Abstract:
A drive device ( 1, 20 ) including an electric machine ( 3 ), a first planetary gear ( 4 ), a differential ( 5 ) and an operative connection between a drive shaft ( 3   a ) of the electric machine ( 3 ) and a first planetary pinion ( 4   a ) of the first planetary gear ( 4 ), said first planetary pinion ( 4 ) engaging with the first planet wheels ( 4   b ) which engage with a stationary first ring gear ( 4 ) and which are rotationally mounted on a first planet carrier ( 4   c ) which is connected in a rotationally fixed manner to a differential cage ( 5   a ) of the differential.

Description:
The present invention relates to a drive device having an electric machine, a planetary gear, a differential, and an operative connection between a drive shaft of the electric machine and a first sun wheel of the first planetary gear, the first sun wheel being in toothed engagement with first planet wheels which are in toothed engagement with a stationary first annulus gear and are rotatably mounted on a first planet carrier, which is rotatably fixedly connected to a differential cage of the differential. 
     BACKGROUND 
     Such a drive device is described in DE 198 41 159 C2. The electric machine in the form of an electric motor is connected to a classic bevel differential gear with the aid of a simple planetary gear. The rotor shaft is provided with a toothing at the end which forms the sun wheel of the planetary gear. The differential cage of the bevel differential gear at the same time is the planet carrier for the planets of the planetary gear which are in toothed engagement with the sun wheel and a stationary annulus gear. The planet carrier is rotatable about the main axis of the drive device. The axle drive bevel gears of the differential are connected to output shafts to which the torques introduced into the differential are distributed via the compensating gears, starting from the planet carrier. Such drive devices have a very compact design and require little installation space. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to create a drive device having a variable drive concept. 
     The present invention provides that the operative connection between the planetary gear and the drive shaft is a second planetary gear. The second planetary gear is formed by at least one second sun wheel, by a second set of planet wheels, by a second planet carrier, and by a second annulus gear. The input of the operative connection is the second sun wheel. The second sun wheel is rotatably fixedly connected to the drive shaft about the rotational axis of the drive shaft for this purpose and is in toothed engagement with the second planet wheels. The second set of planet wheels is rotatably mounted on planetary pins at a radial distance from the main axis of the drive device, the planetary pins being fixed on the second planet carrier. 
     The second planet wheels are in toothed engagement with the internal toothing of the second annulus gear, which may be held in a stationary manner. Within the meaning of the present invention, “may be held in a stationary manner” shall mean that the second annulus gear may be held rotatably fixedly with respect to a housing, for example a housing of the drive device, relative to the main axis of the drive device, but may also be enabled again so as to rotate about the main axis. 
     The second planet carrier of the second planetary gear and the first sun wheel of the first planetary gear are rotatably fixedly connected to each other about the rotational axis of the drive shaft. The first sun wheel is the input of the first planetary gear. 
     The rotational axis of the drive shaft is the main axis of the drive device which centrally extends axially through the drive device, and is thus also the rotational axis of the first planet carrier, of the second planet carrier, of the first annulus gear, and of the second annulus gear. 
     According to the present invention, an engageable and disengageable rotary joint is provided between the second sun wheel and the second annulus gear. When the rotary joint between the second sun wheel and the second annulus gear is engaged, a relative rotation of the annulus gear with respect to the sun wheel and a relative rotation of the sun wheel with respect to the annulus gear are precluded. The function of the second planetary gear is suspended. In this operating state, the rotational speeds and torques at the first sun wheel correspond to those at the drive shaft. When the rotary joint between the second sun wheel and the second annulus gear is disengaged, the further planetary gear is in effect. The rotational speeds and torques at the first sun wheel in this case deviate from those at the drive shaft due to the action of the second planetary gear. 
     Such a system according to the present invention allows the drive device to be operated in at least two operating states, making its use more variable. 
     One embodiment of the present invention provides for the second annulus gear to be fixable in a stationary manner with the aid of at least one brake. The brake is a disk or multi-disk brake, or a band brake, for example. Rotations of the second annulus gear may be decelerated with the aid of the brake from a maximum rotational speed to the rotational speed value of zero in relation to the surroundings. 
     A further embodiment of the present invention provides for the engageable and disengageable rotary joint between the second sun wheel and the second annulus gear to be producible with the aid of at least one clutch. The clutch is a multi-disk clutch, for example, or a synchronous clutch having conical friction rings. During engagement of the clutch, differences in the rotational speeds between the second annulus gear and the second sun wheel may be reduced from maximum values when the clutch is disengaged all the way to the relative rotational speed value of zero when the clutch is fully engaged. 
     The deceleration of the annulus gear is preferably accompanied by a synchronous disengagement of the clutch. The enabling of the annulus gear is accompanied by a synchronous engagement of the clutch, as is provided in one embodiment of the present invention. In this way, at least two operating states may be implemented, the brake being released synchronously with the clutch being engaged in a first operating state. In a second operating state, the clutch is disengaged synchronously with the brake being applied. Moreover, a third operating state is provided, in which both the clutch is disengaged and the annulus gear is enabled by the brake so as to be freely rotatable. In this operating state, no drive power is delivered to the differential. 
     The brake and the clutch may be operated separately and independently from each other using different operating devices. 
     One embodiment of the present invention provides for a joint operating device for the brake and the clutch, whereby the drive device, including the brake and the clutch, has a very compact and accordingly installation space-saving design. This operating device allows the brake and the clutch to be synchronously operated at the same time to shift the different operating states. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described in greater detail hereafter based on two exemplary embodiments. 
         FIG. 1  shows a schematic illustration of a drive device  1  longitudinally along the main axis  2  of the drive device  1 . 
         FIG. 2  shows a schematic illustration of a drive device  20  longitudinally along main axis  2  of drive device  20 . 
     
