Rotor of a rotating electric machine

Abstract

To provide a rotor of a rotary electric machine capable of reducing torque unevenness and suppressing a weight increase.SOLUTION: A rotor (4) of a rotary electric machine (1) has a plurality of magnets 14 arranged in a circumferential direction with a predetermined alignment, and a yoke 13 arranged in a radial direction of the magnets and holding the magnets 14. The yoke 13 has a thick part (34) formed in a position corresponding to a circumferential direction position of a boundary surface of a pair of magnets 14 adjacent to each other in the circumferential direction. By providing the thick part, a magnetic-flux density of this part becomes thin.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a rotor for a rotating electric machine. [Background technology]

[0002] Conventionally, rotating electric machines equipped with Halbach array permanent magnets have been known (for example, Patent Document 1). In conventional rotating electric machines equipped with an iron core, magnetic flux concentrates on the iron core, and the magnetic flux density in the gap between the rotor and stator does not change smoothly in the circumferential direction. This is known to cause torque irregularities (torque ripple), which can be a cause of vibration and noise (see paragraph 1 of Patent Document 1).

[0003] reference).

[0003] In the rotating electric machine described in Patent Document 1, ripples are reduced by using an iron-coreless configuration. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-175755 Summary of the Invention [Problem to be solved by the invention]

[0005] However, an iron-coreless configuration reduces the magnet's holding power, making it difficult to apply to high-output motors. When an iron core (core or yoke) is used to hold the magnet, the magnetic flux density is high in the part of the iron core corresponding to the circumferential position of the magnet's boundary surface, and low in the part corresponding to the circumferential position between the boundary surfaces (the center of the magnet). If the magnetic flux density varies depending on the circumferential position of the iron core, torque fluctuations may occur, resulting in a decrease in the performance of the rotating electric machine. If the iron core's thickness is increased uniformly as a countermeasure, the weight of the rotating electric machine increases. When permanent magnets are used in the rotor, an increase in the rotor's weight causes a decrease in the output of the rotating electric machine. Therefore, improvements in these areas have been required.

[0006] In view of the above background, an object of the present invention is to provide a rotor for a rotating electrical machine that can reduce torque unevenness and suppress an increase in weight. [Means for solving the problem]

[0007] In order to solve the above problem, one aspect of the present invention is a rotor (4) of a rotating electric machine (1), which comprises a plurality of magnets (14) arranged in a predetermined circumferential arrangement, and a yoke (13) arranged radially of the magnets to hold the magnets, and the yoke has a thick portion (34) formed at a position corresponding to the circumferential position of the boundary surface between a pair of the magnets adjacent to each other in the circumferential direction.

[0008] According to this aspect, by forming a thick portion in the yoke at a position corresponding to the circumferential position of the boundary surface of the magnet where the magnetic flux density is high, the magnetic flux density concentrated at that position is reduced, and the magnetic flux density changes smoothly in the circumferential direction. Furthermore, there is no need to make the yoke thick overall. This reduces torque fluctuations and suppresses weight increases.

[0009] In the above aspect, the thick portion may be formed so as to protrude radially from the peripheral surface (13b) of the yoke on the side opposite to the magnet.

[0010] This configuration allows the surface of the yoke facing the magnet to be smooth, eliminating the need for a complex shape for the circumferential surface of the magnet facing the yoke. Furthermore, the thick-walled portion functions as a fin during rotation, generating a swirling airflow, improving the heat dissipation of the yoke.

[0011] In the above aspect, the thick portion may be formed by a ridge (34) extending along the axis (2) of the rotor.

[0012] According to this aspect, the length of the thick-walled portion in the axial direction of the yoke is increased, and the heat dissipation properties of the yoke can be further improved.

[0013] In the above aspect, the ridge may have an arcuate profile in a cross section perpendicular to the axis.

[0014] According to this embodiment, by forming the yoke in an arc shape, the surface area of ​​the yoke can be increased and the heat dissipation of the yoke 13 can be improved while providing a minimum thickness portion along the direction of the magnetic flux.

