Rotary electric machine and driving controller for rotary electric machine

A plurality of salient poles projecting toward a stator are arranged on a rotor core along the circumferential direction while being spaced apart from each other, and rotor windings are wound around these salient poles. The rotor windings are short-circuited through diodes, respectively; and when currents rectified by the diodes flow through the rotor windings, the salient poles are magnetized to produce a magnet where the magnetic pole is fixed. The width θ of each salient pole in the circumferential direction is smaller than a width corresponding to an electric angle of 180° of the rotor, and the rotor windings are wound around each salient pole by short-pitch winding.

TECHNICAL FIELD

The present invention relates to a rotary electric machine including a stator and a rotor that are disposed in spaced confronting relationship, and to a driving controller for the rotary electric machine.

BACKGROUND ART

A brushless power generator disclosed in the following Patent Document 1 includes a main power generation winding and an exciting winding that are wound around a stator, a field winding and an auxiliary field winding that are wound around a rotor, a diode that short-circuits the exciting winding of the stator, and a rectifier that rectifies a current flowing from the auxiliary field winding to the field winding of the rotor. According to Patent Document 1, when the rotor starts rotating, an induced voltage is generated on the exciting winding of the stator due to a residual magnetism of a field core of the rotor. Exciting current flows in one direction via the diode and a static magnetic field is generated on the stator. As the rotor rotates in the static magnetic field, an induced voltage is generated on the auxiliary field winding wound around the field core of the rotor. Field current rectified by the rectifier flows through the field winding. Therefore, magnetic poles of N-poles and S-poles are generated on the rotor.

The following Patent Document 2 discloses a reactor connected to a main power generation winding of a stator, which is arranged as a concentrated full-pitch winding, instead of providing the above-described exciting winding on the stator. According to Patent Document 2, when the rotor starts rotating, a residual field of a rotor core induces an electromotive force on the main power generation winding of the stator. The induced electromotive force causes a reactor exciting current that flows, as armature current, in a closed circuit including the main power generation winding and the reactor. As a result, an armature reaction magnetic field is generated. In this case, because the main power generation winding of the stator is the concentrated full-pitch winding, the generated armature reaction magnetic field includes harmonics components (a fifth space harmonics magnetic field). The armature reaction magnetic field including the fifth space harmonics magnetic field interlinks with the auxiliary field winding of the rotor. Accordingly, an electromotive force is generated on the auxiliary field winding. A diode bridge circuit converts the generated electromotive force into a direct current that can be supplied as field current to a field winding of the rotor. Therefore, magnetic poles of N-poles and S-poles are generated on the rotor.

The following Patent Document 3 discloses an arrangement that does not include the above-described auxiliary field winding of the rotor and, instead, uses a diode that short-circuits a full-pitch field winding of the rotor. According to Patent Document 3, when the rotor starts rotating, a residual field of a rotor core induces an electromotive force on the main power generation winding of the stator. The induced electromotive force causes a reactor exciting current that flows, as armature current, in a closed circuit including the main power generation winding and the reactor. As a result, an armature reaction magnetic field is generated. Further, an electromotive force is induced on the field winding of the rotor that is magnetically connected to odd-order space harmonics components of the armature reaction magnetic field. Field current rectified by the diode flows through the field winding. As a result, magnetic poles of N-poles and S-poles are generated on the rotor. Further, the following Patent Document 4 discloses a parallel connection of the above-described full-pitch field windings of the rotor for the purpose of increasing the field current that flows through the field winding.

According to Patent Documents 1 and 2, the exciting winding or the reactor is provided on the stator in addition to the main power generation winding. Further, the auxiliary field winding is provided on the rotor in addition to the field winding. Therefore, the winding structure tends to be complicated, and downsizing the entire winding structure becomes difficult. According to Patent Documents 3 and 4, the auxiliary field winding of the rotor is omitted because the field winding of the rotor is short-circuited via the diode. However, the exciting winding or the reactor is provided on the stator in addition to the main power generation winding. Therefore, the winding structure tends to be complicated. Further, according to Patent Documents 3 and 4, it is difficult to efficiently generate the electromotive force, which is induced by the space harmonics components, on the field winding of the rotor, because the field winding of the rotor is a full-pitch winding. It is therefore necessary to use the exciting winding or the reactor of the stator, other than the main power generation winding, to generate the electromotive force to be induced by the space harmonics components on the field winding of the rotor.

Patent Document 1: JP 62-23348 A

Patent Document 2: JP 4-285454 A

Patent Document 3: JP 8-65976 A

Patent Document 4: JP 11-220857 A

DISCLOSURE OF THE INVENTION

The present invention has an advantage to efficiently generate the electromotive force to be induced by the harmonics components on the rotor winding and efficiently increase the torque of the rotor. Further, the present invention has another advantage to simplify the winding structure of a rotary electric machine.

