Abstract:
A method for manufacturing multiphase windings ( 32 ) of an electric machine provides the following process steps: Cross-sectional profiles ( 13 ) that increase the slot space factor are stamped onto wire elements ( 7, 11, 12 ). Offsetting dies ( 14, 26 ) are loaded with stamped wire elements ( 7 ) to constitute the winding ( 32 ), stamped wire elements ( 11 ) to constitute an integrated star point ( 21 ), and stamped wire elements ( 12 ) for supplying current to the winding ( 32 ). The offsetting dies ( 14, 26 ) offset the stamped wire elements ( 7, 11, 12 ) in their end regions. An interconnection of the integrated star point ( 21 ) is produced by thermally attaching ( 30 ) the stamped wire elements ( 11 ) for the integrated star point ( 21 ) to a connecting ring ( 40 ) on an inside ( 41 ) of a finished winding head ( 20 ).

Description:
CROSS-REFERENCE 
     The invention described and claimed hereinbelow is also described in PCT/DE 2004/000214, filed Feb. 9, 2004 and DE 103 15 361.6, filed Apr. 3, 2003. 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 
     Windings for electric machines such as asynchronous motors can be manufactured by means of the threading technique. In the manufacture of windings for electric machines, the threading technique is used for low-voltage motors operated at voltages below 50 V and in electric motors operated with higher voltages. When manufacturing windings for low-voltage motors (operating voltage=to 50 V), the windings are manufactured out of parallel wires in order to assure the required winding cross section. 
     Low-voltage motors that are operated with operating voltages below 50 V are used in steering motors for vehicles or for actuators used in vehicles. Electrical systems in motor vehicles today are generally designed as 12 V electrical systems; judging from current development trends, the use of 42 V electrical systems in motor vehicles could conceivably become the new standard. Both electrical system voltages, i.e. an electrical system voltage of 12 V and an electrical system voltage of 42 V, permit the use of low-voltage motors embodied in the form of asynchronous motors, which can be operated with an operating voltage of=50 V. The windings of low-voltage motors are produced from parallel wires in order to assure the winding cross section that these electric machines require. But producing windings for low-voltage motors, e.g. asynchronous motors, out of parallel individual wires results in a high degree of wiring complexity at the ends of the winding, which is generally manufactured by hand. 
     The windings for asynchronous motors manufactured out of parallel wires using the threading technique also have the disadvantage that the threading technique permits only a low slot space factor to be achieved. Because of the low level of utilization of the slots into which the parallel wires are inserted, in order to achieve sufficient winding cross sections, a larger number of slots are required, which in turn requires a large structural volume in electrical machines that can be operated in the low-voltage range below 50 V, for example of the kind represented by asynchronous motors used as steering motors. 
     When manufacturing DC motors, it is also known to use the plugging technique to manufacture winding cores. 
     According to the threading technique, see “Technologie des Elektromaschinenbau&#39;s” [Technology of Electric Machine Engineering] by R. Tzscheutschler, H. Olbrich, and W. Jordan, Verlag Technik GmbH, Berlin, p. 336, Technological Principles For Manufacturing Windings, loose prewound coils of enameled copper wire are inserted into half-closed slots. The threading process is used to wind stators. Depending on the stroke speed of a hydraulic cylinder and the stator core length, a coil side, a coil, or even an entire winding can be threaded in a slot-filling manner; it is also possible to insert cover insulating caps at the same time. The fundamental principle is based on the fact that the coil sides are narrowed to less than the slot width and protected from the slot edges in order to be threaded into the slots through the exertion of force on the front end by means of a stroke motion. The alignment of the wires and the protection from the slot edges can be achieved by means of polished steel profiles that are also referred to as threading needles. In the threading tool, the threading needles are adapted to a particular stator plate cut and to the core length. The coils are wound or suspended in accordance with the winding scheme. 
     At the end of the threading process, it is typical for the layer of threaded coils to be S-shaped in the longitudinal section of the stator. In addition, the coils often are not centered in relation to the stator. At the point at which they emerge, the coil ends bridge over the bore space in a sinuous fashion, which occurs to a particularly pronounced degree in bipolar windings. Additional threading procedures thus require intermediate shaping operations. 
