FIELD OF THE INVENTION 
       [0001]    A hybrid drivetrain for a motor vehicle, having a combustion engine and having an electric machine which is connected to power electronics and to an electrical energy store and which has a stator and a rotor, which combustion engine and electric machine are connectable in torque-transmitting fashion to an output shaft, wherein
       the combustion engine is coupled to a combustion engine driveshaft which bears one or more driveshaft pinions,   the rotor of the electric machine is coupled to an electric machine driveshaft, which bears one or more driveshaft pinions, via a planetary gear set comprising a sun gear, a web and internal gear, of which one element acts as input element and another element acts as output element of the planetary gear set,   at least one driveshaft pinion of the combustion engine driveshaft forms a switchably torque-transmitting pinion pairing with a corresponding collective shaft pinion of a first collective shaft which is coupled in torque-transmitting fashion to the output shaft, and   at least one driveshaft pinion of the electric machine driveshaft forms a torque-transmitting pinion pairing with a corresponding collective shaft pinion of a collective shaft which is coupled in torque-transmitting fashion to the output shaft.       
 
         [0006]    The invention also relates to a motor vehicle having a hybrid drivetrain of said type and to a novel use thereof. 
       PRIOR ART 
       [0007]    Generic drivetrains are known from DE 10 2010046 766 A1. 
         [0008]    Hybrid vehicles having two drive units, specifically a combustion engine and an electric machine which can be operated both in the motor mode and in the generator mode, have long been known. In particular, the principle of the parallel hybrid is known, in which both the combustion engine and the electric machine are connectable in torque-transmitting fashion to the output shaft. In this case, the connection may be performed selectively, leading to purely electric driving operation or purely combustion-engine-powered driving operation, or in combined fashion, with both the electric machine and the combustion engine being connected to the output shaft simultaneously. Within combined operation, boost operation and recuperation operation are known. In boost operation, both drive units output positive torque to the output shaft; in recuperation operation, the electric machine operates in the generator mode and absorbs kinetic energy from the output shaft in order to convert it into electrical energy. This may take place for example during braking maneuvers of the motor vehicle. Alternatively, in this way, it is also possible for excess power which is output by the combustion engine when it is operating at the optimum operating point, but which is not demanded at the drive wheels in the present driving situation, to be recuperated. 
         [0009]    In most known parallel hybrid concepts, the coupling of the two drive units is realized by way of more or less complex power-split transmission arrangements. DE 100 21 025 A1 and WO 2008/046185 A1 are cited here by way of example. Power-split transmissions always comprise at least two electric machines and a multiplicity of planetary gear sets, the individual elements of which are connectable to one another by means of switchable clutches or to a transmission housing by means of brakes. In this way, it is possible to realize the operating modes discussed above and possibly different drive stages within said operating modes, wherein the setting of a suitable transmission ratio may be performed in a downstream shift transmission or, by means of a correspondingly complex construction of the power-split transmission, in continuously variable fashion in the latter. In the case of the downstream shift transmission, concepts from purely combustion-engine-powered drivetrains are often resorted to, in particular the dual-clutch transmission, which permits gearshifts without interruption in traction force. In DE 100 21 025 A1 cited above, the second electric machine is used instead of a dual-clutch transmission to ensure the absence of interruption in traction force. 
         [0010]    The generic document DE 10 2010 046 766 A1 cited above discloses a hybrid drivetrain having a combustion engine and an electric machine which are arranged coaxially with respect to one another and axially adjacent to one another. Each of said drive units is coupled indirectly to a driveshaft assigned thereto, wherein the driveshaft of the combustion engine extends coaxially through that of the electric machine. Each of the driveshafts has multiple driveshaft pinions which mesh with a respectively associated collective shaft pinion of a collective shaft arranged as a parallel countershaft. The pinion pairings thus formed are each of switchable configuration by virtue of in each case one pinion of each pairing being arranged as a fixed gear and the other pinion of each pairing being arranged as a floating gear on the associated shaft, wherein the respective floating gear is connectable rotationally conjointly to its associated shaft by means of a switchable clutch. Through suitable actuation of the clutches and drive units, the torques thereof can be transmitted to the collective shaft with different transmission ratios predefined in each case by the selected pinion pairing. The output pinion of said collective shaft meshes with the input pinion of an output shaft which drives the downstream drivetrain output section, and which may for example be connected to a downstream differential. Whereas the coupling between the combustion engine and its associated driveshaft is substantially direct, aside from a switchable clutch, the driveshaft of the electric machine is coupled indirectly thereto by means of a planetary gear set. In particular, the rotor of the electric machine is connected rotationally conjointly to the sun gear of the planetary gear set, whereas the web of the planetary gear set is connected rotationally conjointly to the electric machine driveshaft. Furthermore, the internal gear of the planetary gear set is connected to the combustion engine driveshaft, such that the two drive paths are not independent of one another. Aside from this lack of independency, the considerable axial structural size of the known device is also a disadvantage; this arises substantially from the axial space requirement of the numerous driveshaft pinions arranged axially adjacent to one another. The number thereof is defined by the desired number of selectable gear ratios in the known drivetrain. 