[0015] In the above aspect, the rotor may further include at least one heat conducting member (35) arranged in a portion of the yoke facing the circumferential center of the magnet so as to be in contact with the magnet.

[0016] According to this aspect, heat from the magnets is absorbed by the heat conduction member located in the circumferential center of the first magnet and second magnet, which has a lower magnetic flux density than the boundary surface, thereby eliminating heat buildup without worsening torque unevenness and improving the heat resistance of the motor.

[0017] In the above aspect, the heat conducting member may be sandwiched between the yoke and the magnet.

[0018] According to this aspect, in the rotor, which is a rotating part, the heat conduction member can be reliably fixed with a simple structure, and an increase in the weight of the yoke can be suppressed.

[0019] In the above aspect, the heat conducting member may be a heat sink (35) having a vapor chamber (35a).

[0020] According to this aspect, the thermal conductivity of the heat conducting member can be increased, thereby improving the cooling performance of the yoke.

[0021] In the above aspect, the predetermined arrangement is a Halbach arrangement in which a third magnet (33) having a magnetic pole direction facing in the circumferential direction is arranged between a first magnet (31) having a magnetic pole direction facing radially inward and a second magnet (32) having a magnetic pole direction facing radially outward, and the thick portion is preferably formed at a position corresponding to each circumferential position of the boundary surface between the first magnet and the third magnet and the boundary surface between the second magnet and the third magnet.

[0022] According to this aspect, by applying thick portions to a rotating electrical machine with a Halbach array that has many boundary surfaces that concentrate magnetic flux, a large cooling effect can be obtained by the large number of thick portions. [Effects of the Invention]

[0023] According to the above aspect, it is possible to provide a rotor for a rotating electrical machine that can reduce torque unevenness and suppress an increase in weight. [Brief explanation of the drawings]

[0024] [Figure 1] Cross-sectional view of a motor according to an embodiment [Figure 2] Rear view of the stator and rotor [Figure 3] Enlarged view of part III in Figure 2 [Figure 4] A perspective view of the main part of the motor [Figure 5] Cross section of a heat sink [Figure 6] (A) A schematic diagram of a conventional example and (B) a schematic diagram of each rotor according to the embodiment. [Figure 7] Magnetic flux density distribution diagram of a rotor according to a conventional example DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an embodiment to which a rotor (rotor 4) according to the present invention is applied will be described in detail with reference to the drawings.

[0026] FIG. 1 is a cross-sectional view of a motor 1 according to an embodiment. As shown in FIG. 1, the motor 1 has a cylindrical case 3 centered on an axis 2, a rotor 4 supported by the case 3 so as to be rotatable about the axis 2, and a stator 5 disposed on the outer periphery of the rotor 4 and fixed to the case 3. In other words, the motor 1 is configured as an inner rotor type radial gap motor. While the motor 1 is used in the position shown in FIG. 1 in which the axis 2 extends horizontally, it may also be used in a position in which the axis 2 extends vertically.

[0027] The case 3 has a case body 6 and a case lid 7 that can be separated in the axial direction, and defines an internal storage space for accommodating the rotor 4 and the stator 5. The case body 6 has a cylindrical side wall 8 and a bottom wall 9 that closes the lower end of the side wall 8. A through hole 10 centered on the axis 2 is formed in the bottom wall 9 of the case body 6 and the case lid 7.

[0028] The rotor 4 includes a rotating shaft 11 that extends along the axis 2 and serves as the output shaft of the motor 1, a rotor hub 12 arranged around the rotating shaft 11, a cylindrical yoke 13 (rotor core) provided at the outer end of the rotor hub 12, and a plurality of permanent magnets (simply referred to as magnets 14). The rotor hub 12 may be provided integrally with the rotating shaft 11, or may be provided so as to be rotatable relative to the rotating shaft 11 via a planetary gear mechanism or the like. In either configuration, the rotating shaft 11 rotates as the rotor hub 12 rotates.