     The threading method can be used to produce 1-phase 2-phase, and 3-phase windings with an arbitrary number of poles. Preferably, they are embodied in the form of single-layer windings with flat arrangements of the winding heads. Two-layer windings can be produced in two threading steps; a covering cap profile should be used for intermediate insulation. 
     SUMMARY OF THE INVENTION 
     The method proposed according to the present invention for manufacturing 3-phase windings with interconnection can be used to achieve high slot space factors, which can only be achieved to a limited degree using the threading technique. Due to the high slot space factors that can be achieved, it is possible to reduce the structural volume of 3-phase windings produced using the method according to the present invention. Moreover, using the method proposed according to the present invention, makes it possible to achieve an automatable manufacture of the windings. Integrally joining the interconnection of the star point to one side of a stator of an electric machine makes it possible to eliminate the previously required separate, manually executed work steps when manufacturing 3-phase windings. The interconnection of the star point can be integrated into the manufacture of the 3-phase windings, thus permitting the achievement of an automatable manufacture of the winding on the one hand and an automatable manufacture of the star point during the same manufacturing process on the other. 
     Another advantage of the method proposed according to present invention is that it permits the achievement of a compact star point arrangement with a minimized structural volume since the manufacture of the star point can be carried out in the course of the same manufacturing process, on one and the same tool-mounting socket. In addition to the integration of the interconnection of the star point arrangement, the method proposed according to the present invention permits wire elements that are stamped with a wedge shape to be used in the shaping of the winding head. Wire elements that are stamped with a wedge shape can be advantageously used to achieve an improved utilization of the slot to increase the slot space factor of an electric machine. This in turn permits an increase in the specific output per unit of structural volume of an electric machine. 
     As a rule, 3-phase windings or rectangular wire windings are manufactured out of stamped round wire shaped elements that can be embodied in the form of U-shaped elements, straight phase wires, an endless wire when using the threading technique, or straight star point wires provided with an offset. 
     According to the method proposed according to present invention, the round wire is first stamped or rolled into a wedge shape. In another work step of the method proposed according to present invention, the wires are positioned in a device for shaping the winding. The star wires, phase wires, and U-shaped elements are inserted at appropriate positions and the winding head to be produced is shaped into a compact form through a subsequent offsetting of the winding templates in relation to each other. The wire cage thus produced is slid into a prepared laminated core by means of an insertion apparatus; the prepared core can either contain paper insulation or an insulation has been produced by means of powder coating. 
     An offsetting on the opposite side yields a winding pitch. After the conductor elements are attached by means of a thermal joining process, for example by means of resistance welding, laser beam welding, electron beam welding, or soldering, an automatic contacting of the star point is executed. In addition to using an integral joining method to attach the conductor elements, they can also be attached by means of hot pressing or by means of a cold contacting technique such as riveting or crimping. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described in greater detail below in conjunction with the drawings. 
         FIG. 1  shows a stamping device for shaping winding wires, 
         FIGS. 2   a ,  2   b  and  2   c  show various embodiment variants of wire elements for manufacturing windings, 
         FIG. 3  is a top view of the offsetting die, 
         FIG. 4  shows the wire elements, part of which are inserted into a offsetting die for the shaping of the winding head, 
         FIG. 5  shows a finished shaped winding head with an integrated star point, 
         FIG. 6  shows an ejected wire basket for insertion into a laminated core, 
         FIG. 7  shows the step in which the wire basket and the laminated core are joined, 
         FIG. 8  shows the offsetting die on the connection side of the winding, 
         FIG. 9  shows the connection side of the winding, 
         FIG. 10  shows the integral connection on the connection side, 
         FIG. 11  shows the welding of the star point on the star point side of the winding, 
         FIGS. 12   a ,  12   b ,  12   c  respectively show a top view, side view, and enlarged detail of the star point side of a first winding variant, 
         FIGS. 13   a ,  13   b ,  13   c  respectively show a top view, side view, and enlarged detail of the star point side of a second winding variant, and 
         FIGS. 14   a ,  14   b ,  14   c  respectively show a top view, side view, and enlarged detail of the star point side of a third winding variant. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a stamping device for shaping wire elements used as winding material. 
