Abstract:
Electric motor, as well as a brush mount component ( 34 ) for positioning of carbon brushes with respect to a commutator ( 30 ) of an electric motor ( 12 ), having at least one attachment means ( 55 ) for fixing the brush mount component ( 34 ) on a printed circuit board ( 28 ), with an earth contact plate ( 70 ) being mounted on the brush mount component ( 34 ) and being designed symmetrically with respect to the arrangement of the carbon brushes ( 32 ). A method for production of an electric motor such as this is also described.

Description:
PRIOR ART 
       [0001]    The invention relates to a brush holder component having a ground contact plate and to an electric motor containing such a brush holder component, as well as to a method for producing such an electric motor, as generically defined by the preambles to the independent claims. 
         [0002]    From German Patent Disclosure DE 100 10 439 A1, an actuator with an electric motor is known, in which the shaft of the electric motor, with a commutator located on it, is supported in a gearbox that is connected to a pole cup. For electrically contacting the commutator, the actuator has a brush holder with carbon brushes located in quivers, and before its assembly the brush holder is loosely coupled to a printed circuit board. After that, the brush holder is inserted together with the printed circuit board into the lower housing shell and secured to the housing, for instance by means of screws. In the assembly, both the printed circuit board and the brush holder are guided relative to the housing by guide elements. Because of the loose coupling of the brush holder to the printed circuit board before its assembly, electrical connection lines of the components located on the brush holder are embodied correspondingly flexibly. If the gearbox is made of plastic rather than metal, electromagnetic interference radiation occurs from the brush fire and has an interfering effect on the electronics unit of the electric motor and the surroundings of the electric motor. 
       DISCLOSURE OF THE INVENTION 
       [0003]    The brush holder component of the invention and the electric motor and its production method that have the definitive characteristics of the independent claims have the advantage that by the arrangement of the ground contact plate on the brush holder component, the carbon brushes are efficiently shielded, so as to suppress electromagnetic interference. By means of the symmetrical design of the ground contact plate with its spring tongues and pins to suit the spatial arrangement of the carbon brushes, the electromagnetic interference generated by the brush fire can be suppressed very effectively over the entire three-dimensional area. Because the ground contact plate is secured to the brush holder component, an additional assembly process for the ground contact plate is dispensed with. 
         [0004]    Advantageous refinements of and improvements to the characteristics recited in the independent claims are obtained by the provisions recited in the dependent claims. Especially effective electromagnetic shielding is attained if the ground contact plate has an axial end face, extending transversely to the armature shaft, against which lateral leg sides each extend—virtually around the spring levers—and these leg sides approximately form a right angle with the axial end face. This kind of shaping of the ground contact plate is especially well suited, in combination with the shielding plate of the gearbox, the printed circuit board, and the pole cup, of forming a closed metal shielding cage around the brush arrangement. 
         [0005]    To establish good electrical contact between the ground contact plate and the shielding plate of the housing, both leg sides have tablike spring contacts, which in the installed state rest over a large area on the shielding plate. As a result, the ground contact plate is especially effectively brought to ground potential. 
         [0006]    If pins that reach through corresponding openings in the bottom face of the brush holder component are integrally formed onto the ground contact plate, then these pins can very simply be connected to a printed circuit board located parallel to the bottom face, in order to establish a ground contact on the printed circuit board. 
         [0007]    It is advantageous if the ground contact plate can be thrust into the brush holder component directly—without using further connecting means—in order to form a form lock with it. This dispenses with one additional assembly step for securing the ground contact plate. 
         [0008]    It is especially favorable if the carbon brushes are embodied as hammer brushes with a spring lever, onto which lever a clamping element is integrally formed. By the firm clamping of the hammer brushes in suitable receptacles in the brush holder component, one additional assembly process for securing and adjusting the hammer brushes is also dispensed with. 
         [0009]    If the brush holder component serves not only to support the carbon brushes and the ground contact plate but also to receive further components, such as interference suppression coils, then this system holder can be preassembled as a separate unit, making more-flexible manufacture possible. 
         [0010]    In the electric motor of the invention, the brush holder component is advantageously located on a printed circuit board that extends approximately parallel to the bottom face of the brush holder component and at a tangent to the commutator. As a result, a direct, short, and symmetrical electrical connection between the ground contact plate and the printed circuit board is made possible, and as a result the printed circuit board contributes to suppressing the electromagnetic interference. 
