Induction motor

Abstract

The stator has stator slots and stator teeth. The rotor has rotor slots, rotor teeth, and rotor slot tips protruding in the circumferential direction from end portions of the rotor teeth over a prescribed length in the radial direction. In a case where the number of the stator slots is set to Nss and the number of the rotor slots is set to Nrs, a relationship of Nss ≥ Nrs is satisfied. In a case where a minimum width in the circumferential direction of the stator teeth is set to Wst, an average width in the circumferential direction of the rotor teeth sandwiched by the rotor bars is set to Wrt, an average width in the circumferential direction of the rotor slots is set to Wrs, a total of the minimum widths Wst of all the stator teeth is set to Tst, a total of the average widths Wrt of all the rotor teeth is set to Trt, and a length in the radial direction of the rotor slot tip is set to Dtip, a relationship of Tst ≤ Trt and (Wst - Wrs) + 2 × Dtip ≥ Wst is satisfied.

Description

Technical Field

[0001] Embodiments of the present invention relate to rotary electric motors. Background Technology

[0002] As an induction motor, a squirrel-cage rotary motor using a so-called squirrel-cage rotor is known. This squirrel-cage rotary motor consists of a stator and a rotor, wherein the stator is configured to have stator coils arranged in a generally cylindrical stator core having multiple stator slots, and the rotor is disposed radially inside the stator and configured to rotate freely relative to the stator.

[0003] The rotor has a rotating shaft that is rotatably mounted about a rotation axis and a rotor core externally fixed to the rotating shaft. Multiple rotor teeth are arranged radially on the rotor core, extending in the radial direction, and rotor slots are formed between adjacent rotor teeth in the circumferential direction. Conductor bars are inserted into these rotor slots. The conductor bars are short-circuited at the axial ends of the rotor core by short-circuit rings.

[0004] Based on this structure, the rotating electric machine utilizes the magnetic flux generated on the primary side (stator side) when current is supplied to the stator coils to induce a current in the conductor bars (secondary conductors). This, in turn, imparts rotational torque to the rotor.

[0005] Typically, the presence of stator and rotor slots creates magnetic irregularities between the rotor and stator. These irregularities cause higher harmonic magnetic fluxes in space, in addition to the fundamental frequency of the primary flux, to link with the conductor bar. The current induced in the conductor bar by these higher harmonic fluxes does not contribute to torque, thus resulting in losses (higher harmonic second-order copper losses).

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 2704666

[0009] Patent Document 2: International Publication No. 2017 / 090159

[0010] Patent Document 3: Japanese Patent Application Publication No. 2016-174507 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] The problem to be solved by the present invention is to provide a rotary motor that can suppress high-order harmonic second-order copper loss and enable the induced current generated in the conductor strip to efficiently contribute to torque.

[0013] Solution for solving the problem

[0014] The rotary electric motor of this embodiment includes a stator and a rotor. The stator has a plurality of stator slots opening on its inner circumferential surface and a plurality of stator teeth formed between adjacent stator slots for winding coils. The rotor has a plurality of rotor slots through which conductive rotor bars are inserted, a plurality of rotor teeth formed between adjacent rotor slots in the circumferential direction along the inner circumferential surface of the stator, and rotor slot tips that project radially outwards from the circumferential ends of the rotor teeth for a predetermined length. The rotor is rotatably disposed about a central axis. When the number of stator slots is Nss and the number of rotor slots is Nrs, the relationship Nss ≥ Nrs is satisfied. Furthermore, when the minimum circumferential width of the stator teeth is set as Wst, the average circumferential width of the rotor teeth sandwiched by the rotor bars is set as Wrt, the average circumferential width of the rotor slots is set as Wrs, the sum of the minimum widths Wst of all the stator teeth is set as Tst, the sum of the average widths Wrt of all the rotor teeth is set as Trt, and the radial length of the rotor slot tip is set as Dtip, the relationship Tst≤Trt and (Wst-Wrs)+2×Dtip≥Wst is satisfied. Attached Figure Description

[0015] Figure 1 This is a longitudinal sectional view showing a portion of the structure of the rotary electric motor according to the first embodiment.

