Magnet cooling structure

Abstract

This magnet cooling structure comprises magnets (3) that are embedded in a rotor core (2) of a motor, end plates (4) that are provided at both ends of the rotor core (2) in an axial direction, and heat dissipation fins (5) that are formed on a surface of each end plate (4) opposite to a surface of the end plate (4) facing the magnets (3).

Description

Magnet cooling structure

[0001] The present invention relates to a magnet cooling structure.

[0002] Magnets are used in drive motors used in vehicles such as electric vehicles (EVs), hybrid vehicles (HVs), and plug-in hybrid electric vehicles (PHEVs) that can be externally charged or powered. These magnets can become demagnetized due to heat generated when the motor is driven, which can cause a decrease in motor performance. For this reason, demagnetization of the magnets is generally prevented by limiting the motor's continuous output torque to suppress heat generation from the motor or by cooling the area around the magnets embedded in the rotor core.

[0003] As a cooling structure for magnets, for example, in Patent Document 1 listed below, an end plate having an opening and a guide wall is provided at the axial end of a rotor having a magnet, and a refrigerant such as cooling oil supplied to the opening is guided along the guide wall to the magnet by utilizing the rotation of the rotor.

[0004] Japanese Patent Application Publication No. 2019-165559

[0005] The magnet cooling structure described in Patent Document 1 requires the creation of complex structures in the components, such as openings and guide walls, to guide the coolant to the magnets, which results in high costs. Furthermore, because the rotational force of the rotor is used to drive the coolant, there is also the problem of loss of rotational torque in the motor.

[0006] Therefore, an object of the present invention is to provide a magnet cooling structure that can efficiently cool a magnet with a simple configuration.

[0007] In order to solve the above problems, the present invention provides a magnet cooling structure having a magnet embedded in a rotor core of a motor, end plates provided at both axial ends of the rotor core, and heat dissipation fins formed at the axial end of the end plate opposite the magnet.

[0008] In all of the above configurations, the heat dissipation fins may be a plurality of ridges formed concentrically around the rotation axis of the rotor core.

[0009] In a configuration in which a plurality of ridges are formed concentrically, the axial projection amount of the plurality of ridges may be smaller on the outer diameter side than on the central side of the concentric circles.

[0010] Instead of the heat dissipation fins being multiple protrusions formed concentrically, the heat dissipation fins can be configured as drop-shaped portions with an arc on one end and an acute angle on the other end when viewed in a plane, with the tip of the acute angle facing in the direction of rotation of the rotor core.

[0011] All of the above configurations may further include a cooling member interposed between the magnet and the end plate.

[0012] In all of the above configurations, the heat dissipation fins may be formed on each of the end plates provided at both axial ends of the rotor core.

[0013] In this invention, heat dissipation fins are formed on the axial ends of the end plates provided at both axial ends of the rotor core, i.e., on the rotating components, so that when the rotor core rotates around its axis, a relative air flow is generated against the heat dissipation fins, allowing heat to be dissipated from the heat dissipation fins. This allows for efficient cooling of the magnets with a simple configuration.

[0014] Fig. 3(a) is a cross-sectional view showing one embodiment of the magnet cooling structure according to the present invention. Fig. 3(b) is a plan view of the magnet cooling structure shown in Fig. 1. Fig. 3(c) is a cross-sectional view showing a main part of modified examples of the magnet cooling structure shown in Fig. 1, where Fig. 3(a) is a first modified example, Fig. 3(b) is a second modified example, and Fig. 3(c) is a third modified example. Fig. 3(b) is a plan view showing a main part of a fourth modified example of the magnet cooling structure shown in Fig. 1.

[0015] One embodiment of a magnet cooling structure 1 according to the present invention will be described with reference to the drawings. As shown in Figure 1, this magnet cooling structure 1 is applied to the rotor of a motor used to drive vehicles such as electric vehicles (EVs), hybrid vehicles (HVs), and plug-in hybrid vehicles (PHEVs) that are capable of external charging and external power supply, and has magnets 3 embedded in a rotor core 2 of the motor, end plates 4 provided at both axial ends of the rotor core 2, and heat dissipation fins 5 formed on the surface of the end plate 4 opposite to the surface facing the magnet 3.

[0016] In this embodiment, heat dissipation fins 5 are formed on each of the end plates 4 provided at both axial ends of the rotor core 2. A shaft 6 is inserted through the axial center of the rotor core 2. The rotational force of this shaft 6 about its axis is transmitted to the wheels. Aluminum is used as the material for the end plates 4, taking into consideration its thermal conductivity, low loss, and workability. Note that components not directly related to this invention, such as the stator of the motor, are not shown in Figure 1.

