Rotor and rotating electric machine

Abstract

A rotor of one embodiment of the present invention is able to rotate about the central axis, and comprises: a rotor core; and an end plate that has a first plate surface facing the rotor core in the axial direction, and a second plate surface facing the inverse side from the first plate surface. The first plate surface comprises a contact surface that makes contact with the rotor core in the axial direction in a state where at least a portion of the end plate is elastically deformed in the axial direction. The contact surface comprises a first surface. In a state where the end plate is not elastically deformed, the first surface is, toward the radially outward side, located increasingly close to a first side of the axial direction where the rotor core is arranged with respect to the end plate. In the state where the end plate is not elastically deformed, a radially outward end of the first surface is a portion of the contact surface that is located closest to the first side. The end plate has a first recess provided to an outer surface of the end plate. At least a portion of the first recess overlaps the first surface in the axial direction.

Description

Rotor and rotating electric machine

[0001] The present invention relates to a rotor and a rotating electric machine.

[0002] Conventionally, squirrel-cage rotors in which conductors are arranged in slots of a rotor core are known. A squirrel-cage rotor requires a structure that prevents the conductors from coming out of the slots. Japanese Patent Laid-Open Publication No. 2016-171627 discloses a structure in which a convex portion that protrudes in the circumferential direction is provided on the inner surface of each slot formed in a rotor core, and the convex portion receives the centrifugal force applied to the conductors.

[0003] Japanese Patent Publication No. 2016-171627

[0004] In recent years, rotating electric machines using squirrel-cage rotors have been adopted as the drive source for automobiles. Such rotating electric machines are required to be smaller and have higher output, which inevitably leads to a trend toward high-speed rotation. When a rotor with a conventional structure is rotated at high speed, a large centrifugal force is applied to the conductors, which locally applies a large force to the rotor core, causing deformation of the rotor core and potentially causing the conductors to come out of the slots.

[0005] In view of the above circumstances, one object of the present invention is to provide a rotor and a rotating electric machine that can suppress deformation of the rotor core while suppressing separation of conductive parts from slots due to centrifugal force.

[0006] One aspect of the rotor of the present invention is a rotor for a rotating electric machine that rotates about a central axis, the rotor comprising: a rotor core having a plurality of slots arranged circumferentially and penetrating axially; a plurality of conductors disposed in the slots; and a pair of end rings located on one axial side and the other axial side of the rotor core, respectively, connecting the plurality of conductors. The slots extend radially and open at their radially outer ends into the outer peripheral surface of the rotor core. The slots have a boundary portion located radially inward of the midpoint of their radial length, an inner narrowed portion whose circumferential width narrows radially inward from the boundary portion, and an outer narrowed portion whose circumferential width narrows radially outward from the boundary portion.

[0007] One aspect of the rotating electric machine of the present invention includes the rotor described above and a stator surrounding the rotor from the outside in the radial direction. The stator has an annular stator core and a coil attached to the stator core.

[0008] According to one aspect of the present invention, it is possible to provide a rotor and a rotating electric machine that can suppress deformation of the rotor core while suppressing separation of conductive parts from slots due to centrifugal force.

[0009] Fig. 1 is a cross-sectional view taken along the central axis of a rotating electric machine according to an embodiment. Fig. 2 is a cross-sectional view perpendicular to the central axis of a rotor according to an embodiment. Fig. 3 is a partially enlarged cross-sectional view of a portion of Fig. 2. Fig. 4 is a partially enlarged cross-sectional view of a rotor according to a first modified example. Fig. 5 is a partially enlarged cross-sectional view of a rotor according to the first modified example.

[0010] A rotor 20 according to the present invention and a rotating electric machine 1 having the rotor 20 will be described in detail below with reference to the drawings. The Z axis is illustrated in each drawing as necessary. The Z axis is a direction parallel to the central axis J of the rotating electric machine 1. In the following description, the direction parallel to the central axis J of the rotating electric machine 1 will be simply referred to as the "axial direction," the radial direction centered on the central axis J will be simply referred to as the "radial direction," and the circumferential direction centered on the central axis J, i.e., around the axis of the central axis J, will be simply referred to as the "circumferential direction."

