Rotary electric machine

A rotary electric machine includes an annular stator, an inner rotor, an outer rotor and a toroidal coil. The annular stator includes inner teeth protruding radially inward and outer teeth protruding radially outward. The inner rotor faces a radially inner side of the annular stator. The outer rotor faces a radially outer side of the annular stator. The toroidal coils are arranged in each inner slot between any adjacent two of the inner teeth and a corresponding one outer slot between adjacent two of the outer teeth. The total number of the plurality of outer slots is larger than the total number of the plurality of inner slots. The number of the coils arranged in all the outer slots is larger than or equal to the number of the coils arranged in all the inner slots.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2017-013145 filed on Jan. 27, 2017, which is incorporated herein by reference in its entirety including the specification, drawings and abstract.

BACKGROUND

1. Technical Field

The disclosure relates to a rotary electric machine and, more particularly, to a rotary electric machine including a rotor provided on a radially inner side of an annular stator and a rotor provided on a radially outer side of the annular stator.

2. Description of Related Art

Conventionally, there has been suggested a toroidal-winding rotary electric machine including a rotor provided on a radially inner side of a stator and a rotor provided on a radially outer side of the stator.

FIG. 11shows the configuration of a motor that is an existing rotary electric machine described in Japanese Patent Application Publication No. 2007-185012 (JP 2007-185012 A). The motor includes a stator100, an inner rotor20and an outer rotor30.

The stator100is formed of a stator yoke114, outer teeth112and inner teeth113. The outer teeth112and the inner teeth113are provided on the stator yoke114. Three-phase toroidal coils115are wound around the stator yoke114. The coils115are connected to one another in star connection or delta connection.FIG. 11shows only one phase coil115out of the three-phase coils.

The inner rotor20is rotatably held inside the stator100. The inner rotor20is formed of an inner yoke and an inner permanent magnet. The outer rotor30is rotatably held outside the stator100. The outer rotor30is formed of an outer yoke and an outer permanent magnet. The inner rotor20and the outer rotor30each rotate under the influence of magnetic fields that are formed by current flowing through each of the coils115. Each of the inner rotor20and the outer rotor30is a surface magnet-type rotor in which the permanent magnet is arranged on the surface of the yoke.

The outer teeth112protrude radially outward from the stator yoke114. The inner teeth113protrude radially inward from the stator yoke114. The inner teeth113are provided in the same number as the outer teeth112. An outer slot116is provided between any adjacent two of the outer teeth112in order to insert the coil115. An inner slot117is provided between any adjacent two of the inner teeth113in order to insert the coil115. The shape and area of each outer slot116are set so as to be the same as the shape and area of each inner slot117.

Japanese Patent Application Publication No. 2008-113480 (JP 2008-113480 A) describes that, in a motor including a rotor provided on a radially inner side of a stator and a rotor provided on a radially outer side of the stator, outer teeth are provided on an outer side of a substantially annular yoke of the stator and inner teeth are provided on an inner side of the substantially annular yoke of the stator. Coils are arranged around the yoke in toroidal winding. A straight line that connects the center point of the distal end of each of the outer teeth with the center point of the distal end of each of the inner teeth and a straight line that connects the center of the motor with the center point of the distal end of each of the inner teeth are shifted from each other by a predetermined angle. That is, these straight lines are arranged in a skew position.

SUMMARY

With the configuration described in JP 2007-185012 A, when the area and shape of each outer slot116are set so as to be the same as the area and shape of each inner slot117, the coil115is wound in normal winding. As a result, a space factor is improved, so a copper loss is reduced.

However, with the configuration described in JP 2007-185012 A, the length of each of the outer teeth in the circumferential direction is considerably larger than the length of each of the inner teeth in the circumferential direction. Thus, among the three-phase coils that are arranged in the outer slots, a spacing between any adjacent two phases increases. For this reason, a cogging torque in the motor is easy to increase.

Moreover, the sum of the lengths of the distal end faces of the outer teeth in the circumferential direction, which is the length of the outer periphery of the stator, is larger than the sum of the lengths of the distal end faces of the inner teeth in the circumferential direction, which is the length of the inner periphery of the stator. Thus, a torque generating face at the radially outer side of the stator is larger than a torque generating face at the radially inner side of the stator, so a torque and torque fluctuations are easy to increase. For this reason, a cogging torque in the motor is further easy to increase. A torque ripple is also easy to increase.

