Abstract:
The invention relates to a DC motor, particularly for a fan device of a motor vehicle, having a stator and a metal grounding plate arranged on the stator, for receiving at least one leadthrough capacitor of an interference suppressor device. The capacitor being arranged in a connection line of the motor. According to the invention, the leadthrough capacitor includes a metal housing with at least one contact section for contacting the stator and/or the metal grounding plate. Thus, a compact interference suppressor device, which can be produced in a cost-effective way and is easy to install, is achieved.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 35 USC 371 application of PCT/EP2008/053395 filed on Mar. 20, 2008. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is based on a direct current motor, in particular a direct current motor for driving a blower of a motor vehicle. 
     2. Description of the Prior Art 
     A direct current motor is known from German Patent Disclosure DE 10 2004 046 299 A1. The motor described there has a stator with an opening for the leadthrough of electrical connection lines to the motor brushes, and in the region of the recess in the stator there is an interference suppressor for reducing and/or eliminating line interference signals. Part of this interference suppressor is a leadthrough capacitor, which is disposed in an electrical path of at least one connection line and is secured to a ground plate seated in the recess in the stator. This known arrangement is said to be improved with regard to its interference suppression effect. 
     ADVANTAGES AND SUMMARY OF THE INVENTION 
     The proposed design of the direct current motor with the characteristics of claim  1  has the advantage in particular that because of the improved design of the contact, close to the metal housing of the leadthrough capacitor and with a disposition of the ground plate in good electrical contact with the stator of the motor, the interference suppression of the motor is markedly improved. It is expedient if the housing of the leadthrough capacitor is embodied cylindrically, because then uniform ground contact can be attained in an especially simple way over the entire outer circumference of the capacitor. 
     Preferably, the housing of the leadthrough capacitor has a contact flange with contact portions disposed symmetrically to the leadthrough axis of the capacitor, and the associated connection line of the motor extends in the leadthrough axis. It is especially expedient for optimal interference suppression if a circular-annular contact flange of a cylindrical housing of the leadthrough capacitor has contact portions disposed concentrically with the leadthrough axis, so that the ground contacts of the capacitor housing surround the connection line at the same spacing. However, to make the sheet-metal cuts easier, it is also alternatively possible to choose a square or rectangular shape for the capacitor housing and the contact flange. 
     With respect to mounting the ground plate on the stator of the motor, it is advantageous if the ground plate fits over the stator with an essentially U-shaped peripheral portion and this peripheral portion is preferably pressed against the stator by a bearing plate of the motor, thereby ensuring secure locking and good electrical contact between the ground plate and the stator. 
     Further details and advantageous features of the invention will become apparent from the description of an exemplary embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in further detail below in conjunction with the drawings, in which: 
         FIG. 1  is an exploded view of the direct current motor of the invention; 
         FIG. 2  is a perspective view of a leadthrough capacitor designed according to the invention; 
         FIG. 3  is a perspective view of a ground plate for holding and contacting a leadthrough capacitor and a further connection line to the motor; 
         FIG. 4  shows a fragmentary section through the stator of a direct current motor having a leadthrough arrangement with a ground plate which carries a capacitor and is locked by a bearing plate of the motor and contacted with the stator; 
         FIG. 5  shows a fragmentary view of the stator of the direct current motor with the interference suppressor inserted; and 
         FIG. 6  is a view of the interference suppressor of the motor with the connection lines to the motor brushes. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In  FIG. 4 , reference numeral  10  indicates a stator of a direct current motor of the kind used for instance for heater or air conditioning blowers in motor vehicles. The stator  10  is embodied in two layers, with an inner housing plate  12  and an outer housing plate  14  that are permanently joined together, for instance welded together. In the stator, recesses  16  are provided for the leadthrough of connection lines  40  and  52 , which are not shown in  FIG. 1 . 
     An interference suppressor  18  is placed in the region of the recesses  16  in the stator  10  and is held during mounting on a brush holder  20 . Securing the brush holder  20  with the interference suppressor  18  in the stator is done by means of a bearing plate  22 , which is permanently locked by calking in the region of protrusions  23  on the stator  10  and in so doing positions and contacts the interference suppressor  18  in the region of the recesses  16  of the stator. A rotor  24  with a collector  26  and a power takeoff shaft  28  is disposed in the stator  10  and drives a blower, not shown, of a motor vehicle. 
       FIG. 2  in an enlarged perspective view shows a leadthrough capacitor  30  of the interference suppressor  18 , with a cylindrical, cup-shaped housing  32 . The term leadthrough capacitor stands here for a plurality of capacitor elements which are interconnected on a printed circuit board and embedded in a potting composition  34 . The potting composition may be omitted if the housing is sealed off in some other way. The housing  32  of the capacitor  30  has an essentially circular-annular contact flange  36 , which is disposed concentrically to the leadthrough axis  38 . The connection line  40  to the positive pole, not shown, of the direct voltage supply of the motor is located in the leadthrough axis  38 . The contact flange  36  is subdivided into individual contact portions  42 , which each have tabs, bent at an angle to the housing, for contacting the stator  10 . 