[0011] FIG. 1 is a cross-sectional view taken along a central axis J of a rotating electric machine 1 according to this embodiment. The rotating electric machine 1 according to this embodiment is a squirrel-cage three-phase AC motor. The rotating electric machine 1 according to this embodiment is mounted on a vehicle powered by a rotating electric machine, such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHV), or an electric vehicle (EV), and is used as the power source thereof. The rotating electric machine 1 has both a function of outputting power as a motor and a function of generating electricity as a generator. The rotating electric machine 1 may also be used as either a motor or a generator. The configuration of the rotating electric machine 1 is not limited to that of this embodiment, and may be, for example, an AC motor with four or more phases.

[0012] The rotating electric machine 1 of this embodiment has a rotor 20 configured as a squirrel-cage rotor, a stator 10 that generates a rotating magnetic flux by an alternating current, and a housing 6 that accommodates the rotor 20 and the stator 10. In the rotating electric machine 1, a rotational force is generated in the rotor 20 by linkage between the rotating magnetic flux generated from the stator 10 and an induced current generated in a conductor portion 40 of the rotor 20 configured as a squirrel-cage rotor.

[0013] The housing 6 has a housing main body 6a, a bearing holder 6b, and a pair of bearings 8a, 8b. The housing main body 6a has a tubular portion 6d and a bottom plate portion 6e. The tubular portion 6d is cylindrical and has a center on the central axis J. The bottom plate portion 6e extends radially inward from the end of the tubular portion 6d on the other axial side (-Z side). The bottom plate portion 6e holds the bearing 8a. The bearing holder 6b covers the opening on one axial side (+Z side) of the housing main body 6a. The bearing holder 6b holds the bearing 8b.

[0014] The stator 10 is fixed to the inner peripheral surface of the cylindrical portion 6d. The stator 10 is annular and centered on the central axis J. The stator 10 surrounds the rotor 20 from the radially outer side. The stator 10 includes an annular stator core 11 and coils 12 attached to the stator core 11. The stator core 11 is formed by stacking multiple electromagnetic steel plates in the axial direction. The stator core 11 includes a cylindrical core back portion 11a centered on the central axis J and multiple stator teeth 11b that protrude radially inward from the inner peripheral surface of the core back portion 11a and are arranged in the circumferential direction. The coils 12 are attached to the stator teeth 11b. The coils 12 include three-phase coils, namely, U-phase, V-phase, and W-phase, through which AC current flows in different phases.

[0015] The rotor 20 rotates about the central axis J. The rotor 20 is rotatably supported by a pair of bearings 8a, 8b. The rotor 20 has a shaft 29, a rotor core 21, a plurality of conductor portions 40, a pair of end rings 50, and a pair of plate members 60. The shaft 29 is cylindrical and extends axially about the central axis J. The shaft 29 is supported by the pair of bearings 8a, 8b.

[0016] The rotor core 21 extends in the axial direction with, for example, a uniform cross section. The rotor core 21 is substantially circular when viewed in the axial direction. The outer peripheral surface of the rotor core 21 faces the inner peripheral surface of the stator 10 in the radial direction with a gap therebetween. The rotor core 21 is formed by laminating multiple electromagnetic steel plates in the axial direction. The rotor core 21 is fixed to the shaft 29. The rotor core 21 also holds multiple conductor portions 40 and a pair of end rings 50.

[0017] FIG. 2 is a cross-sectional view perpendicular to the central axis J of the rotor 20. As shown in FIG. 2, the rotor core 21 is provided with a central hole 21h that penetrates in the axial direction and a plurality of slots 30. The central hole 21h is substantially circular and centered on the central axis J. A shaft 29 is inserted into the central hole 21h. A pair of protrusions 21p that protrude radially inward is provided on the inner circumferential surface of the central hole 21h. Meanwhile, a pair of grooves 29g that extend along the axial direction is provided on the outer circumferential surface of the shaft 29. The protrusions 21p are inserted into the grooves 29g. As a result, the rotor core 21 is positioned circumferentially with respect to the shaft 29.

