Abstract:
The invention relates to a transmission drive device ( 10 ) comprising a shaft ( 14; 14   a ) which is arranged in a housing ( 12 ) in a longitudinally movable manner in the direction of the shaft axis ( 26 ) and comprising a shaft end ( 15; 15   a ) which is formed on an end face and which is supported at least indirectly on the housing ( 12 ) via at least one starting element ( 30 ). Either the shaft end ( 15 ) or the starting element ( 30 ) has a rounded design at least in some regions, a bearing point ( 31 ) being formed between the starting element ( 30 ) and the shaft end ( 15; 15   a ), and the starting element ( 30 ) being coupled to a damping element (32; 32 a  to 32 d ) which allows a movement of the starting element ( 30 ) in the event of an axial application of force (F A , F A1 , F A2 ) by means of the shaft ( 14; 14   a ). According to the invention, the starting element ( 30 ) and/or the damping element ( 32; 32   a  to  32 d) is/are designed and/or arranged such that the distance (r) of the bearing point ( 31 ) to the longitudinal axis ( 26 ) of the shaft ( 14; 14   a ) increases as the axial application of force (F A , F A1 , F A2 ) increases at least starting from a specified level of the application of force (F A , F A1 , FA 2 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a transmission drive device. Furthermore, the invention relates to a comfort drive for a motor vehicle using a transmission drive device according to the invention. 
         [0002]    A transmission drive device is known from the applicant&#39;s DE 10 2006 061 700 A1. The known transmission drive device is used in a comfort drive of a motor vehicle, for example in a power window drive, a seat adjustment drive, a sliding roof drive or the like. It is a requirement of a transmission drive device of this type that the latter remains in its position under a defined load when at a standstill in order to avoid an undesirable adjustment of the element to be adjusted (i.e. the window, the sliding roof, the seat or the like). When at a standstill, the electric drive of the transmission drive device is switched into the currentless state. The greatest portion of the locking is produced here via the transmission stage or, in the event of multi-stage transmissions, via the transmission stages. The required locking in the transmission makes it necessary that, for the operation of the transmission drive device, that is to say for adjusting the window, the sliding roof, the seat or the like, use has to be made of a relatively powerful electric drive in order initially to be able to overcome the locking. With better efficiency of the transmission, the required power demand or the overall size of the electric drive of the transmission drive device can be reduced, which leads, inter alia, in a desired manner to a lighter and more compact transmission drive device. Nevertheless, the transmission drive device has to produce the desired locking when at a standstill. 
         [0003]    For this purpose, it is known, in the case of the document mentioned at the beginning, that a shaft end of spherical design bears against a starting element which, in turn, is supported in a transmission housing via a damping element. In this case, the starting element, which is designed in the form of a starting plate, is arranged at an oblique angle with respect to the longitudinal axis of the shaft. Furthermore, it is mentioned in the known document that, when axial impacts occur along the longitudinal axis of the starting element, both the starting element and the damping means can be adjusted axially along a guide rail, which is likewise arranged at the oblique angle mentioned. By means of a device of this type, when axial forces occur on the shaft, caused by a torque introduced into the transmission drive device by the element to be adjusted, a counterforce which is at least approximately linearly dependent, depending on the axial force, and which brings about the self-locking can be produced. By contrast, the design of a transmission drive device is desirable in which there is only very slight self-locking, if any at all, when relatively small axial forces, if any at all, occur on the shaft, while, as the axial force on the shaft increases, a superproportionally increasing counterforce is desirable for producing a likewise superproportionally increasing self-locking. As a result, use can be made in the driving situation of a driving motor which is particularly lightweight or has a particularly low driving power and which, in conjunction with a transmission having relatively high efficiency, permits a particularly lightweight or compactly constructed transmission drive device. 
       SUMMARY OF THE INVENTION 
       [0004]    Taking the depicted prior art as the starting point, the invention is based on the object of developing a transmission drive device in such a manner that self-locking which increases superproportionally with increasing axial force on the shaft and which opposes a rotation of the shaft can be produced. As a result, a particularly lightweight and compactly constructed transmission drive device can be realized. 
