Patent Publication Number: US-6901649-B2

Title: Method of manufacturing a winding assembly for an alternator

Description:
This is a divisional of application Ser. No. 09/734,680 filed Dec. 13, 2000; now U.S. pat. No. 6,498,413 the disclosure of which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an automotive alternator mounted to an automotive vehicle such as a passenger car or a truck, for example, to a stator winding assembly of the automotive alternator, and to a method of manufacture for the stator winding assembly. 
   2. Description of the Related Art 
   To reduce the size and increase the output of alternators driven by internal combustion engines, it is necessary to increase the space factor of electrical conductors housed within magnetic circuits of a stator, and to line up and increase the density of crossover portions (coil end portions) of a stator winding, and various improvements have been proposed, as for example in Japanese Patent Laid-Open No. HEI 11-164506. 
     FIGS. 27 and 28  are perspectives from a front end and a rear end, respectively, of part of a stator winding of a conventional alternator of this type, and  FIG. 29  is a perspective showing a construction of a conductor segment used in the stator winding of the conventional alternator shown in  FIGS. 27 and 28 . 
   In  FIGS. 27  to  29 , a stator  90  is constituted by a stator core  91 , a stator winding  92  constituted by a number of electrical conductors disposed inside slots  91   a  formed in the stator core  91 , and insulators  93  providing electrical insulation between the stator core  91  and the electrical conductors. 
   In the stator core  91  of this conventional example, ninety-six slots  91   a  are disposed at even pitch so as to house two three-phase alternating current windings such that the number of slots housing each phase portion of the three-phase alternating current windings corresponds to the number of magnetic poles in a rotor. Four electrical conductors are housed within each of the slots  91   a  so as to line up in one row in a radial direction, and these electrical conductors are connected in a predetermined winding pattern to form the stator winding  92 . Here, a first position, a second position, a third position, and a fourth position in a radial direction from an inner circumferential side inside the slots  91   a  in which the electrical conductors are housed will be called a first address, a second address, a third address, and a fourth address, respectively. 
   Large segments  95  and small segments  96  are formed by bending short lengths of a conductor such as copper into general U shapes in which pairs of straight portions  95   a  and  96   a  are linked by turn portions  95   b  and  96   a . The small segments  96  are inserted one at a time from a rear end into pairs of slots  91   a  six slots apart (a pitch of one magnetic pole). Similarly, the large segments  95  are inserted one at a time from the rear end into pairs of slots  91   a  six slots apart (a pitch of one magnetic pole). Then, end portions of the large segments  95  and the small segments  96  extending outwards at a front end are joined to each other to constitute the stator winding  92 . 
   More specifically, in pairs of slots  91   a  six slots apart, the small segments  96  are inserted from the rear end into the second address within first slots  91   a  and into the third address within second slots  91   a , and the large segments  95  are inserted from the rear end into the first address within the first slots  91   a  and into the fourth address within the second slots  91   a . Thus, within each of the slots  91   a , two straight portions  95   a  of the large segments  95  and two straight portions  96   a  of the small segments  96  are disposed to line up in a row of four in a radial direction. 
   Then, end portions  95   c  of the large segments  95  extending outwards at the front end from the first address within the first slots  91   a  are joined to end portions  96   c  of the small segments  96  extending outwards at the front end from the second address within the second slots  91   a  six slots away in a clockwise direction from the first slots  91   a . In addition, the end portions  95   c  of the large segments  95  extending outwards at the front end from the fourth address within the first slots  91   a  are joined to the end portions  96   c  of the small segments  96  extending outwards at the front end from the third address within the second slots  91   a  six slots away in a counter-clockwise direction from the first slots  91   a . Thus, two winding sub-portions are formed, which are lap windings having two turns per lap. These two winding sub-portions are connected in series to form one winding phase portion having four turns. 
   Similarly, a total of six winding phase portions each having four turns are formed by offsetting by one slot at a time the positions of the slots into which the large segments  95  and the small segments  96  are inserted. Then, three each of these winding phase portions are connected into each of the two three-phase alternating current windings which constitute the stator winding  92 . 
   In the conventional stator  90  constructed in this manner, at the rear end of the stator core  91 , the turn portions  95   b  of the large segments  95  are disposed so as to cover outer circumferential sides of the turn portions  96   b  of the small segments  96  inserted into the same pairs of slots  91   a . As a result, the turn portions  95   b  and  96   b  are disposed circumferentially to constitute a rear-end coil end group. 
   At the front end of the stator core  91 , on the other hand, joint portions formed by joining the end portions  95   c  of the large segments  95  extending outwards at the front end from the first address within the first slots  91   a  and the end portions  96   c  of the small segments  96  extending outwards at the front end from the second address within the second slots  91   a  six slots away, and joint portions formed by joining the end portions  95   c  of the large segments  95  extending outwards at the front end from the fourth address within the first slots  91   a  and the end portions  96   b  of the small segments  96  extending outwards at the front end from the third address within the second slots  91   a  six slots away are disposed to line up radially. As a result, joint portions formed by joining the end portions  95   c  and  96   c  to each other are disposed circumferentially in two rows in a radial direction to constitute a front-end coil end group. 
   Because the stator winding  92  of the conventional alternator is constructed by inserting the large segments  95  and the small segments  96  formed by bending the short lengths of conductor into general U shapes into the slots  91   a  of the stator core  91  from the rear end and joining together the end portions of the segments extending outwards at the front end as explained above, one problem has been that a large number of the large segments  95  and the small segments  96  must be inserted into the slots  91   a  of the stator core  91  and end portions thereof must be joined one by one, significantly reducing workability and decreasing mass-producibility. 
   In addition, in order to join the end portions  95   c  of the large segments  95  and the end portions  96   c  of the small segments  96 , it is necessary to clamp a portion of each of the end portions  95   c  and  96   c  together using a jig, and another problem has been that it is necessary to extend the segments out by an extra amount from the stator coil  91  to allow for the clamping, preventing the stator  90  from being reduced in size. 
   In the conventional stator  90 , because the end portions  95   c  and  96   c  are joined to each other by clamping portions thereof in a jig and welding the end portions  95   c  and  96   c  together, the height of the coil ends is increased, and the large segments  95  and the small segments  96  are softened by temperature increases during welding, thereby causing rigidity of the stator to be decreased. As a result, other problems have been that when the conventional stator  90  is mounted to an alternator, coil leakage reactance in the coil end portions is increased to cause output to deteriorate, wind resistance is increased to exacerbate wind noise, and rigidity of the stator is reduced to exacerbate magnetic noise. 
   SUMMARY OF THE INVENTION 
   The present invention aims to solve the above problems and an object of the present invention is to provide a winding assembly for an alternator and a method of manufacture therefor enabling mass-producibility to be improved and size to be reduced. 
   Another objective is to provide an alternator enabling coil end height to be lowered, enabling the number of weld portions on the coil ends to be decreased, and enabling deterioration in output, wind noise and magnetic noise to be suppressed. 
   In order to achieve the above object, according to one aspect of the present invention, there is provided an alternator including: 
   a stator having a cylindrical stator core formed with a plurality of slots extending axially at a predetermined pitch in a circumferential direction, and a stator winding installed into the stator core; and 
   a rotor for forming north-seeking (N) and south-seeking (S) poles about a rotational circumference, the rotor being disposed on an inner circumferential side of the stator core, wherein 
   the stator winding comprises a plurality of winding sub-portions in each of which a strand of wire formed from a continuous wire is wound so as to alternately occupy an inner layer and an outer layer in a slot depth direction within the slots at intervals of a predetermined number of slots by folding over the strand of wire outside the slots at end surfaces of the stator core and form a lap winding having two turns in each lap. 
   Four of the strands of wire constituting the winding sub-portions may be housed so as to line up in each of the slots so as to occupy a first layer, a second layer, a third layer, and a fourth layer in a slot depth direction; 
   turn portions formed by folding the strands of wire over outside the slots at a first end surface of the stator core may be disposed circumferentially to form two rows in a radial direction; and 
   turn portions formed by folding the strands of wire over outside the slots at a second end surface of the stator core may be disposed circumferentially to form two layers in an axial direction. 
   In each of slot pairs in which first and second slots forming each of the slot pairs are a predetermined number of slots apart: 
   the strand of wire housed in the first layer inside the first slot may be folded over outside the slots at the first end surface of the stator core and housed in the second layer inside the second slot; 
   the strand of wire housed in the third layer of the first slot may be folded over outside the slots at the first end surface of the stator core and housed in the fourth layer of the second slot; 
   the strand of wire housed in the third layer inside the first slot may be folded over outside the slots at the second end surface of the stator core and housed in the second layer inside the second slot; and 
   the strand of wire housed in the fourth layer of the first slot may be folded over outside the slots at the second end surface of the stator core and housed in the first layer of the second slot. 
   The strands of wire may be installed two at a time into slot sets constituted by slot groups disposed a predetermined number of slots apart, the two strands of wire installed in each of the slot sets constituting a first strand of wire and a second strand of wire, and 
   the stator winding may be composed of a plurality of stator winding phase portions, each of the stator winding phase portions comprising:
         a first winding sub-portion constructed by joining first and second end portions of the first strand of wire extending outwards outside the slots at the second end surface of the stator core from the fourth layer in the first slot of a first pair and the first layer in the second slot of the first pair, the first pair being one pair of the slot pairs constituting each of the slot sets; and   a second winding sub-portion constructed by joining first and second end portions of the second strand of wire extending outwards outside the slots at the second end surface of the stator core from the third layer in the first slot of the first pair and the second layer in the second slot of the first pair,   wherein each of the stator winding phase portions is constructed by connecting the first and second winding sub-portions in series by crossover connecting the first strand of wire extending outwards outside the slots at the second end surface of the stator core from the fourth layer in the first slot of a second pair, and the second strand of wire extending outwards from the outside of the slots at the second end surface of the stator core from the second layer in the second slot of the second pair, the second pair being another pair of the slot pairs constituting each of the slot sets, and   wherein the second strand of wire extending outwards at the second end surface of the stator core from the third layer in the first slot of the second pair, and the first strand of wire extending outwards at the second end surface of the stator core from the first layer in the second slot of the second pair constitute a neutral point and an output wire of the stator winding phase portion, respectively.       

   The strands of wire may be installed two at a time into slot sets constituted by slot groups disposed a predetermined number of slots apart, the two strands of wire installed in each of the slot sets constituting a first strand of wire and a second strand of wire, and 
   the stator winding may be composed of a plurality of stator winding phase portions, each of the stator winding phase portions being constructed by a first and second winding sub-portions which are connected in series by joining a first end portion of the first strand of wire extending outwards outside the slots at the second end surface of the stator core from the fourth layer in the first slot of a first pair to a second end portion of the second strand of wire extending outwards outside the slots at the second end surface of the stator core from the second layer in the second slot of the first pair, and joining a first end portion of the second strand of wire extending outwards outside the slots at the second end surface of the stator core from the third layer in the first slot of the first pair to a second end portion of the first strand of wire extending outwards outside the slots at the second end surface of the stator core from the first layer in the second slot of the second pair, the first pair being one pair of the slots pair constituting each of the slot sets, 
   wherein the second strand of wire extending outwards at the first end surface of the stator core from the third layer in the first slot of a second pair and from the fourth layer in the second slot of the second pair is cut to constitute a neutral point and an output wire of the stator winding phase portion, the second pair being another pair of the slot pairs constituting each of the slot sets. 