[0018] The multiple slots 30 are arranged at equal intervals along the circumferential direction. The slots 30 extend in the axial direction with a uniform cross-sectional shape. The slots 30 extend radially and open at their radially outer ends to the outer peripheral surface 21a of the rotor core 21. The rotor core 21 also has teeth 22 provided between circumferentially adjacent slots 30. In other words, the slots 30 are located between circumferentially adjacent tooth portions 22. The multiple teeth 22 are arranged at equal intervals along the circumferential direction. The shapes of the slots 30 and the teeth 22 will be described in detail later.

[0019] The conductor portion 40 is a rod-shaped portion that is disposed in the slot 30 and extends along the axial direction. The conductor portion 40 is made of a non-magnetic and conductive material, such as an aluminum alloy. The conductor portion 40 is formed by die-casting into the slot 30. Therefore, the cross-sectional shape of the conductor portion 40 as viewed in the axial direction is substantially the same as the cross-sectional shape of the slot 30.

[0020] As shown in FIG. 1 , the conductor portions 40 extend linearly along the axial direction of the rotor core 21. The conductor portions 40 may extend at a slight circumferential incline relative to the axial direction. The length dimension of the conductor portions 40 is approximately equal to the axial dimension of the rotor core 21. One axial end and the other axial end of each of the multiple conductor portions 40 are connected to an end ring 50, respectively. As a result, the multiple conductor portions 40 lined up in the circumferential direction are short-circuited to each other. An induced current flows through the conductor portions 40 due to the rotational magnetic flux generated by the stator 10 when the rotor 20 rotates. The induced current flows axially through the conductor portions 40.

[0021] The end rings 50 are located on one axial side and the other axial side of the rotor core 21. The end rings 50 are annular and centered on the central axis J. The end rings 50 face the outer peripheral surface of the shaft 29 in the radial direction with a gap therebetween. The end rings 50 connect the multiple conductor portions 40 together. Like the conductor portions 40, the end rings 50 are made of a non-magnetic, conductive material such as an aluminum alloy. In this embodiment, the end rings 50 are formed integrally with the conductor portions 40 by die-cast molding.

[0022] The plate members 60 are plate-shaped and extend along a plane perpendicular to the central axis J. The pair of plate members 60 are located between the end faces of the rotor core 21 on one axial side and the other axial side and the end rings 50, respectively.

[0023] The plate members 60 protect the rotor core 21 during molding of the conductor portions 40 and the end rings 50. As described above, the rotor core 21 is composed of multiple electromagnetic steel plates. The conductor portions 40 and the end rings 50 are die-cast to embed portions of the rotor core 21. If the gaps between the electromagnetic steel plates constituting the rotor core 21 become large, there is a risk that molten metal, which is the material for the conductor portions 40 and the end rings 50, may infiltrate into these gaps. For this reason, the rotor core 21 is placed in a mold that molds the conductor portions 40 and the end rings 50 while being compressed in the axial direction to bring the electromagnetic steel plates into close contact with each other. The plate members 60 protect the axial end faces of the rotor core 21 during compression, thereby preventing damage to the rotor core 21. To ensure sufficient strength and rigidity, the plate members 60 are preferably composed of a metal material such as steel or an aluminum alloy.

[0024] The plate member 60 has a first surface 60a and a second surface 60b facing opposite directions in the axial direction. The first surface 60a faces and contacts the end face of the rotor core 21. The second surface 60b faces and contacts the end ring 50. The second surface 60b is embedded by the end ring 50 when the end ring 50 is molded. The second surface 60b is provided with a protrusion 61 that protrudes in the axial direction. Meanwhile, the end ring 50 is molded to match the protrusion 61. Therefore, the end ring 50 is provided with a housing 51 that houses the protrusion 61. When the rotor 20 rotates around the central axis J, centrifugal force is applied to the end ring 50 and the conductor portion 40. According to this embodiment, the protrusion 61 catches on the inner surface of the housing 51, thereby suppressing radial movement of the end ring 50 and the conductor portion 40.

