Motor

Abstract

This motor comprises a stator, a rotor, and a case to which the stator is fixed. The case has: a first flow path through which a coolant flows; and an inner surface that is positioned between the first flow path and an outer peripheral part of the rotor and faces a surface of the outer peripheral part with an air gap therebetween.

Description

Motor

[0001] The present invention relates to a motor.

[0002] Patent Document 1 discloses a structure of a motor that cools a rotor and a stator by supplying air sent out from a blower to a coil through a flow path of a ring-shaped duct that covers the outer peripheral portion of the rotor.

[0003] Japanese Patent Application Laid-Open No. 2015-228752

[0004] By the way, in the structure of Patent Document 1, depending on the operating conditions, the effect of cooling the rotor of the motor may not be sufficient.

[0005] An object of the present invention is to provide a motor capable of appropriately cooling a rotor.

[0006] A motor according to an aspect of the present invention includes a stator, a rotor, and a case to which the stator is fixed. The case has a first flow path for flowing a coolant, and an inner surface that is located between the first flow path and the outer peripheral portion of the rotor and faces the surface of the outer peripheral portion through an air gap.

[0007] According to the above motor, the rotor can be appropriately cooled.

[0008] FIG. 1A is a cross-sectional view showing the structure of a motor according to an embodiment. FIG.lB is a cross-sectional view taken along line A1-A1 in FIG. 1A. FIG. 2A is a cross-sectional view showing the structure of a motor according to a second embodiment. FIG. 2B is a cross-sectional view taken along line A₂-A₂ in FIG. 2A. FIG. 2C is a perspective view showing the structure of a rib according to the second embodiment. FIG. 3A is a cross-sectional view showing the structure of a motor according to a third embodiment. FIG. 3B is a cross-sectional view taken along line A3-A3 in FIG. 3A. FIG. 3C is a perspective view showing the structure of a first flow path and a second flow path according to the third embodiment. FIG. 4A is a cross-sectional view showing the structure of a motor according to a fourth embodiment. FIG. 4B is a cross-sectional view taken along line A4-A4 in FIG. 4A.

[0009] The motor 1 according to this embodiment will be described below with reference to the drawings. Components having the same function as those already described are denoted by the same reference numerals and their descriptions are omitted. Figures 1A, 2A, and 4A show the upper structure of the motor 1. The lower structure of the motor 1 is the same as the upper structure, so its description and depiction are omitted. Figures 1B, 2B, and 4B show a part of the upper structure of the motor 1. The structure of the other parts of the motor 1 is point-symmetric with respect to the central axis of the upper structure, so its description and depiction are omitted.

[0010] The structure of the motor 1 according to the first embodiment will now be described. The motor 1 according to the first embodiment comprises a stator 2, a rotor 3, and a case 7 to which the stator 2 is fixed (see Figures 1A and 1B). Here, for the sake of explanation, the height direction of the motor 1 in Figures 1A-2B, 3A, 3B, 4A, and 4B will be referred to as the vertical direction. Also, in the left-right direction (axial direction S) in Figures 1A, 2A, 3A, and 4A, the left side will be referred to as one side and the right side as the other side.

[0011] As illustrated in Figures 1A and 1B, a coil 6 is wound around and fixed to the stator core 2A on the radially outer side of the stator 2. The stator 2 is fixed to the inner circumference 7A of the case 7, which will be described later (see Figure 1A). The rotor 3 comprises a shaft 4 that is rotatable about the central axis of the motor 1 passing through the axial direction S, and a rotor core 3A provided at the radially outer end of the shaft 4. The shaft 4 is connected to a rotating body or bearing at its central axis, for example. Note that in Figures 1B, 2B, 3B, and 4B, the reference numerals for the stator core 2A and coil 6 are representative, and some reference numerals for the stator core 2A and coil 6 are omitted.

[0012] As illustrated in Figures 1A and 1B, the shaft 4 extends radially outward from the central axis, and at its radially outer end, it extends from one side to the other in the axial direction S, forming a tip. As illustrated in Figures 1A and 1B, the radially outer surface of the rotor core 3A is fixed to the radially inner surface of the tip. A magnet 5 is fixed to the radially inner surface of the rotor core 3A. Therefore, in the rotor 3, the rotor core 3A and the magnet 5 rotate as the shaft 4 rotates.

