Abstract:
The invention relates to a transmission drive unit ( 10 ), comprising a transmission element ( 11 ) that is rotatably arranged on the drive side in a transmission housing ( 15 ), with which transmission element a driving torque can be transmitted to at least one guiding element ( 25, 26 ) of a coupling element ( 20 ) on the output side, and a load torque lock, with which a torque introduced by the output-side coupling element ( 20 ) via the at least one guiding element ( 25, 26 ) can be locked, wherein the load torque lock comprises a locking element ( 42 ) that is preferably designed as wrap spring that cooperates with a brake element ( 34; 34   a;    34   b ), which comprises a friction surface ( 51 ) and is arranged non-rotatably in the transmission housing ( 15 ), for locking the torque. According to the invention, the brake element ( 34; 34   a;    34   b ) consists of a plurality of sheet metal elements ( 48, 49; 57, 58; 57   b;    58   b ) and the sheet metal elements ( 48, 49; 57, 58; 57   b;    58   b ) are connected to each other.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a transmission drive unit. 
         [0002]    A transmission drive unit is known from DE 10 2005 012 938 A1. In the case of the known transmission drive unit embodied as a power window actuator a wrap spring is arranged in a section of a hollow shaft, which section is used as a brake element. A brake element of this type is also described as a brake drum. In order to manufacture a brake drum of this type, it is known from the prior art that this is embodied either as a turned part, as a deep-drawn part or as a roller-burnished part. However, all these methods have specific disadvantages. For example, when manufacturing the part as a turned part, a relatively cost-intensive manufacturing process is required. If the part is embodied as a deep-drawn part or a roller-burnished part, it is on the other hand relatively difficult to maintain the required tolerances, so that the latter manufacturing method often requires a mechanical reworking of the friction surface, which further increases the manufacturing costs. 
       SUMMARY OF THE INVENTION 
       [0003]    Based on the illustrated prior art, the object of the invention is to develop a transmission drive unit in such a way that its brake element can be manufactured in a cost-effective manner whilst simultaneously maintaining a high level of accuracy. This object is achieved in the case of a transmission drive unit according to the invention. The invention is based on the idea of embodying the brake element from a plurality of mutually connected sheet metal elements. Sheet metal elements of this type have the advantage that they can be manufactured in a relatively cost-effective manner with a high level of accuracy, so that a brake element assembled from the sheet metal elements when seen as a whole can likewise be manufactured in a relatively cost-effective manner and simultaneously comprises the required tolerances or rather accuracies. In addition, the modular construction provides the advantage of being able to change the size of the brake element at a relatively low cost. 
         [0004]    In a particular advantageous embodiment of the invention, it is provided that the brake element is embodied in the shape of a sleeve, that the sheet metal elements are embodied in an annular manner and that the sheet metal elements are stacked one above the other as seen in the longitudinal direction of the brake element. This has the advantage that, for example, fastening elements for the brake element can be produced in a simple manner by virtue of the fact that the required fastening elements are embodied as one on individual sheet metal rings. In addition, an embodiment of this type offers the advantage that the height of the brake element can be adapted in a particularly simple manner to suit the respective overall size of the transmission drive unit, in that the brake element is assembled from more or fewer sheet metal rings. 
         [0005]    As an alternative thereto, it is provided in a different structural embodiment of the invention that the brake element is embodied in the shape of a sleeve and that the sheet metal elements are embodied as curved sleeve segments. This embodiment has the advantage that the brake element viewed as a whole is assembled from relatively few components, which is advantageous with respect to the connection of individual components and the surface characteristic, in particular of the friction surface. 
         [0006]    In the case of the latter embodiment of the invention, it can be provided in particular that the sheet metal elements are mutually connected in a positive-locking manner. As a consequence, a relatively cost-effective assembly process is possible, which in addition prevents, for example, distortion as a result of the process of welding individual sheet metal elements. 
         [0007]    The individual sheet metal elements can be manufactured in a particularly cost-effective manner if these are embodied as stamped sheet metal parts. 
