Coil and rotary electric machine

Abstract

This coil is attached to a stator core that covers, from the outer peripheral side, a rotor that is rotatable about an axis. The coil comprises: a plurality of unit coils; and a sealing body that seals the plurality of unit coils on both sides in the axial direction. Each unit coil has a pair of divided bodies that are divided in the radial direction using divided surfaces thereof as a reference, and a recessed groove is formed on at least one divided surface among the pair of divided bodies and forms a refrigerant flow path through which refrigerant flows. The stator core has an annular yoke, and a plurality of teeth that project from the inner peripheral surface of the yoke toward the inner peripheral side. The refrigerant flow paths are formed only in sections of the unit coils overlapping the teeth as viewed from the circumferential direction.

Description

Coils and rotating electrical machines

[0001] This application claims priority to Japanese Patent Application No. 2023-115673, filed on July 14, 2023, the contents of which are incorporated herein by reference.

[0002] An electric motor, which is a type of rotating electric machine, has a rotor that can rotate around an axis and a cylindrical stator that surrounds the rotor core from the outer periphery. The rotor has a rotor core and permanent magnets. The stator has a stator core and multiple coils attached to the stator core. When current is applied to the coils, electromagnetic forces are generated between the permanent magnets, causing the rotor to rotate around the axis. Forming the coils has typically involved winding copper wire or the like around the teeth of the stator core to form a ring shape. However, to reduce copper loss, it is necessary to insulate the coil windings from each other. For this reason, the technology described in Patent Document 1 below involves irradiating copper powder, which is the conductor material, and ceramic powder, which is the insulating layer material, with a laser to form the insulating coating and coil using three-dimensional additive manufacturing.

[0003] Japanese Patent Application Laid-Open No. 2016-039662

[0004] However, when using ceramic insulation as described above, although an insulating effect can be obtained, there is a problem in that the heat generated in the coil is difficult to dissipate, resulting in the coil temperature becoming excessively high.

[0005] The present disclosure provides a coil and a rotating electric machine that can be easily manufactured and have higher cooling performance.

[0006] The coil according to the present disclosure is a coil attached to a stator core that covers, from the outer periphery, a rotor that can rotate around an axis, and is annular with a central axis that is radially relative to the axis, and includes a plurality of unit coils stacked radially, and a sealing body that seals the plurality of unit coils in the axial direction, wherein the unit coil has a pair of divided bodies that are divided radially based on a dividing surface, and the dividing surface of at least one of the pair of divided bodies has a recessed groove that forms a refrigerant flow path through which a refrigerant flows, and the stator core has an annular yoke centered on the axis, and a plurality of teeth that protrude inward from the inner surface of the yoke and are spaced apart circumferentially, and the refrigerant flow path is formed only in the portion that overlaps with the teeth of the unit coils when viewed from the circumferential direction.

[0007] A rotating electric machine according to the present disclosure includes the rotor core, the stator core, and the coil described above attached to the stator core.

[0008] According to the present disclosure, it is possible to provide a coil and a rotating electric machine that can be easily manufactured and have higher cooling performance.

[0009] Fig. 2 is a cross-sectional view showing a configuration of an electric motor according to an embodiment of the present disclosure; Fig. 3 is a cross-sectional view showing a configuration of a coil according to an embodiment of the present disclosure; Fig. 4 is a cross-sectional view taken along the III-III direction in Fig. 2; Fig. 5 is a cross-sectional view showing a first modified example of a coil according to an embodiment of the present disclosure; Fig. 6 is a cross-sectional view showing a second modified example of a coil according to an embodiment of the present disclosure;

[0010] Hereinafter, a coil 30 and an electric motor 1 (rotating electric machine) according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 3. FIG.

[0011] (Configuration of electric motor 1) As shown in Fig. 1, the electric motor 1 includes a rotor 10 and a stator 20. The rotor 10 is columnar and extends along the axis X, and is supported so as to be rotatable about the axis X. Although not shown in detail, the rotor 10 includes a permanent magnet. The stator 20 is cylindrical and covers the rotor 10 from the outer periphery. In other words, the stator 20 is cylindrical and centered on the axis X. The stator 20 includes a stator core 21 and coils 30.