[0013] As illustrated in Figures 1A and 1B, the case 7 has a ring shape and comprises an inner circumference portion 7A, a main body portion 7B, and an outer circumference portion 7C. The inner circumference portion 7A is the inner circumference of the ring shape and constitutes the radially inner portion of the case 7. The inner circumference portion 7A extends, for example, in the axial direction S, and the stator 2 is fixed to the radially outer surface of the inner circumference portion 7A. As illustrated in Figures 1A and 1B, the main body portion 7B extends outward along the radial direction RD from the other end of the inner circumference portion 7A in the axial direction S. The outer circumference portion 7C is the outer circumference of the ring shape and constitutes the radially outer portion of the case 7. The outer circumference portion 7C extends, for example, from the radially outer end of the main body portion 7B along the axial direction S from one side to the other. Therefore, when the motor 1 is viewed from the other side in the axial direction S, the main body portion 7B covers, for example, the stator 2 (stator core 2A), coil 6, rotor core 3A, and magnet 5. Furthermore, when the motor 1 is viewed from the outside in the radial direction RD, the outer circumference 7C covers, for example, the outer circumference 3A1 of the rotor 3, which will be described later.

[0014] The outer periphery 7C has a first flow path 11 for the flow of coolant and an inner surface 7C1. As illustrated in Figure 1A, the first flow path 11 is a sealed liquid passage formed inside the outer periphery 7C. That is, the first flow path 11 is formed in the circumferential direction of the outer periphery 7C. The first flow path 11 is defined, for example, by the inner and outer sides in the radial direction RD and by one side and the other side in the axial direction S, by the wall surfaces formed by the outer periphery 7C.

[0015] As illustrated in Figures 1A and 1B, the inner surface 7C1 is the inner circumferential portion of the outer circumferential portion 7C that is close to the outer circumferential portion 3A1 of the rotor 3. More specifically, the inner surface 7C1 is the inner circumferential portion of the outer circumferential portion 7C that is between the first flow path 11 and the outer circumferential portion 3A1 of the rotor 3, and is the surface facing the outer circumferential portion 3A1 of the rotor 3. Therefore, the inner surface 7C1 is located between the first flow path 11 and the outer circumferential portion 3A1 of the rotor 3. As illustrated in Figures 1A and 1B, the inner surface 7C1 faces the surface of the outer circumferential portion 3A1 of the rotor 3 via an air gap C. In this case, the air gap C is a gap in the radial direction RD formed between the inner surface 7C1 and the surface of the outer circumferential portion 3A1 of the rotor 3. Alternatively, the inner surface 7C1 may be the radially inner surface of the inner wall portion 7I, which will be described later. The outer circumference 3A1 of the rotor 3 is comprised of the rotor core 3A, the magnet 5, and the portion of the radially outer tip of the shaft 4 to which the rotor core 3A is fixed.

[0016] As illustrated in Figures 1A and 1B, the rotor core 3A of the rotor 3 is positioned radially outward relative to the stator core 2A of the stator 2. That is, the motor 1 according to the first embodiment may be an outer rotor type motor in which the rotor core 3A is positioned radially outward relative to the stator core 2A. In this case, the radially outward outer surface 3A2 of the outer periphery 3A1 of the rotor 3 is a part of the rotor 3 with a relatively high peripheral speed. The inner surface 7C1 faces the radially outward outer surface 3A2 of the outer periphery 3A1 of the rotor 3 via an air gap C. Therefore, the coolant passing through the first flow path 11 in the outer periphery 7C can cool the rotor 3 (outer periphery 3A1 of the rotor 3) via the inner portion of the outer periphery 7C including the inner surface 7C1 and the air gap C.

[0017] As illustrated in Figures 1A and 1B, the inner surface 7C1 of the case 7 is formed substantially parallel to the axial direction S. Similarly, the radially outer outer surface 3A2 of the outer periphery 3A1 of the rotor 3 is formed substantially parallel to the axial direction S. Therefore, the inner surface 7C1 of the case 7 and the radially outer outer surface 3A2 of the outer periphery 3A1 of the rotor 3 are arranged substantially parallel to each other. In other words, the width of the air gap C in the axial direction S is formed substantially uniformly. As a result, uneven heat transfer from the outer surface 3A2 of the rotor 3 to the coolant in the first flow path 11 can be suppressed.