[0025] Fig. 3 is a partially enlarged cross-sectional view of a portion of Fig. 2. As shown in Fig. 3, a virtual straight line passing through the center of the slot 30 and extending in the radial direction is defined as a slot center line SL. Here, "the center of the slot 30" means the center of the slot 30 in the circumferential direction. The slot 30 of this embodiment has a symmetrical shape with respect to the slot center line SL.

[0026] Furthermore, a tooth center line TL is an imaginary straight line that extends radially through the center of the tooth portion 22. Here, "the center of the tooth portion 22" means the center of the tooth portion 22 in the circumferential direction. The slot 30 in this embodiment has a symmetrical shape with respect to the tooth center line TL.

[0027] The slot 30 has an inner end 36, an inner narrowed portion 32, a boundary portion 31, an outer narrowed portion 33, and an open end 34. The inner end 36, the inner narrowed portion 32, the boundary portion 31, the outer narrowed portion 33, and the open end 34 are arranged in this order from the radially inner side to the radially outer side.

[0028] The inner end portion 36 is located at the radially inner end portion of the slot 30. An inner end point 30a is provided on the inner surface of the inner end portion 36, and is located at the radially innermost position of the inner surface of the slot 30. The inner end point 30a is located on the slot center line SL. The inner surface of the inner end portion 36 connects the inner end point 30a and the inner surface 32a of the inner narrowed portion 32 with a uniform radius of curvature. The inner surface of the inner end portion 36 smoothly connects to the inner surface 32a of the inner narrowed portion 32.

[0029] The radially inner end of the inner narrowed portion 32 is connected to the inner end portion 36. On the other hand, a boundary portion 31 is provided at the radially outer end of the inner narrowed portion 32. The circumferential width of the inner narrowed portion 32 narrows as it moves radially inward from the boundary portion 31. Therefore, the inner surface 32a of the inner narrowed portion 32 approaches the slot center line SL as it moves radially inward. The inner surface 32a of the inner narrowed portion 32 extends linearly when viewed in the axial direction.

[0030] A boundary portion 31 is provided at the radially inner end of the outer narrowed portion 33. The radially outer end of the outer narrowed portion 33 is connected to an open end 34. The circumferential width of the outer narrowed portion 33 narrows as it moves radially outward from the boundary portion 31. Therefore, the inner surface 33a of the outer narrowed portion 33 approaches the slot center line SL as it moves radially outward. The inner surface 33a of the outer narrowed portion 33 extends linearly when viewed in the axial direction.

[0031] The boundary portion 31 is located at the boundary between the inner narrowed portion 32 and the outer narrowed portion 33. The boundary portion 31 may connect the inner narrowed portion 32 and the outer narrowed portion 33 with a uniform radius of curvature so as to smoothly connect them.

[0032] The open end 34 is located at the radially outer end of the slot 30. The slot 30 opens radially outward at the open end 34. The open end 34 extends radially with the same circumferential width. Therefore, the inner surface of the open end 34 extends parallel to the slot center line SL.

[0033] As described above, the conductor portion 40 is formed by die-casting into the slot 30, so the cross-sectional shape of the conductor portion 40 is substantially the same as the cross-sectional shape of the slot 30. Therefore, the conductor portion 40 has multiple surfaces that are in contact with or face, via a small gap, the inner surfaces of the inner end portion 36, inner narrowed portion 32, boundary portion 31, outer narrowed portion 33, and open end 34 of the slot 30. In particular, the slot 30 has an outer facing surface 43 that faces the inner surface 33a of the outer narrowed portion 33 and extends parallel to the inner surface.

[0034] In the slot 30 of this embodiment, the circumferential width narrows toward the radially outward direction in the outer narrowed portion 33. Therefore, the normal vector of the inner surface of the outer narrowed portion 33 includes a vector component that faces radially inward. When centrifugal force is applied to the conductor portion 40, the inner surface 33a of the outer narrowed portion 33 comes into contact with the outer opposing surface 43 of the conductor portion 40 and can receive the centrifugal force applied to the conductor portion 40.