[0012] The stator core 21 has a yoke 22 and a plurality of teeth 23. The yoke 22 has an annular shape centered on the axis X. The plurality of teeth 23 are provided on the inner peripheral surface of the yoke 22. The teeth 23 protrude radially inward from the inner peripheral surface of the yoke 22 relative to the axis X. The plurality of yokes 22 are provided at intervals in the circumferential direction relative to the axis X.

[0013] The teeth 23 have a tooth body 41 and a flange portion 42. The tooth body 41 extends radially. The circumferential dimension of the tooth body 41 is constant throughout its radial extension. A coil 30, which will be described later, is arranged around the tooth body 41. A flange portion 42 is provided at the tip end (i.e., the radially inner end) of the tooth body 41. The flange portion 42 protrudes from the tip of the tooth body 41 to both sides in the circumferential direction. The flange portion 42 is provided to prevent the coil 30, which will be described later, from falling off the tooth body 41.

[0014] (Configuration of Coil 30) The coil 30 is wound around the tooth body 41. That is, the coil 30 has an annular shape with a central axis extending radially relative to the axis X. As shown in Figures 2 and 3 , the coil 30 has a plurality of unit coils 31 (four, for example) stacked radially, and a sealing body 32.

[0015] The unit coil 31 has an annular shape with its central axis in the radial direction. The unit coil 31 has a rectangular cross-sectional shape when viewed from the direction of the axis X. The unit coil 31 has a pair of divided bodies 34 divided in the radial direction based on a dividing surface 33. A groove 36 that forms a refrigerant flow path 35 through which a refrigerant flows is formed in the dividing surface 33 of at least one of the pair of divided bodies 34. In the example of FIG. 2 , the groove 36 is formed in each dividing surface 33 of the pair of divided bodies 34. The groove 36 has a rectangular cross-sectional shape that is concave in the radial direction. Therefore, the unit coil 31 has a C-shaped cross-sectional shape when viewed from the direction of the axis X.

[0016] A refrigerant flow path 35 is formed inside the unit coil 31 by arranging the grooves 36 of the pair of divided bodies 34 opposite each other. A refrigerant such as oil or fat flows through this refrigerant flow path 35. The cross-sectional area of ​​the refrigerant flow path 35 as viewed from the axial X direction is constant throughout the entire area in the axial X direction within each unit coil 31. As shown by the dashed lines in Figure 2, a single coil 30 is formed by electrically connecting multiple unit coils 31 to each other. Note that in the example of Figure 2, the circumferential dimensions of the unit coils 31 are the same.

[0017] As shown in Figure 3, the refrigerant flow paths 35 in each unit coil 31 are connected to one another by through-flow paths 37. The through-flow paths 37 extend in the radial direction. One through-flow path 37 is provided at each end in the direction of the axis X. One through-flow path 37 is connected to a refrigerant supply source. The refrigerant supplied from the through-flow path 37 branches off and flows into each refrigerant flow path 35. At this time, heat is exchanged between each unit coil 31 and the refrigerant, and the unit coil 31 is cooled. The other through-flow path 37 is provided to discharge the refrigerant that has passed through the refrigerant flow path 35 to the outside.

[0018] 3, among the multiple refrigerant flow paths 35, the more radially inward the refrigerant flow path 35 is located, the larger the flow path cross-sectional area as viewed from the direction of the axis X. This is because the more radially inward the refrigerant flow path 35 is, the more likely it is to experience pressure loss as it is located further from the inlet (the radially outer end) of the through flow path 37. Furthermore, all of the refrigerant flow paths 35 are formed only in the portions that overlap with the teeth 23 of the unit coil 31 as viewed from the circumferential direction. In other words, the refrigerant flow paths 35 are not formed at the end of the coil 30 in the direction of the axis X (i.e., the end of the coil 30). The above-mentioned through flow paths 37 are formed at the end of the coil 30.

