Abstract:
The invention relates to a transmission arrangement, particularly for adjusting devices in motor vehicles, comprising a gear wheel, which is secured against axial displacement on an axis or a shaft by means of securing element. According to the invention, the axis or the shaft is made of plastic. The securing elements comprise at least a molded part, which has at least one axial stop for the direct or indirect support of the gear wheel, and the molded part is secured by means of a screw against axial displacement on the axis or the shaft.

Description:
TECHNICAL FIELD  
       [0001]    The invention concerns a transmission arrangement according to the generic term of claim  1 . 
       BACKGROUND  
       [0002]    Such transmission arrangements are for example used for adjusting devices in motor vehicles, like power windows or sun roofs, which are operated by an electromotor. Hereby an electromotor is used, which particularly adjusts for example a window between an opening- and a closing-adjustment over a transmission. The gear wheel is thereby usually arranged as a tappet and provides a worm gearing, with which it is operated over a driving worm, which is connected with the electromotor. A hoisting drum is put on the tappet, which transfers the torque of the electromotor onto a power window system. Due to the angle of gradient of the worm gearing an axial force has an effect on the tappet, so that a securing against axial displacement of the gear wheel on the axis or the shaft has to be provided. The axis or the shaft, on which the gear wheel is arranged, is usually build of metal, whereby the axis or the shaft is fixed at a housing made of plastic. It is known for realizing the securing against axial displacement to provide a securing ring in a circumferential groove of the axis or shaft, so that the gear wheel can be supported at this securing ring in axial direction. The familiar transmission arrangement has the disadvantage that it provides a relatively high weight due to the axis or shaft being out of metal. Furthermore the torque-proof fixation of the metal axis or the bearing of the spinning metal shaft at the plastic housing is complex. 
       SUMMARY  
       [0003]    Therefore the invention is based on the task to suggest a transmission arrangement with reduced weight as well as with applicable axial securing means. This task is solved by the characteristics of claim  1 . Advantageous improvements of the invention are stated in the sub-claims. 
         [0004]    The invention is based on the idea to build the axis or the shaft of plastic. The axis is preferably built in one piece with a transmission housing, so that an otherwise necessary attaching step and a separate component can be omitted. The axial securing that is known for metal axes or metal shafts in the form of a securing ring does not qualify at axes or shafts made of plastic, because the groove, which is required for mounting the securing ring, can only be realized with a very high effort from a technical view. Furthermore a swinging of the groove and therefore an increasing axial play of the gear wheel has to be expected due to the lower firmness of the plastic as opposed to metal. According to the invention a molded part comprising at least one axial stop for supporting the gear wheel is therefore provided instead of a securing ring that is incorporated in a groove, whereby the molded part is secured against an axial displacement at the plastic axis or the plastic shaft by a screw, particularly a metal screw. Then there is no risk of a swinging of the axial securing according to the invention during operation. If necessary the gear wheel can be made of two parts, as it is known for example from DE 102 46 711 A1, in order to provided damping elements for damping the transmission components in circumferential direction. Preferably the screw is screwed in to the axis or shaft at the front side, whereby the molded part is held solid between screw head and axis or shaft. The axial stop is then created by a sector of the molded part that sticks out radial over the outer circumference of the axis or shaft, against which the gear wheel, made of one or several pieces, can be directly or indirectly supported in axial direction. 
         [0005]    As an improvement of the invention the advantage is provided that the screw for fixing the molded part at the axis or shaft is arranged as thread forming screw. In doing so it is not necessary to already provide an internal thread for taking in the screw when assembling the axis or the shaft, which makes the assembling significantly easier. It is sufficient to provide a blind hole with a particularly even internal circumferential wall, in which the screw cuts an internal thread when mounting. 
         [0006]    In an embodiment of the invention the advantage is provided, that the molded part is incorporated in a front sided recess of the axis or shaft especially including the screw. In doing so the fixing means do not stick out in axial direction over the axis of shaft, whereby installation space can be saved, which is already tight. 