         [0005]    This object is achieved according to the invention in the case of a transmission drive device in that the starting element and/or the damping element are/is designed and/or arranged in such a manner that, as the axial application of force on the shaft increases, the bearing point between the starting element and the shaft end is at an increasing distance from the longitudinal axis of the shaft, at least from a certain level of the application of force. A design of this type makes it possible for a force which increases superproportionally with the axial application of force on the shaft and which opposes the rotation of the shaft to be produced since the friction force arising between the shaft and the bearing point of the shaft end is produced from the sum of the force acting in the longitudinal direction of the shaft and the moment of friction produced depending on the distance of the bearing point from the longitudinal axis of the shaft. In addition, a transverse force component which is directed perpendicularly to the longitudinal axis of the shaft and which, in the case of radial bearings, leads to increased friction in the bearings, which likewise increases the self-locking, is also produced. 
         [0006]    In order to realize an increase in distance of the bearing point from the longitudinal axis of the shaft, it is proposed, in a preferred refinement of the invention, that the starting element is designed to be tiltable about an axis arranged at a distance from the longitudinal axis of the shaft. 
         [0007]    The damping element serves in particular for reducing noise when switching over the direction of rotation of the driving motor of the transmission drive device on account of the play, which is present in particular because of manufacturing tolerances, between the individual components. In order to reduce the wear of the transmission drive device when axial forces occur on the shaft, it is provided that the damping element is arranged on that side of the starting element which faces away from the shaft end, and therefore the starting element (which is composed, for example, of a particularly low-wear material) is in contact with the shaft end. 
         [0008]    In a specific refinement for realizing the tilting movement, it is proposed that the starting element has a bearing surface which is designed, from a certain application of force, to bear at least in regions against a positionally fixed mating element such that the starting element is tiltable about an axis formed by the bearing surface. This means, conversely, that if the starting element is not yet tilted, the bearing point between the shaft end and starting element is located in particular in the longitudinal axis of the shaft, and therefore the discussed superproportional increase in the self-locking takes place only from a certain point or certain axial force on the shaft, while, in the case of smaller axial forces, an at least approximately linear increase in the self-locking is obtained. 
         [0009]    In a structurally preferred refinement for absorbing the forces acting on the starting element from the shaft, it is proposed that the starting element is arranged in a torsion proof manner in the housing by means of at least one bearing surface which bears against a mating surface in the housing. 
         [0010]    In order to ensure a positionally correct installation of the starting element in the housing, it is furthermore advantageous if the starting element has a positioning element for the positionally correct installation in the housing. 
         [0011]    In order to avoid damage, for example to the damping element or the starting element, in the event of particularly high axial forces on the shaft, it can be provided that the starting element has a stop surface for limiting the tilting angle of the starting element. 
         [0012]    The connection between the starting element and the damping element takes place at least via a form-fitting connection. A form-fitting connection of this type can exist, for example, by means of a corresponding dimensional toleration between the damping element, which is customarily composed of rubber, and the starting element, and therefore a clamping connection is formed between the two mentioned elements, the clamping connection securely holding the two parts together. For this case, it is customarily not required to provide an additional connection, for example an adhesive connection or another mechanical connection. 
         [0013]    The damping element is preferably designed in the form of a preferably rotationally symmetrical body composed of rubber. A particularly simple and cost-effective manufacturing of the damping element can thereby be obtained. 
