Abstract:
Method for stamping multiple coil sides ( 96 ) for a stator winding ( 18 ), characterized in that the multiple coil sides ( 96 ) are arranged in a grooved row ( 90 ), the shaping process taking place at a force (F), the direction of which runs at an angle (α) greater than zero relative to the grooved row ( 90 ).

Description:
BACKGROUND OF THE INVENTION 
     When designing the slot geometry in the stator core of electrical machines, the electrical filling factor, that is to say the quotient of copper area to slot area, is a critical parameter for describing the performance or the efficiency of the overall system. Conventional stator production methods, for example the pull-in method, allow values of from 40% to a maximum of 50% of electrical filling. 
     In order to further increase these values, the wires in the slot region can be compressed by a stamping process, see WO-2001054254 A1 for example. A region of over 60% of electrical filling can be achieved in the stator slots as a result. Assuming certain structural dependencies are taken into consideration (for example compact design of the winding heads, . . . ), more electrical power can be generated with relatively small structural volumes with less material being used. 
     Certain boundary conditions are of critical importance when technically implementing the stamping process: for example, wire crossings in the slot region can lead to pinching with a greatly reduced cross section, this leading to local overheating, and the corresponding consequences, during operation due to an increased non-reactive resistance. 
     High electrical filling factors are made possible particularly due to high mechanical filling in the stamping tools, and therefore the aim is to fill the stamping slot virtually to 100% taking into account the possible wire tolerances. However, this requires all the wires in the slot region to be deformed as uniformly as possible. 
     This requirement is not met if an expedient stamping direction is not chosen. If the wire is stamped in the radial direction (in the direction of the slot height), the wire, which is in contact with the stamping punch, will be deformed to an overproportional extent in comparison to the wire in the stamped slot base because the stamping pressure is not uniformly distributed within the slot due to mechanical friction and other influences. Purely on a calculation basis, a stamped slot filling of greater than 100% is established on the stamping punch. As a result, copper is pushed into the winding heads and therefore into the electromagnetically inactive region of the machine in the longitudinal direction of the wire. Therefore, the wire cannot be stamped in an optimum manner. 
     SUMMARY OF THE INVENTION 
     The invention provides a method for stamping a plurality of coil sides for a stator winding, characterized in that the plurality of coil sides are arranged in a slot row, wherein shaping is performed by means of a force, the direction of this force being at an angle of greater than zero in relation to the slot row. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in greater detail in the text which follows by way of example and using the figures, in which: 
         FIG. 1  shows a longitudinal section through an electrical machine, 
         FIG. 2  shows a row of round wires or coil sides which are intended to be shaped to have parallel flanks, 
         FIG. 3  shows a row of previously round wires which have been shaped to have parallel flanks and have been inserted into a slot after insulation, 
         FIG. 4  shows a row of round wires or coil sides which are intended to be shaped to be trapezoidal, 
         FIG. 5  shows two half-rows of round wires or coil sides which are intended to be shaped to have parallel flanks, 
         FIG. 6  shows four half-rows or two halves of complete-rows of round wires or coil sides with an even number of coil sides which are intended to be shaped to be trapezoidal, and 
         FIG. 7  shows four row elements or two divided complete rows of round wires or coil sides with an odd number of coil sides/rows which are intended to be shaped to be trapezoidal. 
     
    
    
