Abstract:
An adjusting gearing for an adjusting device of a motor vehicle is provided. The adjusting gearing having a gearing housing, having a drive input wheel which is arranged in the gearing housing and which has bearing collars formed at both sides of the drive input wheel, and having a drive output wheel which is arranged in the gearing housing and which meshes with the drive input wheel and the axis of which is aligned substantially perpendicular to the axis of the drive input wheel. The adjusting gearing further comprising a single part gearing housing having a first housing chamber for holding the drive input wheel and having a second housing chamber for holding the drive output wheel, a bearing point which is formed in the first housing chamber and which serves to hold a first bearing collar of the drive input wheel and a bearing point which is formed in the second housing chamber and which serves to hold a first bearing collar of the drive output wheel, and axially adjustable bearing bushes having cylindrical bushes, which are matched to the inner diameters of the housing chambers for centering second bearing collars of the drive input wheel and of the drive output wheel.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
       [0001]    This application is a National Phase Patent Application of International Patent Application Number PCT/EP2009/060384, filed on Aug. 11, 2009, which claims priority of German Utility Model Application Number 20 2008 010 921.3, filed on Aug. 12, 2008. 
     
    
     BACKGROUND 
       [0002]    The invention relates to an adjusting gearing for an adjusting device of a motor vehicle. 
         [0003]    Such an adjusting device is used for adjusting of two adjusting parts in a motor vehicle which are movable relatively to each other, in particular for adjusting a seat part of a motor vehicle seat, and has for this application two guide rails which extend in a longitudinal direction and are moveable relatively to each other, an adjusting gearing, a spindle and a spindle nut. The adjusting gearing is connected to one of the two guide rails, while the spindle is mounted in a first of the two guide rails and is engaged to the adjusting gearing. As in case of a pivotable spindle the adjusting gearing sets the spindle into a rotational motion or alternatively in case of a stationary spindle, a spindle nut of the adjusting gearing unrolls on the spindle, the first of the two guide rails is moved relatively to the other second guide rail and through this an adjusting part, for instance the first guide rail connected to a seat base body for a vehicle seat, is moved. 
         [0004]    An adjusting device of the mentioned kind is known from JP 2005/06521 A in form of a so-called front drive unit, in which the adjusting gearing is arranged at the first end of the first, upper guide rail and transfers a rotational movement onto a spindle connected pivotably to the first guide rail, so that the second, lower guide rail, which engages with the spindle via a spindle nut, is moved relatively to the first guide rail. Through this relative movement of the first and second guide rails a seat part of a motor vehicle seat connected to the first guide rail can be for instance adjusted in the longitudinal direction defined by the guide rails. 
         [0005]    In case of the adjusting gearing known from DE 10337475 A1, a spindle nut, which extends in longitudinal direction and is to be arranged on a spindle of an adjusting device, and a drive worm, which extends crosswise to the longitudinal direction, are mounted in a gearing housing. The gearing housing is separated in two symmetrical housing parts, which can be assembled and which enclose the spindle nut and the drive worm in the assembled status. The drive worm comprises an external thread, which engages via an external toothing on the spindle nut with the spindle nut and drives the adjusting gearing of the spindle nut when operated. 
         [0006]    In case of the adjusting gearing of DE 10337475 A1 the spindle nut and the drive worm are mounted in bearing points in the gearing housing, respectively. Depending on the form of the bearing points, the spindle nut as well as the drive worm can hereby have a certain clearance relatively to the gearing housing, which is caused by tolerances in the formation of the gearing housing and/or the spindle nut or the drive worm, and which is of disadvantage when operating the adjusting gearing. If the spindle nut has in particular a clearance in longitudinal direction, which corresponds to the axial direction of the spindle interacting under operation with the spindle nut, this leads to an insufficient mounting of the adjusting part which is to be adjusted by the adjusting gearing, for instance a vehicle seat, which is in this case exemplarily hold by the adjusting gearing and can move when operating the motor vehicle, in particular in case of a load reversal of the vehicle (breaking, starting) relatively to the adjusting gearing and therefore to the adjusting direction. This is on the one hand unpleasant for an occupant and secondly leads to the development of noise (rattling). 
         [0007]    When operating the adjusting gearing, an undesired noise development can also occur in case of change of direction of the adjusting devices, namely when changing the moving direction while adjusting, due to an exemplarily mounting of the drive worm in the gearing housing and the hitting of the drive worm on the one or the other side of the gearing housing. 
