Rotor

Abstract

To improve the magnetic characteristics of a rotor while providing a balance adjustment part in the rotor, and thus to reduce the size of the rotor.SOLUTION: A rotor may include: a first rotor core in which a permanent magnet is disposed; and a second rotor core that is axially adjacent to the first rotor core and in which no permanent magnet is disposed. The second rotor core may include: a group of magnetic path forming holes that are provided at equal intervals along a circumferential direction and form a magnetic path for giving a salient polarity to the second rotor core; and a balance adjustment part that is provided at least at one position in the circumferential direction and locally increases or decreases the mass of the second rotor core.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a rotor. [Background technology]

[0002] Patent Document 1 describes a rotor. This rotor includes a rotor core in which permanent magnets are arranged, and end plates that are arranged on both axial end surfaces of the rotor core and on which no permanent magnets are arranged. The end plates are provided with balance adjustment portions. These balance adjustment portions are locally cut portions that are provided on parts of the end plates in the circumferential direction, and adjust the mass balance of the rotor in the circumferential direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2010-206884 Summary of the Invention [Problem to be solved by the invention]

[0004] In the rotor described above, the end plates do not have magnets disposed thereon, and therefore do not contribute significantly to the magnetic characteristics of the rotor. However, omitting the end plates would require providing balance adjustment sections to the rotor core. In this case, providing cutout portions in the rotor core as balance adjustment sections raises concerns that they may interfere with the magnets. Alternatively, adding a mass to the rotor core as a balance adjustment section raises concerns about the magnets' influence on the magnetic flux. Therefore, the presence of end plates is considered effective from the perspective of providing balance adjustment sections. On the other hand, the presence of end plates, which do not contribute to the magnetic characteristics, leads to unnecessary increases in the size of the rotor. This specification provides technology that can at least partially solve the above problems. [Means for solving the problem]

[0005] The technology disclosed in this specification is embodied in a rotor for an electric motor. The rotor may include a first rotor core in which permanent magnets are arranged, and a second rotor core axially adjacent to the first rotor core and in which no permanent magnets are arranged. The second rotor core may have a group of magnetic path-forming holes that are arranged at equal intervals along the circumferential direction and form magnetic paths for imparting salient polarity to the second rotor core, and a balance adjustment portion that is arranged at at least one location along the circumferential direction and locally increases or decreases the mass of the second rotor core.

[0006] In the rotor described above, a balance adjustment unit is provided in the second rotor core, which does not have any permanent magnets. This prevents or minimizes the balance adjustment unit from interfering with the permanent magnets of the first rotor core or affecting the magnetic flux of the permanent magnets. Additionally, a group of magnetic path-forming holes is provided in the second rotor core. The group of magnetic path-forming holes forms a magnetic path for imparting salient polarity to the second rotor core. With this configuration, the second rotor core can generate reluctance torque in the magnetic field generated by the stator. This improves the torque output by the electric motor. Therefore, the first rotor core can be made smaller in size, taking into account the reluctance torque generated by the second rotor core. Thus, the technology disclosed in this specification allows the rotor to have a balance adjustment unit while improving its magnetic characteristics, thereby enabling the rotor to be made smaller. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view of a rotor according to a first embodiment. [Figure 2] 2 shows an end view of the first rotor core taken along line II-II in FIG. 1. [Figure 3] 3 shows an end view of the second rotor core taken along line III-III in FIG. 1. [Figure 4] 4 shows an end view of the third rotor core taken along line IV-IV in FIG. [Figure 5]10 is a cross-sectional view of a rotor according to a second embodiment. [Figure 6] 6 shows an end view of the second rotor core taken along line VI-VI in FIG. 5. [Figure 7] 7 shows an end view of the third rotor core taken along line VII-VII in FIG. 5. [Figure 8] 10 is a cross-sectional view of a rotor according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] In a first aspect of the present technology, as described above, a rotor of an electric motor may include a first rotor core in which permanent magnets are arranged, and a second rotor core axially adjacent to the first rotor core and in which no permanent magnets are arranged. The second rotor core may have a group of magnetic path forming holes that form a magnetic path for imparting salient polarity to the second rotor core, and a balance adjustment portion that is provided at at least one location in the circumferential direction and that locally increases or decreases the mass of the second rotor core.

[0009] In a second aspect of the present technology, in addition to the first aspect, the group of magnetic path-forming holes may have slit-shaped holes extending along the magnetic path. With this configuration, leakage flux in the magnetic path is suppressed, and the second rotor core can effectively generate reluctance torque.

[0010] In a third aspect of the present technology, in addition to the second aspect, the balance adjustment portion may be provided on the one axial end face of the second rotor core, radially inward of the group of magnetic path-forming holes. With this configuration, the balance adjustment portion can be provided in an area of the second rotor core where the group of magnetic path-forming holes is not present and where strength is relatively high.

