Coil and rotary electric machine

Abstract

This coil is used in a rotary electric machine comprising: a rotor that is rotatable about an axis; and a cylindrical stator that faces the rotor from the radial direction and is centered on the axis. The stator has: a stator core that has an annular yoke centered on the axis, and a plurality of teeth projecting radially inward from the inner peripheral surface of the yoke and aligned at intervals in the circumferential direction; and the coil that covers the periphery of the teeth. The coil has a plurality of unit coils that cover the teeth from the outer peripheral side and are layered in the radial direction with respect to the axis. A section of each unit coil including end portions on both sides in the circumferential direction with respect to the axis is a high resistivity portion where the electrical resistivity is higher than the electrical resistivity of the remaining section.

Description

Coils and rotating electrical machines

[0001] This application claims priority to Japanese Patent Application No. 2023-116020, 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, increasing the copper area to increase the space factor creates a problem in that large eddy currents are generated inside the copper when the rotating electrical machine is operated at high rotation speeds and high frequencies, which in turn increases copper loss.

[0005] The present disclosure provides a coil and a rotating electric machine with further reduced copper loss.

[0006] The coil according to the present disclosure is a coil used in a rotating electric machine that includes a rotor that can rotate around an axis, and a cylindrical stator that faces the rotor in the radial direction and is centered on the axis, wherein the stator includes an annular yoke centered on the axis, a stator core that protrudes radially inward from the inner surface of the yoke and has a plurality of teeth that are arranged at intervals circumferentially, and the coil that covers the teeth, and the coil includes a plurality of unit coils that cover the teeth from the outer periphery and are stacked radially relative to the axis, and a portion of the unit coil that includes both ends circumferentially relative to the axis is a high resistivity portion whose electrical resistivity is higher than that of the remaining portion.

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

[0008] According to the present disclosure, it is possible to provide a coil and a rotating electric machine in which copper loss is further reduced.

[0009] Fig. 1 is a cross-sectional view showing the configuration of a rotating electric machine according to a first embodiment of the present disclosure; Fig. 2 is an enlarged cross-sectional view of a coil according to a first embodiment of the present disclosure; Fig. 3 is a cross-sectional view of a coil according to a first embodiment of the present disclosure viewed from a radial direction; Fig. 4 is an enlarged view of a main part showing a modified example of the coil according to the first embodiment of the present disclosure; Fig. 5 is an enlarged cross-sectional view of a coil according to a second embodiment of the present disclosure; Fig. 6 is an enlarged cross-sectional view of a modified example of the coil according to the second embodiment of the present disclosure.

[0010] First Embodiment

[0011] 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.

[0012] (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.

[0013] 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.

[0014] 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.

[0015] (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 Fig. 2, the coil 30 has a plurality of unit coils 31 stacked radially.

[0016] Each unit coil 31 has an annular shape with its central axis extending radially relative to the axis X. When viewed from the direction of the axis X, the unit coil 31 has a rectangular cross-sectional shape. The multiple unit coils 31 are arranged in a spiral shape as a whole and surround the tooth body 41. In other words, the unit coils 31 are electrically connected to each other to form a single coil 30. In the example of FIG. 2 , the circumferential dimension of the unit coil 31 gradually decreases from the radially outer side to the radially inner side. This is to avoid physical interference with other circumferentially adjacent coils 30.

[0017] The circumferential portion of the unit coil 31, including both end portions, is a high-resistivity portion 51 having a higher electrical resistivity than the remaining portion (i.e., the central portion in the circumferential direction excluding both end portions). The resistivity changes discontinuously at the boundary between the high-resistivity portion 51 and the remaining portion. When manufacturing the coil 30 using a three-dimensional additive manufacturing (3D AM) device, the high-resistivity portion 51 is formed by lowering the laser output compared to the remaining portion. Therefore, the high-resistivity portion 51 has a lower material filling rate than the remaining portion. In other words, the porosity of the material is higher in the high-resistivity portion 51. As a result, current does not flow easily. That is, the electrical resistivity is higher. Copper is preferably used as the material for forming the coil 30. When performing three-dimensional additive manufacturing, a laser is irradiated onto copper powder, causing the powder to melt and solidify, thereby obtaining the desired shape of the coil 30.

[0018] 3, when the coil 30 is viewed from the radially inner side, the high resistivity portions 51 are provided only in the portions of the unit coil 31 that overlap with the teeth 23. In other words, the high resistivity portions 51 are not provided in the portions of the unit coil 31 that do not overlap with the teeth 23, i.e., the coil ends 60. Such a distribution of the properties of the unit coil 31 can also be realized by the above-mentioned three-dimensional additive manufacturing.