       STATEMENT OF OBJECT 
       [0011]    It is the object of the present invention to further develop a generic drivetrain such that the axial structural size is reduced without a reduction in the number of selectable gear ratios. 
       PRESENTATION OF THE INVENTION 
       [0012]    Said object is achieved, in conjunction with the features of the preamble of claim  1 , in that the rotor of the electric machine is selectively connectable to either the input element or the output element of the planetary gear set by means of a switchable clutch. Said switchable clutch will be referred to hereafter as planetary gear set clutch. 
         [0013]    The dependent claims relate to preferred embodiments of the invention. 
         [0014]    A central feature of the invention is the switchability of the indirect coupling between the electric machine and the driveshaft assigned thereto by means of the planetary gear set. In the situation in which the electric machine is connected by means of the planetary gear set clutch directly to the output element of the planetary gear set, a substantially direct connection between the electric machine and its driveshaft is realized. In the other position of the planetary gear set clutch, in which the electric machine is connected to the input element of the planetary gear set, said connection is realized indirectly, specifically via the transmission mechanism of the planetary gear set, in which the torque flow runs from the input element to the output element connected to the electric machine driveshaft. Correspondingly, a transmission ratio is realized here. It is thus possible for two different gear ratios to be realized per driveshaft pinion of the electric machine driveshaft, which substantially halves the axial structural size in relation to known devices which provide only one gear ratio per driveshaft pinion. 
         [0015]    The invention can be realized in two basic variants which differ in terms of the path of torque transmission from the electric machine driveshaft to the output shaft. Whereas it is the case in the first invention variant, as in the generic prior art, that said torque transmission takes place via the same collective shaft via which torque can also be transmitted from the combustion engine to the output shaft, and which is referred to in this case as first collective shaft, it is the case in the second variant that the flow of the electric machine torque takes place via a dedicated collective shaft, which is referred to in this case as second collective shaft and which in this case, in the strictest sense, does not “collect” torques of different units but acts purely as an intermediate shaft. 
         [0016]    The first invention variant presented in claim  2  can thus be defined as being such that that collective shaft whose collective shaft pinion forms a torque-transmitting pinion pairing with the driveshaft pinion of the electric machine driveshaft is the first collective shaft. By contrast, the second invention variant presented in claim  3  can be defined as being such that that collective shaft whose collective shaft pinion forms a torque-transmitting pinion pairing with the driveshaft pinion of the electric machine driveshaft is a second collective shaft, whose collective shaft pinions do not form a pinion pairing with driveshaft pinions of the combustion engine driveshaft. 
         [0017]    In one refinement of the invention, it is provided that at least one driveshaft pinion of the combustion engine driveshaft forms a switchably torque-transmitting pinion pairing with a corresponding collective shaft pinion of a third collective shaft, which is coupled in torque-transmitting fashion to the output shaft. At the combustion engine driveshaft side, said pinion pairings preferably involve the same pinions as are also involved in the pinion pairings with the first collective shaft. This means that the concept of the collective shaft is realized once again at least for the combustion engine. In this way, further axial structural space is saved because each driveshaft pinion of the combustion engine driveshaft forms, both with a collective shaft pinion of the first collective shaft and with a collective shaft pinion of the third collective shaft, in each case one torque-transmitting pinion pairing with unique transmission ratio. It is thus possible to realize two gear ratios per driveshaft pinion of the combustion engine driveshaft, which again entails a considerable saving in axial structural space. In this case too, said third collective shaft need not be a shaft which “collects” torques of multiple units in the strictest literal sense. An intermediate shaft which merely interacts with a unit is sufficient. 