[0035] As shown in FIG. 3 , the boundary portion 31 in this embodiment is located radially inward of the radial center CP of the slot 30. Therefore, the region of the slot 30 radially outward from the boundary portion 31 is wider than the region of the slot 30 radially inward from the boundary portion 31. According to this embodiment, the outer narrowed portion 33 can be made radially larger than the inner narrowed portion 32. That is, the inner surface 33 a of the outer narrowed portion 33 in the slot 30 can be made wider, thereby preventing an increase in surface pressure on the inner surface 33 a of the outer narrowed portion 33. According to this embodiment, even if a large centrifugal force is applied to the inner surface of the slot 30 by the conductor portion 40 due to high-speed rotation of the rotor 20, the application of a large force locally can be prevented, thereby preventing deformation of the rotor core 21. This prevents the conductor portion 40 from separating from the slot 30 due to the centrifugal force.

[0036] Furthermore, according to this embodiment, the slots 30 have inner narrowed portions 32 radially inward of the boundaries 31, which makes it easier to ensure a wider width of the teeth 22 compared to when the slots 30 do not have the inner narrowed portions 32. When the rotor core 21 rotates, magnetic flux is generated in the teeth 22 in the radial direction due to induced currents flowing through the conductors 40, generating torque in the rotor 20. If there are portions where the width of the teeth 22 is locally narrowed, magnetic saturation occurs in the teeth 22, making it difficult for magnetic flux to flow through the teeth 22. According to this embodiment, the slots 30 have inner narrowed portions 32, which makes it easier to ensure a wider circumferential width of the teeth 22, thereby enabling the rotational torque of the rotor 20 to be increased.

[0037] In the present embodiment, the radial length dimension L1 of the outer narrowed portion 33 is greater than the radial length dimension L2 of the inner narrowed portion 32. According to the present embodiment, the inner surface 33a of the outer narrowed portion 33 can be ensured to be wider than the inner surface of the inner narrowed portion 32. As a result, when the centrifugal force of the conductor portion 40 is applied to the outer narrowed portion 33, an increase in surface pressure on the inner surface 33a of the outer narrowed portion 33 can be suppressed, thereby suppressing deformation of the rotor core 21 due to the centrifugal force and preventing the conductor portion 40 from coming off the slot 30.

[0038] Furthermore, the radial length L1 of the outer narrowed portion 33 is preferably 1.5 times or more the radial length L2 of the inner narrowed portion (L1 ≥ 1.5 × L2). When the dimensions of the outer narrowed portion 33 and the inner narrowed portion 32 satisfy the above-mentioned relationship, it is easy to ensure that the inner surface 33a of the outer narrowed portion 33 is sufficiently wide, and deformation of the rotor core 21 can be more reliably suppressed.

[0039] In this embodiment, the inclination angle θ of the inner surface 33a of the outer narrowed portion 33 with respect to the slot center line SL is preferably 20° or less. By setting the inclination angle θ to 20° or less, it is possible to reduce the surface pressure applied to each part of the inner surface 33a from the conductor portion 40. Note that, when the inner surface 33a of the outer narrowed portion 33 is curved, the inclination angle θ is preferably 10° or less over the entire inner surface 33a of the outer narrowed portion 33.

[0040] In this embodiment, the inner surface 33a of the outer narrowed portion 33 extends linearly when viewed in the axial direction. The inner surface 33a of the outer narrowed portion 33 may be a concavely curved surface or a convexly curved surface. However, by making the inner surface 33a of the outer narrowed portion 33 linear, the centrifugal force applied to the conductor portion 40 can be received by the entire inner surface 33a with uniform surface pressure, making it easier to suppress stress concentration on the rotor core 21.

[0041] In this embodiment, the inner surface 32a of the inner narrowed portion 32 extends linearly when viewed in the axial direction. The inner surface 32a of the inner narrowed portion 32 may be a concavely curved surface or a convexly curved surface. However, by making the inner surface 32a of the inner narrowed portion 32 linear, it becomes easier to ensure a wider circumferential width of the teeth 22 compared to when the inner surface 32a is concavely curved. This allows magnetic flux to flow more easily through the teeth 22, thereby increasing the rotational torque of the rotor 20. Furthermore, by making the inner surface 32a of the inner narrowed portion 32 linear, it becomes easier to ensure a wider cross-sectional area of ​​the slot 30 compared to when the inner surface 32a is convexly curved. This allows the cross-sectional area of ​​the conductor 40 arranged in the slot 30 to be larger, thereby reducing the electrical resistance of the conductor 40.

