Rotor

Abstract

Provided is a rotor for an induction motor, said rotor having a coupling structure for a rotor core and a ring portion which suppresses an increase in the weight of the ring portion that short-circuits conductive bars. A rotor 20 comprises: a plurality of conductive bars 21; a rotor core 22 that accommodates the conductive bars 21; and end rings 23 provided at both end portions of the rotor core 22. The end rings 23 are provided with: a ring portion 23A that is provided to the radially inner side of the rotor 20 not overlapping the conductive bars 21 when viewed from the axial direction of the rotor 20 and short-circuits between the conductive bars; and a protrusion portion 23B that is connected at a position of the ring portion 23A not overlapping the conductive bar 21 and connects the ring portion 23A to the rotor core 22. The rotor core 22 comprises a recessed portion 22D that accommodates the protrusion portion 23B. The protrusion portion 23B comprises: a first portion 23B1 extending in the axial direction of the rotor 20 toward the inside of the recessed portion 22D; and a second portion 23B2 connected to the first portion 23B1 and located radially inward of the first portion 23B1.

Description

Rotor

[0001] The present disclosure relates to a rotor of an induction motor.

[0002] Patent Document 1 discloses a rotor for an induction machine, comprising: a rotation shaft rotatably disposed; a rotor core configured by laminating a plurality of magnetic steel sheets in the axial direction of the rotation shaft and fixed to the rotation shaft; a plurality of secondary conductors distributed and arranged in the circumferential direction of the rotor core and extending in the rotation shaft direction; and an end ring that interconnects ends of the secondary conductors located on an end face side of the rotor core in the axial direction of the rotation shaft. The rotor core includes: a hole extending along the axial direction from an end face of the rotor core in the axial direction of the rotation shaft; and a recess extending from the hole in a direction perpendicular to the axial direction inside the rotor core relative to the end face of the rotor core. The end ring includes a holding portion formed on an inner diameter side of the end ring and inserted into the hole formed in the end face of the rotor core, and a fitting portion formed on the holding portion and fitted into the recess formed in the hole.

[0003] Specifically, the recess is provided inside the rotor core relative to the end face of the rotor core, extending from the hole in a direction perpendicular to the axial direction toward an outer circumferential side of the rotor core, and the fitting portion extends toward the outer circumferential side of the rotor core.

[0004] Patent Document 1 describes that according to the above configuration, deformation of the end ring in the outer diameter direction is suppressed by centrifugal force, and deformation and damage of the end ring can be prevented.

[0005] Japanese Patent Laid-Open No. 2013-236425

[0006] However, in order to adopt a configuration in which the fitting portion extends toward the outer circumferential side of the rotor core, the end ring needs to be provided up to a position corresponding to the radially inner side of the fitting portion. As a result of the increased mass of the end ring, the centrifugal force applied to the end ring increases.

[0007] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a rotor for an induction motor having a connection structure of a rotor core and a ring portion that can suppress an increase in weight of the ring portion that short-circuits conductive bars.

[0008] The rotor of the present disclosure is a rotor for an induction motor, the rotor comprising: a plurality of conductive bars provided in the circumferential direction; a rotor core housing the conductive bars; and end rings provided at both ends of the rotor core, the end rings comprising: a ring portion provided from a position overlapping the conductive bars to a radially inward position of the rotor where it does not overlap the conductive bars, as viewed from the axial direction of the rotor, and short-circuiting the conductive bars; and a protrusion located within the rotor core, connected at the radially inward position of the ring portion where it does not overlap the conductive bars, and connecting the ring portion to the rotor core, the rotor core comprising: a recess housing the protrusion, the protrusion comprising: a first portion extending in the axial direction of the rotor toward the recess; and a second portion connected to the first portion and located radially inward from the first portion.

[0009] According to this disclosure, an induction motor rotor is provided having a rotor core and ring section connection structure that can suppress the weight increase of the ring section that short-circuits the conductive bars.