A rotary electric machine according to the present invention includes a stator and a rotor, which are disposed in spaced confronting relationship. The stator includes a stator core on which a plurality of slots are formed and spaced apart from each other in a circumferential direction around a rotor rotational shaft, and stator windings of a plurality of phases that are provided in the slots and wound around the stator core by concentrated winding, in which a rotating magnetic field including harmonics components is formed when AC currents flow through the stator windings. The rotor includes a rotor core, rotor windings wound around the rotor core to generate an induced electromotive force when interlinked with the rotating magnetic field including the harmonics components formed by the stator, and a rectifying element that rectifies currents flowing through the rotor windings in response to generation of the induced electromotive force. The rotor core includes a plurality of magnetic pole portions, around which the rotor windings are wound, which can function as magnets where the magnetic pole is fixed. The magnetic pole portions are magnetized when the currents rectified by the rectifying element flow through the rotor windings. The magnetic pole portions are disposed in spaced confronting relationship with the stator in a state where the magnetic pole portions are spaced apart from each other in the circumferential direction. Further, the rotor windings are wound around respective magnetic pole portions by short-pitch winding.

According to an aspect of the present invention, it is preferable that the width of the rotor winding wound around each magnetic pole portion in the circumferential direction is substantially equal to a width corresponding to an electric angle of 90°.

According to an aspect of the present invention, it is preferable that each magnetic pole portion of the rotor core has a magnetic resistance that is smaller than a magnetic resistance of a portion corresponding to a position between magnetic pole portions in the circumferential direction. Further, according to an aspect of the present invention, it is preferable that each magnetic pole portion of the rotor core projects toward the stator. Further, according to an aspect of the present invention, it is preferable that the rotor includes a permanent magnet provided at a portion corresponding to a position between magnetic pole portions in the circumferential direction.

According to an aspect of the present invention, it is preferable that the rotor windings wound around respective magnetic pole portions are electrically isolated from each other, the rectifying element is provided for each of the rotor windings that are electrically isolated, and respective rectifying elements rectify currents that flow through the rotor windings wound around respective magnetic pole portions in such a manner that magnetic poles of the magnetic pole portions alternate in the circumferential direction.

According to an aspect of the present invention, it is preferable that the rotor windings wound around the magnetic pole portions that are adjacent to each other in the circumferential direction are electrically isolated from each other, the rectifying element is provided for each of the rotor windings that are electrically isolated, and respective rectifying elements rectify currents that flow through rotor windings wound around the magnetic pole portions, which are adjacent to each other in the circumferential direction, in such a way as to differentiate directions of the magnetic poles of the neighboring magnetic pole portions. In this case, it is preferable that rotor windings wound around the magnetic pole portions that can function as magnets having the same magnetic pole are electrically connected.

Further, a rotary electric machine according to the present invention includes a stator and a rotor, which are disposed in spaced confronting relationship. The stator includes a stator core on which a plurality of slots are formed and spaced apart from each other in a circumferential direction around a rotor rotational shaft, and stator windings of a plurality of phases that are provided in the slots and wound around the stator core by concentrated winding, in which a rotating magnetic field including harmonics components is formed when AC currents flow through the stator windings. The rotor includes a rotor core, rotor windings wound around the rotor core to generate an induced electromotive force when interlinked with the rotating magnetic field including the harmonics components formed by the stator, and a rectifying element that rectifies currents flowing through the rotor windings in response to generation of the induced electromotive force. The rotor core includes a plurality of magnetic pole portions, which can function as magnets where the magnetic pole is fixed. The magnetic pole portions are magnetized when the currents rectified by the rectifying element flow through the rotor windings. The magnetic pole portions are disposed in spaced confronting relationship with the stator in a state where the magnetic pole portions are spaced apart from each other in the circumferential direction. Further, the width of each magnetic pole portion in the circumferential direction is smaller than a width corresponding to an electric angle of 180°.

According to an aspect of the present invention, it is preferable that the width of each magnetic pole portion in the circumferential direction is substantially equal to a width corresponding to an electric angle of 90°.

According to an aspect of the present invention, it is preferable that the rotor core further includes an annular core portion, the rotor windings are wound around the annular core portion by toroidal winding, and each magnetic pole portion projects from the annular core portion toward the stator.

Further, a rotary electric machine according to the present invention includes a stator and a rotor, which are disposed in spaced confronting relationship. The stator includes a stator core on which a plurality of slots are formed and spaced apart from each other in a circumferential direction around a rotor rotational shaft, and stator windings of a plurality of phases that are provided in the slots and wound around the stator core by concentrated winding, in which a rotating magnetic field including harmonics components is formed when AC currents flow through the stator windings. The rotor includes a rotor core, rotor windings wound around the rotor core to generate an induced electromotive force when interlinked with the rotating magnetic field including the harmonics components formed by the stator, and a rectifying element that rectifies currents flowing through the rotor windings in response to generation of the induced electromotive force. The rotor core includes a plurality of magnetic pole portions that can function as magnets where the magnetic pole is fixed. The magnetic pole portions are magnetized when the currents rectified by the rectifying element flow through the rotor windings. The magnetic pole portions are disposed in spaced confronting relationship with the stator in a state where the magnetic pole portions are spaced apart from each other in the circumferential direction. The rotor windings are a common rotor winding wound around each magnetic pole portion. Further, directions of winding portions of the common rotor winding, which are wound around magnetic pole portions that are adjacent to each other in the circumferential direction, are opposite each other.

According to an aspect of the present invention, it is preferable that the width of the rotor winding wound around each magnetic pole portion is set to be larger than a width corresponding to an electric angle of 90° in the circumferential direction and smaller than a width corresponding to an electric angle of 120°.

