Rotor core, rotor, rotating electric machine and vehicle drive device

Abstract

To provide a rotor core that is resistant to stresses generated by shrink-fitting a rotor and a shaft, stresses generated by a centrifugal force of rotation of the rotor, and so on, as well as a rotor including the rotor core, a rotary electric machine, and a device for driving a vehicle.SOLUTION: A rotor core is formed with stress relief holes for relieving stress, magnet holes into which magnets are inserted, and crimping grooves for connecting plate-shaped components. The stress relief holes are arranged symmetrically around a d-axis and a q-axis, overlapping with the crimping grooves in a circumferential direction of a circle around the rotary axis of the rotor core. The magnet holes do not overlap with the stress relief holes or the crimping grooves in the circumferential direction. The crimping grooves are formed on either the d-axis or the q-axis.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a rotor core, a rotor, a rotating electric machine, and a vehicle drive device. [Background technology]

[0002] Rotors of rotating electrical machines such as motors and generators include multiple plate-like members stacked in the direction of the rotor's rotation axis. The plate-like members often have stress relief holes formed therethrough in the direction of the rotation axis to relieve stress generated by shrink-fitting the rotor and the shaft and to relieve stress generated by centrifugal force during rotor rotation. Patent Document 1, for example, is an example of a document that discloses stress relief holes formed in rotors. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-083901 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the rotor disclosed in Patent Document 1 includes a crimped portion located in a first region between circumferentially adjacent through-holes. Therefore, the rotor disclosed in Patent Document 1 may fracture at the crimped portion and its surrounding area due to stresses generated by shrink-fitting the rotor and the shaft, stresses generated by centrifugal force during rotor rotation, etc. In particular, when a large-diameter shaft is shrink-fitted to the rotor, or when the rotor is rotating at high speed, the rotor is likely to fracture due to these stresses.

[0005] Therefore, an object of the present invention is to provide a rotor core that is less likely to break due to stresses generated by shrink-fitting the rotor and shaft, stresses generated by the centrifugal force of the rotor's rotation, etc., and a rotor, rotating electric machine, and vehicle drive device that include such a rotor core. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, a rotor core of the present invention is formed with stress relief holes for relieving stress, magnet holes into which magnets are fitted, and crimping grooves for connecting plate-like members. The stress relief holes are arranged line-symmetrically with respect to the d-axis and line-symmetrically with respect to the q-axis, and overlap with the crimping grooves in the circumferential direction of a circle centered on the rotation axis of the rotor core. Furthermore, the stress relief hole is not symmetrical with respect to any straight line perpendicular to the rotation axis, and is a pentagon in which all interior angles are rounded, one side of which is along the q axis, and the angle formed by the side along the q axis farther from the rotation axis is less than 90 degrees, and the angle formed by the side along the q axis closer to the rotation axis is 90 degrees or greater. The magnet holes do not overlap with the stress relief holes or the crimping grooves in the circumferential direction. The crimping grooves are formed on either the d-axis or the q-axis. The stress relief holes are adjacent to each other in the circumferential direction, and two of the stress relief holes are formed between the d-axis and the q-axis on which the crimping grooves are formed.

[0009] In the rotor core of the present invention, the stress relief hole passes through the center of the crimping groove in the radial direction of a circle centered on the rotation axis, and is included within at least a predetermined percentage of an imaginary circle centered on the rotation axis.

[0011] A rotor according to the present invention includes the rotor core described above.

[0012] A rotating electric machine according to the present invention includes the rotor described above.

