Abstract:
The invention relates to a transmission drive unit ( 10 ), especially for adjusting a mobile part ( 58 ) in the motor vehicle. Said drive unit comprises a drive element ( 18 ) which can be driven by a drive assembly ( 42 ) and which is rotatably received in a support tube ( 14 ) by means of a bearing plate ( 28 ). The drive element ( 18 ) has a first axial stop ( 23 ) which is supported on a first axial bearing surface ( 21 ) of the support tube ( 14 ). The drive element ( 18 ) has a second axial stop ( 35 ) which rests against a second axial bearing surface ( 27 ) of the bearing plate ( 28 ), the bearing plate ( 28 ) being forced against the second axial stop ( 35 ) of the drive element ( 18 ) by a material deformation ( 35 ) of the drive element ( 18 ).

Description:
RELATED ART 
       [0001]    The present invention relates to a transmission drive unit with a zero backlash bearing fastening, in particular for adjusting a movable part in a motor vehicle, according to the preamble of the independent claims. 
         [0002]    Publication DE 198 545 35 A1 makes known a drive device for a windshield wiping system of a motor vehicle, which includes a housing and an armature shaft with a worm rotatably supported therein. Using an axial force-generating device, a sliding wedge element is displaced radially to the armature shaft in order to compensate for the axial play of the armature shaft. The displacement force of the sliding wedge element is applied by a preloaded spring element that presses the sliding wedge element radially against a stop of the armature shaft, thereby displacing the armature shaft axially until the axial play is compensated for. When a strong load is placed on the armature shaft by a driven wheel, an axial force is produced, via which the armature shaft is pressed against the sliding wedge element. The sliding wedge element is pressed back radially away from the armature shaft against the spring element. As a result of this strong, sustained load on the spring element, its service life, i.e., its elastic properties, is/are reduced, and the axial play of the armature shaft is therefore no longer compensated for. The armature shaft therefore moves back and forth axially when loaded, which can result in unpleasant “clacking” sounds being produced. Nor is a sliding wedge element of this type suited for the backlash-free axial support of a drive element in a largely closed support tube that does not have a cover and that is installed radially to the bearing axis. 
       ADVANTAGES OF THE INVENTION 
       [0003]    The inventive transmission drive unit and its inventive manufacturing method with the features of the independent claims have the advantage that, by locating the drive wheel of the spindle in a support tube, a separate standardized assembly is created that is independent of a transmission housing or the drive assembly. By eliminating a conventional transmission housing, with which the driven element of the drive assembly and the drive wheel of the spindle are both located in a closed housing, the transmission drive unit, as a modular system, may be adapted—very flexibly—to different attachment devices of customer-specific applications. The same preassembled assembly may therefore always be used with the standard support tube, and the mechanical interface for attaching the transmission drive unit to the body or a part to be adjusted may be easily varied afterward using a customer-specific receiving module for the attachment device. By deforming the wall material of the support tube, the end shield may be held in a defined position very reliably once the axial play has been eliminated. The material deformation of the support tube makes it possible to redirect very strong axial forces that act on the drive element onto the support tube. 
         [0004]    Advantageous refinements and improvements of the features indicated in the independent claims are made possible by the measures listed in the subclaims. When the jacket tube is pressed radially inwardly, the end shield may be fixed in position axially—practically independently of the axial contact pressure—to eliminate longitudinal play. The attachment of the end shield is not affected by the production-related tolerances of the components to be supported, thereby making it possible to reliably prevent bearing play. In addition, an additional component is not required to fix the bearing in position, thereby making the drive unit more cost-favorable to manufacture. 
         [0005]    It is advantageous to press the wall material of the jacket region radially inward in such a manner that an axial end face is formed as an undercut that bears against the end shield. Depending on the axial forces that are produced, it is therefore possible to vary the width and depth of the undercut via the strength and duration of the caulking force, without the need to modify the design. When the undercut forms an end face that is oriented nearly perpendicularly to the spindle, it is only undergoes shear stress. As a result, the material deformation cannot be reshaped back in the radial direction even when strong axial forces are applied. Axial play is therefore effectively prevented. 
         [0006]    By locating the jacket regions in the region of the support tube with the maximum diameter, several material deformations may be easily carried out and their dimensions may be more easily varied. In addition, a more reliable attachment of the end shield is attained via the maximum radial distance to the drive axis. 