Moreover, a driving controller for a rotary electric machine according to the present invention includes the rotary electric machine according to the present invention, and a control unit that controls the phase of AC currents that flow through the stator windings to thereby control the torque of the rotor.

According to the present invention, the electromotive force to be induced by the harmonics components generated by the rotor windings can be efficiently increased. The magnetic flux of the magnet to be generated on each magnetic pole portion by the current that flows through the rotor winding can be efficiently increased. As a result, the torque of the rotor can be efficiently increased. Further, according to the present invention, the electromotive force to be induced by the harmonics components can be generated on the rotor windings without providing any type of winding other than the stator windings on the stator, and without providing any type of winding other than the rotor windings on the rotor. As a result, the type of the winding to be provided on each of the stator and the rotor can be simplified into one type. Thus, the winding structure of a rotary electric machine can be simplified.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 to 3are views illustrating a schematic configuration of a rotary electric machine10according to an embodiment of the present invention.FIG. 1schematically illustrates an assembled configuration of a stator12and a rotor14, which are seen from a direction parallel to a rotor rotational shaft22.FIG. 2schematically illustrates a configuration of the stator12.FIG. 3schematically illustrates a configuration of the rotor14. The rotary electric machine10according to the present embodiment includes the stator12fixed to a casing (not illustrated), and the rotor14that is rotatable relative to the stator12and is disposed in spaced confronting relationship with the stator12via a predetermined gap. The example illustrated inFIGS. 1 to 3is a radial type rotary electric machine, according to which the stator12and the rotor14are disposed in spaced confronting relationship in a radial direction perpendicular to the rotational shaft22(hereinafter, simply referred to as “radial direction”). The rotor14is disposed on the inner side of the stator12in the radial direction.

The stator12includes a stator core26and multiple-phase (more specifically, odd-phase (e.g., three-phase)) stator windings28u,28v, and28wthat are provided on the stator core26. The stator core26includes a plurality of teeth30that project inward in the radial direction (i.e., toward the rotor14) and are spaced apart from each other in the circumferential direction around the rotational shaft22(hereinafter, simply referred to as “circumferential direction”). A slot31is formed between two teeth30. More specifically, a plurality of slots31are formed on the stator core26along the circumferential direction while being spaced apart from each other. The stator windings28u,28v, and28wof respective phases are located in the slots31and are wound around the teeth30by concentrated short-pitch winding. The teeth30and the stator windings28u,28v, and28wwound around the teeth30constitute magnetic poles. When multiple-phase (e.g., three-phase or odd-phase) AC currents flow through the multiple-phase (e.g., three-phase or odd-phase) stator windings28u,28v, and28w, the teeth30arrayed in the circumferential direction are sequentially magnetized. Thus, a rotating magnetic field that rotates in the circumferential direction is formed on the teeth30. The rotating magnetic field formed on the teeth30acts on the rotor14from the front end surface of the teeth30. In the example illustrated inFIG. 2, three teeth30and a set of three-phase (i.e., u-phase, v-phase, and w-phase) stator windings28u,28v, and28wwound around three teeth30configures a pair of poles. As a result, four-pole three-phase stator windings28u,28v, and28ware wound around respective teeth30. The number of pairs of poles on the stator12is four pairs of poles.

The rotor14includes a rotor core16and a plurality of rotor windings18nand18sprovided on the rotor core16. A plurality of salient poles19projecting outward (i.e., toward the stator12) in the radial direction are arranged on the rotor core16along the circumferential direction while being spaced apart from each other. Each salient pole19opposes the stator12(i.e., the teeth30). A magnetic resistance acting on the rotor14when the magnetic flux of the stator12(i.e., the teeth30) passes through the rotor14is variable in the rotational direction by the salient pole19. The magnetic resistance becomes smaller at a position corresponding to each salient pole19in the rotational direction. The magnetic resistance becomes larger at a position (e.g., midpoint) between two neighboring salient poles19in the rotational direction. The rotor windings18nand18sare wound around these salient poles19so that the rotor windings18nand the rotor windings18sare alternately disposed in the circumferential direction. Each of the rotor windings18nand18shas a winding center-axis that corresponds to the radial direction. As illustrated inFIG. 3, a d-axis magnetic path is a magnetic path that passes through the position between two neighboring salient poles19where the magnetic resistance is large. A q-axis magnetic path is a magnetic path that passes through the salient pole19itself where the magnetic resistance is small. Each of the rotor windings18nand18sis disposed around the q-axis magnetic path where the magnetic resistance is small. In the example illustrated inFIG. 3, the rotor windings18nand18swound around respective salient poles19are electrically disconnected and isolated (i.e., insulated). Diodes21nand21s(i.e., rectifying elements) are connected between two terminal ends of respective rotor windings18nand18sthat are electrically isolated from each other. Each rotor winding18nis short-circuited via the diode21n. Thus, the current that flows through the rotor winding18ncan be rectified by the diode21nso as to flow in one direction. Similarly, each rotor winding18sis short-circuited via the diode21s. Thus, the current that flows through the rotor winding18scan be rectified by the diode21sso as to flow in one direction. In the present embodiment, directions of the diodes21nand21sconnected to the rotor windings18nand18sare opposite each other. Therefore, current flowing directions (i.e., rectifying directions regulated by the diodes21nand21s) are opposite each other between the rotor windings18nand the rotor windings18sthat are alternately disposed in the circumferential direction.