[0013] A vehicle drive device according to the present invention includes the above-described rotating electric machine. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a rotor core that is resistant to fracture due to stresses generated by shrink-fitting the rotor and shaft, stresses generated by the centrifugal force of the rotor's rotation, and the like, as well as a rotor, a rotating electric machine, and a vehicle drive device that include the rotor core. [Brief explanation of the drawings]

[0015] [Figure 1]1 is an exploded perspective view of a vehicle drive device according to a first embodiment. [Figure 2] 2 is a cross-sectional view taken along a plane perpendicular to the rotation axis of the rotor core according to the first embodiment. FIG. [Figure 3] FIG. 10 is a cross-sectional view taken along a plane perpendicular to the rotation axis of a rotor core according to a second embodiment. [Figure 4] FIG. 11 is a cross-sectional view taken along a plane perpendicular to the rotation axis of a rotor core according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0017] (First embodiment) 1 is an exploded perspective view of a vehicle drive device according to a first embodiment. The vehicle drive device 1 is mounted on a vehicle, such as an electric vehicle, for the purpose of driving the vehicle and generating electricity for use in the vehicle. The vehicle drive device 1 also includes a motor, which is an example of a rotating electric machine.

[0018] As shown in Fig. 1, the vehicle drive device 1 includes a housing 10, a bearing 20, a resolver 30, a stator 40, a shaft 50, a rotor 60a, a bearing 70, and a bracket 80. The vehicle drive device 1, excluding the housing 10, forms a motor, which is an example of a rotating electric machine. In the following description, an X-axis parallel to the rotation axis A of the rotor 60a, a Y-axis perpendicular to the X-axis, and a Z-axis perpendicular to the X-axis and Y-axis are used. The X-axis, Y-axis, and Z-axis form a right-handed system.

[0019] The housing 10 incorporates a gear case frame assembly 11, an inverter assembly 12, and a terminal 13. The gear case frame assembly 11 includes a transmission and a group of associated parts. The inverter assembly 12 includes an inverter and a group of associated parts. The terminal 13 is electrically connected to a coil 42 (described later) and supplies AC power generated by the inverter to the coil 42.

[0020] The outer ring of bearing 20 is fitted into housing 10. The shaft 50 is fitted into the inner ring of bearing 20, and the end of shaft 50 on the −X direction side is supported in a manner that allows it to rotate around rotation axis A.

[0021] The resolver 30 is, for example, a one-phase excitation, two-phase output variable reluctance (VR) resolver, and includes a resolver connector 31, a VR resolver stator 32, a VR resolver rotor 33, and a fixing ring .

[0022] The resolver connector 31 is attached to the housing 10, receives the analog signal output by the VR resolver stator 32, and transmits it to a resolver digital (RD) converter (not shown). The RD converter converts the analog signal into a digital signal. This digital signal is used to calculate the rotation angle of the rotor 60a.

[0023] The VR resolver stator 32 is attached to the housing 10 and includes a primary coil that applies a reference signal to the VR resolver rotor 33, and a secondary coil that is electrically connected to the RD converter. When a reference signal is input to the primary coil, the VR resolver stator 32 outputs the above-mentioned analog signal from the secondary coil.

[0024] The VR resolver rotor 33 includes a relay coil and is attached to the shaft 50 by a fixing ring 34. The VR resolver rotor 33 rotates together with the shaft 50 around the rotation axis A, thereby changing the relative position between the primary coil and secondary coil of the VR resolver 32.

[0025] The stator 40 includes a stator core 41, a coil 42, terminals 43, a thermistor 44, and a thermistor connector 45. The stator core 41 is a cylindrical member into which the shaft 50 and rotor 60a are inserted, and has multiple teeth formed on its inside. The coil 42 is formed by winding copper wire around the teeth. When current is applied to the coil 42, it generates a magnetic force that rotates the rotor 60a. The terminals 43 electrically connect the coil 42 to the terminals 13. The thermistor 44 outputs an electrical signal that depends on the temperature of the coil 42. The thermistor connector 45 receives the electrical signal and transmits it to a device that uses the electrical signal to calculate the temperature of the coil 42.

[0026] The shaft 50 is a rod-shaped member that is fitted into a rotor core 61a (described later) and supports the rotor 60a in a manner that allows the rotor 60a to rotate around a rotation axis A. The shaft 50 is hollow, and has a helical gear formed at the end on the +X direction side.

