Squirrel-cage rotor and method for manufacturing squirrel-cage rotor, and induction motor and method for manufacturing induction motor

Abstract

A squirrel-cage rotor (10A) comprises a laminated core (11) and a secondary conductor. The laminated core (11) includes a laminated body that is configured by a plurality of electromagnetic steel sheets (12) being laminated, that includes a rotation shaft insertion hole (111) into the central portion of which a rotation shaft is inserted, and that includes a plurality of slot holes (112) which penetrate in the lamination direction of the electromagnetic steel sheets (12). The secondary conductor has: end ring parts (14) that are provided so as to be in contact with both end portions of the electromagnetic steel sheets (12) of the laminated core (11) in the lamination direction; and slot bar parts (13) that are provided in the plurality of slot holes (112) and are connected to the two end ring parts (14). The laminated core (11) includes: two first structure parts (11a) which are provided to both end portions in the lamination direction; and a second structure part (11b) which is interposed between the two first structure parts (11a) and in which a plurality of the electromagnetic steel sheets (12) are laminated. The first structure parts (11a) have a different structure from that of the second structure part (11b).

Description

Squirrel-cage rotor, method for manufacturing the same, induction motor, and method for manufacturing the same

[0001] The present disclosure relates to a squirrel-cage rotor obtained by integrally casting a laminated core formed by laminating a plurality of electromagnetic steel sheets by die casting or casting, a method for manufacturing the same, an induction motor, and a method for manufacturing the same.

[0002] The rotor of a squirrel-cage induction motor is generally formed by integrally casting a large number of laminated electromagnetic steel sheets by aluminum die casting. Slot holes are formed in the electromagnetic steel sheets, and when the electromagnetic steel sheets are laminated, slot bar formation portions that serve as flow paths for aluminum are formed. By placing the laminated electromagnetic steel sheets in the cavity of a mold and performing aluminum die casting, a pair of end ring formation portions and slot bar formation portions connecting these end ring formation portions are formed. One of the end ring formation portions is connected to a plunger through a runner formation portion. During die casting, molten aluminum is filled in the order of the runner formation portion, the one end ring formation portion, the slot bar formation portions, and the other end ring formation portion, thereby molding the rotor.

[0003] Depending on pressure conditions and the like during die casting, aluminum may leak from gaps between the laminated electromagnetic steel sheets, forming bridges. When a rotor with formed bridges is used in a squirrel-cage induction motor, this may cause an increase in loss. Accordingly, Patent Document 1 discloses a rotor formed of a rotor core made by laminating a large number of electromagnetic steel sheets, wherein the rotor is integrally configured by laminating electromagnetic steel sheets each having an adhesive applied to a surface thereof. Patent Document 1 also discloses a rotor formed of a rotor core made by laminating a large number of electromagnetic steel sheets, wherein the rotor is configured by sintering, integrally with the rotor core, a rotor core member having a silicon oxide paint applied to an end face of a slot thereof.

[0004] Japanese Unexamined Patent Publication No. 10-285889

[0005] The inventors have found that when forming a rotor by die casting, peeling defects in the electrical steel sheet frequently occur near the end ring. However, the conventional techniques described above have the problem of not being able to solve such peeling defects in the electrical steel sheet. Specifically, even when the electrical steel sheets are bonded together with adhesive, the adhesive strength decreases at high temperatures, leading to gas defects. In addition, coating with silicon oxide paint is difficult to apply uniformly, resulting in problems such as uncoated areas and gas defects due to insufficient drying. It should be noted that similar problems can occur not only in die casting but also in casting.

[0006] This disclosure has been made in view of the above, and aims to provide a squirrel-cage rotor that can suppress peeling defects of the electrical steel sheet near the end ring compared to conventional designs.

[0007] To solve the above-mentioned problems and achieve the objective, the squirrel-cage rotor according to this disclosure comprises a laminated core and a secondary conductor. The laminated core includes a laminate in which a plurality of electromagnetic steel sheets are laminated and which has a rotating shaft insertion hole in the center into which a rotating shaft is inserted and a plurality of slot holes penetrating in the direction of lamination of the electromagnetic steel sheets. The secondary conductor has an end ring portion provided so as to be in contact with both ends of the laminated electromagnetic steel sheets of the laminated core in the direction of lamination, and a slot bar portion provided inside the plurality of slot holes and connected to two of the end ring portions. The laminated core has two first structural parts provided at both ends in the direction of lamination, and a second structural part sandwiched between the two first structural parts and in which a plurality of electromagnetic steel sheets are laminated. The first structural parts have a structure different from that of the second structural parts.

[0008] According to this disclosure, the peeling defects of the electrical steel sheet near the end ring can be suppressed compared to conventional methods.

[0009] Cross-sectional view showing an example of the configuration of a typical squirrel-cage rotor. Top view showing an example of the configuration of an electrical steel sheet. Diagram schematically showing an example of the procedure for manufacturing a typical squirrel-cage rotor. Diagram schematically showing an example of the procedure for manufacturing a typical squirrel-cage rotor, enlarged view of area R1 in Figure 3. Diagram schematically showing an example of the procedure for manufacturing a typical squirrel-cage rotor. Diagram schematically showing an example of the procedure for manufacturing a typical squirrel-cage rotor, enlarged view of area R2 in Figure 5. Diagram schematically showing an example of the procedure for manufacturing a typical squirrel-cage rotor. Diagram schematically showing an example of the procedure for manufacturing a typical squirrel-cage rotor, enlarged view of area R3 in Figure 7. Cross-sectional view showing an example of the configuration of a squirrel-cage rotor according to Embodiment 1. Enlarged view of area R4 in Figure 9. Flowchart showing an example of the procedure for manufacturing a squirrel-cage rotor according to Embodiment 1. Diagram showing an example of the procedure for manufacturing a squirrel-cage rotor according to Embodiment 1, enlarged view of area R12 in Figure 12. Enlarged view of 5 Figure showing an example of the procedure for manufacturing a squirrel-cage rotor according to Embodiment 1 Figure showing an example of the procedure for manufacturing a squirrel-cage rotor according to Embodiment 1, enlarged view of region R6 in Figure 14 Cross-sectional view schematically showing an example of the configuration of a squirrel-cage rotor according to Embodiment 2 Enlarged view of region R7 in Figure 16 Partial cross-sectional view showing another example of the configuration of a squirrel-cage rotor according to Embodiment 2 Cross-sectional view schematically showing an example of the configuration of a squirrel-cage rotor according to Embodiment 3 Enlarged view of region R8 in Figure 19 Top view showing an example of the configuration of electromagnetic steel sheets used in a squirrel-cage rotor according to Embodiment 3 Top view showing another example of the configuration of electromagnetic steel sheets used in a squirrel-cage rotor according to Embodiment 3 Cross-sectional view schematically showing an example of the configuration of a squirrel-cage rotor according to Embodiment 4 Enlarged view of region R9 in Figure 23 Cross-sectional view schematically showing another example of the configuration of a squirrel-cage rotor according to Embodiment 4 Figure showing an example of the configuration of an induction motor according to Embodiment 5 Flowchart showing an example of the procedure for manufacturing an induction motor according to Embodiment 5

[0010] The following describes in detail, with reference to the drawings, a squirrel-cage rotor and its manufacturing method according to embodiments of the present disclosure, as well as an induction motor and its manufacturing method.

[0011] Before describing the embodiments, we will explain the problems with conventional squirrel-cage rotors used in squirrel-cage induction motors. Figure 1 is a cross-sectional view showing an example of the configuration of a typical squirrel-cage rotor. The squirrel-cage rotor 10 comprises a laminated core 11, a slot bar section 13, and an end ring section 14.

[0012] The laminated core 11 includes a laminate in which multiple electromagnetic steel sheets 12 are laminated, and which has a rotating shaft insertion hole 111 in the center into which a rotating shaft is inserted, and multiple slot holes 112 that penetrate in the direction of lamination of the electromagnetic steel sheets 12. In the example of Figure 1, the laminated core 11 is a member made by laminating annular electromagnetic steel sheets 12 to form a cylindrical shape. The electromagnetic steel sheets 12 are made into annular shapes by punching out flat electromagnetic steel sheets 12 by press working or the like. In one example, the thickness of the electromagnetic steel sheets 12 is 0.3 mm or more and 0.5 mm or less. Multiple electromagnetic steel sheets 12 are laminated in the axial direction around a rotating shaft insertion hole 111 into which a rotating shaft (not shown) is inserted. An insulating film (not shown) is formed on the electromagnetic steel sheets 12, and adjacent electromagnetic steel sheets 12 are insulated from each other in the lamination direction. At this time, the electromagnetic steel sheets 12 may be arranged rotated by a predetermined angle with respect to the electromagnetic steel sheet 12 placed below in Figure 1. The laminated core 11 has a rotating shaft insertion hole 111 and slot holes 112. The rotating shaft insertion hole 111 penetrates the center of the laminated core 11 in the direction of stacking on a plane perpendicular to the stacking direction. The slot holes 112 are a plurality of through holes that penetrate the laminated core 11 in the direction of stacking on the outer periphery of the center of the laminated core 11 in the direction of stacking.