         [0008]    In addition, it can be advantageous for connecting the individual sheet metal elements to mutually connect said elements by means of at least one weld seam. The weld seam forms a connection by material-engagement between the individual sheet metal elements and renders possible an extremely high level of strength. 
         [0009]    It is particularly advantageous in this case if the weld seam is arranged on a side of the sheet metal elements, which side lies opposite to the friction surface. As a consequence, in particular it is not necessary to rework the friction surface in a mechanical manner and this reduces the manufacturing costs. 
         [0010]    Alternatively or in addition, it is, however, also feasible to mutually connect the individual sheet metal elements in a non-positive manner by means of at least one separate connecting element. A non-positive connection of this type, which, for example, can be embodied with the aid of one or a plurality of connecting pins, creates either an inner connection between the individual sheet metal elements or it is used merely to fasten the sheet metal elements, so that they lie, for example, during the welding process in their correct position. 
         [0011]    In particular it can also be provided that the friction surface is reworked mechanically in order to achieve a required surface characteristic or dimensional stability of the friction surface. However, the cost of the mechanical reworking is relatively low by virtue of the construction in accordance with the invention using sheet metal elements, so that this processing step can be implemented in a relatively cost-effective manner. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Further advantages of the transmission drive unit in accordance with the invention are disclosed in the following description of preferred exemplary embodiments and with reference to the drawings, in which: 
           [0013]      FIG. 1  shows an exploded illustration of a transmission drive unit in accordance with the invention, 
           [0014]      FIG. 2  shows a longitudinal cross-sectional view through the assembled transmission drive unit in accordance with  FIG. 1 , 
           [0015]      FIG. 3  shows a perspective view of a brake drum comprising a plurality of sheet metal rings stacked one on top of the other, 
           [0016]      FIG. 4  shows a perspective view of a brake drum assembled from a plurality of arcuate sheet metal segments, wherein the sheet metal segments are mutually connected by virtue of a positive closure and 
           [0017]      FIG. 5  likewise shows a perspective view of a brake drum that has been modified with respect to the brake drum shown in  FIG. 4  and wherein the individual sheet metal segments are mutually connected by means of weld connections. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Like components or parts having a like function are provided in the figures with identical reference numerals. 
         [0019]      FIGS. 1 and 2  illustrate a transmission drive unit  10  for an adjustment drive in a motor vehicle. The exemplary embodiment is described with reference to a power window actuator. However, it is explicitly within the scope of the invention that a transmission drive unit  10  of this type is feasible for any auxiliary unit and for any unit that adds to the convenience of operation in a motor vehicle, e.g. for sunroof actuators, seat adjusters, windscreen wipers, transmission and clutch regulators, power steering systems, servo drives or other applications. The type of electrically operated drive motors used is also independent of the following description and is to be adapted to the respective application. 
         [0020]    The transmission drive unit  10  comprises a transmission element embodied from a synthetic material as an inclined-tooth driven gear that is described hereinunder as a spur gear  11 . The spur gear  11  is driven by an electric motor [not illustrated], such as is illustrated in DE 10 2005 012 938 A1. The electric motor comprises for this purpose a drive shaft  12  having a likewise inclined-tooth gear wheel  13  that meshes with the outer toothing of the spur gear  11 . The spur gear  11  is accommodated in a transmission housing  15  of the transmission drive unit  10 , said transmission housing being made from a synthetic material. 
         [0021]    The transmission housing  15  comprises a cup-shaped base part  16  and a housing cover  17  that is arranged on the upper face of the base part  16 . The housing cover  17  is embodied in an annular manner and can latch with the base part  16  in particular by means of a positive closure. A bearing spigot  18  whose one end  19  protrudes out of the housing cover  17  is formed as one piece on the transmission housing  15 . An output element  20  is rotatably mounted on the bearing spigot  18 . The output element  20  is secured in an axial manner on the bearing spigot  18  by means of a shaft clamping ring  21 . 
