Abstract:
A drive system for individually driving two driven wheels of a vehicle. The system includes two continuously variable drive motors which are drivingly connected, via a transmission arrangement, with respective driven wheels. Each transmission arrangement includes a shift transmission and a bevel gear transmission, which has a fixed transmission ratio and includes a spur gearset and a bevel gearset. Shift transmissions vary the transmission ratio and the bevel gear transmission enables arranging drive shafts of the drive motors transversely to the rotational axis of the driven wheels. The spur gearsets enable vertical repositioning of the transmissions drive output shafts. Furthermore, with different arrangements of the bevel gears, inclination of respective drive motors and shift transmissions relative to the vehicles longitudinal axis and the angle of the output shafts can be adjusted, such that the drive system can be installed in different vehicle types using largely identical components.

Description:
This application is a national stage completion of PCT/EP2006/008218 filed Aug. 21, 2006, which claims priority from German Application Serial No. 10 2005 045 281.7 filed Sep. 22, 2005. 
     FIELD OF THE INVENTION 
     The invention concerns a drive system for individually driving the two driven wheels of a driven wheel pair or suchlike for a vehicle. 
     BACKGROUND OF THE INVENTION 
     For a long time, drive systems have been fitted into vehicles with slide steering, i.e., in vehicles, such that to drive around a curve the respective driven wheels (or sprocket wheels of a tracked vehicle) on the inside of the curve are slowed relative to the driven wheels on the outside of the curve. In this the continuously variable drive motors allow a largely free choice of the speed ratio between the driven wheel on the inside of the curve and the driven wheel on the outside of the curve. It has been shown, however, that when a transmission arrangement with a fixed transmission ratio is connected downstream from continuously variable drive motors, the latter comes up against their limits so far as final speed and drive torque are concerned. A further disadvantage is considered to be that for reasons of available space, it is often difficult to fit next to one another two drive aggregates arranged out of alignment with one another. Each consists of a drive motor, transmission arrangement and wheel in the direction of the rotation axis of the driven wheel pair and to design a driven axle arrangement for them. 
     From the unpublished DE 10 2005 010 514A, a drive system for individually driving two driven wheels of a driven wheel pair or the like for a vehicle is known. The drive system comprises two continuously variable drive machines each of which is in drive connection, via a transmission arrangement, with an associated driven wheel or the like. The transmission arrangement comprises two respective transmission units arranged one behind the other. One of the transmission units being designed as a shift transmission and the other transmission unit as a bevel gear transmission with a fixed ratio. 
     This drive train solves both of the technical problems outlined in that for each driven wheel two transmission units are used. One of the transmission units is designed to enable the transmission ratio to be changed and the other transmission unit to improve the installation circumstances. With the help of a two-stage shift transmission, two-speed or drive torque ranges can be preselected, while the bevel gear transmission makes it possible to arrange the drive machines and, if necessary, one of the two transmission units perpendicular to the rotational axis of the driven wheels. 
     The respective shift transmission of the transmission units is made as a two-stage planetary gearset in which the sun gear wheel is connected to a drive input shaft and the planetary gear carrier to a drive output shaft. A ring gear wheel of this planetary transmission can optionally be locked in a rotationally fixed manner or coupled to the drive output shaft. In addition, the shift transmission is arranged downstream from the drive machine and the bevel gear transmission downstream from that transmission. 
     Although this drive system is advantageous, nevertheless, it is desirable to further develop such a drive system in such a manner that it can be used without major structural modifications for different types of vehicles, with structural space situations and distances of the drive aggregates above the road that deviate from one another. 
     Against this background, the purpose of the invention is to provide a drive system of the type just outlined, which enables the final speed or drive torque to be varied and which is easier to fit into a vehicle. In addition, the drive system should be designed such that it can be used in different vehicle types, fitting space situations and distances of the drive aggregates above the ground, with only slight structural alterations using most of the same drive system components. 
     SUMMARY OF THE INVENTION 
     The invention is based on recognition of the objectives can be realized by relatively simple constructive measures by distributing the above mentioned, part objectives on which the invention is based between two transmission units; one of these transmission units is designed to enable variation of the transmission ratio while the other is designed to improve the installation requirements. Almost universal utility in different vehicle types is achieved by designing the transmission units in a particular manner. 
     Accordingly, the starting point of the invention is a drive system for individually driving two driven wheels of a driven wheel pair or the like for a vehicle comprising two continuously variable drive motors each of which is drivingly connected, via a transmission arrangement, with an associated driven wheel or the like. 