[0011] In a fourth aspect of the present technology, in addition to the third aspect, the balance adjustment portion may have a balance adjustment hole provided in the end face on the one side in the axial direction of the second rotor core. With this configuration, the balance adjustment hole can be easily formed in the second rotor core by cutting work using, for example, a drill.

[0012] In a fifth aspect of the present technology, in addition to the first aspect, the group of magnetic path-forming holes may have a plurality of point-like holes arranged along the magnetic path. With this configuration, the second rotor core can also generate reluctance torque.

[0013] In a sixth aspect of the present technology, in addition to the fifth aspect described above, the balance adjustment portion may have a balance adjustment hole provided in the outer peripheral surface of the second rotor core. When a balance adjustment hole is provided in the outer peripheral surface of the second rotor core, there is a risk that the balance adjustment hole may reach one of the group of magnetic path forming holes. In this case, depending on the shape of the balance adjustment hole, it is possible that the rigidity and strength of the second rotor core may be unintentionally reduced. In this regard, if the magnetic path forming hole that the balance adjustment hole reaches is a point-like hole that is relatively small compared to the slit, the reduction in rigidity and strength that occurs in the second rotor core is suppressed. Therefore, the balance adjustment hole can be provided in an appropriate position on the outer peripheral surface regardless of its relative position with respect to the group of magnetic path forming holes.

[0014] Therefore, in a seventh aspect of the present technology, in addition to the sixth aspect, the balance adjustment hole may reach at least one of the plurality of point-like holes in the group of magnetic-path forming holes. However, in another embodiment, the balance adjustment hole does not have to reach at least one of the plurality of point-like holes in the group of magnetic-path forming holes. Even if the balance adjustment hole is simply adjacent to the magnetic-path forming hole, as long as the magnetic-path forming hole is a relatively small point-like hole, a decrease in rigidity and strength occurring in the second rotor core is suppressed.

[0015] According to an eighth aspect of the present technology, in addition to the seventh aspect, the group of magnetic path-forming holes may further include slit-shaped holes extending along the magnetic path. In this case, the plurality of point-shaped holes may be located radially outward of the slit-shaped holes. With this configuration, by configuring the magnetic path-forming holes with slit-shaped holes, it is possible to effectively generate reluctance torque in the second rotor core, as long as interference with the balance adjustment holes does not become a problem.

[0016] Therefore, in a ninth aspect of the present technology, in addition to the above-described eighth aspect, the balance adjustment holes do not have to reach the slit-shaped holes of the group of magnetic path forming holes.

[0017] In a tenth aspect of the present technology, in addition to the first aspect, the balance adjustment portion may be provided on the one end face of the second rotor core in the axial direction, radially inward of the group of magnetic path-forming holes. That is, regardless of the specific configuration of the group of magnetic path-forming holes as described above, the balance adjustment portion may be provided on the one end face of the second rotor core.

[0018] In an eleventh aspect of the present technology, in addition to the first aspect, the balance adjustment portion may be provided on the outer circumferential surface of the second rotor core. That is, regardless of the specific configuration of the group of magnetic path-forming holes as described above, the balance adjustment portion may be provided on the outer circumferential surface of the second rotor core.

[0019] In a twelfth aspect of the present technology, in addition to the eleventh aspect, the balance adjustment portion may be located at the d-axis center of the saliency formed by the group of magnetic path-forming holes. With this configuration, the influence of the balance adjustment portion on the magnetic path can be relatively reduced.

[0020] In a thirteenth aspect of the present technology, in addition to the first aspect, the second rotor core may be adjacent to an end face on one side of the first rotor core in the axial direction. With this configuration, the second rotor core can also function as an end plate in a conventional motor at the end face of the first rotor core.

[0021] In a fourteenth aspect of the present technology, in addition to the thirteenth aspect described above, a third rotor core may be further provided adjacent to an end face of the first rotor core on the other side in the axial direction. In this case, the third rotor core may have a group of magnetic path forming holes that form magnetic paths for imparting salient polarity to the third rotor core. With this configuration, the third rotor core can function in the same manner as the second rotor core described above on the other side in the axial direction of the first rotor core.

[0022] In a fifteenth aspect of the present technology, in addition to the fourteenth aspect, the third rotor core may further include a balance adjustment portion provided at at least one location in the circumferential direction and configured to locally increase or decrease the mass of the third rotor core. With this configuration, the balance adjustment portions can be disposed on both sides of the rotor in the axial direction, and, for example, each balance adjustment portion can be made smaller.

[0023] In a sixteenth aspect of the present technology, in addition to the fifteenth aspect described above, the balance adjustment portion of the second rotor core and the balance adjustment portion of the third rotor core may be located at the same position in the circumferential direction. Such a configuration is effective in adjusting the static balance of the rotor. However, as another embodiment, the balance adjustment portion of the second rotor core and the balance adjustment portion of the third rotor core may be located at different positions in the circumferential direction. Such a configuration is effective in adjusting the even balance of the rotor.

