Abstract:
A method of producing a stator winding for a stator of an electrical machine includes positioning a phase winding segment of the stator winding in a same plane in a serpentine manner in a first direction (X) and in a shape of a wave in a second direction (Y) transverse to the first direction. The method includes bending regions (A, B, C) of the phase winding segment toward one another along a folding line to form a lap winding including positioning regions (C) parallel to each other connected by regions (B) where the regions (B) cross the at least one folding line ( 108 ). The phase winding is formed with a continuous wire.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
     The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2005 054 863.6 filed on Nov. 21, 2005. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119 (a)-(d). 
     BACKGROUND OF THE INVENTION 
     Methods for manufacturing a stator winding for a stator of an electrical machine are known from the related art. In these methods, “unordered” windings are often manufactured, for reasons of cost. With this type of winding, it is possible to only approximate the subsequent position of the conductor in advance, since the stator winding is often wound onto winding stars, and the winding stars that are produced are then drawn into the stator. Since the configuration and shape, in particular, of the conductor in the winding overhang are not easily influenced, this type of winding is also referred to as a “wild” winding. It has been shown, however, that unordered windings create loud flow noise during operation, and cooling the conductor in the winding overhang evenly is not entirely possible. These disadvantages may be avoided using ordered windings, since, in this case, the conductors have defined positions. These ordered windings are manufactured as plug-in windings. This is a very laborious process, since the individual U-shaped sections of the winding—once they have been inserted in the stator core—must be bent into position and then welded, to establish the electrical contacts. One possibility for simplifying the manufacture of an ordered winding is described in patent application US 2004/0119362 A1 for the simple case of a single-layer wave winding. 
     SUMMARY OF THE INVENTION 
     With a method for producing a stator winding for a stator of an electrical machine, in particular for a motor vehicle, it is provided according to the present invention that the at least one segment of the stator winding is positioned in a plane, and that regions of the segment are bent toward one another along at least one folding line, thereby resulting in a lap winding. The unique characteristic of the method is that the segment is initially positioned in a plane. It should be understood, in particular, that the segment is located, placed, and/or formed in the plane, or it is produced in another manner. This is how the course of the segment within this plane is formed. Via the positioning, the segment in the top layer forms a certain path within the plane. At least one folding line, and usually several folding lines, which are located parallel to each other in particular, are defined within the plane. Regions of the segment are bent toward each other along at this at least one folding line. The topology of the segment in the plane was selected such that a lap winding is produced after the segment has been bent. The starting point, therefore, is a flat winding, in the case of which the segment—when in the flat state—may be offset and/or stamped particularly easily in any desired position. In the finished state, the segment then forms an at least two-layered structure, which is the stator winding for the electrical machine. Since a segment (for a phase) may be produced individually, the significance of this for an electrical machine with several phases is that they may be produced separately. A further advantage is that this is a multi-layered basic structure, i.e., much fewer offsets are required to obtain the finished state than is the case with a single-layer solution. A preferred variant for performing this method includes the following working steps:
     1. Produce/position the flat segment   2. If necessary, stamp/offset the segment at the required points   3. Fold the segment along the at least one folding line.   

     The further processing of a stator winding produced in this manner is also particularly simple. Only the following steps are required:
     1. Insert the winding in the stator core   2. Bend the stator core, if necessary   3. Shape the winding overhang, if necessary   

     An ordered lap winding may be produced very cost-effectively in this manner. 
     Advantageously, in the folded state, at least a first segment comes to rest in parallel with a second segment. Segments that are oriented relative to each other in this manner may be placed in the slots of the stator core later in a particularly easy manner. A “segment” is a section along the extension of a phase winding. The definition of a segment of this type may be purely virtual, i.e., it is not tied to any certain physical characteristics or to any particular interruption of the segment. However, the beginning or end of a phase winding section is often associated with the fact that the segment often changes direction within the plane, e.g., it bends sharply. 