[0016] Figure 2 It is a brief illustration along Figure 1 A cross-sectional view of a portion of the stator and rotor of a rotating electric machine obtained by cutting along line A-A.

[0017] Figure 3 It is Figure 2 A section of the cross-sectional view is shown in enlarged form.

[0018] Figure 4 This is a simplified illustration of a portion of the stator and rotor of the second embodiment. Figure 1 A sectional view at the position corresponding to line A-A.

[0019] Figure 5 This is a simplified illustration of a portion of the stator and rotor of the third embodiment. Figure 1 A sectional view at the position corresponding to line A-A.

[0020] Figure 6 This is an enlarged and simplified illustration of a portion of the stator and rotor of the fourth embodiment. Figure 1 A sectional view at the position corresponding to line A-A.

[0021] Figure 7This is an enlarged and simplified illustration of a portion of the stator and rotor of a modified example of the fourth embodiment. Figure 1 A sectional view at the position corresponding to line A-A. Detailed Implementation

[0022] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, common structures are labeled with the same symbols in all embodiments, and repeated descriptions are omitted. Additionally, the drawings are schematic diagrams of embodiments and are intended to facilitate understanding of the embodiments. The shapes, dimensions, proportions, etc., in the drawings may differ from actual devices, and these differences can be appropriately addressed by referring to the following description and known techniques.

[0023] (First Implementation)

[0024] Figure 1 This is a longitudinal sectional view of the rotary electric motor of an embodiment, divided in half along its central axis. In this embodiment, it is assumed that the rotary electric motor is used as an example for driving railway vehicles. However, the application of the rotary electric motor is not limited to this and it can be applied to other purposes.

[0025] like Figure 1 As shown, the rotary motor 10 is configured, for example, as an internal rotor type rotary motor. The rotary motor 10 includes an internally sealed housing 12, a stator 14 disposed within the housing 12, and a cage-type rotor 16. In the following description, the direction of the central axis C1 of rotation along the rotor 16 in the rotary motor 10 is defined as the axial direction, and the direction in which the rotor 16 rotates about the central axis C1 is defined as the circumferential direction (rotation direction). Furthermore, the direction orthogonal to both the axial and circumferential directions is defined as the radial direction, and the side of the radial direction closest to the central axis C1 is defined as the inner side, and the side furthest away is defined as the outer side.

[0026] The housing 12 has a generally cylindrical frame 18, a disc-shaped first bracket 19 mounted on one axial end of the frame 18 to close this end, and a disc-shaped second bracket 20 mounted on the other axial end of the frame 18 to close this other end. A first bearing housing 22a housing bearing B1 is threadedly fastened at the center of the first bracket 19. A second bearing housing 22b housing bearing B2 is threadedly fastened at the center of the second bracket 20. Bearings B1 and B2 are arranged along the central axis C1 of the rotary motor 10.

[0027] The stator 14 has a cylindrical stator core 24 and a stator coil 28 wound around the stator core 24. The stator core 24 is supported on the frame 18 with its outer circumferential surface engaged with the inner circumferential surface of the frame 18, and is arranged coaxially with the central axis C1. The stator core 24 is constructed by stacking multiple layers of magnetic components, such as annular metal plates made of silicon steel. A pair of annular core pressing members 26a and 26b are fixed to the axial end faces of the stator core 24. The core pressing members 26a and 26b are formed into annular shapes from metals such as iron, and clamp the stator core 24 from both axial end faces to prevent the stator core 24 from separating. The inner diameter of the core pressing members 26a and 26b is set such that the inner circumference does not contact the stator coil 28, which will be described later. The stator core 24 and the core pressing members 26a and 26b are integrated, for example, by welding.

[0028] Multiple stator teeth 60 protruding toward the central axis C1 are formed on the inner circumference of the stator core 24. The stator teeth 60 are arranged at equal intervals along the circumferential direction. The gaps between adjacent stator teeth 60 in the circumferential direction are respectively formed as stator slots 62. In other words, each stator tooth 60 is formed between adjacent stator slots 62 in the circumferential direction. These multiple stator slots 62 open on the inner circumferential surface of the stator 14, specifically on the stator core 24. The stator teeth 60 and stator slots 62 extend axially. The stator coil 28 is wound around each stator tooth 60 via each stator slot 62. The stator coil 28 is installed in the stator core 24 in a state of being inserted into the stator slots 62. The coil ends 28e of the stator coil 28 extend axially from both end faces of the stator core 24. For example, direct current supplied from the overhead wires via a pantograph (not shown) is converted into alternating current and supplied to the stator coil 28.