[0013] Figure 2 is a top view showing an example of the structure of an electrical steel sheet. In Figure 2, the plane is shown in a direction perpendicular to the lamination direction. As shown in Figure 2, the electrical steel sheet 12 has an opening 121 in the center which constitutes the rotation shaft insertion hole 111 of the laminated core 11, and a plurality of openings 122 which are arranged at predetermined intervals along the circumferential direction on the outer circumference of the opening 121 and constitute the slot holes 112 of the laminated core 11.

[0014] Returning to Figure 1, the slot bar portion 13 is provided inside the multiple slot holes 112 and is connected to and integrated with the two end ring portions 14. The slot bar portion 13 is made of aluminum or an aluminum alloy, which is considered to be a material with high conductivity. The slot bar portion 13 is formed by filling the slot holes 112 of the laminated core 11 with aluminum using aluminum die casting. In other words, the slot bar portion 13 is housed in the slot holes 112 of the laminated core 11.

[0015] The end ring portion 14 is provided so as to be in contact with both ends of the electromagnetic steel sheet 12 of the laminated core 11 in the lamination direction. The end ring portion 14 is made of aluminum or an aluminum alloy, which is considered to be a material with high conductivity. The end ring portion 14 has an annular shape. The end ring portion 14 has an opening 141 that penetrates the center of the plane perpendicular to the rotation axis of the end ring portion 14 in the lamination direction. The opening 141 is provided at the same position as the rotation axis insertion hole 111 of the laminated core 11, but the diameter of the opening 141 is larger than the diameter of the rotation axis insertion hole 111. The end ring portion 14 is formed integrally with a plurality of slot bar portions 13 housed in a plurality of slot holes 112 at both ends of the laminated core 11 in the lamination direction. The slot bar portions 13 and the end ring portion 14 correspond to secondary conductors.

[0016] Next, a method for manufacturing such a squirrel-cage rotor 10 will be described. Figures 3 to 8 are schematic diagrams showing an example of a general procedure for manufacturing a squirrel-cage rotor. Figure 4 is an enlarged view of region R1 in Figure 3, Figure 6 is an enlarged view of region R2 in Figure 5, and Figure 8 is an enlarged view of region R3 in Figure 7. First, an annular-shaped electromagnetic steel sheet 12, as shown in Figure 2, is formed from a flat electromagnetic steel sheet 12. Here, an example of forming the electromagnetic steel sheet 12 using press working is given. As shown in Figure 3, a flat electromagnetic steel sheet 12 is placed between the lower die 51 and the upper die 52 of the press die 50, and the electromagnetic steel sheet 12 is sandwiched between the upper die 52 and the lower die 51, and pressure is applied. This forms the annular-shaped electromagnetic steel sheet 12 shown in Figure 2. When processed by the press die 50, in one example, unnecessary electromagnetic steel sheets 12 such as the opening 121 that constitutes the rotating shaft insertion hole 111 and the opening 122 that constitutes the slot hole 112 are cut off. As shown in the enlarged view of Figure 4, burrs 123 are generated at the cut portion of the electromagnetic steel sheet 12 where the unnecessary parts have been cut off. In addition, waviness 124 is generated in the press-formed annular-shaped electromagnetic steel sheet 12. Thus, the electromagnetic steel sheet 12 is not perfectly flat.

[0017] Next, as shown in Figure 5, the multiple formed electromagnetic steel sheets 12 are stacked to form a laminated core 11. The electromagnetic steel sheets 12 formed by press working have undulations 124 as described above. Therefore, as shown in the enlarged view of Figure 6, in the laminated core 11 formed by stacking electromagnetic steel sheets 12, there are gaps 125 between adjacent electromagnetic steel sheets 12 in the stacking direction. In particular, if the undulation shape of the electromagnetic steel sheets 12 does not match that of the upper and lower electromagnetic steel sheets 12, there will be areas where the gaps 125 between the electromagnetic steel sheets 12 are large. When using electromagnetic steel sheets 12 with a thickness of 0.3 mm or more and 0.5 mm or less, one example of the spacing between adjacent electromagnetic steel sheets 12 in the stacking direction at a position facing the slot hole 112 is 0.3 mm or more.

[0018] Subsequently, as shown in Figure 7, the laminated core 11 is placed in the cavity of the mold 60 of a die-casting machine (not shown), and the slot bar portion 13 and a pair of end ring portions 14 are formed on the laminated core 11 by aluminum die-casting. Before the installation of the laminated core 11, the mold 60 has a pair of end ring forming portions 61 and 62, which are spaces for forming the pair of end ring portions 14; a laminated core installation portion, which is a space for installing the laminated core 11; and a runner forming portion (not shown), which is a space connected to one of the end ring forming portions 61 and 62. After the installation of the laminated core 11, the mold 60 has a pair of end ring forming portions 61 and 62, which are spaces for forming the pair of end ring portions 14; a slot bar forming portion 63, which is a space for forming the slot bar portion 13; and a runner forming portion (not shown), which is a space connected to one of the end ring forming portions 61 and 62. Inside the mold 60, a pair of end ring forming sections 61 and 62, a slot bar forming section 63, and a runner forming section are connected. A sleeve (not shown) is connected to the runner forming section. During die casting, a plunger inside the sleeve moves, pushing out molten aluminum or aluminum alloy 65 from inside the sleeve and filling the runner forming section, one end ring forming section 61, the slot bar forming section 63, and the other end ring forming section 62 in that order. This produces a squirrel-cage rotor 10 in which the slot bar section 13 inside the slot hole 112 of the laminated core 11 and the pair of end ring sections 14 at both ends of the laminated core 11 in the stacking direction are integrally formed, as shown in Figure 1.

[0019] As shown in the enlarged view of Figure 8, during die casting, if there is a wide gap between the electrical steel sheets 12, the pressure of the molten aluminum or aluminum alloy 65 may cause insertion 66a and 66b. In areas other than near both ends of the laminated core 11, deformation and peeling are suppressed by interference with other electrical steel sheets 12 present on both sides in the lamination direction. Specifically, since there are multiple other electrical steel sheets 12 on both sides in the lamination direction and these multiple electrical steel sheets 12 have high rigidity, even if insertion 66a occurs, peeling defects of the electrical steel sheets 12 due to this insertion 66a hardly occur. On the other hand, near both ends of the laminated core 11, there are fewer electrical steel sheets 12 on one side in the lamination direction compared to near the center of the laminated core 11. Therefore, if insertion 66b occurs, the electrical steel sheet 12 will peel up on the side with fewer electrical steel sheets 12, and the tip of insertion 66b will reach further inside the electrical steel sheet 12. Furthermore, the insertions 66a and 66b during die casting are more likely to occur when the gap between the electrical steel sheets 12 and the electrical steel sheets 12 at the position facing the slot bar forming section 63, which serves as a passage for the molten metal 65, is large, for example, when the gap is larger than 0.3 mm. Also, as described above, peeling defects of the electrical steel sheets 12 occur particularly frequently near both ends of the laminated core 11, i.e., near the end ring section 14, where the number of electrical steel sheets 12 on one side of the lamination direction is reduced. A squirrel-cage rotor 10 that has such peeling defects does not meet the requirements of a squirrel-cage rotor 10 and will need to be remanufactured.

[0020] Furthermore, as shown in the enlarged view of Figure 8, if peeling defects 67 occur near both ends of the laminated core 11, the thickness d1 of the end ring portion 14 at the location where the peeling defect 67 occurred will decrease compared to the thickness d0 of the end ring portion 14 at other locations. In other words, a portion of the end ring portion 14, which is designed to have a thickness d0, will have a portion with a thickness d1 that is thinner than d0. This reduced thickness may cause damage to the squirrel-cage rotor 10 during rotation. In addition, the reduced thickness of the end ring portion 14 reduces the volume of current flowing through the end ring portion 14, and also causes a short circuit between adjacent slot bar forming portions 63 via the insertion 66b, resulting in losses in the induction motor using the squirrel-cage rotor 10.

[0021] The following embodiments describe a squirrel-cage rotor 10 and its manufacturing method, as well as an induction motor and its manufacturing method, which can suppress the occurrence of peeling defects 67 caused by the insertion 66b of molten metal 65 in the electromagnetic steel sheets 12 near the end ring portions 14 at both ends of the squirrel-cage rotor 10 in the stacking direction, compared to conventional methods. It is assumed that the material of the molten metal 65 is basically aluminum or an aluminum alloy, but the same applies to materials with high electrical conductivity, such as copper or a copper alloy. Furthermore, the forming method is the same not only for die casting but also for casting.

[0022] Embodiment 1. Figure 9 is a schematic cross-sectional view showing an example of the configuration of a squirrel-cage rotor according to Embodiment 1, and Figure 10 is an enlarged view of region R4 in Figure 9. The same reference numerals are used for components that are the same as those described in Figure 1, and their descriptions are omitted. In the squirrel-cage rotor 10A according to Embodiment 1, the laminated core 11 has two first structural parts 11a provided at both ends in the lamination direction, and a second structural part 11b sandwiched between the two first structural parts 11a, in which a plurality of electromagnetic steel sheets 12 are laminated. The first structural part 11a has a different structure from the second structural part 11b. Specifically, the first structural part 11a has an insertion suppression structure that suppresses the insertion 66b of molten aluminum or aluminum alloy 65 during aluminum die casting or casting to form the secondary conductor.