         [0014]    The invention also comprises a comfort drive in a motor vehicle, such as a power window drive, a seat adjustment drive, a sliding roof drive or the like with a drive device according to the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Further advantages, features and details of the invention emerge from the description below of preferred exemplary embodiments and with reference to the drawing, in which: 
           [0016]      FIG. 1  shows a longitudinal section through a partial region of a transmission drive device according to the invention, 
           [0017]      FIG. 2  shows the transmission drive device according to  FIG. 1  in a partially sectioned top view, 
           [0018]      FIG. 3  shows parts of the transmission drive device according to  FIGS. 1 and 2  in an individual illustration in order to clarify the operative principle of a starting element and a damping element, 
           [0019]      FIG. 4  shows a first embodiment of a damping element and a starting element in a perspective view, 
           [0020]      FIG. 5  shows the elements according to  FIG. 4  in the fitted state in a perspective view, 
           [0021]      FIG. 6  shows a damping element and starting element modified in relation to  FIG. 4 , in a perspective view, 
           [0022]      FIG. 7  shows the elements according to  FIG. 6  in the mounted state, in a perspective view, 
           [0023]      FIG. 8  and  FIG. 9  show a detail of  FIG. 2  in an enlarged illustration for clarifying the manner of operation of the damping element and of the starting element at different axial loadings of an armature shaft, 
           [0024]      FIG. 10  and  FIG. 11  show a modified embodiment of the invention at different positions of the armature shaft, in each case in longitudinal section, 
           [0025]      FIG. 12  shows parts of the arrangement according to  FIG. 10  with a modified armature shaft and a modified starting element in a partially sectioned side view, 
           [0026]      FIG. 13  and  FIG. 14  show a further modified embodiment of the invention at different positions of the armature shaft, in each case in longitudinal section, 
           [0027]      FIG. 15  and  FIG. 16  show, in side view and top view, a starting element as used in the device according to  FIGS. 13 and 14 , and 
           [0028]      FIG. 17  and  FIG. 18  show a further modified embodiment of the invention using a starting disk as starting element, at different positions of the armature shaft, in each case in longitudinal section. 
       
    
    
       [0029]    Identical elements or elements with the same function are provided with the same reference signs in the figures. 
       DETAILED DESCRIPTION 
       [0030]    The transmission drive device  10  illustrated in  FIGS. 1 and 2  is part of a comfort drive  100  in a motor vehicle. Within the context of the invention, a comfort drive  100  is understood by way of example, but not in a restricting manner, as meaning a power window drive, a seat adjustment drive, a sliding roof drive or the like. 
         [0031]    The transmission drive device  10  comprises a driving motor (not illustrated specifically) which is designed as an electric motor and the motor housing or pole pot housing  11  of which is flange-mounted onto a transmission housing  12 . An armature  13  is arranged within the pole pot housing  11 , the armature shaft  14  of which armature projects with the spherically, that is to say rounded shaft end  15  thereof into the transmission housing  12 . 
         [0032]    A single- or multi-stage transmission  18 , the output shaft  19  of which projects out of the upper side of a transmission cover  21 , which is part of the transmission housing  12 , is arranged in the transmission housing  12 . The transmission  18  serves for reducing the rotational speed of the electric motor while simultaneously increasing the torque thereof. For this purpose, the armature shaft  14  within the transmission housing  12  has a partial section with a worm toothing  22  which meshes with a corresponding mating toothing on a gear wheel which is designed as a spur gear  23  and is mounted rotatably within the transmission housing  12 . That section of the output shaft  19  which projects out of the transmission housing  12  is connected at least indirectly to the element to be adjusted, i.e., for example, to a window or a sliding roof. 
         [0033]    According to the illustration of  FIG. 3 , the armature shaft  14  is mounted radially at least in two bearings  24 ,  25 , wherein the first bearing  24  is located in the region of the pole pot housing  11  on that side of the armature  13  which faces away from the transmission housing  12 . The other bearing  25  is arranged between the region of the worm toothing  22  and the armature  13 . It is essential that the two bearings  24 ,  25  are designed only for absorbing radial forces acting on the armature shaft  14 , but cannot absorb any axial forces which act in the direction of the longitudinal axis  26  of the armature shaft  14 . Axial forces of this type acting in the direction of the double arrow  27  are in particular transmitted to the armature shaft  14  if a load is introduced into the transmission  18  via the output shaft  19  from the element to be adjusted (window, sliding roof, etc.) when the transmission drive device  10  is switched into the currentless state. 
         [0034]    It is mentioned in addition that it does, of course, lie within the scope of the invention to use more than two bearings  24 ,  25 . 
         [0035]    According to the invention, the spherically designed shaft end  15  of the armature shaft  14  touches a starting element  30  at a bearing point  31 . The starting element  30  is arranged in turn on the side facing away from the shaft end  15  in operative connection with a damping element  32 . The combination of the starting element  30  and the damping element  32  serves to produce a locking moment or self-locking depending on the axial forces FA introduced into the armature shaft  14  in the direction of the starting element  30 , which opposes rotation of the transmission wheels of the transmission  18  or of the output shaft  19 . 
