Rotary electric machine

Abstract

To provide a rotary electric machine that achieves high output by suppressing a circulating current generated between parallel strands and suppressing a temperature rise of a coil.SOLUTION: In the rotating electrical machine of the present invention, among the wire bundles of the coil 11 disposed in the slot 123, the first wires 11B and 11D from the end close to the rotator 2 among the wires of the third wire bundle, which is the third wire bundle from the end on the rotator 2 side, and the first wires 11B and 11D from the end far from the rotator 2 among the wires of the second wire bundle, which is the wire bundle adjacent to the second wire bundle, are connected in series. Between the second wire bundle and the first wire bundle, which are adjacent wire bundles other than the third wire bundle among the wire bundles of the coil 11 disposed in the slot 123, the first wires 11A and 11c from the end close to the rotator 2 among the wires are connected in series.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a rotating electric machine. [Background technology]

[0002] The recent trend toward reducing CO2 emissions has led to strong demands for CO2 emission regulations in countries around the world in order to realize a zero-carbon society. Electrification, which does not emit CO2 during operation, is being actively promoted as an alternative to CO2-emitting fossil-fuel engines. In particular, in the field of air mobility, such as aircraft and eVTOL (Electric Vertical Take-off and Landing) vehicles, there is a demand for rotating electrical machines such as electric motors and generators to have higher output and torque while reducing their weight, i.e., to increase their power density and torque density, in order to increase their range and payload. One known method for reducing the weight of rotating electrical machines is to increase the number of poles in the machine to achieve multi-polarization, thereby thinning the stator and rotor radially. Furthermore, increasing the rotational speed of a rotating electrical machine and increasing its wattage can increase its power output.

[0003] When a multi-polarized motor is made faster, the electrical angular frequency increases, which increases the induced current generated inside the coil, resulting in eddy current loss and a rise in coil temperature, which hinders higher output. One technique for addressing this issue is to form a coil by bundling multiple thin copper wires (hereinafter referred to as strands) in parallel to reduce the eddy currents generated within the conductor cross section of each strand. However, in this case, differences in resistance and inductance between the multiple parallel strands cause circulating currents to occur between the parallel strands. Patent Document 1 describes a technique for reducing copper loss by minimizing the difference in inductance between the multiple strands. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-110413 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 explains that minimizing the difference in inductance between multiple strands suppresses current imbalance (circulating current) and reduces copper loss. However, the direct cause of circulating current that occurs between multiple strands is the magnetic flux that the coil receives from the stator teeth, rotor, etc., that is, fluctuations in the external magnetic flux as seen from the coil. Since the strands on the air gap side are particularly affected by this, there has been a demand for technology to suppress the circulating current that occurs as a result.

[0006] In addition, in Patent Document 1, the strip copper wire is wound a predetermined number of times in the first layer, and then twisted and moved toward the tip of the tooth to wind the second layer.However, to move from the outer layer of the first layer to the inner layer of the second layer after winding the predetermined number of times, it is necessary to cross between coils of different heights, so space is required for the coil to cross between the first and second layers, which poses the problem of a decrease in the coil space factor.

[0007] The object of the present invention is to provide a rotating electric machine in which a coil is formed from a wire bundle in which multiple wires are bundled in parallel, which suppresses circulating currents that occur between parallel wires, suppresses temperature rise in the coil, and increases output. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a rotating electric machine comprising a stator that generates a magnetic field, and a rotor that is arranged with a gap between it and the stator and generates a rotational force by the magnetic field, wherein the stator comprises a plurality of teeth extending radially, slots provided between the teeth adjacent in the circumferential direction, and coils that are wound around the teeth and housed in the slots, wherein the coils are made up of a first specified number of wires, which is two or more, arranged radially of the teeth to form a wire bundle, and the wire bundles are arranged in the slots in a second specified number of stages, which is three or more, radially of the teeth. Among the wire bundles placed in the slots, the mth wire bundle is the mth (m is any integer between 1 and less than 1 / 2 of the second specified number) wire bundle counting from the end on the rotor side, and the nth (n is any integer between 1 and the first specified number) wire from the end closest to the rotor is connected in series with the nth wire from the end farthest from the rotor among the wires of the (m+1)th wire bundle which is the wire bundle adjacent to the mth wire bundle, and among the wire bundles placed in the slots other adjacent wire bundles except for the mth wire bundle, the nth wires from the end closest to the rotor are connected in series. [Effects of the Invention]

