Abstract:
A transmission drive unit for adjusting a movable part in a motor vehicle has a support tube, a drive wheel, which is drivable using a drive assembly rotatably supported on the support tube and located on a spindle installed first in the support tube as a separate component and received in the bearing receptacle; a customer-specific receiving module, which subsequently and separately is attached to the support tube and includes a receptacle for a fastening device on the motor vehicle or the part to be adjusted, and the material of the receiving module has a higher strength than the material of the support tube.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2005 046 356.8 filed on Sep. 28, 2006. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a transmission drive unit with a receiving module, in particular for adjusting a movable part in a motor vehicle. 
     Publication EP 0 759 374 A2 made known a device for adjusting a seat in a motor vehicle, which may absorb considerably greater forces than during normal operation. Forces such as these may be caused, e.g., by a traffic accident. It is important that the vehicle seat remain fixedly connected with the body, to ensure that the protective measures (seat belt, air bag) provided for the vehicle occupants may function. With the device described above, a counternut that accommodates a threaded spindle is fixedly connected with the body. The threaded spindle is driven via a worm gear pair by an electric motor, which is fixedly connected with the seat. The transmission housing of the worm gear pair is made of plastic and is connected with the drive motor via a further housing part. When the drive motor is actuated, the threaded spindle rotates and displaces the transmission housing, including the drive motor and seat, relative to the counternut. To prevent the transmission housing from tearing loose from the threaded spindle, e.g., when an accident occurs, an additional, metallic, U-shaped support part is provided, which connects the transmission housing via a hinged fastening bolt, as the fastening device, with the drive motor and, therefore, the seat. If the plastic transmission housing is unable to withstand the strong flow of force, it is held by the metallic support part using an additional counternut. The disadvantage of this design is that, when a change is made to the customer interface for attaching the transmission drive unit, the entire transmission housing—including the complex support design—must be redesigned in order to provide the desired mechanical interface for every customer. In addition, the formation of the screw-on eye for the pivot bolt takes up installation space in the axial direction toward the spindle, which is very limited in many applications. 
     SUMMARY OF THE INVENTION 
     The inventive transmission drive unit and its inventive manufacturing method 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 using a standardized support tube, on which different receiving modules may be attached depending on the customer&#39;s wishes, a very high level of flexibility of the spindle drive is attained, in a very cost-effective manner. Advantageously, the receiving module may be subsequently attached to the support tube, fully independently of the installation of the spindle and its drive wheel in the support tube. The overall axial length of the transmission drive unit may be reduced by shortening the support tube, since there is no need to form a receptacle—e.g., a radial bore for a fastening bolt—in the standard support tube. 
     When the receiving module includes, e.g., a circular recess, the receiving module may be attached very easily on the outer circumference of a round support tube. With this design of the receiving module as an outer ring, it may also be installed before the spindle is installed on the support tube. 
     In an alternative embodiment, the receiving module is attached inside the support tube, to the inner wall surface. The receiving module may be designed as an inner ring or a complete disk, and it simultaneously serves to reinforce the support tube. These diverse receiving modules may be connected very easily with the standard support tube in accordance with the particular interface requirements. 
     The annular design of the receiving module is also suited, in particular, for a plunger spindle, in the case of which the spindle extends out of the support tube at both axial ends. 
     The receiving module with a thread may be screwed into or onto the support tube particularly easily. To this end, the support tube includes—on its outer circumferential surface and/or its inner wall, at least on an axial end region—a thread, which engages in a corresponding thread of the receiving module. As an alternative, the support element includes a self-tapping or self-cutting thread that forms a counter-thread in the support tube when installed in/on the support tube. 
     In an alternative embodiment, the receiving module may also be bonded or welded to the support tube, or it may be caulked with the support tube via cold deformation. With these connection methods, the support tube and the receiving module may also have a non-circular cross section. 
     Due to the modular design of the transmission drive unit, the standard support tube may be made of an easily formed deep-drawn metal, and the receiving module may be made of a stronger material, e.g., hardened steel, in order to provide strong crash resistance. The material used to form the receptacle may be optimized in terms of strength, bearing properties, and noise formation. 
     A fastening bolt is a popular customer interface for connecting the spindle drive to the motor vehicle; it may be rotatably supported in a hole-shaped receptacle in the transmission drive unit. The crash forces that act via the fastening device are transferred to the support tube via the fastening bolt in the receptacle. By designing the fastening device as a pivot bolt, the spindle is hingedly supported between the part to be adjusted and the body, thereby resulting in a greater degree of freedom of the adjusting motion. 
     In a further embodiment, the receptacle of the receiving module is designed as a cylindrical bolt that extends radially to the spindle. A hinged fastening bolt is therefore already practically integrally formed with the drive unit, which may be rotatably connected very easily with the body or the part to be adjusted. 