[0017] 2, the heat dissipation fins 5 are a plurality of (five in this embodiment) ridges 5a formed concentrically around the rotation axis (shaft 6) of the rotor core 2. The radial positions of these heat dissipation fins 5 (plurality of ridges 5a) roughly correspond to the radial positions of the magnets 3 embedded in the rotor core 2. The axial protrusion amount and radial width of each ridge 5a are all the same.

[0018] The number and position of the ridges 5a that make up the heat dissipation fins 5 are not limited to the configuration of this embodiment and can be changed as appropriate as long as the desired cooling performance is ensured. Also, in this embodiment, the heat dissipation fins 5 are formed directly on the end plates 4, but it is also possible to form the heat dissipation fins 5 on a member separate from the end plates 4 and then bring that member into contact with the end plates 4. Also, in this embodiment, the heat dissipation fins 5 are formed on each of the end plates 4 at both ends of the rotor core 2, but it is also possible to form the heat dissipation fins 5 on only one of the end plates 4.

[0019] A circumferential groove 7 is formed on the back side of the end plate 4 (the surface opposite to the surface on which the ridges 5a are formed), with the shaft 6 as its center. A cooling member 8 is provided in this circumferential groove 7, interposed between the magnet 3 and the end plate 4 and filling the gap between the magnet 3 and the end plate 4. The cooling member 8 is made of a flexible cooling material (for example, a gel-like cooling sheet), and has the function of transferring heat from the magnet 3 to the end plate 4.

[0020] In the magnet cooling structure 1 described above, the heat dissipation fins 5 are formed on the axial ends of the end plates 4 provided at both axial ends of the rotor core 2, i.e., on the rotating components, so that when the rotor core 2 is rotated around the axis, a relative air flow is generated with respect to the heat dissipation fins 5, and heat is dissipated from the heat dissipation fins 5. This makes it possible to efficiently cool the magnets 3 with a simple configuration.

[0021] Furthermore, in the magnet cooling structure 1, the heat dissipation fins 5 are made up of a plurality of protrusions 5a formed concentrically around the rotation axis of the rotor core 2, and the extension direction of each protrusion 5a is aligned with the rotation direction of the rotor core 2. This ensures the heat dissipation characteristics of the heat dissipation fins 5 while suppressing air resistance caused by the heat dissipation fins 5 when the rotor core 2 rotates.

[0022] Furthermore, since the magnet cooling structure 1 described above has heat dissipation fins 5 formed on each of the end plates 4 provided at both axial ends of the rotor core 2, the cooling performance provided by these heat dissipation fins 5 can be further improved compared to when heat dissipation fins 5 are formed only on one end.

[0023] Furthermore, the above-mentioned magnet cooling structure 1 has a cooling member 8 provided in the gap between the magnet 3 and the end plate 4, so that the heat of the magnet 3 can be quickly transferred to the end plate 4 and then dissipated from the heat dissipation fins 5 formed on this end plate 4.

[0024] FIG. 3( a) shows a main portion of a first modified example of the magnet cooling structure 1. The magnet cooling structure 1 according to the first modified example is similar to the configuration shown in FIG. 1 in that the heat dissipation fins 5 are composed of multiple (five) ridges 5a formed concentrically around the rotation axis (shaft 6) of the rotor core 2. However, it differs in that the axial protrusion amount of the two central ridges 5a of the concentric circles is greater than the axial protrusion amount of the three outer diameter ridges 5a. The protrusion amount of the central ridges 5a is within a range of 1.2 to 5 times, preferably 1.4 to 4 times, more preferably 1.6 to 3 times, and in this embodiment, approximately twice the protrusion amount of the outer diameter ridges 5a. The radial width of each ridge 5a is the same.

[0025] When the rotor core 2 rotates, the peripheral speed at its center is lower than the peripheral speed at its outer diameter side. Therefore, the heat dissipation characteristics of the heat dissipation fins 5 may be lower at the center, where the air flow over the heat dissipation fins 5 is relatively weak, than at the outer diameter side. In the magnet cooling structure 1 according to the first modified example, the axial protrusion amount of the ridges 5a at the center, where heat dissipation characteristics are likely to be lower, is made larger than the axial protrusion amount of the ridges 5a at the outer diameter side, thereby increasing the surface area of ​​the ridges 5a at the center, thereby improving the heat dissipation characteristics at the center and making the heat dissipation characteristics uniform.

