Abstract:
An anti-interference system ( 86 ) for an electric machine ( 10 ) comprises a single-piece or multi-piece housing component ( 56 ) and a single-piece or multi-piece shielding component ( 30 ). The housing component ( 56 ) together with the shielding component ( 30 ) forms a faraday cage ( 84 ). The faraday cage ( 84 ) encloses at least one first interference suppression choke ( 44 ). An electric machine, particularly a wiper motor, comprises an anti-interference system ( 86 ) as described above.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to an interference suppression arrangement for an electric machine. The interference suppression arrangement comprises a single-piece or multi-piece housing component and a single-piece or multi-piece shielding component, the housing component together with the shielding component forming a Faraday cage. In addition, the invention relates to an electric machine, in particular a wiper motor. 
         [0002]    DD 12956 describes a conventional interference suppression element. In this case, a threaded connection piece is fixed in the wall of a metallic shielding housing of a windshield wiper motor, said threaded connection piece providing a tubular joint between the interior of the shielding housing and its surrounding environment. A leadthrough capacitor is inserted into the tubular joint, said leadthrough capacitor completely filling the tubular joint. A positive feed line for the windshield wiper motor is guided through the leadthrough capacitor. The conventional interference suppression element no longer meets the increased requirements placed on electromagnetic compatibility with modern radio services and vehicle systems. 
       SUMMARY OF THE INVENTION 
       [0003]    An object of the present invention is to provide an interference suppression arrangement of the generic type which takes account of the increased requirements placed on electromagnetic compatibility with modern radio services and vehicle systems. Furthermore, an object of the invention is to provide an electric machine, in particular a wiper motor, with this advantage. 
         [0004]    The invention builds upon the interference suppression arrangement of the generic type in such a way that the Faraday cage surrounds at least one first interference suppression inductor. 
         [0005]    A preferred embodiment envisages that the Faraday cage completely surrounds a brushgear of the electric machine. 
         [0006]    In an advantageous embodiment, the Faraday cage surrounds a grounding line of the electric machine, the Faraday cage being electrically connected to the grounding line. 
         [0007]    An embodiment which is also preferred envisages that the first interference suppression inductor or a further interference suppression inductor is introduced in the grounding line. 
         [0008]    A further development envisages that at least one leadthrough capacitor is arranged in a wall of the Faraday cage. 
         [0009]    Preferably, the interference suppression arrangement can be characterized by the fact that the leadthrough capacitor comprises a ceramic tube, which is metal-plated on a tube inner side and/or on a tube outer side. 
         [0010]    It is advantageous if the housing component and/or the shielding component has a receptacle for pressing in the leadthrough capacitor, in particular in an axial and/or in a radial direction. 
         [0011]    It is also particularly preferred if the Faraday cage surrounds a first interference suppression capacitance. 
         [0012]    In addition, the invention builds upon an electric machine of the generic type by virtue of the fact that the electric machine, in particular the wiper motor, comprises an interference suppression arrangement according to the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The invention will now be explained with reference to the attached figures using particularly preferred embodiments. 
           [0014]    In the figures: 
           [0015]      FIG. 1  shows a schematic basic circuit diagram for explaining electrical wiring of the interference suppression components according to the invention; 
           [0016]      FIG. 2  shows a perspective, schematic sketch of a physical arrangement, according to the invention, of interference suppression components in the region of the shielding plate; and 
           [0017]      FIG. 3  shows a perspective sketch of a leadthrough capacitor and a physical arrangement, according to the invention, of the leadthrough capacitor in the tail element. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Low-power motors  10  are generally provided with simple L/C interference suppression in order to suppress electrical interference which is caused by brush sparking. In a standard wiper motor  10 , the two wiper speeds required by law are generally implemented by means of two positive brushes  12 ,  14 . Typically, a first of the two positive brushes  12 ,  14  is diametrically opposite a ground brush  16 , while the other of the two is arranged at an acute circumferential angle of 70°, for example, with respect to the first positive brush  12 . As a result, the other of the two brushes  12 ,  14  is not arranged diametrically opposite the ground brush  16 . In this case, both brushes  12 ,  14  are subjected to interference suppression with in each case one dedicated L/C circuit  18 ,  20  and  22 ,  24 , respectively. In the process, the connection of the respective brush to a respective electrical feed line  34  or  36  takes place via the inductance  18  or  22 , with the connection of the inductance  18  or  22  on the power supply side being short-circuited in terms of radiofrequency with respect to ground  28  by means of a capacitance  20  or  24 . This is then referred to as 2L/2C interference suppression. In order to improve the interference suppression in the long-wave range, a third capacitance  26  can be used, which is connected between the terminals of the two positive brushes  12 ,  14 . 2L/2C and 2L/3C interference suppression systems effectively suppress average levels of interference, but are relatively ineffective with respect to temporarily occurring interference events which are manifested in so-called “interference peaks”. The “interference peaks” tend to be unproblematic for earlier analog radio and telecommunication services, but result in failures in the case of digital communication systems, such as Bluetooth and digital radio services (digital broadcast). 
