JP2024049706A - Stator cooling structure for rotating electrical machine - Google Patents

Abstract

[Problem] To improve stator cooling performance regardless of the attitude of a rotating electric machine. [Solution] The stator cooling structure includes a stator cover 20 including a first portion 21 disposed between a stator 5 and a rotor 4 and a second portion 22 facing a coil 19 in the axial direction, and covers the stator 5 in cooperation with the case to define a cooling passage 25 for cooling the stator 5, an annular passage 28 formed in the second portion 22 of the stator 5 cover in an annular shape facing the coil 19 and through which a coolant is supplied, a plurality of communication holes 29 formed in the second portion 22 of the stator 5 cover corresponding to each of the coils 19 and connecting the annular passage 28 to the cooling passage 25, and a protrusion 35 formed on the second portion 22 of the stator cover 20 so as to extend radially and enter between a pair of coils 19 adjacent to each other in the circumferential direction. [Selected Figure] Figure 1

Description

The present invention relates to a stator cooling structure for a rotating electrical machine.

Conventionally, motors with an oil-cooled structure in which the coils are cooled with oil are known. Patent Document 1 is known as a cooling structure for a motor in which all coils are sprayed with oil 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 contains 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 supplied to the multiple injection holes at a predetermined pressure through the circumferential passage is sprayed toward the gaps between the coils, and the oil is sprayed onto all coils.

Patent No. 5347380

However, in the above-mentioned conventional technology, the oil ejected from the nozzle loses momentum when it adheres to the coil. When the motor is used with the rotating shaft vertical and the nozzle is provided above the coil, the oil flows to the bottom end of the coil while remaining attached to the coil, and the entire coil is cooled. However, in any other position, the oil that has adhered to the coil and lost momentum flows circumferentially due to gravity, and there is a risk that the coil located at a high position will not be sufficiently cooled. Therefore, improvements in cooling performance are desired.

In view of the above background, the present invention aims to improve the stator cooling performance regardless of the attitude of the rotating electric machine.

In order to solve the above problem, one aspect of the present invention is a stator cooling structure for a rotating electric machine (1), which includes 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 the axis (2) of the rotating electric machine and each of which is wound with a coil (19), 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, and which cooperates with the case to cover the stator. The stator cover (20) defines a cooling passage (25) for cooling the stator, an annular passage (28) is formed in the second part of the stator cover so as to face the coil and through which a coolant is supplied, a plurality of communication holes (29) are formed in the second part of the stator cover so as to correspond to each of the coils and connect the annular passage to the cooling passage, and a protrusion (35) is formed on the second part of the stator cover so as to extend in the radial direction of the rotating electric machine and to protrude between a pair of the coils adjacent to each other in the circumferential direction of the rotating electric machine.

According to this aspect, the coolant supplied to the annular passage passes through multiple communication holes, is distributed approximately evenly to the multiple coils, and is then supplied to the cooling passage. The coolant supplied evenly to each coil is prevented from flowing toward the adjacent coil by the presence of the ridges, and flows through the cooling passage along the corresponding coil to cool 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 flowing circumferentially, so that all of the coils are cooled approximately evenly regardless of the attitude of the rotating electric machine. This improves the stator cooling performance.

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 the plurality of communication holes and the plurality of ridges are preferably formed in the passage forming member.

This aspect makes it easy to form the annular passage, the communication holes, and the protrusions, and allows the protrusions to have the desired shape.

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

According to this aspect, since the protrusion includes a base and an extension, the protrusion dimension of the protrusion can be increased to match the arrangement space, thereby improving the cooling passage partitioning effect of the protrusion.

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.

According to this embodiment, the shape of the tip of the ridge that functions as a partition can be made to match the contour curve of the adjacent coil. This reduces the gap between the ridge and the coil, suppressing the mixing of the refrigerant (leakage to the other coil), improving the directionality of the refrigerant flow. Therefore, the multiple coils are cooled more evenly.

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

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 coil from the communication hole from flowing to the adjacent coil. This allows the multiple coils to be cooled more evenly.

