Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority under 35 U.S.C. 199(a)-(d) to German patent application number DE 10 2004 013 543.6, filed Mar. 19, 2004. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to eccentric gearing for displacing two parts positioned in a manner that enables them to move relative to one another. 
   2. Description of Related Art 
   Publication EP 0 981 696 B1 makes known an electric motor with an eccentric gearing system, with which an eccentric gear mounted on an eccentric is located on a bolt integrated in the motor housing. The drive for the eccentric is an electric motor that is either electrically commutated or has brushes, and is located directly in the housing of the eccentric gearing system. A driving element connected with the eccentric is designed integral with the armature of the electric motor, the armature also being rotatably mounted on the bolt. The eccentric gear includes guide elements that are guided either directly in the stationary housing cover in an opening serving as a guide, or they are guided into openings located in a sliding piece which is accommodated in a housing cover and is displaceably guided therein. 
   A device of this type has the disadvantage that, when high levels of torque are produced and act on the output element, e.g., when strong displacement forces are produced or if a crash occurs, the eccentric gear and the gearing housing can become damaged quickly. A gearing device of this type is therefore not suited for use in adjustment applications in the motor vehicle, e.g., seat adjustments, on which high safety requirements are placed. 
   BRIEF SUMMARY OF THE INVENTION 
   The eccentric gearing according to the present invention has the advantage that, by locating a stable fastening flange around a coupling element that interacts with the eccentric gear, it is possible to redirect torques that act on the output element to chassis-mounted parts via the fastening flange. As a result of the frictional connection of the output element via the eccentric gear directly with the coupling element and, via this, directly with the fastening flange, the rotary drive with its force-transmission path to the driving element of the eccentric is protected against excessive force. The gearing housing is also protected against excessive power flow, which means it can be advantageously made of plastic. 
   Due to the measures listed herein , advantageous refinements and improvements of the invention are made possible. If the fastening flange includes recesses which are designed, e.g., as openings in the flange, the gearing housing parts can be fastened to it, and the entire eccentric gearing can be fastened to one of the parts which move relative to each other. 
   If the fastening flange is made of metal, e.g., steel, it can transmit particularly high forces without the gearing being destroyed. In addition, radial flaps can be favorably integrally formed thereon, the radial flaps including recesses used for fastening to one of the parts which move relative to each other. 
   If the gearing housing is made of plastic, additional gearing elements can be mounted therein directly, with minimal friction. Due to the design of an axially installable gearing housing cover, the two housing parts can be advantageously fixed to the stably designed fastening flange. 
   In order to radially center the body and cover of the gearing housing relative to each other and to the remaining gearing components during assembly of the gearing, the fastening flange includes at least one collar with a radial support surface, against which the housing parts bear radially. 
   To force the eccentric gear to make an eccentric motion around the central housing axis, guide elements are located on the coupling element, the guide elements interacting with the eccentric gear and the fastening flange such that the coupling element is guided along a line without rotating. 
   To this end, the fastening flange includes radially oriented projections that interact with radially oriented counter-elements, e.g., open elongated holes, of the coupling element. 
   In addition, the coupling element includes further radially oriented guide elements which are oriented nearly perpendicularly to the first guide rails and interact with corresponding counter-elements of the eccentric gear. 
   To transfer high torques which act on the eccentric gearing, the fastening flange includes support surfaces, against which corresponding support surfaces of the coupling element bear, in order to transfer the torque in both directions. Particularly favorably, the guide surfaces of the guide elements can serve simultaneously as support surfaces. 
   To achieve a compact design of the eccentric gearing, and in particular to attain a small outer diameter, the eccentric gear has external toothing which meshes with corresponding internal toothing—which has a different number of teeth—of the output element. 
   To achieve a small outer diameter of the gearing, a bolt—as an extension of the output element—is designed as the central axis, the individual gearing elements being located on the bolt. To realize a further reduction stage, the driving element can be driven via a wormwheel by a worm shaft of an electric motor. 
   To absorb the forces acting on the output element, the output element is mounted radially and/or axially in the cover of the gearing housing. To this end, the cover of the gearing housing is preferably made of metal. A portion of the output element extends out of an opening of the cover and forms an interface—which can have any shape—with the adjustment mechanisms of the part to be adjusted and/or the part attached to the housing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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. 