On the other hand, with the configuration described in JP 2008-113480 A, on the basis of the relation between a cogging torque of the outer rotor and an angle of the outer rotor with respect to the stator and the relation between a cogging torque of the inner rotor and an angle of the inner rotor with respect to the stator, a predetermined angle at which the sum of the outer cogging torque and the inner cogging torque is reduced is determined. However, in the case of this configuration as well, the spacing between any adjacent two-phase coils is large in the three-phase coils that are arranged in the respective outer slots of the stator. Since the torque generating face at the radially outer side of the stator is larger than the torque generating face at the radially inner side of the stator, a torque increases. Thus, a cogging torque and a torque ripple are easy to increase.

The disclosure provides a rotary electric machine that includes a rotor provided on a radially inner side of a stator and a rotor provided on a radially outer side of the stator and that reduces a cogging torque and a torque ripple.

An aspect of the disclosure provides a rotary electric machine. The rotary electric machine includes an annular stator, an inner rotor, an outer rotor and a toroidal coil. The annular stator includes a plurality of inner teeth and a plurality of outer teeth. The plurality of inner teeth protrude radially inward. The plurality of outer teeth protrude radially outward. The inner rotor faces a radially inner side of the annular stator. The outer rotor faces a radially outer side of the annular stator. The toroidal coil is arranged in each inner slot between any adjacent two of the inner teeth and a corresponding one outer slot between adjacent two of the outer teeth. The total number of the plurality of outer slots is larger than the total number of the plurality of inner slots. The number of the coils arranged in all the outer slots is larger than or equal to the number of the coils arranged in all the inner slots.

With the rotary electric machine according to the aspect of the disclosure, both a cogging torque and a torque ripple are reduced in the rotary electric machine including the rotor provided on the radially inner side of the annular stator and the rotor provided on the radially outer side of the annular stator.

In the rotary electric machine, the ratio of the total number of the plurality of outer slots to the total number of the plurality of inner slots may be two to one. The number of the coils arranged in all the outer slots may be equal to the number of the coils arranged in all the inner slots.

In the rotary electric machine, the plurality of outer slots may be configured such that a first outer slot and a second outer slot are alternately arranged in a circumferential direction. The ratio of the total number of the plurality of outer slots to the total number of the plurality of inner slots may be two to one. The toroidal coil is arranged in each of the inner slots and the first outer slots. A distributed coil may be arranged in each of the second outer slots. The number of the coils arranged in all the outer slots may be larger than the number of the coils arranged in all the inner slots.

In the rotary electric machine, each first outer slot may be arranged at the same position in the circumferential direction as a corresponding one of the inner slots. Each second outer slot may be arranged at a different position in the circumferential direction with respect to a corresponding one of the inner slots.

In the rotary electric machine, a flat wire coil having a rectangular cross section may be arranged in each first outer slot as the coil. A round wire coil having a circular cross section is arranged in each second outer slot as the coil.

In the rotary electric machine, the first outer slots and the second outer slots may be configured such that two of the first outer slots and two of the second outer slots are alternately arranged in the circumferential direction at the radially outer side of the annular stator.

In the rotary electric machine, the distributed coil arranged in each second outer slot may be wound around a plurality of the outer teeth between the second outer slot and another one of the second outer slots.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the disclosure will be described with reference to the accompanying drawings. In the following description, like reference numerals denote equivalent components in all the drawings.

FIG. 1is a view of part of a rotary electric machine in a circumferential direction according to the embodiment when viewed from one side in an axial direction. The rotary electric machine includes an annular stator10, an inner rotor20and an outer rotor30.

The rotary electric machine is a permanent-magnet synchronous motor that is driven by three-phase alternating current. The rotary electric machine is used as a motor that drives an electric vehicle or a hybrid vehicle or used as a generator or used as a motor generator having both functions.

The annular stator10includes a stator yoke14, a plurality of outer teeth12and a plurality of inner teeth13. The plurality of outer teeth12protrude in a radial direction from the outer periphery of the stator yoke14. The plurality of inner teeth13protrude in the radial direction from the inner periphery of the stator yoke14. Three U-phase, V-phase and W-phase coils15u,15v,15ware wound around the stator yoke14. The coils15u,15v,15ware toroidal coils, and are connected in star connection or delta connection. In the following description, the radial direction means a radiation direction that is the radial direction of the annular stator10, and the circumferential direction means a direction along a circular shape about the central axis of the annular stator10. The axial direction means a direction along the central axis of the annular stator10. In the following description, the annular stator10is referred to as stator10. The coils15u,15v,15wmay be referred to as coils15.

