Patent Publication Number: US-2018034332-A1

Title: Rotary electric machine

Description:
TECHNICAL FIELD 
     The present invention relates to a rotary electric machine installed in a vehicle or the like and is used as a motor or a generator. 
     BACKGROUND ART 
     Conventionally, a rotary electric machine is typically known which is installed and used in a vehicle, and which includes a rotatably supported rotor provided with magnetic poles alternately differing in polarity in a circumferential direction, and a stator having a stator core and a stator coil, the stator core having a plurality of slots circumferentially arrayed and radially facing the rotor and the stator coil formed of phase windings of three phases wound as distributed windings in the slots of the core. 
     In Patent Literature 1 and Patent Literature 2, a stator core is disclosed in which respective pairs of slots that house windings of the same phase are consecutively provided in a circumferential direction, at each of the magnetic poles of the rotor, with the slot multiple being 2. Furthermore in Patent Literature 1, a stator coil is disclosed in which long windings and short windings are alternately wound along a circumferential direction of the stator core. 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] JP-A-2014-96986 
     [Patent Literature 2] JP-A-11-285216 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     To improve the performance of such a rotary electric machine, it is in general necessary to efficiently acquire a large flow of magnetic flux between the stator core and the rotor core. However in a case in which the slot multiple is increased or short windings are utilized, for reasons such as decreasing vibration or the like, then the overall amount of magnetic flux will be reduced. In addition, if the slot multiple of the stator coil is 2 or more, with distributed windings, and a number of slots are crossed by short windings, then if the arc ratio of each magnetic pole of the rotor is made large, a problem arises that demagnetizing fields will be produced within the same phase, so that a required amount of magnetic flux cannot be efficiently obtained. 
     The object of the present invention, in view of the above, is to solve the problem by providing a rotary electric machine in which the slot multiple of the stator is made 2 or more and the stator coil is wound with distributed windings and short windings, but in which a flow of magnetic flux between the stator and the rotor can be efficiently acquired. 
     Solution to Problem 
     A rotary electric machine according to the first invention made to solve the above problem includes a rotor ( 30 ,  40 ) which has a plurality of magnetic poles arranged with polarities that alternate in a circumferential direction, and a stator ( 20 ) which has a stator core ( 22 ) having a plurality of slots ( 25 ) circumferentially arranged and radially facing the rotor, and which has a stator coil ( 21 ) housed in the slots and formed of phase windings of three phases that are wound as distributed windings in the stator core. A slot multiple of the slots in the stator core is set as n, with a proportion of n slots per one phase of the stator coil (where n is a natural number of 2 or more). Each of the phase windings of the stator coil is wound as a short winding extending over (n+1) adjacent ones of the slots. With an axis of rotation (O) of the rotor as center, designating α as an arc ratio of the magnetic pole, β as a circumferential-direction angular range of each magnetic flux interchange face ( 36 ,  46 ) of the rotor, which is positioned so as to face the stator core and at which magnetic flux is interchanged with the stator core, and γ as a slot pitch of the slots in the circumferential direction, relationships ⊖≦2nγ and β&lt;α are established. 
     When defining a full winding as a winding which is wound with a slot pitch equal to a number obtained by dividing the number of slots of the stator by the number of magnetic poles of the rotor, the term short winding is used herein to signify a winding which is wound with a slot pitch that is less than that of the full winding. 
     According to the configuration, when, with the axis of rotation of the rotor as center, α is the arc ratio of a magnetic pole, β is the circumferential-direction angular range of a magnetic flux interchange face of the rotor core, which faces the stator core and at which magnetic flux is interchanged with the stator core, γ is the slot pitch of the slots in the circumferential direction, and the slot multiple is n, relationships β≦2nγ and β&lt;α are established. That is, according to the first invention, due to the relationship β&lt;α, a greater amount of magnetic flux is produced in the range of the arc ratio α of a magnetic pole than the amount set by the circumferential-direction angular range β of the magnetic flux interchange face, i.e., with that magnetic flux passing into the slots through the magnetic flux interchange face having the circumferential-direction angular range β which is smaller than the arc ratio α of the magnetic pole. At that time, since the circumferential-direction angular range β of the magnetic flux interchange face is set as β≦2nγ, and each of the phase windings of the stator core is wound as short windings extending over (n+1) adjacent slots, demagnetizing fields are not produced in windings of the same phase, even when the phase windings are connected in series or in parallel. That is, the circumferential-direction angular range β of the magnetic flux interchange face of the rotor facing the stator is set as a range in which demagnetizing fields do not arise. Hence according to the present invention, magnetic flux flowing between the stator and the rotor can be efficiently acquired. 
     A rotary electric machine according to the second invention made to solve the above problem includes a rotor ( 30 ,  40 ) which has a plurality of magnetic poles arranged with polarities that alternate in a circumferential direction, and a stator ( 20 ) which has a stator core ( 22 ) having a plurality of slots ( 25 ) circumferentially arranged and radially facing the rotor, and which has a stator coil ( 21 ) housed in the slots and formed of phase windings of six phases that are wound as distributed windings in the stator core. A slot multiple of the slots in the stator core is set as n, with a proportion of n slots per one phase of the stator coil (where n is a natural number of 2 or more). Each of the phase windings of the stator coil is wound as a short winding extending over n adjacent ones of the slots. With an axis of rotation (O) of the rotor as center, designating α as an arc ratio of the magnetic pole, β as a circumferential-direction angular range of each magnetic flux interchange face ( 36 ,  46 ) of the rotor, which is positioned so as to face the stator core and at which magnetic flux is interchanged with the stator core, and γ as a slot pitch of the slots in the circumferential direction, relationships β≦(3n−1)γ and β&lt;α are established. 
     According to the configuration, with the axis of rotation of the rotor as center, when α is the arc ratio of the magnetic pole, β is the circumferential-direction angular range of the magnetic flux interchange face of the rotor core, which faces the stator core and at which magnetic flux is interchanged with the stator core, and γ is the slot pitch of the slots in the circumferential direction, and the slot multiple is n, relationships β≦(3n−1)γ and β&lt;α are established. That is, according to the second invention, the circumferential-direction angular range β of the magnetic flux interchange face of the rotor core is set based on the relationship β≦(3n−1)γ to a range in which demagnetizing fields do not arise. Due to the relationship β&lt;α, a greater amount of magnetic flux is produced in the range of the arc ratio α of the magnetic pole than the amount set by the circumferential-direction angular range β of the magnetic flux interchange face. Hence, since each of the phase windings of the stator coil is wound as short windings extending over (n+1) adjacent slots, demagnetizing fields are not produced even when the phase windings are connected in series or in parallel, and hence magnetic flux can be efficiently acquired. 
     The signs shown in parentheses after members and parts in Solution to Problem and Claims indicate a relationship between them and specific members and parts in the embodiments described later and do not at all effect the configurations of the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a rotary electric machine according to a first embodiment, taken along an axial direction; 
         FIG. 2  is a partial plan view of a two-pole portion showing the arrangement state of a stator and a rotor of the first embodiment; 
         FIG. 3  is a cross-sectional view of a conductor segment used in the first embodiment; 
         FIG. 4  is an explanatory diagram for illustrating a manner of inserting the conductor segments into slots of a stator core; 
         FIG. 5  is a schematic perspective view showing a set of large/small conductor segments used in the first embodiment; 
         FIG. 6  is a partial plan view showing part of the stator according to the first embodiment; 
         FIG. 7  is a perspective view showing part of a joint-side end portion of the stator according to the first embodiment; 
         FIG. 8  is a schematic explanatory diagram of the arrangement of the conductor segments housed in the slots of the stator core of the first embodiment, viewed from the joint-side end portion side; 
         FIG. 9  is a partial plan view showing a single magnetic pole portion of a rotor according to a first modification; 
         FIG. 10  is a partial plan view showing a single magnetic pole portion of a rotor according to a second modification; 
         FIG. 11  is a partial plan view showing a single magnetic pole portion of a rotor according to a third modification; 
         FIG. 12  is a perspective view of a rotor core according to a fourth modification; 
         FIG. 13  is a partial cross-sectional view of the rotor core according to the fourth modification taken along an axial right-angle direction; 
         FIG. 14  is a partial cross-sectional view of a rotor core according to a fifth modification taken along an axial right-angle direction; 
         FIG. 15  is a partial cross-sectional view of a rotor core according to a sixth modification taken along an axial right-angle direction; 
         FIG. 16  is a partial plan view of a double magnetic pole portion showing the arrangement of the stator and the rotor according to a seventh modification; 
         FIG. 17  is a schematic cross-sectional view of a rotary electric machine according to a second embodiment, taken along an axial direction; 
         FIG. 18  is a plan view of a first pole core of a rotor core and a stator core according to the second embodiment, seen in the axial direction thereof; 
         FIG. 19  is a partial plan view of a single magnetic pole portion, showing the arrangement of the stator and rotor of the second embodiment; 
         FIG. 20  is a perspective view of the first pole core of the rotor core according to the second embodiment; 
         FIG. 21  is a perspective view showing an assembled state of the first pole core and a second pole core of the rotor core according to the second embodiment; 
         FIG. 22  is a partial plan view of a single magnetic pole portion, showing the arrangement of a stator and a rotor of an eighth modification; 
         FIG. 23  is a cross-sectional view of a rotor according to a ninth modification taken along an axial direction thereof; 
         FIG. 24  is a schematic cross-sectional view taken along an axial direction of a rotary electric machine according to a tenth modification; 
         FIG. 25  is a partial plan view showing a double magnetic pole portion showing the arrangement of a stator and a rotor of a third embodiment. 
