Rotor for rotating electric machine

Abstract

This appropriately reduces stress concentration around axial holes caused by an increase in the inner diameter of the rotor core. [Solution] A rotor for a rotating electric machine is disclosed, comprising an annular rotor core when viewed in the axial direction, a rotor shaft positioned radially inside the rotor core and coupled to the rotor core by a radial overlap, and magnets arranged on the rotor core for each magnetic pole in such a manner that they form multiple magnetic poles along the circumferential direction, wherein the rotor core has a plurality of axial holes radially inside the magnets, and the plurality of axial holes include a plurality of first holes regularly arranged circumferentially at a first radial position and a plurality of second holes regularly arranged circumferentially at a second radial position radially inside the first radial position, wherein the outer shape of the first hole, when viewed in the axial direction, has a radially convex shape on the radially inside, and the center line passing through the circumferential center of the first hole passes between the circumferential directions of adjacent second holes, and the outer shape of the radially inside consists of two straight lines and a curve connecting the straight lines that passes radially outside the intersection point where the extensions of the straight lines intersect.

Description

Technical Field

[0001] The present disclosure relates to a rotor for a rotating electrical machine.

Background Art

[0002] In a rotor core of a rotor for a rotating electrical machine, a technique is known in which magnet holes for inserting a plurality of permanent magnets are formed, and axial holes (slits) are formed radially inside the magnet holes.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the prior art as described above, the form of the slit is substantially rectangular (concentric arc-shaped outer contour lines on the radially inner side and the radially outer side). In such a form, it is difficult to appropriately reduce the stress concentration around the axial hole (slit) caused by the increase in the inner diameter (deformation) of the rotor core due to the assembly with the rotor shaft. In particular, in recent years, with the increase in the rotational speed of rotating electrical machines, the centrifugal force tends to increase, and the above problems are prominent due to such an increase in the centrifugal force.

[0005] Therefore, on one side, the present disclosure aims to appropriately reduce the stress concentration around the axial hole caused by the increase in the inner diameter of the rotor core.

Means for Solving the Problems

[0006] On one side, an annular rotor core viewed axially, a rotor shaft disposed radially inside the rotor core and coupled to the rotor core by a radial interference fit, The rotor core comprises magnets arranged for each magnetic pole in a manner that forms multiple magnetic poles along the circumferential direction, The rotor core has a plurality of axial holes located radially inward from the magnet, The plurality of axial holes include a plurality of first holes that are regularly arranged in the circumferential direction at a first radial position, and a plurality of second holes that are regularly arranged in the circumferential direction at a second radial position that is radially inward from the first radial position. The first hole, when viewed in the axial direction, has an outer shape that is convex radially inward, and a radially parallel center line passing through the circumferential center of the first hole passes between the circumferential directions of adjacent second holes. A rotor for a rotating electric machine is provided, wherein the radially inner outline consists of two straight lines and a curve connecting the two straight lines, passing radially outside the intersection point where the extensions of the two straight lines intersect. [Effects of the Invention]

[0007] In one aspect, the present disclosure makes it possible to appropriately reduce stress concentration around axial holes caused by an increase in the inner diameter of the rotor core. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing the cross-sectional structure of a motor according to one embodiment. [Figure 2] This is a cross-sectional view of the rotor core of the rotor. [Figure 3] This is an enlarged view of the portion of the rotor related to one of its magnetic poles. [Figure 4A] This is an enlarged view of the portion of the rotor core related to one magnetic pole according to the first comparative example, and is shown for comparison with Figure 3. [Figure 4B] This is an enlarged view of the portion of the rotor core related to one magnetic pole according to the second comparative example, and is shown for comparison with Figure 3. [Figure 4C] This is an enlarged view of the portion of the rotor core related to one magnetic pole according to the third comparative example, and is shown for comparison with Figure 3. [Figure 5] This is a table showing the analysis results. [Figure 6] This graph shows other analysis results. [Figure 7] This is an enlarged view of the radially inner portion of the rotor core related to one of the magnetic poles according to Example 2. [Figure 8] This is an enlarged view of section Q7 in Figure 7. [Figure 9] This is an explanatory diagram of the further effects of Example 2, and a table showing the analysis results. [Figure 10] This is an enlarged view of the radially inner portion of the rotor core related to one of the magnetic poles according to Example 3. [Modes for carrying out the invention]

[0009] The following describes each embodiment in detail with reference to the attached drawings. Note that the dimensional ratios in the drawings are merely examples and are not exhaustive. Furthermore, shapes and other details in the drawings may be partially exaggerated for illustrative purposes. Also, for clarity, in some cases, only a portion of parts with the same attribute are assigned reference numerals in the drawings.