[0023] The second structural part 11b is made by laminating electrical steel sheets 12, similar to the conventional laminated core 11. The spacing between electrical steel sheets 12 in the second structural part 11b is not particularly limited, but is about the same as that of a typical laminated core 11. In one example, when electrical steel sheets 12 with a thickness of 0.3 mm or more and 0.5 mm or less are used, the spacing between adjacent electrical steel sheets 12 is partially 0.3 mm or more due to the waviness 124 that occurs when forming the annular-shaped electrical steel sheets 12.

[0024] The first structural part 11a is constructed by laminating multiple metal plates, and the spacing between the multiple metal plates at the positions facing the slot hole 112 and the positions facing the rotating shaft insertion hole 111 is smaller than the spacing between the electromagnetic steel plates 12 of the second structural part 11b. In Embodiment 1, the first structural part 11a is a structure in which electromagnetic steel plates 12 are laminated. Furthermore, as an insertion suppression structure, the spacing between adjacent electromagnetic steel plates 12 of the first structural part 11a is narrower than that of the second structural part 11b. The spacing between the electromagnetic steel plates 12 of the first structural part 11a is 0.2 mm or less. This spacing between electromagnetic steel plates 12 is at least the spacing in the portion facing the slot hole 112. However, in the processing method described later, it is considered that no difference will occur depending on the processing position, so the spacing in the portion facing the rotating shaft insertion hole 111 is also 0.2 mm or less, not just in the portion facing the slot hole 112.

[0025] Furthermore, burrs 123 are formed as insertion suppression structures in at least a portion of the space between the electromagnetic steel sheets 12 facing the cut portion of the first structural part 11a. The cut portion is the slot hole 112, the rotating shaft insertion hole 111, etc. As shown in the enlarged view of Figure 10, the burrs 123 are provided so that the gap 125 between adjacent electromagnetic steel sheets 12 at the position facing the slot hole 112 is smaller than the distance between adjacent electromagnetic steel sheets 12 at a position inside the position facing the slot hole 112. Alternatively, the burrs 123 are provided so as to eliminate the gap 125 between adjacent electromagnetic steel sheets 12 at the position facing the slot hole 112. However, burrs 123 are not provided at all positions facing the slot hole 112, but may be provided at only some positions. The portion of the first structural part 11a where the distance between the electromagnetic steel sheets 12 is 0.2 mm or less includes at least the portion facing the slot hole 112 where the burrs 123 are formed. However, in the method for forming the first structural part 11a, in addition to the slot holes 112, the rotating shaft insertion holes 111 and the like are also cut as cutting portions. Therefore, even in the cutting portions other than the slot holes 112, the spacing between the electromagnetic steel sheets 12 is 0.2 mm or less, and burrs 123 are formed in at least a part of the space between the electromagnetic steel sheets 12 facing the cutting portions. In this way, in the cutting portions of the electromagnetic steel sheets 12, which are metal plates constituting the first structural part 11a, the burrs 123 formed by cutting occupy a part of the space between the electromagnetic steel sheets 12, forming an insertion suppression structure that reduces or closes the gap 125 between adjacent electromagnetic steel sheets 12 at the position facing the slot holes 112. The insertion suppression structure is a structure that suppresses the insertion 66b of molten metal 65 into the space between the electromagnetic steel sheets 12 during die casting or casting.

[0026] The thickness of the first structural part 11a is sufficient if it is made of two or more sheets of electromagnetic steel 12. As will be described later, the first structural part 11a is formed by stacking and processing multiple sheets of electromagnetic steel 12, so the thickness is less than or equal to the maximum number of sheets that can be processed by each processing method. For example, when the first structural part 11a is formed using press working, the thickness is in the range of two to five sheets of electromagnetic steel 12, and when the first structural part 11a is formed using laser processing, the thickness is two to 10 mm. In Embodiment 1, the same material as the electromagnetic steel sheet 12 of the second structural part 11b is used for the electromagnetic steel sheet 12 that constitutes the first structural part 11a.

[0027] As described above, in the squirrel-cage rotor 10A according to Embodiment 1, in the laminated core 11, the spacing between the electromagnetic steel sheets 12 of the first structural part 11a near the end ring portion 14 is narrower than the spacing between the electromagnetic steel sheets 12 of the second structural part 11b near the central portion. More specifically, the spacing between the electromagnetic steel sheets 12 of the first structural part 11a at the position facing the slot hole 112 is narrower than the spacing between the electromagnetic steel sheets 12 of the second structural part 11b, and is 0.2 mm or less. In other words, the first structural part 11a has an insertion suppression structure that makes the spacing between the electromagnetic steel sheets 12 0.2 mm or less.

[0028] As described above, by providing first structural parts 11a having insertion suppression structures at both axial ends of the laminated core 11, the insertion 66b of molten aluminum or aluminum alloy 65 into the first structural parts 11a during aluminum die casting can be suppressed. Furthermore, as shown in the enlarged view of Figure 10, the possibility of insertion 66b of molten aluminum or aluminum alloy 65 into the first structural parts 11a can be reduced, so the thickness d0 of the end ring portion 14 formed on the first structural parts 11a does not vary depending on the location. Therefore, damage to the squirrel-cage rotor 10A during rotation of the squirrel-cage rotor 10A and losses in induction motors using the squirrel-cage rotor 10A are suppressed.

[0029] In the above explanation, the same electromagnetic steel sheet 12 is used for the first structural part 11a and the second structural part 11b of the laminated core 11. This indicates that, in a cross-section perpendicular to the lamination direction, the number, position, shape, and size of the openings 122 in the metal sheet constituting the first structural part 11a are the same as the number, position, shape, and size of the openings 122 in the electromagnetic steel sheet 12 constituting the second structural part 11b. However, the electromagnetic steel sheet 12 used in the first structural part 11a and the electromagnetic steel sheet 12 used in the second structural part 11b may be different. In one example, in a cross-section perpendicular to the lamination direction, the number, position, and shape of the openings 122 in the metal sheet constituting the first structural part 11a are the same as the number, position, and shape of the openings 122 in the electromagnetic steel sheet 12 constituting the second structural part 11b, but the size of the openings 122 in the metal sheet constituting the first structural part 11a may be different from the size of the openings 122 in the electromagnetic steel sheet 12 constituting the openings 122. In this case, the size is set so that adjacent openings 122 do not communicate with each other. Furthermore, in the first structural part 11a, the openings 122 of each metal plate are the same size, and in the second structural part 11b, the openings 122 of each electromagnetic steel sheet 12 are the same size. As described above, the openings 122 of the metal plates constituting the first structural part 11a and the openings 122 of the electromagnetic steel sheets 12 constituting the second structural part 11b can be said to have similar shapes. This is also true in embodiments 2 and 3 described later.

[0030] Next, a method for manufacturing a squirrel-cage rotor 10A according to Embodiment 1 will be described. Figure 11 is a flowchart showing an example of the procedure for manufacturing a squirrel-cage rotor according to Embodiment 1. Figures 12 to 15 show examples of the procedure for manufacturing a squirrel-cage rotor according to Embodiment 1. Figure 13 is an enlarged view of region R5 in Figure 12, and Figure 15 is an enlarged view of region R6 in Figure 14. In Embodiment 1, the electromagnetic steel sheet 12 constituting the first structural part 11a near the end face of the laminated core 11 and the electromagnetic steel sheet 12 constituting the other second structural part 11b are formed separately. In other words, the method for manufacturing a squirrel-cage rotor 10A according to Embodiment 1 includes a insertion suppression structure formation step (step S11), an electromagnetic steel sheet formation step (step S12), a laminate formation step (step S13), and a secondary conductor forming step (step S14).

[0031] In step S11, the insertion suppression structure formation process, a metal plate is formed having an insertion suppression structure that suppresses the insertion 66b of molten metal 65 into the gaps between the electromagnetic steel sheets 12 during die casting, and having an opening 121 into which a rotating shaft is inserted, and an opening 122 corresponding to a slot hole 112. In the insertion suppression structure formation process of Embodiment 1, a first structural part 11a having an insertion suppression structure is formed by laminating and processing a plurality of electromagnetic steel sheets 12 as a metal plate. In the insertion suppression structure formation process, an annular electromagnetic steel sheet 12 is formed by stacking a plurality of flat electromagnetic steel sheets 12. The opening 121 of the first structural part 11a corresponds to a third opening, and the opening 122 corresponds to a fourth opening.

[0032] Figures 12 and 13 show an example of forming an electromagnetic steel sheet 12 using press working. As shown in Figure 12, multiple flat electromagnetic steel sheets 12 are stacked and placed between the lower die 51 and the upper die 52 of a press mold 50, and the electromagnetic steel sheets 12 are sandwiched between the upper die 52 and the lower die 51 and pressure is applied. This forms a first structural part 11a having an insertion suppression structure in which multiple annular electromagnetic steel sheets 12 are stacked. Note that the number of electromagnetic steel sheets 12 processed at one time is between two and five.