[0019] (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.

[0020] 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. Furthermore, 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.

[0021] However, increasing the copper area to increase the space factor has the problem that, when the rotating electrical machine is operated at high rotation speeds and high frequencies, large eddy currents are generated inside the copper, which in turn increases copper loss. Therefore, the present embodiment employs the above-described configurations.

[0022] Here, as the rotor 10 rotates, eddy currents tend to flow in large amounts at both circumferential ends of the unit coil 31. With the above configuration, high resistivity portions 51 are formed at both circumferential ends of the unit coil 31, making it difficult for eddy currents to flow in the high resistivity portions 51. Specifically, the high resistivity portions 51 have a relatively low material filling rate, resulting in a high resistivity to current. For this reason, eddy currents tend to be blocked in the high resistivity portions 51. As a result, eddy currents are reduced throughout the coil 30, making it possible to reduce copper loss in the coil 30. Therefore, it is possible to provide an electric motor 1 with even higher efficiency.

[0023] Here, in the portions of the unit coil 31 that do not overlap with the teeth 23, i.e., the coil ends 60, leakage magnetic flux of the coil 30 does not link, so providing the high resistivity portions 51 in these portions may increase DC copper loss. However, with the above configuration, the high resistivity portions 51 are provided in portions other than the coil ends 60, so it is possible to minimize the increase in DC copper loss while maximizing AC copper loss.

[0024] Furthermore, with the above configuration, the high resistivity portion 51 can be easily and inexpensively formed simply by changing the filling rate of the material. In particular, when three-dimensional additive manufacturing is used, the high resistivity portion 51 can be easily formed simply by lowering the laser output and controlling the filling rate of the material. This makes it possible to significantly reduce the manufacturing cost of the coil 30.

[0025] The first embodiment of the present disclosure has been described above. Note that various changes and modifications can be made to the above configuration without departing from the gist of the present disclosure.

[0026] For example, in the first embodiment, an example was described in which the resistivity changes discontinuously at the boundary between the high resistivity portion 51 and the remaining portion. On the other hand, as shown as a modified example in FIG. 4, it is also possible to adopt a configuration in which the electrical resistivity between the high resistivity portion 51 and the remaining portion changes continuously. In other words, the electrical resistivity gradually increases from the central portion toward both ends in the circumferential direction. With this configuration, no localized areas where the resistivity changes significantly are formed. This makes it possible to suppress the occurrence of areas where the eddy current increases locally. This makes it possible to further reduce copper loss in the coil 30 as a whole.

[0027] The electrical resistivity of the region in the circumferential center may also be increased from the radially outer to the radially inner unit coil 31. Furthermore, the electrical resistivity of the high resistivity portions 51 on both sides in the circumferential direction may be gradually increased from the radially outer to the radially inner unit coil 31. Specifically, one example is to increase the volume occupied by the high resistivity portions 51 from the radially outer to the radially inner unit coil 31.

[0028] According to the above configuration, the electrical resistivity is high in the radially inner region (i.e., the region close to the rotor) where eddy currents are particularly likely to occur, making it possible to effectively suppress the occurrence of eddy currents.

[0029] Second Embodiment Next, a second embodiment of the present disclosure will be described with reference to Fig. 5. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0030] 5, in this embodiment, high resistivity portions 51 are provided only in the unit coils 31 closest to the rotor 10. Specifically, in the example shown in the figure, high resistivity portions 51 are formed only in two unit coils 31 counting from the radially inner side where the rotor 10 is located. The configuration and properties of the high resistivity portions 51 themselves are the same as those described in the first embodiment.

[0031] (Effects) Here, because the entire coil 30 is magnetized by the rotor 10, eddy currents tend to flow particularly strongly in the unit coils 31 closest to the rotor 10. With the above configuration, the high resistivity portions 51 are provided only in the unit coils 31 closest to the rotor 10, so eddy currents can be suppressed more efficiently and effectively. This makes it possible to further reduce copper loss in the entire coil 30. Conversely, if the high resistivity portions 51 were formed in locations where eddy currents are unlikely to occur, DC copper loss would increase, potentially reducing the performance of the entire coil 30. With the above configuration, it is possible to avoid this possibility and minimize AC copper loss. This makes it possible to further improve the efficiency of the electric motor 1.

[0032] The second embodiment of the present disclosure has been described above. Note that various changes and modifications can be made to the above configuration without departing from the spirit and scope of the present disclosure.