[0029] The rotor 16 includes a rotating shaft 30, a rotor core 32, multiple conductor bars (rotor bars) 40 embedded in the rotor core 32, and a pair of end rings 42a and 42b connected to both ends of the conductor bars 40. The rotating shaft 30 is arranged coaxially with the central axis C1 within the housing 12, and one end of the shaft is supported axially by bearings B1 and B2 respectively, allowing for free rotation. The drive-side end 30a of the rotating shaft 30 extends outward from the equipment. A connector for connecting a drive gear device, etc., is installed at the drive-side end 30a.

[0030] The rotor core 32 is constructed by stacking multiple layers of magnetic components, such as annular metal plates made of silicon steel, forming a generally cylindrical shape. The rotor core 32 is mounted approximately at the center of the rotating shaft 30 along its axial direction, and is arranged coaxially with the central axis C1 inside the stator core 24. The outer circumferential surface of the rotor core 32 is positioned opposite the inner circumferential surface of the stator core 24 with a gap G between them. The axial length of the rotor core 32 is approximately equal to the axial length of the stator core 24. Furthermore, the rotor core 32 has a first end face 32a at one end along the axial direction and a second end face 32b at the other end. The first end face 32a and the second end face 32b extend approximately orthogonally to the central axis C1. A through hole 32c, which allows the rotating shaft 30 to pass through, is integrally formed throughout the radial center of the rotor core 32 along its axial direction. The rotor core 32 and the rotating shaft 30 are integrated through pressing the rotating shaft 30 into the through hole 32c, bonding, etc.

[0031] The rotor core 32 is supported from both axial ends by a pair of core pressing members 34a and 34b mounted on the rotating shaft 30. The core pressing members 34a and 34b are formed in a ring shape, and their outer diameter is smaller than that of the rotor core 32.

[0032] A plurality of rotor teeth 50 are formed on the outer periphery of the rotor core 32. The rotor teeth 50 are arranged at approximately equal intervals along the circumferential direction of the stator 14, specifically along the inner circumferential surface of the stator core 24. The gaps between adjacent rotor teeth 50 in the circumferential direction are respectively formed as rotor slots 52. In other words, each rotor tooth 50 is formed between adjacent rotor slots 52 in the circumferential direction. These plurality of rotor slots 52 are arranged at approximately equal intervals in the circumferential direction. Furthermore, each rotor tooth 50 extends axially. Each rotor slot 52 extends axially through the rotor core 32 and opens on the first end face 32a and the second end face 32b.

[0033] The conductor bar 40 is a rod-shaped member formed from a conductive material (conductor) such as copper or aluminum, and is non-magnetic. The conductor bar 40 is inserted into each rotor slot 52 and extends axially along the rotor core 32. The cross-sectional shape of the conductor bar 40 corresponds to, for example, the cross-sectional shape of the rotor slot 52, and is formed to be approximately similar in shape but slightly smaller. Therefore, when inserted into the rotor slot 52, there is a small gap between the conductor bar 40 and the rotor slot 52. The conductor bar 40 inserted into the rotor slot 52 is fixed to the rotor slot 52, for example, by riveting, bonding, or the like. One end (first end) 40a of the conductor bar 40 extends outward from the first end face 32a of the rotor core 32 in the longitudinal direction. The other end (second end) 40b of the conductor bar 40 extends outward from the second end face 32b of the rotor core 32 in the longitudinal direction. The extension lengths of the first end 40a and the second end 40b are set to be approximately equal.

[0034] A circular end ring 42a is fixed to the protruding end of the first end 40a. The end ring 42a is arranged coaxially with the central axis C1, connecting multiple end 40as to each other. A circular end ring 42b is fixed to the protruding end of the second end 40b. The end ring 42b is arranged coaxially with the central axis C1, connecting multiple end 40b to each other. The conductor strip 40 and the end rings 42a and 42b are formed of a conductive metal material such as aluminum or copper.

