Abstract:
A driving unit especially adapted to adjusting devices for motor vehicles having an electric motor, a gear box and an electronic control device. At least one element of the electric motor, for example, at the driving shaft, the magnetic short-circuit or the motor side crankcase casing, additionally provides a gear box mechanical feature and/or a mechanical member, for example, a gear box side crankcase casing, provides an electric motor or electronic control device feature.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a division of U.S. application Ser. No. 10/276,431, filed Nov. 15, 2002 now U.S. Pat. No. 7,038,338, which is a National Phase Patent Application of International Application Number PCT/DE01/01910, filed on May 15, 2001, which claims priority of German Patent Application Number 100 24 907.8, filed May 16, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a drive unit for adjustment devices in motor vehicles with an electric motor, gearing and an electronic control device. 
     U.S. Pat. No. 5,272,938 describes a drive unit which has an electric disc rotor motor, and a gearbox formed as a reduction gearing, as well as a control device fed from a direct current voltage source wherein the housing of the disc rotor motor encloses the rotor disc, tablet-shaped permanent magnets and carbon brushes adjoining the rotor disc. Reduction gearing in the form of planetary gearing is integrated in an outwardly directed indentation of one of the two crankcase casings. An outer housing connected to the rotor of the disc rotor motor covers the housing of the disc rotor motor, the reduction gearing and a clutch so that the motor housing which encloses the electric motor is mounted inside the gearbox housing surrounding the gearbox thereby forming the housing of the drive unit. 
     The one crankcase casing of the motor housing receives a part of the reduction gearing and thus provides an additional mechanical function of the gearing but it also separates the electric disc rotor motor from the reduction gearing, but lined up with a double function of the one crankcase casing of the electric motor. 
     Through the double function of the one crankcase casing of the electric motor it is possible to make the drive unit particularly flat so that it can consequently be used as a hub drive for a cycle, but apart from the double function of the one crankcase casing of the electric motor only the common drive shaft is provided as one structural unit which is used both for the disc rotor motor and for the reduction gearing. 
     A drive unit with a reduction gearbox is described in DE 197 08 310A and is termed “harmonic drive gearing” and is located inside a rigid support ring which has a cylindrical internally toothed supporting area and an externally toothed radially flexible rolling bush. The rolling bush is elliptically deformed through a suitable drive device which consists inter alia of a planetary wheel unit mounted inside the rolling bush and having a sun wheel mounted on a drive shaft and driven by same, whereby the teeth of two planetary wheels engage in the external toothing of the sun wheel at two opposite places. The internal and external toothing differ by one tooth or several teeth. The toothed rim of the radially flexible rolling bush is pressed by the elliptically formed inner core of the drive unit into the cylindrical internally toothed supporting face of the rigid support ring. 
     As a result of the different number of teeth in the supporting surface and rolling bush a permanently continuous off-set stagger is produced between the interengaging circumferential sections so that one complete revolution of the drive shaft only causes the rolling bush to move on by the proposed difference between the number of teeth in the support ring and rolling bush. A very high reduction can thereby be achieved with a harmonic drive gearing of this kind. 
     DE 28 31 774 C2 describes an electric motor having a disc rotor in whose flat air gap an iron-free stator winding is mounted which is associated at least on one side with a permanently magnetized ring with axially magnetized segments and on both sides with soft magnetic flat discs for the magnetic short circuit. An electrodynamic tachogenerator is mounted coaxial with the rotor shaft so that the most compact unit possible is produced for the electric motor and tachogenerator. 
     The known unit of electric motor and tachogenerator consists of coaxial function elements of the electric motor and tachogenerator arranged in a row side by side wherein each unit is fully capable of functioning per se when the individual function elements are separated from each other. 
     SUMMARY 
     The object of the present invention is to increase the level of integration of the drive unit mentioned at the beginning through multiple functions of the component parts of the electric motor and the gearbox of the drive unit and thus to reduce the structural volume and weight of the drive unit, the number of component parts required and thus also the production costs which are made up of the structural parts and assembly costs. 
