a core is manufactured by stacking the block cores 10 without rotating them in the second direction DR2, the thickness variations that existed in the mother coil are accumulated, causing problems with the squareness and flatness of the electromagnetic steel sheets 100. Therefore, stacking the block cores by rotating them in the second direction DR2 solves the above problem and provides a coil with excellent squareness and flatness.

[0071] As an example, the first angle θ1 can comply with the following [Mathematical Equation 1]. [Mathematical formula 1] θ1=360° / n Here, θ1 is the first angle (°) and n is a natural number.

[0072] Since the core is rotated at the first angle θ1 in the second direction DR2 to ensure good squareness and flatness, it may be important to distribute the thickness variations that existed in the mother coil evenly throughout the block laminate 15.

[0073] Therefore, the first angle θ1 can be set to a value obtained by dividing 360°, which is the total internal angle of the block stack 15, by n, which is the number of stacked block cores 10a, 10b, 10c, and 10d.

[0074] In this case, the smaller the first angle θ1, the better the squareness and flatness of the core. However, although the squareness and flatness are improved as the first angle θ1 is smaller, the number of block cores 10 that must be stacked accordingly increases, which increases the number of manufacturing processes, which may be disadvantageous in terms of economy and time.

[0075] Therefore, the second length L2 may be 3 to 8 times the first length L1. According to the above mathematical formula 1, the first angle θ1 may be 45 to 120°. The number of stacked layers of the block core 10 may be 3 to 8. However, the first angle θ1 and the number of stacked layers of the block core 10 are not limited to those mentioned above.

[0076] For example, in the lamination step (S30), the first angle θ1 may be based on the punch line B.

[0077] 5 and 6, the lamination of four block cores in the lamination step will be described as an example.

[0078] Within one block core 10a, 10b, 10c, 10d, a plurality of virtual first extension lines E1a, E1b, E1c, E1d are formed, connecting punched lines Ba, Bb, Bc, Bd formed in the electromagnetic steel sheet 100 constituting the block core 10a, 10b, 10c, 10d to the center C of the block core, and the angles between the first extension lines E1a, E1b, E1c, E1d may be the same within one block core 10a, 10b, 10c, 10d.

[0079] Within each block core 10a, 10b, 10c, or 10d, the electromagnetic steel sheets are laminated in the first direction DR1 while being punched, and therefore can be laminated without rotating in the second direction DR2. Therefore, for each block core 10a, 10b, 10c, or 10d, there may only be one imaginary first extension line E1a, E1b, E1c, or E1d connecting the punching lines Ba, Bb, Bc, or Bd to the center C of the block core.

[0080] The first angle may refer to the angle between first extension lines E1a, E1b, E1c, and E1d of two adjacent block cores 10a, 10b, 10c, and 10d in the first direction DR1 among the plurality of block cores 10a, 10b, 10c, and 10d, and the first angle θ1 may be defined as an interior angle.

[0081] The stacked block cores 10 can be designated, in order from the bottom, as a first block core 10a, a second block core 10b, a third block core 10c, and a fourth block core 10d.

[0082] In this case, the angle formed by the first extension line E1a of the first block core 10a and the first extension line E1b of the second block core 10b can be the first angle θ1. Also, the angle between the first extension line E1b of the second block core 10b and the first extension line E1c of the third block core 10c, and the angle between the first extension line E1c of the third block core 10c and the first extension line E1d of the fourth block core 10d are also the first angle θ1.

[0083] The number n of stacked block cores 10 may be 4, the second length L2 may be four times the first length L1, and the first angle θ1 may be 90°. However, these are not limited to these specific values ​​and may vary depending on the design.

[0084] The block cores 10a, 10b, 10c, and 10d included in the block stack 15 have connecting portions 11a, 11b, 11c, and 11d that are separated for each block core 10a, 10b, 10c, and 10d, so the fastening force of the interlocking connecting portions 11a, 11b, 11c, and 11d is sufficient to maintain the electromagnetic steel sheets 100 of the block cores 10a, 10b, 10c, and 10d connected together.

