Rotor

Abstract

The magnet is firmly fixed to the magnetic hole while the coolant is circulated inside the magnetic hole. [Solution] The rotor comprises a shaft extending along the axial direction and a rotor core fixed to the outer circumferential surface of the shaft, each having a plurality of magnet holes that extend along the axial direction. Each of the plurality of magnet holes is provided with at least one magnet and a cooling pipe. The cooling pipe extends along the axial direction and has a path for circulating a coolant inside it.

Description

Technical Field

[0001] The technology disclosed in this specification relates to the rotor of an electric motor.

Background Art

[0002] Patent Document 1 describes a rotor of an electric motor. This rotor includes a shaft extending along the axial direction and a rotor core fixed to the outer peripheral surface of the shaft. The rotor core has a plurality of magnet holes, and magnets are arranged in each of the plurality of magnet holes. Also, in each of the plurality of magnet holes, a space is formed along the axial direction to allow a refrigerant to flow along the magnet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to allow a refrigerant to flow through the magnet hole as in the above-described structure, it is necessary to provide a space serving as a refrigerant path inside the magnet hole. However, if there is a space inside the magnet hole, there is a problem that the fixing strength of the magnet to the magnet hole decreases.

[0005] This specification provides a technology that can firmly fix a magnet to a magnet hole while allowing a refrigerant to flow through the inside of the magnet hole.

Means for Solving the Problems

[0006] The technology disclosed herein is embodied in a rotor for an electric motor. In a first embodiment, the rotor comprises a shaft extending axially and a rotor core fixed to the outer surface of the shaft and having a plurality of magnet holes, each extending axially. Each of the plurality of magnet holes is disposed of a magnet and a cooling pipe. The cooling pipe extends axially and has a path for circulating a coolant inside.

[0007] In the above configuration, a cooling pipe is placed inside the magnet hole, and a path for circulating the coolant is formed inside the cooling pipe. With this configuration, since the cooling pipe has a certain degree of rigidity, even if a space is formed inside it, it is possible to suppress a decrease in the fixing strength of the magnet to the magnet hole.

[0008] In a second embodiment, in the first embodiment described above, at least one magnet and the cooling pipe may be fixed in the magnet hole by a filler material filled in the magnet hole. With this configuration, at least one magnet and the cooling pipe can be firmly fixed to the magnet hole.

[0009] In a third embodiment, in the second embodiment described above, the filler may be made of resin. The resin has electrical insulating properties and excellent moldability.

[0010] In a fourth embodiment, in any of the first to third embodiments described above, the at least one magnet may include a first magnet and a second magnet. In this case, the cooling pipe may extend axially between the first magnet and the second magnet. With this configuration, the first magnet and the second magnet, which are arranged in the same magnet hole, can be effectively cooled.

[0011] In the fifth embodiment, in the fourth embodiment described above, the cooling pipe may be in direct contact with each of the first and second magnets. With this configuration, the first and second magnets can be cooled more effectively.

[0012] In the sixth embodiment, in any of the first to fifth embodiments described above, the cooling pipe may be made of an electrically insulating material. With such a configuration, it is possible to avoid the generation of eddy current losses in the cooling pipe.

[0013] In the seventh embodiment, in any of the first to sixth embodiments described above, the rotor core may have a first end face and a second end face, and may extend along the axial direction from the first end face to the second end face. In this case, the cooling pipe may extend from the first end face to the second end face of the rotor core. With such a configuration, the cooling pipe can cool the magnet along the entire length of the rotor core.

[0014] In the eighth embodiment, in the seventh embodiment described above, the rotor may further include a first end plate fixed to the outer circumferential surface of the shaft and positioned adjacent to the first end face of the rotor. In this case, the first end plate may be provided with a refrigerant supply path for supplying refrigerant to the cooling pipe.

[0015] In the ninth embodiment, in the eighth embodiment described above, the shaft may be provided with a shaft refrigerant path for which refrigerant is supplied from the outside. In this case, the refrigerant supply path of the first end plate may connect the shaft refrigerant path and the cooling pipe.