   In each of slot pairs in which first and second slots forming each of the slot pairs are a predetermined number of slots apart: 
   the strand of wire housed in the second layer inside the first slot may be folded over outside the slots at the first end surface of the stator core and housed in the first layer inside the second slot; 
   the strand of wire housed in the third layer of the first slot may be folded over outside the slots at the first end surface of the stator core and housed in the fourth layer of the second slot; 
   the strand of wire housed in the second layer inside the first slot may be folded over outside the slots at the second end surface of the stator core and housed in the third layer inside the second slot; and 
   the strand of wire housed in the fourth layer of the first slot may be folded over outside the slots at the second end surface of the stator core and housed in the first layer of the second slot. 
   The strands of wire may be installed two at a time into slot sets constituted by slot groups disposed a predetermined number of slots apart, the two strands of wire installed in each of the slot sets constituting a first strand of wire and a second strand of wire, and 
   the stator winding may be composed of a plurality of stator winding phase portions, each of the stator winding phase portions comprising:
         a first winding sub-portion constructed by joining first and second end portions of the first strand of wire extending outwards outside the slots at the second end surface of the stator core from the fourth layer in the first slot of a first pair and the first layer in the second slot of the first pair, the first pair being one pair of the slot pairs constituting each of the slot sets; and   a second winding sub-portion constructed by joining first and second end portions of the second strand of wire extending outwards outside the slots at the second end surface of the stator core from the second layer in the first slot of the first pair and the third layer in the second slot of the first pair,   wherein each of the stator winding phase portions is constructed by connecting the first and second sub-portions in series by crossover connecting the second strand of wire extending outwards outside the slots at the first end surface of the stator core from the third layer in the first slot of a second pair, and the first strand of wire extending outwards from the outside of the slots at the first end surface of the stator core from the first layer in the second slot of the second pair, the second pair being another pair of the slot pairs constituting each of the slot sets, and   wherein the first strand of wire extending outwards at the first end surface of the stator core from the second layer in the first slot of the second pair, and the second strand of wire extending outwards at the first end surface of the stator core from the fourth layer in the second slot of the second pair constitute a neutral point and an output wire of the stator winding phase portion, respectively.       

   Four of the strands of wire constituting the winding sub-portions may be housed so as to line up in each of the slots so as to occupy a first layer, a second layer, a third layer, and a fourth layer in a slot depth direction; 
   turn portions formed by folding the strands of wire over outside the slots at a first end surface of the stator core may be disposed circumferentially to form two rows in a radial direction; and 
   turn portions formed by folding the strands of wire over outside the slots at a second end surface of the stator core may be disposed in one row circumferentially. 
   According to another aspect of the present invention, there is a winding assembly for an alternator, the winding assembly including a winding group composed of 2n winding sub-portions disposed at a pitch of p, each of the winding sub-portions being constructed by folding and bending one strand of wire formed from a continuous wire into a pattern, the pattern having: 
   first straight portions disposed at a pitch of 2np; 
   second straight portions disposed at the pitch of 2np being offset by an amount w to a first side in a width direction from the first straight portions and offset by an amount np forwards relative to a direction of disposal of the first straight portions; 
   third straight portions disposed at the pitch of 2np being offset by the amount w to the first side in the width direction from the second portions and offset by the amount np backwards relative to the direction of disposal of the second straight portions; 
   fourth straight portions disposed at the pitch of 2np being offset by the amount w to the first side in the width direction from the third straight portions and offset by the amount np forwards relative to the direction of disposal of the third straight portions; 
   first turn portions linking first ends of the first straight portions to first ends of the second straight portions offset by the amount np forwards relative to the direction of disposal of the first straight portions; 
   second turn portions linking second ends of the second straight portions to second ends of the third straight portions offset by the amount np backwards relative to the direction of disposal of the second straight portions; 
   third turn portions linking first ends of the third straight portions to first ends of the fourth straight portions offset by the amount np forwards relative to the direction of disposal of the third straight portions; and 
   fourth turn portions linking second ends of the fourth straight portions to second ends of the first straight portions offset by the amount np forwards relative to the direction of disposal of the fourth straight portions, wherein 
   the winding sub-portions are disposed parallel to each other at the pitch of p in the direction of disposal such that the first to fourth straight portions form four layers in the width direction, 
   the first turn portions are disposed parallel to each other at the pitch of p and the third turn portions are disposed parallel to each other at the pitch of p such that the first turn portions and the third turn portions form two rows in the direction of disposal, and 
   the second turn portions are disposed parallel to each other at the pitch of p and the fourth turn portions are disposed parallel to each other at the pitch of p such that the second turn portions and the fourth turn portions form two layers in a longitudinal direction of the straight portions. 
   According to another aspect of the present invention, there is a winding assembly for an alternator, the winding assembly comprising a winding group composed of 2n winding sub-portions disposed at a pitch of p, each of the winding sub-portions being constructed by folding and bending one strand of wire formed from a continuous wire into a pattern, the pattern having: 
   first straight portions disposed at a pitch of 2np; 
   second straight portions disposed at the pitch of 2np being offset by an amount w to a first side in a width direction from the first straight portions and offset by an amount np forwards relative to a direction of disposal of the first straight portions; 
   third straight portions disposed at the pitch of 2np being offset by the amount w to the first side in the width direction from the second portions and offset by the amount np forwards relative to the direction of disposal of the second straight portions; 
   fourth straight portions disposed at the pitch of 2np being offset by the amount w to the first side in the width direction from the third straight portions and offset by the amount np backwards relative to the direction of disposal of the third straight portions; 
   first turn portions linking first ends of the first straight portions to first ends of the second straight portions offset by the amount np forwards relative to the direction of disposal of the first straight portions; 
   second turn portions linking second ends of the second straight portions to second ends of the third straight portions offset by the amount np forwards relative to the direction of disposal of the second straight portions; 
   third turn portions linking first ends of the third straight portions to first ends of the fourth straight portions offset by the amount np backwards relative to the direction of disposal of the third straight portions; and 
   fourth turn portions linking second ends of the fourth straight portions to second ends of the first straight portions offset by the amount np forwards relative to the direction of disposal of the fourth straight portions, wherein 
   the winding sub-portions are disposed parallel to each other at the pitch of p in the direction of disposal such that the first to fourth straight portions form four layers in the width direction, 
   the first turn portions are disposed parallel to each other at the pitch of p and the third turn portions are disposed parallel to each other at the pitch of p such that the first turn portions and the third turn portions form two rows in the direction of disposal, and 
   the second turn portions are disposed parallel to each other at the pitch of p and the fourth turn portions are disposed parallel to each other at the pitch of p such that the second turn portions and the fourth turn portions form two layers in a longitudinal direction of the straight portions. 
   According to another aspect of the present invention, there is a method of manufacture for a winding assembly for an alternator, the method including steps of: 
   disposing a group of 2n straight strands of wire at a pitch p in a first plane; 
   forming a lighting-bolt shaped pattern (i.e. a zigzag shave) composed of a plurality of basic patterns by folding and bending the group of strands of wire in the plane, each of the basic patterns comprising:
         first straight portions having a length l 0 ;   second straight portions having the length l 0  being linked to the first straight portions by first inclined portions having a length l 1 , the second straight portions being offset by an amount np to a first side in a direction of disposal of the strands of wire relative to the first straight portions;   third straight portions having the length l 0  being linked to the second straight portions by second inclined portions having the length l 1 , the third straight portions being offset by the amount np to a second side in a direction of disposal of the strands of wire relative to the second straight portions; and   fourth straight portions having the length l 0  being linked to the third straight portions by third inclined portions having the length  1   l , the fourth straight portions being offset by the amount np to the first side in a direction of disposal of the strands of wire relative to the third straight portions,   wherein the lightning-bolt shaped pattern is constructed by repeating the basic pattern a predetermined number of times by offsetting the basic pattern to the first side in the direction of disposal of the strands of wire by fourth inclined portions having a length l 2 , the length l 2  being greater than the length l 1 ;       

   forming a flattened cylindrical body by folding over the group of strands of wire formed into the lightning-bolt shaped pattern in a first direction at central portions of the first and the third inclined portions, the cylindrical body being constructed by helically winding the group of strands of wire such that the second and third straight portions linked by the second inclined portions and the first and fourth straight portions linked by the fourth inclined portions alternately occupy the first plane and a second plane; and 
   forming a winding group by folding over the cylindrical body at central portions of the second and the fourth inclined portions in a second direction such that the second and the third straight portions face each other, wherein
         the first to fourth straight portions are disposed parallel to each other at the pitch of p in the direction of disposal such that the first to fourth straight portions form four layers in the width direction,   first turn portions formed by folding over the group of strands of wire at the first inclined portions are disposed parallel to each other at the pitch of p and third turn portions formed by folding over the group of strands of wire at the third inclined portions are disposed parallel to each other at the pitch of p such that the first turn portions and the third turn portions form two rows in the direction of disposal, and   second turn portions of the strands of wire formed by folding over the cylindrical body at the second inclined portions are disposed parallel to each other at the pitch of p and the fourth turn portions of the strands of wire formed by folding over the cylindrical body at the fourth inclined portions are disposed parallel to each other at the pitch of p such that the second turn portions and the fourth turn portions form two layers in a longitudinal direction of the straight portions.       

   According to another aspect of the present invention, there is a method of manufacture for a winding assembly for an alternator, the method including steps of: 
   disposing a group of 2n straight strands of wire at a pitch p in a first plane; 
   forming a lightning-bolt shaped pattern composed of a plurality of basic patterns by folding and bending the group of strands of wire in the plane, each of the basic patterns comprising:
         first straight portions having a length l 0 ;   second straight portions having the length l 0  being linked to the first straight portions by first inclined portions having a length l 1 , the second straight portions being offset by an amount np to a first side in a direction of disposal of the strands of wire relative to the first straight portions;   third straight portions having the length l 0  being linked to the second straight portions by second inclined portions having the length l 1 , the third straight portions being offset by the amount np to the first side in a direction of disposal of the strands of wire relative to the second straight portions; and   fourth straight portions having the length l 0  being linked to the third straight portions by third inclined portions having the length l 1 , the fourth straight portions being offset by the amount np to a second side in a direction of disposal of the strands of wire relative to the third straight portions,   wherein the lightning-bolt shaped pattern is constructed by repeating the basic pattern a predetermined number of times by offsetting the basic pattern to the first side in the direction of disposal of the strands of wire by fourth inclined portions having a length l 2 , the length l 2  being greater than the length l 1 ;       

   forming a flattened cylindrical body by folding over the group of strands of wire formed into the lightning-bolt shaped pattern in a first direction at central portions of the first and the third inclined portions, the cylindrical body being constructed by helically winding the group of strands of wire such that the second and third straight portions linked by the second inclined portions and the first and fourth straight portions linked by the fourth inclined portions alternately occupy the first plane and a second plane; and 
   forming a winding group by folding over the cylindrical body at central portions of the second and the fourth inclined portions in a second direction such that the second and the third straight portions face each other, wherein
         the first to fourth straight portions are disposed parallel to each other at the pitch of p in the direction of disposal such that the first to fourth straight portions form four layers in the width direction,   first turn portions formed by folding over the group of strands of wire at the first inclined portions are disposed parallel to each other at the pitch of p and third turn portions formed by folding over the group of strands of wire at the third inclined portions are disposed parallel to each other at the pitch of p such that the first turn portions and the third turn portions form two rows in the direction of disposal, and   second turn portions of the strands of wire formed by folding over the cylindrical body at the second inclined portions are disposed parallel to each other at the pitch of p and the fourth turn portions of the strands of wire formed by folding over the cylindrical body at the fourth inclined portions are disposed parallel to each other at the pitch of p such that the second turn portions and the fourth turn portions form two layers in a longitudinal direction of the straight portions.       