In the above aspect, the passage forming member may be an integrally molded resin product in which the multiple extensions are integral with the multiple bases.

In this embodiment, the base and extension of the multiple protrusions that function as partitions are integrally molded into the passage forming member, reducing the number of parts and improving assembly, thereby increasing productivity.

The above aspects allow for improved stator cooling performance regardless of the position of the rotating electric machine.

1 is a cross-sectional view of a motor according to an embodiment of the present invention; An exploded perspective view of the outer part of the motor FIG. 3 is a perspective view showing an outer portion of the motor in a cutaway view. FIG. 4 is an enlarged cross-sectional view of part IV in FIG. FIG. 4 is a perspective view of a main part of the cover member as viewed from the inside; FIG. 1 is an exploded cross-sectional view of a main part of a stator, the cross-section passing through a communication hole. Graph showing the relationship between the size of the communication hole and the cooling performance 3 is a cross-sectional view showing three modified examples of the protrusions.

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

Figure 1 is a cross-sectional view of a motor 1 according to an embodiment. As shown in Figure 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 around 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 type motor. The motor 1 is used in the position shown in Figure 1 in which the axis 2 extends horizontally, but it may also be used in a position in which the axis 2 extends vertically.

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 housing 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 is formed in the bottom wall 9 of the case body 6 and the case lid 7, centered on the axis 2.

The rotor 4 includes a rotating shaft 11 that extends along the axis 2 and forms 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 in conjunction with the rotation of the rotor hub 12.

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 the 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, is formed integrally with the outer edge of the rotor hub 12, and rotates 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.

The stator 5 is arranged along the 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) arranged on the outside of 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 arranged around the axis 2. The teeth 16 are arranged in the circumferential direction along the teeth retaining ring 17 and protrude radially inward from the inner surface of the teeth retaining ring 17.

2 is an exploded perspective view of the outer part of the motor 1 shown in FIG. 1. As also shown in FIG. 2, a stator cover 20 that cooperates with the case body 6 to cover the stator 5 is attached to the case body 6. As shown in the enlarged view of FIG. 1, the stator cover 20 includes a cylindrical first part 21, a ring-shaped second part 22 that extends radially outward from one axial end of the first part 21, and a ring-shaped third part 23 that extends radially inward from the other axial end of the first part 21. The stator cover 20 is a non-magnetic material with low magnetic permeability, and may be, for example, an injection-molded product of a synthetic resin. The first part 21 is disposed between the stator 5 and the rotor 4 (i.e., the above-mentioned gap). The second part 22 faces the coil 19 in the axial direction of the motor 1, and is in close contact with the side wall 8 of the case body 6 via a seal member 24 at its outer edge. The third portion 23 adheres to the bottom wall 9 of the case body 6 at its inner edge via a seal member 24.

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.

Figure 3 is a perspective view showing the outer part of the motor 1 in a cutaway state. As shown in Figures 1 and 3, the stator cover 20 has a cover body 26 that constitutes the first part 21, a part of the second part 22, and the third part 23, and an annular passage forming member 27 attached to the cover body 26 in the second part 22. The passage forming member 27 is a member for forming an annular passage 28 for distributing refrigerant to the cooling passage 25 at a position facing the coil 19, and defines the side of the annular passage 28 close to the coil 19. The cover body 26 defines the side of the annular passage 28 away from the coil 19.

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 after molding so as to be integral with the cover body 26 by adhesive, welding, or the like. In this way, the annular passage 28 is formed by the cover body 26 and the passage forming member 27, so that the annular passage 28 can be easily formed.

The passage forming member 27 is formed with a plurality of communication holes 29 that connect the annular passage 28 to the cooling passage 25. A refrigerant supply passage 30 that connects to the upper part of the annular passage 28 is formed at the upper end of the case body 6. 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.

Between the bottom wall 9 of the case body 6 and the coil 19, an annular collecting passage 31 is provided to collect the refrigerant that has passed through the cooling passage 25 to cool the coil 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 coil 19 and is collected by the collecting passage 31 is discharged to the outside through the refrigerant discharge passage 33.