[0027] The rotor 60 a includes a rotor core 61 a, an end plate 62 , an end plate 63 , a magnet cover 64 , a magnet cover 65 , a bolt 66 , and a bolt 67 .

[0028] 2 is a cross-sectional view of a rotor core according to the first embodiment taken along a plane perpendicular to the rotation axis. The rotor core 61a is formed by stacking plate-shaped members in the direction of the rotation axis A so that the edges of holes (described later) coincide on a plane perpendicular to the rotation axis A, and the shaft 50 is fitted into the plate-shaped members. The plate-shaped members are circular and made of electromagnetic steel. As shown in FIG. 2, the rotor core 61a has a shaft hole 61H, a magnet hole 610H, a crimping groove 611, a stress relief hole 612a, and a stress relief hole 613a formed therein.

[0029] The shaft hole 61H is formed so as to penetrate the plate-like member in the direction of the rotation axis A, and is a hole into which the shaft 50 is fitted.

[0030] Magnet hole 610H is a hole into which magnet 61M is fitted. Magnet hole 610H is formed at a position shifted radially outward from crimping groove 611, stress relief hole 612a, and stress relief hole 613a. Therefore, magnet hole 610H does not overlap crimping groove 611, stress relief hole 612a, or stress relief hole 613a in the circumferential direction of a circle centered on rotation axis A of rotor core 61a.

[0031] The crimping grooves 611 are grooves for connecting the plate-shaped members together, and are formed in each plate-shaped member. The crimping grooves 611 are formed only on the d-axis, and are not formed on the q-axis. The axis connecting the rotation axis A of the rotor core 61a and the center of any main magnetic pole that generates magnetic torque is the d-axis of the dq coordinate system. This center is located at a position corresponding to the valley of two magnets 61M that are arranged in a V-shape with the crimping groove 611 between them. Furthermore, the axis connecting the rotation axis A of the rotor core 61a and the center of an auxiliary magnetic pole that generates reactance torque is the q-axis of the dq coordinate system. This center is located on an axis that is orthogonal to the d-axis in terms of electrical angle.

[0032] The stress relief holes 612a and 613a are holes formed through the rotor core 61a in the direction of the rotation axis A. The stress relief holes 612a and 613a are formed at positions facing each other across the crimping groove 611 that is closest to them in the circumferential direction. The stress relief holes 612a and 613a are arranged line-symmetrically with respect to the d-axis. The stress relief holes 612a and 613a are also arranged line-symmetrically with respect to the q-axis. The stress relief holes 612a and 613a overlap with the crimping groove 611 in the circumferential direction.

[0033] The stress relief hole 612a is pentagonal and has interior angles 6121a, 6122a, 6123a, 6124a, and 6125a. The interior angles 6121a, 6123a, 6124a, and 6125a are all 90 degrees or greater. The interior angle 6122a is less than 90 degrees and is located near the q-axis. All five of these interior angles are rounded. The larger the radius of the rounded corner, the greater the stress-relieving effect; the smaller the radius, the less effective it is. In other words, the larger the radius of the rounded corner, the less likely it is that stress will concentrate at the interior angles; the smaller the radius, the more likely it is that stress will concentrate at the interior angles.

[0034] The interior angles 6121a, 6123a, and 6124a mainly mitigate stress generated by shrink-fitting the rotor core 61a and the shaft 50. These three interior angles are all 90 degrees or greater, and therefore effectively mitigate the stress. However, these three interior angles also mitigate stress generated by the centrifugal force of the rotation of the rotor core 61a.

[0035] The interior angles 6122a and 6125a mainly mitigate stress generated by the centrifugal force of the rotation of the rotor core 61a. Because the interior angle 6122a is less than 90 degrees, it contributes to widening the circumferential width around the portion through which the q axis passes, thereby mitigating the stress. Because the interior angle 6125a is 90 degrees or more, it has high resistance to stress applied in the elongation direction due to the stress. However, these two interior angles also mitigate stress generated by shrink-fitting the rotor core 61a and the shaft 50.

