Rotor cores, rotors, and rotating electric machines

Abstract

To provide a rotor of a rotary electric machine that improves torque at the start-up.SOLUTION: A rotor core 20 is rotatable around a center axis J, and the rotor core comprises: a plurality of magnetic pole parts P arranged at an interval in a circumferential direction; and a plurality of magnetic pole intermediate parts M arranged between the magnetic pole parts adjacent in the circumferential direction. The plurality of magnetic pole intermediate parts each have a through hole group including a plurality of through holes 30 arranged at an interval in a radial direction. The through holes each have outer end parts 30a, 30b located at an outer edge part 20b in the radial direction of the rotor core, and in each of the plurality of magnetic pole intermediate parts, the outer end parts are arranged in a first area P1 and a second area P2 that are arranged with the center in the circumferential direction of the magnetic pole intermediate part therebetween. The number of the outer end parts arranged in the second area is less than the number of the outer end parts arranged in the first area.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] There is known a rotating electric machine having a rotor including a rotor core and holes provided in the rotor core. For example, the rotor core of Patent Document 1 has a plurality of holes serving as flux barriers that are convex inward in the radial direction when viewed in the axial direction of the rotor core. The plurality of holes have an asymmetric shape with respect to the axis at the circumferential center of two adjacent magnetic pole portions.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to reduce torque ripple, the plurality of holes in Patent Document 1 include asymmetric holes with respect to the axis at the circumferential center of two adjacent magnetic pole portions. However, with holes of such a shape, the performance at the start-up of the rotating electric machine and the efficiency during normal rotation when the rotating electric machine reaches the rated speed may not be sufficiently improved.

[0005] In view of the above circumstances, an object of the present invention is to provide a rotor core, a rotor, and a rotating electric machine having a structure capable of improving the starting torque while suitably maintaining the flow of magnetic flux during normal rotation in the rotating electric machine.

Means for Solving the Problems

[0006] One embodiment of the rotor core of the present invention is a rotor core rotatable about a central axis, comprising a plurality of pole portions arranged at intervals in the circumferential direction, and a plurality of intermediate pole portions located between adjacent pole portions in the circumferential direction. Each of the plurality of intermediate pole portions has a group of through holes, including a plurality of through holes arranged at intervals in the radial direction. Each of the through holes has an outer end located on the radial outer edge of the rotor core, and in each of the plurality of intermediate pole portions, the outer end is located in a first region and a second region arranged on either side of the circumferential center of the intermediate pole portion. The number of outer ends located in the second region is less than the number of outer ends located in the first region.

[0007] One embodiment of the rotor of the present invention comprises the rotor core described above and a conductor located within the through hole.

[0008] One embodiment of the rotating electric machine of the present invention comprises the rotor described above and a stator located radially outward from the rotor. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to provide a rotor core, rotor, and rotating electric machine having a structure that can improve torque at startup while suitably maintaining the flow of magnetic flux during normal rotation in a rotating electric machine. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic cross-sectional view showing the rotating electric machine of this embodiment. [Figure 2] Figure 2 is a cross-sectional view showing the rotor of this embodiment, and is a cross-sectional view taken along line II-II in Figure 1. [Figure 3] Figure 3 is a partially enlarged view of the rotor core of this embodiment. [Figure 4] Figure 4 is a partial cross-sectional view showing a modified example of the rotor core of this embodiment. [Figure 5] Figure 5 is a cross-sectional view showing another modified example of the rotor core of this embodiment. [Figure 6] Figure 6 is a cross-sectional view showing another modified example of the rotor core of this embodiment. [Figure 7A] Figure 7A is a partially enlarged view showing the rotor core of Comparative Example 1. [Figure 7B] Figure 7B is a partially enlarged view showing the rotor core of Comparative Example 2. [Modes for carrying out the invention]

[0011] The Z-axis direction, as shown in each figure, is the vertical direction, with the positive side being the "up" and the negative side being the "down". The central axis J, as shown in each figure, is a virtual line parallel to the Z-axis direction and extending in the vertical direction. In the following explanation, the axial direction of the central axis J, i.e., the direction parallel to the vertical direction, will simply be called the "axial direction", the radial direction centered on the central axis J will simply be called the "radial direction", and the circumferential direction centered on the central axis J will simply be called the "circumferential direction". When viewed from the upper side in the axial direction, the direction moving clockwise in the circumferential direction will be called the +θ side, and the direction moving counterclockwise will be called the -θ side.

[0012] Note that "up and down," "upper side," and "lower side" are merely names used to describe the arrangement of each part, and the actual arrangement may differ from those indicated by these names.

[0013] The rotating electric machine 1 of this embodiment, shown in Figure 1, is an inner rotor type motor. As shown in Figure 1, the rotating electric machine 1 of this embodiment comprises a housing 2, a rotor 10, a stator 3, a bearing holder 4, and bearings 5a and 5b. The housing 2 houses the rotor 10, the stator 3, the bearing holder 4, and the bearings 5a and 5b. The bottom of the housing 2 holds the bearing 5b. The bearing holder 4 holds the bearing 5a. The bearings 5a and 5b are, for example, ball bearings.

[0014] The stator 3 is located radially outward from the rotor 10. As shown in Figure 1, the stator 3 has a stator core 3a, an insulator 3d, and a plurality of coils 3e. The stator core 3a has a core back 3b and a plurality of teeth 3c. The core back 3b is annular with a central axis J. The plurality of teeth 3c extend radially inward from the core back 3b. The plurality of teeth 3c are arranged at equal intervals along the circumference. The plurality of coils 3e are mounted on the stator core 3a via the insulator 3d.