[0085] By carrying out this lamination step (S30), the core laminate 15 is formed, and a core having excellent perpendicularity and flatness can be manufactured.

[0086] FIG. 7 is a view for explaining a welding step in a method for manufacturing a block laminated core according to an embodiment of the present invention, and schematically illustrates a block laminated core according to an embodiment of the present invention.

[0087] As an example, the welding step (S40) is a step of completing the block laminated core 3 by forming a welded portion 20 in the first direction DR1 on the outer surfaces of two of the plurality of block cores 10 that are continuously stacked in the first direction DR1, the welded portion 20 being welded in the first direction DR1 with a third length L3 that is shorter than twice the first length L1.

[0088] If the third length L3 is greater than or equal to twice the first length L1, it may affect three or more consecutively stacked block cores 10, which may cause problems in energizing the block cores 10 connected to the welded portion 20. Therefore, the welded portion 20 may be formed with a third length L3 that is less than twice the first length L1.

[0089] Referring to FIG. 7, the stacked block cores 10a, 10b, 10c, and 10d can be referred to as a first block core 10a, a second block core 10b, a third block core 10c, and a fourth block core 10d, in that order from the bottom.

[0090] If the first-second weld 21, which is the weld 20 connecting the first block core 10a and the second block core 10b, is equal to or greater than three times the first length L1, the weld 20 will be connected continuously to the third block core 10c. In this case, a problem occurs in that current will flow to the third block core 10c through the first-second weld 21. This can cause a sudden increase in iron loss because the insulation of the magnetic steel sheets 100 included in the connected first to third block cores 10a, 10b, and 10c will be destroyed and current will be passed through. Therefore, the weld 20 must be formed with a third length L3 that is less than twice the first length L1.

[0091] This means that the 2-3 weld 22, which is the weld 20 connecting the second block core 10b and the third block core 10c, and the 3-4 weld 23, which is the weld 20 connecting the third block core 10c and the fourth block core 10d, are all the same.

[0092] As an example, a virtual line obtained by extending a part of the plurality of welds 20 formed on any one of the plurality of block cores 10a, 10b, 10c, and 10d in the first direction DR1 may be defined as the second extension line E2. In this case, a plurality of second extension lines E2 may be formed, and any two of the plurality of second extension lines E2 may be formed spaced apart without overlapping.

[0093] If the second extension lines E2 overlap, thermal damage to the core side surface may accumulate, which may increase iron loss. Therefore, the welds 20 may be arranged so that the second extension lines E2 are not aligned on the same line.

[0094] 7, the second block core 10b, which is one of the plurality of block cores 10a, 10b, 10c, and 10d, may include a first-second weld 21 formed to connect the first block core 10a and the second block core 10b, and a second-third weld 22 formed to connect the second block core 10b and the third block core 10c. Therefore, a portion of the first-second weld 21 and a portion of the second-third weld 23 may be formed on the second block core 10b.

[0095] Furthermore, a virtual extension line extending a portion of the 1-2 welding portion 21 in the first direction DR1 can be defined as the 2-1 extension line E21, and a virtual extension line extending a portion of the 2-3 welding portion 22 in the first direction DR1 can be defined as the 2-2 extension line E22.

[0096] At this time, if the 2-1 extension line E21 and the 2-2 extension line E22 overlap, iron loss may tend to increase due to the accumulation of thermal damage on the core side surface caused by the 1-2 welded portion 21 and the 2-3 welded portion 22. Therefore, the 2-1 extension line E21 and the 2-2 extension line E22 may be formed apart from each other.

[0097] However, the second extension lines E2 of the welds 20 formed on the block cores 10a, 10b, 10c, and 10d other than the same block cores 10a, 10b, 10c, and 10d may not be spaced apart. For example, the second extension line E2 extending a portion of the 1-2 weld 21 formed on the first block core 10a and the second extension line E2 extending a portion of the 3-4 weld 23 formed on the third block core 10c may be the same extension line as the 2-1 extension line E21.