[0009] According to the present invention, in a rotating electric machine in which a coil is formed from a wire bundle in which multiple thin wires are bundled in parallel, it is possible to suppress the circulating current that occurs between the parallel wires, thereby suppressing the temperature rise of the coil and increasing output. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a rotating electric machine 100 according to a first embodiment of the present invention. [Figure 2] 1 is an enlarged cross-sectional view of a portion of a stator 1 and a rotor 2 according to a first embodiment of the present invention. [Figure 3] 1 is an enlarged cross-sectional view of a stator 1 of a rotary electric machine 100 according to a first comparative example. [Figure 4]1 is an enlarged cross-sectional view of a stator 1 of a rotating electric machine 100 according to a first embodiment of the present invention. [Figure 5] 10 is a diagram comparing copper loss occurring in the coil 11 of the rotating electric machine 100 in Comparative Example 1 and the first embodiment. FIG. [Figure 6] 2 is an enlarged cross-sectional view of the stator 1 of the rotating electric machine 100. FIG. [Figure 7] FIG. 10 is a diagram showing a waveform of a current passed through a coil. [Figure 8] FIG. 10 is a diagram showing the analysis results of the radial component of magnetic flux density. [Figure 9] FIG. 10 is a diagram showing the analysis results of the circumferential component of magnetic flux density. [Figure 10] 1A and 1B are diagrams illustrating an image of a radial component of magnetic flux and an induced current. [Figure 11] 1A and 1B are diagrams illustrating an image of a circumferential fundamental wave component of magnetic flux and an induced current. [Figure 12] 1A and 1B are diagrams illustrating an image of circumferential harmonic components of magnetic flux and induced current. [Figure 13] 10 is a diagram showing an induced current flowing in a wire A of the rotary electric machine 100 according to the first comparative example. FIG. [Figure 14] 3 is a diagram showing an induced current flowing in a wire A of the rotating electric machine 100 according to the first embodiment of the present invention. FIG. [Figure 15] 4 is a diagram showing waveforms of currents flowing through the wires of the rotary electric machine 100 according to the first comparative example. FIG. [Figure 16] 3 is a diagram showing waveforms of currents flowing through wires of the rotary electric machine 100 according to the first embodiment of the present invention. FIG. [Figure 17] 10 is a diagram showing the effective values ​​of currents flowing through the wires of the rotary electric machine 100 according to the first comparative example. FIG. [Figure 18] 3 is a diagram showing the effective values ​​of currents flowing through the wires of the rotary electric machine 100 according to the first embodiment of the present invention. FIG. [Figure 19] FIG. 10 is an enlarged cross-sectional view of a stator 1 of a rotating electrical machine 100 according to a second embodiment of the present invention. [Figure 20] 10 is a diagram showing waveforms of currents flowing through the wires of the rotary electric machine 100 according to Comparative Example 2. FIG. [Figure 21]FIG. 6 is a diagram showing the waveform of a current flowing through each wire of a rotating electric machine 100 according to a second embodiment of the present invention. [Figure 22] 10 is a diagram showing the effective values ​​of currents flowing through the wires of the rotary electric machine 100 according to the second comparative example. FIG. [Figure 23] FIG. 10 is a diagram showing the effective values ​​of currents flowing through the wires of a rotary electric machine 100 according to a second embodiment of the present invention. [Figure 24] 10 is a diagram showing a comparison of copper loss occurring in the coil 11 of the rotating electric machine 100 in Comparative Example 2 and in the second embodiment. FIG. [Figure 25] FIG. 10 is an enlarged cross-sectional view of a stator 1 of a rotating electric machine 100 according to a third embodiment of the present invention. [Figure 26] FIG. 10 is a diagram showing an image of an induced current flowing in a wire A of a rotating electric machine 100 according to a third embodiment of the present invention. [Figure 27] FIG. 10 is an enlarged cross-sectional view of a stator 1 of a rotating electric machine 100 according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In principle, identical elements are designated by the same reference numerals in all drawings. Furthermore, descriptions of parts having identical functions will be omitted. Note that the configurations described below are merely examples, and it is not intended that the embodiments of the present invention be limited to the specific embodiments below. [Example]

[0012] A rotating electric machine according to a first embodiment of the present invention will be described with reference to Figures 1 to 5. Figure 1 is a cross-sectional view of a rotating electric machine 100 according to a first embodiment of the present invention.

[0013] [Configuration of the rotating electric machine 100] As shown in FIG. 1, the rotating electric machine 100 includes a stator 1 that generates a magnetic field, a rotor 2 that is arranged on the inner periphery of the stator 1 with an air gap (gap) 3 and generates a rotational force by the magnetic field, a housing 10 that holds the stator 1, a shaft 20 that holds the rotor 2, and a bearing 30 that holds the shaft 20 while rotating it relative to the housing 10.

[0014] The rotor 2 is provided with permanent magnets 21 which are field magnetic poles, a rotor core 22 which holds the permanent magnets 21, and a cylindrical rotor core holding portion 23. The shaft 20 is fixed into a through hole of the rotor core holding portion 23 by press fitting or shrink fitting.

[0015] The stator 1 is provided with a coil 11 that generates a magnetic field and a stator core 12, and lead wires 41 extending from an inverter 40 enter the rotating electric machine 100 and are connected to the coil 11 via a connection part 13. A rotating magnetic field is formed by passing a three-phase alternating current from the inverter 40 through the coil 11, and torque is generated by interaction with the permanent magnets 21 that are the field magnetic poles of the rotor 2. The configuration of the rotating electric machine 100 described above is also commonly applied to the embodiments described below.

[0016] The rotating electric machine 100 according to the present invention can be applied to either an inner rotor type in which the rotor 2 is rotatably supported on the inner periphery of the stator 1, or an outer rotor type in which the rotor 2 is rotatably supported on the outer periphery of the stator 1.

[0017] <Configuration of Stator 1 and Rotor 2> Fig. 2 is an enlarged cross-sectional view of a portion of the stator 1 and rotor 2 according to the first embodiment of the present invention. Fig. 2 shows a cross section perpendicular to the axis of rotation.