     To achieve the stated objectives starting from a drive system of that type, a respective transmission arrangement is provided comprising two transmission units; one of these being a shift transmission and the other transmission unit being bevel gear transmission comprising a spur gearset and a bevel gearset. 
     The shift transmission allows the transmission drive ratio to be varied, while the bevel gear transmission enables the drive shafts of the drive motors to be transversely arranged with respect to the rotational axis of the driven wheels. In each case, the spur gearset in each case makes it possible to position the drive shafts of the respective transmission units higher or lower, depending on the type of vehicle. In addition, varying the arrangement of the bevel gears of the bevel gear transmission, relative to one another, enables constructively easy adjustment of the inclination of the respective drive motor and shift transmission, relative to the longitudinal axis of the vehicle, in relation to a horizontal plane and of the drive output angle of the output shafts of the transmission units so that this drive system can be used with a largely identical component configuration for different vehicle types. 
     Thus, with the aid of a multi-stage shift transmission, several speed or drive torque ranges can be preselected, while the bevel gear transmission enables the drive motor and, if necessary, one of the two transmission units to be arranged perpendicularly to the rotation axis of the driven wheels, which considerably improves the fitting possibilities as will be illustrated with reference to example embodiments. In combination with the bevel gear stage, the spur gear stage on the drive output side then enables the spatial orientation of the transmission output to be adjusted within a wide range and the geometrical orientation of the drive motors and the transmissions transverse to the vehicle&#39;s longitudinal axis also to be varied. 
     In a preferred design of a drive system, according to the invention, the shift transmission is a two-stage, planetary gearset whose sun gear wheel is connected to a drive input shaft, whose planetary gear carrier is drivingly connected with a drive output shaft and whose ring gear wheel can optionally be locked in a rotationally fixed manner or coupled to the drive output shaft. 
     Planetary gearsets allow relatively large transmission ratios while being of a compact structure. A shift enables a large transmission ratio changes, again with little structural complexity by way of the ring gear wheel which can optionally be locked or coupled to the drive output shaft and, therefore, to the planetary gear carrier in fixed connection with it. 
     According to a further feature of a drive system, according to the invention, the shift transmission of each transmission unit is arranged downstream from the drive motor and the bevel gear transmission is arranged downstream from the shift transmission. 
     In a first embodiment of the drive system, the drive motors are arranged one behind the other, in the direction of the vehicle&#39;s longitudinal axis. The bevel gearset of the bevel gear transmission has a first bevel gear, which is connected in a rotationally fixed manner with the output shaft of the shift transmission and which meshes with a second bevel gear, while the second bevel gear is connected in a rotationally fixed manner or is integral with a first spur gear which meshes with a second spur gear. The latter is connected in a rotationally fixed manner to the output shaft of the respective transmission arrangement. 
     In a second embodiment of the drive system, the spur gearset of the bevel gear transmission comprises a first spur gear which is connected in a rotationally fixed manner to the drive output shaft of the shift transmission and which meshes with a second spur gear. This second spur gear is connected in a rotationally fixed manner or is integral with a first bevel gear, which meshes with a second bevel gear connected in a rotationally fixed manner to the output shaft of the respective transmission arrangement. 
     In a further embodiment of the drive system, the drive shafts of the two drive motors are arranged substantially perpendicular to the rotational axis of the driven wheel pair and the orientations of the respective bevel gear transmissions can be varied essentially by 90 degrees. 
     Another further embodiment provides that the output shaft of at least one shift transmission and the drive shaft of the associated drive motor are orientated to be at an angle to the vehicle&#39;s longitudinal axis in relation to a horizontal plane, whereby the ground clearance of these drive aggregates can be made larger. 
     The drive system is axially shorter if the output shaft of at least one shift transmission and the drive shaft of the associated drive motor are perpendicularly orientated to the longitudinal axis of the vehicle. Further axial shortening and a reduction of the width of the drive system can be achieved if the output drive shafts of the drive aggregates are also arranged perpendicular to the transverse axis of the vehicle. 
     Another further embodiment provides that the rotational axis of the combined bevel and spur gear lies in a horizontal plane different than that of the rotational axis of the output shaft of the respective transmission arrangement. This embodiment enables the drive output of the transmission arrangement to be located in the vehicle comparatively low, down toward the road so that when the driven wheels of the vehicle are driven by way of synchronous articulated shafts, the maximum deflection angle of the latter can be used to realize particularly large spring deflections. 