[0010] Figure 1 is a schematic cross-sectional view showing the cross-sectional structure of a motor 1 according to one embodiment. Figure 2 is a cross-sectional view (a cross-sectional view taken from a plane perpendicular to the axial direction) of the rotor core 32 of the rotor 30. Figure 3 is an enlarged view of the portion of the rotor 30 relating to one of the magnetic poles.

[0011] Figure 1 shows the rotation axis 12 of motor 1. In the following explanation, axial direction refers to the direction in which the rotation axis (center of rotation) 12 of motor 1 extends, and radial direction refers to the radial direction centered on the rotation axis 12. Therefore, radially outward refers to the side away from the rotation axis 12, and radially inward refers to the side toward the rotation axis 12. Furthermore, circumferential direction corresponds to the direction of rotation around the rotation axis 12.

[0012] Motor 1 may be, for example, a vehicle drive motor used in hybrid vehicles or electric vehicles. However, Motor 1 may be used for any other purpose.

[0013] The motor 1 is, for example, an inner rotor type, and the stator 21 is provided so as to surround the outer side in the radial direction of the rotor 30. The stator 21 is fixed to the motor housing 10. The stator 21 includes, for example, a stator core 211 made of a laminated steel sheet of an annular magnetic material, and a plurality of slots (not shown) around which the coil 22 is wound are formed on the inner side in the radial direction of the stator core 211.

[0014] The rotor 30 is disposed on the inner side in the radial direction of the stator 21.

[0015] The rotor 30 includes a rotor core 32, a rotor shaft 34, end plates 35A and 35B, and magnet pieces 61. Note that the end plates 35A and 35B may be omitted.

[0016] The rotor core 32 is fixed to the surface on the outer side in the radial direction of the rotor shaft 34 and rotates integrally with the rotor shaft 34. The rotor core 32 has a shaft hole 320 (see FIG. 2), and the rotor shaft 34 is fitted into the shaft hole 320. The rotor core 32 is coupled in a manner having a radial interference fit with respect to the rotor shaft 34. That is, the rotor core 32 and the rotor shaft 34 are coupled to each other by fixing with an interference fit. For example, the rotor core 32 and the rotor shaft 34 may be coupled in a manner having a radial interference fit by shrink fitting, press fitting, hydroforming, or the like. However, the coupling force between the rotor core 32 and the rotor shaft 34 may include an axial force by a nut or the like as well as the radial interference fit.

[0017] The rotor shaft 34 is rotatably supported by the motor housing 10 via bearings 14a and 14b. Note that the rotor shaft 34 defines the rotation shaft 12 of the motor 1.

[0018] The rotor core 32 is formed, for example, from a laminated steel plate of an annular magnetic material. A magnet piece 61 (see Figure 3) is embedded inside the rotor core 32. That is, the rotor core 32 has a magnet hole 321 (see Figure 2) that penetrates in the axial direction, and the magnet piece 61 is inserted and fixed into the magnet hole 321. In a modified example, the rotor core 32 may be formed from a compacted body of magnetic powder that has been compressed and solidified.

[0019] The rotor core 32 has an annular shape with an outer diameter r1 and an inner diameter r2 (the diameter of the shaft hole 320). In modified examples, the annular shape of the rotor core 32 does not need to be a perfect circle; for example, it may be a circular shape with a notch in part, or it may be an elliptical shape that is close to a circle.

[0020] As shown in Figure 2, the rotor core 32 has a rotationally symmetrical shape with respect to the rotation axis 12 when viewed in the axial direction. In the example shown in Figure 2, the rotor core 32 is configured such that each set of magnet pieces 61 overlaps every 45 degrees of rotation around the rotation axis 12.