[0024] In a seventeenth aspect of the present technology, in addition to the first aspect described above, the first rotor core may be separated into a first portion and a second portion in the axial direction. In this case, the second rotor core may be located between the first portion and the second portion of the first rotor core in the axial direction. The balance adjustment unit may be provided on the outer peripheral surface of the second rotor core. With this configuration, the second rotor core can be disposed near the center of mass of the entire rotor in the axial direction. This reduces the effect on the even balance of the rotor when the balance adjustment unit is provided on the second rotor core.

[0025] Representative, non-limiting examples of the present invention will now be described in detail with reference to the drawings. This detailed description is intended simply to provide those skilled in the art with details for implementing preferred examples of the present invention, and is not intended to limit the scope of the present invention. Additionally, additional features and inventions disclosed below can be used separately or together with other features and inventions to provide further improved rotors.

[0026] Furthermore, the combinations of features and steps disclosed in the following detailed description are not essential to practicing the invention in its broadest sense, but are described solely to specifically illustrate exemplary embodiments of the invention. Furthermore, the various features of the exemplary embodiments described above and below, and those described in the independent and dependent claims, do not necessarily have to be combined in the exact embodiments described herein, or in the exact order listed, to provide additional and useful embodiments of the invention.

[0027] All features described in this specification and / or claims are intended to be disclosed individually and independently of one another as limitations on the original disclosure and claimed particulars, apart from any configuration of features described in the examples and / or claims. Furthermore, all numerical ranges and group or aggregation descriptions are intended to disclose intermediate configurations thereof as limitations on the original disclosure and claimed particulars. [Example]

[0028] (Example 1) A rotor 10 of Example 1 will be described with reference to Figures 1 to 4. As an example, the rotor 10 is used in an electric motor that drives an electric vehicle. As shown in Figure 1, the rotor 10 includes a shaft 12 and a rotor core 13. The shaft 12 extends along a central axis C of the rotor 10. The shaft 12 passes through the rotor core 13. The rotor core 13 is a generally cylindrical member that extends along the central axis C. The rotor core 13 is fixed to the shaft 12 and rotates together with the shaft 12 around the central axis C as the center of rotation. The rotor core 13 includes a first rotor core 14, a second rotor core 16, and a third rotor core 18.

[0029] Here, in this specification, a cylindrical coordinate system is defined, which is made up of an axial direction, a radial direction, and a circumferential direction, with the central axis C of the rotor 10 as a reference. The axial direction is a direction parallel to the central axis C and is defined by a coordinate axis D1 parallel to the central axis C (see FIG. 1). In this specification, the positive direction of the coordinate axis D1 may be expressed as one side in the axial direction, and the negative direction of the coordinate axis D1 may be expressed as the other side in the axial direction. The radial direction is a direction perpendicular to the central axis C and is defined by a coordinate axis D2 having the central axis C as its origin. In this specification, the positive direction of the coordinate axis D2 may be expressed as the outward radial direction, and the negative direction of the coordinate axis D2 may be expressed as the inward radial direction. The circumferential direction is a direction perpendicular to the axial direction and the radial direction and is defined by a coordinate axis D3 that revolves around the central axis C (see FIG. 2). In this specification, the positive direction of the coordinate axis D3 may be expressed as one side in the circumferential direction, and the negative direction of the coordinate axis D3 may be expressed as the other side in the circumferential direction.

[0030] The first rotor core 14 is a cylindrical member. The first rotor core 14 has a first end face 14a located on one side in the axial direction and a second end face 14b located on the other side in the axial direction. The first rotor core 14 extends between the first end face 14a and the second end face 14b. The first rotor core 14 has an inner circumferential surface 14c and an outer circumferential surface 14d. The inner circumferential surface 14c is the radially inner surface of the first rotor core 14 and extends cylindrically along the circumferential direction. The inner circumferential surface 14c defines a portion of the inner circumferential surface of the rotor core 13. The outer circumferential surface 14d is the radially outer surface of the first rotor core 14 and extends cylindrically along the circumferential direction. The outer circumferential surface 14d defines a portion of the outer circumferential surface of the rotor core 13. The inner peripheral surface 14c and the outer peripheral surface 14d extend between the first end surface 14a and the second end surface 14b of the first rotor core 14.

[0031] The second rotor core 16 is adjacent to a first end face 14a on one axial side of the first rotor core 14. With this configuration, the second rotor core 16 can also function as an end plate in a conventional motor at the first end face 14a of the first rotor core 14. The third rotor core 18 is adjacent to a second end face 14b on the other axial side of the first rotor core 14. With this configuration, the third rotor core 18 can function as an end plate of the first rotor core 14 on the other axial side of the first rotor core 14, similar to the second rotor core 16.

