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This application claims priority to British Application Number GB0009792.3 filed on Apr. 25, 2000. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to the provision of arcuate drive means within a motor vehicle aperture closure such as a vehicle side passenger door, boot lid, sun roof and the like. 
     It is increasingly common for motor vehicles to be provided with electric motors housed within the door assemblies thereof. Typically a vehicle door may be provided with a motor adapted to raise and lower a window glass panel, a motor to drive central locking means of the door, and a further motor to enable security locking or deadlocking of the door. More expensive vehicles may have doors provided with additional motors to enable, for example, automatic closing thereof. 
     The plurality of motors described above increases both the weight and complexity of a door and a corresponding increases manufacturing costs. 
     SUMMARY OF INVENTION 
     According to the present invention there is provided a drive system operable to drive vehicle aperture closure functions comprising a drive actuator operably connected to a drive member, the drive member having at least first and second positions and being movable between the first and second positions, operation of the drive actuator when the drive member is in the first position causing operation of an aperture closure function. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the present invention will now be described with reference to the accompanying drawings in which: 
     FIG. 1 shows a diagrammatic plan view of a drive system according to the present invention; 
     FIG. 1A shows diagrammatic plan view of another drive system according to the present invention. 
     FIG. 2 shows the cross-sectional view indicated by arrows  2 — 2  in FIG.  1 . Image Page  2   
     FIG. 3 shows an alternative cross-sectional profile for a driveshaft for use in the embodiment shown in FIG.  1 . 
     FIG. 4 shows a schematic isometric view of a vehicle including a drive system according to the present invention, and 
     FIG. 5 shows an isometric schematic view of a further vehicle including a drive system according to the present invention. 
     FIG. 6 shows functions of a drive system according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 and 2 there is shown a drive system, generally designated  10  for a vehicle door assembly. The drive system  10  comprises a drive actuator in the form of a main motor  12  having a drive shaft  14  extending therefrom, a stepper motor  16  having a threaded shaft  18  extending therefrom, a drive member  20  slidably mounted on the drive shaft  14 , and a yoke  22  mounted on the threaded shaft  18 . The drive system  10  further includes a plurality of rockers  24  pivotably mounted to a rocker shaft  26  and a window regulator shaft  28  provided substantially co-axially with respect to the drive shaft  14 . The rockers  26  are movable to operate door functions, such as locking functions, via link members  50 . The main motor  12  and stepper motor  16  are electric motors. 
     The stepper motor  16 , threaded shaft  18  and yoke  22  together form a selector actuator. 
     As can be seen from FIG. 2, the drive shaft  14  is substantially square in cross-section and is received in a correspondingly shaped aperture  30  of the drive member  20 . The drive member  20  has the general form of a disc and is provided with abutment surfaces  32 ,  34  adapted to, in use, engage an engagement portion  36  of respective rockers  24 . In the embodiment shown the abutment surfaces  32 ,  34  are defined at opposing sides of a recessed portion  38  of the peripheral edge  40  of the drive member  20 . 
     The yoke  22  is provided with a slot  41  within which the drive member  20  is received. A threaded aperture  42  in the base  44  of the yoke  22  is adapted to receive the threaded shaft  18  and hence enable the yoke  22  to be driven by the stepper motor  16 . 
     The drive member  20  is further provided with drive teeth  46  which are adapted to engage corresponding drive teeth  48  provided on the window regulator shaft  28 . 
     Operation of the drive system  10  is as follows. The stepper motor  16  is operated to rotate the threaded shaft  18  and, via the threaded connection therebetween, move the yoke  22  with respect to the threaded shaft  18 . Movement of the yoke  22  results in corresponding movement of the drive member  20  relative to the drive shaft. Taking the example where it is desired to carry out a locking function via one of the rockers  24 , the stepper motor  16  is operated to move the drive member  20  into position relative to the appropriate rocker  24 . Once in position the stepper motor  16  ceases operation so as to maintain the drive member  20  in the correct position with respect to the rocker  24 . 
     The drive motor  12  is then operated to rotate the drive shaft  14  and drive member  20  and move one of the drive member abutment surfaces  34 ,  32  into engagement with the rocker engagement portion  36 . Continued rotation of the drive member  20  causes pivotal movement of the rocker  24  about the rocker shaft  26  and hence executes the locking function. 
     Alternatively the drive system  10  may be operated so as to raise or lower a window. In such an operative mode, the stepper motor  16  is driven so as to move the drive teeth  46  of the drive member  20  into engagement with the drive teeth  48  of the window regulator shaft  28 . Once these teeth  46 ,  48  are engaged the drive motor  12  is operated to rotate the window regulator shaft  28 . 
     Furthermore it is possible to provide a neutral position of the drive system. Such a position is shown in FIG. 1 wherein the drive member (shown dotted) is positioned adjacent the drive motor such that operation of the drive motor does not cause operation of any door function. Such a position can usefully be included to provided additional safety features such that inadvertent operation of the drive motor  12  does not, for example, cause opening or unlocking of a door. 
     In further embodiments stepper motor  16  can be replaced by a DC motor or any other suitable power source. In particular where the motor is a DC motor it is advantageous for the drive member  20  to only have a first and second position. 
     As shown in FIG. 1A, in further embodiments it is not necessary to provide the selector actuator (i.e., stepper motor  16 , threaded shaft  18  and yolk  22 ) since this function can be performed manually. Such an arrangement is particularly advantageous where only a limited number of door functions are required to be performed by the drive actuator for example where the drive actuator operates raising and lowering of a window glass and also operates to close and/or release the door. 
     In a further embodiment the selector actuator may be arranged to move the drive actuator and the drive member together as a whole. 
     FIG. 3 shows an alternative cross-section profile for a driveshaft  114  for use in the embodiment shown in FIG.  1 . In is case drive shaft  114  is of the Torques™ profile being smoothly contoured and multilobed. 
     FIG. 4 shows a vehicle  100  including various aperture closures, in particular hood  101 , trunk  102 , sunroof  103 , front side passenger door  104  and rear side passenger door  105 . Passenger doors  104  and  105  are pivotally mounted, in this case at a front edge. The aperture closures can include a drive system according to the present invention. 
     FIG. 5 shows a vehicle  110  with various aperture closures, in particular a side passenger door  111  which slides to open, a tailgate  112  and a rear window  113 . 
     Sliding door  111  includes a drive system according to the present invention. 
     Tailgate  112  can be pivoted downwards about pivots  114  and rear window  113  can be pivoted upwards about pivots  115 . In particular it can be seen that the window  113  has a lower edge  113 A which closes against an upper edge  112 A of tailgate  112 . A drive system according to the present invention is mounted in tailgate  112  and interacts with rear window  113 . In particular the drive system in tailgate  112  can be used to lock rear window  113  in a closed position. Alternatively or additionally the drive system mounted in tailgate  112  can be used to drive wiper blade  116 , which is mounted on rear window  113 . Alternatively or additionally the drive system mounted in tailgate  112  can be used to power a washer pump also mounted on tailgate  112  which squirts water onto rear window  113 . 
     It can be seen that in this case the function provided by the drive system on tailgate  112  interacts with the adjacent rear window  113 . 
     FIG. 6 shows schematically functions actuable with drive system  10 .

Summary:
A drive system ( 10 ) operable to drive vehicle door functions comprises a drive member ( 20 ) mounted for rotation about a drive axis by a drive motor ( 12 ), a rocker ( 24 ) operable by the drive member ( 20 ), and translation means ( 16 ), ( 18 ), ( 22 ) operable to move the drive member ( 20 ) to a predetermined position on the drive axis.