Coil and rotary electric machine

Abstract

To provide a coil in which copper loss is further reduced, and a rotating electric machine.SOLUTION: A coil is used in a rotary electric machine that includes a rotor rotatable around an axial line, and a cylindrical stator that radially faces the rotor and is centered on the axial line. The stator has an annular yoke centered on the axial line, a stator core having a plurality of teeth that protrude radially inward from the inner peripheral surface of the yoke and are arranged to be spaced from one another in a circumferential direction, and a coil that covers the teeth. The coil has a plurality of unit coils that cover the teeth from the outer peripheral side and are stacked in the radial direction with respect to the axial line, and in the unit coil, a portion including both end portions in the circumferential direction with respect to the axial line is made as a high resistivity portion whose electrical resistivity is higher than that of a remaining portion.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a coil and a rotating electric machine. [Background technology]

[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 covers the rotor core from the outer periphery. The rotor has a rotor core and a permanent magnet. The stator has a stator core and a plurality of coils attached to the stator core. By passing electricity through the coil, an electromagnetic force is generated between the permanent magnet and the rotor rotates around the axis. Here, when forming the coil, it is common to wind a copper wire or the like around the teeth of the stator core and mold it into a ring shape. However, when forming the coil, it is necessary to insulate the windings of the coil from each other in order to reduce copper loss. For this reason, in the technology according to the following Patent Document 1, it is said that a laser is irradiated to copper powder, which is the material of the conductor, and ceramic powder, which is the material of the insulating layer, to form the insulating coating and the coil by three-dimensional additive manufacturing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-039662 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, increasing the copper area to increase the space factor poses the problem that, conversely, copper loss increases because large eddy currents are generated inside the copper when the rotating electrical machine operates at high speeds and high frequencies.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a coil and a rotating electric machine in which copper loss is further reduced. [Means for solving the problem]

[0006] In order to solve the above problems, the coil disclosed herein is a coil used in a rotating electric machine including a rotor rotatable around an axis, and a cylindrical stator radially opposed to the rotor and centered on the axis, wherein the stator has 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, and the coil has a plurality of unit coils covering the teeth from the outer periphery and stacked in the radial direction relative to the axis, and a portion of the 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.

[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. Effect of the Invention

[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. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a configuration of a rotating electric machine according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a coil according to a first embodiment of the present disclosure. [Diagram 3] 2 is a cross-sectional view of a coil according to a first embodiment of the present disclosure viewed from a radial direction. FIG. [Figure 4] 10 is an enlarged view of a main portion showing a modified example of the coil according to the first embodiment of the present disclosure. FIG. [Diagram 5] FIG. 4 is an enlarged cross-sectional view of a coil according to a second embodiment of the present disclosure. [Figure 6] FIG. 11 is an enlarged cross-sectional view showing a modified example of the coil according to the second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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.

[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 an axis X, and is supported rotatably about the axis X. Although not shown in detail, the rotor 10 has 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 a coil 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 with respect to the axis X from the inner peripheral surface of the yoke 22. The plurality of yokes 22 are provided at intervals in the circumferential direction with respect to the axis X.

[0014] The teeth 23 have a teeth body 41 and a flange portion 42. The teeth body 41 extends in the radial direction. The circumferential dimension of the teeth body 41 is constant throughout its radial extension. A coil 30, which will be described later, is arranged around the teeth body 41. A flange portion 42 is provided at the tip end (i.e., the radially inner end) of the teeth body 41. The flange portion 42 protrudes from the tip of the teeth body 41 towards 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 teeth body 41.

[0015] (Configuration of coil 30) The coil 30 is provided so as to be wound around the tooth body 41. That is, the coil 30 has an annular shape with a central axis extending in the radial direction relative to the axis X. As shown in Fig. 2, the coil 30 has a plurality of unit coils 31 stacked in the radial direction.

[0016] The unit coil 31 has an annular shape with its central axis in the radial direction relative to the axis X. The unit coil 31 has a rectangular cross-sectional shape when viewed from the axis X. The multiple unit coils 31 are spirally arranged as a whole and cover the periphery of the tooth body 41. In other words, the unit coils 31 are electrically connected to each other to form one coil 30. In the example of FIG. 2, the circumferential dimension of the unit coil 31 gradually decreases from the radial outside to the radial inside. This is to avoid physical interference with other coils 30 adjacent to each other in the circumferential direction.