     The solution according to the invention makes it possible to allocate multiple functions to component parts of the electric motor and the gearbox of the drive unit which are subject to different functional and/or static stresses so that it is not component parts which are similarly stressed and which fulfil coinciding functions which raise the degree of integration but component parts used in different functions and static stresses. Through this measure the integration possibilities are clearly increased since the structural conditions need be taken into less consideration when mounting the electric motor and the gearbox than in the case of component parts which are subjected to functionally and/or statically similar stresses. 
     More particularly the solution according to the invention is characterised by the following properties:
         minimal number of parts, minimal weight and volume through a high degree of integration of the drive components electric motor, electronics, sensor system and mechanical component parts as well as possibility of increasing the level of integration through incorporating the drive unit in a base part, such as door module, support plate or the like; low production costs;   dispensing with a separate gear housing and electronics connections as well as the need for providing for right and left housings;   possibility of installing the drive unit in any angular position and providing a single assembly plane and thus a variable use, particularly for adjustment devices;
           widest possible interboxing of component parts of the electric motor and gearbox and thus obtaining a low structural depth of the drive unit.   
               

     The solution according to the invention provides with the minimal number of parts, minimal weight and volume of the drive unit, an extremely high degree of integration of the individual drive components of the drive unit which are no longer arranged in a row independently of each other but are linked together so that when separating the drive components each individual part of the drive unit would be no longer able to function, that is that in particular with the omission of a motor element the gear would be incapable of functioning and with the omission of a gear element the motor would be incapable of functioning. The structural space available for housing the drive unit is thus utilised in optimum manner. 
     Furthermore the solution according to the invention guarantees a variable use of the drive unit since separate gear housing and electronics connections, like the need for providing right and left hand housings are unnecessary and installation of the drive unit in any angular position is possible. Reducing the number of parts and as a result of the high degree of integration as well as providing a single assembly plane all contribute to lowering the production costs of the drive unit. 
     To output maximum torque the gear integrated in the drive unit is formed as a reduction gearbox, more particularly as a revolving wheel gear in the form of a cyclo, Wolfrom, planetary, tumbler or harmonic drive gearbox. 
     Suitable electric motors are direct current and alternating current motors of flat construction with mechanical or electronic commutation, more particularly disc rotor motors. 
     The electric motor formed as a disc rotor can consist selectively of a mechanically commutated motor with a rotor disc supporting the electric windings and the collector, a stator supporting the at least one permanent magnet, and a commutating device connected to the housing shell on the motor side, or of an electronically commutated motor with a disc like permanent magnet rotor and fixed exciter coils. 
     The use of an electronically commutated motor is particularly advantageous in the case of a 42 volt mains network since electronically commutated motors can be connected in a particularly advantageous manner with flat built gearboxes of the cycle or harmonic drive principle. 
     When using an electronically commutated motor the fixed exciter coils can be mounted on one or on both sides of the disc like permanent magnet rotor. 
     The rotating permanent magnet rotor guarantees the shortest flow paths for the magnetic circuit and consists in particular of a combination of a support material of plastic or light metal with embedded permanent magnets. These are particularly formed as sintered or injected neodymium iron bore magnets wherein the injected neodymium iron bore magnets are made using the twin-component technology and are a direct constituent part of the permanent magnet rotor. 
     The high degree of integration of the drive unit according to the invention is reached inter alia in that at least one part of the components of the individual drive components, such as the disc rotor motor and the reduction gearbox, is supported on alternate sides, or serves as a supporting component for holding or supporting component parts of each other drive components or of an electronic control device; more particularly at least one component part of the electric motor, for example the drive shaft, the magnetic short circuit or the housing shell on the motor side additionally provides a mechanical function of the gearbox and/or a mechanical component part, for example the housing shell on the gear side provides a function of the electric motor or of the electronic control device. It is thereby reached that as a result of multiple functions by specific components the number of component parts required and the amount of material used can be reduced. 
     A significant component part for increasing the degree of integration of the drive unit represents the magnetic short circuit of the electric motor, more particularly a disc rotor motor. The magnetic short circuit can serve both as a supporting component part to hold different components of the drive unit and also for supporting and stabilizing drive components which can be correspondingly reduced in the mechanical inherent stability. Furthermore the magnetic short circuit can be used as a supporting element for holding retaining or fixing elements or for fixing the crankcase casings on the motor side and gear side or for attaching the drive unit on a base part such as support plate, door module or other support. 