[0010] This figure schematically shows a cross-section of an induction motor using the rotor of the first embodiment according to the present disclosure. This is an enlarged view showing region A in Figure 1. This figure shows an end ring of a comparative example. This figure illustrates the position of the tip of the second portion of the protrusion of the end ring of the first embodiment according to the present disclosure. This figure illustrates the shortest distance when the conductive bar is not located at the same angular position as the circumferential angular position of the protrusion of the end ring of the first embodiment according to the present disclosure. This figure illustrates the protrusion of the end ring of the second embodiment according to the present disclosure. This figure illustrates the protrusion of the end ring of the third embodiment according to the present disclosure.

[0011] Hereinafter, embodiments for implementing this disclosure (hereinafter referred to as "Embodiments") will be described in detail with reference to the attached drawings. Throughout the description of the embodiments, the same elements are denoted by the same numbers or reference numerals.

[0012] Furthermore, the dimensional ratios in the drawings differ from the actual dimensional ratios and are merely for illustrative purposes to make the explanation easier to understand; there is no guarantee that identical parts are depicted with the same dimensions across different drawings.

[0013] Furthermore, for the sake of readability, in drawings, only some of the parts with the same attribute that exist in multiple locations may be assigned reference numerals.

[0014] <<First Embodiment>> The rotor 20 of the induction motor 1 of the first embodiment according to this disclosure will be described with reference to Figures 1 to 5.

[0015] Furthermore, the induction motor 1 using the rotor 20 of the first embodiment can be suitably used, for example, in a rotating electric machine used for driving automobiles.

[0016] Figure 1 is a schematic diagram showing a cross-section of an induction motor 1 using a rotor 20 according to the first embodiment of the present disclosure, and is a schematic diagram showing a cross-section along the rotor shaft 24. The longitudinal direction of the rotor shaft 24 passing through the rotation center of the rotor shaft 24 is the rotation axis RA of the rotor 20.

[0017] In the following, when viewed in a plane perpendicular to the axis of rotation RA, the direction farther from the axis of rotation RA is defined as the radially outward direction, and conversely, the direction closer to the axis of rotation RA is defined as the radially inward direction.

[0018] Furthermore, when viewed in a plane perpendicular to the rotation axis RA, the direction along the rotation axis RA is defined as the circumferential direction.

[0019] Furthermore, the direction of the rotation axis RA is defined as the axial direction, and in the axial direction, the direction away from the rotor core 22 is defined as the axial outward direction, and the direction towards the rotor core 22 is defined as the axial inward direction.

[0020] Figure 2 is an enlarged view of region A in Figure 1, and the core plate forming the rotor core 22 is also shown on the right. The core plate on the right also shows the region corresponding to region A.

[0021] As shown in Figure 1, the induction motor 1 using the rotor 20 of the first embodiment comprises a stator 10 having coil ends 12A at its axial ends, a rotor 20 rotatably mounted radially inward of the stator 10, and a case 30 for housing the stator 10, rotor 20, and coolant.

[0022] The case 30 comprises a bottomed cylindrical main body 31 having an outlet 31A at its bottom for leading the rotor shaft 24 to the outside, and a lid 32 having an outlet 32A for leading the rotor shaft 24 to the outside and closing the opening of the main body 31, forming a space for housing the stator 10, rotor 20, and coolant.

[0023] Furthermore, the outlet sections 31A and 32A are provided with recesses for housing a bearing section BR that rotatably supports the rotor shaft 24, and the bearing section BR is fixed in these recesses.

[0024] [Stator 10] The stator 10 comprises a stator core 11, a stator coil 12 arranged in the stator rod ST1 of the stator core 11, and coil ends 12A of the stator coil 12 provided at the axial ends of the stator 10 (one axial end 11A of the stator core 11 and the other axial end 11A).

[0025] The stator 10 is fixed to the inner surface of the case 30 (specifically, the main body 31).

[0026] Although not shown in the diagram, the stator core 11 is formed by stacking multiple electromagnetic steel sheets in the axial direction.