         FIG. 26  is a partial plan view of a double magnetic pole portion showing the arrangement of a stator and a rotor of an eleventh modification; 
         FIG. 27  is a partial plan view of a single magnetic pole portion showing the arrangement of a stator and a rotor of a fourth embodiment; 
         FIG. 28  is a partial plan view of a single magnetic pole portion showing the arrangement of a stator and a rotor of a twelfth modification. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, embodiments of a rotary electric machine according to the present invention are described in detail with reference to the drawings. 
     First Embodiment 
     As shown in  FIG. 1 , a rotary electric machine  1  of the first embodiment is a motor generator for a vehicle, and includes a housing  10 , a stator  20  which functions as an armature and has a stator core  22  and a stator coil  21 , a rotor  30  which has a plurality of embedded permanent magnets forming magnetic poles whose polarities are alternately changed in the circumferential direction to act as field magnets, and an electric power converter  50 . The electric power converter  50  is connected to the stator coil  21  by input/output lines  17  or the like. The housing  10  is formed with a substantially cylindrical shape by joining apertures of a pair of housing members  10   a  and  10   b  having a bottomed cylindrical shape in which one end of the cylinder opens. 
     The stator  20  includes the stator core  22  having a plurality of slots  25  formed in a cylindrical shape and arranged in the circumferential direction, a segment-type stator coil  21  that is formed of a plurality of conductor segments (wires)  23 , and an insulation sheet member  24  providing electrical insulation between the stator core  22  and the stator coil  21 . The stator  20  is fixed to the housing  10  by holding an external circumferential portion of the stator core  22  between the pair of housing members  10   a  and  10   b  (see  FIG. 1 ). 
     The stator core  22  is integrally formed by stacking a plurality of cylindrical-shaped magnetic steel sheets along an axial direction. As shown in  FIG. 2 , the stator core  22  is made up of a cylindrical-shaped back core  22   a  constituting an external circumferential portion and a plurality of teeth  22   b  which project radially inward from the back core  22   a  and are arrayed circumferentially, separated by a predetermined distance. The slots  25  penetrate in an axial direction and are formed circumferentially at equal distance so as to house the stator coil  21  that is wound in the stator core  22 , with each of the slots  25  being formed between an adjacent pair of the teeth  22   b  of the stator core  22 . In the first embodiment, mutually opposed surfaces (circumferential-direction side faces) of two adjacent teeth  22   b  of one slot  25 , which partition the both sides of the slot  25  positioned in the circumferential direction, are made parallel to each another. Hence, each of the teeth  22   b  is formed so as to be slightly tapered towards the tip at the radially inward end of the tooth. 
     The number of slots  25  is set corresponding to the number of magnetic poles of the rotor  30  (16 poles, in the case of the first embodiment) such that there is a ratio of n slots  25  (where n is a natural number of 2 or more) per one phase of the stator coil  21 , with the slot multiple being made 2. Hence, in the first embodiment, the number of slots  25  is 16×3×2=96. In addition, the slot pitch γ of the slots  25  in the circumferential direction around the axis of rotation O of the rotor  30  is 360°/96=3.75°. The slot pitch γ is defined as the angle between two straight lines L 3  and L 3  which respectively connect the circumferential-direction centers of the slots  25  and the axis of rotation O. Since the slots  25  and the teeth  22   b  are formed circumferentially at equal intervals, the slot pitch γ is equal to the pitch of the teeth  22   b  in the circumferential direction. 
     The stator coil  21  that is wound in the slots  25  of the stator core  22  consists of three phase windings which are formed as distributed windings. The stator coil  21  consists of a plurality of U-shaped conductor segments  23  whose joint end portions  23   f  (see  FIG. 5 ) are joined to each other. As shown in  FIG. 3 , the conductor segment  23  is formed of a rectangular member that consists of a conductor portion  23   j  having a rectangular cross section and formed of an electrically conductive metal material such as copper or aluminum, and an electrical insulation film  23   k  which covers the outer periphery surface of a conductor portion  23   j  and is formed as a two-layer structure consisting of an inner layer  231   k  and an outer layer  232   k.  It is noted that, at the joint end portions  23   f,  the electrical insulation film  23   k  is removed so that the conductor portion  23   j  thereinside is exposed, and after the predetermined joint end portions  23   f  of the different conductor segments  23  have been connected to each other, electrical insulation processing is applied. 
     As shown in  FIG. 4 , the conductor segment  23  has a U shape with a pair of linear portions  23   g,    23   g  and a turn portion  23   h  which links respective end portions of the linear portions  23   g,    23   g.  In  FIG. 4 , a set of two of conductor segments  23  (large segment  231  and small segment  232 ) is shown which are respectively inserted in two adjoining slots  25 A and  25 B. In this case, the pairs of linear portions ( 23   g   1 ,  23   g   2 ) ( 23   g   3 ,  23   g   4 ) of the pair of large and small segments  231 ,  232  are respectively inserted into two slots  25 A,  25 C which are separated from each another by 5 slot pitches (see  FIG. 8 ), being inserted from one end of each slot and along the axial direction (the direction from the rear side of the paper as seen in  FIG. 2 , from the upper side as seen in  FIG. 4 ). 
     That is, one straight line portion  23   g   1  of the large segment  231  is inserted into the fourth layer (outermost layer) of one slot  25 A, while the other straight line portion  23   g   2  of the large segment  231  is inserted into the first layer (innermost layer) of another slot (not shown) which is separated from slot  25 A by 5 slot pitches in the counterclockwise direction of the stator core  22  (the Y arrow direction in  FIGS. 2 and 4 ). Then, one linear portion  23   g   3  of the small segment  232  is inserted into the third layer of one slot  25 A, while the other linear portion  23   g   4  of the small segment  232  is inserted into the second layer of the other slot (not shown) which is separated by 5 slot pitches in the counterclockwise direction of the stator core  22 . In this way, the linear portions  23   g  of an even number of conductor segments  23  are arranged and inserted into all of the slots  25 . In the first embodiment, a total of 4 linear portions  23   g   1  to  23   g   4  are disposed radially in a single row, in each slot  25 . 
     As shown in  FIG. 5 , the open end portions of the linear portions  23   g   1  to  23   g   4  of the large and small segments  231 ,  232 , which are inserted into each slot  25  from one axial-direction end side in the above manner, extend from the slot  25  to the other axial-direction end side (upper end side in  FIG. 5 ). The open end portions of the pairs of linear portions ( 23   g   1 ,  23   g   2 ) ( 23   g   3 ,  23   g   4 ) of the large and small segments  231 ,  232  are mutually skewed in the circumferential counterclockwise direction so as to incline with respect to the end face of the stator core  22  positioned in the axial direction at a predetermined angle, forming oblique portions  23   e  each having a length of approximately 2.5 slot pitches. 