    
    
     DETAILED DESCRIPTION 
     Drive device  1  includes an electric machine  3  and has a first planetary gear  4  and a differential  5 . An operative connection is established via a second planetary gear  6  between a drive shaft  3   a  of electric machine  3 , which is a rotor shaft  3   a , and a first sun wheel  4   a  of first planetary gear  4 . 
     First sun wheel  4   a  is in toothed engagement with first planet wheels  4   b  which are in toothed engagement with a stationary first annulus gear  4   d  and are supported thereon. Planet wheels  4   b  are rotatably mounted on a first planet carrier  4   c.    
     Planet carrier  4   c  is rotatably fixedly connected to a differential cage  5   a  of differential  5 , so that differential cage  5   a  may be rotatably driven about main axis  2  together with planet carrier  4   c . Differential  5  is a planet differential in this case, whose differential cage  5   a  is a planet carrier  5   a . However, as an alternative, the differential may also be a classic bevel differential gear having a differential cage, compensating gears and output wheels. Compensating gears  5   b  and  5   c  of the planet differential are formed by two sets of planet wheels  5   b  and  5   c . In each case, a planet wheel  5   b  and a planet wheel  5   c  are in toothed engagement with each other. Moreover, planet wheels  5   b  are in toothed engagement with an output wheel  5   d , which in planetary gear  5  is a sun wheel  5   d , and planet wheels  5   c  are in toothed engagement with an output wheel  5   e , which in planetary gear  5  is a sun wheel  5   e . Sun wheels  5   d  and  5   e  are connected in each case to an output shaft  8  and  9 . Output shaft  9  is oriented coaxially to main axis  2 . Output shaft  8  is situated concentrically to rotor shaft  3   a , so that its rotational axis corresponds to main axis  2 . 
     Second planetary gear  6  is formed of a second sun wheel  6   a , second planet wheels  6   b , a second annulus gear  6   d , and a second planet carrier  6   c . Second sun wheel  6   a  is in toothed engagement with second planet wheels  6   b . Planet wheels  6   b  are rotatably mounted on planet carrier  6   c  and are in toothed engagement with second annulus gear  6   d . Second planet carrier  6   c  is connected to first sun wheel  4   a . Second sun wheel  6   a  is rotatably fixedly connected to drive shaft  3   a , so that second sun wheel  6   a  is rotatably driveable about main axis  2 . 
     An engageable and disengageable rotary joint  10  is formed between second sun wheel  6   a  and second annulus gear  6   d . Rotary joint  10  is composed of a clutch K 2  and a brake B 1 . A first clutch element  11   a  is connected to sun wheel  6   a  in that first clutch element  11   a  is rotatably fixedly connected to drive shaft  3   a  and may be driven by the same. A second clutch element  11   b  is fixed concentrically to main axis  2  on second annulus gear  6   d  and is rotatably with the same about main axis  2  relative to first clutch element  11   a . Clutch elements  11   a  and  11   b  may be connected to each other with the aid of an operating device, which is not shown in greater detail, in a form-locked and/or frictionally engaged manner, whereby the clutch K 2  formed of clutch elements  11   a  and  11   b  is engageable. The form lock between clutch elements  11   a  and  11   b  may be suspended again by the operating device and clutch K 2  may thus be disengaged. 
     Second annulus gear  6   d  may be held on a housing  13  in a stationary manner with the aid of a brake B 1  so that it cannot be rotated about main axis  2 . Brake B 1  is formed of a first brake element  12   a , which is fixed on housing  13 , and a second brake element  12   b , which is fixed on second annulus gear  6   d  rotatably about the main axis. 
     Second clutch element  11   b  and second brake element  12   b  are formed together on a disk  14  and have mutually concentric linings  14   a  and  14   b.    