     On the other hand the magnetic short circuit can be simplified for example by reducing its dimensions by integrating the drive unit into a base part so that the base part undertakes at least in part some mechanical supporting functions and in the case of a ferromagnetic design of the base part also serves as part of the magnetic short circuit path. 
     In particular the magnetic short circuit of an electric motor, more particularly a disc rotor motor, can serve in conjunction with a reduction gearbox to take up the internal teeth of a hollow wheel which is fixed relative to the housing. The integration of the internal teeth of the hollow wheel fixed relative to the housing into the magnetic short circuit can take place selectively in that either the magnetic short circuit directly supports the internal teeth of the hollow wheel fixed relative to the housing by for example milling, stamping or shaping in some other way the internal teeth into the inside ring face of a circular ring shaped magnetic short circuit, or by injection moulding the internal teeth of the hollow wheel fixed on the housing as plastic teeth on the magnetic short circuit. 
     Injection moulding the plastic teeth can be carried out by injection moulding the internal teeth on a retracted spline formed on the surface of the magnetic short circuit, that is the spline is shaped by a toothed core formed on the magnetic short circuit and the injected plastic which forms the actual toothed spline, or the internal teeth are injection moulded on the radial recesses and/or projections of the magnetic short circuit. In the last mentioned embodiment protrusions or indentations are formed on the inside face of the magnetic short circuit and serve to take up and fix the position of an injection moulded plastic toothed spline. 
     Furthermore the magnetic short circuit can contain means for locating and positioning the magnetic source of the electric motor which are connected tablet like, circular ring segment like or circular like to the magnetic short circuit and are formed on the magnetic short circuit. Alternatively a one piece assembly of the magnet source and magnetic short circuit is also possible by way of example by using hard and soft magnetic materials. 
     The magnetic short circuit preferably has after the fixing of the drive unit at least in part a first contact with the door inner panel, door module or a support plate of a vehicle door and is only reinforced in the flow-conducting region. 
     As a further component for producing a high degree of integration of the drive unit, the drive shaft forms both the motor and gear shaft of the drive unit and in the case of a reduction gearbox formed as a planetary gearbox directly as the driving sun wheel and/or as the bearing seat for the web of the planetary gearbox and the revolving planetary wheels or rollers. 
     Furthermore the drive shaft can serve with the hub as a support for the energized armature disc of a slip ring rotor motor and as a bearing point for the cable drum of a window lifter drive. 
     In one embodiment of the invention the drive shaft is fixedly connected to a hub which is preferably comprised of a hub plate injection moulded on the rotor disc, and a hub cylinder surrounding the center region of the drive shaft. The hub plate can be fitted with axes spaced radially relative to the drive shaft for holding the planetary wheels which form the drive core of the reduction gearbox. 
     In a further embodiment of the invention the hub supports the rotor disc with the electric windings and the collector, preferably a flat collector. 
     The degree of integration of the drive unit according to the invention can be raised further if the crankcase casing on the motor side consists of a ferromagnetic material and itself is part of the magnetic short-circuit. As an alternative to this the crankcase casing on the motor side can be made of plastic and connected to a ferro-magnetic short circuit element. Furthermore the crankcase casing on the motor side can be an integral constituent part of a support element, for example a conductor plate, of the electronic control device or can be connected to the said electronic control device. 
     In a further development of the solution according to the invention the crankcase casing on the motor side supports the commutating device for the electric motor and/or a sensor unit for the drive unit. 
     Alternatively the rotor disc itself can be the transmitter for the various different sensors, for example optoelectronic or magnetic sensors. 
     A further aid to increasing the degree of integration of the drive unit is achieved if the gearbox side crankcase casing supports a bearing element whose inner region supports the comparatively fast-running drive shaft and whose outer region supports the comparatively slow running output hollow wheel, for example a cable drum for a cable window lifter of a motor vehicle, without interaction, that is without the appearance of mutual friction or bending influences as a result of the radial bearing strain through the cable drum or drive shaft. 