     As shown in  FIG. 5 , a paired set of large/small segments  231 ,  232  has pairs of slot-housed portions  23   a,    23   a  that are housed within slots  25  and extend linearly along an axial direction, and coil end portions which extend outward in circumferential directions from the slots  25 . A coil end portion consists of a turn-side end portion  23   b  which is integrally formed of slot-housed portions  23   a,    23   a  so as to link end portions of the slot-housed portions  23   a,    23   a  and which projects from one axial-direction end side of a slot  25  (at the rear side of the rotary electric machine  1 , the right-hand side as viewed in  FIG. 1 ), and a pair of joint-side end portions  23   c,    23   c  which are formed integrally with the respective other ends of the slot-housed portions  23   a  ,  23  and project from the other axial-direction end side of the slot  25  (at the front side of the rotary electric machine  1 , the left-hand side as viewed in  FIG. 1 ). 
     The turn-side end portion  23   b  has an approximately V-shaped turn portion  23   h  formed by curved deformation of the tip of the turn-side end portion  23   b.  A joint-side end portion  23   c  has oblique portions  23   e  and joint end portions  23   f,  where the oblique portion  23   e  is twisted in the circumferential direction, being skewed diagonally at a predetermined angle with respect to the axial-direction end face of the stator core  22 , and the joint end portion  23   f  is formed integrally with the tip of the oblique portion  23   e  by bending deformation. 
     Each of the slots  25  of the stator core  22  houses an even number (in the present embodiment, 4) of electrical conductors (the slot-housed portion  23   a  of respective conductor segments  23 ). As shown in  FIG. 6 , the four electrical conductors that are housed in a single slot  25  are arranged as a single low, in order of first layer, second layer, third layer, and fourth layer from the inner circumferential side of the stator core  22 . The stator coil  21  is formed by connecting the electrical conductors housed within the slots  25  in a specific pattern. 
     The turn-side end portions  23   b  at one axial-direction end side of the stator core  22  (the lower side, in  FIG. 5 ) of the electrical conductors within each of the slots  25  are electrically connected via turn portions  23   h.  First coil end portions are thereby formed by a plurality of turn portions  23   h  which project from the slots  25 , at one axial-direction end side of the stator core  22 . In addition, the joint-side end portions  23   c  at the other axial-direction end of the stator core  22  (the upper side, in  FIG. 5 ) are electrically connected by joining joint end portions  23   f  by means such as welding. Thus, second coil end portions  21   b  are formed (see  FIG. 7 ) by a number of joint-side end portions  23   c  which project from the slots  25  at the other axial-direction end side of the stator core  22 . 
     One electrical conductor (slot-housed portion  23   a ) within each slot  25  is paired with a single electrical conductor (slot-housed portion  23   a ) within another slot  25  that is separated by five slot pitches. For example, as shown in  FIG. 8 , an electrical conductor  213   a  that is housed in the first layer in one slot  25 A is paired with an electrical conductor  213   b  that is housed in the fourth layer in the other slot  25 C which is separated by five slot pitches in the clockwise rotation direction around the stator core  22  (the X-direction indicated by an arrow in  FIGS. 4, 5 and 8 ). Similarly, an electrical conductor  232   a  that is housed in the second layer in one slot  25 A is paired with an electrical conductor  232   b  that is housed in the third layer in the other slot  25 C separated by five slot pitches in the clockwise rotation direction (X direction indicated by the arrow) around the stator core  22 . 
     At a turn-side end portion  23   b  at one axial-direction end side of the stator core  22 , the electrical conductors that are paired, that is, the electrical conductor  213   a  that is in the first layer and the electrical conductor  213   b  that is in the fourth layer are connected via a turn portion  23   h  ( 231   c ). In addition, the electrical conductor  232   a  that is in the second layer and the electrical conductor  232   b  that is in the third layer are connected via a turn portion  23   h  ( 232   c ). 
     That is, at the turn-side end portions  23   b,  an electrical conductor  231   a  that is in the first layer and an electrical conductor  232   a  that is in the second layer, which are housed within one slot  25 , extend from the slot  25  in the clockwise direction (X direction indicated by the arrow) of the stator core  22 . In addition, an electrical conductor  231   b  that is in the fourth layer and an electrical conductor  232   b  that is in the third layer, which are housed within one slot  25 , extend from the slot  25  in the counterclockwise direction (Y direction indicated by the arrow in  FIGS. 4, 5 and 8 ) of the stator core  22 . 
     In addition, an electrical conductor  232   a  that is in the second layer of one slot  25  is paired with an electrical conductor  231   a′  that is in the first layer of another slot  25 , which is separated by 5 slot pitches in the clockwise direction (X direction indicated by the arrow) around the stator core  22 . The pair of the electrical conductor  232   a  in the second layer and the electrical conductor  231   a′  in the first layer is connected by the joining of joint end portions  23   f  ( 232   d  and  231   d′ ) of the joint-side end portion  23   c  at the other axial-direction end side of the stator core  22  (see  FIG. 5 ). 
     Similarly, the electrical conductor  231   b′  that is in the fourth layer of one slot  25  is paired with an electrical conductor  232   b  that is in the third layer of another slot  25  that is separated by 5 slot pitches in the clockwise direction (X direction indicated by the arrow) around the stator core  22 . That pair of the electrical conductor  231   b′  is in the fourth layer and the electrical conductor  232   b  is in the third layer are connected by the joining of joint end portions  23   f  ( 231   e′  and  232   e ) of the joint-side end portion  23   c  at the other axial-direction end side of the stator core  22  (see  FIG. 5 ). 
     That is, at the joint-side end portion  23   c,  the electrical conductor  213   a  in the first layer and the electrical conductor  232   b′  in the third layer, which are housed in one slot  25 , extend from that slot  25  in the counterclockwise direction of the stator core  22  (Y direction indicated by the arrow). In addition, the electrical conductor  232   a  in the second layer and the electrical conductor  231   b′  in the fourth layer, which are housed in one slot  25 , extend from that slot  25  in the clockwise direction of the stator core  22  (X direction indicated by the arrow). 
     In this way, at the joint-side end portions  23   c  at the other axial-direction end side of the stator core  22 , predetermined joint end portions  23   f  of the electrical conductors  23  are joined to each other by welding or the like. As a result, by connecting the predetermined conductor segments  23  in series, the stator coil  21  is formed of three phase windings (U-phase, V-phase, W-phase) that are wave-wound circumferentially along the slots  25  of the stator core  22 . In this case, each phase winding of the stator coil  21  is wound as short windings of 5 slot pitches across n+1 adjacent slots  25  (3 slots in the case of the first embodiment, with n=2). 
     That is, in each phase winding, as shown in  FIG. 2 , two electrical conductors housed at the inner circumferential side in the slot  25  (in the first layer and in the second layer) are connected to two electrical conductors that are housed (in the third layer and in the fourth layer) at the outer circumferential side in the slot  25  that is separated by 5 slot pitches in the clockwise direction (X direction indicated by the arrow) of the stator core  22 . Thus, in the first embodiment, the slot multiple n is 2, and hence, the slots  25  that house phase windings of the same phase in the first layer and the second layer at the inner circumferential side and also in the third layer and fourth layer at the outer circumferential side successively differ in circumferential position by one slot pitch. 
     Specifically as shown in  FIG. 2 , at the inner circumferential side at which the first layer and the second layer are housed, the slots  25  that house U-phase windings in the first and second layers, the slots  25  that house V-phase windings in the first and second layers, and the slots  25  that house W-phase windings in the first and second layers are each arranged so as to successively occur two at a time in repeated sequence, in the counterclockwise direction (Y direction indicated by the arrow) around the stator core  22 . In addition, at the outer circumferential side at which the third layer and the fourth layer are housed, the slots  25  that house U-phase windings in the third and fourth layers, the slots  25  that house V-phase windings in the third and fourth layers, and the slots  25  that house W-phase windings in the third and fourth layers are arranged so as to successively occur two at a time in sequence in the counterclockwise direction (Y direction indicated by the arrow) around the stator core  22  in the state of one slot pitch displacement. As a result, each of the phase windings is wound over (n+1) adjacent slots  25  (3 slots, when n=2) of stator core  22 . 
