Abstract:
The invention relates to a wiper bearing for a windshield wiper system comprising a bearing housing ( 12 ) provided with an outer tube forming the bearing housing ( 12 ) and an inner tube ( 24 ) arranged in a concentric manner in relation thereto and a journal ( 30 ) arranged on a bearing area ( 14 ) on the bearing housing ( 12 ) for receiving a tubular plate ( 40 ). It is proposed that an annular element ( 16 ), which is arranged in a coaxial manner on the journal ( 30 ), be provided outside the journal ( 30 ) in the region of the front side thereof ( 36 ).

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The invention starts with a wiper bearing.  
         [0002]     A wiper bearing housing is used to support a wiper shaft and to position a wiper axis as well as fastening receptacles for assembly in a vehicle. High forces and moments occur above all in the transition area between the wiper bearing housing and the tubular plate, particularly in the case of snow load or cases of lock-up.  
         [0003]     A wiper system is known from DE 199 25 292 A1 in which the tubular plate in the transition area has an enlarged cross section, which reduces the specific load in the critical transition area and increases flexural strength and resistance to torsion.  
       SUMMARY OF THE INVENTION  
       [0004]     In the case of a wiper bearing in accordance with the invention, it is proposed that an annular element that is arranged in a coaxial manner on the journal be provided outside a journal that is provided to receive a tubular plate. The journal is permanently connected to an outer tube of the wiper bearing forming the bearing housing or to an inner tube arranged in a concentric manner in relation thereto. Due to a positively engaged connection of the tubular plate with the journal, forces are transferred from the bearing housing to the journal including torsional forces. The journal henceforth assumes mainly tensile forces, compressive forces and torsional forces. The annular element and its connecting braces assume bending moments and bending forces. The journal is mechanically stressed less and more uniformly as a whole. The annular element can essentially assume bending forces, which act in a plane, which is formed of a bearing axis and the journal. The tubular plate is supported by the annular element and the journal is relieved correspondingly. Only slight bending loads occur on the journal itself. It is also possible to provide two coaxially arranged annular elements. In this case, the outer annular element has very good stability and eases the connection of the tubular plate with the journal. The construction is especially compact when the journal is fastened to the inner tube. The initiation of force in this case takes place on both the inner tube as well as on the outer tube.  
         [0005]     Because of the low stress, a transitional geometry between the journal and its bearing point on the bearing housing can be designed simply with a shortened distance between a connecting area between the journal and the tubular plate and the bearing area of the journal on the inner tube or outer tube of the bearing housing. The wiper bearing, in particular a wiper bearing made of plastic, can be designed to be shorter and more compact than previous plastic wiper bearings in which attention had to be paid to a long and harmonic transitional area in order to reduce any mechanical tension spikes occurring there. Because of the compact design of the wiper bearing, the tubular plate can be brought closer to the bearing area of the wiper axis, thereby resulting in a more rigid overall system. Because of the uniform mechanical stress of the bearing housing, it can be designed in a uniformly thin-walled manner, which is especially advantageous for a wiper bearing design of plastic in order to avoid bubbles forming in the plastic during manufacturing. In addition, a shorter cooling and cycle time during manufacturing is made possible. In connection with the reduced dead weight, the wiper bearing with the annular element can be cost-effectively manufactured and mounted. The tubular plate can be designed with a small cross section, which signifies a reduction in weight and a lower requirement for construction space. Because of elastic deformation, for example in the case of a lock-up, wiper supports with a smaller cross section of the tubular plate relieve all components of the wiper system, even the wiper lever, thereby making possible additional cost savings since these components can be designed more simply.  
         [0006]     Because of the arrangement of the annular element and the improved support of the tubular plate in the bearing area, less movement occurs when operating the wiper system and even in the case of high loads the connecting point will not fail. The alignment of the wiper shaft remains practically unchanged so that, according to the design, the adjustment angle of the wiper blade to the vehicle window is retained, thereby guaranteeing good wiping quality.  
         [0007]     Because of the special geometry, high component rigidity as well as an improvement in the rigidity of the overall system is achieved despite the preferred use of unreinforced plastics for the wiper bearing. As a result, the scope of use of wiper drives with plastic wiper bearings can be expanded.  