[0029] The rotating shaft 11 is rotatably supported by the case body 6 and the case cover 7 via bearings 15. The rotating shaft 11 passes through through holes 10 in the case body 6 and the case cover 7 and protrudes in the axial direction from both sides of the case 3. In other embodiments, the rotating shaft 11 may protrude from only one side of the case 3. The yoke 13 is a rotor core having a substantially cylindrical shape centered on the axis 2, and is formed integrally with the outer edge of the rotor hub 12, rotating integrally with the rotor hub 12. The motor 1 is a permanent magnet synchronous motor, and a plurality of magnets 14 are arranged in a predetermined circumferential arrangement on the outer periphery of the yoke 13. The rotor 4 forms a field element of the motor 1.

[0030] The stator 5 is disposed along a side wall 8 of the case body 6, with a predetermined radial gap between it and the outer surface of the rotor 4. The stator 5 includes a stator core 18 having a plurality of teeth 16 and a teeth retaining ring 17 (stator yoke) disposed outside the teeth 16 to retain the teeth 16, and a plurality of coils 19 wound around the teeth 16. The stator 5 forms the armature of the motor 1. The teeth retaining ring 17 is cylindrical and is disposed about the axis 2. The teeth 16 are aligned circumferentially along the teeth retaining ring 17 and protrude radially inward from the inner surface of the teeth retaining ring 17.

[0031] A stator cover 20 is attached to the case body 6, cooperating with the case body 6 to cover the stator 5. As shown in the enlarged view of FIG. 1 , the stator cover 20 includes a cylindrical first portion 21, a circular plate-shaped second portion 22 extending radially outward from one axial end of the first portion 21, and a circular plate-shaped third portion 23 extending radially inward from the other axial end of the first portion 21. The stator cover 20 is made of a non-magnetic material with low magnetic permeability, and may be, for example, an injection-molded synthetic resin. The first portion 21 is disposed between the stator 5 and the rotor 4 (i.e., in the gap). The second portion 22 faces the coil 19 in the axial direction of the motor 1, and its outer edge is in close contact with the side wall 8 of the case body 6 via a seal member 24. The third portion 23 is in close contact with the bottom wall 9 of the case body 6 via the seal member 24 at its inner edge.

[0032] In this way, the stator cover 20 cooperates with the case body 6 to cover the stator 5, thereby defining a cooling passage 25 for cooling the stator 5. The cooling passage 25 has a cylindrical shape, and oil supplied as a refrigerant flows through the cooling passage 25 in the axial direction.

[0033] FIG. 2 is a rear view of the stator 5 and rotor 4 as viewed from the bottom wall 9, and FIG. 3 is an enlarged view of portion III in FIG. 2. As shown in FIGS. 2 and 3, the magnets 14 include a first magnet 31 having a magnetic pole direction (magnetization direction) facing radially inward, a second magnet 32 ​​having a magnetic pole direction facing radially outward, and a third magnet 33 disposed between the first magnet 31 and the second magnet 32. The third magnet 33 has a magnetic pole direction that includes a circumferential component. That is, the magnets 14 are arranged in a ring shape in a Halbach array. The magnetic pole direction is indicated by arrows in the figure. The first magnet 31 and the second magnet 32 ​​are main magnets and have the same shape and dimensions. The third magnet 33 is a sub-magnet and has a smaller circumferential dimension than the main magnets. The circumferential dimension of the magnet 14 is expressed as an angle around the axis 2, and in this specification, this is referred to as the circumferential width C. The circumferential width C of the third magnet 33 is set to ½ of the circumferential width C of the first magnet 31 and the second magnet 32.

[0034] The stator 5 has 72 electromagnets, each consisting of teeth 16 and coils 19. The electromagnets are arranged at equal intervals (5° intervals) in the circumferential direction. The rotor 4 has 24 first magnets 31, 24 second magnets 32, and 48 third magnets 33. 24 third magnets 33 have magnetic poles facing in one circumferential direction, and the remaining 24 third magnets 33 have magnetic poles facing in the other circumferential direction. The first magnets 31 and second magnets 32 are arranged at equal intervals (7.5° intervals) in the circumferential direction. The outer peripheral surface 13a of the yoke 13 has a smooth cylindrical shape. On the other hand, the inner peripheral surface 13b of the yoke 13 has an uneven cylindrical shape.