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross section showing a construction of an alternator according to Embodiment 1 of the present invention; 
       FIG. 2  is a perspective showing a stator of this alternator viewed from a rear end; 
       FIG. 3  is a perspective showing the stator of this alternator viewed from a front end; 
       FIG. 4  is a rear end elevation explaining connections in one stator winding phase portion in this alternator; 
       FIG. 5  is a circuit diagram for this alternator; 
       FIG. 6  is a diagram explaining a winding assembly forming process in a method of manufacture for the stator of the alternator according to Embodiment 1 of the present invention; 
       FIG. 7  is a diagram explaining the winding assembly forming process in the method of manufacture for the stator of the alternator according to Embodiment 1 of the present invention; 
       FIG. 8  is a diagram explaining the winding assembly forming process in the method of manufacture for the stator of the alternator according to Embodiment 1 of the present invention; 
       FIG. 9  is a diagram explaining the winding assembly forming process in the method of manufacture for the stator of the alternator according to Embodiment 1 of the present invention; 
       FIG. 10  is a plan showing the winding assembly used in the stator of the alternator according to Embodiment 1 of the present invention; 
       FIG. 11  is a perspective showing the stator of the alternator according to Embodiment 1 of the present invention; 
       FIG. 12A  is a diagram explaining the method of manufacture for the stator of the alternator according to Embodiment 1 of the present invention; 
       FIG. 12B  is a diagram explaining the method of manufacture for the stator of the alternator according to Embodiment 1 of the present invention; 
       FIG. 12C  is a diagram explaining the method of manufacture for the stator of the alternator according to Embodiment 1 of the present invention; 
       FIG. 13  is a rear end elevation explaining connections in one stator winding phase portion in an alternator of a comparative example; 
       FIG. 14  is a front end elevation explaining connections in one stator winding phase portion in an alternator according to Embodiment 2 of the present invention; 
       FIG. 15  is a perspective showing a stator of this alternator viewed from the rear end; 
       FIG. 16  is a perspective showing a stator of this alternator viewed from the front end; 
       FIG. 17  is a rear end elevation explaining connections in one stator winding phase portion in an alternator according to Embodiment 3 of the present invention; 
       FIG. 18  is a perspective showing a stator of this alternator viewed from the rear end; 
       FIG. 19  is a perspective showing the stator of this alternator viewed from the front end; 
       FIG. 20  is a diagram explaining a winding assembly forming process in the method of manufacture for the stator of the alternator according to Embodiment 3 of the present invention; 
       FIG. 21  is a diagram explaining the winding assembly forming process in the method of manufacture for the stator of the alternator according to Embodiment 3 of the present invention; 
       FIG. 22  is a diagram explaining the winding assembly forming process in the method of manufacture for the stator of the alternator according to Embodiment 3 of the present invention; 
       FIG. 23  is a plan showing the winding assembly used in the stator of the alternator according to Embodiment 3 of the present invention; 
       FIG. 24  is a perspective showing a stator of the alternator according to Embodiment 4 of the present invention viewed from the rear end; 
       FIG. 25  is a perspective showing the stator of the alternator according to Embodiment 4 of the present invention viewed from the front end; 
       FIG. 26  is a diagram explaining a winding assembly forming process in a method of manufacture for the stator of the alternator according to Embodiment 4 of the present invention; 
       FIG. 27  is a perspective of part of a stator winding of a conventional alternator viewed from the front end; 
       FIG. 28  is a perspective of part of the stator winding of the conventional alternator viewed from the rear end; and 
       FIG. 29  is a perspective showing a construction of a conductor segment used in the stator winding of the conventional alternator. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The preferred embodiments of the present invention will now be explained with reference to the drawings. 
   Embodiment 1 
     FIG. 1  is a cross section showing a construction of an alternator according to Embodiment 1 of the present invention,  FIGS. 2 and 3  are perspectives showing a stator of this alternator viewed from a rear end and a front end, respectively,  FIG. 4  is a rear end elevation explaining connections in one stator winding phase portion in this alternator, and  FIG. 5  is a circuit diagram for this alternator.  FIGS. 6  to  9  are diagrams explaining a winding assembly forming process in a method of manufacture for the stator of the alternator according to Embodiment 1 of the present invention, and  FIG. 10  is a plan showing the winding assembly used in the stator of the alternator according to Embodiment 1 of the present invention.  FIG. 11  is a perspective showing the stator of the alternator according to Embodiment 1 of the present invention, and  FIGS. 12A ,  12 B, and  12 C are diagrams explaining the method of manufacture for the stator of the alternator according to Embodiment 1 of the present invention. Moreover, in  FIGS. 2 and 3 , crossover connections, neutral points, and output wires have been omitted. 
   In  FIG. 1 , an automotive alternator is constructed by rotatably mounting a Lundell-type rotor  7  by means of a shaft  6  inside a case  3  constructed from an aluminum front bracket  1  and an aluminum rear bracket  2 , and fastening a stator  8  to an inner wall of the case  3  so as to cover an outer circumferential side of the rotor  7 . 
   The shaft  6  is rotatably supported in the front bracket  1  and the rear bracket  2 . A pulley  4  is fastened to a first end of this shaft  6  so that rotational torque from an engine can be transmitted to the shaft  6  by means of a belt (not shown). 
   Slip rings  9  for supplying electric current to the rotor  7  are fastened to a second end of the shaft  6 , and a pair of brushes  10  are housed in a brush holder  11  disposed inside the case such that the pair of brushes  10  slide in contact with the slip rings  9 . A regulator  18  for adjusting the magnitude of alternating voltage generated in the stator  8  is fastened by adhesive to a heat sink  17  fitted onto the brush holder  11 . Rectifiers  12  which are electrically connected to the stator  8  and convert alternating current generated in the stator  8  into direct current are mounted inside the case  3 . 
   The rotor  7  is composed of a rotor coil  13  for generating magnetic flux by passing an electric current, and a pair of pole cores  20  and  21  disposed so as to cover the rotor coil  13 , magnetic poles being formed in the pole cores  20  and  21  by magnetic flux generated in the rotor coil  13 . The pair of pole cores  20  and  21  are made of iron, each has eight claw-shaped magnetic poles  22  and  23  disposed on an outer circumferential perimeter at even pitch in a circumferential direction so as to project axially, and the pole cores  20  and  21  are fastened to the shaft  6  facing each other such that the claw-shaped magnetic poles  22  and  23  intermesh. In addition, fans  5  are fastened to first and second axial ends of the rotor  7 . 
   Front-end and rear-end air intake openings  1   a  and  2   a  are disposed in axial end surfaces of the front bracket  1  and the rear bracket  2 , and front-end and rear-end air discharge openings  1   b  and  2   b  are disposed in two outer circumferential shoulder portions of the front bracket  1  and the rear bracket  2 , opposite the radial outside of front-end and rear-end coil ends  16   f  and  16   r  of the stator winding  16 . 
   As shown in  FIGS. 2 and 3 , the stator  8  includes: a cylindrical stator core  15  composed of a laminated core formed with a number of slots  15   a  extending axially at a predetermined pitch in a circumferential direction; a stator winding  16  wound onto the stator core  15 ; and insulators  19  installed in each of the slots  15   a  for electrically insulating the stator winding  16  from the stator core  15 . The stator winding  16  includes a number of winding sub-portions in each of which one strand of wire  30  is folded over outside the slots  15   a  at end surfaces of the stator core  15  and wound so as to alternately occupy an inner layer and an outer layer in a slot depth direction within slots  15   a  a predetermined number of slots apart, being wound into a lap winding having two turns in each lap. In addition, four strands of wire  30  are disposed in one row in the slot depth direction within each of the slots  15   a , turn portions of the strands of wire  30  which are formed by being folded over outside the slots  15   a  at the front end of stator core  15  being disposed in a circumferential direction so as to be aligned in two rows in a radial direction constituting the front-end coil end group  16   f , and turn portions of the strands of wire  30  which are formed by being folded over outside the slots  15   a  at the rear end of stator core  15  being disposed in a circumferential direction so as to overlap in two layers in an axial direction constituting the rear-end coil end group  16   r.    
   In this case, the stator core  15  is formed with ninety-six slots  15   a  at even pitch so as to house two three-phase alternating-current windings  160  such that the number of slots housing each phase portion of the alternating-current windings  160  corresponds to the number of magnetic poles (sixteen) in the rotor  7 . In other words, there are two slots per pole per phase. Long, insulated copper wire material having a rectangular cross section, for example, is used in the strands of wire  30 . 
   Next, the winding construction of one stator winding phase portion  161  will be explained in detail with reference to FIG.  4 . In  FIG. 4 , the rear-end wiring of the strands of wire is indicated by solid lines, the front-end wiring of the strands of wire is indicated by broken lines, and the connecting portions of the strands of wire are indicated by black dots. 
   One stator winding phase portion  161  is constituted by first and second winding sub-portions  31  and  32  each composed of one strand of wire  30 . 
   The first winding sub-portion  31  is constructed into a lap winding having two turns per lap in which, in pairs of slots constituted by Slot Numbers ( 12   m+ 1) and Slot Numbers ( 12   m+ 7) of the slots  15   a , one strand of wire  30  is passed from the rear end to the front end in the first address of Slot Numbers ( 12   m+ 1) of the slots  15   a , then passed from the front end to the rear end in the second address of Slot Numbers ( 12   m+ 7) of the slots  15   a , thereafter passed from the rear end to the front end in the third address of Slot Numbers ( 12   m+ 1) of the slots  15   a , and then passed from the front end to the rear end in the fourth address of Slot Numbers ( 12   m+ 7) of the slots  15   a . Here, m=0, 1, 2, . . . 7. 
   The second winding sub-portion  32  is constructed into a lap winding having two turns per lap in which, in pairs of slots constituted by Slot Numbers ( 12   m+ 7) and Slot Numbers { 12  (m+1)+1} of the slots  15   a , one strand of wire  30  is passed from the rear end to the front end in the first address of Slot Numbers ( 12   m+ 7) of the slots  15   a , then passed from the front end to the rear end in the second address of Slot Numbers { 12 (m+1)+1} of the slots  15   a , thereafter passed from end the third address of Slot Numbers ( 12   m +7) of the slots  15   a , and then passed from the front end to the rear end in the fourth address of Slot Numbers { 12 (m+1)+1} of the slots  15   a . Here, Slot Number  97  corresponds to Slot Number  1 . 
   Thus, each of the first and second winding sub-portions  31  and  32  constitutes a winding sub-portion in which a single strand of wire  30  is wound into a lap winding having two turns per lap so as to alternately occupy an inner layer and an outer layer in a slot depth direction in every sixth slot  15   a . Four strands of wire  30  are disposed to line up in one row in a radial direction within each slot  15   a  with the longitudinal direction of the rectangular cross sections thereof aligned in a radial direction. 
   Next, at the rear end of the stator core  15 , the turn portion of the first winding sub-portion  31  linking the fourth address of Slot Number  43  and the first address of Slot Number  49  is cut, and the turn portion of the second winding sub-portion  32  linking the third address of Slot Number  43  and the second address of Slot Number  49  is also cut. Then, a first cut end  31   a  of the first winding sub-portion  31  extending from the fourth address of Slot Number  43  and a second cut end  32   b  of the second winding sub-portion  32  extending from the second address of Slot Number  49  are crossover-connected by arc welding, for example, to connect the first and second winding sub-portions  31  and  32  in series. Thus, a stator winding phase portion  161  having four turns is formed. 