         [0011]    Because the ground contact plate and the other components located on the brush holder component reach with their pins through corresponding openings in the bottom face into bores of the printed circuit board, the pins can be electrically contacted with the printed circuit board in a simple way using a standardized soldering process. For instance, the printed circuit board may also be manufactured in a separate, automated production process, for instance by means of THRS methods. 
         [0012]    In an alternative version, the ground contact plate can also be embodied in two parts, the two parts being formed essentially by large-area spring contact tongues. By the symmetrical arrangement of the two separate contact tongues relative to the arrangement of the carbon brushes ( 32 ), the shielding plate can optimally shield against the brush fire. 
         [0013]    Alternatively to securing the ground contact plate to the brush holder component, the one- or two-piece ground contact plate can also be secured directly to the printed circuit board. To that end, the pins of the spring tongues electrically contact the printed circuit board in the immediate vicinity of the electrical contacting of the carbon brushes. 
         [0014]    By the symmetrical shaping of the shielding plate in the gearbox relative to the carbon brushes, or to the armature shaft, especially effective shielding against the electromagnetic interference is possible. Combining the symmetrical shielding plate with the symmetrical ground contact plate brings about an advantageous shaping of the metal shielding cage around the carbon brushes. 
         [0015]    The shielding plate can be attached to the pole cup in a very simple way by means of axial extensions, as a result of which the axial extensions serve as ground terminals for the shielding plate. The ground terminals can be electrically contacted to the pole cup in one process with the connection of the pole cup to the gearbox. The plastic deformation of wedging tabs on the flange of the pole cup here is especially economical. By means of the symmetrical arrangement of the two or three ground terminals, for instance, relative to the carbon brush arrangement, a reduction in interfering radiation can again be attained. 
         [0016]    For producing a sturdy electrical contact in the assembly of the brush holder component, large-area, plane stop faces are embodied on the brush holder component, and the spring tongues are pressed against them. 
         [0017]    The shielding cage, which is composed of the shielding plate, the ground contact plate, and the ground layer of the printed circuit board, advantageously extends over the entire axial width of the carbon brushes, in order to shield them effectively. 
         [0018]    In the method according to the invention for producing the electric motor, the ground contact plate can very simply be preassembled on the brush holder component and electrically connected to the printed circuit board. Then one additional work step for mechanically securing the ground contact plate is dispensed with. At the same time, with the mounting of the carbon brushes on the commutator, reliable electrical contacts are made between the ground contact plate and the shielding plate, so that an effective shielding cage for the carbon brushes is produced without additional effort and expense for assembly. 
         [0019]    Advantageously, the ground contact plate, together with the other components, can be soldered to the printed circuit board in one operation, and as a result, in addition to the electrical connection, a mechanically rigid connection between the brush holder component and the printed circuit board is also made. 
     
    
     
       DRAWINGS 
         [0020]    In the drawings, various exemplary embodiments of a device according to the invention are shown and will be described in further detail in the ensuing description. Shown are: 
           [0021]      FIG. 1 , one exemplary embodiment of an electric motor of the invention; 
           [0022]      FIG. 2 , an enlarged view of the brush holder component of  FIG. 1 ; 
           [0023]      FIG. 3 , a brush holder component of  FIG. 2 , preassembled on a printed circuit board; 
           [0024]      FIG. 4 , an unmounted ground contact plate; 
           [0025]      FIG. 5 , schematically, a section through an arrangement as in  FIG. 1 ; and 
           [0026]      FIG. 6 , an illustration of a further exemplary embodiment. 
       
    
    
     DESCRIPTION 
       [0027]    In  FIG. 1 , a detail of an electric motor  12  according to the invention is shown, in which an armature shaft  14  extends from a pole housing  16  into a gearbox  18  connected to it. The gearbox  18  has a first shell-shaped housing part  20 , which after the mounting of the electric motor  12  and of a gear  22 , not shown in further detail, is closed with a housing cap. The electric motor  12  moreover has an electronics housing  26 , which is embodied for instance in one piece with the lower housing shell  20  and receives a printed circuit board  28 . A commutator  30  is located on the armature shaft  14  and is supplied with current via carbon brushes  32  embodied as hammer brushes. The carbon brushes  32  are clamped into a separate brush holder component  34 , which is shown enlarged in  FIG. 2 . The brush holder component  34  is embodied as a U-shaped plastic part and can be installed in the radial direction  36  to the armature shaft  14 . In a bottom face  38  of the brush holder component  34  that is located between two legs  40  of the brush holder component  34 , a slot  42  is made, as an opening  41 , through which contact pins  44  of the carbon brushes  32  reach. These contact pins  44 , together with pins  46  of a ground contact plate  70  that is likewise located on the brush holder component  34 , are connected electrically to the printed circuit board  28  (see  FIG. 3 ). In  FIG. 1 , the printed circuit board  28 , which extends approximately parallel to the armature shaft  14  and to the housing cap, is cut off in order to open up the view to the brush holder component  34 . Axially adjacent to the commutator  30 , a ring magnet  50  is located on the armature shaft  14 ; it cooperates with corresponding Hall sensors  51 , which reach through corresponding openings  54  in the brush holder component  34 . For adjusting the brush holder component  34  relative to the printed circuit board  28 , centering pins  56  are integrally formed onto the bottom face  38  as securing elements, which engage corresponding centering openings  58  in the printed circuit board  28 . The brush holder component  34  thus forms a U-shaped cage  60 , which partitions off the hammer brushes  32  from the gear  22  and the electronics housing  26 , in order for instance to prevent them from becoming soiled with carbon dust. 