The inner rotor20is rotatably supported inside the stator10. The inner rotor20includes an inner yoke21and an inner permanent magnet22. On the other hand, the outer rotor30is rotatably supported outside the stator10. The outer rotor30includes an outer yoke31and an outer permanent magnet32. The inner rotor20and the outer rotor30each rotate under the influence of magnetic fields that are formed in the stator10by current flowing through the coils15. The inner permanent magnet22is arranged on the surface (outer periphery) of the inner yoke21, and the outer permanent magnet32is arranged on the surface (inner periphery) of the outer yoke31. InFIG. 1, the inner permanent magnet22and the outer permanent magnet32each are shown in a circular arc frame shape; however, actually, a plurality of permanent magnets having different polarities are alternately arranged in each of the permanent magnets22,32in the circumferential direction. Any adjacent permanent magnets in the circumferential direction are magnetized in opposite directions in the radial direction. Thus, an N-pole and an S-pole are alternately arranged at the outer periphery of the inner permanent magnet22in the circumferential direction. Similarly, an N-pole and an S-pole are alternately arranged at the inner periphery of the outer permanent magnet32in the circumferential direction.

In the plurality of outer teeth12that protrude radially outward from the stator yoke14, an outer slot16is provided between any adjacent two of the outer teeth12. In the inner teeth13that protrude radially inward from the stator yoke14and that are half of the outer teeth12in number, an inner slot17is provided between any adjacent two of the inner teeth13.

The toroidal coil15is arranged in each outer slot16and a corresponding one of the inner slots17, and is wound around the stator yoke14. InFIG. 1, the coils15are schematically shown by hatching. InFIG. 1, the straight lines that respectively connect the outer slots16with the corresponding inner slots17schematically represent that a plurality of the coils15inside the outer slots16and a plurality of the coils15inside the corresponding inner slots17are connected at the coil ends.

In addition, the ratio of the total number of the outer slots16to the total number of the inner slots17is two to one, and the total number of the outer slots16is twice as large as the total number of the inner slots17. The coils15that serve as main components for generating a torque are arranged in the outer slots16. In a cross-sectional shape of the stator10, taken along a plane perpendicular to the axial direction, a rectangle that is a shape obtained by connecting all the outer slots16in the circumferential direction and a rectangle that is a shape obtained by connecting all the inner slots17in the circumferential direction have the same shape and area.

Thus, the total number of the plurality of outer slots16is larger than the total number of the plurality of inner slots17. The number of the coils15arranged in all the outer slots16is larger than or equal to the number of the coils15arranged in all the inner slots17. More specifically, of the U, V, W-phase coils15, the coil15arranged in one of the inner slots17is connected to the coils15respectively provided in the corresponding two outer slots16so as to be distributed between the two outer slots16shifted to both sides in the circumferential direction. The number of the coils15arranged in all the outer slots16is equal to the number of the coils15arranged in all the inner slots17. The number of the coils15means the number of the coils15arranged in the corresponding outer slot16or inner slot17in the cross section of the stator10, taken along a plane perpendicular to the axial direction.

A flat wire coil having a rectangular cross section is desirably used as the coil15. With this desirable configuration, the space factor of the coil15in each of the slots16,17is further improved. A round wire coil having a circular cross section may also be used as the coil15.

With the above-described rotary electric machine, the total number of the plurality of outer slots16is larger than the total number of the plurality of inner slots17, and the number of the coils15arranged in all the outer slots16is larger than or equal to the number of the coils15arranged in all the inner slots17. Thus, as for the coils15arranged in the outer slots16, the spacing in the circumferential direction between any adjacent two different phase coils15reduces, so a harmonic magnetic flux reduces. As a result, a cogging torque at the outer rotor30side is reduced. Thus, a cogging torque in the rotary electric machine is reduced as a whole. In addition, a torque ripple in the rotary electric machine is reduced because of a similar reason.