   A first cut end  32   a  of the second winding sub-portion  32  extending from the third address of Slot Number  43  and a second cut end  31   b  of the first winding sub-portion  31  extending from the first address of Slot Number  49  become a neutral point (N) and an output wire (O), respectively, of the stator winding phase portion  161 . 
   Thus, a total of six stator winding phase portions  161  are formed by installing the strands of wire  30  into the stator core  15  such that the slots  15   a  into which the strands of wire  30  are inserted are offset by one slot at a time and connecting the strands of wire  30 . Thus, the stator  8  obtained includes the stator winding  16  which is wound into the stator core  15  as shown in  FIGS. 2 and 3 . 
   As shown in  FIG. 5 , the two three-phase alternating-current windings  160  are constructed by star-connecting such that the three stator winding phase portions  161  therein have a phase difference corresponding to an electrical angle of 120° from each other. Furthermore, the two three-phase alternating-current windings  160  are wound onto the stator core  15  so as to have a phase difference of 30° from each other. Each of these two three-phase alternating-current windings  160  is connected to its own rectifier  12 . The rectifiers  12  are connected in parallel such that the direct-current output from each is combined. 
   In the alternator constructed in this manner, electric current is supplied from a battery (not shown) through the brushes  10  and the slip rings  9  to the rotor coil  13 , generating magnetic flux. The claw-shaped magnetic poles  22  of the first pole core  20  are magnetized with north-seeking (N) poles by this magnetic flux, and the claw-shaped magnetic poles  23  of the second pole core  21  are magnetized with south-seeking (S) poles. At the same time, rotational torque from the engine is transmitted through the belt and the pulley  4  to the shaft  6 , rotating the rotor  7 . Thus, a rotating magnetic field is applied to the stator winding  16 , generating electromotive force in the stator winding  16 . This alternating electromotive force passes through rectifiers  12  and is converted into direct current, the output thereof is adjusted by a regulator  18 , and the battery is recharged. 
   At the rear end, external air is drawn in through the rear-end air intake openings  2   a  disposed opposite heat sinks of the rectifiers  12  and a heat sink  17  of the regulator  18 , respectively, by rotation of the fan  5 , flowing along the axis of the shaft  6 , cooling the rectifiers  12  and the regulator  18 , and is then deflected centrifugally by the fan  5 , cooling the rear-end coil end group  16   r  of the stator winding  16  before being expelled to the outside through the rear-end air discharge openings  2   b . At the same time, at the front end, external air is drawn in axially through the front-end air intake openings  1   a  by the rotation of the fan  5 , and is then deflected centrifugally by the fan  5 , cooling the front-end coil end group  16   f  of the stator winding  16  before being expelled to the outside through the front-end air discharge openings  1   b.    
   Thus, heat generated in the rectifiers  12 , the regulator  18 , the stator  8 , the rotor  7 , etc., is dissipated, and temperature increases in these heat-generating components are suppressed. 
   In Embodiment 1, the stator winding phase portions  161  constituting the stator winding  16  include the first and second winding sub-portions  31  and  32  which are each formed by one strand of wire  30 . The first and second winding sub-portions  31  and  32  are each formed into a lap winding having two turns per lap by winding one strand of wire  30  in order one turn at a time into pairs of slots, the slots in each pair being six slots apart and each pair being disposed at a pitch of twelve slots, the first and second winding sub-portions  31  and  32  also being formed so as to alternately occupy an inner layer and an outer layer in a slot depth direction in every sixth slot  15   a . Four strands of wire  30  are disposed to line up in one row in a slot depth direction within each slot  15   a . The turn portions of the strands of wire  30  which link different layers in slots  15   a  six slots apart at the end surfaces of the stator core  15  constitute the coil ends. 
   At the front end of the stator core  15 , the turn portions linking the first address (a first layer) to the second address (a second layer) and the turn portions linking the third address (a third layer) to the fourth address (a fourth layer) are formed into a substantially identical shape, mutually spaced circumferentially and radially, and disposed neatly in a circumferential direction in two rows to form the front-end coil end group  16   f.  At the rear end of the stator core  15 , the turn portions linking the first address (the first layer) to the fourth address (the fourth layer) and the turn portions linking the second address (the second layer) to the third address (the third layer) are mutually spaced in an axial direction and formed into two layers, mutually spaced circumferentially, and disposed neatly in a circumferential direction to form the rear-end coil end group  16   r.    
   In the stator  8  constructed in this manner, because the coil ends are constituted by the turn portions of the strands of wire  30 , that is, by continuous wires, the number of joints can be significantly reduced, enabling the coil end height to be lowered, softening of the strands of wire  30  due to temperature increases during welding to be reduced, and reductions in rigidity of the stator to be suppressed compared to the conventional stator  90  in which the coil ends are constructed by clamping portions of the end portions  95   c  and  96   c  of the U-shaped large segments  95  and the small segments  96  in a jig and welding the end portions  95   c  and  96   c  together. As a result, an alternator can be provided in which coil leakage reactance in the coil end portions is reduced, improving output, wind resistance is reduced, alleviating wind noise, and deterioration in rigidity is reduced, reducing magnetic noise, compared to an alternator mounted with the conventional stator  90 . 
   The coil end groups  16   f  and  16   r  can be formed into a generally identical shape circumferentially, suppressing circumferential irregularities on radially inner edge surfaces of the coil end groups  16   f  and  16   r , enabling wind noise generated between the rotor  7  and the coil end groups  16   a  and  16   b  to be reduced 
   Because the axial height of the coil end groups  16   f  and  16   r  is lowered and the number of joint portions is reduced, interference noise between the cooling air flow formed by the fans  5  and the coil end groups  16   f  and  16   r  is also reduced. 
   Next, the assembly of the stator  8  will be explained with reference to  FIGS. 6  to  12 . 
   First, twelve long strands of wire  30  are disposed parallel to each other at a pitch (p) of one slot and simultaneously folded and bent in the same plane to form a lightning-bolt shape (i.e. a zigzag shape). In this example, the twelve Ion strands of wire  30  equal a group of 2n strands, where n=6. As shown in  FIGS. 6 and 7 , this group of strands of wire  30  folded and bent into the lighting-bolt shape is formed by repeating a basic pattern a predetermined number of times, the basic pattern being formed by the first to fourth straight portions  30   a  to  30   d  which have a length (l 0 ) equivalent to the groove length of the slots  15   a , in which the first and second straight portions  30   a  and  30   b  are offset at a pitch (np) of six slots ( 6   p ) on a first side in a direction of disposal of the strands of wire  30  and linked by first inclined portions  30   e , the second and third straight portions  30   b  and  30   c  are offset at a pitch of six slots ( 6   p ) on a second side in the direction of disposal of the strands of wire  30  and linked by second inclined portions  30   f , and the third and fourth straight portions  30   c  and  30   d  are offset at a pitch of six slots ( 6   p ) on the first side in the direction of disposal of the strands of wire  30  and linked by third inclined portions  30   g , this basic pattern being repeated such that adjacent fourth and first straight portions  30   d  and  30   a  are offset at a pitch of six slots ( 6   p ) on the first side in the direction of disposal of the strands of wire  30  and linked by fourth inclined portions  30   h . At this time, spacing between each of the first to fourth straight portions  30   a  to  30   d  is l 1 , and spacing l 2  between the adjacent first and fourth straight portions  30   a  and  30   d  is formed so as to be larger than the spacing l 1 . 
   Then, as indicated by arrows in  FIGS. 6 and 7 , a flattened cylindrical body  40  is formed in which the second and third straight portions  30   b  and  30   c  which are linked by the second inclined portions  30   f  and the fourth and first straight portions  30   d  and  30   a  which are linked by the fourth inclined portions  30   h  are wound helically so as to alternately occupy a first plane and a second plane by folding over the first and third inclined portions  30   e  and  30   g  in the same direction at central portions thereof. As shown in  FIG. 8 , this cylindrical body  40  is constructed by arranging the second and third straight portions  30   b  and  30   c , which are linked by the second inclined portions  30   f , at a pitch of one slot in the first plane, and arranging the fourth and first straight portions  30   d  and  30   a , which are linked by the fourth inclined portions  30   h , at a pitch of one slot in the second plane. 
   Then, as shown in  FIG. 8 , terminal processing is performed by cutting six of the third straight portions  30   c  at central portions A at a first end portion of the cylindrical body  40 , and cutting six of the second straight portions  30   b  at central portions B at a second end portion of the cylindrical body  40  to form connecting portions with other end portions of the strands of wire  30 . 
   Thereafter, a winding assembly  41 , shown in  FIG. 10 , is prepared by folding over the cylindrical body  40  at central portions of the second inclined portions  30   f  and the fourth inclined portions  30   h  which are disposed at a pitch of one slot such that the second straight portions  30   b  and the third straight portions  30   c  face each other, as indicated by arrows in  FIGS. 8 and 9 . 
   In this winding assembly  41 , the first to fourth straight portions  30   a  to  30   d  are disposed at a pitch p so as to be lined up in four layers at a pitch w equal to the width of the strands of wire  30  in the width direction of the strands of wire  30 , on a first side of which the folded first inclined portions  30   e , which function as first turn portions, and the folded third inclined portions  30   g , which function as third turn portions, are disposed at a pitch of one slot in the direction of disposal of the straight portions to form two rows. On a second side, the folded second inclined portions  30   f , which function as second turn portions, and the folded fourth inclined portions  30   h , which function as fourth turn portions, are disposed at a pitch of one slot in the direction of disposal of the straight portions to form two layers. 
   Here, lead portions of the output wires and the neutral points extend outwards from the fourth inclined portions  30   h  of the winding assembly  41 , and these lead portions are formed by drawing out specific strands of wire  30  during the process of folding and bending the strands of wire  30  into the lightning-bolt shape. 
   Meanwhile, a parallelepiped laminated core  42  is prepared as shown in  FIG. 11  by laminating a predetermined number of sheets of SPCC material which is a magnetic material formed with trapezoidal slots  42   a  at a predetermined pitch (an electrical angle of 30°) and laser welding an outer portion thereof 
   As shown in  FIG. 12A , the insulators  19  are mounted in the slots  42   a  of the laminated core  42 , and the first to fourth straight portions  30   a  to  30   d  of the winding assembly  41  are inserted so as to stack up within each of the slots  42   a . Thus, the winding assembly  41  is installed in the laminated core  42  as shown in FIG.  12 B. At this time, straight portions of the strands of wire  30  are housed in lines of four in a radial direction within the slots  42   a  and are electrically insulated from the laminated core  42  by the insulators  19 . 
   Next, the laminated core  42  is rolled up and its ends abutted and welded to each other to obtain the cylindrical stator core  15 , as shown in FIG.  12 C. 
   Then, end portions of the same strand of wire  30  are connected so that first and second winding sub-portions  31  and  32  which are wound into slot groups disposed at a pitch of six slots each form lap windings having two turns per lap. Then, as explained previously, the two three-phase alternating-current windings  160  are obtained by cutting each of the lead portions of the winding assembly  41 , forming the crossover connections, then connecting the neutral points. 
   Thus, the stator  8  obtained is formed by installing the stator winding  16  composed of the two three-phase alternating-current windings  160  into the stator core  15 . 
   Thus, in Embodiment 1, because the winding assembly  41  is formed by arranging the twelve strands of wire  30  in the same plane at a pitch of one slot, folding and bending the twelve strands of wire  30  to form the lightning-bolt shaped pattern shown in  FIGS. 6 and 7 , forming the cylindrical body  40  in which the second and third straight portions  30   b  and  30   c  which are linked by the second inclined portions  30   f  and the fourth and first straight portions  30   d  and  30   a  which are linked by the fourth inclined portions  30   h  are wound helically by folding back the first and third inclined portions  30   e  and  30   g  in the same direction at central portions thereof, and then folding the cylindrical body  40  over at central portions of the second and fourth inclined portions  30   f  and  30   h , a winding assembly can be easily manufactured which alternately occupies an inner layer and an outer layer in a slot depth direction in every sixth slot  15   a  and constitutes a lap winding having two turns per lap. 