[0018] The stator 1 has a central axis 1ax (see FIG. 1) that coincides with the rotational axis 2ax (see FIG. 1) of the rotor 2, and includes a stator core 12 formed by laminating multiple core sheets, and a coil 11 formed by winding a copper or aluminum conductor. In this embodiment, the direction along the rotational axis 2ax and the central axis 1ax is called the "axial direction," the direction of rotation about this axial direction is called the "circumferential direction," and the direction perpendicular to the rotational axis 2ax and the central axis 1ax is called the "radial direction."

[0019] The stator core 12 includes an annular stator back yoke 121, a plurality of teeth 122 connected to the stator back yoke 121 and extending radially toward the air gap 3, and slots 123 provided between adjacent teeth 122 in the circumferential direction. The coil 11 is wound around the teeth 122 and housed in the slots 123. The stator core 12 may be formed from an integrally molded solid member. Alternatively, it may be formed by compression molding a powder magnetic material such as a dust core, or may be formed from an amorphous metal or a nanocrystalline material.

[0020] The rotor 2 is an embedded magnet type rotor that includes a rotor core 22 and permanent magnets 21 that are inserted into magnet holes formed in the rotor core 22. The rotor core 22 is formed by laminating multiple core sheets. The rotor core 22 may be formed from an integrally molded solid member. Alternatively, the rotor core 22 may be formed by compression molding a powder magnetic material such as a dust core, or may be formed from an amorphous metal or nanocrystalline material.

[0021] The permanent magnet 21 is composed of spoke magnets 211 and main pole magnets 212. The spoke magnets 211 have a cross section that is long in the radial direction and are magnetized in the circumferential direction. The main pole magnets 212 have a cross section that is long in the circumferential direction and are magnetized in the radial direction. In FIG. 2, the magnetization directions of the spoke magnets 211 and main pole magnets 212 are indicated by arrows. The main pole magnets 212 are positioned radially farther from the air gap 3 than the spoke magnets 211. All of the permanent magnets 21 are composed of rare earth sintered magnets. Of the rotor core 22, the region located on the radial side of the air gap 3 relative to the main pole magnet 212 is called the main core 221, and the region located on the radially opposite side of the air gap 3 relative to the main pole magnet 212 is called the back core 222.

[0022] The back core 222 serves to form a path for magnetic flux from one pole of the rotor 2 to the adjacent pole in the circumferential direction, and to improve the mechanical strength of the rotor core 22. The main core 221 functions to increase the gap magnetic flux density by concentrating the magnetic flux of the main pole magnet 212 and the magnetic flux of the spoke magnets 211. This enables the torque density of the rotating electric machine 100 to be increased.

[0023] Between the spoke magnets 211 and the main pole magnets 212, there is formed an inter-magnet bridge 223, which is a narrow portion of the rotor core 22. The inter-magnet bridge 223 is a path for leakage magnetic flux that short-circuits the magnetic flux of the permanent magnets, so it is desirable to form it with a small circumferential width. On the other hand, the inter-magnet bridge 223 is also a portion where large stress occurs due to the loads of centrifugal force and electromagnetic force acting on the rotor 2. For this reason, in designing the inter-magnet bridge 223, the width of the inter-magnet bridge 223 is determined by balancing magnetic properties such as torque with mechanical strength. In addition, between the spoke magnets 211 and the air gap 3, there is formed a claw portion 224 that extends circumferentially from the tip of the main core 221 on the air gap 3 side. The claw portion 224 serves to prevent the spoke magnets 211 from flying away from the rotor core 22 due to the loads of centrifugal force and electromagnetic force. On the other hand, since the claws 224 become paths for leakage magnetic flux that short-circuit the magnetic flux generated from the permanent magnet 21, it is desirable that the radial width of the claws 224 is small and that the claws 224 are spaced apart from adjacent claws 224 in the circumferential direction. For this reason, the width and circumferential length of the claws 224 are determined by the design of the claws 224, taking into account the balance between magnetic properties such as torque and mechanical strength.

[0024] Fig. 3 is an enlarged cross-sectional view of the stator 1 of the rotating electric machine 100 according to Comparative Example 1. Fig. 4 is an enlarged cross-sectional view of the stator 1 of the rotating electric machine 100 according to the first embodiment of the present invention.

[0025] In Comparative Example 1 shown in FIG. 3 and the First Example shown in FIG. 4, the coil 11 is wound in concentrated winding around the teeth 122 of the stator core 12. The coil 11 is configured by bundling two or more (first specified number) wires arranged radially around the teeth 122. In the first Example and the Comparative Example, in addition to arranging two wires radially around the teeth 122, two wires are also arranged circumferentially around the teeth 122. As a result, the coil 11 in this Example and the Comparative Example is configured as a wire bundle of four copper wires (hereinafter referred to as wires 11A, 11B, 11C, and 11D) with a rectangular cross section. Furthermore, the wire bundle constituting the coil 11 is configured in a number of stages of three or more (second specified number) in the radial direction of the teeth 122 within the slots 123.

[0026] 3 indicate the direction in which coil 11 passes, with solid lines passing in front of teeth 122 and dashed lines passing behind teeth 122. Also, among the multiple wire bundles arranged in slot 123, each of wires 11A, 11B, 11C, and 11D of a certain wire bundle is connected in series with wires 11A, 11B, 11C, and 11D of another wire bundle.