[0021] The multiple magnet pieces 61 are in the form of sintered magnets and may be formed from neodymium or the like. However, in a modified example, magnets formed from bonded magnet material may be used instead of the magnet pieces 61. In this embodiment, as an example, as shown in Figure 3, the multiple magnet pieces 61 are arranged in a manner that is rotationally symmetrical for each magnetic pole when viewed in the axial direction. The multiple magnet pieces 61 are arranged in a manner in which the south poles and north poles appear alternately in the circumferential direction. In this embodiment, there are eight magnetic poles, but the number of magnetic poles is arbitrary. Also, in this embodiment, the magnet pieces 61 are linear and identical when viewed in the axial direction, but they may be different in shape. In addition, at least one of the magnet pieces 61 may be arc-shaped when viewed in the axial direction.

[0022] Although Figure 1 shows a motor 1 with a specific structure, the structure of the motor 1 is not limited to this specific structure. For example, in Figure 1, the rotor shaft 34 is hollow, but it may be solid.

[0023] Next, the rotor core 32 and the magnet piece 61 will be described in more detail with reference to Figure 3 and subsequent figures. The following description will focus on the configuration for one magnetic pole, but the configuration for other magnetic poles may be similar.

[0024] As shown in Figure 3, the configuration for one magnetic pole is basically symmetrical with respect to the d-axis (referred to as "d-axis" in Figure 3), which corresponds to the direction of the main magnetic flux (direction of the field pole). The direction of the d-axis corresponds to the direction of the magnetic field generated by the magnet pieces 61 placed on the rotor 30. Hereafter, "outer circumferentially" refers to the side away from the d-axis, and "inner circumferentially" refers to the side approaching the d-axis. The d-axis is formed at the circumferential center position of the circumferential range for each magnetic pole, while the q-axis (referred to as "q-axis" in Figure 3) is formed at the boundary of the circumferential range for each magnetic pole (the circumferential position between the magnet pieces 61 for each magnetic pole).

[0025] Magnetic holes 321 are formed in the rotor core 32. The magnetic holes 321 are formed in a manner that is rotationally symmetrical for each magnetic pole.

[0026] The magnetic holes 321 are formed in pairs in a roughly V-shape (a roughly V-shape with the radially outward direction opening). However, in modified cases, the magnetic holes 321 may be formed in pairs in a straight line, or they may be realized by a single straight hole (a straight line perpendicular to the d-axis). A magnetic piece 61 is provided in each of the magnetic holes 321. A gap may be provided between the magnetic holes 321 and the magnetic piece 61 at both ends of the magnetic piece 61 in the longitudinal direction. This gap may be a cavity or may be filled with resin or the like.

[0027] The rotor core 32 has such magnetic holes 321 and has two parts 3211 and 3212 (hereinafter also referred to as the first part 3211 and the second part 3212) that are connected only radially via bridges (bridges 41 and 43 described later).

[0028] Specifically, the first portion 3211 extends radially outward from the magnet hole 321. The first portion 3211 forms part of the outer circumferential surface 328 of the rotor core 32. The first portion 3211 forms a magnetic path for the q-axis magnetic flux. Specifically, the q-axis magnetic flux related to the first portion 3211 flows through the first portion 3211 (the region radially outward from the magnet hole 321) from one circumferential end to the other circumferential end of the first portion 3211.

[0029] The second portion 3212 extends radially inward from the magnet hole 321 and circumferentially to the outer surface 328 of the rotor core 32 on both sides. The second portion 3212 forms a part of the outer surface 328 of the rotor core 32 on both sides of the first portion 3211 in the circumferential direction. The second portion 3212 forms a magnetic path for the q-axis magnetic flux. Specifically, the q-axis magnetic flux related to the second portion 3212 flows from one end of the second portion 3212 to the other, passing radially inward from the magnet hole 321. The second portion 3212 also forms inter-pole regions on both sides in the circumferential direction.

[0030] Furthermore, having these two parts 3211 and 3212, the rotor core 32 has multiple bridges 41 and 43 connecting the two parts 3211 and 3212.

[0031] The bridge 41 supports the first portion 3211 radially outward relative to the second portion 3212. That is, the bridge 41 connects the second portion 3212 and the first portion 3211 and extends in the circumferential direction. The bridge 41 is provided in pairs on both sides (circumferentially outward) of the first portion 3211 in the circumferential direction.

[0032] The bridge 43 (hereinafter referred to as "center bridge 43") supports the first part 3211 on the d axis with respect to the second part 3212.