[0032] The second rotor core 16 is a cylindrical member. The second rotor core 16 has a first end face 16a located on one side in the axial direction and a second end face 16b located on the other side in the axial direction. The second rotor core 16 extends between the first end face 16a and the second end face 16b. The axial length of the second rotor core 16 is shorter than the axial length of the first rotor core 14. The second rotor core 16 has an inner circumferential surface 16c and an outer circumferential surface 16d. The inner circumferential surface 16c is the radially inner surface of the second rotor core 16 and extends cylindrically along the circumferential direction. The inner circumferential surface 16c defines a portion of the inner circumferential surface of the rotor core 13. The outer circumferential surface 16d is the radially outer surface of the second rotor core 16 and extends cylindrically along the circumferential direction. The outer circumferential surface 16d defines a portion of the outer circumferential surface of the rotor core 13. The inner peripheral surface 16c and the outer peripheral surface 16d extend between the first end face 16a and the second end face 16b of the second rotor core 16.

[0033] The third rotor core 18 is a cylindrical member and can be configured similarly to the second rotor core 16. The third rotor core 18 has a first end face 18a on one side in the axial direction, a second end face 18b on the other side in the axial direction, and an inner circumferential surface 18c and an outer circumferential surface 18d extending between the first end face 18a and the second end face 18b.

[0034] The rotor 10 includes a shaft cooling passage 20 and a plurality of core cooling passages 22 that communicate with the shaft cooling passage 20. The shaft cooling passage 20 is formed inside the shaft 12 and is a passage that cools the shaft 12. The plurality of core cooling passages 22 are formed inside the rotor core 13 and are passages that cool the rotor core 13. A refrigerant for cooling the shaft 12 or the rotor core 13 flows through the shaft cooling passage 20 and the plurality of core cooling passages 22. For example, lubricating oil sealed inside the casing of the electric motor is used as the refrigerant.

[0035] The shaft cooling flow passage 20 has a shaft main portion 20a and a plurality of shaft communication portions 20b that communicate between the shaft main portion 20a and the plurality of core cooling flow passages 22. The shaft main portion 20a extends along the central axis C inside the shaft 12. The plurality of shaft communication portions 20b extend radially outward from the shaft main portion 20a.

[0036] Each of the multiple core cooling passages 22 has a core main portion 22a and a core communication portion 22b that communicates the core main portion 22a with the shaft cooling passage 20. Each of the multiple core main portions 22a extends along the central axis C inside the rotor core 13. The multiple core communication portions 22b extend radially inward from the corresponding core main portion 22a. The multiple core cooling passages 22 extend from the shaft 12 through the rotor core 13 to one end face of the rotor core 13 (i.e., the first end face 16a of the second rotor core 16). Specifically, the multiple core communication portions 22b are formed inside the third rotor core 18. The multiple core main portions 22a extend from the third rotor core 18 to one end face 16a of the second rotor core 16. That is, the multiple core main portions 22a extend from the third rotor core 18 to the first rotor core 14 and the second rotor core 16. Therefore, the coolant pressure-fed by the pump to the shaft cooling passage 20 passes through the shaft cooling passage 20 and the core cooling passage 22 and flows out from the first end face 16a of the second rotor core 16. This effectively cools the shaft 12 and the rotor core 13.

[0037] The configuration of the first rotor core 14 will be described in detail with reference to FIGS. 1 and 2. As shown in FIGS. 1 and 2, the first rotor core 14 is made of laminated electromagnetic steel sheets. The first rotor core 14 has a plurality of through holes extending from the first end face 14a to the second end face 14b. The plurality of through holes define portions of the core main portions 22a of the plurality of core cooling passages 22. The first rotor core 14 has a plurality of magnet fixing portions 15 radially outward of the core cooling passages 22. The plurality of magnet fixing portions 15 are arranged at equal intervals in the circumferential direction of the first rotor core 14. Each of the plurality of magnet fixing portions 15 has a plurality of fixing holes 15a and a plurality of magnets 15b. Each of the plurality of fixing holes 15a extends from the first end face 14a to the second end face 14b. A corresponding magnet 15b is housed in each of the plurality of fixing holes 15a. The magnets 15b are generally rectangular parallelepiped permanent magnets. For each of the multiple fixing holes 15a, a resin, for example, is filled in the gap between the fixing hole 15a and the magnet 15b. This allows the magnet 15b to be fixed to the fixing hole 15a. The multiple magnets 15b include two pairs of magnets 15b arranged in the radial direction. The pairs of magnets 15b are arranged so that the distance between them increases as they move radially outward.