   Because the winding assembly  41  prepared in this manner is used, six stator winding phase portions  161  can be installed into the stator core  15  by installing one winding assembly  41  into the stator core  15 . Thus, the complex operation of inserting a large number of segments into the slots of the stator core and joining the end portions thereof together one by one is no longer required, significantly improving assembly and workability, thereby enabling producibility to be increased. In addition, cases in which the number of turns in the stator winding is increased can easily be adapted for by stacking and installing a plurality of the winding assemblies  41  into the stator core  15 . 
   Because the coil ends are constituted by the turn portions of the strands of wire  30 , the number of joints in the coil end groups  16   f  and  16   r  is significantly reduced. Thus, there is no need to extend the coil ends out by an extra amount from the end surfaces of the stator core  15 , enabling the stator  8  to be reduced in size. In addition, because the occurrence of short-circuiting accidents which accompany loss of insulation due to the joining process can be suppressed, superior insulation can be obtained and high yield can also be achieved. In addition, reductions in resistance to corrosion which accompany loss of insulation due to joining can be suppressed. 
   Here, an explanation will be given of a winding construction previously proposed by the present applicants in Japanese Patent Application No. 2000-011704, for comparison with the present application. 
     FIG. 13  is a rear end elevation explaining connections in one stator winding phase portion described in Japanese Patent Application No. 2000-011704. 
   In  FIG. 13 , one stator winding phase portion  80  is composed of first to fourth winding sub-portions  81  to  84  each formed from one strand of wire  30 . The first winding sub-portion  81  is constructed by wave winding one strand of wire  30  into every sixth slot from Slot Numbers  1  to  91  so as to alternately occupy the first address and the second address inside the slots  15   a . The second winding sub-portion  82  is constructed by wave winding a strand of wire  30  into every sixth slot from Slot Numbers  1  to  91  so as to alternately occupy the second address and the first address inside the slots  15   a . The third winding sub-portion  83  is constructed by wave winding a strand of wire  30  into every sixth slot from Slot Numbers  1  to  91  so as to alternately occupy the third address and the fourth address inside the slots  15   a . The fourth winding sub-portion  84  is constructed by wave winding a strand of wire  30  into every sixth slot from Slot Numbers  1  to  91  so as to alternately occupy the fourth address and the third address inside the slots  15   a.    
   Thus, each of the first to fourth winding sub-portions  81  to  84  constitutes a winding sub-portion having one turn in which a single strand of wire  30  is wound into every sixth slot  15   a  so as to alternately occupy an inner layer and an outer layer in a slot depth direction. 
   Moreover, although not shown, a total of six stator winding phase portions  80  are formed by offsetting the slots  15   a  into which the strands of wire  30  are wound by one slot each. 
   At a first end of the stator core  15 , a crossover connection (adjacent-address crossover connection C 2-3 ) is formed between a second end portion 81 b  of the first winding sub-portion  81  extending outwards from the second address of Slot Number  67  and a first end portion  83   a  of the third winding sub-portion  83  extending outwards from the third address of Slot Number  61 , and a crossover connection (adjacent-address crossover connection C 2-3 ) is formed between a second end portion  82   b  of the second winding subportion  82  extending outwards from the second address of Slot Number  61  and a first end portion  84   a  of the fourth winding sub-portion  84  extending outwards from the third address of Slot Number  55 , and in addition, a crossover connection (same-address crossover connection C 1-1 ) is formed between a first end portion  81   a  of the first winding sub-portion  81  extending outwards from the first address of Slot Number  61  and a first end portion  82   a  of the second winding sub-portion  82  extending outwards from the first address of Slot Number  55 . Thus, the first to fourth winding sub-portions  81  to  84  are connected in series to form one stator winding phase portion  80  having four turns. 
   At this time, a second end portion  83   b  of the third winding sub-portion  83  extending outwards from the fourth address of Slot Number  67  and a second end portion  84   b  of the fourth winding sub-portion  84  extending outwards from the fourth address of Slot Number  61  become an output wire (Oa) and a neutral point (Na), respectively, of one stator winding phase portion  80 . 
   Because the stator winding phase portion  80  of this comparative example is constituted by the first to fourth winding sub-portions  81  to  84  having one turn in each of which one strand of wire  30  is wound into a wave winding so as to alternately occupy an inner layer and an outer layer in a slot depth direction in every sixth slot  15   a , the complex operation of inserting a large number of segments into the slots of the stator core and joining the end portions thereof together one by one is no longer required, significantly improving assembly and workability, thereby enabling producibility to be increased. 
   In addition, because the coil ends are constituted by the turn portions of the strands of wire  30 , the number of joints in the coil end groups is significantly reduced. Thus, there is no need to extend the coil ends out by an extra amount from the end surfaces of the stator core  15 , enabling the stator to be reduced in size. 
   However, because this stator winding phase portion  80  is constituted by the first to fourth winding sub-portions  81  to  84  which are each formed by winding one strand of wire  30  into a wave winding, three crossover connections are required in order to connect the first to fourth winding sub-portions  81  to  84  in series. 
   By contrast, because the stator winding phase portions  161  in Embodiment 1 of the present invention are each constituted by the first and second winding sub-portions  31  and  32  which are each formed by winding one strand of wire  30  into a lap winding having two turns per lap, one crossover connection is sufficient to connect the first and second winding sub-portions  31  and  32  in series, and it can be seen that the connecting operation can be improved compared to the comparative example. Furthermore, by reducing the number of crossover connections and simplifying the connecting portions, wind noise as a result of circumferential irregularities in the rear-end coil end group  16   r  is suppressed, enabling noise reductions to be achieved. In addition, because wind resistance in the rear-end coil end group  16   r  is lessened by reducing the number of crossover connections and simplifying the connecting portions, the volume of air flow increases proportionally, improving the cooling effect. 
   Embodiment 2 
     FIG. 14  is a front end elevation explaining connections in one stator winding phase portion in an automotive alternator according to Embodiment 2 of the present invention. In the figure, the rear-end wiring of the strands of wire is indicated by solid lines, the front-end wiring of the strands of wire is indicated by broken lines, and the connecting portions of the strands of wire are indicated by black dots. 
   One stator winding phase portion  161 A is constituted by first and second winding sub-portions  31  and  32  each composed of one strand of wire  30 . 
   The first winding sub-portion  31  is constructed into a lap winding having two turns per lap in which, in pairs of slots constituted by Slot Numbers ( 12   m+ 1) and Slot Numbers ( 12   m+ 7) of the slots  15   a , one strand of wire  30  is passed from the front end to the rear end in the first address of Slot Numbers ( 12   m+ 1) of the slots  15   a , then passed from the rear end to the front end in the second address of Slot Numbers ( 12   m+ 7) of the slots  15   a , thereafter passed from the front end to the rear end in the third address of Slot Numbers ( 12   m+ 1) of the slots  15   a , and then passed from the rear end to the front end in the fourth address of Slot Numbers ( 12   m+ 7) of the slots  15   a . Here, m=0, 1, 2, . . . 7. 
   The second winding sub-portion  32  is constructed into a lap winding having two turns per lap in which, in pairs of slots constituted by Slot Numbers ( 12   m+ 7) and Slot Numbers { 12 (m+1)+1} of the slots  15   a , one strand of wire  30  is passed from the front end to the rear end in the first address of Slot Numbers ( 12   m+ 7) of the slots  15   a , then passed from the rear end to the front end in the second address of Slot Numbers { 12 (m+1)+1} of the slots  15   a , thereafter passed from the front end to the rear end the third address of Slot Numbers ( 12   m+ 7) of the slots  15   a , and then passed from the rear end to the front end in the fourth address of Slot Numbers { 12 (m+1)+1} of the slots  15   a . Here, Slot Number  97  corresponds to Slot Number  1 . 
   Thus, each of the first and second winding sub-portions  31  and  32  constitutes a winding sub-portion in which a single strand of wire  30  is wound into a lap winding having two turns per lap so as to alternately occupy an inner layer and an outer layer in a slot depth direction in every sixth slot  15   a.    
   Then, a winding portion having  4  turns in which the first and second winding sub-portions  31  and  32  are connected in series is obtained by joining a first end portion of the first winding sub-portion  31  extending towards the front end from the first address of Slot Number  1  to a second end portion of the second winding sub-portion  32  extending towards the front end from the third address of Slot Number  91 , and by then joining a first end portion of the second winding sub-portion  32  extending towards the front end from the second address of Slot Number  1  to a second end portion of the first winding sub-portion  31  extending towards the front end from the fourth address of the Slot Number  91 . 
   Next, at the rear end of the stator core  15 , the turn portion of the second winding sub-portion  32  linking the third address of Slot Number  43  and the fourth address of Slot Number  49  is cut to form one stator winding phase portion  161 A having four turns in which a first cut end  32   a  of the second winding sub-portion  32  extending from the third address of Slot Number  43  and a second cut end  32   b  of the second winding sub-portion  32  extending from the fourth address of Slot Number  49  become a neutral point (N) and an output wire (O), respectively. 
   Thus, a total of six stator winding phase portions  161 A are formed by installing the strands of wire  30  into the stator core  15  such that the slots  15   a  into which the strands of wire  30  are inserted are offset by one slot at a time and connecting the strands of wire  30 . 
   Thus, a stator  8 A obtained includes a stator winding  16 A which is wound into the stator core  15  as shown in  FIGS. 15 and 16 .  FIG. 15  is a perspective showing the stator viewed from the rear end and  FIG. 16  is a perspective showing the stator viewed from the front end. The neutral points and the output wires have been omitted from these figures. 
   In Embodiment 2, the stator winding phase portions  161 A constituting the stator winding  16 A are constituted by the first and second winding sub-portions  31  and  32  which are each formed into a lap winding having two turns per lap by winding one strand of wire  30  in order one turn at a time into pairs of slots, the slots in each pair being six slots apart and the pairs of slots being disposed at a pitch of twelve slots, the first and second winding sub-portions  31  and  32  also being formed so as to alternately occupy an inner layer and an outer layer in a slot depth direction in every sixth slot  15   a . Four strands of wire  30  are disposed to line up in one row in a slot depth direction within each slot  15   a . The turn portions of the strands of wire  30  which link different layers in slots  15   a  six slots apart at the end surfaces of the stator core  15  constitute the coil ends. 
   Consequently, similar effects to those in Embodiment 1 above can also be obtained in Embodiment 2. 
   According to Embodiment 2, the first and second winding portions  31  and  32  are connected in series to form the winding portion having  4  turns by joining the first end portion of the first winding sub-portion  31  to the second end portion of the second winding sub-portion  32 , and joining the first end portion of the second winding sub-portion  32  to the second end portion of the first winding sub-portion  31 . Thus, the processes of cutting and joining the first and second winding sub-portions  31  and  32  after installation into the stator core  15 , which were required in Embodiment 1 above to form crossover connections between the first and second winding sub-portions  31  and  32 , are no longer required. That is, one portion of the second winding sub-portion  32  extending outwards at the rear end in each phase is cut after the first and second winding sub-portions  31  and  32  are installed into the stator core  15 , and the cut ends thereof can be used as the neutral point and the output wire, improving workability. 