         [0036]    The operative principle of the starting element  30  and of the damping element  23  is clarified below with reference to  FIG. 3 , wherein, in the exemplary embodiment illustrated in  FIG. 3 , the starting element  30  is designed as a starting plate  33  which is arranged tiltably or pivotably in a tilting axis  34 , which runs perpendicular to the plane of projection of  FIG. 3 , in the transmission housing  12  in a manner not illustrated. On that side of the bearing plate  33  which is opposite the tilting axis  34 , said bearing plate is arranged in operative connection to a damping element  32 , which is designed as a compression spring  35 . If an axial force FA is exerted on the armature shaft  14  in the direction of the bearing plate  33 , the bearing point  31 , which runs in the longitudinal axis  26  of the armature shaft  14  if an axial force FA is not present or is small, migrates in the direction of the tilting axis  34  in accordance with the deflection of the bearing plate  33  about the tilting axis  34  such that a distance r which is greater as the axial force FA increases is formed between the longitudinal axis  26  and the bearing point  31 , as can also be seen particularly clearly from  FIGS. 8 and 9 . A counterforce FH is produced here on the shaft end  15  or the armature shaft  14  from the bearing plate  33 , said counterforce being all the more greater, the larger the radius r is. In particular, the reaction force which leads to the self-locking of the transmission  18  increases superproportionally to the axial force FA as a consequence of the larger radius r with the greater axial force FA. 
         [0037]    In the case of the damping element  32  illustrated in  FIGS. 4 and 5 , said damping element is produced from an elastic material, in particular from rubber, and is designed in the form of a ring  37 . The starting element  30  has a plate-like section  38  which is provided with a respective flattened portion  39  on mutually opposite sides. According to  FIG. 2 , the plate-like section  38  of the starting element  30  is accommodated in a form-fitting manner with the two flattened portions  39  thereof between the bearing surfaces of two housing-mounted guide elements  41 ,  42 , and therefore the starting element  30  cannot rotate about the longitudinal axis  43  thereof. The plate-like section  38  has, on an upper side, by way of example, a notch  44  which serves as a positioning element and serves for the positionally correct installation of the starting element  30  by, for example, a corresponding mating element on the transmission cover  21  interacting with the notch  44 , and therefore the installation of the transmission cover  21  is permitted only in one position. 
         [0038]    On the side facing away from the shaft end  15 , the plate-like section  38  has an annular section  45  which has an obliquely arranged end side  46  with respect to the longitudinal axis  43  of the starting element  30 . The height h 1  on that side of the annular section  45  which faces the notch  44  is thus greater than the height h 2  on the side facing away from the notch  44 . In the region of the end side  46  which lies on the side facing the notch  44 , the end side  46  has a bearing surface  47  which is oriented perpendicularly to the flattened portions  39  and forms a tilting axis  48 . According to the illustration of  FIG. 5 , the ring  37  has a height h 3  which approximately corresponds to the height h 1  of the section  45  or is somewhat greater than the height h 1 . Furthermore, the inside diameter of the ring  37  is adapted to the outside diameter of the annular section  45  in such a manner that, when the ring  37  is mounted on the annular section  45 , a form-fitting connection in the form of a clamping connection is formed between the ring  37  and the bearing element  30 . On the side opposite the bearing surface  47 , the end side  46  forms a stop surface  49  which limits the tilting angle α, about which the starting element  30  can be pivoted with the damping element  32 , by bearing against at least one housing-mounted stop element  50 , which can be seen in  FIGS. 1 and 2 . The tilting of the starting element  30  takes place as soon as the latter bears with the bearing surface  47  thereof after compression of the damping element  32 , which bears against a positionally fixed mating element (not shown) on the end side facing away from the starting element  30 , against a mating element  55  which is likewise arranged in a positionally fixed manner in the transmission housing  12  and can be seen in  FIGS. 1 and 2 . 
         [0039]    The damping element  32   a  which can be seen in  FIGS. 6 and 7  differs from the damping element  32  in that said damping element  32   a  is designed as a cylindrical damping element  32   a  which can be introduced into the opening  51  in the annular section  45  of the starting element  30  forming a clamping connection. The damping element  32   a  projects out of the opening  51  and in particular also protrudes over the bearing surface  47  in the axial direction. 