     It is preferred that the positioning of a segment of the phase winding in a first direction of the plane corresponds to a slot number of a subsequent slot position of the phase winding section, and that the positioning of a phase winding segment in a second direction of the plane that is perpendicular to the first direction corresponds to a radial position of the phase winding segment within a slot. A convention of this type simplifies the understanding and realization of the topology of the segment that is required to obtain a certain lap winding. It is then particularly easy to define topologies of the segment, to interpret existing topologies, and to implement desired changes. The work performed based on this principle is explained in greater detail below with reference to the following exemplary embodiments. 
     Advantageously, the segment is positioned in the first direction in a serpentine manner, and/or it is positioned in the second direction in a wave-shaped manner. The serpentine structure ensures that the available plane is utilized in an optimal manner. The wave-shaped positioning in the second direction is a favorable possibility for obtaining the lap winding when the segment is folded. 
     Advantageously, regions in the plane are defined that make it possible to assign segments to at least one winding overhang or to a stator core. This means that, by selecting the topology of the segment, it is possible to specify which segments will lie in the slots of the stator core after the stator winding is produced, and which segments will form the at least one winding overhang. 
     According to a refinement of the present invention, one phase winding segment extends at a slant to the first and second directions in the regions that are assignable to a winding overhang. The technical effect of this procedure is apparent when the following stator winding is considered. For example, such a course of the segment results in the segment being guided further in another slot, and in the radial position of the segment changing within the slot relative to its previous position. A phase winding segment of this type will typically cross the fold line, since the change in the radial position may then be brought about in a particularly simple manner. 
     It is furthermore preferred that the course of a phase winding segment extend parallel to the second direction in the regions that are assignable to a stator core. 
     Advantageously, several segments that extend largely in parallel with each other are used to produce the stator winding. The production of a multi-phase stator winding of this type is realized very easily via repeated application of the method described above. To this end, several segments may be easily manufactured and placed in a magazine before the winding is folded. As soon as the required number of segments in the magazine has been attained, the segment is folded to form the stator winding. 
     The positioning of the segments is preferably designed as a distributed winding. In this manner, the crossings of individual segments are spacially offset, thereby simplifying the handling of the crossings. 
     According to a refinement of the present invention, one end of a phase winding segment that is assignable to a winding overhang leads into a different radial position within a slot than does the other end of this phase winding segment. As a result, the structure of the finished stator winding—which has at least two layers—may be deduced from the topology of the segments in the plane. 
     Advantageously, the number of segments that cross the fold line is equal to the number of slots of the assigned stator core. At least one segment is therefore assigned to each slot in the stator core. 
     It is also advantageous that, for the folded stator winding, the position of the phase winding segments within the slots changes in a radially progressive manner, and the direction of the radial progression is reversed at least one reversal point. This results in a realization of the multi-layered design with a particularly good structure. 
     It is particularly preferred to use a continuous wire for the segment. Even though it is basically possible to also form the segment out of several elements, which are then interconnected electrically, the unique characteristic of the present invention is that a continuous wire may be used. This simplifies manufacture and reduces production costs. 
     According to a refinement of the present invention, a rectangular wire is used for the segment. Particularly high stator fullness factors may be attained as a result. The winding produced with round wire may also be stamped in the slot region after production. This results in a high copper factor. 
     Advantageously, the diameter of the conductor, which forms the phase winding, essentially corresponds to the slot width of the slots in the stator core, or it is greater than the slot width. This prevents or reduces slippage of the conductor in the slots. The stator winding may also be used as an insertion winding for an “open slot” stator core (open slot=stator teeth without crests, and the winding in a round stator core is assembled from the inside). 
     The stator winding is preferably inserted into a flat core. The manufacture of the electrical machine is simplified as a result. 
     According to a preferred refinement of the present invention, the lengths of the phase winding segments located outside of the stator core vary, in particular in order to create a constant winding overhang height. 
     According to a further variant, one layer of the phase winding segments stacked in a slot extends markedly above the other layers, in order to perform a cooling function; this layer is slanted, in particular, toward the inner diameter of the stator. This allows air to flow around the outermost layer particularly well and cool it. 
     The present invention also relates to a stator winding for a stator of an electrical machine, in particular for a motor vehicle, in the case of which the stator winding is designed as a lap winding with at least two layers, using one of the methods described above. The stator winding advantageously has features that it may be attained by using one of the methods described above. 