[0018] When the rotational speed R of the rotor 3 per predetermined time is relatively high, more efficient cooling performance may be required. For example, the motor 1 according to the first embodiment is configured such that when the rotational speed R of the rotor 3 per predetermined time is 2 / 3 or more of the maximum rotational speed R1 of the rotor 3 per predetermined time, the Taylor number T, which indicates the degree of vortex flow in the air gap C, is approximately 41 or more (or the square of the Taylor number T is approximately 1700 or more). By satisfying the above conditions, turbulence due to vortex flow can be generated in the air gap C. In this case, the inventors have experimentally confirmed that the efficiency of heat conduction increases (the Nusselt number, which indicates the heat transfer performance of the fluid by convection, increases) due to convection caused by turbulence in the air gap C. That is, the above configuration can further improve cooling performance. In a rotating coaxial cylinder such as the motor 1 according to the first embodiment, the Taylor number T is calculated, for example, by the following equation (1). Here, Re is the rotational Reynolds number, ν is the kinematic viscosity of the air, b is the width of the air gap C, and r is the radius of the rotor 3. T = Re・ν・b / r ... (1)

[0019] As illustrated in Figures 1A and 2B, the case 7 has an inner wall portion 7I that defines the first flow path 11 radially inward, and an outer wall portion 7O that defines the first flow path 11 radially outward. In this case, the thickness of the inner wall portion 7I in the radial direction RD may be smaller than the thickness of the outer wall portion 7O in the radial direction RD. In this case, since the thickness of the inner wall portion 7I that constitutes the inner circumferential portion close to the air gap C in the case 7 is relatively small, the rotor 3 can be cooled efficiently. Furthermore, by increasing the thickness of the outer wall portion 7O, which is the outer circumferential portion of the case 7, the rigidity of the case 7 can be improved.

[0020] The structure of the motor 1 according to the second embodiment will now be described. As illustrated in Figures 2A-2C, a rib 11A is formed on the radially inner side of the first flow path 11, erected radially in the direction RD. That is, the rib 11A is formed on the radially inner bottom surface of the first flow path 11. In other words, a rib 11A is formed on the radially inner bottom surface of the first flow path 11, protruding from the radially inner side to the outside. This increases the surface area of ​​the radially inner bottom surface of the first flow path 11. The radially inner bottom surface of the first flow path 11 faces the outer circumferential portion 3A1 of the rotor 3. Therefore, the formation of the rib 11A on the radially inner bottom surface of the first flow path 11 increases the surface area that can cool the outer circumferential surface 3A2 of the outer circumferential portion 3A1 of the rotor 3. As a result, more heat from the rotor 3 can be absorbed, and the cooling performance of the rotor 3 by the coolant flowing through the first flow path 11 can be improved. Note that, as illustrated in Figures 2A and 2B, the case 7 may also include a second flow path 21, which will be described later.

[0021] As illustrated in Figure 2C, the ribs 11A may be formed along the rotation direction of the motor 1. That is, the ribs 11A may be formed along the circumferential direction of the first flow path 11 provided on the outer circumference 7C of the ring-shaped case 7. For example, on the radially inner side of the first flow path 11, which is the side facing the outer circumference 3A1 of the rotor 3, the ribs 11A may be formed over substantially the entire first flow path 11, from near the inlet flow path 12 to near the outlet flow path 13, as described later. This improves the rigidity of the case 7. Furthermore, by improving the rigidity of the case 7, or by changing the vibration mode due to the shape change caused by the ribs 11A, the resonance in the annular mode can be suppressed in the motor 1, improving the sound and vibration performance. Note that Figure 2A-2C illustrates multiple ribs 11A protruding in a rectangular shape from the radially inner to the outer side, but the number, shape, and arrangement of the ribs 11A are not limited to those described above.