[0033] In the example shown in Figure 3, each magnet piece 61 inserted into each magnet hole 321 forms the first layer of permanent magnets from the radially outer side. However, in a modified example, further magnet holes (i.e., second layer magnet holes) may be provided radially inward from each magnet hole 321. In this case, each magnet piece inserted into the second layer magnet holes forms the second layer of permanent magnets from the radially outer side. Thus, the number of layers of magnets may be not limited to one layer, but may be two or more layers. In this embodiment, one magnet piece (magnet piece 61) is inserted into one magnet hole 321, but in a modified example, two or more magnet pieces may be inserted into one magnet hole.

[0034] Furthermore, in the example shown in Figure 3, the magnet hole 321 does not extend along the d-axis, and the center bridge 43 is located on the d-axis. However, in a modified example, the magnet hole 321 may extend along the d-axis. Also, if a second layer of magnet holes is provided as described above, either or both of the magnet holes 321 of the first layer and the magnet holes of the second layer may extend along the d-axis.

[0035] Next, the characteristic configuration of this embodiment will be described with further reference to Figure 3.

[0036] In this embodiment, as shown in Figure 3, the rotor core 32 has a first slit 71 and a second slit 72 located radially inward from the magnet hole 321 (and the magnet piece 61 within it). That is, the first slit 71 and the second slit 72 are formed in the second portion 3212 of the rotor core 32. The first slit 71 and the second slit 72 are in the form of axial holes that penetrate the rotor core 32 in the axial direction.

[0037] The first slit 71 is positioned radially inward from the magnet hole 321 and radially outward from the second slit 72 (hereinafter also referred to as the "first radial position"). The second slit 72 is positioned radially inward from the first slit 71 and radially outward from the shaft hole 320 (hereinafter also referred to as the "second radial position").

[0038] Multiple first slits 71 are provided. The multiple first slits 71 are provided at the first radial position in a manner that is rotationally symmetrical for each magnetic pole. The multiple first slits 71 form a row of holes that are regularly arranged in the circumferential direction. In this embodiment, each first slit 71 for a single magnetic pole consists of one slit whose circumferential center is located on the d-axis. When viewed in the axial direction, the first slit 71 has a symmetrical shape with respect to a line parallel to the radial direction passing through the circumferential center (i.e., the d-axis in this example).

[0039] However, in a modified example, the first slit 71 for each magnetic pole may consist of one slit with its circumferential center located on the d-axis and two halves (halves divided by the q-axis) with their circumferential centers located on the q-axis. In this specification, the d-axis may refer to the d-axis of any of the divided cores when a skew structure using divided cores (core blocks) is adopted. Alternatively, the first slit 71 may not have its circumferential center located on the d-axis. Or, the first slit 71 for each magnetic pole may consist of two halves (halves divided by the q-axis) with their circumferential centers located on the q-axis. When the circumferential center is located on the q-axis, the first slit 71 will have a symmetrical form with respect to the q-axis (a straight line parallel to the radial direction passing through the circumferential center of the inter-pole region).

[0040] When viewed in the axial direction, the radially inner outline line L710 of the first slit 71 has a shape that is convex radially inward. In this case, the outline lines L710 on both sides of the d-axis are connected by a curve C712 on the d-axis. The curve C712 has a shape that is concave radially inward, and may be, for example, the shape of the angle R (part of a circular arc with a single radius) at the point where the outline lines L710 on both sides of the d-axis intersect on the d-axis. That is, the radially inner outline line L710 consists of two straight lines L710 and a curve C712 that connects the two straight lines and passes radially outside the intersection point where the extensions of the two straight lines intersect. Also, when viewed in the axial direction, the radially outer outline line L712 of the first slit 71 has a shape that is straight and perpendicular to the radial direction.

[0041] Multiple second slits 72 are provided. The multiple second slits 72 are provided at second radial positions in a manner that is rotationally symmetrical for each magnetic pole. The multiple second slits 72 form a row of holes that are regularly arranged in the circumferential direction, with their circumferential centers being different from those of the first slits 71. The multiple second slits 72 and the multiple first slits 71 are formed in a manner that they share a common circumferential position. In this embodiment, each second slit 72 for a single magnetic pole consists of two halves (halves divided by the q-axis) whose circumferential centers are located on the q-axis. In this case, the second slits 72 are not located on the d-axis. Therefore, in this embodiment, for each magnetic pole, the first slit 71, when viewed in the axial direction, has a radially parallel line (center line) passing through the circumferential center of the first slit 71 located between adjacent second slits (non-slit region). More specifically, the first slit 71 is configured such that, when viewed in the axial direction, a radially parallel line passing through the circumferential center of the first slit 71 is located between the circumferential outlines of the adjacent second slits, which are closer to each other. In this embodiment, the circumferential centers of the first slit 71 and the second slit 72 are offset circumferentially by half the angular range of one magnetic pole, but other configurations are also possible.