[0027] However, the stator core 11 is not limited to a laminated core made by stacking electrical steel sheets, and may also be a compacted core made by press-forming metal powder.

[0028] [Rotor 20] As shown in Figure 1, the rotor 20 comprises a rotor core 22 having a plurality of conductive bars 21 provided in the circumferential direction and rotor slots ST2, which house the conductive bars 21 within the rotor slots ST2, end rings 23 provided at both ends 22A of the rotor core 22 so as to contact the rotor core 22 and short-circuit the conductive bars 21, and a rotor shaft 24 that protrudes axially from both ends 22A of the rotor core 22 and has hollow portions 24A that serve as passages for coolant.

[0029] (Conductive bar 21) The conductive bar 21 is made of, for example, aluminum, aluminum alloy, copper, copper alloy, etc., and in the first embodiment, aluminum is used for the conductive bar 21.

[0030] Alternatively, the conductive bar 21 may be a pre-fabricated rod-shaped conductive bar 21 placed inside the rotor slot ST2.

[0031] In this case, when the end rings 23, described later, are formed on both ends 22A of the rotor core 22 by aluminum casting or the like, even if the interface between the end rings 23 and the conductive bars 21 is not completely fused, the end rings 23 and the conductive bars 21 will be firmly attached.

[0032] On the other hand, when forming the end rings 23, which will be described later, on both ends 22A of the rotor core 22 by aluminum casting or the like, the material may also be injected into the rotor slot ST2 to form the conductive bars 21.

[0033] Furthermore, the conductive bar 21 may be positioned diagonally such that one end and the other end are offset in the circumferential direction.

[0034] (Rotor core 22) The rotor core 22 is an externally cylindrical member having a through hole 22H in the center for housing the rotor shaft 24, a rotor slot ST2 for housing the conductive bar 21, and a recess 22D for housing the protrusion 23B (see Figure 2) of the end ring 23, which will be described later.

[0035] As shown in Figure 1, the rotor core 22 is a laminated core formed by stacking multiple electromagnetic steel sheets in the axial direction.

[0036] Specifically, the rotor core 22 is formed using a first core sheet 22C1, a second core sheet 22C2, and a third core sheet 22C3, as shown in Figure 2.

[0037] The first core sheet 22C1 is a core sheet that forms both axial end faces of the rotor core 22, and includes a circular opening O1 through which the rotor shaft 24 passes in the center, a plurality of circular openings O2 corresponding to the radial outer circumference of the rotor slots ST2 provided at equal intervals in the circumferential direction, and a rectangular opening O3 corresponding to the recess 22D provided between the circular openings O1 and O2.

[0038] The rectangular opening O3 of the first core sheet 22C1 forms a recessed portion 22D that accommodates the first portion 23B1 of the protrusion 23B of the end ring 23, which will be described later.

[0039] In the first embodiment, the case where only one first core sheet 22C1 is used is shown, but multiple sheets may be used in stacks.

[0040] The second core sheet 22C2 is a core sheet provided adjacent to the first core sheet 22C1, and includes a circular opening O1 through which the rotor shaft 24 passes in the center, a plurality of circular openings O2 corresponding to the outer radial rotor slots ST2 provided at equal intervals in the circumferential direction, and a rectangular opening O3 corresponding to the recess 22D provided between the circular openings O1 and O2.

[0041] Furthermore, the rectangular opening O3 of the second core sheet 22C2 has a longer radial length than the rectangular opening O3 of the first core sheet 22C1. Its radially outer position is the same as that of the rectangular opening O3 of the first core sheet 22C1, but its radially inner position is located further radially inward than that of the radially inner position of the rectangular opening O3 of the first core sheet 22C1.

[0042] The rectangular opening O3 of the second core sheet 22C2 forms the recess 22D that accommodates the first portion 23B1 and the second portion 23B2 of the protrusion 23B of the end ring 23, which will be described later.

[0043] In the first embodiment, a case where only one second core sheet 22C2 is used is shown, but a plurality of second core sheets may be stacked and used.