When a DC current flows through the rotor winding18naccording to the rectifying direction of the diode21n, the salient pole19around which the rotor winding18nis wound can be magnetized. Therefore, the salient pole19can function as a magnet where the magnetic pole is fixed (i.e., a magnetic pole portion). Similarly, when a DC current flows through the rotor winding18saccording to the rectifying direction of the diode21s, the salient pole19around which the rotor winding18sis wound can be magnetized. Therefore, the salient pole19can function as a magnet where the magnetic pole is fixed (i.e., a magnetic pole portion). The directions of the DC currents that flow through the rotor winding18nand the rotor winding18s, which are adjacent to each other in the circumferential direction, are opposite each other. Therefore, magnetized directions of two salient poles19, which are adjacent to each other in the circumferential direction, are opposite each other. Magnets having mutually different magnetic poles can be formed on two salient poles19. The magnetic poles of the salient poles19alternate in the circumferential direction. In the present embodiment, an N-pole is formed on the salient pole19around which the rotor winding18nis wound. Further, an S-pole is formed on the salient pole19around which the rotor winding18sis wound. To this end, the setting for the diodes21nand21sis performed to adjust the current rectifying directions of the rotor windings18nand18s. In this manner, the magnets are formed on respective salient poles19so that the N-poles and the S-poles are alternately arrayed in the circumferential direction. Further, two salient poles19(i.e., the N-pole and the S-pole) that are adjacent to each other in the circumferential direction can constitute a pair of poles. According to the example illustrated inFIG. 3, the rotor14includes a total of eight salient poles19. The number of pairs of poles on the rotor14is four pairs of poles. Therefore, according to the example illustrated inFIGS. 1 to 3, the number of pairs of poles on the stator12is four pairs of poles while the number of pairs of poles on the rotor14is four pairs of poles. In this respect, the number of pairs of poles on the stator12is equal to the number of pairs of poles on the rotor14. However, the number of pairs of poles on the stator12and the number of pairs of poles on the rotor14can be any number other than four pairs of poles.

In the present embodiment, the width of each salient pole19in the circumferential direction is set to be shorter than a width corresponding to an electric angle of 180° of the rotor14. Further, the width θ of respective rotor windings18nand18sin the circumferential direction is set to be shorter than the width corresponding to an electric angle of 180° of the rotor14. The rotor windings18nand18sare wound around the salient poles19by short-pitch winding. Regarding the width θ of respective rotor windings18nand18s, it may be useful to regulate the distance between the centers of the cross sections of the rotor windings18nand18sin consideration of the cross-sectional areas of respective rotor windings18nand18s. More specifically, the width θ of respective rotor windings18nand18scan be expressed using an average value obtainable from a gap between inner circumferential surfaces of the rotor windings18nand18sand a gap between outer circumferential surfaces of the rotor windings18nand18s. The electric angle of the rotor14can be expressed using a value that is obtainable by multiplying the mechanical angle of the rotor14by the number of pairs of poles p (p=4 according to the example illustrated inFIG. 3) of the rotor14(namely, electric angle=mechanical angle×p). Therefore, the width θ of respective rotor windings18nand18sin the circumferential direction satisfies the following formula (1) when “r” represents a distance from the center of the rotational shaft22to the rotor windings18nand18s.
θ<π×r/p(1)

In the present embodiment, the magnetomotive force that causes the stator12to generate the rotating magnetic field has a distribution that is not similar to a sine wave distribution (including only the basic wave), because of the layout of the stator windings28u,28v, and28wof respective phases and the shape of the stator core26that includes the teeth30and the slots31. The distribution of the magnetomotive force that causes the stator12to generate the rotating magnetic field includes harmonics components. Particularly, according to the concentrated winding, the stator windings28u,28v, and28wof respective phases are not overlapped with each other. Therefore, the harmonics components appearing in the magnetomotive force distribution of the stator12increase in amplitude level. Further, for example, in a case where the stator windings28u,28v, and28ware three-phase concentrated windings, input electric frequency tertiary components increase as harmonics components increase in amplitude level. In the following description, the harmonics components that may be caused in the magnetomotive force due to the layout of the stator windings28u,28v, and28wand the shape of the stator core26are referred to as space harmonics.

The rotating magnetic field (basic wave component) formed on the teeth30interacts with the rotor14when three-phase AC currents flow through the three-phase stator windings28u,28v, and28w. Correspondingly, the salient poles19are magnetically attracted by the rotating magnetic field of the teeth30in such a manner that the magnetic resistance of the rotor14becomes smaller. Accordingly, a torque (i.e., a reluctance torque) acts on the rotor14. The rotor14rotates in synchronization with the rotating magnetic field (basic wave component) produced by the stator12.