     In order to be able to use the drive unit with its high degree of integration according to the invention in wet and dry space areas, for example in a vehicle door without additional sealing expense, additional structural measures are provided in the integrated drive unit, such as for example
         a conical water drainage channel which is formed in the injection moulded plastic toothed spline of the hollow wheel of the reduction gearbox fixed on the housing and which sealingly adjoins an inner face of the output hollow wheel facing the electric motor. Through this measure it is possible for example to place the driven hollow wheel and the gearbox side crankcase casing as well as parts of the drive core in the wet space area of a vehicle door whilst the motor side crankcase casing, the rotor disc as well as the permanent magnets and bearing of the drive core can be mounted on the dry space side of the vehicle door.   Providing blade elements formed for example as rotating air guide blades in order to create an axial ventilator on the hub with which an air stream is drawn in from the dry space side of the drive unit and discharged to the wet space side of the drive unit through the driven hollow wheel and the crankcase casing on the gearbox side. Through this measure there is an air flow from the dry space (motor chamber) to the wet space (gearbox chamber) for cooling the electronic and motor components and the penetration of dampness and moisture is prevented.       

     In order to increase the smooth running, functional reliability and to generate high torque on the sides of the driven hollow wheel of the gearbox it is advantageous to use a reduction gearbox formed as a revolving wheel gearbox with a toothed radially flexible ring and having the following properties:
         smooth running, high inner system damping, sound and vibration absorbing;   tolerance-compensating, free of backlash;   optimum transfer of different torque and speeds to the outside and inside of the radially flexible ring;   shape stable and permanently durable;   low friction;   transfer of large forces with small surface pressures (large number of teeth or force transfer faces in engagement, i.e. optimum engagement conditions).       

     When using the drive unit according to the invention for a cable window lifter of a motor vehicle the driven hollow wheel is formed as a cable roller and the gearbox side crankcase casing has openings for passing through the window lifter cable. Through these measures and through a variable suspension for the window lifter cable in the cable winding of the cable roller and through the direct connection between the Bowden supports and the gearbox side crankcase casing it is possible to provide variable exits for the window lifter cable and thus to fit the drive unit in any position relative to the cable guides on a support panel or in a door module. 
     Furthermore special cable mountings can be provided on the cable drum so that the window lifter cable can be hung at the end of assembly. 
     When using the drive unit according to the invention for adjusting devices in motor vehicles the drive unit can be connected to a base part such as a door module, support plate or the like so that the base part provides a mechanically stabilising or supporting function. Furthermore the ferro magnetic base part provides in part short circuit functions and serves when using semi conductor end stages to feed the electric motor as coolant body and/or discharge the latent heat of the electric motor. The last-mentioned possibility provides an additional protection against thermal overload of the electric motor and a reduction in the motor weight. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The idea on which the invention is based will now be explained in further detail with reference to the embodiments shown in the drawings in which: 
         FIG. 1  shows a section through a drive unit with a mechanically commutated disc rotor motor and a reduction gearbox designed as a revolving wheel gearbox with a toothed radially flexible ring; 
         FIG. 2  shows an enlarged view of the gearbox parts of the reduction gearbox according to  FIG. 1 ; 
         FIGS. 3 to 6  show diagrammatic perspective views of parts of the drive unit according to  FIG. 1 ; 
         FIG. 7  shows a sectional view through a drive unit with an electronically commutated disc rotor motor with exciter coils fixedly mounted on one side and with a reduction gearbox formed as a revolving wheel gearbox with a toothed radially flexible ring; 
         FIG. 8  shows a section through a drive unit with an electronically commutated disc rotor motor with fixed exciter coils mounted on both sides; 
         FIG. 9  shows a sectional view through a reduction gearbox formed as a revolving wheel gearbox with a toothed radially flexible ring; 
         FIG. 10  shows a sectional view through the reduction gearbox according to  FIG. 9  along the line X-X and 
         FIG. 11  shows an exploded view of a drive unit in connection with a motor vehicle door as a base part seen in two different views. 