[0042] The second slit 72 may have any shape when viewed in the axial direction. In this embodiment, as an example, the radially inner outline line L720 of the second slit 72 has a straight shape perpendicular to the radial direction. Also, when viewed in the axial direction, the radially outer outline line L722 of the second slit 72 has a convex shape radially outward.

[0043] Here, the effects of this embodiment will be explained with reference to the comparative examples shown in Figures 4A to 4C, as well as the analysis results shown in Figure 5, etc.

[0044] Figure 4A is an enlarged view of the portion of one magnetic pole of the rotor core 32' according to the first comparative example, and is shown for comparison with Figure 3. Figure 4B is an enlarged view of the portion of one magnetic pole of the rotor core 32A' according to the second comparative example, and is shown for comparison with Figure 3. Figure 4C is an enlarged view of the portion of one magnetic pole of the rotor core 32B' according to the third comparative example, and is shown for comparison with Figure 3.

[0045] The rotor core 32' according to the first comparative example differs from the rotor core 32 according to this embodiment in that the first slit 71 is replaced by the first slit 71'. The first slit 71' has a different shape when viewed in the axial direction from the first slit 71 according to this embodiment. Specifically, when viewed in the axial direction, the radially inner outline line L710 of the first slit 71' has a straight shape perpendicular to the radial direction. Also, when viewed in the axial direction, the radially outer outline line L712 of the first slit 71' has a convex shape radially outward.

[0046] The rotor core 32A' according to the second comparative example differs from the rotor core 32 according to this embodiment in that the first slit 71 is replaced by the first slit 71A'. The first slit 71A' has a different shape when viewed in the axial direction from the first slit 71 according to this embodiment. Specifically, when viewed in the axial direction, the radially inner outline line L710 of the first slit 71A' has a circular arc shape that is concentric with the rotor core 32A'. Also, when viewed in the axial direction, the radially outer outline line L712 of the first slit 71' has a circular arc shape that is concentric with the rotor core 32A'.

[0047] The rotor core 32B' according to the third comparative example differs from the rotor core 32 according to this embodiment in that the first slit 71 is replaced by the first slit 71B'. The first slit 71B' has a different shape when viewed in the axial direction from the first slit 71 according to this embodiment. Specifically, when viewed in the axial direction, the radially inner outline line L710 of the first slit 71B' has a linear shape perpendicular to the radial direction. Also, when viewed in the axial direction, the radially outer outline line L712 of the first slit 71B' has a linear shape perpendicular to the radial direction.

[0048] Figure 5 is a table showing the analysis results. Figure 5 compares the first comparative example with this embodiment. The analysis results are shown in contour plots. The analysis was performed using a finite element model under the condition that the inner diameter was forcibly displaced (expanded). Figure 5 shows two types of analysis results: the upper side shows the stress distribution in a contour plot, and the lower side shows the displacement distribution in a contour plot. Note that, since the contour plots in this specification cannot be displayed in color, they are shown in grayscale, and the explanation is based on the assumption that the distribution range of the same gradation corresponds to the same numerical range.

[0049] Although not easily discernible from the upper stress distribution contour plot in Figure 5, the following relationship was observed between the stresses σ1 to σ6. σ3 > σ2 > σ1, σ6>σ4>σ5, σ6<σ3, σ5 < σ2, σ4>σ1 From these results, it can be seen that in the regions where relatively high stresses (σ3, σ2, σ6) occur, this embodiment can reduce stress compared to the first comparative example. In particular, σ5 was reduced to a stress value slightly lower than σ4, with σ5 / σ2 ≈ 0.87, indicating a significantly large reduction effect of 13%.