[0033] For example, in the second embodiment described above, an example was described in which the high resistivity portions 51 are formed in only two unit coils 31 counting from the rotor 10 side. However, depending on the dimensions, design, and specifications of the electric motor 1, the high resistivity portion 51 may be formed in only the first unit coil 31 counting from the rotor 10 side, as shown in FIG. 6 . With this configuration, eddy currents can be suppressed more efficiently and effectively than when high resistivity portions 51 are also provided in the remaining unit coils 31. Therefore, it is possible to further reduce AC copper loss in the coil 30 as a whole.

[0034] (Other Embodiments) Although each embodiment of the present disclosure has 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 within the scope that does not deviate from the gist of the present disclosure are also included.

[0035] For example, 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] Furthermore, the configuration of the electric motor 1 is not limited to the above-described embodiments. That is, in the above-described embodiments, an example has been described in which the rotor 10 is disposed on the inner circumferential side of the stator 20, but it is also possible to adopt a configuration in which the rotor 10 is disposed on the outer circumferential side of the stator 20. In this case, when providing high resistivity portions 51 only in the unit coils 31 on the rotor 10 side as described in the second embodiment, the high resistivity portions 51 are formed only in the unit coils 31 on the radially outer side. With this configuration, it is possible to obtain the same effects as those described above.

[0040] <Additional Notes> The coil 30 and the rotating electric machine described in each embodiment can be understood, for example, as follows.

[0041] (1) A coil 30 according to a first aspect is a coil 30 used in a rotating electric machine including a rotor 10 rotatable about an axis X and a cylindrical stator 20 radially opposed to the rotor 10 and centered on the axis X, wherein the stator 20 includes an annular yoke 22 centered on the axis X, a stator core 21 having a plurality of teeth 23 that protrude radially inward from the inner peripheral surface of the yoke 22 and are arranged at intervals in the circumferential direction, and the coil 30 that covers the teeth 23, wherein the coil 30 includes a plurality of unit coils 31 that cover the teeth 23 from the outer periphery and are stacked radially relative to the axis X, and a portion of each unit coil 31 that includes both end portions in the circumferential direction relative to the axis X is a high resistivity portion 51 having an electrical resistivity higher than that of the remaining portion.

[0042] Here, a large amount of eddy current tends to flow at both circumferential ends of the unit coil 31 as the rotor 10 rotates. With the above configuration, since the high resistivity portions 51 are formed at both circumferential ends of the unit coil 31, the eddy current is inhibited by the high resistivity. As a result, it is possible to reduce copper loss in the coil 30 as a whole.

[0043] (2) The coil 30 according to the second aspect is the coil 30 of (1), in which the electrical resistivity of the unit coil 31 gradually increases from the central portion in the circumferential direction toward the ends on both sides.

[0044] According to the above configuration, the electrical resistivity gradually increases toward both ends in the circumferential direction, preventing localized changes in resistivity. This prevents localized increases in eddy currents from occurring. This further reduces copper loss in the entire coil 30.

[0045] (3) The coil 30 according to the third aspect is the coil 30 according to (1) or (2), in which the high resistivity portion 51 is provided only in the unit coil 31 on the side closest to the rotor 10.

[0046] Here, since the entire coil 30 is magnetized by the rotor 10, a large amount of eddy current tends to flow particularly in the unit coil 31 on the side closest to the rotor 10. With the above configuration, the high resistivity portion 51 is provided only in the unit coil 31 on the side closest to the rotor 10, so eddy current can be suppressed more efficiently and effectively. Therefore, it is possible to further reduce copper loss in the entire coil 30.

[0047] (4) The coil 30 according to the fourth aspect is a coil 30 according to any one of aspects (1) to (3), in which the high resistivity portion 51 is provided only in the unit coil 31 in the first row counting from the rotor 10.

[0048] According to the above configuration, the high resistivity portions 51 are provided only in the unit coils 31 in the first row counting from the rotor 10, and therefore eddy currents can be suppressed more efficiently and effectively than when high resistivity portions 51 are also provided in the remaining unit coils 31. Therefore, it is possible to further reduce copper loss in the coil 30 as a whole.

[0049] (5) The coil 30 according to the fifth aspect is the coil 30 according to any one of aspects (1) to (4), and the high resistivity portion 51 is provided only in the portion of the unit coil 31 that overlaps with the tooth 23 when viewed from the radial direction.

[0050] Here, in the portions of the unit coil 31 that do not overlap with the teeth 23, i.e., the coil ends 60, leakage magnetic flux of the coil 30 does not link, so providing the high resistivity portions 51 in these portions may increase DC copper loss. However, with the above configuration, the high resistivity portions 51 are provided in portions other than the coil ends 60, so it is possible to minimize the increase in DC copper loss while maximizing AC copper loss.