[0044] The third core sheet 22C3 is a core sheet provided between the second core sheets 22C2 on one side and the other side, and includes a circular opening O1 through which the rotor shaft 24 passes in the center, and circular openings O2 corresponding to a plurality of rotor slots ST2 provided on the radially outer peripheral side at equal intervals in the circumferential direction.

[0045] The rotor slots ST2 may be provided along the axial direction and have opening slits opening outward in the radial direction.

[0046] (End Ring 23) As shown in Fig. 1 and Fig. 2, the end ring 23 is an annular member that short-circuits between the conductive bars 21, and is formed of an electrically conductive material such as aluminum, aluminum alloy, copper, or copper alloy. In the first embodiment, aluminum is used for the end ring 23. Details of the end ring 23 will be described later.

[0047] (Rotor Shaft 24) As shown in Fig. 1, the rotor shaft 24 is fixed in a through hole 22H provided at the radial center of the rotor core 22 by, for example, shrink fitting or press fitting.

[0048] The rotor shaft 24 is led out of the case 30 through a lead-out portion 31A and a lead-out portion 32A provided at both axial ends of the case 30. Only one end of the rotor shaft 24 may be led out of the case 30.

[0049] Furthermore, the lead-out portion 32A and the lead-out portion 31A of the case 30 are provided with bearing portions BR (for example, ball bearings) that rotatably support the rotor shaft 24. By being supported by the bearing portions BR, the rotor shaft 24 is provided rotatably relative to the case 30 and the stator 10.

[0050] Furthermore, the rotor shaft 24 is provided with discharge holes 24B that release coolant from the rotor core 22 in the portion protruding from the rotor core 22 near both ends 22A of the rotor core 22. The coolant flowing through the hollow portion 24A is discharged from these discharge holes 24B toward the end ring 23, and the end ring 23 is cooled by the coolant.

[0051] Next, the end ring 23 of the first embodiment according to the present disclosure will be described in more detail. As shown in Figure 2, the end ring 23 is provided from a position overlapping the conductive bar 21 to a position radially inward of the rotor 20 where it does not overlap the conductive bar 21, as viewed from the axial direction of the rotor 20, and comprises a ring portion 23A that short-circuits the conductive bar 21, and a protrusion 23B located inside the rotor core 22 that is connected at the position of the ring portion 23A radially inward where it does not overlap the conductive bar 21, and connects the ring portion 23A to the rotor core 22.

[0052] The convex portion 23B comprises a first portion 23B1 that extends in the axial direction of the rotor 20 toward the concave portion 22D, and a second portion 23B2 that is connected to the first portion 23B1 and is located radially inward from the first portion 23B1.

[0053] Therefore, even if the radially inner portion of the ring portion 23A tries to spread out in a V-shape away from the end of the rotor core 22 due to the action of centrifugal force or the like, as shown by arrow AR1, the radially inner portion of the ring portion 23A is connected to the rotor core 22 by the convex portion 23B, so the spreading in a V-shape is suppressed and damage to the end ring 23 can be avoided.

[0054] Figure 3 shows an end ring 23' of a comparative example and corresponds to the left side of Figure 2. In order to have a configuration in which the second portion 23B2' extends radially outward from the first portion 23B1', as in the prior art, it is necessary to provide a portion (the area of ​​the dashed line) that extends the ring portion 23A' radially inward, and to provide the first portion 23B1' radially inward of the second portion 23B2'.

[0055] As a result, the weight will increase by the weight of the portion of the ring 23A' that is extended radially inward (the area indicated by the dashed line).

[0056] On the other hand, in the rotor 20 of the first embodiment, as shown in Figure 2, the second portion 23B2 is positioned radially inward from the first portion 23B1, so the radial width of the ring portion 23A can be kept short, and thus the centrifugal force applied to the ring portion 23A can be reduced.

[0057] Furthermore, the combined effect of reducing the centrifugal force applied to the ring portion 23A and the effect of the ring portion 23A being connected to the rotor core 22 by the convex portion 23B suppresses the ring portion 23A from spreading out in a V-shape, thereby preventing damage to the end ring 23.