Further, when the rotating magnetic field produced by the teeth30, which includes space harmonics components, interlinks with the rotor windings18nand18sof the rotor14, the rotor windings18nand18sare subjected to magnetic flux variations that are caused by the space harmonics components at a frequency that is different from the rotation frequency (i.e., basic wave component of the rotating magnetic field) of the rotor14. The above-described magnetic flux variations cause respective rotor windings18nand18sto produce induced electromotive forces. Currents that flow through the rotor windings18nand18sin accordance with the generation of the induced electromotive force are rectified by respective diodes21nand21s. Therefore, these currents flow in one direction (as DC currents). Further, when the DC currents rectified by respective diodes21nand21sflow through the rotor windings18nand18s, the salient poles19are magnetized correspondingly. Accordingly, magnets each having a magnetic pole (either the N-pole or the S-pole) are produced on the salient poles19. As described above, the current rectifying directions of the rotor windings18nand18s, which are regulated by the diodes21nand21s, are opposite each other. Therefore, the magnets produced on respective salient poles19are arranged in such a manner that N-poles and S-poles are alternately disposed in the circumferential direction. Further, when the magnetic field of each salient pole19(i.e., the magnet where the magnetic pole is fixed) interacts with the rotating magnetic field (i.e., basic wave component) of the teeth30, attractive and repulsive functions are generated. The electromagnetic interaction (i.e., the attractive and repulsive functions) between the rotating magnetic field (basic wave component) of the teeth30and the magnetic field of the salient poles19(magnets) generates a torque (i.e., a torque that corresponds to a magnetic torque) that acts on the rotor14. Therefore, the rotor14rotates in synchronization with the rotating magnetic field (basic wave component) formed by the stator12. As described above, the rotary electric machine10according to the present embodiment can function as a motor that generates motive power (i.e., mechanical power) from the rotor14when electric power is supplied to the stator windings28u,28v, and28w. Meanwhile, the rotary electric machine10according to the present embodiment can function as an electric power generator that generates electric power from the stator windings28u,28v, and28wwhen the rotor14generates motive power.

FIGS. 4A and 4Billustrate calculation results of the flux linkage interacting with the rotor windings18nand18sthat may be generated by the space harmonics. Each waveform illustrated inFIG. 4Arepresents a waveform of the flux linkage that interacts with rotor windings18nand18swhen the phase (i.e., the current vector phase relative to the rotor position) of respective AC currents flowing through the stator windings28u,28v, and28wis changed. Further,FIG. 42represents a result of frequency analysis performed on the waveform of the flux linkage that interacts with the rotor windings18nand18s. From the frequency analysis result illustrated inFIG. 42, it is understood that input electric frequency tertiary components are mainly generated. As illustrated inFIG. 4A, the flux linkage waveform does not substantially change even when the current vector phase is changed, although the bias of the flux linkage is variable.

The amplitude (i.e. variation width) of a flux linkage that interacts with the rotor windings18nand18sis influenced by the width θ of respective rotor windings18nand18sin the circumferential direction.FIG. 5illustrates a calculation result of the amplitude (i.e., variation width) of a flux linkage that interacts with the rotor windings18nand18s, which can be obtained by changing the width θ of the rotor windings18nand18sin the circumferential direction. InFIG. 5, the coil width θ is expressed using a value converted into an electric angle. As illustrated inFIG. 5, the variation width of the flux linkage that interacts with the rotor windings18nand18sincreases when the coil width θ decreases from the angle 180°. Therefore, the amplitude of the flux linkage generated by the space harmonics can be increased by setting the coil width θ to be smaller than the angle 180°; more specifically, by winding the rotor windings18nand18sby short-pitch winding, as compared with the case of full-pitch winding.

Accordingly, in the present embodiment, the induced electromotive forces to be generated by the space harmonics on the rotor windings18nand18scan be efficiently increased by setting the width of each salient pole19to be smaller than the width corresponding to an electric angle of 180° in the circumferential direction and further by winding the rotor windings18nand18saround the salient poles19by short-pitch winding. Therefore, the present embodiment can efficiently generate induced currents that flow through the rotor windings18nand18sby utilizing the space harmonics that do not substantially contribute to the generation of torque. The present embodiment can efficiently increase the magnetic fluxes of the magnets on the salient poles19that are generated by the induced currents. As a result, the torque that acts on the rotor14can be efficiently increased. Further, the present embodiment can efficiently generate the electromotive forces to be induced by the space harmonics on the rotor windings18nand18swithout providing any type of winding (e.g., the exciting winding or the reactor discussed in the Patent Documents 1 to 4) other than the stator windings28u,28v, and28won the stator12. Therefore, the windings to be provided on the stator12can be simplified into only one type (i.e., only the stator windings28u,28v, and28w). As a result, the winding structure of the stator12can be simplified. Further, by rectifying the induced current to be caused by the induced electromotive force with the diodes21nand21s, the magnet where the magnetic pole is fixed can be generated on the rotor14(i.e., each salient pole19) without providing any type of winding (e.g., the auxiliary field winding discussed in the Patent Documents 1 and 2) other than the rotor windings18nand18son the rotor14. Therefore, the windings to be provided on the rotor14can be simplified into only one type (only the rotor windings18nand18s). The winding structure of the rotor14can be simplified. As a result, the winding structure of the rotary electric machine10can be simplified, and the rotary electric machine10can be downsized.