         [0008]    Furthermore, the assembly of the adjusting gearing composed of the two housing halves and four bearing plates for bearing the drive worm of the spindle nut is elaborated, in particular when considering the previously mentioned problems in respect to the bearing clearing and the noise development resulting there from and insufficient adjustment of the adjusting parts of the adjusting device being movable relatively to each other, which requires an elaborate positioning of the bearing points in respect to the toothing elements. 
       SUMMARY 
       [0009]    The object of the present invention is to provide an adjusting gearing which can be obtained by simple means and an easy assembly, which guarantees essentially a clearance-free mounting of a drive-input wheel connected to a driving device, for instance a drive worm, and a drive output wheel, for instance a spindle nut or a screw gear. 
         [0010]    According to an exemplary embodiment of the invention the adjusting gearing comprises a one-piece gearing housing with a first housing chamber for holding a drive input wheel with bearing collars formed at both sides of the drive input wheel, a second housing chamber for holding a drive output wheel, which meshes with the drive input wheel and which has bearing collars formed on both sides of the output wheel, and the axis thereof is aligned essentially perpendicular to the axis of the drive input wheel, bearing points formed in the first and second housing chamber for holding a first bearing collar of the drive input wheel and a first bearing collar of the drive output wheel and axially adjustable bearing bushes with cylindrical bushes which are matched to the inner diameters of the housing chambers for centering the second bearing collars of the drive input wheel and the drive output wheel. 
         [0011]    The adjusting gearing according to the invention guarantees with simple production and assembly a clearance-free arrangement of the drive input wheel or the drive worm and the drive output wheel or the spindle nut or the screw gear in a one-piece gearing housing with bearing points formed at the one end of the housing chamber for holding the one bearing collars of the drive input and drive output wheel so that the housing chambers have a basin shaped form or pot form with a central bore for holding the one bearing collar of the drive input and drive output wheels. 
         [0012]    By assigning of the housing chambers extending in X- and Y-direction, that means perpendicular to each other, in that direction of the motor vehicle with an opening provided in the intersection, a radial clearance-free toothing engagement between the drive input wheel and the drive output wheel is guaranteed, while the bearing bushes which hold and centre the other bearing collars of the drive input wheel and the drive output wheel are axially positioned such and connected to the front face of the respective housing chamber so that no axial play occurs. 
         [0013]    In this connection play-free means that the play in axial direction between the drive input wheel or a drive worm and the gearing housing and between the drive output wheel or a spindle nut or a screw gear and the gearing housing is minimized or eliminated. The drive input wheel (drive worm) and the drive output wheel (spindle nut or screw gear) are mounted axially free of play in the gearing housing, can however simultaneously be freely rotated around their axis. Free of play can also be understood in this connection that the play is adjusted during the assembly in a desired, defined manner. 
         [0014]    The essential advantage of the method according to the invention consists therein that by specifying the one bearing point for the one bearing collar of the drive input wheel and drive output wheel the axial play of the drive input wheel and the drive output wheel can be adjusted simply by the axial positioning of the bearing bushes holding the other bearing collars and can be eliminated through this. The toothing engagement of the drive input wheel and the drive output wheel determined by the distance of the housing chambers of the one piece gearing housing in Z-direction determines that the distance of the axis in vertical direction between the spindle nut or the screw gear and the drive worm is minimised or adjusted in the desired manner. 
         [0015]    The solution according to the invention allows therefore in total for a short tolerance chain as well as a clearance compensation for all toothing parts of the adjusting gearing which can be integrated into an assembly process. 
         [0016]    In an exemplary embodiment the axial adjustable bearing bushes comprise a flange which is connected to the cylindrical bushes centering the drive input wheel and the drive output wheel, whereby the flange rests against the front faces of the housing chambers in the assembled status of the adjusting gearing. 
         [0017]    In this embodiment, the cylindrical bushes allow the centering of the drive input and drive output wheel as well as the compensation for play in axial direction, while the flange connected to the cylindrical bushes serves after the assembly of the bearing bushes for fixing the bearing bushes on the housing chamber of the bearing housing, whereby the connection of the bearing bushes being axial adjustable to the housing chambers occurs preferably firmly bonded, in particular via adhesive or welding joint. 