     
    
    
     DETAILED DESCRIPTION 
     The drive unit illustrated in  FIGS. 1 to 6  consists of the integration of an electric motor formed as a mechanically commutated disc rotor motor  1 , and a reduction gearbox formed as a revolving wheel gearbox with a toothed radially flexible ring, as a drive unit for a cable window lifter. The high degree of integration of the drive unit is shown in particular by the sectional view in  FIG. 1  and the gearbox parts of the reduction gearbox illustrated on a larger scale in  FIG. 2 , which illustrate the multiple functions of individual component parts of the drive unit. 
     The component parts and functional elements of the mechanically commutated disc rotor motor  1  are the rotor disc  3  provided with the conductor loops  30 , the brushes and brush springs  31 ,  32  mounted in the bearing points of a motor side crankcase casing  11 , the permanent magnets  7  according to  FIG. 1 and 71 ,  78  according to  FIG. 2  serving as the magnetic source, as well as the magnetic short circuit  5 . 
     The rotor disc  3  is connected to a hub  80  which consists of a hub plate  800  which adjoins the surface of the rotor disc  3  and of a hub cylinder  801  which encloses the drive shaft  9  which is fixedly connected to the rotor disc  3 . The rotor disc is preferably injection moulded on the hub plate  800  which serves inter alia to increase the mechanical stability of the rotor disc  3 . The motor side crankcase casing  11  preferably consists of a ferromagnetic material for forming a magnetic short circuit path. 
     The component parts and function elements of the reduction gearbox  2  are a hollow wheel  4  fixed on the housing and having an internally toothed spline  40 , a radially flexible ring  6  which meshes by a part of its external teeth  61  with the internal spline  40  of the hollow wheel  4  fixed on the housing, a profiled section  83 ,  84  of a drive core  8  which engages with an internal sleeve face  62  of the radially flexible ring  6 , and a driven hollow wheel  10  which engages by its inner spline  100  with a part of the external spline  61  of the radially flexible ring  6  and which in the illustrated embodiment is formed as a cable drum of a cable window lifter, as well as a gearbox side crankcase casing  12 . 
     The drive core  8  is formed by the hub  80  which is connected to the rotor disc  3  and which has the planetary wheels  81 ,  82  which are spaced radially relative to the drive shaft  9  and whose axes  85 ,  86  are inserted in the hub disc  800  as well as by a collar  850 ,  860 , in the rotor disc  3 . The planetary wheels  81 ,  82  have a profiled ribbed wheel  83 ,  84  preferably made of rubber which is drawn onto a bearing sleeve  87 ,  88  preferably made of a sintered material of iron, bronze or an injection moulding plastic. The bearing sleeves  87 ,  88  are mounted rotatable on the axes  85 ,  86  of the planetary wheels  81 ,  82 . 
     The profiled ribbed wheels  83 ,  84  of the planetary wheels  81 ,  82  are in engagement with a similar profiled inner sleeve face  62  of the radially flexible ring  6 . The circumferential ribbed shape of the radially flexible ring  6  and the planetary wheels  81 ,  82  creates a radial tolerance compensation through a flexible geometry, prevents axial migration of the radially flexible ring  6  and ensures a highly smooth running of the reduction gearbox  2 . 
     The hollow wheel  4  which is fixed relative to the housing is formed by a shaped plastic part  45  injection moulded on the magnetic short circuit  5  of the disc rotor motor  1  and supporting an internally toothed spline  40  which meshes with a part of the externally toothed spline  61  of the radially flexible ring  6 . Differing from the hollow wheel  4  fixed on the housing and illustrated in this embodiment and formed as a shaped plastic part  45  with integral internal toothed spline  40  it is possible to injection mould the internally toothed spline  40  directly on the inside ring face of the magnetic short circuit  5  or to fit it on a recessed toothed spline formed directly in the magnetic short circuit  5 , or to injection mould it as an internally toothed spline  40  of the hollow wheel  4  on other radially aligned recesses or projections of the magnetic short circuit  5 . 