     A stamping die  1  schematically depicted in  FIG. 1  is used to deform a wire material that is supplied in a rod-shaped form. The wire material  3  supplied in a rod-shaped form travels through a material inlet  6  to the region between a first shaping part  4  and a second shaping part  5 . The two shaping parts  4 ,  5  are accommodated in stamping parts of the stamping die  1 , which can be moved toward or away from each other by means of hydraulic pistons  2 . Instead of hydraulic pistons  2 , it is also possible to use pneumatic cylinders or electric drive units to move the shaping parts  4 ,  5  toward or away from each other. In accordance with the design of the first shaping part  4  and the second shaping part  5 , which is complementary to the shape of the first shaping part  4 , a wedge shape  13 , for example, can be stamped onto the rod-shaped wire material  3  traveling into the stamping die  1  via the material inlet  6  (see  FIG. 2 ). 
     In addition to the wedge shape  13 , the stamping die  1  can also stamp the incoming rod-shaped wire material  3  into a different geometry, which increases the slot space factor of slots in an electrical machine. 
       FIGS. 2   a ,  2   b  and  2   c  show various embodiment variants of wire elements for manufacturing multiphase windings. 
     According to  FIG. 2   a , a U-shaped element  7 , which has passed through the stamping die  1  shown in  FIG. 1  before a bending process and is therefore provided with a wedge shape  13  in the region of both of its legs, is bent at a rounded part  10  so that the two legs of the U-shaped element  7  respectively end at a first wire end  8  and a second wire end  9 . In the subsequent manufacture of a winding  32  (see  FIGS. 6 and 7 ), the rounded parts  10  are situated on the outside of a star point side, whereas the wire ends  8 ,  9  are situated on the connection side of the winding  32 . In the production of the U-shaped elements  7 , a bending step can occur first, followed by a stamping step, but the production sequence can also occur in the reverse order. The above-mentioned sequence of production steps applies to the U-shaped elements  7 , the star point wires  11 , and the phase wires  12  in a corresponding way. 
       FIG. 2   b  shows a star point wire  11  that also has the wedge shape  13  stamped onto it. The star point wire  11  has an end piece that is bent at a 90° angle in relation to the rest of the wire and is integrally attached to a star point ring during the manufacture of the winding. 
     In addition,  FIG. 2   c  shows a phase wire  12  that also has the wedge shape  13  stamped onto it, which significantly improves the slot space factor in a winding of an electric machine. The offset of the phase wire  12  shown in  FIG. 2   c  is a result of the shaping of the winding head. First, the phase wires  12 , which are embodied as straight, are inserted into an offsetting die. In principle, it is possible for the phase wires  12 , which are straight at first, to remain straight during the shaping of the winding head; the phase wire  12  offset depicted in  FIG. 2   c  can be produced in them as a function of the pitch diameter of the offsetting die used. 
       FIG. 3  is a top view of an offsetting die. 
     The offsetting die  14  depicted in  FIG. 3  has an outer disk  15  that is stationary and an inner disk  16  that can be rotated in relation to the stationary outer disk  15 . It is also possible for both the outer disk  15  and the inner disk  16  of the offsetting die  14  to be mobile. Both embodiment variants of the offsetting die  14  allow a relative movement of an outer disk  15  in relation to an inner disk  16  to occur, which makes it possible to execute a offsetting to shape a winding head. 
     The inner circumference of the outer disk  15  is provided with first openings  17  that are spaced apart from one another at regular intervals and have an approximately wedge-shaped opening cross section. The outer circumference of the inner disk  16  is provided with second openings  18 , which likewise have an approximately wedge-shaped opening cross section and are spaced apart from one another at intervals identical to the spacing of the first openings  17  on the inner circumference of the stationary outer disk  15 . Rotating the inner disk  16  in relation to the stationary outer disk  15  produces an offsetting of U-shaped elements  7  shown in  FIG. 2 , which are inserted into the first openings  17  and second openings  18 . 
       FIG. 4  shows an offsetting die into which part of the wire elements are inserted for the shaping of a winding head. 