[0015] The rotor 10 is rotatable about a central axis J. As shown in Figures 1 and 2, the rotor 10 comprises a shaft 11, a rotor core 20, a conductor 40, and an annular conductive part 50. The shaft 11 is cylindrical and extends axially about the central axis J. As shown in Figure 1, the shaft 11 is supported by bearings 5a and 5b so as to be rotatable about the central axis J.

[0016] The rotor core 20 is a magnetic material. The material of the rotor core 20 is, for example, silicon steel, which has higher magnetic permeability and lower electrical conductivity than an iron-carbon alloy. The rotor core 20 is fixed to the outer circumferential surface of the shaft 11. The rotor core 20 has a central through-hole 20a that penetrates the rotor core 20 in the axial direction. As shown in Figure 2, the central through-hole 20a is circular in shape with the central axis J as the center when viewed in the axial direction. The shaft 11 passes through the central through-hole 20a. The shaft 11 is fixed in the central through-hole 20a, for example by press-fitting. Although not shown in the figure, the rotor core 20 is constructed by, for example, stacking multiple electromagnetic steel sheets in the axial direction. The annular conductive parts 50 are positioned at both axial ends of the rotor core 20. The annular conductive parts 50 are circular in shape with the central axis J as the center. The outer diameter of the annular conductive parts 50 is equal to the outer diameter of the rotor core 20, and the inner diameter of the annular conductive parts 50 is larger than the inner diameter of the central through-hole 20a of the rotor core 20. The material constituting the annular conductive parts 50 is a material with high electrical conductivity. Examples of materials constituting the annular conductive parts 50 include aluminum, copper, and alloys of aluminum and copper.

[0017] The rotor core 20 has a plurality of through holes 30. In the present embodiment, each through hole 30 is formed by a hole provided in the rotor core 20. The through hole 30 penetrates the rotor core 20 in the axial direction, for example. Each through hole 30 extends along a plane orthogonal to the axial direction and has a shape that is convex radially inward when viewed in the axial direction. A plurality of sets each including two or more through holes 30 are provided in the rotor core 20. A set of through holes 30 is also referred to as a through hole group 130. Each through hole group 130 includes a plurality of through holes 30.

[0018] The rotor core 20 provided with the through holes 30 as described above serves as the rotor core of a synchronous reluctance motor having a magnetic salient pole structure. More specifically, since the through holes 30 through which magnetic flux hardly passes serve as flux barriers of the rotor 10, when viewed from the axial direction, the space between two adjacent through hole groups 130 becomes a salient pole direction in which magnetic flux easily passes, and a direction in which magnetic flux hardly passes is provided at the central portion in the circumferential direction of one through hole group 130. In the following description, the above-mentioned salient pole direction in which magnetic flux easily passes is referred to as the "d-axis direction", and the above-mentioned direction in which magnetic flux hardly passes is referred to as the "q-axis direction". Since the rotor core 20 has magnetic anisotropy in the q-axis direction and the d-axis direction, when a magnetic field is generated by the stator 3, a reluctance torque is generated, making it possible to rotate the rotor 10.

[0019] Also, the d-axis direction is a radial direction passing through the circumferential center of the magnetic pole portion P of the rotor core 20, and the q-axis direction is a radial direction passing through the circumferential center between adjacent magnetic pole portions P in the circumferential direction. The portion located between adjacent magnetic pole portions P in the circumferential direction is hereinafter referred to as a magnetic pole intermediate portion M. The q-axis passes through the magnetic pole intermediate portion M. Thus, the rotor 10 is provided with a plurality of magnetic pole portions P provided along the circumferential direction and a plurality of magnetic pole intermediate portions M respectively located between adjacent magnetic pole portions P in the circumferential direction. Each magnetic pole intermediate portion M has a through hole group 130.

[0020] In this embodiment, a conductor 40 is placed inside the through-hole 30. The inside of all of the multiple through-holes 30 is filled with the conductor 40. The material constituting the conductor 40 is a material with high electrical conductivity. The material constituting the conductor 40 is the same as the material constituting the annular conductive part 50, and examples include aluminum, copper, and alloys of aluminum and copper. The material constituting the conductor 40 is a metal that is not ferromagnetic so as not to affect the magnetic salient pole structure formed by the through-hole 30. Each conductor 40 placed within the through-hole 30 is electrically connected to the annular conductive portion 50. Therefore, the conductors 40 within each through-hole 30 are electrically connected to each other via the annular conductive portion 50, and the annular conductive portion 50 short-circuits the conductors 40 within each through-hole 30. The conductor 40 inside the through hole 30 is made by heating the metal that will become the conductor 40 and pouring it into the through hole 30. In this embodiment, the conductor 40 and the annular conductive portion 50 are part of the same single component. For example, molds for the annular conductive portion 50 are placed on both axial sides of the rotor core 20, and the conductor 40 and the annular conductive portion 50 are manufactured by heating the metal that will become the conductor 40 and the annular conductive portion 50 and pouring it into the through hole 30 and the mold. The conductor 40 and the annular conductive portion 50 may be separate components or made of different materials.

[0021] When a conductor 40 is placed within the through-hole 30 of a synchronous reluctance motor, the conductor is placed in a rotating magnetic field. Therefore, when the magnetic field generated by the stator 3 rotates, an induced current flows through the conductor 40 due to electromagnetic induction, and the Lorentz force of the induced current makes it possible to generate rotational force in the rotor 10. In particular, torque due to the Lorentz force can be obtained when starting the rotation of the stationary rotor 10, thus improving startup performance. A synchronous reluctance motor with improved startup characteristics in this way is also called a DOL SynRM (Direct-On-Line Synchronous Reluctance Motor).

