Abstract:
In a stator of a rotary electric machine that includes a stator winding and a stator core having a plurality of slots, the stator winding is constituted of a plurality of series-connected regular U-shaped segments each of which has a pair of in-slot portions and a plurality of U-shaped irregular segments each of which has a pair of in-slot portions disposed in a pair of slots that is suitable to connect the regular segments to form the stator winding and a continuous crossover portion crossing over some of the regular segments. The irregular U-shaped segments extend to be in contact with the turn portions of the regular segments. Therefore, the regular segments are connected by the irregular segments that have least electric resistance.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This is a division of U.S. patent application Ser. No. 11/140,747 filed Jun. 1, 2005, the disclosure of which is incorporated herein by reference in its entirety. The present application is based on and claims priority from Japanese Patent Application No. 2004-164188 filed Jun. 2, 2004, the contents of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a stator of a rotary electric machine to be mounted in a vehicle such as a passenger car or a truck. 
   2. Description of the Related Art 
   A stator of a rotary electric machine such as a motor or a generator includes a stator core having plural slots. Laid-open patent publications WO92/06527 and JP-A-2003-199304, or its counterpart US 2003/0121139 A1 disclose stators having plural slots in which U-shaped conductor segments are inserted. 
   The stator disclosed in WO92/06527 has irregular U-shaped conductor segments besides regular U-shaped conductor segments, which are welded to one another to form a stator winding. When the stator winding is formed, the turn portion of the irregular U-shaped conductor segments are twisted by a twisting ring. Therefore, it is necessary for the turn portions of the irregular U-shaped conductor segments to have certain height from an axial end of the stator core. In other words, the irregular U-shaped conductor segments increases resistance of the stator winding. 
   The stator disclosed in US 2003/0121139 A1 also has irregular U-shaped conductor segments to connects the regular U-shaped conductor segments. These irregular U-shaped conductor segments are formed to have an S-shaped meander on the top of the turn portions to connect the regular U-shaped conductor segments. That is, the S-shaped meander increases the length and the resistance of the stator winding. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide an improved stator of a rotary electric machine that has a stator winding of a lower resistance. 
   According to a preferred embodiment of the invention, a stator winding includes a plurality of series-connected regular segments having a pair of in-slot portions inserted into a regularly disposed pair of the slots and a turn portion and a plurality of irregular segments having a pair of in-slot portions disposed in a pair of slots whose location is suitable to connect the regular segments to form the stator winding and a continuous crossover portion crossing over some of the regular segments and extending to be in contact with the turn portion of the regular segments. 
   Therefore, the irregular segments can be made straight, so that the regular segments can be connected by its crossover portion as short as possible and do not significantly increase the resistance of the stator winding. 
   Preferably, the crossover portions extends in the circumferential direction of the stator core. Some of the crossover portions may extend in a direction inclined to the circumferential direction of the stator core. The plurality of regular segments of the above embodiment preferably includes first subsets of conductor segments disposed at inner circumference of the stator core that includes a large regular U-shaped conductor segment and a small regular U-shaped conductor segment and second subsets of a conductor segment that includes a regular U-shaped conductor segment that has the same shape as, and a smaller height from an axial end of the stator core than, the first subset. 
   Preferably, the first subset is disposed radially inside the second subset so that the turn portions of the regular segments disposed radially inside of the stator core can be higher than those disposed radially outside of the stator core. This arrangement is effective to limit or minimize the height and the outside diameter of the coil end groups and, also, the length of the stator winding. 
   Further, the crossover portion of the irregular segments is preferably disposed between the first subsets and the second subsets. 
   The irregular segment may have a pair of inclined portions each of which extends from the crossover portion in parallel with an inclined portion of an adjoining regular U-shaped segment. The two neighboring regular segments that are crossed by the crossover portion are arranged to be closer to each other in the circumferential direction than other regular segments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and characteristics of the present invention as well as the functions of related parts of the present invention will become clear from a study of the following detailed description, the appended claims and the drawings. In the drawings: 
       FIG. 1  is a schematic cross-sectional longitudinal view of a motor according to a preferred embodiment of the invention; 
       FIG. 2  is a perspective view of a pair of regular U-shaped conductor segments to be used in the motor according to the preferred embodiment; 
       FIG. 3  is a cross-sectional view of a stator of the motor according to the preferred embodiment; 
       FIG. 4  is a schematic diagram illustrating disposition of irregular U-shaped conductor segments in the stator of the motor according to the preferred embodiment; 
       FIG. 5  is a fragmentary plan view of the stator illustrating disposition of irregular U-shaped conductor segments; 
       FIG. 6  is a schematic cross-sectional side view of the stator illustrating the disposition of irregular U-shaped conductor segments; 
       FIG. 7  is a side view of the stator viewed from radially inside thereof for illustrating the disposition of an irregular U-shaped conductor segment; and 
       FIG. 8  illustrates a modified irregular U-shaped conductor segment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A preferred embodiment of the present invention will be described with reference to the appended drawings. 