[0036] Similarly, stress relief hole 613a is pentagonal and has interior angles 6131a, 6132a, 6133a, 6134a, and 6135a. Interior angles 6131a, 6133a, 6134a, and 6135a are all 90 degrees or greater. Interior angle 6132a is less than 90 degrees and is located near the portion through which the q axis passes. All five interior angles are rounded.

[0037] The interior angles 6131a, 6133a, and 6134a mainly mitigate stress generated by shrink-fitting the rotor core 61a and the shaft 50. These three interior angles are all 90 degrees or greater, and therefore effectively mitigate the stress. However, these three interior angles also mitigate stress and the like generated by the centrifugal force of the rotation of the rotor core 61a.

[0038] The interior angles 6132a and 6135a mainly mitigate stress generated by the centrifugal force of the rotation of the rotor core 61a. Because the interior angle 6132a is less than 90 degrees, it contributes to widening the circumferential width around the portion through which the q axis passes, thereby mitigating the stress. Because the interior angle 6135a is 90 degrees or more, it has high resistance to stress applied in the elongation direction due to the stress. However, these two interior angles also mitigate stress and the like generated by shrink-fitting the rotor core 61a and the shaft 50.

[0039] The stress relief holes 612a and 613a are not symmetrical with respect to any straight line perpendicular to the rotation axis A. For example, as shown in FIG. 2, the stress relief hole 613a is not symmetrical with respect to the straight line La.

[0040] The stress relief hole 612a and the stress relief hole 613a pass through the center of the crimping groove 611 in the radial direction of a circle centered on the rotation axis A, and at least a predetermined percentage is included inside an imaginary circle C centered on the rotation axis A. For example, as shown in FIG. 2, the stress relief hole 612a and the stress relief hole 613a are included at least 50% inside the imaginary circle C.

[0041] The stress relief holes 612a and 613a have the effect of relieving stress generated by the rotation of the rotor 60a and stress generated by the shaft 50 being shrink-fitted to the rotor core 61a. The stress relief holes 612a and 613a also have the effect of reducing the weight of the rotor 60a and improving the cooling efficiency of the rotor 60a.

[0042] As shown in FIG. 1, the end plates 62 and 63 are members that sandwich and fix the rotor core 61a from both sides in the direction of the rotation axis A.

[0043] The magnet cover 64 covers the surface of the end plate 62 that is located opposite the rotor core 61a, i.e., the surface on the -X direction side of the end plate 62. This prevents the magnet 61H from falling off the rotor core 61a.

[0044] The magnet cover 65 covers the surface of the end plate 63 that is located opposite the rotor core 61a, i.e., the surface on the +X direction side of the end plate 63. In this way, the magnet cover 65 prevents the magnet 61H from falling off the rotor core 61a.

[0045] As shown in FIG. 1 , the vehicle drive device 1 preferably includes a magnet cover 64 having at least one hole 64H formed therein and a magnet cover 65 having at least one hole 65H formed therein. In this case, one of the holes 64H and one of the holes 65H at least partially overlap in the direction of the rotation axis A. This allows the vehicle drive device 1 to introduce refrigerant into at least one of the stress relief holes 612a and 613a via the hole 64H and discharge the refrigerant via the hole 65H to cool the rotor core 61a. Alternatively, this allows the vehicle drive device 1 to introduce refrigerant into at least one of the stress relief holes 612a and 613a via the hole 65H and discharge the refrigerant via the hole 64H to cool the rotor core 61a.

[0046] It is preferable that the vehicle drive device 1 has a structure that allows the refrigerant to be discharged through the hole 64H or the hole 65H. Therefore, if the vehicle drive device 1 cannot be provided with the hole 64H and the hole 65H that at least partially overlap in the direction of the rotation axis A, it is preferable that the vehicle drive device 1 be provided with a magnet cover that does not have the hole 64H formed therein and a magnet cover that does not have the hole 65H formed therein.

