Stator cooling structure for rotating electrical machine

Abstract

To improve a stator cooling performance regardless of a posture of a rotary electric machine.SOLUTION: A stator cooling structure includes: a stator cover 20 that includes a first part 21 arranged between a stator 5 and a rotor 4, and a second part 22 facing coils 19 in an axial direction, and defines a cooling path 25 for cooling the stator 5 by covering the stator 5 in cooperation with a case; an annular path 28 that is formed in an annular shape so as to face the coils 19 in the second part 22 of the cover of the stator 5, and that is supplied with a coolant; a plurality of communication holes 29 that is formed in the second part 22 of the cover of the stator 5 so as to correspond to the coils 19, respectively, and causes the annular path 28 to communicate with the cooling path 25; and projections 35 that are formed in the second part 22 of the stator cover 20 so as to each enter between the coils 19 extending in a radial direction and adjacent to each other in a peripheral direction in each one pair.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a stator cooling structure for a rotating electrical machine. [Background technology]

[0002] Conventionally, motors with an oil-cooled structure in which coils are cooled with oil are known. Patent Document 1 discloses a motor cooling structure in which oil is sprayed onto all coils to improve cooling capacity. In this cooling structure, a circumferential oil passage extending along the circumferential direction of the motor is formed inside a housing that houses a rotor and a stator core, and multiple injection holes for cooling the coils are arranged along the circumferential direction facing the gaps between the coils. Oil is supplied to the multiple injection holes at a predetermined pressure through the circumferential passage and sprayed toward the gaps between the coils, so that all coils are sprayed with oil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5347380 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional technology, the oil ejected from the ejection holes loses momentum when it adheres to the coil. When the motor is used with the rotating shaft vertical and the ejection holes are located above the coil, the oil remains attached to the coil and flows to the bottom end of the coil, cooling the entire coil. However, in other positions, the oil that has lost momentum after adhering to the coil flows circumferentially due to gravity, which may result in the coil being insufficiently cooled. Therefore, improvements in cooling performance are desired.

[0005] In view of the above background, an object of the present invention is to improve the stator cooling performance regardless of the attitude of the rotating electrical machine. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, one aspect of the present invention is a stator cooling structure for a rotating electric machine (1), comprising: a case (3); a stator (5) fixed to the case and having a stator core (18) with a plurality of teeth (16) arranged in an annular shape around an axis (2) of the rotating electric machine and each having a coil (19) wound thereon; a rotor (4) supported by the case so as to be rotatable around the axis; a first portion (21) disposed between the stator and the rotor; and a second portion (22) facing the coil in the axial direction of the rotating electric machine, which cooperates with the case to cover the stator. The rotating electric machine has a stator cover (20) that defines a cooling passage (25) for cooling the stator, an annular passage (28) that is formed in an annular shape in the second portion of the stator cover so as to face the coils and through which a refrigerant is supplied, a plurality of communication holes (29) that are formed in the second portion of the stator cover so as to correspond to each of the coils and that connect the annular passage to the cooling passage, and protrusions (35) that extend in the radial direction of the rotating electric machine and are formed in the second portion of the stator cover so as to protrude and enter between a pair of the coils that are adjacent to each other in the circumferential direction of the rotating electric machine.

[0007] According to this aspect, the coolant supplied to the annular passage passes through the multiple communication holes, is distributed approximately evenly to the multiple coils, and is then supplied to the cooling passage. The ridges prevent the coolant supplied evenly to each coil from flowing toward adjacent coils, and the coolant flows through the cooling passage along the corresponding coil, cooling the coil. In this way, the ridges function as partition walls, and the coolant supplied evenly to the coils flows along the coils rather than circumferentially, thereby cooling all coils approximately evenly regardless of the orientation of the rotating electric machine. This improves stator cooling performance.

[0008] In the above aspect, the stator cover includes a cover body (26) that defines the side of the annular passage away from the coil, and a passage forming member (27) that is attached to the cover body and defines the side of the annular passage close to the coil, and it is preferable that a plurality of the communicating holes and a plurality of the protrusions are formed in the passage forming member.