         [0018]    In a further exemplary embodiment the axial adjustable bearing bushes comprise a thread structure, which serves to obtain a larger joint face in particular for adhesive joint with the housing chambers and for increasing the increasing the reception of actual forces. 
         [0019]    In a first modification of the adjusting gearing the drive input wheel consists of a drive worm, which is connected via drive shaft to a driving device, while the drive output wheel is formed as a spindle nut, whereby the external toothing thereof meshes with the drive worm and comprises an internal bore extending in axial direction, said bore has an internal toothing in form of worm thread, said thread engages with a spindle such that the spindle nut driven by the drive worm unrolls on the spindle and moves along the spindle. 
         [0020]    This embodiment is used in a preferred application for an adjusting device for adjusting seat parts of a motor vehicle seat with two guide rails being relatively adjustable to each other, of which the one guide rail is connected to the adjusting gearing comprising the spindle nut, while a spindle being operatively connected to the spindle nut of the adjusting gearing rests against the other guide rail. 
         [0021]    In a second embodiment designated as “front drive unit”, the drive input wheel consists of a drive worm, which is connected via a drive shaft to a driving device, while the drive output wheel is formed as a screw gear, which is tightly connected to a spindle mounted rotatably at a first adjusting part of the adjusting device and rotates the spindle by actuation of the driving device and a second adjusting part adjustable relatively to the first adjusting part of an adjusting device, which is connected to a spindle nut meshing with the spindle, which unrolls on the spindle being set into a rotational movement by the adjusting gearing such that the first adjusting part of the adjusting device is adjusted relatively to the second adjusting part of the adjusting device. 
         [0022]    This embodiment is preferably employed in an adjusting device for adjusting seat parts of a motor vehicle seat with two guide rails being relatively adjustable to each other, of which the one guide rail is connected to the adjusting gearing containing the screw gear and which stores the spindle which is tightly connected to the screw gear while the other guide rail is connected to a spindle nut, which meshes with the spindle, and which is moved along the spindle when actuating the driving device and thus the spindle set into a rotational movement by said actuating. 
         [0023]    In both embodiments, the spindle nut or the screw gear comprise a cylindrical contour continuing in longitudinal direction of the spindle with a surface formed as a cylinder jacket, whereby in said surface the external toothing of the spindle nut or the screw gear formed in radial direction vertical to the longitudinal extension of the spindle nut or the screw gear inwards into the spindle nut or the screw gear is worked into, adjacent to which in axial direction two free sections are formed, which are followed axially a bearing collar ( 61 ,  62 ), respectively. 
         [0024]    Due to the formation of two cylindrical housing chambers being aligned vertical to each other in the bearing housing, of which the first housing chamber holds the drive worm, and which is aligned in Y-direction of the motor vehicle and arranged above the second housing chamber, which holds the spindle nut or the screw gear and which is aligned in X-direction of the motor vehicle, whereby within an opening provided in the area of cross-section between the housing chambers the toothing of the drive worm and the spindle nut or the screw gear mesh with each other, the distance between the first and the second housing chamber in said direction of the motor vehicle determines the toothing engagement of the toothing or formed as worm toothing of the drive worm and the spindle nut or the screw gear so that it is guaranteed by the geometry of the gearing housing, that the drive worm and the spindle nut or the screw gear match with each other essentially with a play. 
         [0025]    This embodiment of the gearing housing does not only determines the toothing engagement of the drive worm and the spindle nut or the screw gear in a defined manner and therefore provides the required freedom of play, but simultaneously simplifies considerably the assembly and due to the formation of the bearing points at the one front faces of the gearing housing as well as due to the mounting of the bearing bushes at the other front faces of the housing chambers, it is guaranteed that also in case of a longer application a centering of the drive worm and the spindle nut or the screw gear and therefore a correct, play-free toothing engagement is maintained. 
         [0026]    A third tubular like-housing chamber is provided for connecting the gearing housing to an adjusting part of the adjusting device, whereby said housing chamber holds a connecting pin connected to the one adjusting part of the adjusting device and is preferably arranged beside the first housing chamber and is aligned parallel to said first housing chamber. 
         [0027]    A reinforcing rib, which encloses the first housing chamber and the third, tubular like-housing chamber and which is essentially aligned in X-direction and leads to the end of the second housing chamber, is provided for increasing the stability of the bearing housing. 
         [0028]    The sides of the second housing chamber are aligned flush with the end of the first and the third housing chamber in a flattened manner. 