[0035] Multiple conductor bars 40 and a pair of end rings 42a and 42b constitute the squirrel-cage rotor of the rotary motor 10. By energizing the stator coil 28, the rotor core 32 is induced to rotate, and the rotating shaft 30 rotates integrally with the rotor core 32.

[0036] Next, the relationship between the stator teeth 60 and stator slots 62 and the rotor teeth 50 and rotor slots 52 in this embodiment will be explained.

[0037] Figure 2 It is a brief illustration along Figure 1 A cross-sectional view of a portion of the stator 14 and rotor 16 obtained by cutting along line A-A. Figure 3 It is Figure 2 A section of the cross-sectional view is shown in enlarged form.

[0038] like Figure 2 and Figure 3 As shown, the rotor slot 52 opens at the outer periphery of the rotor core 32 via the opening 54. The opening 54 extends along the entire axial length of the rotor core 32. The circumferential width of the rotor slot 52 is set to be larger than the circumferential width of the opening 54.

[0039] A pointed portion (rotor slot tip) 36 is provided on the outer periphery of the rotor slot 52 to prevent the conductor bar 40 from falling off. The pointed portion 36 is a portion that protrudes circumferentially from the rotor core 32, specifically from the circumferential end of the rotor tooth 50, extending radially for a predetermined length, and narrows the outer periphery of the rotor slot 52 in the circumferential direction. In other words, the pointed portion 36 is the portion that protrudes circumferentially along the outer periphery of the rotor core 32 (rotor tooth 50) and overlaps radially with the conductor bar 40 inserted in the rotor slot 52. The outer periphery of the rotor slot 52 is narrowed from both sides in the circumferential direction due to a pair of pointed portions 36 protruding in opposite directions, and the outer periphery of the rotor slot 52 narrowed by the pointed portions 36 is formed as an opening 54. The pointed portion 36 is used to prevent the conductor bar 40 from falling off the rotor slot 52.

[0040] In this embodiment, the number of rotor slots 52 (Nrs) is set to be less than or equal to the number of stator slots 62 (Nss) (Nss ≥ Nrs). Figure 2The diagram shows an example where the number of rotor slots 52, Nrs, is less than the number of stator slots 62, Nss (Nss > Nrs). In this case, for example, the number of stator slots 62, Nss, is 36, and the number of rotor slots 52, Nrs, is 26. Wherein, as long as the relationship Nss ≥ Nrs (hereinafter referred to as Equation 1) is satisfied, the combination of the number of stator slots 62, Nss, and the number of rotor slots 52, can be arbitrary.

[0041] Furthermore, in this embodiment, the width dimensions of the stator teeth 60, rotor teeth 50, and rotor slots 52 relative to the circumferential direction have a predetermined relationship. The aforementioned width dimensions are defined as follows.

[0042] The minimum width (Wst) applies as the width dimension of the stator tooth 60. The minimum width Wst is the shortest distance connecting any point on either of the two edges 60a, 60b that define the circumferential side of the stator tooth 60; in other words, any point on either edge 60a, 60b that defines the side in a direction orthogonal to the radial direction. Figure 2 In the example shown, the link Figure 3 The distance between the two points shown (hereinafter referred to as reference points) st1 and st2 is the minimum width Wst. Reference points st1 and st2 are the points located at the innermost radial position in the stator teeth 60. In other words, reference points st1 and st2 are the two points located at the two ends in the circumferential direction of the protruding ends of the stator teeth 60 that protrude toward the central axis C1.

[0043] The average width (Wrt) is used as the width dimension of the rotor tooth 50. The average width Wrt is the average distance between any points located on the same circumference (at the same diameter) of the two sides 50a and 50b that define the circumferential side of the rotor tooth 50; in other words, between any points on the two sides 50a and 50b that define the side in the direction orthogonal to the radial direction. The circumferential side defined by the two sides 50a and 50b is held by a conductor strip 40 inserted into the rotor slot 52. Figure 2 In the example shown, the distance between the two points rt1 and rt2 (hereinafter referred to as reference points) is the average width Wrt. Reference points rt1 and rt2 are points located approximately at the radial midpoint of the rotor teeth 50. In this case, the cross-sectional shape of the rotor teeth 50 is formed as an approximate trapezoidal shape, with the width dimension narrowing towards the radial inner side and widening towards the radial outer side.