[0022] The structure of the motor 1 according to the third embodiment will now be described. As illustrated in Figure 3A-3C, in the motor 1, a first flow path 11 is formed in the outer circumference 7C of the case 7 on the radially outer side of the rotor 3. A second flow path 21 is formed in the inner circumference 7A of the case 7 on the radially inner side of the stator 2. The second flow path 21 is formed inside the inner circumference 7A and is a sealed fluid passage for flowing coolant. The second flow path 21 is formed in the circumferential direction of the inner circumference 7A and is defined by the inner and outer sides in the radial direction RD and one side and the other side in the axial direction S. As illustrated in Figure 3A, a rib 11A erected in the radial direction RD may be formed on the radially inner side of the first flow path 11.

[0023] As illustrated in Figures 3B and 3C, the inlet passage 12 and outlet passage 13 of the first passage 11 are connected to the upper part 7U of the outer circumference 7C of the case 7, respectively. Furthermore, the inlet passage 12 and outlet passage 13 are formed extending approximately parallel to the radial direction RD in the upper part 7U of the outer circumference 7C. This improves the air venting performance in the first passage 11, suppressing increased pressure loss and a decrease in cooling performance due to air remaining in the first passage 11. In addition, the inlet passage 22 and outlet passage 23 of the second passage 21 may be connected to the upper part of the inner circumference 7A of the case 7, respectively.

[0024] As illustrated in Figure 3C, the outlet passage 13 of the first passage 11 and the inlet passage 22 of the second passage 21 are connected. That is, at the upper part 7U of the outer circumference 7C, the coolant flowing in from the inlet passage 12 of the first passage 11 travels approximately once in the circumferential direction within the outer circumference 7C and flows out from the outlet passage 13 at the upper part 7U of the outer circumference 7C. Subsequently, the coolant flows in from the inlet passage 22 of the second passage 21 at the upper part of the inner circumference 7A. Subsequently, it travels approximately once in the circumferential direction within the inner circumference 7A and flows out from the outlet passage 23 at the upper part of the inner circumference 7A. Therefore, the rotor 3 is cooled by the first passage 11, and then the stator 2 is cooled by the second passage 21. In other words, with the above configuration, the rotor 3 can be cooled preferentially. The coolant that flows out from the outlet passage 23 is dissipated by passing through a radiator or the like and returns to the inlet passage 12 of the first passage 11. In other words, the coolant can circulate within the first flow path 11 and the second flow path 21.

[0025] The structure of the motor 1 according to the fourth embodiment will now be described. As illustrated in Figure 4A, in the fourth embodiment, the first flow path 11 for flowing the coolant may be located in the corner portion between the radially outer portion of the main body 7B and the axial end of the outer periphery 7C. In this case, the inner surface 7C1 is the surface facing the outer periphery 3A1 of the rotor 3, which is located in the axial direction of the corner portion between the first flow path 11 and the outer periphery 3A1 of the rotor 3. Therefore, the inner surface 7C1 located between the first flow path 11 and the outer periphery 3A1 of the rotor 3 is a surface substantially parallel to the radial direction RD. Furthermore, the inner surface 7C1 and the surface on the outer periphery 3A1 of the rotor 3 that is parallel to the radial direction RD are facing each other. That is, the air gap C is a gap in the axial direction S formed between the inner surface 7C1 and the surface on the outer periphery 3A1 of the rotor 3 that is parallel to the radial direction RD. In this case, the rotor 3 (outer circumference 3A1 of the rotor 3) can be cooled by the coolant flowing through the first flow path 11 via the axial side portion of the corner portion including the inner surface 7C1 and the air gap C. Also, as illustrated in Figures 4A and 4B, the inner surface 7C1 may face the outer circumference 3A1 and the magnet 5 via the air gap C. In other words, when the motor 1 is viewed in the axial direction S, the inner surface 7C1, the outer circumference 3A1 and the magnet 5 may be arranged in an overlapping manner.