[0009] According to this aspect, it is easy to form the annular passage, the communication holes, and the protrusions, and the protrusions can be formed in a desired shape.

[0010] In the above aspect, the protrusion may include a base (36) that is protruding from the passage forming member and has a first width in the circumferential direction, and an extension (37) that has a second width smaller than the first width and that protrudes further in the axial direction from the center of the base in the circumferential direction.

[0011] According to this aspect, since the protrusion includes a base portion and an extension portion, the protrusion dimension can be increased to suit the installation space, thereby improving the cooling passage partitioning effect of the protrusion.

[0012] In the above aspect, the extension may have a tapered shape that follows the contour curves of a pair of the coils that are adjacent to each other in the circumferential direction.

[0013] According to this configuration, the shape of the tip of the ridges that function as partitions can be made to match the contour curves of the adjacent coils. This reduces the gap between the ridges and the coils, suppressing refrigerant mixing (leakage to other coils), improving the directionality of the refrigerant flow. This allows multiple coils to be cooled more evenly.

[0014] In the above aspect, the extension portion may have a pair of protrusions (38) at both radial ends that protrude further in the axial direction than the radial middle portion, so as to follow the contours of a pair of coils that are adjacent to each other in the circumferential direction.

[0015] According to this aspect, the extension is U-shaped and the pair of protrusions protrude to fill the gap between the coils, effectively preventing the refrigerant supplied to the coils from flowing to adjacent coils through the communication holes, thereby more evenly cooling the multiple coils.

[0016] In the above aspect, the passage forming member may be an integrally molded resin product in which the plurality of extension portions are integral with the plurality of base portions.

[0017] According to this aspect, the bases and extensions of the plurality of protrusions that function as partitions are integrally molded with the passage forming member, thereby reducing the number of parts and improving assembly, thereby increasing productivity. [Effects of the Invention]

[0018] According to the above aspect, the stator cooling performance can be improved regardless of the attitude of the rotating electrical machine. [Brief explanation of the drawings]

[0019] [Figure 1] Cross-sectional view of a motor according to an embodiment [Figure 2] An exploded perspective view of the outer part of the motor [Figure 3] FIG. 1 is a perspective view showing an outer portion of a motor in section. [Figure 4] Enlarged cross-sectional view of part IV in Figure 3 [Figure 5] 1 is a perspective view of a main part of a cover member as viewed from the inside. [Figure 6] An expanded cross-sectional view of a main part of a stator, showing a cross section passing through a communication hole. [Figure 7] Graph showing the relationship between the size of the communication holes and the cooling performance [Figure 8] Cross-sectional view showing three variations of the protrusion DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of a motor 1 to which a cooling structure according to the present invention is applied will be described in detail with reference to the drawings.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] FIG. 2 is an exploded perspective view of the outer portion of the motor 1 shown in FIG. 1. As also shown in FIG. 2, 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 a seal member 24 at its inner edge.

[0027] 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.

[0028] Fig. 3 is a cutaway perspective view of the outer portion of the motor 1. As shown in Figs. 1 and 3, the stator cover 20 has a cover body 26 that forms the first portion 21, part of the second portion 22, and the third portion 23, and an annular passage-forming member 27 attached to the cover body 26 in the second portion 22. The passage-forming member 27 is a member that forms an annular passage 28 that distributes refrigerant to the cooling passages 25 at a position facing the coil 19, and defines the side of the annular passage 28 that is close to the coil 19. The cover body 26 defines the side of the annular passage 28 that is away from the coil 19.

[0029] In this embodiment, the passage forming member 27 is integrally attached to the cover body 26 by being molded integrally with the cover body 26. In other embodiments, the passage forming member 27 may be attached to the cover body 26 by adhesive, welding, or the like after molding so as to be integral with the cover body 26. Since the annular passage 28 is formed by the cover body 26 and the passage forming member 27 in this way, the annular passage 28 can be easily formed.