   Because a coil end group in which the turn portions constituted by folded portions of the strands of wire  30  are disposed circumferentially to form two rows in a radial direction is disposed at the rear end, wind resistance is reduced in a wind channel at the rear end where rectifiers  12  and a regulator  18  which are heat-generating parts are mounted, enabling the rectifiers  12  and the regulator  18  to be cooled efficiently. 
   Embodiment 3 
     FIG. 17  is a rear end elevation explaining connections in one stator winding phase portion in an automotive alternator according to Embodiment 3 of the present invention, and  FIGS. 18 and 19  are perspectives showing a stator of this alternator viewed from the rear end and the front end respectively. In  FIG. 17 , the rear-end wiring of the strands of wire is indicated by solid lines, the front-end wiring of the strands of wire is indicated by broken lines, and the connecting portions of the strands of wire are indicated by black dots. In  FIGS. 18 and 19 , neutral points and output wires have been omitted. 
   In  FIG. 17 , one stator winding phase portion  161 B is constituted by first and second winding sub-portions  31  and  32  each composed of one strand of wire  30 . 
   The first winding sub-portion  31  is constructed into a lap winding having two turns per lap in which, in pairs of slots constituted by Slot Numbers ( 12   m+ 1) and Slot Numbers ( 12   m+ 7) of the slots  15   a , one strand of wire  30  is passed from the rear end to the front end in the fourth address of Slot Numbers ( 12   m+ 1) of the slots  15   a , then passed from the front end to the rear end in the first address of Slot Numbers ( 12   m+ 7) of the slots  15   a , thereafter passed from the rear end to the front end in the second address of Slot Numbers ( 12   m+ 1) of the slots  15   a , and then passed from the front end to the rear end in the third address of Slot Numbers ( 12   m+ 7) of the slots  15   a . Here, m=0, 1, 2, . . . 7. 
   The second winding sub-portion  32  is constructed into a lap winding having two turns per lap in which, in pairs of slots constituted by Slot Numbers ( 12   m+ 7) and Slot Numbers { 12 (m+1)+1} of the slots  15   a , one strand of wire  30  is passed from the rear end to the front end in the fourth address of Slot Numbers ( 12   m+ 7) of the slots  15   a , then passed from the front end to the rear end in the first address of Slot Numbers { 12 (m+1)+1} of the slots  15   a , thereafter passed from the rear end to the front end the second address of Slot Numbers ( 12   m+ 7) of the slots  15   a , and then passed from the front end to the rear end in the third address of Slot Numbers { 12 (m+1)+1} of the slots  15   a . Here, Slot Number  97  corresponds to Slot Number  1 . 
   First and second end portions of the second winding sub-portion  32  which extend outwards at the rear end from the first address of Slot Number  1  and from the second address of Slot Number  91  are joined, and first and second end portions of the first winding sub-portion  31  which extend outwards at the rear end from the fourth address of Slot Number  1  and from the third address of Slot Number  91  are joined. Thus, each of the first and second winding sub-portions  31  and  32  constitutes a winding sub-portion in which a single strand of wire  30  is wound into a lap winding having two turns per lap so as to alternately occupy an inner layer and an outer layer in a slot depth direction in every sixth slot  15   a.    
   Next, at the rear end of the stator core  15 , the turn portion of the first winding sub-portion  31  linking the third address of Slot Number  43  and the fourth address of Slot Number  49  is cut, and the turn portion of the second winding sub-portion  32  linking the second address of Slot Number  43  and the first address of Slot Number  49  is also cut. Then, a first cut end  31   a  of the first winding sub-portion  31  extending from the third address of Slot Number  43  and a second cut end  32   b  of the second winding sub-portion  32  extending from the first address of Slot Number  49  are crossover-connected by arc welding, for example, to connect the first and second winding sub-portions  31  and  32  in series. Thus, a stator winding phase portion  161 B having four turns is formed. 
   A first cut end  32   a  of the second winding sub-portion  32  extending from the second address of Slot Number  43  and a second cut end  31   b  of the first winding sub-portion  31  extending from the fourth address of Slot Number  49  become a neutral point (N) and an output wire (O), respectively, of the stator winding phase portion  161 B. 
   Thus, a total of six stator winding phase portions  161 B are formed by installing the strands of wire  30  into the stator core  15  such that the slots  15   a  into which the strands of wire  30  are inserted are offset by one slot at a time and connecting the strands of wire  30 . Thus, a stator  8 B is obtained which includes a stator winding  16 B which is wound into the stator core  15  as shown in  FIGS. 18 and 19 . 
   In Embodiment 3, the stator winding phase portions  161 B constituting the stator winding  16 B are constituted by the first and second winding sub-portions  31  and  32  which are each formed into a lap winding having two turns per lap by winding one strand of wire  30  in order one turn at a time into pairs of slots, the slots in each pair being six slots apart and the pairs of slots being disposed at a pitch of twelve slots, the first and second winding sub-portions  31  and  32  also being formed so as to alternately occupy an inner layer and an outer layer in a slot depth direction in every sixth slot  15   a . Four strands of wire  30  are disposed to line up in one row in a slot depth direction within each slot  15   a . The turn portions of the strands of wire  30  which link different layers in slots  15   a  six slots apart at the end surfaces of the stator core  15  constitute the coil ends. 
   Consequently, the same effects can be achieved in Embodiment 3 as in Embodiment 1 above. 
   According to Embodiment 3, because a coil end group in which the turn portions constituted by folded portions of the strands of wire  30  are disposed circumferentially to form two rows in a radial direction is disposed at the rear end, wind resistance is reduced in a wind channel at the rear end where rectifiers  12  and a regulator  18  which are heat-generating parts are mounted, enabling the rectifiers  12  and the regulator  18  to be cooled efficiently. 
   Next, the method of manufacture for the winding assembly used in the stator  8 B will be explained in detail with reference to  FIGS. 20  to  23 . 
   First, twelve long strands of wire  30  are disposed parallel to each other at a pitch (p) of one slot and simultaneously folded and bent in the same plane to form a lightning-bolt shape. As shown in  FIGS. 20 and 21 , this group of strands of wire  30  folded and bent into the lightning-bolt shape is formed by repeating a predetermined number of times a basic pattern formed by the first to fourth straight portions  30   a  to  30   d  which have a length (l 0 ) equivalent to the groove length of the slots  15   a  in which the first and second straight portions  30   a  and  30   b  are offset at a pitch of six slots ( 6   p ) on a first side in a direction of disposal of the strands of wire  30  and linked by first inclined portions  30   e , the second and third straight portions  30   b  and  30   c  are offset at a pitch of six slots ( 6   p ) on the first side in the direction of disposal of the strands of wire  30  and linked by second inclined portions  30   f , and the third and fourth straight portions  30   c  and  30   d  are offset at a pitch of six slots ( 6   p ) on a second side in the direction of disposal of the strands of wire  30  and linked by third inclined portions  30   g , this basic pattern being repeated such that adjacent fourth and first straight portions  30   d  and  30   a  are offset at a pitch of six slots ( 6   p ) on the first side in the direction of disposal of the strands of wire  30  and linked by fourth inclined portions  30   h . At this time, spacing between each of the first to fourth straight portions  30   a  to  30   d  is l 1 , and spacing l 2  between the adjacent first and fourth straight portions  30   a  and  30   d  is formed so as to be larger than the spacing l 1 . 
   Then, as indicated by arrows in  FIGS. 20 and 21 , a flattened cylindrical body  40 B is formed in which the second and third straight portions  30   b  and  30   c  which are linked by the second inclined portions  30   f  and the fourth and first straight portions  30   d  and  30   a  which are linked by the fourth inclined portions  30   h  are wound helically so as to alternately occupy a first plane and a second plane by folding back the first and third inclined portions  30   e  and  30   g  in the same direction at central portions thereof. As shown in  FIG. 22 , this cylindrical body  40 B is constructed by arranging the second and third straight portions  30   b  and  30   c , which are linked by the second inclined portions  30   f , at a pitch of one slot in the first plane, and arranging the fourth and first straight portions  30   d  and  30   a , which are linked by the fourth inclined portions  30   h , at a pitch of one slot in the second plane. 
   Then, as shown in  FIG. 22 , terminal processing is performed by cutting six of the third straight portions  30   d  at central portions A at a first end portion of the cylindrical body  40 B, and cutting six of the second straight portions  30   c  at central portions B at a second end portion of the cylindrical body  40  to form connecting portions with other end portions of the strands of wire  30 . 
   Thereafter, a winding assembly  41 B, shown in  FIG. 23 , is prepared by folding over the cylindrical body  40 B at central portions of the second inclined portions  30   f  and the fourth inclined portions  30   h  which are disposed at a pitch of one slot, such that the second straight portions  30   b  and the third straight portions  30   c  face each other,-as indicated by arrows in FIG.  22 . 
   In this winding assembly  41 B, the first to fourth straight portions  30   a  to  30   d  are disposed at a pitch p so as to be lined up in four layers at a pitch w equal to the width of the strands of wire  30  in the width direction of the strands of wire  30 , on a first side of which the folded first inclined portions  30   e , which function as first turn portions, and the folded third inclined portions  30   g , which function as third turn portions, are disposed at a pitch of one slot in the direction of disposal of the straight portions to form two rows. On a second side, the folded second inclined portions  30   f , which function as second turn portions, and the folded fourth inclined portions  30   h , which function as fourth turn portions, are disposed at a pitch of one slot in the direction of disposal of the straight portions to form two layers. 
   Here, lead portions of the output wires and the neutral points extend outwards from the second and third inclined portions  30   e  and  30   g  of the winding assembly  41 B, and these lead portions are formed by drawing out specific strands of wire  30  during the process of folding and bending the strands of wire  30  into the lightning-bolt shape. 
   As shown in  FIG. 12A , insulators  19  are mounted in slots  42   a  of a laminated core  42 , and the first to fourth straight portions  30   a  to  30   d  of the winding assembly  41 B are inserted so as to stack up within each of the slots  42   a . Thus, the winding assembly  41 B is installed in the laminated core  42  as shown in FIG.  12 B. 
   Next, the laminated core  42  is rolled up and its ends abutted and welded to each other to obtain the cylindrical stator core  15 , as shown in FIG.  12 C. 
   Then, end portions of the same strand of wire  30  are connected so that first and second winding sub-portions  31  and  32  which are wound into slot groups disposed at a pitch of six slots each form lap windings having two turns per lap. Then, the two three-phase alternating-current windings are obtained by cutting each of the lead portions of the winding assembly  41 B, forming crossover connections, then connecting the neutral points. 
   Thus, the stator  8 B obtained is formed by installing the stator winding  16 B composed of the two three-phase alternating-current windings in the stator core  15 . 
   Thus, in Embodiment 3, because the winding assembly  41 B is formed by arranging the twelve strands of wire  30  in the same plane at a pitch of one slot, folding and bending the twelve strands of wire  30  to form the lightning-bolt shaped pattern shown in  FIGS. 20 and 21 , forming the cylindrical body  40 B in which the second and third straight portions  30   b  and  30   c  which are linked by the second inclined portions  30   f  and the fourth and first straight portions  30   d  and  30   a  which are linked by the fourth inclined portions  30   h  are wound helically by folding back the first and third inclined portions  30   e  and  30   g  in the same direction at central portions thereof, and then folding the cylindrical body  40 B over at central portions of the second and fourth inclined portions  30   f  and  30   h , a winding assembly can be easily manufactured which alternately occupies an inner layer and an outer layer in a slot depth direction in every sixth slot  15   a  and constitutes a lap winding having two turns per lap. 
