Abstract:
The invention relates to an electric motor ( 10 ) and to a method for producing said electric motor, especially for adjusting mobile parts in a motor vehicle. Said electric motor comprises a collector ( 36 ), arranged on an armature ( 38 ) and electrically contacted via hammer brushes ( 12 ). The armature ( 38 ) is surrounded by a lower housing part ( 32 ) and an upper housing part ( 34 ) which can be assembled in a radial direction ( 50 ) in relation to the armature ( 38 ). The hammer brushes ( 12 ) comprise one fastening element ( 26 ) each which engages directly in a seat ( 30 ) of the lower or upper housing part ( 32, 34 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. 119(a)-(d) to German patent application number DE 102005047428.4, filed Sep. 30, 2006. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electric motor with hammer brushes and to a method for manufacturing such a motor, in particular for actuating moving parts in a motor vehicle. 
     2. Description of Related Art 
     DE 103 52 234 has disclosed an electric motor in which an armature shaft with a commutator mounted on it is supported between two housing shells that can be assembled radially. In this prior electric motor, hammer brushes are fastened, for example welded or riveted, by means of spring clips directly to the printed circuit board. After installation of the armature, the printed circuit board here is mounted radially, by means of which the carbon elements of the hammer brushes are positioned in relation to the commutator. Because of the adjustment of the brushes through positioning of the printed circuit board, it is relatively difficult to position the carbon elements precisely, which can result in the generation of unpleasant noise. In addition, such a system is not very flexible with regard to a structural change of the printed circuit board since this would also require a change of the brush holders. In addition, equipping the printed circuit board with the hammer brushes and producing the contact with a plug connector represent relatively complex assembly processes. 
     BRIEF SUMMARY OF THE INVENTION 
     The electric motor according to the present invention and its manufacturing method, with the characterizing features of their respective independent claims, have the advantage that by supporting the hammer brushes directly in a housing part that also supports the armature of the electric motor, the hammer brushes can be positioned more precisely in relation to the commutator. In this connection, completely independently of the printed circuit board or a brush-holding component, the hammer brushes are inserted into recesses formed into the housing part. By decoupling the hammer brushes from the printed circuit board, it very easy to vary the form and equipment of the printed circuit board without having to adapt the mounting of the hammer brushes. It is thus easier in particular to adapt the sensor system or various plug connectors to customer specifications. Furthermore, no additional brush-holding component is required, which would have to be inserted in an additional assembly step and then sealed. The motor housing can therefore be embodied very simply and cost-effectively by means of two housing shells that are very easy to seal in relation to each other. 
     Advantageous modifications and improvements of the features disclosed in the independent claims result from the steps taken in the dependent claims. In a particularly simple embodiment, the hammer brushes can be clamped into the housing part by means of a clamp element that is situated on the hammer brush. This eliminates the need for additional fastening means. The hammer brush, for example equipped with detent teeth, is simply inserted into the recess of the housing part and locked in detent fashion therein. 
     If the recess has a counterpart detent surface, then the detent teeth hook snugly into this detent stop, which is preferably composed of a material that is softer than that of the fastening element, for example plastic. Consequently, in a simple process, the hammer brush can be inserted into the recess until it reaches an end stop and at the same time, is reliably fixed in place by the hooking engagement of the teeth. 
     It is advantageous if the hammer brush has an insertion contact that is oriented so that during installation of the printed circuit board, the insertion contact is slid into a corresponding opening of the printed circuit board. Thus a mechanical connection to the hammer brush is produced during the process of installing the printed circuit board. 
     If the insertion contact is embodied with a resilient press-fitting zone, then during installation of the printed circuit board, the hammer brush is simultaneously also reliably contacted electrically by means of the press-fitting technique. This eliminates the need for soldering or other contacting methods. 
     So that the insertion contact has the necessary mechanical stability, it is advantageously produced of a different material than the spring clip. Then the insertion contact can be simply connected to the spring clip by means of riveting or welding, preferably before installation of the hammer brush. 
     It is advantageous if the detent teeth are embodied in a directly integral fashion together with the insertion contact. The detent teeth are then likewise composed of a harder material than the corresponding counterpart surface of the recess, thus allowing the detent teeth to better engage therein. 
     If the recess is embodied in the form of a pocket, which, in addition to the insertion opening, has an opening on another side, then the fastening element is reliably fixed in position on the one hand and the spring clip with the carbon element can simultaneously protrude from the latter opening in order to rest against the commutator. 
     In another embodiment, the recess has a guide rail on which the hammer brush can be slid into a detent position. In this case, the function of the guide element is in particular performed by the insertion element, which reaches, for example, through a gap of the guide rail. 
     If the electric motor has two hammer brushes, for example, which are situated on both sides of the armature shaft, then the printed circuit board can accommodate both insertion elements directly if the printed circuit board extends tangentially across the commutator. As a result, the carbon elements are connected to the current supply via very short electrical paths, thus reducing occurrences of electromagnetic interference. With this arrangement of the printed circuit board, it is simultaneously possible for a sensor system to be very favorably situated directly at the armature shaft. 