[0050] As can be seen from the lower stress distribution contour plot in Figure 5, in the first comparative example, the region between the first slit 71' and the second slit 72 in the radial direction shows the following trend. That is, in the first comparative example, if the area between the pair of second slits 72 in the radial direction is considered the central part (see part A), high displacement tends to occur concentrated near the central part. As a result, the displacement is relatively small near both ends of the first slit 71' in the circumferential direction. In contrast, in this embodiment, the region between the first slit 71 and the second slit 72 in the radial direction shows the following trend. That is, in this embodiment, the displacement is relatively high near both ends of the first slit 71 in the circumferential direction, and the displacement is distributed from near the central part between the pair of second slits 72 in the radial direction toward both sides in the circumferential direction. This is thought to be because the rigidity of the central part is significantly higher in this embodiment than in the first comparative example. Thus, according to this embodiment, compared to the first comparative example, the displacement distribution, which tends to be high in the central part, can be extended to both ends of the first slit 71 in the circumferential direction, and as a result, the stress reduction effect described above can be achieved.

[0051] The analysis results for the second comparative example (Figure 4B) are not shown in contour plots here, but compared to the first comparative example, the stress at the location σ2 in the first comparative example is slightly reduced, while the stress at other locations is significantly worse than in the first comparative example. Furthermore, the analysis results for the second comparative example showed that the stress at the location σ2 in the first comparative example is significantly higher than the stress σ5 at the same location in this embodiment.

[0052] Similarly, although the analysis results for the third comparative example (Figure 4C) are not shown in a contour plot here, the stress at the location of stress σ5 in this embodiment was significantly higher than the stress σ5 in this embodiment. Specifically, it was found that this embodiment achieved a significantly larger reduction effect of 13% compared to the third comparative example.

[0053] Figure 6 is a graph showing other analysis results. In Figure 6, the horizontal axis represents the rotational speed of motor 1 (labeled "MG rotational speed"), and the vertical axis represents torque, showing the analysis results of the holding torque characteristics according to the rotational speed of motor 1. Holding torque corresponds to the torque that can be transmitted between the rotor shaft 34 and the rotor core 32.

[0054] In Figure 6, characteristic L60 represents the characteristic when the radial position of the convex tip of the first slit 71 is slightly radially inward from the reference circle L3 (see Figure 3). Characteristic L61 represents the characteristic when the radial position of the convex tip of the first slit 71 is slightly radially outward from the reference circle L3 (see Figure 3).

[0055] As can be seen from Figure 6, as the rotational speed of motor 1 increases, the holding torque decreases due to the increase in centrifugal force. In this case, characteristic L60 has a higher holding torque than characteristic L61 in the high-speed rotation range. From this, it was found that when the radial position of the convex tip of the first slit 71 is slightly radially inward from the reference circle L3 (see Figure 3), it is advantageous in that the holding torque can be efficiently increased. Here, in order to further increase the holding torque in the high-speed rotation range, the radial position of the convex tip of the first slit 71 may be set even further radially inward from the reference circle L3.

[0056] Next, other preferred embodiments will be described with reference to Figure 7 and subsequent figures. For the sake of efficiency, the above-described embodiment will be referred to as "Embodiment 1," and the differences from Embodiment 1 will be the main focus of the description. In the following, components that may be substantially the same as those in Embodiment 1 (or Embodiment 2, which will be described later) may be given the same reference numerals and their descriptions may be omitted.

[0057] Figure 7 is an enlarged view of the radially inner portion of one of the magnetic poles of the rotor core 32A according to Embodiment 2. Figure 8 is an enlarged view of portion Q7 in Figure 7.

[0058] The rotor core 32A according to Embodiment 2 differs from the rotor core 32 according to Embodiment 32 in that the first slit 71 is replaced by the first slit 71A. The first slit 71A has a different shape when viewed in the axial direction from the first slit 71 according to Embodiment 1. In Embodiment 1, when viewed in the axial direction, the radially outer outline line L712 of the first slit 71 is directly connected to the circumferential outline lines L713 on both sides (see Figure 3). The circumferential outline lines L713 on both sides are arc-shaped and convex toward the circumferential outer side (the side away from the d-axis in the circumferential direction). In contrast, when viewed in the axial direction, the first slit 71A according to Embodiment 2 has a shape in which the radially outer outline line L712 and the circumferential outline lines L713 on both sides are connected via a linear outline line L715. The linear outline line L715 slopes radially outward as it approaches the d-axis in the circumferential direction. In this case, the radially outer outline L712 and the linear outline L715 may be connected via the outline L716 relating to the angle R. In this case, the outline L716 relating to the angle R, like the outlines L713 on both sides in the circumferential direction, has its center of curvature inside the first slit 71A. The radius of the outline L716 relating to the angle R may be significantly larger than the radii of the outlines L713 on both sides in the circumferential direction.