         [0018]    This embodiment, which leads to a structural form which is extremely compact also in a radial direction, can be realized in particular if, as is preferably provided, the output shaft is arranged parallel to and radially spaced apart from both the driveshafts of combustion engine and electric machine and each collective shaft. Only the electric machine driveshaft and the combustion engine driveshaft are preferably arranged coaxially with respect to one another, wherein said driveshafts are particularly preferably arranged so as to extend one through the other. 
         [0019]    The sun gear of the planetary gear set expediently acts as the input element thereof, and the web of the planetary gear set expediently acts as the output element connected to the electric machine driveshaft, wherein the internal gear of the planetary gear set is expediently arranged so as to be fixed with respect to a housing. The planetary gear set clutch is preferably configured so as to connect the rotor of the electric machine selectively either to the sun gear or to the web. Since, as explained above, the web, as output element of the planetary gear set, is connected to the electric machine driveshaft, the former switching position means that the planetary gear set acts as a simple transmission stage, whereas in the latter switching position, there is a direct torque flow between rotor and electric machine driveshaft. 
         [0020]    The switchable pinion pairings are expediently each formed by two intermeshing pinions, of which at least one is coupled by means of a switchable positively locking clutch to its associated shaft. The switchable positively locking clutches are in this case preferably in the form of synchronizers or jaw clutches. Whereas the variant with simple jaw clutches exhibits better efficiency, but requires more complex control with regard to the synchronization of the rotational speeds of the shafts involved, the variant with synchronizers is easier to implement from a control aspect, but is associated with low efficiency losses owing to the friction losses of the synchronizing rings of the synchronizers. 
         [0021]    In one refinement of the invention, it is provided that the rotor of the electric machine and the combustion engine driveshaft are connectable to one another by means of a switchable main shaft clutch. A person skilled in the art will identify that, in the context of the embodiments discussed above, the two drive units can operate fully independently of one another. The latter refinement of the invention additionally permits direct interaction between the two units, such that gear ratios, that is to say transmission ratios, which are provided primarily for use with one unit can alternatively also be driven by the other unit. Furthermore, it is possible in this way to realize combined operating modes, such that all known hybrid operating modes can be implemented. This relates for example to boosting and also to recuperation. 
         [0022]    A particular recuperation scenario is the use of a hybrid vehicle with a drivetrain according to the invention as a static generator. The operation of mobile electrical appliances remote from power networks is often desirable. Examples in this regard are forestry appliances such as electric chainsaws or the like in woodland areas. If the hybrid vehicle according to the invention has an electrical connection point, for example a plug socket, which is connected to the power electronics and to the electrical energy store, the motor vehicle itself can be used as a static electrical generator, wherein the rotor of the electric machine and the combustion engine driveshaft are connected rotationally conjointly to one another by means of the main shaft clutch, an electrical consumer is connected to the connection interface, and the electric machine is operated in the generator mode, while the combustion engine is, by way of the power electronics, controlled so as to operate at engine speeds in accordance with the present power consumption of the electrical consumer. 
         [0023]    Further features and advantages of the invention will emerge from the following specific description and from the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    In the drawings: 
           [0025]      FIG. 1  is a schematic cross-sectional illustration of the shaft arrangement of an embodiment of a first invention variant, 
           [0026]      FIG. 2  is a schematic cross-sectional illustration of the shaft arrangement of an embodiment of a second invention variant, 
           [0027]      FIG. 3  shows a schematic overview sketch of an embodiment of the first invention variant, 
           [0028]      FIG. 4  shows the illustration of  FIG. 3 , with the torque profile in a first switching position indicated, 
           [0029]      FIG. 5  shows the illustration of  FIG. 3 , with the torque profile in a second switching position indicated, 
           [0030]      FIG. 6  shows the illustration of  FIG. 3 , with the torque profile in a third switching position indicated, 
           [0031]      FIG. 7  shows the illustration of  FIG. 3 , with the torque profile in a fourth switching position indicated, 
           [0032]      FIG. 8  shows the illustration of  FIG. 3 , with the torque profile in a fifth switching position indicated, 
           [0033]      FIG. 9  shows a schematic overview sketch of an embodiment of the second invention variant. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0034]    In the figures, the same reference signs are used to denote identical or analogous elements. 