[0016] In the tenth embodiment, in the ninth embodiment described above, the rotor may further include a second end plate fixed to the outer circumferential surface of the shaft and positioned adjacent to the second end face of the rotor. In this case, the second end plate may be provided with a refrigerant discharge path for discharging refrigerant from the cooling pipe. [Brief explanation of the drawing]

[0017] [Figure 1] A schematic cross-sectional view showing the configuration of an electric motor 2 employing the rotor 10 of the embodiment. [Figure 2] A cross-sectional view showing the internal configuration of the rotor 10 in the embodiment. In Figure 2, arrow F schematically indicates the flow of the refrigerant. [Figure 3] Cross-sectional view along line III-III in Figure 2. [Figure 4] Enlarged view of section IV in Figure 3. [Modes for carrying out the invention]

[0018] Referring to the drawings, the rotor 10 of the embodiment and the electric motor 2 employing it will be described. The electric motor 2 can be used, for example, as a prime mover to drive the wheels in an electric vehicle. The electric vehicle referred to here includes battery electric vehicles (BEVs), fuel cell electric vehicles (FCEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). The electric motor 2 is a three-phase AC motor. Note that the configuration described in this embodiment is not limited to three-phase AC motors and can be similarly applied to other types of electric motors.

[0019] In this embodiment, cylindrical coordinate systems D1, D2, and D3 are defined with respect to the rotation axis X of the electric motor 2. Direction D1 in the drawing is parallel to the rotation axis X of the electric motor 2 and represents the axial direction in this embodiment. Direction D2 is perpendicular to the rotation axis X and represents the radial direction in this embodiment. Direction D3 is perpendicular to directions D1 and D2 and represents the circumferential direction in this embodiment.

[0020] As shown in FIG. 1, the electric motor 2 mainly includes a stator 4, a rotor 10, and a casing 100. The casing 100 houses the stator 4 and the rotor 10. The stator 4 is fixed to the casing 100, and the rotor 10 is rotatably supported by the casing 100.

[0021] First, the configuration of the stator 4 will be described. However, regarding the rotor 10 of this embodiment, the specific configuration of the stator 4 is not particularly limited. The rotor 10 of this embodiment can be used in combination with stators in various other forms.

[0022] As an example, the stator 4 may have a stator core 6 and a stator coil 8. The stator core 6 generally has a cylindrical shape and is arranged to surround the rotor 10. The stator core 6 has a first end face 6a and a second end face 6b in the axial direction. The stator core 6 extends along the axial direction from the first end face 6a to the second end face 6b. The stator core 6 is formed by laminating a plurality of silicon steel sheets (also referred to as electromagnetic steel sheets). A plurality of slits 6d are formed on the inner peripheral surface 6c of the stator core 6. The plurality of slits 6d are arranged at equal intervals along the circumferential direction. Each of the plurality of slits 6d extends along the axial direction from the first end face 6a to the second end face 6b of the stator core 6.

[0023] The stator coil 8 is arranged across the plurality of slits 6d of the stator core 6. The stator coil 8 is composed of a conducting wire such as a coil segment, for example. The stator coil 8 may have a distributed winding structure or a concentrated winding structure. A three-phase alternating current is supplied to the stator coil 8 from the outside. When a three-phase alternating current is supplied to the stator coil 8, a rotating magnetic field is formed in the internal space of the stator core 6 where the rotor 10 is arranged.

[0024] Next, the configuration of the rotor 10 in the embodiment will be described. As shown in Figures 1 and 3, the rotor 10 comprises a shaft 12, a rotor core 14, and a pair of end plates 16 and 18. The shaft 12 extends along the rotation axis X of the electric motor 2. The shaft 12 is rotatably supported by the casing 100 around the rotation axis X. That is, the rotation axis X of the electric motor 2 strictly refers to the rotation axis of the rotor 10. The shaft 12 is made of a steel material such as stainless steel. However, the material constituting the shaft 12 is not particularly limited. A shaft coolant path 20 is provided inside the shaft 12. The shaft coolant path 20 will be described in detail later.

[0025] The rotor core 14 is fixed to the outer circumferential surface 12a of the shaft 12. Therefore, the rotor core 14 rotates integrally with the shaft 12. The rotor core 14 generally has a cylindrical shape and is arranged to surround the shaft 12. The rotor core 14 has a first end face 14a and a second end face 14b in the axial direction. The rotor core 14 extends along the axial direction from the first end face 14a to the second end face 14b. The rotor core 14 is constructed by laminating a plurality of silicon steel sheets 13 (also called electromagnetic steel sheets). However, the material constituting the rotor core 14 is not limited to silicon steel, but may be other types of magnetic materials.

[0026] A pair of end plates 16 and 18 are fixed to the outer circumferential surface 12a of the shaft 12. The pair of end plates 16 and 18 consists of a first end plate 16 and a second end plate 18. The first end plate 16 is positioned adjacent to the first end face 14a of the rotor core 14. The second end plate 18 is positioned adjacent to the second end face 14b of the rotor core 14. As a result, the rotor core 14 is sandwiched in the axial direction by the pair of end plates 16 and 18. As an example, each of the end plates 16 and 18 is made of a non-magnetic material such as an aluminum alloy. The first end plate 16 is provided with a plurality of refrigerant supply paths 60, and the second end plate 18 is provided with a plurality of refrigerant discharge paths 80. The refrigerant supply paths 60 and the refrigerant discharge paths 80 will be described in detail later.