         [0007]    When the wall material of the support tube is pressed radially inward such that a tab with a free end is formed, this free end may securely fix the end shield in position axially. 
         [0008]    In terms of process engineering, the wall material may be reshaped in a particularly favorable manner using a caulking tool that acts radially on the jacket surface of the support tube. A form-fit connection may therefore be created that fixes the end shield in position axially and, possibly in the circumferential direction. 
         [0009]    To minimize friction, the drive element may be supported—particularly favorably—axially on the end shield nearly at a single point. For this purpose, the axial end of the drive element—in particular, a rotary spindle—includes a bulged surface as the second axial stop, which is designed, e.g., as an integrated ball. 
         [0010]    For this purpose—in a variation of the present invention—the end shield includes a stop face made of a harder material than is the rest of the end shield. This hard stop face may be realized, e.g., by integrating a thrust washer that has been manufactured separately. 
         [0011]    To use a spindle that extends through the support tube and out of both sides, the drive element may be easily supported axially using a circumferential stop collar that is integrally formed with the end shield. The bearing collar is located radially as close as possible to the axial hole of the end shield through which the drive element and/or the shaft are guided. 
         [0012]    For radial support, the end shield includes a sleeve-shaped, inner jacket surface against which the drive element bears radially. As a result, the axial and radial support may be advantageously realized using one component. 
         [0013]    The inventive support of the drive element is suited, in particular, for use with a drive wheel that is supported on a shaft in a rotatable or non-rotatable manner. The shaft may bear directly against the end shield, or it may bear indirectly against the end shield via the drive wheel supported thereon. 
         [0014]    When the transmission drive unit is designed as a spindle drive, with which the shaft is a spindle, particularly high axial forces occur. They may be absorbed—particularly advantageously—via the inventive material deformation of the support tube in order to eliminate axial play. 
         [0015]    The support tube is advantageously designed as a standard component in which the drive wheel with the end shield is preinstalled, as a separate assembly. To this end, a pot-shaped bearing receptacle is formed on one end of the support tube, which serves as the first bearing surface for the drive element. The material deformation takes place on the opposite end of the support tube with the larger diameter, i.e., the end to which the inserted end shield is fixed in position. 
         [0016]    The inventive manufacturing method as recited in independent claim  13  has the advantage that the caulking of the jacket tube for creating a form-fit connection with the end shield is decoupled from the action of the holding force on the end shield. As a result, axial play may be reliably prevented, independently of the manufacturing tolerances of the individual components. 
         [0017]    Due to the caulking process, the process of fixing the bearing in position may be adapted very flexibly, and without additional effort, to different strength requirements and different axial forces. This may be controlled very easily, e.g., via the radial feed of the stamping tool, thereby resulting in an undercut of a varying size for the axial support of the end shield. 
         [0018]    The inventive manufacturing method may also be used with a design of a support tube with a reinforcing base surface in which an installation opening is formed. After the end shield and the drive wheel have been installed in the support tube, a contact pressure may be applied to the end shield through the installation opening in order to eliminate the bearing play. After the jacket wall of the support tube is caulked radially, the end shield is fixed securely in position. The contact pressure applied during installation may therefore be removed. 
     
    
     
       DRAWING 
         [0019]    Various exemplary embodiments of an inventive transmission drive unit are presented in the drawing, and they are described in greater detail in the description below. 
           [0020]      FIG. 1  shows a cross section through an inventive transmission drive unit, 
           [0021]      FIG. 2  show a cross section and view of a further exemplary embodiment, and 
           [0022]      FIG. 4  shows a cross section of a further inventive spindle drive. 