[0033] Warps 124 are generated in the press-formed annular-shaped electromagnetic steel sheet 12. Since multiple stacked electromagnetic steel sheets 12 are press-formed at once to form the first structural part 11a, the shape and position of the warps 124 of each electromagnetic steel sheet 12 constituting the first structural part 11a generated during manufacturing tend to be similar to those of electromagnetic steel sheets 12 above or below. For this reason, as shown in Figure 3, the spacing between the electromagnetic steel sheets 12 can be made smaller, specifically 0.2 mm or less, compared to the case where multiple electromagnetic steel sheets 12 are individually press-formed and then stacked. Also, when processed by the press die 50, burrs 123 are generated at the cut portions, such as the opening 121 that constitutes the rotating shaft insertion hole 111 and the opening 122 that constitutes the slot hole 112, as shown in the enlarged view of Figure 13. The burrs 123 make the spacing between the electromagnetic steel sheets 12 at the cut portions even smaller than the spacing between the electromagnetic steel sheets 12 in the parts without burrs 123, or eliminate the gap 125.

[0034] The first structural part 11a can also be formed by laser processing instead of press processing. Figure 14 shows an example of forming an electromagnetic steel sheet 12 using laser processing. As shown in Figure 14, multiple electromagnetic steel sheets 12 are stacked on the stage 71 of the laser processing apparatus 70. The electromagnetic steel sheets 12 processed at one time are two or more sheets, up to 10 mm thick. This is because laser processing becomes difficult when the stacked electromagnetic steel sheets 12 exceed 10 mm in thickness.

[0035] Next, while irradiating the stacked electromagnetic steel sheets 12 with laser light L from the laser processing head 72, the position of the laser processing head 72 is moved relative to the stacked electromagnetic steel sheets 12 to perform laser processing that cuts at predetermined positions. When the laser light L is irradiated, although not shown, gas such as nitrogen or argon is sprayed into the area including the irradiation position of the laser light L. This blows away the molten material generated by the irradiation of the laser light L. Here, the stacked electromagnetic steel sheets 12 are processed to have a circular external shape, and openings 121 corresponding to the rotation shaft insertion hole 111 and openings 122 corresponding to the slot hole 112 are formed. This forms a first structural part 11a in which multiple annular-shaped electromagnetic steel sheets 12 are stacked.

[0036] As shown in the enlarged view of Figure 15, waviness 124 occurs in the laser-processed annular-shaped electromagnetic steel sheet 12. Since multiple stacked electromagnetic steel sheets 12 are laser-processed at once, the position where the laser beam L strikes, i.e., the way heat enters due to the irradiation of the laser beam L, is the same for all multiple stacked electromagnetic steel sheets 12, so the temperature distribution on each electromagnetic steel sheet 12 is similar to some extent. For this reason, it is thought that the thermal deformation on each electromagnetic steel sheet 12 will also show the same trend. Furthermore, when multiple stacked electromagnetic steel sheets 12 are laser-processed at once, the gas blowing position is also the same for all multiple stacked electromagnetic steel sheets 12, so the deformation trend due to the force received from the gas will also be similar for each electromagnetic steel sheet 12. For this reason, the shape and position of the waviness 124 of each electromagnetic steel sheet 12 constituting the first structural part 11a that occurs during laser processing will show the same trend as that of the electromagnetic steel sheet 12 above or below it. Furthermore, when laser processing is performed, burrs 123 are generated at the cut portions, such as the opening 121 that constitutes the rotating shaft insertion hole 111 and the opening 122 that constitutes the slot hole 112. Due to the burrs 123, the spacing between the electromagnetic steel sheets 12 at the cut portion becomes smaller than the spacing between the electromagnetic steel sheets 12 in the parts without burrs 123, or the gap 125 disappears.

[0037] Here, an example of forming the first structural part 11a by press working and laser processing has been described, but the method of forming the first structural part 11a is not limited to these. In one example, the first structural part 11a may be formed by other cutting methods such as electrical discharge machining or water jet cutting. As described above, in the insertion suppression structure formation step S11, by performing a cutting process such as press working or laser processing on multiple electromagnetic steel sheets 12 at once while the multiple electromagnetic steel sheets 12 are stacked on top of each other, the shape and positional tendency of the undulations 124 that occur on each electromagnetic steel sheet 12 can be aligned. As a result, the gap 125 between the electromagnetic steel sheets 12 in the region facing the slot hole 112 is reduced. As a result, insertion 66b of molten metal 65 into the gaps between the electromagnetic steel sheets 12 during die casting or casting is suppressed.

[0038] Returning to Figure 11, in the electromagnetic steel sheet forming step S12, one annular electromagnetic steel sheet 12 is formed, each having an opening 121 into which the rotating shaft is inserted and an opening 122 corresponding to the slot hole 112. In the electromagnetic steel sheet forming step, the electromagnetic steel sheets 12 constituting the second structural part 11b are formed. The electromagnetic steel sheets 12 constituting the second structural part 11b are obtained by cutting them using a general method, as shown in Figure 3. One example of a general method is press working, which cuts the electromagnetic steel sheets 12 one by one. The opening 121 of the electromagnetic steel sheet 12 of the second structural part 11b corresponds to the first opening, and the opening 122 corresponds to the second opening. Note that the electromagnetic steel sheet forming step is the same as the method for forming the electromagnetic steel sheets 12 in the general manufacturing method of the squirrel-cage rotor 10A described in Figure 3, so a detailed explanation is omitted.

[0039] The order of the insertion-restricting structure formation step in step S11 and the electrical steel sheet formation step in step S12 is not limited. They may be performed in the order of insertion-restricting structure formation step and electrical steel sheet formation step, or in the order of electrical steel sheet formation step and insertion-restricting structure formation step. Alternatively, the insertion-restricting structure formation step and electrical steel sheet formation step may be performed simultaneously.

[0040] In the laminate formation step S13, a metal plate having an insertion-suppressing structure, a plurality of electromagnetic steel sheets 12, and another metal plate having an insertion-suppressing structure are stacked to form a laminate having a rotating shaft insertion hole 111 in which the opening 121 of the electromagnetic steel sheet 12 and the opening 121 of the metal plate are connected in the stacking direction, and a slot hole 112 in which the opening 122 of the electromagnetic steel sheet 12 and the opening 122 of the metal plate are connected in the stacking direction. In the laminate formation step of Embodiment 1, a laminated core 11 is formed using a first structural part 11a formed in the insertion-suppressing structure formation step and electromagnetic steel sheets 12 formed in the electromagnetic steel sheet formation step. In Figures 5 and 6, the laminated core 11 is completed by stacking in the order of a first structural part 11a in which a plurality of electromagnetic steel sheets 12 are stacked, a plurality of electromagnetic steel sheets 12 formed in the electromagnetic steel sheet formation step, and a first structural part 11a in which a plurality of electromagnetic steel sheets 12 are stacked. Multiple electromagnetic steel sheets 12 sandwiched between the first structural part 11a form the second structural part 11b. Since the electromagnetic steel sheets 12 constituting the second structural part 11b are laminated one by one with undulations 124, the spacing between the electromagnetic steel sheets 12 constituting the second structural part 11b is larger than the spacing between the electromagnetic steel sheets 12 constituting the first structural part 11a. In the laminate formation process, the electromagnetic steel sheets 12 are laminated so that the phases of the opening 121 which will become the rotation shaft insertion hole 111 provided in the center of the electromagnetic steel sheet 12 and the opening 122 which will become the slot hole 112 provided on the outer circumference of the opening 121 are aligned.

[0041] In the secondary conductor forming process of step S14, a secondary conductor having a slot bar portion 13 is formed by die casting or casting, filling the slot holes 112 of the laminate with molten aluminum or aluminum alloy 65 and solidifying it. In one example, the laminated core 11 is placed in a mold 60 and aluminum die casting is performed to form a secondary conductor having an end ring portion 14 and a slot bar portion 13 at a predetermined position on the laminated core 11. Specifically, the laminated core 11 is placed in a mold 60 installed in a die casting machine, and molten aluminum or aluminum alloy 65 is injected with the mold 60 closed. As shown in Figure 5, the molten metal 65 is filled in the runner forming portion of the mold 60, one end ring forming portion 61, the slot bar forming portion 63, and the other end ring forming portion 62 in that order. Then, as the filled molten aluminum or aluminum alloy 65 solidifies and cools, a secondary conductor in which a pair of end ring portions 14 and a slot bar portion 13 are integrated is formed on the laminated core 11. Here, aluminum die casting is shown as an example of casting, but the same principles apply to other types of casting.

[0042] At this time, since there is a first structural part 11a at both ends of the laminated core 11 in which the gap 125 between the electromagnetic steel sheets 12 is 0.2 mm or less, the occurrence of insertion 66b of molten aluminum or aluminum alloy 65 into the gaps between the electromagnetic steel sheets 12 due to pressurization is suppressed. Since the gap between the electromagnetic steel sheets 12 in the first structural part 11a is 0.2 mm or less, even if there are two electromagnetic steel sheets 12 constituting the first structural part 11a, the insertion 66b of molten metal 65 into the gaps between the electromagnetic steel sheets 12 in the first structural part 11a is suppressed. As a result, the occurrence of peeling defects 67 as shown in the enlarged view of Figure 8 is suppressed, and as shown in the enlarged view of Figure 10, it is possible to maintain the thickness of the end ring portion 14 at a desired thickness d0 over the entire surface perpendicular to the lamination direction of the laminated core 11. With this, the manufacturing method of the squirrel-cage rotor 10A is completed.

[0043] The electromagnetic steel sheet 12 constituting the first structural part 11a may be the same as the electromagnetic steel sheet 12 of the second structural part 11b, or it may be a metal sheet made of a magnetic material such as steel.