Furthermore, a shape obtained by connecting all the inner slots17in the circumferential direction and a shape obtained by connecting all the outer slots16in the circumferential direction have the same shape and area. Thus, when the toroidal coil15is arranged in each of the outer slots16and a corresponding one of the inner slots17, the space factor of the coil15in each of the slots16,17is improved. Thus, a copper loss is reduced, so the efficiency of the rotary electric machine is improved. When the flat wire coil is used as the coil15, the space factor is further improved.

FIG. 2is a view that shows the relation between a cogging torque and an electrical angle that is a rotation angle of each of the outer rotor30and inner rotor20with respect to the stator10in the rotary electric machine according to the embodiment. InFIG. 2, the continuous line a1represents the relation between a cogging torque of the outer rotor30and an electrical angle of the outer rotor30with respect to the stator10. The broken line b1represents the relation between a cogging torque of the inner rotor20and an electrical angle of the inner rotor20with respect to the stator10.FIG. 2is a graph based on the result of magnetic field analysis.

As shown inFIG. 2, a cogging torque of the outer rotor30at the radially outer side is larger than a cogging torque of the inner rotor20at the radially inner side; however, the difference is reduced, and both the cogging torques are reduced. Thus, a cogging torque in the rotary electric machine is reduced. InFIG. 2, a cogging torque at the radially outer side and a cogging torque at the radially inner side are indicated as a relative magnitude relation.

On the other hand,FIG. 3is a view of part of a rotary electric machine in the circumferential direction according to a first comparative embodiment when viewed from one side in the axial direction. In the first comparative embodiment shown inFIG. 3, different from the embodiment shown inFIG. 1andFIG. 2, the total number of a plurality of outer slots16ain a stator10ais equal to the total number of a plurality of inner slots17ain the stator10a. In addition, the number of the coils15arranged in all the outer slots16ais equal to the number of the coils15arranged in all the inner slots17a. Furthermore, the shape and area of each inner slot17aare respectively the same as the shape and area of each outer slot16a. The other configuration is similar to that of the embodiment shown inFIG. 1.

In the above first comparative embodiment, as shown inFIG. 3, in the coils15arranged in the outer slots16a, the spacing in the circumferential direction between any adjacent two different phase coils15increases as compared to the embodiment shown in FIG.1, so a cogging torque at the radially outer side is easy to increase. Thus, a cogging torque in the rotary electric machine is easy to increase as a whole. In addition, a torque ripple in the rotary electric machine is also easy to increase because of a similar reason.

FIG. 4is a graph that shows the relation between a cogging torque and an electrical angle that is a rotation angle of each of the outer rotor30and inner rotor20with respect to the stator10ain the rotary electric machine according to the first comparative embodiment. InFIG. 4, the meanings of the continuous line a2and broken line b2are the same as the meanings of the continuous line a1and broken line b1inFIG. 2.FIG. 4is a graph based on the result of magnetic field analysis.

FIG. 5is a graph in which a resultant cogging torque in the rotary electric machine according to the embodiment is compared with a resultant cogging torque in the rotary electric machine according to the first comparative embodiment. The resultant cogging torque corresponds to the sum of a cogging torque at the radially inner side and a cogging torque at the radially outer side. InFIG. 5, the continuous line c1represents a resultant cogging torque of the rotary electric machine according to the embodiment, and the broken line c2represents a resultant cogging torque of the rotary electric machine according to the first comparative embodiment. As shown inFIG. 5, the resultant cogging torque according to the embodiment is reduced as compared to the resultant cogging torque according to the comparative embodiment.

FIG. 6is a graph in which a resultant cogging torque in the rotary electric machine according to the first comparative embodiment is compared with a resultant cogging torque in a rotary electric machine according to a second comparative embodiment. The rotary electric machine according to the second comparative embodiment has a similar configuration to the configuration described in JP 2008-113480 A. Specifically, in the rotary electric machine according to the second comparative embodiment, in the case where the rotary electric machine according to the first comparative embodiment shown inFIG. 3is viewed from one side in the axial direction, a second straight line defined for the rotary electric machine and the inner teeth is inclined with respect to a first straight line defined for the outer teeth and the inner teeth. The first straight line is a straight line that connects the center point of the distal end of each of the outer teeth12with the center point of the distal end of a corresponding one of the inner teeth13. The second straight line is a straight line that connects the center point of the rotary electric machine with the center point of the distal end of each of the inner teeth13. The arrangement relation between the outer teeth12and the inner teeth13is regulated such that the second straight line is shifted from the first straight line at an inclination of a predetermined angle θ1, that is, the second straight line and the first straight line are arranged in a skew position. The other configuration is similar to that of the first comparative embodiment shown inFIG. 3.