Further, as illustrated inFIG. 5, the amplitude of the flux linkage generated by the space harmonics can be maximized when the coil width θ is 90°. Accordingly, in the present embodiment, to further increase the amplitude of the flux linkage generated by the space harmonics that interacts with the rotor windings18nand18s, the width θ of the rotor windings18nand18sin the circumferential direction is preferably equal to (or substantially equal to) the width corresponding to an electric angle of 90° of the rotor14. Therefore, it is preferable that the width θ of the rotor windings18nand18sin the circumferential direction satisfies (or substantially satisfies) the following formula (2).
θ=π×r/(2×p)  (2)

As described above, the induced electromotive forces to be generated by the space harmonics on the rotor windings18nand18scan be maximized by setting the width θ of the rotor windings18nand18sin the circumferential direction equal to (or substantially equal to) the width corresponding to the electric angle of 90°. Therefore, the present embodiment can most efficiently increase the magnetic fluxes of the magnets on the salient poles19, which are generated by the induced currents. As a result, the torque acting on the rotor14can be increased further efficiently.

FIGS. 6 and 7illustrate calculation results of the torque of the rotor14, which can be obtained by changing the phase (i.e., current vector phase relative to the rotor position) of respective AC currents that flow through the stator windings28u,28v, and28w.FIG. 6illustrates a calculation result of the torque in a case where the amplitude (i.e., current amplitude) and the phase (i.e., current vector phase) of respective AC currents flowing through the stator windings28u,28v, and28ware changed while the rotational speed of the rotor14is maintained at a constant speed.FIG. 7illustrates calculation results of the torque in a case where the current vector phase and the rotational speed of the rotor14are changed while the current amplitude is maintained at a constant level. As understood fromFIGS. 6 and 7, if the current vector phase changes, the torque of the rotor14changes correspondingly. Therefore, the torque of the rotor14can be controlled by controlling the current vector phase (i.e., the phases of the AC currents that flow through the stator windings28u,28v, and28w). Further, as understood fromFIG. 6, if the current amplitude changes, the torque of the rotor14changes correspondingly. Therefore, the torque of the rotor14can be controlled by controlling the current amplitude (i.e., the amplitude of the AC currents that flow through the stator windings28u,28v, and28w). Further, as understood fromFIG. 7, if the rotational speed of the rotor19changes, the torque of the rotor14changes correspondingly. Therefore, the torque of the rotor14can be controlled by controlling the rotational speed of the rotor14.

FIG. 8illustrates a schematic configuration of a driving controller for the rotary electric machine10according to the present embodiment. An electric power storage device42is a DC power source having the capability of charging and discharging electric power. The electric power storage device42is, for example, constituted by a secondary battery. An inverter40includes switching elements (not illustrated) that perform switching operations for converting the DC power of the electric power storage device42into a plurality of phases of alternating currents (e.g., three-phase alternating currents). Thus, the inverter40can supply alternating currents to respective phases of the stator windings28u,28v, and28w. A control unit41controls the torque of the rotor14by controlling the phase (current vector phases) of respective AC currents that flow through the stator windings28u,28v, and28w. To this end, the control unit41controls the switching operation of respective switching elements of the inverter40. However, to control the torque of the rotor14, the control unit41can control the amplitude of the AC currents that flow through the stator windings28u,28v, and28w, or can control the rotational speed of the rotor14.

Another example configuration of the rotary electric machine10according to the present embodiment is described below.

In the present embodiment, for example, as illustrated inFIG. 9, the magnetic resistance of the rotor14can be changed in the rotational direction by forming slits (i.e., gaps)44on the rotor core16. As illustrated inFIG. 9, the rotor core16includes d-axis magnetic path portions39where the magnetic path has a larger magnetic resistance and q-axis magnetic path portions29where the magnetic path has a smaller magnetic resistance compared to that of the d-axis magnetic path portions39. Formation of the slits44realizes an arrangement of the d-axis magnetic path portions39and the q-axis magnetic path portions29that are alternately disposed in the circumferential direction, in a state where the d-axis magnetic path portions39and the q-axis magnetic path portions29are disposed in spaced confronting relationship with the stator12(i.e., the teeth30). Each d-axis magnetic path portion39is positioned between two q-axis magnetic path portions29in the circumferential direction. The rotor windings18nand18sare disposed in the slits44and are wound around the q-axis magnetic path portions29where the magnetic resistance is small. According to the example configuration illustrated inFIG. 9, the rotating magnetic field that includes the space harmonics components formed by the stator12interlinks with the rotor windings18nand18s. Accordingly, DC currents rectified by the diodes21nand21sflow through the rotor windings18nand18s. The q-axis magnetic path portions29are magnetized. As a result, each q-axis magnetic path portion29can function as a magnet where the magnetic pole is fixed (i.e., a magnetic pole portion). In this case, the induced electromotive forces generated by the space harmonics on the rotor windings18nand18scan be efficiently increased by setting the width of each q-axis magnetic path portion29in the circumferential direction (i.e., the width G of respective rotor windings18nand18s) to be shorter than the width corresponding to electric angle 180° of the rotor14, and further by winding the rotor windings18nand18saround the q-axis magnetic path portions29by short-pitch winding. Further, to maximize the induced electromotive forces generated by the space harmonics on the rotor windings18nand18s, the width θ of the rotor windings18nand18sin the circumferential direction is preferably set equal to (or substantially equal to) the width corresponding to an electric angle of 90° of the rotor14.