[0022] In the rotor 10 having a magnetic salient pole structure, since the conductor 40 is not placed in the magnetic pole portion P, the amount of conductor 40 placed in the circumferential direction is not uniform. For this reason, the Lorentz force generated during startup is smaller compared to conventional induction motors, and startup performance may be poor.

[0023] Therefore, the inventors found that in a rotor core 20 having a plurality of through holes 30 that have an asymmetrical shape when the q-axis is the axis of symmetry, by increasing the cross-sectional area of ​​the radially outermost through hole 30 when viewed from the axial direction, and by increasing the area in which the conductor 40 can be arranged within the through hole 30, a larger torque due to the Lorentz force can be obtained when starting a stationary rotor 10. Furthermore, they found that such a rotor core 20 can also ensure satisfactory efficiency during normal rotation when the rotating electric machine 1 rotates at its rated speed.

[0024] The configuration of the through-hole 30 of the rotor core 20 in this embodiment will be described in more detail below with reference to Figures 2 and 3.

[0025] (Through hole 30) The rotor core 20 of this embodiment has four sets of through-hole groups 130, each containing four through-holes 30, including an outermost through-hole 31, a first intermediate through-hole 32, a second intermediate through-hole 33, and an innermost through-hole 34. The outermost through-hole 31, the first intermediate through-hole 32, the second intermediate through-hole 33, and the innermost through-hole 34 are arranged in this order from the radially outer side to the radially inner side. In the through-hole groups 130 of this embodiment, the through-hole located furthest radially outward among the multiple through-holes 30 is the outermost through-hole 31, and the through-hole located furthest radially inward is the innermost through-hole 34.

[0026] In this embodiment, four through-holes 30 are arranged in a group of through-holes 130. The number of through-holes 30 in a group of through-holes 130 is not limited to four; it is sufficient to have two or more through-holes 30, including the outermost through-hole 31 and the innermost through-hole 34. In other words, intermediate through-holes between the outermost through-hole 31 and the innermost through-hole 34 are not required. The number of through-holes 30 may be appropriately changed depending on the size of the rotor core 20. Hereafter, when referring to the outermost through-hole 31, the first intermediate through-hole 32, the second intermediate through-hole 33, or the innermost through-hole 34, it will also simply be called the through-hole 30.

[0027] The four sets of through-holes 130 are arranged at equal intervals along the circumferential direction of the rotor core 20. Each group of through-holes 130 has a similar configuration, except that they are arranged in a position rotated 90° in the circumferential direction. In the following description of each through-hole 30, we will describe a through-hole 30 that is included in one of the four groups of through-holes 130 as a representative.

[0028] The outermost through-hole 31, the first intermediate through-hole 32, the second intermediate through-hole 33, and the innermost through-hole 34, which are included in the through-hole group 130, are not in contact with each other and are located radially apart. The radially outer region of the outermost through-hole 31, the region between two radially adjacent through-holes 30, and the radially inner region of the through-hole group 130 of the rotor core 20 form a magnetic path MP through which the magnetic flux generated by the stator 3 flows.

[0029] The through-hole 30 is arc-shaped, convex radially inward when viewed in the axial direction. The arc radius of the first intermediate through-hole 32 is larger than the arc radius of the outermost through-hole 31. The arc radius of the second intermediate through-hole 33 is larger than the arc radius of the first intermediate through-hole 32. The arc radius of the innermost through-hole 34 is larger than the arc radius of the second intermediate through-hole 33. In the following explanation, the direction in which the through-hole 30 extends when viewed axially will be referred to as the "extension direction." The directions in which the outermost through-hole 31, the first intermediate through-hole 32, the second intermediate through-hole 33, and the innermost through-hole 34 extend when viewed axially will be referred to as the "first extension direction," "second extension direction," "third extension direction," and "fourth extension direction," respectively.

[0030] Viewed in the axial direction, for the outermost through-hole 31, the first intermediate through-hole 32, and the second intermediate through-hole 33, the through-hole 30 located radially outward has a shorter dimension in the extension direction. That is, the dimension of the outermost through-hole 31 in the first extension direction is shorter than the dimension of the first intermediate through-hole 32 in the second extension direction. The dimension of the first intermediate through-hole 32 in the second extension direction is shorter than the dimension of the second intermediate through-hole 33 in the third extension direction. In the innermost through-hole 34, one of the two ends in the fourth extending direction does not extend to the radial outer edge 20b of the rotor core 20, and the dimension of the innermost through-hole 34 in the fourth extending direction is shorter than the dimension of the second intermediate through-hole 33 in the third extending direction. The radial outer edge 20b of the rotor core 20 is the region of the rotor core 20 that is inside the outer peripheral edge of the rotor core 20 in the radial direction, and is where the ends of the outermost through-hole 31, the first intermediate through-hole 32, and the second intermediate through-hole 33 in the extending direction and the -θ side end of the innermost through-hole 34 in the extending direction are located.

[0031] The outermost through-hole 31, the first intermediate through-hole 32, and the second intermediate through-hole 33, both ends in the extension direction, and the -θ end in the circumferential direction of the innermost through-hole 34 are ends located on the radial outer edge 20b of the rotor core 20, and are hereafter referred to as outer ends. The outermost through-hole 31, the first intermediate through-hole 32, the second intermediate through-hole 33, and the innermost through-hole 34 are denoted by the -θ side as the first outer end 31a, the first outer end 32a, the first outer end 33a, and the first outer end 34a. The outermost through-hole 31, the first intermediate through-hole 32, and the second intermediate through-hole 33 are denoted by the +θ side as the second outer end 31b, the second outer end 32b, and the second outer end 33b. Hereafter, when referring to either of the first outer ends of the through hole 30, it will simply be called the first outer end 30a, and when referring to either of the second outer ends of the through hole 30, it will simply be called the second outer end 30b. The radial positions of the first outer end 30a and the second outer end 30b are equivalent.

