Abstract:
The invention relates to a commutator for an electrical machine, having a commutator body on the outer circumference of which a plurality of electrically conductive, elongated laminations are disposed parallel to the longitudinal axis of the commutator. The laminations disposed adjacent to one another are electrically insulated from one another. The ends of the laminations, oriented toward the wire windings of an armature, are each electrically conductively connected to at least one wire end. According to the invention, it is provided that the ends of the laminations end, perpendicular to the longitudinal axis of the commutator, in planes offset from one another.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based on German Patent Application 10 2009 054 651.0 filed on Dec. 15, 2009. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a commutator for an electrical machine. 
         [0004]    2. Description of the Prior Art 
         [0005]    One such commutator is already general prior art in a direct current motor, and has laminations disposed on a commutator body that are electrically contacted or connected, on the side toward one winding side of an armature, to the winding ends of the wire windings. As a result of the centrifugal forces engendered by the rotation of the armature, the connections between the wire ends or winding ends and the laminations must be embodied so as to be stable, even at relatively high rotary speeds of the armature. 
         [0006]    It is therefore known for the ends, toward the wire windings, of the laminations to be bent over radially outward and back, so that the ends of the laminations point away from the wire windings. This hooklike embodiment of the lamination ends ensures a secure physical contact or in other words fastening of the winding ends on the lamination ends. 
         [0007]    It is furthermore known for slots, in which the ends of the wire or winding can be placed, to be embodied on the laminations. By way of the winding ends, fixed in the slots in particular by soldered or welded connections, a secure connection can likewise be achieved. In commutators with slots on the lamination end, the maximum diameter of the winding wires is restricted by the width at the lamination end, or by the diameter of the lamination face. So that the winding wires can be connected securely to the laminations, additional provisions are therefore necessary. In commutators with hooklike lamination ends, and especially with a high number of laminations, the diameter of the commutator body and the disposition of the laminations are critical, in the sense that the ends of adjacent windings must be prevented from touching in the vicinity of the laminations, because that could lead to a short circuit between the affected windings. 
         [0008]    One provision for reducing or preventing the problems discussed is to reduce the number of laminations, or to reduce the wire diameter of the windings. Another provision is to increase the diameter of the lamination face or to use a plurality of thinner, parallel-connected wires. However, all of these provisions can lead to unwanted properties of the electrical machine. For instance, the geometric replaceability of rotors or machines from the same series for different operating voltages can prove difficult. It is also conceivable that the service life of the carbon brushes and/or of the commutator will be shortened. Furthermore, heating of the windings, reduced efficiency, or running noise can occur. Because of the relatively high power density, these effects are more highly pronounced in relatively small electrical machines than in larger ones. 
       OBJECT AND SUMMARY OF THE INVENTION 
       [0009]    With the prior art described as its point of departure, the object of the invention is to refine a commutator for an electrical machine, in such a way that while the diameter of the commutator is unchanged compared to the prior art, the use of relatively thick winding wires is made possible, without functional impairments or other worsening of the electrical properties of the electrical machine during assembly or operation. 
         [0010]    The invention is based on the concept of creating additional free spaces or additional attachment spaces for the wire ends or winding ends by means of an offset arrangement of the various ends of the laminations, so that these ends, despite the use of relatively thick wires, can be connected to the applicable lamination without problems and without the risk that adjacent laminations or wires will touch. 
         [0011]    In order in particular to keep the axial structural length of the commutator as short as possible, in a preferred refinement of the invention, it is provided that the ends of the laminations terminate in two planes parallel to one another, and that the ends of the laminations are disposed in alternation with one another as viewed in the circumferential direction, relative to the two planes. 
         [0012]    For the sake of the largest possible area for contact of the wire ends with, or their attachment to, the laminations, it is provided in a further feature of the invention that the ends of the laminations are embodied in widened fashion. 
         [0013]    A T-shaped embodiment of the ends, in particular, makes an interested arrangement of the laminations possible, so that the axial structural length of the commutator is made, only relatively slightly greater. 
         [0014]    For securing the wire ends or winding ends, it is furthermore advantageous if securing slots for the wire ends are embodied in the ends. These securing slots can be used in particular for welding or soldering of the wire ends in the slots without thereby increasing the outside diameter of the commutator. 
         [0015]    In order not to increase the outside diameter of the commutator, it is furthermore provided that the ends are radially aligned with the plane of the laminations. 
         [0016]    In an alternative embodiment, it is also possible that the ends are embodied in hook-shaped fashion and are bent over radially outward. In this feature, it is possible in particular to dispense with the embodiment of slots or the like in the ends of the laminations, so that the manufacture of the laminations and of the commutator can be done relatively inexpensively. 