[0038] The configuration of the second rotor core 16 will be described in detail with reference to FIGS. 1 and 3. As shown in FIGS. 1 and 3, the second rotor core 16 is made of laminated electromagnetic steel sheets. The second rotor core 16 has a plurality of through holes extending from the first end face 16a to the second end face 16b. The plurality of through holes define portions of the core main portions 22a of the plurality of core cooling passages 22. The second rotor core 16 has a group of magnetic path-forming holes 24 repeatedly arranged along the circumferential direction. As an example, the group of magnetic path-forming holes 24 is composed of a plurality of slit-shaped holes 24a. Each slit-shaped hole 24a has, for example, a substantially arc-shaped shape that protrudes radially outward. The group of magnetic path-forming holes 24 forms a magnetic path that imparts salient polarity to the second rotor core 16. The plurality of groups of magnetic path-forming holes 24 are arranged at equal intervals in the circumferential direction of the second rotor core 16.

[0039] In this specification, the direction of the magnetic flux of the magnetic path formed by the groups of magnetic path forming holes 24 is defined as the q axis, and the direction electrically and magnetically perpendicular to the q axis is defined as the d axis.

[0040] The second rotor core 16 is further provided with balance adjustment holes 26. The balance adjustment holes 26 are formed so as to locally reduce the mass of the second rotor core 16. The balance adjustment holes 26 are provided in the first end face 16a on one axial side of the second rotor core 16. With this configuration, the balance adjustment holes 26 can be easily formed in the second rotor core 16 by, for example, cutting using a drill or the like. The balance adjustment holes 26 are provided at one location in the circumferential direction. However, in another embodiment, the balance adjustment holes 26 may be provided at multiple locations in the circumferential direction.

[0041] Specifically, the balance adjustment holes 26 are provided in the first end face 16a on one axial side of the second rotor core 16, radially inward of the groups of magnetic path forming holes 24. With this configuration, the balance adjustment holes 26 can be provided in an area of the second rotor core 16 where a group of magnetic path forming holes 24 is not present and where strength is relatively high. More specifically, the balance adjustment holes 26 are provided in positions radially inward of the second rotor core 16 that are different from the through holes of the core main portions 22a of the core cooling passages 22. More specifically, the distances of the balance adjustment holes 26 from the central axis C are approximately equal to the distances of the core cooling passages 22 from the central axis C of the core main portions 22a. The balance adjustment holes 26 are located between two adjacent ones of the core main portions 22a of the core cooling passages 22.

[0042] As an example, the balance adjustment holes 26 have a bottom surface between the first end face 16a and the second end face 16b. The balance adjustment holes 26 extend between the first end face 16a and the bottom surface. However, the specific configuration of the balance adjustment holes 26 is not particularly limited. In another embodiment, the balance adjustment holes 26 may be through holes that extend from the first end face 16a to the second end face 16b. The diameter and depth of the balance adjustment holes 26 are determined depending on the imbalance occurring in the rotor 10.

[0043] The configuration of the third rotor core 18 will be described in detail with reference to FIGS. 1 and 4. As shown in FIGS. 1 and 4, the third rotor core 18 is made of laminated electromagnetic steel sheets. The third rotor core 18 has a plurality of through holes extending from the first end surface 18a to the inner circumferential surface 18c. The plurality of through holes define a portion of the core main portion 22a and the core communication portion 22b in each of the plurality of core cooling passages 22. The third rotor core 18 has a plurality of groups of magnetic path-forming holes 28 and balance adjustment holes 30. The plurality of groups of magnetic path-forming holes 28 form magnetic paths for imparting salient polarity to the third rotor core 18. The plurality of groups of magnetic path-forming holes 28 are arranged at equal intervals in the circumferential direction of the third rotor core 18. Similar to the second rotor core 16, each of the plurality of groups of magnetic path-forming holes 28 of the third rotor core 18 has a plurality of slit-shaped holes 28a.

[0044] The balance adjustment holes 30 of the third rotor core 18 are formed to locally reduce the mass of the third rotor core 18. They are configured similarly to the balance adjustment holes 26 of the second rotor core 16. The balance adjustment holes 30 are provided in the second end face 16b on the other axial side of the third rotor core 18, radially inward of the groups of magnetic path-forming holes 28. The balance adjustment holes 30 are bottomed holes having a bottom between the second end face 16b and the first end face 16a, and are configured similarly to the balance adjustment holes 26 of the second rotor core 16. The balance adjustment holes 30 are provided at one location in the circumferential direction. More specifically, the balance adjustment holes 26 of the second rotor core 16 and the balance adjustment holes 30 of the third rotor core 18 are located at the same position in the circumferential direction. This configuration is effective in adjusting the static balance of the rotor 10. However, in another embodiment, the balance adjustment holes 26 of the second rotor core 16 and the balance adjustment holes 30 of the third rotor core 18 may be located at different circumferential positions. This configuration is effective in adjusting the even balance of the rotor 10.