     Finally, the present invention also relates to an electrical machine, in particular for a motor vehicle, in the case of which a stator winding of the machine is designed as a lap winding with at least two layers, using one of the methods described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be explained in greater detail with reference to the drawing. 
         FIG. 1  shows a flat winding with six phases, five conductors per slot, and 96 slots, 
         FIG. 2  shows a flat winding with six phases, four conductors per slot, and 96 slots, 
         FIG. 3  shows a flat winding with six phases, five conductors per slot, and 96 slots, designed as a distributed winding, 
         FIG. 4  shows a flat winding with three phases, five conductors per slot, and 48 slots, 
         FIG. 5  shows an intermediate step in the production of a 6-phase stator winding, 
         FIG. 6  shows an exemplary embodiment of a fully folded stator winding, 
         FIG. 7  shows different variants of the folding procedure, and 
         FIG. 8  is a symbolic depiction of the difference between a wavy structure and a serpentine structure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A first exemplary embodiment of a flat winding is shown in  FIG. 1 . This is a stator winding  100  with six phases, five conductors per slot, and 96 slots. Stator winding  100  is shown in the unfolded state in this case. To limit the illustration to the essential features, only a portion of the region between slots  19  through  84  is shown. The winding continues in the not-shown region the same as it does in the region shown. Stator winding  100  is composed of six segments. Only first segment  102 , which begins with a segment start  104  in slot  1 , will be discussed here. These descriptions also apply for the further segments, which start in slots  2  through  6 . Segment  102  ends at segment end  106  in slot  91 . Fourfold lines  108  are shown, which extend across all slots. Entire stator winding  100  extends in an XY plane that has a first direction X and a second direction Y. The slots with their ordinal numbers are plotted in increasing order in the X direction. In the Y direction, the segments—including first segment  102 —are subdivided into several regions. A is a region of stator winding  100  that, in the folded state, will lie on the A side of the stator core (connection side), where it forms a first winding overhang. B refers to the second winding overhang, which is located on the “B” side, opposite to the first winding overhang. The regions on the B side are “upside down”. The regions of the segment that will eventually come to rest in the slots of the stator core are labeled “C”). 
     The course of first segment  102  will now be explained, along with the subsequent position of stator winding  100  in the stator core. Beginning with segment start  104 , segment  102  lies initially on the A side, and is guided through the stator core (region C) to the B side. It is assumed that the segment will come to rest in the innermost interior of the slot, i.e., next to the center of the stator. After segment  102  exits the stator core on the B side, it crosses a fold line  108  and is guided to slot  7 . After the obvious change of slots, which occurs when fold line  108  is crossed, segment  102  is now guided further in a different radial position within slot  7  than is the case in slot  1 . When counting starting from the innermost interior of the slot, segment  102  therefore switches from a first layer to a second layer. After this switch, segment  102  in slot  7  is guided through stator core (region C). On the A side, segment  102  is returned from slot  7  to slot  1 , and its radial position within the slot changes. The segment is now guided further in a third layer. Segment  102  is guided back through the stator core, switches slots and the radial position again on the B side, crosses the stator core again, switches from slot  7  to slot  1 , and crosses the stator core again, now in the fifth layer. Back on the B side, segment  102  is guided to a reversal point  110 . Reversal point  110  is described based on the Y direction. From reversal point  110 , segment  102  is now guided back, using slots  7  and  13  in an alternating manner. When viewed radially, segment  102  travels back from the fifth layer to the first layer. The radial direction of motion reverses once more, at reversal point  110 , and continues until segment  102  ends at segment end  106  in slot  91 . 
     Since the segments would come in contact with each other when the subsequent segments are positioned closed to reversal point  110 , segment  102  is now offset in the vicinity of its reversal point  110 . This means that, in this case, the segment portion leading away from reversal point  110  is located a bit lower in the XY plane than is the segment portion leading into reversal point  110 . As a result, the subsequent segments may be guided over the segment section leading away from reversal point  110 . After segment  102  is positioned in the XY plane accordingly, the five subsequent segments are positioned according to the same principle. The topology shown in  FIG. 1  ultimately results. 