         [0019]    According to the invention, a shielding component  30 , which is connected to ground  28 , is arranged in such a way that the brushgear  12 ,  14 ,  16  (and therefore the original source of the radio interference) is encapsulated completely in the pole housing  32 . Preferably, the shielding component  30  is an electrically conductive shielding plate. The electrical feed lines  34 ,  36  are passed through the shielding plate  30 . In order to prevent interference signals from being passed out of the brush area  38 , the two positive lines  34 ,  36  of the two-stage motor  10  are short-circuited in terms of radiofrequency by the shielding plate  30  by means of in each case one leadthrough capacitor  40  or  42 . A further improvement is possible by means of inserting an inductor  44  into the grounding path  46  of the wiper motor  10 . A thermostatic switch  50  can be inserted into the grounding line  48  at any desired point, i.e. between the ground brush  16  and the third inductor  44  or between the third inductor  44  and the brush housing  32 , for example. 
         [0020]    A module  52  for accommodating the interference suppression inductors  18 ,  22  is arranged in the motor housing  54  as follows. The module  52  passes from a pole housing  56  through a motor flange (not illustrated) into a transmission box (not illustrated). The module  52  comprises a tail element  58  with interference suppression inductors  18 ,  22 , a front element  60  with contact springs to form a transmission cover (not illustrated), and a shielding plate  30  between the tail element  58  and the front element  60 . In addition to the shielding function, the shielding plate  30  can also have the function of fixing the front element  60  mechanically to the tail element  58 . For this purpose, the shielding plate  30  can have two lug-like protrusions  64 ,  66 , in the direction towards the front element  60 , each having a cutout  68 , said protrusions being provided for the purpose of surrounding the front element  60  on two sides  72 ,  74  in the manner of clamps. The front element  60  has two tabs  70 , which are provided for engaging, in the manner of hooks, in the cutouts  68  in the lug-like protrusions  64 ,  66 . An identical mechanical connection can also be provided between the shielding plate  30  and the tail element  58 . It is expedient here to arrange the two lugs  64 ,  66  for the front element  60  on a left-hand side  72  and right-hand side  74  of the shielding plate  30  when the two lugs  76 ,  78  for the tail element  58  are arranged on the upper side  80  and lower side  82  of the shielding plate  30 . Alternatively, it may also be expedient to arrange the two lugs  76 ,  78  for the tail element  58  on a left-hand side  72  and right-hand side  74  of the shielding plate  30  and the two lugs  64 ,  66  for the front element  60  on the upper side  80  and lower side  82  of the shielding plate  30 . The pole housing  56 , the transmission flange housing and the shielding plate  30  form a closed Faraday cage  84 . The shielding plate  30  provides a shielding in the passage from the pole housing  56  to the transmission box. It is expedient to preliminary solder the two leadthrough capacitors  40 ,  42  onto connecting wires  34 ,  36  of the inductors  18 ,  22  and to insert them together with the respective inductor  18 ,  22  into the tail element  58 . 
         [0021]    The interference suppression arrangement  86  for the electric machine  10  comprises a single-piece or multi-piece housing component  56  and a single-piece or multi-piece shielding component  30 . The housing component  56  forms, together with the shielding component  30 , a Faraday cage  84 . The Faraday cage  84  surrounds at least a first interference suppression inductor  18 . In addition, the Faraday cage  84  surrounds a brushgear  12 ,  14 ,  16  and a grounding line  48  of the electric machine  10  completely. The Faraday cage  84  is electrically connected to the grounding line  48 . At least one leadthrough capacitor  40 ,  42  is arranged in a wall  30  of the Faraday cage  84 . Each of the leadthrough capacitors  40 ,  42  can surround a metal-plated ceramic tube  88  on a tube inner side and/or on a tube outer side. The housing component  56  and/or the shielding component  30  can surround a receptacle  90  for pressing in the leadthrough capacitor  40 ,  42 , in particular in an axial direction  92  and/or in a radial direction  94  of the tail part  58 . The Faraday cage  84  can also envelop a first interference suppression capacitance  26 . In principle, the invention can be applied to any type of electrical machines with brushes  12 ,  14 ,  16  and is particularly advantageous for wiper motors  10 . A further interference suppression inductor  44  can be inserted in the grounding line  48 .