         [0008]     The bearing housing is resistance to bending and nevertheless can be manufactured of unreinforced, cost-effective materials. During manufacturing, work can be done with very simple sliders. Because of the design of the wiper bearing and the resulting tool structure, in addition to unreinforced plastics, materials that cannot be demolded so easily are also suitable in principle, such as reinforced plastics or metallic diecasting materials, particularly Zn, Mg and Al.  
         [0009]     The annular element is arranged connectionless to the journal on the bearing housing and can therefore keep the bending load away from the journal to a large extent. In addition the annular element is fastened with braces on the bearing housing, via which the journal is accessible from the outside at least in a connecting area, in which the tubular plate is connected to the journal. For one, the preferred fastening with upper and lower braces makes high rigidity of the annular element/brace arrangement possible, and, secondly, both manufacturing of the wiper bearing and connecting the tubular plate to the journal are simplified since the journal is accessible from outside in a simple manner for corresponding tools, for example crimping tools.  
         [0010]     If the annular element is arranged axially in front of the journal, in particular without overlapping with the journal on its front side, the wiper bearing can be manufactured with an advantageous tool without an annular core and a correspondingly simple and solid tool slider. This also makes better tool cooling and core cooling possible with a preferred diecasting or injection molding method. If the journal projects with a front side into the annular element, demolding of hollow profile cores and of the annular core can be accomplished in the same direction, requiring only a single tool slider.  
         [0011]     If the journal is arranged approximately centric with respect to an axial extension of the bearing housing, the annular element is supported broadly on the bearing housing and only slight component distortion occurs during cooling after manufacture, which goes hand in hand with high geometry quality and good processsability. Alternatively, the journal can be arranged off-center with respect to an axial extension of the bearing housing, e.g., on a lower end of the bearing housing. As a result, broad support on the bearing housing is possible.  
         [0012]     The wiper bearing can be designed to be especially rigid if the journal has a cross section embodied as a hollow profile. This embodiment is especially rigid. The tool cores required for this hollow profile can be aligned in such a way that they are pulled in the direction of the journal, i.e., simultaneously with an annular tool core for generating the annular element. Alternatively, the journal has a cross section embodied as a T-support or a double T-support.  
         [0013]     A connecting geometry can be created and demolded in two tool halves. The tool structure is especially simple.  
         [0014]     It is advantageous if a component geometry between the annular element and the bearing point can be demolded laterally during its manufacture. In addition to the simplifications of the tools already described, this makes it possible for the tubular plate to be surrounded after being slipped on in order to connect the tubular plate to the journal with preferred so-called crimping. This guarantees good positive engagement and a qualitatively high quality of the connection between the tubular plate and the journal. In doing so, the tubular plate is deformed plastically and displaced into pockets of the wiper bearing housing or of the journal provided for this purpose. Standard tools for crimping can be used. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The invention will be explained in greater detail in an exemplary embodiment on the basis of the associated drawings. The drawings show:  
         [0016]      FIG. 1 A  wiper bearing with a short annular element with asymmetrical fastening via support profiles;  
         [0017]      FIG. 2 A  wiper bearing with a short annular element with symmetrical fastening with a hollow profile cross section;  
         [0018]      FIGS. 3   a, b  A depiction of sectional planes in the longitudinal direction (a) and perpendicular to a journal line of symmetry (b);  
         [0019]      FIGS. 4   a, b  A tool structure and the separation of tool halves with a cross section with a hollow profile (a) and a cross section with a T-support profile (b);  
         [0020]      FIGS. 5   a, b  A tool structure (a) and a tool core with an annular core (b);  
         [0021]      FIG. 6 A  cross section through a wiper bearing with overlapping of the journal and annular element;  
         [0022]      FIGS. 7   a, b  A tool structure (a) and a tool core without an annular core (b);  
         [0023]      FIG. 8 A  cross section through a wiper bearing without overlapping of the journal and annular element;  
         [0024]      FIGS. 9   a - f  On the basis of a cross section through the journal, a procedural sequence of a crimping process before (a) and after attaching a tubular plate (b), introduction of the tool (c), surrounding of the tubular plate with the tool (d), insertion of the die in the connecting area between the tubular plate and the journal (e) and the completed connection (f);  
         [0025]      FIGS. 10   a, b  A size comparison of a preferred wiper bearing (a) with a known wiper bearing (b);  
         [0026]      FIG. 11 A  section through a wiper bearing with an annular element executed as a double ring;  
         [0027]      FIG. 12 A  depiction of an assembly of wiper bearing and tubular plate;  
         [0028]      FIG. 13 A  comparison of component rigidities of a preferred wiper bearing in accordance with the invention and two known wiper bearings with a hollow profile journal and a T-support journal. 