     In the system described at the outset, annulus gear  6   d  may be enabled by releasing brake B 1 , so that clutch K 1  may be engaged and thus a rotatably fixed connection may be established between annulus gear  6   d  and sun wheel  6   a . After clutch K 1  has been disengaged, annulus gear  6   d  may be fixed with respect to the surroundings  16  with the aid of brake B 1 . These shifting processes are preferably seamless. 
       FIG. 2  shows a schematic illustration of a drive device  20  longitudinally along main axis  2  of drive device  20 . 
     As drive device  1  according to  FIG. 1 , drive device  20  includes electric machine  3 , first planetary gear  4 , and differential  5 . An operative connection is established via a second planetary gear  6  between a drive shaft  3   a  of electric machine  3 , which is a rotor shaft  3   a , and a first sun wheel  4   a  of first planetary gear  4 . The design and the structure of drive devices  20  and  1  are identical regarding planetary gears  4  and  6  and differential  5 . Drive device  20  differs from drive device  1  illustrated in  FIG. 1  only by rotary joint  7 . 
     Rotary joint  7  is engageable and disengageable and is formed between second sun wheel  6   a  and second annulus gear  6   d . Rotary joint  7  is composed of a clutch K 2  and a brake B 1 . A first clutch element  15   a  is connected to sun wheel  6   a  in that first clutch element  15   a  is rotatably fixedly connected to drive shaft  3   a  and may be driven by the same. A second clutch element  15   b  is at least rotatably fixed concentrically to main axis  2  on second annulus gear  6   d , but is displaceable axially to this annulus gear and is rotatable with the same about main axis  2  relative to first clutch element  15   a . Second clutch element  15   b , which has a friction lining  18  situated concentrically to main axis  2 , is illustrated in a neutral position. Clutch elements  15   a  and  15   b  are connectable to each other in a frictionally engaged manner with the aid of a linearly acting actuator A, whereby clutch K 2  formed of clutch elements  15   a  and  15   b  is engageable upon movements of actuator A in the figure to the left. The frictional engagement between clutch elements  15   a  and  15   b  may be suspended again by movements of actuator A to the right side, and clutch K 2  may thus be disengaged. 
     Second annulus gear  6   d  may be held in a stationary manner with respect to surroundings  16  with the aid of a brake B 1  so that it is not rotatable about main axis  2 . Brake B 1  is formed of a brake element  17 , which is fixed on surroundings  16 , and second clutch element  15   b , which is rotatably connected to second annulus gear  6   d  about main axis  2 , but is axially displaceable relative to this annulus gear with the aid of actuator A. For a frictional engagement with the second clutch element, brake element  17  is provided with a friction lining  19  situated concentrically to main axis  2 . The frictional engagement may be established by a movement of actuator A in the figure to the right, and thus by a displacement of second clutch element  15   b  to the right, and may be suspended again by a displacement to the left. 
     Due to the system described at the outset, clutch K 1  is engaged, and synchronously therewith brake B 1  is released, during a displacement of second clutch element  15   b  in the figure to the left, which means that a rotary joint is established between drive shaft  3   a  and thus second sun wheel  6   a  and annulus gear  6   d , while brake B 1 , which has held annulus gear  6   d  on the surroundings, is released at the same time. Upon displacement of second clutch element  15   b  in the figure to the right, clutch K 1  is disengaged, and synchronously therewith brake B 1  is applied, which means that the rotary joint between annulus gear  6   d  and sun wheel  6   a  is suspended, and annulus gear  6   d  is fixed on the surroundings at the same time. 
     REFERENCE NUMERALS 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                  1 
                 drive device 
               