[0027] Next, the internal structure of the rotor core 14 will be described with reference to Figures 2-4. The rotor core 14 has a plurality of magnet holes 40. The plurality of magnet holes 40 are arranged at equal intervals along the circumferential direction. Each of the plurality of magnet holes 40 extends along the axial direction from the first end face 14a to the second end face 14b of the rotor core 14. Here, the number and arrangement of the plurality of magnet holes 40 are not particularly limited. Also, the cross-sectional shape and size of each magnet hole 40 are not particularly limited.

[0028] Each of the multiple magnet holes 40 is fitted with a first magnet 42, a second magnet 44, and a cooling pipe 46. The first magnet 42 and the second magnet 44 are permanent magnets, such as rare-earth magnets. The first magnet 42 and the second magnet 44 extend axially from the first end face 14a to the second end face 14b of the rotor core 14, respectively. The cooling pipe 46 also extends axially from the first end face 14a to the second end face 14b of the rotor core 14, respectively. The cooling pipe 46 is located between the first magnet 42 and the second magnet 44 and is in direct contact with each of the first magnet 42 and the second magnet 44. The number of magnets 42 and 44 is not particularly limited. Each of the multiple magnet holes 40 only needs to have at least one magnet fitted into it.

[0029] The first magnet 42, the second magnet 44, and the cooling pipe 46 are fixed to the magnet hole 40 by a filler material 48 that is filled inside the magnet hole 40. For example, the filler material 48 is made of resin. The filler material 48 completely fills the gap between the outer surface 42a of the first magnet 42 and the inner surface 40a of the magnet hole 40, the gap between the outer surface 44a of the second magnet 44 and the inner surface 40a of the magnet hole 40, and the gap between the cooling pipe 46 and the inner surface 40a of the magnet hole 40. As a result, the two magnets 42, 44 and the cooling pipe 46 are firmly fixed to the magnet hole 40. When manufacturing the rotor 10, the filler material 48 can be formed by placing the two magnets 42, 44 and the cooling pipe 46 inside the magnet hole 40 and then injecting molten resin into the gap inside the magnet hole 40. However, as another form, the filler material 48 can also be formed by placing a foaming resin into the gap inside the magnet hole 40 and foaming it by heating.

[0030] The cooling pipe 46 is a hollow pipe material. An axially extending space 47 is formed inside the cooling pipe 46. This space 47 extends from the first end face 14a to the second end face 14b of the rotor core 14. The space 47 inside the cooling pipe 46 functions as a path for the circulation of a refrigerant. The refrigerant is not particularly limited, but may be an oil such as lubricating oil. As the refrigerant circulates inside the cooling pipe 46, the first magnet 42 and the second magnet 44 adjacent to the cooling pipe 46 are cooled. In particular, the cooling pipe 46 in this embodiment is located between the first magnet 42 and the second magnet 44 and is in direct contact with each of the first magnet 42 and the second magnet 44. As a result, the refrigerant circulating inside the cooling pipe 46 can effectively cool the first magnet 42 and the second magnet 44.

[0031] The manner in which refrigerant is supplied to the cooling pipes 46 is not particularly limited. For example, in the rotor 10 of this embodiment, refrigerant is supplied to the cooling pipes 46 of each magnet hole 40 through a shaft refrigerant path 20 provided on the shaft 12 and a plurality of refrigerant supply paths 60 provided on the first end plate 16. As shown in Figure 2, the shaft refrigerant path 20 comprises a main path 22 extending in the axial direction and a plurality of branch paths 24 extending radially from the main path 22. Each of the plurality of branch paths 24 extends to the outer circumferential surface 12a of the shaft 12 and opens toward the first end plate 16. On the first end plate 16, the plurality of refrigerant supply paths 60 extend radially. The plurality of refrigerant supply paths 60 connect the plurality of branch paths 24 of the shaft 12 to the cooling pipes 46 of the plurality of magnet holes 40, respectively.

[0032] Coolant is supplied to the shaft coolant path 20 of the shaft 12 from outside the rotor 10, for example, by an oil pump (not shown). As indicated by arrow F in Figure 2, the coolant supplied to the shaft coolant path 20 flows from the main path 22 to multiple branch paths 24 and into multiple coolant supply paths 60 of the first end plate 16. The coolant is then supplied to the cooling pipes 46 of the multiple magnet holes 40 through the multiple coolant supply paths 60. The coolant supplied to the cooling pipes 46 flows axially toward the second end face 14b of the rotor core 14.