     The moulded plastic part  45  has an injection moulded water drainage channel  41  which by means of a sealing lip adjoins a radial wall of a recess  102  of the driven hollow wheel  10  and ensures that moisture cannot pass from the gearbox side of the drive unit into the motor side of the drive unit. Between the driven hollow wheel  10  and the moulded plastic part  45  of the hollow wheel  4  fixed on the housing there is additionally a hollow cavity for a seal which can be inserted in this cavity as a lip seal and which preferably acts as a non-return valve which seals when stationary and opens when running so that an air flow through this hollow cavity region is possible. 
     An air guide of this kind can be achieved if the hub  80  has blade elements for forming an axial ventilator with which an air stream is for example sucked in from the motor side (dry space side) of the drive unit and discharged through the driven hollow wheel  10  and the gearbox side crankcase casing  12  to a wet space side of the drive unit. 
     The fast running drive shaft  9  is mounted on the one side in a motor side bearing  91  of the motor side crankcase casing  11  and on the other side in a gearbox side bearing  92  of the gearbox side crankcase casing  12 . The gearbox side bearing  92  supports on its external circumference a bearing  90  for the slow running driven hollow wheel  10  whose internally toothed spline  100  meshes with a part of the externally toothed spline  61  of the radially flexible ring  6 . On its periphery the driven hollow wheel  10  has a spiral shaped groove  101  for holding a window lifter cable  13  which is guided through openings in the gearbox side crankcase casing  12  and which is connected through cable guide rollers to a drive for the window pane of a cable window lifter. The connection between the drive unit and base part is provided according to  FIG. 6  through several flanges  110 ,  111 ,  112  spread out round the circumference of the motor side crankcase casing  11 . 
     The window lifter cable  13  is mounted outside of the drive unit according to  FIG. 6  in a Bowden cable sleeve  130  which is mounted on the gearbox side crankcase casing  12  in Bowden cable supports  14  which can be arranged in variable manner on the gearbox side crankcase casing  12 . 
     The perspective details shown in  FIGS. 3 to 6  of the drive unit shown in  FIGS. 1 and 2  illustrate the construction, functioning and association between the individual component parts of the drive components. Thus  FIG. 3  shows an inclined view of the drive unit from the motor side with the magnetic short circuit  5  and the permanent magnets  71  to  78  with alternating polarity connected integral to the magnetic short circuit  5  and designed in tablet form. In the region of the inner ring face of the magnetic short circuit  5  the plastic moulded part  45  of the hollow wheel  4  fixed on the housing is connected to the magnetic short circuit  5 , that is injection moulded on the inner ring face of the magnetic short circuit  5  or is fitted in the manner described above on the inner ring face of the magnetic short circuit  5 . 
     The radially flexible ring  6  meshes by its external spline  61  with the internal spline  40  of the hollow wheel  4  fixed on the housing, and has on its inner sleeve face  62  a rib-shaped profile which engages with similar formed rib profiles  83 ,  84  of the planetary wheels  81 ,  82 . The planetary wheels  81 ,  82  are mounted on the axes  85 ,  86  which are connected to the drive shaft  9  of the drive unit through the hub, which cannot be seen in this view. 
       FIG. 4  shows a perspective inclined view from the gearbox side of the drive unit with the driven hollow wheel  10  formed as a cable drum with spiral-shaped cable guide groove  101  and mounted on the bearing  90  of the housing side bearing casing which holds the drive shaft  9  simultaneously in an inner bearing. This view shows the rotor disc  3  which is provided with conductor loops  30  and is located in the magnetic circuit and of which the permanent magnets  72  to  77  can be seen in the illustration according to  FIG. 3 . 
       FIG. 5  shows a perspective side view of the drive unit with the rotor disc  3 , the permanent magnet  7 , the magnetic short circuit  5  as well as the radially flexible ring  6  whose external toothed spline  61  projects out for engagement with the internal toothed spline of the driven hollow wheel. The external spline  61  of the radially flexible ring  6  meshes in the illustration according to  FIG. 5  with the internal toothed spline  40  of the hollow wheel  4  which is fixed relative to the housing and is injection moulded on the magnetic short circuit  5 . 