         [0029]    The production of the gearing housing from plastics guarantees on the one hand a lower weight of the adjusting gearing and simplifies on the other hand the assembly of the gearing housing either by a connection of the housing chambers and the bearing points which are connected to the first and second housing chamber and which are formed on the one front faces of the first and the second housing chamber by means of adhesion, friction welding, laser welding or laser melt welding, or alternatively by die-casting or injection moulding of the plastics. 
         [0030]    A method for assembling the adjusting gearing is characterized in that
       a one-piece gearing housing with two cylindrical housing chambers being aligned vertical to each other and with bearing points formed on the one front faces with a centrical bore is obtained by dye casting or injection moulding of a plastic or by connecting the housing chambers by means of laser welding, ultrasound welding, vibration welding, adhesion, hot embossing or welding with inductive heating,   a first bearing collar of a drive worm is inserted into the bearing point of the first housing chamber and a first bearing collar of a spindle nut or a screw gear is inserted into the bearing point of the second housing chamber,   a first bearing bush having a cylindrical bush that matches to the inner diameter of the first housing chamber is inserted for centering the second bearing collar of the drive worm and a second bearing bush having a cylindrical bush that matches the internal diameter of the second housing chamber is inserted for centering the second bearing collar of the spindle nut or the screw gear into the first and second housing chamber and mounted onto the second bearing collar of the drive worm or the spindle nut or the screw gear until a play-free mounting of the drive worm or the spindle nut or the screw gear,   and the first and the second bearing bush are connected to the first and second housing chamber by laser welding, ultrasound welding, vibration welding, adhesion, hot embossing or welding with inductive heating.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    The object of the invention and the idea on which the invention is based on shall be explained in more detail in the following by means of an embodiment shown in the drawing. 
           [0036]      FIG. 1  shows an adjusting gearing for an adjusting device for adjusting an adjusting part in a motor vehicle in an explosive illustration. 
           [0037]      FIG. 2  shows a schematic perspective view of the assembled adjusting gearing according to  FIG. 1 . 
           [0038]      FIG. 3  shows a perspective explosive illustration of an adjusting device with an adjusting gearing. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]      FIG. 3  shows an adjusting gearing for adjusting an adjusting part, for instance a seat part of a motor vehicle seat. The adjusting device has a first guide rail  8  and a second guide rail  9  as well as spindle drive, which is formed by a spindle  7  and an adjusting gearing  1 . The adjusting part can hereby be connected to the first guide rail  8  and is moved by a movement of the first guide rail  8  relatively to the second guide rail  9  by the spindle drives. 
         [0040]    In case of the spindle drive shown in  FIG. 3  the adjusting gearing  1  is arranged at the first guide rail  8 , is engaged with the spindle  7  and moves during adjustment together with the first guide rail  8  along the spindle  7 , which is connected via mounting blocks torque proof to the second guide rail  9 . The spindle  7  comprises an outside thread, which interacts with an inside thread of a spindle nut of the adjusting gearing  1 , and transfers a rotational movement of the spindle nut in a longitudinal movement of the adjusting gearing  1  along the spindle  7  and therefore on the first guide rail  8  which is connected to the adjusting gearing  1  relatively to the second guide rail  9 . 
         [0041]    The adjusting device can be alternatively designed as a so called “front drive unit” in which a screw gear is provided instead of a spindle nut, said screw gear is tightly connected to a spindle  7 , which is rotatably arranged at the first guide rail  8  and sets the spindle  7  into a rotational movement. In this case, a spindle nut is arranged at the second guide rail  9 , whereby said spindle nut unrolls on the spindle  7 , which was set into a rotational movement by the adjusting gearing  1 , and effects therefore, that the first guide rail  8  is adjusted relatively to the second guide rail  9 . In such an arrangement the spindle  7  is thus rotatably connected to the first guide rail  8  and is driven by the screw gear of the adjusting gearing  1 , while a spindle nut is arranged torque proof at the second guide rail  9 . 
         [0042]    The first guide rail  8  and the second guide rail  9  are formed in each case U-shaped in cross section vertical to the longitudinal direction of extension, whereby the first guide rail  8  is bent outwards on the edges of the legs  81 ,  82  and the second guide rail  9  is bent inwards on the edges of the legs  91 ,  92  thereof such that the first guide rail  8  is mounted for instance via rolling elements gliding in longitudinal direction, which corresponds in the assembled status to the X-direction of a motor vehicle, is mounted in the second guide rail  9  and is guided along the second guide rail  9 . The adjusting gearing  1  arranged at the first guide rail  8  moves along the spindle  7  for adjustment of the first guide rail  8  relatively to the second guide rail  9 . 