[0051] (6) The coil 30 according to the sixth aspect is the coil 30 according to any one of the aspects (1) to (5), in which the high resistivity portion 51 is configured to have a higher electrical resistivity by having a lower material filling rate than the remaining portion.

[0052] According to the above configuration, the high resistivity portion 51 can be easily and inexpensively formed simply by changing the filling rate of the material. In particular, when three-dimensional additive manufacturing is used, the high resistivity portion 51 can be formed simply by lowering the laser output. This allows for a significant reduction in the manufacturing cost of the coil 30.

[0053] (7) The coil 30 according to the seventh aspect is a coil 30 according to any one of aspects (1) to (6), in which the electrical resistivity of the region in the circumferential center increases from the radially outer to the radially inner unit coil 31.

[0054] According to the above configuration, the electrical resistivity is high in the radially inner region (i.e., the region close to the rotor) where eddy currents are particularly likely to occur, making it possible to effectively suppress the occurrence of eddy currents.

[0055] (8) The coil 30 according to the eighth aspect is a coil 30 according to any one of aspects (1) to (7), in which the electrical resistivity of the high resistivity portions 51 on both sides of the circumferential direction gradually increases from the radially outer side to the radially inner side of the unit coil 31.

[0056] According to the above configuration, the electrical resistivity is high in the radially inner region (i.e., the region close to the rotor) where eddy currents are particularly likely to occur, making it possible to effectively suppress the occurrence of eddy currents.

[0057] (9) The coil 30 according to the ninth aspect is a coil 30 according to any one of aspects (1) to (8), in which the volume occupied by the high resistivity portions 51 on both sides of the circumferential direction increases from the radially outer side to the radially inner side of the unit coil 31.

[0058] According to the above configuration, the electrical resistivity is high in the radially inner region (i.e., the region close to the rotor) where eddy currents are particularly likely to occur, making it possible to effectively suppress the occurrence of eddy currents.

[0059] (10) A rotating electric machine according to a tenth aspect includes the rotor 10, the stator core 21, and a coil 30 according to any one of the aspects (1) to (9) provided in the stator core 21.

[0060] According to the above configuration, it is possible to provide a rotating electrical machine in which copper loss is reduced and efficiency is greatly improved.

[0061] According to the present disclosure, it is possible to provide a coil and a rotating electric machine in which copper loss is further reduced.

[0062] REFERENCE SIGNS LIST 1... electric motor 10... rotor 20... stator 21... stator core 22... yoke 23... teeth 30... coil 31... unit coil 41... tooth body 42... flange portion 51... high resistivity portion 60... coil end X... axis

Claims

1. A coil used in a rotating electric machine comprising: a rotor rotatable around an axis; and a cylindrical stator radially opposed to the rotor and centered on the axis, wherein the stator comprises: an annular yoke centered on the axis, a stator core having a plurality of teeth protruding radially inward from the inner surface of the yoke and arranged at intervals in the circumferential direction, and the coil covering the periphery of the teeth, wherein the coil comprises a plurality of unit coils covering the teeth from the outer periphery and stacked in the radial direction relative to the axis, and wherein a portion of each unit coil including both ends in the circumferential direction relative to the axis is a high resistivity portion having an electrical resistivity higher than the electrical resistivity of the remaining portion.

2. A coil as claimed in claim 1, wherein the electrical resistivity of each of said unit coils gradually increases from the circumferential center to said opposite end portions.

3. A coil according to claim 1 or 2, wherein the high resistivity portion is provided only in the unit coil on the side adjacent to the rotor.

4. A coil according to claim 1, wherein the high resistivity portion is provided only in the unit coil in the first stage counting from the rotor.

5. A coil as claimed in claim 1, wherein the high resistivity portion is provided only in a portion of the unit coil which overlaps with the tooth when viewed in the radial direction.

6. A coil as claimed in claim 1, wherein the high resistivity portion is configured to have a higher electrical resistivity by having a lower material filling rate than the remaining portion.

7. A coil as claimed in claim 1, wherein the electrical resistivity of the region at the circumferential centre increases from the radially outer side to the radially inner side of the unit coil.

8. A coil as claimed in claim 1, wherein the electrical resistivity of the high resistivity portions on both sides in the circumferential direction gradually increases from the radially outer side to the radially inner side of the unit coil.

9. A coil as claimed in claim 1, wherein the volume occupied by said high resistivity portions on both sides in the circumferential direction increases from the radially outer side to the radially inner side of said unit coil.

10. A rotating electric machine comprising: the rotor; the stator core; and the coil according to claim 1 provided in the stator core.

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