[0044] Here, the effect will be described. In the technology described in Patent Document 1, an adhesive is used to bond a plurality of electromagnetic steel sheets 12 to each other to address the curling defect 67 of the electromagnetic steel sheets 12. In the technology described in Patent Document 1, since the temperature of the molten metal is high during manufacturing by die casting, the adhesive strength decreases, or gas defects occur due to gasification of the adhesive. In contrast, the squirrel-cage rotor 10A according to the first embodiment includes: a laminated core 11 including a laminated body having a rotating shaft insertion hole 111 in which a plurality of electromagnetic steel sheets 12 are laminated and a rotating shaft is inserted into the center, and a plurality of slot holes 112 penetrating in the lamination direction of the electromagnetic steel sheets 12; and a secondary conductor. The secondary conductor has an end ring portion 14 and a slot bar portion 13. The end ring portions 14 are provided so as to be in contact with both end portions of the laminated core 11 in the lamination direction of the electromagnetic steel sheets 12. The slot bar portion 13 is provided inside the plurality of slot holes 112 and connected to the two end ring portions 14. The laminated core 11 has two first structural portions 11a provided at both end portions in the lamination direction, and a second structural portion 11b sandwiched between the two first structural portions 11a and having a plurality of electromagnetic steel sheets 12 laminated therein, and the first structural portion 11a has a structure different from that of the second structural portion 11b. This provides an effect that the curling defect 67 of the electromagnetic steel sheets 12 near the end ring portion 14 can be suppressed compared to the conventional art. In particular, the curling defect 67 of the electromagnetic steel sheets 12 near the end ring portion 14 can be suppressed compared to the technology described in Patent Document 1 without bonding the electromagnetic steel sheets 12 to each other using an adhesive. Furthermore, since no adhesive is used unlike the technology described in Patent Document 1, there is no need to consider a decrease in adhesive strength, and no gas defects occur.

[0045] In the squirrel-cage rotor 10A according to Embodiment 1, the peeling defects 67 of the electromagnetic steel sheet 12 near the end ring portion 14 can be suppressed compared to conventional methods without applying silicon oxide paint to the inside of the slot holes 112 of the laminated core 11, as in the technology described in Patent Document 1. Furthermore, as in the technology described in Patent Document 1, there is no need to apply silicon oxide paint to the inside of the slot holes 112 of the laminated core 11. In other words, the peeling defects 67 can be suppressed compared to conventional methods without creating work that is difficult to perform, such as applying paint uniformly to the inside of the slot holes 112 of the laminated core 11. Moreover, in the technology described in Patent Document 1, there was a problem that if too much silicon oxide paint was applied to the inside of the slot holes 112 of the laminated core 11 and die casting was performed in an insufficiently dry state, gas defects would occur. However, in the squirrel-cage rotor 10A according to Embodiment 1, since silicon oxide paint is not applied to the inside of the slot holes 112 of the laminated core 11, gas defects do not occur.

[0046] Furthermore, the possibility of the thickness of the end ring portion 14 decreasing due to peeling defects 67 caused by the insertion 66b of molten aluminum or aluminum alloy 65 is reduced, making it possible to set the thickness of the end ring portion 14 at the position overlapping with the first structural portion 11a to the desired thickness d0. In other words, the end ring portion 14 can maintain the desired thickness d0 at any position overlapping with the first structural portion 11a, thereby reducing the possibility of breakage during the rotation of the squirrel-cage rotor 10A and reducing losses.

[0047] Furthermore, burrs 123 are formed on the cut portion of the electromagnetic steel sheet 12 of the first structural part 11a, and there are portions where the gap between the electromagnetic steel sheets 12 is 0.2 mm or less. Also, burrs 123 of adjacent electromagnetic steel sheets 12 in the stacking direction may come into contact with each other and block a portion of the gap 125 between the electromagnetic steel sheets 12 at a position facing the slot hole 112. When the space between two electromagnetic steel sheets 12 is blocked by burrs 123, an insulating film remains on the burrs 123, so no current flows between the two contacting burrs 123. For this reason, the area over which current flows is smaller compared to the case where the insertion suppression structure is made of a thick plate, as in Embodiment 2 described later. As a result, losses can be suppressed. In addition, the end ring portion 14 and the slot bar portion 13 are integrally molded from the same material. In other words, the end ring portion 14 and the slot bar portion 13 are integrated without an interface. Therefore, compared to the case where the insertion suppression structure is integrated with the end ring portion 14, as in Embodiment 4 described later, electrical losses when current flows through the secondary conductor can be reduced.

[0048] The method for manufacturing a squirrel-cage rotor 10A according to Embodiment 1 includes an electromagnetic steel sheet forming step, an insertion suppression structure forming step, a laminated body forming step, and a die casting step. In the electromagnetic steel sheet forming step, annular electromagnetic steel sheets 12 each having a first opening into which a rotating shaft is inserted and a second opening corresponding to the slot hole 112 are formed one by one. In the insertion suppression structure forming step, a metal plate is formed, which has an insertion suppression structure that suppresses insertion 66b of the molten metal 65 between the metal plates during die casting, and has a third opening into which the rotating shaft is inserted and a fourth opening corresponding to the slot hole 112. In the laminated body forming step, a metal plate having the insertion suppression structure, a plurality of electromagnetic steel sheets 12, and another metal plate having the insertion suppression structure are laminated to form a laminated body having a rotating shaft insertion hole 111 formed by the first opening and the third opening communicating in the lamination direction, and a slot hole 112 formed by the second opening and the fourth opening communicating in the lamination direction. In the die casting step, molten 65 of aluminum or aluminum alloy is filled into the slot holes 112 of the laminated body by die casting, and a secondary conductor having solidified slot bar portions 13 is molded. This suppresses turning-over defects 67 caused by insertion 66b of the molten aluminum or aluminum alloy 65 during pressure filling in die casting, thereby reducing costs due to quality loss, that is, the cost required for remanufacturing the squirrel-cage rotor 10A. In addition, productivity is improved by reducing the man-hours required for remanufacturing the squirrel-cage rotor 10A.

[0049] Furthermore, when the first structural part 11a is formed by press working, it is composed of two to five electromagnetic steel sheets 12, and when it is formed by laser processing, it is composed of two or more electromagnetic steel sheets 12 with an overall thickness of 10 mm or less. Also, the spacing between the electromagnetic steel sheets 12 of the first structural part 11a is 0.2 mm or less. This suppresses the occurrence of insertion 66b of molten aluminum or aluminum alloy 65 at positions facing the slot holes 112 of the first structural part 11a during the die-casting process. As a result, the possibility of the thickness of the end ring portion 14 being reduced due to peeling defects 67 caused by the insertion 66b of molten metal 65 is reduced. As a result, the thickness d0 of the end ring portion 14 at positions overlapping with the first structural part 11a can be set to the desired thickness. That is, the end ring portion 14 can maintain the desired thickness d0 at any position overlapping with the first structural part 11a, and the possibility of breakage during the rotation of the squirrel-cage rotor 10A can be reduced. Furthermore, the end ring portion 14 will have a uniform thickness, and compared to the case where peeling defects 67 occur and the thickness of a part of the end ring portion 14 becomes smaller, the volume through which current can flow increases, and losses can be reduced.

[0050] Embodiment 2. Figure 16 is a schematic cross-sectional view showing an example of the configuration of a squirrel-cage rotor according to Embodiment 2, and Figure 17 is an enlarged view of region R7 in Figure 16. Components identical to those described in Figures 1, 9, and 10 are denoted by the same reference numerals, and their descriptions are omitted. In the squirrel-cage rotor 10B according to Embodiment 2, the first structural part 11a is composed of a single thick plate 113, which is a metal plate thicker than the electromagnetic steel sheet 12 of the second structural part 11b. As the thick plate 113, electromagnetic steel sheet 12, steel material, magnetic material having strength greater than or equal to that of an aluminum alloy, etc., can be used. Furthermore, the first structural part 11a, i.e., the thick plate 113, is at least twice the thickness of the electromagnetic steel sheet 12 of the second structural part 11b, and has a thickness of 5% or less of the total length of the laminated core 11. The reason for setting the thickness to 5% or less of the total length of the laminated core 11 will now be explained. If adjacent electromagnetic steel sheets 12 in the lamination direction that constitute the second structural part 11b are in electrical contact with each other, an excess current flows in the lamination direction, leading to losses. In an induction motor using a squirrel-cage rotor 10B, the thickness of the thick plate 113, determined from the losses due to contact between electromagnetic steel sheets 12 that are permissible to obtain the specified performance, is 5% of the total length of the laminated core 11.

[0051] Thus, the first structural part 11a is made of a thick plate 113, and since there is no gap 125 between the electromagnetic steel sheets 12 in the inner wall of the slot hole 112 as in the conventional method, insertion 66b due to the pressurization of molten aluminum or aluminum alloy 65 does not occur. For this reason, the uniformity of the thickness d0 of the end ring portion 14 in the portion overlapping with the first structural part 11a can be maintained.

[0052] The method for manufacturing such a squirrel-cage rotor 10B is the same as that described in Embodiment 1, so the differences from Embodiment 1 will be explained. In step S11, the insertion suppression structure formation step, in one example, a thick plate 113 is formed by processing methods such as press working, laser processing, or cutting. As described above, the thick plate 113 is at least twice the thickness of the electromagnetic steel sheet 12 of the second structural part 11b, and has a thickness of 5% or less of the total length of the laminated core 11.