         [0043]    The adjusting gearing  1  shown in  FIG. 1  in an explosive illustration and in  FIG. 2  in the assembled status comprises a one-piece gearing housing  2  with two cylindrical housing chambers  21 ,  22  which are aligned vertically to each other and arranged above each other. In order to employ in an adjusting device for adjusting a seat part of a vehicle seat with two guide rails  8 ,  9 , which are guided into one another and are movable relatively to each other according to the principle illustration of  FIG. 3 , the one-piece gearing housing  2  is connected to the first guide rail  8  such that the first housing chamber  21  is aligned in Y-direction of the motor vehicle and the second housing chamber  22  is aligned in flush with the spindle  7  according to  FIG. 3  in X-direction of the motor vehicle. 
         [0044]    On the one front face  210  of the first housing chamber  21  and the one front face  220  on the second housing chamber  22  bearing points with a central opening are provided of which in  FIG. 2  the bearing point with central opening  212  of the first housing chamber  21  is recognizable. The bearing points with central opening are for instance formed as bores or cylinder bushes on the one front face  210 ,  220  of the first and second housing chamber  21 ,  22  and consists of cylinder bushes, which are connected to the cylindrical wall of the first and second housing chamber  21 ,  22  via spokes extending radially from the bearing bushes. Through this, a tank or pot-shape of the housing chambers  21 ,  22  with a central bore is provided for holding of bearing collars of a drive input and drive output wheel. 
         [0045]    The distance of the central longitudinal axis of the first housing chamber  21  from the central longitudinal axis of the second housing chamber  22  in Z-direction is smaller than the sum of the internal radius of the two housing chambers  21 ,  22  so that an intersecting plane is provided in which an opening  24  is formed between the two housing chambers  21 ,  22 . 
         [0046]    Furthermore, the one-piece gearing housing  2  comprises a third, tubular-like housing chamber  23  through which a connecting pin can be inserted and which is tightly connected to the one adjusting part, for instance the first guide rail  8  according to  FIG. 3 . In order to increase the stability of the one piece gearing housing  2  a re-enforcing rib  25  which encloses the first and the third housing chamber  21 ,  23 , which is aligned in X-direction and ends at the second housing chamber  22  is provided, which serves the stabilisation of the gearing housing  2  for receiving of adjusting forces, in particular if the one piece gearing housing  2  is made of plastics in die-casting or injection molding. 
         [0047]    A drive worm is inserted into the first housing chamber  21  according to  FIG. 1 , said drive worm comprises a bore  55  for connecting to a drive shaft of a preferably electromotive driving device, a worm toothing  50 , two toothing free sections  53 ,  54  adjacent to the worm toothing  50  and bearing collars  51 ,  52  which are attached to said sections, said bearing collars comprise a surface formed as a cylinder jacket, whereby the external diameter of the bearing collars  51 ,  52  is smaller than the diameter of the toothing free sections  53 ,  54  so that a stepped profile of the drive worm  5  is provided in longitudinal direction. 
         [0048]    A screw gear  6  with a longitudinal bore  65  is inserted into the second housing chamber  22  whereby in said bore a spindle  7  according to  FIG. 3  is inserted and tightly connected to the screw gear  6 . The screw gear  6  comprises an external toothing  60  which meshes in the area of the opening  24  between the two housing chambers  21 ,  22  with the worm toothing  50  of the drive worm  5 . The external toothing  60  descends on both sides into toothing free sections  63 ,  64  onto which two bearing collars  61 ,  62  are attached, which comprise a surface formed as a cylinder jacket, whereby the external diameter of the bearing collars  61 ,  62  is smaller than the diameter of the toothing free sections  63 ,  64  so that a stepped profile of the screw gear  6  is provided in longitudinal direction. 
         [0049]    The distance between the first housing chamber  21  and the second housing chamber  22  in Z-direction and therefore the distance of the longitudinal axis of the drive worm  5  and the screw gear  6  in relation to the formation of the worm toothing  50  and the external toothing  60  is measured such that the worm toothing  50  of the drive worm meshes play-free with the external toothing  60  of the screw gear  6 . 