   As shown in  FIG. 1 , a motor  100  according to the preferred embodiment of the invention includes a stator core  1 , a rotor  2 , a stator winding  3 , a housing  5  and a rotary shaft  7 . 
   The stator core  1  is a ring shaped magnetic member that has plural slots  35  at the radially inside surface and is held by the housing  5 . The stator winding  3  is a three-phase winding, which is driven by a three-phase inverter control circuit. The stator winding  3  is held in the slots  35  of the stator core  1  and has a pair of coil end groups  31 ,  32  at the opposite axial ends of the stator core  1 , forming a stator of the motor  100 . The coil-end portions  31 ,  32  respectively extend in the opposite axial directions of the rotary shaft  7  from the opposite axial ends of the stator core  1 . The rotor  2  is rotatably supported by the housing  5  via the rotary shaft  7 . 
   The stator winding  3  is formed of a plural sets of regular U-shaped conductor segments  331 ,  332 , as shown in  FIG. 2 . Each regular U-shaped conductor segment is inserted into a pair of slots  35  of the stator core  1  from one axial end of the stator core  1  so that a preset length of the end portions of each regular conductor segment protrudes from the other axial end of the stator core  1 . Then the end portions of each regular U-shaped conductor segment are respectively twisted and welded to end portions of other conductor segments that are apart by π/2 radian in electric angle from the the end portions. Incidentally, the conductor segments are covered with insulation material except the connected and welded portions. 
   As shown in  FIGS. 1 and 3 , one set S of regular U-shaped conductor segments to be mounted into the stator core  1  includes a first subset S 1  of conductor segments  331 ,  332  disposed at inner circumference of the stator core and a second subset S 2  of a conductor segment  333 . In other words, the first subset S 1  includes four straight in-slot portions  331   a ,  331   b ,  332   a ,  332   b , and the second subset S 2  includes two straight in-slot portions  333   a ,  333   b  (not shown) that corresponds to a straight in-slot portion  333   b  of another conductor segment  333 , as shown in  FIG. 3 . 
   The first subset S 1  includes a large regular U-shaped conductor segment (hereinafter referred to as the large segment)  331  and small regular U-shaped conductor segment  332  (hereinafter referred to as the small segment), each of which has a turn portion (or V-shaped head portion) to be disposed on one axial end of the stator core  1 , a pair of straight in-slot portions that extends from the turn portion to be inserted into a pair of the slots  35  of the stator core  1  and a pair of the above stated end portions that protrudes from the other axial end of the stator core  1 . Before the large or small segment  331 ,  332  is inserted into one of the slots  35 , it is not processed and remains straight. 
   The stator winding  3  includes a first coil end group (head side coil end group)  31  coaxially disposed at one axial end of the stator core  1  and a second coil end group (tail side coil end group)  32  coaxially disposed at the other axial end of the stator core  1  and in-slot group  35  disposed in the slots of the stator core  1 . 
   As shown in  FIG. 2 , the large segment  331  of the first subset S 1  includes a pair of in-slot portions  331   a  and  331   b , a head portion (or turn portion)  331   c  and a pair of end portions  331   f  and  331   g . Each end portion  331   f ,  331   g  has a connection portion  331   d  or  331   e  that is to be welded to a connection portion of another small segment that is to be adjacent thereto. The small segment  332  of the same first subset also includes a pair of in-slot portions  332   a  and  332   b , a head portion (or turn portion)  332   c  and a pair of end portions  332   f  and  332   g . Each end portion  332   f ,  332   g  also has a connection portion  332   d  or  332   e  that is to be welded to a connection portion  331   d ′ or  331   e ′ of another large segment that is to be adjacent thereto in a radial direction of the stator core  1 . 
   The in-slot portion  331   a  of the large segment  331  is disposed in the inner most layer (hereinafter referred to the first layer P 1 ) of a certain slot and the in-slot portion  332   a  of the small segment  332  is disposed in the next inner layer (hereinafter referred to as the second layer P 2 ) of the same slot; and the in-slot portions  332   b ,  331   b  of the same small and large segments  332 ,  331  are respectively disposed in the next layers (the third and fourth layers P 3 , P 4 ) of another slot  35  that is a prescribed pitch T (e.g. one pole pitch or π radian in electric angle) apart from the certain slot. Therefore, the head portion  332   c  of the small segment  332  is surrounded by the head portion  331   c  of the large segment  331  of the same first subset S 1 . 
   The regular U-shaped segment  333  of the second subset S 2  is the same in shape and size as the small segment  332  of the first subset S 1 . However the size and shape can be changed if necessary or preferable. One in-slot portion of the regular U-shaped segment of the second subset S 2  is disposed in the fifth layer P 5  of the certain slot and the other in-slot portion is disposed in the sixth layer P 6  (outermost layer) of another slot  35  that is the prescribed pitch T apart from the certain slot. 
   As shown in  FIG. 3 , each slot  35  provides a space to accommodate the following six in-slot portions in radially aligned six layers P 1 -P 6 : the in-slot portions  331   a ,  332   a  of the certain first subset S 1 ; the in-slot portions  332   b ′,  331   b ′ of another first subset S 1  and the in-slot portions of two second subsets S 2 . 