     So that no electrical contacting processes are required during the installation of the printed circuit board, in addition to the insertion contacts of the hammer brushes, the plug connector pins for the external electrical connection of the electric motor are preinstalled as insertion contacts in the lower shell or are injection molded into it. As a result, at the same time as the mechanical fixing of the printed circuit board by means of guide pins, all of the electrical contacts are also produced, thus eliminating the need for additional contacting methods. 
     Alternatively or in addition to the electrical connection of the carbon elements to the insertion contact via the spring clips, the carbon brush can have a carbon wire attached to it that electrically connects the brush directly to the insertion contact. This has the additional advantage that the spring clip can be mechanically damped by the manner in which the carbon wire is fastened. 
     Thanks to the manufacturing method of the electric motor according to the present invention, which motor can be completely assembled in the radial direction, it is possible to eliminate the separate installation process of the hammer brushes on the printed circuit board. The direct insertion of the fastening regions of the hammer brushes into the corresponding recesses of the lower housing part positions these hammer brushes directly and therefore very precisely in relation to the commutator. The radial installation of the printed circuit board completely connects it mechanically and electrically at the same time and in a single process step. The installation of the upper housing part does not interfere with the positioning of the hammer brushes. This completely eliminates the complex installation of an additional brush-holding component and its sealing in relation to the other housing parts. 
     In a preferred production method, the carbon brushes are inserted radially in relation to the armature so that the spring clips extend in the axial direction; the carbon elements are in particular formed by means of bevels so that they are able to assume their optimum sprung position when they are slid onto the commutator. 
     The insertion of press-fitting zones into the holes of the printed circuit board produces a good mechanical and electrical contact simultaneously and in a single process step, thus making it possible under some circumstances to eliminate an additional mechanical fixing. As a result, no special, complex process evolutions are required For the contacting of the hammer brushes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various exemplary embodiments of a device according to the present invention are shown in the drawings and will be explained in greater detail in the description that follows. 
         FIGS. 1 and 2  show two different exemplary embodiments of a hammer brush according to the present invention, 
         FIG. 3  shows another variant in the installed state, 
         FIG. 4  shows the hammer brush according to  FIG. 1  in the installed state, and 
         FIG. 5  shows the assembly process of the electric motor according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a hammer brush  12  in which a carbon element  13  is mechanically and electrically connected to a spring clip  14 . The hammer brush  12  also has an insertion contact  16  that is attached to the spring clip  14  by means of rivets  15  or by means of welding or another joining process. The spring clip  14  is manufactured of spring steel or of a Cu or CuBe material so that the carbon element  13  is connected to the insertion contact  16  in an electrically conductive fashion via the spring clip  14 . For example, the carbon element  13  in  FIG. 1  is welded to the spring clip  14 , but in other embodiments, can also be riveted to the spring clip  14 , inserted into it, or clamped to it. The insertion contact  16  has a press-fitting zone  18  formed onto it, which has resilient bridge pieces  20  that are elastically deformed upon insertion into a hole  22  of a printed circuit board  24 . The bridge pieces  20  are press-fitted in relation to an inner wall  23  of the hole  22 . The hammer brush  12  also has a fastening element  26  situated on it, which has a number of detent teeth  28  that snugly hook into place when inserted into a recess  30  of a lower housing part  32 . The fastening element  26  in this embodiment is integrally manufactured out of the same material as the insertion contact  16 , for example produced from a copper plate and embodied in the form of a bent, stamped component. The hammer brush  12  has four fastening elements  26 , for example, that all extend approximately perpendicular to the plane of the spring clip  14 . During installation of the hammer brush  12 , the spring clip  14  then extends approximately parallel to a counterpart surface  52  of detent teeth  28 , as shown in  FIG. 4 . 
     In  FIG. 4 , the hammer brush  12  from  FIG. 1  is shown in the installed state, after it has been inserted into the recess  30  of the lower housing part  32 . The lower housing part  32  supports an armature shaft  36  with an armature  38  and a commutator  40  mounted on it by means of a bearing  35 . As a drive element  42 , the armature shaft  36  has a worm  43 , which, by means of a driven element  44 , actuates a moving part in the motor vehicle, for example. In the region of the commutator  40 , on both sides of the armature shaft  36 , the recesses  30 , which are embodied in the form of open pockets  46 , are formed directly into the lower housing part  32 . The hammer brushes  12  are inserted in the installation direction  50  radial to the armature shaft  36  into openings  48  at the ends of the recesses  30 . Each of the spring clips  14  with the carbon elements  13  protrudes out from its respective recess  30  through a lateral gap  49 . Upon insertion in the installation direction  50 , the carbon elements  13  slide over the commutator  40  so that in the final installed state, the spring clips  14  rest against the commutator  40  in a prestressed fashion. Each of the spring clips  14  extends from its recess  30  in the axial direction  51  to the commutator  40 . During the insertion of the hammer brushes  12 , the fastening element  26  wedges in the recess  30  by the engagement of the detent teeth  28  with the counterpart surface  52 . The hammer brush  12  is inserted into the recess  30  until it comes to rest against a stop surface  54  of the recess  30 . In this position, the insertion contacts  16  protrude up from the commutator  40  in the installation direction  50  so that after installation of the armature shaft  36  and the hammer brushes  12 , the printed circuit board  24  can be installed in the radial direction  50 , as depicted in  FIG. 5 . 