[0045] In the rotor 10 described above, balance adjustment holes 26 are provided in the second rotor core 16, which does not have any permanent magnets. This prevents or minimizes the balance adjustment holes 26 from interfering with the permanent magnets of the first rotor core 14 or affecting the magnetic flux of the permanent magnets. Additionally, the second rotor core 16 is provided with multiple groups of magnetic path-forming holes 24. The multiple groups of magnetic path-forming holes 24 form magnetic paths that impart salient polarity to the second rotor core 16. With this configuration, the second rotor core 16 can generate reluctance torque in the magnetic field generated by the stator. This improves the torque output by the electric motor. Therefore, the first rotor core 14 can be made smaller in size by taking into account the reluctance torque generated by the second rotor core 16. As described above, the technology disclosed in this specification allows the rotor 10 to have balance adjustment holes 26 while improving the magnetic characteristics of the rotor 10, thereby enabling the rotor 10 to be made smaller.

[0046] In particular, each of the multiple groups of magnetic path-forming holes 24 in this embodiment has a slit-shaped hole 24a extending along the magnetic path. With this configuration, the generation of leakage magnetic flux in the magnetic path is suppressed, and the second rotor core 16 can effectively generate reluctance torque. Each of the slit-shaped holes 24a extends continuously along one magnetic path. However, the shape of the slit-shaped holes 24a is not limited to this. Each of the slit-shaped holes 24a may extend intermittently along one magnetic path. Even with this configuration, the second rotor core 16 can effectively generate reluctance torque. However, slit-shaped holes 24a extending continuously along one magnetic path are relatively advantageous in terms of suppressing leakage magnetic flux.

[0047] Furthermore, in the rotor 10 of this embodiment, balance adjustment holes 30 are provided not only in the second rotor core 16 but also in the third rotor core 18. With this configuration, balance adjustment holes 26, 30 can be arranged on both axial sides of the rotor 10, and, for example, each of the balance adjustment holes 26, 30 can be made smaller.

[0048] The balance adjustment holes 26 and 30 in this embodiment are an example of the "balance adjustment portion" in the present technology.

[0049] (Second Embodiment) A rotor 100 of a second embodiment will be described with reference to FIGS. 5 to 7. As shown in FIGS. 5 to 7, a rotor core 113 of the rotor 100 of the second embodiment has a second rotor core 116, a third rotor core 118, and the first rotor core 14, similar to the first embodiment. The second rotor core 116 has multiple groups of magnetic path-forming holes 124 and balance adjustment holes 126, and these configurations differ from the second rotor core 16 in the first embodiment. The third rotor core 118 has multiple groups of magnetic path-forming holes 128 and balance adjustment holes 130, and these configurations differ from the third rotor core 18 in the first embodiment. Other configurations of the rotor 100 of the second embodiment can be configured similarly to the rotor 10 of the first embodiment.

[0050] The second rotor core 116 will be described with reference to FIGS. 5 and 6. As described above, as shown in FIGS. 5 and 6, the second rotor core 116 has multiple groups of magnetic path-forming holes 124 and balance adjustment holes 126. The multiple groups of magnetic path-forming holes 124 form magnetic paths for imparting salient polarity to the second rotor core 116. Each of the multiple groups of magnetic path-forming holes 124 of the second rotor core 116 has slit-shaped holes 124a extending intermittently along the magnetic path and multiple dot-shaped holes 124b arranged along the magnetic path. The multiple dot-shaped holes 124b may be located radially outward of the slit-shaped holes 124a. The multiple dot-shaped holes 124b may be arranged in the second rotor core 116, for example, within a length range of approximately 25 mm from the outer circumferential surface 16d. As an example, the slit-shaped holes 124a extend in a curved manner so as to protrude radially inward. The plurality of point-like holes 124b are arranged in a curved line that protrudes radially inward.

[0051] The balance adjustment holes 126 are formed to locally reduce the mass of the second rotor core 116. The balance adjustment holes 126 are provided on the outer peripheral surface 16d of the second rotor core 116. The balance adjustment holes 126 reach the multiple point-like holes 124b of the multiple groups of magnetic path-forming holes 124. The number of point-like holes 124b that the balance adjustment holes 126 reach is not limited to multiple and may be one. The balance adjustment holes 126 are located at the d-axis center of the salient pole formed by each of the multiple groups of magnetic path-forming holes 124. With this configuration, the effect of the balance adjustment parts on the magnetic path can be relatively small.

[0052] The third rotor core 118 will be described with reference to Figures 5 and 7. As described above, as shown in Figures 5 and 7, the third rotor core 118 has multiple groups of magnetic path-forming holes 128 and balance adjustment holes 130. Each of the multiple groups of magnetic path-forming holes 128 can be configured similarly to the second rotor core 116, and has slit-like holes 128a extending discontinuously along the magnetic path and multiple point-like holes 128b arranged along the magnetic path.