[0044] The average width (Wrs) is used as the width dimension of the rotor slot 52. The average width Wrs is the average distance between any points located on the same circumference (at the same diameter) of the two sides 52a and 52b that define the circumferential side of the rotor slot 52; in other words, between any points located on the same circumference (at the same diameter) of the two sides 52a and 52b that define the side in the direction orthogonal to the radial direction. Figure 2 In the example shown, the link Figure 3 The distance between the two points shown (hereinafter referred to as reference points) rs1 and rs2 is the average width Wrs. Reference points rs1 and rs2 are points located approximately at the radial midpoint of the rotor slot 52. Additionally, in Figure 2 In the example shown, the distances obtained by connecting points on the same circumference (at the same diameter) of the two sides 52a and 52b are approximately fixed at all locations (points) of the two sides 52a and 52b. That is, in this case, the cross-sectional shape of the rotor slot 52 is formed to be approximately rectangular.

[0045] For the minimum width Wst of the stator teeth 60 as specified, the sum of the minimum widths Wst of all stator teeth 60 (total width) is set as Tst. Furthermore, for the average width Wrt of the rotor teeth 50, the sum of the average widths Wrt of all rotor teeth 50 (total width) is set as Trt. In this case, the stator teeth 60 and rotor teeth 50 are configured to satisfy the relationship Tst ≤ Trt (hereinafter, this relationship is referred to as Equation 2). That is, the total width Tst of the minimum widths Wst of all stator teeth 60 is set to be less than or equal to the total width Trt of the average widths Wrt of all rotor teeth 50. Figure 2 The image shows the shape of the stator teeth 60 and rotor teeth 50 as an example when the total width Tst is smaller than the total width Trt (Tst < Trt).

[0046] Furthermore, there is a defined relationship between the minimum width Wst of the stator teeth 60 and the average width Wrt of the rotor teeth 50 and the radial length of the tip 36 (hereinafter referred to as the depth Dtip). The depth Dtip of the tip 36 is from the centerline of the rotor slot 52 ( Figure 3 The single-dot dashed line L52 shown is parallel to the outer arc of the rotor slot 52. Figure 3 The shortest distance from the imaginary intersection point X of the double-dotted line R52 to the end face 40c of the conductor strip 40. The centerline L52 of the rotor slot 52 is a straight line orthogonal to the central axis C1 and passing through the midpoint of the straight line connecting the reference points rs1 and rs2, which bisects the circumferential width (e.g., the average width Wrs) of the rotor slot 52. The end face 40c of the conductor strip 40 is the outer radial surface of the conductor strip 40.

[0047] With the depth Dtip of the tip 36 defined in this way, the tip 36, stator teeth 60, and rotor slots 52 are configured to satisfy the relationship (Wst - Wrs) + 2 × Dtip ≥ Wst (hereinafter, this relationship is referred to as Equation 3). That is, the value obtained by adding twice the depth Dtip of the tip 36 to the difference between the minimum width Wst of the stator teeth 60 and the average width Wrs of the rotor slots 52 is a value greater than or equal to the minimum width Wst of the stator teeth 60.

[0048] Thus, according to this embodiment, the stator teeth 60, rotor teeth 50, rotor slots 52, and tips 36 are configured to satisfy Equations 1, 2, and 3 described above. This suppresses the linking of higher harmonic components of the magnetic flux flowing from the stator 14 to the rotor 16 with the conductor bar 40. Consequently, it suppresses the current loss (higher harmonic second-order copper loss) induced in the conductor bar due to higher harmonic magnetic flux, which is common in the prior art, and enables the conductor bar 40 to efficiently generate induced current to assist torque. Therefore, it is possible to suppress torque loss in the rotary motor 10.

[0049] Furthermore, the stator teeth 60, rotor teeth 50, rotor slots 52, and tips 36 are not limited in shape as long as they are configured to satisfy the relationships in equations 1, 2, and 3 above. Figures 1-3 The shape shown. Below, regarding... Figures 1-3 Different embodiments with different forms will be described. Furthermore, in these embodiments, the basic structure of the rotary motor 10 is similar to... Figure 1 The same applies to the embodiment shown. Therefore, the following description will focus on the differences from this embodiment, and the same reference numerals will be used to label the same components as the rotary motor 10 in this embodiment, and the description will be omitted or simplified.