     
    
     DETAILED DESCRIPTION  
       [0029]     The invention is particularly suitable for wiper bearings made of plastic. In general, the same reference numbers are used in the figures for the same parts.  
         [0030]      FIG. 1  shows a wiper bearing  10  for a windshield wiper system with a bearing housing  12  and a journal  30  arranged on a bearing area  14  on a bearing housing  12  and a short annular element  16 . The bearing housing  12  formed by an outer tube concentrically surrounds an inner tube  24 . The short annular element  16  is arranged coaxially outside the journal  30  in the area of its front side  36 . The journal  30  and the annular element  16  are arranged off-center with respect to an axial extension of the bearing housing  12 .  
         [0031]     The annular element  16  is fastened on the bearing housing  12  with an upper brace  18  and a lower brace  20 , through which the journal  30  is accessible from the outside at least in a connecting area  32 . A tubular plate (not shown) will subsequently be connected to the journal  30  in this connecting area  32 . The braces  18 ,  20  are embodied in this case as T-supports. The annular element  16  has no direct connection to the journal  30  so that the tubular plate (not shown) can be slipped on the journal  30  in a small free space between the journal  30  and the inner circumference of the annular element  16 . The free space is dimensioned in such a way that the tubular plate can be adjacent to both the journal  30  as well as the inner circumference of the annular element  16 .  
         [0032]      FIG. 2  shows a wiper bearing  10  with a short annular element  16  with a symmetrical connection of the journal  30  and the annular element  16  on the bearing housing  12 . The lower and upper braces  18 ,  20 , which hold the annular element  16 , have a hollow profile cross section. The journal  30  and the annular element  16  are arranged approximately centric with respect to an axial extension of the bearing housing  12 .  
         [0033]      FIGS. 3   a, b  depict a representation of sectional planes through the wiper bearing  10 .  FIG. 3   a  shows a section in the longitudinal direction of the journal  30 . It is evident that the journal  30  is connectionless to the annular element  16 .  FIG. 3   b  shows a section perpendicular to a journal line of symmetry. The journal  30  has a hollow profile, which has a reinforcing element arranged centrically; the lower and upper braces  18 ,  20 , which hold the annular element  16 , are also embodied as hollow profiles.  
         [0034]      FIGS. 4   a, b  show a cross section of a preferred tool for manufacturing braces  18 ,  20  and the journal  30  as well as the separation of tool halves  50 ,  52  of the tool. The arrangement of the braces  18 ,  20  and of the journal  30  in accordance with the invention advantageously permits the use of a tool, which can be divided in the center into the two tool halves  50 ,  52 .  FIG. 4   a  shows the tool with braces  18 ,  20  embodied as hollow profiles and a journal  30  embodied as a hollow profile.  FIG. 4   b  shows a variation of the tool for braces  18 ,  20  embodied as a T-profile and the journal  30 .  
         [0035]      FIGS. 5   a, b  show as longitudinal section through a preferred tool structure of a tool  60  ( FIG. 5   a ) and an associated preferred tool slider  62  ( FIG. 5   b ) for an embodiment of the journal  30  and braces  18 ,  20  with hollow profiles. In order to demold the four hollow profile cores, as shown in  FIG. 4   a  for example, only a single tool slider  62  is advantageously required, whereby the annular core  64  and the hollow profile cores can be demolded in this same direction. The annular core  64  is required if the journal  30  and annular element  16  overlap, i.e., the front side  36  of the journal  30  projects into the annular element  16 .  FIG. 6  shows a section through this type of wiper bearing  10  with overlapping of the journal  30  and the annular element  16  with a tubular plate  40  slid on. The tubular plate  40  is stably clamped between the annular element  16  and journal  30  in the overlapping area.  