       FIG. 1  shows a cross section through an eccentric gearing, according to the present invention, through A-A, and 
       FIG. 2  shows a radial cross section of the eccentric gearing through II-II. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows eccentric gearing  10  with a gearing housing  12  that includes a body  14  made of plastic and a cover  16 , which is made, e.g., of metal. A bolt  18  is located in gearing housing  12 , on which an eccentric element  20  is rotatably mounted. Eccentric element  20  is rotatably connected with a worm gear  22 , which meshes with a worm  24 . Worm  24  is located, e.g., on an armature shaft  26  of a not-shown electric motor  28  which causes eccentric element  20  to rotate around support bolt  18 . In a further, not-shown exemplary embodiment, eccentric element  20  is driven directly by an armature of electric motor  28 , as shown, e.g., in EP 0 981 696 B1. 
   An eccentric gear  30  with spur gearing  34  designed as external toothing  32  is mounted on eccentric element  20 , eccentric gear  30  being supported such that it can rotate freely around eccentric element  20 . External toothing  32  meshes with internal toothing  36  of a ring gear  38  which is designed as an output element  40 . To transmit the output torque to not-shown kinematics of a seat frame, output element  40  has, e.g., groove toothing  42 , serration  43 , or an inner polyhedron  44 , with which a force-transmission element  9  of seat linkage meshes in a form-fit manner. Eccentric element  20  and output element  40  with internal gear  38  are located axially one above the other on support bolt  18 . Output element  40  is mounted non-rotatably and eccentric element  20  is mounted rotatably on support bolt  18 , for example, support bolt  18  being rotatably mounted in gearing housing  12 . Output element  40  bears radially via a radial outer surface  46  against a circular opening  48  of cover  16 . In addition, cover  16  has an axial shoulder  50 , against which output element  40  and, via this, driving element  20  and eccentric gear  30  bear axially. If cover  16  is made, e.g., of steel, a bearing bush  52  is located between output element  40  and cover  16 , bearing bush  52  being made, e.g., of plastic, in order to support the eccentric gearing with reduced friction. The number of teeth  35  in internal toothing of ring gear  38  differs from the number of teeth in external toothing  32  of eccentric gear  30 , by way of which a differing reduction ratio can be realized. Eccentric gear  30  is guided by eccentric element  20  and is prevented from rotating by a coupling element  54 . To this end, coupling element  54  includes first guide elements  56  which engage in corresponding counter-elements  57  of a fastening flange  60  located between body  14  and cover  16 . As a result, coupling element  54  is capable of being moved relative to fastening flange  60  only along a line  62 . To couple fastening flange  60  with eccentric gear  30 , coupling element  54  includes second guide elements  64  which interact with corresponding counter-elements  65  of eccentric gear  30 . Guide and counter-elements  54 ,  30  are designed such that eccentric gear  30  can also move—relative to coupling element  54 —exclusively along a second line  66 , which is located approximately perpendicular to line  62 . Since eccentric gear  30  can now move—relative to fastening flange  60 —only along two lines  62 ,  66  positioned nearly perpendicularly to each other, eccentric gear  30  is prevented from rotating by coupling element  54 . As a result, output element  40  walks around eccentric gear  30  in accordance with the reduction ratio. 
   In the exemplary embodiment, as shown in the cross section in  FIG. 2 , fastening flange  60  includes radial segments  68 , as first counter-elements  57 , which engage in radial recesses  70  that form first guide elements  56 . Coupling element  54  is guided along lateral guide surfaces  72  of first guide elements  56  along corresponding lateral counter-guide surfaces  73  of fastening flange  60 . Simultaneously, guide and counter-guide surfaces  72 ,  73  serve as support shoulders  75 , via which torque is transmitted between coupling element  54  and fastening flange  60 . Second guide elements  64  of coupling element  54  are designed as second radial recesses  78 , into which guide bolts  80  designed as second counter-guides  65  engage. Radial recesses  78  include both guide surfaces  82 , against which guide bolts  80  bear via counter-guide surfaces  84  and force eccentric gear  30  to move relative to coupling element  54  along line  66 . Second guide and counter-guide surfaces  82 ,  84  are also designed as second support shoulders  85 , via which torque is transmitted between eccentric gear  30  and coupling element  54 . Coupling element  54  includes a central, e.g., circular opening  86 . Eccentric element  20 , which penetrates opening  86 , can rotate around central axis  19  inside opening  86 . In this case, the exterior shape of coupling element  54  is designed nearly circular in shape, and its outer diameter  88  is smaller than the inner diameter  90  of the nearly circular recess  67  of fastening flange  60 , in order to enable displacement of coupling element  54  along axis  62 . First guide elements  56  and second guide elements  64  of coupling element  54  are designed as recesses  70 ,  78  which open radially outwardly or radially inwardly toward opening  86 . In alternative designs, recesses  70 ,  78  can also be designed as closed elongated holes or tangential parallel guide surfaces, depending on the shape of guide elements  56 ,  64  and counter-elements  57 ,  65 . 