[0058] Furthermore, as can be seen from the positional relationship of the rectangular openings O3 corresponding to the recesses 22D that accommodate the protrusions 23B of the core sheets (first core sheet 22C1 and second core sheet 22C2) shown in Figure 2, the protrusions 23B are provided at equal intervals in the circumferential direction. This results in a nearly uniform circumferential weight balance of the rotor 20, thereby suppressing vibration during rotation of the rotor 20.

[0059] In the first embodiment, four protrusions 23B are shown at equal intervals in the circumferential direction. However, if there are three or more protrusions 23B, they can be arranged at equal intervals in the circumferential direction to equalize the weight balance in the circumferential direction. Therefore, it is preferable that three or more protrusions 23B are provided at equal intervals in the circumferential direction.

[0060] Figure 4 is a diagram illustrating the position of the tip portion TC of the second portion 23B2 of the protrusion 23B of the end ring 23 according to the first embodiment of the present disclosure.

[0061] As shown in Figure 4, the second portion 23B2 has a radially inward tip portion TC at a position a first distance D1 from the radially central position P1 at the boundary between the ring portion 23A and the first portion 23B1.

[0062] Furthermore, it is preferable that the first distance D1 is greater than or equal to the shortest distance D2 from the axial center position P2 of the ring portion 23A, which corresponds to the radial center of the end face of the conductive bar 21, to the radial center position P1 of the boundary between the ring portion 23A and the first portion 23B1.

[0063] Thus, because the first distance D1 is greater than or equal to the shortest distance D2, the second portion 23B2 can easily exert a resistance force greater than the moment of force when the ring portion 23A spreads out in a V-shape as indicated by arrow AR1, and the ring portion 23A can be firmly connected to the rotor core 22.

[0064] In the first embodiment, the convex portion 23B is located at the same position as one of the conductive bars 21 in terms of circumferential angular position.

[0065] However, there are also cases in which the conductive bar 21 is not located at the same angular position as the circumferential angular position of the protrusion 23B.

[0066] Figure 5 is a diagram illustrating the shortest distance D2 when the conductive bar 21 is not located at the same angular position as the circumferential angular position of the protrusion 23B of the end ring 23 in the first embodiment of the present disclosure, and is a view of the rotor 20 from one side as shown in Figure 1.

[0067] In Figure 5, the conductive bar 21, which will be hidden beneath the ring portion 23A of the end ring 23, and the protrusions 23B (first portion 23B1 and second portion 23B2) located inside the rotor core 22 are shown with dotted lines.

[0068] Furthermore, the circumference CF connecting the conductive bars 21 (the centers of the ends of the conductive bars 21) is shown by a dashed line.

[0069] As shown in Figure 5, in the case where the conductive bar 21 is not located at the same angular position as the circumferential angular position of the convex portion 23B, the shortest distance D2 can be defined as the distance from the axial center position P2 of the corresponding ring portion 23A on the circumference CF connecting the conductive bars 21 (the centers of the ends of the conductive bars 21) (see Figure 4 for the axial position) to the radial center position P1 of the boundary between the ring portion 23A and the first portion 23B1.

[0070] Furthermore, this definition of the shortest distance D2 also applies when the conductive bar 21 is located at the same angular position as the circumferential angular position of the protrusion 23B, thus representing a generalized definition of the shortest distance D2.

[0071] By the way, the ring portion 23A of the end ring 23 is attached to the conductive bar 21, so the end ring 23 (ring portion 23A) is connected to the rotor core 22 in that area as well. Conversely, when viewed in the circumferential direction, the area between the conductive bars 21 is not connected by the conductive bars 21.

[0072] As shown in Figure 5, if the protrusions 23B are provided at corresponding circumferential positions between adjacent conductive bars 21, the end ring 23 (ring portion 23A) will connect to the rotor core 22 in such a way that the protrusions 23B reinforce the areas where the rotor core 22 is not connected by the conductive bars 21.