[0019] The unit coils 31 are sealed in the axial direction X by sealing bodies 32. The sealing bodies 32 are provided to seal the openings of the refrigerant flow paths 35 and to integrally connect the unit coils 31. Resin is preferably used as the sealing bodies 32. Note that both ends of the unit coils 31 in the axial direction X may also be sealed by the sealing bodies 32.

[0020] Three-dimensional additive manufacturing is preferably used to obtain the coil 30 described above. That is, a laser is irradiated onto metal powder to melt and solidify the powder, thereby obtaining the desired shape. When forming the coil 30 described above, a method of repeating additive manufacturing for each unit coil 31 is conceivable. After the metal element of the coil 30 is completed, an insulating coating is formed on the surface of the element. Thereafter, the element is compressed in the direction of the axis X, and then a seal 32 is formed, thereby completing the coil 30.

[0021] (Operation and Effect) Next, the operation of the electric motor 1 will be described. To drive the electric motor 1, first, current is supplied to each coil 30. This generates an electromagnetic force between the coil 30 and the permanent magnet of the rotor 10. This electromagnetic force applies a rotational force to the rotor 10, causing the rotor 10 to rotate around the axis X. The rotational force of the rotor 10 is extracted from the shaft end and is used in various ways.

[0022] Here, when forming the coil 30, it is common to wind copper wire or the like around the teeth 23 of the stator core 21 to form a ring shape. However, when forming the coil 30, it is necessary to insulate the windings of the coil 30 from each other to reduce copper loss. For this reason, in the past, the insulating coating and the coil 30 were sometimes formed by three-dimensional additive manufacturing, in which a laser was irradiated onto copper powder, which is the material for the conductor, and ceramic powder, which is the material for the insulating layer.

[0023] However, when insulating with ceramic as described above, although an insulating effect can be obtained, there is a problem in that the heat generated in the coil 30 is difficult to dissipate, resulting in an excessive temperature of the coil 30. Therefore, the above-described configurations are adopted in this embodiment.

[0024] According to the above configuration, the refrigerant flow paths 35 are formed by the recessed grooves 36 formed in the divided body 34. By flowing a refrigerant through these refrigerant flow paths 35, the coil 30 can be efficiently cooled. Furthermore, since each unit coil 31 has its own refrigerant flow path 35, the cooling effect can be uniform throughout the entire coil 30. This makes it possible to suppress localized heat generation in the coil 30. Furthermore, since the refrigerant flow paths 35 are formed only in regions where heat generation is likely to increase, i.e., regions that overlap with the teeth 23 when viewed circumferentially, rather than at the ends of the coil 30, heat generation in the coil 30 can be more effectively suppressed. Furthermore, eddy current loss can be effectively reduced while minimizing deterioration of DC copper loss. Conversely, if refrigerant flow paths 35 were also formed at the ends of the coil 30, the heat absorption capacity of the refrigerant would be wasted, potentially preventing the desired heat absorption performance in the most important regions where heat generation is likely to increase. Furthermore, eddy current loss could increase. According to the above configuration, this possibility is reduced, allowing the entire coil 30 to be cooled efficiently and stably. As a result, the efficiency of the electric motor 1 can be further improved. Furthermore, when three-dimensional additive manufacturing is performed to manufacture the coil 30, by dividing the unit coil 31 into a pair of divided bodies 34, the hollow structure is eliminated, which makes the manufacturing process easier, such as reducing the amount of support required and eliminating the need to consider powder removal.

[0025] Furthermore, with the above configuration, the refrigerant can be supplied to the refrigerant flow path 35 through one through-flow path 37, and the refrigerant used to cool the coil 30 in the refrigerant flow path 35 can be discharged to the outside through the other through-flow path 37. This allows the refrigerant to continue to flow smoothly between the refrigerant supply source and the coil 30. As a result, the efficiency of the electric motor 1 can be further improved. Note that a pump is preferably used to pressure-feed the refrigerant.