[0030] A plurality of communication holes 29 are formed in the passage forming member 27, which connect the annular passage 28 to the cooling passage 25. A refrigerant supply passage 30 is formed in the upper end of the case body 6, which communicates with the upper part of the annular passage 28. The refrigerant supplied from the refrigerant supply passage 30 to the annular passage 28 passes through the communication holes 29 and is distributed approximately evenly to the cylindrical cooling passage 25.

[0031] An annular collecting passage 31 is provided between the bottom wall 9 of the case body 6 and the coils 19 to collect the refrigerant that has passed through the cooling passages 25 to cool the coils 19 of the stator 5. The collecting passage 31 is formed by an annular recess 32 formed on the inner surface of the bottom wall 9 on the cooling passage 25 side. A refrigerant discharge passage 33 that communicates with the lower part of the collecting passage 31 is formed at the lower end of the case body 6. The refrigerant that has cooled the coils 19 and is collected by the collecting passage 31 is discharged to the outside through the refrigerant discharge passage 33.

[0032] Fig. 4 is an enlarged cross-sectional view of part IV in Fig. 3, Fig. 5 is a perspective view of the main part of the cover member as viewed from the inside, and Fig. 6 is an exploded cross-sectional view of the main part of the stator shown in a cross section passing through communication holes 29. As shown in Figs. 4 to 6, communication holes 29 are provided in the passage forming member 27 for each of the plurality of coils 19 so as to correspond to each of the plurality of coils 19. Therefore, the refrigerant flowing through the annular passage 28 passes through the communication holes 29, is distributed approximately evenly to the plurality of coils 19, and is supplied to the cooling passage 25.

[0033] Furthermore, a protrusion 35 is formed in each portion of the passage forming member 27 corresponding to the gap between two adjacent communication holes 29. The protrusion 35 extends radially of the motor 1 and is positioned to enter a gap formed between two circumferentially adjacent coils 19. As shown by the arrows in FIG. 6 , the presence of the protrusion 35 prevents the refrigerant supplied to each coil 19 from flowing toward the adjacent coil 19, and the refrigerant flows through the cooling passage 25 along the corresponding coil 19 to cool the coil 19. In this way, the protrusion 35 functions as a partition wall, and the refrigerant evenly supplied to the coils 19 flows along the coil 19 instead of flowing circumferentially. This allows all of the coils 19 to be cooled approximately uniformly, regardless of the orientation of the motor 1. This improves stator cooling performance.

[0034] As described above, the plurality of communication holes 29 and the plurality of ridges 35 are formed in the passage forming member 27. Therefore, the communication holes 29 and the ridges 35 are easily formed, and the ridges 35 can be formed in a desired shape.

[0035] As shown in FIG. 6 , the ribs 35 are formed to protrude from the passage-forming member 27 and include a base 36 having a first circumferential width W1 and an extension 37 having a second width W2 smaller than the first width W1 and extending further in the axial direction from the circumferential center of the base 36. The base 36 of the ribs 35 is positioned so that its tip extends between the two coils 19. The extension 37 of the ribs 35 is positioned so that its tip extends between the two coils 19. Since the ribs 35 include the base 36 and the extension 37, the protrusion dimension of the ribs 35 can be increased to suit the installation space. This improves the partitioning effect of the ribs 35 on the cooling passages 25.

[0036] 4 and 5, the extension portion 37 has a pair of protrusions 38 at both radial ends that protrude further in the axial direction than the radially intermediate portion, so as to follow the contours of a pair of circumferentially adjacent coils 19. In other words, the extension portion 37 has a U-shape (staple shape). The pair of protrusions 38 protrude in this manner so as to fill the gaps between the coils 19, thereby effectively preventing the refrigerant supplied to the coils 19 from the communication holes 29 from flowing to the adjacent coils 19. This allows the multiple coils 19 to be cooled more evenly.

[0037] The extension 37 of the protrusion 35 may be formed from the same material as the base 36, or from a different material from the base 36. In this embodiment, the extension 37 is formed from a different material from the base 36. In this case, the extension 37 is preferably formed from a material that has a lower elastic modulus and is more easily deformed than the material of the base 36. In either case, the extension 37 is preferably molded integrally with the base 36.