     It is noted that in the stator coil  21  of the first embodiment, due to the conductor segments  23  having a basically U-shaped form, each of the phase windings turns four times around the circumference of the stator core  22 , and is formed with irregular segments (not shown in the drawings) having a different shape from that of the basic conductor segment  23 . The irregular segments are segments that are integrally formed with output power lead-out wires or with neutral point lead-out wires, and segments having turn portions for respectively connecting the first and second circumferential turns, for connecting the second and third circumferential turns, and for connecting the third and fourth circumferential turns. The phase windings of the stator coil  21  are wired with star-formation wiring by using these irregular segments. 
     As shown in  FIG. 1 , the rotor  30  rotates integrally with the shaft  13 , which is rotatably supported at both ends by bearings  11  in the housing  10 , and is disposed coaxial with the stator core  22  in the housing  10 , radially facing the stator core  22  and separated from the stator core  22  by a specific air gap G. The rotor  30  consists of a rotor core  31  having a plurality of magnet housing portions  32  arranged in the circumferential direction, with the rotor core  31  being disposed coaxial with the stator core  22 , radially facing the stator core  22 , and separated from the stator core  22  by the specific air gap G, and a plurality of permanent magnets  33  which are housed in the magnet housing portions  32  and form magnetic poles that successively alternate in polarity in the circumferential direction. 
     The rotor core  31  is formed with a thick-walled cylindrical shape by stacking a plurality of cylindrical steel sheets, each having a central through hole  31   a,  in the axial direction, and is fixed by engaging the outer periphery of the shaft  13  in the through hole  31   a.  The outer circumferential part of the rotor core  31  is provided with the plurality of magnet housing portions  32  (in the first embodiment, 16), which penetrate axially, arranged circumferentially at predetermined distances. The magnet housing portions  32  are trapezoidal in a cross-sectional shape, with the long side and the short side of the trapezoid at the outer periphery side and the inner periphery side, respectively, of the rotor core  31 . 
     The permanent magnets  33  are embedded one by one in the magnet housing portions  32 , with each permanent magnet  33  having a rectangular (oblong) cross-sectional shape. Thereby, a plurality of magnetic poles (in the first embodiment, 16 magnetic poles (8 N poles and 8 S poles) having successively alternating polarity are thereby formed around the external circumferential portion of the rotor core  31  by the permanent magnets  33  embedded in the magnet housing portions  32 . Each permanent magnet  33  is formed such that the long side of the oblong cross-sectional shape of the permanent magnet  33  is slightly shorter than the short side of the trapezoidal cross-sectional shape of the magnet housing portion  32 . As a result, magnetic gap portions  34 , each having a triangular cross-sectional shape, are respectively formed at the circumferentially opposed sides of the permanent magnets  33  embedded in the magnet housing portions  32 . In this case, the arc ratio α of each magnetic pole whose center is the axis of rotation (O) of the rotor  30  is defined as the angle between two straight lines L 1 , L 1  which respectively connect the axis of rotation O and the circumferential-direction ends of the outer-side planar face of the permanent magnet  33  that is housed in the magnet housing portion  32 . 
     The outer periphery surface of the rotor core  31  is formed of a plurality of recesses  35  which are recessed radially and inward and arranged circumferentially with predetermined separation spacings, and which are located at a circumferential position corresponding to the space between two circumferentially adjacent magnetic poles. Thereby, magnetic flux interchange faces  36  are thus formed between each of respective pairs of circumferentially adjacent recesses  35 , at the outer periphery of the rotor core  31 . The circumferential angular range β of the magnetic flux interchange face  36 , which has the axis of rotation O of the rotor  30  as center, is defined as the angle between two straight lines L 2 , L 2  which respectively connect the axis of rotation O and the circumferentially opposing sides of the magnetic flux interchange face  36 . 
     In this case, the circumferential angular range β of the magnetic flux interchange face  36  is thereby made smaller than the arc ratio α of the magnetic pole, with the relationship β&lt;α being established. Thus, due to the relationship β&lt;α, the magnetic flux which flows between the stator  20  and the rotor  30  is increased relative to the magnetic flux that is set by the circumferential angular range β of the magnetic flux interchange face  36 , in the range of the arc ratio α of the magnetic pole. 
     In addition, the circumferential angular range β of the magnetic flux interchange face  36  is set with respect to the slot multiple n and the slot pitch γ such that the relationship β≦2nγ is satisfied. Specifically, since n=2, γ=3.75°, the circumferential angular range β of the magnetic flux interchange face  36  is set as β≦2×2×3.75°=15°, being set as a range not exceeding 4 slot pitches of the inner periphery of the stator core  22 . That is, the circumferential angular range β of the magnetic flux interchange face  36  is set so as to be equal to or less than the distance (4 slot pitches) between the two slots  25  housing electrical conductors (slot-housed portions  23   a ) of phase windings of the same phase, in which currents flow in mutually opposite directions. As a result, it is ensured that demagnetizing fields will not be produced by the phase windings of the same phase. 
     In the rotary electric machine  1  for vehicle of the first embodiment configured as described above, when the stator  20  is excited based on a drive current supplied from the electric power converter  50  and subjected to electric power conversion, rotational torque (which may become motive force) is generated by the action of the excitation, thereby rotating the rotor  30 . In this case, the rotary electric machine  1  operates as a motor. The generated rotary torque is output from the rotor  30  and the shaft  13 , for example, to a drive section which drives an axle shaft or the like. 
     In addition, when no power conversion signal is output by the electric power converter  50  and rotational force of an output shaft is transmitted to the shaft  13  by the action of the engine, then since the rotor  30  also rotates, counter-electromotive force is produced by the stator coil  21  of the stator  20 . The generated counter-electromotive force (regenerated power) can charge a battery via the electric power converter  50 . In this case, the rotary electric machine  1  operates as a generator. 
     As described above, according to the rotary electric machine  1  of the first embodiment, the slot multiple is set as n, each phase winding of the stator coil  21  is wound with short windings over (n+1) adjacent slots  25 , and with the axis of rotation (O) of the rotor being the center, designating the arc ratio of the magnetic pole as α, the circumferential angular range of the magnetic flux interchange face  36  being β, and the slot pitch as γ, and the relationships β≦2nγ and β&lt;α are satisfied. As a result, when magnetic flux flows between the stator  20  and the rotor  30 , it is ensured that demagnetizing fields are not produced by the phase windings of the same phase of the stator core  21 , so that a flow of magnetic flux between the stator  20  and the rotor  30  can be efficiently acquired. 
     In addition, according to the first embodiment, since recesses  35  which are recessed in the radial direction are formed at each of the circumferentially opposed sides of the magnetic flux interchange face of the rotor core  31 , the circumferential angular range β (circumferential width) of the magnetic flux interchange face  36  can readily be set. 
     First Modification 
     The rotor  30  of the first embodiment may be configured as shown in  FIG. 9  for the rotor  30  of the first modification, in which an arc-shaped chamfer  37  is formed at each of the circumferentially opposing sides of the magnetic flux interchange face  36  of the rotor core  31 , i.e., is formed on each corner of intersection between the magnetic flux interchange face  36  and a side face  35   a  of the recess  35 , the side face  35   a  extending in radial and axial directions. In this case, the circumferential angular range β of the magnetic flux interchange face  36  is defined as the angle between two straight lines L 4 , L 4  which connect the axis of rotation O of the rotor  30  and the intersection points P 1 , P 1  at which a tangent to the magnetic flux interchange face  36  intersects with a tangent to the side face  35   a  of the recess  35 . In addition, a flat C chamfer may be used, instead of an arc-shaped R chamfer. 
     Second Modification 
     The rotor  30  of the first embodiment may be configured as shown in  FIG. 10  for the second modification, in which the rotor core  31  has a plurality of pairs of magnet housing portions  32   a  arranged in a V formation such that the pair of magnet housing portions  32   a  are separated from each other as they approach the stator  20  side, and a plurality of pairs of permanent magnets  33   a  respectively housed in the pairs of magnet housing portions  32   a  arranged in a V formation to form a single magnetic pole. 