     In the next step, the segments are folded along fold lines  108 . In this case, segment regions  112  are folded toward each other, in the manner of an accordion (see  FIG. 7 , a)). Basically, other types of folding techniques may also be used (see, e.g.,  FIG. 7 , c)). The creation of the windings in stator winding  100  is particularly easy to trace by drawing the topology of the segments on a piece of transparent foil and then folding it along fold lines  108 . The windings that are guided, e.g., through slots  1  and  7 , are then clearly visible when viewed from above. It also becomes obvious that segment portions in regions C come to rest in parallel with each other. Segment sections that are located on top of each other are placed in the same slot in the stator core. 
     As shown in the topology, it is clear that the segments are positioned in a serpentine manner in the first direction, and they are positioned in a wave-shaped manner in the second direction. The segments are guided in parallel up to the region of reversal points  110 , where crossovers must occur. 
       FIG. 2  shows a further exemplary embodiment of a flat winding, in this case with six phases, four conductors per slot, and 96 slots. To explain  FIG. 2 , reference is made to the descriptions of  FIG. 1 , which essentially apply here as well. Compared with  FIG. 1 , which shows the embodiment of the present invention for an uneven number of conductors per slot,  FIG. 2  shows the design for an even number of conductors per slot. 
       FIG. 3  shows a further exemplary embodiment of a flat winding, in this case with six phases, five conductors per slot, and 96 slots, in the embodiment as a distributed winding. The term “distributed winding” means that reversal points  110  are now spacially offset. This is made particularly clear in comparison with  FIG. 1 . In  FIG. 1 , six reversal points  110  are located very close to each other, and the individual groups of six reversal points  110  are each separated by a distinct distance. In comparison, two reversal points  110  in  FIG. 3  form one group, and each group is separdated from the other. Spacial offsetting allows the manufacturing process to be simplified. In addition, the regular shape results in the advantage of low flow noise. To explain  FIG. 3 , reference is made to the descriptions of  FIG. 1 , which also apply here. Reference is made only to the special positioning of segment starts  104 ′,  104 ″ and segment ends  106 ′,  106 ″ of the third and four the segment. 
     A further exemplary embodiment Is shown In  FIG. 4 . This is a flat winding with three phases, five conductors per slot, and 96 slots. To explain  FIG. 4 , reference is made to the descriptions of  FIG. 1 , which also apply here. This exemplary embodiment also demonstrates that the present invention may be used in a very flexible manner. 
       FIG. 5  now transitions from the general explanations of the present invention to a specific design of the segments. Three segments of a stator winding  100  are shown, which, in the finished state, will have a 6-phase design. The topology shown in  FIG. 1  is based on the segments. Only first segment  102  will be discussed in the further explanation. In the specific embodiment, it is clear that the first segment includes one offset  114  or several offsets  114  at its reversal points  110 . It is therefore possible to position the individual segments in parallel, without their touching each other. In addition, intermediate pieces  116  serve to ensure that the segment may be guided in the winding overhang in a well-defined manner and without contact. Two fold lines  108 ′ and  108 ″ are used for this purpose between the layers. 
       FIG. 6  shows a fully-folded, six-phase stator winding  100  with all six segments. The transition into the individual layers and the handling of the crossovers at reversal points  110  are clearly shown. Stator winding  10  may be used directly as a flat winding for insertion into a flat stator core, which will be eventually bent into a round shape, or as an “open slot” winding, which is inserted using an inner mandrel from the interior into a round core. 
       FIG. 7  shows various possibilities for folding the segments placed in a plane.  FIG. 7  a) is a five-layer configuration for five conductors per slot. The folding was carried out in the manner of an accordion. With b), the same folding technique is shown for a four-layer configuration. Part c) shows that the individual layers may also be folded around each other, thereby resulting in a spiral. Finally, with d), the same folding technique is shown for a four-layer configuration. 
     In  FIG. 8 , the meaning of “serpentine” and “wave-shaped” is depicted symbolically. In region a), the serpentine positioning of one or more segments in the first direction, X, is shown. In comparison, the wave-shaped positioning in the second direction, Y, is shown in region b). The result is that these structures overlap in a known manner, thereby resulting in the exemplary embodiments described above.