     In accordance with a further embodiment in relation to the longitudinal axis of the vehicle, the drive motors and the transmissions are arranged essentially one behind another or essentially next to one another. In the first such embodiment, the drive system is comparatively narrow and long in the vehicle&#39;s longitudinal direction whereas, according to the second embodiment, the drive system can be made comparatively short, but wider. 
     Preferably, the drive motors are arranged above the rotational axis of the output shafts of the transmission arrangement in order to obtain optimum ground clearance. 
     In another embodiment of the invention, the drive shafts of the drive motors are, in each case, arranged perpendicular to the rotational axis of the driven wheel pair and the respective bevel gear transmission has a deflection angle essentially of 90 degrees. In this way, the drive motors can be arranged along the vehicle&#39;s longitudinal axis ahead of and behind the rotation axis of the driven wheel pair so that the transmission arrangements are positioned, facing one another, close to the vehicle&#39;s longitudinal axis and can be connected by way of relatively long articulated shafts to driven wheels with individual spring suspensions. 
     The drive motors are preferably electric motors whose speed can be regulated in a simple manner. 
     Finally, the drive system, according to the invention, is preferably used in vehicles in which the driven wheels have individual spring suspensions. The wheels are connected by articulated shafts to the associated drive motors or the transmission units arranged downstream from the latter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described, by way of example, with reference to the accompanying drawings in which: 
         FIG. 1  is a drive system with the drive aggregates arranged in the longitudinal direction of the vehicle in which a respective shift transmission and a bevel gear transmission with a spur gear stage are arranged downstream from each drive motor, 
         FIG. 2  is a drive system, as in  FIG. 1 , but with the drive aggregates in a vertical arrangement 
         FIG. 3  is a schematic side view of a drive system from a point of view normal to the longitudinal direction of the vehicle; 
         FIG. 4  is a schematic top view of a drive system from a point of view normal to the longitudinal direction of the vehicle; 
         FIG. 5  is another schematic side view of a drive system from a point of view normal to the longitudinal direction of the vehicle; and 
         FIG. 6  is a view of a portion of the drive system from a point of view along the longitudinal direction of the vehicle. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The drive system, shown in  FIG. 1 , comprises a first drive motor  2  associated with a first driven wheel  4  and a second drive motor  6  associated with a second driven wheel  8 . Arranged downstream from the first drive motor  2  is a two-stage, shift transmission  10  in the form of a planetary gearset. The sun gear  12  of the transmission  10  is connected with a drive input shaft  14  of the drive motor  2  and is engaged with several planetary gears  18  arranged on a planetary gear carrier  16 ; these being engaged on the other side with the inner teeth of a ring gear wheel  20 . 
     The two drive motors  2 ,  6  and the respective transmissions arranged after them are arranged essentially one behind the other in a horizontal plane in a vehicle (not illustrated further). The plane also contains the longitudinal axis  73  of the vehicle. 
     The planetary gear carrier  16  is connected to a drive output shaft  22  which carries a bevel gear  24  at its free end that is engaged with a bevel gear  26 . According to the invention, this latter bevel gear  26  is connected in a rotationally fixed manner or is integral with a spur gear  29 , which is connected to a spur gear  31  at the transmission end of an output shaft  28  of the transmission arrangement. This output shaft  28  is drivingly connected with the first driven wheel  4  via an articulated shaft  30 . 
     The articulated shaft  30 ,  46  enables a spring-loaded suspension  80 ,  81  of the driven wheel  4 ,  8  in a manner generally known and is not explained further. The driven wheel  4  is driven by the articulated shaft  30 , via an additional planetary gearset  32 , also as known in itself and, therefore, not explained again here. 
     The transmission  10  is made as a two-stage shift transmission. For that purpose, the ring gear  20  can optionally be coupled, via a shift pinion  34 , either with a shift gear wheel  36  which is fixed on the drive shaft  22 , as shown in  FIG. 1 , or with an array of locking teeth  38  fixedly arranged in the transmission housing. In the shift position, shown in  FIG. 1 , the planetary gear carrier  16  and the ring gear wheel  20  are coupled in a rotationally fixed manner with one another. Thus, the planetary gears  18  do not rotate relative to the ring gear  20 , nor relative to the sun gear  12  either so that the drive output shaft  22  rotates at the same speed as the drive input shaft  14 . 