[0050] (Second Implementation)

[0051] Figure 4 This is a simplified illustration of a portion of the stator 14 and rotor 16 of the second embodiment. Figure 1 A cross-sectional view at a position corresponding to line A-A. Unlike the first embodiment (Nss > Nrs), in... Figure 4 The diagram shows an example where the number of rotor slots 522, Nrs, is the same as the number of stator slots 62, Nss (Nss = Nrs). The shapes of the stator teeth 60 and stator slots 62 are the same as in the first embodiment. In this case, for example, the number of stator slots 62, Nss, is 36, and the number of rotor slots 522, Nrs, is 36.

[0052] The rotor slot 522 has a roughly trapezoidal cross-sectional shape, narrowing in the circumferential direction towards the inner radial side and widening in the circumferential direction towards the outer radial side. The conductor strip 402 inserted into the rotor slot 522 has a similar, slightly smaller, trapezoidal cross-sectional shape, corresponding to the rotor slot 522. The average width Wrs of the rotor slot 522 is the distance between two points rs1 and rs2 located approximately at the radial midpoint of the rotor slot 522.

[0053] In contrast, the cross-sectional shape of the rotor teeth 502 is approximately rectangular. Therefore, the circumferential width of the rotor teeth 502 is fixed radially. The total width Tst of the minimum width Wst of all stator teeth 60 is equal to the total width Trt of the average width Wrt of all rotor teeth 502.

[0054] Thus, in this embodiment, since the circumferential width of the rotor teeth 502 is fixed radially, there is no difference in the radial reluctance between the inner and outer radial positions of the rotor teeth 502. As a result, the magnetic reluctance at the rotor teeth 502 can be reduced, and the magnetic flux density can be homogenized. Consequently, induced current can be efficiently generated in the conductor bar 402, and the generated induced current can efficiently contribute to the torque of the rotating shaft 30. Therefore, torque loss of the rotary motor 10 can be suppressed.

[0055] Alternatively, the rotor slots Nrs can be designed to be the same as the stator slots Nss, for example, by forming the cross-sectional shapes of the rotor slots and conductor bars into approximately rectangular shapes and the cross-sectional shape of the rotor teeth into approximately trapezoidal shapes.

[0056] (Third Implementation)

[0057] Figure 5 This is a simplified illustration of a portion of the stator 14 and rotor 16 of the third embodiment. Figure 1 A cross-sectional view at a position corresponding to line A-A. Similar to the first embodiment (Nss > Nrs), in... Figure 5 The diagram shows an example where the number of rotor slots 523, Nrs, is less than the number of stator slots 62, Nss (Nss > Nrs). The shapes of the stator teeth 60 and stator slots 62 are the same as in the first embodiment. In this case, for example, the number of stator slots 62, Nss, is 36, and the number of rotor slots 523, Nrs, is 26.

[0058] On the other hand, the shapes of the rotor teeth 503, rotor slots 523 and conductor bars 403 are different from those of the rotor teeth 50, rotor slots 52 and conductor bars 40 in the first embodiment.

[0059] The cross-sectional shape of the rotor tooth 503 is approximately rectangular. Therefore, the circumferential width of the rotor tooth 503 is fixed in the radial direction. However, the total width Tst of the minimum width Wst of all stator teeth 60 is smaller than the total width Trt of the average width Wrt of all rotor teeth 50 (Tst < Trt).

[0060] In contrast, the cross-sectional shape of the rotor slot 523 is approximately trapezoidal, narrowing towards the radially inner side and widening towards the radially outer side. The cross-sectional shape of the conductor strip 403 inserted into the rotor slot 523 corresponds to that of the rotor slot 523, being a trapezoidal shape that is slightly smaller and approximately similar. The average width Wrs of the rotor slot 523 is the distance between two points rs1 and rs2 located approximately at the radial midpoint of the rotor slot 523.

[0061] Thus, this embodiment is equivalent to the second embodiment in which the number of rotor slots 523, Nrs, is less than the number of stator slots 62, Nss (Nss > Nrs).