[0032] In the intermediate magnetic pole portion M, the region located -θ side of the circumferential center IM of the intermediate magnetic pole portion M is called the first region P1, and the region located +θ side of the circumferential center IM of the intermediate magnetic pole portion M is called the second region P2. In this embodiment, the circumferential center IM of the intermediate magnetic pole portion M is located at a position that coincides with the q-axis of the rotor core 20. However, the positions of the circumferential center IM and the q-axis of the intermediate magnetic pole portion M do not necessarily coincide. The first outer end portion 30a is located in the first region P1. The second outer end portion 30b is located in the second region. In the fourth extension direction, the second end 34m of the innermost through-hole 34, which is the end opposite to the first outer end 34a, does not extend to the radial outer edge 20b of the rotor core 20. In other words, the innermost through-hole 34 does not have a second outer end. Thus, in the through-hole group 130, the innermost through-hole 34, which is located radially inward among the multiple through-holes 30, has only one outer end. This makes it easier to create a suitable shape for the magnetic path MP in the rotor core 20 in the region radially inward from the second intermediate through-hole 33 and the innermost through-hole 34.

[0033] In this embodiment, there are four first outer end portions 30a located in the first region P1, and three second outer end portions 30b located in the second region P2. Thus, the number of second outer end portions 30b located in the second region P2 is less than the number of first outer end portions 30a located in the first region P1. This allows for the arrangement of asymmetrical through-holes 30 when the circumferential center IM of the magnetic pole intermediate portion M is used as the axis of symmetry, making it possible to create a suitable shape for the through-holes 30 to improve both the starting performance and the efficiency during normal rotation of the rotating electric machine 1. The number of second outer end portions 30b located in the second region P2 is one less than the number of first outer end portions 30a located in the first region P1. This makes it possible to optimize the shape of the outermost through-hole 31 located radially to the outermost part in the second region P2, thereby improving the starting performance of the rotating electric machine 1.

[0034] In this embodiment, the second end portion 34m of the innermost through-hole 34 is positioned -θ side from the circumferential center IM of the magnetic pole intermediate portion M. That is, the second end portion 34m is located in the first region P1. This allows for a suitable dimension to be secured between the central through-hole 20a and the innermost through-hole 34, thereby maintaining the strength of the rotor core 20. The position of the second end portion 34m is not limited to the example of this embodiment, and may be located on the circumferential center IM of the intermediate magnetic pole portion M, or it may be located in the second region P2. The position of the second end portion 34m may be appropriately changed considering the strength of the rotor core 20 due to the dimension between the central through hole 20a and the innermost through hole 34, and the dimension of the magnetic pole portion P between the through hole group 130 having the innermost through hole 34 and other through hole groups 130 located on the +θ side of the said through hole group 130.

[0035] <Arrangement of outer ends 30a and 30b in the circumferential direction> As shown in Figure 3, the circumferential angles τ11~τ18 and τ21~τ26 between the circumferential ends of the outer ends 30a and 30b of the through-hole 30 and the circumferential center IM of the magnetic pole intermediate portion M are defined as follows, and the circumferential arrangement of the outer ends 30a and 30b will be explained in more detail. Note that in Figure 3, the illustration of components other than the rotor core 20 is omitted for explanatory purposes. The circumferential angles τ11, τ13, τ15, and τ17 are the circumferential angles between the circumferential end of the first outer end portions 31a, 32a, 33a, and 34a that is closer to the circumferential center IM of the intermediate magnetic pole portion M, and the circumferential center IM of the intermediate magnetic pole portion M, respectively. The circumferential angles τ12, τ14, τ16, and τ18 are the circumferential angles between the circumferential end of the first outer end portions 31a, 32a, 33a, and 34a that is farther from the circumferential center IM of the intermediate magnetic pole portion M, and the circumferential center IM of the intermediate magnetic pole portion M, respectively. The circumferential angles τ21, τ23, and τ25 are, respectively, the circumferential angles between the circumferential end of the second outer end portions 31b, 32b, and 33b that is closer to the circumferential center IM of the intermediate magnetic pole portion M, and the circumferential center IM of the intermediate magnetic pole portion M. The circumferential angles τ22, τ24, and τ26 are, respectively, the circumferential angles between the circumferential end of the second outer end portions 31b, 32b, and 33b that is farther from the circumferential center IM of the intermediate magnetic pole portion M and the circumferential center IM of the intermediate magnetic pole portion M.

[0036] In the outermost through-hole 31, the second outer end portion 31b has a larger circumferential dimension than the first outer end portion 31a. That is, the second outer end portion 30b located in the second region P2 includes at least one second outer end portion 30b that has a larger circumferential dimension than the first outer end portion 30a located in the first region P1. This makes it possible to arrange an asymmetrical through-hole 30 when the circumferential center IM of the magnetic pole intermediate portion M is the axis of symmetry, and thus makes it possible to make the shape of the through-hole 30 suitable in order to improve both the starting performance and the efficiency during normal rotation of the rotating electric machine 1.