   Because the winding assembly  41 B prepared in this manner is used, six stator winding phase portions  161 B can be installed into the stator core  15  by installing one winding assembly  41 B into the stator core  15 . Thus, the complex operation of inserting a large number of segments into the slots of the stator core and joining the end portions thereof together one by one is no longer required, significantly improving assembly and workability, thereby enabling producibility to be increased. In addition, cases in which the number of turns in the stator winding is increased can easily be adapted for by stacking and installing a plurality of the winding assemblies  41 B into the stator core  15 . 
   Because the coil ends are constituted by the turn portions of the strands of wire  30 , the number of joints in the coil end groups  16   f  and  16   r  is significantly reduced Thus, there is no need to extend the coil ends out by an extra amount from the end surfaces of the stator core  15 , enabling the stator  8 B to be reduced in size. In addition, because the occurrence of short-circuiting accidents which accompany loss of insulation due to the joining process can be suppressed, superior insulation can be obtained and high yield can also be achieved. In addition, reductions in resistance to corrosion which accompany loss of insulation due to joining can be suppressed. 
   Embodiment 4 
     FIGS. 24 and 25  are perspectives showing a stator of the alternator according to Embodiment 4 of the present invention viewed from the rear end and the front end, respectively, and  FIG. 26  is a diagram explaining a winding assembly forming process in a method of manufacture for the stator of the alternator according to Embodiment 4 of the present invention. In  FIGS. 24 and 25 , neutral points and output wires have been omitted. 
   In this stator  8 C, four strands of wire  30  are housed so as to line up in a slot depth direction within the slots  15   a  as shown in  FIGS. 24 and 25 . 
   Then, in pairs of first and second slots, in which the slots forming each pair are six slots apart, the strand of wire  30  housed in the first address of the first slot  15   a  is folded back outside the slots at the front end of the stator core  15  and housed in the second address of the second slot  15   a , and the strand of wire  30  housed in the fourth address of the first slot  15   a  is folded back outside the slots at the front end of the stator core  15  and housed in the third address of the second slot  15   a.    
   Furthermore, in the pairs of first and second slots in which the slots forming each pair are six slots apart, the strand of wire  30  housed in the fourth address of the first slot  15   a  is folded back outside the slots at the rear end of stator core  15  and housed in the second address of the second slot  15   a , and the strand of wire  30  housed in the third address of the first slot  15   a  is folded over outside the slots at the rear end of the stator core  15  and housed in the first address of the second slot  15   a.    
   Thus, the stator winding  16 C is constituted by a plurality of winding sub-portions in each of which a single strand of wire  30  is wound into a lap winding having two turns per lap so as to alternately occupy an inner layer and an outer layer in a slot depth direction in every sixth slot  15   a . Turn portions of the strands of wire  30  folded over outside the slots at the front end of the stator core  15  are disposed in a circumferential direction so as to form two rows in a radial direction and constitute a front-end coil end group  16   f , and turn portions of the strands of wire  30  folded over outside the slots at the rear end of the stator core  15  are disposed in a circumferential direction so as to form one row in a radial direction and constitute a rear-end coil end group  16   r . The winding assembly  41 C, formed by integrating a plurality of the winding sub-portions, is formed by folding back the cylindrical body  40 C, in which the first to fourth straight portions  30   a  to  30   d  are wound helically, at central portions of the second and fourth inclined portions  30   f  and  30   h  as shown in FIG.  26 . 
   Moreover, the rest of the construction is constructed similarly to the above embodiments. 
   Consequently, the same effects as in each of the above embodiments can also be obtained in Embodiment 4. 
   Furthermore, because turn portions of the strands of wire  30  in Embodiment 4 are disposed in a circumferential direction so as to form two rows in a radial direction and constitute the front-end coil end group  16   f , and turn portions of the strands of wire  30  are disposed so as to form one row in a circumferential direction and constitute the rear-end coil end group  16   r , the axial heights of the front-end and rear end-end groups  16   f  and  16   r  can be reduced. Thus, coil leakage reactance is further reduced, improving output, and wind resistance is reduced, alleviating wind noise, compared to each of the above embodiments. 
   In each of the above embodiments, the number of slots in the stator was ninety-six slots for sixteen magnetic poles, but three phases and seventy-two slots for twelve magnetic poles, 120 slots for twenty poles, etc., may also be adopted. Furthermore, in the case of one slot per pole per phase, there may also be forty-eight slots for sixteen poles, thirty-six slots for twelve poles, sixty slots for twenty poles, etc. 
   In such cases, if x is the number of slots per pole per phase and y is the number of winding phase portions, then the number of strands of wire constituting the stator winding is given by 2xy, the first to fourth straight portions constituting the winding assembly will each be disposed at a pitch of 2xyp, and the amount of offset between the first straight portions and second straight portions in the direction of disposal is given by xyp. 
   Each of the above embodiments has been explained for four turns, but when even lower-speed output is required eight turns may be used. That case can also be adapted to simply by inserting two winding assemblies  41  ( 41 B) into the stator core  15  so as to line up radially. Furthermore, six turns can be adapted to simply by inserting one winding assembly  41  ( 41 B) and one winding assembly shown in the comparative example above into the stator core  15  so as to line up radially. 
   The present invention is constructed in the above manner and exhibits the effects described below. 
   According to one aspect of the present invention, there is provided an alternator including: 
   a stator having a cylindrical stator core formed with a plurality of slots extending axially at a predetermined pitch in a circumferential direction, and a stator winding installed into the stator core; and 
   a rotor for forming north-seeking (N) and south-seeking (S) poles about a rotational circumference, the rotor being disposed on an inner circumferential side of the stator core, wherein 
   the stator winding comprises a plurality of winding sub-portions in each of which a strand of wire formed from a continuous wire is wound so as to alternately occupy an inner layer and an outer layer in a slot depth direction within the slots at intervals of a predetermined number of slots by folding over the strand of wire outside the slots at end surfaces of the stator core and form a lap winding having two turns in each lap. Thus, because the number of crossover connections is reduced and the connecting portions are simplified, an alternator is provided in which axial height of the coil ends can be lowered, the number of weld portions on the coil ends can be decreased, deterioration in output, wind noise and magnetic noise can be suppressed, and cooling is also improved. 
   Four of the strands of wire constituting the winding sub-portions may be housed so as to line up in each of the slots so as to occupy a first layer, a second layer, a third layer, and a fourth layer in a slot depth direction; 
   turn portions formed by folding the strands of wire over outside the slots at a first end surface of the stator core may be disposed circumferentially to form two rows in a radial direction; and 
   turn portions formed by folding the strands of wire over outside the slots at a second end surface of the stator core may be disposed circumferentially to form two layers in an axial direction, reducing axial height of the coil end at a first end of the stator core, thereby increasing output and reducing wind noise 
   In each of slot pairs in which first and second slots forming each of the slot pairs are a predetermined number of slots apart: 
   the strand of wire housed in the first layer inside the first slot may be folded over outside the slots at the first end surface of the stator core and housed in the second layer inside the second slot; 
   the strand of wire housed in the third layer of the first slot may be folded over outside the slots at the first end surface of the stator core and housed in the fourth layer of the second slot; 
   the strand of wire housed in the third layer inside the first slot may be folded over outside the slots at the second end surface of the stator core and housed in the second layer inside the second slot; and 
   the strand of wire housed in the fourth layer of the first slot may be folded over outside the slots at the second end surface of the stator core and housed in the first layer of the second slot, enabling a stator winding to be achieved by a simple construction. 
   The strands of wire may be installed two at a time into slot sets constituted by slot groups disposed a predetermined number of slots apart, the two strands of wire installed in each of the slot sets constituting a first strand of wire and a second strand of wire, and 
   the stator winding may be composed of a plurality of stator winding phase portions, each of the stator winding phase portions comprising:
         a first winding sub-portion constructed by joining first and second end portions of the first strand of wire extending outwards outside the slots at the second end surface of the stator core from the fourth layer in the first slot of a first pair and the first layer in the second slot of the first pair, the first pair being one pair of the slot pairs constituting each of the slot sets; and   a second winding sub-portion constructed by joining first and second end portions of the second strand of wire extending outwards outside the slots at the second end surface of the stator core from the third layer in the first slot of the first pair and the second layer in the second slot of the first pair,   wherein each of the stator winding phase portions is constructed by connecting the first and second winding sub-portions in series by crossover connecting the first strand of wire extending outwards outside the slots at the second end surface of the stator core from the fourth layer in the first slot of a second pair, and the second strand of wire extending outwards from the outside of the slots at the second end surface of the stator core from the second layer in the second slot of the second pair, the second pair being another pair of the slot pairs constituting each of the slot sets, and   wherein the second strand of wire extending outwards at the second end surface of the stator core from the third layer in the first slot of the second pair, and the first strand of wire extending outwards at the second end surface of the stator core from the first layer in the second slot of the second pair constitute a neutral point and an output wire of the stator winding phase portion, respectively, making the number of crossover connections per stator winding phase portion one, thereby improving the connecting operation. Furthermore, circumferential irregularities in the coil end groups resulting from the crossover connections are reduced, thereby improving the cooling effect.       

   The strands of wire may be installed two at a time into slot sets constituted by slot groups disposed a predetermined number of slots apart, the two strands of wire installed in each of the slot sets constituting a first strand of wire and a second strand of wire, and 
   the stator winding may be composed of a plurality of stator winding phase portions, each of the stator winding phase portions being constructed by a first and second winding sub-portions which are connected in series by joining a first end portion of the first strand of wire extending outwards outside the slots at the second end surface of the stator core from the fourth layer in the first slot of a first pair to a second end portion of the second strand of wire extending outwards outside the slots at the second end surface of the stator core from the second layer in the second slot of the first pair, and joining a first end portion of the second strand of wire extending outwards outside the slots at the second end surface of the stator core from the third layer in the first slot of the first pair to a second end portion of the first strand of wire extending outwards outside the slots at the second end surface of the stator core from the first layer in the second slot of the second pair, the first pair being one pair of the slots pair constituting each of the slot sets, 
   wherein the second strand of wire extending outwards at the first end surface of the stator core from the third layer in the first slot of a second pair and from the fourth layer in the second slot of the second pair is cut to constitute a neutral point and an output wire of the stator winding phase portion, the second pair being another pair of the slot pairs constituting each of the slot sets, eliminating crossover connections in one stator winding phase portion, thereby improving the connecting operation. Furthermore, circumferential irregularities in the coil end groups resulting from the crossover connections are reduced, enabling worsening of wind noise to be further suppressed and wind resistance to be reduced, thereby further improving the cooling effect. 
   In each of slot pairs in which first and second slots forming each of the slot pairs are a predetermined number of slots apart: 
   the strand of wire housed in the second layer inside the first slot may be folded over outside the slots at the first end surface of the stator core and housed in the first layer inside the second slot; 
   the strand of wire housed in the third layer of the first slot may be folded over outside the slots at the first end surface of the stator core and housed in the fourth layer of the second slot; 
   the strand of wire housed in the second layer inside the first slot may be folded over outside the slots at the second end surface of the stator core and housed in the third layer inside the second slot; and 
   the strand of wire housed in the fourth layer of the first slot may be folded over outside the slots at the second end surface of the stator core and housed in the first layer of the second slot, enabling a stator winding to be achieved a simple construction. 