[0073] Therefore, it is preferable that the protrusion 23B is provided at a circumferential position corresponding to the space between adjacent conductive bars 21. By doing so, the spreading of the ring portion 23A in a V-shape can be further reduced, and damage to the end ring 23 can be avoided even more effectively.

[0074] <<Second Embodiment>> Next, the rotor 20 of the induction motor 1 of the second embodiment according to the present disclosure will be described with reference to Figure 6.

[0075] Furthermore, the rotor 20 of the second embodiment has the same basic configuration as the rotor 20 of the first embodiment, and only the shape of the protrusion 23B of the end ring 23 is different. Therefore, the following description will mainly focus on the protrusion 23B, and explanations of points that are the same as in the first embodiment may be omitted.

[0076] Figure 6 is a diagram illustrating the protrusion 23B of the end ring 23 in the second embodiment of the present disclosure, and corresponds to the left side of Figure 2.

[0077] As shown in Figure 6, in the second embodiment, similar to the first embodiment, the convex portion 23B includes a first portion 23B1 that extends in the axial direction of the rotor 20 toward the recess 22D, and a second portion 23B2 that is connected to the first portion 23B1 and is located radially inward from the first portion 23B1.

[0078] On the other hand, in the second embodiment, the second portion 23B2 has a stepped shape in which the distance from the first radial portion 23B1 of the rotor 20 increases as it moves towards the inside (axially inward) side of the rotor core 22.

[0079] In this case as well, since the second portion 23B2 is located radially inward from the first portion 23B1, the radial width of the ring portion 23A can be kept short, as described in the first embodiment, and as a result, the centrifugal force applied to the ring portion 23A can be reduced.

[0080] Therefore, similar to the first embodiment, the combined effect of reducing the centrifugal force applied to the ring portion 23A and the effect of the ring portion 23A being connected to the rotor core 22 by the convex portion 23B, as shown by arrow AR1, suppresses the ring portion 23A from spreading out in a V-shape due to the action of centrifugal force, etc., and prevents damage to the end ring 23.

[0081] <<Third Embodiment>> Next, the rotor 20 of the induction motor 1 of the third embodiment according to the present disclosure will be described with reference to Figure 7.

[0082] Furthermore, the rotor 20 of the third embodiment has the same basic configuration as the rotor 20 of the first embodiment, and only the shape of the protrusion 23B of the end ring 23 is different. Therefore, the following description will mainly focus on the protrusion 23B, and explanations of aspects that are the same as those of the first embodiment may be omitted.

[0083] Figure 7 is a diagram illustrating the protrusion 23B of the end ring 23 in the third embodiment of the present disclosure, and corresponds to the left side of Figure 2.

[0084] As shown in Figure 7, in the third embodiment, similar to the first embodiment, the convex portion 23B includes a first portion 23B1 that extends in the axial direction of the rotor 20 toward the recess 22D, and a second portion 23B2 that is connected to the first portion 23B1 and is located radially inward from the first portion 23B1.

[0085] On the other hand, in the third embodiment, the second portion 23B2 has a tapered shape that inclins radially inward as it approaches the inside (axially inward) side of the rotor core 22.

[0086] In this case as well, since the second portion 23B2 is located radially inward from the first portion 23B1, the radial width of the ring portion 23A can be kept short, as described in the first embodiment, and as a result, the centrifugal force applied to the ring portion 23A can be reduced.

[0087] Therefore, similar to the first embodiment, the combined effect of reducing the centrifugal force applied to the ring portion 23A and the effect of the ring portion 23A being connected to the rotor core 22 by the convex portion 23B, as shown by arrow AR1, suppresses the ring portion 23A from spreading out in a V-shape due to the action of centrifugal force, etc., and prevents damage to the end ring 23.

[0088] By the way, in the third embodiment, as in the first embodiment, the rotor core 22 is shown as a laminated core formed by stacking multiple electromagnetic steel sheets in the axial direction, but for example, the rotor core 22 may be a compacted core formed by press-molding metal powder.