[0037] Furthermore, in the through-hole group 130, the outermost through-hole 31, which is located radially outward among the multiple through-holes 30, has a first outer end 31a located in the first region P1 and a second outer end 31b located in the second region P2, and the circumferential dimension of the second outer end 31b is larger than the circumferential dimension of the first outer end 31a. That is, τ12-τ11<τ22-τ21 is satisfied. As a result, the circumferential width of the second outer end 31b located in the second region P2 can be increased, thereby securing a larger cross-sectional area of ​​the outermost through-hole 31, and thus the area in which the conductor 40 placed inside the outermost through-hole 31 can also be increased. Therefore, the performance of the rotating electric machine 1 during startup can be improved.

[0038] The circumferential angle τ11 between the circumferential end of the first outer end portion 31a that is closer to the circumferential center IM of the magnetic pole intermediate portion M and the circumferential center IM is an angle that is ±1° of the circumferential angle τ21 between the circumferential end of the second outer end portion 31b that is closer to the circumferential center IM and the circumferential center IM. That is, τ11 = τ21 ± 1° is satisfied. This prevents the magnetic path MP located radially outside the outermost through-hole 31 from becoming too narrow, thereby improving the torque at startup while suitably maintaining the magnetic flux flow during normal rotation. In addition, since a region located radially outside the outermost through-hole 31 can be secured in the rotor core 20, the strength of the rotor core 20 can be increased.

[0039] In each of the first region P1 and the second region P2, there are two or more circumferential ends, including the circumferential ends of the outer ends 30a and 30b, spaced apart in the circumferential direction. When k is an integer of 2 or more, the circumferential angle between the (k+2)th circumferential end in the first region P1 and the circumferential center IM is ±1° of the circumferential angle between the kth circumferential end in the second region P2 and the circumferential center IM. That is, when k is an integer satisfying k≧2, τ1(k+2)=τ2k±1° is satisfied. In this embodiment, when k=2, τ14=τ22±1°; when k=3, τ15=τ23±1°; when k=4, τ16=τ24±1°; when k=5, τ17=τ25±1°; and when k=6, τ18=τ26±1°.

[0040] Because the circumferential ends are arranged in this manner, the first outer end 31a and the first outer end 32a are positioned to overlap with the second outer end 31b, with the circumferential center IM as the axis of symmetry. The first outer end 33a and 34a are positioned symmetrically with respect to the second outer end 32b and 33b, respectively, with the circumferential center IM as the axis of symmetry. This increases the circumferential width of the second outer end portion 31b of the outermost through-hole 31, thereby increasing the cross-sectional area of ​​the outermost through-hole 31. Consequently, the area in which the conductor 40 is placed within the outermost through-hole 31 can also be increased. Therefore, the performance of the rotating electric machine 1 during startup can be improved. Furthermore, when viewed in the axial direction, the cross-sectional area in the first region P1 of the outermost through-hole 31 is smaller than that in the second region P2, but the number of first outer end portions 30a in the first region P1 is greater than the number of second outer end portions 30b in the second region P2. Therefore, when viewed in the axial direction, multiple through-holes 30 can be arranged so that the difference between the sum of the cross-sectional areas of the through-holes 30 in the first region P1 and the sum of the cross-sectional areas of the through-holes 30 in the second region P2 does not become excessively large. This improves performance when starting rotation of the rotor 10 in either the +θ or -θ direction.

[0041] <Width of through hole 30> The width of the through-hole 30 is the dimension in the direction perpendicular to the extension direction of each through-hole 30 when viewed in the axial direction. Viewed in the axial direction, the width of the outermost through-hole 31 increases from the first outer end 31a to the second outer end 31b. This increases the circumferential width of the outermost through-hole 31 on the second outer end 31b side, thereby increasing the cross-sectional area of ​​the outermost through-hole 31. Consequently, the area for arranging the conductor 40 within the outermost through-hole 31 can also be increased. Therefore, the performance of the rotating electric machine 1 during startup can be improved. Viewed in the axial direction, the widths of the first intermediate through-hole 32, the second intermediate through-hole 33, and the innermost through-hole 34 (excluding the second end portion 34m) are uniform in the extension direction. This prevents the magnetic paths MP between the outermost through-hole 31 and the first intermediate through-hole 32, between the first intermediate through-hole 32 and the second intermediate through-hole 33, and between the second intermediate through-hole 33 and the innermost through-hole 34 from becoming too narrow, even when the cross-sectional area of ​​the outermost through-hole 31 is increased. Furthermore, at the second end 34m, the width of the innermost through-hole 34 decreases towards the tip of the second end 34m in the fourth extension direction. This ensures that the distance between the central through-hole 20a and the innermost through-hole 34 is maintained in the rotor core 20, thereby preserving the mechanical strength of the rotor core 20.

[0042] <Bridge portion of through hole 30: 30g> The through-hole group 130 includes three or more through-holes 30. In the through-hole group 130, at least one of the through-holes 30, excluding the radially outermost through-hole 30 and the radially innermost through-hole 30, is provided with a bridge portion 30g connecting the radially inner first edge 30e1 and the radially outer second edge 30e2 of the through-hole 30. In this embodiment, as shown in Figure 2, the outermost through-hole 31 and the innermost through-hole 34 do not have a bridge portion 30g, while the first intermediate through-hole 32 and the second intermediate through-hole 33 are each positioned to coincide with the circumferential center IM. This allows for favorable maintenance of the mechanical strength of the rotor core 20. Furthermore, since the outermost through-hole 31 does not have a bridge portion 30g that electrically separates the conductor 40, startup performance can be favorably improved. Furthermore, the bridge portion 30g may be provided in only one of the first intermediate through-hole 32 and the second intermediate through-hole 33. The number of bridge portions 30g provided in each through-hole 30 is not limited to one, but may be two or more. In addition, the bridge portion 30g may be positioned at a location other than the circumferential center IM.