   The stator winding  3  is composed of three phase-windings, each of which is composed of series-connected regular U-shaped conductor segments of the subsets S 1  and series-connected regular U-shaped conductor segments of the subsets S 2 . Therefore, each phase winding winds threefold around the stator core  1 . 
   As shown in  FIG. 4 , plural irregular U-shaped conductor segments are employed to connect the regular U-shaped conductor segments to form the stator winding  3 . Inner irregular segments  133 A,  133 B,  133 C respectively connect the regular segments extending from the first layer P 1  and the regular segments extending from the third layer. The outer irregular segments  133 D,  133 E,  133 F respectively connect the regular segments extending from the fourth layer P 4  and the regular segments extending from the fifth layer P 5 . In  FIG. 4 , numerals  8 - 26  on the radially inner side of the slots represent slot numbers (#) of slots in which the regular segments are twisted and inserted in the first, third and fifth layers, while numerals  17 - 35  on the radially outer side of the slots represent slot numbers (#) of slots in which the regular segments are twisted and inserted in the second, fourth and sixth layers. 
   In other words, the inner irregular segment  133 A has one in-slot portion that is disposed in the first layer P 1  of slot # 22  of the slots  35  and the other in-slot portion that is disposed in the third layer P 3  of slot # 24  of the slots  35 . As shown in  FIG. 5 , the head portion of the inner irregular segment  133 A includes a crossover portion  134 A that extends in radially inside area of a circle on which the centers of the head portions  331   c  of the large segments  331  are located. The crossover portion  134 A is continuous and does not have any connection portion therein. The crossover portion  134 A is straight when projected on a surface in parallel with the axis of the stator core and inclines to the circumferential direction of the stator core. It extends to be almost in contact with a portion of the large segment  331  that extends along the center axis of the stator core, as shown in  FIG. 6 . The head portion of the inner irregular segment  133 A also includes a pair of inclined portions  135 A each of which extends from the crossover portion  134 A to an in-slot portion in parallel with an inclined portion of an adjoining regular U-shaped segment, as shown in  FIG. 7 . The inner irregular segments  133 B and  133 C are substantially the same as the irregular segment  133 A. 
   The outer irregular segment  133 D has one in-slot portion that is disposed in the fifth layer P 5  of slot # 22  (the number on the inner side) of the slots  35  and the other in-slot portion that is disposed in the fourth layer P 4  of slot # 33  of the slots  35 . As shown in  FIG. 5 , the head portion of the outer irregular segment  133 D includes a crossover portion  134 D that extends in an area between the centers of the head portions  311   c  of the large segments  331  of the first subset S 1  and the centers of the head portions  332   c  of the small segments  332  of the second subset S 2 . The crossover portion  134 D is continuous and does not have any connection portion therein. The crossover portion  134 D is straight when projected on a surface in parallel with the axis of the stator core and extends along the circumferential direction of the stator core. It extends almost in contact with portions of both the large segment  331  of the first subset S 1  and the small segment  332  of the second subset S 2 , that extends along the center axis of the stator cores, as shown in  FIG. 6 . The head portion of the inner irregular segment  133 A also includes a pair of inclined portions  135 A each of which extends from the crossover portion  134 A to an in-slot portion in parallel with an inclined portion of an adjoining regular U-shaped segment, as shown in  FIG. 7 . The inner irregular segments  133 B and  133 C are substantially the same as the irregular segment  133 A. 
   As shown in  FIG. 6 , the first subset S 1  has a greater height H 1  from an axial end of the stator core  1  than a height H 2  of the second subset S 2 . In other words, the head portions of the regular segments become higher as they approach the center axis of the stator core  1 . Further, the head portions of large segment  331  of the first subset S 1  and the small segment  332  of the second subset S 2  are disposed in contact with each other. 
   As shown in  FIG. 5 , the crossover portion  134 A of the  133 A crosses over two neighboring regular segments  331 ′,  331 ″ of the first subset S 1 , and the crossover portion  134 D of the  133 D crosses over two neighboring regular segments  332 ′,  332 ″ of the second subset S 2 . Both two neighboring regular segments  331 ′,  331 ″ and two neighboring regular segments  332 ′,  332 ″ are arranged to be closer to each other in the circumferential direction than other regular segments that the irregular segments do not cross over. This arrangement is effective to limit or minimize the height and the outside diameter of the coil end groups and, also, the length of the stator winding  3 . 
   The irregular segment may be shaped so that the central portion of the crossover portion can hang down as shown in  FIG. 8 . This is effective to reduce bending stress between the crossover portion  134 A and the inclined portion  135  A. 
   In the foregoing description of the present invention, the invention has been disclosed with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made to the specific embodiments of the present invention without departing from the scope of the invention as set forth in the appended claims. Accordingly, the description of the present invention is to be regarded in an illustrative, rather than a restrictive, sense.