Abstract:
The invention relates to a gearbox drive unit ( 10 ), especially for displacing a movable part in a motor vehicle, and to a method for producing one such gearbox drive unit. The inventive gearbox drive unit includes a rotary body ( 14 ) which is rotatably mounted in a housing ( 12 ) and bears axially—via at least one end face ( 42 ) thereof—against an adjusting element ( 50 ) which is fixed to the housing ( 12 ). The adjusting element ( 50 ) can be slid axially into the housing ( 12 ) for installation, and can be locked axially by rotating it relative to the housing ( 12 ). The adjusting element ( 50 ) includes a radial bearing surface ( 56, 54 ) in which the rotary body ( 14 ) is radially supported.

Description:
RELATED ART 
       [0001]    The present invention relates to a gearbox drive unit with an adjusting element, and a method for manufacturing a gearbox drive unit of this type, according to the preamble of the independent claims. 
         [0002]    A drive unit was made known in DE 31 50 572 A1, with which the manufacturing tolerances between the armature shaft and the housing that supports it are eliminated using an adjusting screw. To this end, the housing includes an internal thread, in which the adjusting screw engages via an external thread. To offset the axial play of the armature shaft, the adjusting screw is screwed, with a stop face, against the end face of the rotor shaft. 
         [0003]    With a device of this type, manufacturing a thread in the housing and in the adjusting screw is relatively complex. In addition, the contact force of the screw against the end face of the rotor shaft cannot be specified exactly, since undefined friction forces occur during screwing into the thread. In addition, an adjusting screw of this type is not suited for centering the adjusting element such that the shaft can be accommodated in the adjusting element in a radially supported manner. 
       ADVANTAGES OF THE INVENTION 
       [0004]    The inventive device and the method for manufacturing a device of this type with the features of the independent claims have the advantage that a defined contact force against the end face of the rotary body can be specified via the axial insertion of the adjusting element into the housing. When the adjusting element is inserted, it centers itself relative to the housing such that the radial bearing surface of the adjusting element accommodates the rotary body with an exact fit, to support it radially in the adjusting element. As a result, fitting tolerances of the rotary body can be compensated for, since the adjusting element is not secured axially or radially until it is slid axially onto the rotary body and rotated in the housing. 
         [0005]    Advantageous refinements of the device and the manufacturing method described in the independent claims are made possible by the measures listed in the subclaims. When the radial bearing surface of the adjusting element is designed as a circumferential outer cylinder surface of a cylindrical recess, the rotary body is supported radially and evenly around its entire circumference. The fact that the adjusting element is centered in the housing ensures a very even concentricity of the rotary body. The cylindrical recess of the adjusting element can be designed as a blind hole or a through-opening, depending on the design of the rotary body. 
         [0006]    To fix the adjusting element in position axially in the housing, an axial retaining region is formed on a certain axial section of the adjusting element, the axial retaining region locking the adjusting element axially relative to the housing when the adjusting element is rotated. To this end, the retaining region has different outer diameters around its circumference, so that, when the retaining region is rotated, the circumferential surfaces with the larger diameter interact in a non-sliding manner with the corresponding opposite surface of the housing. 
         [0007]    Via the design of an outer profile, e.g., as a knurl or circumferential grooves, the friction force between the adjusting element and the inner shape of the housing wall can be increased, by way of which the adjusting element is reliably secured against axial displacement or rotation. 
         [0008]    To support high axial operating forces, it is advantageous for the outer profile to form a form-fit connection with the housing after it is rotated relative to the housing. It is particularly favorable when the outer profile includes radial projections that penetrate the inner wall of the housing in a self-cutting manner. 
         [0009]    To create a reliable form-fit connection, the retaining region includes sections with a larger outer diameter that transition into areas with a smaller diameter. As a result, the circumference of the retaining region is designed with an undulating shape, it being possible to insert this undulating circumference of the retaining region into a corresponding undulating inner surface of the housing. When these two undulating surfaces are rotated relative to each other, only a relatively small amount of torque is required to press the regions into each other in a form-fit manner with overlapping diameters. 
         [0010]    When the adjusting element includes a guide region located, e.g., axially adjacent to the retaining region, the guide region being guided in an inner guide surface of the housing, a very exact centering of the adjusting element and, therefore, an exact radial support of the rotary body can be attained. It is particularly favorable when the guide region has a circular diameter with a smooth surface. 
         [0011]    The inventive embodiment of the adjusting element is particularly suited for use in a tubular gearbox housing, e.g., a spindle drive, the adjusting element axially and radially supporting the rotary body, which is designed as a worm gear. The worm gear can be located at the end of a spindle, or it can be penetrated by a spindle that passes through it. 
         [0012]    To facilitate installation of the adjusting element, it includes a driving element—a recess, in particular—that interacts with the installation tool in a form-fit manner to rotate the adjusting element in the inner shape of the housing by a fraction of a revolution. 
         [0013]    Using the inventive manufacturing method, a gearbox drive unit—a spindle drive, in particular—can be manufactured very cost-effectively, since no additional parts are required to fix the adjusting element in place. The adjusting element simultaneously performs the axial and radial supporting functions, and it provides support against axial operating forces. Due to the axial contact force, which is adjustable in a defined manner, a reliable compensation of axial play can be attained over the entire service life of the drive unit. 
     