[0043] <Evaluation of Rotor Core 20 characteristics> The following describes, using Table 1, the results of comparing the strength, startup performance, and efficiency during normal rotation of several rotor cores with different through-hole shapes. Note that the rotor core of Example 1 in Table 1 is rotor core 20 shown in Figure 2, the rotor core of comparative example 1 is rotor core 200 shown in Figure 7A, and the rotor core of comparative example 2 is rotor core 201 shown in Figure 7B. Conductors are placed in the through-holes of the rotor cores of Example 1, comparative example 1, and comparative example 2, respectively. Table 1 shows the characteristics of each rotor core when rotated in the +θ direction (CW: clockwise) or the -θ direction (CCW: counter-clockwise).

[0044] [Table 1]

[0045] The rotor core 200 shown in Figure 7A has a plurality of through holes 230, including a first through hole 231, a second through hole 232, a third through hole 233, and a fourth through hole 234. The through holes 230 are arc-shaped and concentric with each other when viewed in the axial direction. The arc radius is larger for the through holes 230 that are radially inward. The width of the through holes 230 is the same for all of them. The plurality of through holes 230 are symmetrical with respect to the circumferential center IM of the magnetic pole intermediate portion M as the axis of symmetry.

[0046] In Figure 7A, the through-holes 30 of the rotor core 20 of Example 1 are shown superimposed with dashed lines. As shown in Figure 7A, the positions of each of the first outer end portions 230a of the rotor core 200 are the same as the positions of the first outer end portions 30a of the rotor core 20. As shown in Figure 7A, the second outer end 231b of the first through-hole 231 and the second outer end 232b of the second through-hole 232 of the rotor core 200 are positioned to overlap with the second outer end 31b of the outermost through-hole 31 of the rotor core 20. The circumferential end of the second outer end 231b of the first through-hole 231 of the rotor core 200 that is closer to the circumferential center IM is positioned at the same location as the circumferential end of the second outer end 31b of the outermost through-hole 31 of the rotor core 20 that is closer to the circumferential center IM, and the circumferential end of the second outer end 232b of the second through-hole 232 of the rotor core 200 that is further from the circumferential center IM is positioned at the same location as the circumferential end of the second outer end 31b of the outermost through-hole 31 of the rotor core 20 that is further from the circumferential center IM. The second outer end 233b of the third through-hole 233 and the second outer end 234b of the fourth through-hole 234 of the rotor core 200 are located in the same positions as the second outer end 32b of the first intermediate through-hole 32 and the second outer end 33b of the second intermediate through-hole 33 of the rotor core 20.

[0047] The rotor core 201 shown in Figure 7B has a similar shape to that of the rotor core 200, except that the shape of the first through-hole 231 differs. More specifically, compared to the rotor core 200, the first through-hole 231 of the rotor core 201 widens radially outward when viewed from the axial direction. As a result, the cross-sectional area of ​​the first through-hole 231 of the rotor core 201 is larger than that of the rotor core 200, and the area in which the conductor 40 is placed within the first through-hole 231 is also larger.

[0048] Table 1 shows the results of the evaluation of the mechanical strength of the rotor core in the "structural rigidity" column. In Comparative Example 1, where the cross-sectional area of ​​the first through-hole located on the outermost side in the radial direction is smaller than that of Comparative Example 2, the strength was very good. This is thought to be because, in Comparative Example 1, the radial outer dimension of the first through-hole 231 in the rotor core 200 is ensured. The strength of Example 1 and Comparative Example 2 was slightly inferior to that of Comparative Example 1, but still good. It can be seen that the rotor core 20 of Example 1 has a structure that makes deformation of the rotor core 20 less likely to occur during the manufacturing process and during rotor rotation.

[0049] The "starting load capacity" column in Table 1 shows the results of evaluating the load capacity required to start the rotor core's rotation. Comparative Example 1 yielded unsatisfactory results. This is likely because the cross-sectional area of ​​the first through-hole 231, which is located on the outermost radial side in Comparative Example 1, is smaller than that of Comparative Example 2 and Example 1, resulting in a narrower area for the conductor 40 positioned on the radial outer edge of the rotor core 200. Consequently, in Comparative Example 1, a suitable torque due to the Lorentz force could not be obtained during startup. In Comparative Example 2, where the area for conductor 40 was wider than in Comparative Example 1, the results were better. It has been shown that increasing the area for conductor 40 by widening the outermost first through-hole 231 radially outward, as in Comparative Example 2 compared to Comparative Example 1, can improve startup performance to some extent, but the effect was limited.

[0050] The startup performance of Example 1 was significantly better than that of Comparative Example 2. This is likely because Example 1 has a through-hole 30 with an asymmetrical shape when the circumferential center IM is the axis of symmetry, and the position and area of ​​the conductor 40 are optimized, allowing for a more favorable acquisition of the Lorentz force at startup compared to Comparative Example 2.

[0051] The "performance at rated condition" column in Table 1 shows the results of the efficiency evaluation under normal rotational conditions where the rotor core rotates at its rated speed. In Example 1, Comparative Example 1, and Comparative Example 2, through-holes that act as flux barriers are provided in all cases, and it can be seen that the rotor core rotates well under normal conditions due to the reluctance torque generated by the magnetic anisotropy of the rotor core.

[0052] From the above results, it can be seen that the rotor core 20 of Example 1 can suitably ensure strength and rotational efficiency during normal rotation while significantly improving performance during startup.