         [0028]    In  FIG. 2 , the brush holder component  34  is shown as a system holder  62  for a preassembled unit, which in addition to the hammer brushes  32  receives still other components  48 . To that end, the brush holder component  34  has sleevelike receptacles  64 , in which interference suppression coils  66  are located that with their pins  45  reach through corresponding holes  68  in the bottom face  38 . The ground contact plate  70  is also supported on the brush holder component  34  and surrounds the hammer brushes  32  in the shape of a U, so as to shield against the electromagnetic interference that is created by the brush fire. The ground contact plate  70  here rests in form-locking fashion, with an axial end face  71  and two angled leg faces  73 , against corresponding cage walls  61  of the brush holder component  34 . The ground contact plate  70  has pins  46 , which reach through holes  68  in the bottom face  38 , in order to establish the electrical connection with the printed circuit board  28 . The holes  68  and the opening  41  are located coincidentally to bores  82  that are shaped out of the printed circuit board  28  that extends along the bottom face  38 . Along the two legs  40 , the ground contact plate  70  has two large-area spring tongues  74 , which after the installation in the gearbox  18  rest resiliently on diametrically opposed stop faces  75  of a shielding plate  76  that in turn is electrically contacted with the pole housing  16 . The hammer brushes  32  have carbons  78 , which are secured to one end of a spring lever  80 . For instance, the carbons  78  are secured by means of laser welding or are press-fitted into an integrally formed-on carbon receptacle  79  of the spring lever  80 . The contact pins  44 , which reach through the slot  42  in the bottom face  38 , are located on the other end of the spring lever  80 . 
         [0029]    In  FIG. 3 , the brush holder component  34  is located as a preassembled system holder  62  on the printed circuit board  28 . The printed circuit board  28  has many bores  82 , which are engaged by the pins  46  of the ground contact plate  70 , the contact pins  44  of the carbon brushes  32 , and the pins  45  of the further components  48 . As an example here, the four pins  45  of the two interference suppression coils  66  are shown. Once the brush holder component  34  has been inserted in form-locking fashion with its centering pins  56  into the corresponding centering openings  58  of the printed circuit board  28 , the pins  44 ,  45  and  46  are soldered to the printed circuit board  28  by means of what is known as the THRS method. In it, the openings  82  in the printed circuit board  28  are filled with solder paste  27 , and the components  48 ,  32  are introduced with their pins  46 ,  45 ,  44  into the openings  82  and are then heated—for instance in an oven—to cure the solder paste  27 . This kind of automatic soldering method is very economical and very flexible with regard to the arrangement of the components  48  on the printed circuit board  28 . Thus the pins  44 ,  45 ,  46 , together with the solder paste  27 , also represent fastening means  55  for a mechanically rigid connection of the brush holder component  34  to the printed circuit board  28 . Thus once the brush holder component  34  is rigidly connected to the printed circuit board  28  both mechanically and electrically, the printed circuit board  28 , with the brush holder component  34 , is mounted radially on the armature shaft  14  located in the gearbox  18 . In this process, the printed circuit board  28  is in turn adjusted relative to the gearbox  18  by means of centering elements  84 . After the mounting of the preassembled system holder  62  in the radial direction  36 , the spring tongues  74  of the ground contact plate  70  rest on the shielding plate  76 , mounted beforehand in the gearbox  18 . 