     Inside the radially flexible ring  6  is the drive core with the planetary wheels  81 ,  82  whose profiled ribbed wheels engage with the ribbed inner sleeve face  62  of the radially flexible ring  6 . Furthermore  FIG. 5  shows the drive shaft  9  which is mounted with its end projecting out in this illustration in the gearbox side crankcase casing. 
     Finally  FIG. 6  shows a perspective inclined view of the assembled drive unit. The motor side crankcase casing  11  has fixing flanges  110 ,  111 ,  112  for attaching to a base part and is connected for example by clip connections to the gearbox side crankcase casing  12 . The gearbox side crankcase casing  12  has openings  120  which provide the access for the window lifter cable  13  to the spiral shaped cable guide groove  101  of the driven hollow wheel  10  formed as the cable drum. The window lifter cable  13  is guided in the Bowden cable sleeves  130  which are fixed on Bowden cable supports  14  which can be fitted anywhere round the circumference of the gearbox side crankcase casing  12 . In the center of the drive side crankcase casing  12  is formed the bearing cover  94  for the bearing  92  for the drive shaft or cable drum or the driven hollow wheel  10 . 
     The drive unit illustrated in  FIGS. 7 and 8  with an electronically commutated disc rotor motor  1   a  with integrated revolving wheel gearbox  2  differs from the drive unit illustrated in  FIGS. 1 to 6  and described above in the configuration of the motor part as electronically commutated disc rotor motor  1   a , which has a rotating permanent magnet rotor  3   a  as well as fixed exciter coils  7   a  so that the reference numerals used in  FIGS. 7 and 8  coincide with the reference numerals of  FIGS. 1 to 6  and consequently reference is made to the aforementioned description of the details relating to the revolving wheel gearbox  2 . 
     The electronically commutated disc rotor motor  1   a  with integrated revolving wheel gearbox  2  is suited especially for higher voltage on-board power supplies and is to be connected with particular advantage to flat-built gearboxes based on the cyclo or harmonic drive principle such as the revolving wheel gearboxes illustrated in  FIGS. 7 and 8 . 
     In  FIG. 7  fixed exciter coils are mounted on the side of the permanent magnet rotor  3   a  opposite the motor side crankcase casing  11   a  while in  FIG. 8  a double-sided arrangement of the fixed exciter coils  7   a  and  7   b  is provided where the coils are mounted on both sides of the permanent magnet rotor  3   a.    
     The rotating permanent magnet rotor  3   a  is in the two embodiments of  FIGS. 7 and 8  a combination of a support material of plastic or light metal and permanent magnets  30   a  which are embedded in or connected to this support material. Sintered or injected neodymium iron bore magnets are preferably used which are manufactured using the twin component technology and form a direct constituent part of the disc rotor motor  3   a.    
     The revolving wheel gearbox  2  corresponds in its details to the revolving wheel gearbox  2  illustrated in  FIGS. 1 to 6  and described above wherein in this embodiment according to  FIGS. 7 and 8  the bearing bolts or axes  85 ,  86  of the planetary wheels  81 ,  82  are incorporated particularly solid and stable in the rotating permanent magnet rotor  3   a.    
       FIG. 9  shows a cross section and  FIG. 10  a longitudinal section through a reduction gearbox along the line X-X of  FIG. 9  with a hollow wheel fixed on the housing with internally toothed spline  40  and with a driven hollow wheel aligned with the hollow wheel  4  fixed on the housing and lying behind this fixed hollow wheel in the viewing direction, whereby the internally toothed spline  100  of the driven hollow wheel is off-set by a different number of teeth relative to the internal teeth  40  of the hollow wheel  4  fixed on the housing. The externally toothed spline  61  of a radially flexible ring  6  whose inner sleeve face  62  is provided with a ribbed profile  62  which engages in profiled ribbed wheels  83 ,  84  of two planetary wheels  81 ,  82  forming the drive core  8  engages with the internally toothed splines  40 ,  100  of the hollow wheel  4  fixed on the housing and of the driven hollow wheel. 
     The planetary wheels  81 ,  82  have bearing sleeves  87 ,  88  preferably made of a sintered material such as iron, bronze or injected plastic, which are mounted rotatable on axes  85 ,  86  of the planetary wheels  81 ,  82 . The axes  85 ,  86  are fitted on a web or a hub  80  which is connected to a drive shaft  9 . 
