Abstract:
A DC machine, particularly a DC motor for use in a motor vehicle, includes a stator, a rotor that is supported rotatably in a pole housing having a commutator, and having a brush-holder support, made substantially of plastic, for fixing at least two brushes and further components. The brush-holder support has a device for improving the positioning of the components situated on or at it relative to the rest of the machine and/or for shortening the tolerance chain of the machine, in particular, a longtime stabilization of the overall equipment being also achieved.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a DC machine, particularly for a DC motor for use in a motor vehicle. 
       BACKGROUND INFORMATION 
       [0002]    Such brush-commutated DC machines having a plastic brush-holder support are basically known, for instance, from DE 38 18 891. This document shows a DC machine having a disk-shaped brush-holder support designated there as a base, which is entirely made of plastic and is connected rigidly, in a predefined position with respect to the commutator of the machine, to its pole housing. As to the positioning of components on the brush-holder support of the machine, the document only makes statements with regard to the connection of the brushes, which are electrically connected and fastened to the connecting lines of the machine in a contact piece. 
       SUMMARY 
       [0003]    Example embodiments of the present invention provide that the tolerance chain of a DC machine, conditioned upon the production and the assembling of the brush-holder support, is clearly reduced. This particularly achieves that the brush-holder support of the machine has sufficient stability in itself, as well as defined fastening and positioning possibilities for the components that are to be situated on it, and at the same time is designed so that its production is able to be automated without difficulties. 
         [0004]    An especially great stability of the brush-holder support is achieved by having its base plate strengthened or stiffened by dome-like structures, whereby a plurality of interconnected planes is created, which clearly increases the bending strength and the resistance to torsion of the brush-holder support, and with that, the positioning accuracy of the components situated on it. 
         [0005]    For the largely voltage-free fastening of the brush-holder support on the pole housing, it is advantageous if the former has a mounting flange on its circumference which is preferably only connected pointwise to the base plate of the brush-holder support. The mounting flange is fitted in between the pole housing and the adjacent bearing cover, and the brush-holder support is thereby largely decoupled from the metal housing of the machine, whereby, on the one hand, different heat expansions may individually develop at the pole housing and at the brush-holder support, without the plastic brush-holder support being deformed. On the other hand, this design additionally yields noise decoupling between the brush-holder support and the housing, since vibrations on the brush-holder support are transferred to the housing, to only a slight degree. 
         [0006]    Another advantageous design possibility for the brush-holder support, with regard to simplifying assembly and to the reliable fastening of the contact springs for the brushes, is yielded if the brushes are locked on the commutator-side end of the brush cartridge, using a Z-shaped end section. 
         [0007]    Such a design of the spring end, on the one hand, ensures the independent alignment of the spring when it is mounted on the brush cartridge, and on the other hand, the Z-shape ensures reliable locking in operation. The locking and adjustment of the brush press-on spring may even be additionally improved, in this instance, if the Z-shaped end section of the press-on spring has an opening for the passage of a positioning pin at the brush cartridge. In this way the press-on spring is held with point accuracy. 
         [0008]    Besides the brushes themselves, particularly interference suppressors, such as chokes and capacitors are situated on the brush-holder support. For the durable, shake-proof fastening of at least one interference suppressing capacitor it is expedient, in this instance, if the latter is situated in a mounting support that is extruded of plastic in one piece with the brush-holder support and that is aligned perpendicular to the machine axis, which is preferably developed as a box type. The interference suppressor capacitor is thus reliably held on all sides, its terminal lugs remaining freely accessible and being able to be connected simply and reliably to the outer electrical connecting leads of the machine. 
         [0009]    When metallic brush cartridges are used, it is for the expedient aim of an especially great firmness and shake-proof stability if, at the assembly cutouts on the underside of the base plate of the brush-holder support, in the area of the passage of little crimpable cartridge feet, bend-over ribs for the latter are situated. This ensures an especially firm seat of the brush-holder support during the crimping of the little cartridge feet. 
         [0010]    Further details and aspects of example embodiments of the present invention are described in more detail below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a sectional view of the DC machine arranged according to an example embodiment of the present invention. 
           [0012]      FIG. 2  is a perspective partial view of the brush-holder support in the area of the connection of the interference suppressor components fastened on it. 
           [0013]      FIG. 3  is a perspective overall view of the unassembled brush-holder support. 
           [0014]      FIG. 4  is a perspective partial view of the brush-holder support in the area of the brush cartridges. 
           [0015]      FIG. 5  is a top view of a brush-holder support assembled with brushes and interference suppressor components. 
           [0016]      FIG. 6  is a perspective partial view of the brush-holder support having a brush press-on spring. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]      FIG. 1  shows a DC machine  10  executed as a DC motor for use in a motor vehicle. The machine has a pot-shaped pole housing  12 , which is closed on one side by a bearing cover  14 . Inside pole housing  12 , a stator  16  is developed by permanent magnets  18 , which are fastened to pole housing  12  in a known manner. A rotor  20  of the machine is positioned on a shaft  22 , which is rotatably supported, on one side in pole housing  12 , and on the other side in bearing cover  14 . Furthermore, there is a commutator  24  situated on rotor shaft  22 , to which the field current for rotor  20  is supplied via brushes  26 . 
         [0018]    Brushes  26  and additional components, especially the required interference suppressor of the machine, are held on a brush-holder support  28 . Of the interference suppressor of the motor, one may see in  FIG. 1  an interference suppression choke  30  and a capacitor  32 . The locking of brush-holder support  28  in pole housing  12  takes place by a mounting flange  34 , which extends over the entire circumference of the brush-holder support and is clamped in between pole housing  12  and bearing cover  14  in the finished assembled state of the machine. The design and the assembling of brush-holder support  28  are explained in detail with the aid of the following figures, in which the same reference numerals are used for the same parts. 