[0053] The balance adjustment hole 130 is provided at one location in the circumferential direction and is formed to locally reduce the mass of the third rotor core 118. The balance adjustment hole 130 includes a first balance adjustment hole 130a and a second balance adjustment hole 130b. The first balance adjustment hole 130a is provided in the second end face 16b on one axial side of the third rotor core 118. As an example, the first balance adjustment hole 130a is a bottomed hole having a bottom surface between the second end face 18b and the first end face 18a and extending from the bottom surface to the second end face 18b. The second balance adjustment hole 130b is provided in the outer peripheral surface 18d of the third rotor core 118. The second balance adjustment hole 130b does not reach the multiple point-like holes 128b of the multiple groups of magnetic path-forming holes 128. That is, the radial length of the second balance adjustment holes 130b is smaller than the radial length of the balance adjustment holes 126 of the second rotor core 116. In the third rotor core 118, the mass of the third rotor core 118 reduced by the amount of the first balance adjustment holes 130a can be reduced.

[0054] In this embodiment, the groups of magnetic path-forming holes 124, 128 have a plurality of point-like holes 124b, 128b arranged along the magnetic path. Even with this configuration, each of the second rotor core 116 and the third rotor core 118 can generate reluctance torque.

[0055] Furthermore, the balance adjustment holes 126, 130b in this embodiment are provided on the outer peripheral surfaces 16d, 18d of the second rotor core 116 and the third rotor core 118, respectively. When the balance adjustment holes 126 are provided on the outer peripheral surface 16d of the second rotor core 116, as in the second rotor core 116 in this embodiment, there is a risk that the balance adjustment holes 126 may reach any one of the groups of magnetic path forming holes 124. In this case, depending on the shape of the balance adjustment holes 126, it is possible that the rigidity and strength of the second rotor core 116 may be unintentionally reduced. In this regard, as in the second rotor core 116, if the magnetic path forming holes 124 that the balance adjustment holes 126 reach are relatively small, point-like holes 124b rather than slit-like holes 124a, the reduction in rigidity and strength of the second rotor core 116 is suppressed. Therefore, the balance adjustment holes 126 can be provided at appropriate positions on the outer peripheral surface 16d regardless of their relative positions with respect to each of the groups of magnetic path forming holes 124.

[0056] However, the second balance adjustment holes 130b of the third rotor core 118 do not reach at least one of the multiple point-like holes 128b of the multiple groups of magnetic path-forming holes 128. Even if the second balance adjustment holes 130b are simply adjacent to the magnetic path-forming holes 128, if the magnetic path-forming holes 128 have relatively small point-like holes 128b, a decrease in rigidity and strength that occurs in the third rotor core 118 is suppressed.

[0057] Furthermore, the groups of magnetic path-forming holes 124, 128 in this embodiment may further include slit-shaped holes 124a, 128a extending along the magnetic path. In this case, the multiple point-shaped holes 124b, 128b are positioned radially outward of the slit-shaped holes 124a, 128a. With this configuration, by configuring the magnetic path-forming holes 124, 128 with the slit-shaped holes 124a, 128a, to the extent that interference with the balance adjustment holes 126, 130b does not become a problem, reluctance torque can be effectively generated in each of the second rotor core 116 and the third rotor core 118.

[0058] The balance adjustment holes 126, 130 in this embodiment are an example of a "balance adjustment portion" in the present technology. The balance adjustment portion is not limited to the balance adjustment holes 26, 30 that locally reduce the mass of each rotor core 116, 118. The balance adjustment portion may be any portion that locally increases or decreases the mass of each rotor core 116, 118. For example, when the balance adjustment portions are provided on the outer peripheral surfaces 16d, 18d as in this embodiment, in another embodiment, the balance adjustment portion may be a mass body added to the second rotor core 116 to locally increase the mass of each rotor core 116, 118. The mass body may be, for example, a clip-shaped body attached so as to sandwich the outer peripheral surface 16d between the first end face 16a and the second end face 16b of the second rotor core 16. The balance adjustment portion is not limited to being provided at one location in the circumferential direction, and may be provided at multiple locations in the circumferential direction.

[0059] (Third Embodiment) A rotor 200 of the third embodiment will be described with reference to FIG. 8. As shown in FIG. 8, the rotor core 213 of the rotor 200 of the third embodiment includes a first rotor core 214 and a second rotor core 116, similar to the second embodiment. The first rotor core 214 is separated into a first portion 14A and a second portion 14B. Each of the first portion 14A and the second portion 14B can be configured similarly to the first rotor core 14 of the first embodiment. The second rotor core 116 is located between the first portion 14A and the second portion 14B. In this respect, the rotor 200 of the third embodiment differs from the rotor 10 of the first embodiment. In addition, as described above, the balance adjustment holes 126 of the second rotor core 116 are provided in the outer peripheral surface 16d. With this configuration, the second rotor core 116 can be positioned near the center of mass of the entire rotor 200 in the axial direction. This reduces the effect on the even balance of the rotor 200 when the balance adjustment holes 126 are provided in the second rotor core 116.