InFIG. 6, the continuous line c3represents a resultant cogging torque of the rotary electric machine according to the first comparative embodiment, and the broken line c4represents a resultant cogging torque of the rotary electric machine according to the second comparative embodiment. The continuous line c3inFIG. 6is the same as the broken line c2inFIG. 5. As shown inFIG. 6, the resultant cogging torque (broken line c4) of the second comparative embodiment is further increased as compared to the resultant cogging torque (continuous line c3) of the first comparative embodiment.

FIG. 7is a view of part of a rotary electric machine in the circumferential direction according to an alternative embodiment to the embodiment when viewed from one side in the axial direction. In the configuration according to the alternative embodiment shown inFIG. 7, different from the embodiment shown inFIG. 1, a plurality of outer slots40provided at the radially outer side of a stator10bare formed such that a first outer slot41and a second outer slot42are alternately arranged in the circumferential direction. A plurality of inner slots17bare provided at the radially inner side of the stator10b.

The ratio of the total number of the plurality of outer slots40to the total number of the plurality of inner slots17bis two to one. Each first outer slot41, each second outer slot42and each inner slot17bhave substantially the same rectangular shape when viewed from one side in the axial direction. The area of the shape of each first outer slot41, the area of the shape of each second outer slot42and the area of the shape of each inner slot17bare substantially the same when viewed from one side in the axial direction. Each first outer slot41, each second outer slot42and each inner slot17bhave substantially the same shape in a cross section taken along a plane perpendicular to the axial direction over the entire length in the axial direction. For this reason, in a cross-sectional shape of the rotary electric machine, taken along a plane perpendicular to the axial direction, the sum of the areas of the plurality of outer slots40is larger than the sum of the areas of the plurality of inner slots17b.

Three toroidal U, V, W-phase coils15u,15v,15ware respectively arranged in the first outer slots41and the corresponding inner slots17b. On the other hand, three distributed U, V, W-phase coils50u,50v,50ware respectively arranged in the second outer slots42. Hereinafter, the coils50u,50v,50wmay be referred to as coils50. InFIG. 7, the toroidal coils15and the distributed coils50are respectively indicated by different oblique lines. Thus, the number of the coils15,50arranged in all the outer slots41,42is larger than the number of the coils15arranged in all the inner slots17b.

The distributed coil50of each phase, arranged in each second outer slot42, extends from the openings of the second outer slot42at both ends in the axial direction toward both sides in the circumferential direction, and are wound around a plurality of the outer teeth12between the second outer slot42and other two of the second outer slots42. InFIG. 7, in each distributed coil50, portions that are arranged at coil ends and that extend in the circumferential direction are indicated by the broken lines. Each distributed coil50is desirably formed of a round wire coil. With this configuration, the distributed coils50are easy to be wound in complex directions by using twistable round wires.

Each distributed coil50is not intensively arranged in one slot but arranged in a plurality of slots in a distributed manner, and the distributed coils50are connected to each other via the coil ends in distributed winding. The distributed coil50in each second outer slot42is wound in a predetermined orientation such that current in the same direction as current flowing through the adjacent toroidal coil15of the same phase on one side (right side inFIG. 7) in the circumferential direction flows at the same timing as the toroidal coil15of the same phase.

For example, the direction of current flowing through each distributed coil50and each toroidal coil15will be described in detail with reference toFIG. 7. It is assumed that current in the toroidal coil15of one phase in the first outer slot41flows from the near side of the drawing sheet toward the far side of the drawing sheet and current in the toroidal coil15of the same phase in the inner slot17bflows from the far side of the drawing sheet toward the near side of the drawing sheet. At this time, current in the distributed coil50of the same phase as the above-described one phase and located adjacent to the other side (left side inFIG. 7) of the toroidal coil15in the circumferential direction conducts in a direction from the near side of the drawing sheet toward the far side of the drawing sheet.