[0059] The analysis results for Example 2 are not shown in contour plots here, but similar to Example 1 described above, the stress reduction effect around the first slit 71A was confirmed compared to the first to third comparative examples. Specifically, the results were better than those for Example 1 described above, with the stress at the location corresponding to stress σ5 being reduced by about 8%, and other stresses being the same or lower.

[0060] Figure 9 is an explanatory diagram illustrating the further effects of Example 2 and is a table showing the analysis results. Figure 9 relates to a comparison between the first comparative example described above and Example 1. The analysis results are shown in contour plots, similar to Figure 5 above. The analysis was performed using a finite element model under conditions where centrifugal force generated when motor 1 is rotated is applied. Note that, since color display is not possible in the specification, the contour plots are shown in grayscale, and the explanation is based on the premise that the distribution range of the same gradation corresponds to the region of the same numerical range. Also, in Figure 9, the contour plot around the magnet hole 321 is omitted in white for convenience.

[0061] As can be seen from Figure 9, Example 2 differs from the First Comparative Example and Example 1 in the following characteristics. Specifically, in the region from both sides of the first slit 71A in the second part 3212 toward the center bridge 43, there is a continuous region (indicated by R90) where the stress is approximately equal. The stress in the region indicated by R90 is greater than the stress in the region indicated by R91. This means that the stress is distributed, and in fact, the stress relationship in the center bridge 43 was as follows. σ91 ≈ σ92 < σ93 As a result, the stress σ97 on both sides of the first slit 71A in the circumferential direction was significantly reduced compared to the stress σ95 at the same location in the first comparative example and the stress σ96 at the same location in Example 1. Specifically, σ95 ≈ σ96 > σ97, and σ97 / σ95 = 0.83, indicating a reduction effect of as much as 17%.

[0062] In the following, the morphological features of this embodiment 2 will also be referred to as the "shape with rounded corners on the inner side in the radial direction of the slit."

[0063] Figure 10 is an enlarged view of the radially inner portion of the rotor core 32B related to one of the magnetic poles according to Embodiment 3.

[0064] The rotor core 32B according to Example 3 differs from the rotor core 32 according to this example in that the first slit 71 is replaced by the first slit 71B. The first slit 71B has a different shape when viewed in the axial direction from the first slit 71 according to this example. Specifically, in addition to having a rounded corner shape on the radially inner side of the slit according to Example 2 described above, the shape of the radially inner outer line L710 of the first slit 71B is different. The radially inner outer line L710 of Example 3 is the same as the radially inner outer line L710 of Example 1 in that it has a convex shape on the radially inner side when viewed in the axial direction, but the angle α of the convexity is different. That is, in Example 3, the angle α is closer to 180 degrees than in Example 1. Thus, the angle α of the convexity is somewhat arbitrary, preferably in the range of 150 to 179 degrees, and more preferably in the range of 160 to 175 degrees.

[0065] Although the analysis results for Example 3 are not shown in contour plots here, similar to Example 1 described above, the stress reduction effect around the first slit 71B was confirmed compared to the first to third comparative examples.