[0047] The outer ring of bearing 70 is fitted into bracket 80. Shaft 50 is fitted into the inner ring of bearing 70, and the end of shaft 50 on the +X direction side is supported in a manner that allows rotation around rotation axis A. In addition, bearing 70 is fixed to shaft 50 by a snap ring 71.

[0048] The bracket 80 is a cover that closes the opening of the housing 10 from the +X direction. The bracket 80 is arranged to sandwich the bearing 20, resolver 30, stator 40, shaft 50, rotor 60a, bearing 70, etc. together with the housing 10 in the X direction.

[0049] The rotor core 61a according to the first embodiment has been described above. The rotor core 61a is formed with magnet holes 610H, crimping grooves 611, stress relief holes 612a, and stress relief holes 613a.

[0050] The crimping grooves 611 are formed only on the d-axis. This makes it possible to prevent a situation in which the strength of the portion of the rotor core 61a through which the q-axis passes and the surrounding area of ​​that portion from being reduced by the crimping grooves 611. This effect is particularly useful because the vehicle drive device 1 is mounted on an electric vehicle and the rotor core 61a often rotates at high speed. Furthermore, this also makes it possible to widen the path through which the magnetic flux passes in the rotor core 61a compared to a case in which the crimping grooves 611 are formed only on the q-axis and the crimping grooves 611 are not formed on the d-axis, thereby improving the characteristics of the motor.

[0051] Furthermore, in rotor core 61a, the interior angles of stress relief holes 612a and 613a that are less than 90 degrees are located around the q axis, which prevents a reduction in strength around these interior angles in the area where the q axis passes. This prevents fracture of the area where the q axis passes and the area around this area due to stress generated by shrink-fitting the rotor and the shaft, stress generated by the centrifugal force of rotor rotation, and the like.

[0052] The stress relief holes 612a and 613a are arranged symmetrically about the d-axis and about the q-axis, respectively, and overlap with the crimping grooves 611 in the circumferential direction of a circle centered on the rotation axis of the rotor core 61a. This allows the rotor core 61a to have a smaller outer diameter and a larger inner diameter than a rotor core in which the crimping grooves 611, the stress relief holes 612a, and the stress relief holes 613a do not overlap in the circumferential direction. The smaller outer diameter of the rotor core 61a contributes to the miniaturization of the motor and the vehicle drive device 1. Furthermore, the larger inner diameter of the rotor core 61a facilitates the use of a shaft with a large diameter through which cooling oil can flow. Furthermore, the larger inner diameter of the rotor core 61a increases the contact area with the shaft 50, enabling the rotor core 61a to be firmly fixed to the shaft 50.

[0053] The stress relief holes 612a and 613a are pentagonal and are not symmetrical with respect to any straight lines perpendicular to the rotation axis A. This increases the degree of freedom in the shapes of the stress relief holes 612a and 613a of the rotor core 61a, making it possible to satisfy various requirements, such as easing various stresses applied to the rotor core 61a and ensuring a path for magnetic flux.

[0054] The four interior angles of the stress relief holes 612a and 613a are equal to or greater than 90 degrees, so that the rotor core 61a can effectively relieve stress by the stress relief holes 612a and 613a, which have large interior angles.

[0055] The stress relief holes 612a and 613a pass through the center of the crimping groove 611 in the radial direction of a circle centered on the rotation axis A, and at least a predetermined percentage of the holes is included inside an imaginary circle C centered on the rotation axis A. This allows the rotor core 61a to effectively relieve stress generated by shrink-fitting the rotor core 61a and the shaft 50.

[0056] Second Embodiment The vehicle drive device according to the second embodiment differs from the vehicle drive device according to the first embodiment in the shape of the stress relief holes formed in the rotor core. Therefore, in the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description of the same content as in the first embodiment will be omitted as appropriate, and the description will focus on the differences from the first embodiment.