         [0019]      FIG. 2  shows a perspective representation of a part of brush-holder support  28  that is made of extruded plastic. The current supply of a DC voltage source (not shown) takes place via two connecting lines  36  and  38 , which are connected on one side to the positive pole, and on the other side to the negative pole of the DC voltage source (not shown), as well as via contact pieces  40  and  42  to interference suppression reactors  30  and  31 . At the same time, connecting line  36  is connected to one electrode and connecting line  38  is connected to the other electrode of interference suppression capacitor  32 . The latter is locked durably and in a shake-proof manner in a mount developed as a pocket  44 , that is aligned perpendicular to the machine axis. Pocket  44  is extruded in one part with brush-holder support  28  from plastic, in this instance. Instead of a pocket-shaped arrangement, the mount could however also be executed in the form of a retention arm or in the form of a retaining hoop, it being essential that the alignment of the mount is perpendicular to the machine axis, in order to ensure a durable, shake-proof locking of capacitor  32 . 
         [0020]      FIG. 3  shows a perspective view of the non-assembled brush-holder support  28 . Besides the arrangements already discussed, its base plate  54  has a plurality of assembly recesses  56  for mounting a variable number of brush cartridges that are not shown in this figure. Brush-holder support  28  according to  FIG. 5  has four assembly recesses  56  of which, depending on the design of the DC machine, optionally two, three or four may be assembled with brush-holder supports  28  in a known manner. 
         [0021]    The brush cartridges, metallic as a rule, that are not shown in  FIG. 3 , are secured using little cartridge feet, which on one side reach through cutouts  58  in base plate  54  of the brush-holder support and around inner end  60  of assembly cutouts  56 , and are crimped below base plate  54 , as may be seen in  FIG. 4 . At the lower side of base plate  54  of brush-holder support  28  that is visible in  FIG. 4 , in the area of the passage of the little cartridge feet  62  of brush cartridges  64 , in this case bend-over ribs  66  are formed on base plate  54  which, upon the crimping of little cartridge feet  62 , ensure a durable seat of brush-holder supports  28  that is free of play. The central opening for the later passage of commutator  24  through brush-holder support  28  is marked  68 . Moreover, in  FIGS. 3 and 4 , dome-like structures  70  will be seen on base plate  54  of brush-holder support  28 , which clearly increase the bending strength of the base plate. In that manner base plate  54  is able to be shaped and stiffened in several planes. 
         [0022]      FIG. 5  shows a top view of a brush-holder support  28  assembled with brushes  26  and interference suppression components  30 ,  31  and  32 , in which one may see the distribution of the assembly components on the brush-holder support. The illustration shows that assembly cutouts  56  for brush-holder supports  28  are situated on base plate  54  such that the brushes are located in a first sector that extends approximately over the upper half of the base plate and the electrical interference suppression means  30 ,  31 ,  32  are located in a second sector on the lower half of base plate  54 . By this arrangement it is achieved that interference suppressed electrical connections to chokes  30  and  31  and to capacitor  32  run outside the outer sector of brush-holder support  28  taken up by brushes  26 , and thus no interference signals are induced any more in the electrical connections of the brushes that have already been interference suppressed, whereby the electromagnetic compatibility (EMC) of the machine is clearly improved. 
         [0023]    In the lower range of central opening  68  in brush-holder support  28 , three centering ribs  72  may be seen, which extend for approximately the same distance into central opening  68  of brush-holder support  28  as brushes  26  themselves, at their contacting rest on commutator  24 , that is not shown in  FIG. 5 . This arrangement is indicated by a circular dotted line  74 . In this way, the centering of an assembly aid, that essentially corresponds to dotted line  74  in its design for fitting commutator  24  into central opening  68  in brush-holder support  28 , is clearly simplified. For reasons of symmetry, in this context, centering ribs  72  are distributed uniformly over the lower sector of brush-holder support  28 , that is not occupied by brushes  26 . 
         [0024]    Furthermore, in  FIG. 5  the design of mounting flange  34  for brush-holder support  28  is also shown, which extends over the entire circumference of brush-holder support  28 , but which is connected only pointwise to it via a plurality of crosspieces  88  that are distributed along the circumference. Mounting flange  34  and crosspieces  88  are extruded of plastic in one part with brush-holder support  28 . In order to lock brush-holder support  28 , flange  34  is firmly clamped between the edge of pole housing  12  and the opposite edge of bearing cover  14 , whereby a reliable holding and an exact axial positioning of brush-holder support  28  are ensured. At the same time, however, because of the pointwise connection of brush-holder support  28  to mounting flange  34 , the brush-holder support element is largely decoupled from pole housing  12 , so that different thermal expansions of brush-holder support  28  and pole housing  12  are able to develop individually, without base plate  54  of brush-holder support  28  becoming domed. In addition, noise decoupling is created between brush-holder support  28  and pole housing  12 , bringing on a clear reduction in the noises eradiated by the machine. 
         [0025]      FIG. 6  shows a perspective partial view of brush-holder support  28  in the vicinity of a brush  26 , from which one is able to see the arrangement of a spring  76  arranged as a coil spring, for pressing brush  26  against commutator  24 . With its rolled end  78 , the spring extends into brush cartridge  64  and presses brush  26  in the direction towards the commutator, and using its Z-shaped end section that faces commutator  24 , it embraces brush cartridge  64  and is locked on it at rest. In addition, Z-shaped end section  80  of spring  76  has an opening  82  for the passage of a positioning pin  84  on brush cartridge  64 , whereby spring  76  is held and positioned, with point accuracy and in a shake-proof manner, on brush cartridge  64 .