         [0035]      FIG. 1  is a schematic cross-sectional illustration of an embodiment of the first invention variant, the topology of which is illustrated in the overview sketch in  FIG. 3 . These two figures will be discussed jointly below. The arrangement shown will hereinafter be referred to, for short, as a  3 -shaft arrangement. A drivetrain  10  has two drive units, specifically a combustion engine  12  and an electric machine  14 , comprising an internal rotor  141  and an external stator  142 . In the embodiment illustrated, the combustion engine  12  is connected to a start/stop unit  16 , which is however not of central significance for the present invention. The crankshaft  121  of the combustion engine  12  is coupled, by way of a dual-mass flywheel  18 , to a combustion engine driveshaft  20 , which in the embodiment shown is in the form of a hollow shaft. The combustion engine driveshaft bears two driveshaft pinions  201 ,  202  which, in the embodiment shown, are arranged, as fixed gears, in an axially fixed and rotationally conjoint manner on the combustion engine driveshaft  20 . Each of the driveshaft pinions  201 ,  202  forms a switchable pinion pairing with a respectively corresponding collective shaft pinion  221 ,  222  which is arranged as a floating gear on a first collective shaft  22 . For this purpose, the first collective shaft  22  is equipped with a first collective shaft clutch  24  which, depending on switching position, couples the floating gear  221 , the floating gear  222  or neither of the two floating gears  221 ,  222  rotationally conjointly to the first collective shaft  22 . A person skilled in the art will identify that, depending on the switching position of the first collective shaft clutch  24 , a torque can be transmitted from the combustion engine  12  to the collective shaft  22  with a transmission ratio predefined by the specific pinion pairing. An output pinion  223  of the first collective shaft  22  meshes with an input pinion of an output shaft  26  which, in the embodiment shown, is connected to the differential cage of a transverse differential  28 . Via the axle flange shafts  30   a ,  30   b  thereof, the torque is transmitted to drive wheels (not illustrated) of a motor vehicle. 
         [0036]    Furthermore, each driveshaft pinion  201 ,  202  of the combustion engine driveshaft  20  forms a switchable pinion pairing with a respectively corresponding collective shaft pinion  321 ,  322  of a further collective shaft, which in this case is referred to as third collective shaft  32 . The collective shaft pinions  321 ,  322  are in the form of floating gears in the embodiment shown. The third collective shaft  32  has a third collective shaft clutch  34  which, depending on switching position, couples either one floating gear  321 , the other floating gear  322  or neither of the two floating gears rotationally conjointly to the third collective shaft  32 . Furthermore, the third collective shaft  32  has an output pinion  323  which, like the output pinion  223  of the second collective shaft  22 , meshes with the input pinion of the output shaft  26 . Said connection is illustrated as a dotted, arrowed line in the illustration of  FIG. 3 . A person skilled in the art will identify that, depending on the switching position of the third collective shaft clutch  32 , a torque of the combustion engine  12  can be transmitted to the output shaft  26  via the third collective shaft  32  with a transmission ratio predefined by the respectively engaged pinion pairing. In this case, it is self-evidently necessary for the switching positions of the two collective shaft clutches  24  and  34  to be coordinated with one another such that the torque flow runs in each case via only one of the two collective shafts  22  or  32 . 
         [0037]    The spatial arrangement of the shafts can be seen more clearly in  FIG. 1 . In said figure, possible torque transmission points are indicated by black squares, although only the shafts themselves and not specific pinions are denoted by reference signs. However, the spatial structure of the drivetrain according to the invention will clearly emerge to a person skilled in the art from the juxtaposition of  FIGS. 1 and 3 . 
         [0038]    The torque of the electric machine  14  is output by the rotor  141  thereof initially to the rotor shaft  36 . Said rotor shaft runs coaxially with respect to the combustion engine driveshaft  20 . However, the rotor shaft  36  does not constitute for example the counterpart to the combustion engine driveshaft  20 . For this purpose, the electric machine driveshaft  40  is provided, which, as a hollow shaft, is arranged coaxially with respect to, and is extended through by, the rotor shaft  36 . The electric machine driveshaft  40  bears a drive pinion  401  which meshes with a further collective shaft pinion  224  of the first collective shaft  22 . In accordance with the terminology used in the general part of the description and in the claims, this would have to be referred to as a “second” collective shaft, which in the embodiment shown in  FIG. 3  is however identical to the first collective shaft. Said collective shaft thus simultaneously performs the function of transmitting combustion engine torque (first collective shaft) and electric machine torque (second collective shaft) to the output shaft  26 , and thus acts as a “true” collective shaft. 