         [0017]    Additional guidance of the wire ends and a secure electrical disconnection of adjacent wire ends is furthermore possible if the commutator body comprises plastic and is embodied as a shaped casting part, if the commutator body, on the side oriented toward the ends of the laminations, has guide zones for the wire ends, and if the guide zones are embodied as indented regions in the commutator body. As a result, the guide zones can be taken into account already during the production of the commutator body and therefore do not require an additional manufacturing step. 
         [0018]    In these last-mentioned guide zones, it is furthermore especially advantageous if the wire ends of the windings disposed in the guide zones are fixed in the guide zones with a medium, in particular an adhesive, or a casting resin or a dribble resin. 
         [0019]    The invention also includes an electrical machine, in particular a direct current motor, having a commutator of the invention. An electrical machine of this kind makes it possible, despite a relatively large wire diameter of the armature windings, to embody a commutator of relatively compact structure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The invention is described further in the ensuing detailed description of preferred embodiments taken in conjunction with the drawings, in which: 
           [0021]      FIG. 1  is a perspective view on the arrangement of laminations of a commutator of the invention; 
           [0022]      FIG. 2  is a sectional view of the arrangement in  FIG. 1 , to show the interior region of the laminations of the commutator; 
           [0023]      FIG. 3  shows a detail of  FIG. 2 , to illustrate the disposition of a reinforcing ring; 
           [0024]      FIGS. 4 and 5  show a perspective view of a commutator body with its laminations during different manufacturing steps; 
           [0025]      FIGS. 6 and 7  are views corresponding to  FIGS. 4 and 5 , in a second, modified manufacturing sequence; 
           [0026]      FIG. 8  is a perspective view on the commutator, showing the commutator with electrical contact provided by wire ends; 
           [0027]      FIG. 9  is a detail of  FIG. 8  in the vicinity of the connection point to the wire ends; 
           [0028]      FIGS. 10 and 11  show a second commutator of the invention in perspective views; 
           [0029]      FIG. 12  shows the commutator of  FIGS. 10 and 11  with connected wire ends, in a perspective view; 
           [0030]      FIG. 13  shows a detail of the attachment of the wire ends of  FIG. 12 , in a perspective view; and 
           [0031]      FIG. 14  shows a commutator of  FIGS. 10 and 11 , partly in section, to illustrate the guide zones in the commutator body. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]    Identical components and components with the same function are provided with the same reference numerals in the drawings. 
         [0033]    In  FIG. 1 , parts of a commutator  10  of the invention are shown, of the kind used in particular as components of an electrical machine, and especially preferably as components of a direct current motor. 
         [0034]    In  FIG. 1 , a plurality of laminations  11  and  12  can be seen, spaced apart from one another at an identical radial spacing r from a longitudinal axis  13  of the commutator  10  and that form a common circumferential surface. The ends  14  and  15  of the laminations  11  and  12 , which ends are disposed on the winding side of an armature, not shown in  FIG. 1 , are each embodied as T-shaped. In the case of the laminations  11 , each of the laminations  11  has a constant width except for the ends  14 , but the other laminations  12  have a portion  16  of reduced width. The T-shaped ends  14  of the first group of laminations  11  are disposed in the portions  16  of reduced width of the other group of laminations  12 . 
         [0035]    It is essential to the invention that the laminations  11  and  12 , and the ends  14  and  15 , alternate with one another as viewed in the circumferential direction of the commutator  10 , so that one group of ends  14  terminate in a first plane  18  perpendicular to the longitudinal axis  13  of the commutator  10 , while the other ends  15  of the laminations  12  terminate in a second plane  19 , which is likewise disposed perpendicular to the longitudinal axis  13  of the commutator  10 . Since the two planes  18  and  19  are disposed parallel to one another, one plane  18  is spaced apart farther on the winding side of the armature from the windings of the armature than the other plane  19 . 
         [0036]    In  FIG. 2 , a partly sectional view of the arrangement of laminations  11  and  12  is shown, in which it can be seen that these laminations, on their inside oriented toward the longitudinal axis  13 , each have riblike portions  21 ,  22 , which on sides facing away from one another form pockets  23  and  24 . The pockets  23  and  24  serve to receive reinforcing rings  25  in particular, which serve to stiffen and radially secure the laminations  11  and  12 . For the sake of simpler introduction or insertion of the reinforcing rings  25  in the assembly direction indicated by the arrow  26 , it is advantageous if the inside circumference of the pockets  23 ,  24  is larger than the outside diameter of the reinforcing rings  25 . 
         [0037]    A structural unit completed to this point, comprising the laminations  11  and  12  and optionally the reinforcing rings  25 , is placed in a tool, not shown in the drawings, which serves to embody a commutator body  27 , shown in particular in  FIGS. 4 through 7 . The commutator body  27  here comprises plastic in particular and is formed by an injection-molding or casting process. 