         [0030]    In  FIG. 4 , a ground contact plate  70  is shown in the unmounted state. The axial end wall  71  of the ground contact plate  70  is embodied in the shape of a U and has a recess  69  for the armature shaft  14 . The two pins  46  are integrally formed onto the axial end wall  71 , symmetrically to the armature shaft  14 . The two leg sides  73  are located approximately perpendicular to the axial end wall  71 , and the entire ground contact plate  70  is embodied as a one-piece bent and stamped part. Large-area contact tongues  74  are embodied on the leg sides  73  and are curved radially outward, as viewed from the armature shaft  14 . The contact tongues  74  have one free end  79 , which is curved once again in the opposite direction, so that the S-shaped contact tongue  74 , upon the assembly of the brush holder component  34 , exerts a spring force against the shielding plate  76 . The axial width  84  of the spring tongues  74  extends in this exemplary embodiment over at least half the axial width  83  of the ground contact plate  70 , thus creating that a large area of contact with the opposed stop face  75 . For premounting the ground contact plate  70 , the ground contact plate is inserted in the radial direction  36  into the brush holder component  34 , and the pins  46  pass through openings  68  in the bottom face  38 . The axial end wall  71  forms an angle with the leg side  73 , and this angle  85  rests in form-locking fashion against the corresponding cage walls  61  of the brush holder component  34 . 
         [0031]    In  FIG. 5 , the brush holder component  34  is shown with the preassembled ground contact plate  70  inside the gearbox  18 . The preassembled system holder  62  in  FIG. 2  is rotated 180° and inserted in the direction  36  into the housing shell  20 . For the sake of clarity, in this view only the shielding plate  76  and the ground contact plate  70  are additionally shown in section. The gearbox  18  is embodied as a shell-shaped housing part  20 , which is connected to the pole housing  16 . The U-shaped shielding plate  76  has been placed in the housing part  20  before the mounting of the brush holder component  34 . Grooves  87  on the free ends of the shielding plate  76  embrace the side walls  21  of the housing part  20  in order to fix the shielding plate  76  relative to the housing part  20 . In the mounted state, the S-shaped spring tongues  74  rest with spring force on the stop faces  75  of the shielding plate  76 . The free end  79  of the spring tongue  74  rests on the brush holder component  34 , in order to generate a spring force. The symmetrically embodied ground contact plate  70 , together with the symmetrically embodied shielding plate  76 , forms a metal shielding cage, which extends over at least the axial width  33  of the carbons  78 . For the sake of simplicity, the printed circuit board  28  is not shown in  FIG. 5 ; its ground layer  29 , together with the ground contact plate  70  and the shielding plate  76 , closes the metal shielding cage over the entire circumference of the commutator  30 . 
         [0032]      FIG. 6  schematically shows a further exemplary embodiment, with a pole housing  16  but without a gearbox  18 . The pole housing  16 , on its open edge, has wedging tabs  17 , which are plastically deformed for the sake of connection to the gearbox  18 . The ground terminals  77  of the shielding plate  76  extend in the axial direction  37  as far as the wedging tabs  17 , so that in the process of connecting the pole housing  16  to the gearbox  18 , the ground terminals  77  are simultaneously put into electrical contact with the pole cup  16 . As a result, the ground potential of the pole cup  16  is applied via the shielding plate  76  to the ground contact plate  70  and likewise, via the pins  46 , to the ground contact  67  of the printed circuit board  28  (not shown). A third ground terminal  97  is embodied on the shielding plate  76 ; it is located centrally to the other two ground terminals  77  and therefore is likewise symmetrically located. The ground terminal  97  rests with its free end  99  on a flange  98  of the pole cup  16  and is pressed against the gearbox  18  in the process of connection to the gearbox  18 , in order to establish a ground contact. 
         [0033]    It should be noted that with regard to the exemplary embodiments shown in the drawings and to the description, manifold possible combinations of the various characteristics with one another are possible. For instance, the specific embodiment and mode of securing the brush holder component  34 , the ground contact plate  70 , and the corresponding shielding plate  76  can be varied accordingly. For instance, the ground contact plate  70  can be embodied as two spring contact tongues  74  located in the immediate vicinity of the brush holder component  34 , directly on the printed circuit board  28 . The connecting means between the brush holder component  34 , or the pins  46 ,  45 ,  44 , and the printed circuit board  28  can be adapted accordingly as well. The brush holder component  34  is preferably embodied as a system holder  62  for a preassembled unit, which before its radial installation in the housing part  20  is connected mechanically firmly to the printed circuit board  28 . The electric motor  12  of the invention is used in particular for power windows, sliding roofs, or other convenience functions in the motor vehicle.