         [0050]    A spindle nut can be provided alternatively to a screw gear  6  tightly connected to the spindle  7 , wherein said spindle nut comprises an internal bore  65  extending in longitudinal direction, said bore is provided with an internal toothing in form of the worm thread and is engaged with the spindle  7  ( FIG. 3 ) when operating the adjusting gearing  1 . The spindle nut  6  unrolls via the internal toothing in the bore  65  on the spindle  7  driven via the drive worm  5 , moves along the spindle  7  and effects there through a relative movement between the adjusting gearing connected to the one adjusting part and the spindle  7  connected to the other adjusting part. 
         [0051]    The bearing points on the one front faces  210 ,  220  of the two housing chambers  21 ,  22 , which serve for holding in each case a first bearing collar  51  of the drive worm  5  or a first bearing collar  61  of the screw gear  6 , are dimensioned such that both bearing collars  51 ,  61  are mounted play-free, but without hindrance of a rotational movement of the drive worm  5  and the screw gear  6  in the bearing points. 
         [0052]    In order to guarantee a reliable operation and to avoid an undesired noise development when operating the adjusting gearing  1  it is essential that the drive worm  5  as well as the spindle nut or the screw gear  6  are mounted radially and axially play-free in the gearing housing  2 . Hereby it is in particular of importance to minimize the play of the spindle nut or the screw gear  6  in longitudinal direction (X direction of the motor vehicle) in order to avoid a relative movement of the guide rails  8 ,  9  towards each other, in particular by load reversal (braking or starting) of the vehicle and clapping noises resulting therefrom. Furthermore, the play of the drive worm  5  in axial direction thereof is also to be suppressed as far as possible in order to avoid a noise development when operating the adjusting device, in particular during shifting from a forward into a backward movement. Such a noise development results therefrom that in case of an axial play between the drive worm  5  and the gearing housing  2  the spindle nut or the screw gear  6  strikes when moving the adjusting device in an adjusting direction (parallel to the longitudinal direction X) against the one side of the gearing housing  2  and moves by reversal of a moving direction to the other side of the gearing housing  2  and strikes against the other side. 
         [0053]    During assembling of the adjusting gearing  1  according to the invention the drive worm  5  is inserted into the first housing chamber  21  and is inserted with a bearing collar  51  thereof into the bearing point  210  provided at the front face  28  of the first housing chamber  21  until the front face of the toothing free section  53  rests against the bearing point  210 . In an analogue manner the screw gear  6  is inserted into the second housing chamber  22  until the one bearing collar  61  of the screw gear  6  engages with the bearing point provided at the front face  220  of the second housing chamber  22  and rests against the bearing point with the inner front face of the toothing free section  63 . 
         [0054]    A first bearing bush  3  is inserted into the open front face  211  of the first housing chamber  21  after inserting the drive worm  5  into the first housing chamber  21 . The first bearing bush  3  comprises a cylindrical bush  30 , the cylindrical surface thereof corresponds to the internal diameter of the first housing chamber  21  and the cylindrical bore thereof corresponds to the external diameter of the other bearing bush  52  of the drive worm  5  so that the first bearing bush  3  centres after the mounting on the other bearing collar  52  of a drive worm  5  the drive worm towards the first housing chamber  21 . 
         [0055]    In analogy, a second bearing bush  4  is inserted into the open front face  221  of the second housing chamber  22  after the insertion of the one bearing collar  61  of the screw gear  6  into the bearing point of the second housing chamber  22 . The second bearing bush  4  comprises a cylindrical bush  40 , the cylindrical surface thereof corresponds to the internal diameter of the second housing chamber  22  and the cylindrical bore thereof corresponds to the external diameter of the other bearing collar  62  of the spindle nut or the screw gear  6  so that the second bearing bush  4  centres the spindle nut or the screw gear  6  of the second housing chamber  22  after inserting said bush into the second housing chamber  22  and mounting on the other bearing collar  62 . 
         [0056]    The axial length of the bearing bushes  3 ,  4  or the cylindrical bushes  30 ,  40  is measured such that a sufficient axial movement of the cylindrical bushes  30 ,  40  into the housing chambers  21 ,  22  is possible in order to mount the drive worm  5  as well as the spindle nut or the screw gear  6  in axial direction play-free in the gearing housing  2 . 