   The strands of wire may be installed two at a time into slot sets constituted by slot groups disposed a predetermined number of slots apart, the two strands of wire installed in each of the slot sets constituting a first strand of wire and a second strand of wire, and 
   the stator winding may be composed of a plurality of stator winding phase portions, each of the stator winding phase portions comprising:
         a first winding sub-portion constructed by joining first and second end portions of the first strand of wire extending outwards outside the slots at the second end surface of the stator core from the fourth layer in the first slot of a first pair and the first layer in the second slot of the first pair, the first pair being one pair of the slot pairs constituting each of the slot sets; and   a second winding sub-portion constructed by joining first and second end portions of the second strand of wire extending outwards outside the slots at the second end surface of the stator core from the second layer in the first slot of the first pair and the third layer in the second slot of the first pair,   wherein each of the stator winding phase portions is constructed by connecting the first and second sub-portions in series by crossover connecting the second strand of wire extending outwards outside the slots at the first end surface of the stator core from the third layer in the first slot of a second pair, and the first strand of wire extending outwards from the outside of the slots at the first end surface of the stator core from the first layer in the second slot of the second pair, the second pair being another pair of the slot pairs constituting each of the slot sets, and   wherein the first strand of wire extending outwards at the first end surface of the stator core from the second layer in the first slot of the second pair, and the second strand of wire extending outwards at the first end surface of the stator core from the fourth layer in the second slot of the second pair constitute a neutral point and an output wire of the stator winding phase portion, respectively, making the number of crossover connections per stator winding phase portion one, thereby improving the connecting operation. Furthermore, circumferential irregularities in the coil end groups resulting from the crossover connections are reduced, enabling worsening of wind noise to be suppressed and wind resistance to be reduced, thereby improving the cooling effect.       

   Four of the strands of wire constituting the winding sub-portions may be housed so as to line up in each of the slots so as to occupy a first layer, a second layer, a third layer, and a fourth layer in a slot depth direction; 
   turn portions formed by folding the strands of wire over outside the slots at a first end surface of the stator core may be disposed circumferentially to form two rows in a radial direction; and 
   turn portions formed by folding the strands of wire over outside the slots at a second end surface of the stator core may be disposed in one row circumferentially, reducing axial height of the coil ends at first and second ends of the stator core, thereby increasing output and educing wind noise. 
   According to another aspect of the present invention, there is a winding assembly for an alternator, the winding assembly including a winding group composed of 2n winding sub-portions disposed at a pitch of p, each of the winding sub-portions being constructed by folding and bending one strand of wire formed from a continuous wire into a pattern, the pattern having: 
   first straight portions disposed at a pitch of 2np; 
   second straight portions disposed at the pitch of 2np being offset by an amount w to a first side in a width direction from the first straight portions and offset by an amount np forwards relative to a direction of disposal of the first straight portions; 
   third straight portions disposed at the pitch of 2np being offset by the amount w to the first side in the width direction from the second portions and offset by the amount np backwards relative to the direction of disposal of the second straight portions; 
   fourth straight portions disposed at the pitch of 2np being offset by the amount w to the first side in the width direction from the third straight portions and offset by the amount np forwards relative to the direction of disposal of the third straight portions; 
   first turn portions linking first ends of the first straight portions to first ends of the second straight portions offset by the amount np forwards relative to the direction of disposal of the first straight portions; 
   second turn portions linking second ends of the second straight portions to second ends of the third straight portions offset by the amount np backwards relative to the direction of disposal of the second straight portions; 
   third turn portions linking first ends of the third straight portions to first ends of the fourth straight portions offset by the amount np forwards relative to the direction of disposal of the third straight portions; and 
   fourth turn portions linking second ends of the fourth straight portions to second ends of the first straight portions offset by the amount np forwards relative to the direction of disposal of the fourth straight portions, wherein 
   the winding sub-portions are disposed parallel to each other at the pitch of p in the direction of disposal such that the first to fourth straight portions form four layers in the width direction, 
   the first turn portions are disposed parallel to each other at the pitch of p and the third turn portions are disposed parallel to each other at the pitch of p such that the first turn portions and the third turn portions form two rows in the direction of disposal, and 
   the second turn portions are disposed parallel to each other at the pitch of p and the fourth turn portions are disposed parallel to each other at the pitch of p such that the second turn portions and the fourth turn portions form two layers in a longitudinal direction of the straight portions, thereby providing a wind assembly enabling the achievement of a stator winding with superior mass-producibility which can be made more compact. 
   According to another aspect of the present invention, there is a winding assembly for an alternator, the winding assembly comprising a winding group composed of 2n winding sub-portions disposed at a pitch of p, each of the winding sub-portions being constructed by folding and bending one strand of wire formed from a continuous wire into a pattern, the pattern having: 
   first straight portions disposed at a pitch of 2np; 
   second straight portions disposed at the pitch of 2np being offset by an amount w to a first side in a width direction from the first straight portions and offset by an amount np forwards relative to a direction of disposal of the first straight portions; 
   third straight portions disposed at the pitch of 2np being offset by the amount w to the first side in the width direction from the second portions and offset by the amount np forwards relative to the direction of disposal of the second straight portions; 
   fourth straight portions disposed at the pitch of 2np being offset by the amount w to the first side in the width direction from the third straight portions and offset by the amount np backwards relative to the direction of disposal of the third straight portions; 
   first turn portions linking first ends of the first straight portions to first ends of the second straight portions offset by the amount np forwards relative to the direction of disposal of the first straight portions; 
   second turn portions linking second ends of the second straight portions to second ends of the third straight portions offset by the amount np forwards relative to the direction of disposal of the second straight portions; 
   third turn portions linking first ends of the third straight portions to first ends of the fourth straight portions offset by the amount np backwards relative to the direction of disposal of the third straight portions; and 
   fourth turn portions linking second ends of the fourth straight portions to second ends of the first straight portions offset by the amount np forwards relative to the direction of disposal of the fourth straight portions, wherein 
   the winding sub-portions are disposed parallel to each other at the pitch of p in the direction of disposal such that the first to fourth straight portions form four layers in the width direction, 
   the first turn portions are disposed parallel to each other at the pitch of p and the third turn portions are disposed parallel to each other at the pitch of p such that the first turn portions and the third turn portions form two rows in the direction of disposal, and 
   the second turn portions are disposed parallel to each other at the pitch of p and the fourth turn portions are disposed parallel to each other at the pitch of p such that the second turn portions and the fourth turn portions form two layers in a longitudinal direction of the straight portions, thereby providing a winding assembly enabling the achievement of a stator winding with superior mass-producibility which can be made more compact. 
   According to another aspect of the present invention, there is a method of manufacture for a winding assembly for an alternator, the method including steps of: 
   disposing a group of 2n straight strands of wire at a pitch p in a first plane; 
   forming a lightning-bolt shaped pattern composed of a plurality of basic patterns by folding and bending the group of strands of wire in the plane, each of the basic patterns comprising:
         first straight portions having a length l 0 ;   second straight portions having the length l 0  being linked to the first straight portions by first inclined portions having a length l 1 , the second straight portions being offset by an amount np to a first side in a direction of disposal of the strands of wire relative to the first straight portions;   third straight portions having the length l 0  being linked to the second straight portions by second inclined portions having the length l 1 , the third straight portions being offset by the amount np to a second side in a direction of disposal of the strands of wire relative to the second straight portions; and   fourth straight portions having the length l 0  being linked to the third straight portions by third inclined portions having the length l 1 , the fourth straight portions being offset by the amount np to the first side in a direction of disposal of the strands of wire relative to the third straight portions,   wherein the lightning-bolt shaped pattern is constructed by repeating the basic pattern a predetermined number of times by offsetting the basic pattern to the first side in the direction of disposal of the strands of wire by fourth inclined portions having a length l 2 , the length l 2  being greater than the length l 1 ;       

   forming a flattened cylindrical body by folding over the group of strands of wire formed into the lightning-bolt shaped pattern in a first direction at central portions of the first and the third inclined portions, the cylindrical body being constructed by helically winding the group of strands of wire such that the second and third straight portions linked by the second inclined portions and the first and fourth straight portions linked by the fourth inclined portions alternately occupy the first plane and a second plane; and 
   forming a winding group by folding over the cylindrical body at central portions of the second and the fourth inclined portions in a second direction such that the second and the third straight portions face each other, wherein
         the first to fourth straight portions are disposed parallel to each other at the pitch of p in the direction of disposal such that the first to fourth straight portions form four layers in the width direction,   first turn portions formed by folding over the group of strands of wire at the first inclined portions are disposed parallel to each other at the pitch of p and third turn portions formed by folding over the group of strands of wire at the third inclined portions are disposed parallel to each other at the pitch of p such that the first turn portions and the third turn portions form two rows in the direction of disposal, and   second turn portions of the strands of wire formed by folding over the cylindrical body at the second inclined portions are disposed parallel to each other at the pitch of p and the fourth turn portions of the strands of wire formed by folding over the cylindrical body at the fourth inclined portions are disposed parallel to each other at the pitch of p such that the second turn portions and the fourth turn portions form two layers in a longitudinal direction of the straight portions, thereby providing a method of manufacture for a winding assembly in which a winding assembly enabling the achievement of a stator winding which can be made more compact can be manufactured with superior mass-producibility.       

   According to another aspect of the present invention, there is a method of manufacture for a winding assembly for an alternator, the method including steps of: 
   disposing a group of 2n straight strands of wire at a pitch p in a first plane; 
   forming a lightning-bolt shaped pattern composed of a plurality of basic patterns by folding and bending the group of strands of wire in the plane, each of the basic patterns comprising:
         first straight portions having a length l 0 ;   second straight portions having the length l 0  being linked to the first straight portions by first inclined portions having a length l 1 , the second straight portions being offset by an amount np to a first side in a direction of disposal of the strands of wire relative to the first straight portions;   third straight portions having the length l 0  being linked to the second straight portions by second inclined portions having the length l 1 , the third straight portions being offset by the amount np to the first side in a direction of disposal of the strands of wire relative to the second straight portions; and   fourth straight portions having the length l 0  being linked to the third straight portions by third inclined portions having the length l 1 , the fourth straight portions being offset by the amount np to a second side in a direction of disposal of the strands of wire relative to the third straight portions,   wherein the lightning-bolt shaped pattern is constructed by repeating the basic pattern a predetermined number of times by offsetting the basic pattern to the first side in the direction of disposal of the strands of wire by fourth inclined portions having a length l 2 , the length l 2  being greater than the length l 1 ;       

   forming a flattened cylindrical body by folding over the group of strands of wire formed into the lightning-bolt shaped pattern in a first direction at central portions of the first and the third inclined portions, the cylindrical body being constructed by helically winding the group of strands of wire such that the second and third straight portions linked by the second inclined portions and the first and fourth straight portions linked by the fourth inclined portions alternately occupy the first plane and a second plane; and 
   forming a winding group by folding over the cylindrical body at central portions of the second and the fourth inclined portions in a second direction such that the second and the third straight portions face each other, wherein
         the first to fourth straight portions are disposed parallel to each other at the pitch of p in the direction of disposal such that the first to fourth straight portions form four layers in the width direction,   first turn portions formed by folding over the group of strands of wire at the first inclined portions are disposed parallel to each other at the pitch of p and third turn portions formed by folding over the group of strands of wire at the third inclined portions are disposed parallel to each other at the pitch of p such that the first turn portions and the third turn portions form two rows in the direction of disposal, and       

   second turn portions of the strands of wire formed by folding over the cylindrical body at the second inclined portions are disposed parallel to each other at the pitch of p and the fourth turn portions of the strands of wire formed by folding over the cylindrical body at the fourth inclined portions are disposed parallel to each other at the pitch of p such that the second turn portions and the fourth turn portions form two layers in a longitudinal direction of the straight portions, thereby providing a method of manufacture for a winding assembly in which a winding assembly enabling the achievement of a stator winding which can be made more compact can be manufactured with superior mass-producibility.