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

In addition, a protrusion 35 is formed in each of the portions of the passage forming member 27 corresponding to the space between two adjacent communication holes 29. The protrusion 35 extends in the radial direction of the motor 1 and is arranged to enter the gap formed between two coils 19 adjacent to each other in the circumferential direction. As shown by the arrows in FIG. 6, the refrigerant supplied to each coil 19 is prevented from flowing toward the adjacent coil 19 by the presence of the protrusion 35, and 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 supplied evenly to the coils 19 flows along the coils 19 without flowing in the circumferential direction. As a result, all coils 19 are cooled approximately evenly regardless of the position of the motor 1. Therefore, the stator cooling performance is improved.

As described above, the multiple communication holes 29 and multiple protrusions 35 are formed in the passage forming member 27. Therefore, the communication holes 29 and protrusions 35 are easily formed, and the protrusions 35 can be formed into the desired shape.

As shown in FIG. 6, the ridge 35 is formed to protrude from the passage forming member 27 and includes a base 36 having a first width W1 in the circumferential direction and an extension 37 having a second width W2 smaller than the first width W1 and protruding further in the axial direction from the circumferential center of the base 36. The base 36 of the ridge 35 is arranged so that its tip enters between the two coils 19. The extension 37 of the ridge 35 is arranged so that its tip enters between the two coils 19. By including the base 36 and the extension 37 in this way, it is possible to increase the protruding dimension of the ridge 35 to match the arrangement space. This improves the partitioning effect of the ridge 35 on the cooling passage 25.

As shown in Figures 4 and 5, the extension 37 has a pair of protrusions 38 that protrude further in the axial direction than the radial middle part at both radial ends so as to follow the contours of a pair of circumferentially adjacent coils 19. In other words, the extension 37 has a U-shape (staple shape). In this way, the pair of protrusions 38 protrude to fill the gap between the coils 19, effectively preventing the refrigerant supplied to the coils 19 from the communication hole 29 from flowing to the adjacent coils 19. This allows the multiple coils 19 to be cooled more evenly.

The extension 37 of the protrusion 35 may be formed from the same material as the base 36, or from a material different from the base 36. In this embodiment, the extension 37 is formed from a material different from the base 36. In this case, the extension 37 is preferably formed from a material that has a smaller 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.

As shown in FIG. 5, the extensions 37 of the ridges 35 are connected to each other by rings 39 on the radially outer side and molded integrally with the base 36 to form a ring. In other words, the passage forming member 27 is a one-piece molded resin product in which the multiple extensions 37 are molded integrally with the multiple bases 36 and connected to each other to form a ring. In this way, the bases 36 and extensions 37 of the multiple ridges 35 that function as partitions are molded integrally with the passage forming member 27, reducing the number of parts and improving assembly, thereby improving productivity.

Here, the relationship between the dimensions of the communication hole 29 and the stator cooling performance will be explained. If the communication hole 29 is large, the pressure loss is small, but the refrigerant cannot be distributed evenly to the cylindrical cooling passage 25, and the refrigerant supply amount to each coil 19 varies greatly. Conversely, if the communication hole 29 is small, the refrigerant supply amount to each coil 19 varies little, but the pressure loss is large. Therefore, the inventor confirmed the relationship between the pressure loss and the variation in the refrigerant supply amount for each case in which the communication hole 29 is a square and the length of one side of the communication hole 29 is 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 refrigerant supply amount is the difference between the maximum flow rate and the minimum flow rate, and is expressed as the flow rate. The results are as shown in Figure 7.

Figure 7 is a graph showing the relationship between the dimensions of the communication holes 29 and the cooling performance. As shown in Figure 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.