       
    
    
     DESCRIPTION 
       [0023]    Transmission drive unit  10  shown in  FIG. 1  is composed of a first assembly  12 , with which a shaft  15  designed as a spindle  16  with a drive element  18  located thereon is supported in a support tube  14 , drive element  18  being designed as a wormwheel  19 . Support tube  14  is manufactured, e.g., using deep drawing, and includes—on an end region  20 —a pot-shaped bearing receptacle  22  for drive element  18 . Spindle  16  extends out of support tube  14  through opening  24  in pot-shaped bearing receptacle  22  and is connected with body  99 , e.g., via a counternut  98 , which is not shown in  FIG. 1 . With this exemplary embodiment, the other spindle end  26  is located inside support tube  14  and is supported axially and radially via an end shield  28  that is attached inside support tube  14 , to its inner wall  70 . To this end, jacket regions  8  of support tube  14  are reshaped radially inwardly, so that the regions of material deformation  82  create a form-fit connection with radially extending back side  84  of end shield  28 . As a result, end shield  28  is pressed against drive element  18 , and drive element  18  is pressed against bearing receptacle  22  of support tube  14 , thereby suppressing the longitudinal axial play of drive element  18 . Spindle end  26  includes, e.g., a spherical stop surface  30 , which rests axially against pot-shaped end shield  28 . Optionally, a stiffer thrust washer  32  may be located in end shield  28 . Drive element  18  is designed as wormwheel  19  that includes axial projections  34  for radial support. Axial projections  34  rest on a cylindrical jacket surface  37  of end shield  28 . Drive element  18  is injection-molded using plastic directly onto spindle  16  and includes toothing  36  that meshes with a driven element  40  of a drive assembly  42 . Drive assembly  42  is designed as an electric motor  43  and is connected with first assembly  12  using a coupling device  44 . Support tube  14  has a projection  46 , which is used to position support tube  14  relative to coupling device  44 , and into which a fixing element  48  of coupling device  44  engages. To transfer the torque from drive assembly  42  to separate assembly  12 , support tube  14  has a radial recess  50  into which driven element  40  engages. Driven element  40  is designed, e.g., as worm  39 , which is located on an armature shaft  41  of electric motor  43 . 
         [0024]    Support tube  14 , which serves as a housing for separate assembly  12 , also includes a receptacle  52  into which a fastening device  54 , e.g., a pivot bolt  55 , may be slid. With this fastening device  54 , support tube  14  is connected—e.g., in a hinged manner—with an adjusting part  58  in the motor vehicle, e.g., a not-shown seat or a seat part that is adjusted relative to another seat part. A support element  62  is attached to support tube  14  between receptacle  52  and an end  60  of support tube  14  located closer thereto. Support element  62  is designed as outer ring  64 , which rests in an outer circumferential surface  66  of support tube  14 . In the top half of the drawing, support element  62  is connected with support tube  14 , e.g., via welds  72 . The lower half of the drawing shows an attachment of support element  62  using caulking  74  via plastic deformation. If an accident occurs, high material stressing occurs between receptacle  52  and end  60  of support tube  14 . These strong forces are absorbed by support element  62 , which therefore increases the absorption of force by support tube  14  without it being destroyed. As a result, spindle end  26  and, therefore, part  58  to be adjusted, remain in their intended places when a crash occurs. 
         [0025]    If, during an adjusting procedure in axial direction  76 , a compression force  80  acts on spindle  16 , shaft  15  is supported via drive element  18  in pot-shaped bearing receptacle  22  of end shield  28 . Compression force  80  is transferred via end shield  28  to material deformation  82  and, therefore, to support tube  14 , which, in turn, bears against fastening device  54 . 
         [0026]    A further exemplary embodiment is shown in  FIGS. 2 and 3 , with which a wormwheel  19  supported on a through-extending spindle  16  is formed, as drive element  18 . Shaft  15 , which is designed as spindle  16 , is located along an axis  76 . As in  FIG. 1 , support tube  14  includes a pot-shaped bearing receptacle  22  with a first axial bearing surface  21 , against which drive element  18  rests via a first axial stop  23 . Second end shield  28  is designed as a sleeve with a circumferential collar  25 , which serves as second axial bearing surface  27  for a second stop  35  of drive element  18 . Drive element  18  and end shield  28  are installed in support tube  14 , then end shield  28  is fixed in position in support tube  14  such that the axial bearing play of drive element  18  is suppressed. To this end, sleeve-shaped end shield  28  is pressed with a predefined contact pressure  81  against drive element  18  and first bearing surface  21 . Jacket regions  8  of support tube  14  are then pressed radially inward using a stamping tool  85 , thereby producing an  10  undercut  87 , which rests axially via an axial end face  89  against end shield  28 . Depending on the caulking force  83  applied by stamping tool  85 , end face  89  has a certain radial depth  91  and a certain breadth  95  around the circumference of support tube  14 . By specifying the depth  91  and breadth  95  of end face  89 , and the number of material deformations  82 , transmission drive unit  10  may be adapted to maximum axial forces  80  that may be expected. End shield  28  includes a central opening  67 , through which spindle  16  extends. End shield  28  bears radially via its entire axial extension against inner wall  70  and includes an annular back side  84 . End face  89  of undercut  87  forms a form-fit connection with back side  84 , which is oriented nearly perpendicularly to shaft  15 . Drive element  18  is fixed securely in position axially in support tube  14  via the form-fit connection. 