Further, in the present embodiment, permanent magnets48can be disposed on the rotor core16, for example, as illustrated inFIG. 10. According to the example configuration illustrated inFIG. 10, a plurality of magnetic pole portions49that can function as magnets where the magnetic pole is fixed are arranged along the circumferential direction in a mutually spaced state and are disposed in spaced confronting relationship with the stator12(i.e. the teeth30). The rotor windings18nand18sare wound around the magnetic pole portions49. Each permanent magnet48is positioned at a portion corresponding to a position (e.g., midpoint) between two neighboring magnetic pole portions49in the circumferential direction and is disposed in spaced confronting relationship with the stator12(i.e., the teeth30). The above-described permanent magnets48can be embedded in the rotor core16or can be exposed on the surface (outer circumferential surface) of the rotor core16. Further, in a case where the permanent magnets48are embedded in the rotor core16, the permanent magnets48can be configured to form a V-shaped arrangement. According to the example configuration illustrated inFIG. 10, the rotating magnetic field including the space harmonics components formed by the stator12interlinks with respective rotor windings18nand18s. The DC currents rectified by the diodes21nand21sflow through the rotor windings18nand18s, and each magnetic pole portion49is magnetized. As a result, each magnetic pole portion49can function as a magnet where the magnetic pole is fixed. In this case, the induced electromotive forces to be generated by the space harmonics on the rotor windings18nand18scan be efficiently increased by setting the width of each magnetic pole portion49in the circumferential direction (i.e., the width θ of respective rotor windings18nand18s) to be shorter than the width corresponding to electric angle 180° of the rotor14, and further by winding the rotor windings18nand18saround the magnetic pole portions49by short-pitch winding. Further, to maximize the induced electromotive forces to be generated by the space harmonics on the rotor windings18nand18s, the width θ of the rotor windings18nand18sin the circumferential direction is preferably set equal to (or substantially equal to) the width corresponding to an electric angle of 90° of the rotor14.

Further, in the present embodiment, for example, as illustrated inFIG. 11, the rotor windings18ndisposed on every other pole in the circumferential direction can be connected to each other so as to be electrically connected in series. The rotor windings18sdisposed on every other pole in the circumferential direction can be connected to each other so as to be electrically connected in series. More specifically, the rotor windings18nwound around the salient poles19that can function as magnets having the same magnetic pole (e.g., N-pole) can be electrically connected to each other as a serial winding. The rotor windings18swound around the salient poles19that can function as magnets having the same magnetic pole (e.g., S-pole) can be electrically connected to each other as a serial winding. However, the rotor windings18nand18swound around the salient poles19that are adjacent to each other in the circumferential direction (i.e., on which magnets having mutually different magnetic poles are formed) are electrically isolated from each other. Two diodes21nand21s(i.e., two diodes) are provided for the rotor windings18nand18sthat are electrically isolated from each other. The diode21nrectifies the current that flows through the rotor windings18nthat are electrically connected as a serial winding. The diode21srectifies the current that flows through the rotor windings18sthat are electrically connected as a serial winding. In this case, it is desired to form the magnets having magnetic poles that are mutually different between the salient poles19around which the rotor windings18nare wound and the salient poles19around which the rotor windings18sare wound (i.e., between the salient poles19that are adjacent to each other in the circumferential direction). To this end, the current-rectifying directions of the rotor windings18nand18sregulated by the diodes21nand21sare set to be opposite each other. According to the example configuration illustrated inFIG. 11, the total number of the diodes21nand21scan be reduced to only two.

Further, in the present embodiment, for example, as illustrated inFIG. 12, the rotor windings18nand18scan be wound by toroidal winding. According to the example configuration illustrated inFIG. 12, the rotor core16includes an annular core portion17and salient poles19that project outward from the annular core portion17in the radial direction (i.e., toward the stator12). Respective rotor windings18nand18sare wound around a predetermined position of the annular core portion17, which is close to each salient pole19, by toroidal winding. According to the example configuration illustrated inFIG. 12, the rotating magnetic field that includes the space harmonics components formed by the stator12interlinks with the rotor windings18nand18s. DC currents rectified by the diodes21nand21sflow through the rotor windings18nand18sand magnetize respective salient poles19. As a result, the salient poles19positioned in the vicinity of the rotor windings18ncan function as N-poles. The salient poles19positioned in the vicinity of the rotor windings18scan function as S-poles. In this case, the induced electromotive forces to be generated by the space harmonics on the rotor windings18nand18scan be efficiently increased by setting the width θ of each salient pole19in the circumferential direction to be shorter than the width corresponding to an electric angle of 180° of the rotor14. Further, to maximize the induced electromotive forces to be generated by the space harmonics on the rotor windings18nand18s, the width θ of each salient pole19in the circumferential direction is preferably set equal to (or substantially equal to) the width corresponding to an electric angle of 90° of the rotor14. Similar to the example configuration illustrated inFIG. 11, in the example illustrated inFIG. 12, the rotor windings18nand185that are adjacent to each other in the circumferential direction are electrically isolated from each other. The rotor windings18ndisposed on every other pole in the circumferential direction are electrically connected to form a serial winding. The rotor windings18sdisposed on every other pole in the circumferential direction are electrically connected to form a serial winding. However, even in the example of the rotor windings18nand18sthat are wound by toroidal winding, similar to the example configuration illustrated inFIG. 3, the rotor windings18nand18swound around the salient poles19can be electrically isolated from each other.