<<Variations>>
Next, a modified example of the cooling structure according to the embodiment will be described with reference to FIG. 8. Elements that are the same as or similar to those in the above embodiment are given the same reference numerals, and duplicated descriptions will be omitted. FIGS. 8(A) to (C) show three modified examples. In these modified examples, the shape of the extension 37 of the protrusion 35 is different from that of the above embodiment. In each modified example, the extension 37 has a tapered shape in which the width on the front end side is narrower than the width on the base end side. In FIG. 8, a pair of extensions 37 are shown with their tips facing each other to facilitate understanding of the deformation action described below. In the modified example of FIG. 8(A), the width of the tip of the extension 37 is slightly smaller than the width of the base end. In the modified example of FIG. 8(C), the width of the tip of the extension 37 is approximately 0. In the modified example of FIG. 8(B), the width of the tip of the extension 37 is intermediate between the widths of (A) and (C), and is approximately half the width of (A).

In either example, the extension 37 is arranged so that the tapered tip portion follows the contour curve of a pair of circumferentially adjacent coils 19. In this way, the extension 37 has a tapered shape that follows the contour curve of a pair of circumferentially adjacent coils 19, so that the shape of the tip of the ridge 35 that functions as a partition can follow the contour curve of the adjacent coil 19. This reduces the gap between the ridge 35 and the coil 19, suppressing the mixing of the refrigerant (leakage to the other coil 19), improving the directionality of the refrigerant flow. Therefore, the multiple coils 19 are cooled more evenly.

The smaller the width of the tip of the extension 37, the easier it is to bend (the easier it is to deform at the tip). Therefore, if there is a pressure difference on both sides of the width of the extension 37, the extension 37 will bend, causing the refrigerant to flow from the higher pressure side to the lower pressure side, reducing the pressure difference on 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 easier to bend for the protrusions 35 located in positions of low pressure and harder to bend for the protrusions 35 located in positions of high pressure.

Although the description of the specific embodiment is finished above, the present invention is not limited to the above embodiment and modified examples, and can be widely modified. For example, in the above embodiment, the present invention is applied to the motor 1, but the present invention can be applied to a rotating electric machine, and may be applied to a generator or a motor generator. Furthermore, the motor 1 may be used in a position in which the axis 2 is inclined relative to the horizontal plane, or in a position in which the axis 2 extends vertically. In addition, the specific configuration, arrangement, quantity, material, etc. of each member and part can be appropriately changed within the scope of the invention. Furthermore, the above embodiment may be combined with some or all of the configurations. On the other hand, not all of the components shown in the above embodiment are necessarily required, and can be selected as appropriate.

1: Motor (an example of a rotating electrical machine)
Reference Signs List 2: Axis 3: Case 4: Rotor 5: Stator 16: Teeth 18: Stator core 19: Coil 20: Stator cover 21: First portion 22: Second portion 25: Cooling passage 26: Cover body 27: Passage forming member 28: Annular passage 29: Communication hole 35: Ridge 36: Base portion 37: Extension portion 38: Protrusion

Claims (6)

A stator cooling structure for a rotating electric machine, comprising:
Case and
a stator having a stator core fixed to the case, the stator core including a plurality of teeth arranged in an annular shape around an axis of the rotating electric machine, each of the teeth being wound with a coil;
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 coolant is supplied;
a plurality of communication holes formed in the second portion of the stator cover so as to correspond 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 radially of the rotating electric machine and penetrating between a pair of the coils adjacent to each other in the circumferential direction of the rotating 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 and 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 said communication holes and a plurality of said protrusions are formed in said passage forming member. The stator cooling structure of a rotating electric machine according to claim 2, wherein 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 portion in the circumferential direction. The stator cooling structure of a rotating electric machine according to claim 3, wherein the extension portion has a tapered shape that follows the contour curves of a pair of the coils adjacent to each other in the circumferential direction. The stator cooling structure for a rotating electric machine according to claim 3 or 4, wherein the extension portion has a pair of protrusions that protrude further in the axial direction than the radial middle portion at both ends in the radial direction so as to follow the contours of a pair of the coils adjacent to each other in the circumferential direction. The stator cooling structure for a rotating electric machine according to claim 3 or 4, wherein the passage forming member is an integrally molded resin product in which the multiple extensions are integral with the multiple bases.

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