[0053] In the laminate formation process of step S13, a laminated core 11 is formed using the thick plate 113 of the first structural part 11a and the electromagnetic steel sheet 12 of the second structural part 11b. That is, the laminated core 11 is completed by laminating the thick plate 113 of the first structural part 11a, the electromagnetic steel sheet 12 of the second structural part 11b, and the thick plate 113 of the first structural part 11a in that order.

[0054] In the squirrel-cage rotor 10B according to Embodiment 2, the first structural part 11a is made of a thick metal plate 113 that is thicker than the electromagnetic steel sheet 12 of the second structural part 11b. As a result, peeling defects 67 caused by the insertion 66b of molten aluminum or aluminum alloy 65 during pressurized filling of die casting do not occur in the first structural part 11a, thus reducing costs due to quality loss. In addition, productivity is improved by reducing the number of man-hours required to remake the squirrel-cage rotor 10B.

[0055] Furthermore, since the thickness d0 of the end ring portion 14 is not reduced by peeling defects 67 caused by the insertion 66b of molten aluminum or aluminum alloy 65, the thickness d0 of the end ring portion 14 at the position overlapping with the first structural portion 11a can be set to the desired thickness. In other words, the end ring portion 14 can maintain the desired thickness d0 at any position overlapping with the first structural portion 11a, thereby reducing the possibility of breakage during the rotation of the squirrel-cage rotor 10B and reducing losses.

[0056] In Embodiment 2, an example was described in which the first structural part 11a is made of a single thick plate 113, but Embodiments 1 and 2 may be combined. In other words, the first structural part 11a may be made of two or more metal plates that are thicker than the electromagnetic steel sheet 12 of the second structural part 11b. Figure 18 is a partial cross-sectional view showing another example of the configuration of a squirrel-cage rotor according to Embodiment 2. Figure 18 shows an enlarged cross-sectional view of a part of the vicinity of the slot bar portion 13 of one of the first structural parts 11a. In the squirrel-cage rotor 10C shown in Figure 18, the first structural part 11a consists of two thick plates 114 that are thicker than the electromagnetic steel sheet 12 of the second structural part 11b. Note that Figure 18 is just one example, and the first structural part 11a may consist of three or more thick plates 114.

[0057] By making the first structural part 11a a plurality of thick plates 114 in this way, the thickness of each thick plate 114 is reduced compared to the cases in Figures 16 and 17, so that the current loss in the entire first structural part 11a when the squirrel-cage rotor 10B is applied to an induction motor can be reduced.

[0058] In the manufacturing method of the squirrel-cage rotor 10B according to Embodiment 2, the insertion suppression structure formation step is performed by forming a thick plate 114 using a processing method such as press working, laser processing, or cutting. In the die-casting process, there is no gap 125 into which molten aluminum or aluminum alloy 65 can be inserted in the first structural portion 11a near both ends in the axial direction of the laminated core 11, thus reducing the possibility of peeling defects 67 compared to Embodiment 1. Furthermore, the end ring portion 14 and the slot bar portion 13 are integrally molded from the same material. In other words, the end ring portion 14 and the slot bar portion 13 are integrated without any interface. Therefore, compared to the case where the insertion suppression structure is integrally configured with the end ring portion 14 as in Embodiment 4 described later, electrical losses when current flows through the secondary conductor can be reduced.

[0059] Embodiment 3. Figure 19 is a schematic cross-sectional view showing an example of the configuration of a squirrel-cage rotor according to Embodiment 3. Figure 20 is an enlarged view of region R8 in Figure 19. Figure 21 is a top view showing an example of the configuration of electromagnetic steel sheets used in the squirrel-cage rotor according to Embodiment 3. Figure 21 shows a plane perpendicular to the lamination direction. Note that the same reference numerals are used for components that are the same as those described in Figures 1, 9 and 10, and their descriptions are omitted. In the squirrel-cage rotor 10F according to Embodiment 3, the first structural part 11a has electromagnetic steel sheets 12 which are a plurality of metal plates, and a sealing material 115 which is arranged on the laminated surfaces of the plurality of electromagnetic steel sheets 12. The sealing material 115 is provided between adjacent electromagnetic steel sheets 12 in the lamination direction.

[0060] As shown in Figure 21, the electromagnetic steel sheet 12 has an opening 121 in the center that constitutes the rotation shaft insertion hole 111 of the laminated core 11, and a plurality of openings 122 that are arranged at predetermined intervals along the circumferential direction on the outer circumference of the opening 121 and constitute the slot hole 112 of the laminated core 11. In Embodiment 3, a sealing material 115 is placed between adjacent openings 122. This structure suppresses the formation of bridges during aluminum die casting or casting. Here, an example is given in which the plurality of metal plates constituting the first structural part 11a are electromagnetic steel sheets 12, but the metal plates may be made of steel material, magnetic material having a strength greater than or equal to that of aluminum alloy, etc.

[0061] In Figure 21, the sealing material 115 is arranged to surround the opening 122, but the embodiment is not limited to this. Figure 22 is a top view showing another example of the configuration of the electromagnetic steel sheet used in the squirrel-cage rotor according to Embodiment 3. As shown in Figure 22, the sealing material 115 may be arranged radially from the center toward the circumference so as to pass between adjacent openings 122.

[0062] Thus, the squirrel-cage rotor 10F according to Embodiment 3 is characterized in that a sealing material 115 is placed on the laminated surfaces of the electromagnetic steel sheets 12, which are metal plates constituting the first structural part 11a. The sealing material 115 is applied directly to the laminated surfaces of the electromagnetic steel sheets 12 and plays a role in reducing or closing the gaps 125 between the electromagnetic steel sheets 12.

[0063] As the sealing material 115, an inorganic material such as a ceramic filler or heat-resistant inorganic paste that does not generate volatile gases even when exposed to high-temperature molten metal 65, which is a secondary conductor in a molten state, in one example, molten metal 65 at approximately 650°C, is used. This suppresses the insertion 66b of the molten metal 65 during the secondary conductor molding process, thereby suppressing peeling and defects caused by molten metal intrusion.

[0064] Furthermore, the sealing material 115 is placed between the electrical steel sheets 12 of the first structural part 11a. Specifically, the sealing material 115 is positioned so that the molten metal 65 leaking from the slot hole 112 does not come into contact with the molten metal 65 in the adjacent slot hole 112. This blocks the leakage path of the molten metal 65, suppressing short circuits and defects caused by the intrusion of molten metal.

[0065] The manufacturing method for this squirrel-cage rotor 10F is the same as that described in Embodiment 1, so the differences from Embodiment 1 will be explained. In the insertion-restricting structure formation step S11, a plurality of metal plates are formed, each having an opening 121 into which the rotating shaft is inserted and an opening 122 corresponding to a slot hole 112. The metal plates are formed by processing methods such as press working, laser processing, and cutting. In the insertion-restricting structure formation step S11, a sealing material 115 is applied to the surfaces on which the metal plates are stacked, and the plurality of metal plates are stacked. The sealing material 115 is applied to the area between adjacent slot holes 112, so that even if molten metal 65 leaks from the slot holes 112 in the subsequent secondary conductor forming step, it will not come into contact with the molten metal 65 in the adjacent slot holes 112. In other words, the sealing material 115 is applied so as to separate the adjacent slot holes 112 of the formed metal plates. Specifically, even if molten metal 65 leaks from the opening 122 during the secondary conductor forming process, the sealing material 115 is placed in the region between adjacent openings 122 of the metal plate so that it does not come into contact with the molten metal 65 of the adjacent opening 122. The sealing material 115 is a material that does not generate volatile gases even when exposed to high-temperature molten metal 65. In this example, an annular-shaped electrical steel plate 12 is formed as multiple metal plates. In this way, the first structural part 11a having an insertion suppression structure is formed. The subsequent processing is the same as the processing from step S12 onwards in Figure 11.

[0066] This example is just one example, and the squirrel-cage rotor 10F may be manufactured by other methods. In one example, in the insertion-restricting structure formation step S11, a plurality of metal plates are formed, each having an opening 121 into which the rotating shaft is inserted and an opening 122 corresponding to the slot hole 112. Then, in the laminate formation step S13, a sealing material 115 is applied to the metal plates, and the plurality of metal plates are laminated together to form the first structural part 11a.

[0067] In the squirrel-cage rotor 10F according to Embodiment 3, the first structural part 11a has a plurality of metal plates and a sealing material 115 arranged on the laminated surfaces of the plurality of metal plates. This suppresses the insertion 66b of molten metal 65 in the secondary conductor forming process, thereby suppressing peeling and defects caused by molten metal intrusion.

[0068] Furthermore, the sealing material 115 reduces or closes the gap 125 between the metal plates, is positioned in the region between the openings 122 corresponding to the slot holes 112 formed in the metal plates, and is made of a material that does not generate volatile gases even at the melting temperature of the secondary conductor. This blocks the leakage path of the molten metal 65, suppressing short circuits and defects caused by the intrusion of molten metal.