         [0040]    In  FIGS. 8 and 9 , the manner of operation of the starting element  30  in conjunction with the damping elements  32 ,  32   a,  which are depicted as spring elements, is explained: in  FIG. 8 , an axial force FA 1 , which brings about a compression of the damping element  32 ,  32   a,  acts on the armature shaft  14  in such a manner that the bearing surface  47  is not yet operatively connected to the housing-mounted stop element  50  (not illustrated). The tilting angle α is therefore 0°. Nonetheless, a counterforce is produced by the starting element  30  in the direction of the shaft end  15 , said counterforce being dependent on the friction values between the shaft end  15  and the starting element  30 . Furthermore, it is seen that the bearing point  31  is aligned with the longitudinal axis  26  of the armature shaft  14 , and therefore a distance a 1  arises between the tilting axis  48  and the bearing point  31  or a distance r of zero arises between the longitudinal axis  26  of the armature shaft  14  and the bearing point  31 . 
         [0041]    In  FIG. 9 , an axial force FA 2  which is greater than the axial force FA 1  in  FIG. 8  acts on the armature shaft  14 . In particular, the axial force FA 2  is of a size that the bearing surface  47  of the starting element  30  is operatively connected to the housing-mounted stop element  50 , and therefore a tilting of the starting element  30  by the tilting angle α about the tilting axis  48  has taken place. Furthermore, it is seen that the bearing point  31  is no longer aligned with the longitudinal axis  26  of the armature shaft  14 , but rather is at a distance a 2  from the tilting axis  50 , which distance is smaller than the distance a 1  in  FIG. 8 , or that a distance r is produced between the longitudinal axis  26  of the armature shaft  14  and the bearing point  31 . Said reduced distance a 2  or the (increased) distance r brings about a superproportional increase of the reaction force of the starting element  30  on the armature shaft  14  by means of a moment of friction, and therefore the level of the self-locking is also superproportionally greater than in  FIG. 8 . Furthermore, a transverse force component FQ, which is arranged perpendicularly to the longitudinal axis  26  of the armature shaft  14 , is produced at bearing point  31 , said transverse force component producing a radial loading of the bearings  24 ,  25  and therefore likewise producing increased friction of the armature shaft  14  in the bearings  24 ,  25 . 
         [0042]    It is mentioned in addition that, in the exemplary embodiment illustrated, a starting element  30  is arranged or provided only on one shaft end  15 . If it is also intended for axial forces FA which act on the armature shaft  14  not in the direction of the starting element  30 , but rather counter to the starting element  30 , to lead to self-locking of the transmission  18 , it is required also to provide the other shaft end (not illustrated in the figures) with a corresponding starting element  30  and with a damping element  32 ,  32   a.    
         [0043]      FIGS. 10 and 11  illustrate part of a modified transmission drive device  10 . The armature shaft  14  which is mounted in a radial bearing  56  is seen in a region, for example of the transmission housing  12 , having a reduced cross section. The spherically designed shaft end  15  interacts with a starting element  30  which is designed as a starting disk  57  and projects with a pin-shaped extension  58  for guiding and positioning the starting disk  57  into a passage opening  59  of the damping element  32   b.  The arrangement of the damping element  32   b  with the longitudinal axis thereof is aligned with the longitudinal axis  26  of the armature shaft  14 . The starting disk  57  has a respective flattened portion  61  on two opposite sides running parallel to the plane of projection of  FIGS. 10 and 11 , the flattened portion interacting with the transmission housing  12  or with a respective side wall of the transmission housing  12 , in order to form a means of securing the starting disk  57  against torsion. In the unloaded state of the armature shaft  14 , the starting disk  57  has a gap  63  from a first end wall  62  of the transmission housing  12 , but, in a modification of the exemplary embodiment illustrated, said gap may also be zero (in the event of a shorter damping element  32   b ). On that side of the starting disk  57  which is opposite the gap  63 , a second gap  65  which is larger than the gap  63  is formed between the starting disk  57  and an axially set-back second end wall  64 . In the event of axial loading of the armature shaft  14  by the axial force FA according to  FIG. 11 , the shaft end  15  of the armature shaft  14  presses against the starting disk  57 , wherein the bearing point  31  of the shaft end  15  migrates outward on the starting disk  57  from the position (illustrated in  FIG. 10 ) in alignment with the longitudinal axis  26 , with a distance r being formed. It is also essential here that the starting disk  57  tilts about its tilting axis  34 , which runs perpendicularly to the plane of projection of  FIG. 11 , at the latest when the starting disk  57  bears against the first end wall  62 . Furthermore, the second end wall  64 , as can be seen in  FIG. 11 , forms a housing-mounted stop for limiting the tilting angle α of the starting disk  57 . 