     In this case, the arc ratio α of a single magnetic pole formed by a pair of permanent magnets  33   a  is defined by the angle between two straight lines L 5 , L 5  which connect the axis of rotation O of the rotor  30  to the corners positioned at the outermost periphery sides of the anti-magnetizing pole center sides of the permanent magnets  33   a.  It is noted that the circumferential angular range β of the magnetic flux interchange face  36  is the same as for the first embodiment. The second modification enables the magnetic force of each magnetic pole to be strengthened. 
     Third Modification 
     In the rotor  30  of the third modification, as shown in  FIG. 11 , for the rotor  30  of the second modification in which a single magnetic pole is formed of a pair of permanent magnets  33   a,  a permanent magnet  33   b  is further added to each magnetic pole. In this case, a magnet housing portion  32   b  having an oblong cross-sectional shape, whose long side extends in the circumferential direction, is disposed centrally at the outer periphery side of each pair of magnet housing portion  32   a  of the rotor core  31  that are arranged in the V formation, the permanent magnet  33   b  having an oblong cross-sectional shape being housed in the magnet housing portion  32   b.  In this case, the arc ratio α of each magnetic pole is similar to that of the second modification. The third modification enables the magnetic force of each magnetic pole to be further strengthened comparison with the second modification. 
     Fourth Modification 
     As shown in  FIGS. 12 and 13 , the rotor  30  of the fourth modification is made up of the rotor core  31  having a compressed-powder magnetic core formed by compressing and hardening powder of ferromagnet, and a plurality of permanent magnets  33   c  which are housed in magnet housing portions  32   c  formed in the rotor core  31  and constitute magnetic poles that alternate in polarity in the circumferential direction. The rotor core  31  is of a so-called cage type which is formed by assembling a plurality of partitioned cores  31   b,  which is divided in the circumferential positions, into a cylindrical shape. 
     In the rotor core  31 , the magnet housing portions  32   c  are provided which have a predetermined radial-direction width and are formed in a cylindrical shape so as to make one complete turn in the circumferential direction, and which open at an end face of the rotor core  31  positioned at one axial-direction end side (the lower side in  FIG. 12 ). A plurality of permanent magnets  33   c  having an oblong cross-sectional shape are arranged and housed in the magnet housing portions  32   c,  the permanent magnets  33   c  constituting a plurality of magnetic poles (in the fourth modification, 16 poles, i.e., 8 N poles and 8 S poles) which successively alternate in polarity in the circumferential direction. Each permanent magnet  33   c  is fixed in the rotor core  31  with an adhesive or the like. In this case, the arc ratio α of the magnetic pole whose center is the axis of rotation O of the rotor  30  is defined by the angle between two straight lines L 6  and L 6  which connect the axis of rotation O and the circumferentially opposing sides of the outer peripheral planar face of the magnet  33   c.    
     The outer peripheral surface of the rotor core  31  is provided with a plurality of recesses  35  (in the fourth modification, 16) which are recessed radially and inward and are separated circumferentially at predetermined distances. As a result, the magnetic flux interchange face  36 , through which magnetic flux is exchanged, is formed at the outer peripheral surface of the rotor core  31  and between the two adjacent recesses  35  so as to face the stator core  22 . As in the case of the first embodiment, the circumferential angular range β of each of the magnetic flux interchange faces  36 , whose center is the axis of rotation O of the rotor  30 , is defined by the angle between two straight lines L 7  and L 7  which connect the axis of rotation O and the circumferentially opposing sides of the magnetic flux interchange face  36 . It is noted that, also in the case of the fourth modification, the relationships between the arc ratio α of the magnetic pole and the circumferential angular range β of the magnetic flux interchange face  36  are set as in the case of the first embodiment so as to satisfy β≦2nγ and β&lt;α. 
     Fifth Modification 
     As shown in  FIG. 14 , the rotor  30  of the fifth modification has permanent magnets  33   d,    33   e  arranged in a Halbach array in magnet housing portions  32   d  of the rotor core  31  having a cage shape formed as in the case of the fourth modification. In this case, the permanent magnets  33   d,    33   e  are arranged so as to form magnetic poles whose polarities alternately differ in the circumferential direction, such that the permanent magnets  33   d,    33   e  have two orientation directions, i.e., the circumferential direction and the radial direction. The permanent magnets  33   d,    33   e  are fixed to the rotor core  31  with an adhesive or the like. It is noted that, also in the case of the fifth modification, the arc ratio α of the magnetic pole and the circumferential angular range β of the magnetic flux interchange face  36  are defined in the same manner as that in the fourth modification so as to satisfy the relationships β≦2nγ 0  and β&lt;aα. 
     In the case of the fifth modification, there are permanent magnets  33   e  which are arranged with their orientation directions in the circumferential direction, so that part of the magnetic force of these magnets is invalid. However, according to the fifth modification, the extent of the invalid magnetic force is reduced, so that it becomes possible to make full use of the characteristics of the permanent magnets  33   e.  As a result, the permeance is increased and resistance to heat is improved, together with the improvement in the obtained magnetic force. 
     Sixth Modification 
     In the rotor  30  of a sixth modification, as shown in  FIG. 15 , an isotropic magnet having a cylindrical shape and magnetized with a plurality of circumferentially arrayed magnetic poles, is used as permanent magnets  33   f  embedded in the cage shaped rotor core  31 , which is formed in the manner similar to that in the fourth modification. The isotropic magnet has a plurality of magnetic poles (in the sixth modification,  12  poles, i.e., 6 N poles and 6 S poles) formed with polarities that alternate in the circumferential direction. Hence, twelve recesses  35  and twelve magnetic flux interchange faces  36  are arranged at the outer peripheral surface of the rotor  30  so as to alternate in the circumferential direction. 
     In this case, the arc ratio α of each magnetic pole, whose center is the axis of rotation O of the rotor  30 , is defined by the angle between two straight lines L 8  and L 8  which connect the axis of rotation O and the corners positioned at the outermost periphery sides at the anti-magnetizing pole center sides of each magnetic pole. Specifically, the arc ratio α is set as 6 slot pitches, which is 22.5°. The circumferential angular range β of each magnetic flux interchange face  36  is defined by the angle between two straight lines L 7  and L 7  as in the case of the fourth modification. It is noted that, also in the case of the sixth modification, the arc ratio α of the magnetic pole and the circumferential angular range β of the magnetic flux interchange face  36  are set so as to satisfy β≦2nγ and β&lt;α as in the case of the first embodiment. 
     Seventh Modification 
     As shown in  FIG. 16 , the stator core  22  of the seventh modification differs from the stator core  22  of the first embodiment in that, in the seventh modification, the tip of each of the teeth  22   b  formed at the inner periphery of the stator core  22  has flange portions  22   c  which project to the circumferentially-opposed sides from the projecting tip of the tooth. In this case, when designating δ as the circumferential angular range, whose center is the axis of rotation O of the rotor  30 , between the circumferential-direction center of a tooth  22   b  and the circumferential-direction tip of the flange portion  22   c  of the tooth  22   b,  the circumferential angular range β of the magnetic flux interchange face  36  is set as β≦2nγ−2δ. It is noted that the circumferential angular range δ is defined by the angle between a straight line L 9  connecting the axis of rotation O and the circumferential-direction center of the tooth  22   b  and a straight line L 10  connecting the axis of rotation O and a circumferential-direction tip of the flange portion  22   c.    
     When each tooth  22   b  has the flange portions  22   c  at the projected tip, as in the seventh modification, the flow of magnetic flux between the stator  20  and the rotor  30  can be efficiently acquired by setting the circumferential angular range β of the magnetic flux interchange face  36  as the above-described range. 
     Second Embodiment 
     The rotary electric machine  2  of the second embodiment differs from the rotary electric machine  1  of the first embodiment, which uses an embedded permanent magnet type rotor  30 , in that an electromagnet type rotor  40  having a Randle-type core  41  and a field coil  44  is used. Hence, the detailed descriptions of members and configurations that are common to the first embodiment are omitted in the following, in which points of difference and important points are described referring to  FIGS. 17 to 21 . It is noted that members that are common to the first embodiment are designated by identical reference numbers to those of the first embodiment. 