[0035] FIG. 4 is a perspective view of the main parts of the motor 1 as viewed from the rear side. As shown in FIGS. 3 and 4, a plurality of ridges 34 extending along the axis 2 (see FIGS. 1 and 2) are formed on the inner peripheral surface 13b of the yoke 13. In this embodiment, 96 ridges 34 are provided. All of the ridges 34 have the same shape and dimensions. The ridges 34 have an arc-shaped outline that protrudes radially from the inner peripheral surface 13b of the yoke 13 and extends over the entire length of the yoke 13 in the axial direction.

[0036] The ridges 34 are arranged alternately in the circumferential direction at first intervals P1 and second intervals P2. The first interval P1 is 2.5°, and the second interval P2 is 5°. The ridges 34 are formed integrally with the yoke 13 at positions on the yoke 13 that correspond to the circumferential positions of the boundaries of the three types of magnets 14, forming thick portions in the yoke 13. The centers of the arcs that define the contours of the ridges 34 are located at positions on the outer peripheral surface 13a of the yoke 13 that correspond to the boundaries of the magnets 14.

[0037] The circumferential width of the ridges 34 is smaller than the circumferential width C of the third magnet 33, which is 2.5°, and is set to approximately 1.5° in this embodiment. Therefore, a substantially flat surface of approximately 1° is formed between two ridges 34 arranged at the first interval P1, and a substantially flat surface of approximately 4° is formed between two ridges 34 arranged at the second interval P2. Each ridge 34 forms a thick portion in the yoke 13.

[0038] A plurality of heat sinks 35 are provided in a portion of the yoke 13 facing the circumferential centers of the first magnet 31 and the second magnet 32. Each heat sink 35 is disposed radially outward of the yoke 13 so as to contact the first magnet 31 or the second magnet 32, and is sandwiched between the yoke 13 and the first magnet 31 or the second magnet 32. In this embodiment, heat sinks 35 are provided for all of the first magnets 31 and the second magnets 32. In other embodiments, heat sinks 35 may be provided for some of the first magnets 31 and the second magnets 32. Each heat sink 35 has a rectangular shape that is long in the axial direction and extends over the entire axial length of the yoke 13. The heat sink 35 functions as a thermally conductive member that absorbs heat on one side and releases it on the other side.

[0039] FIG. 5 is a cross-sectional view of the heat sink 35. The heat sink 35 is formed into a hollow structure using a highly thermally conductive material and defines a vapor chamber 35a therein. A wick 35b is provided in the vapor chamber 35a and a working fluid is sealed inside. The working fluid is vaporized by heat from a heat source, moves through the vapor chamber 35a, and condenses by dissipating heat on the side opposite the heat source. The working fluid is then returned to the heat source through the wick 35b. The magnet 14 can become hot due to the heat from the coil 19. When the magnet 14 becomes hot due to the heat from the coil 19, it is cooled by the heat sink 35.

[0040] The motor 1 is configured as described above. The effects of the motor 1 configured as described above will be described below.

[0041] As shown in Figures 3 and 4, protrusions 34 forming thick portions are provided at positions on the yoke 13 corresponding to the circumferential positions of the boundary surfaces of the magnets 14 where the magnetic flux density is high. This reduces the magnetic flux concentrated at these positions, allowing the magnetic flux density to change smoothly in the circumferential direction. Furthermore, it is not necessary to increase the overall thickness of the yoke 13. This reduces torque fluctuations and suppresses weight increases. The effects of this embodiment will be described with reference to Figures 6 and 7.

[0042] Fig. 6 is a schematic diagram showing (A) a rotor 104 according to a conventional example and (B) the rotor 4 according to the embodiment. Fig. 7 is a magnetic flux density distribution diagram of the rotor 104 according to the conventional example. As shown in Fig. 6, the rotor 104 according to the conventional example differs from the rotor 4 according to the embodiment in that it does not have the ribs 34, but otherwise has the same configuration as the rotor 4 according to the embodiment. As shown in Fig. 6(A), the yoke 113 has a constant thickness t.