         [0036]      FIGS. 7   a, b  depict a tool structure without an annular core. The tool structure of the tool  70  shows a mold for a shorter journal  30  than in  FIG. 5   a  ( FIG. 7   a ) and a tool core without an annular core ( FIG. 7   b ). A solid tool slider structure is possible as a result; moreover the tool and the tool core can be cooled better. The variation of this type of wiper bearing  10  is depicted in  FIG. 8  as a cross section. A tubular plate  40  is slid onto a journal  30  and is simultaneously encircled by an annular element  16 . The journal  30  is shorter than in the exemplary embodiment in  FIG. 6  and does not project into the annular element  16 , which sits axially in front of the journal  30 .  
         [0037]      FIGS. 9   a - f  illustrate on the basis of cross sections through the journal  30  and the braces  18 ,  20  a procedural sequence of a connecting process between the journal  30  and the tubular plate  40  that is executed as a crimping process.  FIG. 9   a  shows the journal  30  and braces  18 ,  20  at the beginning of connection.  FIG. 9   b  also shows the tubular plate  40  that is slid onto the journal  30 . Finally, on both sides of the journal  30 , a tool part  70 ,  72  with die pairs  74 ,  76  each approaches the journal  30  ( FIG. 9   c ) until the journal  30  that is surrounded by the tubular plate  40  is surrounded by the tool parts  70 ,  72  ( FIG. 9   d ). This is possible because of the special wiper bearing geometry and very advantageous for the quality of the connection between the journal  30  and the tubular plate  40 . Finally, the die pairs  74 ,  76  for creating a positive engagement between the wiper bearing or the journal  30  and the tubular plate  40  are pressed into the tubular plate  40 . The die pairs  74 ,  76  displace the tubular material into pockets on the journal  30  provided for this purpose ( FIG. 9   e ).  FIG. 9   f  shows the finished arrangement upon conclusion of the connecting process. The tubular plate  40  is connected with positive engagement to the journal  30  in the connecting area (corresponding to connecting area  32  in  FIG. 1  and  FIG. 2 ).  
         [0038]      FIGS. 10   a, b  depict a size comparison of a preferred wiper bearing  10  ( FIG. 10   a ) with a known wiper bearing  80  ( FIG. 10   b ). The preferred wiper bearing  10  has a journal  30 , which is fastened on an inner tube  24  of the wiper bearing  10  so that an initiation of force occurs both on the inner tube  24  as well as on the bearing housing  12  embodied as the outer tube. The bearing area  26  of the journal  30  and the bearing area  28  of the annular element  16  or of the elements on the inner tube  24  holding the annular element  16  are preferably embodied concentrically in order to guarantee good roundness of the two bearing areas  26 ,  28 . On the other hand, the known wiper bearing  80  shows a journal  82  that must be considerably longer than is the case with the arrangement in accordance with the invention with correspondingly lower flexural strength and tension excesses under load.  
         [0039]      FIG. 11  shows a section through a wiper bearing  10 , in which the annular element  16  is embodied as a double ring. The double ring increases the stability of the annular element  16 . In addition, this creates a greater free space between the journal  30  and the braces  18 ,  20  so that when connecting the tubular plate  40  to the journal  30  there is more space for a tool, particularly a crimping tool.  
         [0040]      FIG. 12  shows a depiction of an assembly of wiper bearing  10  and tubular plate  40 . The tubular plate  40  is connected with positive engagement to the journal  30  in the connecting area  32 . Braces  18 ,  20  hold an annular element  16 , which encircles the tubular plate  40 . The braces  18 ,  20  are embodied as hollow profiles.  
         [0041]     The embodiment in accordance with the invention of a wiper bearing  10  provides a clear improvement in component rigidity.  FIG. 13  shows a comparison of component rigidities of a preferred wiper bearing  10  and two known wiper bearings with a hollow profile journal and a T-support journal similar to the design in  FIG. 10   b.    
         [0042]     The known wiper bearing with the T-support journal has the lowest component rigidity, which is clearly evident in Curve C. Even though a known wiper bearing with a hollow profile journal shows an improvement in the component rigidity (Curve B), the wiper bearing  10  in accordance with the invention is improved in terms of its component rigidity by more than a factor of 2. This is due to the fact that the distribution of the elastic tension in this case is very uniformly distributed on the journal, while in the case of the known wiper bearings local tension excesses occur as analyses using the finite element method (FEM) have shown.