[0027] In Comparative Example 1, the wire bundle starts winding from the first left row located on the radially outer side, then winds in the order of the first right row, the second left row, the second right row, and the third left row, and ends winding in the third right row. Here, the wires are positioned relative to one another in the up-down direction (radial direction), with wires 11A and 11C on the lower side (air gap side) and wires 11B and 11D on the upper side (opposite the air gap side). The wires are positioned relative to one another in the left-right direction (circumferential direction), with wires 11A and 11B on the tooth side and wires 11C and 11D on the anti-teeth side.

[0028] On the other hand, in the first embodiment shown in FIG. 4, the position of each wire in the third-stage coil is different from that of Comparative Example 1 shown in FIG. Similar to Comparative Example 1, the wire bundle starts winding from the first left stage and continues to the first right stage, the second left stage, and the second right stage. However, in the section from the second right stage to the third left stage (indicated by the thick solid arrow), the wire bundle is twisted in a direction that rotates 180° rotationally symmetrically around the center of the cross section. Therefore, in the vertical (radial) positional relationship of the wires in the third stage, wires 11A and 11C are now on the upper side (opposite the air gap), and wires 11B and 11D are now on the lower side (air gap side). Similarly, in the horizontal (circumferential) positional relationship of the wires, wires 11C and 11D are now on the tooth side, and wires 11A and 11B are now on the anti-teeth side.

[0029] In other words, of the wire bundles arranged in the slot 123, the mth wire bundle (third tier) is the mth wire bundle counting from the end on the rotor 2 side (m is any integer between 1 and less than 1 / 2 of the second specified number (3 or more tiers)), and the nth wire (n is any integer between 1 and the first specified number (2 or more)) from the end closer to the rotor 2 (for example, wires 11B, 11D of the third tier) and the m+1th wire bundle adjacent to the mth wire bundle. Of the wires in the bundle (second row), the nth wires from the end farthest from the rotor 2 (for example, wires 11B and 11D in the second row) are connected in series, and of the wire bundles arranged in the slot 123, between adjacent wire bundles (second row and first row) excluding the mth wire bundle (third row), the nth wires from the end closest to the rotor 2 (for example, wires 11A and 11C in the second row and wires 11A and 11C in the first row) are connected in series.

[0030] As described above, by twisting the wire bundle by approximately 180° in the section spanning from the second to the third row, the vertical (radial) positional relationship of each wire in the first and second rows can be reversed from the vertical (radial) positional relationship of each wire in the third row.

[0031] 5 is a diagram comparing the copper loss occurring in the coil 11 of the rotating electric machine 100 in Comparative Example 1 and Example 1. The copper loss is broken down into normal copper loss, which is copper loss when no circulating current flows, and circulating current loss, which is copper loss due to circulating current between strands.

[0032] In Comparative Example 1, a large circulating current flows between the strands, and circulating current loss accounts for approximately half of the copper loss of the entire coil. On the other hand, in Example 1, circulating current loss is significantly reduced, and most of the copper loss is normal copper loss. Therefore, compared to Comparative Example 1, Example 1 improves motor efficiency, reduces the amount of heat generated in the coil, suppresses coil temperature rise, and enables the motor to have higher output.

[0033] The causes of the above-mentioned circulating current and the reduction of the circulating current will be described below.

[0034] [Explanation of factors that cause circulating current] The causes of circulating current will be described with reference to Fig. 6 to Fig. 12. Fig. 6 is an enlarged cross-sectional view of the stator 1 of the rotary electric machine 100. Fig. 7 is a diagram showing the waveform of a current flowing through a coil.

[0035] Coil 11 is wound around tooth 122 in a concentrated winding manner with three turns, designated as the first, second, and third rows from the bottom (radially outer side) of slot 123, with the left coil on the left side of tooth 122 and the right coil on the right side. When a current as shown in Figure 7 is passed through coil 11 for one cycle and rotor 2 is rotated in synchronization with the current to generate a constant torque, the magnetic flux density at the x mark in the center of each coil cross section was found by electromagnetic field analysis.

[0036] Figure 8 shows the analysis results of the radial component of magnetic flux density. In Figure 8, the upper diagram shows the radial component of magnetic flux density for the left coil, and the lower diagram shows the radial component of magnetic flux density for the right coil. Focusing on the dashed line area, the fundamental wave component has opposite polarity for the left and right coils, and the magnitude is largest in the third row, closest to air gap 3, and decreases in order from the second row to the first row.

[0037] Figure 9 shows the analysis results of the circumferential component of magnetic flux density. In Figure 9, the upper diagram shows the circumferential component of magnetic flux density for the left coil, and the lower diagram shows the circumferential component of magnetic flux density for the right coil. Focusing on the dashed line areas, the magnitude of the fundamental wave components of the left coil is relatively small, but the magnitude of the fundamental wave component of the right coil is largest in the third row closest to air gap 3, and decreases in the second row and first row order. On the other hand, the magnitude of the harmonic components is largest in the third row closest to air gap 3 for both the left and right coils, and decreases in the second row and first row order, with the polarities reversed.