     The offsetting die  14  shown in a perspective top view in  FIG. 4  is equipped with the stationary outer disk  15  and the inner disk  16  that can rotate in relation to it. The first openings  17  of the stationary outer disk  15  are arranged in a ring around the second openings  18  provided in the outer circumference surface of the inner disk  16 . Both the first openings  17  and the second openings  18  have an essentially wedge-shaped cross section that is complementary to the wedge shape  13  of the wire elements  7 ,  11 , and  12  depicted in  FIG. 2 . 
     In  FIG. 4 , the legs of the U-shaped elements  7  are inserted into the first openings  17  and second openings  18  so that their rounded parts  10  are situated on a star point side  23  of a winding yet to be produced. In addition, a star point wire  11  is inserted into a second opening  18  on the outer circumference of the inner disk  16  and its end oriented toward the star point side  23  is bent at an angle. Aligned with the star point wire  11  that has the bent end, a conductor element  19  is inserted into the corresponding first opening  17  on the inner circumference of the stationary outer disk  15 . The conductor element  19  is a phase wire. This serves to supply current to the winding of the 3-phase winding or rectangular wire winding to be produced; using a rigid, thick wire as a conductor element  19  offers the possibility of embodying the current connection of the finished winding directly on this conductor element, e.g. in the form of a plug contact. 
       FIG. 5  shows a finished shaped winding head with an integrated star point. 
     After the U-shaped elements  7  are inserted into the corresponding openings  17  and  18  in the outer disk  15  and inner disk  16 , an offsetting of the U-shaped elements  7  occurs, i.e. the two legs of the U-shaped elements  7  contained in the offsetting dies  14  are moved in relation to each other.  FIG. 5  is a perspective top view of the resulting winding head  20 . The winding head  20  has an integrated star point  21 , which is produced in a single work step with the offsetting of the U-shaped elements  7  inserted into the openings  17  and  18 . The bent ends of the star point wires  11  point toward one another in the shape of a star. In  FIG. 5 , the wire basket produced during the offsetting is still enclosed in the offsetting die  14  and is not shown. The conductor elements  19  that will supply current to the finished winding are situated on the outside of the winding head  20 , opposite the individual star point wires  11 . The shape of the winding head  20  shown in  FIG. 5  is the result of an offsetting, i.e. a relative movement of the inner disk  16  and outer disk  15  of the offsetting die  14  in accordance with a winding template. 
       FIG. 6  shows a wire basket that has been ejected from a die and is ready to be inserted into a laminated core of an electric machine. 
     The depiction according to  FIG. 6  shows the winding head  20  on the star point side  23  of a wire basket  22 . Offset winding wires  27  that have a wedge-shaped cross section are depicted underneath the winding head  20 . The circumference surface of the wire basket  22  is comprised of the U-shaped elements  7  whose upper region underneath a rounded part  10  is provided with an offset  27 ; beneath the offset  27 , the U-shaped elements  7  extend essentially vertically in relation to one another. On the star point side  23  of the winding head  20 , the star point wires  11  are depicted, whose ends point toward one another and are connected to one another by means of a star point ring that is not shown in  FIG. 6 . The conductor elements  19  that will later supply current to the as yet unfinished winding are situated on the outside of the winding head  20 , arranged opposite the star point wires  11 . 
       FIG. 7  shows the process in which the wire basket and the laminated core of an electric machine are joined to each other. 
     An insertion device that is only indicated schematically in  FIG. 7  is equipped with a die, which, with the interposition of a transmitting element, slides the wire basket  22  in the direction of the arrow into a laminated core. The transmitting element is placed onto the star point side  23  of the wire basket  22  in order to protect the winding head  20  of the star point  21  integrated into it and in order to protect the conductor elements  19 . The laminated core  24  can already be provided with a paper insulation; it is also possible for the insulation to be provided by means of a powder-coating process. In the joining procedure according to  FIG. 7 , the laminated core  24  is insulated by means of one of the above-mentioned insulation methods. 
       FIG. 8  shows the connection side of the winding. 
     The top view according to  FIG. 8  shows that on the connection side  25  of the winding, the first wire ends  8  and the second wire ends  9  of the U-shaped elements  7  are arranged opposite one another. Offset winding wires  27  are situated underneath the wire ends  8  and  9 , which lie in an essentially flat plane. The offsetting on the connection side  25  of the winding is produced by means of a relative movement of the offsetting die  14  in relation to a stationary part of the offsetting die  26 ; the legs of the U-shaped elements  7 , not shown in  FIG. 8 , which extend parallel to each other and are connected by the rounded part  10  on the star point side  23  of the winding, essentially pass through this offsetting die  26 . 