         [0039]    To transmit the torque of the electric machine  14  from the rotor shaft  36  thereof to the electric machine driveshaft  40 , a planetary gear set  38  is provided, which comprises a sun gear  381 , a web  382  and an internal gear  383 , which is fixed with respect to a housing. The electric machine driveshaft  40  is connected rotationally conjointly to the web  382 , which therefore acts as output element of the planetary gear set  38 . The connection of the rotor shaft  36  to the planetary gear set  38  is realized by means of the planetary gear set clutch  44 , which, depending on switching position, connects the rotor shaft  36  in torque-transmitting fashion to the sun gear  381 , which serves as input element of the planetary gear set  38 , to the web  382 , or to neither of said elements. Depending on the switching position of the planetary gear set clutch  44 , the torque of the electric machine is thus conducted to the driveshaft pinion  401 , and via the latter to the first collective shaft  22  and the output shaft  26 , with a different transmission ratio. The actuation mechanism which serves for the actuation of the planetary gear set clutch  44  is indicated in  FIG. 3  by the reference sign  441 . 
         [0040]    Furthermore,  FIG. 3  also shows a main shaft clutch  50  which, depending on switching position, couples the rotor shaft  36  and the combustion engine driveshaft  20 , which are arranged coaxially and so as to extend one through the other in regions, to one another in switchable fashion. In the connected state, it is for example possible here for torque to be conducted from the electric machine directly to the combustion engine  12  for starting purposes. Conversely, for the generator mode of the electric machine  14 , torque can be conducted from the combustion engine  12  to the electric machine  14 . It is also possible in this way to realize typical hybrid operating modes such as boosting or recuperation. 
         [0041]    Finally,  FIG. 3  also depicts power electronics  60  and a battery  62  as electrical energy store. These are connected to an electrical interface  64  to which external electrical appliances can be connected. 
         [0042]      FIGS. 4 to 8  show the torque flow in a drivetrain as per  FIG. 3  in selected switching positions of the switchable elements discussed above. In  FIG. 4 , a low electric gear ratio is realized. For this purpose, the planetary gear set clutch has been switched such that the rotor shaft  36  is connected to the sun gear  381  of the planetary gear set  38 . The planetary gear set  38  then acts as a transmission stage, such that the torque is conducted via the web  382  thereof to the electric machine driveshaft  40 . Via the driveshaft pinion  401  thereof, the torque flows to the first collective shaft  22 , and from the latter to the output  26 . The other clutches  24 ,  34  and  50  are in this case situated in a non-torque-transmitting switching position. 
         [0043]      FIG. 5  shows the implementation of a higher electric gear ratio. By contrast to the switching position of  FIG. 4 , it is the case here that the planetary gear set clutch  44  connects the rotor shaft  36  directly to the web  382  of the planetary gear set  38 . The electric machine torque is thus conducted to the electric machine driveshaft  40  without a further transmission ratio. Reference may also be made to that which has been stated above with regard to  FIG. 4 . 
         [0044]      FIG. 6  shows the implementation of a low combustion-engine gear ratio. The torque of the combustion engine  12 , which directly drives the combustion engine driveshaft  20 , runs via the pinion pairing  201 / 221  to the third collective shaft  32 . For this purpose, the third collective shaft clutch  34  has been switched such that the collective shaft pinion  321  is connected rotationally conjointly to the third collective shaft  32 . The torque runs to the output shaft  26  via the output pinion  323  of the third collective shaft  32  (along the connection illustrated by a dotted line). 
         [0045]    Aside from the third collective shaft clutch  34 , all of the other clutches are situated in a non-torque-transmitting switching state. 
         [0046]      FIG. 7  shows the implementation of a higher combustion-engine gear ratio. In this case, the torque flows from the combustion engine  12  directly to the combustion engine driveshaft  20  and via the pinion connection  201 / 221  to the first collective shaft  22 . For this purpose, the first collective shaft clutch  24  has been switched such that the collective shaft pinion  221  is connected rotationally conjointly to the first collective shaft  22 . The torque flows to the output  26  via the output gear  223  of the second collective shaft  22 . In this case, all of the other clutches are situated in a non-torque-transmitting switching state. 
         [0047]    A person skilled in the art will identify that two further gear ratios can be realized by way of the pinion pairings  202 / 222  and  202 / 322  in an analogous manner. 