     The envelope curve illustrated in the figures represents the contour of the rows which is intended to be achieved after shaping. 
     DETAILED DESCRIPTION 
       FIG. 1  shows a longitudinal section through an electrical machine  10 , in this case in the form of a generator or AC generator for motor vehicles. This electrical machine  10  has, amongst other things, a two-part housing  13  which comprises a first end plate  13 . 1  and a second end plate  13 . 2 . The end plate  13 . 1  and the end plate  13 . 2  accommodate what is known as a stator  16  between them, said stator firstly comprising a substantially ring-like stator core  17 , and a stator winding  18  being inserted into the radially inwardly directed, axially extending slots in said stator. This annular stator  16 , by way of its radially inwardly directed slotted surface, surrounds a rotor  20  which is in the form of a claw pole rotor. The rotor  20  comprises, amongst other things, two claw pole printed circuits  22  and  23 , with claw pole fingers  24  and  25  which each extend in the axial direction being arranged on the outer circumference thereof. The two claw pole printed circuits  22  and  23  are arranged in the rotor  20  in such a way that their claw pole fingers  24  and, respectively,  25  which extend in the axial direction alternate with one another on the circumference of the rotor  20 . This produces magnetically required intermediate spaces between the claw pole fingers  24  and  25  which are magnetized in opposite directions, said intermediate spaces being called claw pole intermediate spaces. The rotor  20  is rotatably mounted by means of a shaft  27  and in each case one rolling bearing  28 , which is located on in each case one rotor side, in the respective end plates  13 . 1  and  13 . 2 . 
     The rotor  20  has a total of two axial end faces to which a fan  30  is attached in each case. This fan  30  substantially comprises a plate-like or disk-like section from which fan blades extend in a known manner. These fans  30  are used to allow air to be exchanged between the outside of the electrical machine  10  and the interior space in the electrical machine  10  via openings  40  in the end plates  13 . 1  and  13 . 2 . To this end, the openings  40  are provided substantially at the axial ends of the end plates  13 . 1  and  13 . 2 , cooling air being drawn into the interior space in the electrical machine  10  by means of the fans  30  via said openings. This cooling air is accelerated radially outward due to the rotation of the fans  30 , and therefore said cooling air can pass through the winding overhang  45  which is permeable to cooling air. As a result of this effect, the winding overhang  45  is cooled. After passing through the winding overhang  45  or after flowing around said winding overhang  45 , the cooling air moves radially outward through openings—not illustrated in  FIG. 1  in this case. 
     A protective cap  47  which protects various components against environmental influences is located on the right-hand side of  FIG. 1 . This protective cap  47  covers, for example, what is known as a slip ring assembly  49  which serves to supply field current to a field winding  51 . A heat sink  53 , which acts as a positive heat sink in this case, is arranged around this slip ring assembly  49 . The end plate  13 . 2  acts as what is known as a negative heat sink. A connection plate  56  is arranged between the end plate  13 . 2  and the heat sink  53 , said connection plate serving to connect negative diodes  58  which are arranged in the end plate  13 . 2  and positive diodes—not shown in this illustration in this case—in the heat sink  53  to one another and thereby to establish a bridge circuit which is known per se. 
     Description of the Shaping Process 
       FIG. 2  shows a slot row  90  of round wires  93  or coil sides  96  which are intended to be shaped to have parallel flanks Given the desired slot geometry with parallel flanks, also see  FIG. 3  with a slot  99 , all the round wires  93  are uniformly deformed, and accordingly the slot  99  can be filled to a uniform level. Wire damage is not expected. This provides a method for stamping a plurality of coils sides  96  for a stator winding  18 , wherein the plurality of coil sides  96  are arranged in a slot row  90 , wherein shaping is performed by means of a force F, the direction of this force being at an angle α of greater than zero in relation to the slot row  90 . The angle α is virtually or exactly 90°. The slot row  90  defines a direction in which the round wires  93  are stacked The angle α proceeds from this direction. 
     In respect of the direction of the forces F which are directed toward one another, provision can be also made, as an alternative, for the forces F to be oriented such that they act diagonally through the slot row  90 . With reference to the result illustrated in  FIG. 3 , this means that the forces act, for example, firstly from the slot base at the bottom left and secondly from the slot slit side at the top right. Alternatively, provision is made for the forces F to act at an angle α &gt;45° in relation to one another. The observations in this paragraph also apply to trapezoidal slot geometries. 
     When using trapezoidal slot geometries,  FIG. 4 , similar problems to those encountered with radial stamping are also encountered with tangential stamping in a stamping chamber  102 . The deformations in the upper narrow region of the stamping chamber  102  are not ideal, and the deformations in the broad region of the slot  99  (bottom) are not ideal either. 
       FIGS. 5, 6 and 7  illustrate how stator windings or rows  90  of round wires  93  or coil sides  96  are stamped in two stamping chambers  102 . Optimized electromagnetic designs with electrical filling factors of greater than 60% can be implemented by mechanical filling to a uniform level in the chambers. Stator slot designs with trapezoidal slot shapes draw particular benefit from this principle. 
     Uniform mechanical filling of the stamping slots can be achieved by using two stamping chambers  102 . Taking into consideration the possible wire tolerances, this allows a filling level of the stamping slot of virtually 100%. Therefore, optimized electromagnetic designs with electrical filling levels of greater than 60% are possible (see  FIG. 5 ). 
     The invention provides a method wherein the coil sides  96  are arranged in a plurality of row elements  110 , wherein a plurality of row elements  110  form a slot row  90 . 
       FIGS. 6 and 7  provide a method wherein the coil sides  96  are arranged in a plurality of row elements  110 , wherein a plurality of row elements  110  form a slot row  90  and a plurality of slot rows  90  are provided for each slot  99 . The row elements  110  of a slot row  90  have a different number of coil sides  96 . 
     The row elements  110  are stamped in stamping chambers  102  which are separated from one another. 
     Calculated stamped slot filling levels of greater than 100% in subregions of the slot are avoided by means of two stamping chambers. Impermissible deformations on individual wires no longer occur and copper is not pushed into the electromagnetically inactive winding heads in the longitudinal direction (perpendicular to the plane of the illustration). That is to say, the calculated optimized design is also used in reality. 
     Designs with trapezoidal slots can also be implemented with two separated stamping chambers in particular. Compensation movements between the narrow and broad region of the stamping chamber are not necessary. Influences which are difficult to control, for example the friction within the stamping chamber, have no influence on the design quality. There is no restriction in respect of the slot shape in this case; in particular, different trapezoidal shapes can be produced. 
     The proposed principle can be used for various designs. Both single-row wire arrangements, for example in a 5-phase system with 80 slots (see  FIG. 5 ), and also double-row arrangements, for example in a 3-phase system with 48 slots (see  FIG. 6 ), can be realized. Further multi-row arrangements are feasible in principle, the number of slots or number of poles in the design being arbitrary. Furthermore, designs with an odd number of conductors can also be constructed given corresponding calculation of the stamping chamber areas (see  FIG. 7 ). 
     Stamping in two chambers generates a clear and above all reproducible separation plane between the slot upper layer and the slot lower layer. Different conditions within the stamping slot, for example friction, wire strength or wire diameter, have no influence on this separation plane. This can be highly advantageous in subsequent process steps: for example, a setting process of the coil elements can be performed along this separation plane. 
     Provision is made of a stator having a stator winding ( 18 ) which is produced in accordance with one of the method steps presented here.