[0069] Embodiment 4. Figure 23 is a schematic cross-sectional view showing an example of the configuration of a squirrel-cage rotor according to Embodiment 4, and Figure 24 is an enlarged view of region R9 in Figure 23. Components identical to those described in Figures 1, 9, and 10 are denoted by the same reference numerals, and their descriptions are omitted. In the squirrel-cage rotor 10D according to Embodiment 4, the laminated core 11 has a configuration in which multiple electromagnetic steel sheets 12 are laminated, similar to the conventional configuration. That is, the laminated core 11 does not have a first structural part 11a and a second structural part 11b, as in Embodiments 1 and 2. Furthermore, it has a third structural part 14a made of a metal plate thicker than the electromagnetic steel sheets 12 of the laminated core 11, and a fourth structural part 14b arranged in contact with the third structural part 14a and integrally formed with the slot bar part 13. The fourth structural part 14b is formed by aluminum die casting or casting.

[0070] The third structural part 14a is an annular metal plate having an opening 141a in the center through which a rotating shaft can be inserted. The third structural part 14a has the same structure as the electromagnetic steel sheet 12. That is, the third structural part 14a has an opening 141a in the center into which a rotating shaft is inserted, and a plurality of openings 142a arranged at predetermined intervals along the circumferential direction on the outer circumference of the opening 141a, and provided at positions corresponding to the slot holes 112 of the laminated core 11. The diameter of the opening 141a is greater than or equal to the diameter of the opening 122 which becomes the rotating shaft insertion hole 111 of the electromagnetic steel sheet 12, and less than the diameter of the opening 141 of the fourth structural part 14b of the end ring part 14. The material of the third structural part 14a can be any metal material that has an electrical conductivity greater than or equal to the electrical conductivity of the electromagnetic steel sheet 12, such as aluminum, aluminum alloy, or copper alloy, and has a strength greater than or equal to the strength of the aluminum alloy, the same as the end ring part 14. In the example shown in Figure 23, the end ring portion 14 is formed by the third structural portion 14a and the fourth structural portion 14b.

[0071] The thickness of the third structural part 14a is equal to or greater than two sheets of the electromagnetic steel sheet 12 of the laminated core 11, and is less than or equal to the height of the end ring portion 14. Figure 25 is a schematic cross-sectional view showing another example of the configuration of a squirrel-cage rotor according to Embodiment 4. In the squirrel-cage rotor 10E of Figure 25, a case is shown in which the end ring portion 14 is composed only of the third structural part 14a. In such a case, the height of the third structural part 14a becomes the height of the end ring portion 14. Note that one end ring portion 14 may be composed of the third structural part 14a and the fourth structural part 14b as shown in Figure 23, and the other end ring portion 14 may be composed only of the third structural part 14a as shown in Figure 25.

[0072] As shown in Figure 23, in the end ring portion 14 composed of a third structural portion 14a and a fourth structural portion 14b, although the third structural portion 14a is made of a material with high electrical conductivity, a contact interface exists between the third structural portion 14a and the fourth structural portion 14b, resulting in contact resistance. Therefore, current loss occurs in the end ring portion 14. On the other hand, as shown in Figure 25, in the end ring portion 14 composed only of the third structural portion 14a, since it is made of a single material, there is no contact interface as in the case of Figure 23. Therefore, the occurrence of loss can be suppressed compared to the case of Figure 23.

[0073] Thus, a third structural part 14a, which is a thick plate with almost the same shape as the electromagnetic steel sheet 12, is installed in the portion of the end ring part 14 that is in contact with the laminated core 11. Since there is no gap 125 in the inner wall of the opening 142a corresponding to the slot hole 112 of the thick plate, the insertion 66b due to the pressurization of molten aluminum or aluminum alloy 65 can be suppressed.

[0074] The manufacturing method for these squirrel-cage rotors 10D and 10E is the same as that described in Embodiment 1, so the differences from Embodiment 1 will be explained. In step S11, the insertion-restricting structure formation step, the third structural part 14a of the end ring portion 14 is formed. In the insertion-restricting structure formation step, in one example, a thick plate is formed by a processing method such as press working, laser processing, or cutting. As described above, the thick plate is at least twice the thickness of the electromagnetic steel sheet 12 of the laminated core 11 and is less than or equal to the height of the end ring portion 14. In addition, the same aluminum or aluminum alloy as the end ring portion 14 may be used as the thick plate, or a different metal plate such as a copper alloy may be used.

[0075] In the laminate formation process of step S13, a laminate is formed by combining the laminated core 11 and the third structural part 14a, which is part of the end ring portion 14, using the electromagnetic steel sheet 12 and the third structural part 14a. Here, a laminate combining the laminated core 11 and the third structural part 14a is formed by laminating the thick plate of the third structural part 14a, the electromagnetic steel sheet 12, and the thick plate of the third structural part 14a in that order. The third structural part 14a becomes the end ring portion 14, and the electromagnetic steel sheet 12 becomes the laminated core 11. At this time, the third structural part 14a and the electromagnetic steel sheet 12 are laminated so that the phase of the opening 141a in the center of the thick plate of the third structural part 14a and the opening 121 in the center of the electromagnetic steel sheet 12, and the phase of the opening 142a corresponding to the slot hole 112 in the thick plate of the third structural part 14a and the opening 122 corresponding to the slot hole 112 in the electromagnetic steel sheet 12 are aligned. Subsequently, as described in Embodiment 1, the secondary conductor forming process of step S14 is carried out. When manufacturing the squirrel-cage rotor 10E of Figure 25, a mold 60 without end ring forming sections 61 and 62 is used so that the fourth structural section 14b is not formed. Through this process, the squirrel-cage rotors 10D and 10E according to Embodiment 4 are manufactured.

[0076] The squirrel-cage rotors 10D and 10E according to Embodiment 4 include a laminated core 11 having a laminate in which a plurality of electromagnetic steel sheets 12 are stacked, a rotating shaft insertion hole 111 into which a rotating shaft is inserted in the center, and a plurality of slot holes 112 penetrating in the stacking direction of the electromagnetic steel sheets 12, and a secondary conductor. The secondary conductor has an end ring portion 14 and a slot bar portion 13. The end ring portion 14 is provided so as to be in contact with both ends of the electromagnetic steel sheets 12 of the laminated core 11 in the stacking direction. The slot bar portion 13 is provided inside the plurality of slot holes 112 and is connected to two end ring portions 14. The end ring portion 14 has a metal plate that is thicker than the electromagnetic steel sheets 12 that are in contact with both ends of the laminated core 11 in the stacking direction. The metal plate has an opening 142a provided at a position corresponding to the slot hole 112 of the laminated core 11. As a result, peeling defects 67 caused by the insertion 66b of molten aluminum or aluminum alloy 65 during pressurized filling of die casting or casting filling do not occur at both axial ends of the laminated core 11, thus reducing costs due to quality loss. In addition, productivity is improved by reducing the number of man-hours required to remake the squirrel-cage rotors 10D and 10E.

[0077] Furthermore, since the thickness of the end ring portion 14 is not reduced due to peeling defects 67 caused by the insertion 66b of molten aluminum or aluminum alloy 65, the thickness d0 of the end ring portion 14 at the position overlapping with the laminated core 11 can be set to the desired thickness. In other words, the end ring portion 14 can maintain the desired thickness d0 at any position overlapping with the laminated core 11. As a result, the possibility of breakage during rotation of the squirrel-cage rotors 10D and 10E can be reduced, and losses can be reduced.

[0078] In the manufacturing method of the squirrel-cage rotors 10D and 10E according to Embodiment 4, in the insertion suppression structure formation step, a thick plate constituting the third structural part 14a of the end ring part 14 is formed by processing methods such as press working, laser processing, and cutting. In the secondary conductor forming step, there is no gap 125 into which molten aluminum or aluminum alloy 65 can be inserted in the third structural part 14a that is in contact with both ends of the laminated core 11 in the lamination direction, so the possibility of peeling defects 67 occurring can be reduced compared to Embodiment 1.

[0079] Embodiment 5. Figure 26 shows an example of the configuration of an induction motor according to Embodiment 5. The induction motor 1 has an annular stator 2, a squirrel-cage rotor 10x inserted into the annular stator 2, and a shaft 4 which is the rotating shaft inserted into the rotating shaft insertion hole 111 of the squirrel-cage rotor 10x. The squirrel-cage rotor 10A-10F described in Embodiments 1 to 4 is used for the squirrel-cage rotor 10x. The squirrel-cage rotor 10x is surrounded by the annular stator 2 and rotates. The rotating shaft AX is the rotation center of the squirrel-cage rotor 10x. In Figure 26, the right side of the rotating shaft AX shows a longitudinal cross-section of the induction motor 1. The left side of the rotating shaft AX shows a side view of the induction motor 1. In the following description, the direction of the rotating shaft AX corresponds to the axial direction.

[0080] The housing 5, which is the outer shell of the induction motor 1, has a cylindrical frame 6 and an end plate 7. The frame 6 includes a bottom portion 6a at one end in the axial direction. The other end of the frame 6 in the axial direction is open. The end plate 7 is provided at the open end of the frame 6. The stator 2 is fitted inside the frame 6. The shaft 4 passes through the housing 5. The shaft 4 transmits the rotational force of the squirrel-cage rotor 10x to the outside of the induction motor 1.

[0081] The induction motor 1 has two bearings 8 that rotatably support the shaft 4. One bearing 8 is located at the bottom 6a of the frame 6. The other bearing 8 is located at the end plate 7. The bearings 8 are secured by a bracket (not shown).