[0017] The portion including both ends of the unit coil 31 in the circumferential direction 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 ends). At the boundary between the high resistivity portion 51 and the remaining portion, the resistivity changes discontinuously. For example, when the coil 30 is manufactured using a three-dimensional additive manufacturing 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 high in the high resistivity portion 51. As a result, it is difficult for an electric current to flow. That is, the electrical resistivity is high. Copper is preferably used as the material for forming the coil 30. When performing three-dimensional additive manufacturing, a laser is irradiated to copper powder to melt and solidify the powder, thereby obtaining a predetermined shape of the coil 30.

[0018] 3, when the coil 30 is viewed from the radial inside, the high resistivity portions 51 are provided only in those portions of the unit coil 31 that overlap with the teeth 23. In other words, the high resistivity portions 51 are not provided in those 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] (Action and effect) Next, the operation of the electric motor 1 will be described. To drive the electric motor 1, first, a current is supplied to each coil 30. Then, an electromagnetic force is generated between the coils 30 and the permanent magnets of the rotor 10. This electromagnetic force provides a rotational force to the rotor 10. This causes 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 for various purposes.

[0020] Here, in forming the coil 30, it has been common to wind a copper wire or the like around the teeth 23 of the stator core 21 to form a ring shape. In addition, in forming the coil 30, it is necessary to insulate the windings of the coil 30 from each other in order 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 by irradiating a laser onto copper powder, which is the material for the conductor, and ceramic powder, which is the material for the insulating layer.

[0021] However, when the copper area is increased to increase the space factor, there is a problem that large eddy currents are generated inside the copper when the rotating electric machine is operated at high rotation speeds and high frequencies, which in turn increases copper loss. Therefore, the above-mentioned configurations are adopted in this embodiment.

[0022] Here, at both circumferential ends of the unit coil 31, a large amount of eddy currents tend to flow as the rotor 10 rotates. According to the above configuration, since the high resistivity portions 51 are formed at both circumferential ends of the unit coil 31, the eddy currents are less likely to flow in the high resistivity portions 51. Specifically, in the high resistivity portions 51, the filling rate of the material is relatively low, and therefore the resistivity to the current is high. Therefore, the eddy currents tend to be blocked in the high resistivity portions 51. As a result, the eddy currents are reduced throughout the coil 30, and it is possible to reduce the copper loss of the coil 30. Therefore, it is possible to provide an electric motor 1 with even higher efficiency.

[0023] Here, since the leakage magnetic flux of the coil 30 does not link in the portions of the unit coil 31 that do not overlap with the teeth 23, i.e., the coil ends 60, providing the high resistivity portions 51 in these portions may increase DC copper loss. However, according to 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] Moreover, 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 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 of the high resistivity portion 51 and the remaining portion changes continuously. In other words, the electrical resistivity gradually increases from the central portion in the circumferential direction toward the ends on both sides. With this configuration, no portion where the resistivity changes significantly locally is formed. Therefore, it is possible to suppress the occurrence of a portion where the eddy current increases locally. This makes it possible to further reduce the copper loss of the coil 30 as a whole.

[0027] Also, the electrical resistivity of a region in the circumferential center may be increased from the radially outer side to the radially inner side of the 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 side to the radially inner side of the unit coil 31. Specifically, an example may be considered in which the volume occupied by the high resistivity portions 51 is increased from the radially outer side to the radially inner side of the unit coil 31.

[0028] According to the above configuration, since the electrical resistivity is high in the radially inner region (that is, the region close to the rotor) where eddy currents are particularly likely to occur, it is 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, a high resistivity portion 51 is provided only in the unit coil 31 close to the rotor 10. Specifically, in the example of the same figure, the high resistivity portion 51 is 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 portion 51 itself are similar to those described in the first embodiment.

[0031] (Action and effect) Here, the coil 30 as a whole is magnetized by the rotor 10, so that the eddy current tends to flow particularly in the unit coil 31 on the side close to the rotor 10. According to the above configuration, the high resistivity portion 51 is provided only in the unit coil 31 on the side close to the rotor 10, so that the eddy current can be suppressed more efficiently and effectively. Therefore, it is possible to further reduce the copper loss of the coil 30 as a whole. On the other hand, if the high resistivity portion 51 is formed even in a place where the eddy current is unlikely to occur, the DC copper loss increases, and there is a possibility that the performance of the coil 30 as a whole will be reduced. According to the above configuration, it is possible to minimize the AC copper loss while avoiding such a possibility. Therefore, the efficiency of the electric motor 1 can be further improved.

[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 gist of the present disclosure.