[0038] Figure 10 is a diagram illustrating the radial component of magnetic flux and induced current. In Figure 10, the direction of magnetic flux is indicated by a solid arrow, and the thickness of the solid arrow indicates the magnitude of the magnetic flux. The main cause of the radial component of magnetic flux in Figure 10 is the magnetic flux generated by the rotor's permanent magnet. The cross section of coil 11 is divided into four strands, and the direction of the induced current induced in each strand is indicated by a black circle in a circle from the back to the front, and an X in a circle from the front to the back, with the magnitude of the induced current indicated by the size of the circle. When the magnetic flux linking coil 11 fluctuates, the induced current flows in a direction that cancels out the magnetic flux, so it flows in the direction shown, and the magnitude is larger in the strands closer to the air gap (bottom of the figure). The coils 11 located on the left and right of the teeth 122 are connected, as shown by the dashed lines, with the inner layers close to the teeth 122 and the outer layers far from the teeth 122. The induced currents on the left and right flow in opposite directions within the strands as shown by the dashed arrows, and since they are roughly equal in magnitude, they cancel each other out strongly. Therefore, the circulating current between the parallel strands due to the radial component of the magnetic flux is very small and does not pose a major problem.

[0039] Figure 11 is a diagram illustrating the circumferential fundamental component of magnetic flux and induced current. The main cause of the circumferential component of magnetic flux in Figure 11 is the component of magnetic flux generated in the stator core by the armature current leaking between the teeth. When the magnetic flux linking coil 11 fluctuates, the induced current flows in a direction that cancels out the magnetic flux, so it flows in the direction shown in the figure. The coils 11 located on the left and right of tooth 122 have their inner layers and outer layers connected, as shown by the dashed lines. The induced currents on the left and right flow in opposite directions, as shown by the dashed arrows, but because their magnitudes are different, the degree of cancellation is weak. Therefore, this induced current causes a circulating current to flow between adjacent parallel strands above and below.

[0040] Figure 12 is a diagram illustrating the circumferential harmonic components of magnetic flux and induced current. The main cause of the circumferential component of magnetic flux in Figure 12 is the component of magnetic flux generated in the stator core by the current flowing in the armature that leaks between the teeth. When the magnetic flux linking coil 11 fluctuates, the induced current flows in a direction that cancels out the magnetic flux, so it flows in the direction shown in the figure, and its magnitude is larger in the strands on the air gap side (bottom of the figure). The coils 11 located on the left and right of tooth 122 have their inner layers and outer layers connected as shown by the dashed lines, but the induced currents on the left and right flow in the same direction as shown by the dashed arrows, so they do not cancel each other out. Therefore, this induced current causes a circulating current to flow between adjacent parallel strands above and below.

[0041] As described above, the main cause of the circulating current that occurs between the parallel strands is the induced current that flows in a direction that cancels out the magnetic flux when the circumferential component of the magnetic flux linking the coil fluctuates.

[0042] [Explanation of circulating current reduction] The reduction of circulating current will be described with reference to Fig. 13 to Fig. 18. Fig. 13 is a diagram showing the induced current flowing in strand A of the rotating electric machine 100 according to Comparative Example 1, and is obtained by superimposing the induced current image of Fig. 12 on the enlarged cross-sectional view of the stator 1 of Fig. 3. All of the induced current in the left coil flows from the front to the back, and all of the induced current in the right coil flows from the back to the front. Because the left coil and right coil are connected in the order shown by the arrows, the induced currents on the left and right do not cancel each other out, and the sum of the two becomes a large circulating current.

[0043] FIG. 14 is a diagram showing the induced current flowing in wire A of the rotating electric machine 100 according to the first embodiment of the present invention, with the induced current image of FIG. 12 superimposed on the enlarged cross-sectional view of the stator 1 of FIG. 4. The first and second stages of the induced current in the left coil flow from front to back, while the third stage flows from back to front, canceling each other out. The first and second stages of the induced current in the right coil flow from back to front, while the third stage flows from front to back, canceling each other out. By canceling out the induced currents in this way, the circulating current is kept small.

[0044] Fig. 15 is a diagram showing the waveform of a current flowing through each wire of a rotating electric machine 100 according to Comparative Example 1. Fig. 16 is a diagram showing the waveform of a current flowing through each wire of a rotating electric machine 100 according to the first embodiment of the present invention. In Comparative Example 1 shown in Fig. 15, the harmonic components of wires A and C and wires B and D are in opposite phase to each other, and their amplitudes are also large. In contrast, in the first embodiment shown in Fig. 16, the phases of the harmonic components are the same in all wires, and their amplitudes are kept small.

[0045] FIG. 17 is a diagram showing the effective value of the current flowing through each strand of the rotating electric machine 100 according to Comparative Example 1. FIG. 18 is a diagram showing the effective value of the current flowing through each strand of the rotating electric machine 100 according to the first embodiment of the present invention. The dashed line indicates the level of the current effective value when no circulating current is generated. In Comparative Example 1 shown in FIG. 17, all strands exceed the dashed line, indicating that a large circulating current is flowing. In contrast, in the first embodiment shown in FIG. 18, some strands exceed the dashed line and some fall below it, and the average of these roughly coincides with the dashed line.

[0046] As described above, according to the first embodiment, the circulating current can be reduced compared to the first comparative example, and as a result, the effect of reducing the circulating current loss as shown in FIG. 5 can be obtained. [Example]

[0047] A rotating electric machine 100 according to a second embodiment of the present invention will be described with reference to Figs. 19 to 24. The second embodiment can be configured similarly to the first embodiment except for the following points. The following description will focus on the differences from the first embodiment. Fig. 19 is an enlarged cross-sectional view of a stator 1 of a rotating electric machine 100 according to the second embodiment of the present invention.