         [0038]    As can be seen from  FIGS. 4 and 5 , the commutator body  27  has a continuous longitudinal bore  28 , so that the commutator body  27  can in particular be press-fitted onto an armature shaft or in other words connected to an armature shaft in a manner fixed against relative rotation. 
         [0039]    In  FIG. 4 , a first method for manufacturing the commutator  10  and the commutator body  27  is shown, in which a free space  29  for guiding a winding wire in the direction toward the laminations  11  is embodied between each of the group of laminations  12 ; the free spaces  29  are bounded laterally by plastic material  30 , in order to electrically insulate the wire, located in the respective free space  29 , from the laminations  12 . The free spaces  29  are taken into account by means of a suitable design of the tool for creating the commutator body  27 . 
         [0040]    In  FIG. 5 , the commutator  10  is shown after a further manufacturing step, in which a fixation slot  31 ,  32 , extending diagonally in the exemplary embodiment, is embodied in each of the ends  14  and  15  of the laminations  11  and  12  by means of an embossing or milling operation. It will also be noted that the fixation slot  31 ,  32  can be embodied or disposed differently instead. 
         [0041]    In  FIGS. 6 and 7 , an alternative production process for the commutator body  27  is shown. Here, after the spray-coating or embodiment of the commutator body  27  in accordance with  FIG. 6 , the entire space between the laminations  11  and  12  in the vicinity of their ends  14  and  15  is first injected or filled with plastic. Next, as shown in  FIG. 7 , in a single manufacturing step, both the free spaces  29  and the fixation slots  31  and  32  are made simultaneously, in particular by milling. 
         [0042]    In  FIG. 8 , the situation is shown in which the wire ends  1  and  2  of the windings of the armature are disposed in the fixation slots  31  and  32  and in the free spaces  29 . The connection between the wire ends  1  and  2  in the vicinity of the fixation slots  31  and  32  is effected in particular by means of a welded or soldered connection  33 , while the wire ends  2  in the free spaces  29  are additionally secured or fixed by means of a medium  34 , such as an adhesive, or a casting resin or a dribble resin. 
         [0043]    In  FIGS. 10 through 14 , a modified commutator  10   a  is shown. What is essential here is that on the side oriented toward the wire ends  1  and  2 , its laminations  36 ,  37  are bent over radially outward in hooklike fashion. The ends  38  and  39  of the laminations  36  and  37 , viewed in the axial direction of the commutator  10   a , protrude away from the wire ends  1  and  2 , so that they form a radial securing means for the wire ends  1  and  2 . As can be seen particularly from  FIG. 11 , the group of ends  38  of the laminations  36  is disposed at the level of a first plane  41 , while the other ends  39  of the laminations  37  are disposed in the vicinity of a second plane  42 . The second plane  42  has a lesser spacing from the wire ends  1  and  2  than the first plane  41  does. 
         [0044]    In  FIGS. 12 and 13 , it is shown how the wire ends  1  and  2  are wrapped in looplike fashion around the ends  38  and  39  of the laminations  36  and  37 . As can be seen particularly from  FIG. 13 , a spacing a is embodied between the wire ends  1  and  2  and separates the wire ends  1  and  2  spatially and thus also disconnects them electrically from one another; the size of the spacing a is determined by the axially offset arrangement of the ends  38  and  39  and by the looplike course of the wire ends  1  and  2  around the ends  38  and  39 . 
         [0045]    Particularly in  FIG. 14 , guide zones  43  for the laminations  36  can also be seen, which are embodied in the commutator body  27   a  in order to better guide and stabilize the wire ends  1 . By this provision, at the same time the winding head of the rotor winding can be reduced in its outside diameter, because the wire ends, viewed radially, are now located at a lower level. 
         [0046]    It will additionally be noted that in the vicinity of the ends  38  and  39 , the connection between the wire ends  1  and  2  in the commutator  10   a  is again preferably done by means of a soldered or welded connection  33  (not shown). Also in the commutator  10   a , as in the commutator  10 , it is understood that reinforcing rings  25  may also be provided. 
         [0047]    The commutators  10 ,  10   a  described thus far can be modified in manifold ways, without departing from the concept of the invention. This concept is an offset embodiment, viewed in the axial direction of the commutator  10 ,  10   a , of the ends  14 ,  15  and  38 ,  39  of the laminations  11 ,  12  and  36 ,  37 , respectively, and this embodiment provides a relatively large space for securing the wire ends  1  and  2 . Thus in particular, instead of two planes  18 ,  19  and  41 ,  42 , it is also possible to provide more planes than that for the lamination ends. The number is limited solely by the possible axial length of the commutator  10 ,  10   a  and the structural length of the armature. 
         [0048]    The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.