[0057] Fig. 3 is a cross-sectional view of a rotor core according to the second embodiment taken along a plane perpendicular to the rotation axis. As shown in Fig. 3, rotor core 61b is formed with shaft hole 61H, magnet hole 610H, crimping groove 611, stress relief hole 612b, and stress relief hole 613b.

[0058] Magnet hole 610H does not overlap with crimping groove 611, stress relief hole 612b, or stress relief hole 613b in the circumferential direction of a circle centered on rotation axis A of rotor core 61b. Crimping groove 611 is formed only on the d-axis, not on the q-axis.

[0059] The stress relief holes 612b and 613b are holes formed through the rotor core 61b in the direction of the rotation axis A. The stress relief holes 612b and 613b are formed at positions facing each other across the crimping groove 611 that is closest to them in the circumferential direction. The stress relief holes 612b and 613b are arranged line-symmetrically with respect to the d-axis. The stress relief holes 612b and 613b are also arranged line-symmetrically with respect to the q-axis. The stress relief holes 612b and 613b overlap with the crimping groove 611 in the circumferential direction.

[0060] The stress relief hole 612b is pentagonal and has interior angles 6121b, 6122b, 6123b, 6124b, and 6125b. All five interior angles are greater than or equal to 90 degrees. All five interior angles are rounded.

[0061] The interior angles 6121b, 6123b, and 6124b mainly mitigate stress generated by shrink-fitting the rotor core 61b and the shaft 50. These three interior angles are all 90 degrees or greater, and therefore effectively mitigate the stress. However, these three interior angles also mitigate stress generated by the centrifugal force of the rotation of the rotor core 61b.

[0062] The interior angles 6122b and 6125b mainly mitigate stress generated by the centrifugal force of the rotation of the rotor core 61b. Because these two interior angles are 90 degrees or greater, they have high resistance to stress applied in the direction of extension due to the stress. However, these two interior angles also mitigate stress generated by shrink-fitting the rotor core 61b and the shaft 50.

[0063] Similarly, the stress relief hole 613b is pentagonal and has interior angles 6131b, 6132b, 6133b, 6134b, and 6135b. All five interior angles are greater than or equal to 90 degrees. All five interior angles are rounded.

[0064] The interior angles 6131b, 6133b, and 6134b mainly mitigate stress generated by shrink-fitting the rotor core 61b and the shaft 50. These three interior angles are all 90 degrees or greater, and therefore effectively mitigate the stress. However, these three interior angles also mitigate stress generated by the centrifugal force of the rotation of the rotor core 61b.

[0065] The interior angles 6132b and 6135b mainly mitigate stress generated by the centrifugal force of the rotation of the rotor core 61b. Because these two interior angles are 90 degrees or greater, they have high resistance to stress applied in the direction of extension due to the stress. However, these two interior angles also mitigate stress generated by shrink-fitting the rotor core 61b and the shaft 50.

[0066] The stress relief hole 612b and the stress relief hole 613b are shaped to be line-symmetric with respect to a predetermined line perpendicular to the rotation axis A. For example, as shown in Fig. 3, the stress relief hole 613b is shaped to be line-symmetric with respect to the line Lb.

[0067] The stress relief hole 612b and the stress relief hole 613b pass through the center of the crimping groove 611 in the radial direction of a circle centered on the rotation axis A, and at least a predetermined percentage is included inside an imaginary circle C centered on the rotation axis A. For example, as shown in FIG. 3, the stress relief hole 612b and the stress relief hole 613b are included at least 50% inside the imaginary circle C.

[0068] The rotor core 61b according to the second embodiment has been described above. The rotor core 61b has the same features as the rotor core 61a according to the first embodiment, except that the stress relief holes 612b and the stress relief holes 613b are shaped symmetrically with respect to a predetermined line perpendicular to the rotation axis A. Therefore, the rotor core 61b has the same effects as the rotor core 61a according to the first embodiment.