[0048] 19 differs from the first embodiment shown in Fig. 4 in that the coil 11 is made up of an inner layer close to the teeth 122 and an outer layer far from the teeth 122. That is, the coil 11 is made up of multiple layers of wire bundles in the circumferential direction (width direction) of the teeth 122.

[0049] 19 indicate the direction in which coil 11 passes, with the solid line indicating that it passes in front of tooth 122 and the dashed line indicating that it passes behind tooth 122. The thick solid arrow indicates that the wire bundle is twisted in a direction that rotates 180° rotationally symmetrically around the center of the cross section.

[0050] The wire bundle starts winding from the first layer on the left inner layer and is wound in order on the first layer on the right inner layer, the second layer on the left inner layer, and the second layer on the right inner layer. The wires in the first and second layers are positioned in the vertical (radial) direction such that wires 11A and 11C are on the lower side (air gap side) and wires 11B and 11D are on the upper side (opposite the air gap side). The wires are positioned in the horizontal (circumferential) direction such that wires 11A and 11B are on the tooth side and wires 11C and 11D are on the anti-teeth side.

[0051] In the section spanning from the second inner right layer to the third inner left layer (indicated by the thick solid arrow), the wire bundle is twisted and wound in a direction that rotates 180° rotationally symmetrically around the center of the cross section. Therefore, in the third layer, the wires 11A and 11C are now on the upper side (opposite the air gap), and the wires 11B and 11D are now on the lower side (air gap). Similarly, in the left-right direction (circumferential direction), the wires 11C and 11D are now on the tooth side, and the wires 11A and 11B are now on the anti-teeth side. The wires are then wound in the following order: from the third inner left layer to the third inner right layer, the third outer left layer, and the third outer right layer. In the section spanning from the third outer right layer to the second outer left layer (indicated by the thick solid arrow), the wire bundle is twisted and wound in a direction that rotates 180° rotationally symmetrically around the center of the cross section. Therefore, the vertical (radial) positional relationship of the wires in the second row of the left outer layer is such that wires 11A and 11C return to the bottom side (air gap side), and wires 11B and 11D return to the top side (opposite the air gap side). Similarly, the horizontal (circumferential) positional relationship of the wires is such that wires 11A and 11B return to the tooth side, and wires 11C and 11D return to the anti-teeth side. After that, the wires are wound in order from the second row of the left outer layer to the second row of the right outer layer, the first row of the left outer layer, and the first row of the right outer layer, with the winding finishing at the first row of the right outer layer.

[0052] As described above, by twisting the wire bundle 180° in the section spanning from the second to the third row in each of the inner and outer layers, the vertical (radial) positional relationship of each wire in the first and second rows can be reversed from the vertical (radial) positional relationship of each wire in the third row without reducing the space factor of the coil.

[0053] FIG. 20 is a diagram showing the waveform of a current flowing through each wire of a rotating electric machine 100 according to a second comparative example. FIG. 21 is a diagram showing the waveform of a current flowing through each wire of a rotating electric machine 100 according to a second embodiment of the present invention. Comparative example 2 refers to an example in which the wire bundle is wound without twisting, as indicated by the thick solid arrows in FIG. 19, although a diagram showing the configuration is omitted. That is, the vertical (radial) positional relationship of all the wires from the first to third rows is such that wires 11A and 11C are on the lower side (air gap side), and wires 11B and 11D are on the upper side (opposite the air gap side). Furthermore, the horizontal (circumferential) positional relationship of all the wires from the first to third rows is such that wires 11A and 11B are on the tooth side, and wires 11C and 11D are on the anti-teeth side.

[0054] In Comparative Example 2 shown in Fig. 20, the harmonic components of wires A and C and wires B and D are in opposite phase to each other and have large amplitudes. In contrast, in Example 2 shown in Fig. 21, the harmonic components of all wires are in phase and have small amplitudes.

[0055] Fig. 22 is a diagram showing the effective value of the current flowing through each strand of the rotating electric machine 100 according to Comparative Example 2. Fig. 23 is a diagram showing the effective value of the current flowing through each strand of the rotating electric machine 100 according to the second embodiment of the present invention. The dashed line indicates the level of the current effective value when no circulating current is generated.

[0056] In Comparative Example 2 shown in Fig. 22, all wires exceed the dashed line, indicating that a large circulating current is flowing. In contrast, in Example 2 shown in Fig. 23, some wires exceed the dashed line and some fall below it, with the average roughly matching the dashed line.

[0057] FIG. 24 is a diagram comparing the copper loss generated in the coil 11 of the rotating electric machine 100 in Comparative Example 2 and the second embodiment. The copper loss is broken down into normal copper loss, which is the copper loss when no circulating current flows, and circulating current loss, which is the copper loss due to the circulating current between the strands. In Comparative Example 2, a large circulating current flows between the strands, and circulating current loss accounts for approximately half of the total copper loss in the coil. On the other hand, in the second embodiment, circulating current loss is significantly reduced, and most of the copper loss is normal copper loss. Therefore, according to the second embodiment, compared to Comparative Example 2, the efficiency of the motor is improved, the amount of heat generated in the coil is reduced, which suppresses the temperature rise in the coil, and the motor output can be increased. [Example]

[0058] 25 and 26, a rotating electric machine 100 according to a third embodiment of the present invention will be described. The third embodiment can be configured similarly to the first embodiment except for the following points. The following description will focus on the differences from the first embodiment.