[0042] When viewed from the axial direction, the inner surface 32a on one circumferential side of the inner narrowed portion 32 extends parallel to the tooth center line TL of the tooth portion 22 located on one circumferential side of the inner surface 32a. Similarly, the inner surface 32a on the other circumferential side of the inner narrowed portion 32 extends parallel to the tooth center line TL of the tooth portion 22 located on the other circumferential side of the inner surface 32a.

[0043] The inner surface 32a of the inner narrowed portion 32 also functions as the outer surface facing the circumferential direction of the base end portion 22a of the tooth portion 22. Here, the base end portion 22a of the tooth portion 22 refers to the radially inner end portion of the tooth portion 22. According to this embodiment, the outer surface of the base end portion 22a of the tooth portion 22 can be parallel to the tooth center line TL. This allows the circumferential width of the base end portion 22a of the tooth portion 22 to be uniform along the radial direction, making it easier to form a magnetic path in the tooth portion 22 that is parallel to the tooth center line TL. This increases the magnetic flux density of the tooth portion 22 when the rotor 20 rotates, thereby increasing the rotational torque of the rotor 20.

[0044] In this embodiment, the slot 30 has an open end 34 at its radially outer end. The open end 34 extends radially with the same circumferential width. According to this embodiment, the circumferential width of the outer end 41 of the slot 30, located inside the open end 34, can be increased. As described above, during rotation of the rotor 20, an induced current flows in the conductor portion 40 along the axial direction due to the influence of the rotational magnetic flux from the stator 10. Due to the skin effect, the induced current flowing through the conductor portion 40 has the highest current density at the outer end 41, which is close to the outer peripheral surface 21 a of the rotor 20. According to this embodiment, by increasing the circumferential width of the outer end 41 of the conductor portion 40, a large current can be passed through the conductor portion 40, thereby increasing the rotational torque of the rotating electric machine 1. Furthermore, the electrical resistance of the conductor portion 40 can be reduced, thereby improving the driving efficiency of the rotating electric machine 1.

[0045] The slot 30 of this embodiment has a shape symmetrical with respect to the slot center line SL. That is, the outer constriction portion 33 of this embodiment has a shape symmetrical with respect to the slot center line SL. According to this embodiment, the centrifugal force applied to the conductor portion 40 can be received in a balanced manner by the inner surfaces 33a of the outer constriction portion 33 located on one and the other circumferential sides of the slot center line SL. As a result, no portion of the inner surface 33a of the outer constriction portion 33 experiences locally high surface pressure, and deformation of the rotor core 21 due to the centrifugal force can be suppressed.

[0046] Furthermore, according to this embodiment, by making the slots 30 symmetrical, the teeth 22 located between the slots 30 also have a symmetrical shape with respect to the tooth center line TL. This makes it possible to form a stable magnetic path in the teeth 22 regardless of the direction in which the rotor 20 rotates, thereby stabilizing the rotation of the rotor 20.

[0047] <Modifications> Rotors of modifications that can be employed in the rotating electric machine 1 of the above-described embodiment will be described below. In the description of each modification below, the same components as those in the already-described embodiment or modification will be assigned the same reference numerals, and their description will be omitted. The rotors of each modification differ from the above-described embodiment in the shape of the slots and the shape of the conductors housed in the slots.

[0048] 4 is a partially enlarged cross-sectional view of a rotor 120 according to Modification 1. As in the above-described embodiment, the rotor 120 has a rotor core 121 in which a plurality of slots 130 are provided, and a plurality of conductor portions 140 arranged in each of the slots 130. In addition, teeth portions 122 are provided between circumferentially adjacent slots 130 in the rotor core 121. The slots 130 have an inner end portion 136, an inner narrowed portion 132, a boundary portion 131, an outer narrowed portion 133, and an open end portion 134.