[0043] Therefore, in the conventional rotor 104, as shown in Fig. 7, the magnetic flux density is lowest at the position of the yoke 113 corresponding to the circumferential center of the main magnets (first magnet 31 and second magnet 32). On the other hand, the magnetic flux density is highest at the position of the yoke 113 corresponding to the circumferential position of the boundary surface between each pair of adjacent magnets 14.

[0044] In this embodiment and the conventional example, since the magnet 14 has a Halbach array, the magnetic flux density is highest at a position on the yoke 113 corresponding to the circumferential position of the boundary surface between the third magnet 33 and the first magnet 31 or the second magnet 32. If the magnet 14 includes only the first magnet 31 and the second magnet 32, the magnetic flux density would be highest at a position on the yoke 113 corresponding to the circumferential position of the boundary surface between the first magnet 31 and the second magnet 32.

[0045] If portions with high magnetic flux density like this exist partially in the yoke 113 and the magnetic flux density varies depending on the circumferential position of the yoke 113, torque irregularities will occur, degrading the performance of the rotating electric machine. In contrast, in this embodiment, as shown in FIG. 6(B), the protrusions 34 are provided, so that thick-walled portions with arc-shaped outer contours are formed at circumferential positions of the yoke 113 where the magnetic flux density is highest. The contour portion of the thick-walled portion has a center on the outer peripheral surface 13a of the yoke 13 and has a radius R that is larger than the thickness t. As a result, the magnetic flux density of this thick-walled portion is lower than in the conventional example, and the magnetic flux density varies smoothly in the circumferential direction, thereby reducing torque irregularities.

[0046] 3 and 4, this thick portion is formed so as to protrude radially from inner circumferential surface 13b of yoke 13 on the side opposite magnet 14. This allows the surface of yoke 13 facing magnet 14 to be smooth. Therefore, it is not necessary to give the radially inner circumferential surface of magnet 14 a complex shape. Furthermore, the thick portion functions as a fin during rotation to generate a swirling airflow, improving the heat dissipation performance of yoke 13.

[0047] As described above, the thick-walled portion is formed by the ridges 34 extending along the axis 2 (FIGS. 1 and 2) of the rotor 4. This increases the length of the thick-walled portion in the axial direction, further improving the heat dissipation properties of the yoke 13.

[0048] 3 and 6(B), the ridges 34 have an arc-shaped contour in a cross section perpendicular to the axis 2. This allows the heat dissipation of the yoke 13 to be improved by increasing the surface area of ​​the yoke 13 while providing a minimally thick portion along the direction of the magnetic flux.

[0049] Furthermore, a heat sink 35 serving as a thermally conductive member is disposed in contact with the magnet 14 at a portion of the yoke 13 facing the circumferential center of the magnet 14. As a result, the heat is absorbed by the heat sink 35, which is disposed in the circumferential center of the first magnet 31 and the second magnet 32, where the magnetic flux density is lower than at the boundary surface, thereby eliminating heat buildup without worsening torque unevenness and improving the heat resistance of the motor 1. Note that it is sufficient to provide a heat sink 35 for at least one magnet 14, and it is not necessary to provide one for each magnet 14.

[0050] As described above, the heat sink 35 is sandwiched between the yoke 13 and the magnet 14. This allows the heat sink 35 to be reliably fixed to the rotor 4, which is a rotating part, with a simple structure, and also prevents the weight of the yoke 13 from increasing.

[0051] In this embodiment, a heat sink 35 equipped with a vapor chamber 35a (FIG. 5) is provided as the heat conducting member. This increases the thermal conductivity of the heat conducting member, improving the cooling performance of the yoke 13. Note that instead of the heat sink 35 equipped with the vapor chamber 35a, a sheet made of a highly thermally conductive material having a higher thermal conductivity than the material of the yoke 13 may be provided as the heat conducting member.