         [0044]    The modified exemplary embodiment in  FIG. 12  shows a starting disk  57   a  as starting element  30  with an end region  66  formed spherically or in the shape of a section of a ball with respect to the armature shaft  14   a.  The end region  66  runs on a concavely formed recess  67  of the shaft end  15   a  of the armature shaft  14   a.    
         [0045]      FIGS. 13 to 16  illustrate a further modified transmission drive device  10  with a starting disk  70  as starting element  30 , said starting disk having, on the side facing the transmission housing  12 , a continuation  71  of rounded design with two side surfaces  72 ,  73  arranged parallel to each other ( FIG. 16 ). The side surfaces  72 ,  73  bear in a form-fitting manner against boundaries or walls (not illustrated) of the transmission housing  12  in order to form a means of securing the starting disk  70  against torsion. Furthermore, a recess  74  for the form-fitting accommodating of the damping element  32   c  is arranged in the transmission housing  12  on that side of the starting disk  72  which faces the transmission housing  12 . On the side facing the starting disk  70 , the damping element  32   c  rests in regions in a further recess  75  of the starting disk  70 . It is essential that, when the armature shaft is unloaded, according to the illustration of  FIG. 13 , the bearing point  31  between the armature shaft  14  or the shaft end  15  of the armature shaft  14  and the starting disk  70  is aligned with the longitudinal axis  26  of the armature shaft  14 . In the event of axial loading of the armature shaft  14  according to  FIG. 14  with an axial force FA, the starting disk  70  pivots within a concave receptacle  76  formed in the transmission housing  12 , wherein the bearing point  31  migrates upward from the longitudinal axis  26  in the plane of projection of  FIG. 14 , with a distance r being formed. Furthermore,  FIG. 14  illustrates the maximum tilting angle α of the starting disk  70 , in which the starting disk  70  bears against the transmission housing  12  on the side facing the damping element  32   c.    
         [0046]    Finally,  FIGS. 17 and 18  illustrate a further embodiment of the invention in which a starting disk  80  has as starting element  30  two flattened portions  81  which are arranged parallel to the plane of projection of  FIGS. 17 and 18  and which, in analogy to the flattened portions  61 , bear in a form-fitting manner against sections of the transmission housing  12  to form a means of securing the starting disk  80  against torsion. The damping element  32   d  is accommodated in a receptacle  82  of the transmission housing  12  and, in the unloaded state of the armature shaft  14 , ends flush with a first end wall  83  of the transmission housing  12 . In the unloaded state of the armature shaft  14 , a gap  85  from a second end wall  84  is formed between the starting disk  80  and the transmission housing  12  on the side opposite the first end wall  83 . In the unloaded state of the armature shaft  14 , the starting disk  80  is held by a clamping connection between the damping element  32   d  and the spherical shaft end  15  of the armature shaft  14 . In the event of an axial loading of the armature shaft  14  by an axial force FA, according to the illustration of  FIG. 18 , the starting disk  80  tilts about its tilting axis  34  (transition of the end wall  83  to the receptacle  82 ) until the maximum tilting angle α is reached, with the starting disk  80  bearing against the second end wall  84 . 
         [0047]    It is furthermore mentioned that the transmission drive device  10  described to this extent can be modified in diverse ways without departing from the context of the invention. In particular, it can be provided in all of the embodiments that the starting element  30  can be of rounded or spherical design in order to form a punctiform bearing against the shaft end  15 . In this case, the shaft end  15  is preferably, but not in a restrictive manner, provided with a flat bearing surface.