               
                   
                  2 
                 main axis 
               
               
                   
                  3 
                 electric machine 
               
               
                   
                  3a 
                 drive shaft/rotor shaft 
               
               
                   
                  4 
                 first planetary gear 
               
               
                   
                  4a 
                 first sun wheel 
               
               
                   
                  4b 
                 first planet wheel 
               
               
                   
                  4c 
                 first planet carrier 
               
               
                   
                  4d 
                 first annulus gear 
               
               
                   
                  5 
                 differential 
               
               
                   
                  5a 
                 differential cage/planet carrier 
               
               
                   
                  5b 
                 compensating gear/planet wheel 
               
               
                   
                  5c 
                 compensating gear/planet wheel 
               
               
                   
                  5d 
                 output wheel/sun wheel 
               
               
                   
                  5e 
                 output wheel/sun wheel 
               
               
                   
                  6 
                 second planetary gear 
               
               
                   
                  6a 
                 second sun wheel 
               
               
                   
                  6b 
                 second planet wheel 
               
               
                   
                  6c 
                 second planet carrier 
               
               
                   
                  6d 
                 second annulus gear 
               
               
                   
                  7 
                 rotary joint 
               
               
                   
                  8 
                 output shaft 
               
               
                   
                  9 
                 output shaft 
               
               
                   
                 10 
                 rotary joint 
               
               
                   
                 K1 
                 clutch 
               
               
                   
                 11a 
                 first clutch element 
               
               
                   
                 11b 
                 second clutch element 
               
               
                   
                 B1 
                 brake 
               
               
                   
                 12a 
                 first brake element 
               
               
                   
                 12b 
                 second brake element 
               
               
                   
                 13 
                 Housing 
               
               
                   
                 14 
                 Disk 
               
               
                   
                 14a 
                 Lining 
               
               
                   
                 14b 
                 Lining 
               
               
                   
                 K2 
                 Clutch 
               
               
                   
                 15a 
                 first clutch element 
               
               
                   
                 15b 
                 second clutch element 
               
               
                   
                 16 
                 surroundings 
               
               
                   
                 A 
                 Actuator 
               
               
                   
                 17 
                 brake element 
               
               
                   
                 18 
                 friction lining 
               
               
                   
                 19 
                 friction lining 
               
               
                   
                 20 
                 drive device