Where the first outer slot41and the second outer slot42that are located adjacent to each other in the circumferential direction and in which the coils15,50through which current of the same phase flows are arranged are assumed as one set, a plurality of the sets are arranged in the circumferential direction at the radially outer side of the stator10b. At this time, the center position between the outer slots41,42in the circumferential direction in each set and the center position of the inner slot17bin the circumferential direction, in which another portion of the coil15that is inserted in the first outer slot41of that set is arranged coincide with each other in the circumferential direction.

With the above-configuration, the sum of the areas of the plurality of outer slots40is larger than the sum of the areas of the plurality of inner slots17b. Thus, the number of the coils15,50arranged in all the outer slots40is larger than the number of the coils15arranged in all the inner slots17b. The toroidal coil15is arranged in each of the first outer slots41, and the distributed coil50is arranged in each of the second outer slots42. Thus, the amount of magnetic flux that is generated in an outer magnetic path that is formed between the stator10band the outer rotor30is larger than the amount of magnetic flux that is generated in an inner magnetic path that is formed between the stator10band the inner rotor20. As a result, magnetic saturation in the inner teeth13having a shorter circumference as a whole is mostly avoided, so the difference in magnetic saturation between the radially inner side and radially outer side of the stator10bis reduced. Furthermore, a magnetic flux density in the outer teeth12having a longer circumference as a whole is improved. For these reasons, the torque of the rotary electric machine is increased.

As in the case of the embodiment shown inFIG. 1andFIG. 2, the spacing in the circumferential direction between the coils15,50of different phases, respectively arranged in the outer slots40, reduces. That is, the spacing in the circumferential direction between any adjacent two sets of the outer slots41,42reduces. Thus, a harmonic magnetic flux reduces, so a cogging torque and a torque ripple at the outer rotor30side are reduced, with the result that a cogging torque and a torque ripple in the rotary electric machine as a whole are reduced. The other configuration and operation are similar to those of the embodiment shown inFIG. 1andFIG. 2.

FIG. 8is a view of part of a rotary electric machine in the circumferential direction according to an alternative embodiment to the embodiment when viewed from one side in the axial direction. In the configuration according to the alternative embodiment shown inFIG. 8, different from the configuration shown inFIG. 7, each first outer slot41of a stator10cis arranged at the same position in the circumferential direction as a corresponding one of the inner slots17b. On the other hand, each second outer slot42is arranged at a different position in the circumferential direction with respect to a corresponding one of the inner slots17b. Thus, the center position (position indicated by L1) of each set of the outer slots41,42is shifted in the circumferential direction from the center position (position indicated by L2) of a corresponding one of the inner slots17bin the circumferential direction, in which another portion of the coil15inserted in the first outer slot41of that set is arranged. Since each first outer slot41is arranged at the same position in the circumferential direction as a corresponding one of the inner slots17b, the toroidal coil15just needs to be wound in substantially the radial direction of the stator10cso as to be arranged in the first outer slot41and the inner slot17b. Thus, the coil15becomes easy to be wound.

Desirably, each toroidal coil15is formed of a flat wire coil. With this desirable configuration, the toroidal coil15is easy to be aligned, and the space factor of the coil15in each of the first outer slots41and a corresponding one of the inner slots17bis improved. When each first outer slot41and a corresponding one of the inner slots17bare arranged at the same position in the circumferential direction as in the case of the configuration shown inFIG. 8, it is remarkably effective that the coil15is easy to be wound in the case where the flat wire coil15is arranged in each of the first outer slots41and a corresponding one of the inner slots17b. At this time, since the toroidal coil15is allowed to be wound so as to be further closer to the stator10c, the coil ends are reduced. In addition, the center position (position indicated by L1) between the outer slots41,42of each set in the circumferential direction is shifted in the circumferential direction from the center position (position indicated by L2) of a corresponding one of the inner slots17bin the circumferential direction, in which another portion of the coil15that is inserted in the first outer slot41of that set is arranged. InFIG. 8, the alternate long and short dashes line that extends in the radial direction and that represents L1is shifted from the alternate long and short dashes line that extends in the radial direction and that represents L2at an inclination of the predetermined angle θ1. Here, a cogging torque that is a torque that is generated from magnetic interaction between the inner rotor20and the radially inner side of the stator10cis defined as a radially inner-side cogging torque. A cogging torque that is a torque that is generated from magnetic interaction between the outer rotor30and the radially outer side of the stator10cis defined as a radially outer-side cogging torque. In this case, by appropriately selecting the predetermined angle θ1, the configuration in which the radially inner-side cogging torque and the radially outer-side cogging torque cancel out each other is obtained. For example, in order to select the predetermined angle θ1, while θ1is being changed, the relation between the rotation speed of each of the inner and outer rotors20,30and the radially inner-side and radially outer-side cogging torques is obtained by executing simulation. Thus, θ1that gives a small cogging torque in the rotary electric machine as a whole is obtained. For this reason, the cogging torque of the rotary electric machine is reduced. For a similar reason, a torque ripple of the rotary electric machine is also reduced. The other configuration and operation are similar to those of the configuration shown inFIG. 7.