[0026] (1) The motor 1 according to this embodiment comprises a stator 2, a rotor 3, and a case 7 to which the stator 2 is fixed. The case 7 has a first passage 11 for flowing coolant, and an inner surface 7C1 located between the first passage 11 and the outer periphery 3A1 of the rotor 3, facing the surface of the outer periphery 3A1 via an air gap C. That is, the inner surface 7C1 of the case 7 and the air gap C between the inner surface 7C1 and the surface of the outer periphery 3A1 are arranged between the first passage 11 and the outer periphery 3A1 of the rotor 3. As a result, the rotor 3 (outer periphery 3A1 of the rotor 3) can be cooled by the coolant flowing through the first passage 11 via a part of the case 7 including the inner surface 7C1 and the air gap C. That is, with the above configuration, heat can be transferred from the rotor 3 to the coolant in the first passage 11, thereby cooling the rotor 3. In the case of a configuration in which the rotor 3 is cooled by air using a duct or the like, an air compressor or the like would be required, raising concerns about an increase in system size. Furthermore, when the rotor 3 is cooled by air, there is a concern that the cooling performance may be insufficient. With the above configuration, it is possible to use the first flow path 11 through which a coolant with relatively high cooling performance flows, thereby enabling proper cooling of the rotor 3 while suppressing an increase in system size.

[0027] (2) In this embodiment, the rotor core 3A of the rotor 3 is located radially outward relative to the stator core 2A of the stator 2, and the inner surface 7C1 of the case 7 faces the radially outward outer surface 3A2 of the outer periphery 3A1 of the rotor 3 in the radial direction RD. That is, the motor 1 is an outer rotor type motor in which the rotor core 3A is located radially outward relative to the stator core 2A. In this case, the coolant passing through the first flow path can cool the radially outward outer surface 3A2 of the outer periphery 3A1 of the rotor 3, which is a part of the rotor 3 with a relatively high peripheral speed, via the inner surface 7C1 and the air gap C. Therefore, with the above configuration, the rotor 3 (outer periphery 3A1 of the rotor 3) can be cooled more efficiently.

[0028] (3) Furthermore, in this embodiment, the inner surface 7C1 of the case 7 is substantially parallel to the outer surface 3A2 of the rotor 3. This makes it possible to form a substantially uniform width of the air gap C in the axial direction S of the motor 1. As a result, it is possible to suppress uneven heat transfer from the outer surface 3A2 of the rotor 3 to the coolant in the first flow path 11, and to suppress uneven temperature distribution of the outer surface 3A2 of the rotor 3 in the axial direction S. Accordingly, with this configuration, the rotor 3 (outer surface 3A1 of the rotor 3) can be cooled even more efficiently.

[0029] (4) In the embodiment, the motor 1 is configured such that when the rotational speed R of the rotor 3 per predetermined time is 2 / 3 or more of the maximum rotational speed R1 of the rotor 3 per predetermined time, the Taylor number T, which indicates the degree of air vortex flow in the air gap C, is 41 or more. That is, in an operating state where the rotational speed R of the rotor 3 per predetermined time is high and more efficient cooling performance is required, turbulence due to vortex flow can be generated in the air gap C, thereby increasing the efficiency of heat conduction and further improving cooling performance. Therefore, the above configuration can further improve cooling performance.

[0030] (5) Furthermore, in this embodiment, the case 7 has an inner wall portion 7I that defines the first flow path 11 radially inward and an outer wall portion 7O that defines the first flow path 11 radially outward, and the thickness of the inner wall portion 7I is smaller than the thickness of the outer wall portion 7O. Therefore, because the thickness of the inner wall portion 7I that constitutes the air gap C side of the case 7 is small, the rotor 3 can be cooled efficiently. In addition, the rigidity of the case 7 can be improved by increasing the thickness of the outer wall portion 7O, which is on the outer circumference side of the case 7.

[0031] (6) In this embodiment, a rib 11A is formed on the radially inner side of the first flow channel 11, extending radially RD. That is, a rib 11A is formed on the radially inner bottom surface of the first flow channel 11, projecting from the radially inner side outward. This increases the surface area of ​​the radially inner bottom surface of the first flow channel 11. That is, the surface area in the first flow channel 11 that can cool the outer surface 3A2 of the outer peripheral portion 3A1 of the rotor 3 increases. Therefore, with this configuration, the cooling performance of the rotor 3 by the coolant flowing through the first flow channel 11 can be improved.