Further, in the present embodiment, for example, as illustrated inFIG. 13, a common rotor winding18can be wound around respective salient poles19. According to the example configuration illustrated inFIG. 13, the rotor winding18is short-circuited via a diode21. Therefore, the diode21rectifies the current so as to flow through the rotor winding18in one direction (as DC current). The magnetized directions of the rotor windings18wound around two salient poles19, which are adjacent to each other in the circumferential direction, are opposite each other. To this end, the directions of the winding portions wound around the salient poles19, which are adjacent to each other in the circumferential direction, are opposite each other. Even in the example configuration illustrated inFIG. 13, the rotating magnetic field that includes the space harmonics components formed by the stator12interlinks with the rotor winding18. The DC current rectified by the diode21flows through the rotor winding18and magnetizes respective salient poles19. As a result, each salient pole19can function as a magnet where the magnetic pole is fixed. In this case, the magnets having mutually different magnetic poles can be formed by two salient poles19that are adjacent to each other in the circumferential direction. According to the example configuration illustrated inFIG. 13, the total number of the diode21can be reduced to only one.

However, according to the example configuration illustrated inFIG. 13, magnetic flux variations (tertiary) caused by the space harmonics components of respective salient poles19may be canceled, because the common rotor winding18is used for the salient poles19that form the N-poles and the salient poles19that form the S-poles. Therefore, the torque of the rotor14may not effectively increase, as compared with other example configurations.FIG. 14illustrates a calculation result of the amplitude (i.e., variation width) of the flux linkage that interacts with the rotor windings18, which can be obtained by changing the circumferential width θ of the rotor winding18wound around each salient pole19in the example configuration illustrated inFIG. 13. InFIG. 14, the coil width θ is expressed using a value converted into an electric angle. As illustrated inFIG. 14, the variation width of the flux linkage that interacts with the rotor winding18greatly decreases if the coil width θ becomes smaller than 90°. Further, the variation width of the flux linkage that interacts with the rotor winding18greatly decreases if the coil width θ becomes greater than 120°. Further, considering the necessity of the coil width θ that can secure a sufficient cross section for the rotor winding18, to further increase the induced current to be caused by the space harmonics generated by the rotor winding18in the example configuration illustrated inFIG. 13, the width θ of the rotor winding18in the circumferential direction is preferably set larger than the width corresponding to an electric angle of 90° of the rotor14and further to be smaller than the width corresponding to an electric angle of 120° of the rotor14(i.e., satisfy a relationship 90°<θ<120°). Further, as illustrated inFIG. 14, the amplitude of the flux linkage caused by the space harmonics has a peak at the coil width θ of 105°. Accordingly, to further increase the induced current to be caused by the space harmonics generated by the rotor winding18in the example configuration illustrated inFIG. 13, the width θ of the rotor winding18in the circumferential direction is preferably set equal to (or substantially equal to) the width corresponding to an electric angle of 105° of the rotor14.

Further, according to the example configuration illustrated inFIG. 15, the rotor winding18is wound around each salient pole19by wave winding (i.e., series winding). The magnetized directions of the salient poles19, which are adjacent to each other in the circumferential direction, are opposite each other. To this end, the directions of the winding portions wound around the salient poles19, which are adjacent to each other in the circumferential direction, are opposite each other. InFIG. 15, a solid line portion of the rotor winding18extends along one side of the salient pole19(i.e., the foreside of the drawing), which corresponds to one end surface side of the salient pole19in the rotational shaft direction. A dotted line portion of the rotor winding18extends along the other side of the salient pole19(i.e., the backside of the drawing), which corresponds to the other surface side of the salient pole19in the rotational shaft direction. Further, a portion18aindicated by ∘ (white circle mark) with ● (black circle mark) positioned therein is a portion where the current flows in a forward direction relative to the drawing surface. A portion18bindicated by ∘ (white circle mark) with x (crossing mark) positioned therein is a portion where the current flows in a backward direction relative to the drawing surface. Even in the example configuration illustrated inFIG. 15, the rotating magnetic field that includes the space harmonics components formed by the stator12interlinks with the rotor winding18. The DC current rectified by the diode21flows through the rotor winding18and magnetizes respective salient poles19. As a result, each salient pole19can function as a magnet where the magnetic pole is fixed. In this case, the magnets having mutually different magnetic poles can be formed by two salient poles19that are adjacent to each other in the circumferential direction. According to the example configuration illustrated inFIG. 15, the total number of the diode21can be reduced to only one.

In the above-described embodiments, the stator12and the rotor14are disposed in spaced confronting relationship in the radial direction that is perpendicular to the rotational shaft22. However, the rotary electric machine10according to the present embodiment can be configured as an axial-type rotary electric machine, in which the stator12and the rotor14are disposed in spaced confronting relationship in a direction parallel to the rotational shaft22(i.e., in the rotational shaft direction).

Although some embodiments for implementing the present invention have been described, the present invention is not limited to the above-described embodiments and can be embodied in various manners without departing from the gist of the present invention.