     When the ring gear  20  is coupled by the shift pinion  34  to the locking teeth  38 , the ring gear  20  is locked, relative to the housing, and the planetary gears  18  rotate on the inner teeth of the ring gear  20  so that the speed of the drive input shaft  14  is converted, in a known way, into a speed of the drive output shaft  22  that is different from it. 
     The drive system associated with the second driven wheel  8  is made in the same way as the drive system for the driven wheel  4 , described above. It comprises a two-stage shift transmission  40  made as a planetary gearset, arranged downstream from the second drive motor  6  with a drive output shaft  49 , a bevel gear transmission formed of bevel gears  42  and  44 , a spur gear stage  41  on the bevel gear  44  and, meshing with the last-mentioned spur gear stage  41 , a spur gear  43  rotationally attached in a fixed manner onto an output shaft  45  of the second transmission arrangement. This output shaft  45  is in active driving connection with an articulated shaft  46  such that a further planetary gearset  48 , associated with the second driven wheel  8 , can be driven. 
     The two driven wheels  4  and  8  are driven independently of one another by their respective associated drive motors  2  and  6 . No power transfer takes place from one side to the other. Accordingly, the speed or drive torque regulation in the vehicle takes place by way of the shift transmissions  10 ,  40 . 
     To begin driving round a curve, the speed of one of the two driven wheels  4  and/or  8  is slowed or accelerated by correspondingly regulating the associated drive motor  2 ,  6  so that the vehicle drives in a curved path as a result of the different speeds of the driven wheels. 
     As  FIGS. 1 and 3  make clear in relation to the co-operation of the gears of the two transmission arrangements, the respective drive motors  2 ,  6  and their associated transmissions  10 ,  40  can be adjusted through an angle, so to speak out of the plane of the paper in  FIG. 1 , relative to a horizontal plane  76  containing the longitudinal axis  73  of the vehicle as seen in  FIG. 3 , since the point of engagement, between the respective bevel gear  24 ,  42  of the shift transmission  10 ,  40  connected with the output shaft  22 ,  49  and the associated bevel gear  26 ,  44  of a bevel gear transmission  70 ,  72 , can be varied. For this purpose, the engagement point of the respective gears  24  and  26  or  42  and  44  is designed in such manner that the engagement point adopts the position desired on the gear teeth about the circumference of the bevel gear  26  and  44 , respectively, as appropriate for the type of vehicle in question. This measure makes it possible to increase the ground clearance of the drive motors, when designing the drive system. 
     Insofar as the drive input shaft  14  of the respective drive motor  2 ,  6  and the drive output shaft  22 ,  49  of the respective shift transmission  10 ,  40  have a fixed orientation in the horizontal plane substantially along the longitudinal axis  73  of the vehicle, in accordance with another embodiment, the drive output angle of the output shafts  28  and  45  of the two transmission arrangements can be adjusted during construction by the aforesaid adjustment of the point of engagement. Preferably in doing this, the drive output angle is chosen such that the maximum possible deflection angle of an associated synchronous articulated shaft  30 ,  46  can be used in an optimum manner. 
     Finally,  FIG. 1  discloses that, in this drive system, even the location of the output shafts  28  and  45  of the transmission arrangements can be modified in a manner specific for the type of vehicle. This can be done because the engagement point of the respective spur gear  31 ,  43  of the respective drive output shaft  28 ,  45  with the associated spur gear  29 ,  41  of the bevel gear transmission  70 ,  72  can be varied. Accordingly, this design measure enables the rotational axes of the two output shafts  28  and  45  of the transmission units to be raised or lowered relative to the road and to the rotational axes of the combined bevel and spur gears  26 ,  29  and  41 ,  44 , respectively. 
       FIG. 2  shows a drive system, similar to  FIG. 1 , but is represented as viewed in the vehicle&#39;s longitudinal direction  73 . In contrast to the embodiment, according to  FIG. 1 , the two drive motors  2 ,  6  and the shift transmissions  10 ,  40  are fitted vertically in the vehicle instead of horizontally as in  FIG. 1 . Consequently, the output shafts  22  and  49  of the transmission arrangements are essentially perpendicular to the road. In the case of such a vertical arrangement of the drive aggregates, depending on the structural space situation in the vehicle concerned, they can be arranged, in relation to the longitudinal direction of the vehicle, either axially one behind the other or, as shown in  FIG. 2 , next to one another in the vehicle. 