         [0048]      FIG. 8  shows the implementation of the same gear ratio as in  FIG. 5 , wherein, however, the original torque originates not from the electric machine  14  but from the combustion engine  12 . For this purpose, in addition to the switching position of the planetary gear set clutch  44  described in conjunction with  FIG. 5 , the main shaft clutch  50  has been closed such that the torque of the combustion engine  12  flows from the combustion engine driveshaft  20  via the main shaft clutch  50  to the rotor shaft  36 , and from there to the output  26  in the manner described in conjunction with  FIG. 5 . In this case, the rotor  141  of the electric machine  14  may co-rotate freely or may be electrically driven in a synchronized manner, for example in order to implement an extremely high-torque gear ratio, for example for uphill travel with a trailer. 
         [0049]      FIG. 9 , which is to be viewed in conjunction with  FIG. 2 , shows the topology of the second variant of the present invention, which in this case is to be referred to as a  4 -shaft arrangement. In the modified drivetrain  10 ′ of  FIG. 9 , those components which are substantially identical to the components in  FIG. 3  are denoted by the same reference signs as in  FIG. 3 . Modified elements are, in reference to the analogous elements of  FIG. 3 , denoted in each case by the same reference sign with the suffix “′”. The main difference between the drivetrain  10 ′ and the drivetrain  10  of  FIG. 3  is the second collective shaft  42 , which acts as an intermediate shaft between the driveshaft pinion  401  of the electric machine driveshaft  40  and the input pinion  26  of the output. The connection between the second collective shaft  42  and the output  26  is denoted in  FIG. 9  as a dash-dotted, arrowed line. The spatial position of the shafts can be seen more clearly from  FIG. 2 . 
         [0050]    A further modification can be seen in the fact that the main shaft clutch  50 ′ has been “pulled out”. The marginal arrangement has the advantage of better accessibility than the central arrangement in  FIG. 3 . For this purpose, the combustion engine driveshaft  20 ′ is formed no longer as a hollow shaft but as a core shaft which extends over the entire length of the drivetrain  10 ′ and which in particular extends axially through the electric machine driveshaft  40 . Reference is also made directly or in analogous fashion to that which has been stated above. 
         [0051]    The embodiments discussed in the specific description and shown in the figures self-evidently constitute merely illustrative exemplary embodiments of the present invention. A broad spectrum of possible variants emerges to a person skilled in the art in the light of this disclosure. In particular, the number of pinions and corresponding drive stages illustrated in the figures does not constitute a restriction of the present invention. Also, the invention is not restricted to the front/transverse arrangement shown in the figures. For a person skilled in the art, it would be easy, through suitable rearrangement of the elements and possible addition of diverting elements, to realize front/transverse arrangements or arrangements with multiple driven axles, the latter in particular through the use of a longitudinal differential. Rearrangement of the elements, for example of the drive units, in relation to one another and in relation to the core transmission is also possible within the individual arrangements. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
         
           
               10 ,  10 ′ Drivetrain 
               12  Combustion engine 
               121  Crankshaft of  12   
               14  Electric machine 
               141  Rotor of  14   
               142  Stator of  14   
               16  Start/stop unit 
               18  Dual mass flywheel 
               20 ,  20 ′ Combustion engine driveshaft 
               201 ,  202  Driveshaft pinion of  20 ,  20 ′ 
               22  First collective shaft 
               221 ,  222  Collective shaft pinions of  22   
               223  Output pinion of  22   
               24  First collective shaft clutch 
               26  Output shaft 
               28  Differential 
               30   a, b  Driven steering knuckle 
               32  Third collective shaft 
               321 ,  322  Collective shaft pinions of  32   
               323  Output pinion of  32   
               34  Third collective shaft clutch 
               36  Rotor shaft 
               38  Planetary gear set 
               381  Sun gear 
               382  Web 
               383  Internal gear 
               40  Electric machine driveshaft 
               401  Driveshaft pinion of  40   
               42  Second collective shaft 
               44  Planetary gear set clutch 
               50 ,  50 ′ Main shaft clutch 
               60  Power electronics 
               62  Battery 
               64  Electrical interface
A hybrid powertrain for a motor vehicle has an internal combustion engine and an electric machine that is connected to power electronics and to an electric energy storage device. The internal combustion engine is coupled to an internal combustion engine driveshaft and the rotor of the electric machine is coupled to an electric machine driveshaft that is connected to a planetary gear set with a sun gear, a planet carrier, and a ring gear, one element of which functions as an input element and another as an output element. The rotor of the electric machine can be selectively connected either to the input element or to the output element of the planetary gear set by way of a shiftable clutch).