[0059] 25 is an enlarged cross-sectional view of a stator 1 of a rotating electric machine 100 according to a third embodiment of the present invention. Two teeth are adjacent to each other in the circumferential direction, with coil 111 wound around left tooth 1221 and coil 112 wound around right tooth 1222, and the two coils are of the same phase and wound continuously.

[0060] In coil 111, the wire bundle starts winding from the first left row and continues to the first right row, the second left row, and the second right row. In the section from the second right row to the third left row (thick solid arrow), the wire bundle is twisted in a direction that rotates 180 degrees rotationally symmetrically around the center of the cross section, and then continues to the third right row.

[0061] The wire is wound from the third right row of coil 111 to the first right row of coil 112, then to the first left row, the second right row, and the second left row in that order, and then in the section from the second left row to the third right row (thick solid arrow), the wire bundle is twisted in a direction that rotates 180 degrees rotationally symmetrically around the center of the cross section, and then it reaches the third left row, where the winding ends.

[0062] The vertical (radial) positional relationship of each wire in coil 111 is such that in the first and second rows, wires 11A and 11C are on the lower side (air gap side) and wires 11B and 11D are on the upper side (anti-air gap side), and in the third row, wires 11A and 11C are on the upper side (anti-air gap side) and wires 11B and 11D are on the lower side (air gap side).

[0063] On the other hand, the vertical (radial) positional relationship of each wire in coil 112 is such that in the first and second rows, wires 11A and 11C are on the upper side (opposite the air gap) and wires 11B and 11D are on the lower side (air gap side), and in the third row, wires 11A and 11C are on the lower side (air gap side) and wires 11B and 11D are on the upper side (opposite the air gap).

[0064] As described above, by twisting the wire bundle by 180° in the portion spanning from the second to the third row, the vertical (radial) positional relationship of the wires in the first and second rows can be reversed from the vertical (radial) positional relationship of the wires in the third row. Also, by spanning from the third row to the right of coil 111 to the first row to the right of coil 112, the vertical (radial) positional relationship of the wires in coil 111 can be reversed from the vertical (radial) positional relationship of the wires in coil 112.

[0065] In other words, of two adjacent coils 111, 112, the nth wire from the end closest to the rotor 2 in the wire bundle of a certain row (first, second, or third row) of one coil 111 (for example, wires 11A and 11C in the first and second rows of coil 111, and wires 11B and 11D in the third row) is connected in series with the nth wire from the end farthest from the rotor 2 in the wire bundle of the same row (first, second, or third row) of the other coil 112 (for example, wires 11A and 11C in the first and second rows of coil 112, and wires 11B and 11D in the third row).

[0066] 26 is a diagram showing an image of the induced current flowing in wire A of a rotating electric machine 100 according to a third embodiment of the present invention. In Fig. 26, the direction of magnetic flux is indicated by an arrow, and the magnitude of the magnetic flux is indicated by the thickness of the arrow. The cross section of coil 11 is divided into four wires, and the direction of the induced current induced in each wire is indicated by a black circle in a circle from the back to the front and an X in a circle from the front to the back, and the magnitude of the induced current is indicated by the size of the circle.

[0067] When the magnetic flux linking the coil fluctuates, the induced current flows in a direction that cancels out the magnetic flux, so it flows in the direction shown in the figure, and its magnitude is larger for the wires on the air gap side (bottom of the figure). In coils 111 and 112, the wires A and B, and wires C and D, are positioned in opposite vertical (radial) directions, so each wire is positioned in the vertical direction the same number of times, and the positional relationship of each wire is symmetrical, which reduces the variation in induced current between the wires and reduces circulating current. [Example]

[0068] A rotating electric machine 100 according to a fourth embodiment of the present invention will be described with reference to Fig. 27. The fourth embodiment can be configured similarly to the first embodiment except for the following points. The following description will focus on the differences from the first embodiment. Fig. 27 is an enlarged cross-sectional view of a stator 1 of a rotating electric machine 100 according to the fourth embodiment of the present invention.

[0069] In the fourth embodiment shown in Fig. 27, unlike the first embodiment shown in Fig. 4, the number of stages in the vertical direction (radial direction) of the coil 11 is six. Furthermore, the wire bundle is twisted in a direction that rotates 180° rotationally symmetrically around the center of the cross section in two places: from the second stage on the right to the third stage on the left, and from the fifth stage on the right to the sixth stage on the left.

[0070] In coil 11, the wire bundle starts winding from the first left row and continues to the first right row, second left row, and second right row. Then, in the section from the second right row to the third left row (indicated by the thick solid arrow), the wire bundle is twisted in a direction that rotates rotationally symmetrically by 180° around the center of the cross section. Then, after being wound to the third right row, fourth left row, fourth right row, fifth left row, and fifth right row, the wire bundle is twisted rotationally symmetrically by 180° around the center of the cross section from the fifth right row to the sixth left row (indicated by the thick solid arrow), and then continues to the sixth right row, where the winding ends.

[0071] As described above, according to the fourth embodiment, by twisting the wire bundle by 180° in the section spanning from the second to third row and in the section spanning from the fifth to sixth row, the vertical (radial) positional relationships of each wire in the first to sixth rows are mixed, and the induced current flowing in each wire can be canceled out.