[0033] As mentioned above, a second end plate 18 is adjacent to the second end face 14b of the rotor core 14. The second end plate 18 is provided with multiple refrigerant discharge paths 80. Each of the multiple refrigerant discharge paths 80 is connected to a cooling pipe 46 of a plurality of magnet holes 40 at the second end face 14b of the rotor core 14. This allows the refrigerant from the cooling pipe 46 to be discharged to the outside of the rotor 10. In one example, each of the multiple refrigerant discharge paths 80 extends to the outer circumferential surface 18a of the second end plate 18. With this configuration, the refrigerant discharged from the multiple refrigerant discharge paths 80 is supplied to the stator coil 8, which can be cooled.

[0034] As described above, in the rotor 10 of this embodiment, a cooling pipe 46 is arranged inside the magnet hole 40, and a path (space 47) for circulating refrigerant is formed inside the cooling pipe 46. This allows the magnets 42 and 44, which are also arranged inside the same magnet hole 40, to be directly cooled. Conventionally, when a path (space) for circulating refrigerant is formed inside the magnet hole 40, there is a problem that the fixing strength of the magnets to the magnet hole decreases. In this regard, in the rotor 10 of this embodiment, a path (space 47) for circulating refrigerant is formed by the cooling pipe 46. With this configuration, since the cooling pipe 46 has a certain rigidity, even if a space 47 is formed inside it, it is possible to suppress a decrease in the fixing strength of the magnets 42 and 44 to the magnet hole 40.

[0035] The material constituting the cooling pipe 46 is not particularly limited. For example, in this embodiment, the cooling pipe 46 is made of resin. However, it is not limited to resin, and the cooling pipe 46 may be made of an electrically insulating material. With such a configuration, it is possible to avoid the generation of eddy current losses in the cooling pipe 46.

[0036] The specific examples of the technology disclosed in this specification have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples described above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of symbols]

[0037] 2: Electric motor, 4: Stator, 6: Stator core, 8: Stator coil, 10: Rotor, 12: Shaft, 14: Rotor core, 16: First end plate, 18: Second end plate, 20: Shaft refrigerant path, 40: Magnet hole, 42: First magnet, 44: Second magnet, 46: Cooling pipe, 47: Space, 48: Filler, 60: Refrigerant supply path, 80: Refrigerant discharge path, 100: Casing, X: Rotating shaft

Claims

1. It is the rotor of an electric motor, A shaft extending along the axial direction, A rotor core is fixed to the outer circumferential surface of the shaft and has a plurality of magnet holes, each extending along the axial direction, Equipped with, Each of the aforementioned plurality of magnet holes is provided with at least one magnet and a cooling pipe. The cooling pipe extends along the axial direction and has a path for circulating refrigerant inside it. A rotor equipped with a rotor.

2. The rotor according to claim 1, wherein at least one magnet and the cooling pipe are fixed in the magnet hole by a filler material filled in the magnet hole.

3. The rotor according to claim 2, wherein the filler is made of resin.

4. The aforementioned at least one magnet includes a first magnet and a second magnet, The rotor according to claim 1, wherein the cooling pipe extends in the axial direction between the first magnet and the second magnet.

5. The rotor according to claim 4, wherein the cooling pipe is in direct contact with each of the first magnet and the second magnet.

6. The rotor according to claim 1, wherein the cooling pipe is made of an electrically insulating material.

7. The rotor core has a first end face and a second end face, and extends along the axial direction from the first end face to the second end face. The rotor according to claim 1, wherein the cooling pipe extends from the first end face to the second end face of the rotor core.

8. The shaft is further equipped with a first end plate that is fixed to the outer circumferential surface of the shaft and is positioned adjacent to the first end face of the rotor, The rotor according to claim 7, wherein the first end plate is provided with a refrigerant supply path for supplying refrigerant to the cooling pipe.

9. The aforementioned shaft is provided with a shaft refrigerant path through which refrigerant is supplied from an external source. The rotor according to claim 8, wherein the refrigerant supply path of the first end plate connects the shaft refrigerant path and the cooling pipe.

10. The shaft is further equipped with a second end plate that is fixed to the outer circumferential surface of the shaft and is positioned adjacent to the second end face of the rotor, The rotor according to claim 9, wherein the second end plate is provided with a refrigerant discharge path for discharging refrigerant from the cooling pipe.

Images