     It is particularly favorable when the receiving module is inserted axially in the support tube until it bears axially against the end plate of the spindle. As a result, the axial play of the spindle may be eliminated via the installation of the receiving module. At the same time, axial compression forces that act on the spindle are transferred via the end plate to the receiving module and, therefore, to the fastening device of the body, via which the spindle remains positioned with its drive wheel in the support tube. 
     In an advantageous embodiment, the receiving module is designed as an end plate with a pot-shaped bearing receptacle in which the spindle may be supported radially and axially. The number of components may therefore be reduced, while also further shortening the overall axial length of the support tube and, therefore, the transmission drive unit. To this end, the receiving module is made of plastic, in particular, thereby enabling the spindle and/or the drive wheel to be supported directly in the receiving module—which is designed as an end plate—with a minimum of friction. This receiving module may interact axially, e.g., directly with a spherical, metallic axial stop of the spindle. By making the receptacle out of plastic, the friction with the fastening device may be reduced, and the noise formation may be reduced. 
     Ideally, the receiving module is designed and integrally formed with the support tube in such a manner that the mechanical strength of the support tube is reinforced as a result. Regions in the support tube in which recesses—in particular for receiving fastening devices or for adjusting the axial play of the spindle—are integrally formed may therefore also be supported, for example. 
     In a preferred embodiment, the spindle, which is supported in the support tube and includes the receptacle for the fastening device, is a first preassembled assembly, which may be coupled very easily via a coupling device with a standardized drive assembly, e.g., an electric motor with an armature worm. To transfer force to the drive wheel of the spindle, the driven element of the drive assembly extends through an opening in the support tube. Since the recess in the support tube is relatively small, the support tube may absorb high forces without the spindle being torn out of the support tube. This inventive transmission drive unit therefore does not include a classical transmission housing that encloses the driven element of the drive assembly and the drive wheel of the transmission, but rather includes a largely closed support tube, with the driven element being fixed in place relative thereto using the coupling device. To attach the coupling device, further recesses are formed in the support tube, for example, into which a fastening means of the coupling device engages for fixation. The drive assembly with its driven element is located completely outside of the flow of forces that occurs during a crash. 
     The inventive manufacturing method according to independent claim  13  has the advantage that the assembly with the support tube is installed independently of the receiving module. As a result, at the end of the processing of installing the assembly with the support tube, the support tube may be easily varied in terms of the customer interface using different receiving modules. A modular system of this type, with which different drive assemblies may also be used, is very cost-favorable and customer-friendly. 
     When the receiving module may be rotated relative to the support tube during installation, the receptacle may be attached to the support tube in a customer-specific angular position. The location of the fastening device is therefore independent of the radial orientation of the drive assembly. 
     The receiving modules may be very easily varied in terms of shape, connection means, and material without having to change the design and assembly process of the entire transmission drive unit. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a cross section through an inventive transmission drive unit, 
         FIG. 2  shows a side view of a further assembly with the support tube, which may be installed separately, 
         FIGS. 3 and 4  show a view and cross section of a further exemplary embodiment, and 
         FIG. 5  shows a cross section of a further inventive assembly. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Transmission drive unit  10  shown in  FIG. 1  is composed of a first assembly  12 , with which a spindle  16  with a drive wheel  18  located thereon is supported in a support tube  14 . Support tube  14  is manufactured, e.g., using deep drawing, and includes a pot-shaped bearing receptacle  22  for drive wheel  18  on an end region  20 . Spindle  16  extends out of support tube  14  through opening  24  in pot-shaped bearing receptacle  22  and is connected with the body, e.g., via a counternut, which is not shown. 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 . 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 . In this exemplary embodiment, drive wheel  18  is designed as worm wheel  19 , which includes axial projections  34  for radial support. Drive wheel  18  is injection-molded, e.g., 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 . 
     Support tube  14 , as the standard component, practically forms a housing for separate assembly  12 , on which various receiving modules  90  may be located. Receiving module  90  shown in  FIG. 1  includes a receptacle  88 , which is designed as a screw-on eye  86 , into which a fastening device  54 , e.g., a pivot bolt  55 , may be slid. Receptacle  88  is located on axis  76  in the center of support tube  14 . With fastening device  54 , support tube  14  is connected—e.g., in a hinged manner—with a part  58  to be adjusted in the motor vehicle, e.g., a not-shown seat or a seat part that is adjusted relative to another seat part. Receiving module  90  is designed as circular disk  68 , which bears against inner wall  70  of support tube  14 . In the top half of the drawing, receiving module  90  is connected with support tube  14 , e.g., via welds  72 . The lower half of the drawing shows an alternative attachment of receiving module  90  using caulking  74  via plastic material deformation. 