[0033] For example, in the above second embodiment, an example has been described in which the high resistivity portions 51 are formed only in the two unit coils 31 counting from the rotor 10 side. However, depending on the dimensions, size, design, and specifications of the electric motor 1, the high resistivity portion 51 may be formed only in 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 in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do 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 according to the design and specifications. In any 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 according to 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 preferable to use three-dimensional additive manufacturing to obtain the coil 30. However, other methods such as casting may be used as long as the manufacturing 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-mentioned embodiments. That is, in each of the above-mentioned embodiments, an example in which the rotor 10 is disposed on the inner periphery of the stator 20 has been described, but it is also possible to adopt a configuration in which the rotor 10 is disposed on the outer periphery of the stator 20. In this case, when providing high resistivity portions 51 only in the unit coils 31 on the rotor 10 side 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, in which the stator 20 includes an annular yoke 22 centered on the axis X, a stator core 21 having a plurality of teeth 23 protruding radially inward from an inner peripheral surface of the yoke 22 and arranged at intervals in the circumferential direction, and the coil 30 covering the periphery of the teeth 23, the coil 30 including a plurality of unit coils 31 covering the teeth 23 from the outer periphery and stacked in the radial direction relative to the axis X, and a portion of the unit coil 31 including both ends 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. According to 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 the copper loss of the coil 30 as a whole.

[0043] (2) A coil 30 according to a 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, so that no localized changes in resistivity are formed. This makes it possible to suppress the occurrence of localized areas of increased eddy current. This makes it possible to further reduce the copper loss of the coil 30 as a whole.

[0045] (3) The coil 30 according to a 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 adjacent 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 especially in the unit coil 31 on the side close to the rotor 10. According to the above configuration, the high resistivity portion 51 is provided only in the unit coil 31 on the side close to the rotor 10, so that the eddy current can be suppressed more efficiently and effectively. Therefore, the copper loss of the entire coil 30 can be further reduced.

[0047] (4) The coil 30 of the fourth aspect is a coil 30 of 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, since the high resistivity portion 51 is provided only in the unit coil 31 in the first row counting from the rotor 10, eddy currents can be suppressed more efficiently and effectively than when the remaining unit coils 31 are also provided with high resistivity portions 51. Therefore, it is possible to further reduce copper loss in the coil 30 as a whole.

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

[0050] Here, since the leakage magnetic flux of the coil 30 does not link in the portions of the unit coil 31 that do not overlap with the teeth 23, i.e., the coil ends 60, providing the high resistivity portions 51 in these portions may increase DC copper loss. However, according to 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) A coil 30 in a sixth aspect is a coil 30 in any one of the aspects (1) to (5), wherein the high resistivity portion 51 is configured to have a lower material filling rate than the remaining portion, thereby resulting in a higher electrical resistivity.

[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 the manufacturing cost of the coil 30 to be significantly reduced.

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

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

[0055] (8) The coil 30 of the eighth aspect is a coil 30 of any one of the 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, since the electrical resistivity is high in the radially inner region (that is, the region close to the rotor) where eddy currents are particularly likely to occur, it is possible to effectively suppress the occurrence of eddy currents.

[0057] (9) A coil 30 in a ninth aspect is a coil 30 in any one of the aspects (1) to (8), in which the volume occupied by the high resistivity portions 51 on both sides in 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, since the electrical resistivity is high in the radially inner region (that is, the region close to the rotor) where eddy currents are particularly likely to occur, it is 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 the 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 electric machine with reduced copper loss and greatly improved efficiency. [Explanation of symbols]

[0061] Reference Signs List 1...motor 10...rotor 20...stator 21...stator core 22...yoke 23...teeth 30...coil 31...unit coil 41...teeth body 42...flange portion 51...high resistivity portion 60...coil end X...axis

Claims

1. A rotor rotatable about an axis; a cylindrical stator that faces the rotor in a radial direction and is centered on the axis; A coil for use in a rotating electric machine comprising: The stator includes: a stator core having an annular yoke centered on the axis, a plurality of teeth protruding radially inward from an inner peripheral surface of the yoke and arranged at intervals in the circumferential direction, and the coil covering the periphery of the teeth, The coil is a plurality of unit coils covering the teeth from an outer periphery side and stacked in a radial direction with respect to the axis; In the unit coil, a portion 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. The coil according to claim 1 , wherein the electrical resistivity of the unit coil gradually increases from a central portion in the circumferential direction toward the opposite end portions.

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

4. The 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. The coil according to claim 1 , wherein the high resistivity portion is provided only in a portion of the unit coil that overlaps with the tooth when viewed in a radial direction.

6. The coil according to 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. The coil according to claim 1 , wherein the electrical resistivity of a region in the circumferential center portion increases from the radially outer side to the radially inner side of the unit coil.

8. 2. The coil according to 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. The coil according to claim 1 , wherein a volume occupied by the high resistivity portions on both sides in the circumferential direction increases from the radially outer side to the radially inner side of the unit coil.

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

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