[0062] According to this embodiment, similarly to the second embodiment, since the circumferential width of the rotor tooth 503 is fixed radially, there is no difference between the radially inner and radially outer positions of the magnetic reluctance at the rotor tooth 503. As a result, the magnetic reluctance at the rotor tooth 503 can be reduced, and the magnetic flux density can be homogenized. Compared to the rotor tooth 502 of the second embodiment, since the average width Wrt of the rotor tooth 503 is wider, the magnetic flux density at the rotor tooth 503 is smaller, and the magnetic reluctance reduction effect can be further improved.

[0063] (Fourth Implementation)

[0064] In the first to third embodiments described above, the cross-sectional shapes of the rotor slots 52, 522, 523 and the conductor bars 40, 402, 403 are set to quadrilaterals (quadrilaterals), but they can also be configured as polygonal cross-sectional shapes with more than four sides.

[0065] Figure 6 This is an enlarged and simplified illustration of a portion of the stator 14 and rotor 16 of the fourth embodiment. Figure 1 A cross-sectional view at the position corresponding to line A-A. For example... Figure 6 As shown, the rotor slot 524 has a hexagonal cross-sectional shape. Figure 6In the example shown, the rotor slots 524 are configured with a roughly hexagonal cross-sectional shape. This roughly hexagonal shape is obtained by chamfering (e.g., C-chamfering) the inner corners of a roughly trapezoidal shape, which is narrower in the circumferential direction towards the radially inner side and wider in the circumferential direction towards the radially outer side. In other words, the rotor slots 524 with this hexagonal cross-sectional shape are arranged circumferentially to form the rotor teeth 504. The rotor teeth 504 are continuous with the tips 36 in the chamfered shape of the rotor slots 524. The conductor strips 404 inserted into the rotor slots 524 have a cross-sectional shape corresponding to the cross-sectional shape of the rotor slots 524, and are formed into a roughly similar hexagonal shape, slightly smaller than the cross-sectional shape of the rotor slots 524.

[0066] in addition, Figure 7 This is an enlarged and simplified illustration of a portion of the stator 14 and rotor 16 of a modified example of the fourth embodiment. Figure 1 A cross-sectional view at the position corresponding to line A-A. For example... Figure 7 As shown, the cross-sectional shape of rotor slot 524a is set to octagonal. In Figure 7 In the example shown, the rotor slot 524a is constructed with a roughly octagonal cross-sectional shape. This roughly octagonal shape is obtained by chamfering (e.g., C-chamfering) the inner corners of the roughly rectangular shape and bending the two circumferentially opposite faces in a manner that brings them close to each other. In other words, the rotor slots 524a with this octagonal cross-sectional shape are arranged circumferentially to form the rotor teeth 504a. The rotor teeth 504a are continuous with the tips 36 in the chamfered shape of the rotor slots 524a. The conductor strip 404a inserted into the rotor slots 524a has a cross-sectional shape that corresponds to the cross-sectional shape of the rotor slots 524a and is formed as a roughly similar octagonal shape, slightly smaller than the cross-sectional shape of the rotor slots 524a.

[0067] Thus, in this embodiment, the rotor teeth 504, 504a are continuous with the tip 36 in a chamfered shape relative to the rotor slots 524, 524a. In other words, the continuity 56 between the rotor teeth 504, 504a and the tip 36 is chamfered in the rotor slots 524, 524a. Therefore, compared with the first embodiment to the third embodiment (… Figure 3 , Figure 4 , Figure 5 Compared to the previous method, the continuous portion 56 of the rotor teeth 504, 504a that is continuous with the tip 36 is wider. Therefore, the magnetic flux density in the rotor teeth 504, 504a near the tip 36 is smaller, which can reduce magnetic reluctance. As a result, the high-order harmonic components of the magnetic flux flowing from the stator 14 to the rotor 16 can be suppressed from linking with the conductor bars 404, 404a. Therefore, induced current can be efficiently generated on the conductor bar 402 to assist torque, and torque loss of the rotating electric machine 10 can be suppressed.