     The rotary electric machine  2  of the embodiment is a motor generator for a vehicle, and as shown in  FIG. 17  includes a housing  10 , a stator  20  functioning as an armature and having the stator core  22  and the stator coil  21 , and a rotor  40  functioning as a field magnet and having a Randle-type core  41  and a field coil  44 . The housing  10 , the stator  20 , and the electric power converter  50  of the second embodiment are as described in the first embodiment and shown in  FIGS. 1 to 8 , and detailed descriptions of these are omitted. 
     As shown in  FIG. 17 , the rotor  40  includes the shaft  13  which is rotatably supported at both ends by the bearings  11  in the housing  10 , a Randle-type core  41 , and a field coil  44  which is wound in the Randle-type core  41 , with the Randle-type core  41  having a first pole core  42  at the front end and a second pole core  43  at the rear end, which are assembled along the axial direction. 
     As shown in  FIGS. 18 and 20 , the first pole core  42  of the Randle-type core  41  is made up of a boss portion  42   a  which is of cylindrical shape and is fit to and fixed to the outer periphery of the shaft  13 , a disc part  42   b  which extends radially from one axial-direction end of the boss portion  42   a,  and a plurality of (in the second embodiment, 8) first claw magnetic pole portions  42   c  extending from the outer periphery of the disc part  42   b  to the boss portion  42   a  side along the axial direction. As shown in  FIGS. 17 and 21 , the second pole core  43  is configured similarly to the first pole core  42 , and is made up of a boss portion  43   a,  a disk portion  43   b  and eight second claw magnetic pole portions  43   c.    
     The first pole core  42  and the second pole core  43  are assembled with their respective first claw magnetic pole portions  42   c  and second claw magnetic pole portions  43   c  facing each other, such that the respective axial-direction end faces of the boss portions  42   a  and  43   a  contact each another (see  FIGS. 17 and 21 ). As a result, the first claw magnetic pole portions  42   c  and the second claw magnetic pole portions  43   c  are arranged alternately in the circumferential direction, with predetermined distances between them. The field coil  44  is formed by winding conductor wires in a cylindrical and coaxial form in a gap between the outer circumferences of the boss portions  42   a,    43   a  and the first and second claw magnetic pole portions  42   c,    43   c,  with the conductor wires having been treated with electrical insulation processing. The first claw magnetic pole portions  42   c  and the second claw magnetic pole portions  43   c  become magnetized with mutually opposite polarities when current is applied to the field coil  44 . In the case of the second embodiment, there are 8 of each of the first and second claw magnetic pole portions  42   c,    43   c,  so that a total of 16 magnetic poles (8 N poles, 8 S poles) are formed. 
     Each first claw magnetic pole portion  42   c  and second claw magnetic pole portion  43   c  is formed with a tapered shape, which gradually becomes narrower toward the tip end from the axial-direction base end (the side of a disk portion  42   b  or  43   b ). Flat chamfers  42   d ,  43   d  are formed at the corners of the intersections between the outer periphery surface and circumferentially opposing side faces of the first claw magnetic pole portion  42   c  and second claw magnetic pole portion  43   c.  A magnetic flux interchange face  46 , which faces the stator core  22  and at which magnetic flux is interchanged with the stator core  22 , is formed between the pair of circumferentially-opposed chamfers  42   d ,  43   d  of the first claw magnetic pole portion  42   c  and the second claw magnetic pole portion  43   c.    
     The arc ratio α of each first claw magnetic pole portion  42   c  and second claw magnetic pole portion  43   c,  whose center is the axis of rotation O of the rotor  40 , is defined as the angle between two straight lines L 11  and L 11  which connect the axis of rotation O and the corners at which the chamfers  42   d  and  43   d  intersect with the circumferentially-opposed side surfaces of the first claw magnetic pole portion  42   c  and the second claw magnetic pole portion  43   c.  In this case, due to the tapered shape of each first claw magnetic pole portion  42   c  and second claw magnetic pole portion  43   c  along the axial direction, the arc ratio α of the first claw magnetic pole portion  42   c  and second claw magnetic pole portion  43   c  varies along the axial direction, taking a maximum value αmax at the axial-direction base end. 
     The maximum angle αmax of the arc ratio α is set so as to satisfy the relationship between the slot multiple n and the slot pitch γ, of αmax≧3nγ. Specifically, with n=2, γ=3.75°, the maximum angle αmax of the arc ratio α is set as αmax≧3×2×3.75°=22.5°, being set within a range that is not less than 6 slot pitches at the inner periphery of the stator core  22 . 
     In addition, the circumferential angular range β of the magnetic flux interchange face  46  of the first claw magnetic pole portion  42   c  and the second claw magnetic pole portion  43   c  is defined by the angle between two straight lines L 12  and L 12  which connect the axis of rotation O and the circumferentially opposed ends of the magnetic flux interchange face  46 . In this case, the circumferential angular range β of the magnetic flux interchange face  46  is made smaller than the arc ratio α of the first claw magnetic pole portion  42   c  and the second claw magnetic pole portion  43   c,  with the relationship β&lt;α being established. As a result, since β&lt;α, the magnetic flux that flows between the stator  20  and the rotor  40  is made greater than the magnetic flux that is set by the circumferential angular range β of the magnetic flux interchange face  46  in the range of the arc ratio α of the first claw magnetic pole portion  42   c  and the second claw magnetic pole portion  43   c.    
     In addition, the circumferential angular range β of the magnetic flux interchange face  46  is set such that the relationship with the slot multiple n and the slot pitch γ is established as β≦2nγ. Specifically, as in the case of the first embodiment, n=2 and γ=3.75°, and the circumferential angular range β of the magnetic flux interchange face  46  is set as β≦2×2×3.75°=15°, so that the circumferential angular range β of the magnetic flux interchange face  46  is within a range no greater than 4 slot pitches with respect to the inner periphery surface of the stator core  22 . That is, the circumferential angular range β of the magnetic flux interchange face  46  is set to be no greater than the interval (4 slot pitches) between two slots  25  which house electrical conductors (slot-housed portions  23   a ) in which currents flow in mutually opposite directions in the phase windings of the same phase. As a result, demagnetizing fields are not produced in the phase windings of the same phase. 
     In the rotary electric machine  2  for a vehicle of the second embodiment configured as described above, when excitation is produced in the stator  20  based on a drive current obtained through electric power conversion and supplied from the electric power converter  50 , rotational torque (which may become motive force) is produced by excitation action, and the rotor  40  rotates. In this case, the rotary electric machine  2  functions as a motor. The generated rotational torque is output from the rotor  40  and shaft  13 , for example, to a drive section which drives an axle shaft or the like. 
     In addition, when a power conversion signal is not output by the electric power converter  50  and rotational force of an output shaft is transmitted to the shaft  13  by the operation of the engine, then since the rotor  40  also rotates, counter-electromotive force is produced by the stator coil  21  of the stator  20 . The generated counter-electromotive force (regenerated power) can charge a battery via the electric power converter  50 . In this case, the rotary electric machine  2  operates as a generator. 
     As described above, according to the rotary electric machine  2  of the second embodiment, the slot multiple is set as n, each phase winding of the stator coil  21  is wound with short windings over (n+1) adjacent slots  25 , and with the axis of rotation (O) of the rotor being the center, designating the arc ratio of the first and second claw magnetic pole portions  42   c,    43   c  as α, the circumferential angular range of the magnetic flux interchange face  36  being β, and the slot pitch as γ, the relationships β≦2nγ and β&lt;α are satisfied, and the maximum angle of the arc ratio α, αmax, is set as αmax≧3nγ. As a result, when magnetic flux flows between the stator  20  and the rotor  40 , it is ensured that demagnetizing fields are not be produced by the phase windings of the same phase of the stator coil  21 , so that a flow of magnetic flux between the stator  20  and the rotor  40  can be efficiently acquired, so that the same actions and effects as those of the first embodiment can be obtained. 
     In addition, according to the second embodiment, since the electromagnet type rotor  40  having a Randle-type core  41  and a field coil  44  is utilized, compared with the embedded permanent magnet type rotor  30  of the first embodiment which has 2-dimensional planar faces that are continuous along the axial direction, the relationship β≧3n can be established near the end face of the stator core  22  positioned in the axial direction, so that increased magnetic force can be achieved. 