    
     
       DRAWING 
         [0014]    Various exemplary embodiments of a device according to the present invention are presented in the drawing and are described in greater detail in the description below. 
           [0015]      FIG. 1  shows a cross section through an inventive gearbox drive unit, 
           [0016]      FIG. 2  shows a side view of the drive unit in  FIG. 1 , according to  11 , 
           [0017]      FIG. 3  shows a cross section through the drive unit in  FIG. 1 , according to III-III, and 
           [0018]      FIG. 4  shows a further exemplary embodiment of an inventive drive unit. 
       
    
    
     DESCRIPTION 
       [0019]      FIG. 1  shows a gearbox drive unit  10 , with which a rotary body  14  is located in a housing  12 . Gearbox drive unit  10  is designed, e.g., as a spindle drive  10 , with which a spindle  15 —as rotary body  14 —with a worm gear  16  located thereon is supported in housing  12 . Worm gear  16  is injection-moulded, e.g., as a plastic injection-moulded part, on the end of spindle  15 , and is operatively connected with a not-shown worm shaft of a drive motor. To absorb strong axial forces  18 , e.g., crash forces on a seat-adjustment drive, housing  12  is designed as a tubular metal cage  20 . To secure housing  12 , housing  12  includes a through-hole  22  for accommodating a bolt located on the body or seat frame. When housing  12  is securely fastened, e.g., to the seat, and when worm gear  16  is set into motion via an electric motor, spindle  15 —which is non-rotatably connected with worm gear  16 —rotates, spindle  15  engaging, e.g., in a counternut fastened to the body. As a result, a relative motion between the seat and the body, or between different movable parts, is produced. 
         [0020]    Housing  12  has a first region  30 , which is designed as a bearing point  31  for rotary body  14 . Bearing point  31  includes a circular inner wall  24 , against which rotary body  14  bears radially. Bearing point  31  also includes an axial collar  26 , against which rotary body  14  bears directly, or axially via an additional thrust washer  27 . During installation, after rotary body  14  has been inserted into housing  12  in axial direction  38  (from the left as shown in  FIG. 1 ), such that spindle  15  projects through an opening  28  in housing  12  on axial collar  26 , an adjusting element  50  is inserted axially into housing  12 . The purpose of adjusting element  50  is to support rotary body  14  axially and radially at end  36  opposite to axial collar  26  during normal operation. To this end, adjusting element  50  is pressed in axial direction  38  with a selectable contact force  40  against an end face  42  of rotary body  14  and is subsequently secured against axial displacement via a rotation  39  by a fraction of 360°. In the exemplary embodiment according to  FIG. 1 , end face  42  is designed as a sphere  43  with a radius  44  that bears against an axial stop face  46  of adjusting element  50 . A cylindrical recess  52  with a base face  48  is formed in adjusting element  50 , cylindrical recess  52  serving as axial stop face  46  for end face  42  of rotary body  14 . Cylindrical recess  52  also forms a cylindrical wall  54 —as radial bearing surface  56  of adjusting element  50 —against which rotary body  14  bears radially during normal operation. To radially center adjusting element  50 , it has an axial section that is designed as guide region  66 . In the exemplary embodiment, guide region  66  has a circular circumference  68  that is centered when inserted in axial direction  38  into a corresponding circular centering section  35  of housing  12 . During normal operation, end  36  of rotary body  14  therefore bears radially against housing  12  via guide region  66  by way of cylindrical jacket  54  of adjusting element  50 . 
         [0021]    The radial guidance of adjusting element  50  is illustrated in  FIG. 2  in a side view of gearbox drive unit  10  in  FIG. 1  from the left. Diameter  68 —which remains the same around circumference  76 —of guide region  66  is guided in corresponding circular centering section  35  of housing  12 . Adjusting element  50  forms a sliding fit with housing  12  that can be moved with a small amount of force. 
         [0022]    To eliminate axial play, adjusting element  50  has a retaining region  70 , by way of which adjusting element  50  is axially lockable by rotating it in housing  12 . As shown in  FIG. 3 , which is a cross section through gearbox driving unit  10  in  FIG. 1  through retaining region  70 , retaining region  70  has a variable radius  72 , with a minimum radius  73  and a maximum radius  74 . Minimum radius  73  transitions continually into maximum radius  74  in the circumferential direction. As a result, retaining region  70  has a circumference  76  that is designed as an n-cornered polygonal outline  78 . In the exemplary embodiment, n=3, so the cross section of retaining region  70  can also be viewed as a triangle with greatly rounded-off corners. When installed in axial direction  38 , retaining region  70  is inserted into a corresponding locking section  32  of housing  12 , locking section  32  having an inner shape  33  that corresponds to circumference  76  of retaining region  70 . In  FIG. 3 , this inner shape  33  is also designed as a 3-cornered polygonal outline with three minimum and three maximum diameters  93 ,  94 , respectively. To axially lock adjusting element  50 , it is rotated, e.g., by 60°, during installation, so that the points with maximum radii  74  of retaining element  70  press into the regions of minimum radii  93  of inner shape  33 . To increase the frictional connection between retaining region  70  and inner shape  33  of housing  12 , retaining region  70  has an outer profile  80  that is designed, e.g., as knurling or thread grooves with no pitch. 