[0026] Here, the radially inner refrigerant flow passages 35 tend to experience greater pressure loss in the refrigerant because they are farther from the inlet of the through-passage 37. According to the above configuration, the more radially inner the refrigerant flow passages 35 are, where greater refrigerant pressure loss tends to occur, the larger the flow passage cross-sectional area as viewed from the direction of the axis X. This reduces the static pressure of the refrigerant in the radially inner flow passages, making it possible to reduce pressure loss. Therefore, the refrigerant can continue to flow more smoothly through each unit coil 31 regardless of its radial position. As a result, the efficiency of the electric motor 1 can be further improved.

[0027] Furthermore, with the above configuration, the refrigerant flows through the coil 30 of the electric motor 1, so that the coil 30 can be constantly and efficiently cooled. This makes it possible to provide a highly efficient electric motor 1 with a small amount of heat generation.

[0028] (Other Embodiments) Although the embodiments of the present disclosure have been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present disclosure.

[0029] For example, in the above embodiment, an example has been described in which the grooves 36 are formed in the divided bodies 34 of each unit coil 31. However, as a first modified example, it is also possible to adopt the configuration shown in FIG. 4. In the example shown in the figure, the grooves 36 are formed in only one of the pair of divided bodies 34. With this configuration, it is possible to obtain the same effects as those described above. In addition, since there is no need to accurately fit the grooves 36 together, it is possible to simplify the manufacturing process and reduce manufacturing costs.

[0030] As a second modified example, the configuration shown in Fig. 5 can also be employed. In the example shown in Fig. 5, a groove 36 is formed on each side of one divided body 34. In other words, the divided body 34 has an H-shaped cross section. By combining these divided bodies 34 together, the grooves 36 form a refrigerant flow path 35. With this configuration, the same effects as those described above can be obtained.

[0031] Furthermore, the number of coils 30 and the number of teeth 23 described in the above embodiment are merely examples, and can be increased or decreased as appropriate depending on the design and specifications. In either case, the same effects as those described above can be obtained.

[0032] Furthermore, the number of unit coils 31 is also an example, and can be changed as appropriate depending on the design and specifications. In any case, the same effects as those described above can be obtained.

[0033] As described in the above embodiment, it is desirable to use three-dimensional additive manufacturing to obtain the coil 30. However, other methods such as casting may also be used as long as the manufacturing method is physically possible.

[0034] In the above embodiment, the cross-sectional area of ​​the refrigerant flow path 35 increases as it moves radially inward. However, the configuration of the refrigerant flow path 35 is not limited to this, and the cross-sectional area of ​​the refrigerant flow path 35 may be constant throughout the entire radial direction. When manufacturing efficiency is important, adopting such a configuration is advantageous.

[0035] Furthermore, in the above embodiment, an example has been described in which the coil 30 is used in the electric motor 1. However, the application of the coil 30 is not limited to the electric motor 1, and the coil 30 can also be used in a generator, which is another type of rotating electric machine. In this case, by applying a rotational force to the rotor 10, an induced current is generated in the coil 30, and AC power can be obtained.

[0036] <Additional Notes> The coil 30 and the rotating electric machine described in each embodiment can be understood, for example, as follows.

[0037] (1) A coil 30 according to a first aspect is a coil 30 attached to a stator core 21 that covers an outer periphery of a rotor 10 that can rotate around an axis X, and includes a plurality of annular unit coils 31 having central axes that are radially aligned with respect to the axis X, and a sealing body 32 that seals the plurality of unit coils 31 in the direction of the axis X. The unit coils 31 have a pair of division bodies 34 that are divided radially based on a dividing surface 33, and the dividing surface 33 of at least one of the pair of division bodies 34 has a recessed groove 36 that forms a refrigerant flow path 35 through which a refrigerant flows. The stator core 21 has an annular yoke 22 centered on the axis X, and a plurality of teeth 23 that protrude inward from an inner circumferential surface of the yoke 22 and are spaced apart circumferentially. The refrigerant flow path 35 is formed only in a portion that overlaps with the teeth 23 when viewed in the circumferential direction.