   Fastening flange  60  encircles entire coupling element  54 , which is located inside recess  67 . Coupling element  54  is located at the same axial level as fastening flange  60  in a plane perpendicular to support bolt  18 . Recesses  94  for connecting elements  99 , e.g., screws or rivets, are formed in an outer edge region  92  of fastening flange  60 , via which cover  16  and body  14  are connected with each other and/or with fastening flange  60 . To this end, screws  99  are located, e.g., in corresponding counter-recesses  96  of cover  16 , screws  99  penetrating recesses  94  designed as holes and being screwed into body  14 . Gearing housing  12  is therefore tightly closed and fastening flange  60  is integrated in gearing housing  12 . As a result, one of the housing parts  14  or  16  bears against an axial side  59 ,  61  of fastening flange  60 . Fastening flange  60  includes further projections  100  which extend beyond the gearing housing, and recesses  95  for fastening elements  99  which connect fastening flange  60  with one of the parts  8 ,  9  which are movable relative to each other. Recesses  95  are also designed, e.g., as round holes  98  that accommodate, e.g., screws  99  or rivets  99 . Spacers  102  are located on recesses  95  in order to position eccentric gearing  10  relative to one of the parts  8 ,  9  which are movable relative to each other. Fastening flange  60 , which is produced, e.g., as a stamped sheet metal part, has a hole  104  in its interior region, by way of which a radial inner surface  106  and a radial outer surface  108  are formed. As a result, fastening flange  60  serves as a centering element for housing parts  14  and  16 , cover  16  bearing against radial inner wall  106  with an outer edge  107 , and body  14  bearing against radial outer wall  108  with a recess  109 . In addition to this radial fixation, fastening flange  60  includes further recesses  111  as rotation-prevention elements  110 , in which form-fit counter-elements  112  of cover  16  engage. 
   In an application for seat adjustment, according to the present invention, eccentric gearing  10  is connected via recesses  95  of fastening flange  60  with a seat frame  8 ,  9 , output element  40  being operatively connected via interface  42 ,  43 ,  44  with a part  8 ,  9  which is movable relative to the seat frame, e.g., the seat back. If high levels of torque now act on output element  40  when the vehicle is struck from behind, they are transmitted by eccentric gear  30  via support shoulders  85  to coupling element  54 , and, from this, via support shoulders  75  directly to fastening flange  60 , and are therefore absorbed by the seat frame. As a result, electric motor  28  and first gear stage (worm  24 , worm gear  22  and gearing housing  12 ) are not subjected to excessive force. 
   In a not-shown, alternative exemplary embodiment, coupling element  54  is designed integral with eccentric gear  30 . Coupling element  54  has external toothing that engages directly with internal toothing of fastening flange  60 . Eccentric gear  30  with coupling element  54  is located such that it can rotate freely, the reduction resulting from the ratio of the tooth pairing of coupling element  54  with fastening flange  60  to the tooth pairing of internal toothing  36 /external toothing  32 . In this case as well, the high crash torques introduced via output element  40  are transmitted via the external toothing of coupling element  54  directly to the internal toothing of fastening flange  40  and, therefore, to the seat frame. The external toothing of coupling element  54  can be designed to be continuous with the external toothing  32  of eccentric gear  30 , or it can designed as offset toothing. 
   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, the specific embodiment of fastening flange  60 , coupling element  54  and eccentric gear  30  with first and second guide elements  56 ,  64  with corresponding counter-elements  57 ,  65  or the angle between the two lines  62  and  66  can be varied in any manner possible. The important aspect is that it be possible for high torques acting on eccentric gearing  10  to be directed away via a form-fit connection of coupling element  54  with fastening flange  60  via fastening flange  60 , which is designed to have load-bearing capacity. As a result, housing  12  and the other components that are not located in the power flow can be made of lower-cost materials optimized for use for gearing, such as plastic. The application of eccentric gearing  10  is not limited to adjusting seat parts in a motor vehicle. Instead, it can be used with any adjustment devices with which high torques need to be absorbed.

Technology Category: 2