       FIG. 9  shows the offsetting socket the connection side of the winding. 
     On the connection side  25  of the finished winding  32 , the ends  8  and  9  of the offset winding wires  27  are arranged opposite one another in two concentric circles. The U-shaped elements  7  also have a wedge-shaped cross section  13  inside the offset section on the connection side  25  of the winding  32 . 
       FIG. 10  shows the production of the integral connection on the connection side of the winding  32 . 
     In the depiction in  FIG. 10 , the connection side  25  of the winding  32  protrudes out from the offsetting socket. The offset winding wires  27  have the wedge-shaped cross section  13  produced in the stamping die  1  according to  FIG. 1 . The first wire ends  8  and second wire ends  9  of the U-shaped elements  7  are spaced apart from each other on the connection side  25 . A first jaw  28  and a second jaw  29  opposite from it squeeze the ends  8  and  9  of each U-shaped element  7  toward each other before an integral connection is produced on the connection side  25  of the winding  32 . 
       FIG. 11  shows the production of an integral connection on the star point side  23  of the winding. 
     The winding head  20  of the winding encased by the laminated core  24  is situated on the star point side  23 . On the inside of the winding head  20 , the bent ends of three star point wires  11  point toward one another. The individual bent ends of the star point wires  11  are integrally attached to a star point ring  40 . The integral attachment of the bent ends of the star point wires  11  to the star point ring  40  can be produced by means of resistance welding, laser welding, electron beam welding, or soldering; it is also possible to use cold forming attachment techniques to attach the bent ends of the star point wires  11  to the star point ring  40 . Hot pressing can achieve an automatic contacting of the bent ends of the phase wires  11  with the star point ring  40 , thus yielding the integrated star point  21 . Protruding from the connection side  23  of the winding head  20 , next to the bent ends of the star point wires  11 , the conductor elements  19  extend upward from the surface of the winding head  20 . 
     The depiction in  FIG. 11  also shows that beneath the offset winding wires  27  of the winding, the wires are encompassed by insulation  31 . The insulation  31 , which is produced or example by means of powder coating or in the form of paper tubes, is provided inside the laminated core  24  before the execution of the procedure joining the wire basket  22  (see  FIG. 7 ) to the prefabricated laminated core  24 . 
     The positioning of the star point ring  40  above the winding head  20  makes it advantageously possible for the inner diameter of the laminated core  24  to not require any reduction. Due to the positioning of the star point ring  40  on the inside  41  of the winding head  20 , it is also possible to reduce the structural length of the finished winding  32 . Another advantage is that no additional insulation elements such as plastic masks or insulating paper are required. 
       FIGS. 12   a ,  12   b ,  12   c ;  13   a ,  13   b ,  13   c ; and  14   a ,  14   b ,  14   c  show different embodiment variants of windings  32  manufactured using the method proposed according to the present invention. 
     These windings  32  can be used, for example, in electric machines such as asynchronous motors designed for use in the low-voltage range. With regard to their use in motor vehicles, electric machines embodied in the form of asynchronous motors can be used as steering motors, fan drives, hydraulic drives, and actuating drives. Asynchronous motors whose windings have been manufactured using the above-described method can also be used as drive units for forklifts or other factory trucks. 
     A top view, side view, and enlarged detail of the star point side are shown for a first variant in  FIGS. 12   a ,  12   b , and  12   c , for a second variant in  FIGS. 13   a ,  13   b , and  13   c , and for a third variant in  FIGS. 14   a ,  14   b , and  14   c.    
     In each of the embodiment variants shown in a top view in  FIGS. 12   a ,  13   a , and  14   a , the laminated core  24  encloses the winding  32 . The star point ring  40  is always positioned on the inside  41  of the winding head  20  thus permitting an advantageous reduction in the structural length of the winding  32 . 