[0098] For example, in the welding step (S40), a plurality of welds 20 may be formed at the same position in the first direction DR1 and spaced apart in the second direction DR2.

[0099] The welds 20 formed at the same position in the first direction DR1 may be plural, and may be spaced apart from each other in the second direction DR2.

[0100] 7, the first-second welds 21, which are welds 20 connecting the first block core 10a and the second block core 10b, may be spaced apart in the second direction DR2, forming multiple first-second welds 21a, 21b, and 21c. This is because the bonding strength may be insufficient if two adjacent block cores 10 are connected using only one weld 20. The same may be true for the second-third welds 22, 22a, and 22b and the third-fourth welds 23, 23a, 23b, and 23c.

[0101] In the welding step (S40), the weld 20 may be formed on the outer circumferential surface of the core. Partial welding on the inside of a slot or on the side of the core, including the gap between the rotor and the stator, reduces the space for winding the winding conductor, resulting in a poor winding point ratio and acting as friction when the electrical device rotates. Therefore, it is advantageous to form the weld on the outer circumferential surface rather than the inner circumferential surface.

[0102] For example, in the welding step (S40), the welding method may be TIG or laser welding, but is not limited thereto, and may include any welding method used in industry.

[0103] By including the welding step (S40), it is possible to manufacture a core that has low iron loss, is easy to manufacture, and is economical to manufacture.

[0104] FIG. 8 is a view showing a state in which a first block core and a second block core adjacent to each other in the first direction are joined at a first-second welded joint as viewed from the first direction, in accordance with a method for manufacturing a block laminated core according to an embodiment of the present invention.

[0105] As an example, a plurality of the welds 20 are formed to connect two identical block cores 10 out of a plurality of block cores 10, and the second angle θ2, which is the smallest angle among the angles formed by any two of the third extension lines, which are extension lines connecting the centers of the block cores 10 and the plurality of welds 20 connecting the two identical block cores, may be 10 to 180°.

[0106] Referring to FIG. 8, a plurality of third extension lines E3, E3a, E3b, E3c, E3d, E3e, E3f, which are virtual extension lines connecting the first and second welded portions 21, 21a, 21b, 21c, 21d, 21e, 21f that connect the same two block cores 10a, 10b to the center C of the first block core 10a or the second block core 10b, may also be formed. The smallest angle formed by two of the third extension lines E3, E3a, E3b, E3c, E3d, E3e, and E3f adjacent to each other in the second direction DR2 among E3, E3a, E3b, E3c, E3d, E3e, and E3f in the second direction DR2 may be the second angle θ2, which may be 10 to 180°. Since six first-second welds 21, 21a, 21b, 21c, 21d, 21e, and 21f are formed, the second angle θ2 may be 60°. Although the second angles θ2 may be different from each other, it is advantageous for the second angles θ2 formed by the welds 20 joining the same two block cores 10 to be the same in terms of bonding strength. Therefore, a high-quality core can be manufactured with sufficient bonding strength to maintain the stacked state of the block stack 15, in which multiple block cores are stacked, while also having low iron loss.

[0107] In the following description of the block laminated core according to an embodiment of the present invention, the same configurations, contents, and effects as those described in the manufacturing method of the block laminated core will be cited unless otherwise specified. Also, for the block laminated core according to an embodiment of the present invention, please refer to Figures 4 to 8.

[0108] A block laminated core 3 according to one embodiment of the present invention includes a block core 10 in which magnetic steel sheets 100 are stacked in a first direction DR1 to have a first length L1 and including an interlocking joint 11; a block laminate 15 in which a plurality of block cores 10a, 10b, 10c, and 10d are stacked in the first direction DR1 to have a second length L2; and a weld 20 formed on the outer circumferential surface of the block laminate 15 in the first direction DR1 by a third length L3 that is shorter than twice the first length L1, so as to connect two adjacent block cores 10a, 10b, 10c, and 10d among the plurality of block cores 10a, 10b, 10c, and 10d included in the block laminate 15.