     Eighth Modification 
     As shown in  FIG. 22 , as in the case of the seventh modification, the stator core  22  of the eighth modification differs from the stator core  22  of the second embodiment in that, in the eighth modification, the tip of each of the teeth  22   b  formed at the inner periphery of the stator core has flange portions  22   c  which project to the circumferentially-opposed sides from the projecting tip of the tooth. In this case, when designating δ as the circumferential angular range, whose center is the axis of rotation O of the rotor  30 , between the circumferential-direction center of the tooth  22   b  and the circumferential-direction tip of the flange portion  22   c  of the tooth  22   b , the circumferential angular range β of the magnetic flux interchange face  46  is set as β≦2nγ−2δ. It is noted that the circumferential angular range δ is defined by the angle between a straight line L 9  connecting the axis of rotation O and the circumferential-direction center of the tooth  22   b  and a straight line L 10  connecting the axis of rotation O and a circumferential-direction tip of the flange portion  22   c.    
     When each tooth  22   b  has the flange portions  22   c  at the projected tip, as in the eighth modification, the flow of magnetic flux between the stator  20  and the rotor  40  can be efficiently acquired by setting the circumferential angular range β of the magnetic flux interchange face  46  as the above-described range. 
     Ninth Modification 
     As shown in  FIG. 23 , the electromagnet type rotor  40  of the ninth modification has a Randle-type core  41  and a field coil  44  of the second embodiment, and has a first flow path  15  in the interior of the shaft  13 , through which a liquid coolant flows in the axial direction. According to the ninth modification, by circulating the liquid coolant through the flow path  15  provided in the electromagnet type rotor  40 , the field coil  44 , which generates heat, can be intensively cooled. 
     Tenth Modification 
     In the tenth modification, as shown in  FIG. 24 , a plurality of radially extending second flow paths  16  are added to the rotor  40  having the first flow path  15  of the ninth modification, with the second flow paths  16  being positioned at a central part of the shaft  13 . The second flow paths  16  communicate at their radially inner sides with the first flow path  15 , and the radially outer sides of the second flow paths  16  are open to each of the outer peripheries of the boss portions  42   a ,  43   a  of the first and second pole cores  42 ,  43  that form the Randle-type core  41 . A drain hole  19  is provided in a lower part of the housing  10  to collect liquid coolant that has discharged from the second flow paths  16 . 
     According to the tenth modification, the liquid coolant is passed from the first flow path  15  through the second flow paths  16 , to be radially discharged by centrifugal force that is produced by rotation of the rotor  40 , so that the first claw magnetic pole portions  42   c  and the second magnetic claw pole portions  43   c  can be directly cooled by the liquid coolant. As a result, efficient cooling can be performed, so that an excellent cooling effect can be achieved. 
     Third Embodiment 
     The rotary electric machine of the third embodiment differs from the rotary electric machine  1  of the first embodiment in that the stator coil  21  including phase windings of 6 phases is used, though the stator coil  21  including the phase windings of 3 phases is used for the rotary electric machine  1  of the first embodiment. Hence, detailed descriptions of members and configurations common to the first embodiment are omitted in the following, with points of difference and important points being described referring to  FIGS. 3 to 8 and 25 . Members that are common to those of the first embodiment are designated by identical reference symbols to those of the first embodiment. 
     The stator coil  21  of the third embodiment, which has phase windings of 6 phases, is formed using pairs of large and small conductor segments  23  (large segment  231 , small segment  232 ) shown in  FIG. 4 , as in the first embodiment. In this case, a pair of large and small conductor segments  231 ,  232  are inserted from one axial-direction end side (upper side of  FIG. 4 , the back-to-front direction of the paper of  FIG. 25 ) of two slots  25 A,  25 C (see  FIG. 8 ) which are separated by 5 slot pitches. 
     That is, one linear portion  23   g   1  of the large segment  231  is inserted into the fourth layer (outermost layer) of one slot  25 A, while the other linear portion  23   g   2  is inserted into the first layer (innermost layer) of another slot (not shown) which is separated from slot  25 A by 5 slot pitches in the counterclockwise direction of the stator core  22  (the Y arrow direction in  FIGS. 4 and 25 ). One linear portion  23   g   3  of the small segment  232  is inserted into the third layer of one slot  25 A, while the other linear portion  23   g   4  of the small segment  232  is inserted into the second layer of another slot (not shown) which is separated by 5 slot pitches in the counterclockwise direction of the stator core  22 . The linear portions  23   g  of an even number of conductor segments  23  are arranged in that way and inserted into all of the slots  25 . In the third embodiment, a total of  4  linear portions  23   g   1  to  23   g   4  are arranged radially in a single row in each slot  25  (see  FIG. 6 ,  FIG. 8 ). 
     In this case, one electrical conductor (slot-housed portion  23   a ) within each slot  25  is paired with one electrical conductor (slot-housed portion  23   a ) within another slot  25  that is separated by five slot pitches. For example, as shown in  FIG. 8 , an electrical conductor  213   a  that is housed in the first layer in one slot  25 A is paired with an electrical conductor  213   b  that is housed in the fourth layer in another slot  25 C which is separated by 5 slot pitches in the clockwise direction around the stator core  22  (X arrow direction in  FIGS. 4, 5, 8, and 25 ). Similarly, an electrical conductor  232   a  that is housed in the second layer in one slot  25 A is paired with an electrical conductor  232   b  that is housed in the third layer in another slot  25 C which is separated by 5 slot pitches in the clockwise direction (X-arrow direction) around the stator core  22 . 
     Similarly to the first embodiment, the open end portions of the paired linear portions ( 23   g   1 ,  23   g   2 ) ( 23   g   3 ,  23   g   4 ) of the large and small segments  231 ,  232 , i.e. open end portions which extend from one axial-direction end of respective slots  25 , are twisted in mutually opposite circumferential directions, forming oblique portions  23   e  having a length equal to approximately 2.5 slot pitches. The tip of the oblique portion  23   e  is formed integrally with a joint end portion  23   f  by bending deformation. Thereafter, at the axial-direction other end side of the stator core  22 , predetermined paired joint end portions  23   f  of the conductor segments  23  are joined by welding or the like and electrically connected in a predetermined pattern. 
     In this way, by connecting specific conductor segments  23  in series, the stator coil  21  is formed which includes 6 phase windings (U-phase, V-phase, W-phase, X-phase, Y-phase, Z-phase) that are wave-wound circumferentially along the slots  25  of the stator core  22 . In this case, each phase winding of the stator coil  21  is wound with short windings of 5 slot pitches, over n adjacent slots  25  (2 slots in the third embodiment, where n=2). 
     That is, in each phase winding, as shown in  FIG. 25 , two electrical conductors housed at the inner circumferential side in the slot  25  (in the first layer and in the second layer) are connected to two electrical conductors that are housed (in the third layer and in the fourth layer) at the outer circumferential side in the slot  25  that is separated by 5 slot pitches in the clockwise direction (X direction indicated by the arrow) of the stator core  22 . Thus, in the third embodiment, the slot multiple n is 2, and hence, the slots  25  that house phase windings of the same phase in the first layer and the second layer at the inner circumferential side and also in the third layer and fourth layer at the outer circumferential side successively differ in circumferential position by one slot pitch. 
     Specifically as shown in  FIG. 25 , at the inner circumferential side at which the first layer and the second layer are housed, the slots  25  that respectively house the U-phase, X-phase, V-phase, Y-phase W-phase, and Z-phase windings are arranged so as to occur one at a time in repeated sequence, in the counterclockwise direction (Y-arrow direction) of the stator core  22 . In addition, at the outer circumferential side at which the third layer and the fourth layer are housed, the slots  25  that respectively house the U-phase, X-phase, V-phase, Y-phase W-phase, and Z-phase windings are arranged so as to occur one at a time in repeated sequence, in the counterclockwise direction (Y-arrow direction) of the stator core  22  in the state of one slot pitch displacement. As a result, each of the phase windings is wound over n adjacent slots  25  (2 slots, when n=2) of the stator core  22 . 