         [0027]      FIG. 4  shows a further exemplary embodiment of an inventive transmission drive unit  10 , with which support tube  14  includes a largely closed base surface  92  at one end  60 . An installation opening  93  is formed in base surface  92 , to simplify the secure support of spindle  16  in end shield  28 . To this end, end shield  28  is preinstalled with second integrally formed, axial bearing surface  27  and drive element  18  in support tube  14 . With this embodiment, a second separate end shield  28  with a pot-shaped bearing receptacle  22  is located in support tube  14  on end  20  at which spindle  16  extends out of support tube  14 . End shield  28  serves as first bearing surface  21 . First bearing surface  21  is fixed securely in position axially in the support tube via end shield  28 . To eliminate the axial bearing play, end shield  28  with second axial bearing surface  27  is now pressed axially against drive element  18 —which bears against first bearing surface  21 —with a preload force  81 . Preload force  81  is introduced to end shield  28  through installation opening  93 . Jacket regions  8  of support tube  14  are now pressed radially inward, resulting in the formation of securing tabs  94  with a free end  97 . Securing tabs  94  bear axially against back side  84  of end shield  28 . Via material deformation  82 , end shield  28  is pressed axially and tightly against second stop  35  of drive wheel  18 , thereby eliminating its play. 
         [0028]    A receptacle  52  designed as a radial bore is integrally formed directly in support tube  14  for an attachment device  54 . Receptacle  52  is a standard interface for the customer, although it may be modified using a receiving module  90  to be a customer-specific, individual receptacle  88 . To this end, receiving module  90  is designed as outer ring  64 , which is located on outer circumferential surface  66  of support tube  14 . Receiving module  90  includes, e.g., an inner thread  78 , which engages in counter-thread  79 —designed as an outer thread—of support tube  14 . Receiving module  90  covers the radial cut-outs formed via receptacle  52  and caulking tabs  94 . With this embodiment, receiving module  90  also serves as support element  62 , which increases the strength of support tube  14  at its end region  60 . Receiving module  90  includes a cylindrical bolt  96  as receptacle  88 , which extends radially outwardly. Cylindrical bolt  96  corresponds to an integration of pivot bolt  55 —designed as fastening device  54 —in  FIG. 1 . With receptacle  88 , part  58  to be adjusted may be connected via eyes  86  integrally formed therein with spindle drive  10 , e.g., directly. Via receiving module  90 , the crash forces are reliably transferred from adjusting part  58  to support tube  14  and via spindle  16  and counternut  98  to body  99 . 
         [0029]    It should be noted that, with regard for the exemplary embodiments presented in the figures and the description, many different combinations of the individual features are possible. For example, support tube  14  may be manufactured using different methods, and it may have different specific designs. The cross section of support tube  14  is not limited to a circle. Instead of being designed as an integrally formed, pot-shaped bearing receptacle  22 , support tube  14  may also be designed as a smooth cylindrical tube in which two separate end shields  28  for supporting spindle  16  are located. Spindle  16  is preferably supported via drive element  18  supported thereon, although, in one variation, it may also be supported via bearing surfaces that are integrally formed directly on spindle  16 . The device used to transfer torque from drive assembly  42  is not limited to a worm gear  19 ,  39 . Torque may also be transferred, e.g., using a spur gear. The specific shape and material used for material deformation  82  is selected depending on the strength requirement. One or more undercuts  87  or caulking tabs  94  may be pressed inward, as necessary. Likewise, the size of axial end face  89  may be selected for its depth  91  and breadth  95 , thereby making it possible to predetermine the strength of the form-fit connection with radially extending back side  84  of end shield  28 .