[0060] Although not particularly limited, the rotor 200 in this embodiment has a plurality of core cooling channels 222 and the shaft cooling channels 20 similar to the first embodiment. The plurality of core cooling channels 222 extend from the shaft 12 through the rotor core 213 to the end faces 213a, 213b on both axial sides of the rotor core 213. With this configuration, the rotor core 213 can be efficiently cooled over the entire axial direction.

[0061] In the first and second embodiments described above, specific configurations of the groups of magnetic path forming holes have been described, but the configuration of a group of magnetic path forming holes in the present technology is not limited thereto. For example, in the second rotor core 16 of the first embodiment, the balance adjustment portion may be provided on the outer peripheral surface 16d. In the second rotor core 116 of the second embodiment, the balance adjustment portion may be provided on the first end surface 16a on one axial side of the second rotor core 116, radially inward of the group of magnetic path forming holes 24. The same as in the second rotor cores 16, 116 may also be applied to the third rotor cores 18, 118. [Explanation of symbols]

[0062] 10, 100, 200: rotor, 14, 214: first rotor core, 14A: first portion, 14B: second portion, 14a, 14b, 16a, 16b, 18a, 18b: end face, 14d: outer circumferential surface, 15: magnet fixing portion, 15b: magnet, 16, 116: second rotor core, 18, 118: third rotor core, 24, 28, 124, 128: magnet forming hole, 24a, 28a, 124a, 128a: slit-shaped hole, 24b, 124b, 128b: dot-shaped hole, 26, 30, 126, 130, 130a, 130b: balance adjustment hole, C: central axis

Claims

1. A rotor of an electric motor, a first rotor core in which permanent magnets are arranged; a second rotor core that is adjacent to the first rotor core in the axial direction and does not have a permanent magnet disposed therein; Equipped with The second rotor core is a group of magnetic path forming holes that form a magnetic path for imparting salient polarity to the second rotor core; a balance adjustment portion provided at least at one location in the circumferential direction and configured to locally increase or decrease the mass of the second rotor core; Rotor.

2. The rotor according to claim 1 , wherein the group of magnetic path-forming holes has slit-shaped holes extending along the magnetic path.

3. The rotor according to claim 2 , wherein the balance adjustment portion is provided on the end surface of the second rotor core on the one side in the axial direction, radially inward of the group of magnetic path forming holes.

4. The rotor according to claim 3 , wherein the balance adjustment portion has a balance adjustment hole provided in the end face on the one side in the axial direction of the second rotor core.

5. The rotor according to claim 1 , wherein the group of magnetic path-forming holes includes a plurality of point-like holes arranged along the magnetic path.

6. The rotor according to claim 5 , wherein the balance adjustment portion has a balance adjustment hole provided in an outer peripheral surface of the second rotor core.

7. 7. The rotor according to claim 6, wherein the balance adjustment hole reaches at least one of the plurality of point-like holes of the group of magnetic path forming holes.

8. the group of magnetic path-forming holes further includes slit-shaped holes extending along the magnetic path, The rotor according to claim 7 , wherein the plurality of point-like holes are located radially outward of the slit-like holes.

9. 9. The rotor according to claim 8, wherein the balance adjustment holes do not reach the slit-shaped holes of the group of magnetic path forming holes.

10. The rotor according to claim 1 , wherein the balance adjustment portion is provided on the end surface of the second rotor core on the one side in the axial direction, radially inward of the group of magnetic path forming holes.

11. The rotor according to claim 1 , wherein the balance adjustment portion is provided on an outer peripheral surface of the second rotor core.

12. The rotor according to claim 11 , wherein the balance adjustment portion is located at the center of the d axis of the saliency formed by the part of the magnetic path forming holes.

13. The rotor according to claim 1 , wherein the second rotor core is adjacent to an end face of the first rotor core on one side in the axial direction.

14. a third rotor core adjacent to an end surface of the first rotor core on the other side in the axial direction, The rotor according to claim 13 , wherein the third rotor core has a group of magnetic path forming holes that form a magnetic path for imparting salient polarity to the third rotor core.

15. The rotor according to claim 14 , wherein the third rotor core further includes a balance adjustment portion provided at least at one location in the circumferential direction and configured to locally increase or decrease a mass of the third rotor core.

16. The rotor according to claim 15 , wherein the balance adjustment portion of the second rotor core and the balance adjustment portion of the third rotor core are located at the same position in the circumferential direction.

17. the first rotor core is separated into a first portion and a second portion in the axial direction, the second rotor core is located between the first portion and the second portion of the first rotor core in the axial direction, The rotor according to claim 1 , wherein the balance adjustment portion is provided on an outer peripheral surface of the second rotor core.

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