[0053] Table 1 shows only the evaluation results for the rotor core 20 of Example 1 in the counterclockwise direction, but the evaluation results for all items in the clockwise direction were also good, similar to the evaluation results in the clockwise direction. However, because the shape of the through hole 30 of the rotor core 20 of Example 1 is asymmetrical with respect to the circumferential center IM of the intermediate magnetic pole portion M, when comparing the startup performance in clockwise and counterclockwise directions, it was possible to improve performance by starting the rotation in a clockwise direction.

[0054] As described above, the rotor core 20 of this embodiment is a rotor core 20 that is rotatable about a central axis J, and comprises a plurality of magnetic pole portions P arranged at intervals in the circumferential direction, and a plurality of magnetic pole intermediate portions M located between adjacent magnetic pole portions P in the circumferential direction, each of the plurality of magnetic pole intermediate portions M having a group of through holes 130 including a plurality of through holes 30 arranged at intervals in the radial direction, each through hole 30 having outer ends 30a, 30b located at the radial outer edge portion 20b of the rotor core 20, and in each of the plurality of magnetic pole intermediate portions M, outer ends 30a, 30b are arranged in a first region P1 and a second region P2 arranged on either side of the circumferential center IM of the magnetic pole intermediate portion M, and the number of second outer ends 30b located in the second region P2 is less than the number of first outer ends 30a located in the first region P1.

[0055] This increases the circumferential width of one of the second outer end portions 30b located in the second region P2, thereby increasing the size of the through-hole 30 and expanding the area in which the conductor 40 can be placed within the through-hole 30. Furthermore, even when the cross-sectional area of ​​the through-hole 30 is increased when viewed from the axial direction, it is possible to prevent the magnetic path MP between the through-holes 30 from becoming too narrow, and to allow magnetic flux to flow suitably through the magnetic path MP. Therefore, it is possible to improve the torque at startup while suitably maintaining the flow of magnetic flux during normal rotation. In addition, since the dimensions of the rotor core 20 near the through-hole 30 can be suitably secured, the strength of the rotor core 20 can be improved. Also, although torque ripple may occur when the rotor 10 rotates around the central axis J and the circumferential position of the magnetic path MP relative to the stator 3 moves, the width of each magnetic path MP can be suitably secured, thus reducing torque ripple.

[0056] Furthermore, the rotor 10 of this embodiment includes the rotor core 20 described above and a conductor 40 located within the through hole 30. The Lorentz force generated by the conductor 40 can improve the torque of the rotor 10 during startup.

[0057] Furthermore, the rotating electric machine 1 of this embodiment includes the rotor 10 described above and a stator 3 located radially outward from the rotor 10. This makes it possible to obtain a rotating electric machine 1 that has improved startup performance while suitably ensuring the strength of the rotor 10 and the rotational efficiency during normal rotation.

[0058] The present invention is not limited to the embodiments described above, and other configurations can be adopted within the scope of the technical idea of ​​the present invention.

[0059] In the example shown in Figure 2, in the intermediate magnetic pole portion M, a first region P1 is located -θ side of the circumferential center IM of the intermediate magnetic pole portion M, and a second region P2 is located +θ side of the circumferential center IM of the intermediate magnetic pole portion M, having fewer second outer end portions 30b than the number of first outer end portions 30a located in the first region P1. However, this example is not limited to this example. For example, a first region P1 may be located on the +θ side of the circumferential center IM of the intermediate magnetic pole portion M, and a second region P2 may be located on the -θ side of the circumferential center IM of the intermediate magnetic pole portion M, having fewer second outer end portions 30b than the number of first outer end portions 30a located in the first region P1.

[0060] Furthermore, as shown in Figure 4, two adjacent through-hole groups 130 in the circumferential direction may be mirror-image symmetric with respect to the d-axis. The partially enlarged view of the rotor core 20 shown in Figure 4 shows two through-hole groups 130, including through-hole group 130A and through-hole group 130B located on the -θ side of through-hole group 130A. Through-hole groups 130A and 130B are mirror-image symmetric with respect to the d-axis between the two through-hole groups 130A and 130B. In other words, in the through-hole group 130A, the -θ side of the circumferential center IM of the intermediate magnetic pole M becomes the first region P1, and the +θ side becomes the second region P2. In the through-hole group 130B, the +θ side of the circumferential center IM of the intermediate magnetic pole M becomes the first region P1, and the -θ side becomes the second region P2. This improves startup performance regardless of whether the rotor core 20 is initiated to rotate clockwise or counterclockwise.

[0061] Furthermore, the number of through-holes 30 in each through-hole group 130 is not limited to four; it is sufficient to have at least two through-holes 30, namely the outermost through-hole and the innermost through-hole. For example, the number of through-holes 30 in each through-hole group 130 may be two, three, or four or more. For example, in the rotor core 20 shown in Figure 4, each through-hole group 130 has two through-holes 30, and there are no intermediate through-holes.

[0062] Furthermore, the number of magnetic poles P of the rotor core 20 is not limited to 4 poles; it may be fewer than 4 poles or more than 4 poles. The number of magnetic poles P of the rotor 10 may be, for example, 2 poles, 6 poles, or 8 poles. Figure 5 shows a rotor 10 with a 6-pole structure. Six sets of through-holes 130 are arranged at equal intervals along the circumferential direction of the rotor 10. Since magnetic pole sections P are provided between adjacent sets of through-holes 130 in the circumferential direction, the rotor 10 shown in Figure 5 has 6 magnetic pole sections P.