[0089] Specifically, during press molding, a through hole for the conductive bar 21 and a bottomed hole for the first portion 23B1 of the protrusion 23B may be formed, and a grinding tool may be inserted at an angle through the opening of the bottomed hole for the first portion 23B1 to form a space in the recess 22D corresponding to the second portion 23B2.

[0090] Although the above description has been based on specific embodiments, this disclosure is not limited to the embodiments described above. This disclosure also includes modifications and improvements to the embodiments, which will be clear to those skilled in the art from the claims.

[0091] Furthermore, the following additional information is disclosed with respect to the above embodiment. [Addendum 1] A rotor for an induction motor, the rotor comprising: a plurality of conductive bars provided in the circumferential direction; a rotor core housing the conductive bars; and end rings provided at both ends of the rotor core, the end ring comprising: a ring portion provided from a position overlapping the conductive bars to a radially inward position of the rotor where it does not overlap the conductive bars, as viewed from the axial direction of the rotor, and short-circuiting the conductive bars; and a protrusion located within the rotor core, connected at the radially inward position of the ring portion where it does not overlap the conductive bars, and connecting the ring portion to the rotor core, the rotor core comprising: a recess housing the protrusion, the protrusion comprising: a first portion extending in the axial direction of the rotor toward the recess; and a second portion connected to the first portion and located radially inward from the first portion. [Note 2] The rotor according to Note 1, wherein the second portion has a stepped shape, the distance from the first portion in the radial direction of the rotor increases as it moves toward the axially inward side of the rotor core. [Note 3] The rotor according to Note 1 or Note 2, wherein the protrusions are provided at circumferential positions corresponding to the spaces between adjacent conductive bars. [Note 4] The rotor according to Note 1 or Note 2, wherein the second portion has a radially inward tip at a position of a first distance from the radially central position of the boundary between the ring portion and the first portion, and the first distance is greater than or equal to the shortest distance from the axially central position of the ring portion to the radially central position corresponding to the circumference connecting the conductive bars. [Note 5] The rotor according to Note 1, wherein the second portion has a tapered shape that slopes radially inward as it moves toward the axially inward side of the rotor core. [Note 6] The rotor according to any one of Notes 1 to 5, wherein the protrusions are provided at three or more locations at equal intervals in the circumferential direction.

[0092] 1...Induction motor, 10...Stator, 20...Rotor, 21...Conductive bar, 22...Rotor core, 22...Rotor core, 22D...Recess, 23...End ring, 23A...Ring portion, 23B...Convex portion, 23B1...First portion, 23B2...Second portion, D1...First distance, D2...Shortest distance, TC...Tip portion, P1...Radial center position, P2...Axial center position

Claims

1. A rotor for an induction motor, the rotor comprising: a plurality of conductive bars provided in the circumferential direction; a rotor core housing the conductive bars; and end rings provided at both ends of the rotor core, the end rings comprising: a ring portion provided from a position overlapping the conductive bars to a radially inward position of the rotor where it does not overlap the conductive bars, as viewed from the axial direction of the rotor, and short-circuiting the conductive bars; and a protrusion located within the rotor core, connected at the radially inward position of the ring portion where it does not overlap the conductive bars, and connecting the ring portion to the rotor core, the rotor core comprising: a recess housing the protrusion, the protrusion comprising: a first portion extending in the axial direction of the rotor toward the recess; and a second portion connected to the first portion and located radially inward from the first portion.

2. The rotor according to claim 1, wherein the second portion has a stepped shape, the distance from the first portion in the radial direction of the rotor increases as it moves toward the axially inward side of the rotor core.

3. The rotor according to claim 1 or claim 2, wherein the protrusions are provided at circumferential positions corresponding to the space between adjacent conductive bars.

4. The rotor according to claim 1 or claim 2, wherein the second portion has a radially inward tip portion at a position of a first distance from the radially central position of the boundary between the ring portion and the first portion, and the first distance is greater than or equal to the shortest distance from the axial central position of the ring portion corresponding to the circumference connecting the conductive bars to the radially central position.

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