[0109] For example, a plurality of first extension lines E1 are formed as imaginary extension lines connecting punched lines Ba, Bb, Bc, and Bd formed in the magnetic steel sheet 100 to centers C of the block cores 10a, 10b, 10c, and 10d. The first extension lines E1 are formed at the same position in the second direction DR2 within any one of the plurality of block cores 10a, 10b, 10c, and 10d, with the angle between the first extension lines E1 being 0. The angle between the first extension lines E1 formed in any two of the plurality of block cores 10a, 10b, 10c, and 10d arranged adjacent to each other in the first direction DR1 may be a first angle θ1, and the first angle θ1 may be constant.

[0110] For example, the second length L2 may be three to eight times the first length L1.

[0111] For example, a plurality of welds 20 are formed to connect two identical block cores 10a, 10b, 10c, and 10d among the plurality of block cores 10a, 10b, 10c, and 10d, and the second angle θ2, which is the smallest angle between any two of the third extension lines E3, which are extensions connecting the centers of the block cores 10a, 10b, 10c, and 10d, and the plurality of welds 20 to connect the two identical block cores 10a, 10b, 10c, and 10d, may be 10 to 180°. Therefore, the block laminated core 3 can provide excellent fastening strength while preventing the entire magnetic steel sheet 100 from being energized.

[0112] Table 1 below shows a comparison experiment of a block laminated core formed by a method for manufacturing a block laminated core according to an embodiment of the present invention with a comparative example.

[0113] A 0.27mm thick non-oriented electrical steel sheet was punched out to a diameter of 230mm, and the laminated core was wound with copper wire so that the height of a single core was 100mm.The no-load loss was then measured under the condition that an inverter was connected and power was applied.

[0114] If the punched magnetic steel sheets are stacked without rotation and fastened, the squareness and flatness, which represent the core shape, will be poor due to variations in the thickness of the accumulated magnetic steel sheets. Furthermore, since there is no fastening, it is impossible to measure the fastening strength itself, and the no-load loss at this time is set to 100%, assuming that there is no processing stress due to fastening.

[0115] Under the above conditions, when the first angle, which is the rotation angle when the block cores are stacked, is gradually decreased, the experiment was conducted by changing the angle to 180°, 120°, 90°, and 45° based on the case where the block cores are stacked without rotation. As a result, it was confirmed that the perpendicularity and flatness were improved. Based on this, the experiment shown in the table below was conducted.

[0116] [Table 1]

[0117] In Comparative Example 1, four block cores were stacked to form a block laminate, but the individual block cores had no joints. The blocks were then stacked while rotating the first angle by 90°. The block laminate was then interlocked at six locations at 60-degree intervals. In this case, the cores had excellent squareness and flatness, but defects occurred due to insufficient core fastening strength. Therefore, when the top part of the core was lifted, parts of the core fell off, or the spacing between the magnetic steel sheets included in the block cores became excessively wide. In Comparative Example 2, a block laminate was fabricated using the same method as Comparative Example 1, but the number of interlocking fastenings was increased to 12, with the cores fastened at 30-degree intervals. The fastening strength was better than in Comparative Example 1, but was still somewhat insufficient to be considered acceptable. When the top part of the core was lifted, the spacing between the cores was narrower than in Comparative Example 1, but a side impact test revealed that the cores fell off due to a slight external impact.

[0118] Here, the side impact test is an experiment in which a weak impact is applied to the side of the core with a hammer to compare the degree of bonding, and is a test regarding impacts that may occur during core transportation.

[0119] In Comparative Example 3, four block cores are stacked to form a block laminate, as in Comparative Example 1, but the individual block cores have no joints and are stacked while rotated at a first angle of 90°. Then, full welding is performed on the outer periphery of the block laminate using TIG welding. The second angle between adjacent welds is 180°, forming two full welds. In Comparative Example 3, because the cores are welded with an appropriate pressure, springback occurs, in which the unwelded portions bulge during 180-degree welding, resulting in poor squareness and flatness.