[0082] Next, a method for manufacturing such an induction motor 1 will be described. Figure 27 is a flowchart showing an example of the procedure for manufacturing an induction motor according to Embodiment 5. First, a rotor manufacturing process for manufacturing a squirrel-cage rotor 10x is carried out (step S31). In the rotor manufacturing process, the processes described in the manufacturing methods for squirrel-cage rotors 10A-10F of Embodiments 1 to 4 are carried out. In addition, unnecessary parts such as the runner portion of the manufactured squirrel-cage rotor 10x are cut off, and the squirrel-cage rotor 10x is processed into its final shape by machining. Here, heat treatment may be performed before machining.

[0083] Next, a shaft fixing process is performed to fix the shaft 4, which is the rotation axis, to the squirrel-cage rotor 10x (step S32). In one example, the shaft 4 is fixed to the squirrel-cage rotor 10x by inserting the shaft 4 into the rotation axis insertion hole 111 of the laminated core 11 of the squirrel-cage rotor 10x. The balance of the squirrel-cage rotor 10x with the shaft 4 fixed is then adjusted.

[0084] Furthermore, a stator manufacturing process for producing the annular stator 2 is carried out (step S33). Note that the order of steps S31 and S32 and step S33 is not particularly limited. The stator manufacturing process may be carried out before the rotor manufacturing process and the shaft fixing process, or it may be carried out in parallel with the rotor manufacturing process and the shaft fixing process.

[0085] Subsequently, an assembly process is carried out in which the squirrel-cage rotor 10x is inserted into the annular stator 2 and fixed (step S34). Specifically, the squirrel-cage rotor 10x with the shaft 4 fixed to it is inserted inside the stator 2. After attaching bearings 8 to both ends of the shaft 4, the stator 2 is housed in the housing 5. The bearings 8 are fixed to the housing 5 by attaching brackets to both axial ends of the housing 5. After attaching other necessary parts, an induction motor 1 using one of the squirrel-cage rotors 10x from Embodiments 1 to 4 is completed. This concludes the manufacturing method of the induction motor 1.

[0086] The configurations shown in the above embodiments are merely examples, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention.

[0087] 1 Induction motor, 2 Stator, 4 Shaft, 5 Housing, 6 Frame, 6a Bottom, 7 End plate, 8 Bearing, 10, 10A-10F, 10x Squirrel-cage rotor, 11 Laminated core, 11a First structural part, 11b Second structural part, 12 Electromagnetic steel sheet, 13 Slot bar part, 14 End ring part, 14a Third structural part, 14b Fourth structural part, 50 Press mold, 51, 52 Die, 60 Mold, 61, 62 End ring forming part, 63 Slot bar forming part, 65 Molten metal, 66a, 66b Insertion, 67 Peeling defect, 70 Laser processing device, 71 Stage, 72 Laser processing head, 111 Rotary shaft insertion hole, 112 Slot hole, 113, 114 Thick plate, 115 Sealing material, 121, 122, 141, 141a, 142a Opening, 123 Burr, 124 Waviness, 125 Gap, L Laser light.

Claims

1. A squirrel-cage rotor comprising: a laminated core including a laminate having a plurality of electromagnetic steel sheets laminated together, a rotating shaft insertion hole in the center into which a rotating shaft is inserted, and a plurality of slot holes penetrating in the direction of lamination of the electromagnetic steel sheets; a secondary conductor having end ring portions provided so as to be in contact with both ends of the laminated core in the direction of lamination of the electromagnetic steel sheets, and slot bar portions provided inside the plurality of slot holes and connected to two of the end ring portions, wherein the laminated core has two first structural portions provided at both ends in the lamination direction, and a second structural portion sandwiched between the two first structural portions and having a plurality of the electromagnetic steel sheets laminated together, and the first structural portion having a structure different from the second structural portion.

2. The squirrel-cage rotor according to claim 1, characterized in that the first structural part is made up of multiple stacked metal plates, and the spacing between the multiple metal plates at the position facing the slot hole and the position facing the rotating shaft insertion hole is smaller than the spacing between the electromagnetic steel plates of the second structural part.

3. The squirrel-cage rotor according to claim 2, characterized in that the burrs at the cut portion of the metal plate constituting the first structural part occupy a portion of the space between the metal plates and form an insertion suppression structure that reduces or closes the gap between adjacent metal plates at a position facing the slot hole.

4. The squirrel-cage rotor according to claim 2, characterized in that the spacing between the metal plates of the first structural part is 0.2 mm or less.

5. The squirrel-cage rotor according to claim 1, characterized in that the first structural part is made of one or more metal plates that are thicker than the electromagnetic steel plates of the second structural part.

6. The squirrel-cage rotor according to claim 5, characterized in that the first structural part has a thickness of at least twice the thickness of the electromagnetic steel sheet and a thickness of 5% or less of the total length of the laminated core.

7. The squirrel-cage rotor according to claim 1, characterized in that the first structural part comprises a plurality of metal plates and a sealing material arranged on the laminated surfaces of the plurality of metal plates.

8. The squirrel-cage rotor according to claim 7, characterized in that the sealing material reduces or closes the gap between the metal plates, is positioned in the region between the openings corresponding to the slot holes formed in the metal plates, and is a material that does not generate volatile gases even when in contact with the molten secondary conductor.

9. The squirrel-cage rotor according to claim 1, characterized in that, in a direction perpendicular to the stacking direction, the number and position of openings corresponding to the slot holes in the metal plate constituting the first structural part are the same as the number and position of openings corresponding to the slot holes in the electromagnetic steel sheet constituting the second structural part, and the openings in the metal plate of the first structural part and the openings in the electromagnetic steel sheet of the second structural part are similar in shape.

10. The squirrel-cage rotor according to any one of claims 2 to 9, characterized in that the metal plate is an electromagnetic steel plate or a magnetic material.

11. A squirrel-cage rotor comprising: a laminated core including a laminate having a plurality of electromagnetic steel sheets laminated together, a rotating shaft insertion hole in the center into which a rotating shaft is inserted, and a plurality of slot holes penetrating in the lamination direction of the electromagnetic steel sheets; a secondary conductor having end ring portions provided so as to be in contact with both ends of the laminated core in the lamination direction of the electromagnetic steel sheets, and slot bar portions provided inside the plurality of slot holes and connected to two of the end ring portions, wherein the end ring portions have metal plates thicker than the electromagnetic steel sheets in contact with both ends of the laminated core in the lamination direction, and the metal plates have openings provided at positions corresponding to the slot holes of the laminated core.

12. The squirrel-cage rotor according to claim 11, characterized in that the end ring portion comprises a third structural portion made of the metal plate and a fourth structural portion arranged in contact with the third structural portion and integrally formed with the slot bar portion.

13. The squirrel-cage rotor according to claim 11 or 12, characterized in that the metal plate is made of a material having an electrical conductivity greater than or equal to that of an electromagnetic steel plate.

14. An induction motor comprising: an annular stator; a squirrel-cage rotor according to claim 1 or 11 inserted into the annular stator; and a rotating shaft inserted into the rotating shaft insertion hole of the squirrel-cage rotor.

15. A method for manufacturing a squirrel-cage rotor, comprising: an electromagnetic steel sheet forming step of forming one annular electromagnetic steel sheet each having a first opening into which a rotating shaft is inserted and a second opening corresponding to a slot hole; an insertion suppression structure forming step of forming the metal sheet having an insertion suppression structure that suppresses the insertion of molten metal into the metal sheets during die casting or casting, and having a third opening into which the rotating shaft is inserted and a fourth opening corresponding to the slot hole; a laminate forming step of stacking the metal sheet having the insertion suppression structure, a plurality of electromagnetic steel sheets, and the metal sheet having the insertion suppression structure to form a laminate having a rotating shaft insertion hole in which the first opening and the third opening are connected in the stacking direction, and a slot hole in which the second opening and the fourth opening are connected in the stacking direction; and a secondary conductor forming step of filling the inside of the slot hole of the laminate with molten metal by die casting or casting and forming a secondary conductor having a solidified slot bar portion.

16. The method for manufacturing a squirrel-cage rotor according to 15, characterized in that, in the insertion suppression structure forming step, the multiple metal plates are stacked on top of each other and pressed or laser processed together, thereby aligning the shape and positional tendencies of the undulations occurring in each metal plate and reducing the gap between the metal plates in at least the region facing the slot hole.

17. The method for manufacturing a squirrel-cage rotor according to 15, characterized in that in the insertion suppression structure formation step, a sealing material is applied to the laminated surface of the metal plates and a plurality of the metal plates are laminated together.

18. The method for manufacturing a squirrel-cage rotor according to 17, wherein the sealing material is made of a material that does not generate volatile gases even when exposed to the molten metal, and in the insertion suppression structure forming step, the sealing material is positioned in the region between adjacent fourth openings of the metal plate so as not to come into contact with the molten metal of adjacent fourth openings even if the molten metal leaks out of the fourth opening in the secondary conductor forming step.

19. A method for manufacturing an induction motor, comprising the steps of: forming a squirrel-cage rotor by the method for manufacturing a squirrel-cage rotor described in any one of claims 15 to 18; inserting a rotating shaft into the rotating shaft insertion hole of the squirrel-cage rotor; forming an annular stator; and inserting and fixing the squirrel-cage rotor into the annular stator.

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