     It is noted that in the stator coil  21  of the third embodiment, as in the case of the first embodiment, due to the conductor segments  23  having a basically U-shaped form, each of the phase windings turns four times around the circumference of the stator core  22 , and is formed with irregular segments (not shown in the drawings) having a different shape from that of the basic conductor segment  23 . The irregular segments are segments that are integrally formed with output power lead-out wires or with neutral point lead-out wires, and segments having turn portions for respectively connecting the first and second circumferential turns, for connecting the second and third circumferential turns, and for connecting the third and fourth circumferential turns. The phase windings of the stator coil  21  are wired with star-formation wiring by using these irregular segments. 
     In the third embodiment, with the axis of rotation (O) of the rotor  30  as center, designating the arc ratio of the magnetic pole as α, the circumferential angular range of the magnetic flux interchange face  36  as β, and the slot pitch as γ, as in the first embodiment, the relationships β≦(3n−1)γ and β&lt;α are satisfied. That is, due to the relationship β&lt;α, it is ensured that when magnetic flux flows between the stator  20  and the rotor  30 , the amount of magnetic flux within the range of the arc ratio α of the magnetic pole is greater than the magnetic flux that is set by the circumferential angular range β of a magnetic flux interchange face  36 . 
     In addition, from the relationship β≦(3n−1)γ, the circumferential angular range β of the magnetic flux interchange face  36  is set as β≦(3×2−1)×3.75°=18.75°, being set as a range not exceeding 5 slot pitches of the inner periphery surface of the stator core  22 . That is, the circumferential angular range β of the magnetic flux interchange face  36  is set so as to be equal to or less than the distance (5 slot pitches) between the two slots  25  housing electrical conductors (slot-housed portions  23   a ) of phase windings of the same phase, in which currents flow in mutually opposite directions. As a result, it is ensured that demagnetizing fields will not be produced by the phase windings of the same phase. 
     As described above, according to the rotary electric machine of the third embodiment, the slot multiple is set as n, each phase winding of the stator coil  21  is wound with short windings over n adjacent slots  25 , and with the axis of rotation (O) of the rotor being the center, designating the arc ratio of the magnetic pole as α, the circumferential angular range of the magnetic flux interchange face  36  being β, and the slot pitch as γ, and the relationships β≦(3n−1)γ and β&lt;α are satisfied. As a result, as in the case of the first embodiment, when magnetic flux flows between the stator  20  and the rotor  30 , it is ensured that demagnetizing fields are not produced by the phase windings of the same phase of the stator core  21 , so that a flow of magnetic flux between the stator  20  and the rotor  30  can be efficiently acquired. 
     In particular, in the case of the third embodiment, the upper limit of the circumferential angular range β of the magnetic flux interchange face  36  is increased to 5 slot pitches from the 4 slot pitches of the first embodiment, so that the amount of magnetic flux flowing through the magnetic flux interchange face  36  can be increased, thereby improving the performance. 
     Eleventh Modification 
     As shown in  FIG. 26 , as in the case of the seventh and eighth modifications, the stator core  22  of the eleventh modification differs from the stator core  22  of the third embodiment in that, in the eleventh modification, the tip of each of the teeth  22   b  formed at the inner periphery of the stator core  22  has flange portions  22   c  which project to the circumferentially-opposed sides from the projecting tip of the tooth. In this case, when designating δ as the circumferential angular range, whose center is the axis of rotation O of the rotor  30 , between the circumferential-direction center of the tooth  22   b  and the circumferential-direction tip of the flange portion  22   c  of the tooth  22   b , the circumferential angular range β of the magnetic flux interchange face  36  is set as β≦(3n−1)γ−2δ. It is noted that the circumferential angular range δ is defined by the angle between a straight line L 9  connecting the axis of rotation O and the circumferential-direction center of the tooth  22   b  and a straight line L 10  connecting the axis of rotation O and a circumferential-direction tip of the flange portion  22   c.    
     When each tooth  22   b  has the flange portions  22   c  at the projected tip, as in the eleventh modification, the flow of magnetic flux between the stator  20  and the rotor  30  can be efficiently acquired by setting the circumferential angular range β of the magnetic flux interchange face  36  as the above-described range. 
     Fourth Embodiment 
     The rotary electric machine of the fourth embodiment differs from the rotary electric machine of the third embodiment, which uses the embedded permanent magnet type rotor  30 , in that the electromagnet type rotor  40  having the Randle-type core  41  and the field coil  44  is used. That is, the rotary electric machine of the fourth embodiment, as shown in  FIG. 27 , is configured by assembling the stator  20  (see  FIG. 25 ) having the stator coil  21  formed of phase windings of 6 phases of the third embodiment, and the rotor  40  (see  FIG. 19 ) having the Randle-type core  41  and the field coil  44  of the second embodiment. Hence, members in  FIG. 27  that are common to the second or third embodiments are designated by the same reference symbols, and detailed descriptions of the configurations and the like of the rotary electric machine of the fourth embodiment are omitted. 
     As described above, according to the rotary electric machine of the fourth embodiment, the slot multiple is set as n, each phase winding of the stator coil  21  is wound with short windings over n adjacent slots  25 , and with the axis of rotation (O) of the rotor being the center, designating the arc ratio of the first and second claw magnetic pole portions  42   c,    43   c  as α, the circumferential angular range of the magnetic flux interchange face  36  being β, and the slot pitch as γ, the relationships β≦(3n−1)γ and β&lt;α are satisfied, and the maximum angle of the arc ratio α, αmax, is set as αmax≧3nγ. As a result, the same actions and effects as those of the rotary electric machine of the third embodiment can be obtained. 
     Twelfth Modification 
     As shown in  FIG. 28 , as in the case of the seventh, eighth, and eleventh modifications, the stator core  22  of the twelfth modification differs from the stator core  22  of the fourth embodiment in that, in the twelfth modification, the tip of each of the teeth  22   b  formed at the inner periphery of the stator core  22  has flange portions  22   c  which project to the circumferentially-opposed sides from the projecting tip of the tooth. In this case, when designating δ as the circumferential angular range, whose center is the axis of rotation O of the rotor  30 , between the circumferential-direction center of the tooth  22   b  and the circumferential-direction tip of the flange portion  22   c  of the tooth  22   b , the circumferential angular range β of the magnetic flux interchange face  46  is set as β≦(3n−1)γ−2δ. It is noted that the circumferential angular range δ is defined by the angle between a straight line L 9  connecting the axis of rotation O and the circumferential-direction center of the tooth  22   b  and a straight line L 10  connecting the axis of rotation O and a circumferential-direction tip of the flange portion  22   c.    
     When each tooth  22   b  has the flange portions  22   c  at the projected tip, as in the twelfth modification, the flow of magnetic flux between the stator  20  and the rotor  40  can be efficiently acquired by setting the circumferential angular range β of the magnetic flux interchange face  46  as the above-described range. 
     Other Embodiments 
     The present invention is not limited to the above embodiments, and various changes are possible, without departing from the scope of the present invention. 
     For example, in the first to fourth embodiments described above, examples are described in which a rotary electric machine according to the present invention is applied to a motor generator for a vehicle. However, the present invention may be applied to a rotary electric machine which is installed in a vehicle and functions simply as a generator or as a motor. 
     REFERENCE SIGNS LIST 
       1 ,  2  . . . rotary electric machine,  13  . . . shaft,  15  . . . first flow path,  16  . . . second flow path,  20  . . . stator,  21  . . . stator coil,  22  . . . stator core,  22   b  . . . tooth,  22   c  . . . flange portion,  25  . . . slot,  30  . . . rotor,  31  . . . rotor core,  32 ,  32   a,    32   b,    32   c,    32   d,    32   e  . . . magnet housing portion,  33 ,  33   a,    33   b,    33   c,    33   d,    33   e,    33   f  . . . permanent magnet,  35  . . . recess,  36  . . . magnetic flux interchange face,  37  . . . chamfer,  40  . . . rotor,  41  . . . Randle-type core,  42  . . . first pole core,  42   c  . . . first claw magnetic pole portion,  43  . . . second pole core,  43   c  . . . second claw magnetic pole portion,  44  . . . field coil,  46  . . . magnetic flux interchange face, O . . . axis of rotation of rotor