FIG. 9is a view for illustrating that the coil ends increase in the configuration shown inFIG. 7, and is a view in which the length of part of the rotary electric machine shown inFIG. 7in the circumferential direction is extended. In the configuration shown inFIG. 7andFIG. 9, as described above, the distributed coil50arranged in each second outer slot42extends from the openings at both ends of the second outer slot42in the axial direction toward both sides in the circumferential direction and are wound around the plurality of outer teeth12between the second outer slot42and other two second outer slots42.

In such a configuration shown inFIG. 7andFIG. 9, as indicated by portions surrounded by broken-line ellipses α1, α2, . . . , α6inFIG. 9, three broken lines that represent the distributed coils50each overlap the first outer slot41in which the toroidal coil15is arranged. This means that, in each portion indicated by the broken-line ellipse, the distributed coils50of three different phases are arranged outside the coil ends of the toroidal coil15. Therefore, with the configuration shown inFIG. 7andFIG. 9, the coil ends tend to increase. Such a situation also applies to the configuration shown inFIG. 8. Next, a configuration according to an alternative embodiment, which will be described with reference toFIG. 10, is made in order to reduce the coil ends under such a situation.

FIG. 10is a view of part of a rotary electric machine in the circumferential direction according to an alternative embodiment to the embodiment when viewed from one side in the axial direction. In the configuration according to the alternative embodiment shown inFIG. 10, different from the case of the configuration shown inFIG. 7andFIG. 9, adjacent two of the first outer slots41and adjacent two of the second outer slots42are alternately arranged in the circumferential direction at the radially outer side of a stator10d. Thus, the configuration shown inFIG. 10differs from the configuration shown inFIG. 9in the order in which the plurality of first outer slots41and the plurality of second outer slots42are arranged in the circumferential direction of the stator10d.

In addition, the distributed coil50arranged in each second outer slot42extends from the openings at both ends of the second outer slot42in the axial direction toward only one side or the other side in the circumferential direction, and is wound around the plurality of outer teeth12between the second outer slot42and another one of the second outer slots42. Thus, the distributed coil50arranged in each second outer slot42is wound around the plurality of outer teeth12between the second outer slot42and only another one of the second outer slots42.

With the above configuration, a revolving magnetic field that is generated in the stator10dis the same as the revolving magnetic field of the configuration shown inFIG. 9. On the other hand, with the configuration shown inFIG. 10, since the two first outer slots41and the two second outer slots42are alternately arranged in the circumferential direction, a fewer number of the distributed coils50overlap the outside of each first outer slot41in the axial direction. Thus, at each coil end, a fewer number of the distributed coils50overlap the outside of the toroidal coil15arranged in each first outer slot41.

The distributed coil50arranged in each second outer slot42is wound around the plurality of outer teeth12between the second outer slot42and only another one of the second outer slots42. Thus, at each coil end, a further fewer number of the distributed coils50overlap the outside of the toroidal coil15arranged in each first outer slot41. For this reason, with the configuration according to this embodiment, the coil ends are reduced. InFIG. 10, only the distributed coil50of one phase overlaps the inner portion of each of the first outer slots41surrounded by the broken-line ellipses β1, β2. This means that only the distributed coil50of one phase overlaps the outside of the toroidal coil15arranged in each first outer slot41. This also applies to the coil15arranged in each first outer slot41. Therefore, with the configuration shown inFIG. 10, the number of the distributed coils50that overlap each toroidal coil15at each coil end is reduced from three phase to one phase as compared to the configuration shown inFIG. 9, so the coil ends are reduced. The other configuration and operation are similar to those of the configuration shown inFIG. 8andFIG. 9.

The embodiments of the disclosure are described above; however, the disclosure is not limited to the above-described embodiments. Various modifications are applicable.