[0038] As shown in Fig. 5, the extensions 37 of the ridges 35 are connected to one another by rings 39 on the radially outer side and integrally molded with the base 36 to form an annular shape. That is, the passage forming member 27 is an integrally molded resin product in which the extensions 37 are integral with the bases 36 and connected to one another to form an annular shape. In this way, the bases 36 and extensions 37 of the multiple ridges 35 that function as partitions are integrally molded with the passage forming member 27, thereby reducing the number of parts and improving assembly, thereby improving productivity.

[0039] Here, we explain the relationship between the dimensions of the communication holes 29 and the stator cooling performance. Large communication holes 29 reduce pressure loss, but the refrigerant cannot be distributed evenly throughout the cylindrical cooling passages 25, resulting in significant variations in the amount of refrigerant supplied to each coil 19. Conversely, small communication holes 29 reduce variation in the amount of refrigerant supplied to each coil 19, but increase pressure loss. Therefore, the inventors tested the relationship between pressure loss and variation in the amount of refrigerant supplied for square communication holes 29 with side lengths of 0.75 mm, 0.8 mm, and 0.9 mm. The refrigerant temperature was 80°C, and the refrigerant flow rate was 15 L / min. The variation in the amount of refrigerant supplied is the difference between the maximum and minimum flow rates, expressed as flow rate. The results are shown in Figure 7.

[0040] Fig. 7 is a graph showing the relationship between the dimensions of the communication holes 29 and the cooling performance. As shown in Fig. 7, in this embodiment, when the length of one side of the communication holes 29 is 0.8 mm, the pressure loss is 38 kPa and the variation is 0.0063 L / min, which was determined to be optimal. The dimensions of the communication holes 29 may be set appropriately depending on the number of communication holes 29, the temperature and viscosity of the refrigerant, the amount of refrigerant supplied, the refrigerant pressure, etc.

[0041] <<Variations>> Next, modified cooling structures according to the embodiment will be described with reference to FIG. 8. Elements identical or similar to those in the above embodiment are designated by the same reference numerals, and redundant description will be omitted. FIGS. 8A to 8C show three modified examples. In these modified examples, the shape of the extensions 37 of the ribs 35 differs from that of the above embodiment. In all modified examples, the extensions 37 have a tapered shape, with the width at the leading end being narrower than the base end. In FIG. 8, a pair of extensions 37 are shown with their tips facing each other to facilitate understanding of the deformation mechanism described below. In the modified example of FIG. 8A, the width at the leading end of the extensions 37 is slightly smaller than the width at the base end. In the modified example of FIG. 8C, the width at the leading end of the extensions 37 is approximately zero. In the modified example of FIG. 8B, the width at the leading end of the extensions 37 is intermediate between the widths of (A) and (C), and is approximately half the width of (A).

[0042] In either example, the extensions 37 are arranged so that the tapered tip portions thereof follow the contour curves of a pair of circumferentially adjacent coils 19. By forming the extensions 37 in a tapered shape that follows the contour curves of a pair of circumferentially adjacent coils 19, the shape of the tip portions of the ridges 35 that function as partitions can be made to follow the contour curves of the adjacent coils 19. This reduces the gap between the ridges 35 and the coils 19, suppressing refrigerant mixing (leakage toward other coils 19), and improving the directionality of the refrigerant flow. Therefore, the multiple coils 19 are cooled more evenly.

[0043] The smaller the width of the tip of the extension 37, the more easily it bends (the more easily it deforms at the tip). Therefore, when there is a pressure difference between both sides of the width of the extension 37, the extension 37 bends, causing the refrigerant to flow from the higher pressure side to the lower pressure side, thereby reducing the pressure difference between both sides of the extension 37. Therefore, it is advisable to adjust the flow rate of the refrigerant flowing in the circumferential direction by making the extension 37 more flexible for the protrusions 35 arranged in positions where pressure is low and by making the extension 37 less flexible for the protrusions 35 arranged in positions where pressure is high.