         [0057]    Flanges  31 ,  41  are formed on the end sides of the cylindrical bushes  30 ,  40  of the bearing bushes  3 ,  4 , the external diameter of said flanges is adapted to the form and the external diameter of the first or the second housing chamber  21  or  22 . 
         [0058]    After inserting the drive worm  5  into the first housing chamber  21  until the toothing free section  53  of the drive worm  5  rests against the first front face  210  of the first housing chamber  21  with the bearing point  212  the first bearing bush  3  is inserted into the second front face  211  of the first housing chamber  21  and thereby the cylindrical bush  30  of the first bearing bush  3  is adjusted in Y-direction so far until the front face end of the cylindrical bush  30  rests against the front face of the toothing free section  53  of the drive worm  5  so that no axial play of the drive worm  5  in the first housing chamber  21  of the gearing housing  2  is provided without that thereby the rotational movement of the drive worm  5  is hindered. 
         [0059]    In an analogue manner after inserting the spindle nut or the screw gear  6  into the second housing chamber  22  until the toothing free section  63  of the spindle nut or the screw gear  6  rests against the first front face  220  of the second housing chamber  22  the second bearing bush  4  is inserted into the second front face  221  of the second housing chamber  22  and thereby the cylindrical bush  40  of the second bearing bush  4  is adjusted in X-direction so far until the front face end of the cylindrical bush  40  rests against the front face of the toothing free sections  63  of the spindle nut or the screw gear  6  so that no axial play of the spindle nut or the screw gear  6  is provided in the second housing chamber  22  of the gearing housing  2  without that the rotational movement of the spindle nut or the screw gear  6  is hindered. 
         [0060]    After the corresponding positioning of the bearing bushes  3 ,  4  the flanges  31 ,  42  of the bearing bushes  3 ,  4  are connected by laser welding, ultrasound welding, vibration welding, adhesion, hot embossing or welding with inductive heating to the second front face  211 ,  221  of the first and second housing chamber  21 ,  22  of the gearing housing  2 , and hereby a lasting play-free mounting of the drive worm  5  and the spindle nut or the screw gear  6  in the gearing housing  2  is guaranteed. 
         [0061]      FIG. 2  shows the finally assembled adjusting gearing  1  with an axial play-free mounting of the drive worm  5  and the spindle nut or the screw gear  6  as well with play-free toothing engagement of the toothing of the drive worm  5  into the toothing of the spindle nut or the screw gear  6  through the axial distance of the centre longitudinal axis of the drive worm  5  from the centre longitudinal axis of the spindle nut or the screw gear  6  or through the axial distance of the centre longitudinal axis of the first housing chamber  21  from the centre longitudinal axis of the second housing chamber  22 . In the such assembled status of the adjusting gearing  1  a connecting pin is inserted through the bore  26  of the third, tubular-like housing chamber  23  and is connected to one of the two adjusting parts of the adjusting device so that a connection of the adjusting gearing  1  to the corresponding adjusting part of the adjusting device is provided. 
         [0062]    The embodiment shown in  FIGS. 1 and 2  relates to a front drive unit with a screw gear which is tightly connected to a spindle, whereby the spindle meshes with a spindle nut, which is connected to the one of the two adjusting parts of the adjusting device, while the spindle with the adjusting gearing is connected to the other of the two adjusting parts of the adjusting gearing. Alternatively, the spindle nut can be provided instead of the screw gear, whereby the internal toothing of the spindle nut meshes with the toothing of a spindle, which is connected with the one of the two adjusting parts of an adjusting device, while the adjusting gearing with the drive worm and the spindle is connected via the connecting pin to the other of the two adjusting parts of the adjusting device. 
         [0063]    The gearing housing  2 , the bearing bushes  3 ,  4 , the drive worm  5  and the spindle nut or the screw gear  6  of the adjusting gearing  1  consist preferably of plastic in order to obtain a light and inexpensive mounting form of the adjusting gearing  2  and to simplify the assembly, in particular the adjustment of the freedom of play by axially aligning the bearing bushes  3 ,  4  and the connection thereof to the housing chambers  21 ,  22 . 
         [0064]    In order to minimize the lateral dimensions of the adjusting gearing  1  and to allow contact surfaces at the one adjusting part of the adjusting device the sides of the second housing chamber  22  are flattened and aligned flush at the front faces  210 ,  211  of the first housing chamber  21 .