       FIG. 5  shows the same electric motor  10  as  FIG. 4 , in the next assembly step. In the region of a connector plug  56 , the lower housing part  32  has plug connector pins  58  whose insertion direction  60  likewise extends in the installation direction  50 . Centering holes  52  of the printed circuit board  24  are now slid in the radial direction  50  onto corresponding guide pins  64  of the lower housing part  32 . By means of the press-fitting technique, both the insertion contacts  16  of the hammer brushes  12  and the insertion regions  60  of the plug connector pins  58  are press-fitted into corresponding holes  22  of the printed circuit board  24 . As a result, without additional contacting processes, by means of their insertion contacts  16 , the hammer brushes  12  are electrically connected via the printed circuit board  24  to the connector pins  58  of the connector plug  56 . The circuit board  26  extends tangentially to the commutator  40  and covers it completely in the tangential direction  53 . A speed sensor  66 , for example a Hall integrated circuit  67 , is also situated on the printed circuit board  24  so that the sensor is positioned directly opposite a signal transmitter  68 , for example an annular magnet  69  of the armature shaft  36 . Additional components  65  such as relays, capacitors, diodes, interference suppression elements, and a microprocessor are also situated on the printed circuit board  24 . The printed circuit board  24  also has an opening  70  through which, after installation of the upper housing part  34 , not shown, the bearing  35  is press-fitted into the lower housing part  32 . After its installation, the upper housing part  34  rests in the radial direction  50  directly against a seal  72  of the lower housing part  32  so that the two housing parts  32 ,  34  completely enclose the electric motor  10  and the transmission  42 ,  44  connected to it. 
       FIG. 2  shows another exemplary embodiment of a hammer brush  12  according to the present invention in which the carbon element  13  is inserted into the spring clip  14 . The carbon element  13  has a connecting element  74  that electrically connects the carbon element  13  to the spring clip  14 . In addition or alternatively, the carbon element  13  is connected directly to the insertion contact  16  of the hammer brush  12  by means of a connecting wire  76 . If the hammer brush  12  has a connecting wire  76 , then it is also possible for the spring clip  14  to be composed of a poor electrical conductor. In addition, the carbon wire  76  can be fastened in such a way that the hammer brush  12  is mechanically damped. As a fastening element  26 , the detent teeth  28  are formed onto the region between the spring clip  14  and the insertion contact  16 , extending in the plane of the spring clip  14 . The insertion contact  16  in turn has a press-fitting zone  18  that is composed of two resilient bridge pieces  20  that enclose an eyelet  21 . A hammer brush  12  of this kind can also be inserted into a recess  30 , not shown, of a housing part  32  of the electric motor  10 , with the detent teeth  28  wedging into the recess  30 . 
       FIG. 3  shows another embodiment of a hammer brush  12  in which the carbon element  13  is situated in a recess  77  of the spring clip  14 . The spring clip  14  in this case is integrally joined, for example, to the insertion contact  16  and the fastening element  26 . In order to install the hammer brush  12  into the housing part  32 , the insertion contact  16  is inserted into a groove  78  of a guide rail  80  in the radial direction  50 . Then the hammer brush  12  is slid in the tangential direction  53  along the rail  80  until the fastening element  26  engages in detent fashion with a corresponding counterpart surface  52  of the recess  30  and the spring clip  14  rests against a stop surface  54  of the recess  30 .  FIG. 3  schematically depicts only part of the housing  32 ; the two opposing sets of detent teeth  28  engage in the recess  30  in detent fashion at the same time. The insertion contacts  16  in this exemplary embodiment extend through the guide rail  80  so that the printed circuit board  24  is connected to the insertion contacts  16  from the other side of the guide rail  80 . The spring clips  14  in this embodiment do not extend axially in relation to the armature shaft  36 , but rather tangentially to the commutator  40 . 
     It should be noted that with regard to the exemplary embodiments shown in the figures and contained in the description, there are numerous possibilities for combining the individual features with one another. It is thus possible, for example, to vary the concrete embodiment of the fastening elements  26  and their connection to the spring clip  14 . For example, in lieu of the detent teeth  28 , the hammer brushes  12  can also be fixed using other connecting means. It is likewise possible to adapt the form and attachment of the insertion contacts  16 , the corresponding housing geometry, and the printed circuit board  24  used for the electric motor  10 . The embodiment of the recesses  30  and their counterpart surfaces  52  in the lower housing part  32  depends on the concrete assembly geometry of the electric motor  10 . The electric motor according to the present invention is preferably used for actuating windows or other moving parts in the motor vehicle and the housing is preferably composed of two shells  30 ,  32 .