[0049] In this modified example, the inner surface 132a on one circumferential side of the inner narrowed portion 132 extends in a direction away from the tooth center line TL of the tooth 122 located on one circumferential side of the inner surface 132a as it moves radially inward. Similarly, the inner surface 132a on the other circumferential side of the inner narrowed portion 132 extends in a direction away from the tooth center line TL of the tooth 122 located on the other circumferential side of the inner surface 132a as it moves radially inward. According to this modified example, the circumferential width of the base end portion 122a of the tooth 122 can be increased, making it easier for magnetic flux to flow through the tooth 122.

[0050] (Variation 2) Figure 5 is a partially enlarged cross-sectional view of a rotor 220 according to Variation 1. Similar to the above-described embodiment, the rotor 220 includes a rotor core 221 having a plurality of slots 230 and a plurality of conductor portions 240 arranged in each of the slots 230. Furthermore, teeth portions 222 are provided between adjacent slots 230 in the rotor core 221 in the circumferential direction. Each slot 230 has an inner end portion 236, an inner narrowed portion 232, a boundary portion 231, an outer narrowed portion 233, and an open end portion 234. Furthermore, the slot 230 of this variation includes an expanded portion 235 located between the outer narrowed portion 233 and the open end portion 234.

[0051] The expansion portion 235 is located radially outward from the outer narrowed portion 233 and radially inward from the open end 234. The expansion portion 235 extends circumferentially on both sides of the outer narrowed portion 233 and the open end 234. A part of the conductor portion 240 is disposed inside the expansion portion 235. The part of the conductor portion 240 that is disposed inside the expansion portion 235 is called a conductor expansion portion 245.

[0052] According to this modification, the conductor extension portion 245 is disposed inside the extension portion 235 of the slot 230, thereby more reliably suppressing radially outward movement of the conductor portion 240 due to centrifugal force. In this modification, the centrifugal force applied to the conductor portion 240 is received by both the inner surface of the outer narrowed portion 233 and the inner surface of the extension portion 235. According to this modification, stress due to the centrifugal force is less likely to concentrate on the inner surface of the outer narrowed portion 233 and the inner surface of the extension portion 235, respectively, and deformation of the rotor core 221 can be suppressed.

[0053] According to this modification, by disposing the extension portion 235 between the outer narrowed portion 233 and the open end 234, the conductor extension portion 245 can be disposed near the outer peripheral surface of the rotor core 221. The skin effect causes the current density of the induced current flowing through the conductor portion 240 to increase in the region close to the outer peripheral surface of the rotor core 221. According to this embodiment, the conductor extension portion 245 can be disposed closer to the outer peripheral surface of the rotor core 221, allowing a larger current to flow through the conductor portion 240 and increasing the rotational torque of the rotating electric machine 1. Furthermore, according to this modification, the electrical resistance of the conductor portion 240 can be reduced, thereby improving the driving efficiency of the rotating electric machine 1.

[0054] Although the embodiments of the present invention have been described above, the configurations and combinations thereof in the embodiments are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the embodiments.

[0055] For example, the rotor may be manufactured by inserting a preformed rod-shaped conductor into a slot in a rotor core and connecting end rings to both ends of the conductor. Even in this case, the cross-sectional shape of the slot can be configured as described above to prevent the conductor from coming off the slot. Furthermore, the material of the conductor and the end ring is not limited to aluminum alloy, but may also be copper or a copper-based alloy.