     In the embodiment variant according to  FIG. 13   a , the star point ring  40  is provided with three recesses  45  spaced apart from one another by 120°, whereas in the embodiment variant depicted in the top view, the star point ring  40  is provided with individual loops  44  also spaced apart from one another by 120°. In all of the embodiment variants shown in a top view in  FIGS. 12   a ,  13   a , and  14   a , the star point ring  40  is positioned with its integral connection above the winding head  20  so that it is not necessary to reduce the inner diameter of the laminated core  24  encompassing the winding  32 . 
     The side views of the embodiment variants of the winding  32  shown in  FIGS. 12   b ,  13   b , and  14   b  demonstrate that the winding  32  is encompassed by the laminated core  24  between the star point side  23  and the connection side  25 . Offset winding wires  27  are visible on both the connection side  25  and on the star point side  23 . The laminated core  24  encompasses the winding  32  essentially in the region in which the U-shaped elements  7  extend strictly parallel to one another in the wire basket  22 . On the star point side  23 , the star point ring  40  is shown situated on the inside of the winding head  20 . The windings  32  are embodied analogously in the side views in the figure sequences B and C. 
     The individual embodiment variants of the winding  32  depicted in  FIGS. 12   a ,  12   b ,  12   c ;  13   a ,  13   b ,  13   c ; and  14   a ,  14   b ,  14   c  differ from one another in the embodiment of the star point ring  40 . 
     According to  FIG. 12   c , the star point ring  40  is situated against the winding head  20 , which is encompassed by the laminated core  24  and is comprised of the rounded parts  10  of the U-shaped elements  7 . A second connection  43  is provided on this star point ring  40  opposite which a first connection  42  is provided. The first connection  42  according to  FIG. 12   c  corresponds to the conductor element  19 , which serves to supply current to the winding  32 . 
     The enlarged detail shown in  FIG. 13   c  shows that the star point ring  40  encompasses the second connections  43  in the region of recesses  45  provided in the star point ring  40 . The rounded parts  10  of the U-shaped elements  7  constitute the top of the winding head  20 . The laminated core  24  encompasses the outside of the winding  32 . This perspective view clearly depicts the wedge shape  13  of the U-shaped elements  7 . 
     The enlarged detail of the winding  32  according to  FIG. 14   c  shows that the second connections  43  are encompassed by loops  44 , which encompass the outside of the star point ring  40  like a belt. The laminated core  24  encompasses the outside of the winding. The second connection  43  is aligned with a first connection  42  that corresponds to the conductor element  19  for supplying current to the winding  32 . The two connections  42 ,  43  are spaced apart from each other in the radial direction. The enlarged details of the figure sequence A, B, and C show that the star point ring  40 , the star point ring  40  with recesses  45 , and the star point ring  40  whose outside is encompassed by a ring with loops  44 , respectively, rest against the inside  41  of the winding head  20 . This achieves a significant reduction in the structural length of the winding  32  manufactured according to the present invention. 
     On the one hand, the winding  32  described above features a high slot space factor due to the wedge shape  13  stamped onto the U-shaped elements  7 ,  11 , and  20 . In addition, the manufacture of the winding  32  can be automated and in a particularly advantageous way, the interconnection of an integrated star point  21  can take place during production of the winding  32 . The method proposed according to the present invention also makes it possible to automate the interconnection of the integrated star point  21 . Furthermore, the winding  32  with the integrated star point  21  features a compact design with a minimized structural volume. 
     REFERENCE NUMERAL LIST 
     
         
           1  stamping die 
           2  hydraulic piston 
           3  wire material in rod form 
           4  first shaping part 
           5  second shaping part 
           6  material inlet 
           7  U-shaped element 
           8  first wire end 
           9  second wire end 
           10  rounded part 
           11  star point wire 
           12  phase wire 
           13  wedge shape 
           14  offsetting die 
           15  outer disk 
           16  inner disk 
           17  first openings 
           18  second openings 
           19  conductor element for supplying current to winding  32   
           20  winding head 
           21  integrated star point 
           22  wire basket 
           23  star point side 
           24  laminated core 
           25  connection side 
           26  offsetting die 
           27  offset winding wires 
           28  first jaw 
           29  second jaw 
           30  star point side weld 
           31  insulation 
           32  winding 
           40  star point ring 
           41  inside of winding head 
           42  first connection 
           43  second connection 
           44  loop 
           45  recess