     If a compression force  80  acts on spindle  16  when an accident occurs in axial direction  76 , spindle  16  is supported via drive wheel  18  in pot-shaped bearing receptacle  22  of support tube  14 . Tension force  80  is transferred via support tube  14  to receiving module  90  with receptacle  88 . In this exemplary embodiment, receiving module  90  is made of a hardened steel, so that it may absorb very high forces  80  and dissipate them via fastening device  54  to the body or part  58  to be adjusted. 
     As a result, spindle end  26  and, therefore, part  58  to be adjusted, remain in their intended places when a crash occurs. 
     A further exemplary embodiment of an inventive spindle drive  10  is shown in  FIG. 2 , with which receiving module  90  is designed simultaneously as end plate  28  for the radial and axial support of spindle  16  in support tube  14 . To this end, receiving module  90  includes a pot-shaped bearing receptacle  22 , in which an extension  34  of drive wheel  18  bears radially. The axial stop of spindle  16  is formed by a metal ball  30 , which, in this case, bears axially directly against a base surface  33  of pot-shaped bearing receptacle  22  of receiving module  90 . Receiving module  90  is made of plastic, thereby minimizing the friction that occurs between spindle  16  and receiving module  90 . A receptacle  88  is integrally formed as one piece with receiving module  90 , receptacle  88  being designed as eye  86 . Pivot bolt  55 , as fastening device  54 , is slid into receptacle  88 , and hingedly connects spindle drive  10  with a part  58 —which is shown schematically—to be adjusted. Receiving module  90  bears via its entire axial extension against inner wall  70  of support tube  14 , and is fixed in position therein, e.g., via bonding. By eliminating a separate end plate  28 , the overall axial length of support tube  14  is reduced compared with the design in  FIG. 1 . 
     A further variation of the present invention is shown in  FIG. 3  and  FIG. 4 , with which a plunger spindle  16  is supported in support tube  14 . Spindle  16  extends out of support tube  14  at both ends  20 ,  60 . Spindle  16  is supported via drive wheel  18  and its axial extensions  34  on one side directly in pot-shaped bearing receptacle  22  of support tube  14 . Spindle  16  passes through opening  24  in support tube  14 . On the opposite side, drive wheel  18  is supported in pot-shaped bearing receptacle  22  of a separate end plate  28 , which bears against inner side  70  of support tube  14 . In this embodiment, receiving module  90  is designed as an inner ring  65 , through central opening  67  of which spindle  16  passes. Receiving module  90  includes—as receptacle  88 —two eyes  86 , which are located on both sides of spindle  16 . A fastening device  54  engages in receptacles  88 . Fastening device  54  is designed, e.g., as a rivet connection, and it connects transmission drive unit  10  with part  58  to be adjusted, or with the body. Receiving module  90  includes a thread  78  that engages in a counter-thread  79  of support tube  14 , thereby attaching receiving module  90  to support tube  14  in a form-fit manner. 
       FIG. 5  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 , for instance, is formed in base surface  92 , to simplify the secure support of spindle  16  in end plate  28 . In addition, caulking tabs  94  are pressed into support tube  14 . End plate  28  with pot-shaped bearing receptacle  22  bears axially against caulking tabs  94 . 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 . 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 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 in support tube  14  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. 2 . On receptacle  88 , therefore, part  58  to be adjusted may therefore be connected with spindle drive  10 , e.g., directly, via eyes  86  integrally formed on receptacle  88 . If crash forces occur during an accident, which act on part  58  to be adjusted due to its inertia, these forces are transferred via receptacle  88  of receiving module  90  to support tube  14 . Spindle  16  is held fixedly against body  99 , e.g., via a counternut  98 , so that counterforce  80  acts in spindle  16 , in order to hold part  58  to be adjusted in its intended position. With conventional spindle drives, the transmission housing poses the greatest risk, since, if it breaks, part  58  to be adjusted comes loose from spindle  16 . With inventive transmission drive unit  10 , the crash forces are safely absorbed by support tube  14 , however, without the forces acting on drive assembly  42  or its driven element  40 . Via inventive receiving module  90 , the crash forces are safely transferred from part  58  to be adjusted to support tube  14  and via spindle  16  to body  99 . 
     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. 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 wheel  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 pair  19 ,  39 . Torque may also be transferred, e.g., using a spur gear. The specific shape and material used for receiving module  90  are selected depending on the strength requirement. The receiving module may simultaneously provide support for the support tube. The cross section of support tube  14  is not limited to a circle. When support tube  14  is cylindrical in design, receiving module  90  may simply be screwed on or into place.