[0056] The present technology can be configured as follows. (1) A rotor for a rotating electric machine that rotates about a central axis, the rotor comprising: a rotor core having a plurality of slots that are arranged circumferentially and penetrate the rotor core in the axial direction; a plurality of conductor portions arranged in the slots; and a pair of end rings located on one axial side and the other axial side of the rotor core, respectively, and connecting the plurality of conductor portions, the slots extending radially and opening at radially outer ends into an outer peripheral surface of the rotor core, the slots having a boundary portion located radially inward of a midpoint of their radial length, an inner narrowed portion whose circumferential width narrows as it extends radially inward from the boundary portion, and an outer narrowed portion whose circumferential width narrows as it extends radially outward from the boundary portion. (2) The rotor described in (1), wherein the radial length of the outer narrowed portion is greater than the radial length of the inner narrowed portion. (3) The rotor described in (1) or (2), wherein an inner surface of the outer narrowed portion extends linearly when viewed in the axial direction. (4) The rotor according to any one of (1) to (3), wherein the slots have open ends at radially outer ends, and the open ends extend radially with the same circumferential width. (5) The rotor according to any one of (1) to (4), wherein teeth are provided between circumferentially adjacent slots, and assuming a virtual teeth center line extending radially through the center of the teeth, an inner surface on one circumferential side of the inner narrowed portion extends parallel to the teeth center line of the teeth portion located on one circumferential side of the inner surface when viewed from the axial direction. (6) The rotor according to any one of (1) to (5), wherein the slots have a shape symmetrical with respect to a virtual slot center line extending radially through the center of the slot. (7) The rotor according to any one of (1) to (6), wherein the slots have an open end located at an end on the radially outer side, and an expanded portion located between the outer narrowed portion and the open end and expanding on both sides in the circumferential direction relative to the outer narrowed portion and the open end, and at least a part of the conductor portion is disposed in the expanded portion. (8) A rotating electric machine comprising: the rotor according to any one of (1) to (7), and a stator surrounding the rotor from the radially outer side, the stator having an annular stator core and a coil attached to the stator core.

[0057] DESCRIPTION OF SYMBOLS 1... Rotating electric machine, 10... Stator, 11... Stator core, 12... Coil, 20, 120, 220... Rotor, 21, 121, 221... Rotor core, 21a... Outer peripheral surface, 22, 122, 222... Teeth portion, 30, 130, 230... Slot, 31, 131, 231... Boundary portion, 32, 132, 232... Inner narrowed portion, 32a, 33a, 132a... Inner surface, 33, 133, 233... Outer narrowed portion, 34, 134, 234... Open end, 40, 240... Conductor portion, 50... End ring, 235... Expansion portion, J... Central axis, L1, L2... Length dimension, SL... Slot center line, TL... Teeth center line

Claims

1. A rotor for a rotating electric machine that rotates about a central axis, comprising: a rotor core having a plurality of slots that are arranged circumferentially and penetrate in the axial direction, a plurality of conductor portions arranged in the slots, and a pair of end rings located on one axial side and the other axial side of the rotor core, respectively, connecting the plurality of conductor portions, wherein the slots extend radially and open at their radially outer ends into the outer circumferential surface of the rotor core, and the slots have a boundary portion located radially inward than the midpoint of their radial length dimension, an inner narrowed portion whose circumferential width narrows as it moves radially inward from the boundary portion, and an outer narrowed portion whose circumferential width narrows as it moves radially outward from the boundary portion.

2. A rotor as claimed in claim 1, wherein the radial length dimension of said outer constriction is greater than the radial length dimension of said inner constriction.

3. A rotor as claimed in claim 1, wherein the inner surface of said outer narrowed portion extends linearly when viewed in the axial direction.

4. A rotor as claimed in claim 1, wherein said slots have open ends at radially outer ends, said open ends extending radially with the same circumferential width.

5. A rotor as described in claim 1, wherein teeth portions are provided between circumferentially adjacent slots, and an imaginary teeth centerline is assumed to extend radially through the center of the teeth portions, and when viewed from the axial direction, the inner surface on one circumferential side of the inner narrowed portion extends parallel to the teeth centerline of the teeth portion located on one circumferential side of the inner surface.

6. A rotor according to claim 1, wherein said slot has a shape symmetrical about an imaginary slot centerline extending radially through the center of said slot.

7. A rotor as claimed in claim 1, wherein the slot has an open end located at the radially outer end, and an extension located between the outer narrowed portion and the open end and extending circumferentially on both sides of the outer narrowed portion and the open end, and at least a portion of the conductor portion is disposed in the extension.

8. A rotating electric machine comprising: a rotor according to any one of claims 1 to 7; and a stator surrounding said rotor from the radial outside, said stator having an annular stator core and a coil attached to said stator core.

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