[0066] Although each embodiment has been described in detail above, the invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope described in the claims. Furthermore, it is possible to combine all or more of the components of the embodiments described above. Regarding each of the embodiments described above, the following further notes should be added. [Note 1] Viewed in the axial direction, the rotor core is an annular shape, A rotor shaft is positioned radially inward of the rotor core and coupled to the rotor core by a radial overlap, The rotor core comprises magnets arranged for each magnetic pole in a manner that forms multiple magnetic poles along the circumferential direction, The rotor core has a plurality of axial holes located radially inward from the magnet, The plurality of axial holes include a plurality of first holes that are regularly arranged in the circumferential direction at a first radial position, and a plurality of second holes that are regularly arranged in the circumferential direction at a second radial position that is radially inward from the first radial position. The first hole, when viewed in the axial direction, has an outer shape that is convex radially inward, and is a rotor for a rotating electric machine. [Note 2] The rotor for a rotating electric machine as described in Appendix 1, wherein the first hole, when viewed in the axial direction, has a radially outer outline that is a straight line perpendicular to the radial direction. [Note 3] The rotor for a rotating electric machine as described in Appendix 1 or 2, wherein, when viewed in the axial direction, the outer outlines on both sides in the circumferential direction and the outer outline on the radially outer side are connected via a straight outer outline. [Note 4] The rotor for a rotating electric machine as described in Appendix 3, wherein, when viewed in the axial direction, the outer outlines on both sides in the circumferential direction and the outer outline on the radially outer side are connected to the straight outer outline via an angle R. [Note 5] The rotor core has magnetic holes that, when viewed in the axial direction, have a range through which a line parallel to the radial direction passing through the circumferential center of the first hole passes, which is a bridge or an inter-pole region, as described in any one of the appendices 2 to 4. [Note 6] The rotor for a rotating electric machine according to any one of appendices 2 to 5, wherein the first hole has a symmetrical shape with respect to a line parallel to the radial direction passing through the circumferential center of the first hole when viewed in the axial direction. [Note 7] The second hole is positioned radially inward from the reference circle which is concentric with the annular ring when viewed in the axial direction. The rotor for a rotating electric machine according to any one of the appendices 1 to 6, wherein the tip of the convex shape of the first hole is located radially inward from the reference circle. [Explanation of symbols]

[0067] 1 Motor (rotating electric machine), 32 Rotor core, 34 Rotor shaft, 43 Center bridge (bridge), 61 Magnet piece (magnet), 321 Magnet hole, 71 First slit (first hole), 72 Second slit (second hole), L3 Reference circle, L710 Outline (radial inner outline), L712 Outline (radial outer outline), L713 Outline (circumferential outline on both sides), L715 Outline (straight outline), L716 Outline (corner radius)

Claims

1. Viewed in the axial direction, the rotor core is an annular shape, A rotor shaft is positioned radially inward of the rotor core and coupled to the rotor core by a radial overlap, The rotor core comprises magnets arranged for each magnetic pole in a manner that forms multiple magnetic poles along the circumferential direction, The rotor core has a plurality of axial holes located radially inward from the magnet, The plurality of axial holes include a plurality of first holes that are regularly arranged in the circumferential direction at a first radial position, and a plurality of second holes that are regularly arranged in the circumferential direction at a second radial position that is radially inward from the first radial position. The first hole, when viewed in the axial direction, has an outer shape that is convex radially inward, and a center line parallel to the radial direction passing through the circumferential center of the first hole passes between the circumferential directions of adjacent second holes. The radially inner outline of the rotor for a rotating electric machine consists of two straight lines and a curve connecting the two straight lines, passing radially outside the intersection point where the extensions of the two straight lines intersect.

2. The rotor for a rotating electric machine according to claim 1, wherein, when viewed in the axial direction, the outer outline of the first hole has a linear shape perpendicular to the radial direction.

3. The rotor for a rotating electric machine according to claim 2, wherein, when viewed in the axial direction, the outer outlines on both sides in the circumferential direction and the outer outline on the radially outer side are connected by a straight outer outline.

4. The rotor for a rotating electric machine according to claim 3, wherein, when viewed in the axial direction, the outer outlines on both sides in the circumferential direction and the outer outline on the radially outer side are connected to the straight outer outline via an angle R.

5. The rotor for a rotating electric machine according to claim 1, wherein, when viewed in the axial direction, the angle between the two lines relating to the convex shape of the first hole is within the range of 150 degrees to 179 degrees.

6. The rotor for a rotating electric machine according to claim 1, wherein, when viewed in the axial direction, the angle between the two convex lines of the first hole is within the range of 160 degrees to 175 degrees.

7. The rotor for a rotating electric machine according to claim 2, wherein the rotor core has a magnetic hole that, when viewed in the axial direction, has a bridge or inter-pole region in the area through which the center line of the first hole passes.

8. The rotor for a rotating electric machine according to claim 2, wherein the first hole has a symmetrical shape with respect to the center line of the first hole when viewed in the axial direction.

9. The second hole is positioned radially inward from the reference circle which is concentric with the annular ring when viewed in the axial direction. The rotor for a rotating electric machine according to any one of claims 1 to 8, wherein the tip of the convex shape of the first hole is located radially inward from the reference circle.

Images