         [0022]    The output element  20  comprises on the side facing out from the housing cover  17  a toothing arrangement  23  by means of which the driving torque of the electric motor can be transmitted to the mechanics or kinematics (not illustrated in detail) of a window actuator, whereby a window pane as a moving part is adjusted. In addition, the output element  20  comprises two guiding elements  25 ,  26  that extend in parallel and at a spaced disposition with respect to the bearing spigot  18 , said guiding elements protruding into the inside of the transmission housing  15 . Two cut-outs  28 ,  29  are embodied for this purpose in the disk-shaped upper face  27  of the spur gear  11  ( FIG. 1 ). 
         [0023]    The spur gear  11  is axially positioned or rather mounted with its toothed ring  31  in the transmission housing  15 . By way of example and therefore not limiting, the lower face  32  of the toothed ring  31  lies for this purpose on an annular base area  33  of the base part  16  of the transmission housing  15 . The upper face  36  of the toothed ring  31  is in turn arranged in an operative connection with the housing cover  17 . 
         [0024]    A brake drum  34  made from metal is arranged in the transmission housing  15  and partly within the toothed ring  31  and on the side facing out from the housing cover  17 . The brake drum  34  that is embodied substantially in the shape of a sleeve or cup lies with the part of its outer wall  35  that is located beneath the spur gear  11  on a cylindrical wall  37  of the base part  16 . The wall  37  in the base part  16  comprises in addition a plurality of cut-outs  38 , into which engage in a positive-locking manner the fastening brackets  39  of the brake drum  34 . The fastening brackets  39  of the brake drum  34  can be fastened by means of fastening screws  41  by way of through-going bores embodied in the lower face of the base part  16 . 
         [0025]    A locking element that is embodied as a wrap spring  42  and functions as a load torque lock is arranged inside the brake drum  34 . The wrap spring  42  comprises two ends  43 ,  44  that protrude radially inwards and cooperate with the guiding elements  25 ,  26  of the output element  20 . The wrap spring  42  takes up almost the entire height of the wall  35  of the brake drum  34  and is arranged in a radial manner at only a small spaced disposition with respect to the inner face of the wall  35 , so that the wall  35  on its inner face is used as a mounting for the wrap spring  42 . 
         [0026]    It is provided in the case of the illustrated exemplary embodiment that the wall  35  of the brake drum  34  is not used only to receive or mount the wrap spring  42  but rather also for radially mounting the spur gear  11 . It is provided for this purpose that a plurality of mounting ribs  46  that are arranged in uniform angular spaced dispositions with respect to each other are embodied on the circumferential inner face  45  of the toothed ring  31  of the spur gear  11 . The bearing ribs  46  cooperate in so doing with the region of the wall  35  of the brake drum  34  located above the base region  32  of the base body  16 , in that the bearing ribs  46  lie on the outer face of the wall  35  or rather are at a spaced disposition thereto with a minimum amount of clearance. 
         [0027]    The bearing ribs  46  that extend in the longitudinal direction are preferably formed as one piece on the inner face  45 , which in the case of a spur gear  11  embodied as an injection molded part can be achieved in a cost-effective manner. In the regions in which there are no bearing ribs  46 , annular gaps  47  are embodied between the spur gear  11  and the brake drum  34 . 
         [0028]    During the operation of the transmission drive unit  10 , a torque introduced by the electric motor by way of the drive shaft  12  is transmitted as already described by way of the spur gear  11  and the guiding elements  25 ,  26  to the output element  20 . If a torque is now introduced into the transmission drive unit  10  by way of the output element  20 , then the ends  43 ,  44  of the wrap spring  42 , which ends are arranged in an operative connection with the guiding elements  25 ,  26 , cause the wrap spring  42  to widen in diameter and to lie on the inner surface of the wall  35  of the brake drum  34 . As a consequence, the movement of the guiding elements  25 ,  26  is stopped, which guiding elements are connected by way of the cut-outs  28 ,  29  for their part to the spur gear  11 . 
         [0029]    Essential for the invention is the embodiment explained hereinunder in further detail or rather the design of the brake drum  34 ,  34   a  and  34   b  as explained hereinunder in further detail with reference to  FIGS. 3 and 5 . 