       FIG. 3  shows a ground plate  44  with a first opening  46  for receiving the leadthrough capacitor  30  disposed in the connection line  40 . The housing  32  of the capacitor is locked, centered and contacted between identical contact tongues  48  that protrude from the circumference of the opening  46 . The contact tongues  48  are distributed uniformly and symmetrically to the leadthrough axis  38  of the capacitor  30  and of its housing  32  on the circumference of the opening  46 . Extending through a second opening  50  in the ground plate  44  is a negative line, not shown in  FIG. 3 , as a second connection line of the motor, the negative line being connected to ground. This line is secured by clamping for example and electrically contacted at a holding lip  54  of the ground plate  44 . Instead of the second opening  50 , however, to improve the interference suppression effect, a second opening in the version like the opening  46  may be provided, with a further capacitor  30 . 
     Above the openings  46  and  50 , the ground plate  44  has a peripheral portion  56 , bent essentially in the shape of a U, with which it fits over the stator  10  and is electrically contacted with it, as will be described and explained in further detail below. 
       FIG. 4  shows a fragmentary section through the stator  10  of the direct current motor and through the interference suppressor  18 . It can be seen clearly in this view how the contact portions  42 , protruding symmetrically and uniformly from the contact flange  36 , rest on the inner housing plate  12  of the stator  10  and thus establish a secure ground connection from the housing  32  of the capacitor  30  to the stator. The electrical contacting is effected symmetrically here and concentrically to the connection line  40 , thus optimizing the interference suppression effect. The contact between the ground plate  44  and the stator  10  is ensured by pressing the bearing plate  22  against the middle part of the U-shaped peripheral portion  56  of the ground plate  44 . 
     In  FIG. 4 , an insulation mount  58  is also shown, which surrounds the connection line  40  and is fixed on the one hand in the U-shaped peripheral portion  56  of the ground plate  44  and on the other in the recesses  16  of the stator  10 . By means of this insulation mount  58 , the location of the connection lines  40  and  52  ( FIG. 5 ) is defined, and the insulation of the lines in the leadthrough region is ensured, optionally including if flexible pigtail cables for the connection lines are used. The use of pigtail cables for connecting the carbon brushes and the use of flexible connection lines  40 ,  52  also lessens the transmission of noise from the motor to the outside. 
       FIG. 5  in a schematic view shows a part of the stator  10  with the inner housing plate  12 , the outer housing plate  14 , and the ground plate  44  that fits over the inner housing plate  12  with its U-shaped peripheral portion  56 . The connection lines  40  and  52  are shown without the insulation mount  58 . The alignment and positioning of the ground plate  44  is effected by means of the upward-protruding protrusion  23  of the inner housing plate  12 , which after the bearing plate  22  is placed on top and calked ensures the secure locking and contacting of the ground plate  44  at the support point  60  and of the interference suppressor  18  in the stator  10 . 
       FIG. 6 , in a further perspective view, shows the interference suppressor  18  with the positive connection line  40  and the negative connection line  52 , which are secured in a position and alignment in the region of the recess  16  in the stator by the insulation mount  58 . The connection lines  40  and  52  in this version are connected inside the motor to lead lines  68  and  70  to the brushes  72  and  74  by means of clamping bushes  64  and  66 . In this way, for the outer connection lines  40  and  52  on the one hand and for the lead lines  68  and  70  to the motor brushes on the other, different lead line types can be selected, in particular pigtail-like lead lines  68  and  70  to the brushes and solid connection wires for the outer connection lines of the motor. Otherwise, the arrangement in  FIG. 6  corresponds to the embodiment in the foregoing views. 
     By the design according to the invention of the interference suppressor  18  of a direct current motor, on the one hand the expense for interference suppression of the motor can be reduced markedly, and on the other, the quality of interference suppression can be markedly improved, in particular with respect to high interference frequencies. The interference suppression chokes and capacitors in known interference suppressors of direct current motors can be eliminated and the effort and expense for wiring and mounting can be reduced markedly, thus lowering the total system costs for producing the motor while the interference suppression stays the same or is improved, and making it possible to meet increasingly stringent demands for electromagnetic compatibility. Moreover, the proposed new interference suppression module can be achieved using commercially available components that are modified only slightly, making overall production and assembly less expensive, and good interference suppression can be achieved up to frequencies on the order of magnitude of 2 GHz, which occur particularly in mobile telephones. 
     In addition, by means of the provisions of the invention, tension relief for the connection lines  40  and  52  can be attained at no additional expense. With different models and sizes of motor, the design of the ground plate  44  is easily adaptable to the motor model without changing the other components of the interference suppressor  18 , and the ground plate  44  covers the recesses  16  in the stator  10  essentially without gaps and thus also improves the interference suppression with respect to interference other than line interference. 
     The foregoing relates to the preferred exemplary embodiment 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.