[0038] According to the above configuration, the refrigerant flow paths 35 are formed by the recessed grooves 36 formed in the division bodies 34. By flowing a refrigerant through these refrigerant flow paths 35, the coil 30 can be efficiently cooled. Furthermore, since the refrigerant flow paths 35 are formed in each unit coil 31, the cooling effect can be made uniform throughout the coil 30. This makes it possible to suppress localized heat generation in the coil 30. Furthermore, since the refrigerant flow paths 35 are formed only in regions where heat generation is likely to increase, i.e., regions that overlap with the teeth 23 when viewed circumferentially, rather than at the ends of the coil 30, heat generation in the coil 30 can be suppressed even more effectively.

[0039] (2) The coil 30 according to the second aspect is the coil 30 of (1), and has through-flow passages 37 that penetrate the ends of the plurality of unit coils 31 on both sides in the direction of the axis X in the radial direction and communicate with each of the refrigerant flow passages 35.

[0040] According to the above configuration, the refrigerant can be supplied to the refrigerant flow path 35 through one through-flow path 37, and the refrigerant used to cool the coil 30 in the refrigerant flow path 35 can be discharged to the outside through the other through-flow path 37. This allows the refrigerant to continue to circulate smoothly.

[0041] (3) The coil 30 according to the third aspect is the coil 30 of (2), wherein the refrigerant flow paths 35 formed in the unit coils 31 on the radially inner side have a larger flow path cross-sectional area as viewed from the direction of the axis X.

[0042] Here, the radially inner refrigerant flow passages 35 tend to experience greater pressure loss in the refrigerant because they are farther from the inlet of the through-passage 37. With the above configuration, the more radially inner the refrigerant flow passages 35 are where greater refrigerant pressure loss tends to occur, the larger the flow passage cross-sectional area as viewed from the direction of the axis X. This reduces the static pressure of the refrigerant in the radially inner flow passages, making it possible to reduce pressure loss. This allows the refrigerant to continue to flow more smoothly.

[0043] (4) A rotating electric machine according to a fourth aspect includes the rotor 10, the stator core 21, and the coil 30 according to any one of claims 1 to 3 attached to the stator core 21.

[0044] According to the above configuration, the refrigerant flows through the inside of the coil 30, so that the coil 30 can be constantly and efficiently cooled. This makes it possible to provide a highly efficient rotating electric machine with a small amount of heat generation.

[0045] According to the present disclosure, it is possible to provide a coil and a rotating electric machine that can be easily manufactured and have higher cooling performance.

[0046] DESCRIPTION OF SYMBOLS 1... Electric motor 10... Rotor 20... Stator 21... Stator core 22... Yoke 23... Teeth 30... Coil 31... Unit coil 32... Sealing body 33... Dividing surface 34... Dividing body 35... Coolant flow path 36... Groove 37... Through flow path 41... Tooth body 42... Collar portion X... Axis

Claims

1. A coil attached to a stator core which covers from the outer periphery a rotor which can rotate around an axis, comprising: a plurality of unit coils which form a ring shape with a central axis in the radial direction relative to the axis and which are stacked in the radial direction; and a sealing body which seals the plurality of unit coils in the axial direction, wherein the unit coil has a pair of divided bodies which are divided in the radial direction based on a dividing surface, and the dividing surface of at least one of the pair of divided bodies has a recessed groove which forms a refrigerant flow path through which a refrigerant flows, and the stator core has: a ring-shaped yoke which is centered on the axis, and a plurality of teeth which protrude inward from the inner surface of the yoke and are spaced apart in the circumferential direction, wherein the refrigerant flow path is formed only in the portions which overlap with the teeth of the unit coils when viewed from the circumferential direction.

2. A coil as claimed in claim 1, further comprising through-flow passages which extend radially through both ends of said unit coils in the axial direction and communicate with said refrigerant flow passages.

3. A coil according to claim 2, wherein the refrigerant flow paths formed in the unit coils located radially inwards have a larger flow path cross-sectional area as viewed from the axial direction.

4. A rotating electric machine comprising: the rotor; the stator core; and a coil according to any one of claims 1 to 3 attached to the stator core.

Images