[0052] The magnets 14 are arranged in a Halbach array, and the ridges 34 are formed at positions corresponding to the circumferential positions of the boundary surface between the first magnet 31 and the third magnet 33 and the boundary surface between the second magnet 32 ​​and the third magnet 33. By applying the ridges 34 to the Halbach array motor 1, which has many boundary surfaces that concentrate magnetic flux, a large number of the ridges 34 can provide a great cooling effect.

[0053] Although the description of specific embodiments has been completed above, the present invention is not limited to the above-described embodiments and modifications, and can be implemented in a wide variety of modifications. For example, in the above-described embodiments, the rotor according to the present invention is applied to the rotor 4 of an inner rotor motor 1, but it may also be applied to the outer rotor of an outer rotor motor. In this case, the yoke 13 may be disposed radially outside the magnets 14. The rotor may also be applied to a generator rather than the motor 1. In this embodiment, the rotor 4 is equipped with magnets 14 in a Halbach array, but the magnet arrangement is not limited to this. In addition, the specific configuration, arrangement, quantity, and material of each member and part can be changed as appropriate without departing from the spirit of the present invention. Furthermore, not all of the components shown in the above-described embodiments are necessarily required, and can be selected as appropriate. [Explanation of symbols]

[0054] 1: Motor (an example of a rotating electrical machine) 2:Axis 4: Rotor 13: Yoke (rotor core) 13a: Outer surface 13b: Inner surface 14: Magnet 31: First magnet 32: Second magnet 33: Third magnet 34: protrusion 35: Heat sink (an example of a thermal conductive material) 35a: Vapor chamber

Claims

1. A rotor of a rotating electric machine, a plurality of magnets arranged in a predetermined circumferential arrangement; and a yoke arranged radially inside the magnets to hold the magnets, the predetermined arrangement is a Halbach array in which a third magnet having a magnetic pole direction facing the circumferential direction is disposed between a first magnet having a magnetic pole direction facing radially inward and a second magnet having a magnetic pole direction facing radially outward, the first magnet and the second magnet have the same shape and size, and the third magnet has a smaller size in the circumferential direction than the first magnet and the second magnet; the yoke has a plurality of thick portions, including a plurality of first thick portions formed at positions corresponding to each circumferential position of a boundary surface between the first magnet and the third magnet adjacent to each other in the circumferential direction, and a plurality of second thick portions formed at positions corresponding to each circumferential position of a boundary surface between the second magnet and the third magnet, each thick portion is formed by a protrusion that protrudes radially from an inner peripheral surface of the yoke and extends along an axis of the rotor; Each of the ridges has an arc-shaped profile in a cross section perpendicular to the axis, The thick portions are arranged at intervals in the circumferential direction so as not to overlap with one another, A rotor for a rotating electric machine, wherein a first gap is formed between the first thick-walled portion and the second thick-walled portion that are adjacent to each other in the circumferential direction, and a second gap larger than the first gap is formed between two of the first thick-walled portions and two of the second thick-walled portions that are adjacent to each other in the circumferential direction.

2. 2. The rotor for a rotating electric machine according to claim 1, further comprising at least one heat conducting member arranged in contact with said magnet at a portion of said yoke facing said circumferential center portion of said magnet.

3. 3. The rotor for a rotating electric machine according to claim 2, wherein said heat conducting member is sandwiched between said yoke and said magnet.

4. 4. The rotor of claim 3, wherein said heat conducting member is a heat sink having a vapor chamber.

5. The rotor further comprises a rotating shaft extending along the axis line, and a rotor hub disposed around the rotating shaft; The cylindrical yoke is provided at the outer end of the rotor hub, 5. The rotor for a rotating electric machine according to claim 1, wherein the rotor hub is disposed to one side of the yoke in the axial direction.

6. A rotor for a rotating electric machine described in any one of claims 1 to 4, wherein all of the protrusions have the same shape and dimensions.

7. A rotor of a rotating electric machine described in any one of claims 2 to 4, wherein the heat conduction member does not overlap with the thick portion in the circumferential direction.

8. A rotor for a rotating electrical device as described in Claim 7, wherein the heat conduction member is arranged only in the portion of the yoke corresponding to the second spacing.

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