[0120] In Comparative Example 4, four block cores were stacked in the same manner as in Comparative Example 3 to form a block laminate, but the individual block cores had no joints and were stacked while rotated with a first angle of 90°. Then, TIG welding was performed on the outer periphery of the block laminate. Unlike Comparative Example 3, four welds were formed with an interior angle of 90° between the welds. Comparative Example 4 had good perpendicularity and flatness, but a problem occurred in that the no-load loss ratio rapidly deteriorated to 131.6%.

[0121] In Comparative Example 5, a block stack is formed as in Comparative Example 3, and overall welding is performed. Unlike Comparative Example 3, six overall welds are formed with an interior angle of 60° between the welds. Comparative Example 5 has an excellent core shape and fastening strength, but the no-load loss is very poor at 142.3%.

[0122] In Comparative Example 6, a block core is manufactured by laminating magnetic steel sheets and connecting six interlocking fasteners. The block cores are then laminated while rotating the first angle by 90°. Four overall welds are then formed with an interior angle of 90° between the welds during overall welding. In this case, the no-load loss was found to be the worst at 147.90%.

[0123] Examples 1 to 4 according to an embodiment of the present invention will be confirmed.

[0124] The block laminated core 3, which is manufactured by manufacturing the block cores 10, rotating them by a first angle θ1, stacking them, and welding only a portion of the outer periphery, corresponds to Examples 1 to 4. Only Example 4 further includes a heat treatment step (S20). In the examples, the third length L3 is formed by extending ¼ of the first length L1 upward and downward from the stacked surface, and the overall length corresponds to ½ of the first length L1.

[0125] In Example 1, three block cores 10 are stacked with the first angle θ1 set to 120°, and the number of welds at the same position in the first direction Dr1 is four with the second angle θ2 set to 90°. Therefore, a total of 12 welds 20 are formed on the block laminated core 3 formed with a total of three block cores 10.

[0126] In Example 2, four block cores are stacked with the first angle θ1 set to 90°, and the second angle θ2 is also set to 90° as in Example 1, with four welds 20 at the same position in the first direction DR1. Therefore, a total of 16 welds 20 are formed on the block laminated core 3 formed with a total of four block cores 10, and the maximum value of the third length L3 is set smaller in Example 2 than in Example 1.

[0127] In Example 3, similar to Example 2, four block cores 10 are stacked with the first angle set to 90°, but the second angle θ2 is set to 45°, and the number of welded portions 20 at the same position in the first direction DR1 is eight. Therefore, a total of 32 welded portions 20 are formed in the block laminated core 3 formed of a total of four block cores.

[0128] Example 4 was manufactured in the same manner as Example 3, but was manufactured after performing a heat treatment step (S20) before stacking the block cores to remove residual stress caused by processing.

[0129] The joints 11 that fasten the block cores were fabricated as six interlocking joints in all of Examples 1 to 4. This was because the fastening strength was excellent when six interlocking joints were made inside in accordance with Comparative Example 6, and this was set as the standard.

[0130] According to the results of Example 1, the squareness and flatness of the core shape were good, the fastening strength was excellent, and the no-load loss was good at 115.10%. The results of Example 2 show a tendency for the no-load loss to be reduced to about 114.7% compared to Example 1, which can be interpreted as the effect of further reducing the variation in thickness of the magnetic steel sheets, resulting in a more uniform magnetic field within the core. Furthermore, the squareness and flatness were even better than those of Example 1. In other words, it can be seen that the smaller the first angle, the better the squareness and flatness.

[0131] Looking at the results for Example 3, the number of welds 20 at the same position in the first direction DR1 was increased, and the current flow between the magnetic steel sheets was less favorable than in Examples 1 and 2, resulting in a no-load loss of 118.5%. Although not shown in Table 1, the joint strength was even better than in Example 2. Example 4 was otherwise the same as Example 3, but additionally included a heat treatment step (S20), in which 100% nitrogen was injected for 1 hour at a maximum temperature of 820°C. As a result, the no-load loss ratio was reduced to 109.50% compared to Example 3.