[0072] [Variations] The present invention is not limited to the above-described embodiments, and various modifications are possible. The above-described embodiments are provided as examples to facilitate understanding of the present invention, and are not necessarily limited to those including all of the configurations described. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to delete part of the configuration of each embodiment, or to add or replace other configurations. Possible modifications of the above-described embodiments are, for example, as follows.

[0073] (1) In the above-described embodiments, the cross-sectional shape of the coil 11 and the wires 11A, 11B, 11C, and 11D is rectangular, but it may be square, circular, elliptical, or the like.

[0074] (2) In each of the above-described embodiments, the coil 11 is configured with a bundle of four wires, two in the vertical direction (radial direction) and two in the horizontal direction (circumferential direction), but the vertical direction (radial direction) may be configured with three or more wires. The horizontal direction (circumferential direction) may also be configured with one or more than three wires.

[0075] (3) In each of the above embodiments, the coil 11 is a concentrated winding, but it may be a distributed winding.

[0076] (4) In each of the above embodiments, the number of stages of the coil 11 is three, but it may be four or more. The number of layers does not have to be two, but may be three or more. The number of adjacent coils of the same phase does not have to be two, but may be three or more. The coils of the same phase wound consecutively do not have to be adjacent to each other.

[0077] (5) The rotor 2 has been described as an embedded magnet type equipped with spoke magnets 211 and main pole magnets 212, but it may also be an embedded magnet type equipped with only spoke magnets 211 or only main pole magnets 212. It may also be a surface magnet type in which the permanent magnets 21 are arranged on the surface of the rotor core 22.

[0078] (6) The material of the permanent magnet 21 is assumed to be, for example, a rare earth sintered magnet. However, other permanent magnets may also be used, such as rare earth bonded magnets or ferrite magnets made by mixing rare earth magnetic powder such as samarium iron nitrogen magnets or neodymium magnets with an organic binder.

[0079] (7) In each of the above embodiments, the rotor 2 is an inner rotor type in which it is rotatably supported on the inner periphery of the stator 1, but it may also be an outer rotor type in which the rotor 2 is rotatably supported on the outer periphery of the stator 1.

[0080] (8) In each of the above embodiments, one inverter is connected to one rotating electric machine 100, but in order to increase the redundancy of the rotating electric machine 100, a three-phase double winding or open winding may be used in which multiple inverters are connected. [Explanation of symbols]

[0081] 1...stator, 2...rotor, 10...housing, 11, 111, 112...coil, 11A...wire A, 11B...wire B, 11C...wire C, 11D...wire D, 12...stator core, 13...wiring connection portion, 20...shaft, 21...permanent magnet, 22...rotor core, 23...rotor core holding portion, 30...bearing, 40...inverter, 41...lead wire, 100...rotating electric machine, 121...stator back yoke, 122, 1221, 1222...teeth, 123...slot, 211...spoke magnet, 212...main pole magnet, 221...main core, 222...back core, 223...inter-magnet bridge, 224...claw portion.

Claims

1. a stator that generates a magnetic field; and a rotor that is disposed with a gap between itself and the stator and generates a rotational force by the magnetic field; the stator includes a plurality of teeth extending in a radial direction, slots provided between the teeth adjacent in a circumferential direction, and coils wound around the teeth and housed in the slots, In the rotating electric machine, the coil is configured by arranging a first specified number of wires, which is two or more, in a radial direction of the teeth to form a wire bundle, and the wire bundle is configured in a second specified number of stages, which is three or more, in the radial direction of the teeth within the slot, Among the wire bundles arranged in the slots, the mth wire bundle is the mth (m is any integer between 1 and less than 1 / 2 of the second specified number) wire bundle counting from the end on the rotor side, and the nth (n is any integer between 1 and the first specified number) wire from the end closest to the rotor is connected in series with the nth wire from the end farthest from the rotor among the wires of the (m+1)th wire bundle which is the wire bundle adjacent to the mth wire bundle, A rotating electric machine characterized in that, among the wire bundles arranged in the slots, between adjacent wire bundles other than the m-th wire bundle, the n-th wires from the end closest to the rotor are connected in series.

2. 2. The rotating electric machine according to claim 1, A rotating electric machine characterized in that when the coil wound around the tooth passes between the mth and (m+1)th strands of wire counting from the end on the rotor side, the strands of wire are twisted 180 degrees around the center of the cross section.

3. 3. The rotating electric machine according to claim 2, The rotating electric machine is characterized in that the wire has a rectangular cross section.

4. 2. The rotating electric machine according to claim 1, A rotating electric machine characterized in that the coil is composed of a bundle of wires in multiple layers in the circumferential direction of the teeth.

5. 5. The rotating electric machine according to claim 4, The rotating electric machine is characterized in that the coil is wound in multiple stages in the radial direction of the teeth in an inner layer close to the teeth, and then wound in multiple stages in an outer layer far from the teeth.

6. 6. The rotating electric machine according to claim 5, A rotating electric machine characterized in that when the inner and outer layers of the coil pass between the mth and (m+1)th strands counting from the rotor side end, the strands are twisted 180 degrees around the center of the cross section.

7. 2. The rotating electric machine according to claim 1, When the coil is wound continuously around a plurality of the teeth, A rotating electric machine characterized in that, of two adjacent coils, the nth wire from the end closest to the rotor in the wire bundle of a certain stage of one of the coils is connected in series with the nth wire from the end farthest from the rotor in the wire bundle of the same stage of the other coil.

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