     As is also clear from  FIG. 2 , the two shift transmissions  10  and  40  have on their output side respective spur gears  50  and  60 , which are connected in a rotational fixed manner to the associated output shafts  22 ,  49  of the transmission. These spur gears  50 ,  60  respectively mesh with associated spur gears  52  and  62  of bevel gear transmissions  54  and  64  with a fixed transmission ratio. The spur gears  52  and  62  are connected in a rotationally fixed manner or are integral with respective bevel gears  53  and  68 . The bevel gears  53  and  68  mesh, respectively, with an associated other bevel gear  56  and  66 , each of these latter being coupled in a rotationally fixed manner to one or the other of the output shafts  28  and  45 . From there, the torque is passed onto the two driven wheels  4  and  8  by way of associated articulated shafts  30  and  46 , respectively, in the manner described earlier. 
     From  FIG. 2 , it can also be seen that a design variation of the respective engagement point of the spur gear  50 ,  60  of the shift transmission  10 ,  40  in the associated spur gear  52  and  62  of the respective bevel gear transmission  54  and  56 , allows adjustment of the mounting location of the combination consisting of the drive motor  2 ,  6  and shift transmission  10 ,  40 , by swiveling around the perpendicular rotation axis of the respective spur gear  52 ,  62  of the bevel gear transmission  54 ,  64  in a horizontal plane of the vehicle. This, as shown in  FIG. 2 , enables the combinations of the drive motors  2 ,  6  and the shift transmissions  10 ,  40  to be arranged in a horizontal plane transverse to the vehicle&#39;s longitudinal axis  73 , either next to one another or longitudinally one behind the other. 
     Finally,  FIG. 2  shows that in this vertical arrangement of the combination consisting of drive motor  2 ,  6  and shift transmission  10 ,  40 , their drive input shafts  14  and drive output shafts  22 ,  49  can be arranged in a vehicle at an angle which, in relation to the horizontal plane  76 , is not perpendicular to the longitudinal axis  73  of the vehicle. For this, the engagement point of the respective gears  53  and  56  and  66  and  68  is constructively varied in such a manner that the point adopts the position desired, for the vehicle type concerned, on the gear teeth about the circumference of the bevel gear  56 ,  66  connected to the input shaft  28 ,  45 . As shown in  FIGS. 3 and 4 , the output shaft  22 ,  49  of at least one shift transmission  10 ,  40  and the drive input shaft  14  of the associated drive motor  2 ,  6  are orientated at an inclination to the longitudinal axis  73  of the vehicle and to a horizontal plane  76 . As shown in  FIG. 5 , the output shaft  22 ,  49  of at least one shift transmission  10 ,  40  and the drive input shaft  14  of the associated drive motor  2 ,  6  are orientated perpendicularly to the vehicle&#39;s longitudinal axis  73  and to the horizontal plane  76 . The rotation axis  58 ,  74  of the combined bevel and spur gear  26 ,  29 ;  41 ,  44 , as shown in  FIG. 6  lies in a horizontal plane  78  different from that of the rotational axis  82  of the output shaft  28 ,  45  of the respective transmission arrangement. 
     REFERENCE NUMERALS 
     
         
           2 ,  2 ′ first drive motor 
           4  driven wheel 
           6 ,  6 ′ second drive motor 
           8  second driven wheel 
           10  shift transmission 
           12  sun gear 
           14  drive input shaft 
           16  planetary gear carrier 
           18  planetary gears 
           20  ring gear 
           22  drive output shaft 
           24  bevel gear 
           26  bevel gear 
           28  output shaft of the respective transmission arrangement 
           29  spur gear stage, spur gear on the bevel gear  26   
           30  articulated shaft 
           31  spur gear on the output shaft  28   
           32  planetary gearset 
           34  shift pinion 
           36  shift gear wheel 
           38  locking teeth 
           40  shift transmission 
           41  spur gear stage, spur gear on the bevel gear  44   
           42  bevel gear 
           43  spur gear on the output shaft  45   
           44  bevel gear 
           45  output shaft of the respective transmission arrangement 
           46  articulated shaft 
           48  planetary gearset 
           49  drive output shaft 
           50  spur gear 
           52  spur gear 
           53  bevel gear 
           54  bevel gear transmission 
           56  bevel gear 
           58  rotation axis of the combined bevel and spur gear  41 ,  44   
           60  spur gear 
           62  spur gear 
           64  bevel gear transmission 
           66  bevel gear 
           68  bevel gear 
           70  bevel gear transmission 
           72  bevel gear transmission 
           73  longitudinal axis of the vehicle 
           74  rotation axis of the combined bevel and spur gear  26 ,  29