     The core area or the support material of the radially flexible ring  6  can consist in this embodiment of an elastomer whose shape stability increases from the inner sleeve face  62  towards the external teeth  61 , that is changes from a soft, tolerance-compensating and system-damping material into a harder but sufficiently flexible region of the external toothed spline  61 . 
     The profiled ribbed wheels  83 ,  84  of the planetary wheels  81 ,  82  which engage with the profiled inner sleeve face  62  of the radially flexible ring  6  consist of rubber or a soft plastic for a high radial tolerance compensation through a flexible geometry wherein the ribbed structure prevents axial displacement of the radially flexible ring  6  and ensures an extremely smooth running of the reduction gearbox. 
     In order to increase the shape stability and durability as well as guarantee a high force and torque transfer the externally toothed spline  61  of the radially flexible ring  6  can be additionally coated with a hard material. 
       FIG. 11  shows an exploded view of a drive unit for a cable window lifter with disc rotor motor  1 , planetary gearbox  2  with three planetary wheels  81 ,  82 ,  89 , and an electronics unit  15  controlling the disc rotor motor  1 , seen in two different views relative to a vehicle door  18  as the base part. 
     The disc rotor motor  1  and the planetary gearbox  2  are enclosed by two casing halves  11  and  12  which have openings for the entrance and exit of the window lifter cable  13 . The electronics unit  15  contains inter alia the brushes (not shown) as well as sensors, e.g. for the speed or position of the disc rotor motor  1 . It is thereby proposed that the electronics unit  15  and the disc rotor motor  1  be fitted on the dry space side, while the planetary gearbox  2  is located on the wet space side of the vehicle door  18 . 
     In the dry space which is separated for example from the wet space by a support module (not shown) the electronics unit  15  is shown with the necessary connectors for the voltage supply, the brushes as well as the sensor devices for the position and speed of the disc rotor motor  1 . 
     On the wet space side there are the remaining components of the drive unit, namely the planetary gearbox  2  and the driver hollow wheel  10 . The motor side crankcase casing  11  contains openings  111  for sensors S and brushes which are contacted by corresponding elements in the electronics unit  15 . On the side of the motor side crankcase casing  11  remote from the electronics unit  15  there is a magnetic short circuit disc  5 , with a magnetic short circuit designed reinforced only in a flow-guiding region  51  thereof, the rotor disc  3  and the magnetic disc  7 . 
     The motor side crankcase casing  11 , the rotor disc  3 , the magnetic short circuit disc  5  and the magnetic disc  7  with integrated short circuit and hollow wheel  4  fixed on the housing together make up the disc rotor motor  1  which is completed by the electronics unit  15  with the brushes. A drive shaft  9  is fixed on the rotor disc  3  and generates the transfer of the rotary movement to the planetary gearbox  2 . 
     The drive shaft  9  supports a sun wheel  80  which is mounted or moulded rotationally secured thereon and which meshes with the three planetary wheels  81 ,  82 ,  89  which are mounted rotatable on a planetary support  800 . The planetary support  800  itself is mounted rotatable on the drive shaft  9 . 
     The planetary wheels  81 ,  82 ,  89  are thereby in engagement both with the internally toothed spline  40  of a hollow wheel  4  fixed on the housing and with the internally toothed spline  100  of a driven hollow wheel  10  formed as a cable drum, and as a result of the rotatable bearing of the planetary support  800  revolve round on the internally toothed splines  40  and  100 . The window lifter cable  13  which is guided in a spiral shaped groove round the outer circumference of the driven hollow wheel  10  is looped round said driven hollow wheel  10 . 
     In the embodiment illustrated in  FIG. 11  the door inside panel, door module or the support plate of the vehicle door forms the base part  18  and—as explained above—can be incorporated as a support or stabilizing element as well as a magnetic short circuit into the structure of the drive unit. 
     With the embodiment illustrated in  FIG. 11  however it is essential that all the components of the drive unit can be fitted together in one assembly direction and thus enable a simple time-saving cost effective assembly.