[0069] Furthermore, the rotor core 61b rotates in the opposite direction to run the vehicle and to generate electric power for use in the vehicle. Therefore, the stress applied to each part of the rotor core 61b is reversed when the rotation direction is reversed. Furthermore, as described above, the rotor core 61b has the stress relief holes 612b and 613b that are shaped symmetrically with respect to a predetermined line perpendicular to the rotation axis A. Therefore, the rotor core 61b can relieve stress in the same way regardless of the direction of rotation.

[0070] (Third embodiment) The shape of the stress relief holes formed in the rotor core of the vehicle drive device according to the third embodiment differs from that of the vehicle drive device according to the first embodiment and the vehicle drive device according to the second embodiment. Therefore, in the third embodiment, the same components as those in the first or second embodiment are denoted by the same reference numerals as those in the first or second embodiment, and the description of the same content as in the first or second embodiment will be omitted as appropriate, with the description focusing on the differences from the first and second embodiments.

[0071] Fig. 4 is a cross-sectional view of a rotor core according to the third embodiment taken along a plane perpendicular to the rotation axis. As shown in Fig. 4, rotor core 61c has shaft hole 61H, magnet hole 610H, crimping groove 611, stress relief hole 612c, and stress relief hole 613c formed therein.

[0072] Magnet hole 610H does not overlap with crimping groove 611, stress relief hole 612c, or stress relief hole 613c in the circumferential direction of a circle centered on rotation axis A of rotor core 61c. Crimping groove 611 is formed only on the d-axis, not on the q-axis.

[0073] The stress relief holes 612c and 613c are holes formed through the rotor core 61c in the direction of the rotation axis A. The stress relief holes 612c and 613c are formed at positions facing each other across the crimping groove 611 that is closest to them in the circumferential direction. The stress relief holes 612c and 613c are arranged line-symmetrically with respect to the d-axis. The stress relief holes 612c and 613c are also arranged line-symmetrically with respect to the q-axis. The stress relief holes 612c and 613c overlap with the crimping groove 611 in the circumferential direction.

[0074] The stress relief holes 612c and 613c are hexagonal, with all six interior angles equal to or greater than 90 degrees. In addition, the stress relief holes 612c and 613c have all interior angles rounded.

[0075] The stress relief hole 612c and the stress relief hole 613c are shaped to be line-symmetric with respect to a predetermined line perpendicular to the rotation axis A. For example, as shown in Fig. 4, the stress relief hole 613c is shaped to be line-symmetric with respect to the line Lc.

[0076] The stress relief hole 612c and the stress relief hole 613c pass through the center of the crimping groove 611 in the radial direction of a circle centered on the rotation axis A, and at least a predetermined percentage is included inside an imaginary circle C centered on the rotation axis A. For example, as shown in FIG. 3, the stress relief hole 612c and the stress relief hole 613c are included at least 50% inside the imaginary circle C.

[0077] The rotor core 61c according to the third embodiment has been described above. The rotor core 61c has the same features as the rotor core 61a according to the first embodiment, except that the stress relief holes 612c and 613c are hexagonal and have shapes that are line-symmetrical with respect to a predetermined line perpendicular to the rotation axis A. Therefore, the rotor core 61c has the same effects as the rotor core 61a according to the first embodiment.

[0078] Furthermore, the rotor core 61c rotates in the opposite direction to run the vehicle and to generate electric power for use in the vehicle. Therefore, the stresses applied to each part of the rotor core 61c are opposite when the rotation direction is reversed. Furthermore, as described above, the rotor core 61c includes the stress relief holes 612c and 613c, which have shapes that are line-symmetrical with respect to a predetermined line perpendicular to the rotation axis A. Therefore, the rotor core 61c can relieve stress in the same way regardless of the direction of rotation.

[0079] In the above-described embodiment, the rotor core 61a, the rotor core 61b, or the rotor core 61c is incorporated into a motor for a vehicle drive device, but the present invention is not limited to this. The rotor core 61a, the rotor core 61b, or the rotor core 61c may be incorporated into a motor for a general drive device, rather than a vehicle drive device. Furthermore, the rotor core 61a, the rotor core 61b, or the rotor core 61c may be incorporated into a generator that converts mechanical energy into electrical energy, rather than a motor for a drive device.