[0026] FIG. 3( b ) shows a main portion of a second modified example of the magnet cooling structure 1. The magnet cooling structure 1 according to the second modified example has a heat dissipation fin 5 composed of multiple (five) ridges 5 a arranged concentrically around the rotation axis (shaft 6) of the rotor core 2. The axial protrusion of the central ridge 5 a of the concentric circles is greater than that of the outermost ridges 5 a. This configuration is similar to that shown in FIG. 3( a ). However, it differs from the first modified example in that the axial protrusion of the ridges 5 a gradually decreases from the center to the outermost ridge. The protrusion of the most central ridge 5 a is in the range of 1.2 to 10 times, preferably 2 to 8 times, more preferably 3 to 5 times, and in this embodiment, approximately 4 times, the protrusion of the most outermost ridge 5 a. The radial width of each ridge 5 a is the same.

[0027] In the magnet cooling structure 1 according to the second modification, the amount of axial protrusion of the ridge 5a is gradually reduced from the center toward the outer diameter side, thereby achieving even more uniform heat dissipation characteristics.

[0028] Figure 3(c) shows a main portion of a third modified example of the magnet cooling structure 1 described above. The magnet cooling structure 1 according to the third modified example is similar to the configuration shown in Figure 1 in that the heat dissipation fins 5 are composed of multiple ridges 5a formed concentrically around the rotation axis (shaft 6) of the rotor core 2. However, it differs in that the spacing between adjacent ridges 5a in the radial direction gradually increases from the center toward the outer diameter of the concentric circles. The axial protrusion amount and radial width of each ridge 5a are the same.

[0029] The magnet cooling structure 1 of the third modified example increases the surface area of ​​the protrusions 5a located within a predetermined radial range on the central side by gradually increasing the spacing between adjacent protrusions 5a in the radial direction from the center side toward the outer diameter side. As a result, similar to the first and second modified examples described above, the heat dissipation characteristics on the central side can be improved and the heat dissipation characteristics can be made uniform.

[0030] Figure 4 shows essential parts of a fourth modified example of the magnet cooling structure 1. The magnet cooling structure 1 according to the fourth modified example is similar to the configuration shown in Figure 1 in that the heat dissipation fins 5 are formed concentrically around the rotation axis (shaft 6) of the rotor core 2. However, it differs in that the heat dissipation fins 5 have drop-shaped portions 5b with an arc-shaped end and an acute angled end in a plan view. The tip of this acute angle faces the rotation direction of the rotor core 2 (see the arrow in Figure 4). The axial protrusion amount of each drop-shaped portion 5b is the same.

[0031] The magnet cooling structure 1 of the fourth variant has the heat dissipation fins 5 formed as drop-shaped portions 5b, with their acute-angled tips positioned to face the direction of rotation of the rotor core 2. This ensures the heat dissipation characteristics of the heat dissipation fins 5 while suppressing air resistance caused by the heat dissipation fins 5 when the rotor core 2 rotates.

[0032] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Therefore, the scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims.

[0033] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0034] This application is based on a Japanese patent application (Patent Application No. 2023-192184) filed on November 10, 2023, the contents of which are incorporated herein by reference.

[0035] REFERENCE SIGNS LIST 1 magnet cooling structure 2 rotor core 3 magnet 4 end plate 5 heat dissipation fin 5a protrusion 5b drop-shaped portion 6 shaft 7 circumferential groove 8 cooling member

Claims

1. a magnet embedded in a rotor core of the motor; end plates provided at both axial ends of the rotor core; a heat dissipation fin formed on a surface of the end plate opposite to a surface facing the magnet; and The heat dissipation fins are a plurality of protrusions formed concentrically around the rotation axis of the rotor core, the concentric circles having different radii, A magnet cooling structure, wherein at least one of the plurality of ridges is positioned so as to overlap with the magnet when viewed from the axial direction.

2. (delete)

3. the protrusion amounts in the axial direction of the plurality of protrusions are smaller on the outer diameter side than on the central side of the concentric circles, The magnet cooling structure according to claim 1 , wherein the number of the fins with a small protrusion amount is greater than the number of the fins with a large protrusion amount.

4. 2. The magnet cooling structure according to claim 1, wherein the protrusion has a drop-shaped portion having an arc on one end and an acute angle on the other end in a plan view, and the tip of the acute angle faces in the direction of rotation of the rotor core.

5. The magnet cooling structure according to claim 1 , further comprising a cooling member interposed between the magnet and the end plate.

6. 6. The magnet cooling structure according to claim 1, wherein the heat dissipation fins are formed on each of the end plates provided at both axial ends of the rotor core.

7. 4. The magnet cooling structure according to claim 3, wherein the protrusions arranged at positions overlapping the magnets when viewed from the axial direction are fins with a small protrusion amount.