[0063] Furthermore, as shown in Figure 6, a bridge portion 30g is not required in the through hole 30. In the rotor core 20 of Figure 6, compared to the rotor core 20 shown in Figure 2, the bridge portion 30g is not provided in the first intermediate through hole 32 and the second intermediate through hole 33. For example, if the conductor 40 is electrically disconnected by the bridge portion 30g, the Lorentz force generated when starting the rotation of the rotor 10 may not be obtained favorably. By not providing the bridge portion 30g, it becomes possible to obtain the Lorentz force generated at startup more favorably.

[0064] Furthermore, in the rotor core 20 shown in Figure 2, the shape of the multiple through holes 30 is an arc shape that is convex radially inward when viewed in the axial direction, but this is not limited to this example, and they may also be a bent line shape that is convex radially inward when viewed in the axial direction. Also, a group of through holes 130 may include both arc-shaped through holes 30 and bent line-shaped through holes 30.

[0065] Furthermore, the rotor 10 may be provided with magnets located within the through-holes 30. For example, a ferrite magnet may be provided in at least one of the through-holes 30 at a position that overlaps with the circumferential center IM of the intermediate portion M of the magnetic pole. Alternatively, ferrite magnets may be provided on the outer end sides 30a and 30b of at least one of the through-holes 30, respectively. The type of magnet is not particularly limited, and the magnet may be a neodymium magnet. In this case, the magnetic force of the magnet can improve the torque of the rotor 10. The magnet may be placed inside the through-hole 30, and after placement, the molten conductor 40 may be filled into the through-hole 30, thereby sealing the inside of the through-hole 30 with the conductor 40 and the magnet.

[0066] Furthermore, the through-hole 30 does not have to penetrate the rotor core 20 in the axial direction. The through-hole 30 may open into the axial end face of the rotor core 20.

[0067] The through-hole 30 is not particularly limited as long as it can suppress the flow of magnetic flux. In the embodiment described above, a conductor 40 was placed inside the through-hole 30, but the inside of the through-hole 30 may be an empty space. Alternatively, the through-hole 30 may be formed by embedding a non-magnetic material such as resin in the empty space.

[0068] The applications of the rotating electric machine to which the present invention is applied are not particularly limited. The rotating electric machine may be mounted on a vehicle, for example, or on equipment other than a vehicle. The configurations described herein can be combined as appropriate, within the bounds of what is not mutually contradictory. [Explanation of Symbols]

[0069] 1…Rotating electric machine, 3…Stator, 10…Rotor, 20…Rotor core, 20b…Radial outer edge of rotor core, 30…Through hole, 30a…First outer end (outer end), 30b…Second outer end (outer end), 30e1…First edge, 30e2…Second edge, 30g…Bridge section, 31…Outermost through hole, 34…Innermost through hole, 40…Conductor, 130…Through hole group, IM…Circumferential center of the intermediate part of the magnetic pole, J…Central axis, M…Intermediate part of the magnetic pole, P…Magnetic pole section, P1…First region, P2…Second region

Claims

1. A rotor core that can rotate around its central axis, Multiple magnetic pole portions are arranged at intervals in the circumferential direction, A plurality of intermediate magnetic pole portions are located between adjacent magnetic pole portions in the circumferential direction, Equipped with, Each of the aforementioned intermediate portions of the multiple magnetic poles has a group of through holes including multiple through holes arranged at intervals in the radial direction, Each of the through holes has an outer end located at the radial outer edge of the rotor core, In each of the aforementioned plurality of intermediate magnetic pole portions, the outer end portion is positioned in a first region and a second region, which are arranged on either side of the circumferential center of the intermediate magnetic pole portion. The number of outer ends arranged in the second region is less than the number of outer ends arranged in the first region. The outer end portion located in the second region includes at least one outer end portion having a larger circumferential dimension than the outer end portion located in the first region. In the group of through holes, the outermost through hole, which is located radially outward among the plurality of through holes, has a first outer end, which is the outer end located in the first region, and a second outer end, which is the outer end located in the second region. A rotor core in which the circumferential dimension of the second outer end is larger than the circumferential dimension of the first outer end.

2. The rotor core according to claim 1, wherein, when viewed in the axial direction, the width of the outermost through hole increases from the first outer end to the second outer end.

3. The rotor core according to claim 1 or 2, wherein the circumferential angle between the circumferential end of the first outer end that is closer to the circumferential center and the circumferential center is an angle that is ±1° of the circumferential angle between the circumferential end of the second outer end that is closer to the circumferential center and the circumferential center.

4. In each of the first and second regions, two or more circumferential ends, including both circumferential ends of the outer end, are provided at intervals in the circumferential direction. When k is an integer of 2 or more, the circumferential angle between the (k+2)th circumferential end located in the first region and the circumferential center is an angle that is ±1° from the circumferential angle between the kth closest circumferential end located in the second region and the circumferential center, according to any one of claims 1 to 3.

5. The rotor core according to any one of claims 1 to 4, wherein the number of outer ends arranged in the second region is one less than the number of outer ends arranged in the first region.

6. The rotor core according to claim 5, wherein, in the group of through holes, the innermost through hole located radially inward among the plurality of through holes has only one outer end.

7. The group of through holes includes three or more of the through holes. The rotor core according to any one of claims 1 to 6, wherein in the group of through holes, at least one of the through holes, excluding the through hole located furthest radially outward and the through hole located furthest radially inward, is provided with a bridge portion connecting the radially inward first edge and the radially outward second edge of the through hole.

8. A rotor core according to any one of claims 1 to 7, A conductor located within the through hole, A rotor equipped with a rotor.

9. The rotor according to claim 8, further comprising a magnet located within the through hole.

10. A rotor according to claim 8 or 9, A stator located radially outward from the rotor, A rotating electric machine equipped with the following features.

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