         [0007]    According to a practical improvement of the invention it is provided, that the axial stop for a direct support of the gear wheel is arranged as preferably circumferentially closed ring section of the molded part. According to an alternative embodiment the axial stop for a direct support of the gear wheel can also be arranged as separate ring part, which again is supported at the molded part or at an axial stop of the molded part. In the latter case the molded part serves for a indirect, which means mediate, axial support of the gear wheel. By the annular arrangement of the direct axial stop a preferably big stop area is provided, whereby the distributed load can be reduced. 
         [0008]    In order to avoid the entering of moisture between the axis or shaft and the gear wheel into the area that lies behind that, one embodiment of the invention provides a ring seal around the axis or shaft, which preferably lies on a ring area of the gear wheel and presses radial against the gear wheel as well as the axis or shaft. In order to realize an optimal seal compression, one improvement of the invention provides that the ring section or the separate ring part is used for the seal compression. In doing so the ring section or the ring part has a double function. One the one hand it serves as direct axial stop for the gear wheel and on the other hand simultaneously for the seal compression of the ring seal. For the axial support of the ring section or ring part a radial nib is advantageously provided at the molded part. It sticks out in radial direction over the outer circumference of the axis or the shaft. Depending on the embodiment of the invention the nibs are build in one piece with the ring section or only in one piece with the molded part, whereby the ring part is then directly supported at the nibs in radial direction. 
         [0009]    Preferably three nibs are provided in order to realize an equal support of the ring sector or the ring part. It is significant that the nibs are arranged equally over the circumference of the molded part, in particular in a circumferential distance of 120°. 
         [0010]    For securing the molded parts against a twisting, one embodiment of the invention provides that for each nib one radial slot is provided in the circumferential wall of the front sided recess, in which the molded part is at least partially incorporated. The nibs stick out of the radial slots in radial direction and create an axial stop for the ring section or the ring part and therefore for the gear wheel. Preferably the nibs lie on the slot bottom in mounted status, thus they are impinged with power by the screw head in the direction of the slot bottom. 
         [0011]    In order to find the radial slots easier when mounting, it is provided in an embodiment of the invention that the radial slots are arranged in the axial front part, whereby inlet slops for the nibs are created. 
         [0012]    In order for the axis or the shaft to incorporate shear forces better, an embodiment of the invention provides a radial support for the axis or shaft. Preferably the radial support is arranged as a forming hole in a bearing part, in which the axis or shaft encroaches in axial direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Further advantages and practical embodiments of the invention are stated in further claims, the description of the figures and the figures. 
           [0014]    It is shown: 
           [0015]      FIG. 1  is a cut explosion illustration of a transmission arrangement in extracts, 
           [0016]      FIG. 2  is a cut view of the mounted transmission arrangement according to  FIG. 1 , 
           [0017]      FIG. 3  is a side view of the mounted transmission arrangement, 
           [0018]      FIG. 4  is a top view of the mounted transmission arrangement, 
           [0019]      FIG. 5  is a further embodiment of a transmission arrangement in an explosion illustration, and 
           [0020]      FIG. 6  is the transmission arrangement that is shown in  FIG. 5  in a mounted status. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    In the figures the same components and components with the same function are labeled with the same reference signs. 
         [0022]    At first the embodiment in  FIGS. 1 to 4  is explained. The figures show a transmission arrangement  1 . It provides a gear wheel  2 , which is arranged as tappet and which is pivoted on an axis  3  that is arranged as bolt. A worm  5  that is arranged torque-proof on a motor shaft  5  combs with a worm gearing  6  at the big outer circumference of the gear wheel  2 , whereby the gear wheel  2  is twisted. With an axial distance to the worm gearing  6  an external tooth system  7  with a small circumference is provided, onto which a not shown hoisting drum of a power window mechanism can be put. This is put into rotation by the gear wheel  2  and adjusts this way a window between its end positions. 
         [0023]    Due to the gradient of the worm gearing  6  an axial force F has an effect on the gear wheel  2 . In order to avoid an axial movement of the gear wheel that would result from that, axial securing elements  8  are provided, which are fixed after the mounting ( FIG. 2 ) at the axis  3  made of plastic. 