[0080] Furthermore, in the above-described embodiment, the shaft 50 is hollow, but the present invention is not limited to this. The shaft 50 does not have to be hollow.

[0081] Furthermore, in the above-described embodiment, the crimping groove 611 is formed only on the d-axis, but this is not limiting. The crimping groove 611 may be formed only on the q-axis. This makes it possible to prevent a situation in which the crimping groove 611 reduces the strength of the portions of the rotor cores 61a, 61b, and 61c through which the d-axis passes and the surrounding areas of those portions.

[0082] In the above-described embodiment, the stress relief holes 612a, 613a, 612b, and 613b are pentagonal, and the stress relief holes 612c and 613c are hexagonal. However, the present invention is not limited to these examples. The stress relief holes may have any shape as long as they are n-sided (n is an integer of 3 or more). Even if the shape of the stress relief holes in the rotor core is a polygon other than a pentagon or a hexagon, the same effects as those achieved when the shape of the stress relief holes is pentagonal or hexagonal can be achieved.

[0083] However, as the number of vertices of the stress relief holes increases, the radius of each interior angle must be made smaller, which makes it easier for stress to concentrate at each interior angle. For this reason, it is preferable to increase the number of vertices of the stress relief holes when, for example, the rotor core is not rotated at high speed, or when the stress generated by shrink-fitting the rotor core and shaft 50 together is relatively small.

[0084] Furthermore, it is preferable that n-1 or more of the stress relief holes have interior angles of 90 degrees or greater, which allows rotor core 61a, rotor core 61b, and rotor core 61c to effectively relieve stress acting on the interior angles.

[0085] In the above-described embodiment, all the interior angles of the stress relief holes are rounded, but this is not limiting. At least one of the interior angles of the stress relief holes does not have to be rounded. However, it is preferable that all the interior angles of the stress relief holes be rounded in order to effectively relieve stresses generated by the rotation of the rotor core 61a, the rotor core 61b, or the rotor core 61c, and stresses generated by the shaft 50 being shrink-fitted to the rotor core.

[0086] The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. In other words, the present invention includes embodiments in which various modifications, substitutions, design changes, etc. have been made based on the spirit of the present invention, and does not exclude these embodiments. [Explanation of symbols]

[0087] 1... vehicle drive device, 60a... rotor, 61a, 61b, 61c... rotor core

Claims

1. A rotor core having stress relief holes for relieving stress, magnet holes into which magnets are inserted, and crimping grooves for connecting plate-like members, the stress relief holes are arranged line-symmetrically with respect to the d-axis and the q-axis, overlap with the crimping grooves in the circumferential direction of a circle centered on the rotation axis of the rotor core, are not line-symmetric with respect to any straight lines perpendicular to the rotation axis, have a pentagonal shape in which all interior angles are rounded, one side is along the q-axis, the angle formed by the side along the q-axis farther from the rotation axis is less than 90 degrees, and the angle formed by the side along the q-axis closer to the rotation axis is 90 degrees or greater, the magnet hole does not overlap with the stress relief hole and the crimping groove in the circumferential direction, the crimping groove is formed on either the d-axis or the q-axis, the two stress relief holes are formed between the d-axis and the q-axis, which are adjacent to each other in the circumferential direction and on which the crimping groove is formed; Rotor core.

2. The stress relief hole passes through the center of the crimping groove in the radial direction of a circle centered on the rotation axis, and is included within at least a predetermined percentage of an imaginary circle centered on the rotation axis. The rotor core according to claim 1 .

3. A rotor having a rotor core described in claim 1 or claim 2.

4. A rotating electric motor having a rotor as described in claim 3.

5. A vehicle drive device equipped with a rotating electric motor as described in claim 4.

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