[0132] In Table 1 above, Comparative Examples 4 to 6 can be considered as cores manufactured using conventional manufacturing methods. In comparison, Examples 1 to 4 have excellent perpendicularity and flatness, and fastening strength similar to or better than conventional methods, while cores with even lower no-load loss ratios can be manufactured.

[0133] When included in a motor used in an electric vehicle, the block laminated core 3 according to an embodiment of the present invention can significantly increase the driving range of the electric vehicle and improve safety. Of course, the performance of motors generally used other than electric vehicles can also be further improved.

[0134] Although the present invention has been described above with reference to the preferred embodiments, the present invention is not limited to the above-described preferred embodiments and may be modified and implemented by those skilled in the art without changing the technical concept of the present invention as claimed in the claims.

Claims

1. a block core step of laminating and bonding magnetic steel sheets in a first direction to form a block core having a first length; a stacking step of rotating the plurality of block cores in a second direction, which is a circumferential direction, by a first angle and stacking them to a second length in the first direction; and a welding step of welding two consecutive block cores in the first direction along a third length that is shorter than twice the first length to form a welded portion on the outer circumferential surface of each of the plurality of block cores, In the welding step, A method for manufacturing a block laminated core, wherein a plurality of imaginary lines extending a portion of the plurality of welds formed in any one of the plurality of block cores in the first direction are spaced apart.

2. 2. The method of claim 1, wherein the magnetic steel sheets are interlocking-bonded in the block core forming step.

3. the second length is an n-th multiple of the first length; The method for manufacturing a block laminated core according to claim 2 , wherein the first angle is in accordance with the following mathematical formula 1: Mathematical formula 1: θ1=360° / n Here, θ1 is the first angle (°), and n is a natural number.

4. The second length is: The method for manufacturing a block laminated core according to claim 3, wherein the length is 3 to 8 times the first length.

5. In the welding step, The welded portion is The method for manufacturing a block laminated core according to claim 1 , wherein a plurality of the blocks are formed at the same position in the first direction and spaced apart in the second direction.

6. The method for manufacturing a block laminated core according to claim 1 , further comprising a heat treatment step in which the block core is heated to remove residual stress before the lamination step.

7. a block core in which electromagnetic steel sheets are stacked to have a first length in a first direction and which includes an interlocking joint; a block stack in which a plurality of the block cores are stacked to have a second length in the first direction; a weld formed on an outer peripheral surface of the block stack in the first direction with a third length that is shorter than twice the first length, to connect two adjacent block cores among the plurality of block cores included in the block stack.

8. a plurality of imaginary first extension lines are formed connecting punched lines formed on the electromagnetic steel sheets forming the block cores to centers of the block cores, and the first extension lines are formed at the same positions in a second direction, which is a radial direction, within one block core; 8. The block laminated core according to claim 7, wherein an angle between the first extension lines formed on any two block cores arranged adjacent to each other in the first direction among the plurality of block cores forms a first angle.

9. 9. The block laminated core of claim 8, wherein the second length is three to eight times the first length.

10. 10. The block laminated core according to claim 9, wherein a plurality of the welds are formed to join two identical block cores among the plurality of block cores, and a second angle, which is the smallest angle among the angles formed by the plurality of welds joining the two identical block cores and any two of the third extension lines which are extension lines connecting the centers of the block cores, is 10 to 180 degrees.

11. The electrical steel sheet comprises, in weight percent:

8. The block laminated core according to claim 7, which is a non-oriented electrical steel sheet containing Si: 0.25 to 4.8%, Al: 0.05 to 2.0%, Mn: 0.15 to 1.0%, C: 0.0015 to 0.0040%, N: 0.0005 to 0.0030%, S: 0.0005 to 0.003%, Mo: 0.0050 to 0.015%, Ti: 0.0005 to 0.0020%, Nb: 0.0005 to 0.0040%, V: 0.0005 to 0.0040%, the balance being Fe and inevitable impurities.

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