         [0024]    The securing elements comprise a molded part  9  with a through hole  10  for incorporating a screw  11  that is arranged as thread forming screw. The molded part  9  provides three nibs  12 , which are arranged by 120° in circumferential direction and off-standing in radial direction and which run sloped radial inwards to the circumferential wall of the through hole  10 . In the drawing extract below the radial nibs  12  a circumferentially closed ring sector  13  is provided, which serves as direct axial stop for the gear wheel  2  as it can be seen in  FIG. 2 . An inner shoulder  18  of the gear wheel  2  supports itself in axial direction at the ring section  13  of the molded part  9 . The molded part  9  on the hand is supported in axial direction at the screw head  14  of the screw  11 , which is screwed into a centric blind hole  15  in the axis  3 . Therefore the molded part  9  is jammed between the screw head  14  and the axis  3 . 
         [0025]    In mounted status the molded part  9  is incorporated in a front sided recess  16  of the axis  3  over its entire axial length. For each nib  12  a radial slot  17  is provided, which is opened upwards axial in the drawing extract and through which the nibs  12  stick out in radial direction over the circumferential outline of the axis  3 . The radial slots  17  create simultaneously a rotation prevention for the molded part  9 . 
         [0026]    A ring seal  19  is arranged between the ring section  13  and an internal circumferential shoulder  18 , with which the axis  3  is sealed against gear wheel  2 . In mounted status the ring section  13  of the molded part  9  presses the ring seal  19  in its seal seat. The compression of the seal is exactly defined due to be put on the on the circumferential shoulder  20  of the gear wheel. 
         [0027]    It can be seen in  FIGS. 1 and 2  that a cutoff wall  22  is provided between the blind hole  15  and a drying room  21  on the inside of the hollow axis  3 , with which the penetration of water or moisture from the wet room (blind hole  15 ) into the transmission room (drying room  21 ) is avoided. 
         [0028]    Due to the axis  3  being made of plastic according to the invention, it is possible to arrange the axis  3  in one piece with a transmission housing  23  made of plastic. 
         [0029]    In order to compensate shear forces F the axis  3  is supported in a forming hole  24  (draft) of a bearing part  25  made of plastic or metal in radial direction. 
         [0030]    The mounting of the transmission arrangement  1  according to the invention takes place as follows: 
         [0031]    At first the gear wheel  2  is put on the axis  3  and the seal ring put into its seal seat (shoulder  18 ). Subsequently the molded part  9  is put in a targeted manner into the front sided recess  16  of the plastic axis  3 , whereby each nib  12  axially slides into the corresponding radial slot. For a better finding the radial slots  17  have inlet slops  26  that run in axial direction. At the end of the joining process the ring section lies on the ring seal  19  with its lower side in the drawing extract. Simultaneously a small slot still exists between the three nibs  12  and the slot bottoms  27 . Subsequently the screw  11  that is arranged as thread forming screw is put into the through hole  10  of the molded part  9  until it sits on the bottom  28  of a cylindrical clearance  29 . The screw  11  is then screwed into the cylindrical blind hole  15 , whereby an internal thread is grooved into it. When the starting torque is achieved at the end of the screw process, the three nibs abut solidly at the slot bottom  27  with its undersides. Simultaneously the ring section  13  presses on the ring seal  19 . 
         [0032]    When an axial force F has an impact the circumferential shoulder  20  of the gear wheel  2  presses against the ring section  13  of the molded part  9 , whereby the gear wheel  2  is axially secured, which means it can only rotate radial on the axis by an axial function play, but not move axially. 
         [0033]      FIGS. 5 and 6  show an alternative embodiment. In the following it is only referred to the differences to the previously described embodiment to avoid repetitions. As to the similarities it is referred to the previous description. 
         [0034]    At the embodiments according to  FIGS. 5 and 6  the ring section  13  is arranged as separate ring part  30 . That ring part  30  creates the essential axial stop for a direct, which means mediate support of the gear wheel  2 , whereby the ring part  30  is supported in axial direction at the nibs  12  of the molded part  9 . The molded part  9  serves therefore for a direct support of the gear wheel  2  in axial direction. Apart from that the illustrated embodiment corresponds with the previously described first embodiment. 
         [0035]    Due to the screw joint of the molded part  9  with the axis  3  or a shaft according to the invention a repair solution is created, because the molded part  9 , the ring seal  19 , the gear wheel  2  and if necessary the separate ring part  30  can be disassembled by unscrewing the screw  11  and subsequently assembled back onto the plastic axis  3  or a plastic shaft.