         [0023]      FIG. 4  shows a further exemplary embodiment, with which gearbox drive unit  10  is designed as a penetrating spindle gearbox. Rotary body  14  is designed as a worm gear  16 . In this case, however, worm gear  16  is a sleeve  17  positioned such that it can rotate on spindle  15 . When rotary body  14  is set into rotation via a worm gear, spindle  15  makes a linear motion in axial direction  38 , by way of which movable parts can be adjusted. As in  FIG. 1 , rotary body  14  is supported radially in housing  12  on the side of opening  28 . The axial support on housing  12  takes place here, e.g., via an elastic element  82 , the purpose of which is to compensate for wear-induced material losses over the service life of gearbox  10 . Via elastic element  82 , rotary body  14  therefore bears, on an axial side  25 , against axial collar  26 . End face  42  of rotary body  14  is also designed annular in shape, however, due to sleeve shape  17 . Accordingly, cylindrical recess  52  of adjusting element  50  is designed as a passage. As a result, axial stop face  46  of adjusting element  50  has the design of an annular surface  84 . In this exemplary embodiment, retaining region  70  includes circumferential, self-cutting edges  64  as outer profile  80 , which cut into inner shape  33  of locking section  32  of housing  12  during rotation  39 . A form-fit lock that can absorb very strong axial forces is created as a result. Self-cutting edges  64  are integrally formed on several axially separated, radial segments  86 , the radius  72  of which varies around the circumference. As shown in the exemplary embodiment in  FIG. 1 , circumference  76  can also be designed as an n-cornered polygonal outline  78 , or it can have projections designed in the manner of a step function. In both cases, inner shape  33  has a corresponding inner radius  91 ,  93 ,  94  that enables axial insertion of adjusting element  50  during installation. An overlapping of inner radius  91  with outer radius  72  of retaining region is not attained until rotation  39  of adjusting element  50  is carried out to lock it in place. To apply torque to lock adjusting element  50 , adjusting element  50  has a form-fit driving element  90 , into which a corresponding installation tool can engage. Driving element  90  is designed as an inner polyhedron in  FIG. 1 , for example. With annular adjusting element  50  shown in FIG.  4 , it is designed as several individual recesses  92 , into which several pegs of an installation tool engage. To ensure that self-cutting edges  64  cut into inner shape  33  of housing  12  during rotation  39  by a fraction of 360°, they are made of a harder material, e.g., hardened steel, than inner shape  33  of housing  12 . 
         [0024]    In an alternative exemplary embodiment, which is not shown in greater detail, retaining region  70  and guide region  66  of adjusting element  50  and the corresponding opposite surfaces (locking section  32  and centering section  35 ) of housing  12  are axially transposed. During installation in axial direction  38 , guide region  66  is inserted first, with a smooth surface for centering purposes, in corresponding centering section  35 . Subsequently, axially adjacent retaining region  70  with variable radius  72  slides into locking section  32  for interaction. In a further variation, centering section  35  of housing  12  can be designed with the same inner shape  33  as locking section  32 ; the centering of adjusting element  50  in terms of radial support is then ensured in another manner. 
         [0025]    It should be noted that, with regard for the exemplary embodiments presented in the figures and the description, many different combinations are possible. In particular, the cross section of retaining region  70  and the specific shape of outer profile  80  with the particular corresponding inner shape  33  of housing  12  can be varied in accordance with the desired application. The axial locking of adjusting element  50  can be attained using a frictional connection, a form-fit connection, or a combination thereof. It is important that adjusting element  50  be insertable axially in housing  12  for installation using only a small amount of force, and that it be subsequently secured against axial displacement via rotation  39 . Application of an axial contact force  40  is thereby decoupled from the locking, by way of which contact force  40  is adjustable in a very easily defined manner. The angular division of circumference  76  can be specified via the selection of the “n” variable of n-cornered polygonal outline, so that, e.g., with n=2, 3, 4, . . . an ideal angle of rotation  39  of 90°, 60°, 45°, . . . results for locking axially into place. Instead of worm gear  16 , rotary body  14  can also be designed as any other gearbox component, e.g., a spur gear or a threaded worm, or a rotor shaft of an electric motor. Gearbox drive unit  10  according to the present invention is preferably used for spindle drives to absorb strong axial forces, as is required, e.g., for seat-adjustment drives in motor vehicles.