[0068] The foregoing has described several embodiments (including modifications) of the present invention. However, the embodiments described above are merely examples and are not intended to limit the scope of the invention. These embodiments can be implemented in a wide variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included within the scope of the invention as described in the claims and its equivalents.

[0069] For example, in the first to fourth embodiments, the rotor teeth 50, 502, 503, 504, 504a, rotor slots 52, 522, 523, 524, 524a, and conductor bars 40, 402, 403, 404, 404a are made to have different shapes from each other. Alternatively, or based on this, the shapes of the stator teeth 60 and stator slots 62 can be made to have different shapes from each other in a manner that satisfies the relationships in Equations 1, 2, and 3.

[0070] Symbol explanation:

[0071] 10… Rotary motor, 12… Housing, 14… Stator, 16… Rotor, 18… Frame, 24… Stator core, 26a, 26b… Core pressing parts, 28… Stator coil, 30… Rotating shaft, 32… Rotor core, 34a, 34b… Core pressing parts, 36… Tip, 40, 402, 403, 404, 404a… Conductor bars (rotor bars), 40c… End face (outer side), 50, 502, 503, 504, 504a… Rotor teeth, 50a, 50b… Edge, 52, 522, 523, 524, 524a… Rotor slots, 52a, 52b… Side, 54…opening, 56…continuum, 60…stator tooth, 60a, 60b…side, 62…stator slot, C1…central axis, Dtip…depth of the tip, L52…centerline of the rotor slot, R52…outer circumferential arc of the rotor slot, X…intersection, rs1, rs2…reference points of the rotor slot, rt1, rt2…reference points of the rotor teeth, st1, st2…reference points of the stator teeth, Trt…total width of the average width of all rotor teeth, Tst…total width of the minimum width of all stator teeth, Wrs…average width of the rotor slot, Wrt…average width of the rotor teeth, Wst…minimum width of the stator teeth.

Claims

1. An induction motor characterized by, Possessing: a stator having a plurality of stator slots opened on an inner peripheral surface and a plurality of stator teeth formed between the stator slots adjacent to each other and for coil winding; and a rotor having a plurality of rotor slots for rotor bars having electrical conductivity to be inserted therethrough, a plurality of rotor teeth formed between the rotor slots adjacent in a circumferential direction of the inner peripheral surface of the stator, and a tip portion protruding from an end portion in the circumferential direction of the rotor teeth to a prescribed length in a radial direction, the rotor being disposed to be rotatable about a center axis, the rotor has an opening portion in an outer peripheral surface thereof, the opening portion opening the rotor slots in the radial direction, the tip portion narrows the outer peripheral surface of the rotor slots in the circumferential direction to form the opening portion, the tip portion overlapping the rotor bars inserted in the rotor slots in the radial direction, in a case where a number of the stator slots is set to Nss and a number of the rotor slots is set to Nrs, a relationship of Nss ≥ Nrs is satisfied, in a case where a minimum width in the circumferential direction of each of the plurality of stator teeth is set to Wst, an average width in the circumferential direction of each of the plurality of rotor teeth sandwiched by the rotor bars is set to Wrt, an average width in the circumferential direction of each of the plurality of rotor slots is set to Wrs, a total of the minimum widths Wst of all the stator teeth is set to Tst, a total of the average widths Wrt of all the rotor teeth is set to Trt, and a length in the radial direction of the tip portion is set to Dtip, a relationship of Tst ≤ Trt and (Wst - Wrs) + 2 × Dtip ≥ Wst is satisfied, the minimum width Wst is a shortest distance between sides in the circumferential direction of one stator tooth, the average width Wrt is an average distance between sides in the circumferential direction of one rotor tooth, the average width Wrs is an average distance between sides in the circumferential direction of one rotor slot.

2. The induction motor according to claim 1, characterized in that the rotor teeth and the tip portion are continuous in a chamfered form.

3. The induction motor according to claim 1 or 2, characterized in that the length Dtip in the radial direction of the tip portion is a shortest distance from an imaginary intersection point of a straight line passing through a point bisecting a width in the circumferential direction of the rotor slot and orthogonal to the center axis to an outer side surface of the rotor bar inserted in the rotor slot in the radial direction.

4. The induction motor according to claim 3, characterized in that the number Nss of the stator slots is 36.

Images