[0032] (7) Furthermore, in this embodiment, the rib 11A is formed along the rotation direction of the motor 1. With this configuration, the rigidity of the case 7 can be improved. In addition, by improving the rigidity of the case 7, or by changing the vibration mode due to the shape change caused by the rib 11A, resonance in the annular mode can be suppressed and the sound and vibration performance can be improved.

[0033] (8) In this embodiment, the inlet passage 12 and outlet passage 13 of the first passage 11 are connected to the upper part 7U of the case 7. This improves the air venting performance in the first passage 11, and suppresses the increase in pressure loss and decrease in cooling performance caused by air remaining in the first passage 11.

[0034] (9) Furthermore, in this embodiment, the first flow path 11 is located radially outside the rotor 3 and includes a second flow path 21 located radially inside the stator 2, with the outlet flow path 13 of the first flow path 11 connected to the inlet flow path 22 of the second flow path 21. With this configuration, the coolant passes through the first flow path 11 and then through the second flow path 21. Therefore, the rotor 3 is cooled by the first flow path 11 and then the stator 2 is cooled by the second flow path 21. In other words, with this configuration, the rotor 3 can be cooled preferentially. Accordingly, for example, if this configuration is applied to the first embodiment, the rotor 3 and the magnets 5 provided on the rotor 3 can be cooled first, and then the stator 2 and coil 6 can be cooled. As a result, the rotor 3 and the magnets 5 provided on the rotor 3 (outer circumference 3A1 of the rotor 3) can be cooled preferentially, and a predetermined operating performance of the motor 1 (for example, continuous rated output) can be ensured.

[0035] The embodiments described above are merely illustrative examples provided to facilitate understanding of the invention. The technical scope of the invention is not limited to the specific technical matters disclosed in the embodiments above, but also includes various modifications, changes, and alternative technologies that can be easily derived therefrom.

[0036] In the above embodiments, the structures of the motor 1 according to the first to fourth embodiments were described as examples, but these embodiments may be combined as appropriate. Furthermore, when the second and fourth embodiments are combined, the rib 11A may be formed to stand upright in the axial direction S with respect to the first flow path 11, for example.

[0037] 1 Motor 2 Stator 2A Stator core 3 Rotor 3A Rotor core 3A1 Outer circumference 3A2 Outer surface 7 Case 7C1 Inner surface 7I Inner wall 7O Outer wall 7U Upper part 11 First flow path 11A Rib 12 Inlet flow path 13 Outlet flow path 21 Second flow path 22 Inlet flow path C Air gap R Rotor rotations per predetermined time R1 Maximum rotor rotations per predetermined time RD Radial direction T Taylor number

Claims

1. A motor comprising a stator, a rotor, and a case to which the stator is fixed, wherein the case has a first passage for flowing coolant and an inner surface located between the first passage and the outer periphery of the rotor, and facing the surface of the outer periphery via an air gap.

2. The motor according to claim 1, wherein the rotor core of the rotor is located radially outward of the rotor relative to the stator core of the stator, and the inner surface of the case faces radially outward of the outer peripheral surface of the outer peripheral portion of the rotor.

3. The motor according to claim 2, wherein the inner surface of the case is substantially parallel to the outer surface of the rotor.

4. The motor according to claim 2 or 3, wherein, when the rotational speed of the rotor per predetermined time is operating at 2 / 3 or more of the maximum rotational speed of the rotor per predetermined time, the Taylor number, which indicates the degree of air vortex flow in the air gap, is 41 or more.

5. The motor according to any one of claims 2 to 4, wherein the case has an inner wall portion that defines the first flow path radially inward and an outer wall portion that defines the first flow path radially outward, and the thickness of the inner wall portion is smaller than the thickness of the outer wall portion.

6. The motor according to any one of claims 2 to 5, wherein a radially erecting rib is formed on the radially inner side of the first flow path.

7. The motor according to claim 6, wherein the ribs are formed along the rotational direction of the motor.

8. The motor according to any one of claims 2 to 7, wherein the inlet and outlet channels of the first channel are connected to the upper part of the case.

9. The motor according to any one of claims 2 to 8, wherein the first flow path is located radially outward of the rotor and the second flow path is located radially inward of the stator, and the outlet flow path of the first flow path and the inlet flow path of the second flow path are connected.

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