[0044] 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 present invention is applied to motor 1. However, the present invention can also be applied to a rotating electric machine, such as a generator or a motor-generator. Furthermore, motor 1 may be used with its axis 2 inclined relative to a horizontal plane or with its axis 2 extending vertically. Furthermore, the specific configuration, arrangement, quantity, and materials of each member and part can be modified as appropriate without departing from the spirit of the present invention. Furthermore, some or all of the configurations of the above-described embodiments may be combined with each other. Meanwhile, not all of the components shown in the above-described embodiments are necessarily required, and can be selected as appropriate. [Explanation of symbols]

[0045] 1: Motor (an example of a rotating electrical machine) 2: Axis 3: Case 4: Rotor 5: Stator 16: Teeth 18: Stator core 19: Coil 20: Stator cover 21 :1st part 22:Second part 25: Cooling passage 26: Cover body 27: Passage forming member 28: Circular passage 29:Communication hole 35: protrusion 36: Base 37: Extension part 38: Protrusion

Claims

1. A stator cooling structure for a rotating electric machine, Case and a stator having a stator core fixed to the case, the stator core including a plurality of teeth arranged annularly around an axis of the rotary electric machine, each of the teeth having a coil wound thereon; a rotor supported by the case so as to be rotatable about the axis; a stator cover including a first portion disposed between the stator and the rotor and a second portion facing the coil in the axial direction of the rotating electric machine, the stator cover covering the stator in cooperation with the case to define a cooling passage for cooling the stator; an annular passage formed in the second portion of the stator cover so as to face the coil and through which a refrigerant is supplied; a plurality of communication holes formed in the second portion of the stator cover corresponding to the coils, the communication holes connecting the annular passage to the cooling passage; a plurality of protrusions formed on the second portion of the stator cover, the protrusions extending radially in the radial direction of the rotating electric machine and protruding toward between the coils so as to enter between a pair of the coils adjacent to each other in the circumferential direction of the rotating electric machine;

2. the stator cover includes a cover body defining a side of the annular passage away from the coil, and a passage forming member attached to the cover body defining a side of the annular passage adjacent to the coil, The stator cooling structure for a rotating electrical machine according to claim 1 , wherein a plurality of the communication holes and a plurality of the protrusions are formed in the passage forming member.

3. A stator cooling structure for a rotating electrical machine, comprising: Case and a stator having a stator core fixed to the case, the stator core including a plurality of teeth arranged annularly around an axis of the rotary electric machine, each of the teeth having a coil wound thereon; a rotor supported by the case so as to be rotatable about the axis; a stator cover including a first portion disposed between the stator and the rotor and a second portion facing the coil in the axial direction of the rotating electric machine, the stator cover covering the stator in cooperation with the case to define a cooling passage for cooling the stator; an annular passage formed in the second portion of the stator cover so as to face the coil and through which a refrigerant is supplied; a plurality of communication holes formed in the second portion of the stator cover corresponding to the coils, the communication holes connecting the annular passage to the cooling passage; a protrusion formed on the second portion of the stator cover, the protrusion extending in a radial direction of the rotary electric machine and extending between a pair of the coils adjacent to each other in a circumferential direction of the rotary electric machine; the stator cover includes a cover body defining a side of the annular passage away from the coil, and a passage forming member attached to the cover body defining a side of the annular passage adjacent to the coil, a plurality of the communication holes and a plurality of the protrusions are formed in the passage forming member, the protrusion is formed to protrude from the passage forming member and includes a base portion having a first width in the circumferential direction, and an extension portion having a second width smaller than the first width and protruding further in the axial direction from the center of the base in the circumferential direction.

4. 4. The stator cooling structure for a rotating electric machine according to claim 3, wherein the extension portion has a tapered shape that follows contour curves of a pair of the coils that are adjacent to each other in the circumferential direction.

5. 5. The stator cooling structure of claim 3, wherein the extension portion has a pair of protrusions at both radial ends that protrude further in the axial direction than the radial middle portion, so as to follow the contours of a pair of the coils that are adjacent to each other in the circumferential direction.

6. 5. The stator cooling structure for a rotating electrical machine according to claim 3, wherein the passage forming member is an integrally molded resin product in which the plurality of extension portions are integral with the plurality of base portions.

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