         [0030]      FIG. 3  illustrates a first embodiment of the brake drum  34 , wherein said brake drum is embodied from a number of sheet metal segments  48 ,  49  that are in each case annular and are stacked one above the other as seen in the longitudinal direction of the brake drum  34 . The sheet metal segments  48  and  49  are each manufactured as stamped parts. The sheet metal segments  48  comprise in addition integral fastening brackets  50 , while the sheet metal segments  49  are embodied in a circular manner on their outer periphery. In addition, a plurality of lubrication grooves  52  are embodied or arranged in the longitudinal direction on the inner surface of the brake drum  34 , which inner surface functions as a friction surface  51  for the wrap spring  46 . The lubrication grooves  52  are taken into consideration either initially during stamping with the dimensions of the sheet metal segments  48  and  49  or they are subsequently provided in the brake drum  34  by virtue of a corresponding mechanical process. 
         [0031]    The connection between the individual sheet metal segments  48  and  49  can be achieved in numerous ways, wherein in the exemplary embodiment illustrated in  FIG. 3  the sheet metal segments  48  and  49  comprise on the one hand through-going cut-outs  53  which are aligned with each other in the longitudinal direction of the brake drum  34 , into which through-going cut-outs are pressed pin-shaped connecting elements  54 . In so doing, it is feasible that the connecting elements  54  alone create the connection between the sheet metal segments  48  and  49 . Alternatively or in addition, it can, however, also be provided that weld seams  56  that extend in the longitudinal direction of the brake drum  34  are embodied on the outer wall  55  of the brake drum  34  or rather on the sheet metal segments  48  and  49 . In so doing, it is preferably provided that the weld seams  56  are arranged in uniform angular spaced dispositions with respect to each other in order to prevent the sheet metal segments  48 ,  49  from distorting owing to the irregular heat input. 
         [0032]    A modified brake drum  34   a  is illustrated in  FIG. 4 . The brake drum  34   a  likewise comprises a plurality of sheet metal segments  57 ,  58 , wherein the sheet metal segments  57  and  58 , however, are embodied as curved sleeve segments. These are manufactured by virtue of the fact that they are initially stamped out from a corresponding sheet metal blank and subsequently rolled, i.e. are provided with the corresponding curvature. In addition, in the case of the sheet metal segments  57 , fastening brackets  59  are embodied as one thereon and are formed by virtue of a corresponding shaping process during the process of manufacturing the sheet metal segments  57 . The sheet metal segments  57  and  58  are mutually connected by virtue of a positive-locking connection. In so doing, cut-outs  60  are embodied in the sheet metal segments  58  and said cut-outs cooperate with corresponding swallow tail-like protrusions  61  in the sheet metal segments  58  [sic]. 
         [0033]    In the case of the brake drum  34   b  illustrated in  FIG. 5  that has been modified with respect to the brake drum shown in  FIG. 4 , the connection between the sheet metal segments  57   b  and  58   b  is embodied in each case by virtue of a corresponding weld seam  62  that extends in the longitudinal direction. 
         [0034]    In order to achieve a required dimensional stability or a required surface characteristic of the friction surfaces  51  on the brake drums  34 ,  34   a  and  34   b,  it can be necessary to rework the friction surfaces  51  mechanically. This can be achieved, for example, by turning or by polishing. In particular in association with the transmission drive unit  10  illustrated in  FIGS. 1  and wherein the brake drum  34  or rather its outer face is used simultaneously as a bearing element for the spur gear  11 , it can also be necessary to work the outer wall  55  of the brake drum  34 ,  34   a  or  34   b  accordingly. 
         [0035]    In addition, it is also mentioned that the transmission drive unit  10  described can be modified in various ways. Thus, for example, it is not necessary for the transmission drive unit to comprise a wrap spring  42 . Only the design or the embodiment of a brake drum  34 ,  34   a  or  34   b  comprising a friction surface  51  by means of sheet metal segments is essential for the invention.